JP2021113865A - Image forming apparatus - Google Patents

Abstract

To provide an image forming apparatus that sets a target temperature of a fixing member by using a sensor provided in the apparatus, and can prevent a reduction in fixability.SOLUTION: At the start of printing (S10: Yes), a time δrot indicating the amount of heat stored (the amount of remaining residual heat) at a nip of a fixing unit during stoppage of a belt is determined. When the time δrot is less than a threshold th4 (S11: Yes), it is assumed that an internal apparatus temperature detection sensor can correctly determine an environment of a printer, and the environment of the printer is determined from a result of detection made by the sensor (S7 to S9), and when the time is equal to or more than the threshold th4 (S11: No), it is assumed that the sensor cannot correctly determine the environment, and an environment determined immediately before the current time while the sensor can correctly determine the environment is continued as the environment of the printer (S12).SELECTED DRAWING: Figure 12

Description

The present disclosure relates to an image forming apparatus for fixing an image on a sheet.

An image forming apparatus such as a printer forms an unfixed image such as a toner image on a recording sheet, and heat-fixes the formed image using a fixing member whose temperature has been raised by a heater.

In Patent Document 1, the ambient temperature of the image forming apparatus is detected by a sensor provided in the image forming apparatus, and when the detected ambient temperature is lower than the reference range of 15 ° C. to 25 ° C., the target temperature of the fixing member is obtained. Is disclosed as a control for correcting the temperature to a temperature obtained by adding 5 ° C. to the temperature with respect to the reference range.

By this correction of the target temperature, for example, when the temperature of the sheet is also low in a low temperature environment, the amount of heat at the time of fixing to the low temperature sheet can be increased more than when the environmental temperature is within the standard range, and the temperature is low. It is possible to improve the fixability of the sheet in the environment.

Japanese Unexamined Patent Publication No. 2003-280465

The control for correcting the target temperature of the fixing member using the sensor as described above is based on the premise that the sensor correctly detects the actual environment of the image forming apparatus.

However, when performing double-sided printing, it is determined that the environment is higher than this despite the low temperature environment, and the fixability may be lowered.

Specifically, in double-sided printing, an image is formed on the first surface (front surface) of one sheet fed from a tray accommodating a sheet along a transport path, and after fixing, the sheet is switched back. , Return to the transport path, form an image on the second surface (back surface) of the sheet, fix it, and then eject the paper.

When this double-sided printing is performed on one or more sheets, the sheet after heat fixing to the first surface remains at a high temperature for each sheet, and after switching back, it is returned to the transport path and transported. Therefore, the ambient temperature of the sensor may rise due to the heat of the sheet. However, just because a temporary temperature rise occurs around the sensor does not mean that the temperature of the sheet in the tray also rises at the same time. Most of the time it remains.

When double-sided printing is completed and the next print is started immediately with the ambient temperature of the sensor rising, the sheet remains cold, but the sensor detects that the temperature is higher than the low temperature, and the sheet becomes cold. It will not be possible to correct to the target temperature of a suitable fixing member.

The temporary rise in the ambient temperature of the sensor is not limited to performing double-sided printing. When single-sided printing, in which an image is formed and fixed on only one side of a sheet, is performed on a large number of sheets, the heat of the motor such as driving the photoconductor of the image-forming part and rotating the transport roller for transporting the sheet is generated. It can also occur if you are temporarily trapped in the cabin. Further, not only the environmental temperature but also the environmental humidity, for example, may cause the same erroneous determination as described above. For example, when the image forming apparatus is in a low humidity environment, only the humidity around the sensor temporarily rises due to the water vapor released from the sheet after heat fixing on the first surface by double-sided printing.

The present disclosure has been made in view of the above problems, and it is possible to prevent deterioration of fixability in a configuration for determining the environment of the image forming apparatus by using a sensor provided in the image forming apparatus. It is an object of the present invention to provide an image forming apparatus.

In order to achieve the above object, the image forming apparatus according to the present disclosure is an image forming apparatus that heat-fixes an image on a sheet at a fixing portion, and is set as a setting unit for setting a target temperature of the fixing portion. A control unit that controls the temperature of the fixing unit based on the target temperature, a sensor that is arranged inside the image forming apparatus and detects the temperature or humidity around itself, and the sensor determines the environmental temperature or environmental humidity of the image forming apparatus. The setting unit includes a determination unit for determining whether or not the situation can be detected correctly, and when the determination is positive, the setting unit sets a target temperature of the fixing unit based on the detection result of the sensor. If it is negative, the target temperature that was set based on the most recent positive determination before the determination is set as the target temperature of the fixing portion.

Further, the fixing portion performs the heat fixing by pressing a pressure member against the heating rotating body to form a nip between the two, and passing a sheet through the nip to perform the heat fixing, and the determination portion is the fixing portion. At a predetermined timing for setting the target temperature of the above, if the index value for indexing the heat storage amount of the nip is less than the threshold value, a positive determination may be made, and if it is equal to or more than the threshold value, a negative determination may be made.

Here, the predetermined timing may be the start of an image forming job for forming an image on the sheet.

Here, the index value is obtained from the stop time of the heating rotating body before the predetermined timing and the rotation time of the heating rotating body before the stop, and the longer the rotation time and the shorter the stop time, the larger the value. The value may be smaller as the rotation time is shorter and the stop time is longer.

Further, it may have a storage unit that stores the rotation time and the stop time of the heating rotating body, and the determination unit may read the rotation time and the stop time from the storage unit.

Further, the fixing unit includes a heater for heating the heating rotating body, the heating rotating body is an endless belt that circulates, and the control unit controls the calorific value of the heater to perform the fixing. Even if the temperature of the portion is controlled to reach the target temperature and the heater heats a region of one circumference of the belt that is separated from the nip that is in pressure contact with the pressurizing member in the circumferential direction. good.

Further, the temperature detecting means for detecting the temperature of the heating rotating body is provided, the predetermined timing is at the start of warm-up of the image forming apparatus, and the index value is the temperature detecting means at the start of warm-up. It may be the detection result of.

Further, the predetermined timing may be each time point of the predetermined time interval during the waiting of the image forming job for forming an image on the sheet, and the index value may be the detection result of the sensor at each time point.

Further, the sensor detects the temperature, and the determination unit determines that the detection result of the sensor is the first temperature range among the first temperature range and the second temperature range higher than the first temperature range. A positive determination may be made uniformly, and one of affirmative and negative determinations may be made when the temperature is in the second temperature range.

Here, the first temperature range may be a low temperature range, and the second temperature range may be a room temperature range or a high temperature range.

Further, the sheet may be provided with an image forming portion for forming an image, and the sensor may be arranged inside the image forming apparatus and around the image forming portion.

Further, a tray for accommodating sheets and a feeding unit for feeding the sheets contained in the tray to the image forming unit are provided, the fixing unit is arranged above the image forming unit, and the tray is arranged. , It may be arranged below the image forming portion.

The image forming apparatus of another aspect according to the present disclosure is an image forming apparatus that heat-fixes an image on a sheet at a fixing portion, and is arranged inside the image forming apparatus and has a sensor for detecting its own surrounding environment and the above-mentioned. If it is determined to be positive whether or not the sensor is in a state where the environment of the image forming apparatus can be correctly detected, the environment of the image forming apparatus is determined based on the detection result of the sensor, and if it is determined to be negative, the determination is made. It is characterized by including a determination unit that determines the environment determined based on the detection result of the sensor when the previous positive determination is made as the environment of the current image forming apparatus.

Further, a setting unit for setting a target temperature of the fixing unit based on the determination result of the determination unit and a control unit for controlling the temperature of the fixing unit based on the set target temperature may be provided.

Further, the transport member that transports the sheet passing through the fixing unit, the setting unit that sets the transfer speed of the sheet based on the determination result of the determination unit, and the sheet so that the sheet is conveyed at the set transfer speed. A control unit that controls the transport member may be provided.

According to the above configuration, when the judgment unit determines that a negative judgment is made, that is, the sensor cannot correctly detect the environmental temperature or the environmental humidity of the image forming apparatus, it is correctly detected immediately before the judgment. The target temperature set based on the possible judgment is set as the target temperature of the fixing unit.

The surrounding environment of the image forming apparatus does not fluctuate significantly in a short period of time, and even if some fluctuation occurs, the temperature or humidity of the sheet before fixing does not suddenly fluctuate. This is because the temperature or humidity usually changes gradually so as to adapt to environmental changes.

For this reason, it is better to use the latest target temperature set based on the judgment that can be detected correctly, rather than using the detection result of the current sensor that cannot be detected correctly, based on the actual environment of the image forming apparatus. The fixing portion can be controlled by the temperature, and it is possible to prevent the fixing property from being lowered as compared with the conventional case.

It is a schematic diagram which shows the whole structure of a printer. It is sectional drawing which shows the schematic structure of the fixing part of a printer. It is a figure which shows the relationship between a belt rotation time and a nip width. It is a figure which shows the relationship between the belt stop time and the nip width. It is a figure for demonstrating the belt rotation time and the belt stop time. It is a figure which concretely illustrated the graph of the curve which shows the correction rotation time δrot. It is a graph which illustrates the relationship between the correction rotation time δrot and the nip width. It is a block diagram which shows the structure of the whole control part. It is a block diagram which shows the structure of the fixing control part. It is a figure which shows the content example of the information stored in the backup memory when a printer is in a normal temperature environment, and the content example of the information stored in a backup memory when transitioning from a normal temperature environment to a low temperature environment. (A) to (f) are schematic diagrams for explaining the change in the in-flight temperature of the printer in the normal temperature environment and the change in the in-flight temperature when transitioning from the normal temperature environment to the low temperature environment. It is a flowchart which shows the content of the environment judgment processing. It is a figure which shows the content example of the information stored in the backup memory when the printer is in a low temperature environment. (A) to (f) are schematic diagrams for explaining a change in the in-machine temperature in a printer in a low temperature environment. It is a figure which shows the transition of the detection result by the in-flight temperature sensor in a graph. It is a figure which shows the structural example of the fixing control part which concerns on the modification. It is a figure which shows the correspondence relationship between an environment judgment result and a sheet transfer speed.

Hereinafter, embodiments according to the present disclosure will be described with reference to the drawings, taking a printer as an image forming apparatus as an example.

[1] Overall Configuration of Printer FIG. 1 is a schematic cross-sectional view showing the overall configuration of the printer 1.

As shown in the figure, the printer 1 is an electrophotographic method, includes a feeding section 10, an image forming section 20, a fixing section 30, a discharging section 40, and a double-sided transport section 50, and is one side of a recording sheet S. It is possible to execute a single-sided print job that prints an image only on the (front side) and a double-sided print job that prints an image on both sides (front side and back side) of the sheet S.

The feeding unit 10 supplies a paper feed tray 11 for accommodating the sheet S, a feeding roller 12P provided on the paper feeding tray 11 for feeding the sheet S one by one toward the transport path 19, and the fed sheet S. It includes a paper feed roller 12F for transporting paper, a timing roller 13 for timing the sheet S to be fed to the secondary transfer position 29, and the like.

The material of the sheet S that can be accommodated in the paper feed tray 11 is paper, resin, etc., the paper type is plain paper, high-quality paper, color paper, coated paper, etc., and the sizes are A3, A4, A5, etc. Or B4 etc.

The image-creating unit 20 is located above the paper feed tray 11 and forms a toner image on the sheet S sent from the feeding unit 10. Specifically, in the four image forming units 21Y, 21M, 21C, and 21K, the surfaces of the charged photoconductor drums 25Y, 25M, 25C, and 25K are modulated and driven by the laser from the exposure unit 26 based on the image data. It is exposed to light to create an electrostatic latent image on its surface, and the electrostatic latent image is developed with toners of each color of yellow (Y), magenta (M), cyan (C) and black (K).

The four-color toner images visualized by development are the photoconductor drums 25Y, 25M, 25C, 25K, and the primary transfer rollers 22Y, 22M, 22C, 22K facing the photoconductor drums 23 via the intermediate transfer belt 23. The electric field between them causes the primary transfer from the surface of each photoconductor drum to the surface of the intermediate transfer belt 23. In this primary transfer, the toner image formation timing is shifted in the image forming units 21Y to 21K so that the toner images of each color Y to K are transferred to the same position on the intermediate transfer belt 23. As a result, a color toner image formed by multiple transfer of Y to K color toner images on the intermediate transfer belt 23 is formed.

The intermediate transfer belt 23 is located above the photoconductor drums 25Y to 25K, is stretched on a plurality of rollers including the driving roller 23R and the driven roller 23L, and travels in the direction of arrow A. The color toner image on the intermediate transfer belt 23 moves to the secondary transfer position 29, which is the contact position between the intermediate transfer belt 23 and the secondary transfer roller 24, by traveling around the intermediate transfer belt 23.

In the color toner image on the intermediate transfer belt 23, the sheet S conveyed from the feeding unit 10 is intermediate-transferred by the electric field between the intermediate transfer belt 23 and the secondary transfer roller 24 at the secondary transfer position 29. When passing between the belt 23 and the secondary transfer roller 24, the secondary transfer is performed on the surface (first surface) of the sheet S. The sheet S on which the color toner image is secondarily transferred is conveyed in the direction of arrow E by the secondary transfer roller 24 and heads toward the fixing portion 30.

The fixing portion 30 is located above the image forming portion 20, and heat-fixes the color toner image on the sheet S. Specifically, when the sheet S is passed through the nip Np between the heating unit 31 and the pressure roller 32, the heating unit 31 applies the heat of the heater to the first surface of the sheet S to apply the heat of the heater to the pressure roller. 32 applies pressure to the heated portion of the sheet S and presses it against the heating portion 31. The toner image is fixed on the sheet S by the heat from the heating unit 31 and the pressure from the pressure roller 32.

The discharge unit 40 includes a discharge roller 41 and a paper discharge port 45, and discharges the sheet S on which the color toner image is fixed from the paper discharge port 45. The discharge roller 41 is arranged inside the paper discharge port 45, and while rotating (forward rotation) in the direction of arrow B, the sheet S transported from the fixing portion 30 is transported from the paper discharge port 45 to the outside of the machine. Discharge. The ejected paper S is stored in the output tray 46. This completes the single-sided printing that prints only on the first side of the sheet S.

In the above, the single-sided print job has been described, but in the case of the double-sided print job, the operation is as follows.

That is, in the case of a double-sided print job, the sheet S that has passed through the secondary transfer position 29 at the time of printing on the front surface (first surface) is conveyed from the fixing portion 30 to the discharge roller 41.

At this point, the discharge roller 41 is rotating in the normal direction (rotating in the direction of arrow B), and the sheet S is further conveyed in the discharge direction by the discharge roller 41.

When the rear end of the sheet S conveyed by the forward-rotating discharge roller 41 passes through the detection position of the discharge sensor ES composed of an optical sensor, the discharge roller 41 switches from normal rotation to reverse rotation (rotation in the arrow C direction). .. By reversing the discharge roller 41, the sheet S is reversed and guided to the double-sided transport portion 50. This inversion of the sheet S is called switchback.

The sheet S guided to the double-sided transfer section 50 by the switchback is conveyed along the double-sided transfer path in the arrow D direction by the double-sided transfer rollers 51, 52, 53, 54, 55, passes through the double-sided transfer roller 55, and then the timing roller 13. It is conveyed to the secondary transfer position 29 again via. Each color toner image is formed on the back surface (second surface) of the sheet S in the image forming unit 20 in accordance with the transfer timing of the sheet S to the secondary transfer position 29, and is superimposed on the intermediate transfer belt 23. The color toner image is collectively transferred to the second surface of the sheet S at the secondary transfer position 29.

The sheet S on which the color toner image is secondarily transferred to the second surface at the secondary transfer position 29 is conveyed to the fixing portion 30, and the color toner image is fixed to the second surface of the sheet S at the fixing portion 30. The sheet S that has passed through the fixing portion 30 is guided to the discharge roller 41. At this point, the discharge roller 41 is rotating in the normal direction as in the case of printing on the first surface, further conveys the conveyed sheet S, discharges it to the outside of the machine, and stores it in the output tray 46. Let me. As a result, double-sided printing to be printed on both sides (first side and second side) of the sheet S is completed.

In the feeding unit 10 and the image forming unit 20, the rotating members including the paper feeding and conveying rollers, the driving roller 23R, the photoconductor drums 25Y to 25K, etc. are the driving force of the drive motor M1 arranged in the image forming unit 20. Rotates by. The discharge roller 41 is forward and reverse by the driving force of the drive motor M3 arranged in the discharge unit 40, and the double-sided transfer rollers 51 to 55 are rotated by the drive force of the drive motor M4 arranged in the double-sided transfer unit 50.

An in-flight temperature sensor 80 for detecting the environment of the printer 1 is arranged below the fixing unit 30 and in the vicinity of the image forming unit 21K of the image forming unit 20. The environment of the printer 1 refers to the temperature or humidity of the place where the printer 1 is installed, but will be described below as the temperature. The temperature detection signal by the in-flight temperature sensor 80 is sent to the overall control unit 60.

The overall control unit 60 controls the charging current in the charging process, the development bias in the developing process, the transfer current in the transfer process, and the like based on the detection signal of the in-machine temperature sensor 80, and controls the internal temperature (in-machine temperature) of the printer 1. ) Is changed, and the chargeability, developability, and transferability are prevented from deteriorating. In particular, since the charging current and the transfer current are easily affected by environmental fluctuations, deterioration of the image quality of the formed image can be suppressed by changing the current values according to the changes in the environmental fluctuations.

Further, the overall control unit 60 utilizes the detection result of the in-machine temperature sensor 80 not only in each of the charging, developing, and transferring steps, but also in the fixing step. That is, based on the detection result of the in-flight temperature sensor 80, the target temperature of the fixing unit 30, specifically, the target temperature of the heating unit 31 is set. This setting content will be described later.

Further, the overall control unit 60 is connected to an external terminal device via a network (not shown) through the network interface (I / F) 70, and receives and receives print job data sent from this terminal device. Image data to be printed is generated from the data of the printed job, and the generated image data is used for printing.

[2] Structure of Fixing Section FIG. 2 is a schematic cross-sectional view showing the structure of the fixing section 30.

As shown in the figure, the fixing portion 30 has a heating portion 31 and a pressure roller 32. The heating unit 31 includes an endless fixing belt 311 (hereinafter abbreviated as belt 311), a heating roller 312 and a fixing roller 313 for tensioning the belt 311, a heater 314 for applying heat to the heating roller 312, and a belt. Includes a belt temperature sensor 315 for detecting the temperature of 31.

The belt 311 has an elastic layer made of a highly heat-resistant material such as silicone rubber and fluororubber on a base layer made of polyimide or SUS (stainless steel), and a fluororesin such as PFA (perfluoroalkoxy alkane resin). The releasable layer having the releasability is laminated in this order.

The heating roller 312 is formed by laminating a coat layer made of PTFE (polytetrafluoroethylene) on the outer peripheral surface of a cylindrical aluminum hollow core metal. The fixing roller 313 is formed by laminating an elastic layer such as silicone rubber or fluororubber on the outer peripheral surface of a columnar solid core metal made of aluminum, iron, or the like. Each of the heating roller 312 and the fixing roller 313 is rotatably supported at both ends in the axial direction by a frame (not shown) constituting the housing of the fixing portion 30.

The heater 314 is composed of two halogen heaters, is inserted through the inner peripheral side of the cylindrical heating roller 312, and generates heat by supplying electric power from a power source (not shown). The heat generated from each halogen heater is transferred to the heating roller 312 to heat the heating roller 312.

The pressure roller 32 is formed by laminating an elastic layer such as silicone rubber and a release layer such as PFA on the outer peripheral surface of a cylindrical core metal made of aluminum or iron in this order. Both ends of the pressure roller 32 in the axial direction are rotatably supported by the above frame, and the outer peripheral surface of the pressure roller 32 becomes the outer peripheral surface of the belt 311 due to the urging force from an elastic member (not shown) such as a spring. Is pressed against. By this pressure welding, a nip Np is formed between the outer peripheral surface of the pressure roller 32 and the outer peripheral surface of the belt 311.

The pressurizing roller 32 is rotationally driven at a predetermined rotational speed in the direction of arrow F by the rotational driving force of the driving motor M2 (FIG. 1). Due to the rotation of the pressure roller 32, the belt 311 stretched on the heating roller 312 and the fixing roller 313 is driven (runs) in the arrow G direction (belt circumferential direction). The rotation speed of the drive motor M2 is controlled so that the transport speed of the seat S passing through the nip Np stabilizes at a predetermined system speed (reference speed).

When the heater 314 is energized during the orbiting of the belt 311, the heat generated from the heater 314 is transferred from the heating roller 312 to the belt 311 and reaches the nip Np by the orbiting of the belt 311. As a result, the heat of the belt 311 is supplied to the pressure roller 32, and the temperature of the nip Np, which is the contact region between the belt 311 and the pressure roller 32, rises.

The belt temperature sensor 315 is, for example, a thermistor, which is arranged near a portion of the belt 311 in contact with the outer peripheral surface of the heating roller 312, detects the surface temperature of the belt 311 and transmits the detection result to the overall control unit 60. send.

The overall control unit 60 controls the power supply to the heater 314 based on the detection temperature of the belt temperature sensor 315 so that the temperature of the belt 311 is maintained at a target temperature (for example, 150 ° C.) suitable for fixing.

The target temperature is set according to the environment of the printer 1. In the present embodiment, different target temperatures are set for each of the three environments of low temperature, normal temperature, and high temperature.

Here, the low temperature environment is a temperature range of less than 15 ° C., the high temperature environment is a temperature range of 30 ° C. or higher, and the normal temperature environment is a temperature range of 15 ° C. to 30 ° C. In a normal temperature environment, the target temperature is set to a reference temperature, for example 150 ° C., in a low temperature environment, the target temperature is set higher than the reference temperature, for example, 155 ° C., and in a high temperature environment, the target temperature is lower than the reference temperature. For example, it is set to 145 ° C.

By this control, the temperature of the belt 311 becomes stable at a temperature suitable for fixing. When the sheet S transported through the transport path 19 passes through the nip Np, the unfixed image on the sheet S is appropriately heated and melted and pressurized. As a result, the fixability of the sheet S is improved.

[3] Environmental determination using the in-flight temperature sensor When the printer 1 executes a double-sided print job (hereinafter, simply referred to as "printing") in a low temperature environment, for example, the heat of the toner image on the first surface is as described above. After the fixing, the sheet S is switched back, passes through the double-sided transfer path of the double-sided transfer section 50, and is again conveyed to the secondary transfer position 29 via the timing roller 13. When the sheet S after heat fixing is conveyed toward the secondary transfer position 29 via the timing roller 13, the heat of the sheet S is dissipated to the periphery of the image forming unit 30, so that the in-machine temperature sensor 80 The ambient temperature may rise temporarily.

Even if the ambient temperature of the in-flight temperature sensor 80 temporarily rises, there may be a situation where the temperature of the sheet S housed in the tray 11 remains low. This corresponds to a situation in which there is a discrepancy between the actual ambient temperature of the printer 1 and the ambient temperature detected by the in-flight temperature sensor 80 as explained in the section “Problems to be solved by the invention” above. do.

In this situation, the in-flight temperature sensor 80 may detect that the environment of the printer 1 is higher than the actual low temperature. It is said that this is under a situation where it is erroneously detected at a temperature higher than the actual environment.

Under this circumstance, if the target temperature of the fixing unit 30 is set by believing the detection result of the in-flight temperature sensor 80, the target temperature is suitable for fixing to the sheet S in a low temperature environment when it is erroneously detected as room temperature, for example. Instead of the target temperature (for example, 155 ° C), the temperature is suitable for the room temperature environment (for example, 150 ° C).

In this case, the temperature of the fixing portion 30 is about 5 ° C. lower than the temperature suitable for the sheet S which remains low, and the amount of heat tends to be insufficient at the time of fixing, which is more than the case where the fixing portion 30 is fixed at a target temperature suitable for a low temperature environment. As the temperature is lowered by 5 ° C., the fixability is lowered. Similarly, when a high temperature is detected, setting the temperature suitable for a high temperature environment (for example, 145 ° C.) causes a decrease in fixability. In this situation, it can be said that the detection result of the in-flight temperature sensor 80 cannot be trusted.

Since the in-flight temperature sensor 80 only outputs the detection result of its own surrounding environment (atmosphere temperature), it cannot distinguish whether it is in a erroneous detection situation or a correctly detectable situation, and the in-flight temperature sensor 80. It is not possible to determine under which situation only by monitoring the detection result of 80.

Therefore, the inventor of the present application temporarily sets the heat storage amount (residual residual heat amount) of the nip Np and the ambient temperature of the in-flight detection sensor 80 as the residual residual heat amount of the nip Np decreases due to heat dissipation while the belt 311 is stopped. Focusing on the fact that the ambient temperature of the in-flight detection sensor 80, which had risen steadily, decreases, the following control methods (a) and (b) were found.

(A) When starting the next print after the end of the previous print, the longer the elapsed time from the end of the previous print to the start of the next print, the more heat is dissipated from the nip Np, and the amount of residual heat remaining in the nip Np is small. become. In the standby state from the end of the previous print to the start of the next print, the belt 311 is stopped, so that the nip Np is not directly heated by the heater 314.

The fact that the amount of residual residual heat of the nip Np is considerably small in the standby state means that in parallel with this, the ambient temperature of the in-flight temperature sensor 80, which temporarily increased due to the printing operation immediately before, has decreased. It is highly probable that the detection result of the in-flight temperature sensor 80 is the result of adapting to the actual environment of the printer 1 (in the above example, the temperature is low). In this case, it is determined that the in-flight temperature sensor 80 is in a state where the environment of the printer 1 can be correctly detected, the detection result of the current in-flight temperature sensor 80 is trusted, and this is determined as the current environment.

(B) On the other hand, when the elapsed time from the end of the previous print to the start of the next print is considerably short, the heat dissipation of the nip Np is not so advanced, and the residual heat amount of the nip Np is large (still warm). It is in a state.

The fact that the heat dissipation of the nip Np has not progressed means that, in parallel with this, it is highly probable that the periphery of the in-flight temperature sensor 80 is also kept warm in the previous printing operation. At this time, if the detection result of the in-flight temperature sensor 80 is a normal temperature environment other than a low temperature or a high temperature environment, it is determined that the environment of the printer 1 cannot be detected correctly, that is, it is in a situation of erroneous detection. The detection result is not trusted, and the environment determined when the situation was correctly detected before this is read from the backup, and this is determined as the current environment.

In order to realize the control methods (a) and (b) above, it is necessary to know the current residual heat amount of the nip Np, but in order to directly detect this, it is necessary to prepare a dedicated sensor or the like. Yes, not desirable. On the other hand, the amount of heat stored in the nip Np is related to the size of the width (nip width: FIG. 2) Nd of the nip Np in the sheet transport direction.

Specifically, the larger the amount of heat stored in the nip Np, the larger the thermal expansion of the pressure roller 32, and the greater the degree of thermal expansion of the pressure roller 32, the longer the contact length with the belt 311 in the sheet transport direction. A certain nip width Nd becomes wider. On the contrary, the smaller the heat storage amount of the nip Np, the smaller the thermal expansion of the pressure roller 32, that is, the contraction progresses, and the smaller the degree of thermal expansion of the pressure roller 32, the narrower the nip width Nd.

The thermal expansion of the pressure roller 32 varies depending on the amount of heat applied from the heated belt 311 to the pressure roller 32, and the amount of heat applied to the pressure roller 32 differs between when the belt 311 is rotating and when it is stopped.

This is because the heating roller 312 heated by the heat source heater 314 and the pressure roller 32 forming the nip Np are separated from each other. Therefore, when the belt 311 orbits, such as during printing, the heat of the heating roller 312 heated by the heater 314 is directly transferred from the belt 311 to the nip Np.

However, if the belt 311 is stopped while waiting for a print job, the heat transferred to the pressurizing roller 32 separated from the heating roller 312 is only the heat transferred from the heating roller 312 through the stopped belt 311 or radiant heat. This is because the amount of heat applied to the pressurizing roller 32 is significantly reduced.

The nip width Nd fluctuates as shown in FIGS. 3 and 4 depending on whether the belt 311 is rotating or stopped. FIG. 3 is a diagram showing the relationship between the rotation time of the belt 311 (belt rotation time t-rot) and the nip width Nd, and FIG. 4 is a diagram showing the relationship between the belt stop time (belt stop time t-stop) and the nip width Nd. It is a figure which shows the relationship. Both FIGS. 3 and 4 show an example when the relationship between the belt rotation time t-rot, the belt stop time t-stop, and the nip width Nd is actually measured by an experiment.

As shown in FIG. 3, it can be seen that the nip width Nd becomes wider as the belt rotation time t-rot increases. Specifically, the nip width Nd is 4.85 mm at the start of rotation of the belt 311. However, after 300 seconds, the nip width Nd becomes 5.4 mm, and after 900 seconds, the nip width Nd becomes 5.6 mm. It has spread.

When the rotation of the belt 311 is stopped from this state, the amount of heat transferred to the pressurizing roller 32 decreases, so that the nip width Nd becomes narrower as the belt stop time t-stop increases as shown in FIG. Specifically, the nip width Nd, which was 5.6 mm when the belt 311 was stopped, became 5.4 mm after 600 seconds and narrowed to 5.2 mm after 1800 seconds.

Here, in FIG. 4, the reason why the nip width Nd does not return to the original size of 4.8 mm is that even if the rotation of the belt 311 is stopped, the heat from the heating roller 312 is applied through the stopped belt 311. This is because the radiant heat of the heating roller 312 is also transmitted to the pressure roller 32 as well as being transmitted to the pressure roller 32. The size of the nip width Nd is an example, and it goes without saying that the size of the nip width Nd may be different if the device configuration of the fixing portion 30 is different.

In this way, the nip width Nd increases with the rotation time of the belt 31 heated by the heater 314 and decreases with the stop time of the belt 31. That is, the nip width Nd correlates with the rotation time and the stop time of the belt 31. As the rotation time of the belt 31 increases, the amount of heat supplied to the nip Np increases, so that the amount of heat stored in the nip Np increases accordingly. Therefore, it can be said that the heat storage amount of the nip Np is related to the rotation time and the stop time of the belt 31.

Therefore, at the start of printing, the belt rotation time t-rot and the belt stop time t-stop are used as indexes of the residual residual heat amount of the nip Np, and when this index value is small, the control of (a) above is taken and this index is taken. By switching to take the control of (b) above when the value is large, the determination accuracy of the environment of the printer 1 is improved, and the target temperature of the fixing unit 30 suitable for the environment of the printer 1 is set more accurately. Prevents deterioration of fixability.

Hereinafter, a specific description will be given.

First, the belt rotation time t-rot and the belt stop time t-stop are acquired. As shown in FIG. 5, the belt rotation time t-rot indicates the time during which the belt 311 was rotated in the latest (previous) print job before this, and the belt stop time t-stop is the previous time. , Indicates the waiting time that has been stopped until now after the belt 311 has rotated. For example, if the belt 311 rotates for 5 minutes and remains stopped for 7 minutes from the stop of this rotation to the present, the belt rotation time t-rot is 5 minutes and the belt stop time t-stop is 7 minutes.

When the belt 311 rotates for 5 minutes and then stops for 7 minutes as in this example, the belt 311 rotates without stopping in the present embodiment when determining the nip width Nd (corresponding to the heat storage amount of the nip Np). It is judged that it corresponds to a state in which the rotation is continued for 100 seconds from the start.

This determination is made using a conversion table (not shown) stored in advance in the storage area of the overall control unit 60. This conversion table shows how many minutes after the start of rotation of the belt 311 when the nip width Nd in the stop period when the belt 311 is stopped after the belt 311 is rotated is assumed to be rotated without stopping the belt 311. It is a table which recorded the data by the experiment whether it corresponds to the nip width.

This data can be obtained from the following (Equation 1).

δrot = t-rot [1-t-stop / (t-stop + A)] ... (1)
Here, "δ rot" shown in (Equation 1) is the rotation time of the belt 311 indicating the above "minutes", and "t-rot" is the above-mentioned belt rotation time t-rot (minutes). ), And "t-stop" is the above-mentioned belt stop time t-stop (minutes). A is a constant determined in advance in order to properly perform the environmental judgment. Hereinafter, δrot is referred to as a corrected rotation time.

FIG. 6 is a diagram specifically exemplifying a graph of a curve showing (Equation 1), in which the horizontal axis represents the belt stop time t-stop and the vertical axis represents the correction rotation time δrot. This corrected rotation time δrot indicates the rotation time of the belt 311 which is assumed to have the same nip width as the nip width Np corresponding to the belt stop time t-stop as described above.

In FIG. 6, the thick line graph corresponds to the case where the belt rotation time t-rot is 10 minutes, the solid line graph corresponds to the case where the belt rotation time t-rot is 5 minutes, and the broken line graph corresponds to the belt. The graph of the one-point chain line corresponds to the case where the rotation time t-rot is 3 minutes, and corresponds to the case where the belt rotation time t-rot is 1 minute.

Here, the intersection of the vertical axis and each graph corresponds to the initial value of the corrected rotation time δrot when the belt stop time t-stop = 0, that is, the belt rotation time t-rot.

In the above example, since the belt rotation time t-rot is 5 minutes, the solid line graph is selected, and since the belt stop time t-stop is 7 minutes, the vertical axis corresponding to 7 minutes in the solid line graph. When the numerical value of is read, the numerical value, that is, the correction rotation time δrot becomes 100. In this way, the correction rotation time δrot can be obtained.

The corrected rotation time δrot is a nip width having the same size as the nip width Np when the belt 311 rotates over the belt rotation time t-rot and then stops over the belt stop time t-stop as described above. It shows the rotation time of the belt 311 which is supposed to be obtained.

The short correction rotation time δrot is required to obtain a nip width Nd having the same size as the nip width Np when the belt 311 is stopped by the belt stop time t-stop after the belt rotation time t-rot is rotated. It indicates that the amount of heat supplied to the nip Np is small. The small amount of heat supplied to the nip Np means that the amount of heat stored in the nip Np at the end of the belt stop time t-stop is small. This amount of heat storage corresponds to the amount of residual residual heat of the nip Nd. When the correction rotation time δrot is long, it is the opposite of when it is short. From this, it can be said that the corrected rotation time δrot is an index of the heat storage amount of the nip Np, and it can be said that obtaining the corrected rotation time δrot is equivalent to estimating the heat storage amount of the nip Np.

FIG. 7 is a graph illustrating the relationship between the correction rotation time δrot and the nip width Nd, and it can be seen that when the correction rotation time δrot is 100 seconds, the nip width Nd is about 5.3 mm.

In the present embodiment, the nip width Nd is not directly obtained, but the correction rotation time δrot for indexing the residual residual heat amount of the nip Np is obtained by using (Equation 1) in the overall control unit 60, and the obtained correction rotation time is obtained. The decrease transition of the ambient temperature of the in-flight temperature sensor 80 is estimated from the magnitude of δrot, the environment of the printer 1 is determined from the estimated decrease transition of the ambient temperature, and the target temperature of the fixing unit 30 is set from the determination result.

[4] Configuration of Overall Control Unit FIG. 8 is a block diagram showing the configuration of the overall control unit 60.

As shown in the figure, the overall control unit 60 includes a CPU (Central Processing Unit) 61, a ROM (Read Only Memory) 62, and a RAM (Random Access Memory) 63. These can communicate with each other. Further, the CPU 61 can communicate with each other with the feeding unit 10, the image forming unit 20, the fixing unit 30, the discharging unit 40, the double-sided conveying unit 50, and the network I / F 70.

When the network I / F 70 receives the print job data sent from the external terminal device via the network (for example, LAN), the CPU 61 includes the feeding unit 10, the image forming unit 20, the fixing unit 30, and the discharging unit 40. The operation of the double-sided transfer unit 50 is comprehensively controlled to smoothly execute the print job based on the received print job data. The ROM 62 stores in advance a control program or the like for executing a print job. The CPU 61 operates according to the control program stored in the ROM 62. The RAM 63 provides a work area for program execution by the CPU 61.

Further, the CPU 61 determines the environment of the printer 1 based on the detection results of the in-flight temperature sensor 80 and the belt temperature sensor 315, and performs temperature control control to control the temperature of the fixing unit 30 according to the determined environment. This temperature control is executed by the fixing control unit included in the CPU 61.

[5] Configuration of Fixing Control Unit FIG. 9 is a block diagram showing a configuration of the fixing control unit 610.

As shown in the figure, the fixing control unit 610 includes an environment determination unit 611, a target temperature setting unit 612, a backup memory 613, and a heater control unit 614.

The environment determination unit 611 determines the current environment of the printer 1 from the operating state of the printer 1, the detection result of the in-flight temperature sensor 80, the detection result of the belt temperature sensor 315, and the information stored in the backup memory 613. Here, it is determined whether the temperature is low temperature, normal temperature, or high temperature.

The target temperature setting unit 612 sets the target temperature of the fixing unit 30, that is, the target temperature of the belt 311 from the current environment determination result by the environment determination unit 611.

The heater control unit 614 controls the calorific value of the heater 314 so that the current temperature of the belt 311 obtained from the detection result of the belt temperature sensor 315 and the target temperature set by the target temperature setting unit 612 match.

The backup memory 613 is a non-volatile storage unit, and stores information indicating a past operating state, a detection result of the in-flight temperature sensor 80, and an environment determination result.

FIG. 10 is a diagram showing an example of the contents of the information stored in the backup memory 613.

As shown in the figure, the backup memory 613 has a storage area in each column of time, operating state, presence / absence of belt rotation, in-flight detection result, environment determination result, and target temperature configured in a table format.

The time column is divided into fixed time intervals, and in the example of the figure, it is divided in chronological order every minute from 9:00 am.

The operating state is the operating state of the printer 1, and includes three: standby, warm-up (WU), and print. Here, the standby is a state of waiting for an execution instruction of a print job in a state in which printing can be executed, and in the fixing unit 30, the belt 311 in the stopped state is set to a target temperature by the heater 314 so that printing can be executed. Temperature control is performed to maintain the temperature.

The warm-up is an operation of rotating the belt 311 of the fixing unit 30 and raising the temperature to a target temperature when the power of the printer 1 is turned on to make a transition to a state in which printing can be executed. The warm-up is not limited to when the power is turned on. For example, the target temperature of the belt 311 is significantly lowered from the target temperature at the time of printing (for example, 100 ° C.), and the power saving mode for power saving is restored to the standby state. It may be done at the time. Print means that the print job is being executed.

The presence / absence of belt rotation indicates the presence / absence of rotation of the belt 311 for each operating state. In the standby state, the belt 311 does not rotate (stop), and in the warm-up and print, the belt 311 is in the rotating state.

The in-flight detection result indicates one of three environmental categories of low temperature, normal temperature, and high temperature as the detection result by the in-flight temperature sensor 80. As described above, the low temperature is less than 15 ° C, the normal temperature is in the range of 15 ° C to 30 ° C, and the high temperature is in the range of 30 ° C or higher.

The environment determination result indicates the environment of the printer 1 determined by the environment determination unit 611, here, any one of low temperature, normal temperature, and high temperature. This determination is performed by the environment determination process (FIG. 12) described later.

The target temperature is the target temperature of the fixing unit 30, and is set based on the environmental determination result.

The environment determination unit 611 writes the operating state, the presence / absence of belt rotation, the in-flight detection result, and the environment determination result in the columns corresponding to the time when the printer 1 is turned on and every minute thereafter. Each time the environment determination unit 611 makes an environment determination, the target temperature setting unit 612 writes the target temperature in the column corresponding to the time based on the environment determination.

In the example shown in the figure, when today is Monday, the printer 1 that was in a normal temperature environment from the previous day (Sunday) to today (Monday) at night is turned on at exactly 9 am today. The operating state from 9 o'clock to 9:46, the presence or absence of belt rotation, the in-flight detection result, the environmental judgment result, and the transition of the target temperature are shown at 1-minute intervals. Hereinafter, a specific description will be given with reference to FIGS. 11 (a) to 11 (f) and the environment determination process (FIG. 12).

[6] Specific Example 1 Regarding the Method of Environmental Judgment and Setting of Target Temperature of Fixing Part
The power of the printer 1 is turned on at 9 o'clock, and warm-up (WU) is started. At this time, the belt 311 starts rotating and the heater 314 starts heating the belt 311.

The printer 1 was in a room temperature environment from the previous day to 9 am today, the power was off, and the heater 314 was also off. Therefore, as shown in FIG. 11A, the inside of the printer 1 is in a room temperature environment. The temperature of the nip Np and the temperature of the sheet S in the tray 11 are at room temperature. At this point, both the detection result of the belt temperature sensor 315 and the detection result of the in-flight temperature sensor 80 indicate room temperature.

The environment of the printer 1 is determined to be normal temperature by the environment determination process shown in FIG. This environment determination process is executed every time a call is made at a predetermined time interval, here, at a minute interval, according to a main flow (not shown).

Specifically, it is determined whether or not the detection result (in-flight detection temperature) of the in-flight temperature sensor 80 at 9 o'clock is less than the threshold value th1 (for example, 15 ° C.) indicating the lower limit of room temperature (step S1). Here, since the environment is normal temperature, a negative judgment is made (“No” in step S1), and the process proceeds to step S4. In step S4, it is determined whether or not the warm-up has started.

Since it is the start of warm-up at 9 o'clock, a positive judgment is made (“Yes” in step S4), and then whether the belt detection temperature by the belt temperature sensor 315 is less than the threshold value th3 (for example, 60 ° C.). It is determined whether or not (step S5).

This threshold value th3 is a predetermined value set in advance by an experiment or the like in order to determine whether or not the environment of the printer 1 can be correctly detected at the start of warm-up.

The fact that the belt detection temperature is high to some extent at the start of warm-up means that printing was executed until just before the start of warm-up, and after the print was completed, the power of printer 1 was once turned off, but it was turned on immediately. It is assumed that the warm-up will be started. In this scene, it is highly probable that the ambient temperature of the in-flight temperature sensor 80 remains elevated due to the execution of printing immediately before the warm-up.

The in-flight temperature sensor 80 detects a normal temperature or a high temperature other than a low temperature (“No” in step S1), and is this detected normal temperature or high temperature temporarily increased due to the execution of the immediately preceding print or the like? (Sheet S remains at low temperature), it is indistinguishable whether the inside of the aircraft and the sheet S are in a calm state at room temperature or high temperature. That is, there is a possibility that the above-mentioned correctly detectable situation has not been achieved.

The temperature of the sheet S in the machine of the printer 1, for example, in the tray 11, hardly changes suddenly from a low temperature to a high temperature even if the temperature around the machine temperature sensor 80 temporarily rises due to printing, and the printer 1 Even if the installation environment of the printer changes from low temperature to normal temperature and from normal temperature to high temperature, it slowly changes to adapt to the changed temperature.

If the temperature inside the printer 1 is calm and stable, the latest time when the environment determined by the current detection result was in a situation where it could be detected correctly before (past) the present. The environment determined to be should be the same. On the other hand, when the ambient temperature of the in-flight temperature sensor 80 rises temporarily, the environment determined in the latest (recent time) when the situation was correctly detectable before the rise was the original environment. It should be the environment.

That is, both when the ambient temperature of the in-flight temperature sensor 80 is temporarily raised or when it is calm, it is determined before (past) the present and the latest when the situation is correctly detectable. It can be said that if the environment is inherited as it is, no large error will occur in the environmental judgment. The succession of this environment is called continuation of the previous time.

In the present embodiment, it is determined whether or not the above-mentioned correctly detectable situation is obtained at the start of warm-up based on whether or not the belt detection temperature at the start of warm-up is equal to or lower than the threshold value th3 (for example, 60 ° C.). In this sense, step S5 functions as a determination unit for determining whether or not the in-flight temperature sensor 80 is in a state where the environmental temperature of the printer 1 can be correctly detected. Further, when the in-flight temperature sensor 80 detects a low temperature (“Yes” in step 1), it means that the environment temperature of the printer 1 can be correctly detected. Therefore, step S1 also functions as the above-mentioned determination unit. It can be said that.

In the above example as of 9:00 am, it is determined that the belt detection temperature is less than the threshold value th3 (“Yes” in step S5) and the situation is correctly detectable, and the process proceeds to step S7.

In step S7, it is determined whether or not the detection result of the in-flight temperature sensor 80 is less than the threshold value th2 (for example, 30 ° C.) indicating the lower limit of the high temperature environment. In the case of a positive judgment (“Yes” in step S7), the environment of the printer 1 is determined to be room temperature (step S8), and in the case of a negative judgment (“No” in step S7), the environment of the printer 1 is heated to a high temperature. (Step S9), and the process proceeds to step S3. In step S3, the environment determination result is written in the column of the environment determination result corresponding to 9:00 am in the backup memory 613 shown in FIG. 10 (memory). Then, it returns to the main flow.

In the above example, the detection result of the in-flight temperature sensor 80 is determined to be less than the threshold value th2 (“Yes” in step S7) because the aircraft was in a room temperature environment for a long time from the previous day's Sunday to today's Monday at 9:00 am. , The environment of the printer 1 is determined to be room temperature (step S8).

The determination at 9 o'clock is a determination when the situation is correctly detectable. Then, as shown in FIG. 10, "normal temperature" is written in the column of the environment determination result corresponding to the time point of 9 o'clock. By this determination, the target temperature of the fixing portion 30 is set to 150 ° C.

On the other hand, when the belt detection temperature is equal to or higher than the threshold value th3 (“No” in step S5), it is determined that the belt is not in a correctly detectable situation, that is, it is in a erroneous detection situation, and the environment is determined to be continued last time (“No”). Step S6). Specifically, the environment determined most recently when the situation was determined to be correctly detectable at the previous time when 9 o'clock at the present time is set as this time, that is, at a time point before 9 o'clock (not shown) is continued as it is. That is, the determined environment is determined as the current environment. In the case of the above example, since the power of the printer 1 has been turned off for a long time before 9:00 am, a positive judgment is always made in step S5.

The warm-up is finished, and it goes into a standby state at 9:01. As shown in FIG. 11B, in the standby state, the belt 311 is stopped, but the temperature control of the heating roller 312 is controlled to the target temperature by the heater 314, and the temperature is maintained at 150 ° C. At 9:01, the temperature of the nip Np was close to 150 ° C. because it was just after the warm-up was completed, but when the standby state continued, the temperature of the nip Np gradually decreased. In the warm-up, the sheet S is not passed through, so at 9:01 immediately after the warm-up is completed, the temperature around the image forming unit 20 and the temperature of the sheet S in the tray 11 remain at room temperature. There is. From this, as shown in FIG. 10, the detection result of the in-flight temperature sensor 80 indicates room temperature.

In the environment determination process shown in FIG. 12, at 9:01, the environment of the printer 1 remains in the room temperature environment, so the detection result of the in-flight temperature sensor 80 is the threshold value th1 or more (“No” in step S1). , Since it has transitioned to the standby state, it is not at the start of warm-up (“No” in step 4) and not at the start of print operation (“No” in step S10), and the environment of printer 1 is determined to be continued last time. Then (step S12), the process proceeds to step S3.

This previous continuation is the same process as the previous continuation described in step S6. Specifically, when 9:01 is the current time, the environment at 9 o'clock, which was most recently determined to be in a correctly detectable situation, will be inherited as it is. This is due to the following reasons.

That is, printing is not performed in the standby state, and there is little fluctuation in the internal temperature due to printing execution. However, the in-flight temperature sensor 80 detects a room temperature other than a low temperature (“No” in step S1), and the detected room temperature temporarily rises only around the in-flight temperature sensor 80 due to the execution of the immediately preceding print or the like. It is indistinguishable whether the whole cabin (both the periphery of the temperature sensor 80 and the sheet S in the tray 11) is in a calm state at room temperature. That is, there is a possibility that the above false detection situation has occurred.

Therefore, as in step S6, when it is determined that the situation is erroneous detection, the previous continuation is continued (step S12) to prevent a large error in the environmental determination. In FIG. 10, the environment at 9 o'clock, that is, the normal temperature is written in the environment judgment result column at 9:01. In the figure, the takeover is indicated by an arrow pointing to the right.

The standby state continues until 9:02, 3, ... 10 minutes. Since it is still in a room temperature environment, the detection result of the in-flight temperature sensor 80 indicates the room temperature every minute.

In the environment determination process shown in FIG. 12, at each time point of 9:02, 3, ... 10 minutes, the detection result of the in-flight temperature sensor 80 is the threshold value th1 or more (“No” in step S1), and warm-up. Not at the start (“No” in step 4), not at the start of the print operation (“No” in step S10), the environment of the printer 1 is determined to be continued last time (step S12), and the process proceeds to step S3. As a result, as shown in FIG. 10, in the column of the environment judgment result corresponding to each time point of 9:02, 3 minutes, ... 10 minutes, the time point of 9 o'clock judged under the condition of no false detection The environment is taken over and the room temperature is written here.

The print job starts at 9:11. The belt 311 starts rotating when the print job starts. At 9:11, the temperature of the nip Np has dropped considerably as shown in FIG. 11 (c), but the temperature is raised by the rotation of the belt 311. Since the standby state continued for a long time of about 10 minutes from 9:01 in a normal temperature environment, the temperature around the image forming portion 20 and the temperature of the sheet S in the tray 11 remained at room temperature.

In the environment determination process shown in FIG. 12, at 9:11, the detection result of the in-flight temperature sensor 80 is the threshold value th1 or more (“No” in step S1), not at the start of warm-up (“No” in step 4). No. ”), it is determined that the printing operation is started (at the start of the image forming job) (“Yes” in step S10), and the process proceeds to step S11. In step S11, it is determined whether or not the correction rotation time δrot is less than the threshold value th4.

The correction rotation time δrot can be obtained from the above (Equation 1). Here, the belt rotation time t-rot in the above (Equation 1) is the belt rotation time in the warm-up or print operation executed before the current 9:11, and the belt stop time t-stop is. , The belt stop time after the belt rotation time ends.

In the example of FIG. 10, the belt rotation time t-rot is 1 minute required for the warm-up executed at 9 o'clock, and the belt stop time t-stop is 10 minutes between 9: 1 and 11 minutes. Become. When the constant A in the equation (1) is, for example, 10, the correction rotation time δrot is 0.5.

As described above, the corrected rotation time δrot is an index of the residual residual heat amount of the nip Np, and the longer the corrected rotation time δrot is, the larger the residual residual heat amount of the nip Np (heat dissipation is not advanced). At the same time, it can be said that the situation in which the ambient temperature of the in-flight temperature sensor 80, which has risen due to the printing operation immediately before, has not decreased, continues. On the contrary, the shorter the correction rotation time δrot, the smaller the residual residual heat of the nip Np (the heat dissipation of the nip Np is progressing), and the ambient temperature of the in-flight temperature sensor 80 that temporarily increased due to the printing operation immediately before. It can be said that the temperature has dropped to a temperature adapted to the actual environment as the temperature has progressed.

In equation (1), when the belt rotation time t-rot is long and the belt stop time t-stop is short, the correction rotation time δrot is long, the belt rotation time t-rot is short, and the belt stop time t-stop is long. In this case, the correction rotation time δrot becomes shorter. This is due to the following reasons.

That is, the longer the belt rotation time t-rot, the larger the amount of heat stored in the nip Np, and the shorter the belt stop time t-stop, the less heat is dissipated from the nip Np, so that the remaining residual heat amount remains large. On the contrary, the shorter the belt rotation time t-rot, the smaller the amount of heat stored in the nip Np, and the longer the belt stop time t-stop, the more heat is dissipated from the nip Np and the smaller the residual residual heat amount.

In the above example, after warming up for 1 minute (belt rotation time t-rot), the standby state continues for 10 minutes (belt stop time t-stop), the belt rotation time t-rot is short, and the belt. The condition that the stop time t-stop is long is satisfied, and the correction rotation time δrot is a considerably short value.

Since the paper is not passed during warm-up, the ambient temperature of the in-flight temperature sensor 80 hardly rises, and after a 10-minute standby state, the ambient temperature of the in-flight temperature sensor 80 is the actual environment, here the temperature adapted to room temperature. It can be said that it is stable and is not in a situation of false detection.

On the other hand, if the printing operation is performed for 10 minutes (belt rotation time t-rot) and then waits for 1 minute (belt stop time t-stop), the belt rotation time t-rot is long and the belt is belted. The condition that the stop time t-stop is short is satisfied, and the correction rotation time δrot is about 9. In this case, the ambient temperature of the in-flight temperature sensor 80 may temporarily rise to a range of high temperature environment higher than the actual normal temperature environment. In this case, it can be said that the situation is such that false detection occurs.

The corrected rotation time δrot is an index of the residual residual heat amount of the nip Np, and the smaller the corrected rotation time δrot is, the more the ambient temperature of the in-flight temperature sensor 80 is lowered. This means that there is a certain relationship between the decrease in the amount of heat stored in the nip Np (the change in the amount of residual residual heat) and the decrease in the ambient temperature of the in-flight temperature sensor 80.

That is, the magnitude of the correction rotation time δrot is an index of how much the ambient temperature of the in-flight temperature sensor 80 has decreased, and it is correctly detected by how much the ambient temperature of the in-flight temperature sensor 80 has decreased. Judgment of possible situation or false detection situation will be divided.

Therefore, in the present embodiment, if the corrected rotation time δrot is within the range of the actual environment classification, it can be detected correctly, and if it exceeds this, the range of the actual environment classification is changed. The size (threshold value th4) is determined in advance by an experiment or the like according to the device configuration to determine whether the situation transitions to a false detection situation when the value is exceeded. Here, an example in which the threshold value th4 is set to 5 will be described, but of course, it may differ depending on the device configuration.

Then, each time the print job is executed, the correction rotation time δrot is obtained at the start of printing, and the magnitude relationship between the length of the obtained correction rotation time δrot and the threshold value th4 is determined (step S11). From this determination result, it is switched whether the environment determination is based on the detection result of the in-flight temperature sensor 80 or the previous continuation. In this sense, step S11 functions as a determination unit for determining whether or not the in-flight temperature sensor 80 is in a state where the environmental temperature of the printer 1 can be correctly detected.

At the time of 9:11 above, the correction rotation time δrot is 0.5 and is less than the threshold value th4 (“Yes” in step S11), so the process proceeds to step S7 and based on the detection result of the in-flight temperature sensor 80. Environmental judgment is made. In the above example, the environment is determined to be normal temperature (step S8), and the normal temperature is written in the environment determination result column corresponding to 9:11 shown in FIG. This determination is a determination in a situation where it can be detected correctly. Then, 150 ° C. is set as the target temperature corresponding to the room temperature.

The print job started at 9:11 has been completed by 9:12, and has transitioned to the standby state at 9:12. Since the print execution time was within 1 minute, the ambient temperature of the in-flight temperature sensor 80 rose slightly as shown in FIG. 11D, but it was within the room temperature range.

In the environment determination process shown in FIG. 12, at 9:12, the detection result of the in-flight temperature sensor 80 is the threshold value th1 or more (“No” in step S1), not at the start of warm-up (“No” in step 4). Since it is not the start of the print operation (“No” in step S10), the process proceeds to step S12. In step S12, the environment determination is continued from the previous time, and the process proceeds to step S3. In this previous continuation, the judgment was made at 9:11, which was before the present (9:12) and was judged in the most recent correctly detectable situation. In the above example, the room temperature was taken over and the target temperature was 150. Set to ° C. Even in the standby state at 9:13, the same determination and setting as at 9:12 are performed.

Printing will start at 9:14. At this time point, as shown in FIG. 11 (e), the temperature is the same as that in FIG. 11 (d). In the environment determination process shown in FIG. 12, at 9:14, the detection result of the in-flight temperature sensor 80 is the threshold value th1 or more (“No” in step S1), not at the start of warm-up (“No” in step 4). No ”), it is determined that it is the start of the printing operation (“Yes” in step S10), and it is determined whether or not the correction rotation time δrot is less than the threshold value th4 (step S11).

The belt rotation time t-rot in the above (Equation 1) is 1 minute of the belt rotation time in the printing operation executed at 9:11, and the belt stop time t-stop is from 9:12 to 14 minutes. It will be 2 minutes between. The correction rotation time δrot is about 0.83 from the equation (1).

Since the correction rotation time δrot is less than the threshold value th4 (“Yes” in step S11), the process proceeds to step S7, and the environment is determined based on the detection result of the in-flight temperature sensor 80. In the above example, the environment is determined to be normal temperature (step S8), and the normal temperature is written in the environment determination result column corresponding to 9:14 shown in FIG. This determination is a determination in a situation where it can be detected correctly. Then, 150 ° C. is set as the target temperature corresponding to the room temperature.

The print job started at 9:14 has been completed by 9:15, and has transitioned to the standby state at 9:15. Since the print execution time was within 1 minute, the ambient temperature of the in-flight temperature sensor 80 did not rise so much and was within the room temperature range. In the environment determination process shown in FIG. 12, at 9:15, the detection result of the in-flight temperature sensor 80 is the threshold value th1 or more (“No” in step S1), not at the start of warm-up (“No” in step 4). Since it is not the start of the print operation (“No” in step S10), the environment determination is continued from the previous time (step S12), and the process proceeds to step S3. In this previous continuation, the judgment at 9:14, which was made before the present (9:15) and was judged in the most recent correctly detectable situation, and the normal temperature in the above example are taken over.

After 9:15 am, an example is shown when the installation environment of the printer 1 changes from a normal temperature environment to a low temperature environment. Due to this change in the environment, the temperature inside the printer 1 begins to drop. The standby state has continued since 9:15, and as shown in FIG. 11 (f), the detection result of the in-flight temperature detection sensor 80 detects the low temperature environment at 9:45.

In the environment determination process shown in FIG. 12, at 9:45, the detection result of the in-flight temperature sensor 80 is less than the threshold value th1 (“Yes” in step S1), so the temperature is low based on the detection result of the in-flight temperature sensor 80. The environment is determined (step S2), and the process proceeds to step S3. The low temperature is written in the column of the environment judgment result corresponding to 9:45 shown in FIG. This determination is a determination in a situation where it can be detected correctly. Then, 155 ° C. is set as the target temperature corresponding to the low temperature.

At 9:46 am, the standby state continues at a low temperature, and in the environment determination process shown in FIG. 12, the detection result of the in-flight temperature sensor 80 is less than the threshold value th1 (“Yes” in step S1). A low temperature environment is determined based on the detection result of the in-flight temperature sensor 80 (step S2). The low temperature is written in the column of the environment judgment result corresponding to 9:46 shown in FIG. This determination is a determination in a situation where it can be detected correctly. Then, 155 ° C. is set as the target temperature corresponding to the low temperature.

[7] Specific example 2 regarding the method of determining the environment and setting the target temperature of the fixing portion
In the above, an example in which the printer 1 is installed in a normal temperature environment has been described, but for example, when the printer 1 is installed in a low temperature environment, the environment determination is as follows.

That is, when today is Monday, FIGS. 13 to 15 are taken as an example from the time when the printer 1 which was in a low temperature environment from the previous day (Sunday) to today's night is turned on at exactly 9 am today. explain.

FIG. 13 is a diagram showing an example of the contents of information stored in the backup memory when the printer 1 is in a low temperature environment. As shown in FIG. 13, the power of the printer 1 is turned on at 9 o'clock, and warm-up (WU) is started. At this time, the belt 311 starts rotating and the heater 314 starts heating the belt 311.

The printer 1 was in a low temperature environment from the previous day to 9 am today, the power was off, and the heater 314 was also off. Therefore, as shown in FIG. 14A, the inside of the printer 1 is in a low temperature environment. The temperature of the nip Np and the temperature of the sheet S in the tray 11 are both low. At this point, both the detection result of the belt temperature sensor 315 and the detection result of the in-flight temperature sensor 80 indicate a low temperature.

In the environment determination process shown in FIG. 12, at 9 o'clock, the detection result of the in-flight temperature sensor 80 is less than the threshold value th1 (“Yes” in step S1), so that the low temperature environment is based on the detection result of the in-flight temperature sensor 80. A determination is made (step S2), and the process proceeds to step S3. The low temperature is written in the column of the environment judgment result corresponding to 9 o'clock shown in FIG. This determination is a determination in a situation where it can be detected correctly. Then, 155 ° C. is set as the target temperature corresponding to the low temperature.

The warm-up is completed by 9:01 and the print job is started at 9:01. The belt 311 starts rotating when the print job starts. At 9:01, the temperature of the nip Np had risen to around 155 ° C as shown in FIG. 14 (b), but the ambient temperature of the in-flight temperature sensor 80 and the temperature of the sheet S in the tray 11 were low. It remains.

In the environment determination process shown in FIG. 12, at 9:01, the detection result of the in-flight temperature sensor 80 is less than the threshold value th1 (“Yes” in step S1), so the temperature is low based on the detection result of the in-flight temperature sensor 80. The environment is determined (step S2), and the process proceeds to step S3. The low temperature is written in the column of the environment judgment result corresponding to 9:01 shown in FIG. This determination is a determination in a situation where it can be detected correctly. Then, 155 ° C. is set as the target temperature corresponding to the low temperature.

When the detection result of the in-flight temperature sensor 80 is a low temperature, there is no temperature range lower than this, so it is determined that the situation is not erroneous detection, and this low temperature is used as the environmental determination. That is, whether the detection result of the in-flight temperature sensor 80 is used as it is for the environment judgment by determining whether or not the situation can be correctly detected only when the detection result is in the range of normal temperature and high temperature where the temperature is higher than the low temperature range. It is configured to switch whether to continue last time.

The print job started at 9:01 will continue until just before 9:11. By executing this mass print job for a long time, the ambient temperature of the in-flight temperature sensor 80 gradually rises, and as shown in FIG. 15, the temperature enters the low temperature range to the room temperature range during the execution of the print job. The time when the ambient temperature of the in-flight temperature sensor 80 enters the room temperature range is exactly 9:10. As a result, the room temperature is written in the in-flight detection result column corresponding to 9:10 shown in FIG. This is the same until 9:15. However, as shown in FIG. 14C, the temperature of the sheet S in the tray 11 is still low.

In the environment determination process shown in FIG. 12, from 9:01 to 9:09, the detection result of the in-flight temperature sensor 80 is less than the threshold value th1 (“Yes” in step S1), so that the detection result of the in-flight temperature sensor 80 The low temperature environment is determined based on (step S2). As a result, the low temperature is written in each column of the environmental judgment result corresponding to 9:01 to 9: 9 shown in FIG. This determination is a determination in a situation where it can be detected correctly. Then, 155 ° C. is set as the target temperature corresponding to the low temperature.

On the other hand, at 9:10, the detection result of the in-flight temperature sensor 80 is the threshold value th1 or more (“No” in step S1), not at the start of warm-up (“No” in step 4), and the printing operation is performed. Since it is not the start time (“No” in step S10), in step S12, the environment determination is continued last time (step S12), and the process proceeds to step S3.

In this previous continuation, the judgment at 9:09, which is before the present (9:10) and the judgment was made in the most recent correctly detectable situation, the low temperature is taken over in the above example. As a result, the low temperature is written in the column of the environment determination result corresponding to 9:10 shown in FIG. Then, 155 ° C. is set as the target temperature corresponding to the low temperature.

Conventionally, since the in-flight detection result corresponding to 9:10 is at room temperature, the environmental judgment result is at room temperature, and the target temperature of the fixing unit 30 is set to 150 ° C. suitable for room temperature accordingly. In the present embodiment, since the target temperature of 155 ° C. based on the correct environmental judgment (low temperature) is set, it is possible to prevent a decrease in fixability.

The print job started at 9:01 has been completed by 9:11, and has transitioned to the standby state at 9:11. Since the print execution time was as long as 10 minutes, the amount of residual heat remaining in the nip Np was large, and as shown in FIG. 15, the ambient temperature of the in-flight temperature sensor 80 remained elevated to the room temperature range, but FIG. As shown in d), the temperature of the sheet S in the tray 11 is still in the low temperature range.

In the environment determination process shown in FIG. 12, at 9:11, the detection result of the in-flight temperature sensor 80 is the threshold value th1 or more (“No” in step S1), not at the start of warm-up (“No” in step 4). Since it is not the start of the print operation (“No” in step S10), the environment determination is continued from the previous time (step S12), and the process proceeds to step S3.

In this previous continuation, the judgment at 9:09, in which the judgment was made in a situation where it can be detected correctly in the immediate vicinity before the present (9:11), the low temperature is taken over in the above example. As a result, the low temperature is written in the column of the environment determination result corresponding to 9:11 shown in FIG. Then, 155 ° C. is set as the target temperature corresponding to the low temperature. At each of the 9:12 and 9:13 time points, the same determination and setting as at the 9:11 time point is made.

Printing will start at 9:14. At this point in time, the temperature is almost the same as that shown in FIG. 14 (d). In the environment determination process shown in FIG. 12, at 9:14, the detection result of the in-flight temperature sensor 80 is the threshold value th1 or more (“No” in step S1), not at the start of warm-up (“No” in step 4). No ”), it is determined that it is the start of the printing operation (“Yes” in step S10), and it is determined whether or not the correction rotation time δrot is less than the threshold value th4 (step S11).

The belt rotation time t-rot in the above (Equation 1) is 10 minutes of the belt rotation time in the printing operation executed from 9:01 to 9:11, and the belt stop time t-stop. Will be 3 minutes between 9:11 and 14 minutes. The correction rotation time δrot is about 7.7 from the equation (1).

Since the correction rotation time δrot becomes the threshold value th4 or more (“No” in step S11), it is determined that the situation is erroneous detection, the environment determination is continued last time (step S12), and the process proceeds to step S3. In this previous continuation, the judgment at 9:09, which was in a situation where it can be correctly detected immediately before the present (9:14), and the low temperature in the above example are taken over. As a result, the low temperature is written in the column of the environment determination result corresponding to 9:14 shown in FIG. Then, 155 ° C. is set as the target temperature corresponding to the low temperature.

The print job started at 9:14 has been completed by 9:15, and has transitioned to the standby state at 9:15. Since the print execution time was within 1 minute, the ambient temperature of the in-flight temperature sensor 80 did not rise significantly as shown in FIG. 15, and was within the room temperature range.

In the environment determination process shown in FIG. 12, at 9:15, the detection result of the in-flight temperature sensor 80 is the threshold value th1 or more (“No” in step S1), not at the start of warm-up (“No” in step 4). Since it is not the start of the print operation (“No” in step S10), the environment determination is continued from the previous time (step S12), and the process proceeds to step S3. In this previous continuation, the judgment at 9:09, which was the situation that can be correctly detected immediately before the present (9:15), and the normal temperature in the above example are taken over.

After 9:15, the standby state continues, the ambient temperature of the in-flight temperature sensor 80 begins to decrease as shown in FIG. 15, and the ambient temperature of the in-flight temperature sensor 80 drops to the low temperature range at 9:30. During this period, the temperature of the sheet S in the tray 11 remains in the low temperature range as shown in FIGS. 14 (e) and 14 (f).

In the environment determination process shown in FIG. 12, at each time from 9:16 to 9:29, the same environment determination as at 9:15 is performed. At 9:30, the detection result of the in-flight temperature sensor 80 is less than the threshold value th1 (“Yes” in step S1), so the low temperature environment is determined based on the detection result of the in-flight temperature sensor 80 (step S2). , Step S3. The low temperature is written in the column of the environment judgment result corresponding to 9:30 shown in FIG. This determination is a determination in a situation where it can be detected correctly. Then, 155 ° C. is set as the target temperature corresponding to the low temperature. At each time after 9:31, the same environmental judgment as at 9:30 is made.

In the above, an example of the case where the environment of the printer 1 changes from the normal temperature to the low temperature in the standby state has been described, and the case where the environment changes from the low temperature to the normal temperature has not been illustrated, but in this case, it is as follows. That is, in the low temperature environment in the standby state, the detection result of the in-flight temperature sensor 80 is less than the threshold value th1 in the environment determination process shown in FIG. 12 (“Yes” in step S1). The low temperature environment is determined (step S2), and the process proceeds to step S3. While in a cold environment, the cold environment judgment continues.

When the environment is changed from the low temperature environment to the normal temperature environment, the detection result of the in-flight temperature sensor 80 becomes the threshold value th1 or more (“No” in step S1) in the environment determination process shown in FIG. 12, not at the start of warm-up (in step 4). Since it is not the start of the print operation (“No” in step S10), the environment determination is continued last time, and here, the temperature is set to low (step S12), and the process proceeds to step S3.

When the start of the print job is determined while in the normal temperature environment (“Yes” in step S10), it is determined whether or not the correction rotation time δrot is less than the threshold value th4 (step S11). In this example, the transition from low temperature to room temperature occurs in the standby state, and it takes a long time for the environment of the printer 1 to change as described above, so that the correction rotation time δrot is a small value. many. When the correction rotation time δrot is less than the threshold value th4 (“Yes” in step S11), the process proceeds to step S7, and “Yes” is determined in S7, so that the current environment is determined to be normal temperature in step S8. This determination is a determination in a situation where it can be detected correctly. Then, 150 ° C. is set as the target temperature corresponding to the room temperature.

Further, in the above, an example in which the printing operation is a double-sided printing job has been described, but even in a single-sided printing job, the inside of the machine is driven by the heat of the drive motor M1 or the like during printing in which a large number of sheets are continuously passed one by one. The periphery of the temperature sensor 80 may rise, and in this case as well, the environment is determined in the same manner as described above, and the target temperature of the fixing unit 30 is set to a temperature suitable for the determined environment.

As described above, in the present embodiment, when the environment is determined, it is determined whether or not the in-flight temperature sensor 80 is in a state where the environment of the printer 1 can be correctly detected according to the current residual heat of the nip Np. , (I) If it is determined that the situation can be detected correctly, the target temperature is set by using the current detection result of the in-flight temperature sensor 80 for the environment determination, and (ii) the situation cannot be detected correctly (erroneous detection). When the determination is made, the target temperature already set based on the environmental determination determined when the situation was correctly detected immediately before this determination is used as it is, without using the detection result of the in-flight temperature sensor 80. It was configured.

If the temperature in the peripheral area of the in-flight temperature sensor 80 temporarily rises due to the execution of a print job or warm-up, the temperature of the sheet S in the tray 11 does not immediately fluctuate significantly following this, and the printer does not. Even if there is a change in the surrounding environment of 1, it changes fairly slowly. Therefore, when there is a temporary temperature rise due to a print job or the like, even if the environment determined before the temperature rise occurs is taken over and used as it is, there is almost no difference from the actual environment temperature, and the temporary temperature. The judgment accuracy can be improved as compared with the environment judgment in the state where there is a rise.

If the detection result of the in-flight temperature sensor 80 is used in spite of the false detection situation, for example, if it is determined that the environment is a normal temperature environment instead of the actual low temperature environment, the fixability will be lowered. In the above mode, the target temperature of the fixing unit 30 can be set to a temperature more suitable for the environmental temperature by the existing in-flight temperature sensor 80, and thus the deterioration of the fixing property can be prevented.

In the above, an example of an image forming apparatus having a fixing portion has been described, but the present invention is not limited to this, and a method of setting a target temperature of the fixing portion may be used. Further, the method may be a program executed by a computer. The program according to the present disclosure includes, for example, magnetic tapes, magnetic disks such as flexible disks, optical recording media such as DVD-ROMs, DVD-RAMs, CD-ROMs, CD-Rs, MOs, and PDs, and flash memory recording media. It is possible to record on various computer-readable recording media such as, etc., and it may be produced or transferred in the form of the recording medium, or in the form of a program, various wired and wireless networks including the Internet. It may be transmitted and supplied via broadcasting, telecommunications lines, satellite communications, etc.

[8] Modified Examples Although the above description has been made based on the embodiments, the present disclosure is not limited to the above-described embodiments, and the following modified examples can be considered.

(8-1) In the above embodiment, at the start of printing in FIG. 12 (“Yes” in step S10), the correction rotation time δrot is set by using the above (Equation 1) with the belt 311 stopped. The desired example has been explained, but the present invention is not limited to this. For example, when the rotation of the belt 311 starts immediately before the start of printing, the time between the start of rotation of the belt 311 and the start of printing is compared with the case where the rotation of the belt 311 is started from the start of printing. This means that the amount of heat stored in the nip Np is increased by the amount of. In this case, the correction rotation time δrot may be obtained by using (Equation) in which the time is added to the right side of (Equation 1).

Further, instead of the method using (Equation 1), for example, the relationship between the belt rotation time t-rot, the belt stop time t-stop, and the correction rotation time δrot shown in the graph of FIG. 6 is managed by tabular data, and the relationship thereof is managed. It is also possible to obtain the correction rotation time δrot by referring to the data.

(8-2) In the above embodiment, the environmental temperature of the printer 1 is divided into three categories of low temperature, normal temperature, and high temperature, but the present invention is not limited to this, and a plurality of different environmental temperatures such as a low temperature range and a higher temperature range are used. It may be divided into temperature ranges. When the in-flight temperature sensor 80 detects the lowest temperature range, it is determined that the situation can be detected correctly, and when other temperature ranges are detected, it is a situation where it can be detected correctly or a situation where it is erroneously detected. Can be controlled to determine.

(8-3) In the above embodiment, the target temperature of the fixing unit 30 is added to the standard of the normal temperature environment according to the result of the environment determination of the printer 1, and the target temperature is added by 5 ° C. in the case of the low temperature environment. In the case of a high temperature environment, the correction is made to subtract the target temperature by 5 ° C., but the addition value and the subtraction value are not limited to 5 ° C., and may have other sizes.

Further, instead of correcting the target temperature of the fixing portion 30, for example, the rotation speed of the pressurizing roller 32 according to the environmental determination result of the printer 1, that is, the transport speed of the sheet S by the pressurizing roller 32 (sheet transport speed). You can also take control to change. This control is performed by variably controlling the rotation speed of the drive motor M2. When the environment determination is low temperature, the rotation speed of the pressurizing roller 32 is controlled to be slowed down by a predetermined value with respect to the reference speed in the normal temperature environment.

FIG. 16 is a diagram showing a configuration example of the fixing control unit 615 according to this modification, and instead of the target temperature setting unit 612 of the fixing control unit 610 shown in FIG. 9, the transfer speed setting unit 616 and the transfer control unit 617 are shown. The difference is that and is provided. The heater control unit 614 controls the heater 314 so that the temperature of the belt 311 is maintained at a predetermined target temperature based on the temperature detection result of the belt temperature sensor 315.

The transport speed setting unit 616 sets the rotation speed of the pressurizing roller 32, that is, which speed the sheet transport speed should be, according to the environment determination result of the printer 1 by the environment determination unit 611.

The transfer control unit 617 controls the rotation of the drive motor M2 so that the pressurizing roller 32 rotates at a rotation speed corresponding to the set sheet transfer speed. Here, as shown in FIG. 17, based on the sheet transport speed in a normal temperature environment, the control is performed at a speed slower than the standard in a low temperature environment, and controlled at a high speed faster than the standard in a high temperature environment.

By lowering the sheet transfer speed in a low temperature environment, the amount of heat supplied per unit time to the sheet S passing through the nip Np can be increased more than the reference speed with respect to room temperature, which is suitable for the low temperature sheet S. It is possible to perform heat fixing. In the case of a high temperature environment, the opposite is true in the case of a low temperature environment. The information indicating the correspondence between the environment determination result shown in FIG. 17 and the sheet transport speed is stored in advance, and the reference and each speed value of low speed and high speed are set in advance by an experiment or the like.

The pressure roller 32 has a function of a transport member for transporting the sheet S, and the transport control unit 617 serves as a transport member so that the sheet S is transported at the sheet transport speed set by the transport speed setting unit 616. A control unit that controls the rotation of the pressurizing roller 32 is configured. In the above description, a configuration example in which the pressure roller 32 is the drive side and the belt 311 is the driven side has been described. On the contrary, when the belt 311 is the drive side and the pressure roller 32 is the driven side, The rotation of the belt 311 can be controlled as a transport member for the sheet passing through the fixing portion 30.

Further, instead of adjusting the sheet transport speed, for example, after the rear end of the Nth sheet S in the transport direction passes through the nip Np of the fixing portion 30, the tip of the (N + 1) th sheet S in the transport direction It is also possible to adjust the time required to reach the nip Np, that is, the so-called paper spacing. In this paper-to-paper adjustment, the target temperature of the fixing portion 30 is constant, the sheet transfer speed is constant, and the paper-to-paper spacing is longer than the reference when it is determined to be a low-temperature environment based on the paper-to-paper spacing in a room temperature environment. This can be achieved by controlling the transfer of the sheet so that the time is reached, and when it is determined that the environment is high temperature, the sheet is conveyed and controlled so that the time between papers is shorter than the standard time.

It should be noted that at least one of the setting of the sheet transport speed and the setting of the paper spacing can be added to the temperature control control according to the embodiment in which the target temperature of the fixing unit 30 is set.

(8-4) In the above embodiment, it is assumed that each information of the past operating state, the in-flight detection result, the environment determination result, and the target temperature is stored in the backup memory 613 as a storage unit included in the CPU 61 of the overall control unit 60. However, it is not limited to this. It suffices if each of these pieces of information can be acquired. For example, the information stored in a removable portable memory can be read out and used, or the information can be transmitted to an external terminal device, for example, a server, and stored. , It may be configured to receive from the external terminal via the network at the time of acquisition.

Further, although each of the above information is written to the backup memory 613 every minute, it is not limited to 1 minute, and is different, for example, a fixed time interval such as 30 seconds or 2 minutes, or alternately repeating 30 seconds and 1 minute. It can be at each time point of a predetermined time interval including a time interval and the like.

Further, although it is assumed that all the information for each minute is stored, the present invention is not limited to this, and for example, a configuration in which only the information at the time immediately preceding the present is stored may be used. In this configuration, the information at the time immediately before that is inherited from the environment judgment result determined in the most recently correctly detectable situation. Further, the belt rotation time t-rot and the belt stop time t-stop may be managed separately or may be included in the information at the immediately preceding time.

(8-5) In the above embodiment, a configuration example is described in which an environmental parameter (factor) indicating the environment of the printer 1 is set as an environmental temperature, and the in-flight temperature sensor 80 is a sensor that detects its own ambient temperature as an ambient temperature parameter. However, it is not limited to this, and the environmental humidity may be used.

In the example of environmental humidity, an in-flight humidity sensor that detects the humidity around the sensor is used instead of the in-flight temperature sensor 80. Environmental humidity, like environmental temperature, can affect processes such as charging, developing, and transferring, and control values for charging, developing, transferring, etc. (charging current, developing bias, transfer current, etc.) according to changes in environmental humidity. Is adjusted to a value according to the magnitude of the environmental humidity, which leads to improvement in the image quality of the formed image. Further, the water content of the sheet S may change due to the change in humidity, and the fixability may change due to the change in the water content of the sheet S.

Normally, in a low humidity environment, the moisture absorption (water content) of the sheet S in the tray 11 is also small, but in the case of double-sided printing, water vapor may be released from the sheet S after heat fixing to the first surface. After heat fixing to the first surface, when the sheet S on which water vapor is released switches back, passes through the double-sided transfer path of the double-sided transfer section 50, and reaches the secondary transfer position 29 again, the water vapor is still released. However, if the detection result of the in-flight humidity sensor is temporarily improved, it may differ from the actual low humidity environment of the printer 1.

After the completion of double-sided printing, if the ambient temperature of the in-flight humidity sensor decreases as the amount of residual heat remaining in the nip Np decreases, the humidity usually decreases as the temperature decreases. Can be said to be an index of the ambient humidity of the in-flight humidity sensor. Therefore, by replacing the temperature in the embodiment with the humidity, the accuracy of determining the environmental humidity can be improved.

(8-6) In the above embodiment, an example in which the image forming apparatus according to the present disclosure is applied to a tandem color printer has been described, but the present invention is not limited to this. It has a heating rotating body such as a belt 311 and a pressing member such as a pressurizing roller 32, and the pressurizing member presses against the heating rotating body to form a nip Np between the heating rotating body and the pressurizing member. It can be applied to a fixing portion for heat fixing by passing a sheet S through the sheet and an image forming apparatus provided with the fixing portion.

The image forming apparatus can be applied to those capable of performing color image formation and those capable of performing only monochrome image formation, and is not limited to printers, and is not limited to printers, for example, images of copiers, facsimile machines, MFPs (Multiple Function Peripheral), and the like. Applicable to forming equipment. The pressure member is not limited to a rotating body such as the pressure roller 32, and a non-rotating body such as a pressure pad fixed to the frame of the device can also be used.

Further, the heating rotating body is not limited to the belt shape, and may be, for example, a roller shape. In this case, similarly to the belt-shaped configuration, the heater 314 is located in a region of one circumference of the roller-shaped heating rotating body that is separated from the nip Np in the rotation direction (at a position different from the nip Np in the rotation direction). It is placed in a position to heat the existing part).

The size, shape, material, number, etc. of each of the above members are examples, and a suitable size, shape, material, number, etc. are determined in advance according to the device configuration. Further, as long as the formula can obtain an index value for indexing the amount of heat stored in the nip Np, the formula is not limited to the above (formula 1), and another formula may be used.

Further, the contents of the above-described embodiment and the above-described modification may be combined as much as possible. To the extent that the effects of the present disclosure can be obtained, the mechanism of each part such as the fixing portion and each member may be applied instead of another mechanism or a member having a different shape.

The present disclosure can be widely applied to an image forming apparatus having a fixing portion.

1 Printer 20 Image-creating unit 30 Fixing unit 31 Heating unit 32 Pressurizing roller 60 Overall control unit 61 CPU
80 In-flight temperature sensor 311 Fixing belt 314 Heater 315 Belt temperature sensor (temperature detection means)
611 Environmental judgment unit 612 Target temperature setting unit 613 Backup memory (storage unit)
614 Heater control unit 616 Transfer speed setting unit 617 Transfer control unit Np Nip S Recording sheet th3 Threshold (predetermined value)
th4 threshold

Claims (15)

An image forming apparatus that heat-fixes an image on a sheet at a fixing portion.
A setting unit that sets the target temperature of the fixing unit and
A control unit that controls the temperature of the fixing unit based on the set target temperature,
A sensor that is placed inside the image forming device and detects the temperature or humidity around you,
A determination unit that determines whether or not the sensor is in a state where it can correctly detect the environmental temperature or the environmental humidity of the image forming apparatus.
With
When the determination is positive, the setting unit sets the target temperature of the fixing unit based on the detection result of the sensor, and when the determination is negative, the setting unit is set based on the most recent positive determination before the determination. An image forming apparatus characterized in that the target temperature is set as the target temperature of the fixing portion. In the fixing portion, a pressure member is pressed against a heating rotating body to form a nip between the two, and a sheet is passed through the nip to perform the heat fixing.
The determination unit makes a positive determination when the index value for indexing the heat storage amount of the nip is less than the threshold value at a predetermined timing for setting the target temperature of the fixing unit, and negatively when the index value is equal to or more than the threshold value. The image forming apparatus according to claim 1, wherein the image forming apparatus is characterized in that the determination is performed. The image forming apparatus according to claim 2, wherein the predetermined timing is at the start of an image forming job for forming an image on a sheet. The index value is obtained from the stop time of the heating rotating body before the predetermined timing and the rotation time of the heating rotating body before the stop, and the longer the rotation time and the shorter the stop time, the larger the value. The image forming apparatus according to claim 3, wherein the shorter the rotation time and the longer the stop time, the smaller the value. Further, it has a storage unit that stores the rotation time and the stop time of the heating rotating body.
The image forming apparatus according to claim 4, wherein the determination unit reads out the rotation time and the stop time from the storage unit. The fixing portion includes a heater for heating the heating rotating body.
The heating rotating body is an endless belt that orbits.
The control unit controls the calorific value of the heater so that the temperature of the fixing unit reaches the target temperature.
The heater according to any one of claims 2 to 5, wherein the heater heats a region of one circumference of the belt that is separated from the nip that is in pressure contact with the pressurizing member in the circumferential direction. The image forming apparatus according to the description. Further, it has a temperature detecting means for detecting the temperature of the heating rotating body.
The predetermined timing is the start of warm-up of the image forming apparatus.
The image forming apparatus according to claim 2, wherein the index value is a detection result of the temperature detecting means at the start of warm-up. The predetermined timings are at each time point of a predetermined time interval while waiting for an image forming job for forming an image on a sheet.
The image forming apparatus according to claim 2, wherein the index value is a detection result of the sensor at each time point. The sensor detects the temperature and
The determination unit
Of the first temperature range and the second temperature range higher than this, when the detection result of the sensor is the first temperature range, a positive determination is uniformly made, and in the second temperature range. The image forming apparatus according to any one of claims 1 to 8, wherein in some cases, one of positive and negative determinations is made. The image forming apparatus according to claim 9, wherein the first temperature range is a low temperature range, and the second temperature range is a room temperature range or a high temperature range. In addition, the sheet is equipped with an image-forming unit that forms an image.
The image forming apparatus according to any one of claims 1 to 10, wherein the sensor is inside the image forming apparatus and is arranged around the image forming portion. In addition, a tray for accommodating sheets and
A feeding unit for feeding the sheets housed in the tray to the image forming unit is provided.
The image forming apparatus according to claim 11, wherein the fixing portion is arranged above the image forming portion, and the tray is arranged below the image forming portion. An image forming apparatus that heat-fixes an image on a sheet at a fixing portion.
A sensor that is placed inside the image forming device and detects its own surrounding environment,
If it is determined to be positive whether or not the sensor is in a state where the environment of the image forming apparatus can be correctly detected, the environment of the image forming apparatus is determined based on the detection result of the sensor, and if it is determined to be negative, the environment is determined. A determination unit that determines the environment determined based on the detection result of the sensor when the most recent positive determination is made before the determination is the environment of the current image forming apparatus.
An image forming apparatus comprising. A setting unit that sets a target temperature of the fixing unit based on the determination result of the determination unit, and a setting unit.
A control unit that controls the temperature of the fixing unit based on the set target temperature,
13. The image forming apparatus according to claim 13. A transport member that transports the sheet that passes through the fixing portion, and
A setting unit that sets the sheet transfer speed based on the determination result of the determination unit, and
A control unit that controls the transfer member so that the sheet is transferred at a set transfer speed, and
13. The image forming apparatus according to claim 13.

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