JP4311645B2 - Image forming apparatus - Google Patents

Description

The present invention relates to an image forming apparatus that forms a toner image on a sheet based on image data and fixes a toner image on the sheet to the sheet using a fixing roller .

  In recent years, it has become important to improve the energy consumption efficiency of equipment for the purpose of environmental conservation. Also, for the user side, the energy consumption of the device when not in use is economically wasteful.

  Therefore, in recent years, even in an image forming apparatus such as a composite apparatus (multifunction apparatus) having a plurality of functions such as a copying apparatus, a facsimile apparatus, a printer and a copy function, a facsimile function, and a printer function, the power energy consumption efficiency has been improved. Many image forming apparatuses have a fixing heater with a short warm-up time from the viewpoint of improving operability / convenience.

  In order to shorten the warm-up time, conventionally, a thin fixing roller having a small heat capacity and a low thermal resistance is used, and a high-power halogen heater or a plurality (2) are used as a heating source for heating the fixing roller. This) halogen heaters are often used.

  Since the fixing device with a short warm-up time uses a fixing roller having a small capacity and a low thermal resistance, the state greatly varies depending on the environmental variation and the size, thickness, and type of the paper to be passed.

  Therefore, the present applicant has previously proposed a heater temperature control method in which a data table is searched from the control temperature and detected temperature of the fixing roller, and the lighting interval of the heater for heating the fixing roller is determined from the search result of the data table. (See Patent Document 1).

  In other words, this conventional technique suppresses the influence of external factors such as environmental fluctuations that affect the temperature change of the fixing roller and the size, thickness, and type of the paper to be passed without using complicated control, and the fixing roller. I am trying to control the temperature.

JP-A-7-175363

  However, in the above prior art, since the table reference method with high visibility is used, it is possible to improve the maintainability while having a high application capability against changes in various conditions, but it is more efficient. In order to improve the image quality by controlling the temperature of the fixing member precisely and precisely, there is a need for improvement.

  In other words, in order to comply with the standards and regulations such as flicker in Europe in recent years and to extend the life of the heater, the heater lighting interval during standby when printing is not performed is increased (the heater changes from off to on and from on to off). Request to reduce the number of times) has been generated.

  Therefore, conventionally, in an electrophotographic image forming apparatus, for example, the data table used when the heater for heating the fixing member is turned on is different from the data table used when the heater is turned off, and the control temperature is not changed. Hysteresis is provided to reduce the number of on / off switching operations.

  However, reducing the heater on / off switching interval is effective in extending the life of the heater, but as a side effect, there is a problem that the fixing temperature fluctuates greatly, and the temperature is high. Therefore, there is a problem that the image quality is deteriorated because the fixability of the first sheet is different between when printing is started and when printing is started from a low state.

The present invention has been made in view of such circumstances, and provides an image forming apparatus capable of reducing the number of times the fixing heater is turned on and off in a standby state and making the fixing property of the first printed matter constant. The purpose is that.

The present invention is an image forming apparatus for forming a toner image on a sheet based on image data and fixing the toner image on the sheet to the sheet using a fixing roller, and a fixing heater for heating the fixing roller; The temperature detection means for detecting the temperature of the fixing roller, and whether the fixing heater is turned on or off in the next control cycle when the fixing heater is on in a certain control cycle. A heater-on lighting determination table determined in correspondence with the difference between the control temperature target value of the fixing roller and the detected value of the temperature detecting means, and the next control cycle when the fixing heater is off in a certain control cycle Whether to turn on or off the fixing heater in accordance with the difference between the control temperature target value of the fixing roller and the detected value of the temperature detecting means. A heater-off lighting determination table that is set to turn on the fixing heater in the next control cycle from when the detected value of the temperature detection means is lower than the on-time lighting determination table; In the standby state of the apparatus, the fixing heater is controlled by hysteresis to control its lighting driving, and (a) when the fixing heater is turned on in a certain control cycle every predetermined control cycle. Based on the difference between the control temperature target value of the fixing roller and the detected value of the temperature detecting means, it is determined whether the fixing heater is turned on or off according to the contents of the heater-on lighting determination table. Then, in the next control cycle, the fixing heater is turned on in the determined ON state or OFF state, and (b) the fixing heater is turned OFF in a certain control cycle. When the fixing heater is turned on or off based on the difference between the control temperature target value of the fixing roller and the detected value of the temperature detecting means according to the contents of the heater-off lighting determination table. And the first control means for lighting the fixing heater in the determined ON state or OFF state in the next control cycle.

In such an image forming apparatus, the fixing heater includes a first fixing heater that heats an axial center portion of the fixing roller, and a second fixing heater that heats an axial end portion of the fixing roller. The temperature detecting means includes first temperature detecting means for detecting the temperature at the axial center of the fixing roller, and second temperature detecting means for detecting the temperature at the axial end of the fixing roller. And the difference between the control temperature target value at the axial center of the fixing roller and the detection value of the first temperature detecting means, and the control temperature target value at the axial end of the fixing roller and the second A fixing heater selection table for selecting one of the first fixing heater and the second fixing heater to be used according to the difference between the detected value of the temperature detecting means and the control means. In the standby state of the device, (a For each control cycle, the difference between the control temperature target value at the axial center of the fixing roller and the detection value of the first temperature detection means, and the control temperature target value at the axial end of the fixing roller Based on the difference between the detected value of the second temperature detecting means and the fixing heater selection table, either the first fixing heater or the second fixing heater is used in the next control cycle. (B) When the selected fixing heater is turned on in a certain control cycle, the fixing heater is turned on based on the difference between the control temperature target value of the fixing heater and the detected value of the temperature detecting means. Determine whether the selected fixing heater is to be turned on or off according to the contents of the heater-on lighting determination table, and select the selected on-state or off-state in the next control cycle. (C) when the selected fixing heater is turned off in a certain control cycle, based on the difference between the control temperature target value of the fixing heater and the detected value of the temperature detecting means, In accordance with the contents of the heater-off lighting determination table, it is determined whether the selected fixing heater is to be turned on or off, and in the next control cycle, the selected fixing is performed in the determined on-state or off-state. It is preferable that the heater is driven to turn on.

Further, the following control is performed in correspondence with the difference between the control temperature target value of the fixing roller and the detection value of the temperature detection means, and the difference between the previous detection time and the current detection time of the detection value of the temperature detection means. In a normal operation lighting duty determination table that determines the lighting duty of the fixing heater in a cycle, and in a normal operation state that shifts when a function start condition for use with image formation occurs in the standby state of the apparatus, the fixing heater is turned off. Hysteresis control to control the lighting drive, and for each control cycle, the difference between the control temperature target value of the fixing roller and the detected value of the temperature detecting means, and the detected value of the temperature detecting means Based on the difference between the previous detection time and the current detection time, the lighting duty is determined in accordance with the contents of the normal operation lighting duty determination table, and it is changed to the next control cycle. The determined turn-on duty may further comprise a second control means for driving and lighting the fixing heater.

Such an image forming apparatus includes a copy function and operation means for performing various key operations. In the standby state, as the use start condition, copying such as a key operation on the operation means and a document setting operation is performed. When an operation indicating the start of use of the function is detected, the standby state may be shifted to the normal operation state.
Such an image forming apparatus has a facsimile function. In the standby state, when facsimile reception is detected as the use start condition, the standby state may be shifted to the normal operation state.
Such an image forming apparatus has a printer function, and in the standby state, when a print request is detected as the use start condition, the standby state may be shifted to the normal operation state.

According to the image forming apparatus of the present invention as described above, it is possible to reduce the number of times the fixing heater is turned on and off in the standby state, and to obtain an effect that the fixability of the first printed matter can be made constant.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In addition, since the Example described below is a suitable Example of this invention, various technically preferable restrictions are attached | subjected, However, The scope of the present invention limits this invention especially in the following description. As long as there is no description of the effect, it is not restricted to these aspects.

  1 to 12 are diagrams showing an embodiment of an image forming apparatus according to the present invention. FIG. 1 is a schematic front view of an image forming apparatus 1 to which an embodiment of the image forming apparatus according to the present invention is applied. is there.

  In FIG. 1, the image forming apparatus 1 has a main body housing 3 mounted on an upper portion of a paper feed unit 2, and a plurality of paper feed cassettes 4a and 4b in FIG. Is stored.

  Further, in the main body casing 3, a paper feed cassette 5 is accommodated in the lowermost part, and an image forming unit 6 is disposed in the upper part of the paper feed cassette. A transfer paper stack 7 for stacking image-formed transfer papers is disposed above the image forming unit 6 in the main body housing 3, and a reading for reading an image of a document is provided above the transfer paper stack 7. A unit 8 and an operation display unit 9 for performing various operations are provided.

  A plurality of transfer sheets can be stored in each of the sheet feed cassettes 4 a and 4 b of the sheet feed unit 2 and the sheet feed cassette 5 in the main body housing 3, and each sheet feed cassette 5 can transfer different sheet sizes. Paper can be stored. The transfer paper in each of the paper feed cassettes 4a and 4b of the paper feed unit 2 is transported to the image forming unit 6 of the main body housing 3 by a paper transport mechanism (not shown).

  The paper feed cassette 5 in the main body housing 3 is provided with a paper feed roller 5 a, and the paper feed roller 5 a sends the transfer paper in the paper feed cassette 5 to the image forming unit 6.

  Further, a manual feed tray 10 is provided on the side surface of the main body housing 3. The manual feed tray 10 is provided with a manual paper feed roller 10 a, and manually feeds transfer paper set on the manual feed tray 10. A paper roller 10 a feeds the image forming unit 6.

  The reading unit 8 performs main scanning of the document by photoelectrically converting the reflected light of the reading light irradiated from the light source to the document by a photoelectric conversion element such as a CCD (Charge Coupled Device) as the light source and the document relatively move. And the sub-scan is performed to read the image of the document.

  The operation display unit 9 includes various operation keys necessary for operating the image forming apparatus 1 such as a numeric keypad and a start key, and uses an LCD (Liquid Crystal Display), an LED (Light Emitting Diode), 7seg, and the like. A display (for example, a liquid crystal display) is provided for displaying the operation contents of the operation keys and various types of information notified from the image forming apparatus 1 to the operator.

  In the image forming unit 6, as shown in FIG. 2, a charging roller 21, a developing unit 22, and a transfer roller 23 are disposed around the photoconductor 20, and transfer is performed between the photoconductor 20 and the transfer roller 23. A registration sensor 25 is disposed in the paper conveyance path 24 for conveying the paper, in front of the transfer direction of the transfer paper of a registration roller (not shown), and the paper feed cassettes 4a, 4b, 5 and The transfer paper from the manual feed tray 10 is conveyed between the photoconductor 20 and the transfer roller 23 via a registration roller.

  A fixing unit 26 is disposed on the downstream side of the photoconductor 20 in the transfer sheet conveyance direction. The fixing unit 26 includes a fixing roller 27 and a pressure roller 28.

  The developing unit 23 includes a toner case 30 that stores toner and a magnet roller 31 and an agitator 32 that face the photoreceptor 20. A toner bottle that stores replenishment toner is stored in the toner case 30. The toner is supplied from 33. Further, a toner sensor 34 for detecting the remaining amount of toner in the toner case 30 is attached to the lower surface of the toner case 30. When the toner is in the toner case 30, for example, When the toner level becomes “High (H)” and there is no toner in the toner case 30, a toner detection signal that becomes “Low (L)” is output. The developing unit 23 frictionally charges the toner in the toner case 30 when the agitator 32 stirs, and the charged toner is supplied to the photoconductor 20 by the mag roller 31, whereby the electrostatic latent image on the photoconductor 20. Develop.

  The photosensitive member 20, the charging roller 21, and the developing unit 23 are housed in a cartridge case (not shown) as a whole and configured as a toner cartridge 40, and each toner cartridge 40 can be replaced.

  The registration sensor 25 detects the leading edge of the transfer paper conveyed from the manual feed tray 10 and the paper state, and the image forming apparatus 1 detects the detection result of the registration sensor 25 and the formation position of the toner image on the photoconductor 20. The registration roller is driven so that the leading edge of the toner image on the photosensitive member 20 and the leading edge of the transfer paper are synchronized with each other at the contact position between the photosensitive member 20 and the transfer roller 23, and the fixing roller 23 causes The toner image is transferred to transfer paper.

  The image forming unit 6 rotates the photosensitive member 20 in the clockwise direction in FIG. 2 by a motor (not shown), is uniformly charged by the charging roller 21, and is based on image data by an optical writing unit (not shown). An electrostatic latent image is formed on the photoconductor 20 by irradiation with the modulated laser beam. The image forming unit 6 develops toner by supplying toner from the developing unit 23 to the photosensitive member 20 on which the electrostatic latent image is formed, forms a toner image on the photosensitive member 20, and transfers the toner image by rotation of the photosensitive member 20. At the timing when the tip of the toner image comes to the position of the roller 23, the transfer paper is conveyed to the transfer roller 23 by the registration roller, and the toner image on the photoconductor 20 is transferred to the transfer paper by the transfer roller 23.

  The image forming unit 6 conveys the transfer sheet on which the toner image has been transferred to the fixing unit 26, and is heated to the fixing temperature while conveying the transfer sheet by the fixing roller 27 and the pressure roller 28 of the fixing unit 26. The toner image on the transfer paper is fixed on the transfer paper by being heated by the fixing roller 27, and is discharged to the transfer paper stack 7 in FIG.

  As shown in FIG. 3, the image forming apparatus 1 has a circuit block configuration, and includes a system control unit 50, a reading control unit 51, the operation display unit 9, a writing control unit 52, an I / O control unit 53, The toner sensor 34, various image forming I / Os 54, a high-voltage power supply unit 55, and the like are provided.

  The reading control unit 51 controls the operation of the reading unit 8. The reading control unit 51 mainly controls the operation and timing control of a photoelectric conversion element such as a CCD, and outputs an image signal of a document photoelectrically converted by the photoelectric conversion element. It converts into a digital signal and outputs it to the system control part 50 as image data.

  In the system control unit 50, the power of the CPU (Central Processing Unit), the ROM (Read Only Memory) for storing programs and various system data, the RAM (Random Access Memory) used as work memory, and the image forming apparatus 1 are turned off. The image forming apparatus 1 as a whole is provided with a non-volatile RAM and a calendar function chip that store data that needs to be stored, and the CPU uses the RAM as a work memory based on a program in the ROM. Timing control, data input / output control of the operation display unit 9, other I / F and operation control with applications (applications such as facsimile, printer, scanner, etc.) not shown, image processing of image data (magnification processing, Filtering, γ processing, etc.) and image data storage / reading using an image memory (not shown) For your like it is performed. The system control unit 50 also controls the operation display unit 9.

  The writing control unit 52 controls the operation of an LD (Laser Diode) of the optical writing unit (not shown) and its drive circuit, and irradiates the photoconductor 20 with laser light modulated based on the image data. An electrostatic latent image is formed on 20.

  The I / O control unit 53 is an aggregation part of various sensors such as the reading unit 8 and the image forming unit 6, input signals of actuators, and output signals of motors, solenoids, clutches, high-voltage power supplies, and the like. And the output of each thermistor, paper presence / absence information of the paper feed trays 4a, 4b, 5 and manual feed tray 10, size information, the output of the registration sensor 25 for transferring the transfer paper, and various image forming I / O 54. The digital signal is digitally converted by an ADC (analog / digital converter) and output to the system control unit 50. The system control unit 50 performs various controls based on various signals input from the I / O control unit 53.

  The high-voltage power supply unit 55 rectifies, smoothes, and steps down the commercial power supply to generate various DC power supplies used in the image forming apparatus 1, heater power supplies for turning on the fixing heaters of the fixing unit 26, and the like.

  As shown in FIG. 4, AC (alternating current) commercial power is supplied to the high-voltage power source 55 from the outside, and a halogen heater (C) 60 a and a halogen heater (E) 60 b as fixing heaters of the fixing unit 26. Is connected. The halogen heater (C) 60a and the halogen heater (E) 60b are energized from the high voltage power supply 55 to generate heat, thereby heating the fixing roller 27. The halogen heater (C) 60a is in the axial direction of the fixing roller 27. The central portion has a high light distribution and heats the central portion in the axial direction of the fixing roller 27. The halogen heater (E) 60b has a high light distribution at the axial end portion of the fixing roller 27 and the axial end portion of the fixing roller 27. Heat.

  As described above, the high-voltage power supply unit 55 includes a circuit for supplying various power supplies of the image forming apparatus 1 and drives the halogen heater (C) 60a and the halogen heater (E) 60b that are fixing heaters. The heater drive circuit includes a relay for AC power cutoff and a triac circuit that is turned on / off at a specific cycle in order to control the AC output.

  A relay signal and a trigger signal are input from the I / O control unit 53 to the high voltage power supply unit 55, and a zero cross signal is output from the high voltage power supply unit 55 to the I / O control unit 53. This zero cross signal has AC (alternating current) because the heater power output to the halogen heater (C) 60a and halogen heater (E) 60b is AC (alternating current). This is a signal that detects the moment when the heater power supply becomes 0V. Then, under the control of the system control unit 50, the high voltage power supply unit 55 supplies the halogen heater (C) 60a and the halogen heater (E) 60b based on the relay signal and trigger signal input from the I / O control unit 53, respectively. Drive on / off independently.

  Then, when the standby state continues for a preset waiting time, the image forming apparatus 1 shifts to a power saving mode for reducing power consumption, and the system control unit 50 performs high voltage via the I / O control unit 53. The energization of the halogen heater (C) 60a and the halogen heater (E) 60b by the power supply unit 55 is controlled to lower the temperature of the fixing roller 27, or to the halogen heater (C) 60a and the halogen heater (E) 60b. Stop energization. When the fixing roller 27 shifts to the power saving mode or the image forming apparatus 1 is turned off, the surface temperature decreases to, for example, about room temperature, and when the power is turned on or the power saving mode is restored. The halogen heater (C) 60a and the halogen heater (E) 60b are turned on to raise the temperature of the fixing roller 27.

  On the other hand, the temperature of the fixing roller 27 is detected by the fixing thermistor 61 a and the fixing thermistor 61 b as temperature detecting means, and is input to the system control unit 50 via the I / O control unit 53. As the fixing thermistor 61a and the fixing thermistor 61b, for example, a contact thermistor is used. The fixing thermistor 61a detects the temperature of the central portion in the axial direction of the fixing roller 27, and the fixing thermistor 61b The temperature at the axial end is detected.

  The axially central portion of the fixing roller 27 that is heated by the halogen heater (C) 60a and detected by the fixing thermistor 61a is transferred at a small size (for example, postcard, HLT, etc.). A small size transfer paper passing position through which the paper passes and the axial end of the fixing roller 27 detected by the fixing thermistor 61b heated by the halogen heater (C) 60b is a large size (for example, A3 size). This is the large-size transfer paper passing position in the vicinity of the roller bearing portion through which the portion of the large-size transfer paper beyond the small size region passes during transfer of the transfer paper.

  When the fixing roller 27 is a thin-walled roller and the small-size transfer paper is continuously fed, if the temperature control of the fixing roller 27 is performed based on the detection result of only the fixing thermistor 61a at the center of the fixing roller 27, Since the transfer paper is not passed through the end portion of the fixing roller 27, the bearing portion of the fixing roller 27 is in an excessively raised state.

  Next, the operation of this embodiment will be described. First, temperature control of the fixing roller 27 by the image forming apparatus 1, that is, energization control of the halogen heater (C) 29a and the halogen heater (E) 29b will be described.

  Since the halogen heater (C) 29a and the halogen heater (E) 29b consume a large amount of power, when switching from off to on, the high voltage power supply unit 55 suddenly changes to the halogen heater (C) 29a and the halogen heater (E) 29b. When 100% power supply is performed, the power supply voltage fluctuates, causing the light source of the reading unit 8 to flicker. Therefore, the high voltage power supply unit 55 performs a soft start control process for gradually increasing the energization power to the halogen heater (C) 29a and the halogen heater (E) 29b to prevent a sudden power fluctuation.

  That is, the heater power supplied from the high-voltage power supply 55 to the halogen heater (C) 29a and the halogen heater (E) 29b is alternating current as shown in FIG. 5, and the instantaneous voltage value is constantly changing. Then, the high voltage power supply 55 detects the moment when the heater power supply voltage becomes 0 V and notifies the system controller 50 via the I / O controller 53 as a zero cross signal, as shown by hatching in FIG. The soft start process is performed by changing the output for each period (half wave) from 0 V to 0 V, and finally, the output that becomes 100% in the entire half wave period is performed.

  Further, the halogen heater (C) 29a and the halogen heater (E) 29b are control systems having a large system delay, and whether or not energization to the halogen heater (C) 29a and the halogen heater (E) 29b is performed. Whether the light is turned on or off is determined based on the temperature detected by the fixing thermistors 61a and 61b on the fixing roller 27. The halogen heater (C) 29a and the halogen heater (E) 29b are turned on and the halogen heater (C ) 29a and the halogen heater (E) 29b are turned on to raise the temperature of the fixing roller 27, the detected temperatures of the fixing thermistors 61a and 61b are raised, and the detected temperature values of the fixing thermistors 61a and 61b are set to the I / O control unit. The system control unit 50 captures the temperature via 53 and detects the temperature. Therefore, the fluctuation of the heat of the fixing roller 27 by the halogen heater (C) 29a and the halogen heater (E) 29b that are currently lit cannot be detected until several tens of ms to several hundreds of ms later.

  Since the control system of the halogen heater (C) 29a and the halogen heater (E) 29b has such a large delay characteristic, the halogen heater (C) 29a and the halogen heater (E) 29b are turned on. In order to determine whether to turn off the light, the temperature control ripple increases unless a certain time interval is exceeded, and appropriate control cannot be performed. Therefore, in the image forming apparatus 1 of the present embodiment, the following description will be made assuming that the fixing heater control interval is 1 second.

  Then, the control state of the fixing heater (halogen heater (C) 29a, halogen heater (E) 29b) for 1 second is determined at a certain point in time. The determined control is performed no matter how the detected temperature changes during the one second. There are various parameters that determine the control state of the fixing heater (how long it will be lit during one second?). For example, as a factor, the central detection temperature at the previous control, the current central detection temperature, the central control The following are used as parameters using the temperature, the end detection temperature at the previous control, the current end detection temperature, and the end control temperature.

Parameter example:
(Current center detection temperature-previous center detection temperature)
(Central control temperature-Current center detection temperature)
(Current edge detection temperature-previous edge detection temperature)
(Edge control temperature-current edge detection temperature)
When lighting control of one halogen heater (C) 29a or halogen heater (E) 29b is performed, two types of these parameters are selected, and a lighting control table (image formation time point, etc.) illustrated in FIG. The vertical axis and the horizontal axis of the interval table) are determined, and the value of the intersection point on the selected lighting control table is set as a ratio of the time during which the fixing heater is turned on in one second (heater lighting duty (Duty)). For example, when 30% of a 1 second period is lit, the second half of 1 second is 0.3 second, the fixing heater is turned on, and the soft start control is performed when the fixing heater is switched from OFF to ON. Process.

  That is, as shown in FIG. 7, when the fixing heater is turned on only for the periods indicated by%, the soft start control process is performed as shown by the diagonal lines in FIG.

  As described above, in order to control one fixing heater, it is possible to control if there is at least one lighting control table. However, when the control is changed depending on the state of the image forming apparatus 1 such as in operation or standby. The lighting control can be changed simply by preparing a lighting control table corresponding to each state and switching the lighting control table depending on the state of the image forming apparatus 1.

  When there are two fixing heaters, as described above, there are various methods for controlling the two fixing heaters using the method for determining the heater lighting duty by the lighting control table. In the image forming apparatus 1, a method for reducing the number of lighting control tables will be described.

  Now, it is assumed that there are two lighting control tables shown in FIGS. 8 and 9 used for one lighting control. The lighting heater selection table shown in FIG. 8 has two fixing heaters (halogen heaters (C ) 29a, halogen heater (E) 29b), which is used to select which one of the fixing heaters is to be lit or whether both are to be lit. The lighting duty determination table shown in FIG. In the same manner as the lighting control table, the fixing heater lighting duty selected in FIG. 8 is selected.

  At this time, the parameters for determining the vertical and horizontal axes used in the two tables may be the same or different parameters.

  Next, hysteresis control processing using two types of tables will be described. In the fixing temperature control of the fixing roller 27, as described above, the fixing heaters (halogen heater (C) 29a, halogen heater (E) 29b) to be used and their lighting intervals are determined by table search based on the control temperature and the detected temperature. However, in order to reduce the number of times the fixing heaters (halogen heater (C) 29a, halogen heater (E) 29b) change from off to on and from on to off, the fixing heater (halogen heater (C) 29a, halogen heater is used. The tables used when determining the lighting interval of (E) 29b) are the lighting duty determination table for turning off (lighting interval table for turning off) in FIG. 9 and the lighting duty determining for turning on in FIG. Two types of tables (on-time lighting interval table) are prepared and used properly as shown in FIG.

  That is, the system control unit 50 acquires the control target temperature of the fixing roller 27 (step S101), acquires the current temperature of the fixing roller 27 from the detection results of the fixing thermistors 61a and 61b (step S102), and FIG. From the lighting heater selection table shown, selection setting of the fixing heater (lighting heater) to be controlled, that is, one of the halogen heater (C) 29a and the halogen heater (E) 29b is selected (step S103).

  Then, the system control unit 50 checks whether the halogen heater (C) 29a or the halogen heater (E) 29b, which is the fixing heater selected and set, is currently lit (on) (step S104), and is lit (on). 10 is selected (step S105), the halogen heater (C) 29a or the halogen heater (E) 29b is turned on using the selected table. Lighting is controlled by setting an interval (step S106).

  In step S104, when the halogen heater (C) 29a or the halogen heater (E) 29b, which is the fixing heater selected and set in step S103, is currently extinguished (off), the system control unit 50 performs FIG. The off-state lighting duty determination table shown is selected (step S107), and the lighting interval of the halogen heater (C) 29a or the halogen heater (E) 29b is set using the selected table. Control is performed (step S106).

  Further, as can be seen from FIG. 9 showing the off-time lighting duty determination table and FIG. 10 showing the on-time lighting duty determination table, the off-time lighting duty determination table shown in FIG. The conditions for determining that the fixing heaters (halogen heater (C) 29a, halogen heater (E) 29b) are on (conditions where the lighting duty in FIG. 9 is 100%) are shown in FIG. Compared with the same condition of the lighting duty determination table for time, it is set at a place where a low temperature is detected.

  Therefore, the same effect as changing the control temperature can be obtained, and the number of times the halogen heater (C) 29a and halogen heater (E) 29b, which are fixing heaters, are switched from on to off and from off to on can be reduced. .

  Then, as described above, when the image forming apparatus 1 is in the standby state, the image forming apparatus 1 performs the hysteresis control process so that the halogen heater (C) 29a and the halogen heater (E) 29b, which are fixing heaters, are turned on and off. Although the number of times of switching to ON is reduced, in this standby state, an operation (copy instruction operation) for causing the image forming apparatus 1 to perform a copying operation by the user (for example, a key input operation on the operation display unit 9, an original document When setting to the reading unit 8 or the like is performed and a signal indicating that this copy instruction operation has been detected is input to the system control unit 50 via the I / O control unit 53, the system control unit 50 performs the hysteresis control. The control state is switched from the normal printing operation control using the regular interval table at the time of image formation performed during the normal printing operation.

  Therefore, in the hysteresis control process, even when the temperature of the fixing roller 27 is the lowest temperature, the user performs various operations that require the copy operation, and finally presses the start key of the operation display unit 9 to perform the copy operation. At the time of starting, the temperature of the fixing roller 27 can be raised to a predetermined fixing temperature necessary for fixing.

  As described above, in the image forming apparatus 1 according to the present embodiment, when the halogen heaters 60a and 60b are turned on in the standby state, as the lighting interval table, in addition to the image forming lighting interval table used during the image forming operation. On-time lighting interval table used to determine the next lighting interval and off-time lighting interval used to determine the next lighting interval when the halogen heaters 60a, 60b are off in the standby state The table is prepared, and in the standby state, the halogen heaters 60a and 60b to be lit among the plurality of halogen heaters 60a and 60b are determined based on the detected temperature of the fixing thermistors 61a and 61b and the control target temperature, and the determination is made. As the lighting interval table to be used depending on whether the halogen heaters 60a and 60b are turned on or off, the lighting interval table for on time is used. The hysteresis control for determining the lighting interval of the fixing roller 27 is performed by switching between the lighting interval table and the OFF lighting interval table, and when a function mode start condition is generated during the hysteresis control, the hysteresis control causes the image to be displayed. With reference to the lighting interval table at the time of formation, the operation is switched to the normal operation control for controlling the lighting intervals of the halogen heaters 60a and 60b.

  Therefore, the number of times the halogen heaters 60a and 60b are turned on / off in the standby state can be reduced, and when the function mode start condition is generated, the fixing roller 27 can be quickly heated. The life of 60b can be extended, and the image quality can be improved by fixing the first transfer sheet at an appropriate fixing temperature.

  Further, the image forming apparatus 1 according to the present embodiment has a copy function such as key operation on the operation display unit 9 for performing various key operations and document setting operation as a use start condition in the hysteresis control state in the copy function mode. When an operation indicating the start of use is detected, the control is switched from hysteresis control to normal operation control.

  Accordingly, the number of times the halogen heaters 60a and 60b are turned on / off in the standby state can be reduced, and when the use start condition of the copy function is generated, the fixing roller 27 can be quickly heated, and the halogen heaters 60a, 60a, In addition to extending the life of the 60b, it is possible to improve the image quality of the copy image by fixing the first transfer sheet of the copy at an appropriate fixing temperature.

  The image forming apparatus 1 does not switch from the hysteresis control to the normal printing operation control when the copy instruction operation is performed. For example, when the facsimile reception is detected in the facsimile mode, Alternatively, when the image forming apparatus 1 is connected to a personal computer or the like and a print request from the personal computer is detected in the printer mode, the control may be switched from the hysteresis control to the normal printing operation control.

  That is, as shown in FIG. 12, the system control unit 50 checks whether or not it is in a standby state (step S201), and if it is not in the standby state, it is not necessary to switch the temperature control state of the fixing roller 27. The switching process is terminated. If the system is in the standby state in step S201, the system control unit 50 checks whether the use mode is the copy mode, the facsimile (FAX) mode, or the printer mode (step S202). If the mode is the copy mode, it is checked whether the copy instruction operation (key input, document setting, etc.) has been performed (step S203).

  In step S203, when there is no copy instruction operation, the system control unit 50 performs the temperature control of the fixing roller 27 by the hysteresis control (step S204). If there is a copy instruction operation in step S203, the temperature of the fixing roller 27 is determined. The control is switched from hysteresis control to normal printing operation control (step S205).

  If the use mode is the facsimile (FAX) mode in step S202, the system control unit 50 checks whether there is a facsimile (FAX) reception (step S206), and if there is no facsimile reception, controls the temperature of the fixing roller 27. The hysteresis control is performed (step S204), and when there is a facsimile reception in step S206, the temperature control of the fixing roller 27 is switched from the hysteresis control to the normal printing operation control (step S205).

  In step S202, if the use mode is the printer mode, the system control unit 50 checks whether there is a print request from an information processing apparatus such as an externally connected personal computer (step S207). Then, the temperature control of the fixing roller 27 is performed by the hysteresis control (step S204), and when there is a print request in step S206, the temperature control of the fixing roller 27 is switched from the hysteresis control to the normal printing operation control (step S205).

  As described above, in the hysteresis control state in the facsimile function mode, the image forming apparatus 1 according to the present embodiment switches from the hysteresis control to the normal operation control when the facsimile reception is detected as the use start condition.

  Accordingly, the number of times the halogen heaters 60a and 60b are turned on / off in the standby state can be reduced, and when the facsimile reception is detected, the fixing roller 27 can be quickly heated, and the life of the halogen heaters 60a and 60b can be shortened. It is possible to increase the image quality of the received facsimile image by fixing the transfer sheet of the first facsimile reception sheet at an appropriate fixing temperature.

  The image forming apparatus 1 according to the present embodiment switches from hysteresis control to normal operation control when a print request is detected as a use start condition in the hysteresis control state in the printer function mode.

Therefore, the number of times the halogen heaters 60a and 60b are turned on / off in the standby state can be reduced, and when the print request for the printer function is detected, the fixing roller 27 can be quickly heated, and the halogen heaters 60a and 60b. The image quality of the print image can be improved by fixing the transfer sheet of the first printed sheet at an appropriate fixing temperature.
As can be seen from the above description, in the image forming apparatus, in addition to the image forming lighting interval table used during the image forming operation, the next lighting interval when the fixing heater is on in the standby state is used as the lighting interval table. An on-time lighting interval table that is used to determine the lighting time, and an off-time lighting interval table that is used to determine the next lighting interval when the fixing heater is off in a standby state. In the standby state, a fixing heater to be lit is determined from among a plurality of fixing heaters based on the detected temperature of the temperature detecting means and the control target temperature, and is used depending on whether the determined fixing heater is on or off. A hysteresis interval that determines the lighting interval of the fixing roller by switching between the lighting interval table for on time and the lighting interval table for off time. When the function mode start condition is generated during the hysteresis control, the hysteresis control is switched to the normal operation control for controlling the fixing heater lighting interval by referring to the lighting interval table at the time of image formation. For example, it is possible to reduce the number of times the fixing heater is turned on / off in the standby state, and when a function mode start condition is generated, the fixing roller can be heated quickly, and the life of the fixing heater can be extended. In addition, the first transfer sheet can be fixed at an appropriate fixing temperature, and the image quality can be improved.
In addition, in the hysteresis control state in the copy function mode, if an operation indicating the start of use of the copy function such as a key operation on an operation unit that performs various key operations or a document setting operation is detected as a use start condition, the hysteresis control is started. By switching to normal operation control, the number of times the fixing heater is turned on / off in the standby state can be reduced, and when the use start condition of the copy function occurs, the fixing roller can be quickly heated. The life of the fixing heater can be extended, and the first copy sheet can be fixed at an appropriate fixing temperature to improve the image quality of the copy image.
Further, when the facsimile reception is detected as a use start condition in the hysteresis control state in the facsimile function mode, if the hysteresis control is switched to the normal operation control, the number of times the fixing heater is turned on / off in the standby state is reduced. In addition, when the facsimile reception is detected, the fixing roller can be quickly heated, the life of the fixing heater can be extended, and the fixing of the first transfer paper on the facsimile reception can be performed at an appropriate fixing temperature. This can improve the image quality of the received facsimile image.
In addition, when a print request is detected as a use start condition in the hysteresis control state in the printer function mode, the number of times the fixing heater is turned on / off in the standby state can be reduced by switching from the hysteresis control to the normal operation control. In addition, when the print request of the printer function is detected, the fixing roller can be heated quickly, the life of the fixing heater can be extended, and the fixing of the first transfer sheet can be appropriately fixed. Performing at temperature can improve the image quality of the printed image.

  The invention made by the present inventor has been specifically described based on the preferred embodiments. However, the present invention is not limited to the above, and various modifications can be made without departing from the scope of the invention. Needless to say.

  An image forming apparatus such as a copying apparatus, a facsimile machine, a printer, and a composite apparatus that forms an image by an electrophotographic method and finally fixes it at a fixing unit, and controls the temperature of a fixing roller of the fixing unit to extend the life of the fixing unit. In addition, the present invention can be applied to an image forming apparatus that improves the image quality while shortening the image forming time of the first sheet.

1 is a schematic front view of an image forming apparatus to which an embodiment of a fixing control device of the present invention is applied. FIG. 2 is a detailed front view of the image forming unit in FIG. 1. FIG. 2 is a circuit block configuration diagram of the image forming apparatus in FIG. 1. FIG. 4 is a circuit block configuration diagram of the fixing control system of FIG. 3. FIG. 5 is a waveform diagram of a power supply voltage during soft start control processing supplied to the halogen heater from the high-voltage power supply unit in FIG. 4. FIG. 5 is a diagram illustrating an example of a lighting control table for controlling the temperature of the fixing roller based on the detection result of one fixing thermistor and the control temperature of one halogen heater in FIG. 4. FIG. 7 is a waveform diagram when energizing a halogen heater while performing a soft start control process using the lighting control table of FIG. 6. An example of a lighting heater selection table for controlling the temperature of the fixing roller based on the detection results of the two fixing thermistors and the control temperature using the two lighting control tables when the heater is turned on and when the heater is turned off in FIG. FIG. Using the two lighting control tables when the heater is turned on and when the heater is turned off in FIG. 4, the lighting duty is determined when the heater is turned off when the temperature of the fixing roller is controlled based on the detection results of the two fixing thermistors and the control temperature. The figure which shows an example for a table. Using the two lighting control tables when the heater is on and when the heater is off in FIG. 4, the lighting duty is determined when the heater is turned on when the temperature of the fixing roller is controlled based on the detection results of the two fixing thermistors and the control temperature. The figure which shows an example for a table. FIG. 4 is a flowchart showing hysteresis control processing of a fixing roller using two lighting control tables when the heater is turned on and when the heater is turned off by the system control unit of FIG. 3. 4 is a flowchart showing switching processing from hysteresis control of the fixing roller to normal printing operation control by the system control unit of FIG. 3.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 2 Paper feed unit 3 Main body housing | casing 4a, 4b, 5 Paper feed cassette 6 Image forming part 7 Transfer paper stack 8 Reading part 9 Operation display part 10 Manual tray 10a Manual paper feed roller 20 Photoconductor 21 Charging roller 22 Developing unit 23 Transfer roller 24 Paper transport path 25 Registration sensor 26 Fixing unit 27 Fixing roller 28 Pressure roller 30 Toner case 31 Mag roller 32 Agitator 33 Toner bottle 34 Toner sensor 40 Toner cartridge 50 System control unit 51 Read control unit 52 Write control Part 53 I / O control part 54 I / O for image formation
55 High Voltage Power Supply 60a Halogen Heater (C)
60b Halogen heater (E)
61a, 61b fixing thermistor

Claims (6)

An image forming apparatus that forms a toner image on a sheet based on image data, and fixes the toner image on the sheet to the sheet using a fixing roller,
A fixing heater for heating the fixing roller;
Temperature detecting means for detecting the temperature of the fixing roller;
When the fixing heater is on in a certain control cycle, whether the fixing heater is turned on or off in the next control cycle is detected by the control temperature target value of the fixing roller and the temperature detection means. A lighting determination table for heater on that is determined according to the difference between the value and
When the fixing heater is turned off in a certain control cycle, whether the fixing heater is turned on or turned off in the next control cycle is detected by the control temperature target value of the fixing roller and the temperature detection means. The fixing heater is turned on in the next control cycle from the time when the detected value of the temperature detecting means is lower than that in the heater-on lighting determination table. The heater turn-on lighting determination table,
In the standby state of the apparatus, the fixing heater is controlled by hysteresis to control the lighting driving thereof, and (a) when the fixing heater is turned on at a certain control cycle for each predetermined control cycle. Based on the difference between the control temperature target value of the fixing roller and the detected value of the temperature detection means, it is determined whether the fixing heater is turned on or off according to the contents of the heater-on lighting determination table. In the next control cycle, the fixing heater is turned on in the determined ON state or OFF state, and (b) when the fixing heater is turned OFF in a certain control cycle, the control temperature target of the fixing roller Whether the fixing heater is turned on according to the contents of the heater-off lighting determination table based on the difference between the value and the detected value of the temperature detecting means. Determine a state, in the next control cycle, a first control means for lighting and driving the fixing heater to the determined turned on or off
An image forming apparatus comprising the. The fixing heater includes a first fixing heater that heats an axial center portion of the fixing roller, and a second fixing heater that heats an axial end portion of the fixing roller,
The temperature detection unit includes a first temperature detection unit that detects a temperature of an axially central portion of the fixing roller, and a second temperature detection unit that detects a temperature of an axial end portion of the fixing roller. ,
The difference between the control temperature target value at the axial center of the fixing roller and the detection value of the first temperature detection means, and the control temperature target value at the axial end of the fixing roller and the second temperature detection A fixing heater selection table for selecting one of the first fixing heater and the second fixing heater to be used according to a difference from the detected value of the means;
In the standby state of the apparatus, the first control unit (a) difference between the control temperature target value at the central portion in the axial direction of the fixing roller and the detection value of the first temperature detection unit for each control cycle. And the first fixing heater by referring to the fixing heater selection table based on the difference between the control temperature target value at the axial end of the fixing roller and the detected value of the second temperature detecting means. Alternatively, when one of the second fixing heaters is selected as a fixing heater to be used in the next control cycle, and (b) the selected fixing heater is turned on in a certain control cycle, the control temperature of the fixing heater is set. Based on the difference between the target value and the detected value of the temperature detecting means, it is determined whether to turn on or off the selected fixing heater according to the contents of the heater-on lighting determination table, and the next control Zhou In addition, when the selected fixing heater is turned on in the determined ON state or OFF state, and (c) the selected fixing heater is turned OFF in a certain control cycle, the control temperature target value of the fixing heater is Based on the difference from the detected value of the temperature detection means, it is determined whether to turn on or off the selected fixing heater according to the content of the heater-off lighting determination table, in the next control cycle, The image forming apparatus according to claim 1 , wherein the selected fixing heater is driven to light in the determined on state or off state . In correspondence with the difference between the control temperature target value of the fixing roller and the detection value of the temperature detection means, and the difference between the previous detection time and the current detection time of the detection value of the temperature detection means, in the next control cycle A lighting duty determination table for normal operation that determines the lighting duty of the fixing heater;
In the normal operation state that shifts when the use start condition of the function accompanied by image formation occurs in the standby state of the apparatus, the fixing heater is controlled by the non-hysteresis control to control the lighting drive, and for each control cycle, The normal operation lighting duty is determined based on the difference between the control temperature target value of the fixing roller and the detection value of the temperature detection means, and the difference between the previous detection time and the current detection time of the detection value of the temperature detection means. A second control means for determining a lighting duty according to the contents of the table and lighting the fixing heater with the determined lighting duty in the next control cycle;
The image forming apparatus according to claim 1 , further comprising: The image forming apparatus includes a copy function and operation means for performing various key operations.
In the standby state, when an operation indicating the start of use of the copy function, such as a key operation on the operation unit or a document setting operation, is detected as the use start condition, the transition from the standby state to the normal operation state is performed. The image forming apparatus according to claim 3 . The image forming apparatus has a facsimile function,
4. The image forming apparatus according to claim 3, wherein, in the standby state, when facsimile reception is detected as the use start condition, the standby state is shifted to the normal operation state . The image forming apparatus has a printer function,
The image forming apparatus according to claim 3, wherein in the standby state, when a print request is detected as the use start condition, the image forming apparatus shifts from the standby state to the normal operation state .

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