JP2018049242A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To appropriately set an image forming condition to maintain the quality of an image formed on a sheet.SOLUTION: An image forming part 20 forms a developer image on a sheet. A fixing unit heats and fixes an unfixed developer image formed by the image forming part 20 to the sheet. A temperature sensor S4 detects a heating temperature Tf of the fixing unit. A CPU 201 sets, on the basis of the temperature Tf detected by the temperature sensor S4, an image forming condition for the image forming part 20, specifically, a charge voltage VE to be applied to a charging roller 22 and a transfer voltage VT to be applied to a transfer roller 25.SELECTED DRAWING: Figure 2

Description

  The present invention relates to an image forming apparatus that sets image forming conditions of an image forming unit.

  In an electrophotographic image forming apparatus, a developer image is formed on a sheet (for example, paper) in an image forming unit serving as an image forming unit, and the sheet is pressed and heated in a fixing unit serving as a fixing unit, whereby the developer is applied to the sheet. The image is fixed to form an image on the sheet. The fixing device is provided with a temperature sensor such as a thermistor in order to control the temperature of the fixing device to a target temperature.

  In addition, in order to prevent the sheet from curling when the sheet is pressed and heated in the fixing unit, the timing of conveying the sheet to the fixing unit, specifically the warm-up time, is controlled according to the moisture content of the sheet. doing. The moisture content of the sheet varies depending on the surrounding environment (temperature and humidity) where the sheet (that is, the image forming apparatus) is placed. For this reason, in order to obtain a value indicating the moisture content of the sheet, an environmental sensor for detecting the temperature and humidity around the apparatus is provided. In order to accurately obtain a value indicating the moisture content of the sheet, it is necessary to place the environmental sensor at a location that is not easily affected by heat of the fixing device or the image forming unit (a location that is easily exposed to the outside air).

  In the image forming unit, since process components such as a charging member and a transfer member are highly temperature-dependent, image forming conditions such as a charging bias applied to the charging member and a transfer bias applied to the transfer member are set in the image forming unit (process). It is adjusted according to the temperature of the component. For example, a bias voltage such as a charging voltage or a transfer voltage is set higher as the temperature of the image forming unit is lower, and control is performed to apply a current necessary for image formation to the charging member or the transfer member.

  Applying an appropriate bias according to the temperature of the process component is a control necessary for maintaining a good image. That is, when a bias lower than the value that is originally required according to the temperature is applied, the current required for image formation does not flow. For example, if the bias is a charging bias, the photosensitive drum becomes insufficiently charged, resulting in an image defect such as transfer. If the bias is applied, an image defect occurs due to insufficient transfer.

  On the other hand, even when a bias that is significantly higher than a necessary value corresponding to the temperature is applied, a current exceeding the current necessary for image formation is discharged, reducing the image defect and the life of the process component.

  For this problem, if the temperature sensor is also arranged in the image forming unit, the image forming conditions can be set appropriately. However, in order to reduce the cost, conventionally, the ambient temperature detected by the environmental sensor has been used. The temperature of the image forming unit was estimated using the above information, and the image forming conditions were set.

  On the other hand, when an environmental sensor is arranged in the vicinity of the image forming unit to detect the temperature of the image forming unit and the temperature around the image forming apparatus (outside air) is detected, outside air is introduced into the apparatus using a fan. A technique for spraying an environmental sensor has also been proposed (see, for example, Patent Document 1).

JP 2014-119526 A

  However, when the ambient temperature of the image forming apparatus changes rapidly in an air conditioner or the like, the temperature of the image forming unit does not immediately become the same as the ambient temperature, but gradually approaches the ambient temperature. There is a discrepancy between the temperature of the image forming unit and the ambient temperature. In the conventional method of estimating the temperature of the image forming unit using the temperature information detected by the environmental sensor, the larger the difference between the temperature of the image forming unit and the ambient temperature, the more the estimated temperature of the image forming unit is obtained. Deviation from actual temperature increases. Therefore, the image forming conditions are set so as to deviate from an appropriate state, so that the quality of the image formed on the sheet may be deteriorated.

  On the other hand, in the method of Patent Document 1, the temperature of the image forming unit can be detected by the environmental sensor. However, when the ambient temperature of the image forming apparatus is detected by the environmental sensor, the environmental sensor is operated by operating the fan. There was a need to blow outside air. When outside air is blown to the environmental sensor to detect the ambient temperature, the environment blown by the fan is different from the airless environment where the image forming apparatus is installed. An error may occur in the detection result.

  Accordingly, an object of the present invention is to maintain image quality formed on a sheet by appropriately setting image forming conditions.

  The image forming apparatus according to the present invention includes an image forming unit that forms a developer image on a sheet, a fixing unit that heat-fixes an unfixed developer image formed by the image forming unit on the sheet, and heating the fixing unit. The image forming apparatus includes: a fixing temperature detecting unit that detects a temperature; and a control unit that sets an image forming condition of the image forming unit based on the temperature detected by the fixing temperature detecting unit.

  According to the present invention, it is possible to appropriately set image forming conditions and maintain the quality of an image formed on a sheet.

1 is an explanatory diagram illustrating a printer as an example of an image forming apparatus according to an embodiment. 2 is a block diagram illustrating a control system of the image forming apparatus according to the embodiment. FIG. It is a flowchart which shows the processing operation of CPU which concerns on embodiment. (A) is a graph which shows the change of the temperature of the image formation apparatus with respect to time passage, and the temperature of process components. (B) is a graph showing the actual charging voltage applied to the process component and the necessary charging voltage with respect to the ambient temperature of the image forming apparatus.

  Hereinafter, embodiments for carrying out the present invention will be described in detail with reference to the drawings. Hereinafter, the sheet represents not only paper but also cloth, plastic film, metal plate, glass, ceramics, wood, leather and the like that can accept the developer.

  FIG. 1 is an explanatory diagram illustrating a printer as an example of an image forming apparatus according to an embodiment. As shown in FIG. 1, the image forming apparatus 100 is a monochrome printer that forms an image on a sheet by an electrophotographic method. The image forming apparatus 100 includes a sheet feeding unit 10, an image forming unit 20 as an image forming unit, a fixing device 30 as a fixing unit, and a sheet discharge, which are sequentially arranged from the upstream side to the downstream side in the sheet conveying direction. Part 40 is provided. In addition, the image forming apparatus 100 includes a sheet refeeding unit 50 for supporting double-sided printing. Further, the image forming apparatus 100 includes a control device 200.

  The sheet feeding unit 10 feeds the sheets P stacked on the cassette 11 or the manual feed tray 16 to the image forming unit 20. The sheet feeding unit 10 includes a pickup roller 12, a separation roller pair 13, a supply roller 17 and a separation pad 18, and a supply roller pair 19. In the vicinity of the cassette 11, a sheet detection sensor S <b> 1 that detects whether or not the sheet P is stored in the cassette 11 is disposed. The pick-up roller 12 is driven to rotate by a drive device (not shown), thereby sending the sheet P stored in the cassette 11 to the separation roller pair 13.

  The separation roller pair 13 includes a normal rotation roller and a reverse roller. When a plurality of sheets P are double-fed and fed to the separation roller pair 13, the sheets P are separated into one sheet P at the nip portion of the separation roller pair 13. One sheet P that has passed the separation roller pair 13 is conveyed to a feeding path PS1 indicated by a solid line.

  Between the sheet feeding unit 10 and the image forming unit 20, a feeding roller pair 14 and a registration roller pair 15 are arranged in order from the upstream side to the downstream side in the sheet conveying direction.

  When the sheet P is fed from the manual feed tray 16, the supply roller 17 and the supply roller pair 19 are rotationally driven by a driving device (not shown). As a result, one sheet P is separated from the manual feed tray 16 by the supply roller 17 and the separation pad 18 and conveyed to the supply roller pair 19, and further conveyed to the feed roller pair 14 by the supply roller pair 19.

  The feed roller pair 14 conveys the sheet P sent out by the separation roller pair 13 or the supply roller pair 19 to the registration roller pair 15. A sensor (hereinafter referred to as “registration”) between the feeding roller pair 14 and the registration roller pair 15, specifically, in the vicinity of the registration roller pair 15 and upstream in the sheet conveyance direction. S2) (referred to as “front sensor”) is arranged. Specifically, the pre-registration sensor S2 detects the timing at which the downstream end (front end) of the sheet P in the sheet conveyance direction reaches the nip of the registration roller pair 15.

  The registration roller pair 15 corrects the skew of the sheet P. More specifically, when the sheet P is conveyed to the nip portion of the registration roller pair 15 by the feeding roller pair 14 while the registration roller pair 15 is stopped rotating, the leading edge of the sheet P is moved to the nip portion. The skew of the sheet P is corrected by copying. The registration roller pair 15 starts rotating at a predetermined timing and conveys the sheet P to the image forming unit 20.

  The image forming unit 20 forms a developer image on the sheet P. As shown in FIG. 1, the image forming unit 20 includes a rotating photosensitive drum 21 that is an example of an image carrier. The image forming unit 20 includes a charging roller 22 that is an example of a charging member, an exposure device 23, a developing device 24, a transfer roller 25 that is an example of a transfer member, and a drum cleaning device that are arranged around the photosensitive drum 21. (Not shown).

  FIG. 2 is a block diagram illustrating a control system of the image forming apparatus according to the embodiment. As illustrated in FIG. 2, the image forming unit 20 includes a high-voltage substrate 210 that is a power supply device. The high-voltage substrate 210 includes a circuit unit that applies a charging voltage (charging bias) VE to the charging roller 22 and a circuit unit that applies a transfer voltage (transfer bias) VT to the transfer roller 25. Further, the high voltage substrate 210 has a circuit unit that applies the developing voltage VD to the developing device 24.

  The photosensitive drum 21 carries a developer image. The charging roller 22 applies a charging voltage VE to charge the surface of the photosensitive drum 21. The charging roller 22 is disposed in contact with or close to the surface of the photosensitive drum 21. A charging voltage VE in which an AC voltage and a DC voltage are superimposed is applied to the charging roller 22. As a result, the peripheral surface of the photosensitive drum 21 is charged to a uniform potential equal to the potential of the DC voltage.

  The exposure device 23 has a laser light source, scans the laser light emitted from the laser light source with a rotating mirror, and forms an electrostatic latent image of an image corresponding to the image information on the surface of the photosensitive drum 21. On the surface of the photosensitive drum 21, the portion exposed to the exposure device 23 is removed of the electric charge charged by the charging roller 22, and an electrostatic latent image corresponding to the image is formed.

  The developing device 24 includes a developing roller 24A. The developing roller 24A carries a developer and conveys the carried developer to a portion facing the photosensitive drum 21. By applying a developing voltage VD, in which an AC voltage is superimposed on a DC voltage, to the developing roller 24A, the developer adheres to the electrostatic latent image on the photosensitive drum 21 and is visualized as a developer image. The developer image is conveyed to the transfer nip portion N1 as the photosensitive drum 21 rotates.

  The sheet P is conveyed to the transfer nip portion N1 by the registration roller pair 15 in synchronization with the conveyance of the developer image. The sheet P conveyed to the transfer nip portion N1 is nipped and conveyed between the photosensitive drum 21 and the transfer roller 25 in pressure contact with the photosensitive drum 21 (via the sheet P) in the transfer nip portion N1. Therefore, the transfer roller 25 transfers the developer image formed on the photosensitive drum 21 onto the sheet P. At this time, a transfer voltage VT having a polarity opposite to the charging polarity of the developer is applied to the transfer roller 25.

  The sheet P on which the unfixed developer image is formed is conveyed to the fixing device 30. The fixing device 30 heat-fixes the unfixed developer image formed by the image forming unit 20 on the sheet P. The fixing device 30 includes a heater 33 that is a heat source such as a halogen lamp. In addition, the fixing device 30 includes a fixing roller 31 as a first rotating body, and a pressure roller 32 as a second rotating body that is pressed against the fixing roller 31 with a predetermined pressure (via the sheet P). .

  The fixing roller 31 is composed of an aluminum roller or the like. A heater 33 is disposed inside the fixing roller 31 and is heated by the heat of the heater 33. The fixing roller 31 heated by the heater 33 heats the conveyed sheet P. When the fixing roller 31 and the pressure roller 32 are in pressure contact (via the sheet P), a fixing nip portion N2 that sandwiches the sheet P between the fixing roller 31 and the pressure roller 32 is formed. Therefore, the developer image is fixed on the sheet P conveyed to the fixing nip portion N <b> 2 by heating the fixing roller 31. That is, the fixing device 30 fixes the developer image on the sheet P by heating and pressurizing the sheet P on which the developer image is formed at the fixing nip portion N2.

  A sensor (hereinafter referred to as “fixing sensor”) S3 for detecting the presence or absence of the sheet P is disposed on the downstream side of the fixing device 30 in the sheet conveying direction. Specifically, the fixing sensor S3 detects whether the leading edge of the sheet P has passed through the fixing nip portion N2. The sheet P on which the image is fixed is conveyed to the sheet discharge unit 40 and discharged to the discharge tray 42 by the discharge roller pair 41.

  When images are formed on both sides of the sheet P, the upstream end (rear end) of the sheet P in the sheet conveyance direction forms the discharge roller pair 41 after the leading edge of the sheet P on which the image is formed on the first surface passes through the fixing sensor S3. Before exiting, the discharge roller pair 41 is temporarily stopped. Further, by rotating the discharge roller pair 41 in the reverse direction, the sheet P is reversed and conveyed to the sheet refeeding unit 50.

  The sheet P conveyed to the sheet re-feeding section 50 is conveyed on a re-feed path PS2 indicated by a broken line by re-feed roller pairs 51 and 52, and is conveyed to a registration roller pair 15 by a re-feed roller pair 53. The Then, after the skew is corrected by the registration roller pair 15, the developer image is formed on the second surface of the sheet P by being conveyed to the transfer nip portion N 1.

  Thereafter, the developer image is fixed on the sheet P by being conveyed through the fixing nip N2 in the same manner as when the image is formed on the first side, and the sheet P on which the image is formed on both sides is discharged by the discharge roller pair 41 to the discharge tray. 42 is discharged.

  As shown in FIG. 2, the control device 200 includes a CPU (Central Processing Unit) 201 that is a control means. The control device 200 includes a ROM (Read Only Memory) 202 and a RAM (Random Access Memory) 203 which are storage means. In addition, the control device 200 includes a timer 204 as time measuring means for measuring time, and various interfaces (I / F) 205. The ROM 202 may be a rewritable nonvolatile memory such as an EEPROM (Electrically Erasable Programmable Read Only Memory).

  The ROM 202 stores in advance various data necessary for controlling the entire apparatus, in addition to the operation program. A RAM 203 is a temporary storage device, and temporarily stores a calculation result of the CPU 201. The timer 204 measures time based on a command from the CPU 201.

  The CPU 201 operates according to an operation program stored in the ROM 202 and controls the entire apparatus. More specifically, the CPU 201 performs on / off control (temperature control) of energization to the heater 33. Further, the CPU 201 develops image forming conditions (process conditions) of the image forming unit 20, specifically, a charging voltage VE applied to the charging roller 22, a transfer voltage VT applied to the transfer roller 25, and a developing applied to the developing roller 24A. Each condition such as voltage VD is set. The high voltage substrate 210 applies the respective bias voltages VE, VT, VD under the conditions set in the CPU 201 to the charging roller 22, the transfer roller 25, and the developing roller 24A, respectively.

  The control device 200 is connected to a temperature sensor S4 that is a fixing temperature detection unit, an environment sensor S5 that is an environment detection unit, a high-voltage board 210, and a heater 33.

  The temperature sensor S4 detects a temperature Tf that is a heating temperature of the fixing device 30. The temperature sensor S4 is, for example, a thermistor, and is disposed at a position that detects the temperature Tf of the fixing device 30, specifically, the fixing roller 31. The temperature sensor S4 may be arranged at a position where the temperature of the heater 33 is detected. The temperature sensor S4 outputs a signal (information) indicating the temperature Tf to the control device 200.

  The environment sensor S5 is a temperature / humidity sensor, and detects the temperature (environment temperature) Ta and humidity (environment humidity) Ha of the apparatus environment (that is, the surroundings where the image forming apparatus 100 is installed). The environmental sensor S5 is arranged at a position where the influence of heat of the fixing device 30 and the image forming unit 20 in the apparatus is small and is separated from the fixing device 30 and the image forming unit 20. The environmental sensor S5 outputs a signal (information) indicating the temperature Ta and a signal (information) indicating the humidity Ha to the control device 200.

  The CPU 201 acquires temperature information indicating the detected temperature Tf at a predetermined sampling interval from the temperature sensor S4 via the interface 205. Further, the CPU 201 acquires temperature information and humidity information indicating the detection results Ta and Ha from the environment sensor S5 through the interface 205 at predetermined sampling intervals.

  Here, immediately after the heating by the heater 33 is started, the temperature difference between the fixing roller 31 and the pressure roller 32 is large. Further, when the temperature and humidity around the sheet P are high, the amount of moisture in the sheet P is large. In such a state, when the sheet P is nipped and conveyed between the fixing roller 31 and the pressure roller 32 and heated and pressed, a large amount of moisture on the fixing roller 31 side of the sheet P is evaporated, and the sheet P is fixed to the fixing roller 31. Curls greatly to the side.

  Therefore, the CPU 201 supplies the sheet P to the fixing device 30 based on the information on the temperature Tf detected by the temperature sensor S4, the information on the temperature Ta detected by the environment sensor S5, and the information on the humidity Ha detected by the environment sensor S5. To control the timing of transporting. Specifically, the CPU 201 conveys the sheet P to the fixing device 30 so that the temperature Tf detected by the temperature sensor S4 (in this embodiment, the temperature of the fixing roller 31) is raised to a target temperature necessary for fixing. Warm-up is performed to turn on the heater 33 before starting. At this time, the CPU 201 adjusts the warm-up time from when the heating of the heater 33 is started (turned on) to when the sheet P is conveyed to the fixing device 30 according to the ambient temperature and humidity. As described above, the fixing device 30 is controlled to a predetermined fixing temperature using the heater 33 in accordance with the ambient temperature Ta and humidity Ha detected by the environment sensor S5 based on the information on the temperature Tf of the temperature sensor S4. The Thereby, the temperature difference between the fixing roller 31 and the pressure roller 32 is reduced, and curling of the sheet P is suppressed. The ambient temperature is the temperature detected by the environmental sensor S5. The ambient humidity is the absolute humidity calculated from the detected humidity (relative humidity) of the environmental sensor S5, the detected temperature and the detected humidity.

  Here, the process components such as the charging roller 22 and the transfer roller 25 in the image forming unit 20 are highly temperature dependent. That is, the lower the temperature of the process component, the higher the impedance of the process component. Therefore, the CPU 201 performs control to set the bias voltages VE and VT applied to the process component higher as the temperature of the process component is lower, and to apply a current necessary for image formation to the process component.

  In the present embodiment, temperature detection means such as a temperature sensor is not disposed in the image forming unit 20, and image forming conditions (process conditions) such as bias voltages VE and VT are determined according to the estimated temperature, not the actual temperature of the image forming unit 20. ) Is set. As a result, the cost of the image forming apparatus 100 is reduced.

  FIG. 3 is a flowchart illustrating the processing operation of the CPU according to the embodiment. The CPU 201 performs the following processing operation according to the operation program stored in advance in the ROM 202.

  Here, when the ambient temperature of the image forming apparatus 100 hardly changes and is constant, the temperature of the image forming unit 20 is substantially the same as the ambient temperature. In such a case, even if the estimated temperature of the image forming unit 20 used for setting the image forming conditions is determined (estimated) as the temperature information detected by the environmental sensor S5, the image formed on the sheet P is defective. Will not occur.

  However, under a situation where the temperature around the image forming apparatus 100 changes, the temperature detected by the environment sensor S5 may not match the temperature of the process component of the image forming unit 20. FIG. 4A is a graph showing changes in the ambient temperature of the image forming apparatus and the temperature of the process components with time.

  In FIG. 4A, the solid line is the temperature around the image forming apparatus 100, that is, the temperature Ta detected by the environment sensor S5. A broken line indicates an actual temperature of the process component, specifically, the charging roller 22 or the transfer roller 25. Note that the charging roller 22 and the transfer roller 25 are separate members, but have substantially the same temperature.

  When the outside air around the image forming apparatus 100 is suddenly warmed by a heating device or the like, as shown in FIG. 4A, the temperature of the process component rises with a delay from the ambient (outside air) temperature. There is a divergence (temperature difference) between the temperature and the temperature of the process component.

  Assume that the estimated temperature of the image forming unit 20 (process component) is determined based on the temperature information detected by the environmental sensor S5 in a state where a temperature difference is generated such that the ambient temperature is high and the process component temperature is low. In this case, the image forming conditions such as the set bias voltages VE and VT are not in an appropriate state. That is, since the bias voltages VE and VT are set low, the photosensitive drum 21 is not sufficiently charged and the transfer current is insufficient. As a result, an image formed on the sheet P may be defective.

  FIG. 4B is a graph showing the actual charging voltage (output voltage) applied to the process component with respect to the ambient temperature of the image forming apparatus and the necessary charging voltage (output voltage). If the temperature of the process component having high temperature dependence such as the charging roller 22 and the transfer roller 25 is estimated to be higher than the actual temperature, as shown in FIG. 4B, the actually applied bias voltage is more than the necessary bias voltage. Will be set too low. As described above, when it is determined that the temperature of the process component is higher than the actual temperature, image defects (sandy ground due to insufficient charging current and scattering of developer due to insufficient transfer current) occur.

  Here, before the heater 33 is turned on (before heating is started), the fixing device 30 is also at substantially the same temperature as the image forming unit 20. Even when the temperature of the outside air changes, the fixing device 30 changes in temperature with the same tendency as the image forming unit 20.

  Therefore, in this embodiment, the CPU 201 sets image forming conditions such as the bias voltages VE and VT of the image forming unit 20 based on the information on the temperature Tf detected by the temperature sensor S4. More specifically, the CPU 201 forms an image such as the bias voltages VE and VT of the image forming unit 20 based on the information on the temperature Tf detected by the temperature sensor S4 and the information on the temperature Ta detected by the environment sensor S5. Set conditions. Hereinafter, a specific description will be given along the flowchart of FIG.

  When the CPU 201 receives a print command, it starts a print job (S101). First, the CPU 201 acquires information on the temperatures Tf and Ta from the temperature sensor S4 and the environment sensor S5 (S102, S103). Specifically, since the CPU 201 receives the information on the temperatures Tf and Ta at a predetermined sampling cycle, the CPU 201 selects the information on the temperatures Tf and Ta at a certain timing. Next, the CPU 201 starts temperature control of the fixing device 30 by turning on the heater 33 (starting heating) (S104). That is, the CPU 201 starts energization of the heater 33 and controls the heater 33 to be turned on / off so that the temperature detected by the temperature sensor S4 becomes a preset target temperature.

  As described above, in this embodiment, the CPU 201 determines the temperature Tf and Ta information from the temperature sensor S4 and the environment sensor S5 before turning on the heater 33 (before starting the heating of the heater 33) in steps S102 and 103. To get. That is, the CPU 201 uses the information of the temperature Tf detected by the temperature sensor S4 before starting the heating of the heater 33 to set the image forming conditions. This is because the temperature Tf detected by the temperature sensor S4 deviates from the actual temperature of the image forming unit 20 after the heating of the heater 33 is started.

  If the temperature of the heater 33 does not affect the temperature Tf detected by the temperature sensor S4 or if the influence of the heat is negligible, the temperature from the temperature sensor S4 immediately after or immediately after the heating of the heater 33 is started. You may make it acquire the information of Tf.

  Further, since the environmental sensor S5 is arranged at a position away from the fixing device 30 and the influence of the heat of the heater 33 is small, the information on the temperature Ta acquired from the environmental sensor S5 is acquired after the heater 33 is turned on. You may do it. However, if the environmental conditions for acquiring the information on the temperatures Tf and Ta are different, the accuracy of the estimated temperature of the image forming unit 20 is reduced. Therefore, the information on the temperatures Tf and Ta is acquired before the heating of the heater 33 is started. Is preferred.

  Next, the CPU 201 compares the magnitude relationship between the temperature Tf detected by the temperature sensor S4 and the temperature Ta detected by the environment sensor S5 (S105). For example, the CPU 201 determines whether Ta> Tf.

  When Ta = Tf, the ambient temperature of the image forming apparatus 100 and the temperature of the fixing device 30 coincide with each other. Therefore, the temperatures of the image forming unit 20 and the fixing device 30 are adjusted to the ambient temperature. That is, the print job has not been executed for a long time, and the ambient temperature has hardly changed. In this case (S105: No), the CPU 201 sets the image forming conditions of the charging voltage and the transfer voltage according to the information on the temperature Ta detected by the environmental sensor S5 (S106). Since Ta = Tf, the image forming conditions for the charging voltage and the transfer voltage may be set according to the information on the temperature Tf detected by the temperature sensor S4.

  When Ta> Tf, since the temperature of the fixing device 30 is lower than the temperature around the image forming apparatus 100, the temperature around the image forming apparatus 100 is increased by a heater or the like. That is, the print job has not been executed for a long time, but the ambient temperature has increased. In this case (S105: Yes), the CPU 201 sets the image forming conditions of the charging voltage and the transfer voltage according to the information on the temperature Tf detected by the temperature sensor S4 (S107).

  When Ta <Tf, since the temperature of the fixing device 30 is higher than the ambient temperature of the image forming apparatus 100, the internal temperature of the image forming apparatus 100 is high, that is, the passage of time from the immediately preceding print job is short, and the fixing is performed. There will be residual heat in the machine 30 due to the previous print job. In this case (S105: No), the CPU 201 sets the image forming conditions of the charging voltage and the transfer voltage according to the information on the temperature Ta detected by the environmental sensor S5 (S106).

Table 1 summarizes the above criteria.

  As described above, in the present embodiment, the CPU 201 sets the image forming condition according to one of the information on the temperature Tf detected by the temperature sensor S4 and the information on the temperature Ta detected by the environment sensor S5. That is, the CPU 201 sets an image forming condition according to the estimated temperature of the image forming unit 20, and this estimated temperature is set to the temperature Tf detected by the temperature sensor S4 or the temperature Ta detected by the environment sensor S5. .

  More specifically, when the temperature Tf detected by the temperature sensor S4 is lower than the temperature Ta detected by the environment sensor S5, the CPU 201 changes the image forming condition to the temperature Tf detected by the temperature sensor S4. Set accordingly. That is, the CPU 201 sets the temperature Tf detected by the temperature sensor S4 as the estimated temperature of the image forming unit 20 (process component), and sets the image forming conditions according to the estimated temperature.

  As a result, even if the temperature around the image forming apparatus 100 varies depending on the heating device or the like, the image forming conditions are set based on the information of the temperature Tf of the fixing device 30 close to the temperature of the image forming unit 20. Therefore, the image forming conditions of the image forming unit can be set appropriately, and the quality of the image formed on the sheet P can be maintained.

  When the temperature Tf detected by the temperature sensor S4 is higher than the temperature Ta detected by the environment sensor S5, the CPU 201 sets the image forming condition according to the temperature Ta detected by the environment sensor S5. . That is, the CPU 201 sets the temperature Ta detected by the environment sensor S5 as the estimated temperature of the image forming unit 20 (process component), and sets the image forming conditions according to the estimated temperature.

  As a result, when there is residual heat due to the previous print job in the fixing device 30, the difference between the temperature Tf of the fixing device 30 and the actual temperature of the image forming unit 20 is large. The temperature Ta around the apparatus 100 is determined as the estimated temperature of the image forming unit 20. Therefore, the image forming conditions of the image forming unit 20 can be set appropriately, and the quality of the image formed on the sheet P can be maintained.

  As described above, according to the present embodiment, by using the information of the temperature Tf detected by the temperature sensor S4, it is not necessary to provide a temperature detecting unit in the image forming unit 20, and the image forming conditions of the image forming unit 20 are appropriately set. Can be set. Even when the temperature around the image forming apparatus 100 changes, a developer image can be quickly formed on the sheet P under appropriate image forming conditions (process conditions), and finally formed on the sheet P. Image defects can be suppressed.

  The present invention is not limited to the embodiment described above, and many modifications are possible within the technical idea of the present invention. In addition, the effects described in the embodiments are merely a list of the most preferable effects resulting from the present invention, and the effects of the present invention are not limited to those described in the embodiments.

  In the above-described embodiment, the case where the image forming apparatus is a printer has been described. However, the present invention is not limited to this.

  In the above-described embodiment, the case where the fixing device is a heating roller system in which the fixing device is heated by the fixing roller has been described. However, the present invention is not limited to this. An on-demand fixing system in which the fixing device forms a fixing nip part by pressing a heat source such as a ceramic heater through an endless film with a pressure roller, and heats and presses the sheet while nipping and conveying the sheet at the fixing nip part. It may be the case.

DESCRIPTION OF SYMBOLS 20 ... Image formation part (image formation means), 30 ... Fixing device (fixing means), 100 ... Image forming apparatus, 201 ... CPU (control means), S4 ... Temperature sensor (fixing temperature detection means), S5 ... Environment sensor ( Environmental detection means)

Claims (5)

Image forming means for forming a developer image on the sheet;
Fixing means for heating and fixing an unfixed developer image formed by the image forming means to a sheet;
Fixing temperature detecting means for detecting the heating temperature of the fixing means;
An image forming apparatus comprising: a control unit that sets an image forming condition of the image forming unit based on the temperature detected by the fixing temperature detecting unit.   2. The image forming unit according to claim 1, wherein the control unit sets an image forming condition of the image forming unit based on a temperature before the heating of the fixing unit detected by the fixing temperature detecting unit. Image forming apparatus. It further comprises an environmental detection means for detecting the environmental temperature of the device,
3. The image according to claim 1, wherein the control unit sets the image forming condition based on a temperature detected by the fixing temperature detection unit and a temperature detected by the environment detection unit. Forming equipment. The control means includes
The image forming apparatus according to claim 3, wherein the image forming condition is set based on a lower one of a temperature detected by the fixing temperature detecting unit and a temperature detected by the environment detecting unit. . The image forming unit includes:
An image carrier for carrying a developer image;
A charging member for charging the image carrier;
A transfer member for transferring the developer image to the sheet;
A power supply device that applies a charging bias to the charging member and a transfer bias to the transfer member, and
The image forming apparatus according to claim 1, wherein the control unit sets the charging bias and the transfer bias as the image forming conditions.

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