JP2010134407A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suitably control an image forming apparatus so that temperature of a developing motor may not be excessively raised without directly detecting the temperature of the developing motor that drives the developing roller. <P>SOLUTION: The image forming apparatus executes a program including: a step (S100) of calculating developing motor varying temperature on the basis of an action mode of the image forming apparatus; a step (S200) of estimating power source off time when the power source is turned off on the basis of the temperature change in a fixing thermistor; a step (S300) of correcting the developing motor varying temperature on the basis of the power source off time; a step (S400) of calculating developing motor estimated temperature by adding the environmental temperature to the corrected developing motor varying temperature; and a step (S600) of lowering the temperature of the developing motor by carrying out intermittent image forming processes until the temperature becomes less than 80°C when the estimated developing motor temperature becomes 100°C or more. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an image forming apparatus such as a copying machine, a printer, a facsimile machine, or a combination machine combining two or more of them, which forms a toner image by electrophotography, and more particularly to control of a developing motor that drives a developing roller.

  In an image forming apparatus such as a copying machine, a printer, a facsimile machine, or a combination machine combining two or more of them, which normally forms a toner image, an electrostatic latent image is usually formed on an image carrier such as a photosensitive member in an exposure process. Then, the electrostatic latent image is developed by a development process to form a visible toner image, and the visible toner image is transferred to a recording medium such as a recording paper by a transfer process, or is temporarily transferred by an intermediate transfer belt or the like. The toner image transferred to the recording medium in the fixing process is fixed onto the recording medium (hereinafter referred to as recording paper). it can.

  In the development process, for example, a drum-type photosensitive member that is an electrostatic latent image carrier and a developing roller that is a developer carrier are carried at a certain interval, and between the developing roller and the drum-type photosensitive member. A so-called non-contact type development is performed in which an electric field is formed, and a toner as a developer on the developing roller is made to fly to an electrostatic latent image on a drum type photosensitive member to form a toner image. Sometimes. In such an image forming apparatus, for example, a developing roller, a toner supply roller that supplies toner as a developer to the developing roller, a thin layer forming blade that uniformly applies a thin layer on the developing roller, a toner seal member, A developing device is formed by a static elimination mechanism, a toner storage unit, a stirring blade for stirring the toner, and the like. It has been put into practical use that the developing device is made into a cartridge (toner cartridge) and can be easily attached to and detached from the image forming apparatus.

  In the fixing process, it is necessary to fix an unfixed toner image formed on the recording paper to obtain a permanent image, and a heat fixing method is widely used as the fixing method. In the heat fixing method, generally, a fixing device is used that includes a heating roller on the side where an unfixed toner image on the recording paper contacts, and a pressure roller that conveys the recording paper between the heating rollers. . In such a fixing device, a fixing thermistor is provided in the vicinity of the heating roller or in the heating roller, and the temperature detected by the fixing thermistor is controlled to a predetermined temperature (feedback control or on / off control), so A fixed toner image is formed on the recording paper that has passed through. The recording paper on which the toner image is formed in this manner is discharged to a discharge tray or the like of the image forming apparatus.

  In such an image forming apparatus, when the image forming apparatus is operated after being stopped for a certain period of time, there may be a problem such as a significant decrease in the charge amount of the developer. . Japanese Patent Laid-Open No. 8-62984 (Patent Document 1) discloses an image forming apparatus that operates a toner stirring member as a warm-up process in such a case. Japanese Patent Laid-Open No. 2000-47487 (Patent Document 2) discloses an image forming apparatus in which the warm-up time does not become long even if such warm-up processing is appropriately performed.

  An image forming apparatus disclosed in Patent Document 1 includes an image forming apparatus main body, a developing unit that supplies developer charged by a stirring member to an image carrier on which a latent image is formed, A fixing means for fixing an image on an image forming medium onto which an image on the image carrier developed with the developer is transferred, a temperature detecting means for detecting the temperature of the fixing means, and a temperature detected by the temperature detecting means. And a stirring member driving unit that drives the stirring member of the developing unit at a higher speed than usual when the power of the image forming apparatus main body is turned on at a temperature equal to or lower than a predetermined temperature.

  According to the image forming apparatus disclosed in Patent Document 1, when the power is turned on while the temperature of the fixing unit is lowered, the charge amount of the developer is rapidly increased to a predetermined value or more by high-speed driving of the stirring member. Therefore, the image forming operation after a predetermined time can be executed without any trouble.

  An image forming apparatus disclosed in Patent Document 2 includes a developing unit that develops an electrostatic latent image formed on the surface of an image carrier as a toner image, and a transfer unit that transfers the toner image on the image carrier to a transfer material. An image forming apparatus comprising: a fixing unit that heats and fixes a toner image transferred onto a transfer material; and a control unit that controls the operation of the developing unit, wherein the developing unit stores a toner container. A toner conveying member that stirs and conveys the toner in the developing container, and the toner conveyed by the toner conveying member is carried on the surface and conveyed to the developing position, and is attached to the electrostatic latent image on the image carrier. A developing member that develops the toner image; and a regulating member that applies a charge to the toner carried on the surface of the developing member and regulates the toner layer thickness. Fixing member and fixing member Temperature detecting means for detecting the temperature, and the control means idles the toner conveying member after power-on or reset of the image forming apparatus main body, and the idling time according to the output value of the temperature detecting means It is characterized by changing.

  According to the image forming apparatus disclosed in Patent Document 2, the image forming apparatus is subjected to the purpose of stabilizing the image density during the initial check of the main body of the image forming apparatus according to the output value of the temperature detecting means for detecting the temperature of the fixing member. By changing the initial idle rotation time of the toner conveying member of the developing unit and the initial idle rotation of the developing member, it is possible to shorten the start-up time of the image forming apparatus main body, and excessive initial idle rotation of the developing member Therefore, it is possible to suppress excessive charge-up of the toner in the developing unit.

JP-A-8-62984 JP 2000-47487 A

  The image forming apparatus disclosed in Patent Document 1 or Patent Document 2 described above detects the temperature of the fixing unit or the fixing member, and based on the temperature, operates the stirring member of the developing unit at a higher speed than usual. For example, the time for idly rotating the toner conveying member is changed. In such a case, if the temperature of the motor that rotates the stirring member or the toner transport member is high, the stirring member or the toner transport member cannot be operated normally.

  However, in the image forming apparatus disclosed in Patent Document 1 or Patent Document 2 described above, the temperature of the motor for operating the stirring member or the toner conveying member is not described.

  By the way, with the downsizing and cost reduction of the toner cartridge, the agitation blade in the toner cartridge is deleted, or the toner storage part is formed only with a simple partition wall (supplied to the hopper and developing roller for storing the toner) In some cases, the toner is not divided into a buffer for storing toner). In such a case, toner tends to aggregate and the driving load of the developing roller tends to increase. When the driving load of the developing roller is large, the driving load of the developing motor increases. In such a case, by increasing the driving current of the developing motor, the developing motor is normally operated to rotate the developing roller normally even when the driving load of the developing roller increases. However, when the drive current is increased in this way, the motor temperature rises and problems such as insulation failure may occur inside the motor. For this reason, it is necessary to suppress the temperature rise of the developing motor.

  Providing a thermistor in the developing motor itself to suppress the temperature rise of the developing motor increases the cost because a new thermistor is required. On the other hand, it is conceivable to control the developing motor based on the temperature of the fixing means or the fixing member in consideration of the above-mentioned Patent Document 1 and Patent Document 2. However, in this case, since the temperature of the developing motor is not directly detected, it may be difficult to appropriately suppress the temperature increase of the developing motor.

  Accordingly, the present invention provides an image in which an electrostatic latent image is formed on an electrostatic latent image carrier, the electrostatic latent image is developed by a developing device to form a toner image, and the toner image is fixed on a recording medium by a fixing device. Appropriate control of image forming processing so that the temperature of the developing motor does not rise above a predetermined temperature without directly detecting the temperature of the developing motor that drives the developing roller included in the developing device. It is an object of the present invention to provide an image forming apparatus capable of performing the above.

In order to solve the above-described problems, the present invention provides the following image forming apparatus.
Forming an electrostatic latent image on the electrostatic latent image carrier, developing the electrostatic latent image with a developing device to form a toner image, and fixing the toner image onto a recording medium with a fixing device;
The developing device includes a developing roller and a developing motor that drives the developing roller,
The fixing device is an image forming apparatus including a fixing roller, a fixing heater for heating the fixing roller, and a fixing device temperature detecting unit for detecting a fixing device temperature,
A developing motor temperature calculation unit that estimates the temperature of the developing motor by integrating the fluctuating temperature of the developing motor at predetermined time intervals corresponding to the operating state of the image forming apparatus;
The image forming apparatus includes a developing motor temperature reduction processing unit that controls the image forming apparatus so that the temperature of the developing motor does not rise above a predetermined temperature based on the calculated temperature of the developing motor.

  In the image forming apparatus having such a configuration, the temperature of the developing motor can be estimated from the operation state (in other words, the operation mode) of the image forming apparatus. That is, depending on the operation state (operation mode), the fixing heater is energized, the motor that drives the recording medium conveyance roller is energized, or the developing motor is energized. Based on these operation modes, the temperature of the developing motor is not directly detected by obtaining the varying temperature of the developing motor at predetermined time intervals and integrating the varying temperature at the certain time intervals ( The temperature of the developing motor can be estimated without providing a temperature sensor in the developing motor). When the temperature of the developing motor estimated as described above increases, for example, the image forming apparatus can be operated intermittently so that the temperature of the developing motor does not rise above a predetermined temperature. As a result, without directly detecting the temperature of the developing motor that drives the developing roller included in the developing device, the image forming apparatus, and more specifically, image forming, can be performed so that the temperature of the developing motor does not rise above a predetermined temperature. The image forming process by the apparatus can be appropriately controlled. The fixing device temperature may be the temperature of the fixing roller (in other words, the heating roller) of the fixing device or the temperature near the heating roller. In short, the fixing device temperature is the fixing roller (heating roller). ) Is detected by a temperature detection unit provided in a conventional fixing device in order to control (feedback control or on / off control) to a predetermined temperature (typically a fixing temperature at which a toner image can be fixed on a recording medium). Temperature.

Here, for example, the image forming apparatus
A storage unit for storing a temperature change table indicating a change in temperature of the developing motor, which is set according to the operation state of the image forming apparatus;
An environmental temperature detection unit for detecting the environmental temperature of the image forming apparatus,
The developing motor temperature calculation unit calculates a motor fluctuation temperature obtained by integrating the fluctuation temperature for each predetermined time interval using a temperature change table corresponding to the operation state of the image forming apparatus, and calculates the calculated motor fluctuation temperature and The temperature of the developing motor can be calculated based on the environmental temperature detected by the environmental temperature detector.

  For example, if the operation state of the image forming apparatus is different, the temperature change of the developing motor depends on whether the fixing heater is energized, whether the motor that drives the recording medium conveyance roller is energized, whether the developing motor is energized, etc. Is different. The motor fluctuation temperature is calculated using a temperature change table set according to such an operating state. The temperature of the developing motor can be calculated by adding the environmental temperature of the image forming apparatus (for example, the temperature near the transfer roller) to the motor fluctuation temperature.

In addition, the image forming apparatus
A power-off time calculating unit that calculates a power-off time from when the image forming apparatus is turned off to when it is turned on based on the fixing device temperature detected by the fixing device temperature detecting unit;
The image forming apparatus may further include a developing motor temperature correcting unit that corrects the calculated developing motor temperature based on the power off time calculated by the power off time calculating unit.

  When the power is turned off, the developing motor temperature decreases. However, when the power is turned off, the developing motor temperature cannot be estimated. Even in such a case, the power off time is calculated based on the temperature of the fixing device, and the developing motor temperature is corrected by assuming that the developing motor temperature has decreased by a temperature corresponding to the power off time. The temperature of the developing motor can be calculated. A developing motor temperature correction unit for this calculation can be provided.

Here, the image forming apparatus includes a fixing device temperature change table indicating a change in fixing device temperature while the power is turned off, and a developing motor temperature change table indicating a change in temperature of the developing motor while the power is turned off. And further comprising a storage unit for storing
The power-off time calculation unit calculates the power-off time based on the fixing device temperature at the time of power-off detected by the fixing device temperature detection unit, the fixing device temperature at the time of power-on, and the fixing device temperature change table,
The developing motor temperature correction unit can be configured to correct the temperature of the developing motor based on the power-off time and the developing motor temperature change table.

  By using the fixing device temperature change table, it is possible to calculate how long the difference in the fixing device temperature (subtracting the fixing device temperature when the power is turned on from the fixing device temperature when the power is turned off) is realized. Based on this, the power-off time can be calculated. If the development motor temperature change table is used, it is possible to calculate how much the temperature of the development motor is lowered due to the length of the power-off time, and based on this, the temperature of the development motor can be corrected. By correcting in this way, the temperature of the developing motor can be calculated.

  For example, when the calculated developing motor temperature reaches a predetermined first temperature, the developing motor temperature lowering processing unit performs image forming processing until the developing motor temperature lowering processing unit decreases to a second temperature lower than the first temperature. The image forming apparatus can be controlled to operate intermittently.

  When the temperature of the developing motor reaches a predetermined first temperature, the image forming process is intermittently operated so that the developing motor is not driven, and the temperature of the developing motor is lowered. Such intermittent operation processing is continuously performed until the temperature of the developing motor is lowered to a second temperature lower than the first temperature. Thereby, it can suppress that the temperature of a developing motor rises more than predetermined temperature.

Further, for example, the image forming apparatus
A non-volatile memory with a limited number of writes;
When the temperature of the developing motor changes to a predetermined value or more, it can be configured to further include a processing unit that writes at least one of the temperature of the developing motor and the temperature of the fixing device to the nonvolatile memory.

  In order to respond to power off, at least one of the temperature of the developing motor and the temperature of the fixing device is written and stored in a non-volatile memory that retains memory without supplying power. In this case, the data is written in the nonvolatile memory only when the temperature of the developing motor with little change has changed greatly (changed to a predetermined value or more). As a result, the number of times of writing to the nonvolatile memory can be greatly reduced, so that the limitation on the number of times of writing to the nonvolatile memory does not become a problem.

  In the image forming apparatus according to the present invention, image stabilization processing for stably performing toner image formation may be performed at a predetermined timing. For this purpose, the image forming apparatus includes an image stabilization processing unit. Further, it may be included. In addition, when image stabilization processing can be performed, the image stabilization processing unit may further include an interruption prevention processing unit that prevents interruption of the image stabilization processing by the image stabilization processing unit so that appropriate image stabilization processing can be performed. Good.

  Here, the “interruption prevention processing unit” determines whether or not the developing motor temperature is equal to or higher than a predetermined image stabilization processing start limit temperature prior to the start of the image stabilization processing by the image stabilization processing unit. If the temperature is higher than the temperature, the image stabilization process is prohibited, and if it is lower than the temperature, the image stabilization process is permitted.

In this case, the image forming apparatus may further include a process start limit temperature storage unit that stores the image stabilization process start limit temperature.
The image stabilization process start limit temperature is selected from among one or more types of image stabilization processes by the image stabilization processing unit when the developing motor temperature is the limit temperature. In order to decrease the developing motor temperature, the developing motor temperature rises to the predetermined temperature or more after the processing time normally known in advance required for the processing has elapsed. A temperature at which the image forming process is controlled (for example, control for switching from continuous printing to intermittent printing is performed) can be exemplified. In this case, if the image stabilization process is started at a temperature lower than the image stabilization process start limit temperature, the process ends (until the processing time normally known in advance required for the image stabilization process elapses). ) The developing motor temperature does not reach the predetermined temperature or higher.

As the above "image stabilization process"
(1) Stabilization processing for setting an appropriate AC voltage so as not to cause image defects when a developing AC voltage is applied to the developing roller
(2) Stabilization process to set the development bias to obtain the proper toner adhesion amount (appropriate image density) (3) Stabilization process to adjust the exposure by the image exposure device so that even thin lines can be properly reproduced (4 ) One or more stabilization processes selected from a stabilization process for performing a gamma correction process, etc.
(5) The developing roller leveling process (developing roller aging process) can be exemplified.
If the developing device is left unused for a long time without using the developing device, the developing roller is deformed at the nip portion between the developing roller and the developer supply roller facing the developing roller. Since development unevenness and the like occur when development is performed, this is a rotation process of the developing device for waiting for the deformation to recover.

  Thus, prior to the start of the image stabilization processing by the image stabilization processing unit, it is determined whether or not the developing motor temperature is equal to or higher than a predetermined image stabilization processing start limit temperature. By prohibiting the stabilization process and permitting the image stabilization process if the temperature is lower than the temperature, the image stabilization process can be performed appropriately.

  For example, in a color image forming apparatus using yellow (Y), magenta (M), cyan (C), and black (K) toners, if the stabilization process is interrupted due to an increase in the developing motor temperature, the stability of each color is stabilized. When the stabilization process cannot be performed in the same environment (temperature / humidity), the development or primary transfer changes depending on the environment, and the proper stabilization process cannot be performed. By adopting an interruption prevention processing unit that prevents interruption, stabilization processing for each color can be performed in the same environment, and appropriate stabilization processing can be performed regardless of environmental fluctuations.

  At the start of leveling rotation of the developing roller, it is determined whether the developing motor temperature is equal to or higher than a predetermined image stabilization processing start limit temperature before the leveling rotation starts. If the rotation is prohibited and the rotation is allowed to be lower than the temperature, the rotation can be completed smoothly and easily in a relatively short time.

  As described above, according to the present invention, an electrostatic latent image is formed on an electrostatic latent image carrier, the electrostatic latent image is developed by a developing device to form a toner image, and a toner is applied to a recording medium by a fixing device. An image forming apparatus capable of fixing an image, wherein an image is formed so that the temperature of the developing motor does not rise above a predetermined temperature without directly detecting the temperature of the developing motor that drives the developing roller included in the developing device. An image forming apparatus capable of appropriately controlling processing can be provided.

1 is a perspective view illustrating an outline of a configuration of an image forming apparatus according to an embodiment of the present invention. It is a figure which shows the outline | summary of a structure of the image forming apparatus shown in FIG. FIG. 2 is a cross-sectional view illustrating a developing rack of the image forming apparatus illustrated in FIG. 1. FIG. 2 is a cross-sectional view illustrating a developing device (toner cartridge) of the image forming apparatus illustrated in FIG. 1. FIG. 2 is a control block diagram of the image forming apparatus shown in FIG. 1. 6A is a diagram showing a developing motor temperature fluctuation table (part 1) stored in the table storage unit shown in FIG. 5, and FIG. 6B is a diagram in the operation mode described in FIG. 6A. It is a figure which shows the time change of developing motor fluctuation | variation temperature, Comprising: It is the figure used as the basis of table preparation of FIG. 6 (A). FIG. 7A is a diagram showing a development motor temperature fluctuation table (part 2) stored in the table storage unit shown in FIG. 5, and FIG. 7B is a diagram in the operation mode shown in FIG. It is a figure which shows the time change of developing motor fluctuation | variation temperature, Comprising: It is the figure which became the basis of table preparation of FIG. 7 (A). FIG. 8A is a diagram showing a developing motor temperature fluctuation table (part 3) stored in the table storage unit shown in FIG. 5, and FIG. 8B is a diagram in the operation mode shown in FIG. It is a figure which shows the time change of developing motor fluctuation | variation temperature, Comprising: It is the figure which became the basis of table preparation of FIG. 8 (A). It is a figure which shows the fixing thermistor temperature fall table memorize | stored in the table memory | storage part shown in FIG. It is a figure which shows the time change of fixing thermistor temperature. It is a figure which shows the developing motor temperature fall table memorize | stored in the table memory | storage part shown in FIG. It is a figure which shows the time change of developing motor temperature. It is a flowchart which shows the control structure of the main program performed by the control part shown in FIG. It is a flowchart which shows the control structure of the developing motor fluctuation temperature calculation processing program (subroutine program) shown in FIG. It is a flowchart which shows the control structure of the power-off time estimation processing program (subroutine program) shown in FIG. It is a flowchart which shows the control structure of the developing motor fluctuation temperature correction processing program (subroutine program) shown in FIG. It is a flowchart which shows the control structure of the developing motor estimated temperature calculation processing program (subroutine program) shown in FIG. It is a flowchart which shows the control structure of the developing motor estimated temperature memory processing program (subroutine program) shown in FIG. It is a flowchart which shows the control structure of the developing motor temperature fall process program (subroutine program) shown in FIG. It is a flowchart which shows the control structure of the image stabilization process interruption prevention process program (subroutine program) shown in FIG. It is a flowchart which shows the control structure of the developing roller aging interruption prevention processing program (subroutine program) shown in FIG. It is a figure which shows the time change of the developing motor temperature when the developing motor temperature fall process program shown in FIG. 19 is performed.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the following description, the same parts are denoted by the same reference numerals. Their names and functions are also the same. Therefore, detailed description thereof will not be repeated.
[Overall configuration of image forming apparatus]
Hereinafter, an example 10 of the image forming apparatus according to the present embodiment will be described. FIG. 1 is a perspective view of the image forming apparatus 10. Note that the image forming apparatus according to the present embodiment is not limited to such an image forming apparatus 10, and a developing motor that drives a developing roller (this developing motor is not provided with a temperature detection sensor). Any temperature may be used as long as the image forming apparatus is controlled so that the temperature of the developing motor is not excessively high.

  In the image forming apparatus 10, the image reading apparatus 12 and the image forming unit 14 are separated from each other, and the image reading apparatus 12 is disposed above the image forming apparatus 10. This is a so-called in-body discharge type image forming apparatus in which a discharge tray T for discharging recording paper is formed in a space in the housing of the image forming apparatus 10. The image forming apparatus 10 includes an automatic document feeder 11, an image reading device 12, an operation panel PA, a discharge tray T, a manual feed tray 13 (in a closed state in FIG. 1), and an image forming unit 14. Including.

  The image forming apparatus 10 includes an upper part of the image forming apparatus 10 (the automatic document feeder 11, the image reading device 12, the operation panel PA, and the discharge tray T, which may be collectively referred to as a cover). Then, the image forming apparatus 10 is opened obliquely upward with the left and right fulcrums on the back side as the rotation center. For example, when the recording paper is jammed, the upper portion of the image forming apparatus 10 can be opened obliquely (the cover is opened), and the jammed recording paper can be taken out.

  The automatic document feeder 11 can be opened and closed with respect to the image reading device 12, and also serves as a cover that covers a document placed on a glass plate that is a document placement table of the image reading device 12. The operation panel PA is equipped with a liquid crystal display D in addition to a start key SW for instructing copy image formation and facsimile transmission, a key group K such as a numeric keypad for setting the number of image formations, and the like. The liquid crystal display unit D reflects key operations by the user, displays an instruction menu for the user, and displays information from an image forming unit 14 (described later in detail) that performs image formation. The operation panel is also provided with a power button.

  The image reading device 12 can optically read an image of a document placed stationary on the platen glass, and is conveyed from the document placing tray 11A by the automatic document feeder 11 to the document discharge tray 11B. It is also possible to optically read an image of a document that is discharged and moves along the glass plate for document panning of the image reading device 12 in the middle thereof.

  The image data read by the image reading device 12 is sent to the image forming unit 14 for image formation, and is used for image formation there or for facsimile transmission. Image data transmitted from a computer (not shown) or the like is sent to the image forming unit 14 and used for image formation there.

  The image forming unit 14 forms a toner image on recording paper by an electrophotographic method. In the following description, the recording medium is assumed to be recording paper, and the image forming apparatus according to the present embodiment shown in FIG. 1 is assumed to be a multifunction device capable of full-color copying. The image forming apparatus shown in FIG. 1 may be capable of forming images on both sides of the recording paper. In addition to this, the present invention may be a tandem type full-color image forming apparatus or a monochrome image forming apparatus.

  FIG. 2 shows an internal configuration of the image forming apparatus 10. The image forming apparatus 10 in FIG. 2 is a so-called four-cycle color image forming apparatus. A mechanism (image forming unit 14) for forming an image on recording paper will be described with reference to FIG.

  The image forming apparatus 10 includes a drum-type photosensitive member 1 (hereinafter referred to as a photosensitive member 1), and a charger 2, a developing unit 4, an intermediate transfer belt 6, and a cleaning device 5 are arranged around the drum-type photosensitive member 1 in this order. An image exposure device 3 that exposes an image to the photoreceptor 1 from between the charger 2 and the developing unit 4 is provided, and below that is a recording paper that supplies the recording paper set on the manual feed tray 13 to the image forming unit. A supply unit 9 is provided. The recording paper is not limited to the paper set on the manual feed tray 13 and supplied to the image forming unit 14 via the recording paper supply unit 9, but from the paper supply unit provided in the image forming apparatus 10 to the image forming unit 14. It may be supplied.

  The photoreceptor 1 is rotationally driven in the clockwise direction in the figure by a photoreceptor drive motor (not shown). A photosensitive member charging voltage is applied to the charger 2 at a predetermined timing from a charging power source (not shown) whose output is variable.

  The developing unit 4 has a developing rack 40 mounted with a black developing device 4K, a cyan developing device 4C, a magenta developing device 4M, and a yellow developing device 4Y. The developing rack 40 can be driven to rotate counterclockwise in the figure by a driving unit (not shown) including a stepping motor. The developing devices are mounted on the developing rack 40 in the order of the yellow developing device 4Y, the black developing device 4K, the cyan developing device 4C, and the magenta developing device 4M in the rack rotation direction at equal central angular intervals of 90 degrees.

  The black developing device 4K is formed in the form of the black toner cartridge KC. Similarly, the cyan developing device 4C is in the form of the cyan toner cartridge CC, the magenta developing device 4M is in the form of the magenta toner cartridge MC, and the yellow developing device 4Y. Are formed in the form of a yellow toner cartridge YC, and are mounted on the developing rack 40 in a replaceable manner. Each developing device is equipped with a developing roller (toner carrier roller) 41 for developing the electrostatic latent image on the photoreceptor 1. Each developing roller 41 has an elastic surface layer portion, for example.

  In addition to the developing roller 41, each developing device includes a toner supply roller that supplies toner to the developing roller 41, a toner regulating blade that regulates the layer thickness of toner supplied from the toner supply roller on the developing roller 41, and the like. . Each developing device can reversely develop the electrostatic latent image on the photoreceptor 1 using negatively chargeable toner.

  Each developing device can be placed at a developing position where the electrostatic latent image on the photoreceptor 1 is developed by the developing roller 41 by rotating the developing rack 40. The developing roller 41 disposed at the developing position faces the surface of the photosensitive member 1, and a developing bias can be applied from a developing bias power source (not shown) whose output is variable. Further, the developing roller 41 disposed at the developing position can be driven to rotate counterclockwise in the figure by a developing motor. Further, a toner supply bias can be applied to the toner supply roller from a power supply (not shown), and a regulation bias can be applied to the toner regulation blade. Details of the developing device will be described later.

  The intermediate transfer belt 6 is connected to a driving roller 61, a driven counter roller 62 opposite to the driving roller 61, a primary transfer roller 63 disposed opposite to the photosensitive member 1, and a primary transfer roller 63, so that the intermediate transfer belt 6 is attached to the photosensitive member 1. It is wound around a roller group composed of rollers 64 to be brought into contact with each other.

  A primary transfer voltage can be applied to the primary transfer roller 63 from a primary transfer power supply (not shown). The intermediate transfer belt 6 can be rotated counterclockwise by driving the drive roller 61 counterclockwise in the figure by a transfer belt drive motor (not shown).

  A secondary transfer roller 7 is disposed on a portion of the intermediate transfer belt 6 that is wound around the driving roller 61. The secondary transfer roller 7 is brought into contact with and separated from the intermediate transfer belt 6 at a predetermined timing. A secondary transfer voltage can be applied to the secondary transfer roller 7 from a secondary transfer power supply (not shown).

  A cleaning device 65 that removes and cleans secondary transfer residual toner and the like from the portion of the intermediate transfer belt 6 that is wound around the driven counter roller 62 is disposed. The cleaning device 65 is provided with a cleaning blade for removing, for example, secondary transfer residual toner on the intermediate transfer belt 6.

  A fixing device 8 is provided above the secondary transfer roller 7, and a recording paper discharge roller pair R2 and a discharge tray T are sequentially provided on the downstream side thereof. The fixing device 8 includes a heating roller 81 on the side where the unfixed toner image on the recording paper S comes into contact, and a pressure roller 82 that conveys the recording paper with the heating roller 81 interposed therebetween. Below the secondary transfer roller 7, a pair of paper feed rollers R <b> 1 that conveys the recording paper supplied from the recording paper supply unit 9 to the secondary transfer roller 7 at a predetermined timing is disposed.

  According to the image forming apparatus 10 described above, on the recording paper S using one or more of 4K, 4C, 4M, and 4Y developing devices under the instruction of a control unit (not shown in FIGS. 1 and 2). A toner image can be formed. An example of forming a full-color image using four developing devices will be described below.

  First, the developing rack 40 is rotated by a rack driving unit (not shown) so that the yellow developing device 4Y is disposed at a developing position where the developing roller 41 faces the photosensitive member 1, and the photosensitive member 1 is rotated clockwise in the drawing. The intermediate transfer belt 6 is also rotated. At this stage, the secondary transfer roller 7 is separated from the intermediate transfer belt 6.

  The surface of the rotating photosensitive member 1 is uniformly charged to a predetermined potential by a charger 2 to which a charging voltage is applied from a charging power source, and image exposure is performed on the charged region from an image exposure device 3 to thereby cause a yellow electrostatic latent image. An image is formed, and the latent image is developed by the developing device 4Y to form a yellow toner image. The yellow toner image is primarily transferred onto the intermediate transfer belt 6 by a primary transfer roller 63 to which a primary transfer voltage is applied.

  Further, in the same manner as in the case of forming the yellow toner image, the magenta developing device 4M is arranged at the developing position to form a magenta toner image on the photosensitive member 1, and this is transferred onto the intermediate transfer belt 6, and then cyan. The developing device 4C is arranged at the developing position to form a cyan toner image on the photosensitive member 1, and this is transferred onto the intermediate transfer belt 6, and then the black developing device 4K is arranged at the developing position and placed on the photosensitive member 1. A black toner image is formed and transferred onto the intermediate transfer belt 6. The formation of each color toner image on the photosensitive member 1 and the primary transfer onto the intermediate transfer belt 6 are performed at the timing when these toner images are superimposed and transferred onto the intermediate transfer belt 6.

  On the other hand, when the recording paper is pulled out and supplied from the recording paper supply unit 9 by the paper feed roller pair R1, and the leading edge of the recording paper is detected by a timing sensor (not shown) on the exit side of the paper feed roller pair R1, the paper feed roller The pair R1 is stopped and the recording paper is kept waiting there.

  Prior to the multiple toner image on the intermediate transfer belt 6 reaching the secondary transfer roller 7 by the rotation of the intermediate transfer belt 6, the secondary transfer roller 7 is brought into contact with the intermediate transfer belt 6 so that the multiple toner image is secondary. The recording paper is also fed into the secondary transfer area by the pair of paper feed rollers R1 at the timing of reaching the transfer area.

  Thus, the multiple toner image is secondarily transferred onto the recording paper. The recording paper onto which the multiple toner images have been transferred is fixed on the toner image by the fixing device 8 and discharged onto the discharge tray T by the recording paper discharge roller pair R2. Thus, a recording sheet on which a full color image is formed can be obtained.

  The primary transfer residual toner or the like on the photoreceptor 1 is removed and cleaned by the cleaning device 5, and the secondary transfer residual toner or the like on the intermediate transfer belt 6 is removed and cleaned by the cleaning device 65.

  A developing unit including a developing motor that drives the developing roller 41, which is a characteristic control target of the image forming apparatus 10, will be described below.

[Driving rack and developing roller drive]
FIG. 3 is a cross-sectional view schematically showing the vicinity of the developing rack 40 of the image forming apparatus 10. As described above, the black development device 4K, the cyan development device 4C, the magenta development device 4M, and the yellow development device 4Y are mounted on the development rack 40 to form the development unit 4.

  As shown in FIG. 3, the developing rack 40 is driven to rotate counterclockwise in the drawing by a developing rack motor 40B via a developing rack docking gear 40A. The development rack motor 40B is, for example, a two-phase excitation stepping motor, and the rotation direction and rotation speed are controlled by pulses output from the control unit. The developing rack 40 is rotated by the developing rack motor 40B when returning to the initial rack position or when moving the next developing device to the developing position during full color image formation as described above.

  Further, the developing roller 41 is driven to rotate counterclockwise in the figure by the developing motor 41B via the developing motor docking gear 41A. The development motor 41B is, for example, a two-phase excitation stepping motor, and the rotation direction and rotation speed are controlled by pulses output from the control unit.

  When the developing rack 40 rotates and the developing roller 41 reaches or passes through the developing position, the developing motor docking gear 41A and the driving gear of the developing roller 41 are engaged with each other. At this time, if the developing motor 41B is not rotating, tooth skipping of the developing motor docking gear 41A occurs, and the rotation load of the developing rack 40 becomes large and cannot be normally rotated. In order to suppress this, when the developing rack 40 is rotated, the developing motor 41B is rotated in synchronization with the rotation of the developing rack 40. In addition to such synchronous rotation, the development motor 41B is rotated to form a toner image on the photoreceptor 1 as described above.

  When the developing motor 41B is driven in this way (when a driving current is applied), the temperature of the developing motor 41B rises. If the temperature of the developing motor 41B rises, the winding temperature in the developing motor 41B through which the drive current flows increases, and if it rises too much, there is a possibility of insulation failure or ignition. As will be described later, the image forming apparatus 10 estimates the temperature of the developing motor 41B and controls itself (the image forming apparatus 10) based on the estimated temperature so that the temperature of the developing motor 41B does not rise too much.

[Development equipment]
A developing device in such a four-cycle type image forming apparatus 10 will be described. Since each developing device in the developing unit 4 of the image forming apparatus 10 has basically the same configuration except for the toner used, the black developing device 4K will be described as a representative here. The toner in the developing device here is a so-called one-component developer (developer mainly composed of toner without using a carrier), but a so-called two-component developer (developer mainly composed of toner and carrier) is used. You may employ | adopt the developing device to be used. In particular, a polymerized toner having a small particle size has a high fluidity and easily enters into a small gap and is hardened there. In particular, the driving load of the developing roller 41 may be increased.

  FIG. 4 shows a cross-sectional view of the vicinity of a central portion of the black developing device (hereinafter sometimes simply referred to as “developing device”) 4K (the central portion of the developing device 4K in the direction along the rotation axis). As shown in FIG. 4, the developing device 4K includes a toner storage unit 410, a head unit 420 having the developing roller 41 and the like, a partition wall 412 between the toner storage unit 410 and the head unit 420, and a partition wall 412. And a communication opening 411 that continues to. The developing roller 41 is an elastic rubber roller having a mandrel or a hollow aluminum blast roller. The outer diameter of the developing roller 41 is, for example, about 10 mm to 20 mm.

  In other developing devices including the black developing device 4K, the internal toner agitating blade is omitted in accordance with the downsizing and cost reduction of the developing device in the cartridge mode. In addition, the toner storage unit 410 may be formed with only simpler partitions than shown in FIG. In such a case, toner tends to aggregate and the driving load of the developing roller 41 tends to increase. When the driving load of the developing roller 41 is large, the driving load of the developing motor 41B increases. In such a case, as will be described later, when the temperature of the developing motor 41B rises by increasing the driving current of the developing motor 41B, etc., this temperature is set so that the temperature of the developing motor 41B does not rise above a predetermined temperature. The image forming apparatus 10 is controlled.

  In addition to the developing roller 41, the head unit 420 regulates the layer thickness of the toner supplied to the developing roller 41, a toner supply roller 422, and the toner carried on the developing roller 41 and conveyed to the electrostatic latent image developing region. The blade-type toner regulating member (toner thin layer forming member) 423 that frictionally charges the toner and the toner returning to the case of the developing device 4K while being carried on the developing roller 41 without being used in the developing region, and the toner Has a seal member 425 for sealing so as not to leak from the developing device 4K.

  The toner regulating member 423 (toner thin layer forming member) is a position facing the developing roller 41 and is longer than the developing region formed by the developing roller 41 provided along the rotation axis direction of the developing roller 41. For example, it is formed of a plate-shaped body made of stainless steel. The toner regulating member 423 may be any member as long as it can regulate a thin layer of toner conveyed to the developing area facing the photoreceptor 1 by the developing roller 41 and can frictionally charge the toner. And a flat plate member provided along the rotation axis of the developing roller 41.

  The seal member 425 is located at a position facing the developing roller 41 and is longer than the developing region formed by the developing roller 41 provided along the rotation axis direction of the developing roller 41, for example, conductive on a sponge material. Laminated with a conductive film. This conductive film faces the developing roller 41. Therefore, the seal member 425 is a seal member that abuts against the developing roller 41 by the elastic force of the sponge material to prevent the toner from leaking from the developing device 4K, and is carried on the developing roller 41 by the conductive film. It also serves as a charge removal member that removes the toner that returns to the case of the developing device 4K.

  Each developing device can be sequentially arranged at the developing position by rotating the developing rack 40 counterclockwise (hereinafter sometimes referred to as “positive direction”). FIG. 4 shows a state in which the black developing device 4K is disposed at the developing position. As shown in these drawings, at the developing position, the developing roller 41 of the developing device arranged there faces the photoreceptor 1 so that the electrostatic latent image on the photoreceptor 1 can be developed. The developing device disposed at the developing position is slightly inclined in the reverse rotation direction of the developing rack 40 from the horizontal plane including the central axis of the rotating shaft of the developing rack 40.

  When each developing device is placed at the developing position and rotates once around the rack rotation axis by one rotation in the forward direction of the developing rack 40, the toner in the toner storage unit 410 is weighted toward the communication opening 411 side. The toner that has moved and further moved to the communication opening 411 side can flow into the head unit 420 by its own weight through the communication opening 411. In the head unit 420, toner is stored around the toner supply roller 422.

  A developing bias is provided for the developing roller 41 of the developing device that is disposed at the developing position and is used for developing the electrostatic latent image on the photoreceptor 1, a supply bias is provided for the toner supply roller 422, and a restriction is provided for the toner regulating member 423. A neutralization bias is applied from a power supply (not shown) to the seal member 425 that also serves as a neutralization member.

  The developing roller 41 and the toner supply roller 422 of the developing device that is disposed at the developing position and is used for developing the electrostatic latent image on the photoreceptor 1 are rotationally driven by the developing motor 41B. At this time, the developing roller 41 and the toner supply roller 422 are rotated counterclockwise in the drawing. The toner supply roller 422 has, for example, at least a surface layer portion made of a foam material, and the toner stored in the head portion 420 is supplied with a physical force due to a difference in peripheral speed between these rollers and a supply bias supplied from a power supply (not shown). To the developing roller 41. The toner supply roller 422 also has a function of peeling off the toner that is carried on the developing roller 41 and returns to the case of the developing device from the developing roller 41. When the toner supply roller 422 is not provided, only the developing roller 41 is rotationally driven by the developing motor 41B.

[Control Configuration of Image Forming Apparatus: Control Circuit]
FIG. 5 is a block diagram schematically showing a control circuit of the image forming apparatus 10. As shown in FIG. 5, the control block of the image forming apparatus 10 includes a control unit 200 that controls the entire image forming apparatus 10, and an operation panel PA connected to an input port (not shown) of the control unit 200. An IF (interface) 220 connected to the control unit via it, a fixing thermistor 230 provided in the vicinity of the heating roller 81 (fixing roller 81) of the fixing device 8 or the heating roller 81 for detecting the fixing device temperature. And an environmental temperature detection sensor 240 that is provided in the vicinity of the secondary transfer roller 7 and detects an environmental temperature that is an internal temperature of the image forming apparatus 10, and detects the density of the toner image formed on the intermediate transfer belt 6. And an image density sensor 66. The environmental temperature detection sensor 240 is provided in the vicinity of the secondary transfer roller 7 because the secondary transfer roller 7 easily changes the resistance of the roller due to environmental changes, and changes the setting of the transfer voltage even if the environment changes. Otherwise, transfer failure will occur, so the environment in the vicinity is monitored so that the transfer voltage can be quickly changed when the environment changes.

  Further, other signals are input to the control unit 200 through the input port of the control unit 200, and other signals are output from the control unit 200 through the output port of the control unit 200. The control unit 200 includes a non-volatile memory (such as an EEPROM) 250 that stores a development motor temperature (development motor estimated temperature) and a fixing thermistor temperature that are calculated as described later, and a table storage unit that stores various tables described later. 260 is connected. Further, a limit temperature storage unit 270 that stores a predetermined image stabilization process start limit temperature, which serves as a reference for determining whether or not to allow start of an image stabilization process described later, is also connected. The nonvolatile memory 250, the table storage unit 260, and the storage unit 270 may be built in the control unit 200.

  The control unit 200 calculates a development motor estimated temperature, which is the estimated temperature of the development motor 41B, and executes a program for controlling the image forming apparatus 10 based on the development motor estimated temperature. Further, the control unit 200 is a subroutine program of this program, and a development motor fluctuation temperature calculation processing unit 202 that executes a development motor fluctuation temperature calculation processing program, and a power off time estimation processing part that executes a power off time estimation processing program. 204, a development motor fluctuation temperature correction processing section 206 that executes a development motor fluctuation temperature correction processing program, a development motor estimation temperature calculation processing section 208 that executes a development motor estimation temperature calculation processing program, and a development motor estimation temperature storage processing program Includes a developing motor estimated temperature storage processing unit 210 and a developing motor temperature lowering processing unit 212 that executes a developing motor temperature lowering processing program. The control unit 200 also includes an image stabilization processing unit 214 that executes a processing program for image stabilization, and an image stabilization processing interruption prevention processing unit that executes a processing program for preventing interruption of the image stabilization processing. 216.

  The image forming apparatus 10 estimates the temperature of the developing motor 41B using the time during which the developing motor 41B is excited or rotated and the environmental temperature that is the internal temperature of the image forming apparatus 10. At this time, the image forming apparatus 10 estimates the temperature change of the developing motor 41 </ b> B according to the operation mode of the image forming apparatus 10. For this purpose, the developing motor temperature fluctuation table shown in FIGS. 6A to 8A is stored in the table storage unit 260. The tables shown in FIGS. 6A to 8A are examples of developing motor temperature change tables (developing motor temperature fluctuation tables).

  FIG. 6A shows a developing motor temperature fluctuation table [applied in printing (image formation on recording paper) operation, initial operation, and image stabilization processing] stored in the table storage unit 260 shown in FIG. . This developing motor temperature variation table energizes a fixing heater (such as a halogen lamp heater provided on the shaft core side of the heating roller 81), energizes a recording paper conveyance motor, and rotates or excites the developing motor 41B. It is a table that is applied to the status. Since the developing motor 41B is energized, the developing motor 41B itself generates heat, and the temperature of the developing motor 41B rises.

  The “initial operation” is an operation performed when the power of the image forming apparatus is turned “on” or when the image forming apparatus main body cover opened for jam processing or the like is closed. When the main unit cover is closed, the developing rack 40 or the intermediate transfer belt 6 may not stop at the correct position, or the intermediate transfer belt may be dirty after the jam processing. This is an operation for cleaning the inside of the image forming apparatus.

  The “image stabilization process” is the following process. In the image stabilization process, at least one of the processes may be executed. However, in this case, the process is not executed independently, and the conditions described below are used. Multiple are executed.

<Image stabilization processing>
(1) Development leak detection When a voltage in which AC voltage and DC voltage are superimposed is used as the development bias applied to the development roller, if the development AC voltage is too high, an image failure occurs due to leakage, and the development AC voltage is low. If it is too high, image density unevenness occurs. Therefore, as the development AC voltage, for example, the development AC voltage is gradually increased, and a development AC voltage 100 V lower than the development AC voltage in which the leak is detected by the leak detection circuit is set, so that an appropriate image can be output. To.
The development leak detection is performed, for example, when the cartridge-type developing device or the photoconductor is replaced and the distance between the developing roller and the photoconductor changes or the environment changes greatly.
(2) Adjusting the maximum toner adhesion amount Determine the development bias at which the solid image has an appropriate toner adhesion amount.
A plurality of solid image adjustment patch images are formed with various development biases (particularly development DC voltages) changed, and the density of the patch images is read by an image density sensor so that an appropriate toner adhesion amount can be obtained. Adjust. In the case of the image forming apparatus 10, the patch image is formed on the intermediate transfer belt 6, and the density is read by the image density sensor 66.
(3) Image exposure adjustment Determine the amount of exposure that can reproduce thin lines properly.
A plurality of oblique patches are formed with different exposure amounts at the development output determined by the development leak detection and the maximum toner adhesion amount adjustment, and the patches are read by an image density sensor to determine an appropriate exposure amount. In the image forming apparatus 10, the laser light amount of the image exposure apparatus 3 is adjusted as the exposure amount adjustment.
(4) Gamma (γ) correction Create multiple gradation patterns with the development output and exposure determined by development leak detection, maximum toner adhesion adjustment, exposure control, and read the patch density with the image density sensor. Perform gamma correction.

The following can be exemplified as the timing of the above-described stabilization processing (1) to (4).
(1) When the units such as the developing unit 4 and the developing device (toner cartridge) are replaced, all stabilization processes are executed. (2) When 1000 sheets are printed, deterioration of the toner, developing roller, photoconductor, intermediate transfer belt, and the like may progress and an appropriate image may not be formed. Therefore, all stabilization processing is executed.
(3) If the environment (temperature and / or humidity) changes, the characteristics of the toner, developing roller, photoconductor, intermediate transfer belt, etc. may change, making it impossible to form a proper image. Perform stabilization.
(4) Since there is a possibility that a proper image cannot be formed after 200 sheets are printed, toner maximum adhesion amount control, exposure amount adjustment, and γ correction are executed, excluding development leak detection.

Here, the image stabilization process includes the development leak detection, the maximum toner adhesion amount adjustment, the image exposure adjustment, the γ correction, the developing roller leveling process, in other words, the developing roller aging process. .
When the developing device is left unused for a long time without using the developing device, the developing roller is deformed at the nip portion between the developing roller 41 and the developer supply roller 422 in contact therewith, and the deformation remains. When development is performed using these rollers, uneven development or the like occurs, and this is a rotation process of the developing device to wait for the deformation to recover.
The developing roller aging process can be instructed here by the user using an aging process instruction section (not shown) provided on the operation panel PA.

  FIG. 7A shows another developing motor temperature fluctuation table (applied to the standby state) stored in the table storage unit 260 shown in FIG. This development motor temperature fluctuation table is a table applied when the fixing heater is energized to adjust the temperature as a standby mode, the recording paper transport motor is not energized, and the development motor 41B is not excited. It is. Since the developing motor 41B is not energized, the developing motor 41B itself does not generate heat, and the temperature of the developing motor 41B decreases.

  FIG. 8A shows a further developing motor temperature fluctuation table (applied to the sleep state and the cover open state) stored in the table storage unit 260 shown in FIG. This developing motor temperature variation table is applied to a state where the fixing heater is not energized, the recording paper conveyance motor is not energized, and the developing motor 41B is not energized (sleep state or cover open state). Table Since the developing motor 41B is not energized, the developing motor 41B itself does not generate heat, and the fixing heater is not energized, so the temperature of the developing motor 41B quickly decreases. As described above, the cover is the upper part of the image forming apparatus 10 (the automatic document feeder 11, the image reading device 12, the operation panel PA, and the discharge tray T), and the recording paper is jammed in the paper passing path or the like. It is a cover that is opened from time to time. The cover opens obliquely upward with the left and right fulcrum of the image forming apparatus 10 as the center of rotation. This state is the cover open state.

The “development motor fluctuation temperature” in the leftmost column in the tables of FIGS. 6A to 8A is calculated before calculating the development motor fluctuation temperature based on the table, as will be described later. The developing motor fluctuation temperature stored in the memory 250.
The development motor temperature fluctuation tables shown in FIGS. 6A, 7A, and 8A are experimental values for rates of temperature rise and temperature fall of the development motor 41B for each operation mode of the image forming apparatus 10. It was created in search of.
That is, FIG. 6B, FIG. 7B, and FIG. 8B are the development motor fluctuation temperature and the development motor temperature fluctuation rate based on the temperature change of the development motor in each operation mode measured by experiment. Shows the relationship. FIG. 6A shows the fluctuation rate of the developing motor temperature during printing, initial operation, and image stabilization. In the state where the temperature of the developing motor has not risen immediately after the power is turned on (the developing motor fluctuation temperature is around 0 ° C.), the temperature of the developing motor is greatly increased and increases by 6800 (10 ⁻⁶ ° C.) in 100 milliseconds. As the temperature rises, it becomes saturated and the fluctuation rate becomes smaller. The table shown in FIG. 6A is an approximate expression of this relationship and is tabulated.
FIG. 7B is a graph showing the relationship between the fluctuation temperature and the fluctuation rate of the developing motor on standby. If the temperature of the development motor does not rise immediately after the power is turned on (the development motor fluctuation temperature is around 0 ° C), the temperature of the development motor hardly decreases even in the standby state, and the temperature around the development motor rises due to printing or the like. This shows that as the developing motor fluctuation temperature increases, the temperature that decreases in 100 milliseconds increases. The table shown in FIG. 7A is an approximate expression of this relationship.
The relationship between the developing motor fluctuation temperature and the fluctuation rate of the sleep and cover opening in FIG. The table shown in FIG. 8A is an approximate expression of this relationship.

The temperature at which the development motor fluctuation temperature changes in 100 milliseconds [100 ms] can be expressed by a linear expression of (development motor fluctuation temperature) × (fluctuation rate slope) + (fluctuation rate offset). The “rate slope” is the “variable rate slope” in the tables of FIGS. 6 (A) to 8 (A), which is the slope of the temperature that changes during 100 milliseconds [100 ms]. “Variation rate offset” is “variation rate offset” in the tables of FIGS. 6 (A) to 8 (A).

  Based on these tables, the temperature change amount of the developing motor 41B (the developing motor fluctuation temperature every 100 msec) can be calculated. The control unit 200 calculates the development motor temperature change amount based on the development motor fluctuation temperature, the fluctuation rate inclination, and the fluctuation rate offset before one cycle (100 msec is the cycle time) at 100 msec intervals. Calculate and add the development motor temperature change amount to the development motor fluctuation temperature in the previous cycle (resulting in addition because it is added every 100 msec) and calculate the development motor fluctuation temperature in this cycle. To do. The estimated developing motor temperature is calculated by adding the environmental temperature, which is the temperature inside the image forming apparatus 10 detected by the environmental temperature detection sensor 240, to the developing motor fluctuation temperature.

  In this way, the temperature of the developing motor 41B is estimated at a time interval (cycle time) of 100 msec. However, if the power of the image forming apparatus 10 is turned off, the temperature of the developing motor 41B cannot be estimated in this way. For this reason, when the power is turned on after the power is turned off, the time during which the power is turned off is calculated from the temperature change (temperature decrease amount) of the fixing thermistor, and the amount of decrease in the developing motor fluctuation temperature is corrected, The estimated developing motor temperature is calculated from the corrected developing motor fluctuation temperature. For this reason, in the table storage unit 260, a fixing thermistor temperature decrease table (FIG. 10 shows a change over time of the fixing thermistor temperature decrease) as an example of the fixing device temperature change table shown in FIG. 9 and the development shown in FIG. A developing motor temperature lowering table (FIG. 12 shows a time change of the developing motor temperature lowering) as an example of the motor temperature changing table is stored.

  The fixing thermistor temperature lowering table shown in FIG. 9 will be described. The temperature in the vicinity of the heating roller 81 (fixing thermistor temperature) detected by the fixing thermistor 230 is, for example, 160 ° C. during temperature adjustment in the standby mode, 180 ° C. during full color printing, and 170 ° C. during monochrome printing. Has been. If the fixing thermistor temperature detected by the fixing thermistor 230 is stored in the nonvolatile memory 250, the fixing thermistor temperature when the power is turned off is held in the nonvolatile memory 250 when the power is turned on. The power-off time is estimated based on the fixing thermistor temperature when the power is turned off, the fixing thermistor temperature when the power is turned on, and the fixing thermistor temperature lowering table shown in FIG.

The fixing thermistor temperature while the power is off is not greatly affected by the environmental temperature and the environmental humidity in which the image forming apparatus 10 is placed, and decreases. FIG. 10 shows an example of an actual time change of the fixing thermistor temperature drop with 200 ° C. as a base point. That is, it is an actually measured value at which the fixing temperature actually drops from 200 ° C.
The fixing thermistor temperature decrease table shown in FIG. 9 is created by approximating the temporal change of the fixing thermistor temperature decrease of FIG. 10 with a linear regression line. The solid line shown in FIG. 10 shows the fixing thermistor temperature decrease curve, and the alternate long and short dash line shown in FIG. 10 shows the approximation of the fixing thermistor temperature decrease curve by a linear regression line.
The table shown in FIG. 9 is obtained by calculating an approximate point from the actually measured value of FIG. 10 in order to calculate the approximate value of the actually measured temperature decrease value of FIG.

  The developing motor temperature lowering table shown in FIG. 11 will be described. If the development motor fluctuation temperature is stored in the nonvolatile memory 250 when the power is turned off (closest to the time when the power is turned off), the development motor fluctuation temperature when the power is turned off is stored in the nonvolatile memory 250 when the power is turned on. Is held in. Based on the developing motor fluctuation temperature when the power is turned off and the developing motor temperature drop table shown in FIG. 11, the developing motor fluctuation temperature when the power is turned on is estimated (the developing motor fluctuation temperature is corrected).

  The developing motor fluctuation temperature while the power is off is not greatly affected by the environmental temperature and the environmental humidity where the image forming apparatus 10 is placed, and decreases. FIG. 12 shows an example of an actual time change of the developing motor temperature drop with 100 ° C. as a base point. The developing motor temperature drop table shown in FIG. 11 is created by approximating the time change of the developing motor temperature drop of FIG. 12 with a linear regression line. The solid line shown in FIG. 12 shows the developing motor temperature drop curve, and the alternate long and short dash line shown in FIG. 12 shows the approximation of the developing motor temperature drop curve by a linear regression line. The table shown in FIG. 11 is obtained by calculating an approximate point from the actually measured value of FIG. 12 in order to calculate the approximate value of the actually measured temperature decrease value of FIG.

[Control Configuration of Image Forming Apparatus: Flowchart]
A control structure of the image forming apparatus 10 will be described with reference to flowcharts shown in FIGS. The flowcharts shown in FIGS. 13 to 19 are programs executed by the control unit 200 shown in FIG. 5, and mainly show the main routine program and subroutine program related to the development motor temperature suppression control of the image forming apparatus 10. The details of the image reading process and the image forming process are not shown. Further, such a control unit 200 mainly includes a CPU and a memory included in the control unit 200 and a program that is read from the memory and executed by the CPU even in hardware mainly configured of a digital circuit or an analog circuit. It can also be realized with the software. In general, it is said that it is advantageous in terms of operation speed when realized by hardware, and advantageous in terms of design change when realized by software. Below, the case where the control part 200 is implement | achieved as software is demonstrated. Note that such a program itself and a recording medium on which the program is recorded are also one embodiment of the present invention.

≪Main routine≫
The control structure of the image forming apparatus 10 will be described with reference to the flowchart shown in FIG.

  In step (hereinafter, step is referred to as S) 100, control unit 200 calculates the developing motor fluctuation temperature. At this time, more specifically, for example, the development motor fluctuation temperature calculation processing unit 202 of the control unit 200 executes a development motor fluctuation temperature calculation processing program (subroutine program).

  In S <b> 200, control unit 200 estimates a power-off time that is a time during which power of image forming apparatus 10 has been turned off. At this time, more specifically, for example, a power-off time estimation processing program (subroutine program) is executed by the power-off time estimation processing unit 204 of the control unit 200.

  In step S300, the control unit 200 corrects the developing motor fluctuation temperature calculated in step S100 in consideration of the time during which the image forming apparatus 10 is turned off. At this time, more specifically, for example, the developing motor fluctuation temperature correction processing unit 206 of the control unit 200 executes a developing motor fluctuation temperature correction processing program (subroutine program).

  In S400, control unit 200 calculates an estimated temperature (development motor estimated temperature) of developing motor 41B using the developing motor fluctuation temperature corrected in S300. At this time, more specifically, for example, a developing motor estimated temperature calculation processing program (subroutine program) is executed by the developing motor estimated temperature calculation processing unit 208 of the control unit 200.

  In S500, control unit 200 stores development motor estimated temperature calculated in S400 in nonvolatile memory 250. At this time, more specifically, for example, the development motor estimated temperature storage processing unit 210 of the control unit 200 executes a development motor estimated temperature storage processing program (subroutine program).

  In S600, based on the estimated developing motor temperature calculated in S400, control unit 200 executes a developing motor temperature lowering process if the estimated developing motor temperature is equal to or higher than a threshold value. At this time, more specifically, for example, the development motor temperature reduction processing unit 212 of the control unit 200 executes a development motor temperature reduction processing program (subroutine program).

  Here, as described above, the image stabilization processing unit 214 in the control unit 200 replaces the developing device (toner cartridge), image formation 1000 sheets, image formation 200 sheets, and predetermined environmental change timings. Perform image stabilization processing. However, the control unit 200 determines that the estimated development motor temperature is selected from the stabilization processing (development leak detection, toner maximum adhesion amount adjustment, image exposure adjustment, and γ correction based on the estimated development motor temperature calculated in S400. The stabilization processing by the image stabilization processing unit 214 is prohibited when the temperature is equal to or higher than the image stabilization processing start limit temperature defined for the stabilization processing, and when the temperature is lower than the limit temperature, the stabilization processing is permitted. At this time, more specifically, as shown in FIG. 20, the image stabilization processing interruption prevention processing unit 216 of the control unit 200 performs the stabilization processing by the portion in charge of the image stabilization processing interruption prevention processing such as image exposure adjustment. A process for preventing interruption of the process is executed.

  Further, the image stabilization processing unit 214 in the control unit 200 executes the developing roller aging process when the developing roller is left unrotated for a predetermined time. However, based on the estimated developing motor temperature calculated in S400, the control unit 200 determines that the estimated developing motor temperature is equal to or higher than the image stabilization process start limit temperature determined for the developing roller aging process. The developing roller aging process by the stabilization processing unit 214) is prohibited. When the temperature is lower than the limit temperature, the aging process is permitted. At this time, more specifically, as shown in FIG. 21, the stabilization process interruption prevention process is performed by the part in charge of the development roller aging process interruption prevention process in the image stabilization process interruption prevention process part 216 of the control unit 200. The program is executed.

<< Subroutine: Development motor fluctuation temperature calculation process >>
The developing motor fluctuation temperature calculation process in the control structure of the image forming apparatus 10 will be described with reference to the flowchart shown in FIG. This program is executed with a cycle time of 100 msec (100 milliseconds).

  In S <b> 102, control unit 200 (developing motor fluctuation temperature calculation processing unit 202) acquires the operation mode of image forming apparatus 10. At this time, the acquired operation mode is any one of (A) printing, initial operation, image stabilization, (B) standby, (C) sleep, and cover open. In S104, control unit 200 reads a development motor temperature variation table corresponding to the operation mode from table storage unit 260. The developing motor temperature fluctuation table read at this time is one of the developing motor temperature fluctuation tables shown in FIGS. 6 (A) to 8 (A).

  In S106, control unit 200 calculates a developing motor temperature change amount. At this time, the change in the development motor temperature by adopting the fluctuation rate and the fluctuation rate offset in the development motor estimated temperature column to which the estimated development motor temperature stored in the memory 250 is applied among the estimated development motor temperature column in the read table. Calculate the amount. The developing motor temperature change amount is calculated by developing motor fluctuation temperature of one cycle before x fluctuation rate inclination + fluctuation rate offset. In S108, control unit 200 calculates the development motor fluctuation temperature in this cycle by the development motor fluctuation temperature of the previous cycle + the development motor temperature change amount. In the processes in S106 and S108, conversion (multiplication by 10 to the sixth power) is performed in order to match the number of digits of the developing motor temperature change amount and the developing motor fluctuation temperature.

≪Subroutine: Power-off time estimation process≫
The power-off time estimation process in the control structure of the image forming apparatus 10 will be described with reference to the flowchart shown in FIG.

  In S202, control unit 200 (power-off time estimation processing unit 204) determines whether or not a request to turn off the power of image forming apparatus 10 has been detected. At this time, the control unit 200 determines whether a request to turn off the power is detected based on information input from the operation panel IF 220 or the like. If it is determined that a request to turn off image forming apparatus 10 is detected (YES in S202), the process proceeds to S204. If not (NO in S202). This process ends.

  In S204, control unit 200 stores fixing thermistor temperature TH (1) in nonvolatile memory 250 based on the signal input to control unit 200 by fixing thermistor 230. At this time, the control unit 200 stores the fixing thermistor temperature TH (1) in the nonvolatile memory 250, and then executes a process of stopping the operation of the image forming apparatus 10.

  In S206, control unit 200 determines whether or not a request to turn on power of image forming apparatus 10 has been detected. At this time, the control unit 200 makes a determination based on information input from the operation panel IF 220 and the like. If it is determined that a request to turn on power of image forming apparatus 10 has been detected (YES in S206), the process proceeds to S208. If not (NO in S206), this process ends. In S208, control unit 200 stores fixing thermistor temperature TH (2) in nonvolatile memory 250 based on the signal input to control unit 200 by fixing thermistor 230. In the process of S208, if it is assumed that the process after S210 is executed in a state where the power of the image forming apparatus 10 is not turned off, the fixing thermistor temperature TH (2) is not the nonvolatile memory 250. You may make it memorize | store in a simple memory.

  In S 210, control unit 200 reads out the fixing thermistor temperature lowering table shown in FIG. 9 from table storage unit 260. In S212, control unit 200 estimates the time required to decrease from fixing thermistor temperature TH (1) to fixing thermistor temperature TH (2) as the power-off time using the fixing thermistor temperature decreasing table. .

≪Subroutine: Development motor fluctuation temperature correction process≫
The developing motor fluctuation temperature correction process in the control structure of the image forming apparatus 10 will be described with reference to the flowchart shown in FIG.

  In S302, control unit 200 (developing motor fluctuation temperature correction processing unit 206) determines whether or not a request to turn off the power of image forming apparatus 10 has been detected. At this time, the control unit 200 determines whether a request to turn off the power is detected based on information input from the operation panel IF 220 or the like. If it is determined that a request to turn off image forming apparatus 10 has been detected (YES in S302), the process proceeds to S304. If not (NO in S302). This process ends. In S304, control unit 200 stores development motor fluctuation temperature calculated in S108 in nonvolatile memory 250 as development motor fluctuation temperature TH (M). At this time, the control unit 200 stores the developing motor fluctuation temperature TH (M) in the nonvolatile memory 250 and then executes a process of stopping the operation of the image forming apparatus 10.

  In S306, control unit 200 determines whether or not a request to turn on power of image forming apparatus 10 has been detected. At this time, the control unit 200 makes a determination based on information input from the operation panel IF 220 and the like. If it is determined that a request to turn on power of image forming apparatus 10 has been detected (YES in S306), the process proceeds to S308. If not (NO in S306). This process ends. In S308, control unit 200 reads the development motor temperature decrease table shown in FIG. In S310, control unit 200 corrects the developing motor fluctuation temperature in consideration of the temperature lowering from developing motor fluctuation temperature TH (M) due to power-off.

<< Subroutine: Estimated development motor temperature calculation process >>
The developing motor estimated temperature calculation process in the control structure of the image forming apparatus 10 will be described with reference to the flowchart shown in FIG.

  In S402, control unit 200 (development motor estimated temperature calculation processing unit 208) detects the in-machine environmental temperature of image forming apparatus 10 based on the signal input from environmental temperature detection sensor 240. In S404, control unit 200 calculates the estimated developing motor temperature by adding the in-machine environmental temperature to the developing motor fluctuation temperature corrected in S310.

≪Subroutine: Development motor estimated temperature storage process≫
The developing motor estimated temperature storage process in the control structure of the image forming apparatus 10 will be described with reference to the flowchart shown in FIG.

  In S502, control unit 200 (development motor estimated temperature storage processing unit 210) determines whether or not the development motor fluctuation temperature calculated in S108 or the development motor fluctuation temperature corrected in S310 has changed by 5 ° C. or more (temperature). It is determined whether or not the amount of change is 5 ° C. or higher. If it is determined that developing motor fluctuation temperature has changed by 5 ° C. or more (YES in S502), the process proceeds to S504. Otherwise (NO in S502), this process ends. Note that 5 ° C., which is the threshold value for the developing motor fluctuation temperature in the processing of S502, is an example, and is appropriately determined depending on the relationship with the number of times of writing to the nonvolatile memory 250.

  In S504, control unit 200 stores the estimated developing motor temperature calculated in S404 in nonvolatile memory 250. In S506, control unit 200 stores the fixing thermistor temperature in nonvolatile memory 250.

<< Subroutine: Development Motor Temperature Reduction Process (In other words, Development Motor Temperature Increase Suppression Process >> The development motor temperature reduction process in the control structure of the image forming apparatus 10 will be described with reference to the flowchart shown in FIG.

  In S602, control unit 200 (developing motor temperature reduction processing unit 212) determines whether or not the estimated developing motor temperature calculated in S404 is 100 ° C. or higher. If it is determined that the estimated developing motor temperature is 100 ° C. or higher (YES in S602), the process proceeds to S608. If not (NO in S602), the process proceeds to S604.

  In S604, control unit 200 determines whether or not the estimated developing motor temperature is 80 ° C. or higher. If it is determined that the estimated developing motor temperature is equal to or higher than 80 ° C. (YES in S604), the process proceeds to S606. If not (NO in S604), the process proceeds to S610.

  In S606, control unit 200 determines whether or not the estimated developing motor temperature is equal to or higher than 80 ° C. once it reaches 100 ° C. or higher. If it is determined that the estimated developing motor temperature is 80 ° C. or higher once it reaches 100 ° C. or higher (YES in S606), the process proceeds to S608. If not (NO in S606), the process proceeds to S610.

  In step S608, the control unit 200 executes intermittent printing processing even if the printing request is continuous. At this time, for example, printing is continuously performed for 60 seconds, and the image forming apparatus 10 is kept on standby for 60 seconds until the next continuous printing.

  In S610, control unit 200 executes a continuous printing process. At this time, printing is continuously performed without causing the image forming apparatus 10 to wait.

<Subroutine: Stabilization processing interruption prevention processing excluding developing roller aging during image stabilization processing>
With reference to the flowchart shown in FIG. 20, the interruption prevention process of the image stabilization process excluding the developing roller aging during the image stabilization process in the control structure of the image forming apparatus 10 will be described.

  At S702, control unit 200 (the part in charge of image stabilization processing interruption prevention processing other than developing roller aging in image stabilization processing interruption prevention processing unit 216) has a stable developing motor estimated temperature calculated at S404. It is determined whether or not the heat treatment start temperature limit (98 ° C. in this example) is not less than (S702). If the temperature is equal to or higher than the limit temperature (YES in S702), the stabilization process is prohibited and the process waits for the estimated developing motor temperature to be equal to or lower than the limit temperature. If the temperature is lower than the limit temperature (NO in S702), the stabilization process is permitted (S704).

Here, the stabilization process start limit temperature memorize | stored in the memory | storage part 270 is demonstrated.
(1) Development leak detection takes a maximum of 15 seconds, although the required time varies depending on the leaking voltage.
(2) It takes 6 seconds to detect the maximum amount of toner.
(3) It takes 3 seconds to adjust the exposure (here, laser light).
(4) Gamma correction takes 6 seconds.
Each of the above is the required time for each color, and four times are required because the image stabilization of four colors is necessary.
Since the required time per color is 30 seconds, the required time for four colors is 120 seconds.
Therefore, the time required for image stabilization such as development leak detection is 120 seconds.

  In this example, before starting the image stabilization process so that the settling temperature of the development motor does not reach 100 ° C. during the image stabilization process, the estimated development motor temperature is higher than the stabilization process start limit temperature as described above. Whether the temperature is lower or not is determined, and if the temperature is equal to or higher than the stabilization processing start limit temperature, the process waits in a standby state until the temperature falls below the limit temperature. By waiting in the standby state, the developing motor temperature decreases.

  The image stabilization process start limit temperature is measured in advance through various experiments to determine how much the developing motor temperature rises in 120 seconds of the required time when the image stabilization process is performed at around 100 ° C. The temperature at which the estimated developing motor temperature does not exceed 100 ° C. is determined as the stabilization start limit temperature even after 120 seconds have elapsed since the start of processing, that is, until the end of the image stabilization processing. Therefore, in this example, the limit temperature is set to 98 ° C.

For example, even when continuous printing is continued and the estimated developing motor temperature is around 100 ° C., if a toner empty or the like occurs and the toner cartridge (developing device) is replaced, the image stabilization process is performed. At this time, if the estimated developing motor temperature exceeds the stabilization start limit temperature, the process waits in a standby state before image stabilization.
In other cases, during continuous printing, if image stabilization processing is performed before printing 1000 sheets or 200 sheets, image stabilization processing is required. At this time, the estimated developing motor temperature is stabilized. If the start limit temperature is exceeded, it will wait in a standby state.
In addition, about 7 seconds can be exemplified as the time required for the temperature to drop by 1 ° C. around 100 ° C. during standby.

<< Subroutine: Development roller aging process interruption prevention process in image stabilization process >>
With reference to the flowchart shown in FIG. 21, the interruption prevention process of the developing roller aging process during the image stabilization process in the control structure of the image forming apparatus 10 will be described.

  In S802, the control unit 200 (the part in charge of preventing the interruption of the developing roller aging process in the image stabilization process interruption prevention processing unit 216) determines that the estimated developing motor temperature calculated in S404 is about the developing roller aging process. It is determined whether or not the processing start limit temperature (in this example, 99 ° C.) or higher (S802). If the temperature is equal to or higher than the limit temperature (YES in S802), the aging process is prohibited, and the process waits until the estimated developing motor temperature becomes equal to or lower than the limit temperature. If the temperature is lower than the limit temperature (NO in S802), the aging process is permitted (S804).

Here, the process start limit temperature for the developing roller aging process stored in the storage unit 270 will be described.
In developing roller aging, for example, the developing motor is rotated for 10 seconds for each color, and the required time for four colors is 40 seconds.

  In this example, before starting the aging so that the estimated developing motor temperature does not become 100 ° C. during the developing roller aging, it is confirmed that the estimated developing motor temperature is lower than the aging start limiting temperature as described above. When the temperature is equal to or higher than the temperature, the standby state is waited until the temperature becomes lower than the aging start limit temperature. By waiting in the standby state, the developing motor temperature decreases.

  The aging process start limit temperature is measured in advance through various experiments to determine how much the developing motor temperature rises in the required time of 40 seconds when the aging process is performed in the vicinity of 100 ° C., and after the aging process is started. A temperature at which the estimated developing motor temperature does not exceed 100 ° C. is determined as the aging process start limit temperature even after 40 seconds have elapsed, that is, until the aging process is completed. In this example, the limit temperature is set to 99 ° C.

  For example, even when continuous printing is continued and the estimated developing motor temperature is in the vicinity of 100 ° C., aging processing is performed when toner empty or the like occurs and the toner cartridge (developing device) is replaced. The newly mounted toner cartridge (developing device) is left in a packaged state, and there are many cases where deformation occurs at the mutual nip portion between the developing roller and the developer supply roller facing this, and the image is immediately formed as it is. If used, uneven development may occur. Therefore, when the user instructs the aging process on the operation panel PA, the aging process is about to start. At this time, if the estimated developing motor temperature is equal to or higher than the aging process start limit temperature, the developing motor temperature decreases in the standby state. Wait to do.

[Control operation of image forming apparatus]
The developing motor temperature rise suppressing operation in the image forming apparatus 10 having the above-described structure and flowchart will be described.

≪Development motor temperature estimation operation≫
The operation mode of the image forming apparatus 10 is acquired (S102), and a developing motor temperature fluctuation table (any one shown in FIGS. 6A to 8A) corresponding to the acquired operation mode is a table. The data is read from the storage unit 260 (S104). Using the fluctuation rate slope and fluctuation rate offset of the development motor temperature fluctuation table corresponding to the operation mode, the development motor temperature change amount is calculated by the development motor fluctuation temperature of the previous cycle × fluctuation rate slope + fluctuation rate offset. (S106). The developing motor fluctuation temperature in this cycle is calculated by adding the developing motor temperature change amount to the developing motor fluctuation temperature (° C.) one cycle before (S108). As described above, the development motor fluctuation temperature is calculated every 100 msec, and the development motor estimated temperature can be calculated by adding the in-machine environmental temperature to the development motor fluctuation temperature.

  When the user operates the operation panel PA of the image forming apparatus 10 or when there is no operation request to the image forming apparatus 10 for a certain period of time, a request to turn off the power is detected (YES in S202). The fixing thermistor temperature TH (1) is stored in the nonvolatile memory 250 (S204). Thereafter, when a request to turn on the power supply that has been turned off is detected (YES in S206), fixing thermistor temperature TH (2) is stored in nonvolatile memory 250 (S208).

  When the fixing thermistor temperature lowering table is read (S210), the time required to decrease from the fixing thermistor temperature TH (1) to the fixing thermistor temperature TH (2) using the fixing thermistor temperature lowering table is Estimated as the off time (S212).

  Here, assuming that the fixing thermistor temperature TH (1) = 185 ° C. and the fixing thermistor temperature TH (2) = 125 ° C., the following is obtained. The fixing thermistor temperature TH (1) of 185 ° C. is interpolated by a linear regression line between (200 ° C., 0 minutes) and (125 ° C., 3 minutes) in the fixing thermistor temperature lowering table shown in FIG. [(3 min-0 min) / (125 ° C.-200 ° C)] × (185 ° C.-200 ° C.) = 0.6, the temperature may drop to 185 ° C. after 0.6 minutes from 200 ° C. Recognize. The fixing thermistor temperature TH (2) of 125 ° C. is found to decrease to 125 ° C. after 3 minutes from 200 ° C. from the fixing thermistor temperature lowering table. As a result, the time required to drop from the fixing thermistor temperature TH (1) of 185 ° C. to the fixing thermistor temperature TH (2) of 125 ° C. is 2.4 minutes of 3 minutes to 0.6 minutes. It can be estimated that the image forming apparatus 10 has been powered off for 2.4 minutes.

  Similarly, when the user operates the operation panel PA of the image forming apparatus 10 or when there is no operation request to the image forming apparatus 10 for a certain period of time, a request to turn off the power is detected (S302). YES) The developing motor fluctuation temperature TH (M) is stored in the nonvolatile memory 250 (S304). Thereafter, when a request to turn on the power that has been turned off is detected (YES in S306), the developing motor temperature lowering table is read (S308), and the power is turned off using the developing motor temperature lowering table. The developing motor fluctuation temperature is corrected in consideration of the temperature drop from the developing motor fluctuation temperature TH (M) (S310).

  Here, assuming that the developing motor fluctuation temperature TH (M) (temperature in the storage unit immediately before the power is turned off) = 85 ° C. and the power off time = 2.4 minutes, the following results. Interpolation is performed with a linear regression line between (0 min, 100 ° C.) and (7 min, 72 ° C.) in the developing motor temperature lowering table shown in FIG. 11, [(7 min−0 min) / (72 (° C-100 ° C)] × (85 ° C-100 ° C) = 3.75, the time required for the temperature to drop from 100 ° C to 85 ° C, which is the developing motor fluctuation temperature TH (M), is 3.75 minutes. Recognize. Since the power-off time is 2.4 minutes, 3.75 minutes + 2.4 minutes = 6.15 minutes, and the temperature that decreases from 100 ° C. in 6.15 minutes becomes the developing motor fluctuation temperature when the power is turned on. . Interpolate by linear regression line between (0 min, 100 ° C) and (7 min, 72 ° C) on the developing motor temperature drop table [(72 ° C-100 ° C) / (7 min-0 min) ] × (6.15 minutes−0 minutes) + 100 ° C. = 75.4 ° C. It is corrected that the developing motor fluctuation temperature decreased from 85 ° C. to 75.4 ° C. during the power-off for 2.4 minutes.

  When the in-machine environmental temperature is added to the developing motor fluctuation temperature of 75.4 ° C., the estimated developing motor temperature is calculated (S404). When the estimated developing motor temperature changes by 5 ° C. or more (YES in S502), the estimated developing motor temperature and the fixing thermistor temperature are stored in nonvolatile memory 250 (S504, S506).

  This is preferable as follows when there is a limit to the number of times data can be written to an EEPROM or the like, which is an example of the nonvolatile memory 250. The number of times such writing to the EEPROM is generally limited (for example, 10 to the sixth power). Here, if it is stored in the non-volatile memory 250 every 1 sec, the number of writings will be exceeded in about 11 days. However, as in this embodiment, when the estimated developing motor temperature changes by 5 ° C. or more, the estimated developing motor temperature is written into the nonvolatile memory 250. Since the estimated developing motor temperature does not change greatly, the writing limit of the nonvolatile memory 250 is not reached in practice.

  Further, when the estimated developing motor temperature changes by 5 ° C. or more, the fixing thermistor temperature is written into the nonvolatile memory 250. When the fixing thermistor temperature is changed to 5 ° C. or more and the fixing thermistor temperature is written in the nonvolatile memory 250, the fixing thermistor temperature is adjusted when the temperature is adjusted by energizing the fixing heater. Since the rise and fall are repeated, a temperature change of about 5 ° C. frequently occurs and the write limit of the nonvolatile memory 250 is reached. However, since the fixing thermistor temperature is written into the nonvolatile memory 250 when the estimated developing motor temperature that does not change significantly changes by 5 ° C. or more, the writing limit of the nonvolatile memory 250 is not reached in practice. .

  If the estimated developing motor temperature calculated in this way becomes 100 ° C. or higher (YES in S602), the winding temperature of the developing motor 41B may rise and insulation failure may occur. Even if it is a request, an intermittent printing process (printing continuously for 60 seconds and waiting for this image forming apparatus 10 for 60 seconds until the next continuous printing) is executed (S608). This intermittent printing process is continued until the estimated developing motor temperature becomes 100 ° C. or lower until it is less than 80 ° C. (NO in S602, YES in S604, YES in S606).

  Until the estimated developing motor temperature reaches 100 ° C. or higher (NO in S602), even if the estimated developing motor temperature is 80 ° C. or higher (YES in S604), the normal printing process is performed (S606). NO, S610).

  This state is shown in FIG. At time T (5), the estimated developing motor temperature becomes 100 ° C. or higher (YES in S602), and until the estimated developing motor temperature is less than 80 ° C. (NO in S604), The temperature of the developing motor 41B is lowered so as to be printed only intermittently (S608). When this intermittent printing process is being performed, it is a standby mode in which the fixing heater is energized to adjust the temperature, the recording paper transport motor is not energized, and the developing motor 41B is energized. It is not in a state. Since the developing motor 41B is not energized, the developing motor 41B itself does not generate heat, and the temperature of the developing motor 41B decreases. Since such intermittent printing processing reduces printing efficiency, if the estimated developing motor temperature is less than 80 ° C. (YES in S604), the intermittent printing processing is canceled and continuous printing is executed ( S610). As a result, intermittent printing processing is intermittently performed between time T (5) and time T (6), and the estimated developing motor temperature is between 80 ° C. and 100 ° C.

  In FIG. 22, from time T (0) to time T (1), from time T (2) to time T (3), from time T (4) to time T (5). In the meantime, since the estimated developing motor temperature has not once exceeded 100 ° C. (even if it is 80 ° C. or higher) (YES in S604, NO in S606), normal printing processing is performed. It should be noted that the standby state is from time T (1) to time T (2), and the sleep state is from time T (3) to time T (4).

  As described above, the temperature of the developing motor is estimated by accumulating the fluctuating temperature at regular intervals (every 100 msec) according to the operation mode of the image forming apparatus. In this case, when the power supply of the image forming apparatus is turned off, the amount of decrease in the developing motor temperature is estimated using the fixing thermistor temperature to correct the developing motor temperature. When the temperature of the developing motor calculated in this way is equal to or higher than a threshold value, intermittent printing processing is performed in order to reduce the temperature of the developing motor. For this reason, even if the developing motor is not provided with a temperature detection unit, the temperature of the developing motor can be estimated in consideration of power-off of the image forming apparatus, and temperature reduction control can be executed based on the estimated temperature.

  In order to cope with power-off, the developing motor temperature and the fixing thermistor temperature are stored in a non-volatile memory that retains the memory without supplying power. In this case, the developing motor temperature and the fixing thermistor temperature are stored in the non-volatile memory only when the developing motor temperature with little change changes greatly. As a result, the number of times of writing to the nonvolatile memory can be greatly reduced, so that the limitation on the number of times of writing to the nonvolatile memory does not become a problem. The non-volatile memory may be written with at least one of the developing motor temperature and the fixing thermistor temperature.

  The embodiment disclosed this time is merely an example, and the present invention is not limited to the above-described embodiment. The image forming apparatus 10 shown in FIG. 1 is a so-called four-cycle color image forming apparatus. However, the present invention can be applied to a so-called tandem type color image forming apparatus, and can also be applied to a monochrome image forming apparatus. It is.

  The present invention forms an electrostatic latent image on an electrostatic latent image carrier, develops the electrostatic latent image with a developing device to form a toner image, and fixes the toner image onto a recording medium with a fixing device. The image forming process is appropriately controlled so that the temperature of the developing motor does not rise above a predetermined temperature without directly detecting the temperature of the developing motor that drives the developing roller included in the developing device. The present invention can be used to provide an image forming apparatus that can perform such a process.

DESCRIPTION OF SYMBOLS 1 Photoconductor 2 Charger 3 Image exposure apparatus 4 Developing unit 5, 65 Cleaning apparatus 6 Intermediate transfer belt 66 Image density sensor 8 Fixing apparatus 7 Secondary transfer roller 10 Image forming apparatus 11 Automatic document feeder 12 Image reader 13 Manual tray 14 Image forming section 40 Developing rack 40A Developing rack docking gear 40B Developing rack motor 41 Developing roller 41A Developing motor docking gear 41B Developing motor 200 Control section 202 Developing motor fluctuation temperature calculation processing section 204 Power off time estimation processing section 206 Developing motor fluctuation temperature Correction processing unit 208 Development motor estimated temperature calculation processing unit 210 Development motor estimated temperature storage processing unit 212 Development motor temperature decrease processing unit 214 Image stabilization processing unit 216 Image stabilization processing interruption prevention processing unit 220 Operation panel interface 230 Fixing thermist Star 240 Environmental temperature sensor 250 Non-volatile memory 260 Table storage unit 270 Limit temperature storage unit 410 Toner storage unit 411 Communication opening 412 Wall 420 Head unit 422 Toner supply roller 423 Toner regulating member 425 Seal member

Claims (9)

Forming an electrostatic latent image on the electrostatic latent image carrier, developing the electrostatic latent image with a developing device to form a toner image, and fixing the toner image onto a recording medium with a fixing device;
The developing device includes a developing roller and a developing motor that drives the developing roller,
The fixing device is an image forming apparatus including a fixing roller, a fixing heater for heating the fixing roller, and a fixing device temperature detecting unit for detecting a fixing device temperature.
A developing motor temperature calculation unit that estimates the temperature of the developing motor by integrating the fluctuating temperature of the developing motor at predetermined time intervals corresponding to the operating state of the image forming apparatus;
And a developing motor temperature reduction processing unit that controls the image forming apparatus so that the temperature of the developing motor does not rise above a predetermined temperature based on the calculated temperature of the developing motor. apparatus. A storage unit for storing a temperature change table indicating a temperature change of the developing motor, which is set according to the operation state of the image forming apparatus;
An environmental temperature detection unit for detecting the environmental temperature of the image forming apparatus,
The developing motor temperature calculation unit calculates a motor fluctuation temperature obtained by integrating the fluctuation temperature for each predetermined time interval using a temperature change table corresponding to the operation state of the image forming apparatus, and calculates the calculated motor fluctuation temperature and The image forming apparatus according to claim 1, wherein the temperature of the developing motor is calculated based on the environmental temperature detected by the environmental temperature detection unit. A power-off time calculating unit that calculates a power-off time from when the image forming apparatus is turned off to when it is turned on based on the fixing device temperature detected by the fixing device temperature detecting unit;
3. The image forming apparatus according to claim 1, further comprising: a developing motor temperature correcting unit that corrects the calculated temperature of the developing motor based on the power off time calculated by the power off time calculating unit. A storage unit for storing a fixing device temperature change table indicating a change in the fixing device temperature while the power is off and a developing motor temperature change table indicating a change in the temperature of the developing motor while the power is off; ,
The power-off time calculation unit calculates a power-off time based on the fixing device temperature when the power is turned off, the fixing device temperature when the power is turned on, and the fixing device temperature change table detected by the fixing device temperature detection unit. Calculate
The image forming apparatus according to claim 3, wherein the developing motor temperature correction unit corrects the temperature of the developing motor based on the power-off time and the developing motor temperature change table.   When the calculated developing motor temperature reaches a predetermined first temperature, the developing motor temperature lowering processing unit performs image forming processing until the developing motor temperature lowering processing unit decreases to a second temperature lower than the first temperature. The image forming apparatus according to claim 1, wherein the image forming apparatus is controlled so as to operate intermittently. A non-volatile memory with a limited number of writes;
2. The processing device according to claim 1, further comprising: a processing unit that writes at least one of the temperature of the developing motor and the temperature of the fixing device in the nonvolatile memory when the temperature of the developing motor changes to a predetermined value or more. Item 6. The image forming apparatus according to Item 5.   An image stabilization processing unit for stably performing toner image formation, and an interruption prevention processing unit for preventing interruption of the image stabilization processing by the image stabilization processing unit, the image stabilization processing interruption The prevention processing unit determines whether or not the developing motor temperature is equal to or higher than a predetermined image stabilization processing start limit temperature prior to the start of image stabilization processing by the image stabilization processing unit. The image forming apparatus according to claim 1, wherein image stabilization processing is prohibited and image stabilization processing is permitted if the temperature is lower than the limit temperature. Image stabilization processing by the image stabilization processing unit,
Processing for rotating the developing roller of the developing device prior to image formation and one or more types of stabilization processing for stabilizing the toner image to be formed in a predetermined state prior to image formation The image forming apparatus according to claim 7, wherein the processing is selected from among the processes.   A temperature limit storage unit for storing the image stabilization processing start limit temperature is further provided, and the limit temperature is set by the image stabilization processing unit when the developing motor temperature is the limit temperature. 9. The image forming apparatus according to claim 7 or 8, wherein when the processing is started, the developing motor temperature rises to the predetermined temperature or more with the passage of time required for the image stabilization processing.

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