JP2011154055A - Control method of image forming apparatus, and image forming apparatus using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus suppressing developer deterioration and fogging to the minimum without causing middle-missing. <P>SOLUTION: Regarding the control method of the intermediate transfer system image forming apparatus (color printer 1) including a driving device configured to individually drive latent image carriers (photoreceptor drums Y, M, C, K) and developing devices (3Y, 3M, 3C, 3K), the driving time of the developing device is determined based on a contact traveling time in which the latent image carrier and a intermediate transfer body (intermediate transfer belt 50) are driven to rotate in contact with each other. Concretely, a time, until at least one of the latent image carrier and the intermediate transfer body stops after the latent image carrier and the intermediate transfer body start operating in contact with each other, is measured as the contact traveling time, and a first minimum driving time (minimum driving time A1) of the developing device obtained by subtracting a predetermined time from the contact traveling time is determined, and the developing device is driven so that the driving time of the developing device within the contact traveling time is not below the first minimum driving time. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic image forming apparatus such as a copying machine, a facsimile machine, a printer, and a composite machine thereof, and more particularly to control of driving timings of a driving motor and a developing motor of a photosensitive drum and an intermediate transfer belt. is there.

  In the conventional image forming apparatus, the deterioration of the developer and the fogging phenomenon at the start and stop of driving of the photosensitive drum (a phenomenon in which toner is excessively supplied and scatters on the surface of the photosensitive drum to cause scumming) are minimized. For example, when starting up the main power-on device (image forming device), when recovering from a paper jam, or when calibrating an optical sensor that reads a patch on the intermediate transfer belt (when adjusting the light intensity of the light emitting element) In this case, while the photosensitive drum (latent image carrier) and the intermediate transfer belt (intermediate transfer member) are being driven, control is performed to stop driving of the developing device.

  However, when lubricant is applied to the photosensitive drum, excess lubricant is scraped off by the developer's ears if the developing device is driven, so that unnecessary lubricant does not move to the intermediate transfer belt. However, when the photosensitive drum and the intermediate transfer belt are driven and the developing device is not driven, the lubricant on the photosensitive drum moves to the intermediate transfer belt, lowering the friction coefficient of the intermediate transfer belt, and The toner image transferred to the belt is partly detached and causes a phenomenon of bugging out.

  On the contrary, in order to prevent the hollowing out phenomenon, the developing device may be driven at least while the photosensitive drum and the intermediate transfer belt are in contact with each other. It is stressing more than necessary. In addition, fogging occurs at the start and end of driving of the photosensitive drum due to a deviation in the timing of rising and falling of the developing bias and the photosensitive member potential. For this reason, in the conventional image forming apparatus, the driving of the developing drum is started after driving the photosensitive drum, and the driving of the photosensitive drum is stopped after the developing device stops.

  For example, Patent Document 1 includes a detection unit that detects whether or not a photoconductor unit is new. When the photoconductor unit is detected as new by the detection unit, a coating operation is performed by a lubricant application unit, and a photosensitive unit is detected. An image forming apparatus that detects a current value of a body driving motor, measures a photosensitive member torque, and determines a coating operation time is disclosed (see FIG. 2 of Patent Document 1).

  However, in the invention described in Patent Document 1, there is no knowledge that the driving time of the developing device affects the friction coefficient of the intermediate transfer belt, and the coating operation time is determined by whether or not the photosensitive unit is new and the photosensitive member torque. Therefore, the lubricant applied to the photosensitive drum moves to the intermediate transfer belt, and it is not possible to effectively prevent the hollow-out (worm biting) phenomenon due to a partial decrease in the friction coefficient of the intermediate transfer belt. There is a problem.

  In view of the above, in order to solve the problems of the conventional image forming apparatus, the present invention uses a time during which the photosensitive drum (latent image carrier) and the intermediate transfer belt (intermediate transfer body) are in contact with each other to drive the developing device. By determining the drive time of the image forming apparatus, it is possible to minimize the deterioration and fog of the developer within a range where no void occurs, and an image forming apparatus using the image forming apparatus control method The purpose is to provide.

  In order to solve the above-mentioned problem, the invention of the control method of the image forming apparatus according to claim 1 is characterized in that a latent image carrier that carries a latent image on a surface and is driven to rotate, and a latent image on the latent image carrier. A developing device for developing a toner image with toner, a lubricant application device for applying a lubricant to the latent image carrier, and a rotational drive in contact with the surface of the latent image carrier, and being developed by the developing device. Control of an intermediate transfer type image forming apparatus comprising: an intermediate transfer body to which a toner image on the latent image carrier is transferred; and a driving device capable of individually driving the latent image carrier and the developing device. In the method, the driving time of the developing device is determined based on a contact travel time in which the latent image carrier and the intermediate transfer member are in contact with each other and are rotationally driven.

  According to a second aspect of the present invention, there is provided a method for controlling an image forming apparatus according to the first aspect, wherein the latent image carrier and the intermediate transfer member are brought into contact with each other and start to be driven. The time until at least one of the transfer member and the intermediate transfer member stops is measured as the contact travel time, and the first minimum drive time of the developing device is determined by subtracting a predetermined time from the contact travel time. The developing device is driven such that the driving time of the developing device does not fall below the first minimum driving time.

  According to a third aspect of the present invention, there is provided a method for controlling an image forming apparatus according to the second aspect, wherein the latent image carrier and the intermediate transfer member are brought into contact with each other and start to be driven. The time until at least one of the body and the intermediate transfer member stops is measured as the contact travel time, the measurement of the contact travel time is repeated a predetermined number of times, the average value of the contact travel time is calculated, and the calculated average value is predetermined. The second minimum driving time of the developing device is determined by multiplying the coefficient, and when the second minimum driving time exceeds the first minimum driving time, the driving time of the developing device is extended and the next contact travel time The developing device is driven such that the driving time of the developing device is not less than the second minimum driving time.

  According to a fourth aspect of the present invention, there is provided a control method for an image forming apparatus according to the first aspect, wherein the latent image carrier and the intermediate transfer member are driven in contact with each other, and the developing device is The development stop travel time is measured from the time of the stop, and when the development stop travel time has passed a predetermined time, the stopped developing device is driven.

  The image forming apparatus control method according to claim 5 is the image forming apparatus control method according to claim 1, wherein the latent image carrier and the intermediate transfer member are driven in contact with each other, and the developing device is stopped. The developing stop travel time is accumulated and measured, and when the development stop travel cumulative time exceeds a predetermined time, the stopped developing device is driven.

  The image forming apparatus control method according to a sixth aspect of the present invention is the image forming apparatus control method according to the fifth aspect, wherein the development stop running cumulative time is determined when the continuous drive time of the developing device exceeds a predetermined time. It is characterized by being cleared.

  According to a seventh aspect of the present invention, there is provided an image forming apparatus according to any one of the first to sixth aspects.

  According to an eighth aspect of the present invention, in the image forming apparatus according to the seventh aspect, the friction coefficient of the surface of the latent image carrier is less than the friction coefficient of the surface of the intermediate transfer member when new. It is characterized by being 2 or more smaller.

  According to a ninth aspect of the present invention, in the image forming apparatus according to the seventh or eighth aspect, the toner supplied to the developing device comprises the same component as the lubricant applied by the lubricant applying device. It is characterized by containing substances.

  The present invention is as described above. According to the first aspect of the present invention, the latent image carrier that carries the latent image on the surface and is driven to rotate, and the latent image on the latent image carrier is converted into toner by toner. A developing device that develops an image, a lubricant application device that applies a lubricant to the latent image carrier, and a latent image carrier that is driven to rotate in contact with the surface of the latent image carrier and is developed by the developing device. In a control method for an intermediate transfer type image forming apparatus, comprising: an intermediate transfer body to which a toner image on a body is transferred; and a driving device capable of individually driving the latent image carrier and the developing device. Since the driving time of the developing device is determined based on the contact running time in which the latent image carrier and the intermediate transfer member are in contact with each other and are rotationally driven, excess lubricant is generated by driving the developing device and using the spikes of the developer. Can be scraped off and surely prevent the hollowing out phenomenon It can be. Further, the deterioration and fogging of the developer can be suppressed to the minimum as long as no void occurs.

  According to a second aspect of the present invention, in the control method for an image forming apparatus according to the first aspect, at least the latent image carrier and the intermediate transfer member are started after the latent image carrier and the intermediate transfer member start to contact and drive. The time until one stops is measured as the contact travel time, and the first minimum drive time of the developing device is determined by subtracting a predetermined time from the contact travel time, and the drive time of the developing device within the contact travel time is Since the developing device is driven so as not to fall below the first minimum driving time, the developing device is based on the contact travel time in which the latent image carrier to which the lubricant can move and the intermediate transfer member are in contact with each other and are rotationally driven. The minimum drive time to drive the printer can be ensured, the hollowing out phenomenon can be surely prevented, and the deterioration and fogging of the developer can be minimized to the extent that the hollowing out does not occur. .

  According to a third aspect of the present invention, in the method for controlling an image forming apparatus according to the second aspect, at least the latent image carrier and the intermediate transfer member are started after the latent image carrier and the intermediate transfer member start to contact and drive. The time until one side stops is measured as the contact travel time, this contact travel time measurement is repeated a predetermined number of times, the average value of the contact travel time is calculated, the calculated average value is multiplied by a predetermined coefficient, and the developing device When the second minimum driving time is determined and the second minimum driving time exceeds the first minimum driving time, the driving time of the developing device is extended and the driving time of the developing device within the next contact travel time However, since the developing device is driven so as not to fall below the second minimum driving time, it is possible to cope with the case where small-size paper is continuously output, and it is possible to surely prevent the hollowing out phenomenon. , Stupid happened Degradation and fogging developer had a range can be minimized.

  According to a fourth aspect of the present invention, in the image forming apparatus control method according to the first aspect, the latent image carrier and the intermediate transfer member are driven in contact with each other, and the development stop running is started from the time when the developing device is stopped. Time is measured, and when the development stop running time has passed a predetermined time, the stopped developing device is driven, so that the drive control of the developing device, the latent image carrier and the intermediate transfer member can be simplified, The phenomenon can be surely prevented, and the deterioration and fogging of the developer can be minimized as long as no void occurs.

  According to a fifth aspect of the present invention, in the method for controlling an image forming apparatus according to the first aspect, the development stop running time in which the latent image carrier and the intermediate transfer member are driven in contact with each other and the developing device is stopped is set. When the accumulated development stop running time exceeds a predetermined time, the stopped developing device is driven, so that the lubricant can be more reliably transferred from the latent image carrier to the intermediate transfer member. In addition, it is possible to reliably prevent the hollowing out phenomenon, and it is possible to minimize the deterioration and fogging of the developer as long as the hollowing out does not occur.

  According to a sixth aspect of the present invention, in the image forming apparatus control method according to the fifth aspect, the development stop running cumulative time is cleared when the continuous drive time of the developing device exceeds a predetermined time. Mechanical stress applied to the agent can be reduced.

  According to the invention of claim 7, since the method for controlling an image forming apparatus according to any one of claims 1 to 6 is used, the effect can be exhibited in the image forming apparatus.

  According to the eighth aspect of the present invention, in the image forming apparatus according to the seventh aspect, the friction coefficient of the surface of the latent image carrier is 0.2 or more smaller than the friction coefficient of the surface of the intermediate transfer member when new. In addition, it is possible to prevent the hollowing out phenomenon even in a new state in which the normal lubricant is not stable because it does not reach the latent image carrier or the intermediate transfer member.

  According to the ninth aspect of the present invention, in the image forming apparatus according to the seventh or eighth aspect, the toner supplied to the developing device includes a substance composed of the same component as the lubricant applied by the lubricant applying device. Therefore, when collecting excess lubricant with the developing device, there is little risk that the lubricant is mixed into the developer, and there are no side effects.

1 is a configuration explanatory diagram illustrating an outline of an internal structure of an image forming apparatus according to an embodiment in a front view; FIG. 3 is an enlarged vertical sectional view showing the vicinity of the yellow image forming unit. It is explanatory drawing of control of the drive timing of the conventional drive motor and developing motor. It is explanatory drawing for demonstrating the measuring method of the friction coefficient of a photoconductor drum. It is explanatory drawing of control of the drive timing of the drive motor which concerns on the Example of this invention, and a developing motor. It is a flowchart which shows control of the drive timing of a drive motor and a development motor.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[Image forming apparatus]
FIG. 1 is a configuration explanatory diagram showing an outline of an internal structure of an image forming apparatus according to an embodiment of the present invention in a front view. Reference numeral 1 in the figure denotes a four-tandem type intermediate transfer type image forming apparatus exemplified as an embodiment of the image forming apparatus of the present invention. The four-color toners of yellow, magenta, cyan, and black are used. A color printer for forming an image. The color printer 1 includes an apparatus main body 10 that is a casing of the entire apparatus, and four toner containers that are arranged on the upper portion of the apparatus main body 10 and correspond to toners of four colors of yellow, magenta, cyan, and black. An image forming unit 3 that is disposed in the center of the toner container housing unit 2 and the apparatus main body 10 and forms respective single color toner images from the four color toners, and is disposed below the image forming unit 3, 3, an exposure unit 4 that writes an electrostatic latent image on each latent image carrier, a transfer unit 5 that is disposed above the image forming unit 3 and transfers a toner image formed by the image forming unit 3 to a sheet material, A sheet which is disposed near one side above the transfer unit 5 and fixes the toner image transferred by the transfer unit 5 to a sheet material, and a sheet which is a transfer target material, which is disposed at the bottom of the apparatus main body 10. A sheet feeding unit 7 for feeding a material to the transfer unit 5, and an apparatus It is formed on the upper surface of the body 10, and a sheet ejection unit 8 for stacking the sheet material on which the image is fixed by the fixing unit 6.

  The toner container storage unit 2 includes four toner containers 2Y, 2M, 2C, and 2K that individually store new toners of yellow, magenta, cyan, and black. The toner containers 2Y, 2M, 2C, and 2K are Each is configured to be detachable from the apparatus main body 10 and has a function of supplying new toner to each corresponding developing apparatus described later. When the new toner stored in each toner container is exhausted, the toner container is removed from the apparatus main body 10 and replaced with a new toner container.

  The image forming unit 3 includes four image forming units 3Y, 3M, 3C, and 3K centering on four photosensitive drums Y, M, C, and K, which are latent image carriers corresponding to the four color toners. The image forming units 3Y, 3M, 3C, and 3K use yellow, magenta, cyan, and black toners that are supplied from the corresponding toner containers 2Y, 2M, 2C, and 2K, respectively, and use single color toners. An image is formed. The detailed configuration of the image forming unit will be described later.

  The exposure unit 4 includes a laser light source (not shown) such as a semiconductor laser (LD) and a light emitting diode (LED), a polygon mirror that can be rotated, an fθ lens, and the like. The laser light emitted from the laser light source is a polygon mirror, an fθ lens, and the like. Irradiates the photosensitive drums Y, M, C, and K by deflecting, condensing, and scanning, and exposes the outer peripheral surfaces of the photosensitive drums Y, M, C, and K uniformly charged to a predetermined polarity. The exposure apparatus 40 is configured to change the charge level and form an electrostatic latent image.

  The transfer unit 5 supports and stretches the intermediate transfer belt 50 including an endless belt having a multilayer structure provided with a release layer having a semiconductive resin as a base as an intermediate transfer member, and the intermediate transfer belt 50. It comprises four support rollers 51, 52, 53, 54, four primary transfer rollers 55 facing the four photosensitive drums Y, M, C, K with the intermediate transfer belt 50 interposed therebetween. . The support roller 51 is configured to transmit a drive force of a drive motor (not shown) as drive means, and is a drive roller that rotationally drives the intermediate transfer belt 50 in the direction of arrow A in the figure. 53 and 54 are driven rollers. Of course, any one of the support rollers 51, 52, 53, and 54 may be a drive roller. A secondary transfer roller 56 is provided at a position facing the drive roller 51 with the intermediate transfer belt 50 interposed therebetween. The secondary transfer roller 56 is in pressure contact with the drive roller 51 with the intermediate transfer belt 50 interposed therebetween. A secondary transfer nip is formed between the drive roller 51 and the secondary transfer roller 56. A cleaning unit 57 for cleaning the intermediate transfer belt 50 is provided at a position facing the support roller 52 and the intermediate transfer belt 50, and the support roller 52 functions as a backup roller for the cleaning unit 57. have.

Each primary transfer roller 55 takes into account the gap discharge, and slightly moves from the directly facing position where the photosensitive drums Y, M, C, and K are in contact with the intermediate transfer belt 50 to the downstream side in the moving direction of the intermediate transfer belt 50. It is a contact-type transfer bias (transfer voltage) applying means that is disposed at a shifted position and is connected to a bias power source (not shown). These primary transfer rollers 55 are configured to be able to come into contact with and separate from the inner peripheral surface of the intermediate transfer belt 50 by a contact / separation mechanism (not shown), and are pressed by the contact / separation mechanism to each photosensitive drum Y, M, C. , K to form a primary transfer nip, and a primary transfer bias having a polarity opposite to that of the toner image on each photosensitive drum is applied to each primary transfer nip to form a transfer electric field. The toner image is attracted by Coulomb force to transfer the toner image from each photosensitive drum to the outer peripheral surface of the intermediate transfer belt 50.
The transfer bias applying means may be a non-contact type using a transfer charger, but in this embodiment, a primary transfer roller that generates little transfer dust is employed.

  The secondary transfer roller 56 is configured to be in pressure contact with the intermediate transfer belt 50 on the outer periphery of the driving roller 51 by an urging unit (not shown) to form a secondary transfer nip, and is connected to a bias power source (not shown). This is a contact-type transfer bias applying means for applying a secondary transfer bias having a polarity opposite to the above. Further, the drive roller 51 may be a transfer bias applying unit, and in this case, a transfer bias having the same polarity as the toner image to be transferred is applied.

  The cleaning unit 57 is a cleaning device that scrapes and collects transfer residual toner attached to the outer peripheral surface of the intermediate transfer belt 50 with a cleaning blade, and applies a release agent with a fur brush or the like. The toner is transported from the cleaning unit 57 to a waste toner tank (not shown) by a transport means (not shown) and discarded.

  Further, an optical sensor (not shown) is attached to face the outer peripheral surface of the intermediate transfer belt 50, and this optical sensor outputs according to the toner adhesion amount on the intermediate transfer belt 50, and uses the output value. The image density is adjusted.

  The fixing unit 6 includes a fixing belt 60 formed of an endless belt, a pressure roller 61 that can be pressed against the fixing belt 60 by a biasing unit (not shown), and the like. The fixing roller, which is a driving roller that rotationally drives 60, and a heating roller that has a heating means including a halogen heater inside and heats the fixing belt 60, are stretched between the fixing belt 60 and the pressure roller 61. A fixing nip is formed by press-contacting with the outer periphery of the fixing roller. In the fixing nip, heat and pressure are applied to the conveyed sheet material, and the toner image transferred by the transfer unit 5 is fixed to the sheet material.

  The paper feeding unit 7 includes a paper feeding cassette 70 that stores and stocks a sheet material of a predetermined size (not limited to paper such as copy paper and postcards but indicates a sheet-like material including a resin sheet such as an OHP sheet) A pick-up roller 71 is provided that is driven to rotate based on a control signal from a control means (not shown) and feeds the sheet material to the conveyance path R. Each sheet feeding cassette 70 has a mechanism in which a bottom plate is urged upward by an urging means, and a bundle of sheet materials to be accommodated is pressed against the pickup roller 71. The conveyance path R includes a plurality of conveyance roller pairs 72 that convey the sheet material, a registration roller pair 73 that adjusts the timing of conveyance of the sheet material to the secondary transfer nip, and the like.

  The paper discharge unit 8 includes a paper discharge tray 80 formed on the upper surface of the apparatus main body 10, a paper discharge roller pair 81 that discharges a sheet material from the apparatus main body 10 to the paper discharge tray 80, and the like. The passed sheet material is discharged from the discharge roller pair 81 and accumulated on the discharge tray 80.

[Image creation unit]
Next, the configuration of the image forming unit of the color printer 1 will be described.
FIG. 2 is an enlarged vertical sectional view showing the vicinity of the yellow image forming unit in FIG. As described above, the color printer 1 includes the four image forming units 3Y, 3M, 3C, and 3K in the order of yellow, magenta, cyan, and black from the upstream side in the surface movement direction along the lower surface of the intermediate transfer belt 50. (See FIG. 1). Since these image forming units 3Y, 3M, 3C, and 3K have substantially the same configuration except for the color of the toner to be used, the image forming unit 3Y for yellow disposed at the most upstream is taken as an example. Will be described, and description of others will be omitted.

  As shown in FIG. 2, the yellow image forming unit 3Y includes a charging device 30Y that charges the outer peripheral surface of the photosensitive drum Y uniformly around the photosensitive drum Y that is rotationally driven, and a photosensitive device. A developing device 31Y that supplies toner (yellow color) to the electrostatic latent image formed on the photosensitive drum Y and develops the toner image, and a lubricant coating device that applies a lubricant to the outer peripheral surface of the photosensitive drum Y 32Y and a cleaning device 33Y that cleans residual toner that remains and adheres to the photosensitive drum Y even after the primary transfer, and the like. These are integrated to form a process cartridge, which is attached to and detached from the color printer 1. It is possible. An exposure region is provided between the charging device 30Y and the developing device 31Y as a space through which the laser beam is passed and irradiated from the exposure device 40 (see FIG. 1). The developing device 31Y and the lubricant applying device 32Y The above-mentioned primary transfer roller 55 is opposed to the primary transfer nip described above where transfer is performed.

  The photosensitive drum Y is a roller-shaped organic material in which an organic photosensitive layer is formed on the outer peripheral surface of an aluminum hollow cylindrical substrate having a diameter of about 30 mm, and a protective layer is further formed on the photosensitive layer with a polycarbonate resin. It is a photoconductor [OPC (Organic Photoconductors)], and can be rotationally driven in the direction of the arrow in the figure by a drive motor (not shown) which is a drive means common to the drive roller 51. In addition, an intermediate layer may be provided between the photosensitive layer and the protective layer, and the diameter can be applied as long as it is about 30 to 90 mm.

  The charging device 30Y is disposed in close proximity to the photosensitive drum Y with a minute gap of about 5 to 100 μm, and a charging roller 30Ya as a charging member that uniformly charges the outer peripheral surface of the photosensitive drum Y to a predetermined polarity. The charging roller 30Ya includes a charging cleaning member 30Yb for cleaning the toner adhering to the outer surface of the charging roller 30Ya while rotating.

  This charging roller 30Ya is composed of a thermoplastic resin composition (polyethylene, polypropylene, polymethyl methacrylate, polystyrene and their co-polymers) in which a polymer type ion conductive agent is dispersed on the outer peripheral surface of a conductive core on a hollow cylinder having a diameter of 10 mm. A polymer or the like) is formed by coating, and the surface thereof is subjected to a cured film treatment with a curing agent. In addition, a preferable range of the minute gap with the above-described photosensitive drum Y is 30 to 65 μm, and is set to 50 μm in the charging device according to the present embodiment.

  It is possible to use a member such as rubber which is easily deformed on the surface of the charging roller 30Ya. However, if the member is easily deformed, it is difficult to maintain a small gap with respect to the photosensitive drum Y. Since the center of 30Ya may bend and come into contact with the photosensitive drum Y, and the toner image may be disturbed, it is desirable to use a hard member with little bending when the non-contact charging method is adopted.

  The charging roller 30Ya according to the present embodiment is connected to a power source (not shown) so that a predetermined voltage can be applied, and the outer peripheral surface of the photosensitive drum Y is uniformly charged by discharging in the minute gap. It is configured as follows. In this embodiment, an alternating voltage obtained by superimposing a DC voltage of 700 V, which is a DC component, and an AC voltage of a rectangular wave having a frequency of an AC component of 2 kHz and a peak-to-peak voltage of 2 kV, is used as the voltage to be applied. As described above, it is preferable to apply the alternating voltage as described above as the applied voltage to the charging roller 30Ya because the influence of the variation of the charging potential due to the variation of the minute gap is suppressed and uniform charging is possible. .

  The developing device 31Y is a two-axis conveying type developing device using a two-component developer, and a developing case that is a housing of the entire apparatus that accommodates a powdery two-component developer mainly composed of toner and a magnetic carrier. 31Ya, a developing roller 31Yb that is a developer carrying member that carries the developer and supplies toner to the electrostatic latent image on the photosensitive drum, and supplies the developer to the developing roller 31Yb while being charged with stirring. Two conveying screws 31Yc, a doctor blade 31Yd, which is a layer thickness regulating member which is disposed opposite to the developing roller 31Yb with a gap of a predetermined interval and regulates the layer thickness of the developer carried on the developing roller 31Yb, It mainly comprises a density sensor (not shown) that is a density detection means for detecting the toner density of the component developer.

  Further, the developing roller 31Yb can be rotated by being driven by a magnet MY that is a permanent magnet fixed to the developing case 31Ya and a developing motor that is externally fitted to the magnet MY and that is driving means (not shown) in the direction indicated by the arrow. A developing sleeve SY, and the developer carried on the developing sleeve SY by the magnetic force of the magnet MY is conveyed to a developing area that is in close proximity to the photosensitive drum Y as the developing sleeve SY rotates. The electrostatic latent image on the photosensitive drum Y is supplied. The developer that has not been supplied to the electrostatic latent image reaches the repulsion area of the magnet MY as the developing sleeve SY further rotates, falls into the developing case 31Ya, and is supplied again to the developing roller 31Yb by the conveying screw 31Yc. The

  The lubricant application device 32Y includes a lubricant application case 32Ya that is a casing of the entire device, a solid lubricant 32Yb made of rectangular parallelepiped zinc stearate accommodated in the lubricant application case 32Ya, and the solid lubricant. The brush roller 32Yc is scraped while rotating 32Yb and applied to the outer peripheral surface of the photosensitive drum Y, and a pressurizing means 32Yd having a coil spring for pressing the solid lubricant 32Yb against the brush roller 32Yc. The solid lubricant 32Yb pressed by the pressure means 32Yd is scraped while being gradually rotated by the brush roller 32Yc and applied to the outer peripheral surface of the photosensitive drum Y.

  As this solid lubricant 32Yb, a dry solid hydrophobic lubricant can be used. Besides zinc stearate, barium stearate, lead stearate, iron stearate, nickel stearate, cobalt stearate, Those having a stearic acid group such as copper stearate, strontium stearate, calcium stearate, cadmium stearate and magnesium stearate can be used. In addition, the same fatty acid groups such as zinc oleate, manganese oleate, iron oleate, cobalt oleate, lead oleate, magnesium oleate, copper oleate, and palmitic acid, zinc cobalt palmitate, copper palmitate, palmitate Magnesium acid, aluminum palmitate, and calcium palmitate may be used. In addition, fatty acids such as lead caprylate, lead caproate, zinc linolenate, cobalt linolenate, calcium linolenate and cadmium ricolinolenate, metal salts of fatty acids, and the like can also be used. Further, waxes such as candelilla wax, carnauba wax, rice wax, wax, ooba oil, beeswax, and lanolin can be used.

If the brush roller 32Yc is too thin, the brush roller 32Yc is liable to fall down when it comes into contact with the outer peripheral surface of the photosensitive drum Y. Conversely, if the brush fiber is too thick, the density of the fiber is increased. Can not be. Also, if the density of the brush fibers is low, the number of brush fibers that contact the surface of the photosensitive drum Y is small, so that the lubricant cannot be uniformly applied. Conversely, if the density of the brush fibers is too high, The gap between the fibers is reduced, and the amount of the lubricant powder scraped off is reduced, resulting in an insufficient amount of coating. Therefore, the brush thickness of the fibers of the brush roller 32Yc is preferably 3 to 8 deniers [D], the density of the brush fibers from 20,000 to 100,000 present / inch ² is preferable.

  The cleaning device 33Y contacts the photosensitive drum Y and scrapes off the primary transfer residual toner that adheres to the outer peripheral surface of the photosensitive drum Y after the primary transfer, and cleans the cleaning blade 33Ya with the photosensitive drum. A pressing means 33Yb that presses the drum Y at a predetermined pressure, and a transport screw 33Yc that transports residual toner scraped off by the cleaning blade 33Ya to a waste toner bottle (not shown), and the like.

(Operation of image forming unit)
Next, the operation of the image forming unit will be described with reference to FIG.
First, the outer peripheral surface of the photosensitive drum Y is uniformly charged to a predetermined polarity by the charging roller 30Ya, and laser light is emitted from the exposure unit 4 on the basis of image information in the downstream area in the rotational direction of the photosensitive drum Y from the charging roller 30Ya. , And the surface potential of the uniformly charged photoreceptor drum Y is reduced only by the irradiated portion, whereby an electrostatic latent image is formed on the photoreceptor drum Y. Then, as described above, the electrostatic latent image is converted into a toner image (development) by the developing device 31Y, and this toner image moves to the primary transfer nip as the photosensitive drum Y rotates. A primary transfer bias is applied from the next transfer roller 55, and the toner image is moved and transferred to the surface of the intermediate transfer belt 50 by Coulomb force. Further, the primary transfer residual toner that adheres to the outer peripheral surface of the photosensitive drum Y after the primary transfer is cleaned by the cleaning device 33Y, and is prepared for another image formation.

(Image forming operation)
Next, the image forming operation of the color printer 1 will be described with reference to FIGS.
First, as described above, a yellow single color toner image is formed on the photosensitive drum Y in the image forming unit 3Y. Subsequently, the photosensitive drum Y is rotated to the primary transfer nip, where a primary transfer bias having a polarity (for example, plus) opposite to the polarity of the toner is applied by the primary transfer roller 55, and electrostatic attraction is applied. A yellow monochrome toner image is transferred to the intermediate transfer belt 50. Similarly, in the other image forming units 3M, 3C, and 3K, a monochromatic toner image is formed and 1 in the order of yellow, magenta, cyan, and black in accordance with the rotation timing of the intermediate transfer belt 50. Next transfer is performed and superimposed on the intermediate transfer belt 50 to form a full-color toner image.

  On the other hand, the sheet material conveyed from the paper feeding unit 7 is sent to the secondary transfer nip after the transfer timing is adjusted by the registration roller pair 73. Therefore, a secondary transfer bias is applied by the secondary transfer roller 56, and the full-color toner image on the intermediate transfer belt 50 is transferred onto the sheet material by electrostatic attraction. Next, the sheet material carrying the unfixed toner image on the surface is sent to the fixing nip of the fixing unit 6 and is fixed by applying heat and pressure. As described above, after the image is fixed on the sheet material, the sheet material is discharged to the paper discharge unit 8 by the paper discharge roller pair 81 and stacked. Further, the transfer residual toner that adheres to the surface of the intermediate transfer belt 50 after the secondary transfer after the transfer is removed by the cleaning unit 57 and is prepared for another image forming operation. The transfer residual toner removed by the cleaning unit 57 is carried to a waste toner tank (not shown) and discarded.

(Control of drive timing)
Next, control of the drive timing of the conventional drive motor and developing motor will be described with reference to FIG.
In conventional general control, in order to prevent deterioration of the developer, a time T ₁₁ slightly delayed from a drive start time T _{10 of} a drive motor (drive means for driving a drive roller and each photosensitive drum, the same applies hereinafter). Then, the development motor starts to be driven. After imaging is completed, the developing motor is stopped at time T _12, stops the drive motor at time T ₁₃ after performing the job end operation, such as neutralization of the surface of the photosensitive drum. T ₂₀ , T ₂₁ , T ₂₂ , and T ₂₃ are the second image forming operations, and correspond to the first T ₁₀ , T ₁₁ , T ₁₂ , and T ₁₃ , respectively. Although not shown, the third image forming operation is T ₃₀ , T ₃₁ , T ₃₂ , T ₃₃ , and the nth image _forming operation is T _n0 , T _n1 , T _n2 , T _n3 . The above-described control is repeated corresponding to the first T ₁₀ , T ₁₁ , T ₁₂ , and T ₁₃ , respectively.

The timing shown here may take different values depending on how many sheets are printed at a time, the presence / absence of a toner density adjustment operation, the presence / absence of an image density adjustment operation, the presence / absence of a sensor configuration operation, and the like. In the control of the color printer 1 according to this embodiment, the developing start-up operation is 1 second, the developing falling-down operation is 3 seconds, the printing is 1 second, the interval between continuous prints is 0.5 seconds, and the image density adjustment operation is performed. Since it takes 10 seconds, if only one sheet is printed at a time and the image density adjustment operation is not performed, time T ₁₂ -T ₁₁ = startup 1 second + startup 3 seconds + printing 1 second = 5 seconds. When printing 100 sheets at a time and performing an image density adjustment operation at the end of the job, T ₁₂ −T ₁₁ = startup 1 second + falling 3 seconds + printing 1 second × 100 sheets + paper interval 0.5 seconds × 99 sheets + image density adjustment 10 seconds = 163.5 seconds.

Further, when the calibration operation of the optical sensor facing the intermediate transfer belt is performed at the job end, the calibration operation is normally performed in a state where no toner is present on the intermediate transfer belt, so that it is not necessary to rotate the developing motor. Therefore, in the conventional control, the operation is performed between _T 12 _{through T 13} in Figure 3. That is, the developing motor is stopped, but the driving motor is driven. In the control of the printer 1 of this embodiment, this operation takes 20 seconds. If you do not want to calibrate the optical sensor requires only operations such as neutralization of the photosensitive drum, but T ₁₃ -T ₁₂ is 3 seconds, the case of performing calibration of the optical sensor does not perform calibration of the optical sensor T ₁₃ -T ₁₂ is longer than the case by 20 seconds and becomes 23 seconds.

(Relationship between rotation time, friction coefficient, and dropout phenomenon)
Next, the relationship between the rotation times of the drive motor and the developing motor, the respective friction coefficients, and the hollowing out phenomenon will be considered through the following experiment. FIG. 4 is an explanatory diagram for explaining a method of measuring the friction coefficient of the photosensitive drum.

  The method for measuring the coefficient of friction of the photosensitive drum was measured by the Euler belt method as shown in FIG. That is, a medium-quality high-quality paper as a belt is stretched around the drum circumference ¼ of the photosensitive drum so that the paper sheet is in the longitudinal direction, a load of 0.98 N (100 gf) is applied to one of the belts, A digital push-pull gauge, which is a force gauge, was installed in the sensor, and the load measured by the digital push-pull gauge when the belt moved was read and substituted into the following equation (Equation 1). In addition, RICOH Type6000 70W was used as medium-quality high-quality paper.

但し、μ_ｓ：静止摩擦係数、Ｆ：測定値

Where μ _s : coefficient of static friction, F: measured value

  The friction coefficient of the intermediate transfer belt was measured using a white cotton cloth JISL-0803 cotton No. 3 and HEIDON tribogear muse type: 94i-II.

<Experiment 1>
Both the driving motor and the developing motor were driven, and the intermediate transfer belt, the photosensitive drum, and the developing roller were rotated for 150 seconds, and then the friction coefficients of the intermediate transfer belt and the photosensitive drum were measured. However, the friction coefficient of the intermediate transfer belt was 0.4, and the photosensitive member friction coefficient was 0.13. Even if printing was performed in this state, no void occurred in the output image. The printing operation after the idling of the driving motor and the developing motor for 150 seconds is an experimentally created printing operation after 100 sheets are continuously printed.

<Experiment 2>
The drive motor was driven, the intermediate transfer belt and the photosensitive drum were rotated, the developing motor was not driven, and the belt was idled for 20 seconds, and then the friction coefficients of the intermediate transfer belt and the photosensitive drum were measured. The friction coefficient of the intermediate transfer belt was 0.24, and the friction coefficient of the photosensitive drum was 0.13. When printing was performed in this state, a void occurred in the output image. This printing operation after 20 seconds idling of only the drive motor is an experimentally created printing operation immediately after the calibration operation of the optical sensor.

<Experiment 3>
The drive motor is driven to continuously rotate the intermediate transfer belt and the photosensitive drum, and after the developing roller is idled by the developing motor for 5 seconds and then stopped for 4 seconds, the intermediate transfer belt and the photosensitive drum are repeated 10 times. The friction coefficient of the intermediate transfer belt was 0.35, and the friction coefficient of the photosensitive drum was 0.13. Even if printing was performed in this state, no void occurred. This series of operations corresponds to a state where a printing operation for outputting only one sheet is repeated 10 times.

  According to the above experiment, the relationship between the driving time of the developing motor and the driving time of the driving motor varies greatly depending on the printing operation status, and the friction coefficient of the intermediate transfer belt also changes greatly, resulting in a dropout phenomenon in the output image. It can be seen that it has a big effect. In particular, since the developing motor is stopped from Experiment 2, the lubricant is not transferred from the photosensitive drum by the contact transfer between the intermediate transfer belt and the photosensitive drum without removing excessive lubricant by the spike of the developer. It is presumed that the frictional resistance of the surface of the intermediate transfer belt was lowered due to the transition to the belt. However, in the conventional control, although it is considered that the drive time of the developing motor is reduced as much as possible to prevent the developer deterioration, the drive time of the developing motor is extended by the drive time of the drive motor. There is no idea of preventing excessive lubricant transfer by controlling such an operation. As can be seen from Experiment 2, in the printing operation immediately after the calibration operation of the optical sensor, it is not possible to prevent the output image from being lost.

  Next, control of drive timings of the drive motor and the development motor according to the embodiment of the present invention will be described.

The problem that excessive lubricant is transferred from the photosensitive drum to the intermediate transfer belt and the friction coefficient of the surface of the intermediate transfer belt is lowered to cause a hollowing out phenomenon is that the developing motor is driven to idle the developing roller. The problem can be solved by scraping off the excess lubricant with the spikes of the developer carried by the developing roller. Therefore, in the control according to the present embodiment, the driving motor is driven to drive the photosensitive drum as the latent image carrier and the intermediate transfer belt as the intermediate transfer member, and this time is set as the driving time t (contact travel time). Measured and subtracted from the drive time t a predetermined time X ₁ (4 seconds in the present embodiment) obtained through experiments and the like in consideration of prevention of deterioration of the developer, and the minimum drive time A1 (first time of the developing device) Minimum drive time). In the next printing, the developing device is driven so that the driving time of the developing device within the driving time t from the photosensitive drum to the intermediate transfer belt does not fall below the minimum driving time A1. In other words, the developing device is always driven only during the minimum drive time A1 of the time during which the photosensitive drum and the intermediate transfer belt are driven. This is because sometimes it can be scraped off by the developer spikes carried by the developing roller.

  If control is performed as described above, it is possible to perform control that normally does not cause a void. However, when the minimum driving time A1 of the developing device is determined by subtracting a predetermined time from the driving time t of the photosensitive drum and the intermediate transfer belt, the driving time of the developing device becomes extremely short when the driving time t is short. there is a possibility. For example, when a small size paper smaller than A4 paper is passed through and output, the minimum driving time A1 of the developing device relative to the driving time t becomes relatively small, and the lubricant on the photosensitive drum is excessively transferred to the intermediate transfer belt. May not prevent migration.

Therefore, the above-described control may be performed for a sheet having a length of A4 size or more, but when the driving time t may be shorter than that, the control is performed as follows. First, similarly to the above, the drive motor is driven to drive the photosensitive drum as the latent image carrier and the intermediate transfer belt as the intermediate transfer member, and this time is set as the drive time tn (n-th contact travel time). The measurement of the drive time tn is repeated a predetermined number of times (three times in this embodiment), and an average value ta [ta = (t1 + t2 + t3) / 3] of the drive times t1 to t3 is calculated. Next, to determine the minimum drive time of the developing device A2 (second minimum driving time) the calculated average value ta is multiplied by a predetermined factor X ₂ is a predetermined ratio. If the minimum drive time A2 exceeds the above-described minimum drive time A1, the drive time of the developing device is extended during the next (n + 1) printing to reduce the drive time of the developing device within the drive time tn + 1. The developing device is driven so as not to fall below the driving time A2. In other words, the driving time of the developing motor is extended even when the average value of the driving time of the developing motor of the past predetermined number of times with respect to the average value of the driving time of the driving motor of the predetermined number of times exceeds a certain value. The method of setting a predetermined coefficient X ₂ will be described later.

More specifically, as shown in FIG. 5, in the control according to the embodiment of the present invention, also a drive motor after the developing motor is started to measure the time from the timing of stopping, the predetermined time a has elapsed at time T ₁₂ If is rotating, control is performed so that the driving of the developing motor is started again. The predetermined time a can be obtained by conducting an experiment in which the developing motor is intermittently driven in a state where the driving motor is continuously driven as in Experiment 3 above, and confirming the presence or absence of a void in the subsequent printing. it can. The driving time of the developing motor in the experiment is preferably set to the driving time of the developing motor at the time of printing one sheet. The experiment was performed while changing the time for stopping the developing motor, and the predetermined time a was obtained by obtaining the stop time at which the hollowing out phenomenon does not occur. In the printer 1 of this embodiment, a = 4 seconds.

  Although the present embodiment refers to the operation after the job end, the control according to the present embodiment is applied not only to the operation after the job end but also when the main power of the image forming apparatus is turned on or various adjustment operations. Can do. If the developing motor is stopped while the drive motor is driven and the intermediate transfer belt and the photosensitive drum are rotating, the time is counted up. When the predetermined time a is exceeded, the developing roller is driven. As for counting up the time, even if the photosensitive drum is stopped once, if the driving motor starts to be driven with the developing motor stopped again, the previous value is not cleared and accumulated.

  Further, the count up at the time when the developing motor is not driven while the driving motor is driven is cleared if the developing motor is continuously driven longer than the predetermined time b so as not to apply excessive stress to the developer. Shall be. Here, the predetermined time b is set to the driving time of the developing motor when only one sheet is printed.

Further, the driving time of the developing motor is extended also when the average value of the driving time of the developing motor of the past predetermined number of times with respect to the average value of the driving time of the driving motor of the predetermined number of times exceeds a certain value. That is, the driving time of the n-th developing motor T _dm (n) = (T _n2 −T _n1 ) + (T _n5 −T _n4 ), the driving time of the n-th driving motor T _om (n) = T _n3 −T When _{n0, (T dm (n)} + T dm (n-1) + ··· + T dm (n-C)) / (T om (n) + T om (n-1) + ··· + T om ( If n-C)) exceeds a predetermined value X _2, in the (n + 1) th imaging, to stop the developing motor after leaving the drive motor stop command to stop the drive motor by performing processing such as neutralization. Here, C is the number of times of averaging, and is 3 times in the control according to the present embodiment. The predetermined value (predetermined coefficient) X ₂ is determined to be X ₂ = 5 because, according to an experiment equivalent to Experiment 3, if the developing motor is rotated for 5 seconds with respect to the rotation of the driving motor for 5 seconds, a hollow will not occur. / 9.

Referring to the flowchart, as shown in FIG. 6, the developing motor is driven in a state where the driving motor is driven (in a state where the photosensitive drum and the intermediate transfer belt are in contact with each other and rotated) with the end of printing as a trigger. Simultaneously with the stop, the development stop running time is counted up. Then, in step 1, it is confirmed whether or not a drive motor stop command is issued at the same time. If a drive motor stop command is issued, a stop preparation operation such as charge removal or bias lowering is performed to stop the drive motor.
If the developing motor is driven at the time of step 1, the developing motor is stopped, and then the driving motor is stopped by performing a stop preparation operation such as static elimination or bias lowering.
When the drive motor is stopped, the count-up of the development stop travel time is also stopped, and the measured time is stored as the development stop travel time. At this time, the development stop running time is accumulated and added until it is cleared and stored as the development stop running cumulative time, and then all the processes are completed.

  If the stop command for the drive motor is not issued in step 1, it is determined in step 2 whether the development stop running cumulative time exceeds a predetermined time a (4 seconds in this embodiment). Step 1 and step 2 are looped until the accumulated development stop running time exceeds a predetermined time a or a stop command for the drive motor is issued.

  In step 2, when the accumulated development stop running time exceeds the predetermined time a, the development motor driving is restarted, the development stop running time is stopped, and the measured time is accumulated and added. And save it as the accumulated development stop running time. In addition, the development motor drive time starts counting up. If the development motor drive time exceeds a predetermined time b in step 3, the accumulated development stop running time is cleared and the process returns to step 1. If the continuous drive time does not exceed the predetermined time b, the development stop travel time returns to step 1 with the accumulated development stop travel cumulative time, and loops until a drive motor stop command is issued.

  As described above, by controlling the driving timing of the driving motor and the developing motor, the excess transfer agent is scraped off by the developer ears carried by the developing roller when the developing roller idles, so that the intermediate transfer belt can be removed from the photosensitive drum. In addition to preventing excessive transfer of lubricant to the surface and preventing the surface resistance of the intermediate transfer belt from decreasing, it is possible to prevent the hollowing out phenomenon. It is possible to reduce the stress applied to the developer and suppress the deterioration and fog of the developer.

  However, the above-described control is effective when the amount of lubricant on the photosensitive drum and the intermediate transfer belt is stabilized by continuously using the image forming apparatus. However, when the image forming apparatus is new, the photosensitive drum In addition, the amount of lubricant on the intermediate transfer belt is not stable, and it is difficult to prevent voids by control. For this reason, it is preferable that the friction coefficient of the new photosensitive drum is smaller than the friction coefficient of the intermediate transfer belt, since the hollowing out phenomenon can be prevented even in a new state. Specifically, from the experimental results such as Experiment 3, the friction coefficient of the surface of the photosensitive drum as a latent image carrier when new is 0.2 or more than the friction coefficient of the surface of the intermediate transfer belt as an intermediate transfer member. If it is smaller, the above-described control can prevent hollowing out.

  In the control according to the present embodiment, the lubricant that has been applied to the photosensitive drum is collected by the developing device to prevent the unnecessary lubricant from moving to the intermediate transfer belt. When the developer is mixed in the developer, there are side effects such as an increase in charging abnormality and formation of an aggregate depending on the compatibility with the developer. For this reason, it is preferable to use a system containing a lubricant component in advance as a developer because the risk of the lubricant being mixed into the developer is low and the developer can be recovered without side effects. That is, the toner used in the developing device according to the embodiment of the present invention only needs to contain a substance composed of the same component as the lubricant applied by the lubricant applying device. When the developer containing no lubricant is recovered by 0.01% of the lubricant, the charging characteristics change dramatically. However, the developer originally containing 0.1% of the lubricant component This is because even if 0.01% of the lubricant is recovered, it can be used without significant change.

  The four-tandem type intermediate transfer type color printer 1 has been described as an example of the image forming apparatus according to the embodiment of the present invention. However, the image forming apparatus is not necessarily limited to this, and is, for example, a monochrome printer. The present invention can also be applied to a facsimile (FAX) or the like. In particular, the case where the photosensitive drum as the latent image carrier and the intermediate transfer belt as the intermediate transfer member are driven by a single drive motor has been described as an example. It is clear that For example, when printing in a monochrome mode in a color printer, there is known a control in which the Y, M, and C photosensitive drums and the intermediate transfer unit are separated from each other and the drive is stopped. Applicable (same for 2-color mode printing). Further, the developing device of the two-component developing system is exemplified as the developing device, but the developing device of the one-component developing system is also applicable. In short, an intermediate transfer type image forming apparatus having a latent image carrier, a developing device, a lubricant application device, an intermediate transfer member, and a driving device capable of individually driving the latent image carrier and the developing device. Can be applied.

  The toner container storage unit, the exposure unit, the transfer unit, the fixing unit, the paper feed unit, the paper discharge unit, the image forming unit, etc. in the description of the embodiments are merely examples, and other known It is possible to adopt a configuration of a device / means. Even in such a case, it is clear that the same effect can be achieved with respect to the problem. Further, the shapes, structures, and the like of the respective constituent members shown in the drawings are merely preferable examples, and it goes without saying that the design can be appropriately changed within the scope of the claims.

1 Color printer (image forming device)
Y, M, C, K Photosensitive drum (latent image carrier)
3Y, 3M, 3C, 3K Image forming unit 30Y Charging device 31Y Developing device 31Yb Developing roller (developer carrier)
32Y Lubricant coating device 5 Transfer section 50 Intermediate transfer belt (intermediate transfer body)

JP 2005-181742 A

Claims (9)

A latent image carrier that carries a latent image on its surface and rotates, a developing device that develops the latent image on the latent image carrier into a toner image with toner, and lubrication that applies a lubricant to the latent image carrier An agent application device, an intermediate transfer member that is rotationally driven in contact with the surface of the latent image carrier and to which a toner image on the latent image carrier developed by the developing device is transferred, and the latent image carrier. In a control method of an image forming apparatus of an intermediate transfer system comprising a driving device capable of individually driving the developing device,
A control method for an image forming apparatus, comprising: determining a driving time of a developing device based on a contact travel time in which the latent image carrier and the intermediate transfer member are in contact with each other and are rotationally driven. The time from when the latent image carrier and the intermediate transfer member start to contact and start to drive until at least one of the latent image carrier and the intermediate transfer member stops is measured as a contact running time,
A first minimum drive time of the developing device is determined by subtracting a predetermined time from the contact travel time, and the development is performed so that the drive time of the developing device within the contact travel time does not fall below the first minimum drive time. The method of controlling an image forming apparatus according to claim 1, wherein the apparatus is driven. The time from when the latent image carrier and the intermediate transfer member start to contact and start to drive until at least one of the latent image carrier and the intermediate transfer member stops is measured as a contact running time,
The measurement of the contact travel time is repeated a predetermined number of times, an average value of the contact travel time is calculated, and the second minimum drive time of the developing device is determined by multiplying the calculated average value by a predetermined coefficient, and the second minimum drive time is determined. If the driving time exceeds the first minimum driving time, the driving time of the developing device is extended so that the driving time of the developing device within the next contact travel time does not fall below the second minimum driving time. The image forming apparatus control method according to claim 2, wherein the developing device is driven.   The latent image carrier and the intermediate transfer member are in contact with each other and are driven. The development stop travel time is measured from the time when the developing device is stopped, and the development stop travel time is stopped when a predetermined time has passed. 2. The method of controlling an image forming apparatus according to claim 1, wherein the developing device is driven.   When the latent image carrier and the intermediate transfer member are driven to come into contact with each other and the developing device is stopped and the development stop travel time is accumulated and measured, and the development stop travel cumulative time exceeds a predetermined time 2. The method of controlling an image forming apparatus according to claim 1, wherein the stopped developing device is driven.   6. The method of controlling an image forming apparatus according to claim 5, wherein the development stop running cumulative time is cleared when a continuous driving time of the developing device exceeds a predetermined time.   An image forming apparatus using the control method for an image forming apparatus according to claim 1.   8. The image forming apparatus according to claim 7, wherein the friction coefficient of the surface of the latent image carrier is 0.2 or more smaller than the friction coefficient of the surface of the intermediate transfer member when new.   9. The image forming apparatus according to claim 7, wherein the toner supplied to the developing device contains a substance composed of the same component as the lubricant applied by the lubricant applying device.

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