Image forming device

Abstract

To reduce FPOT while preventing toner from moving to an area on a photoreceptor exposed during start-up of an exposure device.SOLUTION: An image forming apparatus 100 has: a photoreceptor 1; an electrifying device 2; an exposure device 11; a developing device 8 including a developing member 4; a motor 101 that drives the developing member 4; and a contact and separation mechanism 500 that receives transmission of driving force from the motor 101 and switches the developing member 4 between a contact state and a separation state with respect to the photoreceptor 1, and the image forming apparatus executes, before image formation, preparation operations including a light emitting operation of exposing the photoreceptor 1 in a light emitting period, start-up of the motor 101, and a contact operation of switching the developing member from the separation state to the contact state in a switching period. The image forming apparatus has: an acquisition unit 407 that acquires information on a switching time that is the time required for the contact and separation mechanism 500 to perform the contact operation to switch the developing member 4 from the separation state to the contact state; and a setting unit 403 that, on the basis of, the information on the switching time acquired by the acquisition unit 407, sets start timing for the contact and separation mechanism to start the contact operation in the preparation operations.SELECTED DRAWING: Figure 14

Description

[Technical field]

[0001] The present invention relates to an image forming apparatus, such as a printer, a copying machine, or a facsimile machine, that uses an electrophotographic method. [Background technology]

[0002] In image forming devices such as electrophotographic laser beam printers, efforts are being made to extend the lifespan of various parts in order to improve image quality and reduce running costs. For example, in a configuration that employs a contact development method in which a developing member such as a developing roller contacts a photoconductor to develop an electrostatic latent image on the photoconductor, the developing member is separated from the photoconductor during standby and is contacted with the photoconductor during image formation. With such a configuration, deterioration of the photoconductor and developing member can be suppressed to extend their lifespan.

[0003] In addition, in an image forming apparatus using an electrophotographic method, various adjustment operations are performed when the exposure device is started up in order to stabilize the image. For example, there is a configuration in which a part of the scanning light from the exposure device is detected by a sensor ("BD sensor") to synchronize the image writing position by the exposure device. In this configuration, when the exposure device is started up, the laser may be turned on ("forced emission") over the entire main scanning direction including the image forming area for a predetermined period of time in order to stably acquire a signal acquired by the BD sensor detecting the laser light.

[0004] When the forced light emission is performed at the start of a printing operation, an electrostatic latent image is formed on the photoconductor. Therefore, if the developing member is brought into contact with the photoconductor when the area on the photoconductor exposed by the forced light emission passes through the development position where the photoconductor and the developing member are in contact, toner will move from the developing member to the area on the photoconductor, resulting in wasteful consumption of toner. In addition, this toner may cause toner stains on the image and recording material during subsequent image formation.

[0005] Patent document 1 proposes a configuration in which the charged potential of the photosensitive member and the potential of the developing member are adjusted so that toner is not consumed even when the developing member is brought into contact with the photosensitive member when the area on the photosensitive member exposed during adjustment of the exposure device passes through the development position. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2013-109322 A Summary of the Invention [Problem to be solved by the invention]

[0007] It is believed that the method of Patent Document 1 can prevent toner from moving to the area on the photoconductor that is exposed when the exposure device is started up. However, this method requires the application and control of the charging voltage and the developing voltage at all times when the exposure device is started up, which tends to make the control relatively complicated and may be detrimental to the life of the photoconductor and the developing device.

[0008] Here, if the operation of bringing the developing member into contact with the photoconductor is started after waiting for the area on the photoconductor exposed during start-up of the exposure device to pass the development position, it is possible to prevent toner from moving to the area on the photoconductor. However, it is also required for the image forming apparatus to shorten the first print out time (hereinafter referred to as "FPOT"), which is the time from when a print command is input until the recording material of the first page on which an image is formed is output. If the operation of bringing the developing member into contact with the photoconductor is started after waiting for the area on the photoconductor to pass the development position, the FPOT becomes long.

[0009] SUMMARY OF THE PRESENT EMBODIMENT An object of the present invention is to reduce the FPOT while suppressing the movement of toner to the area on the photoconductor that is exposed when the exposure device is started up. [Means for solving the problem]

[0010] The above object is achieved by the image forming apparatus according to the present invention. In summary, the present invention provides a photoconductor rotatable in a predetermined rotation direction, a charging device for charging the surface of the photoconductor at a charging position in the rotation direction, an exposure device for exposing the surface of the photoconductor at an exposure position downstream of the charging position in the rotation direction, and a developing device including a rotatable developing member capable of contacting the surface of the photoconductor at a development position downstream of the exposure position and upstream of the charging position in the rotation direction, the developing member supplying a developer to the photoconductor. ,before a contact / separation mechanism for switching the developing member between a contact state in which the developing member is in contact with the photoconductor and a separation state in which the developing member is separated from the photoconductor; a motor that drives the photoconductor, the developing member, and the contact / separation mechanism; an image forming apparatus which performs preparatory operations before image formation, the preparatory operations including a light emitting operation for exposing an area including an image forming area in a rotation axis direction of the photoconductor by the exposure device during a light emitting period to form a potential at which a developer can adhere to the photoconductor, starting the motor, and a contact operation for switching the developing member from the separated state to the contact state by the contact / separation mechanism during a switching period, the motor is configured to rotate the photoconductor and the developing member when the contact operation starts in the preparatory operation, an acquisition unit that acquires information regarding a switching time that is a time required for switching the developing member from the separated state to the contact state by performing the contact operation by the contact / separation mechanism; and and the rotation of the photoreceptor and the developing member. and a setting unit that sets the start timing, which is the timing before the area on the photoconductor exposed during the light emission period reaches the development position. Effect of the Invention

[0011] According to the present invention, it is possible to reduce the FPOT while suppressing the movement of toner to the area on the photoconductor that is exposed when the exposure device is started up. [Brief description of the drawings]

[0012] [Figure 1]FIG. 1 is a schematic cross-sectional view of an image forming apparatus. [Diagram 2] FIG. 2 is a functional block diagram illustrating a system configuration of the image forming apparatus. [Diagram 3] 2A and 2B are a schematic cross-sectional view of a process cartridge and a schematic view of a contact / separation mechanism. [Figure 4] 5A and 5B are schematic diagrams for explaining a contact and separation state of a developing roller. [Diagram 5] FIG. 4 is a functional block diagram of a development contact control unit. [Figure 6] FIG. 1 is a schematic diagram of an exposure apparatus. [Figure 7] 2 is a block diagram showing functional blocks and hardware of an optical control unit. FIG. [Figure 8] FIG. 11 is a timing chart for explaining an example of a problem. [Figure 9] FIG. 11 is a timing chart for explaining a measurement process during an initialization operation. [Figure 10] FIG. 11 is a timing chart illustrating an example of a contact operation at the start of a printing operation. [Figure 11] FIG. 11 is a timing chart of another example of the contact operation at the start of the printing operation. [Figure 12] FIG. 11 is a flowchart illustrating an example of a measurement process during an initialization operation. [Figure 13] FIG. 13 is a flowchart illustrating an example of a part of the processing in FIG. [Figure 14] FIG. 11 is a flowchart illustrating an example of a contact operation at the start of a printing operation. [Figure 15] FIG. 11 is a flowchart of another example of the contact operation at the start of the printing operation. [Figure 16] FIG. 13 is a functional block diagram showing a system configuration of an image forming apparatus according to another embodiment. [Figure 17] FIG. 11 is a timing chart of an example of a contact operation at the start of a print operation in a case where an input voltage to an image forming apparatus fluctuates in another embodiment. [Figure 18] FIG. 11 is a flowchart showing an example of a contact operation at the start of a printing operation in another embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] Hereinafter, the image forming apparatus according to the present invention will be described in more detail with reference to the drawings.

[0014] [Example 1] 1. Configuration of image forming apparatus and image forming operation 1 is a schematic cross-sectional view of an image forming apparatus 100 according to this embodiment. The image forming apparatus 100 according to this embodiment is a tandem printer (color image forming apparatus) that employs an intermediate transfer method and is capable of forming a full-color image using an electrophotographic method.

[0015] The image forming apparatus 100 has a plurality of image forming units (stations), namely, first, second, third and fourth image forming units SY, SM, SC and SK, which form images using toners of the respective colors of yellow (Y), magenta (M), cyan (C) and black (K). These four image forming units SY, SM, SC and SK are arranged in a line at approximately regular intervals along the moving direction of the surface of the intermediate transfer belt 80, to which the image is transferred, as described later. In this embodiment, the image forming units for each color are arranged in the order of yellow (Y), magenta (M), cyan (C) and black (K) from the most upstream to the most downstream with respect to the moving direction of the intermediate transfer belt 80. Note that elements having the same or corresponding functions or configurations provided for each color may be generally described by omitting the Y, M, C and K at the end of the reference numerals indicating that the elements are for any of the colors. In this embodiment, the image forming unit S is configured with a photosensitive drum 1, a charging roller 2, an exposure device 11, a developing device 8, a primary transfer roller 81, a cleaning device 3 and the like, which will be described later.

[0016] The image forming section S has a photosensitive drum 1, which is a rotatable drum-type (cylindrical) photosensitive member (electrophotographic photosensitive member) serving as a first image carrier. The photosensitive drum 1 is constructed by laminating multiple layers of functional organic materials, such as a carrier generation layer that is photosensitive to light and generates charges, and a charge transport layer that transports the generated charges, on a metallic cylindrical member, and the outermost layer has low conductivity and is almost electrically insulating. During image formation, the photosensitive drum 1 receives a driving force from a developing motor 101 (FIG. 3(b)) that is also used as a driving source for a developing roller 4 (described later) and rotates at a predetermined peripheral speed (process speed) in the direction of arrow R1 in FIG. 1 (counterclockwise direction).

[0017] The surface of the rotating photosensitive drum 1 is uniformly charged to a predetermined potential of a predetermined polarity (negative in this embodiment) by a charging roller (charging device) 2, which is a roller-type charging member serving as a charging means. The charging roller 2 contacts the photosensitive drum 1 and rotates in accordance with the rotation of the photosensitive drum 1, while charging the surface of the photosensitive drum 1 approximately uniformly. The charging roller 2 is connected to a charging power source 20 serving as a charging voltage application unit. During the charging process, a DC voltage or a voltage in which a DC voltage and an AC voltage are superimposed is applied to the charging roller 2 from the charging power source 20 as a charging voltage (charging bias). In this embodiment, the DC component of the charging voltage has the same polarity as the normal charging polarity of the toner (negative in this embodiment). The surface of the photosensitive drum 1 is charged by discharge generated in a minute gap (gap) between the charging roller 2 and the photosensitive drum 1 formed upstream and downstream of the contact portion between the charging roller 2 and the photosensitive drum 1 with respect to the rotation direction of the photosensitive drum 1.

[0018] The surface of the charged photosensitive drum 1 is scanned and exposed by an exposure device 11 serving as an exposure means (light irradiation means), and an electrostatic latent image (electrostatic image) is formed on the photosensitive drum 1. The exposure device 11 is composed of a scanner unit (light scanning device) that scans a laser beam using a polygonal mirror. The exposure device 11 irradiates the photosensitive drum 1 with a laser beam 12 modulated based on an image signal, thereby forming an electrostatic latent image on the photosensitive drum 1 according to the image signal. The exposure device 11 may be configured to irradiate light using an LED array.

[0019] The electrostatic latent image formed on the photosensitive drum 1 is developed (visualized) by supplying toner as a developer by a developing device 8 as a developing means, and a toner image (toner image, developer image) is formed on the photosensitive drum 1. The developing device 8 is configured to have a developing container 5, a developing roller 4 as a developing member, and a developer application blade 7 as a developer regulating member. A non-magnetic one-component developer (toner) is contained in the developing container 5 as a developer. The developing roller 4 is connected to a developing power source 21 as a developing voltage application unit. During the developing process, the developing roller 4 is abutted against the photosensitive drum 1. During the developing process, the developing roller 4 receives a driving force from a developing motor 101 (FIG. 3(b)) as a driving source and rotates at a predetermined peripheral speed in the clockwise direction in FIG. 1. During the developing process, a voltage in which a DC voltage and an AC voltage are superimposed is applied to the developing roller 4 from the developing power source 21 as a developing voltage (developing bias). As a result, toner is supplied from the developing roller 4 to the photosensitive drum 1 at a developing position (developing section) where the photosensitive drum 1 and the developing roller 4 come into contact with each other. In this embodiment, toner charged with the same polarity as the charging polarity of the photosensitive drum 1 (negative polarity in this embodiment) adheres to the exposed section (image section) on the photosensitive drum 1, which has been uniformly charged and then exposed to light to reduce the absolute value of the potential (reverse development). In this embodiment, the normal charging polarity of the toner, which is the charging polarity of the toner during development, is negative. The DC component of the developing voltage has the same polarity as the normal charging polarity of the toner (negative polarity in this embodiment). In addition, the potential of the DC component of the developing voltage is set to a potential between the surface potential (charging potential) of the non-image section (non-exposed section) on the photosensitive drum 1, which has been uniformly charged, and the surface potential of the image section (exposed section), the absolute value of the potential of which has been reduced by exposure.

[0020] An intermediate transfer belt 80, which is an intermediate transfer body formed of an endless belt as a second image carrier, is disposed so as to face each of the photosensitive drums 1Y, 1M, 1C, and 1K. The intermediate transfer belt 80 is supported by three rollers, namely, a secondary transfer facing roller 86 as a tension member, a driving roller 14, and a tension roller 15, so that an appropriate tension is maintained. The driving roller 14 receives a driving force from a driving source (not shown) and rotates in the clockwise direction in FIG. 1, so that the intermediate transfer belt 80 rotates (moves around) in the direction of arrow R2 (clockwise direction) in FIG. 1. The intermediate transfer belt 80 moves at approximately the same speed in the forward direction relative to the photosensitive drum 1 at the portion facing the photosensitive drum 1. On the inner peripheral surface side of the intermediate transfer belt 80, primary transfer rollers 81Y, 81M, 81C, and 81K, which are roller-type primary transfer members as primary transfer means, are disposed corresponding to each of the photosensitive drums 1Y, 1M, 1C, and 1K, respectively. The primary transfer roller 81 is disposed at a position facing the photosensitive drum 1 via the intermediate transfer belt 80, and is rotated in contact with the inner circumferential surface of the intermediate transfer belt 80 as the intermediate transfer belt 80 moves. The primary transfer roller 81 abuts against the photosensitive drum 1 via the intermediate transfer belt 80 and is pressed toward the photosensitive drum 1 to form a primary transfer portion (primary transfer nip) N1 where the photosensitive drum 1 and the intermediate transfer belt 80 come into contact with each other. The primary transfer rollers 81Y, 81M, 81C, and 81K are connected to primary transfer power sources 84Y, 84M, 84C, and 84K, respectively, as primary transfer voltage application portions. In addition, static eliminators 23Y, 23M, 23C, and 23K are disposed downstream of the primary transfer rollers 81Y, 81M, 81C, and 81K with respect to the rotation direction of the intermediate transfer belt 80. The drive roller 14, tension roller 15, secondary transfer opposing roller 86, and each of the charge removing members 23Y, 23M, 23C, and 23K are electrically grounded (connected to ground). As described above, the toner image formed on the photosensitive drum 1 is transferred (primary transfer) onto the rotating intermediate transfer belt 80 at the primary transfer portion N1 by the action of the primary transfer roller 81. During the primary transfer process, a primary transfer voltage (primary transfer bias), which is a DC voltage of the opposite polarity (positive polarity in this embodiment) to the normal charging polarity of the toner, is applied to the primary transfer roller 81 from a primary transfer power source 84.For example, when a full-color image is formed, the toner images of yellow, magenta, cyan and black formed on the respective photosensitive drums 1 are transferred in sequence onto the intermediate transfer belt 80 so as to be superimposed on each other.

[0021] A secondary transfer roller 82, which is a roller-type secondary transfer member serving as a secondary transfer means, is disposed at a position facing the secondary transfer opposing roller 86 on the outer peripheral surface side of the intermediate transfer belt 80. The secondary transfer roller 82 contacts the outer peripheral surface of the intermediate transfer belt 80 and rotates in accordance with the movement of the intermediate transfer belt 80. The secondary transfer roller 82 contacts the secondary transfer opposing roller 86 via the intermediate transfer belt 80 and is pressed toward the secondary transfer opposing roller 86 to form a secondary transfer portion (secondary transfer nip) N2 where the intermediate transfer belt 80 and the secondary transfer roller 82 contact each other. The secondary transfer roller 82 is connected to a secondary transfer power source 85 serving as a secondary transfer voltage application portion. As described above, the toner image formed on the intermediate transfer belt 80 is transferred (secondarily transferred) onto the recording material P, which is being conveyed while being sandwiched between the intermediate transfer belt 80 and the secondary transfer roller 82, by the action of the secondary transfer roller 82 at the secondary transfer portion N2. During the secondary transfer process, a secondary transfer voltage (secondary transfer bias), which is a DC voltage of opposite polarity (positive polarity in this embodiment) to the normal charging polarity of the toner, is applied to the secondary transfer roller 82 from a secondary transfer power source 85.

[0022] A recording material (recording medium, transfer material, sheet) P such as paper or a plastic sheet is stored in a recording material cassette 16 as a recording material storage section, and is fed from the recording material cassette 16 to the secondary transfer section N2. When feeding the recording material P from the recording material cassette 16, a pickup roller 17 as a feeding member is driven by a feeding motor (not shown) constituted by a stepping motor. Accordingly, a bottom plate 29 provided in the recording material cassette 16 rises, and the recording materials P stacked in the recording material cassette 16 are pushed up. As a result, the topmost sheet of recording material P among the recording materials P in the recording material cassette 16 comes into contact with the pickup roller 17, and this recording material P is sent out from the recording material cassette 16 by the rotation of the pickup roller 17. This recording material P is conveyed to a registration roller 18 as a conveying member. In addition, when a registration sensor 35 as a recording material detection means detects the leading edge of the recording material P in the conveying direction, the driving of the feeding motor is stopped, and the conveyance of the recording material P is temporarily stopped. Then, this recording material P is transported by the registration rollers 18 to the secondary transfer portion N2 at a predetermined timing in accordance with the movement of the toner image on the intermediate transfer belt 80.

[0023] The recording material P onto which the toner image has been transferred is conveyed to a fixing device 19 as a fixing means. The fixing device 19 is configured to have, for example, a fixing film as a heating member and a pressure roller as a pressure member. The fixing device 19 applies heat and pressure to the recording material P carrying the unfixed toner image, thereby fixing (melting and bonding) the toner image to the recording material P. The recording material P onto which the toner image has been fixed by the fixing device 19 is discharged (output) to the outside of the device body 110 of the image forming apparatus 100, and is stacked on a discharge tray 36 provided on the upper part of the device body 110.

[0024] Meanwhile, any adhering matter such as primary transfer residual toner remaining on the photosensitive drum 1 after the primary transfer is removed from the photosensitive drum 1 and collected by a cleaning device 3 serving as a cleaning means. In this embodiment, the cleaning device 3 is configured to include a cleaning blade serving as a cleaning member that contacts the photosensitive drum 1, and a cleaning container that contains the toner and the like removed from the photosensitive drum 1 by the cleaning blade. In addition, any adhering matter such as secondary transfer residual toner remaining on the intermediate transfer belt 80 after the secondary transfer is removed from the intermediate transfer belt 80 and collected by an intermediate transfer body cleaning means (not shown).

[0025] Here, the position on the photosensitive drum 1 where charging is performed by the charging roller 2 in relation to the rotation direction of the photosensitive drum 1 is the "charging position." As described above, in this embodiment, the photosensitive drum 1 is charged by discharge generated in the gaps formed upstream and downstream of the contact portion between the charging roller 2 and the photosensitive drum 1, but the contact portion between the charging roller 2 and the photosensitive drum 1 may also be considered as the charging position. Also, the position on the photosensitive drum 1 where the laser light is irradiated by the exposure device 11 in relation to the rotation direction of the photosensitive drum 1 is the "exposure position," and the position on the photosensitive drum 1 where the developing roller 4 contacts is the "developing position."

[0026] In this embodiment, the photosensitive drum 1, the charging roller 2 as a process means acting on the photosensitive drum 1, the developing device 8, and the cleaning device 3 constitute a process cartridge 9 that is detachably attached to the apparatus main body 110. However, the cartridge configuration is not limited to this. For example, the photosensitive drum 1 (which may further include the charging roller 2 and the cleaning device 3) may be one cartridge (drum cartridge), and the developing device 8 may be another cartridge (developing cartridge).

[0027] In the present embodiment, the image forming apparatus 100 can perform image formation in a full-color mode (first image forming mode) and a monochrome mode (second image forming mode) as image forming modes. In the full-color mode, a toner image can be formed in all of the four image forming units SY, SM, SC, and SK to form and output a full-color image. In the monochrome mode, a toner image can be formed only in the black image forming unit SK among the four image forming units SY, SM, SC, and SK to form a black monochrome image. During image formation in the full-color mode, in all of the four image forming units SY, SM, SC, and SK, the developing roller 4 is brought into contact with the photosensitive drum 1, the photosensitive drum 1 and the developing roller 4 are driven, and a charging voltage, a developing voltage, and a primary transfer voltage are applied. In the monochrome mode, in only the black image forming unit SK among the four image forming units SY, SM, SC, and SK, the developing roller 4 is brought into contact with the photosensitive drum 1, the photosensitive drum 1 and the developing roller 4 are driven, and a charging voltage, a developing voltage, and a primary transfer voltage are applied.

[0028] 2. System configuration of image forming device FIG. 2 is a functional block diagram for explaining the system configuration of the image forming apparatus 100 in this embodiment.

[0029] The image forming apparatus 100 is provided with a printer controller 401. The printer controller 401 is configured to have a microcomputer. The printer controller 401 receives code data sent from an external device 400 such as a host computer, and performs processing to expand the code data into bitmap data (image data) and print information (various setting information) required for image formation. The printer controller 401 also has a function of performing processing to display information inside the image forming apparatus 100 on a display unit of an operation unit provided in the image forming apparatus 100 and a display unit of the external device 400.

[0030] The image forming apparatus 100 is also provided with an engine control unit 403. The engine control unit 403 controls the operation of each unit of the image forming apparatus 100 according to instructions from the printer controller 401. The operations of each unit of the image forming apparatus 100 include forming an electrostatic latent image on the photosensitive drum 1, developing the electrostatic latent image, primary and secondary transfer of the toner image, fixing the toner image onto the recording material P, and conveying the recording material P. The engine control unit 403 also notifies the printer controller 401 of internal information of the image forming apparatus 100 indicating the state of each unit of the image forming apparatus 100. The engine control unit 403 and each unit of the image forming apparatus 100 controlled thereby constitute a printer engine 402.

[0031] The engine control unit 403 is configured to include a CPU as a control unit, a memory (ROM, RAM, etc.) as a storage unit in which various control information is stored, and an input / output unit (I / F) that controls the transmission and reception of signals between the engine control unit 403 and each unit. The engine control unit 403 is configured, for example, as a one-chip microcomputer incorporating a ROM, a RAM, etc. The engine control unit 403 can transmit and receive information to and from the printer controller 401, for example, through serial communication. The engine control unit 403 also controls each control unit of the image forming apparatus 100 according to an instruction from the printer controller 401. These control units include a recording material conveying unit 404, a fixing control unit 405, an optical control unit 406, a development contact control unit 407, and an image control unit 408.

[0032] Engine control unit 403 waits until it receives a print instruction (print operation start instruction) from printer controller 401. Then, when engine control unit 403 receives the print instruction, it controls each control unit and starts the print operation. When image control unit 408 receives the print instruction, it determines whether the image forming mode is a full-color mode or a monochrome mode based on the information received from printer controller 401 in a preparation operation. Then, development contact control unit 407 executes a contact / separation operation (contact / separation state switching operation) to switch the contact / separation state between the photosensitive drum 1 and the development roller 4 in the image forming unit S for each color according to the specified image forming mode.

[0033] Image control unit 408 determines whether or not it is time to form an image, and transmits information regarding the image formation timing to engine control unit 403. When engine control unit 403 receives a signal indicating that it is time to form an image from image control unit 408, it transmits to printer controller 401 an image synchronization signal ("TOP signal") that is the reference timing for outputting a video signal as image data.

[0034] When the printer controller 401 receives an image synchronization signal from the engine control unit 403, it outputs a video signal based on the color specified by the reference color designation. When the recording material transport unit 404 receives a print instruction, it starts feeding and transporting the recording material P. When the fixing control unit 405 receives a print instruction, it starts preparation for fixing. In accordance with the information in the print reservation command, the fixing control unit 405 starts adjusting the temperature of the fixing device 19 in accordance with the timing when the recording material P on which the secondary transfer has been performed is transported to the fixing device 19, and fixes the toner image on the recording material P. The optical control unit 406 will be described later.

[0035] In FIG. 2, each of the control units 404-408 is shown separately from the engine control unit 403, but the engine control unit 403 may have some of the functions of each of the control units 404-408 (which may be some of the functions of each control unit) or all of the functions.

[0036] 3.Developing roller contact / separation operation Next, we will explain the contact / separation operation between the photosensitive drum 1 and the developing roller 4 (herein, also simply referred to as the "contact / separation operation of the developing roller") that switches the contact / separation state between the photosensitive drum 1 and the developing roller 4 in this embodiment (herein, also simply referred to as the "contact / separation state of the developing roller").

[0037] Fig. 3(a) is a cross-sectional view of the process cartridge 9 in this embodiment. The process cartridges 9Y, 9M, 9C, and 9K for each color are substantially identical in configuration except for the different colors of toner contained in the developer containers 5. Fig. 3(b) is a schematic diagram of a contact / separation mechanism 500 for switching the contact / separation state of the development roller 4 in this embodiment.

[0038] In this embodiment, the photosensitive drum 1 and the developing roller 4 rotate by receiving a driving force from a common developing motor 101 (FIG. 3(b)) serving as a driving source. The photosensitive drum 1 rotates at a predetermined peripheral speed in the direction of arrow R1 (counterclockwise direction) in FIG. 3(a). The developing roller 4 rotates at a predetermined peripheral speed in the direction of arrow R3 (clockwise direction) in FIG. 3(a). In other words, the photosensitive drum 1 and the developing roller 4 each rotate so as to move in the forward direction relative to each other at the contact portion. The rotation axis of the photosensitive drum 1 and the rotation axis of the developing roller 4 are approximately parallel to each other.

[0039] As described later, in this embodiment, the developing motor 101 is used as a drive source for the developing roller 4 and the photosensitive drum 1, and is also used as a drive source for the contact / separation mechanism 500.

[0040] As shown in FIG. 3A, the process cartridge 9 has a drum unit 13 and a developing device (developing unit) 8. The drum unit 13 is configured by supporting the photosensitive drum 1, the charging roller 2, the cleaning device 3, etc., on a drum unit frame 93. The developing device 8 is configured by supporting the developing roller 4, the developer application blade 7, etc., on a developing container (developing frame) 5. The developing device 8 (developing container 5) is attached to the drum unit frame 93 so as to be rotatable (swingable) around a rotation axis 94 that is substantially parallel to the rotation axis of the photosensitive drum 1. The developing device 8 (developing container 5) is biased by a pressure spring 91, which is an elastic member serving as a biasing means, so as to rotate in a direction in which the developing roller 4 abuts against the photosensitive drum 1. In addition, a receiving portion 92 for receiving a force from a contact / separation mechanism 500, which will be described later, is provided at an end of the developing device 8 (developing container 5) in the direction of the rotation axis of the developing roller 4 (longitudinal direction). In the developing device 8 (developing container 5), a predetermined force is applied to the receiving portion 92 by a slider 506 (506f or 506m) of a contact / separation mechanism 500 (described later), so that the developing roller 4 is rotated in a direction away from the photosensitive drum 1 against the biasing force of the pressure spring 91. In this way, the developing roller 4 is brought into contact with the photosensitive drum 1 when the force applied to the receiving portion 92 is released, and is brought into a separated state away from the photosensitive drum 1 when a force is applied to the receiving portion 92.

[0041] As shown in FIG. 3B, the contact / separation mechanism 500 includes an input gear 501, a partially-toothed gear mechanism 502, a solenoid (electromagnetic solenoid, flapper solenoid) 503, and an output unit 504. The contact / separation mechanism 500 also includes a first contact / separation cam 505f, a second contact / separation cam 505m, a first slider 506f, a second slider 506m, a sensor flag 507, and an HP (home position) sensor 508. The input gear 501 is a drive transmission member for inputting a driving force from the development motor 101 as a driving source to the contact / separation mechanism 500. The partially-toothed gear mechanism 502 is a drive transmission member for transmitting a drive force from the input gear 501 to the output unit 504 and for releasing the drive transmission. The solenoid 503 is a switching member (drive transmission switching member) for switching the state of the partially-toothed gear mechanism 502 between drive transmission and drive transmission release. The first contact / separation cam 505f is a switching member (contact / separation state switching member) for switching the contact / separation state of the developing roller 4 in the image forming section S for each of the colors yellow, magenta, and cyan. The second contact / separation cam 505m is a switching member (contact / separation state switching member) for switching the contact / separation state of the developing roller 4 in the image forming section S for the black color. The first slider 506f is a moving member moved by the first contact / separation cam 505f for applying force to the receiving portion 92 of the developing device 8 for each of the colors yellow, magenta, and cyan. The second slider 506m is a moving member moved by the second contact / separation cam 505m for applying force to the receiving portion 92 of the developing device 8 for the black color.

[0042] A known configuration may be appropriately used as the configuration for switching between the drive transmission and drive transmission release states by the missing tooth gear mechanism 502 and the solenoid 503. Therefore, a detailed description of this configuration is omitted, but the outline is as follows. The missing tooth gear mechanism 502 has a first missing tooth gear, a second missing tooth gear, and a locking claw, and these three members are arranged coaxially in parallel in the axial direction. The solenoid 503 is configured with a locking claw stopper that can engage with and hold the locking claw. When a current is supplied to the solenoid 503, it releases the locking claw from being held by the locking claw stopper. When the locking claw stopper holds the locking claw, the missing teeth of the first missing tooth gear and the second missing tooth gear face the input gear 501, and the drive force of the input gear 501 is not transmitted. When the current supply is cut off, the solenoid 503 engages with the locking claw by the locking claw stopper and holds it. When a current is supplied to the solenoid 503 to release the locking claw from the locking claw stopper, the second missing tooth gear, which is coaxial with the locking claw, rotates due to the action of a spring provided between the second missing tooth gear and the first missing tooth gear. The second missing tooth gear then meshes with the input gear 501 and rotates with the driving force from the input gear 501. When the second missing tooth gear rotates, the first missing tooth gear also rotates as an engaging portion provided on the second missing tooth gear engages with an engaged portion provided on the first missing tooth gear. The first missing tooth gear also meshes with the input gear 501 and rotates with the driving force from the input gear 501. As a result, the drive is connected from the input gear 51 to the output portion (output gear, output shaft, etc.) 504 via the first missing tooth gear and the second missing tooth gear. Furthermore, when the second missing tooth gear rotates, the supply of current to the solenoid 503 is cut off, and the locking claw can be held by the locking claw stopper. Then, when the second missing tooth gear rotates by a predetermined phase (for example, one revolution), the locking claw stopper again engages with the locking claw and holds it. At this time, the missing tooth portion of the second missing tooth gear faces the input gear 502. When the first missing tooth gear also rotates by a predetermined phase (for example, one revolution), the missing tooth portion faces the input gear 502 and stops rotating. Until the first missing tooth gear stops, a spring provided between the first missing tooth gear and the second missing tooth gear is compressed.As a result, the input gear 501 rotates freely against the missing tooth portions of the first missing tooth gear and the second missing tooth gear, and the drive transmission from the input gear 501 to the output section 504 via the first missing tooth gear and the second missing tooth gear is released.

[0043] The contact / separation mechanism 500 intermittently transmits the drive force to the output unit 504 as necessary. This intermittent drive force is transmitted by a tooth-missing gear mechanism 502 and a solenoid 503. The output unit 504 operates by a predetermined phase each time the tooth-missing gear mechanism 502 (the first tooth-missing gear and the second tooth-missing gear) rotates by a predetermined phase (for example, one revolution). The contact / separation state of the developing roller 4 in the image forming unit S for each color is switched by a first contact / separation cam 505f and a second contact / separation cam 505m fixed on the same axis as the output unit 504. The first contact / separation cam 505f and the second contact / separation cam 505m reciprocate the first slider 506f and the second slider 506m, which move in accordance with the first contact / separation cam 505f and the second contact / separation cam 505m, respectively. The first slider 506f switches between applying and releasing the force to the receiving unit 92 of the developing device 8 for each color of yellow, magenta, and cyan. Also, the second slider 506m switches between applying and releasing force to the receiving portion 92 of the developing device 8 for black. This switches the contact / separation state of the developing roller 4 in the image forming portion S for each color. In this manner, in this embodiment, the solenoid 503 is operated to control whether the first and second contact / separation cams 505f and 505m are operated or stopped. When the solenoid 503 is not operated, the input gear 501 that inputs the driving force to the first and second contact / separation cams 505f and 505m rotates idly. When the solenoid 503 is driven, the locking claw stopper of the solenoid 503 is released from the locking claw of the missing tooth mechanism 502, and the input gear 501 drives the first and second contact / separation cams 505f and 505m. When the input gear 501 rotates a predetermined amount, the locking claw stopper abuts against the locking claw again, and the input gear 501 continues to rotate freely.

[0044] In this embodiment, each time the solenoid 503 is driven once and the missing tooth gear mechanism 502 (the first missing tooth gear and the second missing tooth gear) rotates once, the output portion (output gear, output shaft, etc.) 504 rotates in one direction by 1 / 3 rotation (120°). In addition, in accordance with the rotation of the output portion 504, the first contact / separation cam 505f and the second contact / separation cam 505m rotate 1 / 3 rotation (120°) at a time. The first and second contact / separation cams 505f and 505m rotate 1 / 3 rotation at a time to sequentially switch the contact / separation state of the developing roller 4 in the image forming portion S for each color to a fully separated state, a fully contact state, and a single contact state, which will be described later. In other words, the cam profiles of the first and second contact / separation cams 505f and 505m are set so as to perform such switching.

[0045] A sensor flag 507 is fixed coaxially with the first and second contact / separation cams 505f and 505m. An HP sensor 508 is provided to detect the phase (position in the rotation direction) of the sensor flag 507, i.e., the phase of the first and second contact / separation cams 505f and 505m. The sensor flag 507 is, for example, disk-shaped and has a slit in one part, and transmits detection light of the HP sensor 508 composed of a photointerrupter at the slit part and blocks light at the other part. In this embodiment, the sensor flag 507 transmits detection light of the HP sensor 508 in a fully separated state described later. This allows the HP sensor 508 to detect that the contact / separation state of the development roller 4 of the image forming unit S for each color is in a fully separated state described later.

[0046] The first approach / separate cam 505f and the second approach / separate cam 505m may be integrated. Also, the first approach / separate cam 505f or the second approach / separate cam 505m and the sensor flag 507 may be integrated.

[0047] FIG. 4 is a schematic diagram showing the contact / separation state of the developing roller 4 of the image forming section S for each color in this embodiment. FIG. 4(a) shows a fully separated state (fully separated position) in which the developing roller 4 is separated from the photosensitive drum 1 in all four image forming sections SY, SM, SC, and SK. FIG. 4(b) shows a fully contacted state (fully contacted position) in which the developing roller 4 is in contact with the photosensitive drum 1 in all four image forming sections SY, SM, SC, and SK. FIG. 4(c) shows a single contact state (single contact position) in which the developing roller 4 is in contact with the photosensitive drum 1 only in the image forming section SK for black color among the four image forming sections SY, SM, SC, and SK. In this embodiment, the contact / separation state of the developing roller 4 in the image forming section S for each color is the fully separated state when the image forming apparatus 100 is in a standby state waiting for input of a print command or in a power-off state. Also, the fully contacted state is set during image formation in full-color mode. Also, the single contact state is set during image formation in monochrome mode. As described above, in this embodiment, the HP sensor 508 can detect the contact / separation state of the developing roller 4 of the image forming unit S for each color, with the full separation state being the reference state (reference position).

[0048] From the full separation state of FIG. 4(a), the force applied to the receiving portion 92 of the developing device 8 for each color by the first and second sliders 506f and 506m is released, thereby changing to the full contact state of FIG. 4(b). The amount of rotation of the developing motor 101 required to switch from the full separation state (FIG. 4(a)) to the full contact state (FIG. 4(b)) is defined as "Dfull". From the full contact state of FIG. 4(b), a force is applied to the receiving portion 92 of the developing device 8 for each color of yellow, magenta, and cyan by the first slider 506f, and the developing rollers 4 for these colors are separated from the photosensitive drum 1, thereby changing to the single contact state of FIG. 4(c). The amount of rotation of the developing motor 101 required to switch from the full contact state (FIG. 4(b)) to the single contact state (FIG. 4(c)) is defined as "DMono". Furthermore, from the single contact state of FIG. 4(c), a force is applied to the receiving portion 92 of the black developing device 8 by the second slider 506m, and the black developing roller 4 is separated from the photosensitive drum 1, resulting in the fully separated state of FIG. 4(a). The amount of rotation of the developing motor 101 required to switch from this single contact state (FIG. 4(c)) to the fully separated state (FIG. 4(a)) is designated as "Doff". Thus, in this embodiment, the contact / separation mechanism 500 is configured to perform a full state transition type contact / separation state switching operation by sequentially transitioning between the states of FIG. 4(a) to FIG. 4(c).

[0049] In this embodiment, a motor that performs sensorless vector control is used as the developing motor 101, and the rotation speed of the motor can be detected (estimated) based on the value of the current passed through the motor. However, the present invention is not limited to this configuration. of Alternatively, a motor of another configuration, such as a brushless motor, may be used as long as there is a means for detecting (estimating) the rotation speed of the motor.

[0050] 4.Development contact control section 5 is a functional block diagram of the developer contact control unit 407 in this embodiment. The developer contact control unit 407 has the following units, and operates based on instructions from the engine control unit 403. That is, the developer contact control unit 407 has, as functional blocks, a drive control unit 910, a contact / separation unit 911, a drive speed detection unit 912, and a speed acquisition interval storage unit 916. The developer contact control unit 407 also has, as functional blocks, a rotation amount estimation unit 913, a rotation amount storage unit 914, a contact / separation state determination unit 915, a time storage unit 917, and a contact operation start determination unit 918.

[0051] The drive control unit 910 controls the drive of the developing motor 101. When the developing motor 101 is driven, the contact / separation unit 911 drives the solenoid 503 to operate the first and second contact / separation cams 505f and 505m, thereby switching the contact / separation state of the developing roller 4 in the image forming unit S for each color. The drive speed detection unit 912 detects the rotation speed of the developing motor 101. The rotation amount estimation unit 913 estimates (calculates) the short-term rotation amount of the developing motor 101 based on the rotation speed of the developing motor 101 detected by the drive speed detection unit 912 and the speed acquisition interval (detection interval) stored in the speed acquisition interval storage unit 916. The rotation amount storage unit 914 accumulates the short-term rotation amount of the developing motor 101 estimated by the rotation amount estimation unit 913 and stores the accumulated value. A contact / separation state determination unit 915 determines whether or not the transition of the contact / separation state has been completed based on information on the amount of rotation of the developing motor 101 required for the transition between the contact / separation states stored in the contact / separation unit 911 and the amount of rotation of the developing motor 101 stored in the rotation amount memory unit 914. A time memory unit 917 stores information on various times (timings) related to the contact operation of the developing roller 4, such as a contact completion time described below. A contact operation start determination unit 918 determines a contact operation start timing described below based on the information stored in the time memory unit 917 and the like, and controls the start of the contact operation of the developing roller 4.

[0052] In the following explanation, for simplicity, the operation (processing) of each functional block of the development contact control unit 407 as described above may be described as the operation (processing) of the development contact control unit 407 or the engine control unit 403 that gives instructions to the development contact control unit 407.

[0053] 5. Exposure equipment 6 is a schematic diagram of the exposure device (scanner unit) 11 in this embodiment. The configuration of the exposure device 11 for each color image forming section S is substantially the same. Also, a part of the configuration of the exposure device 11 may be common to multiple image forming sections S.

[0054] The laser driving system circuit 130 operates according to the light emission level set by the engine control unit 403. As a result, a driving current flows through the laser diode 107, which is a light emitting element (light source). The laser diode 107 emits a laser beam at an intensity level according to the driving current. The laser beam emitted by the laser diode 107 is shaped into a parallel beam by a collimator lens 134, and then scanned in the horizontal direction (rotation axis direction, main scanning direction) of the photosensitive drum 1 by a polygon mirror 133. The laser beam scanned by the polygon mirror 133 is imaged by an fθ lens 132 on the surface of the photosensitive drum 1, which rotates in the direction of the arrow R1 in FIG. 6 around the rotation axis. As a result, the surface of the photosensitive drum 1 is exposed in a dot pattern. Meanwhile, a reflecting mirror 131 is provided corresponding to a scanning position on one end side of the photosensitive drum 1 in the rotation axis direction. The reflecting mirror 131 reflects the laser beam projected to the scanning start position toward a BD sensor (beam detect sensor) 121, which is a light receiving element. Then, based on the output of the BD sensor 121, the timing to start scanning with the laser light is determined.

[0055] 6.Optical control unit FIG. 7 is a block diagram showing the functional blocks of the optical control unit 406 in this embodiment and the hardware 600 controlled thereby.

[0056] The optical control unit 406 has the following units, and operates based on instructions from the engine control unit 403. That is, the optical control unit 406 has, as functional blocks, a scanning unit 612, a scanner motor control unit 610, a laser light amount switching unit 611, a BD detection unit 613, and a scanner motor speed detection unit 614. The optical control unit 406 controls the operation (including acquisition of detection signals) of hardware 600 including a scanner motor 630, a laser driving system circuit 130, a laser diode 107, a BD sensor 121, and a polygon mirror 133.

[0057] The scanning unit 612 controls the scanner motor 630 as a drive source of the polygon mirror 133 based on information (signal) from the BD sensor 121. Specifically, the BD detection unit 613 detects a BD signal based on information (signal) acquired from the BD sensor 121, and the scanner motor speed detection unit 614 detects the rotation speed of the scanner motor 630 based on the BD signal detected by the BD detection unit 613. The scanning unit 612 controls the scanner motor 630 by the scanner motor control unit 610 based on the rotation speed of the scanner motor 630 detected by the scanner motor speed detection unit 614 so that the rotation speed of the scanner motor 630 is stabilized at the target speed. In other words, the scanning unit 612 determines the rotation speed of the scanner motor 630, and controls the scanner motor 630 by the scanner motor control unit 610 so that the rotation speed of the scanner motor 630 is stabilized at the determined rotation speed.

[0058] Moreover, the scanning unit 612 calculates the amount of laser light based on the rotation speed of the scanner motor 630 detected by the scanner motor speed detection unit 614. Then, the scanning unit 612 sets the calculated amount of laser light in the laser driving system circuit 130 by the laser light amount switching unit 611, and causes the laser diode 107 to emit light.

[0059] In this embodiment, the scanning unit 612 does not light the laser diode 107 when the scanner motor 630 is started (when the start-up starts). That is, the scanning unit 612 forcibly rotates the scanner motor 630 for a predetermined time without using an input from the BD detection unit 613. After rotating the scanner motor 630 for a predetermined time, the scanning unit 612 continues to forcibly emit light from the laser diode 107 for a predetermined time so that the BD detection unit 613 can stably detect the BD signal. During this forced emission, the laser light is irradiated over the entire area in the main scanning direction including the image forming area. Then, when the scanning unit 612 continues to forcibly emit light from the laser diode 107 for a predetermined time and detects the BD signal, it starts to control the rotation speed of the scanner motor 630 by the BD signal from the BD sensor 121. Furthermore, the scanning unit 612 shifts the emission of the laser diode 107 to emission only in the non-image forming area (hereinafter, also referred to as "unblanking emission") at approximately the same time as starting to control the rotation speed of the scanner motor 630 by the BD signal. Thereafter, the scanning unit 612 maintains the unblanking emission. When image formation starts, in addition to the unblanking emission, the laser diode 107 also emits light in the image formation area in response to an image signal.

[0060] In the following explanation, for simplicity, the operation (processing) of each functional block of the optical control unit 406 as described above may be described as the operation (processing) of the optical control unit 604 or the engine control unit 403 that gives instructions to the optical control unit 604.

[0061] 7. Challenges Next, the problematic phenomenon will be described in more detail. FIG. 8 is a timing chart showing an example of the operation of each part at the start of a print operation in a comparative example in which the start timing of the operation of contacting the developing roller 4 with the photosensitive drum 1 in this embodiment (hereinafter, also simply referred to as the "contact operation") is not controlled. FIG. 8(a) shows a case in which the development motor 101 rises relatively slowly (it takes a relatively long time to reach a predetermined rotation speed). FIG. 8(b) shows a case in which the development motor 101 rises relatively quickly (it takes a relatively short time to reach a predetermined rotation speed). Such a difference may be caused by individual differences in the device or its parts, or fluctuations in the power supplied to the device. T0a to T5a in FIG. 8(a) and T0b to T5b in FIG. 8(b) respectively indicate timings. Also, here, a case in which a print instruction is input to the image forming device 100 in a standby state and a print operation in a full-color mode is started is taken as an example.

[0062] The image forming apparatus 100 of this comparative example has substantially the same configuration as the image forming apparatus 100 of this embodiment, except that the image forming apparatus 100 of this embodiment does not control the start timing of the contact operation of the developing roller 4, which will be described later. Elements of the comparative example that have the same or corresponding functions or configurations as those of this embodiment will be described with the same reference numerals.

[0063] In this embodiment (as well as in the comparative example), with regard to the image forming units S that form toner images in each image formation mode, when the developing motor 101 starts to rotate, the photosensitive drum 1 and the developing roller 4 start to rotate, and at approximately the same time, application of the charging voltage and the developing voltage starts. With regard to the image forming units S for each color of yellow, magenta, and cyan that do not form toner images in the monochrome mode, a clutch or the like may be provided that releases the drive transmission from the developing motor 101 so as to stop the photosensitive drum 1 and the developing roller 4 in the monochrome mode.

[0064] The case of FIG. 8(a) will be described. When the print operation starts, the engine control unit 403 starts the scanner motor 630 and the development motor 101, drives the solenoid 503, and starts the contact operation of the development roller 4 (T0a). After the engine control unit 403 forcibly accelerates the scanner motor 630 for a predetermined time, it starts the forced emission of the laser diode 107 (T1a). The surface of the photosensitive drum 1 is exposed by this forced emission of the laser diode 107. Here, the area on the photosensitive drum 1 exposed by this forced emission (the irradiation position of the laser light by the forced emission) is also called the "forced emission area". After the forced emission for a predetermined time, the engine control unit 403 switches to unblanking emission, which lights up the laser diode 107 in a non-image forming area and controls the rotation speed of the scanner motor 630 based on the output of the BD sensor 121 (T2a). When the rotation speed of the developing motor 101 reaches a predetermined rotation speed (T3a) and the developing motor 101 is driven for a predetermined time, the contact / separation state of the developing roller 4 switches from the fully separated state to the fully contact state (T5a). Meanwhile, the entire surface of the photosensitive drum 1 is exposed from the start of the forced light emission of the laser diode 107 (T1a) until the forced light emission is completed (T2a). In the case of FIG. 8(a), the contact / separation state of the developing roller 4 switches from the fully separated state to the fully contact state (T5a) after the forced light emission area on the photosensitive drum 1 passes the development position (T4a).

[0065] The case of FIG. 8(b) will be described. When the print operation starts, the engine control unit 403 starts the scanner motor 630 and the developing motor 101, drives the solenoid 503, and starts the contact operation of the developing roller 4 (T0b). After the engine control unit 403 forcibly accelerates the scanner motor 630 for a predetermined time, it starts the forced emission of the laser diode 107 (T1b). The surface of the photosensitive drum 1 is exposed by this forced emission of the laser diode 107. After the forced emission for a predetermined time, the engine control unit 403 switches to unblanking emission in which the laser diode 107 is turned on in a non-image forming area and the rotation speed of the scanner motor 630 is controlled based on the output of the BD sensor 121 (T2b). When the rotation speed of the developing motor 101 reaches a predetermined rotation speed (T3b) and the developing motor 101 is driven for a predetermined time, the contact / separation state of the developing roller 4 is switched from the fully separated state to the fully contact state (T4b). On the other hand, the entire surface of the photosensitive drum 1 is exposed from the start of the forced light emission of the laser diode 107 (T1b) until the forced light emission is completed (T2b). In the case of FIG. 8(b), the contact / separation state of the developing roller 4 is switched from the fully separated state to the fully contacted state (T4b) before the forced light emission area on the photosensitive drum 1 passes the development position (T5b). In this case, toner moves from the developing roller 4 to the forced light emission area on the photosensitive drum 1 to form a toner image. Therefore, the toner is wasted. In addition, for example, this toner may move to the intermediate transfer belt 80, which may cause toner stains on the image or recording material P during subsequent image formation.

[0066] In this way, when the start-up of the exposure device 11 and the start-up of the development motor 101 overlap, depending on the time it takes for the development motor 101 to reach a predetermined rotation speed, there is a possibility that toner may move to the area on the photosensitive drum 1 that was exposed when the exposure device 11 was started up. Therefore, it is desirable to start the contact operation of the development roller 4 taking into consideration the time it takes to start up the development motor 101 (the time it takes to reach a predetermined rotation speed). On the other hand, if the contact operation of the development roller 4 is started after waiting for the forced light emission area on the photosensitive drum 1 to pass the development position, the FPOT will be long.

[0067] Here, the following can be done according to the time required for starting up the development motor 101 (the time required for the contact operation of the development roller 4 to be completed). That is, the start timing of the contact operation of the development roller 4 is set according to the time so that the timing when the forced light emission area on the photosensitive drum 1 passes the development position and the timing when the contact operation of the development roller 4 is completed are matched. This makes it possible to suppress the movement of toner to the area on the photosensitive drum 1 exposed when the exposure device 11 is started up while shortening the FPOT as much as possible. However, as described above, the time required for starting up the development motor 101 (the time required for the contact operation of the development roller 4 to be completed) may vary due to individual differences in the device and its parts, or fluctuations in the power supplied to the device. In particular, when a drive source common to other driven parts such as the development roller 4 and the photosensitive drum 1 is used as the drive source of the contact / separation mechanism 500 as in this embodiment, the above-mentioned variation may be easily caused due to individual differences in each part. For this reason, it may be difficult to accurately set the start timing of the contact operation of the development roller 4 in advance.

[0068] 8. Operation during initialization In this embodiment, the engine control unit 403 executes a process (also simply referred to as a "measurement process" here) for estimating (calculating) various times (timings) related to the contact operation of the developing roller 4 according to the time required to start up the developing motor 101 during the initialization operation of the image forming apparatus 100. In this embodiment, the contact / separation mechanism 500, the developing roller 4, and the photosensitive drum 1 are driven by the developing motor 101, which is a common drive source. Therefore, in this embodiment, in the measurement process during the initialization operation, the time until the contact operation of the developing roller 4 is completed and the time until the forced light emission area on the photosensitive drum 1 passes the development position are estimated (calculated). Then, based on these times, the start timing of the contact operation of the developing roller 4 during the next print is determined.

[0069] The initialization operation (initialization process) is a preparatory operation for putting the image forming apparatus 100 into a state in which it is possible to form an image, and is executed when the image forming apparatus 100 is powered on or when the process cartridge 9 is replaced. In the initialization operation, in addition to the above-mentioned measurement process, self-diagnosis processes of the apparatus, such as checking whether or not the recording material P remains in the conveying path of the recording material P and checking whether or not each actuator is operating normally, are performed.

[0070] 9 is a timing chart showing an example of the operation of the measurement process during the initialization operation in this embodiment, in which T0 to T4 indicate respective timings.

[0071] In this embodiment, the scanner motor 630 is not started in the measurement process during the initialization operation. It is assumed that the scanner motor 630 starts up with a predetermined rotation speed transition, assuming that the scanner motor 630 starts up (starts start-up, starts power supply) at approximately the same time as the development motor 101 starts up (starts start-up, starts power supply). This suppresses the movement of toner from the development roller 4 to the photosensitive drum 1 in the measurement process. Then, based on the rotation speed of the development motor 101, the time Tattach until the contact operation of the development roller 4 is completed (also simply referred to as the "contact completion time" here) and the time Tf until the forced light emission area on the photosensitive drum 1 passes the development position (also simply referred to as the "light emission area passing time" here) are estimated (calculated). In addition, the start timing Tsol of the contact operation of the development roller 4 during printing (also simply referred to as the "contact operation start timing" here) is determined based on the estimated contact completion time Tattach and light emission area passing time Tf. This contact operation start timing is used when starting the contact operation of the developing roller 4 during subsequent (next and subsequent) printing operations until it is determined (updated) again. Note that in this embodiment, the contact operation start timing Tsol is determined in the measurement process during the initialization operation, but it is also possible to determine Tattach and Tf in the measurement process and then determine Tsol when the print operation is performed.

[0072] First, a method will be described for determining the contact completion time Tattach according to the time required to start up the developing motor 101. The contact completion time Tattach is determined by the time required from the start of the developing motor 101 (start of start-up) until the contact operation of the developing roller 4 is completed.

[0073] When the image forming apparatus 100 is powered on, the engine control unit 403 executes an initialization operation. At the start of the initialization operation, the contact / separation state of the developing roller 4 is in a fully separated state. Then, when the engine control unit 403 starts the initialization operation, it starts to ramp up the developing motor 101 toward the target rotation speed (target number of rotations) Vtarget (T0). Almost simultaneously with starting the ramp up of the developing motor 101, the engine control unit 403 drives the solenoid 503 (starts supplying power for a predetermined time) in order to change the contact / separation state of the developing roller 4 from the fully separated state to the fully contact state (T0). Also, almost simultaneously with starting the ramp up of the developing motor 101, the engine control unit 403 starts measuring the time until the contact / separation state of the developing roller 4 switches from the fully separated state to the fully contact state (T0).

[0074] Next, the engine control unit 403 waits until the forced light emission is completed. Here, the time Te from when the developing motor 101 (scanner motor 630) is started to when the forced light emission is completed when the developing motor 101 and the scanner motor 630 are started substantially simultaneously is also referred to simply as the "forced light emission completion time". When the forced light emission completion time Te has elapsed, the engine control unit 403 stores the rotation speed of the developing motor 101 at that time (T1). In addition, the engine control unit 403 stores the time Tr required for the developing motor 101 to reach the target rotation speed Vtarget after the developing motor 101 is started (T2).

[0075] The contact / separation state of the developing roller 4 transitions from the fully separated state to the fully contact state via an intermediate state between the fully separated state and the fully contact state. Under the control of the engine control unit 403, the developing contact control unit 407 acquires the rotation speed V1a of the developing motor 101 when a predetermined time has elapsed from the start timing t0 (corresponding to the above T0) of the initialization operation to timing t1. Here, this predetermined time (speed acquisition interval) is t1. The time from timing t0 to timing t1 can also be said to be the driving time of the developing motor 101 from the start of the initialization operation (the start of the developing motor 101). The developing contact control unit 407 calculates the amount of rotation L1a of the developing motor 101 from timing t0 to timing t1 using the following formula (1).

[0076]

number

[0077] Further, the development contact control unit 407 calculates and stores an accumulated value D1a=L1a, which is an integrated value of the amount of rotation of the development motor 101 from the start of the initialization operation (startup of the development motor 101).

[0078] Similarly, when a predetermined time has elapsed from timing t1 to timing t2, the rotation speed V2a of the developing motor 101 is acquired. The time from timing t1 to timing t2 can also be said to be the driving time of the developing motor 101. The developing contact control unit 407 calculates the amount of rotation L2 of the developing motor 101 from timing t1 to timing t2 using the following formula (2).

[0079]

number

[0080] Further, the development contact control unit 407 calculates and stores an accumulated value D2a=D1a+L2a, which is an integrated value of the amount of rotation of the development motor 101 from the start of the initialization operation (startup of the development motor 101).

[0081] Thereafter, the development contact control unit 407 acquires the rotation speed Vna (n=1, 2, ... x) of the development motor 101 every time a predetermined time elapses until the contact / separation state of the development roller 4 switches from the fully separated state to the fully contact state, and repeats calculation of the integrated value of the rotation amount of the development motor 101. The development contact control unit 407 calculates the rotation amount Lna of the development motor 101 by the following formula (3) every time time tna elapses until the cumulative added value Dna of the rotation amount of the development motor 101 and the previously obtained rotation amount DFull of the development motor 101 from the start of the contact operation of the development roller 4 to the completion of the contact operation become Dna ≧ Dfull (n=1, 2, ... x).

[0082]

number

[0083] Further, the development contact control unit 407 calculates a cumulative sum Dna of the amount of rotation of the development motor 101 from the start of the initialization operation (startup of the development motor 101) by the following formula (4).

[0084]

number

[0085] When the time txa has elapsed from the start of the initialization operation (T0), if Dna≧Dfull, the development contact control unit 407 determines that the transition of the contact / separation state of the development roller 4 from the fully separated state to the fully contact state has been completed. In other words, when the cumulative added value Dna is equal to or greater than a predetermined value (equal to or greater than Dfull), the development contact control unit 407 determines that the transition of the contact / separation state of the development roller 4 from the fully separated state to the fully contact state has been completed. Then, at the timing when it is determined that the transition has been made to the full contact state, the development contact control unit 407 stores the time required from the start of the initialization operation (starting the development motor 101) to the determination that the transition has been made to the full contact state, that is, the contact completion time Tattach (T3).

[0086] Next, we will explain a method for determining the light emitting area passing time Tf depending on the time required to start up the development motor 101. The light emitting area passing time Tf is determined by the time required for the development motor 101 to rotate by an amount of rotation Ddev equivalent to the distance from the exposure position to the development position in the rotation direction of the photosensitive drum 1 after the forced emission is completed.

[0087] Under the control of the engine control unit 403, the development contact control unit 407 acquires the rotation speed V1b of the development motor 101 when a predetermined time has elapsed from the timing (T1) at which the forced emission is completed. Here, this predetermined time (speed acquisition interval) is t1. In this embodiment, the photosensitive drum 1 is driven by the development motor 101, which is a drive source common to the development roller 4 and the contact / separation mechanism 500. Therefore, this time can be said to be the drive time of the development motor 101 after the forced emission is completed, and is correlated with the rotation amount of the photosensitive drum 1 (movement distance of the position on the photosensitive drum 1). The development contact control unit 407 calculates the rotation amount L1b of the development motor 101 after the forced emission is completed (correlated with the movement distance of the forced emission area (forced emission completion position) on the photosensitive drum 1) by the following formula (5).

[0088]

number

[0089] Further, the development contact control unit 407 calculates and stores an accumulated value D1b=L1b, which is an accumulated value of the amount of rotation of the development motor 101 after the forced light emission is completed.

[0090] Similarly, when the next predetermined time t1 has elapsed, the rotation speed V2b of the developing motor 101 is acquired. This time can be said to be the driving time of the developing motor 101, and is correlated with the rotation amount of the photosensitive drum 1 (the moving distance of the position on the photosensitive drum 1). The developing contact control unit 407 calculates the rotation amount L2b of the developing motor 101 during this time by the following formula (6).

[0091]

number

[0092] Further, the development contact control unit 407 calculates and stores an accumulated value D2b=D1b+L2b, which is an accumulated value of the amount of rotation of the development motor 101 after the forced light emission is completed.

[0093] Thereafter, the development contact control unit 407 acquires the rotation speed Vmb (m=1, 2, ..., x) of the development motor 101 every time a predetermined time elapses until the forced light emission area (forced light emission completion position) on the photosensitive drum 1 passes the development position, and repeats calculation of the integrated value of the rotation amount of the development motor 101. The development contact control unit 407 calculates the rotation amount Lmb of the development motor 101 by the following formula (7) every time time tmb elapses until the cumulative added value Dmb of the rotation amount of the development motor 101 and the rotation amount Ddev of the development motor 101 corresponding to the distance from the exposure position to the development position in the rotation direction of the photosensitive drum 1 obtained in advance become Dmb ≧ Ddev (m=1, 2, ..., x).

[0094]

number

[0095] Further, the development contact control unit 407 calculates the cumulative sum Dmb of the rotation amount of the development motor 101 after the forced light emission is completed, using the following formula (8).

[0096]

number

[0097] When the time txb has elapsed since the forced light emission was completed and Dmb≧Ddev holds, the development contact control unit 407 determines that the forced light emission area (forced light emission completion position) on the photosensitive drum 1 has passed the development position. In other words, when the cumulative added value Dmb becomes equal to or greater than a predetermined value (equal to or greater than Ddev), the development contact control unit 407 determines that the forced light emission area (forced light emission completion position) on the photosensitive drum 1 has passed the development position. Then, the development contact control unit 407 stores the time required from the completion of the forced light emission until it is determined that the forced light emission area (forced light emission completion position) on the photosensitive drum 1 has passed the development position, that is, the light emission area passing time Tf (T4).

[0098] Then, the development contact control unit 407 determines and stores the contact operation start timing Tsol based on the contact completion time Tattach and the light emitting area passing time Tf determined as described above. For convenience, the details of the method for determining the contact operation start timing Tsol will be described later in the description of the operation during printing.

[0099] In this embodiment, in the measurement process, various times such as Tattach and Tf were measured on the assumption that the start of the developing motor 101 begins approximately simultaneously with the start of the scanner motor 630, but this is not limited to this. Various times such as Tattach and Tf can also be measured on the assumption that the developing motor 101 is started after a given predetermined time has elapsed since the start of the scanner motor 630.

[0100] 9. Printing behavior 10 and 11 are timing charts showing an example of the operation of each part at the start of the printing operation when the start timing of the contact operation of the developing roller 4 in this embodiment is controlled. FIG. 10 shows a case where the developing motor 101 is started and the solenoid 503 is driven substantially simultaneously after the scanner motor 630 is started at the start of the printing operation. FIG. 11 shows a case where the developing motor 101 and the scanner motor 630 are started substantially simultaneously at the start of the printing operation, and the solenoid 503 is driven. T0a to T2a in FIG. 10 and T0b to T3b in FIG. 11 respectively indicate timings. Here, a case where a print instruction is input to the image forming apparatus 100 in a standby state and a print operation in a full-color mode is started is taken as an example.

[0101] 10 will be described. When the engine control unit 403 receives a print instruction from the printer controller 401, it starts a print operation and starts (starts to start) the scanner motor 630 (T0a). In this case, under the control of the engine control unit 403, the development contact control unit 407 (more specifically, the contact operation start determination unit 918) calculates and stores the contact operation start timing Tsola, which is the timing at which the development motor 101 is started and the solenoid 503 is driven substantially simultaneously, using the following formula (9).

[0102]

number

[0103] In formula (9), Te is the time from when the scanner motor 630 is started to when the forced light emission is completed. Also, Tf is the time from when the forced light emission is completed to when the forced light emission area (forced light emission completion position) on the photosensitive drum 1 passes the development position. Also, Tattach (TattachA in the figure) is the time until the transition of the contact / separation state of the developing roller 4 from the full separation state to the full contact state is completed when the development motor 101 is started and the solenoid 503 is driven substantially simultaneously. This contact operation start timing Tsola can also be said to be the time from the start of the print operation to when the contact operation of the developing roller 4 is started (the development motor 101 is started and the solenoid 503 is driven substantially simultaneously). As described above, in this embodiment, this contact operation start timing Tsola is calculated in the measurement process during the initialization operation, but it may be calculated when the print operation is executed.

[0104] Then, when (substantially simultaneously with) the time Tsola has elapsed since the start of the print operation (T0a), the development contact control unit 407 starts the development motor 101 and drives the solenoid 503 substantially simultaneously (T1a).

[0105] Thereby, thereafter, the contact operation of the developing roller 4 is completed at the timing when the forced light emission area on the photosensitive drum 1 passes through the developing position (almost simultaneously with the passing timing) (T2a).

[0106] 11 will be described. When the engine control unit 403 receives a print instruction from the printer controller 401, it starts the print operation and starts (starts to start up) the development motor 101 and the scanner motor 630 substantially simultaneously (T0b). In this case, under the control of the engine control unit 403, the development contact control unit 407 (more specifically, the contact operation start determination unit 918) calculates and stores the contact operation start timing Tsolb as the timing for driving the solenoid 503, using the following formula (10).

[0107]

number

[0108] In formula (10), Dxa is the cumulative sum of the rotation amount of the developing motor 101 from when the developing motor 101 and the scanner motor 630 are started substantially simultaneously until the forced light emission area (forced light emission completion position) on the photosensitive drum 1 passes the development position. Also, Dxb is the cumulative sum of the rotation amount (correlated with the moving distance of the position on the photosensitive drum 1) of the developing motor 101 from when the forced light emission is completed until the forced light emission area (forced light emission completion position) on the photosensitive drum 1 passes the development position. Note that Dxa and Dxb can be calculated and stored in the same manner as the above-mentioned Dmb. Also, Ve is the rotation speed of the developing motor 101 at the time when the forced light emission is completed. This abutment operation start timing Tsolb can be said to be the time from the start of the print operation to when the abutment operation of the developing roller 4 starts (the solenoid 503 is driven). In this case, the abutment completion time Tattach (TattachB in the figure) is also obtained based on the relationship expressed by formula (9). As described above, in this embodiment, the contact operation start timing Tsolb is calculated in the measurement process during the initialization operation, but it may be calculated when the print operation is performed.

[0109] Then, the development contact control unit 407 drives the solenoid 503 (T1b) when (almost simultaneously with) the time Tsolb has elapsed since the start of the print operation (T0b). Note that T2b in the figure is the timing at which the forced emission is completed.

[0110] Thereby, thereafter, the contact operation of the developing roller 4 is completed at the timing when the forced light emission area on the photosensitive drum 1 passes the developing position (almost at the same time as the passing) (T3b).

[0111] By such control, when the time until the contact operation is completed in the measurement process (test operation) is relatively long, the time until the timing to start the contact operation in the preparatory operation for printing can be relatively short. Also, when the time until the contact operation is completed in the measurement process (test operation) is relatively short, the time until the timing to start the contact operation in the preparatory operation for printing can be relatively long.

[0112] 10. Measurement process procedure during initialization Fig. 12 is a flow chart showing an example of the procedure of the measurement process during the initialization operation of the image forming apparatus 100 in this embodiment. Also, Fig. 13 is a flow chart showing an example of the procedure of part of the process in Fig. 12.

[0113] The engine control unit 403 executes an initialization operation when the power supply of the image forming apparatus 100 is turned on or when the process cartridge 9 is replaced. Then, under the control of the engine control unit 403, the development contact control unit 407 clears (resets to an initial value (0 in this embodiment)) the accumulated added value Dna of the rotation amount of the development motor 101 since the start of the development motor 101 that has already been stored. Then, measurement of the rotation amount of the development motor 101 is started (S101). Also, the development contact control unit 407 turns on the development motor 101 and the solenoid 503 in order to transition the contact / separation state of the development roller 4 from the full separation state to the full contact state (S102). Also, under the control of the engine control unit 403, the optical control unit 406 starts measuring the time until the forced emission is completed without starting the scanner motor 630 in order to notify the engine control unit 403 of the timing when the forced emission is completed (S103). Note that the method of updating the rotation amount of the development motor 101 in the next S104 will be described with reference to FIG. 13.

[0114] 13, the development contact control unit 407 judges whether a predetermined sampling time (speed acquisition interval) T has elapsed since the previous acquisition of the rotation speed of the development motor 101 (S201). If the sampling time T has elapsed, the development contact control unit 407 acquires the rotation speed Vmotor of the development motor 101 (S202). Then, the development contact control unit 407 calculates the rotation amount Lna of the development motor 101 from the start of the development motor 101 based on the sampling time T and the rotation speed Vmotor using the following formula (11) (S203). Also, the development contact control unit 407 calculates the rotation amount Lmb of the development motor 101 after the forced emission is completed based on the sampling time T and the rotation speed Vmotor using the following formula (12) (S203).

[0115]

number

[0116] After calculating the amount of rotation Lna, the development contact control unit 407 calculates a cumulative sum Dna of the amount of rotation of the development motor 101 from the start of the development motor 101 using the following formula (13) (S204). In addition, after calculating the amount of rotation Lmb, the development contact control unit 407 calculates a cumulative sum Dmb of the amount of rotation of the development motor 101 from the completion of the forced emission using the following formula (14) (S204).

[0117]

number

[0118] In this manner, the development contact control unit 407 updates the amount of rotation of the development motor 101 in S104 of FIG.

[0119] The engine control unit 403 judges whether or not measurement of the amount of rotation of the developing motor 101 after the forced emission is completed (correlated with the amount of movement of the forced emission area (forced emission completion position) on the photosensitive drum 1) has started (S105). If it has not started (No in S105), the engine control unit 403 judges whether or not the forced emission is completed (whether or not information has been acquired from the optical control unit 406 that the time has elapsed from the start of the initialization operation until the forced emission is completed) (S106). If it has been completed (Yes in S106), the engine control unit 403 stores that the forced emission is completed, and clears (resets to an initial value (0 in this embodiment)) the accumulated added value Dmb of the amount of rotation of the developing motor 101 after the forced emission is completed that has already been stored. Then, measurement of the amount of rotation of the developing motor 101 starts (S107).

[0120] When S105 is Yes, S106 is No, or S107 is executed, the engine control unit 403 judges whether or not the time required for the forced light emission area to reach the development position is stored (S108). When it is not stored (S108 is No), the development contact control unit 407 judges whether or not the cumulative added value Dmb of the rotation amount of the development motor 101 after the forced light emission is completed reaches the rotation amount Ddev of the development motor 101 corresponding to the distance from the exposure position to the development position in the rotation direction of the photosensitive drum 1 (S109). That is, it is judged whether or not Dmb≧Ddev is satisfied, and if it is satisfied, it is judged that the forced light emission area (forced light emission completion position) has passed the development position. When it is judged that the forced light emission area (forced light emission completion position) has passed the development position (S109 is Yes), the development contact control unit 407 stores the time Tf required for the forced light emission area (forced light emission completion position) to pass the development position after the forced light emission is completed (S110).

[0121] After Yes in S108, No in S109, or S110, the engine control unit 403 determines whether or not it stores the time Tr required for the development motor 101 to reach the target rotation speed Vtarget after it is started (S111). If it is not stored (No in S111), the development contact control unit 407 determines whether or not the rotation speed of the development motor 101 acquired by the drive speed detection unit 912 has reached the target rotation speed Vtarget (S112). If it has reached the target rotation speed (Yes in S112), the development contact control unit 407 stores the time Tr required for the development motor 101 to reach the target rotation speed Vtarget after it is started (S113).

[0122] If S111 is Yes, S112 is No, or S113 is executed, the engine control unit 403 judges whether or not it stores the time Tattach required from the start of the contact operation of the developing roller 4 to the completion of the transition from the full separation state of the contact / separation state to the contact state (S114). If it is not stored (No in S114), the development contact control unit 407 judges whether or not the cumulative added value Dna of the rotation amount of the developing motor 101 from the start of the developing motor 101 reaches the rotation amount Dfull of the developing motor 101 required for the contact / separation state of the developing roller 4 to transition from the full separation state to the full contact state (S115). In other words, it is judged whether or not Dna≧Dfull is satisfied, and if it is satisfied, it is judged that the transition of the contact / separation state of the developing roller 4 from the full separation state to the full contact state is completed. When it is determined that the transition of the developing roller 4 from the fully separated state to the fully contact state is completed (Yes in S115), the developing contact control unit 407 stores the time Tattach required from the start of the contact operation of the developing roller 4 to the completion of the transition of the developing roller 4 from the fully separated state to the contact state (S116).

[0123] The engine control unit 403 determines whether measurements of the time Tf, the time Tr, and the time Tattach are all complete (S117). If all measurements are not complete (No in S117), the engine control unit 403 repeats the processes of S104 to S116. If all measurements are complete (Yes in S117), the engine control unit 403 determines the timing Tsol of the start of the contact operation during printing (S118). The method of determining the timing Tsol of the start of the contact operation during printing is as described with reference to FIGS. 10 and 11.

[0124] 11. Control procedure for the start timing of contact operation during printing Fig. 14 is a flowchart showing an example of a control procedure for the start timing of the contact operation of the developing roller 4 at the start of the print operation in the case described using Fig. 10. Also, Fig. 15 is a flowchart showing an example of a control procedure for the start timing of the contact operation of the developing roller 4 at the start of the print operation in the case described using Fig. 11. Here, a case is taken as an example where a print instruction is input to the image forming apparatus 100 in a standby state and a print operation in full color mode is started.

[0125] The case of FIG. 14 will be described. When the engine control unit 403 receives a print instruction from the printer controller 401, it starts the print operation. The engine control unit 403 starts the scanner motor 630 by the optical control unit 406 (S301). The engine control unit 403 waits until the time Tsola has elapsed since starting the scanner motor 630 (S302). When the time Tsola has elapsed, the engine control unit 403 starts the development motor 101 by the development contact control unit 407 in order to transition the contact / separation state of the development roller 4 from the full separation state to the full contact state, and at the same time, turns on the solenoid 503 (S303). The engine control unit 403 waits until the time Tattach has elapsed since starting the contact operation of the development roller 4 (S304). When the time Tattach has elapsed, the engine control unit 403 starts image formation (S305).

[0126] The case of FIG. 15 will be described. When the engine control unit 403 receives a print instruction from the printer controller 401, it starts a print operation. The engine control unit 403 starts the scanner motor 630 by the optical control unit 406, and at substantially the same time starts the development motor 101 by the development contact control unit 407 (S401). The engine control unit 403 waits until the time Tsolb has elapsed since starting the scanner motor 630 and the development motor 101 (S402). When the time Tsolb has elapsed, the engine control unit 403 turns on the solenoid 503 by the development contact control unit 407 in order to transition the contact / separation state of the development roller 4 from the full separation state to the full contact state (S403). The engine control unit 403 waits until the time Tattach has elapsed since starting the contact operation of the development roller 4 (S404). When the time Tattach has elapsed, the engine control unit 403 starts image formation (S405).

[0127] In this embodiment, the photosensitive drum 1 is driven by the developing motor 101, which is a common driving source for the contact / separation mechanism 500 and the developing roller 4, but the photosensitive drum 1 may be driven by a motor separate from the contact / separation mechanism 500 and the developing roller 4. In that case, for example, the light emitting region passing time Tf can be obtained by detecting (estimating) the rotation speed and detecting (estimating) the amount of rotation for the motor driving the photosensitive drum 1 in the same manner as in the case of the developing motor 101 described above, or a predetermined value obtained in advance can be used.

[0128] In this embodiment, the measurement process is described as measuring the time Tr required from starting the developing motor 101 to reaching the target rotation speed Vtarget (time required to start up the developing motor 101: start-up completion time). If the start-up completion time Tr is not used to set the contact operation start timing, the process of measuring the start-up completion time Tr may be omitted. However, if the start-up completion time Tr is measured and stored, it is possible to grasp the current load. This start-up completion time Tr can also be said to be information on the switching time, which is the time required to switch the developing member from the separated state to the contact state. Then, the contact operation start timing can be set (predicted) based on this start-up completion time Tr. For example, the relationship between the start-up completion time Tr and the contact completion time Tattach (and further the light emitting area passing time Tf) is obtained in advance. Then, based on the start-up completion time Tr measured and stored in the measurement process, the contact operation start timing Tsol can be determined from the relationship. Also, for example, the relationship between the start-up completion time Tr and the contact operation start timing Tsol based on the contact completion time Tattach (and further the light-emitting area passing time Tf) corresponding to the time Tr is obtained in advance. Then, the contact operation start timing Tsol can be determined from the relationship based on the start-up completion time Tr measured and stored in the measurement process. Typically, when the start-up completion time Tr is relatively long, the time until the start of the contact operation in the preparatory operation for printing can be relatively short. Also, when the start-up completion time Tr is relatively short, the time until the start of the contact operation in the preparatory operation for printing can be relatively long.

[0129] Thus, the image forming apparatus 100 of this embodiment includes the photoconductor 1 that can rotate in a predetermined rotation direction, the charging device 2 that charges the surface of the photoconductor 1 at a charging position in the rotation direction, the exposure device 11 that exposes the surface of the photoconductor 1 at an exposure position downstream of the charging position in the rotation direction, the developing device 8 that can come into contact with the surface of the photoconductor 1 at a development position downstream of the exposure position and upstream of the charging position in the rotation direction, and supplies developer to the photoconductor 1 by the developing device 4, and the motor 10 that drives the developing device 4. The developing device has a motor 101 and a contact / separation mechanism 500 for transmitting a driving force from a motor 101 to switch the developing member 4 between a contact state in which the developing member 4 is in contact with the photosensitive member 1 and a separated state in which the developing member 4 is separated from the photosensitive member 1, and performs preparatory operations before image formation, including a light emitting operation in which an area including an image forming area in the direction of the rotation axis of the photosensitive member 1 is exposed by an exposure device 11 during a light emitting period to form a potential at which a developer can adhere to the photosensitive member 1, start-up of the motor 101, and a contact operation in which the developing member 4 is switched from the separated state to the contact state by the contact / separation mechanism 500 during a switching period. The image forming apparatus 100 of this embodiment has an acquisition unit (development abutment control unit) 407 that acquires information on a switching time, which is a time required for the contact operation by the contact / separation mechanism 500 to switch the developing member 4 from a separated state to a contact state, and a setting unit (engine control unit) 403 that sets a start timing, which is a timing to start the contact operation by the contact / separation mechanism 500 in the preparatory operation, based on the information on the switching time acquired by the acquisition unit 407, and is a timing before the area on the photoconductor exposed during the light emission period reaches the development position. In this embodiment, the setting unit 403 sets the start timing so that, when the time indicated by the information on the switching time is a first time, the time from the start of the preparatory operation to the start timing is a second time, and, when the time indicated by the information on the switching time is a third time shorter than the first time, the time from the start of the preparatory operation to the start timing is a fourth time longer than the second time. More specifically, the start time of the preparatory operation can be the time when a print instruction is input to the engine control unit 403.In this embodiment, the exposure device 11 has a light-emitting unit (laser diode) 107 that emits light, and a polygon mirror 133, and the light emitted by the light-emitting unit 107 is reflected by the rotating polygon mirror 133 and irradiated onto the photosensitive member 1, and the above-mentioned light emission period is included in the period during which the rotation of the polygon mirror 133 is not in a steady state.

[0130] In this embodiment, the acquisition unit 407 includes a speed acquisition unit (driving speed detection unit) 912 that acquires information about the rotation speed of the motor 101, and a rotation amount acquisition unit (rotation amount estimation unit) 913 that acquires information about the rotation amount of the motor 101 based on information about a plurality of rotation speeds acquired by the speed acquisition unit 912 over time, and acquires information about the switching time based on the time required to rotate the motor 101 by a predetermined rotation amount. In this embodiment, the predetermined rotation amount is the rotation amount of the motor 101 required for the contact mechanism 500 to switch the developing member 4 from the separated state to the contact state. In this embodiment, the setting unit 403 sets the start timing so that the developing member 4 is in the contact state after the area on the photoconductor exposed during the light emission period has passed the development position. Typically, the setting unit 403 sets the start timing so that the developing member 4 is in the contact state substantially simultaneously with the area on the photoconductor exposed during the light emission period having passed the development position. However, the timing at which the developing member 4 comes into contact may be shifted from the time when the area on the photoconductor exposed during the light emission period finishes passing the developing position within an allowable range from the viewpoint of, for example, shortening the FPOT. In this embodiment, the acquisition unit 407 executes a test operation (measurement process) for acquiring information regarding the switching time by performing a contact operation by the contact / separation mechanism 500 before executing the preparatory operation, and the setting unit 403 sets the start timing of the preparatory operation to be executed after executing the test operation based on the information regarding the switching time acquired in the test operation. In this embodiment, the test operation is executed when the image forming apparatus 100 is powered on or when a replacement unit (such as the process cartridge 9) of the image forming apparatus 100 is replaced.

[0131] Particularly, in this embodiment, the photoconductor 1 is driven by the motor 101, which is a driving source common to the developing member 4 and the contact / separation mechanism 500. In this embodiment, the acquisition unit 407 acquires information about the switching time based on the time required to rotate the motor 101 by a predetermined first rotation amount, and acquires information about the passing time, which is the time required for the area on the photoconductor exposed during the light emission period to finish passing the development position, based on the time required to rotate the motor 101 by a predetermined second rotation amount, and the setting unit 403 sets the start timing so that the developing member 4 is in the contact state after the area on the photoconductor exposed during the light emission period finishes passing the development position. The first rotation amount is the rotation amount of the motor 101 required for the contact / separation mechanism 500 to switch the developing member 4 from the separated state to the contact state, and the second rotation amount is the rotation amount of the motor 101 required for the area on the photoconductor exposed during the light emission period to move from the exposure position to the development position. In this case, before executing the preparatory operation, the acquisition unit 407 executes a test operation in which the contact mechanism 500 performs a contact operation to acquire information related to the switching time and information related to the passing time.

[0132] As described above, in this embodiment, the start timing of the contact operation of the developing roller 4 is controlled (adjusted) according to the time required to start up the developing motor 101. This allows the developing roller 4 to be brought into contact with the photosensitive drum 1 after the area on the photosensitive drum 1 exposed when the exposure device 11 is started up passes the development position, according to the time required to start up the developing motor 101. Therefore, it is possible to reduce the FPOT by starting the developing motor 101 as early as possible while suppressing the movement of toner to the area on the photosensitive drum 1 exposed when the exposure device 11 is started up.

[0133] [Example 2] Next, another embodiment of the present invention will be described. The basic configuration and operation of the image forming apparatus of this embodiment are the same as those of the image forming apparatus of embodiment 1. Therefore, in the image forming apparatus of this embodiment, elements having the same or corresponding functions or configurations as those of the image forming apparatus of embodiment 1 are given the same reference numerals as those of embodiment 1, and detailed explanations are omitted.

[0134] In this embodiment, the start timing of the contact operation of the developing roller 4 is changed by predicting that the time required to start up the developing motor 101 varies depending on the input of the commercial power source used by the image forming apparatus 100.

[0135] Fig. 16 is a functional block diagram for explaining the system configuration of the image forming apparatus 100 in this embodiment. The system configuration of the image forming apparatus 100 in this embodiment is roughly similar to the system configuration of the image forming apparatus 100 in the first embodiment described with reference to Fig. 2. However, in this embodiment, the printer engine 402 is provided with a power supply control unit 409. The power supply control unit 409 controls the supply of power required for output by each control unit (recording material conveying unit 404, fixing control unit 405, optical conveying unit 406, development contact control unit 407, image control unit 408) based on an instruction from the engine control unit 403.

[0136] The power control unit 409 has, as its functional blocks, an input voltage detection unit 950, a detected power storage unit 951, and an operating power fluctuation determination unit 952. The input voltage detection unit 950 detects the input voltage input from a commercial power source. The detected power storage unit 951 stores the voltage of the power source input from the outside every time the image forming apparatus 100 starts a print operation based on the input of the input voltage detection unit 950. The operating power fluctuation determination unit 952 determines whether the input voltage of the image forming apparatus 100 is fluctuating based on the difference between the input voltage detected by the input voltage detection unit 950 at the start of the print operation and the input voltage at the previous print stored in the detected power storage unit 951. Note that the input voltage to be compared with the input voltage at the current print is not limited to the input voltage at the previous print, and an input voltage at any print before this can be used as long as the input voltage fluctuation can be detected with sufficient accuracy. For example, the input voltage at any print up to a predetermined time ago can be compared with the input voltage at the current print.

[0137] Fig. 17 is a timing chart showing an example of the operation of each part when it is determined that the input voltage has changed at the start of a print operation in controlling the start timing of the contact operation of the developing roller 4 in this embodiment. T0 to T3 in Fig. 17 each indicate timing. Also, here, an example is taken of a case where a print instruction is input to the image forming apparatus 100 in a standby state and a print operation in a full-color mode is started.

[0138] In this embodiment, the engine control unit 403 acquires the input voltage of the power source inputted from the outside to the image forming apparatus 100 based on the input of the input voltage detection unit 950 of the power control unit 409 at the start of the print operation. Then, the engine control unit 403 compares the input voltage at the start of the previous print operation stored in the detected power storage unit 951 of the power control unit 409 with the input voltage acquired this time by the operating current fluctuation determination unit 952 of the power control unit 409. When the difference (absolute value) between the previous and current input voltages is less than a predetermined fluctuation amount determined in advance, the engine control unit 403 starts the contact operation of the developing roller 4 using the contact operation start timing Tsol determined as described in the first embodiment (FIGS. 10 and 11). On the other hand, when the difference between the previous and current input voltages is equal to or greater than the predetermined fluctuation amount, the engine control unit 403 performs the operation shown in FIG. 17 without using the contact operation start timing Tsol determined as described in the first embodiment.

[0139] That is, when the engine control unit 403 receives a print instruction from the printer controller 401, it starts a print operation (more specifically, a preparation operation before image formation), starts the scanner motor 630 by the optical control unit 406, and at approximately the same time starts the development motor 101 by the development contact control unit 407 (T0). After that, when the rotation speed of the development motor 101 reaches the target rotation speed Vtarget, the engine control unit 403 judges whether the forced emission of the exposure device 11 is completed or not. If the forced emission is completed, the engine control unit 403 drives the development motor 101 by an amount of rotation corresponding to the distance from the exposure position to the development position in the rotation direction of the photosensitive drum 1 from the completion of the forced emission. Then, after driving the development roller 101 by that amount of rotation, the engine control unit 403 drives the solenoid 503 to start the contact operation of the development roller 4 at approximately the same time (T2). Thereafter, the engine control unit 403 drives the developing motor 101 by an amount of rotation that switches the contact / separation state of the developing roller 4 from the fully separated state to the fully contacted state, and then starts image formation (T3).

[0140] 18 is a flow chart showing an example of a control procedure for the start timing of the contact operation of the developing roller 4 at the start of a print operation in this embodiment. Here, a case is taken as an example where a print instruction is input to the image forming apparatus 100 in a standby state to start a print operation in full color mode.

[0141] When the engine control unit 403 receives a print command from the printer controller 401, it starts the print operation. The engine control unit 403 acquires an input voltage from an external power source by the power supply control unit 409 (S501). The engine control unit 403 compares the input voltage at the start of the current print operation acquired in S501 with the stored input voltage at the start of the previous print operation by the power supply control unit 409. Then, it is determined whether the difference between the previous and current input voltages fluctuates by a predetermined amount or more (S502). Here, the input voltage fluctuates when it fluctuates by a predetermined amount or more determined in advance based on an experiment or the like. In this embodiment, for example, when the difference between the previous and current input voltages is 10 [v] or more, it is determined that the input voltage has fluctuated.

[0142] When it is determined that the input voltage has fluctuated (Yes in S502), the engine control unit 403 starts the scanner motor 630 and the developing motor 101 substantially simultaneously (S503), and waits until the rotation speed of the developing motor 101 reaches the target rotation speed Vtarget (S504). When the rotation speed of the developing motor 101 reaches the target rotation speed Vtarget, the engine control unit 403 waits until the forced emission of light by the exposure device 11 is completed (S505). When the forced emission is completed, the engine control unit 403 executes updating of the rotation amount of the developing motor 101 (S506). The method of updating the rotation amount of the developing motor 101 is the same as that in the first embodiment described with reference to FIG. 13.

[0143] The engine control unit 403 waits until the development motor 101 is driven by an amount of rotation equivalent to the distance from the exposure position to the development position in the rotation direction of the photosensitive drum 1 after the forced emission is completed (S507). Here, in this embodiment, the time required for the development motor 101 to start up is measured even at the start of the print operation, and the time required for the development motor 101 to start up, which may vary due to fluctuations in the input voltage, is stored. Then, the contact operation start timing Tsol is updated for the next print operation.

[0144] After driving the developing motor 101 by an amount of rotation equivalent to the distance from the exposure position to the developing position, the engine control unit 403 drives the solenoid 503 to start the contact operation of the developing roller 4 (S508). The engine control unit 403 waits for the time Tattach required to complete the contact operation of the developing roller 4 to elapse (S509). Then, when the time Tattach has elapsed, the engine control unit 403 starts image formation (S510).

[0145] On the other hand, when it is determined that the input voltage is not fluctuating (No in S502), the engine control unit 403 starts the scanner motor 630 and the developing motor 101 substantially simultaneously (S511), and waits until the time Tsol determined in the same manner as in the first embodiment has elapsed (S512). When the time Tsol has elapsed, the engine control unit 403 drives the solenoid 503 to start the contact operation of the developing roller 4 (S513). The engine control unit 403 waits until the time Tattach required to complete the contact operation of the developing roller 4 has elapsed (S513). Then, when the time Tattach has elapsed, the engine control unit 403 starts image formation (S514). Note that, in this embodiment, when the input voltage is not fluctuating, the timing of starting the contact operation is controlled in the same manner as in the procedure of FIG. 15 described in the first embodiment, but the timing of starting the contact operation may be controlled in the same manner as in the procedure of FIG. 14 described in the first embodiment.

[0146] In addition, the start-up completion time Tr measured and stored in the measurement process can be reflected in, for example, the judgment of whether to use the contact operation start timing determined by the measurement process. For example, the predetermined fluctuation amount (threshold value) to be compared with the above-mentioned input voltage difference (absolute value) can be changed based on the start-up completion time Tr. Typically, when the start-up completion time Tr is relatively short (the load is relatively small), this threshold value can be made relatively large (tolerating relatively large input voltage fluctuations). Also, when the start-up completion time Tr is relatively long (the load is relatively large), this threshold value can be made relatively small (tolerating only relatively small input voltage fluctuations).

[0147] In this way, the image forming apparatus 100 of this embodiment has an input voltage detection unit 950 that detects the voltage input to the image forming apparatus 100, and the setting unit (engine control unit) 403, when performing the preparatory operation, determines whether or not to set the start timing for starting the contact operation based on the information on the switching time required to switch the developing member 4 from the separated state to the contact state acquired by the acquisition unit (development contact control unit) 407 based on the detection result of the input voltage detection unit 950. In this embodiment, when the difference between the voltage indicated by the detection result of the input voltage detection unit 950 when performing the previous preparatory operation and the voltage indicated by the detection result of the input voltage detection unit 950 when performing the current preparatory operation is less than a predetermined value, the setting unit 403 sets the start timing based on the information on the switching time acquired by the acquisition unit 407, and when the difference is equal to or greater than the predetermined value, the contact operation by the contact / separation mechanism 500 is started after the area on the photoconductor exposed during the light emission period in the preparatory operation has passed the development position.

[0148] As described above, in this embodiment, the input voltage to the image forming apparatus 100 is detected, and if it is determined that the input voltage has not changed from the expected input voltage, it is estimated that the developing motor 101 will start up in the same time as the time measured in the initialization operation. Then, based on the estimated time, the start timing of the contact operation of the developing roller 4 is controlled (adjusted). On the other hand, if it is determined that the input voltage has changed from the expected input voltage, the developing motor 101 may not start up in the expected time, or may start up earlier than expected. In that case, the developing motor 101 is started, and the contact operation of the developing roller 4 is started after waiting for the forced light emission area to pass the development position. As a result, even if the time required for starting up the developing motor 101 changes, it is possible to suppress the toner from moving to the area on the photosensitive drum 1 exposed when the exposure device 11 is started up.

[0149] [others] Although the present invention has been described above with reference to specific embodiments, the present invention is not limited to the above-mentioned embodiments.

[0150] In the above embodiment, the case where the exposure device (laser) is forced to emit light in the main scanning direction area including the image forming area for a predetermined time in order to stably acquire the BD signal during the light emission period of the preparatory operation before the image formation is described. However, the present invention is not limited to such an embodiment. In place of or in addition to the above operation, the exposure device (laser) may be forced to emit light in the main scanning direction area including the image forming area for a predetermined time in order to control the light amount (laser light amount) of the exposure device during the light emission period of the preparatory operation before the image formation. In this way, the present invention is effective for any light emission operation that can form a potential that can move toner from the developing member to the image forming area on the photoconductor, which is performed during the light emission period of the preparatory operation before the image formation.

[0151] In one configuration, non-image areas (areas where toner should not adhere) on substantially the entire area of ​​the photoconductor are exposed by the exposure device emitting weak light to the extent that toner does not move from the developing member. When such weak light emission is performed in a preparatory operation before image formation, the developing member may be brought into contact with the photoconductor when the area on the photoconductor exposed by the weak light emission passes the development position. In the present invention, the area on the photoconductor exposed in the preparatory operation before image formation, which is the target for suppressing toner movement, is an area exposed by the exposure device so as to form a potential at which toner can move from the developing member and adhere when the developing member comes into contact.

[0152] In addition, in the above-described embodiment, the image forming apparatus is a color image forming apparatus having a plurality of image forming units, but the present invention can also be applied to a monochrome image forming apparatus having a single image forming unit that forms, for example, a black monochrome image. [Explanation of symbols]

[0153] 1 Photosensitive drum 4 Developing roller 8. Developing device 11 Exposure equipment 101 Development motor 403 Engine control unit 407 Development contact control section 500 Approach / separation mechanism

Claims

1. A photoconductor that is rotatable in a predetermined rotation direction; a charging device that charges a surface of the photoconductor at a charging position relative to the rotation direction; an exposure device that exposes a surface of the photoconductor at an exposure position downstream of the charging position in the rotation direction; a developing device including a developing member capable of contacting a surface of the photoconductor at a developing position downstream of the exposure position and upstream of the charging position in the rotation direction, the developing member supplying a developer to the photoconductor; a contact / separation mechanism for switching the developing member between a contact state in which the developing member is in contact with the photoconductor and a separation state in which the developing member is separated from the photoconductor; a motor that drives the photoconductor, the developing member, and the contact / separation mechanism; an image forming apparatus which performs preparatory operations before image formation, the preparatory operations including a light emitting operation in which an area including an image forming area in a rotation axis direction of the photoconductor is exposed by the exposure device during a light emitting period to form a potential at which a developer can adhere to the photoconductor, start of the motor, and a contact operation in which the contact / separation mechanism switches the developing member from the separated state to the contact state during a switching period, the motor is configured to rotate the photoconductor and the developing member when the contact operation starts in the preparatory operation, an acquisition unit that acquires information regarding a switching time required for switching the developing member from the separated state to the contact state by performing the contact operation by the contact / separation mechanism; a setting unit that sets a start timing of the contact operation by the contact / separation mechanism and the rotation of the photoconductor and the developing member in the preparatory operation based on information about the switching time acquired by the acquisition unit, the start timing being a timing before an area on the photoconductor exposed during the light emission period reaches the developing position; An image forming apparatus comprising:

2. The image forming apparatus according to claim 1, characterized in that the setting unit sets the start timing so that when the time indicated by the information regarding the switching time is a first time, the time from the start of the preparatory operation to the start timing is a second time, and when the time indicated by the information regarding the switching time is a third time shorter than the first time, the setting unit sets the start timing so that the time from the start of the preparatory operation to the start timing is a fourth time longer than the second time.

3. The image forming apparatus according to claim 1 or 2, characterized in that the acquisition unit has a speed acquisition unit that acquires information regarding the rotational speed of the motor, and a rotation amount acquisition unit that acquires information regarding the rotation amount of the motor based on information regarding the multiple rotational speeds acquired by the speed acquisition unit over time, and acquires information regarding the switching time based on the time required to rotate the motor a predetermined rotation amount.

4. 4. The image forming apparatus according to claim 3, wherein the predetermined rotation amount is an amount of rotation of the motor required for the contact / separation mechanism to switch the developing member from the separated state to the contact state.

5. The image forming apparatus according to any one of claims 1 to 4, characterized in that the setting unit sets the start timing so that the developing member is in the abutment state after the area on the photoconductor exposed during the light emission period has finished passing through the developing position.

6. The image forming apparatus according to any one of claims 1 to 5, characterized in that before performing the preparatory operation, the acquisition unit performs a test operation in which the contact operation is performed by the contact / separation mechanism to acquire information regarding the switching time, and the setting unit sets the start timing of the preparatory operation to be performed after performing the test operation based on the information regarding the switching time acquired in the test operation.

7. 7. The image forming apparatus according to claim 6, wherein the test operation is executed when the image forming apparatus is powered on or when a replacement unit of the image forming apparatus is replaced.

8. The acquisition unit has a speed acquisition unit which acquires information regarding the rotational speed of the motor, and a rotation amount acquisition unit which acquires information regarding the rotation amount of the motor based on information regarding the multiple rotational speeds acquired by the speed acquisition unit over time, and acquires information regarding the switching time based on the time required to rotate the motor a first rotation amount, which is the rotation amount of the motor required to switch the developing member from the separated state to the abutted state by the contact / separation mechanism, and acquires information regarding the passing time, which is the time required for the area on the photosensitive member exposed during the light emission period to finish passing through the developing position, based on the time required to rotate the motor a second rotation amount, which is the rotation amount of the motor required for the area on the photosensitive member exposed during the light emission period to move from the exposure position to the developing position; The image forming apparatus according to claim 1 or 2, characterized in that the setting unit sets the start timing so that the developing member is in the abutment state after the area on the photoconductor exposed during the light emission period has finished passing through the developing position.

9. The image forming apparatus according to claim 8, characterized in that before performing the preparatory operation, the acquisition unit performs a test operation in which the contact operation is performed by the contact / separation mechanism to acquire information regarding the switching time and information regarding the passing time, and the setting unit sets the start timing of the preparatory operation to be performed after performing the test operation based on the information regarding the switching time and information regarding the passing time acquired in the test operation.

10. 10. The image forming apparatus according to claim 9, wherein the test operation is executed when the image forming apparatus is powered on or when a replacement unit of the image forming apparatus is replaced.

11. an input voltage detection unit that detects a voltage input to the image forming apparatus; the setting unit is configured to determine, when performing the preparatory operation, whether or not to set the start timing based on information related to the switching time acquired by the acquisition unit, based on a detection result of the input voltage detection unit; The image forming apparatus of any one of claims 1 to 10, characterized in that when the difference between the voltage indicated by the detection result of the input voltage detection unit when the previous preparatory operation was performed and the voltage indicated by the detection result of the input voltage detection unit when the current preparatory operation is performed is less than a predetermined value, the setting unit sets the start timing based on information regarding the switching time acquired by the acquisition unit, and when the difference is equal to or greater than the predetermined value, starts the contact operation by the contact / separation mechanism after the area on the photosensitive body exposed during the light emission period has finished passing the development position.

12. the exposure device has a light emitting unit that emits light and a polygon mirror, and the light emitted by the light emitting unit is reflected by the rotating polygon mirror and irradiated onto the photoconductor; 12. The image forming apparatus according to claim 1, wherein the light emission period is included in a period in which the rotation of the polygon mirror is not in a steady state.

13. An image forming apparatus as described in any one of claims 1 to 12, characterized in that it has a switching member for switching between a state of drive transmission from the motor to the separation mechanism and a state of drive transmission release, and the switching member is configured so that when drive transmission from the motor to the separation mechanism is performed and the contact operation is started, drive transmission from the motor to the separation mechanism is continued until the developing member switches from the separated state to the contact state.

Images