JP6100072B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus such as a copying machine, a printer, and a facsimile using an electrophotographic system.

  In an electrophotographic copying machine having a plurality of image forming units, for example, Y (yellow), M (magenta), C (cyan), K (black), and four color image forming units, a full color image is formed. In this case, image formation is started from the image forming unit upstream in the recording material conveyance direction. When a monochrome image is formed, only one of the image forming units is used, and the other image forming units are not used. Therefore, from the viewpoint of life management (durability) of the image forming unit, it is general to use each image forming unit by selectively driving or stopping driving.

  For example, in Patent Document 1, the above-described drive switching of the developing sleeve of the image forming unit is performed at a predetermined angle by using a small and simple mechanism, that is, a plurality of cam mechanisms called “Geneva mechanism original vehicle” with one drive source. This is realized by a mechanism that rotates them one by one. As the cam mechanism rotates by a predetermined angle and the phase (rotation angle) changes, the “Geneva mechanism follower” that transmits the driving force to the developing sleeve moves. When the “Geneva mechanism follower” moves, the drive gear for receiving the drive force from the developing motor and the Geneva mechanism follower mesh with each other. A driving force is transmitted to the developing sleeve. As described above, in the configuration proposed in Patent Document 1, the transmission / disconnection of the drive from the developing motor to the developing sleeve is switched by changing the phase of the Geneva mechanism original vehicle. Further, in Patent Document 1, the drive transmission of the developing motor is sequentially performed from the developing sleeve of the image forming unit arranged on the upstream side in the recording material conveyance direction, so that the developing sleeve of the downstream image forming unit is unnecessary. A configuration for reducing driving has been proposed.

JP 2006-047424 A

  As described in Patent Document 1, when driving of a driving source is sequentially transmitted to a developing sleeve of each image forming unit by one driving source and a plurality of cam mechanisms, development is performed from a developing motor as a driving source. Many gears are interposed in the drive transmission path to the sleeve. For this reason, it is difficult to adjust the phase (angle) when assembling the gear so that the drive of the developing motor is transmitted to the developing sleeve at an ideal angle. Furthermore, the timing at which the drive is transmitted also varies due to individual differences in the mechanical parts caused by the meshing of the gear teeth.

  When performing image formation, the image forming apparatus performs high voltage control for developing the electrostatic latent image on the photosensitive drum by applying a predetermined high voltage to the developing sleeve. At that time, the timing at which a high voltage is applied to the developing sleeve of each image forming unit (hereinafter, also referred to as a high voltage control timing) is normally a constant interval. However, the drive transmission timing to the developing sleeve is deviated from the ideal design time due to individual differences of the mechanical parts described above, and the driving timing of the developing sleeve and the high-pressure control timing are the same timing in each image forming unit. It is not that there is a shift. As a result, the timing at which the developing sleeve is driven deviates from the high-pressure control timing, so that the entire photosensitive drum is covered with toner, and the carrier constituting the developer adheres to the photosensitive drum. Toner contamination occurs in the apparatus. Furthermore, when a high voltage is applied when the photosensitive drum is stopped, an abnormal image such as a drum memory is generated, which may affect the life of parts such as the photosensitive drum.

  The present invention has been made under such circumstances, and an object thereof is to correct a deviation between the drive timing of the developing sleeve and the high-pressure control timing.

  In order to solve the above-described problems, the present invention is configured as follows.

  (1) having a toner carrier for supplying toner to the electrostatic latent image formed on the image carrier, a plurality of developing means for developing the electrostatic latent image, and applying a high voltage to the toner carrier High-pressure control means for controlling start and stop of the toner, development drive means for driving the toner carrier, and drive connection for transmitting the drive of the development drive means to the toner carrier according to the phase angle A connecting means for cutting, a connecting drive means for rotationally driving the connecting means, a detecting means provided in the developing means for detecting the driving or stopping of the toner carrier, and the toner carrying by the connecting drive means; Control means for controlling the driving or stopping of the body, wherein the control means drives the toner carrier in accordance with the timing when the high voltage control means starts or stops applying a high voltage to the toner carrier. or The connecting means is driven until the detecting means detects the driving or stopping of the toner carrier after the connecting driving means starts driving the connecting means at a predetermined driving speed so as to be stopped. An image forming apparatus that corrects a driving speed of the connection driving unit according to a phase angle.

  According to the present invention, it is possible to correct a deviation between the driving timing of the developing sleeve and the high-pressure control timing.

Sectional view of the color image forming apparatus main body of the embodiment 1 is a diagram illustrating a control block of an image forming apparatus according to an embodiment. The figure which shows the structure of the image development apparatus of the image forming apparatus of an Example. The perspective view of the clutch mechanism of an Example, The figure explaining operation | movement of a clutch mechanism FIG. 2 is a schematic cross-sectional view of the developing drive coupling motor and each control cam of the image forming apparatus of the embodiment, and a perspective view of the HP detection sensor The figure showing the drive connection and cutting state of the developing sleeve and the conveying screw at the phase (rotation angle) of each control cam of the embodiment The graph which shows the output signal value of the inductive sensor at the time of the development drive of an Example, and the time of development non-drive The timing chart showing the relationship between the drive connection timing of the developing sleeve and the phase of the control cam in the embodiment, and the diagram for explaining the calculation method of the correction speed of the development drive connection motor The flowchart which shows the control sequence which calculates the correction speed of the developing drive connection motor of an Example. The figure which shows the table | surface (table | surface) which preserve | saves the theoretical time interval at the time of development drive connection of an Example, and development drive cutting | disconnection, a measurement time interval, and a correction speed. 6 is a flowchart illustrating a control sequence for correcting development drive timing during printing in the image forming apparatus according to the embodiment.

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

  FIG. 1 is a cross-sectional view of a color image forming apparatus according to the present embodiment, and FIG. 2 is a diagram illustrating control blocks of the color image forming apparatus according to the present embodiment. FIG. 3 is a cross-sectional view of the photosensitive drum and the developing device in the process unit of the color image forming apparatus of this embodiment. Hereinafter, an outline of the color image forming apparatus will be described with reference to FIGS. 1, 2, and 3.

[Outline of image forming apparatus]
(Outline of image forming apparatus configuration and image forming operation)
First, the configuration of the color image forming apparatus and the basic image forming operation will be described with reference to FIG. When an instruction to start printing is input from the user via the operation unit 330 (FIG. 2), the CPU 301 (FIG. 2) that controls the image forming apparatus records a recording material conveyance unit 270 (FIG. 2) that controls conveyance of the recording material. ) To start feeding the recording material from the paper feed cassette 150 or the like. Under the control of the CPU 301, the paper feed pickup roller 151 is driven to rotate, and the recording material in the paper feed cassette 150 is fed and conveyed one by one.

  In parallel with the above-described control, the CPU 301 starts an image forming operation in the process unit 120 so as to be in time for the leading edge of the recording material to reach the secondary transfer unit 140. The process unit 120 serving as an image forming unit includes an image carrier, which will be described later, such as a photosensitive drum 241 (FIG. 3), a developing device 250 (FIG. 3), a charging roller, and a photosensitive drum cleaner. The process unit 120 is for Y (yellow), M (magenta), C (cyan), and K (black) in order from the upstream side of the rotation direction of the intermediate transfer belt 130 (arrow in FIG. 1). Has been placed. This arrangement is an example, and the arrangement may be changed. Each process unit has the same configuration, and in this description, a K (black) process unit 120K will be described as an example. In the following description, unless otherwise required, the process unit 120 is simply referred to, and when referring to the individual process units 120, Y, M, C, and K are suffixed as 120Y, 120M, 120C, and 120K. Will be attached. Similarly, devices that constitute the process unit 120 (for example, the developing device 250 and an inductive sensor 124 to be described later) and components that are provided corresponding to the process unit 120 (for example, a control cam 258 to be described later) are similarly Y suffixed. , M, C, K. In the process unit 120, the surface of the photosensitive drum 241 is charged by the charging roller, and then a latent image is formed on the photosensitive drum 241 by the laser light emitted from the laser scanner unit 122. The formed latent image is developed with toner in the developing device 250, and a toner image is formed on the photosensitive drum 241. Thereafter, the toner image on the photosensitive drum 241 is transferred to the intermediate transfer belt 130 in the primary transfer unit 121 by applying a primary transfer voltage from a high voltage control unit 245 (FIG. 2) described later. The toner image transferred to the intermediate transfer belt 130 in each process unit 120 is conveyed to the secondary transfer unit 140 by the rotation of the intermediate transfer belt 130.

  The pre-registration conveyance sensor 160 monitors the arrival of the leading edge of the recording material conveyed by the conveyance rollers 153, 154, and 155. Based on the timing when the pre-registration conveyance sensor 160 detects the leading edge of the recording material, the CPU 301 causes the leading edge of the recording material and the leading edge of the toner image on the intermediate transfer belt 130 to reach the secondary transfer unit 140 at the same timing. The conveyance of the recording material is controlled by the registration roller 161. By applying a secondary transfer voltage from the high voltage control unit 245 to the secondary transfer unit 140, the toner image on the intermediate transfer belt 130 is transferred to the recording material.

  The recording material to which the toner image has been transferred is conveyed to the fixing device 170. Then, in the fixing device 170, the toner image on the recording material is fixed to the recording material by being heated and pressed, and then conveyed to the downstream side of the conveying path. When the leading end of the heat-fixed recording material reaches the paper transport sensor 171, the recording material is transported along transport paths 231 and 180 by transport rollers 162, 232, and 233 and transport flappers 172 and 190 disposed downstream of the transport path. Then, the paper is discharged to the paper discharge tray 200.

(Control of image forming apparatus)
Next, control of the entire system of the image forming apparatus will be described with reference to FIG. FIG. 2 is a diagram illustrating a control block of the image forming apparatus according to the present exemplary embodiment. 2, the control unit 300 includes a CPU 301, a ROM 302, a RAM 303, and a timer 305, and performs system control of the image forming apparatus illustrated in FIG. A CPU 301 that controls the image forming apparatus is connected to a ROM 302 that stores a control program for controlling the image forming apparatus and a RAM 303 that is used as a work memory by the control program via an address bus and a data bus. The timer 305 measures time under the control of the CPU 301.

  The operation unit 330 is used to select an image forming mode / recording material finishing mode or to display a status of the image forming apparatus. The selected mode setting information is stored in the RAM 303. When an instruction from the user is input via the operation unit 330, the CPU 301, based on input signals from various sensors such as an inductive sensor 124 and an HP detection sensor 304 described later, the developing motor 125, the developing drive coupling motor 126, and the like. The various loads are operated to perform image forming operations.

  The high voltage control unit 245 controls the start and stop of application of a high voltage to the developing sleeve 244, the primary transfer voltage to the primary transfer unit 121, and the start and stop of application of the secondary transfer voltage to the secondary transfer unit 140. Do. The inductive sensor 124 is a sensor that detects the toner concentration in the developing device 250 (FIG. 3), which will be described later, and detects the magnetic permeability of the developer using the inductance of the coil. A developer, such as a two-component developer, is composed of a toner and a carrier. If the magnetic permeability is high, the amount of toner in the developer is small, and if the magnetic permeability is low, the amount of toner in the developer is large. be able to. A signal (analog signal) indicating the magnetic permeability output from the inductive sensor 124 is input to the CPU 301. The CPU 301 performs A / D conversion on the input signal, and based on the converted digital signal, the inside of the developing device 250. The toner density is determined. Further, the image forming apparatus according to the present exemplary embodiment includes only one developing motor 125, and a plurality of developing sleeves 244 and a conveying screw attached to a developing device 250 (FIG. 3) provided in each process unit 120. This is a drive source for driving 240 (FIG. 3).

  The development drive connection motor 126, which is a connection drive means, drives a clutch mechanism (FIG. 4A), which will be described later, and switches between the following two states. One is a driving connection state in which the driving (rotation) of the developing motor 125 is transmitted to the developing sleeve 244 and the conveying screw 240 of each process unit 120, and the other is the driving (rotating) of the developing motor 125 for developing. In this state, the drive is disconnected without being transmitted to the sleeve 244 or the like.

(Developer configuration)
Next, the configuration of the developing device of this embodiment will be described with reference to FIG. FIG. 3 is a diagram illustrating a configuration of the developing device 250 provided in the process unit 120 of the image forming apparatus according to the present exemplary embodiment. The configuration of the developing device 250 is the same in each process unit 120. In FIG. 3, the developing device 250 is divided into a developing chamber R1 and a stirring chamber R2 by a partition wall 242. A hopper 246 disposed above the agitation chamber R2 is provided with a toner storage chamber R3, which stores replenishment toner. An open supply port 248 is provided below the toner storage chamber R3, and an amount of toner corresponding to the amount of toner consumed by developing the electrostatic latent image is supplied from the supply port 248 to the stirring chamber R2. .

  The replenished toner is mixed with the magnetic carrier in the developing chamber R1 and the agitating chamber R2 by the rotation of the conveying screw 240, which is a toner conveying member, and is stored as a developer in the developing chamber R1 and the agitating chamber R2. The

  The developer is transported along the longitudinal direction of the developing sleeve 244 that is a toner carrier (a direction perpendicular to the paper surface of FIG. 3) as the transport screw 240 rotates. Then, by applying a high voltage to the developing sleeve 244 by the high-voltage control unit 245, toner is supplied from the developing sleeve 244 that is rotationally driven to the photosensitive drum 241 and attached thereto, whereby the electrostatic latent image is developed. The conveying screw 240 and the developing sleeve 244 are driven by the developing motor 125 described above. Further, the aforementioned inductive sensor 124 is installed on the outer wall surface of the stirring chamber R2 so as to face the conveying screw 240.

[Clutch mechanism for controlling the drive transmission of the developing motor]
(Configuration of clutch mechanism)
Next, a mechanism for transmitting the driving of the developing motor 125 to the developing sleeve 244 and the conveying screw 240 described in FIG. 3 will be described in detail. First, the configuration of the clutch mechanism that transmits the driving of the developing motor 125 to the developing sleeve 244 and the conveying screw 240 will be described with reference to FIG. FIG. 4A is a perspective view of a clutch mechanism that is a drive transmission control mechanism of this embodiment. The structure of the clutch mechanism shown in FIG. 4A is provided in each process unit 120, and each structure is the same.

  The clutch mechanism used in the present embodiment is roughly composed of four units: an input unit, an output unit, a control unit, and an initial torque generating unit. The input unit receives a driving input from the developing motor 125, and the output unit takes a driving output to the developing sleeve 244 and the conveying screw 240. The control unit controls drive connection / disconnection between the input unit and the output unit by driving the development drive connection motor 126, and the initial torque generating unit is a steady torque for a predetermined time immediately after the drive connection between the input unit and the output unit. Lower initial torque.

  The input unit includes an input gear 255, a movable ratchet (coupling) 251, and a biasing spring 256 that biases the movable ratchet 251 toward the fixed ratchet (coupling) 252 of the output unit. The movable ratchet 251 is disposed inside the input gear 255 and is configured to rotate integrally with the input gear 255 and to be slidable in the axial direction of the clutch shaft 257. The input gear 255 is connected to the developing motor 125 via a gear (not shown), and rotates in synchronization with the rotation of the developing motor 125. Further, the input unit is provided to be rotatable with respect to the clutch shaft 257.

  The output unit includes a clutch shaft 257 that is rotatably supported by the image forming apparatus main body by a guide member 260 and a bearing 261, and a fixed ratchet 252 that is fixed to the clutch shaft 257 and rotates integrally. The movable ratchet 251 and the fixed ratchet 252 that are a pair of drive transmission members are rotatably provided, and by engaging each other, the rotation of the developing motor 125 is transmitted to the clutch shaft 257, and the input unit and the output unit are connected. Drive coupled.

  The control unit includes a guide member 260, a control cam 258, and a movable cam 259. Here, the guide member 260 is arranged coaxially with the clutch shaft 257 and is fixed to the main body of the image forming apparatus. The control cam 258 is pivotally supported with respect to the guide member 260. In addition, the movable cam 259 is regulated by the guide member 260 and supported so as to be slidable in the axial direction of the clutch shaft 257, and moves the movable ratchet 251 in the axial direction of the clutch shaft 257.

  When the developing drive coupling motor 126 connected to the gear of the control cam 258 is driven via a gear (not shown) and the control cam 258 of the control unit is rotated, the movable cam 259 engaged with the control cam 258 is moved. It moves in the axial direction of the clutch shaft 257. The movable cam 259 is in a slidable contact state with the movable ratchet 251 of the input unit, and the movable ratchet 251 moves in conjunction with the movement of the movable cam 259. The movable ratchet 251 and the fixed ratchet 252 are disposed on the same rotation shaft and have engaging claws that protrude toward the opposing surfaces. Therefore, when the movable ratchet 251 moves to the fixed ratchet 252 side, the engaging claws of both are engaged, and the movable ratchet 251 and the fixed ratchet 252 are in an engaged state. By controlling the phase (rotation angle) of the control cam 258 with this mechanism, the clutch mechanism can be switched between connection and disconnection.

  The initial torque generating unit includes a delay gear 253 and an initial torque generating spring 254. The delay gear 253 is supported with a backlash of a predetermined angle in the rotational direction with respect to the clutch shaft 257 that transmits drive by engaging with each other. This play is a gap provided between the delay gear 253 and the clutch shaft 257. When the clutch shaft 257 rotates in the rotational direction for transmitting the drive, the clutch is not engaged until it engages with the delay gear 253. This is a gap that allows only the shaft 257 to rotate. The delay gear 253 and the clutch shaft 257 constitute a drive train that extends from the developing motor 125 that is a drive source to the output gear 262 via the movable ratchet 251 and the fixed ratchet 252 that are a pair of drive transmission members, and are engaged with each other. Thus, drive transmission is performed.

  The initial torque generating spring 254 urges the delay gear 253 in the play expansion direction (direction in which the gap increases) with respect to the rotational drive transmission direction in order to increase the play of the delay gear 253. The magnitude of the biasing force of the initial torque generating spring 254 is smaller than the steady torque required for the output sleeve 262 that drives the developing sleeve 244 and the conveying screw 240.

  The drive of the developing motor 125 is transmitted to the output gear 262 by drivingly connecting the input unit and the output unit. A developing sleeve 244 and a conveying screw 240 are connected to the output gear 262. When the driving of the developing motor 125 is transmitted, the developing sleeve 244 and the conveying screw 240 are rotationally driven.

(Operation of clutch mechanism)
Next, the operation of the clutch mechanism of this embodiment will be described. FIGS. 4B and 4C are diagrams for explaining the operation of the clutch mechanism in this embodiment. FIG. 4B shows a standby state in which the input unit and the output unit are not drivingly connected. FIG. The state of the drive connection with which the unit and the output unit were connected is shown. 4B and 4C, a schematic sectional view is shown on the left side, and a schematic perspective view is shown on the right side.

  In the standby state of FIG. 4B, the movable ratchet 251 is in a state (position) where the movable cam 259 is pushed and retracted from the fixed ratchet 252. At this time, the movable ratchet 251 and the fixed ratchet 252 are in a released state where they are not engaged, and the drive transmission from the input unit to the output unit is cut off.

  When the drive connection operation is started by rotating the development drive connection motor 126, the control cam 258 starts to rotate, and the movable ratchet 251 moves to the fixed ratchet 252 side. The engaging claws of the movable ratchet 251 and the fixed ratchet 252 are engaged, and the movable ratchet 251 and the fixed ratchet 252 are in an engaged state. At this time, the input unit and the output unit are drivingly connected, but the drive transmission is not yet transmitted to the output gear 262, and first, the relative backlash of a predetermined angle between the delay gear 253 and the clutch shaft 257 starts to be consumed. Until this relative play becomes zero, the torque generated by the initial torque generating spring 254 (a predetermined initial torque smaller than the steady torque) acts on the movable ratchet 251 and the fixed ratchet 252, that is, the drive train of the clutch mechanism. It is in the state to do. During this time, the movable ratchet 251 moves to a position where the meshing with the fixed ratchet 252 is greater than or equal to the engagement amount necessary for stable operation of the clutch mechanism. When the relative backlash between the delay gear 253 and the clutch shaft 257 is consumed, a steady torque acts on the movable ratchet 251 and the fixed ratchet 252, that is, the drive train of the clutch mechanism, and the drive of the output gear 262 is started (FIG. 4 ( The connection state shown in c)). Then, driving of the developing sleeve 244 and the conveying screw 240 is started via the output gear 262.

  Similarly, the drive disconnection (release of the drive connection state between the input unit and the output unit) is performed by moving the movable ratchet 251 to disengage the fixed ratchet 252 from engagement. When the connection state between the input unit and the output unit is released and the drive unit is disconnected, the fixed ratchet 252 is released from the engagement with the movable ratchet 251. The clutch shaft 257 is reversely rotated by the action of the delay gear 253 and the initial torque generating spring 254 to recover a predetermined relative play relative to the delay gear 253.

[Gear configuration to connect development drive coupling motor and control cam]
Next, a gear configuration that connects the development drive coupling motor 126 and the control cam 258 provided in each process unit 120 will be described. FIG. 5A is a schematic cross-sectional view of the developing drive coupling motor 126 of the image forming apparatus and the control cam 258 of each image forming unit in this embodiment. In FIG. 5A, the gears (outer peripheral portions) of the control cams 258 (258Y, 258M, 258C, 258K) provided in each process unit 120 are idler gears 401 (401Y, 401M, 401C, 401K). It is connected. The idler gear 401 is connected to the shaft 403 via a worm gear A 402 (402Y, 402M, 402C, 402K). Further, the shaft 403 is connected to the development drive coupling motor 126 via the worm gear B 404. As a result, when the developing drive coupling motor 126 rotates, the shaft 403 rotates via the worm gear B 404, and the rotation of the shaft 403 is controlled via the worm gear A 402 and the idler gear 401 provided for each process unit 120. Is transmitted to. As a result, when the developing drive coupling motor 126 is rotated, all the control cams 258 are simultaneously rotated by the same angle. The number of control cams 258 is an example according to the configuration of the present embodiment, and is not limited to the configuration described above.

[Outline of HP detection sensor]
Next, the HP detection sensor 304 that detects a home position (HP) that is a position serving as a reference for rotation control of the control cam 258 will be described. FIG. 5B is a perspective view of the control cam 258K provided in the black (K) process unit 120K as viewed from the guide member 260 side shown in FIG. 4A. The HP detection sensor 304 is provided in the control cam 258K. The control cam 258K is provided with a slit plate 420 on the rib. Further, the slit plate 420 is provided with a slit 421 that is a notch. The HP detection sensor 304 is shaped to sandwich the slit plate 420 and detects the passage of the slit 421 of the rotating slit plate 420. When the HP detection sensor 304 detects the passage of the slit 421, the home position where the phase angle of the control cam 258K is 0 degree can be detected. By rotating the control cam 258 using the position where the phase angle is 0 degree as a reference position (home position), drive connection / disconnection in each process unit 120 is controlled. In this embodiment, the HP detection sensor 304 is disposed on the black (K) control cam 258K, but may be other control cams 258Y, 258M, and 258C, or may be moved in conjunction with the control cam 258. It may be arranged in a gear dedicated to the slit plate.

[Drive connection / disconnection control by control cam]
Next, drive control of the developing sleeve 244 and the conveying screw 240 of the image forming unit according to the phase (also referred to as a rotation angle) of the control cam 258 will be described. FIG. 6A shows the driving connection / disconnection state of the developing sleeve 244 and the conveying screw 240 for each phase of the control cam 258 provided in each process unit 120. The control cams 258 provided in each process unit 120 are assembled with gear teeth so as to have a phase difference of 45 degrees from each other. Finally, depending on the rotation angle of the control cam 258, a drive connection state is established in which the drive of the developing motor 125 is transmitted to the developing sleeve 244 and the conveying screw 240 of each process unit 120.

  Specifically, when the control cam 258 provided in each process unit 120 rotates and the phase is changed from 0 degree (home position) to 45 degrees, the yellow (Y) developing sleeve 244Y and the conveying screw 240Y are driven. It is in a connected state (indicated as Y drive in the figure). When the phase is 45 degrees, the magenta (M), cyan (C), and black (K) developing sleeves 244 and the conveying screw 240 are stopped (cut). When the phase of each control cam 258 reaches 90 degrees, in addition to yellow (Y), the magenta (M) developing sleeve 244M and the conveying screw 240M are in a driving connection state (shown as M driving in the figure). . Subsequently, when the phase of each control cam 258 reaches 135 degrees, in addition to yellow (Y) and magenta (M), the cyan (C) developing sleeve 244C and the conveying screw 240C are in a drivingly connected state (C in the figure). Drive and display). Further, when the phase of each control cam 258 reaches 180 degrees, the black (K) developing sleeve 244K and the conveying screw 240K are in a driving connection state (indicated as K driving in the drawing). As a result, the developing sleeves 244 and the conveying screws 240 of all the process units 120 are driven and connected.

  Each time the control cam 258 further rotates 45 degrees from 180 degrees, the developing sleeve 244 of each process unit 120 and the yellow (Y), magenta (M), cyan (C), and black (K) in this order. The drive connection state of the conveying screw 240 is cut (released). In FIG. 6A, Y stop, M stop, C stop, and K stop are displayed. Finally, when the HP detection sensor 304 detects the slit 421 (position), that is, when the rotation of the control cam 258 is stopped at a phase of 0 degree, the developing sleeves 244 and the conveying screws 240 of all the image forming units are The drive connection is disconnected.

  The control cam 258 rotates in the direction in which the phase (rotation angle) increases by rotating the developing drive coupling motor 126 forward. That is, the developing motor 125 is rotated to keep the input gear 255 in FIG. Then, when the control cam 258 is in the phase of 0 degree, the developing drive connecting motor 126 is rotated forward, and when the phase of the control cam 258 reaches from 0 degree to 45 degrees, the developing sleeve 244Y and the conveying screw 240Y rotate. start. Further, when the phase reaches 90 degrees, the developing sleeve 244M and the conveying screw 240M start rotating, and when the phase reaches 135 degrees, the developing sleeve 244C and the conveying screw 240C start rotating. When the phase of the control cam 258 reaches 180 degrees, the developing sleeve 244K and the conveying screw 240K start to rotate, and the developing sleeve 244 and the conveying screw 240 of all the image forming units are rotated. Further, as the development drive coupling motor 126 continues to rotate, every time the phase increases from 180 degrees to 45 degrees, the development sleeve 244 is in the order of Y (yellow), M (magenta), C (cyan), and K (black). And the rotation of the conveying screw 240 stops. As described above, the driving of the developing motor 125 is sequentially connected to and disconnected from the developing sleeve 244 and the conveying screw 240 of each process unit 120 in synchronization with the phase (rotation angle) of the control cam 258 by the mechanism described above. be able to.

  However, in practice, as shown in FIG. 6A, the developing sleeve 244Y and the conveying screw 240Y are accurately driven at a phase of 45 degrees, and the developing sleeve 244M and the conveying screw 240M are driven at a phase of 90 degrees. It is difficult to assemble gears at intervals. As shown in FIG. 5A, a number of gears such as a worm gear B 404, a worm gear A 402, and an idler gear 401 are interposed before the rotation of the development drive coupling motor 126 is transmitted to the control cam 258 of each image forming unit. doing. For this reason, if even one gear tooth is displaced, the designed phase difference cannot be satisfied. FIG. 6A described above shows a state in which the drive connection / disconnection of the developing sleeve 244 and the conveying screw 240 is performed based on the designed phase difference of each control cam 258. On the other hand, FIG. 6B shows an example in which the driving connection / disconnection of the developing sleeve 244 and the conveying screw 240 is not executed with the phase difference as designed for the control cam 258. In FIG. 6B, the driving connection / disconnection of the developing sleeve 244Y and the conveying screw 240Y is performed at a phase (rotation angle) larger than 45 degrees and 225 degrees, respectively. Conversely, the drive connection / disconnection of the developing sleeve 244M and the conveying screw 240M is performed at a phase (rotation angle) smaller than 90 degrees and 270 degrees, respectively, and the same applies to the developing sleeve 244C and the conveying screw 240C. According to the configuration described in the present embodiment, for example, when the control cam 258 and the idler gear 401 are shifted by one tooth from the design value, as shown in FIG. 6B, the phase difference is 45 degrees as designed. The phase difference changed by 8 degrees to 53 degrees. The phase change rate with respect to one gear tooth is an example according to the configuration of the present embodiment, and is not limited to the phase change rate described above.

[Induct sensor overview]
Next, a drive detection sensor that detects that the developing sleeve 244 and the conveying screw 240 are driven will be described. In this embodiment, an inductive sensor 124 provided in the developing device 250 is used as a drive detection sensor.

  FIG. 7A is a diagram illustrating an output signal of the inductive sensor 124 disposed to face the conveying screw 240 when the conveying screw 240 of the developing device 250 is rotating. In FIG. 7A, a sine wave is an output signal of the inductive sensor 124, the vertical axis indicates the voltage of the output signal, and the horizontal axis indicates time. The configurations of the conveying screw 240 and the inductive sensor 124 are the same in each process unit 120. As shown in FIG. 7A, it can be seen that the output voltage of the inductive sensor 124 is not a constant voltage value but periodically fluctuates in a voltage range of 1.5V to 3.5V. This is because the toner is agitated inside the developing device by the rotation of the conveying screw 240, so that the bulk density of the toner contained in the developer passing near the induct sensor 124 varies. The fluctuation period f coincides with the developer conveyance period determined by the rotation speed N of the conveyance screw 240. In this embodiment, the rotation speed N of the conveying screw 240 is 600 rpm (the rotation speed per minute is 600 rotations), and the vibration period f is 100 msec (milliseconds). In addition, the rotation speed and the period of vibration mentioned above are examples, and are not limited to the structure mentioned above. Since the conveying screw 240 is driven in synchronism with the developing sleeve 244, it can be detected that the developing sleeve 244 is in a driving state by detecting that the output voltage of the inductive sensor 124 is fluctuating.

  FIG. 7B is a diagram illustrating an output signal of the inductive sensor 124 when the conveying screw 240 of the developing device 250 is not rotating (stopped), and the vertical axis represents the voltage of the output signal, and the horizontal axis Indicates time. FIG. 7B shows that when the conveying screw 240 is not rotating, the output voltage of the inductive sensor 124 does not vary from 2.5V. This is because the toner in the stirring chamber R2 is not stirred because the conveying screw 240 is not rotating, and the bulk density of the toner contained in the developer passing near the induction sensor 124 does not fluctuate. Therefore, if it is detected that the output voltage of the inductive sensor 124 has not changed, it can be detected that the developing sleeve 244 is not driven. Therefore, the existing inductive sensor 124 can be used as a sensor for detecting that the developing sleeve 244 and the conveying screw 240 are driven without adding a new detection sensor. The output signal value of the inductive sensor 124 described in the present embodiment is an example and is not limited to the voltage value described above.

  As described above, the development drive coupling motor 126 may not be able to drive the development sleeve 244 and the conveyance screw 240 by satisfying the designed phase difference through many gears and the control cam 258. Therefore, the time required to reach the phase corresponding to the development drive connection / disconnection of each process unit 120 varies with respect to the design time. Originally, each development drive and the high voltage control timing by the high voltage control unit 245 are controlled at regular intervals. Therefore, in this embodiment, the control cam 258 is set so that the time until the control cam 258 of each process unit 120 reaches the rotation angle corresponding to the drive connection / disconnection is the designed time interval (theoretical time interval T). The speed of the development drive coupling motor 126 that rotates the motor is corrected. By correcting the speed of the development drive coupling motor 126, even when each control cam 258 cannot satisfy the designed phase difference, the time variation until the control cam 258 reaches a predetermined rotation angle is eliminated. The As a result, each development drive and the high voltage control timing can be set at a constant interval.

[Calculation of correction speed of development drive coupling motor]
First, an outline of a method for calculating the correction speed v of the development drive coupling motor 126 will be described with reference to FIG. FIG. 8A is a timing chart showing the relationship between the drive connection timing of the developing sleeve 244Y and the phase (phase angle (degree)) of the control cam 258 at that time. The waveform in FIG. 8A is based on the output voltage signal of the inductive sensor 124. The OFF state indicates the state where the conveying screw 240 is stopped, and the ON state indicates the state where the conveying screw 240 is rotating. Yes. FIG. 8B is a graph showing the relationship among speed, time, and phase angle for explaining a method of calculating the correction speed v.

  As described with reference to FIG. 6, when the development drive coupling motor 126 is rotated, the development drive (drive of the development sleeve 244) is in the order of Y (yellow) → M (magenta) → C (cyan) → K (black). Drive coupled. After the drive connection of K (black), if the development drive connection motor 126 continues to rotate, the drive disconnection is performed in the order of Y (yellow) → M (magenta) → C (cyan) → K (black). . Therefore, the inductive sensor 124 is used to measure the drive connection time interval and the drive disconnection time interval in each process unit 120 (measurement time interval t). When measuring the measurement time interval t, the development drive coupling motor 126 is rotated at the reference speed V. The reference speed V is a speed at which the development drive and the high-pressure control timing become the theoretical time interval T when the control cam 258 satisfies the designed phase angle D.

  Next, the correction speed v is calculated from the measured measurement time interval t of drive connection / disconnection and the theoretical time interval T which is a theoretical value thereof. As will be described later, the correction speed v can be calculated from the reference speed V and the ratio of the designed theoretical time interval T to the measurement time interval t.

Next, a method for calculating the correction speed v will be described with reference to FIGS. FIG. 8A shows a deviation from the theoretical drive timing of the developing sleeve 244Y and the conveying screw 240Y and the design timing when the control cam 258 is assembled so as to satisfy the designed phase angle. Represents the actually measured drive timing. As described above, the control cam 258 has a 45 degree phase angle (theoretical phase angle D) as designed. The theoretical time interval T is the time required to rotate the theoretical phase angle D when the development drive coupling motor 126 is rotated at the reference speed V. From the relationship between the speed and time, the following formula ( 1).
D = V × T (1)

On the other hand, taking the case where the gear of the control cam 258 is shifted by one tooth and the phase angle does not increase to 53 degrees (the timing is not shifted), the driving of the developing sleeve 244Y and the conveying screw 240Y is not connected. The calculation method of will be described. A phase angle when the driving of the developing sleeve 244Y and the conveying screw 240Y is connected is defined as an actual phase angle d. When the developing drive connecting motor 126 is rotated at the reference speed V, the time interval (measurement time interval t) until the developing sleeve 244Y and the conveying screw 240Y actually start driving is as follows, similar to the equation (1): It is represented by Formula (2).
d = V × t (2)

FIG. 8B is a graph showing the relationship between the theoretical phase angle D, the actual phase angle d, the theoretical time interval T, and the measurement time interval t, where the horizontal axis indicates time and the vertical axis indicates the phase angle. By driving the developing drive connecting motor 126 at the reference speed V for the measurement interval t, the control cam 258 reaches the actual phase angle d, and the driving of the developing sleeve 244Y and the conveying screw 240Y is connected. Here, even if the theoretical speed interval T is driven at the reference speed V, the control cam 258 reaches only the theoretical phase angle D (= d−8 degrees). The correction speed v required to shift the phase angle to the actual phase angle d at the theoretical time interval T is expressed as in equation (3), and by substituting equation (2) into equation (3), the equation (4) is derived.
v = d ÷ T (3)
v = V × (t ÷ T) (4)

  From equation (4), the correction speed v is expressed as the reference speed V multiplied by the ratio of the theoretical time interval T and the measurement time interval t. As a result, the development drive connection motor 126 is driven at the reference speed V, and the measurement time interval t of the drive connection / disconnection of the development sleeve 244 and the conveying screw 240 of each image forming unit is measured. Can be calculated at a theoretical time interval T. In this embodiment, the correction speed v of the development drive coupling motor 126 is calculated when the image forming apparatus is turned on. In the case of the configuration in which the correction speed v is calculated when the image forming apparatus is turned on, the correction can be appropriately performed even when the shift amount of the drive connection timing is changed due to a change in time measurement. Note that the calculation of the correction speed at the timing when the power is turned on is an example, and the calculation of the correction speed is not limited to this timing. For example, the correction speed may be calculated every time printing is completed (at the end of image formation). .

[Control sequence for calculating the correction speed]
Next, the control sequence for calculating the correction speed v described above will be described in detail with reference to FIGS. 9 and 10. FIG. 9 is a flowchart showing a control sequence in which the CPU 301 calculates the correction speed v of the development drive coupling motor 126 based on the output of the induction sensor 124. FIG. 10 is a diagram showing a table for storing theoretical time intervals, measurement time intervals, and correction speeds when the development drive is connected and when the development drive is disconnected. 10, measurement time interval t1 (unit: msec) ((a) in the figure), t2 (unit: msec) ((c) in the figure), correction speed v (unit: mm / sec) (in the figure (e A table indicating)) is stored in the RAM 303. On the other hand, the theoretical time intervals T1 (unit: msec) ((b) in the figure) and T2 (unit: msec) ((d) in the figure) are stored in the ROM 302. In FIG. 10, a measurement time interval t1 is a measurement time interval when the development drive is connected, and a measurement time interval t2 is a measurement time interval when the development drive is disconnected. The theoretical time interval T1 is a theoretical time interval when the development drive is connected, and the theoretical time interval T2 is a theoretical time interval when the development drive is disconnected. Further, the correction speed v in FIG. 10E is composed of a correction speed v1 when the development drive is connected and a correction speed v2 when the development drive is disconnected.

  In FIG. 9, when the power of the image forming apparatus is turned on and the CPU 301 is activated, in step 1001 (hereinafter referred to as S1001), the CPU 301 starts to rotate the developing motor 125. In step S <b> 1002, the CPU 301 drives the development drive connecting motor 126 at the reference speed V in the forward rotation (clockwise) direction. In step S <b> 1003, the CPU 301 resets the timer 305 and then starts the time measurement in order to measure the time interval at which the driving of the developing sleeve 244 and the conveying screw 240 in each process unit 120 is started.

  In step S <b> 1004, the CPU 301 starts sampling a signal indicating the toner density output from the inductor sensor 124 attached to the developing device 250 of each process unit 120. In this embodiment, sampling of the output signal of the inductive sensor 124 is performed at a cycle of 5 msec (milliseconds) from the start of driving of the developing drive connecting motor 126 in S1002, and driving of the developing drive connecting motor 126 is performed in S1026 described later. This is continued until is stopped. In addition, the sampling period of the inductor sensor output signal in the present embodiment is an example, and is not limited to this sampling period.

  In S1005, the CPU 301 performs A / D conversion on the output signal from the inductive sensor 124Y provided in the process unit 120Y as shown in FIG. 7A, and determines whether the output signal is fluctuating. Then, if a change is detected, the CPU 301 proceeds to S1006, and if not detected, repeats the process of S1005. In this embodiment, the output signal of the inductive sensor 124 is monitored at a cycle of 5 msec. When the voltage value of the output signal is different three times in succession, the developing sleeve 244Y and the conveying screw 240 are driven. Is determined to have fluctuated. It should be noted that the number of times that the variation of the output signal of the inductive sensor 124 in this embodiment is determined to be effective is an example, and is not limited to this number. In step S <b> 1006, the CPU 301 determines that the current time (current time) is the timing when the developing sleeve 244 </ b> Y starts driving, and reads the time from the timer 305. Then, the CPU 301 measures the measurement time interval t1Y from the rotation start (reference) of the development drive coupling motor 126 to the output fluctuation (Y drive) of the inductive sensor 124Y, which is measured by the timer 305, as shown in a table shown in FIG. Save to table value 1101).

  Subsequently, in S1007, the CPU 301 determines whether or not the output signal from the inductive sensor 124M of the process unit 120M is changing. If a change is detected, the process proceeds to S1008. Repeat the process. In step S <b> 1008, the CPU 301 determines that the current time (current time) is the timing when the developing sleeve 244 </ b> M starts driving, and reads the time from the timer 305. Then, the CPU 301 shows a table (table value 1102) shown in FIG. 10A as a measurement time interval t1M that is an elapsed time from when the output signal of the inductive sensor 124Y fluctuates until the output signal of the inductive sensor 124M fluctuates. Save to The measurement time interval t1M subtracts the measurement time of the timer 305 when it is determined that the output signal of the inductive sensor 124Y has changed from the measurement time of the timer 305 when it is determined that the output signal of the inductive sensor 124M has changed. Can be calculated.

  Based on the output signal of the inductive sensor 124C in S1009 and the output signal of the inductive sensor 124K in S1011, the CPU 301 detects fluctuations in the output signals of the inductive sensor 124C and the inductive sensor 124K in the same manner as the above-described processing. When detecting a change in the output signal of the inductive sensor 124, in S1010, the CPU 301 calculates a measurement time interval t1C from the output fluctuation of the inductive sensor 124M to the output fluctuation of the inductive sensor 124C, and is shown in FIG. 10 (a). Save to table. Similarly, in S1012, the CPU 301 stores the measurement time interval t1K from the output fluctuation of the inductive sensor 124C to the output fluctuation of the inductive sensor 124K in the table shown in FIG. As a result, measurement of the measurement time interval t1 of each process unit 120 at the time of development drive connection is completed.

  Next, the CPU 301 calculates a correction speed v1 from the actually measured drive connection measurement time interval t1 and the theoretical time interval T1 which is a theoretical value of the design. First, in S1013, the CPU 301 sets the theoretical time interval T1Y (table value 1110 in FIG. 10B) from the rotation start (reference) of the development drive coupling motor 126 to the output fluctuation (Y drive) of the inductive sensor 124Y. Read from the table shown in (b). Similarly, the CPU 301 reads the theoretical time intervals T1M, T1C, and T1K from the table of FIG. T1M is a theoretical time interval from the output fluctuation (Y driving) of the inductive sensor 124Y to the output fluctuation (M driving) of the inductive sensor 124M, and T1C is the output fluctuation (C driving) of the inductive sensor 124M to the output fluctuation (C of the inductive sensor 124M). This is the theoretical time interval until (drive). T1K is a theoretical time interval from the output fluctuation (C driving) of the inductive sensor 124C to the output fluctuation (K driving) of the inductive sensor 124K. Subsequently, in S1014, the CPU 301 determines the measurement time interval t1Y (table value 1101 in FIG. 10A), t1M (table value 1102 in FIG. 10A), t1C, from the table shown in FIG. Read t1K. Then, the CPU 301 calculates the correction speeds v1Y, v1M of the developing drive connecting motor 126 from the theoretical time intervals T1Y, T1M, T1C, T1K and the measurement time intervals t1Y, t1M, t1C, t1K based on the above-described equation (4). v1C and v1K are calculated. Then, the CPU 301 stores the calculated correction speed v1 in the table shown in FIG.

Here, the processing of S1014 will be supplementarily described using the table values of FIG. For example, a method of calculating the correction speed v1Y for driving the developing sleeve 244Y and the conveying screw 240 of the process unit 120Y when the reference speed V of the developing drive coupling motor 126 is 150 mm / sec (150 millimeters per second) will be described. The correction speed v1Y (table value 1112 in FIG. 10E) is measured using the measurement time interval t1Y (table value 1101 in FIG. 10A) and the theoretical time interval T1Y (table value 1110 in FIG. 10B). Based on the above-described equation (4), the following equation (5) is calculated.
v1Y = V × (t1Y ÷ T1Y) = 150 × (250 ÷ 300) = 125 (5)
The correction speeds v1M, v1C, and v1K for the process units 120M, 120C, and 120K can be calculated in the same manner as the correction speed v1Y. This is the end of the calculation of the correction speed v1 of the development drive coupling motor 126.

  Next, in S1015 to S1022, the measurement time interval t2 when the development drive is cut in the order of Y → M → C → K is measured.

  In S1015, the CPU 301 A / D converts the output signal from the inductive sensor 124Y provided in the process unit 120Y, and determines whether the output signal is constant and stable. If the stable state of the output signal is detected, the CPU 301 proceeds to S1016, and if not, repeats the process of S1015. In this embodiment, the development drive coupling motor 126 continues to rotate, so that the phase (rotation angle) of the control cam 258 increases, and as a result, the rotation of the developing sleeve 244 and the conveying screw 240 stops. Since the toner is not stirred inside the developing device 250, the output signal of the inductive sensor 124 does not fluctuate. The CPU 301 monitors the output signal of the inductive sensor 124 at a cycle of 5 msec, and when the voltage value of the output signal is the same three times continuously, the driving of the developing sleeve 244Y and the conveying screw 240Y is stopped. Therefore, it is determined that the output signal is stable. The number of times that the output signal of the inductive sensor 124 in this embodiment is determined to be stable is an example, and is not limited to this number. When the CPU 301 determines that the output signal is stable, the table of FIG. 10C shows a measurement time interval t2Y that is an elapsed time from when the output signal of the inductive sensor 124K fluctuates until the output signal of the inductive sensor 124Y becomes stable. Save to (table value 1111). The measurement time interval t2Y is obtained by subtracting the measurement time of the timer 305 when it is determined that the output signal of the inductive sensor 124K has changed from the measurement time of the timer 305 when the output signal stability of the inductor sensor 124Y is detected. Is calculated by

  In step S1017, the CPU 301 detects the stable state of the output signals of the inductive sensors 124M, 124C, and 124K based on the output signal of the inductive sensor 124M in S1019, the output signal of the inductive sensor 124K in step S1019, and the inductive sensor 124K in step S1021. When the stable state (output stability) of the output signal of the inductive sensor 124 is detected, in step S1018, the CPU 301 calculates a measurement time interval t2M from the stable output of the inductive sensor 124Y to the stable output of the inductive sensor 124M. Save to the table of c). Similarly, in S1020, the CPU 301 calculates a measurement time interval t2C from the stabilization of the output of the inductive sensor 124M to the stabilization of the output of the inductive sensor 124C, and stores it in the table of FIG. In S1022, the CPU 301 stores the measurement time interval t2K from the stabilization of the output of the inductive sensor 124C to the stabilization of the output of the inductive sensor 124K in the table of FIG. Thus, measurement of the measurement time interval t2 at the time of development driving in each process unit 120 at the time of disconnection of development driving is completed.

  Next, the CPU 301 calculates the correction speed v2 from the actually measured drive disconnection measurement time interval t2 and the theoretical time interval T2 which is a theoretical value for the design. First, in S1023, the CPU 301 sets the theoretical time interval T2Y (table value 1113 in FIG. 10D) from the output fluctuation (K drive) of the inductive sensor 124K to the output stabilization of the inductive sensor 124Y (Y stop) in FIG. Read from the table shown in d). Similarly, the CPU 301 reads theoretical time intervals T2M, T2C, and T2K from the table of FIG. T2M is a theoretical time interval from the output stability (Y stop) of the inductive sensor 124Y to the output stability (M stop) of the inductive sensor 124M, and T2C is the output stability (M stop) of the inductive sensor 124M to the output stability of the inductive sensor 124C (M stop). The theoretical time interval until C stop). T2K is a theoretical time interval from the output stabilization (C stop) of the inductive sensor 124C to the output stabilization (K stop) of the inductive sensor 124K. Subsequently, in S1024, the CPU 301 reads the measurement time interval t2Y (table value 1111 in FIG. 10C), t2M, t2C, and t2K from the table shown in FIG. Then, the CPU 301 calculates correction speeds v2Y, v2M, v2C, and v2K from the theoretical time intervals T2Y, T2M, T2C, and T2K and the measurement time intervals t2Y, t2M, t2C, and t2K based on the above-described equation (4). Then, it is stored in the table of FIG.

Here, the process of S1024 will be supplementarily described using the table values of FIG. For example, a method of calculating the correction speed v2Y for stopping the driving of the developing sleeve 244Y and the conveying screw 240 of the process unit 120Y when the reference speed V of the developing drive coupling motor 126 is 150 mm / sec (150 millimeters per second) will be described. . The correction speed v2Y (table value 1114 in FIG. 10E) is measured using the measurement time interval t2Y (table value 1111 in FIG. 10C) and the theoretical time interval T2Y (table value 1113 in FIG. 10D). Based on the above-described equation (4), the following equation (6) is calculated.
v2Y = V × (t2Y ÷ T2Y) = 150 × (280 ÷ 300) = 140 (6)
The correction speeds v2M, v2C, and v2K for the process units 120M, 120C, and 120K can be calculated in the same manner as the correction speed v2Y. This is the end of the calculation of the correction speed v2 of the development drive coupling motor 126.

In step S <b> 1025, the CPU 301 determines whether the control cam 258 </ b> K is in an HP state (a state in which the HP detection sensor 304 detects the slit 421) based on an output from the HP detection sensor 304. As described above, when the HP detection sensor 304 detects the passage of the slit 421 provided in the slit plate 420 of the control cam 258K, the home position where the phase angle of the control cam 258K is 0 degree is detected. be able to. If the CPU 301 determines that the HP detection sensor 304 has detected the slit 421, the CPU 301 proceeds to S1026, and if not, repeats the processing of S1025.
In step S <b> 1026, the CPU 301 stops driving the development drive connection motor 126. In step S <b> 1027, the CPU 301 stops time measurement by the development motor 125 and the timer 305 and ends the process. Note that the execution timing of calculating the correction speeds v1 and v2 of the development drive coupling motor 126 described above is an example, and is not limited to the execution timing in this embodiment. The correction speeds v1 and v2 for connecting / disconnecting the development drive at the ideal time interval T, which is a design value, can be calculated by the control sequence of FIG. 9 described above.

[Development drive timing control sequence during printing]
Next, a correction sequence of the drive connection / disconnection control timing of the development drive connection motor 126 using the correction speed v (correction speed at the time of drive connection: v1, correction speed at the time of drive disconnection: v2) calculated in FIG. explain. By this correction, the time until the control cam 258 reaches the phase (rotation angle) corresponding to the connected state / disconnected state of the development drive is corrected to the design time (theoretical time interval T). As a result, the timing / cutting timing at which the development drive in each process unit 120 is connected and the on / off timing of the high voltage control can be set at regular intervals.

  FIG. 11 is a flowchart showing a control sequence for correcting the development drive timing during printing of the image forming apparatus. When a user print request is input to the CPU 301 from the operation unit 330, a printing operation is started. In S1301, when the printing operation is started, the CPU 301 starts the developing motor 125 to rotate. In step S <b> 1302, the CPU 301 starts sampling a signal indicating the toner density output from the inductor sensor 124 attached to the developing device 250 of each process unit 120. The sampling method of the output signal of the inductive sensor 124 (124Y, 124M, 124C, 124K) and the conditions for determining fluctuation / stability are the same as those described with reference to FIG.

  Next, the CPU 301 performs control for driving and connecting the process units 120 at predetermined time intervals in response to the high voltage application by the high voltage control unit 245. In S <b> 1303 to S <b> 1312, the CPU 301 controls the rotation speed of the development drive connection motor 126 during the development drive connection until the drive connection is performed in each process unit 120 using the inductive sensor 124. In S1303, the CPU 301 reads the correction speeds v1Y, v1M, v1C, and v1K of the development drive coupling motor 126 at the time of development drive coupling from the table shown in FIG. Next, in S1304, the CPU 301 starts to rotate the development drive coupling motor 126 in the normal rotation (clockwise) direction at the correction speed v1Y. In S1305, the CPU 301 determines whether or not the output signal is fluctuating based on the output signal from the inductive sensor 124Y provided in the process unit 120Y. If fluctuation is detected, the process proceeds to S1306. Repeats the process of S1305. In S1306, the CPU 301 determines that the developing sleeve 244Y has been driven, changes the speed of the developing drive coupling motor 126 to the correction speed v1M, and starts rotation. In S1307, the CPU 301 determines whether the output signal is fluctuating based on the output signal from the inductive sensor 124M provided in the process unit 120M. If a fluctuation is detected, the process proceeds to S1308. Repeats the process of S1307.

  In S1308, the CPU 301 determines that the developing sleeve 244M has been driven, changes the speed of the developing drive coupling motor 126 to the correction speed v1C, and starts rotation. In S1309, the CPU 301 determines whether the output signal is fluctuating based on the output signal from the inductive sensor 124C provided in the process unit 120C. If a fluctuation is detected, the process proceeds to S1310. Repeats the process of S1309. In S1310, the CPU 301 determines that the developing sleeve 244C has been driven, changes the speed of the developing drive coupling motor 126 to the correction speed v1K, and starts rotation. In S1311, the CPU 301 determines whether the output signal is fluctuating based on the output signal from the inductive sensor 124K provided in the process unit 120K. If fluctuation is detected, the process proceeds to S1312, and if not detected. Repeats the process of S1311. In S1312, the CPU 301 determines that the developing sleeve 244K has been driven, and stops the rotation of the developing drive connecting motor 126. In step S1313, the CPU 301 determines whether printing on the recording material has been completed. If the printing has been completed, the process proceeds to step S1314. If the printing has not been completed, the processing in step S1313 is repeated.

  Next, in S1314 to S1322, the rotation speed control when the development drive connection motor 126 stops the development drive is performed using the inductive sensor 124 until the development drive of K (black) is stopped. In step S1314, the CPU 301 reads the correction speeds v2Y, v2M, v2C, and v2K of the development drive coupling motor 126 when the development drive is stopped from the table illustrated in FIG. Next, in S1315, the CPU 301 starts to rotate the development drive coupling motor 126 in the normal rotation (clockwise) direction at the correction speed v2Y. In S1316, the CPU 301 determines whether the output signal is stable based on the output signal from the inductive sensor 124Y provided in the process unit 120Y. If the stable state is detected, the process proceeds to S1317. Repeats the process of S1316. In S1317, the CPU 301 determines that the developing sleeve 244Y has stopped, changes the speed of the developing drive coupling motor 126 to the correction speed v2M, and starts rotation. In S1318, the CPU 301 determines whether the output signal is stable based on the output signal from the inductive sensor 124M provided in the process unit 120M. If a stable state is detected, the process proceeds to S1319. Repeats the process of S1318.

  In step S1319, the CPU 301 determines that the developing sleeve 244M has stopped, changes the speed of the developing drive coupling motor 126 to the correction speed v2C, and starts rotation. In S1320, the CPU 301 determines whether the output signal is stable based on the output signal from the inductor sensor 124C provided in the process unit 120C. If a stable state is detected, the process proceeds to S1321, and if it is not detected. Repeats the process of S1320. In S1321, the CPU 301 determines that the developing sleeve 244C has stopped, changes the speed of the developing drive coupling motor 126 to the correction speed v2K, and starts rotation. In S1322, the CPU 301 determines whether the output signal is stable based on the output signal from the inductive sensor 124K provided in the process unit 120K. If a stable state is detected, the process proceeds to S1323, and if not detected. Repeats the process of S1322.

  Next, in S1323, based on the output from the HP detection sensor 304, the CPU 301 determines whether or not the control cam 258K is in the HP position (the position in which the HP detection sensor 304 is detecting the slit 421). to decide. If the CPU 301 determines that the HP detection sensor 304 has detected the slit 421, the CPU 301 proceeds to step S1324, and if not, repeats the processing in step S1323. In step S <b> 1324, the CPU 301 stops driving the development drive connection motor 126. In step S1325, the CPU 301 stops the developing motor 125 and ends the process. By the above-described correction control of the rotation speed of the development drive coupling motor 126, it is possible to eliminate the time variation until the phase (rotation angle) at which the development coupling state of the control cam 258 of each process unit 120 changes is reached.

  Further, the control sequence shown in the flowchart in FIG. 11 is a control sequence for performing color printing on a recording material. On the other hand, when monochrome printing is performed, it is sufficient that only the developing sleeve 244K and the conveying screw 240K of the K (black) process unit 120K are drivingly connected. That is, in FIG. 6A described above, the phase angle is 315 degrees to 0 degrees (360 degrees), Y (yellow), M (magenta), and C (cyan) are stopped, and K (black ) Only being driven. At the time of color printing, the CPU 301 stops the rotation of the developing drive coupling motor 126 in S1312 when a change in the output signal of the inductive sensor 124K is detected in S1311 of FIG. On the other hand, in the case of monochrome printing, the processing order of FIG. 11 is changed as follows. When the change in the output signal of the inductive sensor 124K is detected in S1311 of FIG. 11, the CPU 301 does not perform the processing of S1312, S1313 at this time, and then performs the processing of S1314. That is, when a change in the output signal of the inductive sensor 124K is detected, the CPU 301 does not stop the rotation of the development drive coupling motor 126 at this point, and does not determine the end of printing. A process of reading the correction speed v2 is performed. In S1315 to S1320, when the rotation stop of the developing sleeve 244 and the conveying screw 240 of each of the Y (yellow), M (magenta), and C (cyan) process units 120 is detected, the developing driving which is the processing of S1312. The connection motor 126 is stopped. As a result, the developing sleeve 244 and the conveying screw 240 of each process unit 120 of Y (yellow), M (magenta), and C (cyan) are stopped. Then, only the developing sleeve 244K and the conveying screw 240K of the K (black) process unit 120K are rotated. Next, the CPU 301 determines whether or not the printing, which is the process of S1313, is finished (here, monochrome printing is finished). When the monochrome printing is finished, the process proceeds to S1321, and when it is not finished, the process of S1313 is performed. repeat. In step S1321, the CPU 301 sets the speed of the development drive coupling motor 126 to the correction speed v2K, starts rotation, and performs the processing in and after step S1321 based on the flowchart of FIG. Through the processing described above, the development drive timing can be corrected in monochrome printing as well as in color printing.

  In the above-described embodiments, the image forming apparatus including the intermediate transfer belt 130 has been described. However, the above-described embodiments may be applied to an image forming apparatus including a conveyance belt that conveys a recording material.

  As described above, according to this embodiment, it is possible to correct the deviation between the drive timing of the developing sleeve and the high-pressure control timing. In this embodiment, the time from when the drive of the control cam that performs drive connection of the image forming unit is started to when the drive connection to the process unit is actually performed is measured. Then, the drive timing shift of each process unit is corrected by correcting the drive speed of the control cam according to the shift between the actually measured time and the design time. Thereby, even if the gear teeth mesh when the gear is assembled, the timing of the development drive and the high voltage output of each process unit can be eliminated. As a result, even when the control cam of each process unit cannot satisfy the designed phase difference, the time until each control cam reaches the phase (rotation angle) corresponding to the development drive connection / disconnection is as designed. It becomes possible to be time. For this reason, it is possible to appropriately perform the timings of driving / stopping the developing device in each process unit and starting (high voltage application) / falling (high voltage application stop) of the high voltage control unit at a predetermined timing. It becomes. As a result, it is possible to reduce the influence on the contamination in the image forming apparatus, the abnormal image and the life of the parts due to the toner fog or the carrier adhering to the image defect.

124 Induct sensor 126 Development drive coupling motor 244 Development sleeve 245 High pressure control unit 258 Control cam 301 CPU

Claims (14)

A plurality of developing means for developing the electrostatic latent image, comprising a toner carrier for supplying toner to the electrostatic latent image formed on the image carrier;
High voltage control means for controlling the start and stop of application of a high voltage to the toner carrier;
Development drive means for driving the toner carrier;
Coupling means for performing drive coupling / disconnection for transmitting the driving of the development driving means to the toner carrier according to a phase angle;
Connection drive means for rotationally driving the connection means;
A detecting means provided in the developing means for detecting driving or stopping of the toner carrier;
Control means for controlling the driving or stopping of the toner carrier by the connection driving means;
With
The control means may be configured so that the connection driving means is driven in a predetermined manner so that the toner carrier is driven or stopped at a timing when the high voltage controller starts or stops applying a high voltage to the toner carrier. The drive speed of the connection drive means is determined according to the phase angle at which the connection means is driven from when the drive of the connection means is started at the drive speed until the detection means detects the drive or stop of the toner carrier. An image forming apparatus characterized by correcting the above. The developing unit includes a toner conveying member that is driven together with the toner carrier and conveys toner to the toner carrier;
The image forming apparatus according to claim 1, wherein the detecting unit detects driving or stopping of the toner carrier by detecting a density of toner conveyed by the toner conveying member.   3. The image forming apparatus according to claim 2, wherein the control unit determines that the toner carrier has been driven or stopped by continuously detecting the toner density a predetermined number of times. apparatus.   The image forming apparatus according to claim 2, wherein the detection unit is an inductive sensor.   The image forming apparatus according to claim 1, wherein the development driving unit is a single development motor.   The measurement of the phase angle of the connecting means from when the connecting driving means starts driving the connecting means at a predetermined driving speed until the detecting means detects the driving or stopping of the toner carrier is performed by the power source of the apparatus. 6. The image forming apparatus according to claim 1, wherein the image forming apparatus is turned on.   The measurement of the phase angle of the connecting means from when the connecting driving means starts driving the connecting means at a predetermined driving speed until the detecting means detects the driving or stopping of the toner carrier is as follows. The image forming apparatus according to claim 1, which is performed at the end of printing. The connecting means is provided for each developing means,
The image forming apparatus according to claim 1, wherein the connection driving unit drives a plurality of the connection units. The coupling means includes a pair of drive transmission members that are rotatably provided and can transmit drive when engaged with each other.
The image forming apparatus according to claim 1, wherein the connecting unit transmits the driving of the developing driving unit to the toner carrier via the pair of driving transmission members.   The connection means includes a drive connection state in which the state of the pair of drive transmission members engage with each other and transmits the drive of the development drive means to the toner carrier, and a state in which the pair of drive transmission members engage with each other. There are two states: a released state in which the driving of the development driving unit is not transmitted to the toner carrier, and the two states are switched according to the phase angle driven by the connection driving unit. The image forming apparatus according to claim 9.   11. The phase angle at which the connecting unit switches to the driving connection state and the phase angle at which the connection unit switches to the release state are provided with a constant phase angle interval for each developing unit. The image forming apparatus described.   12. The image forming apparatus according to claim 8, wherein one of the connection units includes a position detection unit that detects a home position that is a reference of a phase angle of the connection unit. apparatus.   The start or stop of the application of a high voltage to the toner carrier by the high voltage control means is performed at a predetermined phase angle interval for each of the developing means. The image forming apparatus described in the item.   The control means is a phase in which the connection means is driven from when the connection drive means starts driving the connection means at a predetermined drive speed until the detection means detects the drive or stop of the toner carrier. The time required for each of the developing means to reach the corner is the same as the time required for the connection driving means to drive the connection means at the predetermined phase angle interval at a predetermined drive speed. The image forming apparatus according to claim 13, wherein the connecting driving unit corrects the speed at which the connecting unit is driven for each developing unit.

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