JP6419272B2 - Image forming apparatus - Google Patents

Description

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

  Conventionally, there are various image forming apparatuses adopting an electrophotographic system or an electrostatic recording system in an image forming process. These various image forming apparatuses include the following types. As an example, there is an intermediate transfer tandem type in which a plurality of process cartridges are arranged in a line along the rotation direction of a rotatable intermediate transfer belt, and a color image is formed via the intermediate transfer belt.

  In such an intermediate transfer tandem type image forming apparatus, an endless intermediate transfer belt is stretched by a plurality of stretching rollers including a driving roller. This image forming apparatus has a primary transfer portion formed by a photosensitive drum and a primary transfer roller which are arranged to face each other at a position sandwiching an intermediate transfer belt between two stretching rollers. In addition, a secondary transfer inner roller and a secondary transfer outer roller that are disposed opposite to each other so as to sandwich the intermediate transfer belt on the downstream side in the rotation direction of the intermediate transfer belt and that can move toward and away from the secondary transfer inner roller. A secondary transfer portion is formed.

  In an intermediate transfer tandem type full-color image forming apparatus, for example, a monochrome mode (image formation only with black (Bk) is performed in a configuration in which an image is formed (image formation) using four colors (yellow, magenta, cyan, and black). (Bk single color mode) can be executed. This configuration prevents yellow, magenta, and cyan photosensitive drums and developing units from rotating when they are not required to form a monochrome image, thereby preventing deterioration of the photosensitive drum and developer and reducing the running cost of the device. Can be.

  In the full color mode in which a full color image is formed using all four colors, the intermediate transfer belt is brought into contact with all the photosensitive drums of yellow, magenta, cyan, and black that operate. In contrast, in the monochrome mode, the intermediate transfer belt is temporarily separated from the stopped photosensitive drums of yellow, magenta, and cyan. In addition, an all-separation mode that separates the intermediate transfer belt from all the stopped yellow, magenta, cyan, and black photosensitive drums during maintenance of the transfer unit equipped with the intermediate transfer belt, etc., and during transportation of the image forming apparatus. Is also present.

  In such an image forming apparatus, a plurality of primary transfer rollers and stretching rollers are supported by a fixed frame that supports a plurality of stretching rollers via a swingable movable frame, and the movable frame is selectively swung. There exists what was comprised so that it might do (refer patent document 1). As a result, the monochrome transfer mode is executed by separating the primary transfer rollers other than black from the corresponding photosensitive drum, and the full color mode is executed by moving all the primary transfer rollers to the corresponding photosensitive drum side. Alternatively, as another mode, there is also known an image forming apparatus that is capable of executing an all-separation mode in which all primary transfer rollers are separated from a corresponding photosensitive drum during maintenance or transportation of the apparatus.

  On the other hand, there is also an image forming apparatus having a separation mode in which the secondary transfer outer roller is separated from the intermediate transfer belt when the toner image does not exist on the intermediate transfer belt. This image forming apparatus aims to extend the life of the secondary transfer roller by preventing contamination and deterioration of the secondary transfer roller due to toner adhering to an area other than the image forming area on the intermediate transfer belt. In some of these apparatuses, the secondary transfer outer roller is further separated at the time of maintenance of the secondary transfer unit including the secondary transfer outer roller or the like or when the apparatus is transported. Even in such an apparatus, the position in the contact mode in which the secondary transfer outer roller contacts the intermediate transfer belt during image formation, the position in the separation mode in which the secondary transfer outer roller is separated from the intermediate transfer belt, and both It is switched to a standby position between positions.

  As described above, in the configuration having the contact mode of the primary transfer roller and the secondary transfer outer roller in three modes, one sensor and one motor are used to reduce user stress by further shortening the switching time and to reduce the cost of the apparatus. A configuration that switches between the three modes is required. As an image forming apparatus having three modes, there is an image forming apparatus that is applied not only to a transfer roller but also to a developing roller or the like, in which a separation mode is set as a standby position and is switched by one sensor and one motor (Patent Document 2). reference).

JP 2010-282124 A JP 2006-323235 A

  However, in the image forming apparatus described in Patent Document 1, since the standby position is the separation mode, there is a possibility that errors may accumulate if the monochrome mode and the color mode are repeatedly switched between forward and reverse rotations of the motor. In this case, finally, there is a possibility that the toner image is not transferred due to being unable to stop in a desired mode, or the life is shortened. In order to avoid this, it is conceivable to always set the rotation direction of the motor to one direction, but in this case, the time required for switching becomes long. Thus, there has been a trade-off between switching the mode reliably and switching the mode in a short time.

  Also in the image forming apparatus described in Patent Document 2, all the flags need to be detected once in order to return to the standby position when the apparatus is turned on or when the separation switching is initialized. For this reason, the motor has to be rotated at least once each time, and there has been a problem that the apparatus startup time is prolonged.

  As described above, when mode switching or device start-up time is lengthened, the downtime of the device becomes long, which may cause new problems such as stress on the user and short life of the device.

  The present invention avoids the occurrence of problems such as user stress and shortening of the life of the apparatus by avoiding mode switching and prolonged apparatus start-up time, and suppressing the prolongation of downtime to increase productivity. An object is to provide an image forming apparatus.

An image forming apparatus according to the present invention includes an image carrier, a motor that can be driven to rotate in both directions, and a cam that is rotated by the motor, and the position of the moving object is determined by switching the phase of the cam. A moving mechanism that can be changed to a first arrangement arranged at the time of formation, a second arrangement different from the first arrangement arranged at the time of image formation, and a third arrangement that is not arranged at the time of image formation ; a sensor for detecting the phase of the cam, on the basis of the detection result of the sensor, in an image forming apparatus and a control unit for controlling the driving of the motor, before Symbol sensor corresponds to the first arrangement Only the phase of the cam is configured to be detectable , and the moving mechanism is configured to reciprocate between the first arrangement and the second arrangement without going through the third arrangement , The control unit includes the second arrangement and When switching the third arrangement, the switching from the second arrangement to the third arrangement is allowed without going through the first arrangement, but without going through the first arrangement. The switching from the third arrangement to the second arrangement is not allowed .
The image forming apparatus according to the present invention includes an image carrier, a motor that can be driven to rotate in both directions, and a cam that is rotated by the motor. A moving mechanism that can be changed to a first arrangement that is arranged at the time of image formation, a second arrangement that is different from the first arrangement that is arranged at the time of image formation, and a third arrangement that is not arranged at the time of image formation. And a sensor that detects the phase of the cam and a control unit that controls driving of the motor based on a detection result of the sensor, wherein the sensor corresponds to the first arrangement. Only the phase of the cam is configured to be detectable, and the moving mechanism is configured to reciprocate between the first arrangement and the second arrangement without going through the third arrangement, The object to be moved is the image carrier. A transfer member provided so as to be capable of contacting and separating from a body and transferring an image carried on the image carrier to a recording material; and in the first arrangement, the transfer member is attached to the image carrier. When in the second arrangement, the transfer member is positioned at a first separation position that is separated from the image carrier, and in the third arrangement, the transfer member is in contact with the transfer member and the transfer member. The separation distance between the image carriers is a second separation position that is larger than the first separation position.

  According to the present invention, it is possible to prevent the occurrence of problems such as user stress and shortening of the life of the apparatus by avoiding mode switching and lengthening of the apparatus start-up time and suppressing the increase in downtime to increase productivity. It becomes possible.

1 is a cross-sectional view illustrating an overall configuration of an image forming apparatus according to a first embodiment of the present invention. FIG. 3 is a perspective view showing an attaching / detaching direction of the intermediate transfer belt unit according to the first embodiment. 1 is a schematic perspective view showing a primary transfer contact / separation mechanism according to a first embodiment. 1 is a schematic perspective view showing a primary transfer contact / separation mechanism according to a first embodiment. 1 is a schematic perspective view showing a primary transfer contact / separation mechanism according to a first embodiment. (A), (b) is a front view which shows the cam member at the time of full color image formation which concerns on 1st Embodiment. (A), (b) is a front view which shows the cam member at the time of the monochrome image formation which concerns on 1st Embodiment. (A), (b) is a front view which shows the cam member at the time of the full separation which concerns on 1st Embodiment. 1 is a schematic perspective view showing a drive transmission device according to a first embodiment. The schematic perspective view which shows the driven gear train which concerns on 1st Embodiment. (A)-(d) is the schematic which shows a coupling part. (A)-(c) is schematic which shows the state of the coupling part before the intermediate transfer belt unit 12 starts detachment | leave. (A)-(c) is the schematic which shows the state by which the contact of the 1st engaging part of a coupling part and the 2nd engaging part was cancelled | released. (A)-(c) is the schematic which shows the distance between the rotating shafts of a coupling part. The schematic diagram which shows operation | movement with the flag part and sensor of the drive transmission apparatus which concern on 1st Embodiment. The schematic diagram which shows another operation | movement with the flag part and sensor of the drive transmission apparatus which concerns on 1st Embodiment. The schematic diagram of the state seen from the arrow U direction of FIG. 9 which shows the rotation position of the flag gear which concerns on 1st Embodiment. 5 is a flowchart showing a control flow relating to switching from a full color mode to a monochrome mode. 7 is a flowchart showing a control flow relating to switching from a monochrome mode to a full color mode. The flowchart which shows the control flow which concerns on the switch from full color mode to all separation mode. (A), (b) is explanatory drawing which shows the structure in a comparative example. (A) is a cross-sectional view of the second embodiment of the present invention with the secondary transfer outer roller in contact with the drive roller, and (b) is a cross-section with the secondary transfer outer roller moved to the standby position. Figure. Sectional drawing of the state which moved the secondary transfer outer roller in 2nd Embodiment to the separation position.

<First Embodiment>
Hereinafter, embodiments according to the present invention will be described in detail with reference to the drawings. Throughout the drawings, the same reference numerals indicate the same or corresponding parts. In the present embodiment, main parts relating to the formation and transfer of a toner image (toner image) will be mainly described. However, the present invention adds a necessary device, equipment, and housing structure to a printer and various printing machines. It can be implemented in various applications such as a copying machine, a fax machine, and a multifunction machine.

[Image forming apparatus]
First, an image forming apparatus according to the present embodiment will be described with reference to FIG. FIG. 1 is a schematic cross-sectional view showing a schematic configuration of an image forming apparatus 50 such as a tandem intermediate transfer type full-color printer in this embodiment.

  As shown in FIG. 1, the image forming apparatus 50 has an apparatus main body 50a. The apparatus main body 50a includes a control unit 45 having a ROM, a RAM, and a CPU that controls each unit of the image forming apparatus 50. The controller 45 is connected to a primary transfer contact / separation mechanism 30 connected via a drive motor 41 described later, another drive mechanism (not shown), and the like.

  In the image forming apparatus 50, the toner image is formed by the photosensitive drum 1 (1a to 1d) as an image carrier (photosensitive member), the charging roller 2 (2a to 2d) as a charging unit, and the exposure unit 3 as an exposure unit. The developing unit 4 (4a to 4d) as developing means is used.

  Hereinafter, for example, when referring to the photosensitive drums individually, they are expressed as photosensitive drums 1a, 1b, 1c, and 1d, and when the photosensitive drums are collectively referred to as photosensitive drums 1, they are expressed. The same applies to other parts.

[Toner image formation process]
Each of the photosensitive drums 1a, 1b, 1c, and 1d is irradiated with a laser on the basis of the image information and charging rollers 2a, 2b, 2c, and 2d for uniformly charging the surface of the photosensitive drum in order along the rotation direction. And an exposure unit 3 for forming an electrostatic latent image on the photosensitive drum. Developing units 4a, 4b, 4c, and 4d, and primary transfer rollers 12a, 12b, 12c, and 12d that primarily transfer a toner image on the photosensitive drum to an intermediate transfer belt 12e as a movable body are arranged. The developing units 4a to 4d attach toner to the electrostatic latent image on the photosensitive drum to visualize the toner image. Further, a cleaning means 8 (8a, 8b, 8c, 8d) for removing post-transfer toner remaining on the surface of the photosensitive drum after the primary transfer is disposed.

  The primary transfer rollers 12a to 12d are driven by a drive motor 41 formed of a pulse motor such as a stepping motor, so that an intermediate transfer belt 12e as a moving body is arranged in three different positions with respect to the photosensitive drums (image carriers) 1a to 1d ( Position). The drive motor 41 composed of a pulse motor is configured to be capable of rotating in both directions based on the number of pulses of the drive signal. The above three arrangements will be described later.

  The charging roller 2 and the cleaning means 8 are integrally unitized as a cleaning unit 5 (5a, 5b, 5c, 5d). The photosensitive drum 1, the cleaning unit 5, the developing unit 4, and the like are integrally formed as a process cartridge 7 (7a, 7b, 7c, 7d).

  Each of the process cartridges 7a to 7d is configured to be insertable and detachable (detachable) from the apparatus main body 50a. The four process cartridges 7a to 7d are different in that images of different colors are formed using yellow (Y), magenta (M), cyan (C), and black (Bk) toners. The basic configuration is the same.

  Each of the developing units 4a, 4b, 4c, and 4d includes developing rollers 24a, 24b, 24c, and 24d, developer application rollers 25a, 25b, 25c, and 25d, and a toner container (not shown). Each toner container contains toner of each color of yellow (Y), magenta (M), cyan (C), and black (Bk).

  The cleaning units 5a, 5b, 5c, and 5d include photosensitive drums (image bearing members and photosensitive members) 1a, 1b, 1c, and 1d, charging rollers 2a, 2b, 2c, and 2d, and cleaning units 8a, 8b, 8c, and 8d. And a transfer residual toner collecting container (not shown).

  Each of the photosensitive drums 1a to 1d is configured by applying an organic optical conductor layer (OPC) to the outer peripheral surface of an aluminum cylinder, and both ends thereof are rotatably supported by flanges. When a driving force is transmitted to one end of each of the photosensitive drums 1a to 1d from a driving motor (not shown), the photosensitive drums 1a to 1d are rotationally driven in the clockwise direction indicated by arrows in FIG.

  Each of the charging rollers 2a to 2d is a conductive roller formed in a roller shape. The conductive rollers are brought into contact with the surfaces of the photosensitive drums 1a to 1d, and a charging voltage is applied from a power supply circuit (not shown), so that the surfaces of the photosensitive drums 1a to 1d are uniformly charged. The The exposure unit 3 is arranged below the process cartridges 7a to 7d in the vertical direction, and performs exposure based on the image signal to the photosensitive drums 1a, 1b, 1c, and 1d.

  The developing rollers 24a to 24d are disposed adjacent to the respective surfaces of the photosensitive drums 1a to 1d, and are driven to rotate by a driving unit (not shown), and are applied with a voltage, whereby the photosensitive drums 1a to 1d are applied. Develop each surface of.

  With the above configuration, yellow (Y), magenta (M), cyan (C), and black (Bk) toner images are formed on the respective surfaces of the photosensitive drums 1a to 1d. The toner images formed on the respective surfaces of the photosensitive drums 1a to 1d are sequentially transferred onto the surface of the intermediate transfer belt (movable body) 12e sequentially. Thereafter, the toner remaining on each surface of the photosensitive drums 1a to 1d is removed by the corresponding cleaning means 8a to 8d, and collected in a transfer residual toner collection container (not shown) in the cleaning units 5a to 5d.

[Transfer and fixing process to recording material]
A paper feed cassette 11 that stores the recording material S is disposed below the apparatus main body 50a. The paper feed cassette 11 is mounted so that it can be pulled out toward the front side of the apparatus main body 50a (the left side of the apparatus main body 50a in FIG. 1). After the user pulls out the paper cassette 11 and pulls it out from the apparatus main body 50a, the recording material S is stored and loaded in the paper cassette 11 and inserted into the apparatus main body 50a, whereby the recording material S is replenished. Can be performed.

  At the time of image formation, the recording material S is sent out from the paper feeding cassette 11 by the paper feeding roller 9 of the paper feeding device 13 and is conveyed to the registration roller pair 17 through the conveying roller pair 10. The paper feeding device 13 includes a half-moon shaped paper feeding roller 9, a separating unit 23, and a transport roller pair 10 that sandwiches and transports the recording material S. A registration roller pair 17 is disposed downstream of the conveyance roller pair 10.

  The paper feed roller 9 is disposed so as to be able to contact the recording material S stored in the paper feed cassette 11, and is rotated at a predetermined control timing by the control unit 45 to send out the recording material S. The sent recording material S is separated one by one by the separating means 23 and sent to the downstream conveying roller pair 10. Thereafter, the recording material S is conveyed to the registration roller pair 17 by the conveyance roller pair 10, temporarily stopped by the registration roller pair 17, and then sent to the secondary transfer unit 15 at a predetermined timing.

  On the other hand, in the intermediate transfer belt unit 12 as an intermediate transfer unit, a toner image is carried on the intermediate transfer belt 12e formed by the primary transfer process, and the toner image is conveyed to the secondary transfer unit 15 by the intermediate transfer belt 12e. . The four-color toner images on the intermediate transfer belt 12e are secondarily transferred to the recording material S conveyed by the registration roller pair 17 at the secondary transfer portion 15 including the secondary transfer nip portion at the same timing. Is done. That is, in the secondary transfer unit 15, a bias is applied to the secondary transfer outer roller 16, and the toner image on the intermediate transfer belt 12 e is secondarily transferred onto the recording material conveyed to the secondary transfer unit 15. .

  The secondary transfer outer roller 16 is disposed on the surface of the intermediate transfer belt 12e at a position facing the driving roller 12f as the secondary transfer inner roller. The secondary transfer outer roller 16 is provided in a secondary transfer unit 61 configured to be detachable from the apparatus main body 50a. The secondary transfer outer roller 16 sandwiches the intermediate transfer belt 12e between the driving roller 12f, and the secondary transfer portion 15 is formed between the secondary transfer outer roller 16 and the intermediate transfer belt 12e. Yes.

  The fixing device 14 disposed downstream of the secondary transfer unit 15 includes a fixing nip N between the fixing belt 14a in which the heating body 14c is disposed and the fixing belt 14a being pressed by the fixing belt 14a. And a pressure roller 14b to be formed. The fixing belt 14a is an endless cylindrical belt, and the outer peripheral surface thereof is located on the toner image surface side on the recording material. The heating element 14c is disposed inside the fixing belt 14a, and the pressure roller 14b is pressed against the fixing belt 14a.

  In this fixing device 14, when the pressure roller 14b is rotationally driven by a driving means (not shown), the fixing belt 14a rotates along with it (driven rotation), and the fixing belt 14a is heated by the heating element 14c. Is done. When the recording material S conveyed from the secondary transfer unit 15 is nipped and conveyed by the fixing nip N between the fixing belt 14a and the pressure roller 14b, the toner image is heated and pressed by the fixing nip N. To be fixed on the recording material.

  A paper discharge roller pair 20 is disposed downstream of the fixing device 14. The recording material S fixed by the fixing device 14 is discharged to the paper discharge tray 100 above the apparatus main body 50a via the paper discharge roller pair 20.

[Intermediate transfer belt unit]
Next, the intermediate transfer belt unit 12 in this embodiment will be described with reference to FIGS. 1 and 2. FIG. 2 is a perspective view illustrating the entire image forming apparatus 50 so that the attaching / detaching direction (direction of arrow R) of the intermediate transfer belt unit 12 can be understood.

  The intermediate transfer belt unit 12 in the present embodiment is configured as a unit that can be attached to and detached from the apparatus main body 50a. As shown in FIG. 2, the intermediate transfer belt unit 12 is configured to be detachable from the apparatus main body 50a in the direction of the arrow R. An opening / closing door 50b supported to be openable and closable with respect to the apparatus main body 50a is supported on one side of the apparatus main body 50a (the right side in FIGS. 1 and 2).

  As shown in FIG. 2, when the intermediate transfer belt unit 12 is attached to and detached from the apparatus main body 50a with the open / close door 50b opened, a guide portion 62 that guides the intermediate transfer belt unit 12 in the attachment / detachment direction (arrow R direction). It is provided on both sides in the attaching / detaching direction. An inclined guide surface 62a is formed on the front side of the guide portion 62. The inclined guide surface 62a guides the guide portion 62 while pushing back against a biasing force of a driven coupling 47 (described later) provided on the intermediate transfer belt unit 12 side. . The inclined guide surface 62a is also formed in a guide portion 62 (not shown) located on the near side in FIG. In addition, a drive coupling 46 (described later) mounted on the apparatus main body side is disposed in a protruding state on the back side of the one guide portion 62.

  The intermediate transfer belt unit 12 includes an intermediate transfer belt 12e, a driving roller 12f as a secondary transfer inner roller, a driven roller 12g, primary transfer rollers 12a to 12d as primary transfer means, and a cleaning device 22. Further, the intermediate transfer belt unit 12 has a primary transfer contact / separation mechanism 30 (see also FIG. 3). The endless belt-like intermediate transfer belt 12e is stretched so as to be rotatable in the circumferential direction by a driving roller 12f and a driven roller 12g, which are a plurality of rollers.

  The driven roller 12g is urged in the direction of arrow E in FIG. 1 by an urging means (not shown) to apply a predetermined tension (tension force) to the intermediate transfer belt 12e. The intermediate transfer belt 12e is rotated at a predetermined speed in the direction of arrow F in FIG. 1 when the driving roller 12f is driven to rotate by receiving the driving force of a motor (not shown).

  The primary transfer rollers 12a to 12d are disposed on the inner peripheral side of the intermediate transfer belt 12e so as to face the corresponding ones of the photosensitive drums 1a to 1d, respectively, and a biasing member 31 such as a compression coil spring (see FIG. 3). Is biased toward the corresponding photosensitive drum. By applying primary transfer bias voltages to the primary transfer rollers 12a to 12d, the toner images formed on the surfaces of the photosensitive drums 1a to 1d are sequentially primary transferred onto the intermediate transfer belt 12e. As described above, when the four-color toner images are primarily transferred and superimposed on the intermediate transfer belt, the toner images are conveyed to the secondary transfer unit 15 by the intermediate transfer belt 12e.

  When the toner image on the intermediate transfer belt is secondarily transferred to the recording material S by the secondary transfer unit 15, the transfer residual toner remaining on the intermediate transfer belt 12 e is removed by the cleaning device 22. The removed transfer residual toner is collected in a transfer residual toner collection container (not shown) disposed in the apparatus main body 50a via a transfer residual toner conveyance path (not shown).

  The intermediate transfer belt unit 12 is operated by the primary transfer contact / separation mechanism 30 so that the primary transfer rollers 12a of Y, M, and C that are in contact with the photosensitive drums 1a, 1b, and 1c through the intermediate transfer belt 12e at the time of color image formation. , 12b, 12c are separated from the photosensitive drums 1a to 1c. This is performed to extend the life of the photosensitive drums 1a to 1c by avoiding that the photosensitive drums 1a to 1c that are not used at the time of image formation in the monochrome mode (Bk single color mode) rub against the photosensitive drums 1a to 1c. Is called.

  Further, the primary transfer contact / separation mechanism 30 has a separation configuration of the primary transfer roller 12d corresponding to Bk that operates independently of the separation configuration of the primary transfer rollers 12a, 12b, 12c corresponding to Y, M, and C. doing. This avoids scratches caused by rubbing between the intermediate transfer belt 12e and the photosensitive drum 1d when the belt unit 12 and the cartridges 7a to 7d are respectively attached to and detached from the apparatus main body 50a. This is to prevent image defects.

[Details of primary transfer contact / separation mechanism]
Next, the details of the primary transfer contact / separation mechanism 30 in the present embodiment will be described with reference to FIGS. 3, 4, and 5. 3 is a schematic perspective view (including phase G) showing the primary transfer contact / separation mechanism 30 according to the present embodiment, and FIG. 4 is a schematic perspective view (including phase H) showing the primary transfer contact / separation mechanism 30. FIG. 5 is a schematic perspective view (including phase L) showing the primary transfer contact / separation mechanism 30. 3 to 5, the intermediate transfer belt 12e is illustrated in a transparent state.

  As shown in FIGS. 3 to 5, the primary transfer contact / separation mechanism 30 includes slide members 33a, 33b, 33c, and 33d, and cam members 34a and 34b (see FIG. 6A) and 34c (see FIG. 6B). )), 34d. As shown in FIGS. 6 (a), 7 (a) and 8 (a), the cam member 34a and the cam member 34b are respectively fixed to both ends of the cam shaft 32 so as to be symmetrical and have the same phase. ing. As shown in FIGS. 6 (b), 7 (b) and 8 (b), the cam member 34c and the cam member 34d are respectively fixed to both ends of the cam shaft 32 so as to be symmetrical and have the same phase. ing.

  The cam shaft 32 extends in the width direction of the intermediate transfer belt unit 12 (the width direction of the intermediate transfer belt 12e) while being supported so as to be rotatable by receiving the rotation of the drive motor 41. Rotation from the driven coupling 47 is transmitted to the cam shaft 32 via a transmission gear train 49 (see FIG. 10). The intermediate transfer belt 12e is driven by the rotational drive of the drive motor 41 by the cam shaft 32, the cam members (rotating members) 34a to 34d, the driven coupling 47, the transmission gear train 49, and the like. A moving mechanism that can be changed in arrangement is configured.

  As shown in FIGS. 3 to 5, slide members 33a and 33b are respectively disposed at both ends of the primary transfer rollers 12a, 12b and 12c, and slide members 33c and 33d are disposed at both ends of the primary transfer roller 12d. Are arranged respectively. The slide members 33 a and 33 b and the slide members 33 c and 33 d are arranged so as to be parallel to each other with a predetermined interval in the width direction of the intermediate transfer belt unit 12. The slide members 33a and 33b and the slide members 33c and 33d are supported by a slide mechanism (not shown) so as to be movable in the left-right direction in FIG.

  The paired slide members 33a, 33b are moved in the direction of arrow Q in FIG. 3 (the circumferential direction of the intermediate transfer belt 12e) by the rotation of the paired cam members 34a, 34b. The paired slide members 33c and 33d are moved in the direction of arrow Q in FIG. 3 by the rotation of the paired cam members 34c and 34d. Each of the cam members 34a, 34b, 34c, and 34d is formed in a fan shape that spreads in the range of 90 ° in the radial direction about the cam shaft 32 having a circular cross section. As the slide members 33a to 33d move in the direction of the arrow Q, the primary transfer rollers 12a, 12b, and 12c are in contact with and separated from the photosensitive drums 1a, 1b, and 1c, and the primary transfer roller 12d is in contact with the photosensitive drum 1d. The separation position is changed.

[Operation of slide member and cam member]
Next, regarding the operation of the slide members 33a to 33d and the cam members 34a to 34d, FIGS. 3 to 5 and FIGS. 6 (a), 6 (b), 7 (a), 7 (b) and 8 (a). ) And (b) will be described in detail.

  3 corresponds to FIGS. 6A and 6B, FIG. 4 corresponds to FIGS. 7A and 7B, and FIG. 5 corresponds to FIGS. 8A and 8B. Yes. FIGS. 6A and 6B are diagrams illustrating the operations of the cam members 34a to 34d and the slide members 33a to 33d during color image formation (full color mode, full contact arrangement). FIGS. 7A and 7B are diagrams illustrating the operation of the cam members 34a to 34d and the slide members 33a to 33d when a monochrome image is formed (particularly disposed in the monochrome mode). FIGS. 8A and 8B are diagrams illustrating the operation of the cam members 34a to 34d and the slide members 33a to 33d at the time of full separation (all separation mode, full separation arrangement).

  In the full color mode (all contact arrangement), the intermediate transfer belt (movable body) 12e is brought into contact with all of the photosensitive drums 1a to 1d which are a plurality of image carriers. In the monochrome mode (partially abutting arrangement), the intermediate transfer belt 12e is brought into contact with a part (the photosensitive drum 1d) of the photosensitive drums 1a to 1d. In the all separation mode (all separation arrangement), the intermediate transfer belt 12e is separated from all of the photosensitive drums 1a to 1d. The control unit (control means) 45 is driven by a drive motor (pulse motor) 41 to control a full color mode (full contact arrangement), a monochrome mode (partial contact arrangement), and a full color mode (full contact arrangement). And switch.

Slide members 33a, 33b is a portion corresponding to the cam shaft 32 is provided with an engaging portion 33S ₁ having a cam member 34a, respectively insertable rectangular space 34b. The slide member 33c, 33d is a portion corresponding to the cam shaft 32 is provided with an engaging portion 33S ₂ having a cam member 34c, respectively insertable rectangular space 34d.

Then, the slide member 33a, 33b, the cam member 34a which is inserted into the engaging portion 33S _1, so as to follow the rotational movement of the 34b, always in the right direction in FIGS. 6 (a) in the biasing member (not shown) It is energized. The slide member 33c, 33d, the cam member 34c which is inserted into the engaging portion 33S _2, so as to follow the rotational movement of the 34d, always in the right direction shown in FIG. 6 (b) in the biasing member (not shown) It is energized.

[In full color mode]
At the time of color image formation, the cam members 34a, 34b in FIG. 3 transmit power to the cam shaft 32 from a drive transmission device 40, which will be described later, so that the phase G shown in FIG. , 33b are held in the position J shown in FIG. As a result, both axial ends of the primary transfer rollers 12a, 12b, and 12c are released from the claw portions 38 of the slide members 33a and 33b, and are pressed by the urging member 31, thereby passing through the intermediate transfer belt 12e. Are in contact with the photosensitive drums 1a, 1b, and 1c, respectively.

  At the same time, the cam members 34c and 34d in FIG. 3 are in the state of the phase G shown in FIG. 6B by the rotation of the cam shaft 32, and the slide members 33c and 33d are held at the position J shown in FIG. 6B. Is done. Thus, both axial ends of the primary transfer roller 12d in the axial direction of the primary transfer roller 12d are released from the claw portion 39 of the slide member, and are pressed against the photosensitive drum 1d via the intermediate transfer belt 12e by being pressed by the urging member 31.

  As described above, during color image formation, the primary transfer rollers 12a, 12b, 12c, and 12d are in full contact with the corresponding photosensitive drums 1a, 1b, 1c, and 1d via the intermediate transfer belt 12e.

[Monochrome mode]
At the time of monochrome image formation, the cam members 34a and 34b in FIG. 4 are rotated by 90 ° in the counterclockwise direction (direction of arrow C) in FIG. Thus, the slide members 33a and 33b are held at the position K shown in FIG. In other words, the sliding member 33a, the engaging portion 33S ₁ of 33b, the cam member 34a that rotates, by following the shape of the 34b, the slide member 33a, 33b is moved by the respective predetermined distance in the arrow D direction.

  As a result, both axial ends of the primary transfer rollers 12a, 12b, and 12c corresponding to Y, M, and C resist the urging force of the urging member 31 by the claw portions 38 of the slide members 33a and 33b. It is lifted in a direction away from the photosensitive drums 1a, 1b, 1c. Therefore, the primary transfer rollers 12a, 12b, and 12c are held in a state of being separated from the opposing photosensitive drums 1a, 1b, and 1c.

At the same time, the cam members 34c and 34d in FIG. 4 are also brought into the phase H state of FIG. 7B by the rotation of the cam shaft 32. However, the cam members 34c and 34d and along a 33S _1. For this reason, the slide members 33c and 33d are held at the same position J as FIG. As a result, the primary transfer roller 12d corresponding to Bk is maintained in contact with the corresponding photosensitive drum 1d.

  As described above, during monochrome image formation, the primary transfer rollers 12a to 12c are retracted from the inner peripheral surface of the intermediate transfer belt 12e to separate the intermediate transfer belt 12e from the photosensitive drums 1a to 1c, and the primary transfer roller 12d is moved to the photosensitive drum 1d. It will be in the state made to contact.

[In full separation mode]
At the time of full separation, the cam members 34a and 34b in FIG. 5 rotate 90 ° counterclockwise in FIG. 8A due to the rotation of the cam shaft 32, and the phase L shown in FIG. , 33b are held in the same position K as in FIG. In other words, the sliding member 33a, the engaging portion 33S ₁ of 33b, the cam member 34a to rotate, but to follow the shape of the 34b, the cam member 34c, 34d is the engaging portion 33S ₁ to the cam shaft 32 and concentric portions Just keep it along.

  For this reason, the slide members 33c and 33d are held at the same position K as FIG. As a result, the primary transfer rollers 12a, 12b, and 12c corresponding to Y, M, and C are held in a state of being separated from the opposing photosensitive drums 1a, 1b, and 1c, as described above.

At the same time, since the cam member 34c in FIG. 8, 34d is the state of the phase L shown in FIG. 8 (b) by rotation of the cam shaft 32, cam member 34c, the circular tip of 34d away from the engaging portion 33S ₁ Rotate. As a result, the slide members 33c and 33d move in the direction of the arrow D to reach the position K. For this reason, the primary transfer roller 12d is held in a state of being separated from the opposing photosensitive drum 1d.

  As described above, when fully separated, the primary transfer rollers 12a, 12b, 12c, and 12d are all retracted from the corresponding photosensitive drums 1a, 1b, 1c, and 1d, and the intermediate transfer belt 12e is moved to the photosensitive drums 1a, 1b, 1c, and 1d. It will be in the all separation state separated from.

[Drive transmission device with drive coupling]
Next, the drive transmission device 40 according to the present embodiment will be described in detail with reference to FIG. FIG. 9 is a schematic perspective view showing the drive transmission device 40 in the present embodiment.

  As shown in FIG. 9, the drive transmission device 40 includes a control unit 45 as a control unit, and a drive motor 41 including a pulse motor (stepping motor) driven by the control of the control unit 45. Further, the drive transmission device 40 has a pinion 41 b fixed to the rotation shaft 41 a of the drive motor 41. The drive transmission device 40 further includes a transmission gear 42 that meshes with the pinion 41b, a flag gear 43 that meshes with the transmission gear 42, and a sensor 44 that detects a flag portion (light-shielding portion) 43a of the flag gear 43. The pinion 41b, the transmission gear 42, and the flag gear 43 are supported so that the axis directions of the rotation shaft 41a, the rotation shaft 42c, and the rotation shaft 43c are parallel to each other.

  The flag unit 43a constitutes a flag indicating a predetermined rotational position of the drive motor (pulse motor) 41, and the sensor 44 constitutes a detection unit that detects the flag unit 43a. The flag section (flag) 43a rotates in synchronization with the arrangement of the intermediate transfer belt (movable body) 12e, and is a cam member (rotating member) 34a provided in the moving mechanism (32, 34a to 34d, 47, 49). It is arranged at a position corresponding to a specific rotational phase range of .about.34d.

  The control unit 45 controls the moving mechanism (32, 34a to 34d, 47, 49) using either the first stop mode or the second stop mode. In the first stop mode, when the intermediate transfer belt (moved body) 12e is changed from one of three different arrangements to another, the movement mechanism is activated based on the detection of the sensor (detection unit) 44. It is a mode to stop. The second stop mode is a mode in which the moving mechanism is stopped based on the number of pulses of the drive signal to the drive motor (pulse motor) 41.

  The controller 45 uses the first stop mode when changing from the second or third arrangement to the first arrangement among the three arrangements of the intermediate transfer belt (movable body) 12e. The control unit 45 uses the second stop mode when changing from the first or third arrangement to the second arrangement and when changing from the first or second arrangement to the third arrangement. The control unit 45 moves the movement mechanism (32, 34a to 34d, 47, 49) so as to change at least the arrangement between the second arrangement and the third arrangement by only rotating the drive motor 41 in one direction. To control.

  A drive coupling 46 is disposed on the apparatus main body 50a side. A driven coupling 47 (see FIG. 10) is disposed at a position in the intermediate transfer belt unit 12 that can be opposed to the driving coupling 46 when attached and detached. The drive coupling 46 is attached to the rotation shaft 43c of the flag gear 43 so as to be in a position opposite to the gear portion 43b in the axial direction.

  The transmission gear 42 includes a large-diameter gear 42a that meshes with the pinion 41b and a small-diameter gear 42b that is smaller in diameter than the large-diameter gear 42a. The flag gear 43 has a large-diameter gear portion 43b that meshes with the small-diameter gear 42b, and a flag portion (light-shielding portion) 43a that protrudes from the gear portion 43b in an arcuate cross section in the axial direction. The rotation of the drive motor 41 is transmitted from the pinion 41 b to the large-diameter gear 42 a to rotate the transmission gear 42, and is transmitted from the small-diameter gear 42 b to the gear portion 43 b to rotate the flag gear 43. 46 is rotated in the same direction.

  The sensor 44 includes a light emitting unit 44a and a light receiving unit 44b. The flag unit 43a enters the gap 44c between the light emitting unit 44a and the light receiving unit 44b, and the light projected and received through the gap 44c is shielded from light and transmitted. It is a photo interrupter type sensor that outputs a detection signal by switching to a state. The sensor 44 detects the flag part 43a when the flag part 43a enters the gap 44c and transmits a flag ON signal to the control part 45, and does not detect the flag part 43a when the flag part 43a does not enter the gap 44c.

[Transmission gear train with driven coupling]
On the intermediate transfer belt unit 12 side, the driven coupling 47, the biasing member 48, and the transmission transmitted from the drive coupling 46 to the driven coupling 47 shown in FIG. A gear train 49 is provided. The transmission gear train 49 includes gears 49a, 49b, 49c, and 49d. The driven coupling 47 that can be connected to the driving coupling 46 transmits the rotation to a gear 58 fixed coaxially, and the rotation of the gear 58 is connected to the gear 49 d via the transmission gear train 49. It is transmitted to the cam shaft 32.

  The gear 58 is urged in the direction of arrow B, that is, toward the apparatus main body 50a by an urging member 48 formed of a compression coil spring. The driven coupling 47 is disposed so as to face the driving coupling 46 in a state where the intermediate transfer belt unit 12 is mounted on the apparatus main body 50a.

  When the intermediate transfer belt unit 12 is attached to the apparatus main body 50a (see FIG. 2), the driven coupling 47 is pressed by the guide force from the inclined guide surface 62a. It is pushed in the direction of the arrow M against the urging member 48. When the intermediate transfer belt unit 12 is properly mounted, the driven coupling 47 is released from the guide portion 62 at this time and protrudes by the urging force of the urging member 48 and meshes with the driving coupling 46. As a result, the driven coupling 47 is rotated by the rotation of the drive motor 41 transmitted through the drive coupling 46.

[Relationship between flag part and sensor position]
Next, the positional relationship between the flag part 43a and the sensor 44 will be described with reference to FIGS. FIG. 15 is a schematic diagram illustrating the operations of the flag unit 43a and the sensor 44 of the drive transmission device 40 according to the present embodiment. FIG. 17 is a schematic diagram showing the rotational position of the flag gear 43 according to the present embodiment as seen from the direction of the arrow U in FIG. FIG. 15 is also shown in a state viewed from the direction of arrow U in FIG.

  A symbol A shown in FIG. 15 indicates a positional relationship between the flag unit 43a and the sensor 44 in the full color mode (when a color image is formed). This state A corresponds to the phase G of the cam members 34a to 34d described above in the primary transfer contact / separation mechanism 30 (see FIGS. 3, 6A, and 6B). At this time, in the intermediate transfer belt unit 12, as shown in FIGS. 3 and 6, the cam members 34a and 34b and the cam members 34c and 34d are in phase G, so that the slide members 33a and 33b and the slide members 33c and 33d. Are held at position J, respectively.

  Here, in FIG. 17, the flag portion 43 a of the flag gear 43 is in the phase G indicated by the solid line, and the circumferential width (arc length) is W. When the arc length of the flag portion 43a is W, when the flag portion 43a is rotated in the counterclockwise direction (CCW direction) in FIG. The time required for rotation is T1. When the flag unit 43a is rotated in the clockwise direction (CW direction) in FIG. 17 by driving the drive motor 41, the time required for the flag unit 43a to rotate from the phase H to the phase G is T2. Further, when the flag unit 43a is rotated counterclockwise (CCW direction) in FIG. 17 by driving the drive motor 41, the time required for the flag unit 43a to rotate from the phase H to the phase L is T3.

  Next, when the flag gear 43 is rotated in the counterclockwise direction (CCW direction) in FIG. 15 by further rotation of the drive motor 41 from the state A, a state indicated by reference numeral B in FIG. This state B corresponds to the phase H of the cam members 34a to 34d described above in the primary transfer contact / separation mechanism 30 (see FIGS. 4, 7A and 7B). Here, in FIG. 17, the flag section 43a moves to the broken line phase H with the center of the arc length W advanced by time T1.

  At this time, in the intermediate transfer belt unit 12, the cam members 34a and 34b and the cam members 34c and 34d are in the phase H as shown in FIGS. However, as described above, the slide members 33a and 33b move to the position K, but the slide members 33c and 33d remain at the position J. As a result, the intermediate transfer belt unit 12 enters a monochrome mode (Bk single color mode).

  Next, when the flag gear 43 is rotated in the counterclockwise direction (CCW direction) in FIG. 15 by the further rotation of the drive motor 41 from the state B, the state indicated by the symbol C in FIG. This state C corresponds to the phase L of the cam members 34a to 34d described above in the primary transfer contact / separation mechanism 30 (see FIGS. 5, 8A, and 8B). Here, in FIG. 17, the flag portion 43 a moves the center of the arc length W from the phase H to the phase L of the broken line by a time T3.

  At this time, in the intermediate transfer belt unit 12, as shown in FIGS. 5 and 8, the cam members 34a and 34b and the cam members 34c and 34d are in the phase H, and the slide members 33a and 33b are at the position K as described above. The slide members 33c and 33d move to the position K. As a result, the intermediate transfer belt unit 12 is in the fully separated mode.

  Next, the switching operation from the full color mode to the monochrome mode will be described with reference to FIG. 15, FIG. 17, and FIG. FIG. 18 is a flowchart showing a control flow relating to switching from the full color mode to the monochrome mode.

  First, the drive motor 41 responding to the control of the control unit 45 drives the flag unit 43a to rotate in the counterclockwise direction (CCW direction) in FIG. 17 (step S1). Based on the fact that the flag unit 43a enters the gap 44c and the sensor 44 outputs a flag OFF signal, when the control unit 45 detects the flag OFF (S2: Yes), the control unit 45 performs the time T1-W / 2. Waiting for the passage (S3: Yes), the drive motor 41 is stopped (S4).

  Based on the detection of the sensor 44, the control unit 45 determines whether or not the flag is OFF (S5). If the flag is OFF (S5: Yes), the process is terminated. If the flag is not OFF (S5: No) An error is assumed (S6). When this error occurs, for example, on the operation unit (not shown) provided on the apparatus main body 50a, characters such as “Please contact service” are displayed together with an error code (multi-digit number), etc. The operation of 50a can be stopped.

  Next, switching operation from the monochrome mode to the full color mode will be described with reference to FIG. 15, FIG. 17, and FIG. FIG. 19 is a flowchart showing a control flow relating to switching from the monochrome mode to the full color mode.

  First, the drive motor 41 responding to the control of the control unit 45 drives the flag unit 43a to rotate in the clockwise direction (CW direction) in FIG. 17 (S11). Next, the control unit 45 waits for the time T2 from the start of rotation of the drive motor 41 (S12: Yes), stops the drive motor 41 (S13), the flag unit 43a enters the gap 44c, and the flag is turned ON. (S14). If the flag is ON (S14: Yes), the control unit 45 terminates the process, and if the flag is not ON (S14: No), an error is generated (S15).

  Next, the switching operation from the full color mode to the full separation mode will be described with reference to FIG. 15, FIG. 17, and FIG. FIG. 20 is a flowchart showing a control flow relating to switching from the full color mode to the full separation mode.

  First, in response to the control of the control unit 45, the drive motor 41 drives the flag unit 43a to rotate in the counterclockwise direction (CCW direction) in FIG. 17 (S21). Next, when detecting the flag OFF (S22: Yes), the control unit 45 waits for the time T1 + T3-W / 2 (S23: Yes), stops the drive motor 41 (S24), and turns off the flag. (S25). If the flag is OFF (S25: Yes), the control unit 45 terminates the process, and if the flag is not OFF (S25: No), an error is generated (S26).

  As described above, the control unit 45 in the present embodiment controls the three positions of the intermediate transfer belt 12e as a moving body that is moved via the primary transfer rollers 12a to 12d as follows. That is, three different arrangements of the intermediate transfer belt 12e with respect to the photosensitive drums 1a to 1d are a full contact arrangement, a partial contact arrangement, and a full separation arrangement. As described above, the all contact arrangement is an arrangement in which all of the photosensitive drums 1a to 1d are in contact with the intermediate transfer belt 12e. In the partial contact arrangement, a part (1d) of the photosensitive drums 1a to 1d is in contact with the intermediate transfer belt 12e. The all separation arrangement is an arrangement in which all of the photosensitive drums 1a to 1d are separated from the intermediate transfer belt 12e.

  The control unit 45 has a first arrangement based on the detection of the flag part 43a of the sensor 44 (for example, a full contact arrangement (full color mode)) and a drive signal to the drive motor 41 without detecting the flag part 43a by the sensor 44. When the second and third arrangements based on the number of pulses are performed, the following control is performed. That is, the control unit 45 changes the arrangement between at least the second arrangement (for example, the partial contact arrangement (monochrome mode)) and the third arrangement (for example, the completely separated arrangement (all separated mode)). The moving mechanism is controlled so as to perform the rotation only in one direction of 41 (see FIG. 15).

  In other words, the three arrangements are the first arrangement (for example, state A in FIG. 15), the second arrangement (for example, state B in FIG. 15), and the third arrangement (for example, state C in FIG. 15). The first arrangement is a position based on the detection of the flag part 43a of the sensor 44, and the second arrangement and the third arrangement are for the drive signal to the drive motor 41 without the flag part 43a being detected by the sensor 44. The position is based on the number of pulses. In this case, the control unit 45 performs control so that at least the movement between the second arrangement and the third arrangement is performed by one-way rotation of the drive motor 41. This avoids mode switching and long device start-up time, and prevents downtime from prolonging downtime to increase productivity and prevent problems such as user stress and shortened device life. Become.

  The controller 45 changes the arrangement of the intermediate transfer belt 12e between the first arrangement (for example, state A) and the second arrangement (for example, state B) by bi-directional rotation of the drive motor 41. Then, control is performed to change the arrangement between the first arrangement and the third arrangement (for example, the state C) by one-way rotation of the drive motor 41. As a result, transition from state A to state B to state C in FIG. It can contribute to stuffing.

  Alternatively, the control of the control unit 45 can be partially changed and implemented as shown in FIG. That is, the change of the arrangement of the intermediate transfer belt 12e between the first arrangement and the second arrangement is performed by bidirectional rotation of the drive motor 41, and the change of the arrangement between the first arrangement and the third arrangement is also performed by the drive motor 41. The control is performed so as to perform the two-way rotation. In this case, the above-mentioned effects against backlash are slightly reduced, but the effects such as avoiding mode switching and long device start-up time, preventing downtime from being prolonged and increasing productivity are the same. Can get to.

[Drive coupling mechanism when the intermediate transfer belt unit is attached / detached]
Next, with reference to FIGS. 10 and 11 to 14, a coupling unit used when the intermediate transfer belt unit 12 is attached to and detached from the apparatus main body 50 a will be described. In addition, Fig.11 (a)-(d) is the schematic which shows a coupling part.

  The intermediate transfer belt 12e is configured to be attachable to and detachable from the apparatus main body 50a in a fully separated arrangement in the fully separated mode by attaching / detaching the intermediate transfer belt unit 12 to / from the apparatus main body 50a. The drive motor (pulse motor) 41 is provided on the apparatus main body side. The coupling unit is provided so as to be connectable and detachable to and from the intermediate transfer belt 12e, and can transmit power between the drive motor 41 and the intermediate transfer belt 12e in the connected state.

  That is, the intermediate transfer belt unit 12 includes an intermediate transfer belt 12e and moving mechanisms (32, 34a to 34d, 47, 49), and is disposed so as to be attached to and detached from the apparatus main body 50a. The coupling unit is provided between a drive motor 41 provided on the apparatus main body 50a side and a moving mechanism, and moves with the drive motor 41 when the intermediate transfer belt 12e is disposed at a fully spaced position relative to the photosensitive drums 1a to 1d. It is possible to switch power transmission to and release from the mechanism.

  As shown in FIGS. 10 and 11 to 14, the coupling portion includes a driving coupling 46 and a driven coupling 47 that can be connected and separated in a completely spaced arrangement. As a result, the belt unit 12 is very easily and reliably moved relative to the apparatus main body 50a simply by moving the intermediate transfer belt unit 12 in the insertion and extraction directions along the guide portion 62 (see FIG. 2) on the apparatus main body 50a side. Can be desorbed.

  That is, the drive coupling 46 and the driven coupling 47 are slightly more than the driven coupling 47 so that the drive coupling 46 and the driven coupling 47 can be engaged with each other in an opposed state as shown in FIG. It is configured as a large-diameter cylindrical member.

  In the engaged state (engaged state) between the drive coupling 46 and the driven coupling 47 shown in FIG. 10, the second engagement portion 47 a of the driven coupling 47 shown in FIG. In contact with an inclined surface 46e (FIG. 11C). Therefore, when the intermediate transfer belt unit 12 is pulled out from the apparatus main body 50a, the pulling force acts on the intermediate transfer belt unit 12 in the attaching / detaching direction (the direction of arrow A in FIG. 12, the direction of arrow R in FIG. 2). The second engaging portion 47a is in sliding contact with the inclined surface 46e.

  As a result, a force that moves the driven coupling 47 in the arrow M direction opposite to the biasing direction (the arrow B direction in FIG. 10) by the biasing member 48 acts. For this reason, the driven coupling 47 is temporarily retracted from the driving coupling 46 in the direction of the arrow M, and when the engagement between the first engaging portion 46b and the second engaging portion 47a is released, the intermediate transfer is performed. The belt unit 12 can be pulled out from the apparatus main body 50a.

  As shown in FIG. 11C, on the inner peripheral side of the inclined surface 46e of the drive coupling 46, the first engagement portion protrudes in a “T-shape” from the flat bottom portion 46a. 46b is formed. On the other hand, as shown in FIG. 11 (b), the T-shaped first engagement portion 46b can be engaged with the driven coupling 47 on the side facing the drive coupling 46 so as to be sandwiched from above, below, left and right. The second engaging portion 47a is formed so as to protrude from the edge portion of the flat surface 47b. As shown in FIG. 11D, when the drive coupling 46 rotates, for example, in the direction of the arrow L, the contact surface 46c of the T-shaped first engagement portion 46b engages with the second engagement portion 47a. However, the driven coupling 47 is rotated in the same direction via the second engaging portion 47a.

  Hereinafter, the coupling unit will be described in more detail with reference to FIGS. 12 and 13. FIGS. 12A to 12C are schematic views showing the state of the coupling portion before the intermediate transfer belt unit 12 starts to be detached. FIGS. 13A to 13C are schematic views showing a state in which the contact between the first engagement portion and the second engagement portion of the coupling portion is released, and FIGS. 14A to 14C are views. It is the schematic which shows the distance between the rotating shafts of a coupling part.

  FIGS. 12A and 13A show the state of engagement between the drive coupling 46 and the driven coupling 47. FIGS. 12B and 13B are cross-sectional views showing the state of engagement between the drive coupling 46 and the driven coupling 47 as viewed from the direction orthogonal to the rotation axis. Further, FIG. 12C and FIG. 13C are views showing the state of engagement between the drive coupling 46 and the driven coupling 47 as seen from the direction of the rotation axis.

  FIG. 12B shows a state before the intermediate transfer belt unit 12 is detached from the apparatus main body 50a. That is, among the three second engaging portions 47a, the second engaging portion 47a (hereinafter referred to as the second engaging portion 47f) positioned on the most upstream side in the intermediate transfer belt unit detaching direction, and the first There is a sufficient gap in the rotational direction between the contact surface 46c of the engaging portion 46b. This is because the flag gear 43 is in the phase L state at this time (see FIGS. 5 and 8). As described above, this is because the transition to the phase L is always performed only by the rotation in the CCW direction from the phase H (see FIGS. 15 and 16).

  When the intermediate transfer belt unit 12 is pulled out from the apparatus main body 50a in a direction perpendicular to the rotation axis J of the drive coupling 46, the second engaging portion 47f is brought into contact with the contact surface 46c by a force acting in the direction in which the unit 12 is detached. The driven coupling 47 is rotated so as to approach At this time, the driven coupling 47 is located at a position different from the rotation axis J of the driving coupling 46 and the position where the driving coupling 46 and the driven coupling 47 are in contact with each other.

  As shown in FIG. 12C and FIG. 13C, the second engagement portion positioned between the second engagement portion 47f and the first engagement portion 46b is hereinafter referred to as a second engagement portion 47h. Called. Therefore, the position k at which the second engaging portion 47h and the contact surface 46c come into contact is the center of rotation.

  When the driven coupling 47 starts to rotate around the position k, the second engagement portion 47f approaches the contact surface 46c of the first engagement portion 46b, so that the second engagement portion 47f and the contact surface 46c The gap between is reduced. When the driven coupling 47 is rotated, a second engagement portion (hereinafter referred to as a second engagement portion 47g) located on the most downstream side in the direction in which the belt unit 12 is detached in the second engagement portion 47a. Then, the belt unit 12 moves along the inclined surface 46e in the detaching direction (arrow M direction).

  As a result, the driven coupling 47 is retracted in the disengagement direction (the direction of the arrow M), so that the first engagement portion 46b and the second engagement portions 47f and 47g are used as shown in FIGS. , 47h is released. That is, the contact surfaces of the second engagement portions 47f, 47g, and 47h are separated from the contact surface 46c of the first engagement portion 46b. Until the engagement between the first engaging portion 46b and the second engaging portions 47f, 47g, 47h is released, the rotary shaft V of the driven coupling 47 is detached from the rotary shaft J of the drive coupling 46. The distance traveled in the direction is β.

  Next, when the belt unit 12 is pulled out in a direction perpendicular to the rotation axis J of the drive coupling 46, the rotation axis V of the driven coupling 47 is more than the rotation axis J by the force acting in the unit detachment direction. A structure that can move in the direction of separation will be described.

  That is, as can be seen from FIGS. 11A to 11D, the driven coupling 47 has a sufficiently wide region for the drive coupling 46 to be fitted. As a result, when the drive coupling 46 and the driven coupling 47 are engaged with each other and rotated, a gap is formed.

  Here, as shown in FIGS. 14A to 14C, the rotation axis V of the driven coupling 47 can move in the unit disengagement direction (direction of arrow A) with respect to the rotation axis J of the drive coupling 46. The maximum distance is α.

  In the coupling portions (46, 47) of the present embodiment, the distance α is configured to be larger than the distance β. When the distance α is equal to or greater than the distance β, the driven coupling 47 is moved before the second engagement portion 47f contacts the first engagement portion 46b when the driven coupling 47 rotates about the position k. Evacuation in the M direction is completed.

  Therefore, according to the configuration using the coupling portion of the present embodiment, the first engagement portion 46b and the second engagement portions 47f, 47g, 47h can be engaged only by pulling out the belt unit 12 from the apparatus main body 50a. Can be easily and reliably released. Thereby, the meshing between the drive coupling 46 and the driven coupling 47 can be easily released. On the contrary, the belt unit 12 can be attached to the apparatus main body 50a very simply and surely only by inserting the belt unit 12 along the guide portion 62 of the apparatus main body 50a.

  In the present embodiment, as described with reference to FIG. 15, the flag gear 43 is rotated only in the CCW direction by the power of the drive motor 41 in a series of mode switching, but only when switching from the monochrome mode to the full color mode. Is rotated in the CW direction. And the position of the sensor 44 is arrange | positioned in the phase G which is a full color mode.

  The reason is that a sufficient clearance is created in the rotational direction between the second engaging portion 47a and the contact surface 41c of the first engaging portion 46b, so that the intermediate transfer belt unit 12 can be easily detached from the apparatus main body 50a. It is to do. Further, in the switching between the monochrome mode and the full color mode, which are frequently switched, if the shortest switching is performed by repeatedly switching the motor rotation direction without arranging the sensor 44 in the phase of the full color mode, the shift of the stop phase of the flag unit 43a may occur. It is likely to accumulate. This is to avoid this problem.

  Hereinafter, effects obtained by adopting the configuration of the present embodiment will be described with reference to comparative examples shown in FIGS.

  In this comparative example, the flag gear 43 'is used, and the sensor 44 is set to the flag ON when the flag position is in the all separation mode as shown in FIGS. 21 (a) and 21 (b). With this configuration, when the switching between the full color mode and the monochrome mode is performed by repeatedly switching the motor rotation direction, the deviation of the stop position of the flag unit 43a is accumulated.

  For example, when switching from the phase G of the full color mode to the phase H of the monochrome mode, when the stop position of the flag unit 43a is shifted as shown in FIG. The operation starts from the phase H ′ instead of the phase H. For this reason, if further disturbance occurs when stopping at the phase G, there is a risk of promoting the deviation.

  If the stop position deviation accumulates in this way, the primary transfer roller corresponding to the color rotates in spite of the monochrome mode, resulting in a decrease in the life of the apparatus, or the image forming operation is performed with all the primary transfer rollers separated. There is a possibility that a blank paper output problem may occur due to the start.

  On the other hand, according to the configuration of this embodiment, even if the rotation direction of the drive motor 41 is repeatedly switched in order to perform switching in the shortest time, the flag 44 is detected by the sensor 44 once every two times. It can be operated without accumulating. Thereby, productivity can be improved without deteriorating the life of the image forming apparatus 50.

  As another comparative example, in order to prevent the accumulation of errors, it is conceivable to arrange flags having different widths at all the phase positions of the flag gear. However, in this case, since the flag ON is detected in all modes, it is necessary to rotate the motor to distinguish the modes, which causes a problem that the downtime becomes long when the power of the apparatus main body is turned on or reset. Become.

  According to the configuration of the present embodiment, only the home position (full color mode) detects the flag ON, and therefore, the drive motor 41 needs to be rotated only when the flag is not detected when the apparatus main body 50a is turned on or reset. Downtime can be reduced.

<Second Embodiment>
Next, a second embodiment in which the present invention is applied to the secondary transfer unit 61 of the image forming apparatus 50 will be described with reference to FIGS. 22A is a cross-sectional view of a state where the secondary transfer outer roller in this embodiment is in contact with the driving roller, and FIG. 22B is a state where the secondary transfer outer roller is moved to the standby position. It is sectional drawing. FIG. 23 is a cross-sectional view showing a state where the secondary transfer outer roller in the present embodiment is moved to the separation position. In the present embodiment, the same members as those in the first embodiment are denoted by the same reference numerals, and descriptions of components having the same configuration and function are omitted.

  As shown in FIGS. 22A and 22B, a secondary transfer unit 61 detachably attached to the apparatus main body 50a (see FIG. 1) includes a secondary transfer outer roller (transfer roller) 16, a secondary transfer. A roller contact / separation mechanism 63 for moving the outer roller 16 and a contact / separation drive unit 68 are provided. The roller contact / separation mechanism 63 has a support member 69 supported by the apparatus main body 50a of the image forming apparatus 50 so as to face the drive roller (secondary transfer inner roller) 12f. The support member 69 is provided with a secondary transfer arm 53 having a slightly bent shape so as to be positioned at the center portion. A rotation support hole 53 a is formed at the center of the secondary transfer arm 53.

  The support member 69 is formed with a storage portion 64 that is formed in a substantially linear shape toward the drive roller 12f. In the storage portion 64, the roller holder 70 is stored in a state in which the roller holder 70 is movable so as to move closer to the drive roller 12f and is not restricted to protrude toward the drive roller 12f beyond the position shown in FIG. ing. On the opposite side of the roller holder 70 from the drive roller 12f in the storage portion 64, a holder biasing spring 52 made of a compression spring is provided in a contracted manner between the rear end portion of the roller holder 70 and the bottom portion 64a. .

  The roller holder 70 has a projection 67 that projects to the near side of FIGS. 22 (a) and 22 (b). The protrusion 67 is slidably inserted into the rotation support hole 53 a of the secondary transfer arm 53. The secondary transfer arm 53 has a base end portion rotatably supported on a support member 69 by a rotation support shaft 66, and a rotatable disk-shaped pressed member 65 is supported on a free end portion.

  With the above configuration, the secondary transfer outer roller 16 is brought into contact (pressure contact) with the driving roller 12 f by the urging force of the holder urging spring 52 with the rotating shaft 51 held by the roller holder 70. The roller holder 70 and the secondary transfer outer roller 16 are separated from the driving roller 12f by the abutting direction toward the driving roller 12f by the secondary transfer arm 53 held rotatably about the rotation support shaft 66. It is configured to be movable in the direction. The secondary transfer outer roller 16 is in pressure contact with the drive roller 12f with the intermediate transfer belt 12e sandwiched therebetween in the contact direction.

  A cam support shaft 55 that supports the eccentric cam 54 is disposed at a position facing the pressed member 65 of the support member 69. The pressed member 65 abuts against the eccentric cam 54 supported by the cam support shaft 55 with the center position shifted via the secondary transfer arm 53 urged at the center by the holder urging spring 52. ing.

  In the present embodiment, the toner images carried on the photosensitive drums 1a to 1d as other image carriers are transferred onto the intermediate transfer belt 12e as the image carrier. Further, a secondary transfer outer roller (transfer roller) 16 as a movable body forms a secondary transfer portion (nip portion) 15 with the intermediate transfer belt 12e, and passes through the secondary transfer portion 15. The toner image is transferred from S to the intermediate transfer belt 12e.

  The cam support shaft 55 is rotated by driving of a motor 71 including a pulse motor provided in the contact / separation drive unit 68 in a state where the eccentric cam 54 is fixedly supported and rotatably supported with respect to the support member 69. Then, the eccentric cam 54 is rotated. The eccentric cam 54 is rotated by the drive of the motor 71 driven by the control of the control unit 45 (see FIG. 1), thereby changing the contact position (contact phase) with the pressed member 65, so that the secondary transfer outside The roller 16 is moved between the contact position, the standby position (intermediate position), and the separation position.

  That is, three different arrangements of the secondary transfer outer roller 16 with respect to the intermediate transfer belt 12e are the contact position, the separation position, and the standby position (intermediate position). The contact position is an arrangement in which the secondary transfer outer roller 16 and the intermediate transfer belt 12e are in contact. The separation position is a position where a secondary transfer unit (transfer unit) 61 having the secondary transfer outer roller 16 can be attached to and detached from the apparatus main body 50a (see FIG. 1), and the secondary transfer outer roller 16 and the intermediate transfer belt. 12e. The standby position (intermediate position) is an arrangement between the separation position and the contact position.

  As described above, the control unit 45 as a control unit performs control so as to switch to the contact position, the standby position, and the separation position by the drive control of the motor (pulse motor) 71. In other words, the contact position is a position when secondary transfer is being performed during printing (printing), and the standby position is a reference toner pattern (correction patch) formed on the intermediate transfer belt during printing. It is a position that is separated when hitting. Furthermore, the separation position is a separation position other than during printing. The standby position is a minimum required separation amount that does not adhere to the secondary transfer outer roller 16 side when the correction patch passes. The separation position is a separation amount in consideration of the processing performance of jammed paper, or the insertion and extraction performance (insertion / removability) of the secondary transfer unit 61 from the apparatus main body 50a during maintenance and transportation. The first arrangement according to the present invention corresponds to the “contact position”, the second arrangement corresponds to the “standby position (intermediate position)”, and the third arrangement corresponds to the “separation position”.

  The contact position, the standby position, and the separation position in the present embodiment described above correspond to the phase G, phase H, and phase L (see FIGS. 15 and 16) in the first embodiment, respectively. Also according to this embodiment, substantially the same effect as that of the first embodiment can be obtained.

  1a to 1d: image carrier, another image carrier (photosensitive drum) / 12 ... intermediate transfer unit (intermediate transfer belt unit) / 12e ... moved body (intermediate transfer belt) / 15 ... nip part (secondary transfer part) ) / 16 ... moving object, transfer roller (secondary transfer outer roller) / 32, 34a to 34d, 47, 49 ... moving mechanism (cam shaft, rotating member (cam member), driven coupling, transmission gear train) / 41 ... Pulse motor (drive motor) / 43a ... Flag (flag part) / 44 ... Detection part (sensor), 45 ... Control means (control part) / 46, 47 ... Coupling part (drive coupling, driven cup) Ring) / 50: Image forming apparatus / 50a: Main body of apparatus / 61: Transfer unit (secondary transfer unit) / S: Recording material

Claims (7)

An image carrier;
A motor that can be driven to rotate in both directions;
The first arrangement that is arranged at the time of image formation and the first arrangement that is arranged at the time of image formation include a cam that is rotated by the motor and switches the phase of the cam to change the position of the moving object. A moving mechanism that can be changed to a different second arrangement and a third arrangement that is not arranged during image formation ;
A sensor for detecting the phase of the cam;
An image forming apparatus comprising: a control unit that controls driving of the motor based on a detection result of the sensor ;
Before SL sensors, only the phase of the cam corresponding to the first arrangement is configured to be detected,
The moving mechanism is configured to reciprocate between the first arrangement and the second arrangement without going through the third arrangement ,
When the control unit switches between the second arrangement and the third arrangement, the control unit permits switching from the second arrangement to the third arrangement without passing through the first arrangement. , Switching from the third arrangement to the second arrangement is not permitted without going through the first arrangement.
An image forming apparatus. When the image formation is performed in the second arrangement, the control unit controls the motor so as to be in the first arrangement when the image formation ends.
The image forming apparatus according to claim 1 . Wherein, the case first arrangement and the second arrangement of Ru switch e is possible to obtain switching said second arrangement and the first arrangement without passing through the pre-Symbol third arrangement Tolerate ,
The image forming apparatus according to claim 1 , wherein the image forming apparatus is an image forming apparatus. In the third arrangement, the image carrier is provided so as to be detachable from the apparatus main body. When the first arrangement is switched to the third arrangement, the control unit performs the second arrangement. to via the arrangement controlling the motor so Waru switched to the third arrangement,
The image forming apparatus according to claim 1 , wherein the image forming apparatus is an image forming apparatus. The movable body includes a first transfer member and a second transfer member which are provided so as to be able to contact and separate from the image carrier and transfer an image to the image carrier.
In the first arrangement, both the first transfer member and the second transfer member are in contact with the image carrier,
In the second arrangement, the first transfer member contacts the image carrier, and the second transfer member is separated from the image carrier,
In the third arrangement, both the first transfer member and the second transfer member are separated from the image carrier.
The image forming apparatus according to any one of claims 1 to 4, characterized in that. An image carrier;
A motor that can be driven to rotate in both directions;
The first arrangement that is arranged at the time of image formation and the first arrangement that is arranged at the time of image formation include a cam that is rotated by the motor and switches the phase of the cam to change the position of the moving object. A moving mechanism that can be changed to a different second arrangement and a third arrangement that is not arranged during image formation;
A sensor for detecting the phase of the cam;
An image forming apparatus comprising: a control unit that controls driving of the motor based on a detection result of the sensor;
The sensor is configured to detect only the phase of the cam corresponding to the first arrangement,
The moving mechanism is configured to reciprocate between the first arrangement and the second arrangement without going through the third arrangement,
The movable body is a transfer member that is provided so as to be able to contact and separate from the image carrier, and that transfers an image carried on the image carrier to a recording material ,
When the previous SL first arrangement, the transfer member is in contact with the image bearing member,
When the previous SL second arrangement, the transfer member is located at a first spaced position away and the image bearing member,
When the previous SL third arrangement, the transfer member is in the second spaced position spaced distance is greater than the first spaced position between the image carrier and the transfer member,
Images forming device you wherein a. Wherein, when the reference pattern is not performed transferred onto the recording material during image formation is formed on the image bearing member, controls the first said motor to obtain the switching to the second arrangement from the arrangement of To
The image forming apparatus according to claim 6 .

Images