JP2006047424A - Image forming device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming device which can control a change of position to an image carrier of a development means, and start and stop driving thereof by a small and simple mechanism. <P>SOLUTION: The image forming device 200 is provided with at least two drivers 1, and followers 2 which perform intermittent turning motion to the rotary motion of the drivers 1 prepared correspondingly to two or more respective image forming parts P and operate transfer means 4 and drive change-over means 3 of each image forming part P, and at least two of the above drivers 1 have change-over mechanisms which are driven to rotate interlocking with each other and act on the followers 2 in different phases, and forward rotation of at least two of the above drivers 1 shifts the development means 241 from a 1st position to a 2nd position sequentially from the image forming part P upstream in the transfer direction of the toner carrier 251 and also starts driving thereof, and further, shifts the development means 241 from the 2nd position to the 1st position sequentially from the image development part P upstream in the transfer direction of the toner carrier 251, and stops driving thereof. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

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

  2. Description of the Related Art Conventionally, an image forming apparatus using an electrophotographic method forms an electrostatic image on an electrophotographic photosensitive member (hereinafter referred to as “photosensitive member”) as an image bearing member, and uses this as a developer image (developing means). After development as a toner image), this toner image is finally transferred onto a recording material, for example, a recording paper, a plastic sheet (OHP sheet), a cloth, etc. to obtain a recorded image.

  Also, for example, in an image forming apparatus capable of forming full-color images of four colors of yellow, magenta, cyan, and black, a plurality of image forming units each having a photoconductor are juxtaposed and sequentially formed on each photoconductor. The toner images of the respective colors are transferred to a recording material on a recording material carrier arranged to face each photoconductor, or transferred to an intermediate transfer body arranged to face each photoconductor, and then the recording material There is something to transcribe to. These recording material carrier and intermediate transfer member function as a toner image carrier that receives and conveys a toner image from the image carrier.

  In the image forming apparatus in which a plurality of image forming units are juxtaposed as described above, for example, when all of the plurality of image forming units are used, image formation is started sequentially from the image forming unit upstream in the transport direction of the toner image transport body. The For example, when only one image forming unit such as a monochrome image is used, the other image forming units are not used. For this reason, various proposals for selectively stopping / driving the driving of a plurality of image forming units have been made in order to improve the durability of the apparatus elements or solve the problems caused by driving the unused image forming units. ing. Some examples are given below.

  In an image forming apparatus, in order to prevent unnecessary toner development, a configuration is known in which a developing unit is placed at a position away from a photoreceptor when not operating (see Patent Document 1).

  Also, a configuration is known in which driving of a developing unit that is not used during image formation is stopped in order to realize a long life of the developing unit (see Patent Document 2).

  Furthermore, a mechanism is known in which the photosensitive member of another image forming unit that does not contribute to image formation during mono-color mode printing and the developing unit are not in contact with each other (see Patent Document 3).

  By the way, when a four-color full-color image is formed, for example, images are sequentially formed on the photoconductors of the plurality of image forming units. For example, the first image forming unit that forms the first color and the last color are formed. When the position of the developing unit relative to the photosensitive member is changed and the driving thereof is started at the same timing, the developing unit of the fourth image forming unit is unnecessary when the image forming starts. It is also driven in the image area. Conversely, at the end of image formation, the developing means of the first image forming unit is driven even in an unnecessary non-image area.

  Therefore, it is considered to be extremely effective to change the position of the developing means relative to the photosensitive member and start / stop driving sequentially from the upstream side of the image forming process.

  However, the conventional technique does not sequentially change the position of the developing unit relative to the photosensitive member and start / stop driving thereof from the image forming unit upstream in the conveying direction of the toner image conveying member during image formation.

Conventionally, a configuration using a lever, a cam or the like as a means for making the developing means non-contact with the photosensitive member when not in operation is common. When the position of each developing unit with respect to the photosensitive member is changed using a common drive source by a conventional mechanism and the driving is started / stopped, generally, the apparatus main body is increased in size and complexity. There are various restrictions such as. For this reason, the position of the developing unit relative to the photosensitive member is sequentially changed and started / stopped from the image forming unit upstream in the conveying direction of the toner image conveying member at the time of image formation with a small and simple configuration. Is desired.
Japanese Patent Laid-Open No. 2001-215796 JP 2001-343809 A JP 2003-76103 A

  An object of the present invention is to provide an image forming apparatus capable of controlling the change of the position of the developing unit relative to the image carrier and the start and stop of the driving by a small and simple mechanism.

The above object is achieved by the image forming apparatus according to the present invention. In summary, the present invention provides an image forming unit comprising: an image carrier; and a developing unit that supplies toner to the electrostatic image formed on the image carrier to form a toner image. In an image forming apparatus having a plurality along a moving direction of a toner image transport body that receives and transports a toner image from a body,
A moving unit that is provided corresponding to each of the plurality of image forming units and moves a position of the developing unit of each image forming unit with respect to the image carrier between a first position and a second position;
A drive switching unit provided corresponding to each of the plurality of image forming units to stop or start driving of the developing unit of each image forming unit;
The moving means and the drive switching means of each image forming unit are operated by intermittently rotating with respect to at least two moving nodes and the rotating motion of the moving nodes provided corresponding to each of the plurality of image forming units. A switching mechanism, wherein the at least two movements are rotationally driven in conjunction with each other and act on the driven nodes at different phases;
Have
The switching mechanism moves the developing unit from the first position to the second position sequentially from the image forming unit upstream in the transport direction of the toner transport body by forward rotation of the at least two moving nodes. And the drive is started, and the developing means is sequentially moved from the second position to the first position and driven from the image forming section upstream in the transport direction of the toner transport body. The image forming apparatus is characterized in that is stopped.

  According to the present invention, it is possible to control the change of the position of the developing unit with respect to the image carrier and the start and stop of the driving by a small and simple mechanism.

  The image forming apparatus according to the present invention will be described below in more detail with reference to the drawings.

Example 1
[Overall Configuration and Operation of Image Forming Apparatus]
First, the overall configuration and operation of the image forming apparatus of this embodiment will be described with reference to FIG. The image forming apparatus 200 according to the present embodiment is a personal computer that is communicably connected to an image forming apparatus main body (apparatus main body) A, or an original reading apparatus that optically reads image information of an original and converts it into an electrical signal. This is an electrophotographic color laser beam printer capable of forming a four-color full-color image in response to an image information signal from an external device. This image forming apparatus 200 employs an intermediate transfer method and a process cartridge method.

  The image forming apparatus 200 serves as first, second, third, and fourth images that form yellow (Y), magenta (M), cyan (C), and black (K) images as image forming units, respectively. It has an image forming unit (station) PY, PM, PC, PK. Corresponding to each image forming unit, four process cartridges BY, BM, BC, BK are arranged in a substantially horizontal direction. In this embodiment, the configuration of each image forming unit is substantially the same except that the development colors are different. Therefore, if no distinction is required, it belongs to one of the image forming units below. The subscripts Y, M, C, and K given to the reference numerals in the figure to indicate that they are elements will be omitted for general explanation.

  Each image forming unit has a cylindrical electrophotographic photosensitive member (hereinafter referred to as “photosensitive drum”) 201 as an image carrier. Around the photosensitive drum 201, a charging roller 202 as a charging unit for uniformly charging the surface of the photosensitive drum 201, and an electrostatic image (latent image) corresponding to an image of a specific color on the surface of the charged photosensitive drum 201 is provided. A laser scanner 203 as a latent image forming unit to be formed, a developing device 204 that visualizes an electrostatic image formed on the photosensitive drum 201 with toner, and each color toner image visualized on the photosensitive drum 201 An intermediate transfer belt 251 as an intermediate transfer body on which a color toner image is formed by being sequentially superimposed and transferred, and a primary transfer roller as a primary transfer means for transferring the toner image formed on the photosensitive drum 201 to the intermediate transfer belt 251 252, a cleaning device 206 is disposed as a cleaning unit for removing toner remaining on the photosensitive drum 201 after the primary transfer process.Each toner storage means 207 is independent and supplies toner to each process cartridge B via a toner supply means (not shown). The intermediate transfer belt 251 is a toner image carrier that receives and conveys a toner image from the photosensitive drum 201 of each image forming unit.

  The developing unit 204 will be further described. The developing unit 204 stores toner as a developer in the developer storage unit 242. The developer accommodating portion 242 is partially opened at a portion facing the photosensitive drum 201. A roller-shaped developer carrying member (hereinafter referred to as “developing roller”) 241 that rotates the developer to the developing member is provided rotatably as a developing unit. The developing roller 241 is disposed substantially parallel to the longitudinal direction (rotational axis direction) of the photosensitive drum 201 and can be separated from and contacted to the photosensitive drum 201 as will be described in detail later. In this embodiment, the developing device 204 supplies a toner to the photosensitive drum 201 by using a non-magnetic one-component developer as a developer and rotating in contact with the photosensitive drum 201. That is, during the development process, the toner in the developer container 242 is frictionally charged and supplied at a predetermined layer thickness on the rotating developing roller 241. Then, when the developing roller 241 comes into contact with the photosensitive drum 201 and rotates, the toner conveyed to the portion facing the photosensitive drum 201 (developing portion) becomes an electrostatic image formed on the photosensitive drum 201. In response, the toner is supplied to the photosensitive drum 201. As a result, a toner image is formed on the photosensitive drum 201.

  The intermediate transfer belt 251 is wound around a plurality of rollers, and is driven by a driving roller 253 among the plurality of rollers, and as shown by an arrow in the drawing, the first image is formed on a plane facing the photosensitive drum 201. It is rotated (circulated) in the direction from the forming unit PY to the fourth image forming unit PK. Then, the toner images of the respective colors formed by the respective process cartridges B at a predetermined timing are subjected to the action of the primary transfer roller 252 at the primary transfer portion T1 where the respective photosensitive drums 201 and the intermediate transfer belt 251 face each other. Then, the images are sequentially transferred onto the intermediate transfer belt 251. Thus, a full-color image is formed on the intermediate transfer belt 251. The full color image is then transferred to the recording material S all at once by the action of a secondary transfer roller 254 as a secondary transfer means. A transfer device 205 is configured to transfer the toner image formed in each image forming unit to the recording material S by the intermediate transfer belt 251, the primary transfer roller 252, the secondary transfer roller 254, and the like.

  The recording material S is stored in a cassette 281 as recording material storage means, and is pressed by a pickup means (not shown) by a pressing base 282 as recording material lifting / lowering means. The recording material S conveyed by the pick-up means is separated and conveyed by the conveyance roller 283 and the retard roller 284. The recording material S thus conveyed is temporarily stopped by a registration roller pair 285 as registration means, and the feeding is resumed in accordance with the timing of the full-color toner image formed on the intermediate transfer belt 251. In this way, the recording material S is separated and conveyed from the cassette 281 serving as a recording material storage unit, and conveyed to a portion (secondary transfer portion) T2 between the intermediate transfer belt 251 and the secondary transfer roller 254.

  The full-color image transferred to the recording material S is then fixed on the recording material S by a fixing device 209 as fixing means. The recording material S on which the full-color image is fixed is discharged out of the apparatus main body A through a pair of discharge rollers 286 and 287 as recording material discharge means.

  In this embodiment, the recording material conveying means is constituted by the cassette 281, the pickup means, the conveying roller 283, the retard roller 284, the registration roller pair 285, the discharge roller pairs 286, 287 and the like.

[Process cartridge]
In this embodiment, the photosensitive drum 201 and a charging roller 202 as a process means acting on the photosensitive drum 201, the developing device 204, and the cleaning device 206 are integrally formed into a cartridge and can be attached to and detached from the apparatus main body A. It is referred to as cartridge B. In this embodiment, the process cartridge B includes a first frame (drum frame) that supports the photosensitive drum 201, the charging roller 202, and the cleaning device 206, and a second frame (development) that supports the developing device 204. The frame is integrally formed into a cartridge.

  The aspect of the process cartridge B is not limited to that of the present embodiment, and includes at least one of a photoconductor and a charging unit, a cleaning unit, and a developing unit as a process unit that acts on the photoconductor. The cartridge can be integrally formed and can be attached to and detached from the apparatus main body.

[Development means separation and drive control]
(Development means separation and drive switching mechanism)
Since the image is sequentially formed on the photosensitive drum 201, when the first image forming unit PY that forms the first color and the fourth image forming unit PK that forms the last color are compared, development is performed at the same timing. When the roller 241 is brought into contact with the photosensitive drum 201, when the full color image is formed, the developing roller 241 of the fourth image forming unit PK rotates even in an unnecessary non-image area at the start of image formation. Conversely, at the end of image formation, the developing roller 241 of the first image forming unit PY rotates even in an unnecessary non-image area.

  Accordingly, the developing roller 241 is contacted / operated / separated / stopped only at a timing required for image formation, in particular, the position of the developing unit relative to the photosensitive member is changed sequentially from the upstream side of the image forming process, and Starting / stopping driving is extremely advantageous, for example, in the following points.

  That is, it is usually necessary to start the rotation of the intermediate transfer member and the image carrier before the start of image formation in order to stabilize the rotation of the image carrier and stabilize the charging. Further, if the image carrier that is in contact with the intermediate transfer member does not continue to rotate while the intermediate transfer member is rotating, the contacted surface is worn and the image is adversely affected. Further, the intermediate transfer member cannot perform the contact / separation operation with the image carrier until the transfer of the formed image onto the paper or the like is completed. This is because an operation that gives vibration such as a separation operation causes image blurring.

  That is, the most severe use condition may be a case where a document having a low printing rate is intermittently printed. The first image carrier starts to rotate before the start of image formation and must continue to rotate until the transfer of the image onto the paper or the like is completed. For example, in the apparatus configuration shown in FIG. 1, when one small-size sheet is intermittently printed, it is formed on the intermediate transfer member from the image transfer unit that transfers the first color toner image to the intermediate transfer member. Until the image transfer is completed, the image carrier of the first color rotates by an amount corresponding to 3 to 4 prints. At this time, if the developing means is in contact with the first color image carrier, the developing means needs to continue to rotate.

  However, since the toner is electrostatically charged by friction, the toner deteriorates due to friction between the toners while the developing unit is rotating, and the life is determined by the rotation amount of the developing unit. The toner deteriorates due to friction with the charging means and the drum. As described above, under the strictest usage conditions, the image carrier, the developing means, etc. need to be rotated by 3 or 4 sheets each time one sheet is printed. May be reached. If the development life is extended until the toner consumption is completed, there is a concern that the image deteriorates and the quality cannot be maintained. Also, if development replacement is requested before toner consumption is completed, the user is forced to replace the toner even though the toner remains, so the usability is not good.

  On the other hand, if the developing means is separated from the image carrier after the image transfer from the image carrier to the intermediate transfer body is completed, the rotation of the developing means can be stopped without affecting the image. Furthermore, by sequentially performing the contact / separation of the developing means, the developing means for each color can be kept at the minimum rotation amount necessary for forming an image. When all color developing means are simultaneously brought into contact / separated, the final color developing means starts rotating at the start of image formation of the first color, and the first color developing means starts the final transfer after transferring the image. Since it must rotate until the color transfer is completed, a rotation amount corresponding to two sheets is generated in order to print one sheet.

  Therefore, the image forming apparatus 200 according to the present exemplary embodiment includes a developing unit separation / drive switching mechanism described below.

  2 and 3 show a contact / separation and drive switching mechanism (hereinafter simply referred to as “switching mechanism”) 100 for controlling the contact / separation of the developing means and the start / stop of driving in this embodiment. 4 to 6 show the drive switching means 3 and the moving means 4 of the developing roller 241 of the developing roller 241 operated by the switching mechanism 100. FIG.

  That is, the image forming apparatus 200 is provided corresponding to each of the plurality of image forming units PY, PM, PC, and PK, and the position of the developing roller 241 of each image forming unit with respect to the photosensitive drum 201 is the first position and the first position. And a driving unit 4 for stopping or starting the driving of the developing roller 241 of each image forming unit provided corresponding to each of the plurality of image forming units PY, PM, PC, and PK. Switching means 3. The switching mechanism 100 is provided corresponding to each of at least two moving nodes 1 and a plurality of image forming units PY, PM, PC, and PK, and intermittently rotates with respect to the rotating motion of the moving node 1 to form each image. The moving means 4 and the driven switching means 3 for operating the drive switching means 3 are provided, and the at least two moving nodes 1 are driven to rotate in conjunction with each other and act on the driven nodes 2 at different phases. The forward rotation of the moving node 1 causes the developing roller 241 to sequentially move from the first position to the second position and start to drive from the image forming unit upstream in the conveyance direction of the intermediate transfer belt 3, or Then, the developing roller 241 is sequentially moved from the second position to the first position from the image forming unit upstream in the conveyance direction of the intermediate transfer belt 251 and the driving thereof is stopped.

  More specifically, in the present embodiment, the switching mechanism 100 is configured by a Geneva mechanism including a Geneva mechanism slave vehicle 2 as the driven node and a Geneva mechanism original vehicle 1 as the movable node, as illustrated. Is done.

  In this embodiment, the same number of Geneva mechanism slave wheels 2 as the number of image forming units as the Geneva mechanism slave wheels 2 (first, second, third, and fourth Geneva mechanism slave wheels 2Y, 2M, 2C, and 2K). Have In this embodiment, the number of Geneva mechanism original vehicles 1 (first, second, second) is the same as the number of image forming units provided as the Geneva mechanism original vehicles 1 corresponding to the respective Geneva mechanism slave vehicles 2. 3, 4th Geneva mechanism original vehicle 1Y, 1M, 1C, 1K). That is, in the present embodiment, the Geneva mechanism slave vehicle 2 (2Y, 2M, 2C, 2K) and the Geneva mechanism original vehicle 1 (1Y, 1M, 1C, respectively) corresponding to the image forming units PY, PM, PC, and PK. 1K) is provided for each pair.

  The image forming apparatus 200 uses the photosensitive drum 201 and the developing roller 241 as the moving unit 4 that moves the position of the developing roller 241 of each image forming unit with respect to the photosensitive drum 201 between the first position and the second position. A contact / separation mechanism for switching between contact / separation (ie, contact and non-contact). Further, the image forming apparatus 200 operates / stops the development roller 241 as an operation switching unit for stopping or starting the driving of the developing roller 241 of each image forming unit, that is, independent of the driving of the photosensitive drum 201 (that is, driving driving). It has a drive transmission / release mechanism for switching between transmission / release. In particular, in this embodiment, the moving means 4 and the drive switching means 3 are controlled by a common drive source.

  With this mechanism, the switching mechanism 100 causes the developing roller 241 to sequentially contact the photosensitive drum 201 from the image forming unit upstream in the conveyance direction of the intermediate transfer belt 251 during image formation (that is, the first roller separated from the photosensitive drum 201). From the position to the second position in contact with the photosensitive drum 201), and the driving thereof is started. Further, the switching mechanism 100 makes the developing roller 241 non-contact with the photosensitive drum 201 sequentially from the upstream side in the conveyance direction of the intermediate transfer belt 251 after the image formation is completed by the above-described mechanism (that is, the first contacted with the photosensitive drum 201). From the position 2 to the first position separated from the photosensitive drum 201), and the drive is stopped.

  Referring to FIG. 2, the Geneva mechanism follower (Geneva gear) 2 has a radial groove 21 in a gear body 23 that rotates about a rotation shaft 22. A portion between the groove 21 and the groove 21 is a restricting portion 24 having an arcuate contour curve that is convex toward the center of rotation. As will be described later, the outer periphery of the disc portion 13 of the Geneva mechanism original vehicle 1 (Circumferential part) and contact each other. The Geneva mechanism original vehicle 1 rotates around a rotating shaft 12 and has a protruding portion 14 at a part of the disk portion 13, and a drive transmission portion (pin) 11 is fixed to the protruding portion 14. The drive transmission portion 11 slides in a radial groove 21 of the Geneva mechanism follower 2 parallel to the rotation shaft 12. Further, a part of the projecting portion 14 on the disc portion 13 side is cut off so that the Geneva mechanism original vehicle 1 and the Geneva mechanism slave wheel 2 can be rotated.

  The first Geneva mechanism original vehicle 1Y in FIG. 2 will be further described as an example. This Geneva mechanism original vehicle 1Y rotates as a moving node in the direction of arrow R1 (forward rotation direction) in the drawing to the position shown in the figure (solid line). If it exists, the drive transmission site | part 11Y and the groove | channel 21Y will mesh, and the Geneva mechanism follower wheel 2 will rotate. When the drive transmission portion 11Y comes to the position indicated by the broken line, the engagement between the drive transmission portion 11Y and the groove 21Y is disengaged, and the arc outline of the restricting portion 24 and the outer periphery (circumference) of the disc portion 13 come into contact with each other. Since the relative sliding motion is performed, the Geneva mechanism slave is stationary. Next, when the Geneva mechanism original vehicle 1 makes one rotation and the drive transmission part 11Y again reaches the position shown in the figure (solid line), the Geneva mechanism slave wheel 2 rotates again and the drive transmission part 11Y comes to the position indicated by the broken line. When it stops. As described above, in this embodiment, the Geneva mechanism slave wheel 2 is rotated 1/4 by one rotation of the Geneva mechanism original vehicle 1.

  Then, as shown in FIG. 2, the first to fourth Geneva mechanism original vehicles 1Y, 1M, 1C, and 1K act on the Geneva mechanism slave vehicles 2Y, 2M, 2C, and 2K at different phases, respectively. Each is assembled with a different phase. That is, at least two Geneva mechanism original vehicles 1 as at least two moving nodes included in the switching mechanism 100 have drive transmission portions 11 that act on the Geneva mechanism slave vehicle 2 at different phases.

  In this embodiment, the first to fourth Geneva mechanism original vehicles 1Y, 1M, 1C, and 1K are meshing start positions of the first to fourth Geneva mechanism slave vehicles 2Y, 2M, 2C, and 2K, respectively. They are assembled with a phase difference of 90 ° from Q as the origin. That is, the phase difference in the forward rotation direction of the second to fourth Geneva mechanism original vehicles 1M, 1C, and 1K with respect to the first Geneva mechanism original vehicle 1Y is the first to fourth Geneva mechanism subordinates to which each acts. The engagement start positions Q with the cars 2Y, 2M, 2C, and 2K are set to 90 °, 180 °, and 270 °, respectively. And the 1st-4th Geneva mechanism original vehicles 1Y, 1M, 1C, and 1K are driven by the same phase by the common drive source 61 (FIG. 14) with which the drive means 6 is provided in a present Example.

  When the Geneva mechanism original vehicle 1 rotates 360 ° in the direction of the arrow R1 in the figure, the operations of the respective Geneva mechanism followers 2Y, 2M, 2C, and 2K are as shown in Table 1 below.

  That is, at the home position before the image forming operation, the first Geneva mechanism original vehicle 1Y arranged as shown in FIG. 2 rotates 90 ° in the direction of the arrow R1 in the drawing (at the same time, the second to fourth Geneva at the same time). The mechanism original vehicle also rotates 90 ° in the same direction.) The drive transmission portion 11Y of the first Geneva mechanism original vehicle 1Y engages with the groove 21Y of the first Geneva mechanism slave vehicle 2Y and transmits the drive thereto. . As a result, the first Geneva mechanism follower wheel 2Y rotates 90 ° in the direction of the arrow R2 in the figure.

  Further, when the first to fourth Geneva mechanism original vehicles 1Y, 1M, 1C, and 1K rotate 90 ° in the direction of arrow R1 in the drawing, the drive transmission portion 11M of the second Geneva mechanism original vehicle 1M becomes the second Geneva mechanism. Engage with the groove 21M of the follower wheel 2M to transmit the drive thereto. As a result, the second Geneva mechanism follower wheel 2M rotates 90 ° in the direction of arrow R2 in the figure.

  Similarly, the first to fourth Geneva mechanism original vehicles 1Y, 1M, 1C, and 1K are further rotated by 90 ° in the direction of the arrow R1 in the drawing, so that the third and fourth Geneva mechanism slave vehicles 2C and 2K Are sequentially rotated by 90 ° in the direction of arrow R2 in the figure.

  Here, in the present embodiment, the first to fourth Geneva mechanism followers 2Y, 2M, 2C, and 2K have the same number of grooves 21 as the number of image forming units. The moving means 4 and the drive switching means 3 of the developing roller 241 described later in detail are interlocked with the 90 ° rotation of the first to fourth Geneva mechanism followers 2Y, 2M, 2C, and 2K, and the developing roller 241. Is brought into contact with or separated from the photosensitive drum 201, and the driving of the developing roller 241 is started or stopped.

  Accordingly, while the first to fourth Geneva mechanism original vehicles 1Y, 1M, 1C, and 1K make one rotation, the first to fourth Geneva mechanism slave wheels 2Y, 2M, 2C, and 2K corresponding to the respective image forming units. Are sequentially rotated by 90 °, and the contact / separation of the developing roller 241 with respect to the photosensitive drum 201 and the transmission / release of driving are sequentially performed from the image forming unit upstream in the conveyance direction of the intermediate transfer belt 251.

  In the present embodiment, the first to fourth Geneva mechanism original vehicles 1Y, 1M, 1C, and 1K are rotated twice to perform contact / separation of the developing roller 241 with respect to the photosensitive drum 201 and start / stop operation of driving. One cycle can be realized. Table 2 shows the contact / separation state of the developing roller 241 with respect to the photosensitive drum 201 of each image forming unit and the start / stop of driving when the four-color image formation is started from the stop state of the image forming operation in this embodiment. Indicates the state.

(Drive switching means)
Next, the drive switching unit 3 that switches the start / stop of the driving of the developing roller 241 by the operation of the Geneva mechanism followers 2Y, 2M, 2C, and 2K will be described. As described above, the drive switching unit 3 is controlled by the switching mechanism 100. Since the control method of the drive switching means 3 by each Geneva mechanism slave vehicle 2Y, 2M, 2C, 2K is substantially the same, only one Geneva mechanism slave vehicle will be described below.

  Referring to FIG. 4, Geneva mechanism original vehicle 1 receives drive transmission from drive source 61 and rotates in the direction of arrow R1 in the figure. The drive transmission portion 11 fixed to the Geneva mechanism master vehicle 1 acts on the Geneva mechanism slave vehicle 2 while the Geneva mechanism master vehicle 1 makes one round, and rotates the Geneva mechanism slave vehicle 2 by 90 °. The rotation operation of the Geneva mechanism follower 2 is transferred to the clutch cam 31 which is the first switching operation member provided in the drive switching means 3 via the idle gear 51 which is the first switching drive transmission member provided in the switching drive transmission means 5. Communicated.

  FIG. 5 shows the clutch mechanism in more detail. The clutch cam 31 has a concave portion 31 a and a convex portion 31 b and is rotated by the idle gear 51. The clutch cam 31 acts on the convex portion 32a of the clutch control cam 32 which is a second drive switching operation member provided in the drive switching means. That is, when the clutch cam 31 is rotated by the idle gear 51 and the convex portion 32a of the clutch control cam 32 and the convex portion 31b of the clutch cam 31 face each other, the clutch control cam 32 moves upward in the figure. Then, the ratchet 33 which is a drive connecting portion provided in the drive switching means 3 is pushed upward.

  The ratchet 33 is fixed in the rotational direction with respect to the drive shaft 72 provided in the developing unit drive system 7, and the rotational force of the ratchet 33 is transmitted to the drive shaft 72.

  When the ratchet 33 is pushed upward as described above, it engages with a drive gear ratchet groove (drive connecting portion) 71a provided in the drive gear 71 as a developing means drive transmission member provided in the developing means drive system 7, The rotational force of the drive gear 71 that is constantly rotating is transmitted to the drive shaft 72 by a drive source (not shown) of the developing means drive system 7.

  Conversely, when the clutch cam 31 is rotated by the idle gear 51 and the concave portion 31a of the clutch cam 31 and the convex portion 32a of the clutch control cam 32 face each other, the clutch control cam 32 is pushed downward, The ratchet 33 is also pushed downward. At that time, the engagement between the ratchet 33 and the drive gear 71 is released, and the transmission of the rotational force to the drive shaft 72 is released.

  In this embodiment, every time the Geneva mechanism follower wheel 2 rotates 90 °, the convex portion 31b of the clutch cam 31 moves from the position where the concave portion 31a of the clutch cam 31 faces the convex portion 32a of the clutch control cam 32. It switches to the position which opposes the convex part 32a. As a result, every time the Geneva mechanism original vehicle 1 makes one rotation, the drive of the developing roller 241 is transmitted / released.

  In the present embodiment, the drive switching means 3 is configured to include the clutch cam 31, the clutch control cam 32, and the ratchet 33.

(transportation)
Next, the moving means 4 that switches the contact / separation of the developing roller 241 with respect to the photosensitive drum 201 by the operation of the Geneva mechanism followers 2Y, 2M, 2C, and 2K will be described. As described above, the moving unit 4 is controlled by the switching mechanism 100. Since the control method of the moving means 4 by each Geneva mechanism slave vehicle 2Y, 2M, 2C, 2K is substantially the same, only one Geneva mechanism slave vehicle will be described below.

  FIG. 6 shows the moving means (contact / separation mechanism) 4 of the developing means 241 with respect to the photosensitive drum 201. Referring also to FIG. 4, the Geneva mechanism slave vehicle 2 includes the moving means 4 via idle gears 51, 52, and 53 that are first, second, and third switching drive transmission members included in the switching drive transmission means 5. It acts on the separating cam 41 which is a moving actuating member provided in the.

  The separation cam 41 is pivotally supported by a rotation shaft 41a fixed to the same casing (a drum frame constituting a part of the process cartridge B) as the photosensitive drum 201. The separation cam 41 acts on the rotation shaft 241a of the developing roller 241 fixed to a casing (developing frame body constituting a part of the process cartridge B) different from the photosensitive drum 201 every time it rotates 180 °. To do. Thereby, the contact / separation of the developing roller 241 with respect to the photosensitive drum 201 is performed.

  In this embodiment, every time the Geneva mechanism slave wheel 2 rotates 90 °, the separating cam 41 rotates 180 °, and the Geneva mechanism original vehicle 1 makes one rotation, whereby the contact / separation of the developing means is performed.

(Linkage of drive switching means and moving means)
FIG. 7 shows a state where the driving of the developing roller 241 is stopped and the developing roller 241 is separated from the photosensitive drum 201. In the drive switching unit 3, the drive of the drive gear 71 is not transmitted to the drive shaft 72 because the ratchet 33 is not engaged with the ratchet groove 71 a. At this time, the separation cam 4 of the moving means 4 acts on the rotating shaft 241 a of the developing roller 241 to separate the developing roller 241 from the photosensitive drum 201.

  As shown in FIG. 8, when the Geneva mechanism original vehicle 1 rotates 360 °, the Geneva mechanism slave vehicle 2 rotates 90 °. At the same time, the idle gear 51 acts on the clutch cam 31 of the drive switching means 3 and the drive gears (idle gears 52, 53) of the moving means 4 in conjunction with the Geneva mechanism follower 2. The clutch cam 31 of the drive switching means 31 rotates 90 °, and the convex portion and the convex portion come to coincide with each other from the state where the concave portion and the convex portion of the clutch control cam 32 and the clutch cam 31 coincide when the drive transmission is stopped. . As a result, the ratchet 33 is pushed upward in the figure and engages with the ratchet groove 71a. Then, the rotational force of the drive gear 71 is transmitted to the drive shaft 72. The driving force of the driving shaft 72 is transmitted to the developing roller 241 by a gear train (arrow) (not shown). At the same time, the separation cam 4 of the moving means 4 rotates 180 °, and the developing roller 241 contacts the photosensitive drum 201. Further, when the Geneva mechanism original vehicle 1 rotates 360 °, the state returns to the state of FIG.

(Switching control)
FIG. 14 shows a schematic control block relating to separation / contact and drive control of the developing means of this embodiment.

  The image forming apparatus 200 includes an image forming control unit 300 including a CPU 301 as a central element (control means) for control, a ROM 302 and a RAM 303 as storage means. The image forming control unit 300 causes the image forming apparatus 200 to perform a sequence operation according to programs, data, and the like stored in the ROM 302 and the RAM 303. The image forming control unit 300 includes image forming units such as a charging roller 202, a laser scanner 203, a developing unit 204, a primary transfer roller 252, an intermediate transfer belt 251, a secondary transfer roller 254, a fixing unit 209, and a recording material feeding unit. The overall operation of the apparatus 200 is controlled. In particular, in this embodiment, the CPU 301 serving as the control unit of the image forming control unit 300 operates the driving source 61 of the driving unit 6 to control the operation of the switching mechanism 100, thereby moving the developing unit 241. The drive switching means 3 is controlled. Further, the CPU 301 may be connected to the output of the phase detection means 8 for detecting the position in the rotational direction of the Geneva mechanism slave vehicle 2 described later. The CPU 301 can detect the rotational direction position of the Geneva mechanism follower 2 from the change in the output of the phase detector 8 and can control the operation of the drive source 61 based on this.

  An image processing unit 400 is connected to the image forming control unit 300, and the image processing unit 400 receives image signals from an external device such as a document reading device or a personal computer that are communicably connected to the apparatus main body A. In addition to receiving, the image forming control unit 300 transmits a signal related to image forming. The image formation control unit 300 controls the operation of each unit of the image forming apparatus 300 according to the image formation signal. It will be easily understood that the document reading device may be a document reading unit integrally formed with the apparatus main body.

  In the present embodiment, before the image forming operation, the first to second Geneva mechanism original vehicles 1Y, 1M, 1C, and 1K are in the home positions shown in FIG. 2 (that is, the first Geneva mechanism original vehicle 1Y. Is at the engagement start position Q with the first Geneva mechanism follower wheel 2Y.). At this time, the developing roller 241 of each developing device 204 is separated from the photosensitive drum 201 in the first to fourth image forming portions PY, PM, PC, and PK.

  In the case of forming a four-color full-color image, when image formation is started, at least at a predetermined timing until the electrostatic image formed on the photosensitive drum 201Y of the first image forming unit PY reaches the developing device 204Y. The CPU 301 of the image formation control unit 300 drives the drive source 61 of the switching mechanism 100 to rotate the first to fourth Geneva mechanism original vehicles 1Y, 1M, 1C, 1K by 90 ° in the direction of the arrow R1 in FIG. . Next, the CPU 301 drives the drive source of the switching mechanism 100 at a predetermined timing until at least the electrostatic latent image formed on the photosensitive drum 201M of the second image forming unit PM reaches the developing device 204M. The first to fourth Geneva mechanism original vehicles 1Y, 1M, 1C, and 1K are further rotated by 90 ° in the same direction. Similarly, at a predetermined timing until the electrostatic images formed on the photosensitive drums 201C and 201K of the third and fourth image forming units PC and PK reach at least the corresponding developing devices 204C and 204K, respectively. The CPU 301 drives the driving source of the switching mechanism 100 to sequentially rotate the first to fourth Geneva mechanism original vehicles 1Y, 1M, 1C, 1K in the same direction by 90 °.

  As a result, the developing roller 241 is brought into contact with and driven by the photosensitive drum 201 sequentially from the image forming unit upstream of the image forming process.

  For example, when the formation of an image to be transferred onto the final recording material S of a series of recording materials S (single or plural) is completed, first, at least the first image forming unit PY applies the intermediate transfer belt 251. At a predetermined timing after the toner image to be transferred is formed on the photosensitive drum 201Y, the CPU 301 drives the drive source of the switching mechanism 100 to turn the first to fourth Geneva mechanism original vehicles 1Y, 1M, 1C, 1K. Rotate 90 ° in the direction of arrow R1 in FIGS. Next, at a predetermined timing after the toner image to be transferred from at least the second image forming unit PM to the intermediate transfer belt 251 is formed on the photosensitive drum 201M, the CPU 301 drives the drive source of the switching mechanism 100 to perform the first operation. The fourth Geneva mechanism original vehicle 1Y, 1M, 1C, 1K is further rotated by 90 ° in the same direction. Similarly, in the third and fourth image forming units PC and PK, the CPU 301 displays the switching mechanism 100 at a predetermined timing after at least a toner image to be transferred to the intermediate transfer belt 251 is formed on the photosensitive drums 201C and 201K. The first to fourth Geneva mechanism original vehicles 1Y, 1M, 1C, and 1K are further rotated sequentially in the same direction by 90 °.

  As a result, the developing roller 241 is sequentially separated from the photosensitive drum 201 and the drive is stopped sequentially from the image forming unit on the upstream side of the image forming process after the toner image has been transferred to the intermediate transfer belt 251.

  More specifically, FIG. 15 shows a timing chart of the image forming operation by each image forming unit and the contact / separation of the developing roller 241 with respect to the photosensitive drum 201.

  Before the first color image starts to be formed, the contact operation of the first color developing roller 241 to the photosensitive drum 201 starts and ends. Image formation is started after a predetermined time after the abutting operation.

  The second color image starts image formation with a certain time lag so as to overlap the first color image on the intermediate transfer belt 251.

  The contact of the developing roller 241 of the second color with the photosensitive drum 201 is ended a certain time before the image formation of the second color is started as in the first color.

  Similarly, the contact of the third and fourth color developing rollers 241 to the photosensitive drum 201 and the image forming sequence are repeated.

  A certain time after the end of image formation, the developing roller 241 of the color for which image formation has been completed is sequentially separated from the photosensitive drum 201.

  The rotation speed of the drive source (drive motor) 61 that controls the contact / separation means of the developing roller 241 to the photosensitive drum 201 is set so as to match the image formation timing as shown in the motor drive chart in FIG. . However, the drive source (drive motor) 61 may be intermittently driven at the contact / separation timing of each color, not limited to the operation mode illustrated. However, in this case, the stop control for the first to third colors is an open loop. That is, the stop position depends only on the position accuracy of the motor.

  Specifically, as will be described in Example 3 described later, phase detection means 8 for detecting the rotational direction position of the Geneva mechanism follower vehicle 2 can be provided in the fourth Geneva mechanism follower vehicle 2K, for example. When the contact / separation operation of the developing roller 241 of the fourth color with respect to the photosensitive drum 201 starts and the corresponding fourth Geneva mechanism slave wheel 2K rotates by a certain angle, the fourth Geneva mechanism slave wheel 2K is provided. The position detection flag 81 of the phase detection means 8 blocks / transmits the photo sensor 82, and the phase detection signal is inverted (see FIG. 12). After inversion of the phase detection signal, the Geneva mechanism original vehicle 1 can be stopped at the home position by stopping the drive source (drive motor) 61 after rotating a certain angle. Further, if the phase detection signal does not reverse within a certain time after the start of driving, it can be regarded as a driving abnormality and the apparatus can be stopped.

  Here, as described above, Patent Documents 1 to 3 describe that the developing units of a plurality of image forming units are selectively brought into contact / separated or started / stopped. However, these conventional techniques do not change the position of the developing unit relative to the photosensitive member and start / stop driving sequentially from the image forming unit upstream in the conveying direction of the toner image conveying member during image formation.

  Conventionally, a configuration using a lever, a cam or the like as a means for making the developing means non-contact with the photosensitive member when not operating is generally used, but each developing means can be controlled by using a common drive source by a conventional mechanism. In the case of realizing a configuration in which the photosensitive body is sequentially contacted / separated from the upstream in the transport direction of the toner image transport body, the apparatus main body is increased in size and complexity.

  In the configuration using the cam, it is necessary to provide a region where the developing units of all the image forming units are in contact with each other and a region where the developing units of all the image forming units are separated. Further, since a stroke amount for reliably realizing contact / separation is also required, this leads to an increase in the size of the cam.

  Further, conventionally, there has been known a process cartridge system in which the photosensitive member and the process means acting on the photosensitive member are integrally formed into a cartridge and can be attached to and detached from the main body of the image forming apparatus. When the configuration in which the process cartridge is detachable from the longitudinal direction of the photosensitive member is used, the cross-sectional area of the cam cannot be used, which causes a reduction in the capacity of the cartridge.

  Even in a configuration using a lever or the like, it is necessary to realize a contact / separation operation sequentially using another mechanism such as a cam. Further, when the lever is separated, the contact force of the developing means is transmitted to the lever, so that a lock mechanism is necessary.

  In the configuration for starting / stopping the driving of the developing means, a configuration interlocking with the contact / separation mechanism is generally used, but since the same mechanism is used, the overall size of the apparatus is increased.

  Although a method of controlling each image forming unit using different drive sources is conceivable, the apparatus becomes expensive due to an increase in the number of drive sources, an increase in the number of sensors, and the like.

  On the other hand, as described above, according to the present embodiment, the contact / separation of the developing roller 241 with respect to the photosensitive drum 201 and the start / stop control of the developing roller 241 can be controlled by a small and simple mechanism. it can.

  By using the switching mechanism 100 as a Geneva mechanism as described above, intermittent motion of the image forming units PY, PM, PC, and PK can be realized in the same space as a normal reduction drive gear. Then, with respect to the Geneva mechanism original vehicles 1Y, 1M, 1C, and 1K of the image forming units PY, PM, PC, and PK, the meshing start positions Q of the Geneva mechanism slave wheels 2Y, 2M, 2C, and 2K on which they operate are the origins. By providing a phase difference as described above, each station can realize developing means control at different timings while the Geneva mechanism original vehicles 1Y, 1M, 1C, and 1K make one rotation by the common drive source 61. Accordingly, the developing roller 241 can be sequentially brought into contact / separated from the image forming unit upstream in the transport direction of the toner transport body, and the driving thereof can be started / stopped.

  The operations of the image forming units PY, PM, PC, and PK (the contact / separation of the developing roller 241 with respect to the photosensitive drum 201 and the start / stop of driving) are the operations of the previous image forming unit in the image forming process ( Since the development roller 241 is started after the contact / separation of the developing roller 241 and the start / stop of driving) are completed, the load is distributed and control by a small motor becomes possible.

  In the above embodiment, the Geneva mechanism follower wheel 2 has been described as having the same number of image forming units, that is, four grooves 21, but the present invention is not limited to this. The groove 21 of the Geneva mechanism slave wheel 2 may be an integer multiple of the number of image forming units.

Further, the phase of the Geneva mechanism original vehicle 1 is set at a phase shifted by an integer multiple when 360 ° is an integral multiple of the number of image forming portions with the origin of engagement with the corresponding Geneva mechanism slave vehicle 2 as the origin. . That is, the engagement start position Q with the corresponding Geneva mechanism slave vehicle 2 of the other Geneva mechanism master vehicle 1 with respect to one Geneva mechanism master vehicle 1 of at least two Geneva mechanism master vehicles 1 provided in the switching mechanism 100 is set. The phase difference α (°) in the forward rotation direction with respect to the origin is represented by N as the number of the plurality of image forming units.
α (°) = [360 ° / (N × n1)] × n2
(However, n1 and n2 are positive integers.)
Can be set to satisfy.

Example 2
Next, another embodiment of the present invention will be described. The basic configuration and operation of the image forming apparatus according to the present exemplary embodiment are the same as those of the first exemplary embodiment, and the configuration of the Geneva mechanism in the separation / contact of the developing unit and the drive switching mechanism is different. Accordingly, elements having substantially the same or corresponding functions and configurations as those of the first embodiment are denoted by the same reference numerals, and detailed description thereof is omitted.

  As shown in FIGS. 9 to 11, in this embodiment, the switching mechanism 100 includes the same number of Geneva mechanism original vehicles 1 (first and second Geneva mechanism original vehicles 1 a and 1 b) and the number of image forming units. Are four Geneva mechanism slave wheels 2 (first, second, third, and fourth Geneva mechanism slave wheels 2Y, 2M, 2C, and 2K). Similarly to the first embodiment, each Geneva mechanism follower wheel 2 has the same number of grooves 21 as the number of image forming portions.

  The first and second Geneva mechanism original vehicles 1a and 1b are engaged with corresponding Geneva mechanism slave vehicles 2 (first Geneva mechanism slave vehicle 2Y and third Geneva mechanism slave vehicle 2C). With the phase difference of 180 ° as the origin. That is, the phase difference in the forward rotation direction of the second Geneva mechanism original vehicle with respect to the first Geneva mechanism original vehicle 1a is different from that of the first and third Geneva mechanism slave vehicles 2Y and 2C that act first. It is 180 degrees with the meshing start position Q as the origin.

  As shown in FIG. 10, the second Geneva mechanism original vehicle 1b transmits the driving force from the drive source 61 via gears 62 and 63 as first and second drive transmission members provided in the switching mechanism drive means 6. Is done. The first Geneva mechanism original vehicle 1a is drivingly connected to the second Geneva mechanism original vehicle 1b by a belt 64 as a third drive transmission member provided in the switching mechanism driving means 6.

  As described above, in this embodiment, the two Geneva mechanism slave vehicles 2Y, 2M (or 2C, 2K) are operated by one Geneva mechanism original vehicle 1a (or 1b).

  When the first and second Geneva mechanism original vehicles 1a and 1b are rotated 360 ° in the direction of arrow R1 in the figure by the drive source 61, the respective Geneva mechanism followers 2Y, 2M, 2C and 2K are shown in Table 1 above. Works in the same way as

  That is, at the home position before the image forming operation, the first Geneva mechanism original vehicle 1a arranged as shown in FIG. 9 rotates 90 ° in the direction of the arrow R1 in the drawing (at the same time, the second Geneva mechanism original vehicle 1b also rotates 90 ° in the same direction.), The drive transmission portion 11a of the first Geneva mechanism master vehicle 1a engages with the groove 21Y of the first Geneva mechanism slave vehicle 2Y to transmit the drive thereto. As a result, the first Geneva mechanism follower wheel 2Y rotates 90 ° in the direction of the arrow R2 in the figure.

  Further, when the first and second Geneva mechanism original vehicles 1a and 1b rotate 90 ° in the direction of the arrow R1 in the drawing, the drive transmission portion 11a of the first Geneva mechanism original vehicle 1a becomes the second Geneva mechanism slave vehicle 2M. Engage with the groove 21M to transmit the drive thereto. As a result, the second Geneva mechanism follower wheel 2M rotates 90 ° in the direction of arrow R2 in the figure.

  Similarly, when the first and second Geneva mechanism original vehicles 1a and 1b are further rotated by 90 ° in the direction of the arrow R1 in the drawing, the drive transmission portion 11b of the second Geneva mechanism original vehicle 1b is now changed. The third and fourth Geneva mechanism followers 2C, 2K are sequentially engaged with the grooves 21C, 21K to transmit the drive thereto. As a result, the third and fourth Geneva mechanism followers 2C, 2K sequentially rotate 90 ° in the direction of the arrow R2 in the figure.

  Here, as in the first embodiment, in the present embodiment, the first to fourth Geneva mechanism followers 2Y, 2M, 2C, and 2K have the same number of grooves 21 as the number of image forming units. As in the first embodiment, the moving unit 4 and the drive switching unit 3 of the developing roller 241 are interlocked with the 90 ° rotation of the first to fourth Geneva mechanism followers 2Y, 2M, 2C, and 2K. The developing roller 241 is brought into contact with or separated from the photosensitive drum 201 and the driving of the developing roller 241 is started or stopped.

  Therefore, while the first and second Geneva mechanism original vehicles 1a and 1b make one rotation, the first to fourth Geneva mechanism slave wheels 2Y, 2M, 2C, and 2K corresponding to the respective image forming units are sequentially turned 90. Rotating, the contact / separation of the developing roller 241 with respect to the photosensitive drum 201 and the drive transmission / release are sequentially performed from the image forming unit upstream in the conveyance direction of the intermediate transfer belt 251.

  In this embodiment, the first and second Geneva mechanism original vehicles 1a and 1b rotate twice to realize one cycle of contact / separation of the developing roller 241 with respect to the photosensitive drum 201 and start / stop operation of the drive. it can.

  The control mode of the switching mechanism 100 according to the present embodiment can be the same as that of the first embodiment shown in FIG.

  As described above, according to the present embodiment, the same effects as those of the first embodiment can be obtained, and the two Geneva mechanism followers 2Y, 2M (or 2C, 2K) can be provided by one Geneva mechanism original vehicle 1a (or 1b). By operating, further miniaturization and simplification of the mechanism can be achieved.

Example 3
Next, another embodiment of the present invention will be described. In the present embodiment, a case will be described in which the image forming apparatus according to the second embodiment is provided with a mode for forming a monochrome image (usually monochrome).

  As shown in FIG. 12, an image forming unit used for monochromatic image formation, and although not limited to this, usually, a plurality of image forming units (monochrome print color image forming units) for forming a black image are provided. Among these image forming units, the most downstream image forming unit in the conveyance direction of the intermediate transfer belt 251 (hereinafter referred to as “the most downstream image forming unit”).

  In the monochrome image formation mode, the first and second Geneva mechanism original vehicles 1a and 1b are rotated by 90 ° in the normal rotation direction, that is, the direction opposite to the rotation direction in the color image formation mode. As a result, only the fourth Geneva mechanism driven vehicle 2K can be operated, and the developing roller 241 of only the fourth image forming unit PK among the first to fourth image forming units PY, PM, PC, PK. Contact with the photosensitive drum 201 and transmission of driving force can be performed.

  That is, in the monochrome image forming mode, when the second Geneva mechanism original vehicle 1b is rotated 90 ° in the direction of the arrow R3 from the home position shown in FIG. 9 before the image forming operation (at this time, the first Geneva mechanism original The vehicle 1a also rotates by 90 ° in the same direction.), The drive transmission portion 11b of the second Geneva mechanism original vehicle 1b engages with the groove 21 of the fourth Geneva mechanism slave vehicle 2K, and transmits the drive thereto, The 4 Geneva mechanism follower wheel 2K is rotated 90 ° in the direction of arrow R4 in the figure.

  As described above, the drive switching means 3 and the moving means 4 of the developing roller 241 are interlocked with the 90 ° rotation of the Geneva mechanism follower. Accordingly, by rotating the fourth Geneva mechanism follower wheel 2K by 90 ° in the reverse direction as described above, only the developing roller 241 of the fourth image forming unit PK is brought into contact with the photosensitive drum 201 and driven. Can be started.

  Thus, according to this embodiment, it is possible to start monochrome image formation in a time equivalent to the image formation start time in the full color mode.

  In the monochrome image formation mode, after the image formation is completed, the first and second Geneva mechanism original vehicles 1a and 1b are rotated by 90 ° in the normal rotation direction, that is, in the same direction as the rotation direction in the color mode. Only the developing roller 241 of the fourth image forming unit PK can be separated from the photosensitive drum 201 and the transmission of the driving force can be released.

  The control mode of the switching mechanism 100 according to the present embodiment may be the same as that of the first and second embodiments. However, in this embodiment, the CPU 301 of the image formation control unit 300 performs image processing when forming a monochrome image as described above. When the forming operation starts, the driving source 61 is rotated in a direction opposite to that at the time of color image formation at a predetermined timing, and is rotated in the same direction (forward rotation direction) as that at the time of color image formation after the image formation is completed.

  In particular, when the monochrome image forming mode by the most downstream image forming unit as described above is provided, the drive source 61 of the Geneva mechanism is disposed at a position closest to the Geneva mechanism slave vehicle of the most downstream image forming unit. Is preferred. In other words, the image forming unit for monochrome image formation is the most downstream image forming unit, and the Geneva mechanism original vehicle acting on the Geneva mechanism slave vehicle corresponding to the most downstream image forming unit is compared with other Geneva mechanism original vehicles. Therefore, it is preferable to arrange the drive source so that the drive is transmitted through the shortest path. In this way, by disposing the drive source near the most downstream image forming unit, it is difficult to be affected by backlash and other backlash, and high-precision positioning is possible.

  In addition, the fourth geneva mechanism slave wheel 2K corresponding to the most downstream image forming unit can be provided with phase detection means 8 for detecting the position of the fourth geneva mechanism slave wheel 2K in the rotational direction.

  In the present embodiment, as the phase detection means 8, as shown in FIG. 12, position detection flags 81 and 81 as detection light shielding members are provided at 180 ° symmetrical positions of the fourth Geneva mechanism driven vehicle 2K, and this position detection. A sensor (photo interrupter) 82 for optically detecting the presence or absence of the flags 81 and 81 is provided.

  The state in which the position detection flags 81 and 81 block the detection light of the sensor 82 corresponds to the state in which the developing roller 241 is separated from the photosensitive drum 201 and the driving thereof is stopped. . Further, the state in which the position detection flags 81 and 81 do not block the detection light of the sensor 82 corresponds to the state in which the developing roller 241 is in contact with the photosensitive drum 201 and the driving thereof is started. The correspondence relationship between the transmission / interruption state of the detection light and the contact / separation / drive / stop state may be reversed. Thereby, the contact / separation of the developing roller 241 and the operating / stopped state can be detected from the change in the output of the sensor 82. Further, by rotating the specific angle drive source 61 after the state of the sensor 82 is changed and then stopping, the positioning of the second Geneva mechanism original vehicle 1b can be realized.

  With the above configuration, the contact / separation of the developing roller 241 and the operating / stopped state are detected by one sensor, and at the same time, the second Geneva mechanism original vehicle 1b (and naturally driven in conjunction with this) Positioning control of one Geneva mechanism original vehicle 1a) can be performed.

  More specifically, FIG. 16 shows a timing chart of the image forming operation during monochrome printing and the contact / separation of the developing roller 241 with respect to the photosensitive drum 201.

  When the Geneva mechanism original vehicle 1b rotates in the reverse direction, first, the fourth Geneva mechanism slave vehicle 2K rotates. After reversing the phase detection signal, the fixed angle driving source (driving motor) 61 is rotated and then stopped, so that the contact / separation of only the fourth color developing roller 241 with the photosensitive drum 201 can be realized.

  When the Geneva mechanism master vehicle 1 is engaged with the Geneva mechanism slave wheel 2 and then rotated 45 °, the Geneva mechanism slave vehicle 1 is also rotated 45 °. When the position detection flag 81 of the phase detection means 8 is provided so that the phase detection signal is inverted at a position of 45 ° after the Geneva mechanism original vehicle 1 is engaged with the Geneva mechanism slave vehicle 2, after the phase detection signal is inverted, the Geneva When the mechanism original vehicle 1 is rotated by 45 ° and stopped, the Geneva mechanism original vehicle 1 stops at the home position.

  The phase detection means 8 for detecting the rotational position of the Geneva mechanism slave vehicle having such a configuration can also be applied to the switching mechanism 100 of another embodiment, and the development means is separated and attached with high accuracy. And drive control. In addition, providing the phase detection means 8 only for the most downstream Geneva mechanism follower as described above is extremely advantageous in that it can detect the rotational direction position of the Geneva mechanism follower and reduce the number of parts with high accuracy. However, a plurality of phase detection means may be provided, for example, phase detection means may be provided for all Geneva mechanism slave vehicles.

  As described above, according to the present embodiment, in the image forming apparatus including the switching mechanism 100 according to the present invention, it is possible to quickly execute the image forming mode using only the most downstream image forming unit with a small and simple configuration. it can.

  In the present embodiment, the configuration in which the monochrome image forming mode is provided in the image forming apparatus having the Geneva mechanism described in the second embodiment has been described as an example. It should be understood that the present invention can be arbitrarily applied to an image forming apparatus to which the present invention is applied, such as an image forming apparatus having a Geneva mechanism.

Example 4
Next, another embodiment of the present invention will be described. The basic configuration and operation of the image forming apparatus according to the present embodiment are the same as those of the first and second embodiments, and the developing unit separating and contacting mechanism and the drive switching mechanism are different. Accordingly, elements having substantially the same or corresponding functions and configurations as those of the first embodiment are denoted by the same reference numerals, and detailed description thereof is omitted.

  As shown in FIG. 13, in this embodiment, the switching mechanism 100 includes three Geneva mechanism original vehicles (first, second, and third Geneva mechanism original vehicles 1a, 1b, and 1c) and the number of image forming units. And four Geneva mechanism followers 2Y, 2M, 2C, 2K. In this embodiment, the third and fourth Geneva mechanism slave vehicles 2M and 2C corresponding to the third and fourth image forming units PC and PK are driven by the common Geneva mechanism original vehicle 1d.

  The first to third Geneva mechanism original vehicles 1c, 1d, and 1e are respectively Geneva mechanism slave vehicles (first Geneva mechanism slave vehicle 2Y, second Geneva mechanism slave vehicle 2M, and fourth Geneva mechanism slave vehicle). Assembling with the phase difference of 0 °, 90 ° and 270 °, respectively, with the meshing start position Q with the vehicle 2K) as the origin That is, the phase difference in the forward rotation direction of the second and third Geneva mechanism original vehicles 1d and 1e with respect to the first Geneva mechanism original vehicle 1c is the Geneva mechanism subordinate vehicle 1Y and 1M in which each acts (first). 90 ° and 270 ° with the meshing start position Q with 1K as the origin.

  The first to third Geneva mechanism original vehicles 1c, 1d, and 1e are drivingly coupled by idle gears 65 and 66 as drive transmission members provided in the switching mechanism driving means 6, respectively.

  When the first to third Geneva mechanism original vehicles 1c, 1d, and 1e are rotated 360 ° in the direction of the arrow R1 in the drawing by the drive source, the respective Geneva mechanism followers 2Y, 2M, 2C, and 2K are shown in Table 1 above. It works in the same way as

  That is, at the home position before the image forming operation, when the first Geneva mechanism original vehicle 1c arranged as shown in FIG. 13 rotates 90 ° in the direction of the arrow R1 in the drawing (at the same time, the second and third Geneva The mechanism original vehicles 1d and 1e also rotate 90 ° in the same direction.), The drive transmission portion 11c of the first Geneva mechanism original vehicle 1c engages with and drives the groove 21Y of the first Geneva mechanism slave vehicle 2Y. To communicate. As a result, the first Geneva mechanism follower wheel 2Y rotates 90 ° in the direction of the arrow R2 in the figure.

  Further, when the first to third Geneva mechanism original vehicles 1c, 1d, and 1e are rotated by 90 ° in the direction of the arrow R1 in the drawing, the drive transmission portion 11d of the second Geneva mechanism original vehicle 1d is now turned into the second Geneva mechanism. Engage with the groove 21M of the mechanism follower 2M and transmit the drive to this. As a result, the second Geneva mechanism follower wheel 2M rotates 90 ° in the direction of arrow R2 in the figure.

  Further, when the first to third Geneva mechanism original vehicles 1c, 1d, and 1e rotate 90 ° in the direction of the arrow R1 in the drawing, the drive transmission portion 11d of the second Geneva mechanism original vehicle 1d becomes the third Geneva mechanism follower. The third Geneva mechanism follower wheel 2C rotates 90 ° in the direction of arrow R2 in the drawing by engaging with the groove 21C of 2C and transmitting the drive thereto.

  Similarly, the first to third Geneva mechanism original vehicles 1c, 1d, and 1e are rotated by 90 ° in the direction of the arrow R1 in the drawing, so that this time, the drive transmission portion of the third Geneva mechanism original vehicle 1e. 11e is engaged with the groove 21K of the fourth Geneva mechanism slave wheel 2K and transmits the drive thereto. As a result, the fourth Geneva mechanism follower wheel 2K rotates 90 ° in the direction of arrow R2 in the figure.

  Here, as in the first and second embodiments, in the present embodiment, the first to fourth Geneva mechanism followers 2Y, 2M, 2C, and 2K have the same number of grooves 21 as the number of image forming units. As in the first embodiment, the moving unit 4 and the drive switching unit 3 of the developing roller 241 are interlocked with the 90 ° rotation of the first to fourth Geneva mechanism followers 2Y, 2M, 2C, and 2K. The developing roller 241 is brought into contact with or separated from the photosensitive drum 201 and the driving of the developing roller 241 is started or stopped.

  Accordingly, while the first to third Geneva mechanism original vehicles 1c, 1d, and 1e make one rotation, the first to fourth Geneva mechanism slave wheels 2Y, 2M, 2C, and 2K corresponding to the respective image forming units sequentially The developing roller 241 contacts / separates the photosensitive drum 201 and drives transmission / release sequentially from the image forming section upstream of the intermediate transfer belt 251 in the conveyance direction.

  In the present embodiment, one cycle of the contact / separation of the developing roller 241 with respect to the photosensitive drum 201 and the start / stop operation of the drive can be realized by rotating the first to third Geneva mechanism original vehicles twice.

  As described above, according to the present embodiment, the switching mechanism 100 can be further miniaturized and simplified as in the second embodiment, and the distance between the three Geneva mechanism original vehicles 1c, 1d, and 1e can be set short. The number of gears required for driving connection can be reduced.

  As mentioned above, although this invention was demonstrated according to some specific Example, it should be understood that this invention is not limited to the form of these Examples. For example, in the above-described embodiment, the developing roller is moved as the developing unit to be brought into contact / separated from the image carrier. However, by moving the developing unit, the developing roller is brought into contact with the photosensitive drum. You may make it make it / separate. As is well known to those skilled in the art, a recording material carrier that carries and transports a recording material is provided as a toner image carrier that receives and transports toner images formed by a plurality of image forming units. There is an image forming apparatus. In such an image forming apparatus, the toner images formed in the respective image forming units are sequentially superimposed and transferred onto the recording material carried on the recording material carrier, and then the recording material is separated from the recording material carrier. Then, the toner image is fixed on the recording material by the fixing means to obtain a recorded image. The present invention is equally applicable to such an image forming apparatus.

1 is a schematic cross-sectional view of an embodiment of an image forming apparatus to which the present invention can be applied. It is principal part detail drawing of one Example of the switching mechanism according to this invention. It is principal part detail drawing of one Example of the switching mechanism according to this invention. FIG. 5 is a detailed view of a main part of a contact / separation mechanism of a developing roller with respect to a photosensitive drum and a drive start / stop mechanism by a switching mechanism according to the present invention. It is a principal part detail drawing of the drive clutch of a developing roller. FIG. 6 is a detail view of a main part of a contact / separation mechanism of the developing roller. FIG. 10 is an explanatory diagram for explaining a separation / contact of the developing roller and a drive switching operation. FIG. 10 is an explanatory diagram for explaining a separation / contact of the developing roller and a drive switching operation. It is principal part detail drawing of the other Example of the switching mechanism according to this invention. It is a whole perspective view of the other Example of the switching mechanism according to this invention. It is a whole perspective view of the other Example of the switching mechanism according to this invention. It is principal part detail drawing of the further another Example of the switching mechanism according to this invention. It is principal part detail drawing of the further another Example of the switching mechanism according to this invention. It is a general | schematic control block diagram of the switching mechanism according to this invention. It is a timing chart figure which shows one Example of the operation timing of the image formation operation | movement and switching mechanism according to this invention. It is a timing chart figure which shows the other Example of the operation timing of the image formation operation | movement and switching mechanism according to this invention.

Explanation of symbols

1Y, 1M, 1C, 1K, Geneva mechanism
1a, 1b, 1c, 1d, 1e Geneva mechanism original vehicle (nodal)
2Y, 2M, 2C, 2K Geneva mechanism follower (follower)
3 Drive switching means 4 Moving means 11Y, 11M, 11C, 11K Drive transmission part 11a, 11b, 11c, 11d, 11e Drive transmission part 21Y, 21M, 21C, 21K Groove 61 Drive source 201Y, 201M, 201C, 201K Photosensitive drum ( Image carrier)
241Y, 241M, C, 241K Developing roller (developing means)

Claims (14)

An image forming unit including an image carrier and a developing unit that supplies toner to the electrostatic image formed on the image carrier to form a toner image. The image forming unit receives the toner image from the image carrier. In an image forming apparatus having a plurality of toner image transport bodies to be transported along the moving direction,
A moving unit that is provided corresponding to each of the plurality of image forming units and moves a position of the developing unit of each image forming unit with respect to the image carrier between a first position and a second position;
A drive switching unit provided corresponding to each of the plurality of image forming units to stop or start driving of the developing unit of each image forming unit;
The moving means and the drive switching means of each image forming unit are operated by intermittently rotating with respect to at least two moving nodes and the rotating motion of the moving nodes provided corresponding to each of the plurality of image forming units. A switching mechanism, wherein the at least two movements are rotationally driven in conjunction with each other and act on the driven nodes at different phases;
Have
The switching mechanism moves the developing unit from the first position to the second position sequentially from the image forming unit upstream in the transport direction of the toner transport body by forward rotation of the at least two moving nodes. And the drive is started, and the developing means is sequentially moved from the second position to the first position and driven from the image forming section upstream in the transport direction of the toner transport body. An image forming apparatus characterized in that the image forming apparatus is stopped.   The image forming apparatus according to claim 1, wherein the at least two moving nodes of the switching mechanism are driven by a common driving source. The follower node provided corresponding to each of the plurality of image forming units is a Geneva mechanism driven vehicle having a groove that is an integral multiple of the number of the plurality of image forming units,
The at least two gangs are Geneva mechanism original vehicles having drive transmission parts that act on the Geneva mechanism slave wheel at different phases.
The image forming apparatus according to claim 1, wherein the image forming apparatus includes: Of the at least two Geneva mechanism original vehicles, the phase difference α (°) in the forward rotation direction of another Geneva mechanism original vehicle with respect to one Geneva mechanism original vehicle is the number N of the plurality of image forming units. As
α (°) = [360 ° / (N × n1)] × n2
(However, n1 and n2 are positive integers.)
The image forming apparatus according to claim 3, wherein: Having four image forming portions of first, second, third, and fourth image forming portions along the toner image transport direction of the toner image transport body;
The switching mechanism is provided corresponding to each of the first, second, third, and fourth image forming units, and includes first, second, third, and fourth Geneva mechanism followers each having four grooves. And first, second, third, and fourth Geneva mechanism original vehicles that act on the first, second, third, and fourth Geneva mechanism followers, respectively.
The phase differences in the forward rotation direction of the second, third, and fourth Geneva mechanism original vehicles with respect to the first Geneva mechanism original vehicle are 90 °, 180 °, and 270 °, respectively. The image forming apparatus according to claim 3 or 4.   5. The image forming apparatus according to claim 3, wherein a plurality of Geneva mechanism slaves are operated by one Geneva mechanism original vehicle. Having four image forming portions of first, second, third, and fourth image forming portions along the toner image transport direction of the toner image transport body;
The switching mechanism is provided corresponding to each of the first, second, third, and fourth image forming units, and includes first, second, third, and fourth Geneva mechanism followers each having four grooves. And a first Geneva mechanism master vehicle that acts on the first and second Geneva mechanism slave vehicles, and a second Geneva mechanism master vehicle that acts on the third and fourth Geneva mechanism slave vehicles. And
The image forming apparatus according to claim 6, wherein the phase difference in the forward rotation direction of the second Geneva mechanism original vehicle with respect to the first Geneva mechanism original vehicle is 180 °. Having four image forming portions of first, second, third, and fourth image forming portions along the toner image transport direction of the toner image transport body;
The switching mechanism is provided corresponding to each of the first, second, third, and fourth image forming units, and includes first, second, third, and fourth Geneva mechanism followers each having four grooves. A first Geneva mechanism original vehicle that acts on the first Geneva mechanism slave vehicle, a second Geneva mechanism original vehicle that acts on the second and third Geneva mechanism slave vehicles, and the fourth Geneva A third Geneva mechanism original vehicle acting on the mechanism follower,
7. The image formation according to claim 6, wherein the phase difference in the forward rotation direction of the second and third Geneva mechanism original vehicles with respect to the first Geneva mechanism original vehicle is 90 ° and 270 °, respectively. apparatus.   The moving means and the drive switching means are operated by a 90 ° rotational movement of the Geneva mechanism follower to move the position of the developing means relative to the image carrier between the first position and the second position. The image forming apparatus according to claim 3, wherein driving of the developing unit is stopped or started.   By rotating the at least two moving nodes of the switching mechanism in the reverse direction, a Geneva mechanism follower provided corresponding to the image forming unit on the most downstream side in the transport direction of the toner image transport body is operated to generate the image. The developing unit of the forming unit is moved from the first position to the second position and started to drive, and image formation is performed using only the most downstream image forming unit among the plurality of image forming units. The image forming apparatus according to claim 1, which can be performed.   The image forming apparatus according to claim 10, wherein the most downstream image forming unit is an image forming unit for forming a black image.   A drive source of the switching mechanism is arranged so that the drive is transmitted to the drive node acting on the follower node provided corresponding to the most downstream image forming unit through the shortest path compared to other drive nodes. The image forming apparatus according to claim 10, wherein the image forming apparatus is an image forming apparatus.   A phase detecting means for detecting the rotational direction position of the driven node provided corresponding to the most downstream image forming unit is provided, and the rotational position of the at least two moving nodes is controlled by the phase detecting means. The image forming apparatus according to claim 1, wherein:   2. The developing unit according to claim 1, wherein the developing unit is separated from the image carrier when in the first position, and is in contact with the image carrier when in the second position. 14. The image forming apparatus according to any one of items 13 to 13.

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