JP5691626B2 - Developing device and image forming apparatus - Google Patents

Description

  The present invention relates to a developing device and an image forming apparatus.

As a prior art described in the publication, an engagement plate having a recess is fixed to a side plate of a rack that holds four developing devices. A pin of a rack push lever provided at the tip of a slider having a charge spring is pressed against the side of the engagement plate. The slider moves up based on the clockwise rotation of the charge gear driven by the motor. During this upward movement, the charge spring extends to accumulate the spring force, and the pin engages with the upper recess. The rack is locked by engaging the concave portion of the positioning lever with the pin of the side plate. When this lock is released, there is a developing device that rotates clockwise by the spring force of the charge spring (patent) Reference 1).
Further, as a prior art described in the publication, in a rotating body drive device in which a rotating body is connected to a drive source via a rotation drive shaft and the rotating operation of the rotating body is repeated intermittently, the rotating direction of the rotating body when the rotating body stops Rotation assisting means is provided that accumulates auxiliary energy for energizing and that rotates with the driving energy of the driving source when the rotating body rotates. Here, as the rotation assisting means, there is a rotating body that uses, for example, the torsional energy of a spring member or the positional energy of an eccentric rotating member (Patent Document 2).

Japanese Patent Laid-Open No. 08-190235 JP 09-054475 A

  SUMMARY OF THE INVENTION An object of the present invention is to start and stop accumulation of urging force used when rotating a plurality of developing units around a shaft by mechanical operation without performing electrical drive control. And

  The invention according to claim 1 is a plurality of developing units provided so as to be rotatable together with the shaft part around the shaft part, and a developing part provided so as to be rotatable together with the shaft part. From a biased state, an arrangement portion that arranges the shaft portion in a predetermined position, a rotating portion that rotates around the shaft portion by receiving a driving force from a driving source without being fixed to the shaft portion, and And the rotation of the placement unit is stopped while the rotation of the placement unit is stopped, but the rotation of the rotation unit is continued and urged. And a cutting unit for disconnecting the connection between the urging unit that is urged and the rotating unit that continues to rotate after the urging unit is urged.

According to a second aspect of the present invention, the biasing portion is provided in the placement portion, and the biasing portion is released from the biased state. The developing device according to claim 1, wherein the developing device is pressed and contacts the rotating portion.
According to a third aspect of the present invention, in the developing device according to the first or second aspect, the urging portion is a torsion spring.
The invention according to claim 4 is characterized in that the urging portion is urged in accordance with a change in the angle between the arrangement portion that has stopped rotating and the rotating portion that continues to rotate. A developing device according to any one of claims 1 to 3.

  According to a fifth aspect of the present invention, there is provided a plurality of developing units rotatably provided with the shaft portion around the shaft portion, and a developing portion of any of the plurality of developing portions provided rotatably with the shaft portion. And a rotating unit that receives a driving force from a driving source and rotates around the shaft in the same direction as the plurality of developing units without being fixed to the shaft. And one end portion is movably provided along with elastic deformation, and the other end portion is fixed to the arrangement portion and biased. With the release from the state, the rotation of the arrangement portion is started, and the rotation of the arrangement portion is stopped, but the one end portion is in the state where the rotation of the rotation portion is continued. Energized by moving by rotating part The rotation start portion that is in a state of being connected, and the one end portion of the rotation start portion is connected to the rotation start portion that is biased after the rotation start portion is biased and the rotation portion that continues to rotate. And an end moving part that is cut by moving the.

According to a sixth aspect of the present invention, the developing device according to any one of the first to fifth aspects, a charging unit that charges the image holding member, and the image holding member charged by the charging unit are exposed to static electricity. An operation in which the arrangement unit rotates, including an exposure unit that forms an electrostatic latent image, and a transfer unit that transfers the image held on the image carrier to a recording material sandwiched between the image carrier Is an image forming apparatus that is started after the transfer section completes the transfer operation, and is completed before the exposure section starts the exposure operation in the next image forming operation.
The invention according to claim 7 is an image holding member that is rotatably arranged and holds an image on an outer peripheral surface, a plurality of developing units that are rotatably provided with the shaft portion around the shaft portion, and the shaft portion. And an arrangement portion that is rotatably provided, and arranges a developing portion of any of the plurality of developing portions at a developing position where development is performed facing the image carrier, a driving source that supplies a driving force, and the shaft A rotating part that rotates around the shaft part by receiving a driving force from the driving source without being fixed to the part, one end part is fixed to the arrangement part, and the other end part is a free end. The arrangement part rotating body rotates the arrangement part by the energy accumulated by elastic deformation, and the arrangement part rotation body changes the posture of the arrangement part rotation body according to the rotation angle of the arrangement part. The accumulated energy and the accumulated energy An image forming apparatus including a posture change unit for obtaining a state in which release was.
According to an eighth aspect of the present invention, there is provided a charging unit that charges the image carrier, an exposure unit that exposes the image carrier charged by the charging unit to form an electrostatic latent image, and the image carrier. A transfer unit that transfers the image held on the image holding member to the recording material sandwiched between them, and the operation of rotating the arrangement unit starts after the transfer operation of the transfer unit is completed. The image forming apparatus according to claim 7, wherein the exposure unit completes before starting the exposure operation in the next image forming operation.
A ninth aspect of the present invention is the image forming apparatus according to the eighth aspect, wherein the driving source supplies a driving force to the transfer section and the rotating section.

According to the first aspect of the present invention, the accumulation start and / or the accumulation end of the urging force used when rotating the plurality of developing portions around the shaft portion is mechanically performed without performing electrical drive control. It can be done by movement.
According to invention of Claim 2, compared with the case where it does not have this structure, it is urged | biased by being pushed by the arrangement | positioning part in connection with the state from which the urging | biasing part was released. It can be realized that the accumulation of the urging force in the section is started by a mechanical operation.
According to the third aspect of the present invention, compared to the case where the present configuration is not provided, the accumulation start of the urging force used when rotating the plurality of developing units around the shaft portion and / or with a simpler configuration and / or Alternatively, the accumulation can be terminated by a mechanical operation without performing electrical drive control.
According to the fourth aspect of the present invention, the accumulation start of the urging force used when rotating the plurality of developing portions around the shaft portion and / or with a simpler configuration as compared with the case where the present configuration is not provided. Alternatively, the accumulation can be terminated by a mechanical operation without performing electrical drive control.

According to the fifth aspect of the present invention, the accumulation start and / or the accumulation end of the urging force used when rotating the plurality of developing portions around the shaft portion is mechanically performed without performing electrical drive control. It can be done by movement.
According to the sixth aspect of the present invention, it is possible to suppress the quality of the image formed on the recording material from being reduced in accordance with the operation of rotating the arrangement portion, as compared with the case where this configuration is not provided.
According to the seventh aspect of the invention, the accumulation start and / or the accumulation end of the urging force used when rotating the plurality of developing portions around the shaft portion is mechanically performed without performing electrical drive control. An image forming apparatus that performs an operation can be provided.
According to the eighth aspect of the present invention, it is possible to suppress the quality of the image formed on the recording material from being reduced in accordance with the operation of rotating the arrangement portion as compared with the case where the present configuration is not provided.
According to the ninth aspect of the present invention, the accumulation start of the urging force used when rotating the plurality of developing portions around the shaft portion and / or the simpler configuration as compared with the case where the present configuration is not provided. Alternatively, the accumulation can be terminated by a mechanical operation without performing electrical drive control.

1 is a schematic configuration diagram illustrating an image forming apparatus according to an exemplary embodiment. FIG. 2 is a schematic configuration diagram of a drive system around a developing device. It is a perspective view of a developing device. It is a disassembled perspective view of a transmission mechanism. It is a schematic block diagram of a rear plate. It is a disassembled perspective view of a position plate. It is a schematic block diagram of a rotation disc. It is a schematic block diagram of a raising member. It is a schematic block diagram of a torsion spring. It is a schematic block diagram of a gear plate. It is a schematic block diagram of a locking member. It is a schematic block diagram of a transmission mechanism. 6 is a timing chart illustrating a transmission mechanism switching operation in a four-color image forming operation. It is a schematic block diagram of the transmission mechanism in a 2nd state. It is a schematic block diagram of the transmission mechanism in a 3rd state. It is a schematic block diagram of the transmission mechanism in a 4th state. It is a schematic block diagram of the transmission mechanism in a 5th state. It is a schematic block diagram of the transmission mechanism in a 6th state.

Hereinafter, this embodiment will be described in detail with reference to the accompanying drawings.
<Overall Configuration of Image Forming Apparatus 1>
First, each configuration of the image forming apparatus 1 to which the exemplary embodiment is applied will be described with reference to FIG. Here, FIG. 1 is a schematic configuration diagram showing an image forming apparatus 1 to which the exemplary embodiment is applied.

  The image forming apparatus 1 includes an image forming unit 10 on which a toner image is formed, a paper supply unit 40 that supplies and conveys paper S, and the image forming unit 10 that holds and holds the supplied paper S. And a transfer device 20 for transferring the toner image. The image forming apparatus 1 also includes a fixing device 30 that fixes the toner image on the paper S released from the transfer device 20 and a control unit 50 that controls the entire image forming device 1. Here, each component of the image forming apparatus 1 is accommodated in the housing 2, and a paper discharge stacking unit 3 on which the paper S discharged from the fixing device 30 is stacked is provided on the top of the housing 2. ing.

<Configuration of each member>
First, the image forming unit 10 includes a photosensitive drum 11. Further, the image forming unit 10 includes a charging device 12 that charges the photosensitive drum 11, an exposure device 13 that exposes the charged photosensitive drum 11, a developing device 14 that performs development using a developer, and the photosensitive drum 11. A cleaning device 15 for cleaning the developer remaining in the printer is included. Each member will be described below.

  A photosensitive drum 11, which is an example of an image carrier, includes a photosensitive layer 11 </ b> A having a negative charging polarity on its surface and is attached so as to rotate in the direction of arrow A. The charging device 12, the exposure device 13, the developing device 14, and the cleaning device 15 are installed around the photosensitive drum 11 in this order along the direction of the arrow A. Here, the outer diameter of the photosensitive drum 11 is, for example, 30 mm.

The charging device 12, which is an example of a charging unit, is a contact roller type discharging device in the present embodiment, and is configured to charge the photosensitive drum 11 while rotating together with the photosensitive drum 11.
The exposure device 13 which is an example of an exposure unit is configured to form an electrostatic latent image by irradiating the charged surface of the photosensitive drum 11, and in the present embodiment, a plurality of LEDs (not shown) are arranged. )including.

The developing device 14 is detachably attached to the housing 2. Further, the developing device 14 includes a so-called rotary developing device 14R. Although details will be described later, the rotary developer 14R includes a rotating shaft 14A as an example of a shaft portion, and yellow (Y), magenta (M), cyan (C), black (installed around the rotating shaft 14A. K) developing devices (developing units) 14Y, 14M, 14C, and 14K, which rotate in the direction of arrow C about the rotating shaft 14A.
Further, in the rotary developing device 14R, any one of the developing devices 14Y, 14M, 14C, and 14K is stopped at a position (developing position) facing the photosensitive drum 11.
When only a single color image is formed instead of a multicolor image, the developing device 14 may be replaced with a developing device having only a single color developing device (for example, only the black (K) developing device 14K).

The developing device 14 develops the electrostatic latent image formed on the photosensitive drum 11 by the exposure device 13 using toner. The outer diameter of the developing device 14 is 100 mm, for example.
These developing units 14Y, 14M, 14C, and 14K contain a one-component developer made of only toner. Here, in the present embodiment, a one-component developer is used, but a two-component developer including a toner and a carrier may be used.

  The cleaning device 15 removes the developer remaining on the surface of the photosensitive drum 11 and the deposits other than the developer. The cleaning device 15 of the present embodiment is a blade type cleaner.

Next, the transfer device 20 will be described. The transfer device 20 includes a transfer drum 21 that transfers the toner image on the photosensitive drum 11 onto the paper S. The transfer device 20 also includes a leading edge gripper 23 that holds the leading edge of the paper S on the transfer drum 21, and a trailing edge gripper 27 that holds the trailing edge of the paper S on the transfer drum 21. Further, the transfer device 20 includes a paper detection sensor 25 that detects the passage of the paper S.
The transfer device 20 is detachably attached to the housing 2. Here, the transfer device 20 according to the present embodiment is configured to fix the leading end and the trailing end of the paper S and rotate around the transfer drum 21, but is not limited thereto. For example, when only a single color image is formed instead of a multicolor image, the transfer drum 21 may be replaced with a roll that applies a transfer bias without fixing the paper S (so-called transfer roll).

  The transfer drum 21, which is an example of a transfer unit, faces the photosensitive drum 11 and is disposed so as to be rotatable about a rotation shaft 21 </ b> D. The transfer drum 21 includes a drum-shaped base 21A and an elastic layer 21B formed on the outer peripheral surface of the base 21A. More specifically, the elastic layer 21B extends along the outer periphery of the drum-shaped base 21A from the elastic layer front end 21BL that is the front end of the paper S in the transport direction to the elastic layer rear end 21BT that is the rear end of the paper S in the transport direction. Stretched. On the other hand, the elastic layer 21B does not cover a part of the outer peripheral surface of the base portion 21A along the axial direction of the base portion 21A (between the elastic layer rear end 21BT and the elastic layer front end 21BL). The part is an exposed portion 21C where the base portion 21A is exposed.

The transfer drum 21 is provided to rotate in the direction of arrow B in synchronization with the rotation of the photosensitive drum 11 in a state where the elastic layer 21B is elastically deformed to form a nip portion with the photosensitive drum 11. Further, the exposed portion 21 </ b> C of the transfer drum 21 is not in contact with the photosensitive drum 11. Further, the outer diameter of the transfer drum 21 is larger than the outer diameter of the photosensitive drum 11.
The base 21A is applied with a transfer bias composed of a voltage having a polarity opposite to that of the toner from a high voltage power source (not shown). The toner constituting the toner image on the photosensitive drum 11 is transferred to the paper S on the elastic layer 21B at the transfer portion Tr.

The paper detection sensor 25 is disposed to face the outer peripheral surface of the transfer drum 21 and detects the passage of the paper S that is wound around the transfer drum 21 and conveyed. Further, the paper detection sensor 25 measures the phase of the rotating transfer drum 21 by detecting a mark (not shown) provided on the transfer drum 21.
The fixing device 30 includes a heating roll 31 having a heating source (not shown) and rotatably arranged, and a pressure roll 32 pressed against the heating roll 31.

  The paper supply unit 40 includes a paper storage unit 41 that is provided below the transfer drum 21 and stores the paper S therein, and a paper size sensor (not shown) that is provided in the take-out roll 42 and detects the size of the stored paper. Prepare. Further, the paper supply unit 40 includes a take-out roll 42 that takes out the paper S from the paper storage unit 41, a separating roll 43 that separates the closely contacted paper S, and a transport roll 44 that transports the paper S.

  The control unit 50 receives a signal from a user interface (not shown) that receives an instruction from the user. In addition, an image signal is input to the control unit 50 from an image output instruction unit (not shown) provided inside or outside the image forming apparatus 1. Further, the control unit 50 is supplied with a paper S passing signal and a phase signal of the photosensitive drum 11 sent from the paper detection sensor 25.

And the control part 50 outputs a control signal to each following part. That is, the control unit 50 outputs a control signal to the photosensitive member driving unit (the photosensitive drum driving motor M2 and the photosensitive drum gear G2 in FIG. 2), the charging device 12, and the exposure device 13 that rotationally drives the photosensitive drum 11. To do. In addition, the control unit 50 is connected to a developing bias setting unit (not shown) that sets a developing bias to be supplied to the developing devices 14Y, 14M, 14C, and 14K disposed at the developing position that is the position facing the photosensitive drum 11. Output a control signal.
Further, the control unit 50 outputs a control signal to a transfer drum drive unit (see transfer drum drive motor M1 and transfer drum gear G1 in FIG. 2) that rotationally drives the transfer drum 21. Furthermore, a rear end gripper driving unit (not shown) for rotationally driving the rear end gripper 27, a transfer bias setting unit (not shown) for setting a transfer bias to be supplied to the transfer drum 21, a front end gripper 23, a rear end gripper 27, a control signal is output to the paper supply unit 40 and the fixing device 30.

Here, the image forming apparatus 1 includes a supply path 51 for supplying the sheet S from the sheet storage unit 41 to the transfer portion Tr. Further, the image forming apparatus 1 includes a discharge path 52 for discharging the paper S on which the toner image is transferred via the fixing device 30 to the paper discharge stacking unit 3.
Further, in the present embodiment, the sheet S supplied toward the transfer drum 21 rotates in a state where it is wound around the transfer drum 21 by the leading edge gripper 23 and the trailing edge gripper 27. At this time, a path through which the sheet S passes is referred to as a rotation path 53.

<Drive system>
Now, with reference to FIG. 2, a drive system such as the developing device 14 will be described. Here, FIG. 2 is a schematic configuration diagram of a drive system around the developing device 14.
First, the developing device 14 in the present embodiment does not have a dedicated drive motor for driving the developing device 14. The developing device 14 in the present embodiment is driven by a transfer drum drive motor (drive source) M1 that drives the transfer drum 21 and a photoconductor drum drive motor M2 that rotates the photoconductor drum 11. This configuration will be described in detail below.

As shown in FIG. 2, the transfer device 20 includes a transfer drum drive motor M <b> 1 that drives the transfer drum 21. The transfer device 20 is provided integrally with the rotation shaft 21D of the transfer device 20, and has a transfer drum gear G1 that rotates the rotation shaft 21D under the drive of the transfer drum drive motor M1.
The photoconductor drum 11 has a photoconductor drum drive motor M <b> 2 that drives the photoconductor drum 11. The photoconductor drum 11 is coaxial with the photoconductor drum 11 and is provided integrally with the photoconductor drum 11, and is a photoconductor drum gear that rotates the photoconductor drum 11 by being driven by the photoconductor drum drive motor M2. G2.

  On the other hand, the developing device 14 is provided integrally with the rotating shaft 14A and has a developing device gear G3 that rotates the rotary developing device 14R. The developing devices 14Y, 14M, 14C, and 14K (see FIG. 1) provided in the rotary developing device 14R rotate and drive the developing rolls and the like provided in the developing devices 14Y, 14M, 14C, and 14K, respectively. Developer gears G4Y, G4M, G4C, and G4K are provided.

  Here, the developing device gear G3 that rotates the rotary developing device 14R about the rotating shaft 14A is configured to rotate by receiving the driving of the transfer drum driving motor M1 via the intermediate gears G5 and G6. Further, the developing device gears G4Y, G4M, G4C, and G4K that rotate the developing devices 14Y, 14M, 14C, and 14K (see FIG. 1) are disposed at positions facing the photosensitive drum 11 when performing development. The photosensitive drum drive motor M2 is driven via the photosensitive drum gear G2 to rotate.

<Developing device 14>
Next, the detailed structure of the developing device 14 will be described with reference to FIGS. 1, 2, and 3. Here, FIG. 3 is a perspective view of the developing device 14.
First, the developing device 14 includes the rotary developing device 14R, the developing device gear G3, and the gears G4Y, G4M, G4C, and G4K (see FIG. 2) as described above. Further, the developing device 14 includes a frame body 90 that rotatably supports the rotary developing device 14R. Furthermore, the developing device 14 includes a transmission mechanism 100 that transmits the driving of the transfer drum driving motor M1 to the rotary developing device 14R and cuts off the transmission of the driving.

The rotary developing device 14R includes a rotating shaft 14A and yellow (Y), magenta (M), cyan (C), and black (K) developing devices 14Y, 14M, 14C, and 14K (around the rotating shaft 14A). 1). The rotary developing unit 14R includes a developing rack 80 that is fixedly attached to the rotating shaft 14A, holds the developing units 14Y, 14M, 14C, and 14K, and rotates integrally with the rotary developing unit 14R. In the rotary developing device 14R, the developing devices 14Y, 14M, 14C, and 14K rotate in the direction of arrow C around the rotation shaft 14A.
Here, as shown in FIG. 3, the developing rack 80 includes holding plates 61 and 63 that hold the developing devices 14Y, 14M, 14C, and 14K from outside in the longitudinal direction, and holding plates 61 and 63. And a reinforcing member (not shown) for connecting and reinforcing the gaps.

  The frame 90 has a front plate 91 and a rear plate that hold the developing rack 80 that holds the developing units 14Y, 14M, 14C, and 14K so as to be sandwiched from the outside in the longitudinal direction of the developing units 14Y, 14M, 14C, and 14K. 93 and a bottom plate 95 that connects the front plate 91 and the rear plate 93. Although the developing device 14 is detachable from the housing 2 as described above, here, for convenience, the state where the developing device 14 is mounted on the housing 2 is used as a reference, and the image forming apparatus 1 in FIG. The configuration will be described using the expressions “front” and “rear” in association with the front side (the side disposed on the front side in FIG. 1) and the rear side (the side disposed on the back side in FIG. 1). .

The developing device 14 is fixed in the image forming apparatus 1 by the frame 90. In the present embodiment, the frame 90 has an attachment / detachment mechanism for fixing the developing device 14 to the image forming apparatus 1 so that the removal is easy. Although not described above, the image forming apparatus 1 also has an attachment / detachment mechanism for fixing the developing device 14. Each of these attachment / detachment mechanisms is configured, for example, by providing a hook and a pin (not shown) provided on the image forming apparatus 1 side and a bottom plate 95 for receiving the hook and the pin on the developing apparatus 14 side. .
The configuration of the transmission mechanism 100 will be described later.

Here, as shown in FIGS. 1 and 3, the developing units 14Y, 14M, 14C, and 14K are provided such that the rotation center axes of the developing units 14Y, 14M, 14C, and 14K are along the rotation axis 14A. Yes. The developing units 14Y, 14M, 14C, and 14K are provided around the rotating shaft 14A in this order.
The developing rack 80 is fixed with respect to the rotating shaft 14A, and is provided rotatably with the rotating shaft 14A and the developing devices 14Y, 14M, 14C, and 14K.
In addition, the frame body 90 rotatably supports the rotating shaft 14 </ b> A and is fixed to the housing 2 of the image forming apparatus 1. Here, in the frame 90, the front plate 91 is the front side of the image forming apparatus 1 (the left front side in FIG. 3), and the rear plate 93 is the rear side of the image forming apparatus 1 (the right rear side in FIG. 3). Are arranged respectively.

<Transmission mechanism 100>
Next, the transmission mechanism 100 will be described with reference to FIGS. Here, FIG. 4 is an exploded perspective view of the transmission mechanism 100.
As shown in FIG. 3, the transmission mechanism 100 is provided on one side of the developing device 14 (on the right back side in FIG. 3). Specifically, the transmission mechanism 100 is disposed between the holding plate 63 of the developing rack 80 and the rear plate 93 of the frame body 90. Moreover, the transmission mechanism 100 is provided so that the rotating shaft 14A may penetrate the center part.

  Here, the transmission mechanism 100 includes a position plate 110 that rotates integrally with the rotating shaft 14A and arranges the developing devices 14Y, 14M, 14C, and 14K at predetermined positions. Further, the transmission mechanism 100 is rotated by receiving the drive of the transfer drum driving motor M1 via the intermediate gears G5 and G6 (see FIG. 2), and is engaged with the position plate 110 to rotate the position plate 110. Have Furthermore, the transmission mechanism 100 includes a lock member 160 that stops the position plate 110 that rotates together with the rotating shaft 14A. Furthermore, the transmission mechanism 100 includes guide ribs 170 that maintain the transmission of the drive of the gear plate 150 to the position plate 110 by engaging with the position plate 110 and cut the transmission of the drive. Each will be described below.

In the present embodiment, the guide rib 170 is provided integrally with the rear plate 93 on the surface 93a of the rear plate 93 that faces the position plate 110. In the following description, the transmission mechanism 100 will be described as a configuration including the rear plate 93.
Further, the developing device gear G3 is provided on the surface of the gear plate 150 opposite to the side facing the position plate 110 (see FIG. 10, described later). In the following description, the transmission mechanism 100 will be described as including a developing device gear G3.

<Rear plate 93>
First, the rear plate 93 will be described with reference to FIG. Here, FIG. 5 is a schematic configuration diagram of the rear plate 93. More specifically, FIG. 5A is a perspective view of the rear plate 93 viewed from the front side of the developing device 14, and FIG. 5B is a front view of the rear plate 93.
The rear plate 93, which is an example of the cutting part and the end part moving part, includes the guide rib 170 as described above. The guide rib 170 protrudes from the surface 93a on the side facing the position plate 110, and extends along the circumferential direction of the rotating shaft 14A. The guide rib 170 has a specific height (described later) in the direction protruding from the surface 93a (the direction along the arrow E direction).

Further, the same number of guide ribs 170 as the developing devices 14Y, 14M, 14C, and 14K provided in the developing device 14 are provided. In the illustrated example, four guide ribs 170 are provided every 90 degrees in the circumferential direction of the rotating shaft 14A (see FIG. 4).
Further, each guide rib 170 has an inclined portion 171 at an end portion in the circumferential direction and at an end portion on the rear end side in the arrow C direction in which the rotary developing device 14R (see FIG. 1) rotates. The inclined portion 171 is inclined with respect to the surface 93 a of the rear plate 93. Here, the hooking portion 173 that is the end opposite to the side where the inclined portion 171 is provided and on which the torsion spring 140 is hung (details will be described later) is not inclined. In the illustrated example, the hanging portion 173 has a surface substantially orthogonal to the surface 93 a of the rear plate 93.
Furthermore, the rear plate 93 has a through hole 94 into which the rotating shaft 14A is inserted at the center of the surface.

<Position plate 110>
Next, the position plate 110 will be described with reference to FIGS. 4 and 6. Here, FIG. 6 is an exploded perspective view of the position plate 110.
As shown in FIG. 4, the position plate 110 has a rotating disk 120 that rotates integrally with the rotating shaft 14A. The position plate 110 includes a push-up member 130 that is provided on the surface of the rotating disk 120 and pushes up a torsion spring 140 (described later) from the surface of the rotating disk 120. Furthermore, the position plate 110 has a torsion spring 140 that is provided on the surface of the rotating disk 120 and receives the drive from the transfer drum drive motor M1 (see FIG. 2) when the posture changes.
In the example shown in FIG. 6, the rotating disk 120, the push-up member 130, and the torsion spring 140 are arranged in this order from the rear side to the front side of the image forming apparatus 1 (see arrow E). Each will be described below.

<Rotating disc 120>
The rotating disk 120 will be described with reference to FIG. Here, FIG. 7 is a schematic configuration diagram of the rotating disk 120. More specifically, FIG. 7A is a perspective view of the rotating disk 120 as viewed from the front side of the developing device 14, and FIG. 7B is a front view of the rotating disk 120.
The rotating disk 120, which is an example of an arrangement unit, is a circular metal plate. The rotating disk 120 has a through hole 121 into which the rotating shaft 14A is inserted at the center of the surface. Further, the rotating disk 120 protrudes from the periphery of the through hole 121 on the front side surface (the surface disposed on the front side of the paper in FIG. 1) 120a in the direction along the rotating shaft 14A (see arrow E). The projection 123 is provided.

Further, the rotating disk 120 has a protrusion 125 that engages with the lock member 160 (see FIG. 4) on the outer periphery of the rotating disk 120. The protrusion 125 is formed on the outer periphery of the rotating disk 120 so as to extend in a direction away from the center of rotation. In the present embodiment, the same number of protrusions 125 as the developing devices 14Y, 14M, 14C, and 14K provided in the developing device 14 are provided. Further, the same number of protrusions 125 as the above-described guide ribs 170 are provided. In the illustrated example, four protrusions 125 are provided every 90 degrees in the circumferential direction of the rotating shaft 14A.
In the present embodiment, the protrusion 125 is described, but the present invention is not limited to this. Any structure that engages with the lock member 160 (see FIG. 4) may be used. For example, a notch provided on the outer periphery of the rotating disc 120 or a convex portion provided on the surface of the rotating disc 120. Good.

<Push-up member 130>
Next, the push-up member 130 will be described with reference to FIG. Here, FIG. 8 is a schematic configuration diagram of the push-up member 130. More specifically, FIG. 8A is a perspective view of the push-up member 130 as viewed from the front side of the developing device 14, and FIG. 8B is a front view of the push-up member 130.
The push-up member 130 is an arc-shaped plate member provided coaxially with the rotating disk 120. The push-up member 130 has a specific thickness in the direction along the arrow E direction.
The push-up member 130 has a holding surface 130a that is a surface that holds the arm portion 147 (see FIG. 9) of the torsion spring 140 in a state where the arm portion 147 is brought close to the gear plate 150 side. In the illustrated example, the holding surface 130a is a flat surface disposed on the front side of the push-up member 130 (the surface disposed on the front side in FIG. 1). Therefore, the holding surface 130 a has a specific height from the surface of the rotating disk 120.

In addition, the tip of the push-up member 130 in the rotational direction (see arrow C) is formed with an inclined portion 133 that is inclined toward the rear side. The inclined portion 133 moves the arm portion 147 (see FIG. 9) of the torsion spring 140 that moves in a direction opposite to the arrow C (see FIG. 8) relative to the inclined portion 133 to the surface of the rotating disk 120. Push up from.
The push-up member 130 and the guide rib 170 are examples of the posture changing unit, and the push-up member 130 may be integrated with the rotating disk 120.

<Torsion spring 140>
Next, the torsion spring (torsion spring) 140 will be described with reference to FIG. Here, FIG. 9 is a schematic configuration diagram of the torsion spring 140. More specifically, FIG. 9A is a perspective view of the torsion spring 140 viewed from the front side of the developing device 14, FIG. 9B is a front view of the torsion spring 140, and FIG. 9C is a torsion spring. FIG.
The torsion spring 140 as an example of the urging unit, the rotation start unit, and the arrangement unit rotating body is made of a metal wire. The torsion spring 140 has a winding part 145 wound in a circular shape a plurality of times. One end of the torsion spring 140 extends from the winding portion 145 as an arm portion 147, and the other end extends from the winding portion 145 as a fixing portion 149.

Here, the tip of the arm portion 147 is a free end 141 that is not fixed, whereas the tip of the fixed portion 149 is a fixed end 143 that is fixed to the rotating disk 120 (see FIG. 4). is there. The push-up member 130 has a notch (not shown) in a region where the fixed end 143 is disposed. In the present embodiment, the fixed end 143 is fixed to the rotating disk 120.
Further, as shown in FIG. 9C, when viewed from the side, the arm portion 147 of the torsion spring 140 is inclined and extends from the winding portion 145 to the rotating disc 120 side (upstream side of the arrow E) in the free state. It has become. More specifically, the free end 141 of the torsion spring 140 is on the rotating disc 120 side (upstream side of the arrow E) from the base of the arm portion 147.

  Note that the free end 141 of the torsion spring 140 moves in the circumferential direction around the winding portion 145, so that the torsion spring 140 is opened and narrowed (see the broken line in FIG. 9B). ). Further, as shown by a broken line in FIG. 9B, in a state where the torsion spring 140 is contracted due to the torsional moment, the torsion spring 140 is in a state where elastic energy (biasing force) is accumulated. is there. In other words, energy is stored as the torsion angle of the torsion spring 140.

<Gear plate 150>
Next, the gear plate 150 will be described with reference to FIG. Here, FIG. 10 is a schematic configuration diagram of the gear plate 150. More specifically, FIG. 10A is a perspective view of the gear plate 150 as viewed from the front side of the developing device 14, and FIG. 10B is a perspective view of the gear plate 150 as viewed from the back side of FIG. 10A. FIG. 10C is a front view of the gear plate 150.

The gear plate 150, which is an example of a rotating part, is a disk-shaped member made of resin. The gear plate 150 has a through hole 151 into which the rotation shaft 14A is inserted at the center of the surface.
As shown in FIG. 10A, the front side surface (the surface disposed on the front side of the paper in FIG. 1) 150a of the image forming apparatus 1 in the gear plate 150 is fed from the transfer drum drive motor M1 (see FIG. 2). A developing device gear G <b> 3 that rotates by being driven is fixed coaxially with the gear plate 150.
Further, as shown in FIG. 10B, a claw portion 153 protruding from the rear side surface 150b is provided on the rear side surface (the surface disposed on the back side of the paper surface in FIG. 1) 150b of the image forming apparatus 1 in the gear plate 150. Have. Eight claw portions 153 are provided at substantially equal intervals in the circumferential direction of the rotating shaft 14A. Here, the claw portions 153 are provided more than the number of the guide ribs 170 (that is, the number of the protrusions 125). In the present embodiment, the claw portions 153 are provided as many times as the guide ribs 170 (or the protrusions 125).

<Lock member 160>
Next, the lock member 160 will be described with reference to FIG. Here, FIG. 11 is a schematic configuration diagram of the lock member 160.
In the present embodiment, the lock member 160 is supported by the housing 2 (see FIG. 1) so that the support shaft 163 can swing (see arrow F). The lock member 160 may be supported on the developing device 14 side (for example, the frame 90).

The lock member 160 is a plate-like metal member. And it has the protrusion receiving part 161 which hooks with the protrusion 125 of the rotating disc 120 in one edge part.
Although not described above, the transfer drum 21 (see FIG. 1) is provided with a cam (not shown) that rotates together with the transfer drum 21. A cam follower (not shown) pushed by a cam (not shown) provided on the transfer drum 21 is opposite to the side where the projection receiving portion 161 of the lock member 160 is provided with the support shaft 163 interposed therebetween. It is provided at the end.

  Each time the transfer drum 21 rotates once, a cam (not shown) pushes a cam follower (not shown). As a result, the lock member 160 swings, and the protrusion receiving portion 161 provided at one end of the lock member 160 moves. Then, the protrusion 125 of the rotating disk 120 that engages with the protrusion receiving portion 161 is released.

<Structure of transmission mechanism 100>
Next, the structure of the transmission mechanism 100 will be described with reference to FIGS. 4 and 12. Here, FIG. 12 is a schematic configuration diagram of the transmission mechanism 100. More specifically, FIG. 12A is a front view of the transmission mechanism 100, and FIG. 12B is a cross-sectional view of the transmission mechanism 100 as viewed from an arrow XIIB in FIG. 12A and 12B, the developing device gear G3 of the gear plate 150 is omitted. Further, in FIG. 12A, the portion hidden behind the gear plate 150 is also shown by a solid line.

First, the transmission mechanism 100 includes the rear plate 93, the position plate 110, the gear plate 150, and the lock member 160 as described above. Further, the rotary development is performed in the through hole 94 (see FIG. 5) of the rear plate 93, the through hole 121 (see FIG. 7) of the rotating disk 120 in the position plate 110, and the through hole 151 (see FIG. 10) of the gear plate 150. The rotating shaft 14A of the container 14R is inserted.
As shown in FIG. 12B, the rotating disc 120 in the position plate 110 is fixed to the rotating shaft 14A so as to rotate together with the rotating shaft 14A. On the other hand, the rear plate 93 and the gear plate 150 are provided without being fixed to the rotating shaft 14A.

  Here, as shown in FIG. 12A, guide ribs 170 of the rear plate 93 are provided on the outer periphery of the position plate 110. The guide rib 170 is provided at a position where the guide rib 170 does not come into contact with the protrusion 125 provided on the rotating disk 120 and the arm portion 147 of the torsion spring 140 reaches.

As shown in FIG. 12A, the lock member 160 is disposed on the outer periphery of the position plate 110 and between the two guide ribs 170 provided on the rear plate 93. Further, the lock member 160 is disposed such that a cam follower (not shown) of the lock member 160 is positioned on a moving path of a cam (not shown) provided on the transfer drum 21.
The lock member 160 is provided so as to swing around a support shaft 163 (see FIG. 11) (see arrow F in FIG. 11). In other words, as the lock member 160 swings, the protrusion receiving portion 161 of the lock member 160 advances and retreats with respect to the movement path of the protrusion 125 provided on the rotating disk 120. Therefore, depending on the position of the protrusion 125 of the rotating disk 120, the protrusion 125 hits the protrusion receiving portion 161 of the lock member 160 so as to prevent the rotation of the rotating disk 120. The protrusion receiving portion 161 of the lock member 160 is configured to advance and retract with respect to the movement path of the protrusion 125 by moving in the radial direction of the rotating disk 120 or moving in the tangential direction of the rotating disk 120, for example. It may be.

Further, when the protrusion receiving portion 161 of the lock member 160 engages with the protrusion 125 provided on the rotating disk 120, the rotary developer 14R that rotates together with the rotating disk 120 via the rotating shaft 14A also stops. . In the stopped rotary developing unit 14R, any of the developing units 14Y, 14M, 14C, and 14K included in the rotary developing unit 14R is disposed at a developing position that is a position facing the photosensitive drum 11.
Furthermore, while the protrusion receiving portion 161 of the lock member 160 is engaged with the protrusion 125 provided on the rotating disk 120, the protrusion 125 is released, and while the protrusion 125 is again engaged with the protrusion 125, the rotary development is performed. The container 14R rotates 90 degrees.

  When the arm portion 147 of the torsion spring 140 is in contact with the claw portion 153 of the gear plate 150, the drive from the transfer drum drive motor M1 (see FIG. 2) is driven by the torsion spring 140, the rotating disk 120, and the rotation. It is transmitted to the rotary developer 14R via the shaft 14A. When the arm portion 147 of the torsion spring 140 does not contact the claw portion 153 of the gear plate 150, the drive from the transfer drum drive motor M1 (see FIG. 2) is not transmitted to the rotary developer 14R.

  The winding portion 145 of the torsion spring 140 is wound around the convex portion 123 provided on the rotating disc 120 and is provided coaxially with the rotating shaft 14A. The fixed end 143 of the torsion spring 140 is fixed to the rotating disk 120 as described above. The free end 141 of the torsion spring 140 extends outward from the movement path of the protrusion 125 provided on the rotating disk 120 with respect to the rotating shaft 14 </ b> A, and can contact the guide rib 170.

  Here, as shown in FIG. 12B, the free end 141 of the torsion spring 140 is on the rotating disk 120 side (upstream side of the arrow E) from the root of the arm portion 147.

<Function of transmission mechanism 100>
Next, the function of the transmission mechanism 100 will be described with reference to FIGS. 1, 12, and 14 to 18. Here, the operation in which the transmission mechanism 100 rotates the rotary developing device 14R by 90 degrees is divided into a first state to a sixth state (details will be described later), and some of them will be described. Here, the function of the transmission mechanism 100 will be described by focusing on the function of the torsion spring 140 and the function of the rotating disk 120. Note that the transmission mechanism 100 shown in FIG. 12 is in the first state. 14 to 18 are schematic configuration diagrams of the transmission mechanism 100 in the second state to the sixth state, respectively.

<Function of torsion spring 140>
The function of the torsion spring 140 in the first state shown in FIG. 12 will be described. Here, the state of the torsion spring 140 and the force acting on the torsion spring 140 will be described separately.
First, the state of the torsion spring 140 will be described.
The torsion spring 140 shown in FIG. 12 is in a state of being squeezed by accumulating elastic energy. In addition, the arm portion 147 of the torsion spring 140 is about to rotate in the direction opposite to the arrow C direction, and the fixed end 143 of the torsion spring 140 is about to rotate in the arrow C direction.
12B, the free end 141 of the torsion spring 140 is at a position where the height from the rear plate 93 in the direction of arrow E is low. This is because the arm portion 147 of the torsion spring 140 extends while being inclined from the winding portion 145 toward the rotating disc 120 side. Further, the arm portion 147 of the torsion spring 140 is not in contact with the claw portion 153 of the gear plate 150 because the arm portion 147 is located at a low height from the rear plate 93.

Next, the force acting on the torsion spring 140 will be described.
As shown in FIG. 12A, the arm portion 147 of the torsion spring 140 receives a force in the arrow C direction from the hook portion 173 of the guide rib 170 in the circumferential direction of the rotating shaft 14A. Further, the arm portion 147 of the torsion spring 140 is not in contact with the claw portion 153 of the gear plate 150, and therefore does not receive a force from the claw portion 153 of the gear plate 150. Further, the fixed end 143 of the torsion spring 140 receives a force in the direction opposite to the arrow C direction from the rotating disk 120 in the circumferential direction of the rotating shaft 14A. This force is a reaction force received from the rotating disk 120 that has stopped rotating. As a result, the torsion spring 140 is squeezed and stopped.
On the other hand, as shown in FIG. 12B, the arm portion 147 of the torsion spring 140 does not receive force from the inclined portion 133 and the guide rib 170 of the push-up member 130 in the direction along the rotation shaft 14A.

Next, the function of the torsion spring 140 in the third state shown in FIG. 15 will be described.
First, the state of the torsion spring 140 will be described.
The torsion spring 140 shown in FIG. 15 is not in a squeezed state but in an open state. Furthermore, as shown in FIG. 15B, the free end 141 of the torsion spring 140 is at a position where the height from the rear plate 93 in the direction of arrow E is high. This is because the arm portion 147 of the torsion spring 140 receives a force pushed in the direction of arrow E from the inclined portion 133 of the push-up member 130. Further, since the arm portion 147 of the torsion spring 140 is at a position where the height from the rear plate 93 in the arrow E direction is high, the arm portion 147 is in contact with the claw portion 153 of the gear plate 150.
The specific height of the push-up member 130 is a height at which the push-up member 130 can bring the arm portion 147 into contact with the claw portion 153 of the gear plate 150 by pushing the arm portion 147 of the torsion spring 140 in the arrow E direction. Say that.

Next, the force acting on the torsion spring 140 will be described.
As shown in FIG. 15A, the arm portion 147 of the torsion spring 140 does not receive a force from the hook portion 173 of the guide rib 170 in the circumferential direction of the rotating shaft 14A. Further, the arm portion 147 of the torsion spring 140 receives a force in the direction of arrow C from the claw portion 153 of the gear plate 150. As a result, the torsion spring 140 is rotated around the rotation shaft 14A in the direction of arrow C.
On the other hand, as shown in FIG. 15B, the arm portion 147 of the torsion spring 140 receives a force pushed in the direction of arrow E from the inclined portion 133 of the push-up member 130 in the direction along the rotation shaft 14A. Note that the arm portion 147 of the torsion spring 140 does not receive a force from the guide rib 170.

Next, the function of the torsion spring 140 in the fifth state shown in FIG. 17 will be described.
First, the state of the torsion spring 140 will be described.
The torsion spring 140 shown in FIG. 17 is in the middle of changing from the opened state to the squeezed state. Further, as shown in FIG. 17B, the free end 141 of the torsion spring 140 is at a position where the height from the rear plate 93 in the direction of arrow E is high. This is because the arm portion 147 of the torsion spring 140 receives a force pushed from the guide rib 170 in the arrow E direction. The arm portion 147 of the torsion spring 140 is in contact with the claw portion 153 of the gear plate 150 because the free end 141 is at a position where the height from the rear plate 93 in the direction of arrow E is high.
The specific height of the guide rib 170 described above is such a height that the guide rib 170 can bring the arm portion 147 into contact with the claw portion 153 of the gear plate 150 by pushing the arm portion 147 of the torsion spring 140 in the arrow E direction. Say that.

Next, the force acting on the torsion spring 140 will be described.
As shown in FIG. 17A, the arm portion 147 of the torsion spring 140 does not receive a force from the hook portion 173 of the guide rib 170 in the circumferential direction of the rotating shaft 14A. Further, the arm portion 147 of the torsion spring 140 receives a force in the direction of arrow C from the claw portion 153 of the gear plate 150. Further, the fixed end 143 of the torsion spring 140 receives a force in the direction opposite to the arrow C direction from the rotating disk 120 in the circumferential direction of the rotating shaft 14A. This force is a reaction force received from the rotating disk 120 that has stopped rotating.
In addition, the torsion spring 140 receives a force in the direction opposite to the arrow C direction from the rotating disk 120 whose fixed end 143 has stopped rotating, and the arm portion 147 of the torsion spring 140 extends from the claw portion 153 in the arrow C direction. Because it receives force, it is in a state where it is receiving force in the direction of being squeezed.

  On the other hand, as shown in FIG. 17B, the arm portion 147 of the torsion spring 140 does not receive a force from the inclined portion 133 of the push-up member 130 in the direction along the rotation shaft 14A. On the other hand, the arm portion 147 of the torsion spring 140 receives a force pushed in the direction of arrow E from the guide rib 170.

<Function of the rotating disk 120>
The function of the rotating disk 120 in the first state shown in FIG. 12 will be described. Here, the state of the lock member 160 and the force acting on the rotating disk 120 will be described separately.
First, the state of the lock member 160 will be described.
The lock member 160 shown in FIG. 12 is in an on state. In other words, the protrusion receiving portion 161 of the lock member 160 enters the movement path of the protrusion 125 provided on the rotating disk 120.

Next, the force that acts on the rotating disk 120 will be described.
The rotating disk 120 receives a force in the direction of arrow C from the fixed end 143 of the torsion spring 140. This force is due to a force that attempts to rotate the fixed end 143 in the direction of arrow C by the elastic force of the torsion spring 140 that is in the squeezed state.
Further, the protrusion 125 of the rotating disk 120 receives a force in the direction opposite to the arrow C direction by contacting the protrusion receiving portion 161 of the lock member 160.
The rotating disk 120 is stopped by these forces without rotating around the rotating shaft 14A.

The function of the rotating disk 120 in the second state shown in FIG. 14 will be described.
The lock member 160 shown in FIG. 14 is in an off state. That is, the protrusion receiving portion 161 of the lock member 160 is retracted with respect to the movement path of the protrusion 125 provided on the rotating disk 120.

Next, the force that acts on the rotating disk 120 will be described.
The rotating disk 120 receives a force in the direction of arrow C from the fixed end 143 of the torsion spring 140. This force is due to the force that the torsion spring 140, which is changing from being squeezed to being released, tries to rotate the fixed end 143 provided on the rotating disk 120 in the direction of arrow C by elastic force. It is.
Further, the protrusion 125 of the rotating disk 120 is not receiving a force from the protrusion receiving portion 161 of the lock member 160.
The rotating disk 120 is rotated in the direction of arrow C around the rotating shaft 14A by these forces.

The function of the rotating disk 120 in the fourth state shown in FIG. 16 will be described.
The lock member 160 shown in FIG. 16 is in an on state. In other words, the protrusion receiving portion 161 of the lock member 160 enters the movement path of the protrusion 125 provided on the rotating disk 120.

Next, the force that acts on the rotating disk 120 will be described.
The rotating disk 120 receives a force in the direction of arrow C from the fixed end 143 of the torsion spring 140. This force is caused by the force that the arm portion 147 of the torsion spring 140 rotates in the direction of arrow C by the claw portion 153 of the gear plate 150, and the fixed end 143 of the torsion spring 140 receives the force that rotates in the direction of arrow C. Because.
Further, the protrusion 125 of the rotating disk 120 is not receiving a force from the protrusion receiving portion 161 of the lock member 160. This is a state in which the protrusion receiving portion 161 of the lock member 160 has entered the movement path of the protrusion 125 of the rotating disk 120 as described above, but is not in contact with the protrusion 125 of the rotating disk 120. Because.
Then, by receiving the rotational driving force via the torsion spring 140, the rotating disk 120 rotates around the rotating shaft 14A in the direction of arrow C.

<Operation of Image Forming Apparatus 1>
Next, the overall operation of the image forming apparatus 1 will be described with reference to FIGS. 1 and 2. Here, a case where a plurality of color images are formed on one sheet S by the image forming apparatus 1 will be described.

  First, a color material reflected light image of a document read by a document reading device (not shown), and color material image data formed by a personal computer (not shown) or the like are, for example, R (red), G (green). , B (blue) data is input to an image signal processing device (not shown) and subjected to predetermined image processing. The image data subjected to the image processing is converted into color material gradation data of four colors of yellow (Y), magenta (M), cyan (C), and black (K), and is output to the exposure device 13.

  With the start of the image forming operation, the photosensitive drum 11 and the transfer drum 21 start to rotate in synchronization. At this time, the front end gripper 23 rotates together with the transfer drum 21, whereas the rear end gripper 27 does not rotate together with the transfer drum 21 and is stationary at the standby position (the peripheral speed is zero).

  Then, after the photosensitive layer 11 </ b> A of the rotating photosensitive drum 11 is charged by the charging device 12, an electrostatic latent image of the first color (for example, yellow) corresponding to the image information is formed by the exposure device 13. Further, as the transfer drum 21 starts to rotate, the paper detection sensor 25 measures the phase of the transfer drum 21. The measured phase is sent to the control unit 50.

On the other hand, in the developing device 14, a developing device (for example, yellow developing device 14 Y in the case of yellow) having a color component toner corresponding to the electrostatic latent image formed on the photosensitive drum 11 is connected to the photosensitive drum 11. It has been rotated in advance so as to be placed at the opposite position, and stopped.
Then, for example, the electrostatic latent image on the photosensitive drum 11 is developed by the developing device 14 </ b> Y, and a toner image is formed on the photosensitive drum 11. Then, the toner image (here, a yellow toner image) is sent toward the transfer portion Tr facing the transfer device 20 as the photosensitive drum 11 rotates.

  Also, the paper S is supplied in response to the start of the recording image forming operation. Specifically, the paper S taken out from the paper storage unit 41 by the take-out roll 42 is sent out to the supply path 51 using the transport roll 44 through the separation roll 43. Then, the conveyance is controlled so that the sheet S reaches the position where the leading edge gripper 23 reaches the position (supply position) where the sheet S is supplied to the transfer drum 21.

  And in the supply position, it transfers from the state where the front-end | tip gripper 23 was open to the closed state. Accordingly, the leading edge of the sheet S in the transport direction is gripped by the leading edge gripper 23. At this time, the rear end gripper 27 is at the outer periphery of the transfer drum 21 and is stationary at the standby position. The leading edge gripper 23 holding the sheet S passes between the stationary trailing edge gripper 27 and the rotation center of the transfer drum 21.

The leading edge gripper 23 that has passed between the trailing edge gripper 27 and the elastic layer 21 </ b> B passes through the transfer portion Tr while holding the sheet S. The sheet S that has been gripped by the leading edge gripper 23 and passed through the transfer portion Tr is wound around the transfer drum 21 while being gripped by the leading edge gripper 23 and is conveyed along the rotation path 53 (see FIG. 1).
Then, after the first color (for example, yellow) electrostatic latent image corresponding to the image information is formed by the exposure device 13, the paper detection sensor 25 detects that the rear end of the paper S in the transport direction has passed. Then, the control unit 50 receiving the signal from the paper detection sensor 25 issues an instruction to the rear end gripper 27. Receiving the instruction, the rear end gripper 27 shifts from an open state to a closed state.

  Now, the closed rear end gripper 27 starts to rotate in synchronization with the transfer drum 21. In other words, the sheet S rotates with the transfer drum 21 while the leading end in the transport direction is held by the leading end gripper 23 and the trailing end is held by the trailing end gripper 27. The toner image of the first color (for example, yellow) formed on the photosensitive drum 11 is transferred onto the sheet S on the transfer drum 21 at a transfer portion Tr where the photosensitive drum 11 and the transfer drum 21 face each other. The toner remaining on the photosensitive drum 11 after the transfer is removed by a cleaning device 15 (see FIG. 1).

Then, from the second color, latent image formation (for example, magenta, cyan) before the final color (for example, black), development and transfer are similarly repeated according to the above-described procedure. However, when the toner images of the respective colors are formed, the developing device 14 performs a rotation operation, and the corresponding developing devices 14M and 14C are arranged at the stop position.
Meanwhile, the sheet S is rotated and conveyed while being wound around the transfer drum 21 by the leading edge gripper 23 and the trailing edge gripper 27, and the toner images of the second and subsequent colors are overlapped each time the sheet S passes the transfer portion Tr. Sequentially transferred. As a result, for example, when full-color image formation is performed, toner images of each color of yellow (Y), magenta (M), and cyan (C) excluding black (K) are multiple-transferred onto the sheet S on the transfer drum 21. Is done.

  When the final color is transferred, unlike the transfer before the final color (for example, black), the leading edge gripper 23 shifts from the closed state to the open state at the transfer site Tr. As a result, the sheet S on which the gripping by the leading edge gripper 23 is released and a full-color image is formed is discharged after the leading edge in the transport direction of the sheet S is peeled off from the transfer drum 21 by the nip between the elastic layer 21B and the photosensitive drum 11. Enter the route 52.

  Thereafter, as the paper S is transported, the rear end gripper 27 that holds the rear end in the transport direction of the paper S shifts from a closed state to an open state. Note that the transition from the closed state to the opened state of the trailing edge gripper 27 is after the electrostatic latent image of the final color (for example, black) corresponding to the image information has already been formed by the exposure device 13. . Then, the rear end gripper 27 in the opened state stops at the standby position.

Then, the rear end in the transport direction of the paper S released from being held by the rear end gripper 27 is peeled off from the transfer drum 21 and enters the discharge path 52. The sheet S that has entered the discharge path 52 is sent to the fixing device 30. Then, the toner image on the paper S is fixed by the heating roll 31 and the pressure roll 32 of the fixing device 30.
The sheet S after completion of fixing is discharged out of the image forming apparatus 1 by the transport roll 44 and is stacked on the paper discharge stacking unit 3.

<Timing of transmission mechanism 100 operation>
Next, the timing at which the transmission mechanism 100 operates will be described with reference to FIGS. 1 and 13. Here, FIG. 13 is a timing chart showing the switching operation of the transmission mechanism 100 in the four-color image forming operation.

As shown in FIG. 13, in the present embodiment, when the image forming apparatus 1 forms an image, a developing operation is performed by the developing devices 14Y, 14M, 14C, and 14K (see FIG. 1) of the developing device 14.
Here, when the developing operations of the developing devices 14Y, 14M, 14C, and 14K are completed, the moving operations (switching operations) of the developing devices 14Y, 14M, 14C, and 14K are performed for the development cycle of the next color. . The switching operation of the developing units 14Y, 14M, 14C, and 14K is performed by rotating the rotary developing unit 14R (see FIG. 1) by the transmission mechanism 100 (see arrow C in FIG. 1). Hereinafter, the timing of the switching operation of the transmission mechanism 100 will be described in detail.

First, in a state before the image forming operation of the image forming apparatus 1 is started, the transmission mechanism 100 is in an off state (a state where the free end 141 of the torsion spring 140 is not rotating around the rotation shaft 14A). At this time, the lock member 160 of the transmission mechanism 100 is in an ON state (a state in which the protrusion receiving portion 161 has entered the movement path of the protrusion 125). Further, a developing device 14Y corresponding to the first color (herein described as yellow (Y)) is disposed at the development position.
Then, with the start of the image forming operation of the image forming apparatus 1, a yellow (Y) electrostatic latent image is formed by the exposure device 13. Then, after development by the developing device 14Y is started, transfer by the transfer device 20 is performed.

After the transfer of yellow (Y) is completed, the lock member 160 of the transmission mechanism 100 is turned from on to off (a state in which the protrusion receiving portion 161 is retracted from the movement path of the protrusion 125) (see reference numeral 13a). As the lock member 160 is turned off, the transmission mechanism 100 is turned on (the free end 141 of the torsion spring 140 is rotating around the rotation shaft 14A) (see reference numeral 13b). Then, the transmission mechanism 100 rotates the rotary developing device 14R around the rotation shaft 14A (see FIG. 1) (see arrow C in FIG. 1). By this rotation, the developing device 14M corresponding to the second color (described here as magenta) is arranged at the developing position.
On the other hand, the locking member 160 is turned on again after a predetermined time has elapsed after being turned off. Then, after the lock member 160 is turned on again, the transmission mechanism 100 is turned off. After the transmission mechanism 100 is turned off, the next magenta (M) exposure is started (see reference numeral 13c).

  Here, in the present embodiment, the switching operation of the developing units 14Y, 14M, 14C, and 14K by the transmission mechanism 100 is performed while the developing units 14Y, 14M, 14C, and 14K are not performing development. More specifically, the switching operation of the developing devices 14Y, 14M, 14C, and 14K by the transmission mechanism 100 forms a toner image by developing any of the developing devices 14Y, 14M, 14C, and 14K (for example, the developing device 14Y). The toner image is started after the toner image is transferred by the transfer device 20. Then, the switching operation of the developing devices 14Y, 14M, 14C, and 14K by the transmission mechanism 100 ends before the exposure device 13 starts to form the next electrostatic latent image (for example, a magenta electrostatic latent image). Accordingly, it is possible to suppress the image quality from being affected by the occurrence of vibration, impact, or the like in the image forming unit 10, the transfer device 20, or the like with the switching operation of the transmission mechanism 100.

<Operation of Transmission Mechanism 100>
Next, the operation of the transmission mechanism 100 will be described with reference to FIGS. 1, 12, and 14 to 18. Here, the developing units 14Y, 14M, 14C, and 14K provided in the rotary developing unit 14R are switched from one developing unit (for example, the developing unit 14Y) to another developing unit (for example, the developing unit 14M) adjacent in the circumferential direction. Accordingly, it rotates 90 degrees around the rotating shaft 14A. By rotating 90 degrees about the rotating shaft 14A four times, the rotary developer 14R rotates 360 degrees about the rotating shaft 14A.

(A) First State With reference to FIGS. 1 and 12, the transmission mechanism 100 in the first state will be described.
In the first state, the transmission mechanism 100 has stopped operating, and the rotary developer 14R has stopped rotating. In addition, any of the developing devices 14Y, 14M, 14C, and 14K provided in the developing device 14 is disposed at the developing position. Here, description will be made assuming that the developing device 14Y is disposed at the developing position.

  Here, the driving force is transmitted from the transfer drum driving motor M1 to the developing device gear G3 via the intermediate gears G5 and G6 (see FIG. 2). As a result, the gear plate 150 rotates in the direction of arrow C in FIG. Note that, in any of the second state to the sixth state, which will be described later, the gear plate 150 continues to rotate in the direction of arrow C under the driving of the transfer drum drive motor M1.

In the first state, the lock member 160 is in an on state, and the protrusion receiving portion 161 of the lock member 160 has entered the movement path of the protrusion 125 provided on the rotating disk 120. .
Further, when the protrusion 125 of the rotating disk 120 contacts the protrusion receiving portion 161 of the lock member 160, the position plate 110 is stopped from rotating. The rotating disk 120 receives a force to rotate it in the direction of arrow C by the elastic force of the torsion spring 140 in a squeezed state.

  Here, as shown in FIG. 12B, the arm portion 147 of the torsion spring 140 is in a position where the height from the rear plate 93 in the direction of arrow E is low, so that it contacts the claw portion 153 of the gear plate 150. Not. Therefore, when the claw portion 153 of the gear plate 150 rotates around the rotation shaft 14A, the arm portion 147 of the torsion spring 140 is not pushed. In the first state, the gear plate 150 is idle.

(B) Second State The transmission mechanism 100 in the second state will be described with reference to FIGS. 1 and 14.
In the second state, the rotary developer 14R (see FIG. 1) starts to rotate in the direction of arrow C.

  In the second state, the lock member 160 is turned off from on, and the protrusion receiving portion 161 of the lock member 160 is retracted from the movement path of the protrusion 125. Then, as the torsion spring 140 that has been squeezed is changed to an open state, the rotating disk 120 is rotated in the direction of arrow C. Then, the rotary developing device 14R (see FIG. 1) starts to rotate in the direction of arrow C via the rotating shaft 14A that rotates together with the rotating disk 120.

Here, as the fixed end 143 of the torsion spring 140 rotates in the direction of arrow C with the portion of the arm portion 147 of the torsion spring 140 in contact with the hook portion 173 of the guide rib 170 as a fulcrum, the fixed end 143 and the arm portion 147 The relative position of changes. The arm portion 147 of the torsion spring 140 is in contact with the inclined portion 133 provided on the push-up member 130 and moves along the inclined portion 133. As a result, the arm portion 147 of the torsion spring 140 is pushed in the direction from the rear side toward the front side by the inclined portion 133 and moves to the gear plate 150 side (see arrow E).
In the state shown in FIG. 14, the arm portion 147 of the torsion spring 140 is not yet in contact with the claw portion 153 provided on the gear plate 150. Therefore, the gear plate 150 in the second state is in a state of continuing idling.

(C) Third State The transmission mechanism 100 in the third state will be described with reference to FIGS.
In the third state, the rotary developing device 14R (see FIG. 1) continues to rotate in the direction of arrow C.

  In the third state, the lock member 160 is kept off. Further, the relative position between the fixed end 143 of the torsion spring 140 and the arm portion 147 further changes (the torsion spring 140 is further opened). The arm portion 147 of the torsion spring 140 is further pushed in the direction from the rear side toward the front side (see arrow E) by the inclined portion 133 of the push-up member 130. As a result, the arm portion 147 of the torsion spring 140 is disposed at a position where the height from the rear plate 93 in the direction of arrow E is high.

  Then, the claw portion 153 of the rotating gear plate 150 comes into contact with the arm portion 147 of the torsion spring 140, and the arm portion 147 is pushed in the direction of arrow C. More specifically, when the claw portion 153 of the gear plate 150 presses the arm portion 147 of the torsion spring 140, the drive of the transfer drum drive motor M1 (see FIG. 2) is transmitted to the torsion spring 140 via the gear plate 150. This is a state.

(D) Fourth State The transmission mechanism 100 in the fourth state will be described with reference to FIGS. 1 and 16.
In the fourth state, the rotary developing device 14R (see FIG. 1) continues to rotate in the direction of arrow C.

  In the fourth state, the lock member 160 is turned on from off, and the protrusion receiving portion 161 of the lock member 160 enters the movement path of the protrusion 125 provided on the position plate 110. Here, in the fourth state, the protrusion receiving portion 161 of the lock member 160 and the protrusion 125 of the position plate 110 are not in contact with each other. That is, it is a state before the lock member 160 locks the rotating disk 120.

  Further, as the torsion spring 140 rotates around the rotating shaft 14A, the free end 141 of the torsion spring 140 passes through the inclined portion 171 of the guide rib 170 and rides on the guide rib 170 (FIG. 16B). )reference). As a result, the free end 141 of the torsion spring 140 is maintained at a position where the height from the rear plate 93 in the arrow E direction is high. Accordingly, the arm portion 147 of the torsion spring 140 maintains a state where the arm portion 147 is pushed by the claw portion 153 of the gear plate 150 (see arrow C).

(E) Fifth State The transmission mechanism 100 in the fifth state will be described with reference to FIGS. 1 and 17.
In the fifth state, the rotary developer 14R (see FIG. 1) stops rotating. In the fifth state, the developing device 14M is disposed at the developing position. In addition, the fifth state shown in FIG. 17 is a state in which the position plate 110 is rotated 90 degrees in the direction of arrow C in FIG. 17A with reference to the first state shown in FIG.

In the fifth state, the lock member 160 remains on. Then, as the protrusion 125 of the position plate 110 rotates, the protrusion receiving portion 161 of the lock member 160 comes into contact with the protrusion 125. As a result, the protrusion receiving portion 161 of the lock member 160 stops the rotation of the position plate 110 (the lock member 160 locks the rotary disc 120).
Here, in the fifth state, the protrusion receiving part 161 of the lock member 160 contacts the protrusion 125 adjacent to the protrusion 125 that the protrusion receiving part 161 of the lock member 160 was in contact in the first state in the circumferential direction. 125.

As the position plate 110 stops rotating, the fixed end 143 of the torsion spring 140 connected to the position plate 110 also stops rotating. On the other hand, the arm portion 147 of the torsion spring 140 continues to be pressed by the claw portion 153 provided on the gear plate 150 (see arrow C).
As a result, the relative position between the free end 141 and the fixed end 143 of the torsion spring 140 changes. More specifically, in the fifth state, the posture of the torsion spring 140 starts to change (starting to accumulate urging force), and is in a state of being narrowed from the released state.

(F) Sixth State The transmission mechanism 100 in the sixth state will be described with reference to FIGS. 1 and 18.
In the sixth state, the operation of the transmission mechanism 100 is stopped.

  In the sixth state, the lock member 160 remains on. The protrusion receiving portion 161 of the lock member 160 is in contact with the position plate 110 and stops rotating.

  Further, in the sixth state, the arm portion 147 of the torsion spring 140 that rides on the guide rib 170 and rotates in the direction of arrow C passes through the guide rib 170 and is hooked on the hook portion 173. In other words, the arm portion 147 of the torsion spring 140 is not pushed by the guide rib 170 in the direction from the rear side to the front side (see arrow E). As a result, the free end 141 of the torsion spring 140 moves in the direction from the front side toward the rear side (see arrow D), and the height from the rear plate 93 in the direction of arrow E is low. Note that the movement of the free end 141 of the torsion spring 140 is due to the arm portion 147 of the torsion spring 140 extending from the winding portion 145 to the rotating disk 120 side as seen from the side as described above. (See FIG. 9C).

  The free end 141 of the torsion spring 140 moves in the direction from the front side toward the rear side (see arrow D), so that the arm portion 147 of the torsion spring 140 does not come into contact with the claw portion 153 provided on the gear plate 150. It becomes. As a result, the claw portion 153 of the gear plate 150 does not press the arm portion 147 of the torsion spring 140 (end of accumulation of the urging force). Therefore, the gear plate 150 is idled.

  As described above, the transmission mechanism 100 according to the present embodiment switches the lock member 160 between on and off, so that the developing units 14Y, 14M, 14C, and 14K (see FIG. 1) are sequenced by the mechanical mechanism. Switching operation is performed. In addition, the transmission mechanism 100 of the present embodiment does not require an electrical control circuit or the like for the switching operation of the developing devices 14Y, 14M, 14C, and 14K. Further, there is no need for an electrical drive source that is driven when the developing devices 14Y, 14M, 14C, and 14K are switched.

DESCRIPTION OF SYMBOLS 1 ... Image forming apparatus, 2 ... Housing, 10 ... Image forming part, 11 ... Photosensitive drum, 12 ... Charging device, 13 ... Exposure device, 14 ... Developing device, 14A ... Rotating shaft, 20 ... Transfer device, 21 ... Transfer Drum, 23 ... leading edge gripper, 27 ... trailing edge gripper, 30 ... fixing device, 40 ... paper supply unit, 50 ... control unit, 51 ... supply path, 52 ... discharge path, 93 ... rear plate, 100 ... transmission mechanism, 110 ... Position plate, 120 ... Rotating disk, 130 ... Push-up member, 140 ... Torsion spring, 150 ... Gear plate, 160 ... Lock member, S ... Paper

Claims (9)

A plurality of developing units provided to be rotatable together with the shaft portion around the shaft portion;
An arrangement portion that is rotatably provided with the shaft portion, and arranges a developing portion of any of the plurality of developing portions at a predetermined position;
A rotating part that rotates around the shaft part by receiving a driving force from a driving source without being fixed to the shaft part;
The rotation of the placement unit is started in accordance with the release from the biased state, and the rotation of the placement unit is stopped but the rotation of the rotation unit is continued. An urging unit that is connected and energized;
A developing device that includes a cutting unit that disconnects the biased biasing unit and the rotating unit that continues to rotate after the biasing unit is biased.   The biasing portion is provided in the placement portion, and the biasing portion is pushed by the placement portion and comes into contact with the rotating portion as the biasing portion is released from the biased state. The developing device according to claim 1.   The developing device according to claim 1, wherein the biasing portion is a torsion spring.   4. The urging unit is in a state of being urged in accordance with a change in an angle between the arrangement unit that has stopped rotating and the rotating unit that continues to rotate. The developing device according to claim 1. A plurality of developing units provided to be rotatable together with the shaft portion around the shaft portion;
An arrangement portion that is rotatably provided with the shaft portion, and arranges a developing portion of any of the plurality of developing portions at a predetermined position;
A rotating part that receives a driving force from a driving source without rotating to the shaft part and rotates around the shaft part in the same direction as the plurality of developing parts;
It is provided between the arrangement part and the rotation part, and one end part is provided so as to move in accordance with elastic deformation, and the other end part is fixed to the arrangement part and is in a biased state. With the released state, the rotation of the arrangement unit is started, and the rotation of the arrangement unit is stopped, but the rotation of the rotation unit is continued and the one end is the rotation unit. A rotation start unit that is energized by being moved by,
After the rotation start portion is urged, the end portion that cuts the connection between the urged rotation start portion and the rotation portion that continues to rotate by moving the one end portion of the rotation start portion. A developing device including a moving unit. A developing device according to any one of claims 1 to 5,
A charging unit for charging the image carrier;
An exposure unit that exposes the image carrier charged by the charging unit to form an electrostatic latent image; and
A transfer unit for transferring an image held on the image holding body to a recording material sandwiched between the image holding body and
The operation of rotating the arrangement portion is started after the transfer operation of the transfer portion is completed, and is completed before starting the exposure operation of the exposure portion in the next image forming operation. Forming equipment. An image carrier that is rotatably arranged and holds an image on an outer peripheral surface;
A plurality of developing units provided to be rotatable together with the shaft portion around the shaft portion;
An arrangement portion that is rotatably provided with the shaft portion, and that is disposed at a development position where the development portion of any of the plurality of development portions is opposed to the image carrier and performs development;
A driving source for supplying driving force;
A rotating part that rotates around the shaft part by receiving a driving force from the drive source without being fixed to the shaft part;
An arrangement portion rotating body in which one end portion is fixed to the arrangement portion, the other end portion is a free end, and the arrangement portion is rotated by energy accumulated by elastic deformation;
A posture changing unit that obtains a state in which the placement unit rotating body has accumulated energy and a state in which the stored energy has been released in accordance with changing the posture of the placement unit rotating body according to the rotation angle of the placement unit. An image forming apparatus including: A charging unit for charging the image carrier;
An exposure unit that exposes the image carrier charged by the charging unit to form an electrostatic latent image; and
A transfer unit for transferring an image held on the image holding body to a recording material sandwiched between the image holding body and
The operation of rotating the arrangement portion is started after the transfer operation of the transfer portion is completed, and is completed before the operation of exposing the exposure portion in the next image forming operation. Item 8. The image forming apparatus according to Item 7. The image forming apparatus according to claim 8 , wherein the driving source supplies driving force to the transfer unit and the rotating unit.

Images