JP3780809B2 - Transfer device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a transfer device for transferring a toner image on an image carrier to the recording material by bringing a transfer roller into contact with the image carrier through the recording material at a predetermined transfer position.
[0002]
[Prior art]
In an image forming apparatus such as a printer, a facsimile machine, or a copying machine, a process of primary transfer of a toner image formed on a photosensitive member to an intermediate transfer member is performed by yellow (Y), cyan (C), magenta (M), black ( K), and these four color toner images are superimposed on the intermediate transfer member to form a color toner image. Then, the color toner image is secondarily transferred to the recording material by the secondary transfer roller to form a color image on the recording material, and the toner image on the surface of the recording material is further heated by the fixing unit to form the color image on the recording material. Is firmly established.
[0003]
In the image forming apparatus configured as described above, the secondary transfer roller needs to be separated from the intermediate transfer member while the toner image of each color is primarily transferred to the intermediate transfer member. More specifically, the transfer roller contacts and separates from the intermediate transfer member at the following timing.
[0004]
During the primary transfer process, the secondary transfer roller is separated from the intermediate transfer member as described above. Then, when four color toner images are superimposed on the area where the toner image is primarily transferred over the entire circumference of the intermediate transfer body, that is, the image area, the tip of the image area moves to the position of the secondary transfer roller. In response to this, the secondary transfer roller is brought into contact with the intermediate transfer member via the recording material, and secondary transfer onto the recording material is started. On the other hand, when the rear end of the image area passes through the secondary transfer roller, the secondary transfer roller is separated from the intermediate transfer member to complete the secondary transfer.
[0005]
[Problems to be solved by the invention]
By the way, when the stationary transfer roller contacts the intermediate transfer member that circulates and rotates at a predetermined speed, the contact causes a load fluctuation on the intermediate transfer member, and the intermediate transfer member is temporarily decelerated. As a result, an image defect called so-called banding occurs. In order to solve this problem, conventionally, in addition to the separation contact drive device that separates and contacts the transfer roller with respect to the intermediate transfer member, a rotation drive device that rotates the transfer roller is provided. This rotation driving device rotates the transfer roller in a direction opposite to the rotation direction of the intermediate transfer member. Then, when the transfer roller is moved and brought into contact with the intermediate transfer member by the separation contact driving device while the transfer roller is rotated by the rotation drive device, the intermediate transfer generated when the transfer roller contacts the intermediate transfer member. Banding is suppressed by reducing fluctuations in the load on the body.
[0006]
However, in the conventional transfer device, it is necessary to provide two independent driving devices, which causes an increase in the size of the device and an increase in the cost of the device due to an increase in the number of parts. Note that such a problem is not a problem peculiar to a color image forming apparatus using an intermediate transfer member, but an image having a structure in which a transfer roller comes in contact with an image carrier such as a photosensitive member or an intermediate transfer member. This is a problem common to forming apparatuses.
[0007]
The present invention has been made in view of the above problems, and an object of the present invention is to provide a transfer device that is small in size and can suppress the occurrence of banding due to the contact of the transfer roller with the image carrier at low cost. .
[0008]
[Means for Solving the Problems]
The present invention provides a transfer apparatus for transferring a toner image on the image carrier to the recording material by bringing a transfer roller into contact with the image carrier through the recording material at a predetermined transfer position, To achieve this, there is provided a swinging member provided swingably in the vicinity of the transfer position, the transfer roller being rotatably attached to one end thereof, a cam shaft, and a cam fixed to the cam shaft. A swing mechanism that moves the transfer roller toward the image carrier by swinging the swing member by the cam that rotates together with the cam shaft, and the transfer roller includes the image And a rotation mechanism that rotates the transfer roller in a direction opposite to the rotation direction of the image carrier in accordance with a rotation operation of the cam shaft when moving toward the carrier.
[0009]
In the transfer device configured as described above, the cam rotates about the cam shaft in accordance with the rotation operation of the cam shaft, and the swing member is swung. Therefore, the transfer roller attached to one end of the swing member moves toward the image carrier and comes into contact therewith. In addition, along with the movement of the transfer roller, the transfer roller rotates in the direction opposite to the rotation direction of the image carrier in response to the rotation of the cam shaft. In this way, the transfer roller rotates and moves to contact with the image carrier as the cam shaft rotates. As a result, the occurrence of banding due to the contact of the transfer roller with the image carrier is effectively suppressed.
[0010]
Here, a mechanism for rotating the transfer roller in response to the rotation operation of the cam shaft, that is, a rotation mechanism, includes, for example, a first gear fixed to the rotation shaft of the transfer roller and a substantially fan shape fixed to the cam shaft. When the second gear and the transfer roller move toward the image carrier, the second gear and the gear portion of the second gear mesh with each other to receive the rotational motion of the cam shaft, and the rotational motion is transferred to the first gear. You may comprise with the transmission mechanism which transmits and rotates the said transfer roller. With this configuration, the transfer roller is rotated only while the gear portion of the second gear is engaged with the transmission mechanism, for example, while the transfer roller is moving toward the image carrier, and the other states. Then, the transfer roller can be configured not to receive the restraining force of the second gear, and the transfer roller can be operated by the rotation of the image carrier.
[0011]
Further, the transmission mechanism can be constituted by, for example, an idle gear which is rotatably attached to the swing shaft and whose outer peripheral surface can mesh with the first and second gears. With this configuration, these three gears mesh with each other with a reference pitch circle, and the rotation speed of the transfer roller to which the rotational driving force is transmitted by the gear train (first gear, second gear, and idle gear). Can be kept constant.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 is a view showing an image forming apparatus incorporating a transfer device according to the present invention. This image forming apparatus forms a full color image by superposing four color toners of yellow (Y), cyan (C), magenta (M), and black (K), or uses only black (K) toner. This is an apparatus for forming a monochrome image. In this image forming apparatus, when an image forming command (a signal indicating the content of a print request) is given to the control unit from an external device such as a host computer, the main controller provided in the control unit causes the engine unit 1 of the image forming apparatus to It is converted into job data (printing information) in a format suitable for operation instructions and given to the sub-controller. Receiving this, the sub-controller controls the engine unit 1 of the image forming apparatus according to the job data.
[0013]
In the engine unit 1, a toner image can be formed on the photoconductor 21 of the image forming unit 2. That is, the image forming unit 2 includes a photoconductor 21 that can rotate in the direction of the arrow in FIG. 1, and further, around the photoconductor 21 along the rotation direction, a charging roller 22 as a charging unit, and a developing unit. The developing units 23Y, 23C, 23M, and 23K, and the cleaning unit 24 are arranged. A charging bias is applied to the charging roller 22 from a charging bias circuit (not shown), and contacts the outer peripheral surface of the photoreceptor 21 to uniformly charge the outer peripheral surface.
[0014]
Then, the laser beam LB is irradiated from the exposure unit 3 toward the outer peripheral surface of the photosensitive member 21 charged by the charging roller 22. The exposure unit 3 scans and exposes the photosensitive member 21 with the laser beam LB in accordance with image data obtained by developing the image forming command to develop an electrostatic latent image corresponding to the image forming command on the photosensitive member 21. Form.
[0015]
The electrostatic latent image thus formed is developed with toner by the developing unit 23. That is, in this embodiment, as the developing unit 23, a yellow developing unit 23Y, a cyan developing unit 23C, a magenta developing unit 23M, and a black developing unit 23K are provided to be rotatable about an axis. . These developing units 23Y, 23C, 23M, and 23K are rotationally positioned and selectively abut against the photoreceptor 21 to apply toner to the surface of the photoreceptor 21. As a result, the electrostatic latent image on the photosensitive member 21 becomes obvious. The toner image developed by the developing unit 23 is primarily transferred onto the intermediate transfer drum 41 of the transfer unit 4 in the primary transfer region TR1.
[0016]
A cleaning unit 24 is disposed at a position advanced in the circumferential direction (the arrow direction in FIG. 1) from the primary transfer region TR1, and the toner remaining on the outer peripheral surface of the photoreceptor 21 after the primary transfer. Scrap off.
[0017]
The intermediate transfer drum 41 of the transfer unit 4 rotates while receiving a rotational driving force from a drive motor (not shown) while being in contact with the photoreceptor 21. When a color image is transferred to a recording material, the color image is formed by superimposing the toner images of the respective colors formed on the photosensitive member 21 on the intermediate transfer drum 41. In addition, when transferring a monochrome image to a recording material, only the black toner image on the photoreceptor 21 is formed on the intermediate transfer drum 41.
[0018]
Further, the toner image thus carried on the intermediate transfer drum 41 is secondarily transferred onto the recording material by the secondary transfer unit 7. The secondary transfer unit 7 corresponds to a transfer device according to the present invention, and has a secondary transfer roller 71. Then, by a swinging member, a swinging mechanism, and a rotating mechanism, which will be described in detail later, while being rotated at an appropriate timing, it is moved and brought into contact with the intermediate transfer drum (image carrier) 41, along the transport path 61. The toner image is secondarily transferred to the recording material conveyed to the next transfer region TR2. Thus, in this embodiment, the toner image to be transferred to the recording material is carried on the intermediate transfer drum 41, and this intermediate transfer drum 41 corresponds to the “image carrier” of the present invention. The secondary transfer region TR2 corresponds to the “predetermined transfer position” in the present invention.
[0019]
A cleaning unit 43 is provided in the vicinity of the secondary transfer region TR2 so as to be able to come into contact with and separate from the intermediate transfer drum 41. The cleaning unit 43 comes into contact with the intermediate transfer drum 41 at an appropriate timing and performs intermediate transfer after the secondary transfer. The toner remaining on the outer peripheral surface of the drum 41 is scraped off by the cleaning unit 43.
[0020]
Further, a fixing unit 5 is disposed on the downstream side of the secondary transfer region TR2 along the conveyance path 61, and fixes the toner image on the recording material conveyed along the conveyance path 61 to the recording material. . The recording material is further conveyed along a conveyance path 61 to a discharge tray (not shown).
[0021]
Next, the configuration and operation of the secondary transfer unit as one embodiment of the transfer apparatus according to the present invention will be described in detail with reference to FIGS. FIG. 2 is a perspective view showing the configuration of the secondary transfer unit. FIG. 3 is a side view of FIG. The secondary transfer unit 7 includes a secondary transfer roller 71, a swinging member 72 swingably provided in the vicinity of the secondary transfer region TR2, a swinging mechanism 73 that swings the swinging member 72, 2 The rotation mechanism 74 is configured to rotate the next transfer roller 71 in a direction β opposite to the rotation direction α of the intermediate transfer drum 41.
[0022]
As shown in FIG. 2, the secondary transfer roller 71 is a cylindrical roller disposed in parallel with the intermediate transfer drum 41 in the secondary transfer region TR2. In the vicinity of one end of the secondary transfer roller 71, a swing plate 721 finished in a hammer shape in a side view is disposed. Although not shown in FIG. 2, a swing plate is also disposed near the other end of the secondary transfer roller 71. The pair of swing plates 721 are connected to each other by a connecting member 722 and supported by the frame around the swing shaft 723. The swing plate 721 and the connecting member are centered on the swing shaft 723 as a swing center. 722 is swingable integrally. In this embodiment, the rocking plate 721 and the connecting member 722 are individually formed, but it goes without saying that these may be integrally formed.
[0023]
At one end 721 a of each swing plate 721, the rotation shaft 711 of the secondary transfer roller 71 is rotatably supported, and the secondary transfer roller 71 is moved together with the swing operation of the swing plate 721 and the connecting member 722. The intermediate transfer drum 41 can be separated and contacted freely. Then, as will be described later, when the secondary transfer roller 71 comes into contact with the intermediate transfer drum 41 via the recording material, the toner formed on the intermediate transfer drum 41 while being driven by the intermediate transfer drum 41 and rotating. The image is secondarily transferred to the recording material. As described above, in this embodiment, the swing member 72 is configured by the swing plate 721, the connecting member 722, and the swing shaft 723.
[0024]
In the vicinity of the other end 721b of the swing plate 721, a cam shaft 731 is disposed substantially parallel to the rotating shaft 711 and the swing shaft 723, and is rotatably supported by the frame. Further, on one end side of the secondary transfer roller 71, that is, on the lower right side in FIG. 2, a cam 732 is fixed to the cam shaft 731 corresponding to the other end portion 721 b of the swing plate 721. Therefore, when the cam 732 is rotated by applying a rotational driving force to the cam shaft 731, a part of the cam 732 is engaged with the other end 721 b of the swing plate 721 according to the amount of rotation, and the swing member 72. Swings with the swinging shaft 723 as the swing center.
[0025]
In this embodiment, a biasing spring 733 is attached to a part of the swing plate 721 to bias the secondary transfer roller 71 toward the intermediate transfer drum 41. Therefore, as shown in FIG. 3, when the cam 732 is away from the other end 721 b of the swing plate 721, the secondary transfer roller 71 is brought into contact with the intermediate transfer drum 41 by the biasing force of the biasing spring 733. On the other hand, when the cam 732 is positioned as shown in FIG. 4 and engages with the other end 721b of the swinging plate 721, the swinging member 72 is moved clockwise in the plane of the drawing against the biasing force of the biasing spring 733. And the secondary transfer roller 71 is separated from the intermediate transfer drum 41. Thus, in this embodiment, the swing mechanism 73 is configured by the cam shaft 731, the cam 732, and the biasing spring 733. However, the biasing spring 733 is not an essential component for configuring the swing mechanism 73, and the swing mechanism may be configured only by a cam.
[0026]
A first gear 741 and a second gear 742 are fixed to the rotating shaft 711 and the cam shaft 731, respectively. The second gear 742 has a substantially sector shape and rotates with the rotation of the cam shaft 731. An idle gear 743 that functions as a transmission mechanism is provided between the first and second gears 741 and 742 in order to transmit the rotational motion of the camshaft 731 to the first gear 741 via the second gear 742. Yes. The idle gear 743 is rotatably attached to the swing shaft 723, and the rotational movement of the cam shaft 731 is performed by the three gears 741 only while the gear portion 742 a of the second gear 742 is engaged with the idle gear 743. The secondary transfer roller 71 can be rotationally driven in the rotational direction β by being transmitted to the rotational shaft 711 by a gear train consisting of ˜743.
[0027]
In addition, in this embodiment, the three gears 741 to 743 are set so as to mesh with each other at a reference pitch circle (a chain line in FIGS. 3 and 4). For this reason, even if the swing member 72 swings as described above, the rotation speed of the secondary transfer roller 71 can be kept constant. Thus, in this embodiment, the rotation mechanism 74 is comprised by the three gears 741-743.
[0028]
Next, the operation of the secondary transfer unit 7 configured as described above will be described. FIG. 5 is a timing chart showing the operation of the secondary transfer unit. First, during the primary transfer process, the cam 732 engages with the other end 721b of the swing plate 721 as shown in FIG. 4 to perform the secondary transfer against the biasing force of the biasing spring 733. The roller 71 is separated from the intermediate transfer drum 41 (FIG. 4).
[0029]
Then, when the four color toner images are superimposed on the image area of the intermediate transfer drum 41 and the leading edge of the image area approaches the secondary transfer area TR2, the rotation of the cam shaft 731 starts at an appropriate timing T1. Then, the cam 732 rotates clockwise in FIG. 4 according to the rotation of the cam shaft 731. As a result, the swing member 72 swings counterclockwise about the swing shaft 723 as the swing center. . Further, the second gear 742 fixed to the camshaft 731 is rotated in the clockwise direction on the paper surface in conjunction with the swinging operation, and the gear portion 742a of the second gear 742 is engaged with the idle gear 743 at the timing T2. Thus, a gear train is formed. As a result, the rotational movement of the cam shaft 731 is given to the secondary transfer roller 71 by this gear train (second gear 742-idle gear 743-first gear 741), and the secondary transfer roller 71 rotates in the intermediate transfer drum direction. It rotates in the direction β opposite to α.
[0030]
When the camshaft 731 further rotates, the gear portion 742a of the second gear 742 and the idle gear 743 are disengaged (timing T3), and the secondary transfer roller 71 moves along the transport path 61 to the secondary transfer region TR2. The recording material (not shown) conveyed is brought into contact with the intermediate transfer drum 41 and rotated by the intermediate transfer drum 41 (timing T4). Thus, the secondary transfer process is performed. It should be noted that after the secondary transfer process is started, the cam shaft 731 stops rotating for a while and is ready for the next secondary transfer process.
[0031]
As described above, according to this embodiment, the secondary transfer roller 71 is moved in the rotational direction α of the intermediate transfer drum 41 while the secondary transfer roller 71 is moved toward the intermediate transfer drum 41 by the rotation operation of the cam shaft 731. And rotated in the opposite direction β. Therefore, the occurrence of banding due to the contact of the secondary transfer roller 71 with the intermediate transfer drum 41 can be effectively suppressed. Further, as described above, the separation contact driving of the secondary transfer roller 71 with respect to the intermediate transfer drum 41 and the rotation driving of the secondary transfer roller 71 are simultaneously performed only by the rotation of the cam shaft 731. The configuration is simpler than that, which is advantageous in reducing the size and cost of the apparatus.
[0032]
In particular, in the above embodiment, by using the substantially fan-shaped second gear 742, the meshing with the idle gear 743 is released while the secondary transfer roller 71 is in contact with the intermediate transfer drum 41 with the recording material interposed therebetween. Therefore, it is possible to prevent an extra external force from being applied to the secondary transfer roller 71 in the contact state.
[0033]
The present invention is not limited to the above-described embodiment, and various modifications other than those described above can be made without departing from the spirit of the present invention. For example, in the above embodiment, the rotational speed during which the secondary transfer roller 71 is being moved close to the intermediate transfer drum 41 is slightly lower than the driven rotational speed during the secondary transfer process, for example, by about several percent to 10%. However, it may be set to be slightly higher than the same rotational speed or the driven rotational speed, for example, about several to 10%. In short, it is desirable to make the secondary transfer roller 71 contact the intermediate transfer drum 41 while rotating the secondary transfer roller 71 at a rotational speed approximately equal to the driven rotational speed.
[0034]
In the above embodiment, the first and second gears 741 and 742 are connected to each other by an idle gear 743 as a transmission mechanism to form a gear train. However, a plurality of gears are combined in place of the idle gear 743. You may make it comprise a transmission mechanism.
[0035]
In the above embodiment, the swing mechanism 73 and the rotation mechanism 74 are provided only on one end side (the lower right side in FIG. 2) of the secondary transfer roller 71, but the swing mechanism 73 and the rotation mechanism 74 are also provided on the other end side. A rotation mechanism 74 may be provided, and the secondary transfer roller 71 may be simultaneously driven to separate and rotate at both ends of the secondary transfer roller 71.
[0036]
Further, the above embodiment relates to a transfer device that secondarily transfers a toner image formed on the intermediate transfer drum 41 to a recording material. However, an intermediate transfer medium other than the intermediate transfer drum (intermediate transfer belt, intermediate transfer sheet, etc.) The present invention can also be applied to a transfer device that secondarily transfers a toner image. Further, the present invention can be applied to a transfer device that transfers a toner image on a photosensitive member to a recording material without forming an intermediate toner image. In this apparatus, the photosensitive member corresponds to the “image carrier” of the present invention. The present invention can also be applied to an image forming apparatus that employs a so-called tandem system as an image forming system. The image forming apparatus described above is a printer, but examples of the image forming apparatus include image forming apparatuses such as copying machines and facsimile machines.
[0037]
【The invention's effect】
As described above, according to the present invention, the transfer roller is moved and brought into contact with the image carrier by swinging the swing member by the cam rotating with the cam shaft, and the transfer roller is moved together with the cam. Since the transfer roller is rotated in the direction opposite to the rotation direction of the image carrier in response to the rotation of the shaft, banding due to the contact of the transfer roller with the image carrier is effectively suppressed. can do. In addition, such an effect can be achieved only by rotating the camshaft, and the apparatus can be reduced in size and cost.
[Brief description of the drawings]
FIG. 1 is a diagram showing an image forming apparatus incorporating a transfer device according to the present invention.
FIG. 2 is a perspective view showing a configuration of a secondary transfer unit which is an embodiment of a transfer apparatus according to the present invention.
FIG. 3 is a side view of FIG. 2 and shows a state during secondary transfer processing.
FIG. 4 is a diagram illustrating a state during a primary transfer process.
FIG. 5 is a timing chart showing the operation of the secondary transfer unit in FIG. 2;
[Explanation of symbols]
7. Secondary transfer part (transfer device)
41. Intermediate transfer drum (image carrier)
71 ... Secondary transfer roller 72 ... Swing member 73 ... Swing mechanism 74 ... Rotating mechanism 711 ... Rotating shaft 721 (of the secondary transfer roller) ... Swing plate 721a ... (One end of the swing plate) 721b ... The other end 722 of the rocking plate ... the connecting plate 723 ... the rocking shaft 731 ... the cam shaft 732 ... the cam 741 ... the first gear 742 ... the second gear 742a ... (the second gear) gear part 743 ... the idle gear (transmission) mechanism)
TR2 ... secondary transfer area (predetermined transfer position)
α: rotation direction (of the intermediate transfer drum) β ... rotation direction (of the secondary transfer roller)

Claims (3)

In the transfer device for transferring the toner image on the image carrier to the recording material by bringing a transfer roller into contact with the image carrier via the recording material at a predetermined transfer position,
A swinging member provided so as to be swingable in the vicinity of the transfer position, and having the transfer roller rotatably attached to one end thereof;
A camshaft and a cam fixed to the camshaft, and the swinging member is swung by the cam rotating together with the camshaft to move the transfer roller toward the image carrier, A rocking mechanism to be contacted;
A rotation mechanism that rotates the transfer roller in a direction opposite to the rotation direction of the image carrier according to the rotation of the cam shaft when the transfer roller moves toward the image carrier; Characteristic transfer device. The rotation mechanism is
A first gear fixed to the rotation shaft of the transfer roller;
A substantially fan-shaped second gear fixed to the camshaft;
When the transfer roller moves toward the image carrier, the transfer roller meshes with the gear portion of the second gear and receives a rotational motion of the cam shaft, and transmits the rotational motion to the first gear to transfer the transfer roller. The transfer device according to claim 1, further comprising a transmission mechanism for rotating the roller. The transfer device according to claim 2, wherein the transmission mechanism is rotatably attached to the swing shaft, and an outer peripheral surface thereof is configured by an idle gear that can mesh with the first and second gears.

Images