JP3649381B2 - Driving device in image forming apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an image forming apparatus provided with a processing member that performs predetermined processing (for example, transfer processing, cleaning processing, development processing, etc.) in contact with an image carrier such as a photosensitive member or an intermediate transfer member. The present invention relates to a drive device that drives the image carrier to separate and abut at an appropriate timing.
[0002]
[Prior art]
In an image forming apparatus such as a printer, a facsimile machine, or a copier, a process of primary transfer of a toner image formed on a photosensitive member to an intermediate transfer member is performed by yellow (Y), magenta (M), cyan (C), 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. Therefore, conventionally, a drive device comprising a combination of an urging spring and a cam mechanism is provided in the groove forming device, and the secondary transfer roller is driven to come into contact with the intermediate transfer member by this drive device.
[0004]
In this driving device, a swinging member is swingably provided at a position near the secondary transfer position, and a secondary transfer roller is rotatably supported by the swinging member. An urging spring is attached to the swinging member, and the secondary transfer roller is urged toward the intermediate transfer member, whereby the secondary transfer roller contacts the intermediate transfer member to perform the secondary transfer process.
[0005]
A rotating shaft is disposed in the vicinity of the swing member, and a cam is fixed to the rotating shaft. The cam rotates with the rotation of the rotation shaft, and the protruding portion of the cam engages with a part of the swinging member, so that the swinging member is opposed to the spring force of the biasing spring, and the swinging member is opposite to the intermediate transfer member. Rocks. As a result, the secondary transfer roller held by the swing member is separated from the intermediate transfer member.
[0006]
[Problems to be solved by the invention]
However, in the drive device configured as described above, the secondary transfer roller is separated from the intermediate transfer member by the cam mechanism, and then the timing at which the secondary transfer roller contacts the intermediate transfer member (contact timing). Then, the cam rotates and moves with the rotation of the rotating shaft, and the protruding portion of the cam is removed accordingly, and the secondary transfer roller moves and contacts the intermediate transfer member by the spring force of the biasing spring. At this time, the secondary transfer roller suddenly comes into contact with the intermediate transfer member that circulates and rotates at a predetermined speed, a load fluctuation is generated on the intermediate transfer member, and the intermediate transfer member is temporarily decelerated. Image defects called so-called contact banding occur.
[0007]
In order to prevent contact banding, it is also conceivable to reverse the relationship between the urging bar and the cam mechanism. That is, the swinging member is biased in the direction of separating the secondary transfer roller from the intermediate transfer member by the biasing spring, and the swinging member is pushed to the secondary transfer side by the cam mechanism at the contact timing. You may comprise so that a secondary transfer roller may be contact | abutted to an intermediate transfer body, resisting a biasing spring.
[0008]
However, in such a configuration, the contact banding is eliminated, but the secondary transfer roller is suddenly separated from the intermediate transfer member at the separation timing, and so-called separation banding occurs. In addition, when the configuration in which the secondary transfer roller is moved against the biasing spring using the cam mechanism as described above is used, a relatively large torque drive is performed to rotationally drive the rotating shaft against the spring force. It is necessary to use a motor, and as a result, problems such as an increase in size and cost of the apparatus occur.
[0009]
Here, instead of separating the secondary transfer roller from the intermediate transfer member using the biasing spring as described above, it is also conceivable to perform the separating operation by the weight of the secondary transfer roller. However, in this proposed example, the arrangement position of the secondary transfer roller, that is, the secondary transfer position is restricted. For example, when a drum-shaped intermediate transfer member is used, the secondary transfer position is uniquely determined at the lowest position of the intermediate transfer drum. Therefore, the secondary transfer position is restricted by design, and another problem that the design flexibility of the image forming apparatus is greatly impaired occurs.
[0010]
Such a problem is not limited to the secondary transfer roller, but a processing member (such as a developing unit or a cleaning unit) that performs predetermined processing by contacting an image carrier such as a photosensitive member or an intermediate transfer member. This is a problem common to a driving device that drives to separate and contact the image carrier.
[0011]
The present invention has been made in view of the above problems, and an object of the present invention is to provide a driving device in an image forming apparatus that has a high degree of design freedom and can suppress a speed variation of an image carrier.
[0012]
[Means for Solving the Problems]
The present invention is a drive device that drives a processing member that performs a predetermined process by abutting against an image carrier of an image forming apparatus to separate and abut against the image carrier at an appropriate timing, and achieves the above object. Therefore, the rotating shaft, a cam fixed to the rotating shaft, a protrusion formed on a part of the outer peripheral portion thereof, and an inner surface cam groove formed on the inner surface thereof, and the image while holding the processing member A movable holding member provided so as to be movable toward and away from the carrier, and at the contact timing, the outer peripheral surface of the protruding portion moves the movable holding member toward the image carrier as the rotary shaft rotates. While pushing and bringing the processing member into contact with the image carrier, at the separation timing, the side surface of the inner cam groove protrudes from the movable holding member toward the cam as the rotation shaft rotates. The movable while engaging with the engaging part Pull back the support member on the opposite side of the image bearing member to separate the said processing member from said image bearing member.
[0013]
In the driving apparatus configured as described above, the protrusion of the cam pushes the movable holding member toward the image carrier and the processing member contacts the image carrier as the cam rotates. On the other hand, when the processing member is separated from the image carrier, the inner cam groove of the cam is used. That is, an inner surface cam groove is formed on the inner surface of the cam, and the side surface of the inner surface cam groove engages with the engaging portion of the movable holding member as the cam rotates, and the movable holding member is opposite to the image carrier. Pull back to. Thus, the processing member is separated from the image carrier. As described above, according to the present invention, the separation member is driven to come into contact with the image carrier by the rotational operation of the cam, so that the arrangement position of the treatment member can be arbitrarily set.
[0014]
Here, the movable holding member is swingably fitted to the swinging lever in the vicinity of the image carrier while supporting the processing member, and is loosely fitted to the swinging lever. You may comprise with the cap part comprised so that contact | abutment, and the compression spring accommodated in the storage space formed by the loose fitting of the said cap part to the said rocking lever. In such a configuration, at the contact timing, the outer peripheral surface of the projecting portion comes into contact with the cap portion with the rotation of the rotating shaft to swing the swing lever, thereby pushing the swing lever toward the image carrier. The processing member is brought into contact with the image carrier. Subsequently, when the rotating shaft further rotates, only the cap portion is pushed toward the image carrier while compressing the compression spring. Therefore, the pressing force of the processing member against the image carrier becomes a value corresponding to the compression spring, and the pressing force can be stabilized.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 is a view showing an image forming apparatus incorporating a drive device according to the present invention. This image forming apparatus forms a full color image by superposing four color toners of yellow (Y), magenta (M), cyan (C), 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.
[0016]
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 devices 23Y, 23M, 23C, 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.
[0017]
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.
[0018]
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 magenta developing unit 23M, a cyan developing unit 23C, and a black developing unit 23K are provided to be rotatable about an axis. . These developing units 23Y, 23M, 23C, 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.
[0019]
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.
[0020]
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. When transferring a monochrome image to a recording material, only a black toner image is formed on the intermediate transfer drum 41 on the photosensitive member 21.
[0021]
Further, the toner image thus carried on the intermediate transfer drum 41 is secondarily transferred onto the recording material by the secondary transfer roller 42. The secondary transfer roller 42 is driven to come into contact with and contact with the intermediate transfer drum (image carrier) 41 at an appropriate timing by the driving device according to the present invention. That is, at the contact timing, the secondary transfer roller 42 moves and contacts the intermediate transfer drum 41, and the toner image is secondarily transferred onto the recording material conveyed to the secondary transfer region TR2 along the conveyance path 61. . The secondary transfer roller 42 moves away from the intermediate transfer drum 41 when the secondary transfer process is completed. 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 roller 42 corresponds to a “processing member” of the present invention.
[0022]
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.
[0023]
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).
[0024]
Next, an embodiment of a drive device according to the present invention will be described in detail with reference to FIGS. FIG. 2 is a perspective view showing a configuration of a drive device that drives the secondary transfer roller to come into contact with and separate from the intermediate transfer drum. FIG. 3 is a side view of FIG. 4 is a partial cross-sectional view of FIG.
[0025]
The driving device 7 is a device that drives the secondary transfer roller 42 to come into contact with and separate from the intermediate transfer drum 41. In this drive device 7, a pair of swing levers 71, 71 are provided so as to be swingable around a swing shaft 711 near the intermediate transfer drum 41. Here, since the configuration corresponding to each of the swing levers 71 and 71 is the same, in the following description, the configuration on the near side in FIG. 2 will be described, and the configuration on the back side will be described with the same reference numerals. Is omitted.
[0026]
The swing lever 71 is formed in a substantially hammer shape, and a swing shaft 711 is attached to the rear end portion of the swing arm portion 712 corresponding to the handle portion. A rotating shaft 421 of the secondary transfer roller 42 is rotatably supported via a bearing 72 at the tip end of the swing arm 712. Further, as shown in FIG. 4, the swinging portion 713 corresponding to the hammer portion is formed so as to be recessed, and the cap portion 73 can be loosely fitted.
[0027]
More specifically, the inner diameter of the recess provided in the swing part 713 is larger than the outer diameter of the cap part 73, and the cap part 73 is completely inserted into the recess of the swing part 713. 2 and 3, a notch 713a is formed on the side surface of the swinging portion 713, and an engaging claw 731 formed at the tip of the cap portion 73 is engaged with the notch 713a. Is possible. With this configuration, the cap portion 73 is loosely fitted to the swing lever 71 and can move forward and backward within the swing portion 713 with a certain play amount.
[0028]
When the cap portion 73 is loosely fitted to the swing lever 71 in this way, a storage space SP is formed between them as shown in FIG. Therefore, in this embodiment, the compression spring 74 is accommodated in the space SP, thereby adjusting the pressing force F of the secondary transfer roller 42 against the intermediate transfer drum 41. This point will be described in detail later.
[0029]
Further, the cam 76 fixed to the rotating shaft 75 acts on the cap portion 73, and the cap portion 73 moves forward and backward with the rotation operation of the rotating shaft 75 to swing the swing lever 71. The secondary transfer roller 42 is moved away from and in contact with the intermediate transfer drum 41 by swinging about the moving shaft 711. More detailed description is as follows.
[0030]
As shown in FIGS. 2 and 4, the rotating shaft 75 is disposed substantially in parallel with the secondary transfer roller 42, and rotates by receiving a rotational driving force from a driving motor (not shown). A cam 76 is fixed to the rotating shaft 75 so as to correspond to the swing lever 71. The cam 76 has a protruding portion 761 formed at a part of the outer peripheral portion, and the outer peripheral surface of the protruding portion 761 pushes the cap portion 73 toward the intermediate transfer drum 41 side as the rotating shaft 75 rotates. The next transfer roller 42 is brought into contact with the intermediate transfer drum 41. At this time, the swing lever 71 is pushed to the intermediate transfer drum 41 side by the movement of the cap portion 73 toward the intermediate transfer drum 41 side with the rotation of the rotary shaft 75, so that the secondary transfer roller 42 contacts the intermediate transfer drum 41. Make contact. Subsequently, when the rotating shaft 75 further rotates, only the cap portion 73 is pushed toward the intermediate transfer drum 41 while the compression spring 74 is compressed. Accordingly, the pressing force F of the secondary transfer roller 42 against the intermediate transfer drum 41 becomes a value corresponding to the compression spring 74, and the pressing force F can be stabilized.
[0031]
On the other hand, an inner surface cam groove 762 is formed on the inner surface of the cam 76, and an engaging boss 732 is projected from the cap portion 73 toward the inner surface cam groove 762 as shown in FIG. When the cam 76 rotates together with the rotating shaft 75, the cap portion 73 is moved to the opposite side of the intermediate transfer drum 41 while the side surface 762 a of the inner cam groove 762 is engaged with the engaging boss 732 as the cam 76 rotates. Retreat (FIG. 5). As a result, the swing lever 71 and the secondary transfer roller 42 are moved away from the intermediate transfer drum 41.
[0032]
As described above, according to this embodiment, since the secondary transfer roller 42 is driven to come into contact with and separate from the intermediate transfer drum 41 by the rotational operation of the cam 76, the arrangement position of the secondary transfer roller 42 is arbitrary. Can be set to Further, unlike the conventional example and the proposed example, the biasing spring is not used for the contact and separation drive, and the secondary transfer roller 42 is moved away from and in contact with the intermediate transfer drum 41 only by a so-called cam mechanism. Therefore, contact banding and separation banding can be suppressed, and good image quality can be obtained. Further, the load on the drive motor is reduced, and the drive motor can be downsized.
[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 swing lever 71 and the cap portion 73 constitute the “movable holding member” of the present invention and are compressed into the storage space SP formed between the swing lever 71 and the cap portion 73. Although the spring 74 is disposed, the provision of the compression spring 74 is not an essential component, and a movable holding member in which the swing lever 71 and the cap portion 73 are integrated may be provided. However, in order to stabilize the pressing force F of the secondary transfer roller 42 against the intermediate transfer drum 41 as described above, it is desirable to provide the compression spring 74.
[0034]
In the above embodiment, the movable holding members (the swing lever 71 and the cap portion 73) provided at both ends of the secondary transfer roller 42 are driven one-on-one by the corresponding cams 76 and 76, respectively. However, the two movable holding members may be driven by one cam 76.
[0035]
In the above embodiment, the present invention relates to a driving device for driving the secondary transfer roller 42 for secondary transfer of the toner image formed on the intermediate transfer drum 41 to the recording material. The present invention can also be applied to a driving device that drives a secondary transfer roller for secondary transfer of a toner image onto an intermediate transfer belt, an intermediate transfer sheet, or the like. Further, the present invention can be applied to a driving device that drives a transfer roller that transfers a toner image on a photosensitive member to a recording material without forming an intermediate toner image. Corresponds to “image carrier”. 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 all image forming apparatuses such as a copying machine and a facsimile machine.
[0036]
Further, in the above-described embodiment, the transfer roller is exemplified as the processing member, and the driving device that drives the transfer roller has been described. However, the processing that performs a predetermined process in contact with an image carrier such as a photosensitive member or an intermediate transfer member. The present invention can be applied to all drive devices that drive members (development units, cleaning units, etc.) away from and contact the image carrier.
[0037]
【The invention's effect】
As described above, according to the present invention, as the cam rotates, the movable holding member is pushed to the image carrier side by the protruding portion of the cam, thereby bringing the processing member into contact with the image carrier, while the cam Since the engaging portion of the movable holding member is engaged with the side surface of the inner cam groove, and the movable holding member is pulled back to the opposite side of the image carrier as the cam rotates, The processing member can be driven to come into contact with the image carrier by the rotation of the cam, and the processing member can be disposed at an arbitrary position.
[0038]
Further, unlike the conventional example and the proposed example, the biasing spring is not used for the contact and separation drive, and the processing member is moved away from and in contact with the image carrier only by a so-called cam mechanism. Contact banding and separation banding can be suppressed, and good image quality can be obtained.
[Brief description of the drawings]
FIG. 1 is a diagram showing an image forming apparatus incorporating a drive device according to the present invention.
FIG. 2 is a perspective view illustrating a configuration of a driving device that drives a secondary transfer roller to come into contact with and separate from an intermediate transfer drum.
FIG. 3 is a side view of FIG. 2;
4 is a partial cross-sectional view of FIG. 3;
FIG. 5 is a side view showing a driving device when a secondary transfer roller is separated from an intermediate transfer drum.
[Explanation of symbols]
7 ... Drive device 41 ... Intermediate transfer drum (image carrier)
71 .. swing lever (movable holding member)
73 ... Cap part (movable holding member)
74 ... Compression spring 75 ... Rotating shaft 76 ... Cam 732 ... Engagement boss (engagement part)
761 ... Projection 762 ... Internal cam groove 762a ... Side surface SP (of internal cam groove) ... Storage space

Claims (2)

A driving device that drives a processing member that performs a predetermined process in contact with an image carrier of an image forming apparatus to be separated from and contacted with the image carrier at an appropriate timing
A rotation axis;
A cam fixed to the rotating shaft, a protrusion is formed on a part of the outer periphery thereof, and an inner surface cam groove is formed on the inner surface thereof;
A movable holding member provided so as to be able to approach and separate from the image carrier while holding the processing member;
At the contact timing, as the rotation shaft rotates, the outer peripheral surface of the protrusion pushes the movable holding member toward the image carrier to bring the processing member into contact with the image carrier,
At the separation timing, the movable holding member is moved to the image carrier while the side surface of the inner cam groove is engaged with an engaging portion protruding from the movable holding member toward the cam as the rotation shaft rotates. A drive device in an image forming apparatus, wherein the processing member is pulled back to the opposite side to separate the processing member from the image carrier. The movable holding member is
A swing lever provided to be swingable in the vicinity of the image carrier while supporting the processing member;
A cap portion that is loosely fitted to the swing lever and configured to be able to contact the protruding portion;
The drive device in the image forming apparatus according to claim 1, further comprising a compression spring housed in a housing space formed by loosely fitting the cap portion to the swing lever.

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