JP3750478B2 - Image forming apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention transfers a toner image on an image carrier onto a recording material such as copy paper, transfer paper, paper, and an OHP transparent sheet by a transfer unit, and removes toner remaining on the image carrier after the transfer by a cleaning unit. In particular, the present invention relates to an image forming apparatus in which a transfer unit and a cleaning unit are separated from and contacted to an image carrier at an appropriate timing.
[0002]
[Prior art]
As this type of image forming apparatus, for example, a color printer, a color facsimile, a color copying machine, and the like are conventionally known. In these image forming apparatuses, the toner image formed on the photoreceptor is primarily transferred to the intermediate transfer member for each of yellow (Y), magenta (M), cyan (C), and black (K). 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. 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.
[0003]
In addition, a cleaning unit is provided to remove toner remaining on the surface of the intermediate transfer member after the secondary transfer. This cleaning means is disposed downstream of the secondary transfer roller in the rotation direction of the intermediate transfer member. As a cleaning means, a blade cleaning method using a blade is generally adopted because of its simple structure. This blade is made of a material such as rubber having an appropriate hardness, for example, and removes residual toner by elastically abutting an edge formed at one end in the width direction on the surface of the intermediate transfer member with an appropriate pressure. ing. Note that the cleaning unit configured as described above needs to be separated from the intermediate transfer member during the primary transfer as in the case of the secondary transfer roller.
[0004]
Therefore, conventionally, the secondary transfer roller is driven to come into contact with the intermediate transfer member by the secondary transfer drive mechanism, while the cleaning means is driven by another drive mechanism (cleaning drive mechanism) with respect to the intermediate transfer member. It is separated and driven. Specifically, the secondary transfer roller and the cleaning unit are in contact with and separated from the intermediate transfer member at the next contact timing.
[0005]
During the primary transfer process, the secondary transfer roller and the cleaning unit are 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. Correspondingly, the secondary transfer roller comes into contact with the intermediate transfer member via the recording material, and secondary transfer onto the recording material is started. Further, the cleaning means comes into contact with the intermediate transfer member with a slight delay, and the cleaning process for the intermediate transfer member is started.
[0006]
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. On the cleaning means side, the trailing edge of the intermediate transfer member passes through the cleaning means, and when the toner image reaches the non-primary transfer area, that is, the non-image area, the cleaning means separates from the intermediate transfer body and performs the cleaning process. Complete.
[0007]
By the way, in the blade cleaning method, when the blade is separated from the intermediate transfer member, a separation streak is generated in which toner accumulated in the blade remains in a streak form in a non-image area on the intermediate transfer member. If such a separation line exists in the non-image area, the secondary transfer roller is contaminated by the separation line when the secondary transfer roller is brought into contact with the intermediate transfer member in the next image forming process. There was a problem that it adhered to the back surface and contaminated the recording material.
[0008]
Therefore, the separation contact timing of the secondary transfer roller and the cleaning unit is controlled so that the secondary transfer roller is brought into contact with the intermediate transfer member after the separation line passes so that the secondary transfer roller is not contaminated by the separation line. Has been.
[0009]
[Problems to be solved by the invention]
However, when the cleaning unit and the secondary transfer roller are driven to come into contact with each other by independent driving mechanisms as described above, the timing of the contact between the cleaning unit and the secondary transfer roller to come into contact with the intermediate transfer member is changed. It is practically impossible to make this zero. Therefore, it is necessary to consider both timing variations. For example, if the non-image area is set to be relatively long, it can be set so that the secondary transfer roller does not pick up the separation line generated by the cleaning means even if both timings are slightly shifted. However, when the non-image area becomes long in this way, there is a problem that the intermediate transfer body itself must be enlarged and the apparatus becomes large.
[0010]
In addition, such a problem is not a problem peculiar to a color image forming apparatus using an intermediate transfer member. A transfer unit such as a transfer roller or a transfer belt and a cleaning unit are used for an image such as a photosensitive member or an intermediate transfer member. This is a problem common to an image forming apparatus having a structure that comes into contact with and separates from a carrier.
[0011]
The present invention has been made in view of the above problems, and is small in size and can effectively prevent the transfer unit from being contaminated by the separation stripe generated on the image carrier due to the separation of the cleaning unit. An object is to provide an apparatus.
[0012]
[Means for Solving the Problems]
In order to achieve the above object, an image forming apparatus according to the present invention includes an image carrier that carries a toner image and a surface that can be separated from and contacted with the surface of the image carrier. A transfer means for transferring the toner image on the image carrier to the recording material by being brought into contact with the carrier, and a structure that can be separated from and brought into contact with the surface of the image carrier. Cleaning means for removing toner remaining on the image carrier after transfer by contact, cleaning urging means for urging the cleaning means in a direction to contact the image carrier, the transfer means, and And a driving unit that drives the cleaning unit to come into contact with and separate from the image carrier. The driving unit is fixed to the rotating shaft and rotates together with the rotating shaft to rotate the cleaning unit. A cleaning cam that acts to move the cleaning means away from the image carrier against the urging force of the urging means, and is fixed to the rotary shaft and rotates together with the rotary shaft, thereby A transfer cam that acts to abut the spaced apart transfer means against the image carrier, and a rotation driving force to the rotation shaft to rotate the transfer cam and the cleaning cam simultaneously. And a driving unit that causes the cleaning unit to contact the image carrier by the biasing force of the cleaning biasing unit, and the transfer unit to contact the image carrier by the action of the transfer cam And the cleaning cam is separated from the image carrier by the action of the cleaning cam, and the transfer cam does not act. When the stage is separated from the image carrier, neither the transfer cam nor the cleaning cam acts, and the cleaning means comes into contact with the image carrier by the urging force of the cleaning urging means. In addition, the transfer cam and the cleaning cam are fixed to the rotary shaft so that the transfer unit can selectively take one of the states separated from the image carrier.
[0013]
In the image forming apparatus configured as described above, the transfer cam and the cleaning cam are fixed to the same rotational shaft, and when the rotational drive is applied to the rotational shaft, the two cams rotate simultaneously. . Therefore, the transfer unit and the cleaning unit can be brought into contact with and separated from the image carrier by a single driving unit, and the apparatus can be simplified and downsized.
[0014]
In addition, since the transfer cam and the cleaning cam are fixed to the same rotating shaft, the cause of the separation stripe is only the variation in the separation contact timing generated from the drive means. Can set the length of the non-image area so as not to pick up the separation line, and the non-image area can be shortened as compared with the conventional example. More specifically, in the conventional example, in order to drive the transfer means and the cleaning means, respectively, independent dedicated drive means are provided. It was necessary to set a non-image area in consideration. On the other hand, in the present invention, the non-image area may be set in consideration of only the variation in separation / contact timing caused by one driving means. Inevitably, in the present invention, the non-image area can be shortened as compared with the conventional example, and the image carrier can be downsized, and the apparatus can be further downsized.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 is a diagram showing an embodiment of an image forming apparatus 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 transfer unit 4 rotates while receiving a rotational driving force from a drive motor (reference numeral 5 in FIG. 2) while being in contact with the photosensitive member 21. A primary transfer bias is applied to the intermediate transfer drum 41 from a primary transfer bias circuit (not shown). 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. Note that a toner image is not formed on the entire outer peripheral surface of the intermediate transfer drum 41, and as shown in FIG. 1, the maximum image (for example, an image in which two A4-size images are arranged in the circumferential direction) is formed on the outer peripheral surface. In addition to the image area A1 corresponding to the above, an area where the toner image is not transferred, that is, a non-image area A2 is provided in consideration of variations in separation / contact timing, as will be described later.
[0021]
Further, the toner image carried on the intermediate transfer drum 41 is secondarily transferred onto the recording material by the secondary transfer unit 42. As will be described in detail later, the secondary transfer portion 42 can be brought into contact with and separated from the intermediate transfer drum 41 and is brought into contact with the intermediate transfer drum 41 at an appropriate timing by a cam mechanism of a driving device (driving means) 43. The toner image is secondarily transferred to the recording material that is in contact with and conveyed along the conveyance path 61 to the secondary 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 intermediate transfer drum is grounded, and a secondary transfer bias is applied to the secondary transfer unit 42 by the secondary transfer bias circuit 44 during the secondary transfer.
[0022]
In the vicinity of the secondary transfer region TR2, a cleaning unit 45 is provided so as to be able to come into contact with and separate from the intermediate transfer drum 41 and is in contact with the intermediate transfer drum 41 at an appropriate timing. The toner remaining on the outer peripheral surface of the intermediate transfer drum 41 after the secondary transfer is scraped off by the cleaning unit 45.
[0023]
Further, a fixing unit 7 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, a configuration for executing the secondary transfer and the removal of the toner remaining on the intermediate transfer drum will be described with reference to FIGS. 2 is an overall view showing the configuration of the secondary transfer unit and the cleaning unit, FIG. 3 is a cross-sectional view taken along line AA in FIG. 2, and FIG. 4 is a displacement of the secondary transfer unit and the cleaning unit. It is a figure which shows a state.
[0025]
First, the configuration of the secondary transfer unit 42 will be described with reference to FIG. In the secondary transfer portion 42, a support lever 422 is supported in a swingable manner with the support shaft 421 as a swing center in the vicinity of the secondary transfer region TR2. A secondary transfer roller 423 is rotatably attached to one end of the support lever 422, and comes into contact with the intermediate transfer drum 41 in accordance with the swinging operation of the support lever 422. On the other hand, a spring casing 424 is attached to the other end of the support lever 422.
[0026]
The spring casing 424 includes a lid 425 that covers the upper portion of the spring casing 424 and a compression spring 426 provided inside the spring casing 424, and one end of the compression spring 426 is fixed to the bottom of the spring casing 424. The other end is fixed inside the lid portion 425. In a normal state, the secondary transfer roller 423 is separated from the intermediate transfer drum 41, but when the casing cover 425 is pressed by a cam described later, the support lever 422 is swung around the support shaft 421 and 2. The next transfer roller 423 is brought into contact with the intermediate transfer drum 41. The secondary transfer roller 423 presses the intermediate transfer drum 41 with an appropriate pressure by the urging force of the compression spring 426 compressed by the cam. In the secondary transfer roller 423, a metal cored bar 427 is covered with a conductive rubber 428. Further, the core metal 427 is electrically connected to the secondary transfer bias circuit 44 through the current detector 46.
[0027]
Next, the configuration of the cleaning unit 45 will be described with reference to FIG. In the cleaning unit 45, a collection case 452 is swingably provided with the support shaft 451 as a swing center. In the collection case 452, an opening 455 is provided on the surface facing the intermediate transfer drum 41, and a blade 456 is attached to one side of the opening 455. Further, one end of the swing lever 453 is fixed to the surface facing the opposite side of the intermediate transfer drum 41. Further, a biasing spring 454 is connected to the other end of the swing lever 453 to bias the collection case 452 toward the intermediate transfer drum 41 side.
[0028]
While no external force is applied to the cleaning unit 45 configured in this way, the tip of the blade 456 contacts the surface of the intermediate transfer drum 41 and scrapes off the toner remaining on the intermediate transfer drum 41. The residual toner scraped off by the blade 456 is collected in the collection case 452 through the opening 455.
[0029]
On the other hand, when the cleaning cam of the driving device 43 described below is engaged with the swing lever 453 and an external force is applied, the tip of the swing lever 453 is pressed against the biasing force of the spring, and the recovery case 452 swings around the support shaft 451 and the blade 456 is separated from the intermediate transfer drum 41.
[0030]
Next, the drive unit 43 for bringing the secondary transfer unit 42 and the cleaning unit 45 into contact with and away from the intermediate transfer drum 41 will be described. FIG. 3 is a view taken along line AA in FIG. As shown in the figure, the driving device 43 includes a rotating shaft 431, a transfer cam 432 fixed to the rotating shaft 431 and causing the secondary transfer portion 42 to come into contact with and separate from the intermediate transfer drum 41, and the rotating shaft 431. A cleaning cam 433 that is fixedly attached to the intermediate transfer drum 41 so as to separate and contact the cleaning unit 45 with the intermediate transfer drum 41. That is, the transfer cam 432 and the cleaning cam 433 are fixed to the same rotating shaft 431, and when the rotating shaft 431 is driven to rotate, both the cams 432 and 433 rotate simultaneously. The rotating shaft 431 is connected to the driving motor (driving unit) 5 via the clutch 434. When the clutch 434 is closed by a command from the sub-controller 71, the driving force of the driving motor 5 is transmitted to the rotating shaft 431. Both cams 432 and 433 rotate.
[0031]
Here, the transfer cam 432 and the cleaning cam 433 are rotated so that the secondary transfer portion 42 and the cleaning portion 45 are selectively rotated and positioned at one of the three positions as shown in FIG. It is fixed to the shaft 431.
[0032]
That is, FIG. 4A shows a state in which the secondary transfer roller 423 and the blade 456 are both in contact with the intermediate transfer drum 41, and the transfer cam 432 is attached to the spring casing 424 of the secondary transfer unit 42. The cleaning cam 433 is separated from the swing lever 453 of the cleaning unit 45 (hereinafter referred to as “position 1”). 4B shows a state in which the secondary transfer roller 423 and the blade 456 are both separated from the intermediate transfer drum 41, and the transfer cam 432 is separated from the spring casing 424 of the secondary transfer portion. In addition, the cleaning cam 433 is in contact with the swing lever 453 of the cleaning unit 45 (hereinafter referred to as “position 2”). Further, FIG. 4C shows a state in which the secondary transfer roller 423 is separated from the intermediate transfer drum 41 and the blade 456 is in contact with the intermediate transfer drum 41. At this time, the transfer cam 432 and the cleaning cam 433 are not in contact with the secondary transfer portion 42 or the cleaning portion 45 (hereinafter referred to as “position 3”).
[0033]
Further, the sub-controller 71 sends a command to the clutch 434 as needed to rotationally drive the rotary shaft 431 in order to rotationally position the secondary transfer unit 42 and the cleaning unit 45 to any one of the three positions described above. Further, by configuring as described above, at any of the three positions, only one of the transfer cam 432 and the cleaning cam 433 is subjected to a load or is not subjected to the load, and the rotary shaft 431 is not subjected to the load. And the burden on the drive motor 5 are reduced. Therefore, an increase in the size of the drive motor can be prevented.
[0034]
Next, a secondary transfer process and a residual toner cleaning process in the image forming apparatus according to this embodiment will be described. In this image forming apparatus, when an image forming command (a signal indicating the contents of a print request) is given to the main controller 72 from an external device such as a host computer, the main controller 72 develops and analyzes the image forming command and analyzes the engine unit. The job data (printing information) in a format suitable for one operation instruction is created and given to the sub-controller 71. Then, the sub controller 71 controls the engine unit 1 to form a color toner image or a monochrome toner image in the image area A 1 on the intermediate transfer drum 41.
[0035]
In a state where a toner image is formed on the intermediate transfer drum 41, that is, in a state where primary transfer is performed, the cams 432 and 433 of the driving device 43 are positioned at the position 2 and the secondary transfer roller 423. The blade 456 is separated from the intermediate transfer drum 41. When all the toner images are superimposed and the primary transfer is completed, and the leading end of the image area moves to the position of the secondary transfer portion 42, the sub-controller 71 rotates the cams 432 and 433 to the position 1. A command is sent to the clutch 434 to position it, and the secondary transfer roller 423 and the blade 456 are brought into contact with the intermediate transfer drum 41. Then, the toner image is transferred to the recording material by the secondary transfer unit 42, and the toner remaining on the intermediate transfer drum 41 is removed and collected by the cleaning unit 45.
[0036]
When the rear end of the image area passes through the cleaning unit 45, the sub-controller 71 sends a command to the clutch 434 to separate the secondary transfer roller 423 and the blade 456 from the intermediate transfer drum 41 in the non-image area. The next transfer is completed.
[0037]
Here, when the blade 456 of the cleaning unit 45 is separated from the intermediate transfer drum 41, the toner accumulated on the blade 456 remains in the non-image area on the intermediate transfer drum 41 and generates a separation stripe (symbol T in FIG. 1). Let Then, when the leading edge of the next image area moves to the position of the secondary transfer portion 42, the sub-controller 71 sends a command to the clutch 434 again so that the secondary transfer roller 423 and the blade 456 contact the intermediate transfer drum 41. Touched. In this case, the transfer cam 432 and the cleaning cam 433 are relatively positioned and fixed to the same rotating shaft 431 so that the secondary transfer portion 42 does not pick up the separation line. The only cause of this is the variation in the timing for opening and closing the clutch 434. Considering this, the length of the non-image area can be set such that the secondary transfer roller 423 does not pick up the separation line, The non-image area can be shortened compared to the conventional example.
[0038]
More specifically, in the conventional example, in order to drive the secondary transfer roller and the blade, respectively, independent dedicated drive means are provided. It was necessary to set a non-image area in consideration of the above. On the other hand, in this embodiment, the non-image area A2 may be set in consideration of only the variation in the separation contact timing (timing for opening and closing the clutch 434) generated from one driving device 43. As a result, the non-image area A2 can be shortened in the circumferential direction as compared with the conventional example, and the intermediate transfer drum 41 can be downsized, and the apparatus can be further downsized.
[0039]
In addition, when the recording material is not supplied to the secondary transfer portion side due to the occurrence of paper cut or paper jam in the middle of the secondary transfer, the secondary transfer roller 423 contacts the image area without passing through the recording material. There is a risk of contamination. In such a case, when it is detected that the paper is out by a sensor (not shown), the sub-controller 71 sends a command to the clutch 434 so that the cams 432 and 433 are rotationally positioned at the position 3. That is, the secondary transfer roller 423 is separated from the intermediate transfer drum 41 so that the secondary transfer roller 423 is not contaminated, and the blade 456 is brought into contact with the intermediate transfer drum 41 to remove the toner image being transferred. .
[0040]
By the way, when the device is restarted, it is necessary to initialize the device. As part of the initialization process, the home position (origin position) of the secondary transfer roller 423 needs to be obtained. Therefore, in this embodiment, the home position of the secondary transfer roller 423 is determined as follows.
[0041]
When the apparatus is restarted, the drive motor 5 starts operating in response to a command from the sub-controller 71, and the clutch 434 is closed to transmit the rotational drive from the drive motor 5 to the rotary shaft 431. As a result, the rotating shaft 431 rotates and the secondary transfer unit 42 and the cleaning unit 45 are brought into contact with and separated from the intermediate transfer drum 41. In parallel with the separation and contact operation, a secondary transfer bias is applied from the secondary transfer bias circuit 44 to the secondary transfer roller 423. Therefore, when the secondary transfer roller 423 that has been separated from the intermediate transfer drum 41 moves toward the intermediate transfer drum 41 and comes into contact with the secondary transfer roller 423, a bias current is generated between the secondary transfer roller 423 and the intermediate transfer drum 41. Begins to flow.
[0042]
Therefore, in this embodiment, a current detector 46 that detects a bias current to detect the home position of the secondary transfer roller 423 using this phenomenon is provided between the secondary transfer bias circuit 44 and the secondary transfer roller 423. And an output signal from the current detector 46 is given to the sub-controller 71. Note that the bias current is not limited to the secondary transfer bias, and an appropriate bias may be applied for home position detection.
[0043]
On the other hand, when the sub-controller 71 determines that the bias current value has exceeded a preset current value, it determines that the secondary transfer roller 423 has contacted the intermediate transfer drum 41 at that time. Then, the sub-controller 71 controls the apparatus with the position of the secondary transfer roller 423 at the time when a predetermined number of pulses are counted from this time as the home position, for example. In this embodiment, since the transfer cam 432 and the cleaning cam 433 are fixed to the same rotation shaft, the cleaning unit 45 is determined when the home position of the secondary transfer roller 423 is determined as described above. The home position is also uniquely determined.
[0044]
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, the above embodiment relates to a transfer unit that secondarily transfers a toner image formed on the intermediate transfer drum 41 to a recording material and a cleaning unit that removes and collects residual toner after the secondary transfer. The present invention can also be applied to transfer means and cleaning means for other intermediate transfer media (intermediate transfer belt, intermediate transfer sheet, etc.).
[0045]
Even in an image forming apparatus that transfers a toner image on a photoconductor to a recording material without forming an intermediate toner image and cleans residual toner after transfer, the transfer unit and the cleaning unit are used as the photoconductor. In some cases, they may be separated from each other. It goes without saying that the present invention can also be applied to such an image forming apparatus. In this apparatus, the photosensitive member corresponds to the “image carrier” of the present invention.
[0046]
Furthermore, 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.
[0047]
【The invention's effect】
As described above, according to the present invention, the transfer unit and the cleaning unit are brought into contact with and separated from the image carrier by simultaneously rotating the transfer cam and the cleaning cam fixed to the same rotating shaft. Therefore, the transfer unit and the cleaning unit can be separated and brought into contact with each other by one driving unit, and thus the apparatus can be simplified and miniaturized.
[0048]
In addition, since the timing at which the transfer unit and the cleaning unit separate and come into contact with the image carrier is controlled by a single drive unit, a non-image is considered in consideration of only the variation in the separate contact timing associated with one drive unit. An area can be set. For this reason, conventionally, the driving means independent of the transfer means and the cleaning means are provided, and therefore, the non-image area is set to be relatively long in consideration of the variation of the separation contact timing in each driving means. On the other hand, in the present invention, there is only one driving means, and only the variation in separation / contact timing due to this driving means needs to be taken into consideration, so the non-image area can be set shorter than before. Therefore, it is possible to reduce the size of the image carrier and further reduce the size of the apparatus.
[Brief description of the drawings]
FIG. 1 is a diagram showing an embodiment of an image forming apparatus according to the present invention.
FIG. 2 is a diagram illustrating a configuration for performing secondary transfer and cleaning of residual toner.
FIG. 3 is a view taken along the line AA in FIG. 2;
FIG. 4 is a diagram illustrating separation and contact between a secondary transfer unit and a cleaning unit with respect to an intermediate transfer drum.
[Explanation of symbols]
5 ... Drive motor (drive unit)
41. Intermediate transfer drum (image carrier)
42 ... Secondary transfer section (transfer means)
43 ... Driving device (driving means)
44 ... Secondary transfer bias circuit (transfer bias applying means)
45 ... Cleaning section (cleaning means)
46 ... Current detector (current detection means)
426 ... Compression spring
431 ... Rotating shaft
432 ... Transfer cam
433 ... Cleaning cam
454 ... Biasing spring

Claims (3)

An image carrier for carrying a toner image;
Transfer means configured to be able to come into contact with and separate from the surface of the image carrier and to transfer the toner image on the image carrier to the recording material by being brought into contact with the image carrier via a recording material When,
Cleaning means configured to be able to come into contact with and separate from the surface of the image carrier, and remove toner remaining on the image carrier after transfer by being in contact with the image carrier;
A biasing means for cleaning for biasing the cleaning means in a direction in contact with the image carrier;
Drive means for driving the transfer means and the cleaning means to separate and abut against the image carrier,
The driving means includes
A rotating cam, and a cleaning cam fixed to the rotating shaft and rotating together with the rotating shaft to act to separate the cleaning means from the image carrier against the urging force of the cleaning urging means A transfer cam that is fixed to the rotation shaft and rotates together with the rotation shaft so as to contact the transfer means spaced apart from the image carrier with respect to the image carrier; A drive unit that applies a rotational driving force to the rotation shaft to simultaneously rotate the transfer cam and the cleaning cam;
A state in which the cleaning unit abuts on the image carrier by the urging force of the cleaning urging unit, and the transfer unit abuts on the image carrier by the action of the transfer cam;
A state where the cleaning means is separated from the image carrier by the action of the cleaning cam, and the transfer means is separated from the image carrier without the transfer cam acting;
Neither the transfer cam nor the cleaning cam acts, the cleaning means abuts on the image carrier by the urging force of the cleaning urging means, and the transfer means is separated from the image carrier. The image forming apparatus, wherein the transfer cam and the cleaning cam are fixed to the rotating shaft so that one of the two states can be selectively taken.   And a transfer urging unit that is interposed between the transfer cam and the transfer unit and adjusts a pressing force applied to the image carrier by the urging force of the transfer cam. Item 4. The image forming apparatus according to Item 1. A transfer bias applying means for applying a transfer bias to the transfer means;
A current detection means for detecting a bias current flowing between the transfer means and the image carrier;
The image forming apparatus according to claim 1, wherein a home position of the transfer unit is determined based on a current value detected by the current detection unit while the transfer unit is moving with respect to the image carrier.

Images