JP3353568B2 - Image transfer device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as a color copying machine, and more particularly, to a technique for reducing the influence of a cleaning means on the transfer speed of a transfer belt or the like due to contact with a transfer roller. It is.

[0002]

2. Description of the Related Art Conventionally, as a color copying machine, a toner image formed on a photosensitive drum is transferred (primary transfer) to an intermediate transfer member such as a transfer belt, and this operation is performed in cyan, magenta,
There is known a method of transferring (secondary transfer) a color toner image formed by lamination for each color of yellow and black from an intermediate transfer body to a sheet. Also, Japanese Patent Application Laid-Open
No. 226767 proposes a color copying machine in which cyan, magenta, yellow and black toner images are sequentially laminated on a photosensitive drum, and the color toner images thus formed are collectively transferred to a sheet. .

In such a color copying machine, a transfer roller is pressed against an intermediate transfer member or a photosensitive drum, and a paper is inserted between the transfer roller and a toner while a charge of a reverse bias is formed on the transfer roller. Then, the transfer of the color toner image to the paper is performed. In this case, the transfer roller directly contacts the intermediate transfer member or the like for a while before and after the sheet passes, and a portion of the transfer roller exceeding the sheet width also directly contacts the intermediate transfer member or the like. For this reason, the residual toner adhering to the surface of the intermediate transfer member or the like adheres to the transfer roller.

Japanese Patent Application Laid-Open No. 4-44071 proposes a technique in which a toner attached to a transfer roller is scraped off by a cleaning blade made of an elastic material such as rubber in a color copying machine using a transfer belt. According to this proposal, the cleaning blade is constantly pressed against the transfer roller, and in this state, the transfer roller is pressed against the transfer belt. Then, the transfer roller starts driven rotation by being pressed by the transfer belt. This technique is also applicable to a color copier or a single-color copier in which toner images are formed on a photosensitive drum and transferred collectively to paper.

[0005]

The load applied to the transfer belt in the image forming process includes the following. Friction resistance by a cleaning blade that scrapes off residual toner on the transfer belt. Rotational load of the transfer roller. Inertial load when the transfer roller is pressed against the transfer belt and driven to rotate. Friction resistance caused by the cleaning blade that cleans the surface of the transfer roller being strongly pressed against the transfer roller. When the cleaning blade is strongly pressed against the soft sponge-like transfer roller and is left for a long time, a large resistance is generated when the transfer roller starts due to the leading edge of the cleaning blade biting into the transfer roller. Bearing resistance of the idle roller and backup roller that hold the transfer belt.

As described above, the load on the transfer belt before the image is transferred to the paper is as described above. However, when the transfer process is started, the load is applied. Among them, the following problems have occurred because of the large size. That is, when performing continuous copying in a color copying machine using a transfer belt, the next image forming process has already started at the time of starting the transfer process, and the toner image formed on the photosensitive drum is transferred to the transfer belt. During this operation, the transfer roller is pressed against the transfer belt. However, since the resistance at the time of starting the transfer roller is large, the traveling speed of the transfer belt becomes slow at the moment of the start, and as a result, the toner image transferred to the transfer belt is shifted from a predetermined position.

In a color copying machine in which a toner image is formed on the photosensitive drum in a stacked manner and is collectively transferred to a sheet, the next image forming step may be started at the time of starting the transfer step. In some cases, the transfer roller is pressed against the photosensitive drum while the latent image is being written on the photosensitive drum. Even in such a case, at the moment when the transfer roller starts to follow and follow the movement of the photoconductor drum, the rotation speed of the photoconductor drum becomes slow due to the starting resistance of the transfer roller, and as a result, the data is written on the photoconductor drum. A shift occurs in the latent image.

The above problem is caused by the configuration in which the transfer roller is pressed against the transfer belt or the photosensitive drum and is driven to rotate, so that a drive source such as a motor is connected to the transfer roller. It is also conceivable that the apparatus is configured to be rotated independently of each other. However, in such a case, not only the device becomes large and complicated, but also a new problem that the manufacturing cost becomes expensive arises. In addition, it is conceivable to perform control such that the transfer or latent image writing process is started after the transfer roller is pressed against the transfer belt or the like. However, in this case, the time required for copying is greatly increased. It creates new problems.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and it is possible to simplify the structure without increasing the copying time and to reduce the starting resistance of the transfer roller. It is an object of the present invention to provide an image transfer apparatus that can reduce the number of images, thereby preventing the image from shifting and enabling high-quality image formation.

[0010]

According to the present invention, there is provided an image transfer apparatus comprising: a transfer roller which is driven to rotate by being brought into contact with a movable image carrier via a recording sheet; First moving means for moving the transfer roller in the opposite direction, cleaning means for contacting the outer peripheral surface of the transfer roller to clean the transfer roller, and moving the cleaning means relative to the transfer roller and in the opposite direction. And a second moving unit configured to increase a contact pressure between the cleaning unit and the transfer roller after the transfer roller contacts the image bearing member. It is characterized by having.

According to the image transfer apparatus having the above-mentioned structure, when the first moving means brings the transfer roller into contact with the image carrier, the transfer roller starts driven rotation, and thereafter, the second moving means makes contact with the cleaning means. Increase the contact pressure with the rollers. Therefore, when the transfer roller starts, almost only the starting resistance of the transfer roller is applied to the image carrier. Then, after the transfer roller starts, a dynamic frictional resistance due to the rotation of the transfer roller, which is much smaller than the starting resistance, is applied to the image carrier, and thereafter, the contact pressure between the cleaning means and the transfer roller further increases, and Friction resistance is applied to the image carrier. As described above, the timing of the load increase due to the starting resistance of the transfer roller and the timing of the load increase due to the frictional resistance between the cleaning unit and the transfer roller are shifted, so that the moving speed of the image carrier does not suddenly decrease. In addition, the displacement of the image is suppressed.

In the above configuration, the cleaning unit may be configured to be separated from the transfer roller when the transfer roller is separated from the image bearing member, or not to be separated from the transfer roller. In addition, a configuration may be employed in which the contact pressure on the transfer roll is reduced. When the cleaning means is separated from the transfer roller, when the transfer roller is started, the load caused by pressing the cleaning means against the transfer roller is not applied to the image carrier, and only the starting resistance of the transfer roller is reduced. To be loaded. Thereafter, the cleaning means is brought into contact with the transfer roller, and the frictional resistance between the two is applied to the image carrier. Therefore, the starting resistance of the transfer roller and
Since the frictional resistance between the cleaning unit and the transfer roller is not simultaneously applied to the image carrier, it is possible to further suppress a reduction in the moving speed of the image carrier when the transfer roller is started.

On the other hand, when the cleaning unit weakens the contact pressure on the transfer roller without separating from the transfer roller, the cleaning unit is always in contact with the transfer roller despite the low contact pressure. Therefore, when the transfer roller contacts the image carrier and starts driven rotation, the surface of the transfer roller is cleaned by the cleaning unit. Thereby, the transfer of the residual toner on the surface of the transfer roller to the sheet passing between the transfer roller and the image carrier is reduced, so that a higher quality image can be formed. In addition, since the timing of the load increase due to the starting resistance of the transfer roller and the time of the load increase due to the frictional resistance between the cleaning unit and the transfer roller are shifted, there is also an effect of suppressing the above-described image shift.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION

A. 1. First Embodiment (1) Configuration of First Embodiment Hereinafter, a first embodiment of the present invention will be described with reference to FIGS. 1 and 3 to 7. First, prior to description of the image transfer apparatus of the embodiment, an outline of an image forming apparatus to which the embodiment is applied will be described. FIG. 1 is a front sectional view of an image forming apparatus to which the image transfer device of the embodiment is applied, and reference numeral 20 in the figure denotes a photosensitive drum. The photosensitive drum 20 has a cylindrical shape and is rotatable around its axis in the direction of the arrow in the figure. In the vicinity of the outer periphery of the photosensitive drum 20, a developing device 1 is provided.
0, the charging roller 22 and the cleaner 23 are arranged in this order in the clockwise direction. Further, an image writing device 21 is arranged slightly apart from the photosensitive drum 20. The image writing device 21 is configured to irradiate the surface of the photoconductor drum 20 with laser light, and scans the surface of the photoconductor drum 20 uniformly charged by the charging roller 22 in the axial direction thereof, thereby forming an image. An electrostatic latent image is written based on the image data read by the reading device 5.

The developing device 10 includes a cyan developing unit 10.
a, a magenta developing unit 10b, a yellow developing unit 10c, and a black developing unit 10d.
The development of the electrostatic latent image corresponding to each color written by 1 is performed. Specifically, in the first rotation of the photosensitive drum 20, a cyan electrostatic latent image is written to form a toner image of the same color, and a transfer belt (image carrier) 37 of a primary transfer unit 30 described later. Is transferred to In the next rotation, the magenta electrostatic latent image is written to form a toner image of the same color, which is transferred to the transfer belt 37 so as to overlap the cyan toner image. Then, while the photosensitive drum 20 rotates four times, the cyan to black toner images are sequentially superimposed on the transfer belt 37, and a color toner image is formed on the transfer belt 37.

Next, the primary transfer unit 30 is connected to the photosensitive drum 20.
It is arranged above. The primary transfer device 30 includes a drive roller 31, a primary transfer roller 32, an idle roller 33, a backup roller 34, and an idle roller 35 arranged in this order in a clockwise direction. , And is schematically configured.

FIG. 3 is a view showing a driving mechanism for rotating the driving roller 31. As shown in FIG. As shown in this figure, an output shaft 26 a of a servo motor 26 disposed inside the image forming apparatus is connected to a gear 3 of a driving roller 31 via an idle gear 27.
1a is connected. The output shaft 26a is connected to a gear 20a of the photosensitive drum 20 via an idle gear 27 and a double gear 28. Then, under this configuration, the photosensitive drum 20 and the transfer belt 37 rotate or run in the same circumferential direction at the same speed.

Although not shown, the photosensitive drum 2 is not shown.
The rotary encoder 20 is connected to a rotary encoder, and a controller (not shown) controls the photosensitive drum 20 based on a pulse signal output from the rotary encoder.
Is controlled so as to keep the rotation speed constant. Note that a hybrid step motor can be used instead of the servo motor 26. Further, the drive roller 31 can be configured to be driven by another servomotor. In this case, a rotary encoder is connected to the rotation shaft 31b of the drive roller 31 to perform high-precision speed control. Can be.

Next, on the left side of the backup roller 34, a secondary transfer device (image transfer device) 40 provided with a transfer roller 47 that can contact and separate from the backup roller 34 is arranged. The secondary transfer device 40 is for transferring the color toner images laminated and formed on the transfer belt 37 to the paper P. Details of the secondary transfer unit 40 will be described later.

Reference numerals 60 and 61 in the figure denote paper feed trays,
Reference numerals 62 and 63 denote feed rollers for feeding out the sheets P stored in the sheet feeding trays 60 and 61 one by one. The feed rollers 62 and 63 supply the paper P between the registration roller 64 and the pinch roller 65, and the registration roller 64 and the pinch roller 65 further supply the supplied paper P to the backup roller 34 and the transfer roller 4.
Supply between 7 At that time, the paper P is brought into close contact with the transfer belt 37, and the color toner image held on the transfer belt 37 is transferred onto the paper P by the charge applied to the transfer roller 47. Reference numeral 66 denotes a heating roller, and 67 denotes a pressing roller pressed against the heating roller 66. When the sheet P is inserted between the heating roller 66 and the pressing roller 67, a color is applied to the sheet P. The toner image is fixed. Further, reference numeral 68 denotes a paper discharge roller for discharging the fixed paper P, and reference numeral 69 denotes a paper discharge tray for storing the discharged paper P.

Next, the configuration of the image transfer device of the embodiment, that is, the secondary transfer device 40 will be described in detail. In FIG. 5, reference numeral 42 denotes an arm (first moving means). The arm 42 has an L-shape whose upper end is bent substantially at right angles to the lower end. The lower end of the arm 42 is a shaft 43
Rotatably supported by the arm 42
Rotates in a direction in which its upper end approaches and separates from the backup roller 34. At the upper end of the arm 42, an elongated hole (second moving means, guide portion) 44 whose longitudinal direction is directed to the direction in which the upper end extends is formed. Slot 44
, A slider (second moving means) 45 slidable in the longitudinal direction is supported, and the slider 45 rotatably supports a shaft 46 of a transfer roller 47. Also,
The slider 45 is urged toward the backup roller 34 by a coil spring (second elastic member) 48 attached to the upper end of the arm 42.

A holder 49 is attached to the upper end of the arm 42, and a cleaning blade (cleaning means) 51 is fixed to the holder 49. The cleaning blade 51 is for cleaning residual toner transferred from and adhered to the outer peripheral surface of the transfer roller 47 from the transfer belt 37, and is made of an elastic material such as rubber. The upper end of the cleaning blade 51 is
5 is separated from the transfer roller 47 in a state where it is located on the right side of the long hole 44.

The arm 42 is urged by a coil spring (first elastic member) 50 in a clockwise direction in the figure. Further, an outer peripheral surface of a cam (drive member) 52 rotatable by a shaft 53 is in contact with a side portion of the arm 42. And, with this configuration, the cam 5
When 2 rotates from the state shown in FIG. 5, the arm 42 rotates clockwise by the urging force of the coil spring 50.
The transfer roller 47 abuts the transfer belt 37 on the outer periphery of the backup roller 34 at a position just before the cam 52 rotates by 180 ° from the state of FIG. 5, and the slider 45 moves in the elongated hole 44 by the urging force of the coil spring 50 in the figure. Move relatively to the left. Thus, the cleaning blade 51 is pressed against the surface of the transfer roller 47 as shown in FIG.

The cleaning blade 5 is attached to the transfer roller 47.
The force of the coil spring 50 is set sufficiently higher than the force of the coil spring 48 in order to compress the coil spring 48 until 1 is pressed. Further, the transfer roller 47 is connected to the transfer belt 3.
7 so that the force of pressing the coil spring 4 becomes a predetermined value.
A spring constant and a compression dimension of 8 are selected. Further, the tip of the cleaning blade 51 is displaced by about 1 mm per 10 mm in length at the rotation end of the arm 42 (bending by pressing against the transfer roller 47 from a linear state where no force is applied to the cleaning blade 51). Are arranged as follows. In FIG. 6, the curvature of the cleaning blade 51 is exaggerated.

Next, referring to FIG. 7 and FIG.
The mechanism for rotating is described. As shown in FIG. 7, the shaft 53 of the cam 52 is
6 is connected to a gear 55, and the gear 55 is connected to a gear 54 of an output shaft 54a of a motor (not shown). As shown in FIG. 8, the spring clutch 56 is schematically configured by arranging a coil spring (not shown) on an inner peripheral surface of a cylindrical sleeve 56a, and a shaft 53 and a gear 5 are provided inside the coil spring.
5 shaft 55a. The inner diameter of the coil spring is
The diameter of the shaft 53, 55a is smaller than that of the shaft 53, 55a in a no-load state, and the shaft 53, 55a is tightened by its elastic force.

The shafts 53 and 55a are connected to each other by reducing the diameter of the coil spring by its own elastic force, and become free by increasing the diameter of the coil spring. The diameter of the coil spring is expanded by applying a torsional moment to both ends. That is, one end of the coil spring is attached to the sleeve 56a, and the other end is connected to the sleeve 56a.
Are connected to the claws 56b, 56b projecting 180 ° apart from each other on the outer periphery of the hook. On the other hand, in the vicinity of the outer periphery of the sleeve 56a, a stopper 5 whose one end is rotatably supported by the shaft 58 is provided.
9 are arranged. The stopper 59 is rotatable by the solenoid 57, and is engaged with the claw 56b so as to be freely detachable. Then, by applying a torque to the sleeve 56a with the claw 56b engaged with the stopper 59, a torsional moment is applied to the coil spring, and the diameter of the coil spring expands, so that the shafts 53 and 55a become free.

The shaft 55a of the gear 55 is constantly rotated by a motor, and a torque for expanding the diameter of the coil spring is applied to the sleeve 56a by the frictional force between the shaft 55a and the coil spring. Then, when the stopper 59 is rotated and the engagement state with the claw 59 is released, the diameter of the coil spring is reduced and the shafts 53 and 55a are tightened. Shaft 55a
Is the direction in which the coil spring is tightened. Therefore, the rotation of the shaft 55a is transmitted to the shaft 53 accurately.
Then, when the sleeve 56a rotates by 180 °, the other claw 56b is engaged with the stopper 59, the diameter of the coil spring is expanded, and the shafts 53 and 55a become free. Under such a configuration, the cam 52 rotates 180 ° and stops. The stop positions are the position shown in FIG. 5 where the arm 42 is farthest from the backup roller 34 and the position shown in FIG. 6 where the arm 42 is closest to the backup roller 34.

(2) Operation of the First Embodiment Next, the operation of the image transfer apparatus having the above configuration will be described. First, the photosensitive drum 20 rotates while the charger 2 rotates.
2, a latent image corresponding to a cyan image is first formed by the laser light L emitted from the image writing device 21. Next, development is performed by the cyan developing section 10a of the developing device 10, and a cyan toner image is formed. Thereafter, the photosensitive drum 20 continues to rotate, and the cyan toner image is transferred to the transfer belt 37. Then, in this way, the cyan toner image, the yellow toner image, and the black toner image are sequentially superimposed on the transfer belt 37, and thus a color toner image is formed. During this time, the transfer roller 47 is separated from the backup roller 34 so as not to disturb the formed toner image.

Next, when the color toner image formed on the transfer belt 37 approaches the secondary transfer unit 40, the transfer roller 47 is pressed against the transfer belt 37 around the backup roller 34 as follows. First, the solenoid 57 is driven in the state shown in FIG.
It is pivoted toward the center and downward to release the engagement state with the claw 56b. Then, the spring clutch 56 operates and the shaft 5
The rotation of the gear 55 is transmitted to the shaft 53 and the cam 52 rotates. After that, the solenoid 5
7 is driven again to return the stopper 59 to the state shown in FIG. 8 so that the stopper 59 can be engaged with the other claw 56b.

The rotation of the cam 52 causes the arm 42 to rotate clockwise from the state shown in FIG. Then, first, the transfer roller 47 comes into contact with the transfer belt 37 on the outer periphery of the backup roller 34, and follows the traveling of the transfer belt 37, and is driven to rotate. Further, the slider 45 slides in the long hole 44 to the left in the drawing while compressing and contracting the coil spring 48 by the elastic force of the coil spring 50. As a result, the cleaning blade 51 is pressed against the surface of the transfer roller 47. The transfer roller 47 is pressed against the transfer belt 37 by a predetermined force due to the elastic force of the coil spring 48. When the cam 52 rotates by 180 °, the claw 56b of the spring clutch 56 engages with the stopper 59, and the spring clutch 56 is disengaged. As a result, the shaft 53 becomes free and the rotation of the cam 52 stops.

Thereafter, the paper P sent from the paper feed tray 60 and the color toner image on the transfer belt 37 come into contact at the nip portion between the transfer roller 47 and the backup roller 34 and are given to the transfer roller 47. The color toner image is transferred to the sheet P by the charge. Further, the residual toner adhered to the transfer roller 47 at the time of the secondary transfer is scraped off by the cleaning blade 51. Here, when the cleaning blade 51 is pressed against the transfer roller 47,
The outer peripheral distance from the pressure contact to the nip portion between the transfer roller 47 and the transfer belt 37 in the rotation direction of the transfer roller 47 is larger than the distance from the nip portion between the transfer roller 47 and the transfer belt 37 to the leading end of the paper P. Is also set short. As a result, the portion of the outer peripheral surface of the transfer roller 47 cleaned by the cleaning blade 51 is transferred to the transfer belt 37.
After that, the leading end of the paper P reaches the transfer roller 47, so that the residual toner adhered to the transfer roller 47 does not adhere to the paper P.

Next, when the paper P passes through the nip between the transfer roller 47 and the transfer belt 37, the solenoid 57 is driven, and the cam 52 is rotated by 180 ° in the same manner as described above. This causes the arm 42 to rotate in the counterclockwise direction from the state shown in FIG. With the operation, first, the slider 45 slides in the elongated hole 44 to the right end in FIG. 6 by the urging force of the coil spring 48, and the transfer roller 47 is separated from the cleaning blade 51. Subsequently, the transfer roller 47
Are separated from the backup roller 34, and then the state shown in FIG. The sheet P to which the color toner image has been transferred is supplied to the nip portion between the heating roller 66 and the pressure roller 67, and is discharged to the sheet discharge tray 69 after the fixing of the color toner image is performed.

In the secondary transfer device 40 having the above-described structure, when the arm 42 is rotated to bring the transfer roller 47 into contact with the transfer belt 37, the transfer roller 47 starts to rotate, and the slider 45 slides to transfer. The roller 47 is pressed against the cleaning blade 51. Therefore, when the transfer roller 47 starts, only the starting resistance of the transfer roller 47 is applied to the transfer belt 37. After the transfer roller 47 is started, a kinetic frictional resistance due to the rotation of the transfer roller 47, which is much smaller than the starting resistance, is applied to the transfer belt 37. In this state, the cleaning blade 51 contacts the transfer roller 47, and Is applied to the transfer belt 37. As described above, since the starting resistance of the transfer roller 47 and the frictional resistance between the cleaning blade 51 and the transfer roller 47 are not simultaneously applied to the transfer belt 37, the traveling speed of the transfer belt 37 does not suddenly decrease. In particular, since the cleaning blade 51 is pressed against the transfer roller 47 after the transfer roller 47 starts driven rotation, the cleaning blade 51 does not bite into the transfer roller 47 unlike a conventional image transfer device, and In addition, the load on the transfer belt 37 is significantly reduced, and image displacement can be greatly suppressed.

FIG. 12 is a diagram showing a change in the speed of the transfer belt in a conventional image transfer apparatus in which the transfer roller is pressed against the transfer belt while the cleaning blade is pressed against the transfer roller. As is apparent from this figure, in the conventional image transfer apparatus, when the transfer roller is pressed against the transfer belt, the traveling speed of the transfer belt is greatly reduced, so that the last toner image (for example, Large color misregistration (image misregistration) occurs during transfer of the black (black) to the transfer belt. FIG. 13 is a diagram showing a change in the traveling speed of the transfer belt 47 in the secondary transfer device 40 of the embodiment. As can be seen from this figure, in the secondary transfer device of the embodiment, the transfer roller 47 is
7, and the speed reduction of the transfer belt 37 when the cleaning blade 51 is pressed against the transfer roller 47 is much smaller than in the conventional case, and the image shift is sufficiently within the allowable range.

Here, as in the secondary transfer unit 40 having the above-described configuration, the load on the transfer belt 37 is divided into two, that is, the load by the transfer roller 47 and the load by the cleaning blade 51, so that the image shift is greatly reduced. The reason for the reduction will be described. That is, generally, in a servomotor, the larger the load fluctuation, the slower the response for correcting the speed fluctuation, and the speed fluctuation sharply increases as the load fluctuation increases. Table 1 shows the speed fluctuation with respect to the load fluctuation on the output shaft of the servo motor, and shows that the degree of the image shift increases as the load fluctuation increases. For example, when the transfer roller 47 is pressed against the transfer belt 37 and when the cleaning blade 51
Assuming that the load fluctuation on the output shaft when pressed into contact with each other is 0.05 N · m, in the present invention, a simple calculation causes a total of 60 μm image shift due to two load fluctuations. If such a load change occurs at once,
An image shift of 98 μm occurs. In general, if the image shift exceeds 125 μm, it is recognized as an image quality defect.

[0036]

[Table 1]

As described above, in the image transfer apparatus having the above-described configuration, the image shift can be greatly reduced by dividing the load fluctuation on the transfer belt 37 into two times, and a high-quality image can be formed. It can be. Moreover, unlike the image transfer apparatus proposed in the related art, the copying time does not increase, and the transfer roller 47 does not need to be driven, so that the configuration can be simplified.

In particular, in the image transfer apparatus having the above-described configuration, the transfer roller 47 slides the slider 45 by the force of pressing the transfer belt 37 and presses the transfer belt 47 against the cleaning blade 51. By simply adding the slider 45 and the coil spring 48 to the conventional apparatus, the transfer roller 47 and the cleaning blade 51 described above can be used.
In two stages. Therefore, the manufacturing cost can be greatly reduced, and the number of failures can be reduced, and the maintenance and inspection cost can be reduced. Further, in the above-described embodiment, after the portion of the outer peripheral surface of the transfer roller 47 cleaned by the cleaning blade 51 reaches the transfer belt 37, the leading end of the sheet P reaches the transfer roller 47, and thus the sheet P adheres to the transfer roller 47. The residual toner does not adhere to the paper P.

B. 2. Second Embodiment (1) Configuration of Second Embodiment Next, a second embodiment of the present invention will be described with reference to FIGS. In the second embodiment, the same components as those in the first embodiment are denoted by the same reference numerals, and description thereof is omitted. In FIG. 9, reference numeral 80 denotes a second transfer unit (image transfer device), and reference numeral 81 denotes an arm.
The lower end of the arm 81 is rotatably supported by a shaft 82 so that the upper end thereof can approach and separate from the backup roller 34. The arm 81 is urged toward the backup roller 34 by the coil spring 50. A transfer roller 47 is slidably supported on the upper end of the arm 81 in a direction approaching and separating from the backup roller 34, as in the first embodiment. 3
It is urged to the 4 side.

In the middle part of the arm 81 in the longitudinal direction,
A lower end of a holder 83 having an upper end to which the cleaning blade 51 is fixed is rotatably supported by a shaft 84. The holder 83 is a coil spring (second moving means)
85 is urged toward the backup roller 34 side. The arm 81 and the holder 83 are rotatable by a cam (drive member) 90.

As shown in FIG. 9 and FIG.
Is rotatable by a shaft 91, and includes a small cam 92 and a large cam 93 having an outer diameter larger than that of the small cam 92. The outer periphery of the small cam 92 contacts the side of the arm 81, and the outer periphery of the large cam 93 contacts the side of the holder 83. With this configuration, by rotating the cam 90, the arm 81 is biased by the coil springs 50 and 85.
And the holder 83 rotates clockwise in the figure.
The cam 90 is also rotated by 180 ° by the same spring clutch 56 as in the first embodiment.

(2) Operation of the Second Embodiment Next, the operation of the image transfer apparatus having the above configuration will be described.
When the color toner image formed on the transfer belt 37 approaches the secondary transfer device 80, the transfer roller 47 is pressed against the transfer belt 37 on the outer periphery of the backup roller 34 as follows. First, the cam 90 rotates in the state shown in FIG.
Due to the elastic force of 0,85, it turns clockwise from the state shown in FIG. Then, first, the transfer roller 47 abuts on the transfer belt 37 on the outer periphery of the backup roller 34, and rotates following the movement of the transfer belt 37.

Thereafter, when the cam 90 is further rotated, the arm 81 is further rotated accordingly, and the transfer roller 47 is rotated.
As a result, it moves to the coil spring 48 side. With it,
The cleaning blade 51 rotates toward the transfer roller 47, and the cleaning blade 51 is pressed against the transfer roller 47. Then, when the cam 90 rotates by 180 °,
The spring 91 is disengaged, the shaft 91 becomes free, and the rotation of the cam 90 stops. In this state, the transfer roller 47 applies the elastic force of the coil spring 48 to the transfer belt 37.
The cleaning blade 51 is pressed against the transfer roller 47 with a constant force by the elastic force of the coil spring 85.

Next, when the paper P passes through the transfer roller 47, the solenoid 57 is driven, and the cam 90 rotates in the same manner as described above. As a result, first, the arm 81 rotates counterclockwise from the state shown in FIG. 10 while keeping the transfer roller 47 in contact with the transfer belt 37 around the backup roller 34. On the other hand, the rotation of the cam 90 causes the cleaning blade 51 to rotate in the counterclockwise direction,
The rotation of the arm 81 and the cleaning blade 51 separates the cleaning blade 51 from the transfer roller 47. Thereafter, as the arm 81 further rotates, the transfer roller 47 reaches the right moving end at the upper end of the arm 81, and then moves in a direction away from the backup roller 34 together with the arm 81. Thereafter, the cam 90 completes the 180 ° rotation, and the arm 81 stops at the position farthest from the backup roller 34 shown in FIG.

In the image transfer apparatus having the above-described structure, the cleaning blade 51 is pressed against the transfer roller 47 after the transfer roller 47 is pressed against the transfer belt 37, so that the starting resistance of the transfer roller 47 is the same as in the first embodiment. And the frictional resistance between the cleaning blade 51 and the transfer roller 47 are not simultaneously applied to the transfer belt 37. Therefore, the traveling speed of the transfer belt 37 does not suddenly decrease, and image displacement can be suppressed. In particular, in the above embodiment, the cleaning blade 51 is pressed against the transfer roller 47 by the elastic force of the coil spring 85, so that the pressing force can be easily adjusted.

C. Third Embodiment In the first and second embodiments, after the transfer roller 47 contacts the transfer belt 37, the cleaning blade 51
Are transferred by the transfer rollers 4 according to the rotation of the cams 52 and 90.
7, the cleaning blade 51 is also separated from the transfer roller 47 in accordance with the rotation of the cams 52 and 90 immediately before the transfer roller 47 is separated from the transfer belt 37. However, even if the transfer roller 47 is separated from the transfer belt 37, the cleaning blade 51
The contact pressure may be weakened without separating from the transfer roller 47. Hereinafter, such an embodiment will be described.

(1) Configuration and Operation of Third Embodiment FIGS. 15 and 16 show a third embodiment of the present invention.
This embodiment is a modification of the first embodiment, and common components are denoted by the same reference numerals and description thereof is omitted. As shown in FIG. 15, in the present embodiment, the cam 5
2, the arm 42 is most separated from the shaft 53 of the cam 52, and the transfer roller 47 is separated from the transfer belt 37.
Remain in contact with the transfer roller 47. However, the cleaning blade 51 contacts the transfer roller 47 with a small contact pressure.

The operation procedure is exactly the same as that of the first embodiment. In response to the rotation of the cam 52 driven by the solenoid 57 (FIG. 7), the arm 42 biased by the coil spring 50 moves clockwise. When rotated, first, the transfer roller 47 comes into contact with the transfer belt 37 on the outer periphery of the backup roller 34, and rotates following the movement of the transfer belt 37. Also,
Due to the elastic force of the coil spring 50, the slider 45 slides in the long hole 44 to the left in the drawing while compressing the coil spring 48. As a result, the cleaning blade 51 is pressed against the surface of the transfer roller 47.

After that, when the sheet P passes through the transfer roller 47, the solenoid 57 is driven, and in the same manner as described above,
The cam 52 rotates. As a result, first, the arm 42 rotates counterclockwise from the state shown in FIG. 16 while keeping the transfer roller 47 in contact with the transfer belt 37 around the backup roller 34. With this operation, first, the slider 45 slides in the long hole 44 to the right end in FIG. 16 by the urging force of the coil spring 48, and the transfer roller 47 is separated from the cleaning blade 51. Subsequently, the transfer roller 47 is separated from the backup roller 34, and then the state is as shown in FIG.

Therefore, the cleaning blade 51
Are always in contact with the transfer roller 47. In this case, the bending when the cleaning blade 51 is pressed against the transfer roller 47 with the weakest pressure (as shown in FIG. 15) is caused when the cleaning blade 51 is pressed against the transfer roller 47 with the strongest pressure (as shown in FIG. 16). Cleaning blade 5
Preferably, it is about one third of one deflection.

As a specific example, for example, the tip of the cleaning blade 51 when pressed most strongly against the transfer roller 47 shown in FIG. 16 is displaced by about 1 mm at the rotating end of the arm 42 (force is applied to the cleaning blade 51). The holder 49 of the cleaning blade 51 is disposed so as to bend from a non-linear state, and the spring constant and compression size of the coil spring 48 are selected. The length of the cleaning blade 51 is about 10 mm. In this case, it is preferable to make the long hole 44 longer than the slider 45 by about 0.7 mm so that the slider 45 can slide by 0.7 mm. As a result, as shown in FIG.
The deflection of the tip of the cleaning blade 51 when pressed most strongly is about 0.3 mm. However, FIG.
16 and FIG. 16, the curvature of the cleaning blade 51 is exaggerated for easy understanding.

(2) Effect of Third Embodiment The force applied from the cleaning blade 51 to the transfer roller 47 is proportional to the bending if the cleaning blade 51, which is an elastic body, is regarded as a spring. Therefore, by setting the deflection to one third in this manner, the pressing force acting between the cleaning blade 51 and the transfer roller 47 is also reduced to three.
About 1 /

By reducing the pressing force without completely separating the cleaning blade 51 from the transfer roller 47, the following effects can be obtained. That is, the cleaning blade 51 has a low contact pressure,
This means that the transfer roller 47 is in contact with the transfer roller 47. For this reason,
When the transfer roller 47 comes into contact with the transfer belt 37 and starts driven rotation, the surface of the transfer roller 47 is cleaned by the cleaning blade 51.

Incidentally, the transfer belt 3 serving as an image carrier is
7 is short, or when two images are formed on one circumference of the transfer belt 37 separately from the above operation, a non-image area (inter-image area) between the images is formed. Be shorter. In such a case, after being separated from the transfer belt 37, the transfer roller 47 is brought into contact with the transfer belt 37 again in a short time in order to transfer the next image from the transfer belt 37 to the sheet P. At this time, when a portion of the surface of the transfer roller 47 that has not been cleaned by the cleaning blade 51 comes into contact with the back surface of the paper P to be transferred next, residual toner on the surface of the transfer roller 47 is removed. Transfer to the paper P passing between the transfer belt 37 and the transfer belt 37.

However, as in the present embodiment, the cleaning blade 51 is always moved to the transfer roller 4 while the contact pressure is low.
By contacting the contact 7, such inconvenience can be reduced, and a higher quality image can be formed. In this case, even if the toner is slightly transferred to the rear surface of the sheet P, the toner is transferred only to the leading end in the traveling direction of the sheet P, and the amount is small, and it is possible to make the toner invisible. .

Further, in the present embodiment, the contact pressure of the cleaning blade 51 when it is weakest is about one third of the contact pressure when it is strongest. It is about 3 mm. With this degree, the cleaning blade 51 is prevented from digging into the soft transfer roller 47, and the load when the transfer roller 47 comes into contact with the transfer belt 37 to start the driven rotation can be reduced. . Thereafter, the contact pressure between the cleaning blade 51 and the transfer roller 47 is increased so that sufficient cleaning can be performed, and the load on the transfer belt 37 is gradually increased. Therefore, a load increase due to the starting resistance of the transfer roller 47 and
Since the timing of the load increase due to the frictional resistance between the cleaning blade 51 and the transfer roller 47 is shifted, there is also an effect of suppressing the image shift on the transfer belt 37 as in the first embodiment.

D. 4. Fourth Embodiment (1) Configuration of Fourth Embodiment FIGS. 17 and 18 show a fourth embodiment of the present invention.
This embodiment has the same basic configuration as the second embodiment (see FIG. 9 and FIG. 10), and the components having the same functions are denoted by the same reference numerals and description thereof is omitted. However, the difference is that even if the transfer roller 47 is separated from the transfer belt 37, the cleaning blade 51 does not separate from the transfer roller 47, and the contact pressure therebetween is weakened. Therefore, as in the third embodiment, the sliding distance of the slider 45 in the elongated hole 44, the arrangement of the cleaning blade 51, the spring constant of the coil spring 48, and the compression size are selected.

In this embodiment, the holder 83 of the cleaning blade 51 is generally thin, and the shaft 8 is provided at the lower end.
4 is provided, and one surface of the thin portion of the holder 83 is pressed by the coil spring 85 and the opposite surface is pressed by the large cam 93 of the cam 90. On the other hand, in the second embodiment, the length of the lower end of the holder 83 is increased, and the shaft 84 is attached thereto, one surface of the lower end is pressed by the coil spring 85, and the opposite surface is cam 9
It is designed to be pressed by a large cam 93 of zero. In this regard, the present embodiment and the second embodiment are slightly different, but of course, the shape of the holder 83 between the embodiments can be interchanged.

(2) Operation and Effect of the Fourth Embodiment The operation procedure of the image transfer apparatus having the above configuration is the same as that of the second embodiment, and the detailed description thereof will be omitted. However, the cleaning blade 51 is not separated from the transfer roller 47 by the large cam 93 while the cam 90 is being rotated by 180 ° from the state shown in FIG. Thereafter, the cam 90 has been rotated by 180 ° and the small cam 9 has been rotated.
2, the arm 81 is rotated to the position farthest from the backup roller 34 shown in FIG. 17, and stops here. However, even in this state, the cleaning blade 51 is in contact with the transfer roller 47, and the contact pressure is , FIG.
About one third of the contact pressure in the state described above.

In this embodiment, as in the third embodiment, the cleaning blade 5 is always kept at a low contact pressure.
1 is in contact with the transfer roller 47. Therefore, when the transfer roller 47 contacts the transfer belt 37 and starts to rotate, the surface of the transfer roller 47 is cleaned by the cleaning blade 51. Thereby, the transfer of the residual toner on the surface of the transfer roller 47 to the paper P is reduced, so that a higher quality image can be formed. In addition, since the load increase due to the starting resistance of the transfer roller 47 and the load increase due to the frictional resistance between the cleaning blade 51 and the transfer roller 47 are shifted,
There is also an effect of suppressing the above-described image shift.

The contact pressure of the cleaning blade 51 with the transfer roller 47 by the coil spring 85 can be set independently of the contact pressure of the transfer roller 47 with the transfer belt 37 by the coil spring 48. The position of the cleaning blade 51 is controlled by the large cam 93, and the position of the arm 81 is controlled by the small cam 92. The cams 92 and 93 share the shaft 91, and the movement locus of the cleaning blade 51 and the movement locus of the transfer roller 47 can be easily controlled by the contour design of each cam. Since the cams 92 and 93 share the shaft 91, a single drive source (solenoid 5) is used.
According to 7), both the cams 92 and 93 can be driven, and a new drive source is unnecessary.

E. Fifth Embodiment FIGS. 19 and 20 show a fifth embodiment of the present invention.
FIG. 19 shows a state in which the transfer roller 47 is separated from the transfer belt 37, and FIG. This embodiment is a modification of the fourth embodiment, and differs from the fourth embodiment in that a cam 52 having a single cam surface is used instead of the cam 90 formed by combining the cams 92 and 93 of the fourth embodiment. Here, the arm 81 and the holder 83 of the cleaning blade 51 are pushed by the single cam 52. For this reason, a pushing piece 86 protrudes from the surface of the holder 83 facing the cam 52, and the pushing piece 86 is flush with the side end face of the arm 81. The operation and effect of this configuration are the same as those of the fourth embodiment, and there is another effect that the cam can be easily manufactured.

F. Sixth Embodiment FIGS. 21 and 22 show a fifth embodiment of the present invention,
FIG. 21 shows a state in which the transfer roller 47 is separated from the transfer belt 37, and FIG. This embodiment is a modification of the fourth embodiment, and differs from the fourth embodiment in the position of the shaft 82 serving as the rotation center of the arm 81, the position of the coil spring 50, and the position of the cam 90. The shaft 82 is also used as the center of rotation of the arm 81 of the cleaning blade 51.

The shaft 82 is provided substantially at the center of the arm 81. The cleaning blade 51 is attached to the upper end of a thin holder 83 as a whole, and an attachment portion 87 is attached to the center of the holder 83, and a shaft 82 is attached to the attachment portion 87. Thus, both the arm 81 and the holder 83 are rotatable about the shaft 82. However, the arm 81 and the holder 83 are not directly restrained from each other when rotating,
Only when the cleaning blade 51 contacts the transfer roller 47, the rotation of the holder 83 is restricted.

A coil spring 50 is attached to the lower end of the arm 81. The coil spring 50 is disposed on the left side of the arm 81 in the drawing, and thereby the arm 81 is moved clockwise about the axis 82. Energize. At the lower end of the holder 83, a pushing piece 88 is projected in a clockwise direction about the axis 82, and the pushing piece 88 and the arm 81 are located on the left side in the drawing so as to face the pushing piece 88. The cam 90 is disposed at the center. When the cam 90 rotates 180 ° from the position shown in FIG. 22, the large cam 93 pushes the holder 83 against the elastic force of the coil spring 85 to reduce the contact pressure between the cleaning blade 51 and the transfer roller 47. Weaken. Further, the small cam 92 of the cam 90 is
The arm 81 is pushed against the elastic force of 0 to separate the transfer roller 47 from the transfer belt 37.

On the other hand, from the position shown in FIG.
When rotated by 0 °, the regulation of the small cam 92 gradually weakens, and the elastic force of the coil spring 50 causes the arm 81 to rotate clockwise so that the transfer roller 47 comes into contact with the transfer belt 37. Next, as the regulation of the large cam 93 is gradually reduced, the contact pressure between the cleaning blade 51 and the transfer roller 47 is increased by the elastic force of the coil spring 85.
With this configuration, the same effect as in the fourth embodiment is achieved.

G. Seventh Embodiment FIGS. 23 and 24 show a seventh embodiment of the present invention.
This embodiment is different from the sixth embodiment shown in FIGS.
This is a configuration in which a cam 95 is added. The cam 95 is a cam 90
This is the same configuration as. That is, the small cam 97 and the large cam 98 having an outer diameter larger than that of the small cam 97 can be rotated by the shaft 96. As shown in FIG. 21, when the transfer roller 47 is separated from the transfer belt 37, the outer periphery of the small cam 97 contacts the right side of the arm 81, and the outer periphery of the large cam 98 contacts the right side of the holder 83.

Thus, the cam 90 and the cam 95 complement each other in their functions. If both are driven by different driving sources, the power required for each driving source can be reduced. In addition, the cam 90 may be omitted, and the arm 81 and the holder 83 may be driven by only one cam 95. In the sixth and seventh embodiments, even when the transfer roller 47 is separated from the transfer belt 37,
Although the cleaning blade 51 is configured not to be separated from the transfer roller 47, the cleaning blade 51 is moved immediately before the transfer roller 47 is separated from the transfer belt 37 as in the second embodiment by extending the moving range of the slider 45 or the like. May be separated from the transfer roller 47 so that the cleaning blade 51 contacts the transfer roller 47 after the transfer roller 47 contacts the transfer belt 37.

H. Modification In the above embodiment, the present invention is applied to an image forming apparatus having a primary transfer device 30.
2 can be applied to the image forming apparatus shown in FIG. In this case, the photosensitive drum 2
The transfer roller 47 can be brought into contact with or separated from the transfer roller 47, and the contact pressure of the cleaning blade 51 is adjusted when the transfer roller 47 moves. In FIG. 2, the same components as those in FIG. 1 are denoted by the same reference numerals.
Further, the present invention is not limited to the multi-color image forming apparatus as in the above embodiment, and can be applied to a single-color image forming apparatus. In the above embodiment, the arm is rotated by the cam, but any structure such as a piston cylinder and a link mechanism can be used. FIG. 14 shows the arm 4
2 is rotated by a link mechanism, and the image transfer apparatus shown in FIG. 1 includes an output shaft 100 of a motor (not shown).
The one end of the link plate 102 is rotatably supported by a pin 103 on the end face of the gear 101 attached to the gear a, and the other end of the link plate 102 is rotatably attached to a pin 104 attached to the arm 42. ing. The pin 104 is inserted into a long hole 102a formed in the link plate 102. As a result, while the transfer roller 47 is pressed against the transfer belt 37, the arm 4
2 is free, and the transfer roller 47 is pressed against the transfer belt 37 only by the elastic force of the coil spring 48. Note that in FIG.
Although the cleaning roller 51 is completely separated from the transfer roller 47, the contact pressure between the cleaning blade 51 and the transfer roller 47 may be weakened without separating the cleaning blade 51 from the transfer roller 47. In the above embodiment, a spring clutch is used to rotate the cam by 180 ° at a time, but the cam may be rotated by a stepping motor. In this case, a disk is attached to the output shaft of the stepping motor, and the projection formed on the outer periphery of the disk crosses the optical axis of the photointerrupter so that the output shaft can be rotated by 180 °. In the above embodiment, the transfer roller 47 is configured to be cleaned by the cleaning blade 51. However, a cylindrical or flat cleaning brush may be used. As the coil spring, a compression spring or a tension spring can be appropriately used, and other leaf springs or the like can also be used.

[0070]

As described above, according to the present invention, when the first moving means brings the transfer roller into contact with the image carrier, the transfer roller starts to rotate, and then the second moving means cleans. Since the device and the transfer roller are brought into contact with each other, the starting resistance of the transfer roller and the frictional resistance between the cleaning device and the transfer roller are not simultaneously applied to the image carrier. Therefore, the moving speed of the image carrier does not suddenly decrease, and it is possible to suppress the image shift and improve the image quality (claim 1).

If the cleaning means is separated from the transfer roller when the transfer roller is separated from the image bearing member, the starting resistance of the transfer roller and the frictional resistance between the cleaning means and the transfer roller are reduced. Since the load is not simultaneously applied to the body, it is possible to further suppress a reduction in the moving speed of the image carrier when the transfer roller is started (claim 2). Alternatively, when the transfer roller separates from the image bearing member, the cleaning unit may weaken the contact pressure on the transfer roll without separating the transfer roller from the transfer roller. In this case, the cleaning unit is always in contact with the transfer roller despite the low contact pressure. Therefore, when the transfer roller contacts the image carrier and starts driven rotation, the surface of the transfer roller is cleaned by the cleaning unit. This allows
Since the transfer of the residual toner on the surface of the transfer roller to the paper is reduced, it is possible to form an image with higher image quality.

Further, since the transfer roller is moved in the direction approaching the cleaning means by the force of pressing the image carrier, the force for pressing the cleaning means against the transfer roller is increased, which is simpler than the conventional apparatus. The transfer roller and the cleaning means can be added simply by adding
The step-by-step contact becomes possible, so that the manufacturing cost can be greatly reduced, and the number of failures is small, and the maintenance and inspection cost can be reduced (claim 4).

[Brief description of the drawings]

FIG. 1 is a front sectional view showing an image forming apparatus to which an image transfer device according to a first embodiment of the present invention is applied.

FIG. 2 is a front sectional view showing another example of the image forming apparatus to which the image transfer device of the first embodiment is applied.

FIG. 3 is a front view illustrating a driving mechanism of a photosensitive drum and a transfer belt according to the first embodiment.

FIG. 4 is a front view showing the image transfer device according to the first embodiment, showing a state in which a transfer roller is separated from a backup roller.

FIG. 5 is a front view illustrating the image transfer apparatus according to the first embodiment, and is an enlarged view illustrating a state where a transfer roller is separated from a backup roller.

FIG. 6 is a front view illustrating the image transfer device according to the first embodiment, and is a diagram illustrating a state in which a transfer roller is pressed by a backup roller.

7 is a view in the direction of arrow VII in FIG. 5;

FIG. 8 is a front view showing a mechanism for rotating a cam.

FIG. 9 is a front view illustrating an image transfer apparatus according to a second embodiment of the present invention, and illustrates a state where a transfer roller is separated from a backup roller.

FIG. 10 is a front view illustrating the image transfer device according to the second embodiment, and is a diagram illustrating a state in which a transfer roller is pressed by a backup roller.

11 is a view in the direction of the arrow XI in FIG. 9;

FIG. 12 is a diagram showing a change in a traveling speed of a transfer belt in a conventional image transfer device.

FIG. 13 is a diagram illustrating a change in a traveling speed of a transfer belt in the image transfer device of the present invention.

FIG. 14 is a diagram showing a modification of the image transfer device shown in FIG.

FIG. 15 is a front view illustrating the image transfer apparatus according to the third embodiment, and is an enlarged view illustrating a state where a transfer roller is separated from a backup roller.

FIG. 16 is a front view illustrating the image transfer apparatus according to the third embodiment, and is an enlarged view illustrating a state where a transfer roller is pressed by a backup roller.

FIG. 17 is a front view illustrating the image transfer apparatus according to the fourth embodiment, and is an enlarged view illustrating a state where a transfer roller is separated from a backup roller.

FIG. 18 is a front view illustrating the image transfer apparatus according to the fourth embodiment, and is an enlarged view illustrating a state where a transfer roller is pressed by a backup roller.

FIG. 19 is a front view illustrating the image transfer device according to the fifth embodiment, and is an enlarged view illustrating a state where a transfer roller is separated from a backup roller.

FIG. 20 is a front view illustrating the image transfer device according to the fifth embodiment, and is an enlarged view illustrating a state where a transfer roller is pressed by a backup roller.

FIG. 21 is a front view illustrating an image transfer device according to a sixth embodiment, and is an enlarged view illustrating a state where a transfer roller is separated from a backup roller.

FIG. 22 is a front view illustrating the image transfer device according to the sixth embodiment, and is an enlarged view illustrating a state where a transfer roller is pressed by a backup roller.

FIG. 23 is a front view showing the image transfer device of the seventh embodiment, and is an enlarged view showing a state where a transfer roller is separated from a backup roller.

FIG. 24 is a front view illustrating the image transfer apparatus according to the seventh embodiment, and is an enlarged view illustrating a state where a transfer roller is pressed by a backup roller.

[Explanation of symbols]

Reference numeral 20: photosensitive drum, 37: transfer belt (image carrier), 42, 81: arm (first moving means), 44:
Slot (second moving means), 45: slider (second moving means), 47: transfer roller, 48: coil spring (second elastic member) 50: coil spring (first moving means, first elasticity) Members: 51, cleaning blade (cleaning means), 52, 90, 95: cam (first moving means, drive member).

Claims (4)

(57) [Claims] 1. A transfer roller that is driven to rotate by being brought into contact with a movable image carrier via a recording sheet, and a first moving unit that moves the transfer roller in the image bearing member side and in the opposite direction. A cleaning unit that contacts the outer peripheral surface of the transfer roller to clean the transfer roller; and a second moving unit that relatively moves the cleaning unit toward the transfer roller and in the opposite direction. The image transfer apparatus according to claim 2, wherein the second moving unit is configured to increase a contact pressure between the cleaning unit and the transfer roller after the transfer roller contacts the image bearing member. 2. The image transfer apparatus according to claim 1, wherein the cleaning unit is configured to separate from the transfer roller when the transfer roller separates from the image bearing member. apparatus. 3. The cleaning device according to claim 1, wherein the cleaning unit is configured to reduce a contact pressure on the transfer roll without separating from the transfer roller when the transfer roller separates from the image bearing member. The image transfer device according to claim 1, wherein: 4. An arm having one end rotatably supported so that one end thereof can approach and separate from the image carrier and the opposite direction, and the arm is provided with the image carrier. A first elastic member that urges the body side; and a driving member that moves the arm to the opposite side of the image carrier against the urging force of the elastic member. A guide portion for supporting the transfer roller at the one end of the arm so as to be movable in the image carrier side and in the opposite direction, and a second elastic member for urging the transfer roller toward the image carrier side; The first elastic member and the second elastic member are configured such that when the arm rotates and the transfer roller comes into contact with the image carrier, the transfer roller moves to the second position in the guide portion.
The elastic force is set so that the elastic member moves relative to the image carrier in the opposite direction against the urging force of the elastic member. 4. The image transfer device according to claim 1, wherein the image transfer device is arranged on the arm so as to increase a contact pressure on the transfer roller by relatively moving the support member in a reverse direction. apparatus.