Transfer device and image forming apparatus

Provided is a transfer device including a primary transfer roller that selectively takes a contact position where an intermediate transfer belt is brought into contact with an image holding member, and a separation position where the intermediate transfer belt is separated from the image holding member, a tension applying roller on which the intermediate transfer belt is wound thereon together with a driving roller and which is urged in a direction receding from the driving roller, and a relaxing member that is attached to a shaft portion of the tension applying roller, is urged by an urging unit in a direction approaching the driving roller, and relaxes an urging force of the tension applying roller in a direction receding from the driving roller when the primary transfer roller is at the separation position.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based on and claims priority under 35 USC 119 from Japanese Patent Application No. 2015-177825 filed Sep. 9, 2015.

BACKGROUND

Technical Field

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

SUMMARY

According to an aspect of the invention, there is provided a transfer device including:

a primary transfer roller that selectively takes a contact position where an intermediate transfer belt is brought into contact with an image holding member, and a separation position where the intermediate transfer belt is separated from the image holding member;

a tension applying roller on which the intermediate transfer belt is wound thereon together with a driving roller and which is urged in a direction receding from the driving roller; and

a relaxing member that is attached to a shaft portion of the tension applying roller, is urged by an urging unit in a direction approaching the driving roller, and relaxes an urging force of the tension applying roller in a direction receding from the driving roller when the primary transfer roller is at the separation position.

DETAILED DESCRIPTION

Hereinafter, an exemplary embodiment according to the present invention will be described in detail with reference to the accompanying drawings. Meanwhile, for convenience of description, an arrow UP illustrated inFIG. 1is set to be an upper direction of an image forming apparatus10, and an arrow RH is set to be a right direction of the image forming apparatus10. In addition, a front direction of the paper inFIG. 1is set to be a front direction of the image forming apparatus10. In addition, inFIGS. 2, 3, 7, and 8, a primary transfer unit60is illustrated in a state of not being inclined in a right-left direction, and a direction in a case where the primary transfer unit60is slightly inclined in the right-left direction is also set to be a “right-left direction”.

As illustrated inFIG. 1, an image processing unit14performing image processing on image data to be input is provided inside an apparatus main body12of the image forming apparatus10. The image processing unit14processes the input image data to four-color tone data of yellow (Y), magenta (M), cyan (C), and black (K).

Image forming units16Y,16M,16C, and16K as examples of image forming sections that form toner images of yellow (Y), magenta (M), cyan (C), and black (K) colors are disposed on the center side of the apparatus main body12so as to be inclined in the right-left direction. The image forming units16Y,16M,16C, and16K of the respective colors are configured to be capable of being drawn out to the front side from the apparatus main body12, and a front wall of the apparatus main body12is configured to be openable and closable. Meanwhile, hereinafter, when it is not necessary to give a description by distinguishing between the colors, the alphabetic characters of Y, M, C, and K will be omitted.

The image forming units16of the respective colors are configured in the same manner. Each of the image forming units includes a cylindrical image holding member20which is rotatable, a charger22that charges the surface of the image holding member20, an LED head24that irradiates the charged surface of the image holding member20with exposure light to thereby forming an electrostatic latent image, a developing device26that develops the electrostatic latent image formed by the LED head24using a toner (developer) and visualizes the developed electrostatic latent image as a toner image, and a cleaning blade (not shown) that cleans the surface of the image holding member20.

The developing device26includes a developing roller28which is disposed facing the image holding member20and is configured such that an electrostatic latent image on the image holding member20is developed by a toner supplied from the developing roller28and is visualized as a toner image. Meanwhile, the charger22, the LED head24, the developing roller28, and the cleaning blade face the surface of the image holding member20, and are disposed in this order from an upstream side of the image holding member20in a rotation direction toward a downstream side thereof.

The primary transfer unit60having toner images, formed by the image forming units16of the respective colors, multiply transferred thereto is disposed on the upper side of the image forming units16of the respective colors. As illustrated inFIGS. 1 to 3, the primary transfer unit60as an example of a transfer device includes an endless intermediate transfer belt62to which a toner image is multiply transferred, and a driving roller64, a sensor roller66, a leveling forming roller68, and a tension applying roller70on which the intermediate transfer belt62is wound.

The driving roller64circulates the intermediate transfer belt62in a direction of an arrow A by its own rotation. The tension applying roller70is urged in the right direction (direction receding from the driving roller64) at all times by a compression coil spring100(seeFIGS. 8A and 8B) as an urging member, and applies tension to the intermediate transfer belt62.

Meanwhile, the sensor roller66that detects the toner image multiply transferred onto the intermediate transfer belt62is disposed on the lower side of the driving roller64. In addition, the leveling forming roller68setting the position of the intermediate transfer belt62is disposed on the lower side of the tension applying roller70in order to bring the intermediate transfer belt62supported by a primary transfer roller58to be described later into contact with the image holding members20of the respective colors.

The primary transfer unit60includes plural (four) primary transfer rollers58which are disposed on the side opposite to the image holding members20of the respective colors with the intermediate transfer belt62interposed therebetween. Primary transfer rollers58Y,58M,58C, and58K of the respective colors are disposed at intervals on the inner circumferential surface side of the intermediate transfer belt62between the sensor roller66and the leveling forming roller68, and press the intermediate transfer belt62against the image holding member20so as to bring the intermediate transfer belt62into contact with the image holding members20of the respective colors.

Thereby, the toner images of yellow (Y), magenta (M), cyan (C), and black (K) colors which are formed on the image holding members20of the respective colors are sequentially transferred (multiply transferred) onto the intermediate transfer belt62. Meanwhile, a cleaning blade63that comes into contact with the surface of the intermediate transfer belt62and cleans a residual toner remaining on the surface without being primarily transferred is also disposed in the primary transfer unit60.

In addition, the primary transfer unit60is provided with a retracting mechanism80(seeFIGS. 2 and 3) that moves the primary transfer rollers58upward at the time of drawing the image forming units16of the respective colors out of the apparatus main body12to separate the intermediate transfer belt62from the image holding members20of the respective colors. Meanwhile, the retracting mechanism80will be described later in detail.

As illustrated inFIG. 1, toner cartridges18of respective colors which are capable of being attached to and detached from the apparatus main body12and which are filled with a toner to be replenished to the developing device26are disposed on the upper side of the primary transfer unit60so as to be lined up. The toner cartridges18of the respective colors are connected to the developing devices26of the respective colors through a replenishing pipe (not shown).

On the other hand, a supply transporting unit30that supplies and transports recording paper P as an example of a recording sheet is disposed on the lower side of the image forming units16of the respective colors. The supply transporting unit30includes a paper feeding unit32having the plural pieces of recording paper P accumulated therein, a paper feeding roller34that sends out the pieces of recording paper P accumulated in the paper feeding unit32to a transporting path40, and a separation roller36that separates the pieces of recording paper P sent out by the paper feeding roller34one by one.

The supply transporting unit30includes a positioning roller38that adjusts a transport timing of the recording paper P. Therefore, the recording paper P which is supplied from the paper feeding unit32and is transported by the paper feeding roller34and the separation roller36is sent out at a timing when the recording paper is determined to be a contact portion (secondary transfer position) between the intermediate transfer belt62and a secondary transfer roller42to be described later by the positioning roller38.

The secondary transfer roller42that transfers the toner image, multiply transferred onto the intermediate transfer belt62of the primary transfer unit60, to the recording paper P transported along the transporting path40by the supply transporting unit30is provided on the left side of the primary transfer unit60. The secondary transfer roller42is provided on the side opposite to the driving roller64with the intermediate transfer belt62interposed therebetween, and is grounded.

The driving roller64forms a counter electrode of the secondary transfer roller42, and a secondary transfer voltage is applied thereto. Thereby, the toner image multiply transferred onto the intermediate transfer belt62is transferred to the recording paper P at the contact portion (secondary transfer position) between the intermediate transfer belt62and the secondary transfer roller42.

A fixing device50that fixes the toner image, transferred to the recording paper P, onto the recording paper P by heat and pressure is provided on the side closer to the downstream side of the recording paper P in a transport direction than the secondary transfer roller42. A discharge roller44that exits the recording paper P having the toner image fixed thereto to an exit section52provided in the upper portion of the apparatus main body12is provided on the side closer to the downstream side of the recording paper P in the transport direction than the fixing device50.

In addition, in order to form a toner image on the other surface of the recording paper P having one surface onto which a toner image is fixed by the fixing device50, the supply transporting unit30is provided with a reversal transport device54that transports the recording paper P to the secondary transfer position. The reversal transport device54includes a reversal path48that reverses the front and back sides of the recording paper P and transports the recording paper toward the positioning roller38from the discharge roller44, and a transport roller46that transports the recording paper P along the reversal path48.

Next, an image forming process of the image forming apparatus10configured as described above will be briefly described.

First, pieces of tone data of the respective colors are output from the image processing unit14to the LED heads24of the respective colors. The surfaces of the image holding members20of the respective colors which are charged by the charger22are irradiated with exposure light emitted from the LED heads24of the respective colors in accordance with the pieces of tone data of the respective colors. Thereby, an electrostatic latent image is formed on the surfaces of the image holding members20of the respective colors.

The electrostatic latent images formed on the image holding members20of the respective colors are developed by the developing devices26of the respective colors, and are visualized as toner images of yellow (Y), magenta (M), cyan (C), and black (K) colors. The toner images of the respective colors which are formed on the image holding members20of the respective colors are sequentially transferred (multiply transferred) onto the circulating intermediate transfer belt62by the primary transfer roller58of the primary transfer unit60.

The toner images of the respective colors multiply transferred onto the circulating intermediate transfer belt62are secondarily transferred to the recording paper P, transported along the transporting path40from the paper feeding unit32by the paper feeding roller34, the separation roller36, and the positioning roller38, at the secondary transfer position by the secondary transfer roller42. The recording paper P having the toner images secondarily transferred thereto is transported to the fixing device50, and the toner images are fixed onto the recording paper P by the fixing device50.

The recording paper P having the toner image fixed to the surface thereof by the fixing device50is discharged onto the exit section52by the discharge roller44, or is transported to the secondary transfer position again by the reversal transport device54, and the toner image is transferred to the rear surface thereof. The recording paper P having the toner image transferred to the rear surface thereof is transported to the fixing device50. As described above, the toner image is fixed and is discharged onto the exit section52.

Next, the retracting mechanism80of the primary transfer unit60of the image forming apparatus10configured as described above will be described in detail.

As illustrated inFIGS. 2 to 4, the primary transfer unit60includes a frame72, extending in the right-left direction, on the front portion side and the rear portion side thereof, and a rotation axis65of the driving roller64, a rotation axis67of the sensor roller66, and a rotation axis69of the leveling forming roller68are rotatably supported by the frames72on the front and back sides. Meanwhile, the sensor roller66and the leveling forming roller68are configured to move upward during retraction to be described later.

The primary transfer rollers58of the respective colors are supported by link mechanisms82provided in the respective frames72, and are configured to move upward about respective support shafts56during retraction to be described later. The link mechanism82includes a slider84as an example of a movement member which is configured to be movable in the right-left direction inside the frame72in the front-back direction.

The slider84extends in the right-left direction, and upper ends of arm members86Y,86M, and86C of yellow (Y), magenta (M), and cyan (C) colors having a substantially L shape, when seen in a front view, are rotatably attached to an appropriate position of the slider in the right-left direction. Bent portions of the respective arm members86Y,86M, and86C are rotatably supported by the support shafts56, and the primary transfer rollers58Y,58M, and58C are rotatably supported by the lower ends of the respective arm members86Y,86M, and86C.

In addition, the upper end of an black (K) arm member86K is attached to a supporting member87constituting the link mechanism82through the support shaft56, and the primary transfer roller58K is rotatably supported by the lower end of the arm member86K. The supporting member87is configured to move the primary transfer roller58K upward when the slider84moves in the left direction during retraction to be described later.

In addition, a cam member74is fixed to a support shaft76at the left end of the primary transfer unit60, and the cam member74is configured to rotate by manually (handle not shown in the drawing) rotating the support shaft76. The cam member74presses a cam receiving member78rotatably provided in the rotation axis67of the sensor roller66to thereby position the sensor roller66in a direction receding from the support shaft76as illustrated inFIG. 2.

This state is an image forming posture of the primary transfer unit60, and the primary transfer roller58of the respective colors are configured to take contact positions for bringing the intermediate transfer belt62into contact with the image holding members20of the respective colors, as illustrated inFIG. 2. In other words, the intermediate transfer belt62pressed and supported by the primary transfer rollers58of the respective colors from the inner circumferential surface side comes into contact with the image holding members20of the respective colors.

On the other hand, as illustrated inFIG. 3, when the cam member74is rotated counterclockwise inFIG. 3, the rotation axis67of the sensor roller66moves in a direction approaching the support shaft76. As illustrated inFIGS. 5A and 5B, a to-be-engaged portion85formed to protrude toward the back side of the slider84in the left end moves in the left direction in a state of engaging with an engagement portion75associated with the cam member74, and the slider84moves in the left direction.

Thereby, the arm members86Y,86M, and86C are rotated counterclockwise inFIG. 3about the support shaft56, and the arm member86K is rotated clockwise inFIG. 3about the support shaft56. Accordingly, the primary transfer rollers58of the respective colors move upward, and the intermediate transfer belt62is separated from the image holding members20of the respective colors.

This state is a retraction posture of the primary transfer unit60, and the primary transfer rollers58of the respective colors are configured to take separation positions for separating the intermediate transfer belt62from the image holding members20of the respective colors, as illustrated inFIG. 3. The tension applying roller70is urged in the right direction (direction receding from the driving roller64) at all times by the compression coil spring100(seeFIGS. 8A and 8B), and thus moves in the right direction (direction receding from the driving roller64).

Here, when an urging force of the tension applying roller70which is applied in the direction receding from the driving roller64is excessively strong, the tension of a portion of the intermediate transfer belt62which is wound around the tension applying roller70becomes stronger than necessary, which results in a tendency for curling to be caused. For this reason, the retracting mechanism80of the primary transfer unit60according to the present exemplary embodiment is provided with a relaxation mechanism90(seeFIG. 7) relaxing an urging force of the tension applying roller70which is applied in the right direction (direction receding from the driving roller64).

In detail, as illustrated inFIG. 7, the relaxation mechanism90includes a relaxing member92of which one end is attached to a rotation axis71as an example of a shaft portion of the tension applying roller70. The relaxing member92is disposed on the outer side of the frame72(slider84) in the front-back direction, and the right-left direction serves as a longitudinal direction. The relaxing member92is urged in the left direction (direction approaching the driving roller64) at all times by an urging unit94illustrated inFIGS. 4 and 6.

As illustrated inFIGS. 4 and 6, the urging unit94includes an extension coil spring96of which the left end (one end) is attached to a shaft88, extending in the front-back direction and having both ends respectively fixed to the frames72on the front and back sides, and a shaft98extending in the front-back direction (axial direction of the tension applying roller70) and having the right end (the other end) of the extension coil spring96attached thereto.

Both ends of the shaft98pass through a long hole portion83(seeFIGS. 2 and 3) formed in the slider84and are inserted into a long hole portion73(seeFIG. 6) formed in the frame72. Meanwhile, both ends of the shaft88also pass through a hole portion81(seeFIGS. 2 and 3) formed in the slider84and are fixed to the frame72. In addition, inFIG. 6, only the frame72is shown, and the slider84and the like are not shown.

As illustrated inFIG. 6andFIG. 8A, the long hole portion73is formed to have a substantially elliptical shape in which the right-left direction is set to be a longitudinal direction, and both ends of the shaft98are held while coming into contact with a left side edge portion of the long hole portion73(pressing the left side edge portion of the long hole portion73to the left) by an urging force of the extension coil spring96during image formation in which the primary transfer roller58takes an image forming posture (contact position).

In addition, as illustrated inFIG. 7andFIG. 8A, both ends of the shaft98are also inserted into a long hole portion93as an example of a hole portion formed in the relaxing member92. The long hole portion93is formed to have a substantially elliptical shape in which the right-left direction is set to be a longitudinal direction, and both ends of the shaft98are configured not to come into contact with right and left side edge portions of the long hole portion93(or not to press the right and left side edge portions in the right and left directions in spite of coming into contact therewith) during image formation in which the primary transfer roller58takes an image forming posture.

During retraction in which the primary transfer roller takes a retraction posture (separation position), the tension applying roller70moves in the right direction (direction receding from the driving roller64) by an urging force of the compression coil spring100, and the relaxing member92moves in the right direction, but the movement is suppressed by the shaft98inserted into the long hole portion93. That is, as illustrated inFIG. 8B, when the relaxing member92moves in the right direction, the left side edge portion of the long hole portion93comes into contact with both ends of the shaft98to attempt to move the shaft98in the right direction.

However, since the shaft98is urged in the left direction at all times by the extension coil spring96, the movement of the shaft98in the right direction is suppressed by an urging force of the extension coil spring96. Accordingly, an urging force of the tension applying roller70in the right direction is relaxed through the relaxing member92, and the tension of the intermediate transfer belt62wound around the tension applying roller70is reduced to the extent of not causing curling.

Meanwhile, when the tension of the intermediate transfer belt62at this time (during retraction in which the primary transfer roller58takes a retraction posture) is set to be T, the tension of the intermediate transfer belt62generated due to the weight of at least four primary transfer rollers58is set to be Tm, and the tension of the intermediate transfer belt62when curling occurs in the intermediate transfer belt62is set to be Te, the relation of Tm<T<Te is satisfied.

Next, operations of the primary transfer unit60including the retracting mechanism80(relaxation mechanism90) configured as described above will be described.

When the image forming units16of the respective colors are drawn out of the apparatus main body12, the intermediate transfer belt62is separated from the image holding members20of the respective colors by the retracting mechanism80. That is, the cam member74is rotated counterclockwise inFIG. 3by operating a handle not shown in the drawing. Then, as illustrated inFIGS. 5A and 5B, the to-be-engaged portion85of the slider84moves in the left direction in a state of engaging with the engagement portion75associated with the cam member74, and the slider84moves in the left direction.

Thereby, the arm member86of the link mechanism82rotates about the support shaft56, and thus the primary transfer roller58moves upward, and pressing against the intermediate transfer belt62from the inner circumferential surface side of the primary transfer roller58is released. In other words, the intermediate transfer belt62is separated from the image holding members20of the respective colors. Accordingly, the image forming units16of the respective colors may be drawn out of the apparatus main body12.

On the other hand, when the cam member74is rotated counterclockwise inFIG. 3, the rotation axis67of the sensor roller66moves in a direction approaching the support shaft76of the cam member74, and the tension applying roller70urged in the right direction at all times by the compression coil spring100moves in the right direction (direction receding from the driving roller64).

When the tension applying roller70moves in the right direction, the relaxing member92attached to the rotation axis71moves in the right direction, but the shaft98is inserted into the long hole portion93of the relaxing member92. Here, the shaft98is urged in the left direction (direction approaching the driving roller64) at all times by the extension coil spring96.

Therefore, as illustrated inFIG. 8B, when the relaxing member92moves in the right direction, the left side edge portion of the long hole portion93comes into contact with both ends of the shaft98, and the movement of the relaxing member92in the right direction is suppressed by the extension coil spring96through the shaft98. In other words, the tension applying roller70is held at a position where an urging force of the compression coil spring100for urging the tension applying roller70in the right direction and an urging force of the extension coil spring96for urging the relaxing member92in the left direction through the shaft98are balanced with each other.

Thereby, an urging force of the tension applying roller70in the right direction is relaxed during retraction in which the primary transfer roller58takes a retraction posture, and the tension of the intermediate transfer belt62wound around the tension applying roller70is reduced, compared to the case of the primary transfer unit60that does not include the relaxation mechanism90. Accordingly, the occurrence of curling in the intermediate transfer belt62is suppressed or prevented by the tension applying roller70.

At this time, the relation of T<Te is established as described above. Therefore, the occurrence of curling in the intermediate transfer belt62is suppressed or prevented, compared to a configuration in which the relation of T≧Te is established. In addition, the occurrence of an image defect due to the curling occurring in the intermediate transfer belt62is suppressed or prevented. At this time, the relation of T>Tm is established as described above. Therefore, the damage of the intermediate transfer belt62, which is caused by the intermediate transfer belt being loosened downward and coming into contact with a component (for example, the image forming unit16or the like) inside the apparatus main body12, is suppressed or prevented compared to a configuration in which the relation of T≦Tm is established.

In addition, in the primary transfer unit60according to the present exemplary embodiment, the urging unit94for suppressing the movement of the relaxing member92in the right direction is configured to include the shaft98and the extension coil spring96. Therefore, there is an advantage in that the configuration of the urging unit94is simplified, compared to a case where the urging unit94is not configured to include the shaft98and the extension coil spring96.

While the primary transfer unit60(transfer device) according to the present exemplary embodiment has been described so far with reference to the accompanying drawings, the primary transfer unit60according to the present exemplary embodiment is not limited to that shown in the drawing and may be appropriately modified in design without departing from the scope of the present invention. For example, the urging unit94is not limited to being constituted by the shaft98and the extension coil spring96.