JP2020201294A - Secondary transfer device and image forming apparatus - Google Patents

Abstract

To provide a secondary transfer device that can prevent the occurrence of reduction in pressure reduction performance and a shock to an intermediate transfer belt, and an image forming apparatus including the secondary transfer device.SOLUTION: A secondary transfer device comprises: a crimp releasing mechanism (crimp releasing unit 50) that displaces a secondary transfer roller to a pressing position and a separated position; a first driving unit 52 that drives the crimp releasing mechanism; a high-speed pressure reduction mechanism (high-speed pressure reduction unit 70) that temporarily reduces a nip pressure; a second driving unit 72 that drives the high-speed pressure reduction unit; and a control unit that controls the drive generated by the first driving unit 52 and the second driving unit 72. The high-speed pressure reduction mechanism includes a pressure reduction cam 74 that is driven by the second driving unit 72, pressure reduction gears (pressure reduction gear train 71) that is formed by meshing of a plurality of gears from the second driving unit 72 to the pressure reduction cam 74, and a pressure reduction arm 75 that displaces the secondary transfer roller 41 at the pressing position to a direction in which the nip pressure is reduced. The control unit changes the use positions of the pressure reduction cam 74 and the pressure reduction gears according to a condition.SELECTED DRAWING: Figure 5

Description

The present invention relates to a secondary transfer device and an image forming device including the secondary transfer device.

In many electrophotographic image forming devices, yellow (yellow) that forms a toner image of one color component along the outer peripheral surface of an intermediate transfer belt having an endless annular shape and a predetermined width, which is wound around a plurality of rollers and orbits. A configuration is adopted in which image forming units for each color such as Y), magenta (M), cyan (C), and black (K) are arranged. Then, by sequentially superimposing the toner images of each color on the intermediate transfer belt by these image forming units, a full-color color toner image is formed on the intermediate transfer belt, and this is secondarily transferred to the paper. ..

At the secondary transfer position, the intermediate transfer belt is sandwiched between a roller that supports it from the inside and a secondary transfer roller that is urged and pressed by a spring or the like from the outside to form a transfer nip. When the conveyed paper passes through the transfer nip (between the outer peripheral surface of the intermediate transfer belt and the secondary transfer roller), the toner image on the intermediate transfer belt is transferred to the paper.

When the tip of the thick paper enters the transfer nip or the rear end comes out, the load changes significantly, so the orbital speed of the intermediate transfer belt may fluctuate or vibration may occur, causing streaks or unevenness in the image. is there.

To address this issue, the nip pressure is temporarily reduced as the front and rear edges of the paper pass through the transfer nip. For example, in the apparatus disclosed in Patent Document 1, a cam is provided on the same axis as the shaft of the roller arranged so as to face the secondary transfer roller with the intermediate transfer belt interposed therebetween, and the convex portion of the cam is used as the shaft of the secondary transfer roller. The nip pressure is temporarily reduced by widening the distance between the axes of the secondary transfer roller and the roller facing the secondary transfer roller by contacting the contact body provided in the above.

Further, in the device disclosed in Patent Document 2, the driving force of the motor is transmitted to the secondary transfer roller by a transmission mechanism to press the secondary transfer roller toward the intermediate transfer belt and control the torque of the motor. As a result, the pressure is temporarily reduced. The transmission mechanism of this device consists of a first lever and a second lever that are long in the substantially horizontal direction. One end of the first lever is pivotally supported (fulcrum), and the secondary transfer roller is pivotally supported in the middle (point of action). ), The other end is pivotally supported by a slide hole (the point of action of the second lever) provided at the tip of the second lever. The second lever is pivotally supported with a position slightly closer to the tip than the middle as a fulcrum, and the other end is a force point for receiving the force from the motor.

Specifically, the other end of the second lever extends in a fan shape, and the dentition that meshes with the gear provided on the shaft of the motor is arranged in an arc shape. The first lever and the second lever have a link mechanism, and when the second lever swings according to the rotation angle of the motor shaft, the secondary transfer roller is displaced up and down. A motor is driven to press the secondary transfer roller against the intermediate transfer belt to form a transfer nip. The secondary transfer roller stands still while the force with which the secondary transfer roller is pushed back from the intermediate transfer belt and the torque of the motor are balanced, and the torque of the motor is temporarily weakened when the front and rear edges of the paper pass through the transfer nip. The nip pressure is reduced with.

Japanese Patent No. 5299772 JP-A-2017-83503

However, in the devices disclosed in Patent Document 1 and Patent Document 2, only the same surfaces of the decompression cam and the decompression gear constituting the decompression mechanism are used in the decompression operation, so that the degree of wear of the decompression cam and the decompression gear is biased. appear. Generally, in the decompression mechanism, the accuracy of the stop position of the decompression cam is important, but when the wear is large, the accuracy of the stop position of the decompression cam is not obtained, so that the decompression performance deteriorates (change in the amount of decompression) or intermediate. There is a risk of shock to the transfer belt (deterioration of image quality).

An object of the present invention is to provide a secondary transfer device capable of suppressing a decrease in decompression performance and a shock to an intermediate transfer belt, and an image forming device including the secondary transfer device.

The invention according to claim 1 has been made in order to achieve the above object.
A secondary transfer device that secondarily transfers a toner image primaryly transferred to the outer peripheral surface of an intermediate transfer belt to paper at a predetermined secondary transfer position.
At the secondary transfer position, the intermediate transfer belt is sandwiched between the opposing rollers that abut on the inner peripheral surface thereof and pressed, and the separation position is separated from the outer peripheral surface of the intermediate transfer belt. A crimp release mechanism that displaces the transfer roller,
The first drive unit that drives the crimp release mechanism and
The nip pressure that the secondary transfer roller in the pressing position presses by sandwiching the intermediate transfer belt between the opposing rollers is applied to the secondary transfer roller and the intermediate transfer belt at the front and rear ends of the paper. A high-speed decompression mechanism that temporarily decompresses when passing between
The second drive unit that drives the high-speed decompression mechanism and
A control unit that controls driving by the first drive unit and the second drive unit,
With
The high-speed decompression mechanism
A decompression cam driven by the second drive unit and
A decompression gear train in which the second drive unit and the decompression cam are connected and a plurality of gears are meshed from the second drive unit to the decompression cam.
A decompression arm that displaces the shaft of the secondary transfer roller at the pressing position in a direction in which the nip pressure weakens by abutting on the decompression cam and swinging.
With
The control unit is characterized in that the used positions of the pressure reducing cam and the pressure reducing gear train are changed according to conditions.

The invention according to claim 2 is the secondary transfer apparatus according to claim 1.
The decompression gear train is configured so that the gear ratios of the plurality of gears do not become an integral multiple, and each gear used when each gear makes one rotation is a new combination.

The invention according to claim 3 is the secondary transfer apparatus according to claim 1 or 2.
The control unit is characterized in that the decompression cam is periodically operated once.

The invention according to claim 4 is the secondary transfer apparatus according to any one of claims 1 to 3.
The decompression cam has a plurality of decompression positions in which decompression is performed by the high-speed decompression mechanism and a crimping position in which the decompression is not performed, respectively, in the outer circumference.
The control unit is characterized in that the position where the decompression cam is used is switched according to the durability of the decompression cam.

The invention according to claim 5 is the secondary transfer apparatus according to any one of claims 1 to 3.
The decompression cam has a plurality of crimping positions in the outer circumference that do not perform decompression by the high-speed decompression mechanism, and one decompression position in the outer circumference that causes the decompression.
The control unit is characterized in that the position where the decompression cam is used is switched according to the durability of the decompression cam.

The invention according to claim 6 is the secondary transfer apparatus according to any one of claims 1 to 5.
The decompression cam is characterized in that it has a symmetrical shape.

The invention according to claim 7 is the secondary transfer apparatus according to any one of claims 1 to 5.
The decompression cam is characterized by having different cam gradients in clockwise and counterclockwise directions.

The invention according to claim 8 is the secondary transfer apparatus according to any one of claims 1 to 7.
The control unit is characterized in that the rotation direction of the pressure reducing cam is periodically switched.

The invention according to claim 9 is the secondary transfer apparatus according to any one of claims 1 to 8.
The control unit is characterized in that the use position of the decompression cam is periodically switched.

The invention according to claim 10 is the secondary transfer apparatus according to any one of claims 1 to 9.
The control unit is characterized in that the used positions of the pressure reducing cam and the pressure reducing gear train are changed according to the number of prints.

The invention according to claim 11 is the secondary transfer apparatus according to any one of claims 1 to 10.
The control unit is characterized in that the used positions of the pressure reducing cam and the pressure reducing gear train are changed at a timing when an image is not formed on the paper.

The invention according to claim 12 is the secondary transfer apparatus according to any one of claims 1 to 11.
The control unit is characterized in that after the image is formed on the paper, the use positions of the pressure reducing cam and the pressure reducing gear train are changed when the fluctuation of the transfer deviation detected by the detection unit is equal to or more than a predetermined value. And.

The invention according to claim 13 is the secondary transfer apparatus according to any one of claims 1 to 12.
The crimp release mechanism and the high-speed decompression mechanism are arranged on the opposite side of the intermediate transfer belt with respect to the secondary transfer position.

The invention according to claim 14 is the secondary transfer apparatus according to any one of claims 1 to 13.
The crimp release mechanism and the high-speed decompression mechanism are characterized in that the projected images when projected in the axial direction of the secondary transfer roller are arranged so as to overlap each other.

The invention according to claim 15 is the secondary transfer apparatus according to any one of claims 1 to 14.
The rotation shaft of the crimping cam driven by the first drive unit and the rotation shaft of the decompression cam are coaxial with each other.

The invention according to claim 16 is the secondary transfer apparatus according to any one of claims 1 to 15.
The first drive unit and the second drive unit are characterized in that the projected images when projected in the axial direction of the secondary transfer roller are arranged so as to overlap each other.

The invention according to claim 17 is the secondary transfer apparatus according to any one of claims 1 to 16.
The decompression arm is characterized in that it abuts on the decompression cam with a rotating body.

The invention according to claim 18 is the secondary transfer apparatus according to any one of claims 1 to 17.
A rotation fulcrum of the decompression arm is provided between a force point at which the decompression arm receives a force from the decompression cam and an action point at which the decompression arm applies a force in a direction in which the nip pressure is weakened. ..

The invention according to claim 19 is the secondary transfer apparatus according to claim 18.
The distance from the rotation fulcrum to the action point is longer than the distance from the force point to the rotation fulcrum of the pressure reducing arm.

The invention according to claim 20 is the secondary transfer apparatus according to any one of claims 1 to 19.
The crimp release mechanism is
The crimping cam driven by the first drive unit and
A crimping arm that displaces the secondary transfer roller to the pressing position and the separating position by abutting against the crimping cam and swinging.
With
The crimping arm pushes and moves the secondary transfer roller toward the pressing position via the spring and the decompression arm in this order.
The high-speed decompression mechanism is characterized in that the decompression arm pushes the spring back toward the crimping arm to perform the decompression.

The invention according to claim 21 is the secondary transfer apparatus according to any one of claims 1 to 20.
The decompression cam has a slope portion and a flat surface portion on the outer periphery as a region where a decompression state is formed.
The control unit is characterized in that the slope portion and the flat surface portion are used properly according to the length of time for maintaining the decompression.

The invention according to claim 22
In the image forming apparatus
An image forming part that forms a toner image on paper,
The secondary transfer device according to any one of claims 1 to 21, wherein the toner image formed by the image forming unit is secondarily transferred to the paper.
It is characterized by having.

According to the present invention, it is possible to suppress a decrease in decompression performance and a shock to the intermediate transfer belt.

It is a front view which shows the schematic structure of the image forming apparatus including the secondary transfer apparatus which concerns on this embodiment. It is a left side view of the secondary transfer apparatus. It is a figure corresponding to the AA cross section of FIG. It is a figure corresponding to the BB cross section of FIG. It is a perspective view which shows each part of a secondary transfer apparatus separately. It is a figure which shows the main part of a high-speed decompression part. It is a figure which shows the main part of the secondary transfer apparatus at the time of separation. It is a figure which shows the main part of the secondary transfer apparatus at the time of crimping. It is a figure which shows the main part of the secondary transfer apparatus at the time of decompression. It is explanatory drawing which shows the overlapping condition of the 1st drive part and the 2nd drive part. It is a figure which shows the secondary transfer apparatus of the structure which arranged only one decompression cam in the center in the front-back direction. It is a figure which shows the normal state and the state which released the lock mechanism and moved the rotating shaft in comparison. It is a figure which shows the decompression cam which has a plurality of decompression positions and crimping positions, respectively. It is a figure which shows the decompression cam which has a plurality of crimping positions and one decompression position. It is a figure which shows the decompression cam which made the shape symmetrical.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

The image forming apparatus 10 according to the present embodiment has a copy function of forming an image obtained by optically reading a document on a recording material such as recording paper and outputting the image, and rasterizing based on print data input from the outside. It is a so-called compound machine equipped with a printing function for forming an image on a recording paper and outputting the image. The recording material is not limited to recording paper, and may be a film or cloth. Hereinafter, the recording material will be described as a recording paper (paper).

As shown in FIG. 1, the image forming apparatus 10 includes a scanner unit 11 that optically reads a document, an operation panel 12 that accepts user operations and displays various information, and a control circuit that controls the operation of the entire apparatus and performs image processing. Unit (control unit) 13, image forming unit 20 that forms an unfixed toner image on the recording material, fixing device 15 that fixes the unfixed toner image on the recording paper, and a large number of recording papers used for image formation. It is configured to include a paper feed tray 14 that can be accommodated, a transport unit 16 that transports paper fed from the paper feed tray 14, and the like.

The image forming unit 20 forms a toner image by an electrophotographic method. The image forming unit 20 forms a toner image of one color component on the outer peripheral surface of the intermediate transfer belt 21 having an endless annular shape and a predetermined width wound around a plurality of rollers (primary transfer). Image forming units 22Y, 22M, 22C, 22K for each color of yellow (Y), magenta (M), cyan (C), and black (K), and a toner image formed on the outer peripheral surface of the intermediate transfer belt 21. It has a secondary transfer device 30 for secondary transfer to a recording paper. The color-coded image forming units 22Y, 22M, 22C, and 22K are collectively referred to as the image forming unit 22.

The image forming units 22Y, 22M, 22C, and 22K have different toner colors, but have the same structure as each other. The image forming units 22Y, 22M, 22C, and 22K have a cylindrical photoconductor drum 24 as an electrostatic latent image carrier on which an electrostatic latent image is formed on the surface, and a charging device, a developing device, and the like around the cylindrical photoconductor drum 24. A transfer device, a photoconductor cleaning device, etc. are arranged and provided. Further, it includes a print head 26 composed of a laser diode (LD) which is a laser element, a polygon mirror, various lenses, a mirror, and the like.

In each image forming unit 22Y, 22M, 22C, 22K, the photoconductor drum 24 is driven by a drive unit (not shown) and rotates in a certain direction, and the charging device uniformly charges the photoconductor drum 24 and prints. The head 26 scans the photoconductor drum 24 with a laser beam controlled on / off according to a drive signal based on image data of the corresponding color to form an electrostatic latent image on the surface of the photoconductor drum 24.

The developing apparatus performs a developing step of developing an electrostatic latent image on the surface of the photoconductor drum 24 with toner to visualize it. The toner image formed on the surface of the photoconductor drum 24 is transferred (primary transfer) to the intermediate transfer belt 21 at a point where it comes into contact with the intermediate transfer belt 21. The photoconductor cleaning device removes and recovers the toner remaining on the surface of the photoconductor drum 24 after transfer by rubbing with a blade or the like.

The intermediate transfer belt 21 wound around the plurality of rollers is driven by a drive unit (not shown) and orbits in the direction of arrow A in the drawing. A full-color color image is obtained by sequentially transferring and superimposing toner images formed on the photoconductor drums 24 of the image forming units 22Y, 22M, 22C, and 22K of each color on the intermediate transfer belt 21 in the process of circulation. Is synthesized on the intermediate transfer belt 21. This toner image is transferred (secondary transfer) from the intermediate transfer belt 21 onto the recording paper by the secondary transfer device 30 arranged at the secondary transfer position D. Further, the toner remaining on the intermediate transfer belt 21 after the secondary transfer is removed from the intermediate transfer belt 21 by the cleaning device 27 provided downstream of the secondary transfer position D.

The fixing device 15 is provided in the middle of the transfer path of the recording paper and downstream of the secondary transfer position D, and the toner image transferred on the surface of the recording paper at the secondary transfer position D is transferred to the recording paper. Pressurize and heat to fix.

The transport unit 16 has a function of transporting the recording paper fed from the paper feed tray 14 to the paper output tray 17 through the secondary transfer position D and the fixing device 15. The transport unit 16 is composed of a transport roller and a guide that form a transport path, a motor that drives the transport roller, and the like. Although not shown, the transport unit 16 is a paper reversing mechanism for double-sided printing in which the recording paper that has left the fixing device 15 is turned upside down and sent back to the transport path upstream of the secondary transfer position D. Is equipped with.

The control circuit unit 13 is configured with a CPU, ROM, RAM, and the like as main units. Each function as the image forming apparatus 10 is realized by the CPU executing the process according to the program stored in the ROM. The control circuit unit 13 controls the operations of the transport unit 16, the image forming unit 20, the secondary transfer device 30, and the like.

As shown in FIGS. 2 to 5, the secondary transfer device 30 pushes the secondary transfer roller 41 whose axial direction is the width direction of the intermediate transfer belt 21 onto the outer peripheral surface of the intermediate transfer belt 21 at the secondary transfer position D. By hitting the intermediate transfer belt 21, the intermediate transfer belt 21 is sandwiched between the secondary transfer roller 41 and the roller (opposed roller 28) arranged at a position facing the secondary transfer roller 41 among the plurality of rollers around which the intermediate transfer belt 21 is wound. Form a transfer nip. Hereinafter, the width direction of the intermediate transfer belt 21 (axial direction of the secondary transfer roller 41) is referred to as the "front-back direction". Further, the relative position on the end side in the front-back direction is called "outside", and the relative position on the center side in the front-back direction is called "inside".

The secondary transfer roller 41 is incorporated in the secondary transfer unit 40 as shown in FIGS. 3 to 5. The secondary transfer unit 40 is configured by rotatably supporting the secondary transfer roller 41 on the frame member 42 and attaching a guide plate 43 or the like that guides the paper to the transfer nip to the frame member 42.

In the secondary transfer device 30, the secondary transfer unit 40, the pressing (crimping) position where the secondary transfer roller 41 presses against the intermediate transfer belt 21 to form a transfer nip, and the secondary transfer roller 41 form an intermediate transfer belt. A first drive consisting of a crimp release portion (crimp release mechanism) 50 that displaces the secondary transfer unit 40 so as to be displaced to a separation (disengagement) position away from 21 and a motor, gear, or the like that drives the crimp release portion 50. The nip pressure that the portion 52 and the secondary transfer roller 41 in the pressing position press by sandwiching the intermediate transfer belt 21 between the opposing roller 28 is applied to the secondary transfer position D (secondary) by the front and rear ends of the paper. A high-speed decompression unit (high-speed decompression mechanism) 70 that temporarily depressurizes when passing between the transfer roller 41 and the intermediate transfer belt 21 and a second drive unit 72 including a motor or the like that drives the high-speed decompression unit 70. It is configured by being attached to the frame member 32 (see FIG. 5). Note that FIG. 5A is a perspective view showing the secondary transfer unit 40 separately. FIG. 5B is a perspective view showing the crimp release portion 50 separated. FIG. 5C is a perspective view showing the high-speed decompression unit 70 separately.

As shown in FIGS. 2 to 5, the frame member 32 stands with the rectangular flat plate-shaped bottom plate portion 32a long in the front-back direction of the secondary transfer device 30 and the bottom plate portion 32a facing each other from the vicinity of both ends in the front-back direction. It has a pair of support plates 32b provided. The lower portion of each of the opposing support plates 32b is screwed to the bottom plate portion 32a, and the upper portion has a shape narrower than that of the lower portion. A unit support shaft (rotational fulcrum of the secondary transfer unit 40) 34 having a predetermined length that swingably supports the secondary transfer unit 40 is provided near the upper end of each support plate 32b so as to project outward in the front-back direction. ing.

The secondary transfer unit 40 is pivotally supported at both ends in the front-back direction by the unit support shaft 34, and swings around the unit support shaft 34 to move from the unit support shaft 34 to the downstream side in the paper transport direction. The secondary transfer roller 41 having an axial center at a position separated by a predetermined distance is displaced between the pressing position and the separating position.

The crimp release portion 50 abuts on the crimp cam 54 that rotates in the same direction as the shaft of the secondary transfer roller 41 and is supported by the rotating shaft 53 driven by the first drive portion 52, and shakes. It has a crimping arm 55 that displaces the secondary transfer unit 40 to a pressing position and a separating position by moving. The crimping cam 54 and the crimping arm 55 are provided at both ends in the front-back direction corresponding to each support plate 32b.

The crimping arm 55 can swing with the rotation fulcrum 55a at one end pivotally supported by the support shaft 36 (see FIGS. 2 to 5) attached to the support plate 32b slightly below the unit support shaft 34. There is. The axial direction of the support shaft 36 that pivotally supports the rotation fulcrum 55a of the crimping arm 55 is the same direction as the shaft of the secondary transfer roller 41.

As shown in FIGS. 3 and 7, the rotary shaft 53 is rotatably supported by the support plate 32b at a position slightly shifted upstream from directly below the rotary fulcrum 55a of the crimping arm 55 in the paper transport direction. ing.

The crimping arm 55 has the above-mentioned rotation fulcrum 55a at one end (upper end), and has a contact roller 55b at the other end (lower end) that abuts on the crimp cam 54 and serves as a force point, and has a side in the middle. It is provided with an acting arm 55c protruding toward the side (upstream side in the paper transport direction) (see FIGS. 2 to 7).

A spring 56 that extends upward in a spiral shape is attached to the upper surface of the crimping arm 55 near the tip of the working arm 55c, and the upper end of the spring 56 is joined to the lower surface of the tip of the decompression arm 75, which will be described later. .. The crimping arm 55 has a point of action where the spring 56 near the tip of the working arm 55c is attached, and when the transfer nip is formed, the secondary transfer unit 40 is formed via the spring 56 and the pressure reducing arm 75. The back surface is pressed toward the opposing roller 28.

The crimp release portion 50 is provided with two crimp cams 54 arranged separately at both ends in the axial direction (front-back direction) of the secondary transfer roller 41 in the same phase, and the crimp arms 55 at both ends are used. The back surface of the secondary transfer unit 40 is pressed in the same manner at both ends in the front-back direction at the same time, and the pressing is released.

The high-speed decompression unit 70 comes into contact with the decompression cam 74, which rotates in the same direction as the axis of the secondary transfer roller 41 and is attached to the rotation shaft 73 driven by the second drive unit 72, and the decompression cam 74. It has a pressure reducing arm 75 that displaces the secondary transfer unit 40 at the pressing position in a direction in which the nip pressure weakens by swinging. The rotary shaft 73 has a tubular shape, is fitted onto the rotary shaft 53 of the crimp release portion 50, and is coaxial with the rotary shaft 53.

As shown in FIG. 6, the high-speed decompression unit 70 connects the decompression cam 74, the second drive unit 72, and the decompression cam 74, and a plurality of gears mesh with each other from the second drive unit 72 to the decompression cam 74. It has a gear train (decompression gear) 71. The decompression gear train 71 is configured so that the gear ratios of the plurality of gears do not become an integral multiple. Further, in the decompression gear row 71, each tooth surface used when each gear makes one rotation is a new combination. As a result, wear of the compression gear / cam can be suppressed, so that deterioration of decompression performance and occurrence of shock to the intermediate transfer belt can be suppressed.

The control circuit unit 13 periodically causes the decompression cam 74 to perform one rotation operation. In this way, the used portion of the intermediate gear / motor gear can be changed by periodically performing one rotation operation of the pressure reducing cam 74.

The pressure reducing cam 74 has a slope portion 74a and a flat surface portion 74b as regions of the outer circumference where a pressure reducing state in which the nip pressure is weakened is formed (see FIG. 8). In the control of the high-speed decompression unit 70, these regions are properly used according to the length of time for maintaining the decompression.

The coaxial pressure reducing cam 74 and the crimping cam 54 have a positional relationship in which the projected images projected in the axial direction of the secondary transfer roller 41 overlap with each other to the maximum extent. Further, the maximum diameter of the crimping cam 54 is smaller than the minimum diameter of the decompression cam 74.

As shown in FIGS. 2 to 5 and the like, the pressure reducing arm 75 is provided corresponding to each of the two crimping arms 55 at both ends in the front-back direction. One end of the pressure reducing arm 75 is a pressing portion 75a that presses the back surface of the secondary transfer unit 40 toward the intermediate transfer belt 21 (see FIG. 3 and the like), and the above-mentioned spring is on the back surface of the pressing portion 75a. The upper ends of 56 are in contact. The portion where the upper end of the spring 56 is in contact is the action point 75b of the decompression arm 75 in the decompression operation.

The other end of the pressure reducing arm 75 is a force point 75d that receives a force from the pressure reducing cam 74. That is, the force point 75d and the action point 75b of the decompression arm 75 are located on opposite sides of the rotation fulcrum 55a of the crimping arm 55 (rotation fulcrum 75c of the decompression arm 75). That is, there is a rotation fulcrum 75c of the decompression arm 75 between the force point 75d of the decompression arm 75 and the action point 75b where the decompression arm 75 applies a force in the direction in which the nip pressure is weakened. Here, the force points 75d at the ends of the two decompression arms 75 provided separately at both ends in the front-back direction corresponding to the crimping arm 55 are connected to each other by a decompression shaft 77 long in the front-back direction. The pressure reducing shaft 77 is fitted with a cylindrical rotating body 78 that is long in the front-back direction and rotates freely around the pressure reducing shaft 77.

When the rotating body 78 comes into contact with the decompression cam 74, the decompression arm 75 swings. That is, the decompression arm 75 comes into contact with the decompression cam 74 at the rotating body 78. By using the rotating body 78 as a member that abuts on the pressure reducing cam 74, friction with the pressure reducing cam 74 is reduced, and the durability of the pressure reducing cam 74 is improved. The pressure reducing shaft 77 may come into contact with the pressure reducing cam 74 without providing the rotating body 78.

Here, in the conventional configuration, in consideration of the responsiveness of the motor and the inclination of the cam curve, the decompression cam is from the abutting position of the decompression cam 74 to the rotating body 78 to the high-speed decompression position where the high-speed decompression operation is performed. The reciprocating operation is performed within a range of 60 ° out of the outer circumference of the 74 of 360 °.
In the present embodiment, the control circuit unit 13 uses the decompression cam 74 and the decompression gear train 71 of the high-speed decompression unit 70 depending on the conditions (for example, the number of prints, the level of transfer deviation, etc.) (tooth surface / phase). I am trying to change. For example, the control circuit unit 13 changes the used positions of the pressure reducing cam 74 and the pressure reducing gear train 71 according to the number of prints. Further, the control circuit unit 13 has a level (variation) of transfer deviation (shock noise of the image) detected by a reading sensor (detection unit) provided in the main body or the post-processing device after the image is formed on the paper. Is greater than or equal to a predetermined value, the positions in which the decompression cam 74 and the decompression gear train 71 are used are changed. As a result, wear of the compression gear / cam can be suppressed, so that deterioration of decompression performance and occurrence of shock to the intermediate transfer belt can be suppressed.
In addition, since it is not a drive system that directly forms an image or crimps a roller, the reduction operation can be freely performed under conditions that are not used (for example, between papers, between jobs, while the machine is idling, etc.). .. For example, the control circuit unit 13 changes the used positions of the pressure reducing cam 74 and the pressure reducing gear train 71 at the timing when the image is not formed on the paper.

The rotation fulcrum 75c of the decompression arm 75 is located slightly closer to the connected end of the decompression shaft 77 than the center of the decompression arm 75 in the longitudinal direction. Further, the rotation fulcrum 75c is pivotally supported by the support plate 32b so as to be coaxial with the rotation fulcrum 55a of the crimping arm 55. In the decompression arm 75, the point of action 75b (spring 56) during decompression operation from the rotation fulcrum 75c is determined from the distance between the force point 75d (where the decompression shaft 77 is connected) receiving the force from the decompression cam 74 and the rotation fulcrum 75c. The distance to the part that is in contact with the back surface) is increased. That is, the length from the rotation fulcrum 55a to the action point 75b of the decompression arm 75 is longer than the length from the rotation fulcrum 55a of the crimping arm 55 to the force point 75d of the decompression arm 75. As a result, it is possible to reduce the size and cost of the second drive unit 72.

Further, between the rotation fulcrum 55a of the crimping arm 55 and the crimping cam 54, the power point of the decompression arm 75 (rotating body 78 of the decompression shaft 77), that is, a portion that comes into contact with the decompression cam 74 is located. As a result, the main portion of the high-speed decompression portion 70 is included in the crimp release portion 50, and the device is miniaturized.

As shown in FIG. 2, the pressure reducing cams 74 are arranged so as to be close to the inside of the two crimping cams 54 that are separately arranged at both ends in the front-back direction. Further, a second drive unit 72 (motor or the like) for rotating the rotation shaft 73 of the pressure reducing cam 74 and a position detection sensor 76 for detecting the angular position of the pressure reducing cam 74 are arranged inside the two pressure reducing cams 74.

The first drive unit 52 (motor or the like) for rotating the rotary shaft 53 to which the crimp cam 54 is attached is attached to one end of the secondary transfer device 30 in the front-back direction. Specifically, it is attached at a position outside the crimping cam 54 and the crimping arm 55.

Further, as shown in FIG. 10, the first drive unit 52 and the second drive unit 72 are arranged so that the projected images when projected in the axial direction of the secondary transfer roller 41 overlap each other. That is, the second drive unit 72, which is the drive source of the high-speed decompression unit 70, is provided at a position where the cross section overlaps with the first drive unit 52 that operates the crimp release unit 50.

Further, in the image forming apparatus 10, the crimp release portion 50 and the high-speed decompression portion 70 of the secondary transfer device 30 are arranged on the opposite side of the intermediate transfer belt 21 with respect to the secondary transfer position D. As shown in FIGS. 1, 3 and the like, the secondary transfer device 30 (crimp release unit 50, high-speed decompression unit 70) is below the secondary transfer position D, and the intermediate transfer belt 21 is located at the secondary transfer position D. The crimp release portion 50 and the high-speed decompression portion 70 are located on the opposite side of the intermediate transfer belt 21 with respect to the secondary transfer position D. That is, a crimp release portion 50 and a high-speed decompression portion 70 are provided on the side opposite to the intermediate transfer belt 21 with respect to the transfer nip between the secondary transfer roller 41 and the opposing roller 28.

Next, the operation of the secondary transfer device 30 will be described.
In the secondary transfer device 30, when the rotary shaft 53 of the crimp release portion 50 is rotated by the first drive unit 52, the crimp cam 54 attached to the rotary shaft 53 rotates, and the contact roller at the lower end of the crimp cam 54 is rotated. The crimping arm 55 with which the 55b is in contact swings around the rotation fulcrum 55a according to the angular position of the crimping cam 54.

When the secondary transfer unit 40 is displaced from the separation position to the pressing position, the crimping arm 55 rotates to the right (clockwise) from the position shown in FIG. 7 and the spring 56 is located near the tip of the acting arm 55c. The secondary transfer unit 40 is pressed toward the intermediate transfer belt 21 via the pressure reducing arm 75 and the pressure reducing arm 75 in this order. FIG. 8 shows a state in which decompression by the high-speed decompression unit 70 is not acting, and the decompression cam 74 is at an angle position where it does not abut on the force point of the decompression arm 75 (rotating body 78 of the decompression shaft 77). Therefore, in this state, the pressure reducing arm 75 does not receive a force from the pressure reducing cam 74 and is displaced according to the crimping operation of the crimping release portion 50.

When the decompression cam 74 of the high-speed decompression unit 70 is rotated to a predetermined angle position while the crimp cam 54 of the crimp release portion 50 is held at the position shown in FIG. 8, the decompression cam 74 depressurizes as shown in FIG. In contact with the force point of the arm 75 (rotating body 78 of the decompression shaft 77), the decompression arm 75 rotates slightly counterclockwise around the rotation fulcrum 75c, and is on the opposite side of the force point 75d with the rotation fulcrum 75c in between. At the point of action 75b at the end, the crimping arm 55 is displaced to a position to be pushed back via the spring 56.

That is, the pressure reducing arm 75 reduces the nip pressure by blocking the pressing force exerted by the crimping arm 55 on the secondary transfer unit 40 via the spring 56. At this time, the distance between the axes of the opposing roller 28 and the secondary transfer roller 41 is somewhat shorter than the sum of the radius of the opposing roller 28 and the radius of the secondary transfer roller 41 at the time of non-contact, and the nip pressure is two. It is caused by the elasticity of the outer peripheral members of the next transfer roller 41 and the opposing roller 28.

As described above, the secondary transfer device 30 according to the present invention temporarily forms a decompression state by the high-speed decompression unit 70, which is a mechanism different from the crimp release unit 50 that displaces the secondary transfer unit 40 to the pressing position. Therefore, a temporary decompression state can be easily and smoothly formed at an accurate timing.

That is, the crimping operation is performed by the crimping arm 55 pressing the secondary transfer unit 40 via the spring 56 and the decompression arm 75, and the decompression operation is performed so that the decompression arm 75 pushes the spring 56 back to the crimping arm 55 side. Therefore, an appropriate degree of decompression can be easily obtained as compared with a mechanism in which the crimp release portion 50 slightly displaces the crimp arm 55 toward the separation position to reduce the pressure. That is, the crimping arm 55 and the decompression arm 75 have a double structure with the spring 56 sandwiched between them, and the parts operated by the crimping arm 55 and the decompression arm 75 are different. That is, the crimping arm 55 pushes the secondary transfer roller 41 toward the pressing position through the spring 56 and the decompression arm 75 in this order, and the high-speed decompression unit 70 pushes the spring 56 on the crimping arm 55 side with the decompression arm 75. Push back to depressurize. Further, since the operation stroke of the decompression arm 75 in the decompression operation is small, the decompression and decompression release operations can be performed at high speed.

The control circuit unit 13 controls the second drive unit 72 of the high-speed decompression unit 70 so that the crimping is temporarily depressurized when the front end and the rear end of the paper pass through the secondary transfer position D. Specifically, a sensor for detecting the front and rear edges of the paper is provided slightly upstream in the paper transport direction at the secondary transfer position D, and the sensor is based on the timing when the front and rear edges of the paper are detected. The second drive unit 72 controls the angular position of the pressure reducing cam 74 so that the front and rear ends of the paper are decompressed for a predetermined period before and after the time when the paper passes through the secondary transfer position D.

The decompression cam 74 is provided with a slope portion 74a and a flat surface portion 74b on the outer circumference (outer diameter) as a region where a decompression state is formed, and the control circuit unit 13 can control the high-speed decompression unit 70. (High speed) Use these regions properly according to the length of time to maintain decompression.

Specifically, when the control circuit unit 13 maintains the decompression state for a certain period of time or longer, the decompression cam 74b comes into contact with the power point of the decompression arm 75 (rotating body 78 of the decompression shaft 77). An angular position of 74 is set to form a decompression state, and the second drive unit 72 is stopped at that position to maintain the decompression state.

On the other hand, in the control circuit unit 13, if the time to maintain the decompression state is a short time of less than a certain time, the power point of the decompression arm 75 (rotating body 78 of the decompression shaft 77) uses the slope portion 74a of the decompression cam 74. Form a decompressed state. Specifically, the control circuit unit 13 continuously drives the slope portion 74a over an angle range in which the decompression state occurs for a required time while driving the second drive unit 72 (while the decompression cam 74 is rotating). The decompression state for the required time is formed while driving the second drive unit 72 and maintaining the rotation of the decompression cam 74.

For example, as shown in FIG. 8, when the slope portions 74a are provided on both sides of the flat surface portion 74b, the rotating body 78 continues to rotate the decompression cam 74 so that the rotating body 78 has the slope portion 74a and the flat surface portion of the decompression cam 74. The 74b and the slope portion 74a are brought into contact with each other in order, and a depressurized state is continuously formed during that time. If the rotation of the decompression cam 74 is temporarily stopped when the rotating body 78 is at an angle position where it comes into contact with the flat surface portion 74b from one slope portion 74a, the decompression state can be extended while the decompression cam 74 is paused.

By providing the flat surface portion 74b on the decompression cam 74, it is possible to form a decompression state for a certain period of time or longer by stopping the excitation of the motor, so that it is possible to reduce power consumption and reduce the size and power consumption of the motor. Further, when the decompression state is formed for a short time and released, the decompression cam 74 may be continuously rotated, so that the control of the second drive unit 72 becomes easy.

Further, since the rotating shaft 53 holding the crimp cam 54 and the rotating shaft 73 holding the decompression cam 74 are coaxial with each other, the position accuracy when controlling the angular position of these cams is improved.

The secondary transfer device 30 is miniaturized by the following configuration. First, the crimp release portion 50 and the high-speed decompression portion 70 are arranged so that the projected images when projected in the axial direction of the secondary transfer roller 41 overlap. That is, the high-speed decompression section 70 is provided at a position where the cross section overlaps with the crimp release section 50. More specifically, when the crimping cam 54 and the decompression cam 74 are projected in the axial direction of the secondary transfer roller 41, the projected images are partially or completely overlapped. As a result, the area of the secondary transfer device 30 in the cross section perpendicular to the axis of the secondary transfer roller 41 is reduced.

In the present embodiment, the rotation shaft 53 of the crimping cam 54 and the rotation shaft 73 of the decompression cam 74 are coaxial with each other, so that the overlap of these cams is the largest.

Further, as shown in FIG. 10, the first drive unit 52 and the second drive unit 72 are also arranged so that the projected images when projected in the axial direction of the secondary transfer roller 41 overlap with each other. The area of the secondary transfer device 30 in the cross section perpendicular to the axis of the roller 41 is reduced.

Further, by arranging them on the opposite side of the intermediate transfer belt with respect to the secondary transfer position, the circumferential route of the intermediate transfer belt can be made smaller than the case where these are provided inside the intermediate transfer belt, and the secondary transfer device can be installed. It is possible to reduce the size of the including image forming apparatus. Furthermore, by providing the crimp release unit 50 and the high-speed decompression unit 70 below the secondary transfer unit 40, the entire image forming unit 20 including the secondary transfer device 30 is miniaturized.

Further, as shown in FIG. 2, the crimping arm 55 and the crimping cam 54 are provided at two locations divided into both ends in the front-back direction (axial direction of the secondary transfer roller 41), and the pressure reducing cam 74 is arranged inside these. Therefore, the size of the device in the front-back direction can be reduced as compared with the case where the pressure reducing cam 74 is provided on the outside of the crimping cam 54. In the configuration shown in FIG. 2, since the decompression cams 74 are separated in the front-back direction and provided at two locations near the inside of each crimping cam 54, a force for decompression is applied to the decompression shaft 77 near the decompression arm 75. Can be applied to the rotating body 78, and the deflection of the pressure reducing shaft 77 can be reduced.

As shown in FIG. 11, the decompression cam 74 is arranged inside the two crimping cams 54 provided at both ends in the front-back direction, and only one is arranged in the center in the front-back direction. You may. When the decompression cams 74 are provided at two locations divided in the front-back direction as shown in FIG. 2, there is a possibility that the decompression operation may differ depending on the shape of the cam, the phase shift, etc., but the center 1 in the front-back direction In the configuration in which the decompression cam 74 is provided only at the location, the decompression operation can be performed by synchronizing the decompression arms 75 at both ends without being affected by the above difference.

Further, as shown in FIG. 2, when two decompression cams 74 are arranged at both ends in the front-back direction, a position detection sensor that detects the angular positions of the second drive unit 72 and the decompression cam 74 inside them. By arranging the 76, the size of the secondary transfer device 30 in the front-back direction is reduced. As shown in FIG. 11, even if the decompression cam 74 is one configuration, the second drive unit 72 and the position detection sensor 76 are arranged inside the two crimp cams 54 divided into both ends in the front-back direction. Therefore, the size of the secondary transfer device 30 in the front-back direction is reduced.

Further, between the force point at which the decompression arm 75 receives the force from the decompression cam 74 (the connection point of the decompression shaft 77) and the action point of the decompression arm 75 (the point where the tip of the spring 56 abuts), the decompression arm 75 Since the rotation fulcrum 75c is provided, the direction in which the point of action of the decompression arm 75 applies a force to the spring 56 for decompression and the direction in which the force point of the decompression arm 75 is pressed during decompression are opposite, and the degree of freedom of arrangement is increased. It is possible to select an arrangement that increases and contributes to miniaturization.

Further, since the secondary transfer roller 41 is incorporated into the secondary transfer unit 40 to form a unit, miniaturization, improved maintainability, and replaceability of the high-speed decompression unit 70 are improved. Further, since the place where the force for displacementing the secondary transfer roller 41 is applied can be set at an arbitrary place of the frame member 42 of the secondary transfer unit 40, the degree of freedom in arranging each part is increased.

Further, the relationship between the crimping cam 54 and the decompression cam 74 is coaxial, and the maximum diameter of the crimping cam 54 is smaller than the minimum diameter of the decompression cam 74. As a result, the decompression operation by the decompression cam 74 can be performed regardless of the position of the crimp cam 54. Further, since the maximum diameter of the crimping cam 54 is smaller than the minimum diameter of the pressure reducing cam 74, the crimping operation by the crimping cam 54 can be performed regardless of the position of the pressure reducing cam 74.

In addition, the rotating shaft 53 of the crimping cam 54 can be moved in the axial direction by releasing the lock mechanism (not shown), and the movement causes the crimping cam 54 and the contact roller 55b on the crimping arm 55 side to be displaced from each other. These engagements are released. FIG. 12 (a) shows a normal use state locked by the lock mechanism, and FIG. 12 (b) shows the above-mentioned engagement by releasing the lock mechanism and simultaneously moving the rotary shaft 53 and the rotary shaft 73 coaxial with the lock mechanism. Indicates a state in which the case is released. In the case of FIG. 12, the crimping cam 54 and the contact roller 55b of the crimping arm 55 are displaced from each other and their engagement is released, so that the crimping arm 55 is in a separated position as shown in FIG. Along with this, the pressure reducing arm 75 is also displaced, the rotating body 78 of the pressure reducing shaft 77 and the pressure reducing cam 74 are separated from each other, and the engagement is simultaneously released.

For example, when the secondary transfer device 30 stops in the crimping state or the depressurized state due to some trouble, the crimping state or the depressurized state is released by releasing the lock mechanism and moving the rotating shafts 53 and 73. And the paper can be removed smoothly.

As for the high-speed decompression unit 70, the decompression cam 74 and the rotating body 78 of the decompression shaft 77 engage with each other in a normal use state in which the movement of the rotating shaft 73 in the front-back direction is restricted by the lock mechanism, and the lock mechanism is released. Then, when the rotating shaft 73 is moved in the front-back direction, the rotating body 78 of the decompression shaft 77 and the decompression cam 74 may be misaligned and disengaged. For example, the diameter of the rotating body 78 may be made larger than the other portions only in the portion corresponding to the pressure reducing cam 74 in the normal use state.

Although the embodiments of the present invention have been described above with reference to the drawings, the specific configuration is not limited to those shown in the embodiments, and there are changes and additions within the scope of the gist of the present invention. Is also included in the present invention.

For example, as shown in FIG. 13, the pressure reducing cam 74 may be configured to have a plurality of pressure reducing positions P1 for performing pressure reduction by the high speed pressure reducing unit 70 and a plurality of crimping positions P2 for not performing pressure reduction in the outer circumference. .. In this case, the control circuit unit 13 may switch the use position of the decompression cam 74 according to the durability of the decompression cam 74. As a result, the durability of the decompression cam 74 can be improved, so that deterioration of decompression performance and occurrence of shock to the intermediate transfer belt can be suppressed.

Further, as shown in FIG. 14, the decompression cam 74 may be configured to have a plurality of crimping positions P2 in the outer circumference and one decompression position P1 in the outer circumference. In this case as well, the control circuit unit 13 may switch the use position of the pressure reducing cam 74 according to the durability of the pressure reducing cam 74. As a result, the durability of the decompression cam 74 can be improved, so that deterioration of decompression performance and occurrence of shock to the intermediate transfer belt can be suppressed. Further, by setting one decompression position P1 that does not cause a problem even if it wears, the angle that can be used per position can be increased, so that the cam gradient can be made gentle and the torque can be reduced. it can. Further, by setting the stop position to the decompression position P1 which does not require position accuracy in the reciprocating operation, it is possible to avoid the occurrence of problems due to wear.

Further, as shown in FIG. 15, the decompression cam 74 has a symmetrical shape so that the decompression amount is the same regardless of whether it is rotated clockwise or counterclockwise when viewed from the stop position. It may be configured. As a result, the durability of the decompression cam 74 can be improved, so that deterioration of decompression performance and occurrence of shock to the intermediate transfer belt can be suppressed.

Further, the decompression cam 74 may have different cam gradients (gradient according to the required decompression amount) in the clockwise direction and the counterclockwise direction. Conventionally, the high-speed decompression unit 70 is a mechanism for high-speed decompression from the state in which the secondary transfer roller 41 is crimped. Therefore, when the original crimping state has a plurality of positions in the decompression cam 74, the required decompression amount at each position is different. Therefore, even when the decompression amount is small, it is necessary to make the cam gradient of the decompression cam 74 a severe inclination according to the case where the decompression amount is maximum. However, by setting the decompression cam 74 to have different cam gradients for clockwise and counterclockwise rotation, the gradient can be adjusted to the required decompression amount, so that the cam gradient can be made gentle and the torque can be increased. It can be mitigated.

Further, the control circuit unit 13 may periodically switch the rotation direction (clockwise / counterclockwise) of the pressure reducing cam 74. As a result, the uneven wear of the decompression cam 74 can be reduced, so that the durability of the decompression cam 74 can be improved.

Further, the control circuit unit 13 may periodically switch the use position of the pressure reducing cam 74. As a result, it is possible to reduce the uneven wear of the pressure reducing cam 74 at the position where it is used, so that the durability of the pressure reducing cam 74 can be improved.

Further, the secondary transfer roller 41 does not have to be incorporated in the secondary transfer unit 40, and the crimp release portion 50 may press the shaft of the secondary transfer roller 41.

In the embodiment, the crimping arm 55 presses the secondary transfer unit 40 via the spring 56 and the decompression arm 75, and the decompression arm 75 pushes back the spring 56 at the time of decompression. For example, the crimping arm 55 has the spring 56. The secondary transfer unit 40 is pressed through the secondary transfer unit 40, and the pressure reducing arm 75 engages with hooks provided at both ends of the secondary transfer unit 40 and applies a force to the secondary transfer unit 40 in a direction toward a separation position. It may be. The shape of the spring 56 is not limited to that illustrated in the embodiment, and may be a leaf spring or the like, or may be an elastic body having necessary elasticity.

In addition, the detailed configuration of each device constituting the image forming apparatus and the detailed operation of each device can be appropriately changed without departing from the spirit of the present invention.

10 Image forming device 11 Scanner unit 12 Operation panel 13 Control circuit unit (control unit)
14 Paper tray 15 Fixing device 16 Conveying unit 20 Image forming unit 21 Intermediate transfer belt 22 Image forming unit 24 Photoreceptor drum 26 Print head 27 Cleaning device 28 Opposing roller 30 Secondary transfer device 32 Frame member 32a Bottom plate 32b Support plate 34 Unit support shaft 36 Support shaft 40 Secondary transfer unit 41 Secondary transfer roller 42 Frame member 43 Guide plate 50 Crimping release part (crimp release mechanism)
52 First drive unit 53 Rotating shaft 54 Crimping cam 55 Crimping arm 55a Rotating fulcrum 55b Contact roller 55c Acting arm 56 Spring 70 High-speed decompression unit (high-speed decompression mechanism)
71 Decompression gear train (decompression gear)
72 Second drive unit 73 Rotation shaft 74 Decompression cam 74a Slope 74b Flat surface 75 Decompression arm 75a Pressing unit 75b Action point during decompression operation of decompression arm 75c Rotation fulcrum 75d Power point of decompression arm (connection point of decompression shaft 77)
76 Position detection sensor 77 Decompression shaft 78 Rotating body D Secondary transfer position A Circulation direction of intermediate transfer belt

Claims (22)

A secondary transfer device that secondarily transfers a toner image primaryly transferred to the outer peripheral surface of an intermediate transfer belt to paper at a predetermined secondary transfer position.
At the secondary transfer position, the intermediate transfer belt is sandwiched between the opposing rollers that abut on the inner peripheral surface thereof and pressed, and the separation position is separated from the outer peripheral surface of the intermediate transfer belt. A crimp release mechanism that displaces the transfer roller,
The first drive unit that drives the crimp release mechanism and
The nip pressure that the secondary transfer roller in the pressing position presses by sandwiching the intermediate transfer belt between the opposing rollers is applied to the secondary transfer roller and the intermediate transfer belt at the front and rear ends of the paper. A high-speed decompression mechanism that temporarily decompresses when passing between
The second drive unit that drives the high-speed decompression mechanism and
A control unit that controls driving by the first drive unit and the second drive unit,
With
The high-speed decompression mechanism
A decompression cam driven by the second drive unit and
A decompression gear train in which the second drive unit and the decompression cam are connected and a plurality of gears are meshed from the second drive unit to the decompression cam.
A decompression arm that displaces the shaft of the secondary transfer roller at the pressing position in a direction in which the nip pressure weakens by abutting on the decompression cam and swinging.
With
The control unit is a secondary transfer device, characterized in that the used positions of the pressure reducing cam and the pressure reducing gear train are changed according to conditions. The first aspect of the present invention is that the decompression gear train is configured so that the gear ratios of the plurality of gears do not become an integral multiple, and the tooth surfaces used when each gear makes one rotation are a new combination. The secondary transfer device described. The secondary transfer device according to claim 1 or 2, wherein the control unit periodically performs one rotation operation of the pressure reducing cam. The decompression cam has a plurality of decompression positions in which decompression is performed by the high-speed decompression mechanism and a crimping position in which the decompression is not performed, respectively, in the outer circumference.
The secondary transfer device according to any one of claims 1 to 3, wherein the control unit switches the use position of the pressure reducing cam according to the durability of the pressure reducing cam. The decompression cam has a plurality of crimping positions in the outer circumference where decompression by the high-speed decompression mechanism is not performed, and one decompression position in the outer circumference where the decompression is performed.
The secondary transfer device according to any one of claims 1 to 3, wherein the control unit switches the use position of the pressure reducing cam according to the durability of the pressure reducing cam. The secondary transfer device according to any one of claims 1 to 5, wherein the decompression cam has a symmetrical shape. The secondary transfer device according to any one of claims 1 to 5, wherein the decompression cam has different cam gradients in clockwise and counterclockwise directions. The secondary transfer device according to any one of claims 1 to 7, wherein the control unit periodically switches the rotation direction of the pressure reducing cam. The secondary transfer device according to any one of claims 1 to 8, wherein the control unit periodically switches the position in which the decompression cam is used. The secondary transfer device according to any one of claims 1 to 9, wherein the control unit changes the use position of the pressure reducing cam and the pressure reducing gear train according to the number of prints. The secondary according to any one of claims 1 to 10, wherein the control unit changes the used position of the pressure reducing cam and the pressure reducing gear train at a timing when an image is not formed on the paper. Transfer device. The control unit is characterized in that after the image is formed on the paper, the used positions of the pressure reducing cam and the pressure reducing gear train are changed when the fluctuation of the transfer deviation detected by the detection unit is equal to or more than a predetermined value. The secondary transfer apparatus according to any one of claims 1 to 11. 2. The second item according to any one of claims 1 to 12, wherein the crimp release mechanism and the high-speed decompression mechanism are arranged on the opposite side of the intermediate transfer belt with respect to the secondary transfer position. Next transfer device. The crimping release mechanism and the high-speed decompression mechanism are arranged so as to overlap the projected images when projected in the axial direction of the secondary transfer roller, according to any one of claims 1 to 13. The secondary transfer device described. The secondary according to any one of claims 1 to 14, wherein the rotation shaft of the crimping cam driven by the first drive unit and the rotation shaft of the pressure reducing cam are coaxial. Transfer device. Any one of claims 1 to 15, wherein the first driving unit and the second driving unit are arranged so that projected images when projected in the axial direction of the secondary transfer roller overlap each other. The secondary transfer device according to the section. The secondary transfer device according to any one of claims 1 to 16, wherein the decompression arm abuts on the decompression cam with a rotating body. A rotation fulcrum of the decompression arm is provided between a force point at which the decompression arm receives a force from the decompression cam and an action point at which the decompression arm applies a force in a direction in which the nip pressure is weakened. The secondary transfer device according to any one of claims 1 to 17. The secondary transfer device according to claim 18, wherein the distance from the rotation fulcrum to the action point is longer than the distance from the force point to the rotation fulcrum of the pressure reducing arm. The crimp release mechanism is
The crimping cam driven by the first drive unit and
A crimping arm that displaces the secondary transfer roller to the pressing position and the separating position by abutting against the crimping cam and swinging.
With
The crimping arm pushes and moves the secondary transfer roller toward the pressing position via the spring and the decompression arm in this order.
The secondary transfer device according to any one of claims 1 to 19, wherein the high-speed decompression mechanism pushes the spring back to the crimping arm side with the decompression arm to perform the decompression. The decompression cam has a slope portion and a flat surface portion on the outer periphery as a region where a decompression state is formed.
The secondary transfer device according to any one of claims 1 to 20, wherein the control unit uses the slope portion and the plane portion properly according to the length of time for maintaining the decompression. An image forming part that forms a toner image on paper,
The secondary transfer device according to any one of claims 1 to 21, wherein the toner image formed by the image forming unit is secondarily transferred to the paper.
An image forming apparatus comprising.

Images