JP2011185987A - Contact/separating mechanism and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a contact/separating mechanism maximum in which load torque and rotational load torque at the contact/separating action of roller members with respect to members to be abutted are relatively small, an impact sound at the contact/separating action is relatively small, and can be reduced in size and cost, and an image forming apparatus. <P>SOLUTION: A joint 32a of an arm member 31 with a spring 32 is movable. Then, the joint 32a is moved in a direction separating from a rotating shaft 31a of the arm member 31 when the arm member 31 is turned in a direction in which the roller members 9Y, 9M, 9C abut on the members 1Y, 1M, 1C to be abutted. In addition, the joint 32a is moved in a direction in which it approaches the rotating shaft 31a of the arm member 31 when the arm member 31 is turned in a direction in which the roller members 9Y, 9M, 9C separate from the members 1Y, 1M, 1C to be abutted. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a contact / separation mechanism in which a roller member such as a primary transfer roller that directly or indirectly contacts a member to be contacted such as a photosensitive drum can be contacted / separated, and a copying machine and printer provided with the contact / separation mechanism And an image forming apparatus such as a facsimile machine or a multifunction machine thereof.

  2. Description of the Related Art Conventionally, in an image forming apparatus such as a copying machine or a printer, a contact / separation mechanism in which a roller member such as a primary transfer roller that directly or indirectly contacts a member to be contacted such as a photosensitive drum is detachably movable. There is known a technique for providing (see, for example, Patent Documents 1 and 2).

Specifically, the image forming apparatus of Patent Document 1 is a tandem type color image forming apparatus including an intermediate transfer belt. At a position facing the intermediate transfer belt, four photosensitive drums (image carrier) and primary transfer roller (roller member) are juxtaposed so as to sandwich the intermediate transfer belt. On these four photosensitive drums, black (black), yellow, magenta, and cyan toner images are formed, respectively. Then, the toner images of the respective colors formed on the respective photosensitive drums are transferred onto the intermediate transfer belt at the position of the primary transfer roller. Further, the toner images of a plurality of colors carried on the intermediate transfer belt are transferred onto a recording medium as a color image.
Such an image forming apparatus is provided with a contact / separation mechanism for moving an intermediate transfer belt in a freely movable manner together with a primary transfer roller (roller member) with respect to a photosensitive drum (contacted member). The four primary transfer rollers are all separated from the intermediate transfer belt during non-image formation, and the three primary transfer rollers for yellow, magenta, and cyan are separated from the intermediate transfer belt during monochrome image formation. .

  Here, Patent Document 1 discloses a technique for installing a braking member so as not to exceed the maximum load torque with respect to the cam shaft of the eccentric cam for the purpose of reducing the impact sound without increasing the torque in the contact / separation mechanism. It is disclosed.

In the image forming apparatus disclosed in Patent Document 1 and the like, by installing a braking member so as not to exceed the maximum load torque with respect to the cam shaft of the eccentric cam, the impact sound is reduced without increasing the torque in the contact / separation operation of the contact / separation mechanism The effect can be expected.
However, since this technique does not reduce the maximum load torque itself or the rotational load torque itself in the contact / separation operation of the contact / separation mechanism, it is difficult to reduce the size and cost of the drive motor that drives the eccentric cam. In particular, such a problem is a large-sized image forming apparatus, and when the contact / separation mechanism itself is enlarged, the maximum load torque and the rotational load torque of the contact / separation mechanism increase, and therefore cannot be ignored. It was.

  Such a problem is not limited to the contact / separation mechanism that contacts and separates the primary transfer roller as the roller member with respect to the photosensitive drum as the contact member, and the roller with respect to the contact member. A contact / separation mechanism for contacting / separating the members may be a contact / separation mechanism for contacting / separating the transfer roller with respect to the transfer / conveying belt, transfer belt, or photosensitive belt, or The mechanism is also common. Furthermore, the contact / separation mechanism that contacts and separates the transfer roller and the pressure roller with respect to the photosensitive drum and the fixing roller is also common.

  The present invention has been made to solve the above-described problems. The maximum load torque and the rotational load torque in the contact / separation operation of the roller member with respect to the contacted member are relatively small, and the impact sound in the contact / separation operation. It is another object of the present invention to provide a contact / separation mechanism and an image forming apparatus that are relatively small and can be reduced in size and cost.

  The contact / separation mechanism according to claim 1 of the present invention is a contact / separation mechanism in which a roller member that abuts on a member to be contacted that rotates or travels in a predetermined direction is movable in contact with and separates from the member to be contacted. The roller member is rotatably held, and the arm member is supported so as to be rotatable about a rotation shaft, and the arm member is disposed in a direction in which the roller member comes into contact with the contacted member. A spring for biasing, and a separating means for pushing the arm member in a direction against the biasing force of the spring to separate the roller member from the contacted member. A joint portion with a spring is configured to be movable, and when the arm member rotates in a direction in which the roller member abuts on the contacted member, the joint portion moves away from the rotation shaft of the arm member. And moving, said roller member when the arm member in a direction away from the abutted portion is rotated is to move in a direction in which the joint approaches the axis of rotation of the arm member.

  The contact / separation mechanism according to a second aspect of the invention is the invention according to the first aspect, wherein the joining portion is a support shaft that supports one end of the spring, and the arm member is A groove-shaped or hole-shaped guide portion extending from a position close to the rotation shaft to a position away from the rotation shaft is provided so that the support shaft of the spring slides as the arm member rotates.

  The contact / separation mechanism according to a third aspect of the invention is the arm member according to the first or second aspect, wherein the roller member is in a position where the roller member is in contact with the contacted member. The biasing force of the spring against the arm member is configured not to act in a direction separating the arm member from the contacted member, and when the roller member is at a position away from the contacted member, The biasing force of the spring is configured so as not to act in a direction in which the arm member is brought closer to the contacted member.

  The contact / separation mechanism according to a fourth aspect of the invention is the invention according to any one of the first to third aspects, wherein the contacted member includes an intermediate transfer belt, a transfer conveyance belt, a transfer belt, The roller member is pressed against the roller member via any one of the photosensitive belt and the fixing belt, and the belt member is brought into contact with and separated from the contacted member together with the roller member.

  An image forming apparatus according to a fifth aspect of the present invention includes the contact / separation mechanism according to any one of the first to fourth aspects.

  According to the present invention, a joining portion between an arm member that rotatably holds a roller member and rotates around a rotation shaft and a spring that biases the arm member in a contact direction is configured to be movable. Yes. The contact portion moves in a direction away from the rotation axis of the arm member when contacting, and the connection portion moves in a direction approaching the rotation axis of the arm member when separated. As a result, the maximum load torque and rotational load torque in the contact / separation operation of the roller member with respect to the contacted member are relatively small, the impact sound in the contact / separation operation is also relatively small, and downsizing and cost reduction are possible. An approach / separation mechanism and an image forming apparatus can be provided.

1 is an overall configuration diagram illustrating an image forming apparatus according to Embodiment 1 of the present invention. FIG. 2 is a cross-sectional view illustrating an image forming unit in the image forming apparatus of FIG. 1. FIG. 2 is a configuration diagram illustrating an intermediate transfer belt device installed in the image forming apparatus of FIG. 1. FIG. 4 is a diagram illustrating a state when a contact / separation mechanism is operated in the intermediate transfer belt device of FIG. 3. It is a figure following FIG. It is a figure following FIG. It is a figure which shows operation | movement of the arm member and spring in an approach / separation mechanism. It is a block diagram showing a conventional intermediate transfer belt device. It is a figure for comparing with the operation | movement of the arm member in the contacting / separating mechanism of the conventional intermediate transfer belt apparatus. It is a graph which shows the relationship between the rotational position of an eccentric cam, and the rotational load torque of an eccentric cam. It is a block diagram which shows the transfer conveyance belt apparatus in Embodiment 2 of this invention. It is the schematic which shows operation | movement of the contact-and-separation mechanism of the secondary transfer roller in Embodiment 3 of this invention. It is the schematic which shows operation | movement of the contact / separation mechanism of the fixing device in Embodiment 4 of this invention.

  Hereinafter, embodiments for carrying out the present invention will be described in detail with reference to the drawings. In addition, in each figure, the same code | symbol is attached | subjected to the part which is the same or it corresponds, The duplication description is simplified or abbreviate | omitted suitably.

Embodiment 1 FIG.
A first embodiment of the present invention will be described in detail with reference to FIGS.
First, the configuration and operation of the entire image forming apparatus will be described with reference to FIGS.
FIG. 1 is a block diagram showing a printer as an image forming apparatus, and FIG. 2 is an enlarged view showing an image forming unit thereof.
As shown in FIG. 1, an intermediate transfer belt device 15 is installed in the center of the image forming apparatus main body 100. Further, image forming portions 6Y, 6M, 6C, and 6K corresponding to the respective colors (yellow, magenta, cyan, and black) are arranged in parallel so as to face the intermediate transfer belt 8 (belt member) of the intermediate transfer belt device 15. Yes.

  Referring to FIG. 2, an image forming unit 6Y corresponding to yellow includes a photosensitive drum 1Y as a contact member, a charging unit 4Y disposed around the photosensitive drum 21, a developing unit 5Y, and a cleaning unit. 2Y, a static elimination unit (not shown), and the like. Then, an image forming process (charging process, exposure process, developing process, transfer process, cleaning process) is performed on the photosensitive drum 1Y, and a yellow image is formed on the photosensitive drum 1Y.

  The other three image forming units 6M, 6C, and 6K have substantially the same configuration as that of the image forming unit 6Y corresponding to yellow except that the color of the toner used is different. A corresponding image is formed. Hereinafter, description of the other three image forming units 6M, 6C, and 6K will be omitted as appropriate, and only the image forming unit 6Y corresponding to yellow will be described.

Referring to FIG. 2, photosensitive drum 1Y is driven to rotate counterclockwise by a motor (not shown). Then, the surface of the photosensitive drum 1Y is uniformly charged at the position of the charging unit 4Y (a charging process).
Thereafter, the surface of the photosensitive drum 1Y reaches the irradiation position of the laser beam L emitted from the exposure unit 7, and an electrostatic latent image corresponding to yellow is formed by exposure scanning at this position (in the exposure process). is there.).

Thereafter, the surface of the photosensitive drum 1Y reaches a position facing the developing portion 5Y, and the electrostatic latent image is developed at this position to form a yellow toner image (developing process).
Thereafter, the surface of the photosensitive drum 1Y reaches a position facing the intermediate transfer belt 8 (belt member) and the primary transfer roller 9Y (roller member), and the toner image on the photosensitive drum 1Y is intermediately transferred at this position. Transferred onto the belt 8 (this is a primary transfer process). At this time, a small amount of untransferred toner remains on the photosensitive drum 1Y.

Thereafter, the surface of the photosensitive drum 1Y reaches a position facing the cleaning unit 2Y, and untransferred toner remaining on the photosensitive drum 1Y at this position is collected in the cleaning unit 2Y by the cleaning blade 2a (cleaning). Process.)
Finally, the surface of the photosensitive drum 1Y reaches a position facing a neutralization unit (not shown), and the residual potential on the photosensitive drum 1 is removed at this position.
Thus, a series of image forming processes performed on the photosensitive drum 1Y is completed.

The image forming process described above is performed in the other image forming units 6M, 6C, and 6K in the same manner as the yellow image forming unit 6Y. That is, a laser beam L based on image information is irradiated from the exposure unit 7 disposed above the image forming unit onto the photosensitive drums 1M, 1C, and 1K of the image forming units 6M, 6C, and 6K. Is done. Specifically, the exposure unit 7 emits a laser beam L from a light source, and irradiates the photosensitive drum through a plurality of optical elements while scanning the laser beam L with a polygon mirror that is rotationally driven.
Thereafter, the toner images of the respective colors formed on the respective photosensitive drums through the developing process are transferred onto the intermediate transfer belt 8 in an overlapping manner. In this way, a color image is formed on the intermediate transfer belt 8.

  Here, the intermediate transfer belt device 15 (belt device) includes an intermediate transfer belt 8, four primary transfer rollers 9Y, 9M, 9C, and 9K (roller members), a driving roller 12, and a driven roller with reference to FIG. 13 and contact / separation mechanisms 31 to 36. The intermediate transfer belt 8 is stretched and supported by the driving roller 12 and the driven roller 13, and is endlessly moved in the direction of the arrow (counterclockwise) in FIG.

The four primary transfer rollers 9Y, 9M, 9C, and 9K (roller members) respectively sandwich the intermediate transfer belt 8 between the photosensitive drums 1Y, 1M, 1C, and 1K to form primary transfer nips. Yes. Then, a transfer voltage (transfer bias) opposite to the polarity of the toner is applied to the primary transfer rollers 9Y, 9M, 9C, and 9K.
The intermediate transfer belt 8 travels in the direction of the arrow, and sequentially passes through the primary transfer nips of the primary transfer rollers 9Y, 9M, 9C, and 9K. In this way, the toner images of the respective colors on the photosensitive drums 1Y, 1M, 1C, and 1K are primarily transferred while being superimposed on the intermediate transfer belt 8.

  Thereafter, the intermediate transfer belt 8 on which the toner images of the respective colors are transferred in a superimposed manner reaches a position facing the secondary transfer roller 19. At this position, the driving roller 12 (secondary transfer counter roller) sandwiches the intermediate transfer belt 8 with the secondary transfer roller 19 to form a secondary transfer nip. The four-color toner images formed on the intermediate transfer belt 8 are transferred onto a recording medium P such as transfer paper conveyed to the position of the secondary transfer nip. At this time, untransferred toner that has not been transferred to the recording medium P remains on the intermediate transfer belt 8.

Thereafter, the intermediate transfer belt 8 reaches the position of an intermediate transfer cleaning unit (not shown). At this position, the untransferred toner on the intermediate transfer belt 8 is removed.
Thus, a series of transfer processes performed on the intermediate transfer belt 8 is completed. The configuration and operation of the contact / separation mechanisms 31 to 36 in the intermediate transfer belt device 15 will be described in more detail later with reference to FIGS.

Here, referring to FIG. 1, the recording medium P conveyed to the position of the secondary transfer nip is fed from a sheet feeding unit 26 disposed below the apparatus main body 100 to a sheet feeding roller 27 and a registration roller pair 28. Etc., which are conveyed via
Specifically, a plurality of recording media P such as transfer paper are stored in the paper supply unit 26 in a stacked manner. When the paper feed roller 27 is driven to rotate counterclockwise in FIG. 1, the uppermost recording medium P is fed toward the rollers of the registration roller pair 28.

  The recording medium P transported to the registration roller pair 28 temporarily stops at the position of the roller nip of the registration roller pair 28 whose rotation drive has been stopped. Then, the registration roller pair 28 is rotationally driven in synchronization with the color image on the intermediate transfer belt 8, and the recording medium P is conveyed toward the secondary transfer nip. In this way, a desired color image is transferred onto the recording medium P.

Thereafter, the recording medium P on which the color image is transferred at the position of the secondary transfer nip is conveyed to the position of the fixing unit 20. At this position, the color image transferred to the surface is fixed on the recording medium P by heat and pressure generated by the fixing roller and the pressure roller.
Thereafter, the recording medium P is discharged out of the apparatus by a pair of paper discharge rollers. The transferred P discharged from the apparatus by the pair of paper discharge rollers is sequentially stacked on the stack unit as an output image.
Thus, a series of image forming processes in the image forming apparatus is completed.

Next, the image forming unit in the image forming apparatus will be described in detail with reference to FIG.
As shown in FIG. 2, the process cartridge 6Y as an image forming unit includes a photosensitive drum 1Y (image carrier), a charging roller 4Y, a developing device 5Y (developing unit), a cleaning unit 2Y, and the like.
The photoreceptor drum 1Y is a negatively charged organic photoreceptor, and is driven to rotate clockwise in FIG. 2 by receiving a driving force from a motor (not shown) installed on the apparatus main body 100 side.

The charging roller 4Y is a roller having elasticity in which a medium-resistance urethane foam layer in which urethane resin, carbon black as conductive particles, a sulfurizing agent, a foaming agent and the like are formulated is formed on a core metal. The material of the middle resistance layer of the charging roller 4Y is urethane, ethylene-propylene-diene polyethylene (EPDM), butadiene acrylonitrile rubber (NBR), silicone rubber, isoprene rubber, etc. It is also possible to use a rubber material in which a conductive material such as the above is dispersed or a foamed material of these materials. In the first embodiment, the charging roller 4Y is configured to contact the photosensitive drum 1Y. However, the charging roller 4Y may be configured not to contact the photosensitive drum 1Y. .
The cleaning unit 2Y is provided with a cleaning blade 2a that is in sliding contact with the photosensitive drum 1Y, and mechanically removes and collects untransferred toner on the photosensitive drum 1Y.

  The developing device 5Y (developing portion) is disposed so that the developing roller 51Y contacts the photosensitive drum 1Y, and a developing region (developing nip portion) is formed between both members. In the developing device 5Y, toner (one-component developer) is accommodated. The developing device 5Y develops the electrostatic latent image formed on the photosensitive drum 1Y (forms a toner image).

Hereinafter, the developing device 5Y (developing unit) will be described in detail.
Referring to FIG. 2, developing device 5Y according to the first embodiment is a one-component developing type developing device, and includes developing roller 51Y (developer carrier), supply roller 55Y, and a doctor as a thinning member. The blade 52Y, the stirring member 56Y, the agitator 58Y, the toner supply port 57Y, and the like are included. Further, the developing device 5Y is provided with a toner storage portion B1 and a toner supply portion B2.

The developing device 5Y configured as described above operates as follows.
First, a part of the toner supplied and stored in the toner supply unit B2 from the toner storage unit B1 through the toner supply port 57Y is carried on the supply roller 55Y. The toner carried on the supply roller 55Y is frictionally charged at the pressure contact portion with the developing roller 51Y, and then moved and carried on the developing roller 51Y. Thereafter, the toner carried on the developing roller 51Y reaches a contact position (development region) with the photosensitive drum 1Y after being thinned and uniformed at the position of the doctor blade 52Y. At this position, the toner is attracted to the latent image formed on the photosensitive drum 1Y by the electric field (developing electric field) formed in the developing region.

Next, referring to FIG. 3, the intermediate transfer belt device 15 (belt device) in the first embodiment will be described in detail.
Referring to FIG. 3, an intermediate transfer belt device 15 includes an intermediate transfer belt 8 as a belt member, four primary transfer rollers 9Y, 9M, 9C, and 9K as roller members, a driving roller 12, a driven roller 13, and a contact roller. The separation mechanism 31 to 36 is configured.

  The intermediate transfer belt 8 (belt member) is disposed so as to face the photosensitive drums 1Y, 1M, 1C, and 1K (image bearing members) as the four contact members that respectively carry the toner images of the respective colors. It is an endless belt. The intermediate transfer belt 8 is stretched and supported mainly by a driving roller 12 and a driven roller 13.

In the first embodiment, the intermediate transfer belt 8 is made of a single layer or a plurality of layers of PVDF (vinylidene fluoride), ETFE (ethylene-tetrafluoroethylene copolymer), PI (polyimide), PC (polycarbonate), and the like. In this configuration, a conductive material such as carbon black is dispersed. The intermediate transfer belt 8 is adjusted so that the volume resistivity is in the range of 10 ⁷ to 10 ¹² Ωcm, and the surface resistivity on the back side of the belt is in the range of 10 ⁸ to 10 ¹² Ωcm. The intermediate transfer belt 8 is set to have a thickness in the range of 70 to 160 μm.
If necessary, a release layer can be coated on the surface of the intermediate transfer belt 8. At that time, materials used for the coating are ETFE (ethylene-tetrafluoroethylene copolymer), PTFE (polytetrafluoroethylene), PVDF (vinylidene fluoride), PEA (perfluoroalkoxy fluororesin), FEP (four A fluororesin such as fluorinated ethylene-hexafluoropropylene copolymer) or PVF (vinyl fluoride) can be used, but is not limited thereto.
Further, as a method for manufacturing the intermediate transfer belt 8, there are a casting method, a centrifugal molding method, and the like, and a step of polishing the surface is performed as necessary.

  The primary transfer rollers 9Y, 9M, 9C, and 9K (roller members) are in pressure contact with the corresponding photosensitive drums 1Y, 1M, 1C, and 1K (contacted members) via the intermediate transfer belt 8, respectively. Specifically, the primary transfer roller 9Y for yellow is pressed against the photosensitive drum 1Y for yellow via the intermediate transfer belt 8, and the primary transfer roller 9M for magenta is photosensitive for magenta via the intermediate transfer belt 8. The cyan primary transfer roller 9C is in pressure contact with the cyan photosensitive drum 1C via the intermediate transfer belt 8, and the black (black) primary transfer roller 9K is in contact with the intermediate drum 1M. 8 is in pressure contact with the photosensitive drum 1K for black (for black).

  The drive roller 12 is rotationally driven by a motor (not shown). As a result, the intermediate transfer belt 8 travels in a predetermined traveling direction (counterclockwise in FIG. 3). The driving roller 12 is in contact with the secondary transfer roller 19 via the intermediate transfer belt 8.

Hereinafter, the configuration and operation of the contact / separation mechanisms 31 to 36 that are characteristic of the intermediate transfer belt device 15 will be described in detail.
In the first embodiment, the contact / separation mechanisms 31 to 36 are photosensitive drums 1Y, 1M and 1C (except for the monochrome photosensitive drum 1K) as photosensitive members 1Y, 1M and 1C which rotate in a predetermined direction. The primary transfer rollers 9Y, 9M, and 9C as roller members that are in contact with the photosensitive drums 1Y, 1M, and 1C are movable together with the intermediate transfer belt 8 so as to be in contact with and away from the photosensitive drums 1Y, 1M, and 1C. .
Referring to FIG. 3, the contact / separation mechanism includes three arm members 31, three tension springs (springs) 32, a swing plate 33, an eccentric cam 34, a drive shaft 35, a drive motor 36, and the like.

The three arm members 31 respectively hold primary transfer rollers 9Y, 9M, and 9C (roller members) rotatably via bearings (not shown). Further, each of the three arm members 31 is supported by a casing (not shown) of the intermediate transfer belt device 15 so as to be rotatable about a rotation shaft 31a (see also FIG. 7). ing.
The three tension springs 32 are respectively in a direction in which the primary transfer rollers 9Y, 9M, and 9C (roller members) come into contact with the photosensitive drums 1Y, 1M, and 1C (contacted members) via the intermediate transfer belt 8. The arm member 31 is biased.
The swing plate 33, the eccentric cam 34, the drive shaft 35, and the drive motor 36 push the arm member 31 in a direction against the urging force of the tension spring 32, and the photosensitive drums 1Y, 1M, 1C (contacted) It functions as a separating means for separating the primary transfer rollers 9Y, 9M, and 9C (roller members) from the member. Specifically, the swing plate 33 is configured to contact the contact portion 31b (the other end side where the primary transfer roller is not installed) of the three arm members 31, and one end side is an eccentric cam. It is comprised so that it may contact | abut. The eccentric cam 34 is connected to a drive motor 36 via a drive shaft 35. Then, the rotational driving force of the drive motor 36 is transmitted to the eccentric cam 34 via the drive shaft 35, and the eccentric cam 34 rotates in the clockwise direction in FIG. The oscillated plate 33 is oscillated in the direction of the double arrow in FIG.

Here, the primary transfer roller 9K for black is also rotatably held by the arm member 32, and the arm member 31 is urged by the tension spring 32 so that the primary transfer roller 9K passes through the intermediate transfer belt 8. It is in pressure contact with the photosensitive drum 1K for black. However, in the first embodiment, the primary transfer roller 9K for black is not connected to the separation means 33 to 36 described above.
Then, when forming a monochrome image, the separating means 33 to 36 rotate the arm members 31 of the three primary transfer rollers 9Y, 9M, and 9C for color, so that the three primary transfer rollers 8 can be moved from the intermediate transfer belt 8. The transfer rollers 9Y, 9M, and 9C are separated from each other, and the intermediate transfer belt 8 is brought into contact with only the black photosensitive drum 1K.

  Here, with reference to FIGS. 3 to 6 and FIGS. 7A to 7D, the contact / separation mechanism in the first embodiment is a joint portion between the arm member 31 and the tension spring 32 (in FIG. 7). The support shaft 32a shown in FIG. When the arm member 31 rotates in a direction in which the primary transfer rollers 9Y, 9M, and 9C (roller members) come into contact with the photosensitive drums 1Y, 1M, and 1C (contacted members), the joint portion 32a becomes the arm member. It moves in the direction away from the rotating shaft 31a. In contrast, when the arm member 31 rotates in a direction in which the primary transfer rollers 9Y, 9M, and 9C (roller members) are separated from the photosensitive drums 1Y, 1M, and 1C (contacted members), the joint portion 32a. Moves in a direction approaching the rotation shaft 31 a of the arm member 31.

Specifically, referring to FIG. 7, the arm member 31 and the tension spring 32 are joined with a support shaft 32 a that supports one end of the tension spring 32 as a joint portion. The other end side of the tension spring 32 is supported by a housing (not shown) of the intermediate transfer belt device 15.
On the other hand, the arm member 31 has a groove shape (or a hole shape) extending from a position close to the rotation shaft 31a to a position away from the rotation shaft 31a because the support shaft 32a of the tension spring 32 slides as the arm member 31 rotates. ) Guide portion 31c (guide groove). That is, the support shaft 32a that supports one end of the tension spring 32 is slidably held in the guide groove 31c of the arm member 31.

Hereinafter, the contact / separation operation of the contact / separation mechanisms 31 to 36 will be described with reference to FIGS.
As shown in FIG. 3, when the eccentric cam 34 is in the rotational position in the figure, the regulating force to the swing plate 33 by the eccentric cam 34 is the weakest, and the swing plate is driven by the arm member 31 biased by the tension spring 32. 33 is in the leftmost position. At this time, the primary transfer rollers 9Y, 9M, and 9C are in the direction in which the photosensitive drums 1Y, 1M, and 1C are pressed against each other by the arm member 31 biased by the tension spring 32, and the intermediate transfer belt 8 is in the photosensitive body. A primary transfer nip is formed between both members so as to wind around a part of the drums 1Y, 1M, and 1C. In this state, the image forming process described above is performed. At this time, the arm member 31 and the tension spring 32 are in the state shown in FIG.

  When monochrome image formation is performed, first, as shown in FIG. 4, when the eccentric cam 34 is rotated about 90 degrees from the state of FIG. 3 by the drive motor 36, the urging force of the tension spring 32 is resisted. The swing plate 33 moves rightward and is pushed by the swing plate 33 so that the arm member 31 rotates counterclockwise about the rotation shaft 31a so as to resist the urging force of the tension spring 32. . As the arm member 31 rotates at this time, the primary transfer rollers 9Y, 9M, and 9C move in a direction away from the photosensitive drums 1Y, 1M, and 1C, and the intermediate transfer belt 8 moves to the photosensitive drums 1Y and 1M. 1C is lightly touched. At this time, the arm member 31 and the tension spring 32 are in the state shown in FIG. At this time, since the urging force of the tension spring 32 always acts on the swing plate 33, the eccentric cam 34 is in the reverse direction (counterclockwise in the figure) on the rotation shaft portion of the eccentric cam 34. ) Acts as a rotational load torque applied to the drive motor 36.

  After that, as shown in FIG. 5, when the eccentric cam 34 is further rotated about 90 degrees from the state of FIG. 4 by the drive motor 36, the upper fulcrum of the eccentric cam 34 comes into contact with the swing cam 33. The rocking plate 33 is further moved to the right so as to be pushed by the eccentric cam 34 and resist the urging force of the tension spring 32. Then, the arm member 31 is pushed by the swing plate 33 and further rotates counterclockwise around the rotation shaft 31a so as to resist the urging force of the tension spring 32. By the rotation of the arm member 31 at this time, the primary transfer rollers 9Y, 9M, and 9C are further moved in a direction away from the photosensitive drums 1Y, 1M, and 1C, and the intermediate transfer belt 8 is moved to the photosensitive drums 1Y, 1Y, 1M and 1C are completely separated from each other. In this state, an image forming process for forming a monochrome image is performed. At this time, the arm member 31 and the tension spring 32 are in the state shown in FIG.

  When shifting from the monochrome image forming mode to the color image forming mode again, first, as shown in FIG. 6, the eccentric cam 34 is rotated by about 90 degrees from the state of FIG. 5 by the drive motor 36. Accordingly, the swing plate 33 is moved to the left by the arm member 31 biased by the tension spring 32. The arm member 31 is rotated clockwise about the rotation shaft 31a by the urging force of the tension spring 32. As the arm member 31 rotates at this time, the primary transfer rollers 9Y, 9M, and 9C move in a direction in contact with the photosensitive drums 1Y, 1M, and 1C, and the intermediate transfer belt 8 moves to the photosensitive drums 1Y and 1M. 1C is lightly touched. At this time, since the urging force of the tension spring 32 always acts on the swing plate 33, the eccentric cam 34 is accelerated in the positive direction (clockwise in the figure) on the rotating shaft portion of the eccentric cam 34. A rotating force is applied.

  After that, as shown in FIG. 3, when the eccentric cam 34 is further rotated 90 degrees from the state of FIG. 6 by the drive motor 36, the lower fulcrum of the eccentric cam 34 comes into contact with the swing cam 33. The swing plate 33 is further moved leftward by the arm member 31 biased by the tension spring 32. The arm member 31 is further rotated clockwise about the rotation shaft 31a by the urging force of the tension spring 32. By the rotation of the arm member 31 at this time, the primary transfer rollers 9Y, 9M, and 9C further move in a direction in contact with the photosensitive drums 1Y, 1M, and 1C, so that the intermediate transfer belt 8 is moved to the photosensitive drums 1Y, 1Y, 1Y, and 1C. 1M and 1C are in full contact. In this state, an image forming process for forming a color image is performed.

Hereinafter, in FIGS. 7A to 7D, the arm member 31 and the tension spring 32 accompanying the separation operation of the contact / separation mechanisms 31 to 36 (operation from the state of FIG. 3 to the state of FIG. 5). The operation will be described.
First, as shown in FIG. 7A, when the intermediate transfer belt 8 is in a contact state (the state shown in FIG. 3), the support shaft 32a (joint portion) of the tension spring 32 is provided on the arm member 31. It is stationary in a state where it hits the lower end of the guide groove 31c. At this time, the angle θ formed by the urging force F of the tension spring 32 and the arm member 31 (guide groove 31c) is set to be 90 degrees or more. As a result, the support shaft 32a of the tension spring 32 comes to rest in a state in which the shaft 32a hits the lower end of the guide groove 31c without moving the guide groove 31c without permission. That is, when the primary transfer rollers 9Y, 9M, and 9C are in positions that contact the photoreceptor drums 1Y, 1M, and 1C via the intermediate transfer belt 8, the urging force F of the tension spring 32 against the arm member 31 is 31 is configured not to act in a direction away from the photosensitive drums 1Y, 1M, and 1C.

Then, as shown in FIG. 7B, the arm member 31 rotates counterclockwise about the rotation shaft 31a as the intermediate transfer belt 8 is separated, and the urging force F of the tension spring 32 is increased. When the angle θ formed by the arm member 31 (guide groove 31c) is 90 degrees or less, the tension spring 32 is extended by the amount of movement of the support shaft 32a in the direction against the urging force, and the urging force F1 is increased (F1>). F). Further, due to this urging force F1, a component force Fx in the sliding direction and a component force Fy in the direction orthogonal to the sliding direction act on the guide groove 31c. Then, by the component force Fx in the sliding direction, the support shaft 32a of the tension spring 32 slides in the guide groove 31c in a direction approaching the rotation shaft 31a.
Then, as shown in FIG. 7C, when the arm member 31 further rotates counterclockwise about the rotation shaft 31a, the direction of the urging force F2 of the tension spring 32 and the direction orthogonal to the sliding direction are obtained. It reaches a position where the direction of the component force Fy overlaps.

Further, as shown in FIG. 7D, when the arm member 31 is further rotated counterclockwise about the rotation shaft 31a, the support shaft 32a of the tension spring 32 is in contact with the upper end of the guide groove 31c. Quiesce. At this time, the intermediate transfer belt 8 is completely separated (the state shown in FIG. 5). At this time, the angle θ formed by the urging force F of the tension spring 32 and the arm member 31 (guide groove 31c) is 90 degrees or more. As a result, the support shaft 32a of the tension spring 32 comes to a standstill in a state where it abuts against the upper end of the guide groove 31c without moving the guide groove 31c without permission. That is, when the primary transfer rollers 9Y, 9M, and 9C are located at positions away from the photosensitive drums 1Y, 1M, and 1C via the intermediate transfer belt 8, the urging force F of the tension spring 32 against the arm member 31 is 31 is configured so as not to act in a direction to approach the photosensitive drums 1Y, 1M, and 1C.
Note that the operations of the arm member 31 and the tension spring 32 when the intermediate transfer belt 8 shifts from the separated state to the contact state are opposite to those in the above-described separated operation.

Hereinafter, the effects of the contact / separation mechanisms 31 to 36 in the first embodiment will be described with reference to FIGS. 8 to 10.
FIG. 8 is a configuration diagram showing contact / separation mechanisms 131 to 136 installed in the conventional intermediate transfer belt device 115. FIG. 8A is a diagram showing the state of the contact / separation mechanisms 131 to 136 when the intermediate transfer belt 8 is in contact, and FIG. 8B is the state when the intermediate transfer belt 8 is in the separation state. It is a figure which shows the state of these contact / separation mechanisms 131-136. In the conventional contact / separation mechanisms 131 to 136, the support shaft 132 a of the tension spring 132 is fixed on the arm member 131.
FIG. 9A is a diagram illustrating the operation of the arm member 31 and the tension spring 32 in the contact / separation mechanism according to the first embodiment. In the figure, “H” is the spring length of the tension spring 32 when the intermediate transfer belt 8 is in contact, and “H1” is the spring length of the tension spring 32 when the intermediate transfer belt 8 is in the separated state. It is. On the other hand, FIG. 9B is a diagram showing the operation of the arm member 131 and the tension spring 132 in the conventional contact / separation mechanism shown in FIG. In the drawing, “H” is the spring length of the tension spring 132 when the intermediate transfer belt 8 is in contact, and “H0” is the spring length of the tension spring 132 when the intermediate transfer belt 8 is in the separated state. It is. FIG. 9C is a schematic diagram showing changes in the spring lengths of both the tension springs 32 and 132 accompanying the contact and separation operation of the intermediate transfer belt 8.
Further, FIG. 10 is a graph showing the relationship between the rotational position (horizontal axis) of the eccentric cam and the rotational load torque (vertical axis) of the eccentric cam in the contact / separation mechanism. In FIG. 10, the graph shown by the solid line shows the relationship between the rotational position of the eccentric cam 32 and the rotational load torque in the contact / separation mechanisms 31 to 36 of the first embodiment, and the graph shown by the broken line shows the conventional one in FIG. 3 shows the relationship between the rotational position of the eccentric cam 132 and the rotational load torque in the contact / separation mechanisms 131 to 136.

As shown in FIG. 9C, the conventional contact / separation mechanisms 131 to 136 have the position of the joint portion (support shaft 132a) between the arm member 131 and the tension spring 132 fixed to the arm member 131. The change amount ΔH0 (= H0−H) of the spring length of the tension spring 132 accompanying the contact / separation operation of the intermediate transfer belt 8 increases.
In contrast, in the contact / separation mechanisms 31 to 36 according to the first embodiment, the position of the joint portion (support shaft 32a) between the arm member 131 and the tension spring 132 moves as the intermediate transfer belt 8 contacts and separates. Therefore, as shown in FIG. 9C, the change amount ΔH1 (= H1−H) of the spring length of the tension spring 32 accompanying the contact / separation operation of the intermediate transfer belt 8 is reduced (ΔH1 <ΔH0). As a result, the maximum load torque and the rotational load torque when rotating the eccentric cam 34 can be reduced. This can be understood from the experimental results shown in FIG. Therefore, the drive motor 36 can be reduced in size and cost. Further, the acceleration force when rotating the eccentric cam 34 (acceleration torque generated when shifting from the state of FIG. 5 to the state of FIG. 6) can be reduced. The reason why the acceleration force when rotating the eccentric cam 34 is reduced is that the support shaft 32a is located close to the rotation shaft 31a when the tension spring 32 is most extended and has a large energy. Therefore, it is possible to relatively reduce the impact sound in the contact / separation operation of the intermediate transfer belt 8 by the contact / separation mechanisms 31 to 36.
In particular, as in the first embodiment, the intermediate transfer belt 8 is disposed so as to be wound around a part of the photosensitive drums 1Y, 1M, 1C, and 1K, so that the primary transfer process (such transfer process is referred to as “ In the case of the intermediate transfer belt device 15 that performs “offset transfer”), the moving distances (separation distances) of the primary transfer rollers 9Y, 9M, and 9C by the contact / separation mechanisms 31 to 36 are also increased, and thus the above-described effects are remarkable. become.

  As described above, in the first embodiment, the arm member 31 that rotatably holds the primary transfer rollers 9Y, 9M, and 9C (roller members) and rotates around the rotation shaft 31a, and the contact direction The support shaft 32a as a joint portion with the spring 32 that biases the arm member 31 toward the head is configured to be movable. The support shaft 32a moves in a direction away from the rotation shaft 31a of the arm member 31 at the time of contact, and the support shaft 32a moves in a direction closer to the rotation shaft 31a of the arm member 31 at the time of separation. As a result, the maximum load torque and rotational load torque in the contact / separation operation of the primary transfer rollers 9Y, 9M, 9C with respect to the photosensitive drums 1Y, 1M, 1C (contacted members) are relatively small, and the impact in the contact / separation operation. The sound is relatively small, and the contact / separation mechanisms 31 to 36 (or the image forming apparatus 100) can be reduced in size and cost.

In the first embodiment, the three primary transfer rollers 9Y, 9M, and 9C for color are moved from the photosensitive drums 1Y, 1M, and 1C for color together with the intermediate transfer belt 8 by the contact / separation mechanisms 31 to 36. It comprised so that it might space apart.
On the other hand, all four primary transfer rollers 9Y, 9M, 9C, and 9K are moved from all four photosensitive drums 1Y, 1M, 1C, and 1K together with the intermediate transfer belt 8 by the contact / separation mechanisms 31 to 36. It can also be configured to be spaced apart. Further, a contact / separation mechanism for separating only the black primary transfer roller 9K from the black photosensitive drum 1K together with the intermediate transfer belt 8 may be provided separately from the color contact / separation mechanisms 31-36. it can. In any case, at the time of non-image formation (when the image formation process on the intermediate transfer belt 8 is not performed), all four primary transfer rollers 9Y, 9M, 9C, and 9K are subjected to intermediate transfer. By separating the belt 8 from all four photosensitive drums 1Y, 1M, 1C, and 1K, it is possible to reduce wear deterioration of the intermediate transfer belt 8.

  In the first embodiment, the elongated guide groove 31c is used as the guide portion for guiding the support shaft 32a of the tension spring 32. However, the guide portion for guiding the support shaft 32a of the tension spring 32 has the same shape. There is no limit.

  In the first embodiment, the intermediate transfer belt 8 is connected to the contact / separation mechanisms 31 to 36 of the intermediate transfer belt device 15 arranged so as to be wound around a part of the photosensitive drums 1Y, 1M, 1C, and 1K. Although the present invention is applied, the intermediate transfer belt 8 is in contact with the contact / separation mechanisms 31 to 36 of the intermediate transfer belt device 15 disposed so as not to be wound around the photosensitive drums 1Y, 1M, 1C, and 1K. Of course, the present invention can be applied.

Embodiment 2. FIG.
A second embodiment of the present invention will be described in detail with reference to FIG.
FIG. 11 is a configuration diagram illustrating the transfer conveyance belt device according to the second embodiment. The image forming apparatus according to the second embodiment is provided with a transfer conveyance belt device 215 for transferring images formed on the four photosensitive drums 1Y, 1M, 1C, and 1K on the recording medium P in an overlapping manner, The contact / separation mechanisms 31 to 36 are installed in the transfer / conveying belt device 215 in order to transfer the images formed on the four photosensitive drums 1Y, 1M, 1C, and 1K on the intermediate transfer belt 8 in an overlapping manner. The intermediate transfer belt device 15 is installed, and the intermediate transfer belt device 15 is provided with contact / separation mechanisms 31 to 36, which is different from the first embodiment.

As shown in FIG. 11, in the image forming apparatus according to the second embodiment, a transfer conveyance belt device 215 is provided so as to face four photosensitive drums 1Y, 1M, 1C, and 1K (contacted members). is set up. The transfer / conveying belt device 215 includes a transfer / conveying belt 208 as a belt member, four primary transfer rollers 9Y, 9M, 9C, and 9K as roller members, a driving roller 212, a driven roller 213, contact / separation mechanisms 31 to 36, and the like. Consists of.
The transfer / conveying belt 208 (belt member) is disposed so as to face the photosensitive drums 1Y, 1M, 1C, and 1K (image bearing members) as the four contact members that respectively carry the toner images of the respective colors. It is an endless belt. The transfer conveyance belt 208 is stretched and supported mainly by a driving roller 212 and a driven roller 213.

Then, the recording medium P conveyed from the paper supply unit 26 is temporarily stopped at the position of the roller nip of the registration roller pair 28 that has stopped rotating. Then, the recording medium P is conveyed by the transfer conveying belt 208 so that the images formed on the photosensitive drums 1Y, 1M, 1C, and 1K are synchronized with each other, and the images of the respective colors are superimposed on the recording medium P. Transcribed. Thus, a desired color image is transferred onto the recording medium P.
Thereafter, the recording medium P carrying the color image is separated from the transfer conveyance belt 208 and conveyed to the position of the fixing unit 20. At this position, the color image transferred to the surface is fixed on the recording medium P by heat and pressure generated by the fixing roller and the pressure roller.

  Here, the transfer / conveying belt device 215 according to the second embodiment is also provided with contact / separation mechanisms 31 to 36 as in the intermediate transfer belt device 15 according to the first embodiment. The contact / separation mechanisms 31 to 36 are three photosensitive drums for color, excluding the photosensitive drums 1Y, 1M, and 1C (monochrome photosensitive drums 1K) as contact members that rotate in a predetermined direction. The primary transfer rollers 9Y, 9M, and 9C as the roller members that come into contact with the photosensitive drums 1Y, 1M, and 1C together with the transfer conveyance belt 208 are movable to and from the photosensitive drums 1Y, 1M, and 1C. The configuration is the same as that of the first embodiment.

Also in the second embodiment, when the monochrome image is formed, the separating means 33 to 36 rotate the arm members 31 of the three primary transfer rollers 9Y, 9M, and 9C for color, thereby transferring the image. The three primary transfer rollers 9Y, 9M, and 9C are separated from the conveyance belt 208, and the transfer conveyance belt 208 is opposed to only the black photosensitive drum 1K.
In such a contact / separation operation of the transfer conveyance belt 208, also in the second embodiment, the primary transfer rollers 9Y, 9M, and 9C (roller members) are replaced with the photosensitive drums 1Y, 1M, and 1C (contacted members). When the arm member 31 is rotated in the direction in which the arm member 31 is in contact with the arm member 31, the joint portion 32 a is moved away from the rotation shaft 31 a of the arm member 31. In contrast, when the arm member 31 rotates in a direction in which the primary transfer rollers 9Y, 9M, and 9C (roller members) are separated from the photosensitive drums 1Y, 1M, and 1C (contacted members), the joint portion 32a. Moves in a direction approaching the rotation shaft 31 a of the arm member 31.

  As described above, also in the second embodiment, similarly to the first embodiment, the primary transfer rollers 9Y, 9M, and 9C (roller members) are rotatably held and rotated around the rotation shaft 31a. A support shaft 32a as a joint portion between the arm member 31 to be engaged and the spring 32 that biases the arm member 31 toward the contact direction is configured to be movable. The support shaft 32a moves in a direction away from the rotation shaft 31a of the arm member 31 at the time of contact, and the support shaft 32a moves in a direction closer to the rotation shaft 31a of the arm member 31 at the time of separation. As a result, the maximum load torque and rotational load torque in the contact / separation operation of the primary transfer rollers 9Y, 9M, 9C with respect to the photosensitive drums 1Y, 1M, 1C (contacted members) are relatively small, and the impact in the contact / separation operation. The sound is relatively small, and the contact / separation mechanisms 31 to 36 (or the image forming apparatus 100) can be reduced in size and cost.

In the second embodiment, the present invention is applied to a belt device (transfer / conveying belt device 215) using a transfer / conveying belt 208 instead of the intermediate transfer belt 8 as a belt member. In contrast, a belt device using a transfer belt as a belt member (forming a toner image on a photosensitive drum on a recording medium conveyed to the transfer nip position while forming a transfer nip with the photosensitive drum). The present invention can also be applied to a contact / separation mechanism that performs a contact / separation operation of the transfer belt in the transfer belt device). Further, in a belt device using a photosensitive belt (which functions in the same manner as the photosensitive drum in each of the above embodiments and is an endless belt-shaped photosensitive member) as a belt member, the contact and separation of the photosensitive belt is performed. The present invention can also be applied to an approach / separation mechanism that performs an operation.
And also in these cases, the same effect as each said embodiment can be acquired by comprising a contacting / separating mechanism similarly to the thing of each said embodiment.

Embodiment 3 FIG.
A third embodiment of the present invention will be described in detail with reference to FIG.
FIG. 12 is a schematic diagram illustrating the operation of the contact / separation mechanism of the secondary transfer roller 19 according to the third embodiment. The image forming apparatus according to Embodiment 3 is provided with contact / separation mechanisms 71 to 73 that contact and separate the secondary transfer roller 19 from the intermediate transfer belt 8. This is different from that of the first embodiment in which the contact / separation mechanisms 31 to 36 that contact and separate the intermediate transfer belt 8 together with the primary transfer rollers 9Y, 9M, 9C, and 9K with respect to 1K are installed.

As shown in FIG. 12, the image forming apparatus according to the third embodiment is provided with contact / separation mechanisms 71 to 73 that contact and separate the secondary transfer roller 19 shown in FIG. 1 from the intermediate transfer belt 8. .
The contact / separation mechanisms 71 to 73 are capable of moving a secondary transfer roller 19 as a roller member that comes into contact with the intermediate transfer belt 8 as a contacted member that travels in a predetermined direction so that the secondary transfer roller 19 can come into contact with and separate from the intermediate transfer belt 8. To do. The contact / separation mechanism includes an arm member 71, a tension spring 72, an eccentric cam 73 serving as a separation means, a drive motor (not shown) that drives the eccentric cam 73, and the like.

The arm member 71 rotatably holds the shaft portions 19a at both ends of the secondary transfer roller 19 via a bearing (not shown). Furthermore, the arm member 71 is supported by a housing (not shown) of the apparatus main body 100 so as to be rotatable about a rotation shaft 71a.
The tension spring 72 biases the arm member 71 in a direction in which the secondary transfer roller 19 (roller member) contacts the intermediate transfer belt 8 (contacted member).
The eccentric cam 73 serving as the separating means is rotationally driven by a drive motor (not shown), and pushes the arm member 71 in a direction against the urging force of the tension spring 72 to cause the intermediate transfer belt 8 (contacted member) to move. On the other hand, the secondary transfer roller 19 (roller member) is separated. That is, the eccentric cam 73 in the state of FIG. 12A rotates by a predetermined angle and pushes the arm member 71 to the right in the figure, whereby the secondary transfer roller 19 is separated from the intermediate transfer belt 8 ( This is the state of FIG.

The eccentric cam 73 rotates the arm member 71 of the secondary transfer roller 19 during non-image formation (when the secondary transfer process is not performed at the position of the secondary transfer nip). The secondary transfer roller 19 is separated from the intermediate transfer belt 8 to reduce wear deterioration of the intermediate transfer belt 8 and the secondary transfer roller 19.
In such a contact / separation operation of the secondary transfer roller 19, also in the third embodiment, as shown in FIG. 12A, the secondary transfer roller 19 (roller member) is moved by the intermediate transfer belt 8 (covered member). When the arm member 71 rotates in a direction in which it abuts against the abutting member), the joint portion of the arm member 71 and the tension spring 72 (the support shaft 72a that supports one end of the tension spring 72) is the arm member 71. It moves in a direction away from the rotating shaft 71a. On the other hand, as shown in FIG. 12B, when the arm member 71 rotates in a direction in which the secondary transfer roller 19 (roller member) is separated from the intermediate transfer belt 8 (contacted member), the bonding is performed. The portion (support shaft 72a) moves in a direction approaching the rotation shaft 71a of the arm member 71.

  As described above, in the third embodiment, the arm member 71 that rotatably holds the secondary transfer roller 19 (roller member) and rotates about the rotation shaft 71a, and the arm toward the contact direction. A support shaft 72a as a joint portion with a spring 72 that biases the member 71 is configured to be movable. The support shaft 72a moves in a direction away from the rotation shaft 71a of the arm member 71 at the time of contact, and the support shaft 72a moves in a direction approaching the rotation shaft 71a of the arm member 71 at the time of separation. As a result, the maximum load torque and the rotational load torque in the contact / separation operation of the secondary transfer roller 19 with respect to the intermediate transfer belt 8 (contacted member) are relatively small, and the impact sound in the contact / separation operation is relatively small. The separation mechanisms 71 to 73 (or the image forming apparatus 100) can be reduced in size and cost.

Embodiment 4 FIG.
A fourth embodiment of the present invention will be described in detail with reference to FIG.
FIG. 13 is a schematic diagram illustrating the operation of the contact / separation mechanism of the fixing device 20 according to the fourth embodiment. In the image forming apparatus according to the fourth embodiment, the photosensitive drums 1Y, 1M, 1C, and 1K are provided with contact / separation mechanisms 81 to 83 that contact and separate the pressure roller 22 with respect to the fixing roller 21. In contrast, the primary transfer rollers 9Y, 9M, 9C, and 9K are different from those in the first embodiment in which the contact / separation mechanisms 31 to 36 that contact and separate the intermediate transfer belt 8 are installed.

As shown in FIG. 13, the image forming apparatus according to the fourth embodiment is provided with contact / separation mechanisms 81 to 83 for contacting and separating the pressure roller 22 with respect to the fixing roller 21 in the fixing device 20 shown in FIG. ing.
The contact / separation mechanisms 81 to 83 are configured to move a pressure roller 22 as a roller member that comes into contact with the fixing roller 21 as a contacted member that rotates in a predetermined direction so as to come into contact with and separate from the fixing roller 21. is there. The contact / separation mechanism includes an arm member 81, a tension spring 82, an eccentric cam 83 as a separation means, a drive motor (not shown) for driving the eccentric cam 83, and the like.

The arm member 81 rotatably holds the shaft portions 22a at both ends of the pressure roller 22 via a bearing (not shown). Further, the arm member 81 is supported by the casing (not shown) of the fixing device 20 so as to be rotatable about the rotation shaft 81a.
The tension spring 82 urges the arm member 81 in a direction in which the pressure roller 22 (roller member) contacts the fixing roller 21 (contacted member).
The eccentric cam 83 serving as the separation means is driven to rotate by a drive motor (not shown), and pushes the arm member 81 in a direction against the urging force of the tension spring 82 to move against the fixing roller 21 (contacted member). Thus, the pressure roller 22 (roller member) is separated. That is, the eccentric cam 83 in the state of FIG. 13A rotates by a predetermined angle and pushes the arm member 81 rightward in the drawing, so that the pressure roller 22 is separated from the fixing roller 21 (FIG. 13). (B) state.)

When the non-image is formed (when the fixing process is not performed at the position of the fixing nip) or the like, the eccentric cam 83 rotates the arm member 81 of the pressure roller 22 so as to add from the fixing roller 21. The pressure roller 22 is separated to reduce wear deterioration of the fixing roller 21 and the pressure roller 22.
In such contact / separation operation of the pressure roller 22, also in the fourth embodiment, as shown in FIG. 13A, the pressure roller 22 (roller member) is replaced with the fixing roller 21 (contacted member). When the arm member 81 rotates in the direction in which the arm member 81 is in contact with the arm member 81, the joint portion of the arm member 81 and the tension spring 82 (the support shaft 82a that supports one end of the tension spring 82) is the rotation shaft 81a of the arm member 81. Move away from. On the other hand, as shown in FIG. 13B, when the arm member 81 rotates in a direction in which the pressure roller 22 (roller member) is separated from the fixing roller 21 (contacted member), the joint ( The support shaft 82a) moves in a direction approaching the rotation shaft 81a of the arm member 81.

  As described above, in the fourth embodiment, the arm member 81 that rotatably holds the pressure roller 22 (roller member) and rotates around the rotation shaft 81a, and the arm member toward the contact direction. A support shaft 82a as a joint portion with a spring 82 that biases 81 is configured to be movable. The support shaft 82a moves in a direction away from the rotation shaft 81a of the arm member 81 when contacting, and the support shaft 82a moves in a direction approaching the rotation shaft 81a of the arm member 81 when separated. As a result, the maximum load torque and the rotational load torque in the contact / separation operation of the pressure roller 22 with respect to the fixing roller 21 (contacted member) are relatively small, and the impact sound in the contact / separation operation is relatively small. 81-83 (or image forming apparatus 100) can be reduced in size and cost.

  In addition, the present invention is not limited to each of the above-described embodiments, and within the scope of the technical idea of the present invention, this embodiment can be modified as appropriate in addition to those suggested in each of the above-described embodiments. it is obvious. In addition, the number, position, shape, and the like of the constituent members are not limited to the above embodiments, and can be set to a number, position, shape, and the like that are suitable for carrying out the present invention.

1Y, 1M, 1C, 1K photosensitive drum (contact member),
8 Intermediate transfer belt (belt member),
9Y, 9M, 9C, 9K primary transfer roller (roller member),
12 Drive roller,
13 Followed roller,
15 Intermediate transfer belt device (belt device),
31 arm member,
31a Rotating shaft, 31b Contact part, 31c Guide groove (guide part),
32 tension spring,
32a spindle (joint),
33 Swing plate (separating means),
34 Eccentric cam (separation means),
35 Drive shaft (separation means),
36 drive motor (separation means),
100 Image forming apparatus main body (apparatus main body).

JP 2008-216969A Japanese Patent No. 3968238

Claims (5)

A contact / separation mechanism that moves a roller member that contacts a contacted member that rotates or travels in a predetermined direction so as to be able to contact and separate from the contacted member.
An arm member that holds the roller member rotatably and is supported rotatably about a rotation axis;
A spring that biases the arm member in a direction in which the roller member abuts on the abutted member;
Separation means for pushing the arm member in a direction against the urging force of the spring to separate the roller member from the contacted member;
With
The joint between the arm member and the spring is configured to be movable,
When the arm member rotates in a direction in which the roller member contacts the contacted member, the joint moves in a direction away from the rotation shaft of the arm member, and the roller member moves to the contacted portion. When the arm member rotates in a direction away from the arm member, the joining portion moves in a direction approaching the rotation axis of the arm member. The joint is a support shaft that supports one end of the spring,
The arm member includes a groove-shaped or hole-shaped guide portion that extends to a position away from a position close to the rotation shaft so that the support shaft of the spring slides as the arm member rotates. The contact / separation mechanism according to claim 1. The biasing force of the spring against the arm member is configured not to act in a direction separating the arm member from the abutted member when the roller member is in a position to abut against the abutted member,
The biasing force of the spring against the arm member is configured not to act in a direction to bring the arm member closer to the abutted member when the roller member is at a position away from the abutted member. The contact / separation mechanism according to claim 1, wherein: The contact member is in pressure contact with the roller member via any one of an intermediate transfer belt, a transfer conveyance belt, a transfer belt, a photosensitive belt, and a fixing belt,
The contact / separation mechanism according to any one of claims 1 to 3, wherein the belt member is brought into contact with and separated from the contacted member together with the roller member.   An image forming apparatus comprising the contact / separation mechanism according to claim 1.

Images