JP3562932B2 - Image forming apparatus and transfer apparatus - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an image forming apparatus such as a copying machine, a facsimile, a printer, and the like, and a transfer device used in the image forming apparatus.
[0002]
[Prior art]
Conventionally, as this type of image forming apparatus, an image forming apparatus that forms an electrostatic latent image on a photoconductor as an image carrier and visualizes the latent image with charged toner is known. Further, the toner image on the photoreceptor was directly transferred to a transfer paper as a final transfer material under a transfer electric field, or was once transferred to an intermediate transfer member as an intermediate transfer material under a transfer electric field. Later, what is transferred to a transfer paper as a final transfer material is known.
[0003]
Further, it has a transfer belt as an endlessly movable transfer member, and a support roller as a plurality of transfer member supports for supporting the transfer belt, and has a predetermined tension in contact with the image carrier. An image forming apparatus having a transfer device for transferring a toner image from an image carrier is also known.
[0004]
In the image forming apparatus having the above configuration, when the transfer belt is replaced, for example, at the end of the life of the transfer belt, it is necessary to relax the tension in order to remove the belt. However, conventionally, in order to loosen the tension of the belt, a predetermined roller among the plurality of support rollers has been removed. That is, when replacing the transfer belt, first, the predetermined roller is removed, the belt is replaced, and then the removed roller is mounted again. Therefore, there is a problem that the operability is poor, the positional accuracy at the time of re-attaching the roller once removed is poor, and the tension of the belt changes before and after the removal of the belt.
There is also known a configuration in which a tension releasing mechanism for relaxing the tension of the transfer belt is provided. According to this configuration, the tension of the belt does not change before and after the attachment and detachment of the belt.
[0005]
Further, in the transfer device of the image forming apparatus having the above configuration, when the photoreceptor as an image bearing member with which the belt is in contact with a predetermined tension is attached to or detached from the main device for replacement or the like, the transfer device is connected to the main device. When detaching the belt from the photosensitive member, it is necessary to separate the belt from the photosensitive member. In a conventional apparatus, a contact / separation mechanism for contacting / separating the transfer belt from / to the photosensitive member is provided, and the transfer belt is separated from the photosensitive member by the mechanism to perform the detaching operation.
[0006]
[Problems to be solved by the invention]
However, if the tension release mechanism and the contact / separation mechanism are provided in the transfer device of the image forming apparatus having the above-described configuration, there is a problem that the device becomes large and complicated.
[0007]
Such a problem is caused not only by the transfer device but also by a belt-shaped member that can move endlessly for image formation, three or more belt supports that support the belt-shaped member, and contact with the belt-shaped member. This can occur in an image forming apparatus having an image forming member that performs an operation for forming a predetermined image in a state where the image forming apparatus is in a state of being performed.
[0008]
The present invention has been made in view of the above problems, and an object of the present invention is to provide an image forming apparatus and a transfer apparatus that can reduce the size and simplify the apparatus.
[0009]
[Means for Solving the Problems]
In order to achieve the above object, according to the first aspect of the present invention, an endlessly movable belt-like member for image formation, a plurality of belt supports supporting the belt-like member, and the belt-like member are in contact with the belt-like member. An image forming member that performs an operation for forming a predetermined image in a state, wherein an extending portion of the belt-like member between the plurality of belt supports is opposed to the image forming member. Providing a movable support member for supporting the belt-shaped member, displacing the support member to three positions, such that the belt-shaped member comes into contact with the image forming member with a predetermined tension, To be able to selectively take a state in which the belt-shaped member is separated from the image forming member and a state in which the belt-shaped member is slackened to such an extent that the belt-shaped member can be removed from the belt support, Up In which it characterized in that a state change means for changing the state of the belt-shaped member.
[0010]
In this image forming apparatus, the movable member supporting the belt-shaped member on the surface of the stretched portion between the plurality of belt supports of the belt-shaped member facing the image forming member by the state changing means. By displacing the belt-shaped member to three positions, a state in which the belt-shaped member contacts the image-forming member with the predetermined tension, a state in which the belt-shaped member is separated from the image-forming member, The belt-shaped member can selectively take three states, that is, a state in which the belt-shaped member is slackened to such an extent that the belt-shaped member can be removed from the support.
[0011]
According to a second aspect of the present invention, in the image forming apparatus according to the first aspect, when the belt-shaped member is separated from the image forming member, the tension of the belt-shaped member is smaller than the predetermined tension, and The state changing means is configured so that the tension is set to such a level that the belt-shaped member does not separate from the support.
[0012]
In this image forming apparatus, when the belt-shaped member is separated from the image-forming member by the state changing means, the tension of the belt-shaped member is smaller than the predetermined tension, and The tension is set so that the member does not separate from the support.
[0013]
According to a third aspect of the present invention, in the image forming apparatus according to the first or second aspect, an image carrier that carries a toner image on a surface is used as the image forming member, and toner from the image carrier is used as the belt-shaped member. A transfer member on which an image is transferred is used, and a transfer member support is used as the belt support.
[0014]
In this image forming apparatus, the movable member is displaced to three positions by the state changing means, and the state of the transfer body on which the toner image is transferred from the image carrier is changed to the three states. Can be changed selectively.
[0015]
The invention according to claim 4 has an endlessly movable belt-shaped transfer member, and a plurality of transfer member supports for supporting the transfer member, wherein the transfer member is in contact with the image carrier with a predetermined tension. In a transfer apparatus for transferring a toner image from an image carrier, a movable support member for supporting the transfer body on a surface of the extending portion of the transfer body between the plurality of transfer body supports opposed to the image carrier. By displacing the support member to three positions, the transfer member has a predetermined tension, the transfer member is separated from the image carrier, and the transfer member is provided on the transfer member. Is provided with a state changing means for changing the state of the transfer body so as to selectively take a state in which the transfer body is loosened to such an extent that the transfer body can be removed from the transfer body support.
[0016]
In this transfer device, the movable member for supporting the transfer body on the surface of the extending portion of the transfer body between the plurality of transfer body supports facing the image carrier is provided by the state changing means. By displacing the transfer member to the position, the transfer member is brought into contact with the image carrier with the predetermined tension, the transfer member is separated from the image carrier, and the transfer member is attached to the transfer member. Can be selectively taken into three states, i.e., a state in which the slack is loose enough to be detached from the support.
[0017]
According to a fifth aspect of the present invention, in the transfer device according to the fourth aspect, when the transfer body is separated from the image carrier, the tension of the transfer body is smaller than the predetermined tension, and the transfer body is The state changing means is configured to set the tension to such a level that the tension does not separate from the support.
[0018]
In this transfer device, when the transfer body is separated from the image carrier by the state changing means, the tension of the transfer body is smaller than the predetermined tension, and the transfer body is Set the tension so that it does not come off.
[0019]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, an embodiment in which the present invention is applied to an electrophotographic color copying machine (hereinafter, referred to as a “color copying machine”) that is an image forming apparatus will be described.
[0020]
First, the schematic configuration and operation of an image forming unit, which is a main part of the color copying machine, will be described with reference to FIG. This color copying machine includes, in addition to the image forming unit shown in FIG. 4, a color image reading unit (hereinafter, referred to as a color scanner) (not shown), a paper feeding unit, a control unit, and the like. The image forming unit includes a photoconductor drum 100 as an image carrier, which is an image forming member, a charging charger 200, a photoconductor cleaning device 300 including a cleaning blade and a fur brush, a writing optical unit (not shown), a revolver developing unit 400, The image forming apparatus includes an intermediate transfer unit 500 as an intermediate transfer device, a paper transfer unit 600, a fixing unit using a fixing roller pair 701, and the like.
[0021]
The photoconductor drum 100 is rotated in a counterclockwise direction indicated by an arrow by a drive motor (not shown). Around the circumference, the charger 200, the photoconductor cleaning device 300, the selected developing device of the revolver developing unit 400, and the intermediate transfer unit 500 And an intermediate transfer belt 501 as an intermediate transfer member.
[0022]
The revolver developing unit 400 uses a Bk (Black) toner using a Bk developing device 401, a C (Cyan) toner using a C (Cyan) toner, a M developing device 403 using an M (Mazennt) toner, and a Y (Yellow) toner. It comprises a Y developing device 404 and a developing revolver drive unit (not shown) for rotating the whole unit counterclockwise. The toner in each developing unit is charged to a desired polarity by agitation with the carrier, and a developing bias voltage is applied to each developing sleeve by a developing bias power supply (not shown). Is biased to a predetermined potential.
[0023]
The intermediate transfer unit 500 includes an intermediate transfer belt 501 or the like as an intermediate transfer member stretched over a plurality of rollers functioning as a transfer member support, and a secondary transfer charge application around the intermediate transfer belt 501. A secondary transfer bias roller 605 as a unit, a belt cleaning blade 504 as an intermediate transfer body cleaning unit, a lubricant applying brush 505 as a lubricant applying unit, and the like are provided so as to face each other.
[0024]
The intermediate transfer belt 501 includes the plurality of rollers, specifically, a primary transfer bias roller 507 as a primary transfer charge applying unit, a belt driving roller 508 also serving as a cleaning opposing roller, a belt tension roller 509, and a secondary transfer roller. The transfer opposing roller 510 is stretched around a belt discharging roller 512 as a pre-primary transfer discharging device. Each roller is formed of a conductive material, and each roller other than the primary transfer bias roller 507 is grounded. To the primary transfer bias roller 507, a transfer bias of a predetermined magnitude of current or voltage is applied by a primary transfer power supply 801 controlled by a constant current or constant voltage method. The intermediate transfer belt 501 is driven in a clockwise direction indicated by an arrow by a belt driving roller 508 that is rotationally driven by a driving motor (not shown).
[0025]
In a transfer unit (hereinafter, referred to as a “primary transfer unit”) that transfers the toner image on the photosensitive drum 100 to the intermediate transfer belt 501, a primary transfer bias roller 507 and a belt charge removal roller 512 serving as a charge removal unit before the primary transfer. The intermediate transfer belt 501 is stretched so as to be pressed against the photosensitive drum 100 side, thereby forming a nip portion having a predetermined width between the photosensitive drum 100 and the intermediate transfer belt 501. Further, a grounded belt neutralization brush 513 as a primary transfer unit neutralization unit is in contact with the inner peripheral surface of the intermediate transfer belt 501 in the nip portion.
[0026]
The belt cleaning blade 504 is in contact with the intermediate transfer belt 501 around the belt driving roller 508 also serving as a cleaning opposite roller by a counter method.
[0027]
The belt cleaning blade 504 and the lubricant application brush 505 are configured to be able to be separated from and contacted with the intermediate transfer belt 501, and are controlled so as to contact the intermediate transfer belt 501 at a predetermined timing.
0024
The secondary transfer bias roller 605 is disposed so as to sandwich the intermediate transfer belt 501 and the transfer paper between the secondary transfer bias roller 605 and the secondary transfer facing roller 510, and transfers a predetermined current with a secondary transfer power supply 802 controlled at a constant current. A bias is applied.
[0028]
In the above-described color copying machine, for example, when a four-color full-color copying operation is started, the photosensitive drum 100 is uniformly charged to a negative polarity by the charging charger 200, exposed by the writing optical unit, and developed at a predetermined timing. By developing the electrostatic latent image by the developing device moved to the position, a Bk toner image, a C toner image, an M toner image, and a Y toner image are sequentially formed on the photosensitive drum 100. Each toner image on the photosensitive drum 100 is transferred in a primary transfer portion while being superimposed on the same surface of the intermediate transfer belt 501. Note that a small amount of untransferred residual toner remaining on the surface of the photoconductor drum 100 after the transfer of the toner image is cleaned by the photoconductor cleaning device 300.
[0029]
The four-color superimposed toner image on the intermediate transfer belt 501 is fed from a paper supply unit (not shown) in a secondary transfer unit where a nip is formed by a secondary transfer facing roller 510 and a secondary transfer bias roller 605. Is transferred onto a transfer paper as a transfer material. The transfer sheet onto which the four-color superimposed toner image has been transferred is fixed by the fixing roller pair 701, and then is discharged to a discharge unit (not shown).
[0030]
On the other hand, the toner remaining on the surface of the intermediate transfer belt 501 after the transfer of the toner image to the transfer paper is cleaned by a belt cleaning blade 504 abutted on the intermediate transfer belt 501 by a contact / separation mechanism (not shown).
[0031]
The above is the case of four-color full-color copying. However, in the case of three-color copying and two-color copying, the same operation as described above is performed for the designated color and the number of times. In the case of a mono-color copy, only the developing device of the predetermined color of the revolver developing unit 400 is in the developing operation state until the predetermined number of sheets is completed, and the belt cleaning blade 504 is pressed against the intermediate transfer belt 501. The copy operation is performed continuously with the operation as it is.
[0032]
Next, an operation of changing the state of the intermediate transfer belt in the intermediate transfer unit 500 according to the present embodiment will be described with reference to FIGS. FIGS. 1 to 3 are cross-sectional views for explaining the operation of the intermediate transfer unit 500 for changing the state of the intermediate transfer belt. The intermediate transfer unit 500 is fixed to the apparatus main body via a face plate 514 on the front side of the apparatus. In this intermediate transfer unit, a tension changing mechanism as a state changing means includes a cam shaft 515a, a cam 515 rotatable around the cam shaft, a primary transfer bias roller 507 as a movable support member, and a belt neutralization. A tension bracket 517 that can swing around a shaft 516 while holding the roller 512 is provided. Further, a lever 518 for an operator to operate the tension varying mechanism when the belt is attached or detached is attached to a shaft end of the cam shaft 515a on the front side of the apparatus. The lever 518 is located closer to the apparatus than the face plate 514, and a hole 514a for allowing the lever 518 to escape is provided in the face plate 514. FIG. 5 is an explanatory diagram of the lever 518. The direction of the arrow in the figure is the front side of the apparatus. The operator operates the lever 518 by grasping the handle 518a. The lever 518 is configured to be swingable about a cam shaft 515a and swingable in the direction of arrow A in the figure. The tension variable mechanism can be operated by the operator rotating the lever 518 about the cam shaft 515a. An opening 518b is provided at a predetermined position of the lever 518, and the opening 518b is engaged with a pin 519a provided on the face plate 514 or a pin 519b provided on the front plate of the intermediate transfer unit. As a result, the state of the intermediate transfer unit can be fixed as described later.
[0033]
Then, the intermediate transfer unit can selectively take the first state shown in FIG. 1, the second state shown in FIG. 2, and the third state shown in FIG. 3 by the variable tension mechanism. Is configured. Hereinafter, each state will be described.
(Hereinafter, margin)
[0034]
When the copying machine is left for a long time before shipment, or when the intermediate transfer unit or the photosensitive drum 100 is detached from the copying machine main body, the intermediate transfer unit is set to the first state shown in FIG. In the first state, the intermediate transfer belt of the intermediate transfer unit is at a position separated from the photosensitive drum 100. In this state, in order to prevent the belt from being curled, the tension of the belt is set smaller than the tension during the transfer operation of the intermediate transfer unit. Further, the tension is set to such a level that the intermediate transfer belt does not separate due to the vibration or the like in order to prevent the intermediate transfer belt from separating from the roller supporting the belt due to vibration during transportation of the apparatus. I do. For example, when the tension is set to a value of 0N or more and 20N or less, and the tension is set to 0N, the belt may be set so that the slack of the belt does not separate from the belt. In this state, as described above, the opening 518b of the lever 518 is engaged with a pin (not shown) provided on the front side plate of the intermediate transfer unit to prevent the cam shaft from rotating due to vibration during transportation of the apparatus. Fix the lever position.
[0035]
When performing the transfer operation to the intermediate transfer belt, the intermediate transfer unit is set to the second state shown in FIG. In the second state, the intermediate transfer belt is in contact with the photosensitive drum 100 with a predetermined tension. In order to operate the intermediate transfer unit to take this second state, the lever 518 is rotated so as to be located at the position shown in FIG. 2, and the opening 518b of the lever 518 is moved as described above. It is engaged with a pin (not shown) formed on the face plate 514 and fixed at this position. At this time, the cam shaft 515a is rotated by the rotation of the lever 518, and the cam 515 pushes up the tension bracket 517, so that the primary transfer bias roller 507 and the belt discharging roller 512 are displaced, and push up the intermediate transfer belt 501. Thus, the intermediate transfer belt comes into contact with the photosensitive drum 100 as shown in FIG.
[0036]
When the intermediate transfer belt 501 needs to be replaced due to abrasion or the like by performing the transfer operation, first, the lever 518 is rotated and fixed so as to take the first state, and then the intermediate transfer belt 501 is rotated. The unit 500 is removed from the apparatus main body. Next, the fixing of the lever 518 is released, and the lever is rotated to the position shown in FIG. The rotation of the lever 518 rotates the cam shaft 515a, and the primary transfer bias roller 507 and the belt neutralizing roller 512 move down together with the tension bracket 517, so that the intermediate transfer belt 501 is moved between the belt driving roller 508 and the belt tension roller 509. Becomes a substantially straight line. In the third state shown in FIG. 3, the tension of the intermediate transfer belt is released, and the intermediate transfer belt becomes slack. Normally, the intermediate transfer belt is provided with a belt detent member 520 to prevent the intermediate transfer belt from shifting in the axial direction of a roller for supporting the belt, in the illustrated example, a belt tension roller 509 as shown in FIG. I have. For the operability of attaching and detaching the belt, it is preferable that a slack of, for example, 15 mm or more is generated by the thickness of the stopper member. This makes it possible to easily replace only the belt without attaching and detaching the roller supporting the belt.
[0037]
As described above, according to the present embodiment, the primary transfer bias roller 507 and the belt neutralizing roller 512 as the movable support members fixed to the tension bracket 517 are moved to the three positions by the cam 515 by the tension varying mechanism. A first state in which the intermediate transfer belt 501 is separated from the photosensitive drum 100 only by displacement, and a second state in which the intermediate transfer belt 501 contacts the photosensitive drum 100 with a predetermined tension. And the third state in which the tension of the intermediate transfer belt 501 is released and the slack occurs. Accordingly, unlike the case where a tension release mechanism for releasing the tension of the intermediate transfer belt 501 and a contact / separation mechanism for bringing the intermediate transfer belt 501 and the photosensitive drum 100 into and away from each other are provided, the size and simplification of the apparatus can be reduced. It becomes possible.
[0038]
According to this embodiment, when the intermediate transfer belt 501 is separated from the photosensitive drum 100, the tension of the intermediate transfer belt 501 is smaller than the predetermined tension, and the belt supports the belt. The tension is set to such a degree that the intermediate transfer belt does not separate from the support roller, which prevents the belt from being curled and prevents the intermediate transfer belt from separating from the support roller due to vibration during transportation of the apparatus. can do.
[0039]
In the above-described embodiment, an example is described in which the photosensitive drum 100 serving as an image carrier is used as an image forming member and the intermediate transfer belt 501 serving as a transfer body is used as a belt-shaped member. Also, an image forming apparatus using, for example, a photoreceptor belt that is stretched between two rollers and is endlessly moved as an image carrier as a belt-shaped member, and a transfer roller for transfer is used as an image forming member. Can be applied.
[0040]
Further, in the above-described embodiment, an example was described in which a charge elimination brush was used as the primary transfer portion charge elimination means in the nip portion of the primary transfer portion. It can also be applied to those using members of other shapes.
[0041]
Further, in the above-described embodiment, an example in which the primary transfer bias applying roller is used as the primary transfer charge applying unit has been described. However, the present invention is also applied to an apparatus employing a primary transfer charge applying unit having another shape. be able to.
[0042]
In the above-described embodiment, the example in which the belt static elimination roller 512 is used as the pre-primary transfer static elimination means has been described. Can be applied.
[0043]
In the above-described embodiment, an example in which a secondary transfer bias roller is used as the secondary transfer charge applying unit has been described. However, the present invention is applicable to a device using another member such as a blade or a brush instead of this roller. Can also be applied.
[0044]
In the above-described embodiment, the secondary transfer belt 601 is used as the transfer material carrier for supporting the transfer material in the secondary transfer unit. However, the present invention uses a member of another shape such as a drum instead of the belt. It can also be applied to what was there.
[0045]
Further, in the above embodiment, the case where the charging potential of the photosensitive drum 100 is negative and the developing device adopting the reversal developing method using the two-component type developer is described. The charging potential of the body drum 100 is not limited to the one having a negative polarity, and can be similarly applied to the one using a one-component developer or the one using a regular development system.
[0046]
Further, the above embodiment is an example in which the present invention is applied to an image forming apparatus having an intermediate transfer unit. The present invention can be similarly applied to an image forming apparatus configured to directly transfer to a sheet. In this case, specifically, a transfer belt can be used as the belt-shaped member, and an image carrier can be used as the image forming member.
[0047]
【The invention's effect】
According to the first to third aspects of the present invention, the state in which the belt-shaped member has the predetermined tension is achieved only by displacing the movable support member to three positions by the state-changing means. Can be selectively removed between a state in which the belt-shaped member is separated from the image forming member and a state in which the belt-shaped member is slackened to such an extent that the belt-shaped member can be removed from the support. In contrast to the case where a tension release mechanism for releasing the pressure and a contact / separation mechanism for contacting / separating the belt-shaped member and the image forming member are provided, there is an excellent effect that the apparatus can be reduced in size and simplified.
[0048]
According to the invention of claims 2 and 3, when the transfer body is separated from the image carrier, the tension of the transfer body is smaller than the predetermined tension, and the transfer body is supported by the support. Since the tension is set so as not to be detached from the body, it is possible to prevent the transfer body from being curled, and also to prevent the transfer body from being detached from the support due to vibration during transportation of the apparatus. There is an excellent effect that it can be done.
[0049]
According to the third aspect of the present invention, the state of the transfer member where the transfer of the toner image from the image carrier is performed only by displacing the movable support member to three positions by the state changing means. The above three states can be selectively changed, so that a tension releasing mechanism for releasing the tension of the belt-shaped member and a contact / separation mechanism for bringing the belt-shaped member and the image forming member into and out of contact with each other are provided. In contrast, there is an excellent effect that the device can be reduced in size and simplified.
[0050]
According to the fourth and fifth aspects of the present invention, the state in which the transfer member has the predetermined tension is obtained only by displacing the movable support member to three positions by the state changing means. Can be selectively removed from a state in which the transfer body is separated from the image carrier, and a state in which the transfer body is slackened to such an extent that the transfer body can be removed from the support. Unlike the case where a release mechanism and a contact / separation mechanism for bringing the transfer member and the image carrier into and out of contact with each other are provided, there is an excellent effect that the apparatus can be reduced in size and simplified.
[0051]
In particular, according to the invention of claim 5, when the transfer member is separated from the image carrier, the tension of the transfer member is smaller than the predetermined tension, and the transfer member is moved from the support. Since the tension is set to such a level that the transfer member is not detached, it is possible to prevent the transfer member from being curled and to prevent the transfer member from detaching from the support due to vibration during transportation of the apparatus. Has an excellent effect.
[Brief description of the drawings]
FIG. 1 is an explanatory diagram of an intermediate transfer unit of a color copying machine according to an embodiment.
FIG. 2 is another explanatory diagram of the intermediate transfer unit.
FIG. 3 is another explanatory view of the intermediate transfer unit.
FIG. 4 is a front view showing a schematic configuration of an example of a color copying machine having the intermediate transfer unit.
FIG. 5 is an explanatory diagram of a lever of a variable tension mechanism of the intermediate transfer unit.
FIG. 6 is an explanatory diagram of a belt deviation preventing member of the intermediate transfer belt.
[Explanation of symbols]
100 Photoconductor drum
200 Charger
300 Photoconductor cleaning device
400 revolver developing unit
500 Intermediate transfer unit
501 Intermediate transfer belt
507 Primary transfer bias roller
512 belt static elimination roller
514 face plate
515 cam
515a camshaft
516 axes
517 Tension bracket
518 lever
600 paper transfer unit
701 fusing roller pair

Claims (5)

For image formation, an endlessly movable belt-shaped member,
A plurality of belt supports for supporting the belt-shaped member,
An image forming apparatus having an image forming member that performs an operation for forming a predetermined image while being in contact with the belt-shaped member,
A movable support member for supporting the belt-shaped member is provided on a surface of the extending portion of the belt-shaped member between the plurality of belt supports facing the image forming member, and the support member is displaced to three positions. Thereby, the state in which the belt-shaped member contacts the image forming member with a predetermined tension, the state in which the belt-shaped member is separated from the image forming member, and the state in which the belt-shaped member is An image forming apparatus comprising: a state changing unit that changes a state of the belt-shaped member so that the member can be selectively removed from a state in which the member is loosened so as to be detachable from the belt support. The image forming apparatus according to claim 1,
When the belt-shaped member is separated from the image forming member, the tension of the belt-shaped member is set to a tension smaller than the predetermined tension and to such a degree that the belt-shaped member does not separate from the support. An image forming apparatus comprising the above-mentioned state changing means. The image forming apparatus according to claim 1, wherein
As the image forming member, using an image carrier that carries a toner image on the surface,
Using a transfer body on which a toner image is transferred from the image carrier as the belt-shaped member,
An image forming apparatus, wherein a transfer member support is used as the belt support. A belt-shaped transfer body that can move endlessly,
Having a plurality of transfer member supports for supporting the transfer member,
In a transfer device that transfers a toner image from the image carrier in a state of being in contact with the image carrier with a predetermined tension,
By providing a movable support member that supports the transfer body on a surface of the extending portion of the transfer body between the plurality of transfer body supports facing the image carrier, and displacing the support member to three positions. And a state in which the transfer body has a predetermined tension, a state in which the transfer body is separated from the image carrier, and a state in which the transfer body is slackened to such an extent that the transfer body can be removed from the transfer body support. A transfer device comprising a state changing means for changing a state of the transfer body so that the state can be selectively taken. The transfer device according to claim 4,
When the transfer body is separated from the image carrier, the tension of the transfer body is smaller than the predetermined tension, and set such that the transfer body does not separate from the support. A transfer device comprising the state changing means.

Images