JP2004198680A - Transfer device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problems that an endless belt used to transfer a transfer sheet or to transfer an image becomes longer in terms of circumferential length, then, the apex part of a tension roller for applying a fixed tensile force on the belt becomes higher, and also, the belt unit becomes higher in height, besides, the resistance applied on the belt is increased, then, a slip easily occurs at a belt drive by a driving roller, as for an apparatus for forming an image by using several photoreceptors. <P>SOLUTION: In a belt device to be used in this transfer device, a primary transfer belt 10 is constituted so as to be rotated in a direction shown by arrow A by the driving roller 11 and supporting rollers 12, 15 and 17. In the belt device, a prescribed tensile force is applied on the belt by the tension roller 16 and a curving roller 14 being a curving member is allowed to abut on the belt from the outside between the driving roller 11 and the tension roller 16, and the belt is largely curved inwardly. Thus, the belt winding angle to the driving roller is increased, thereby downsizing the belt unit in the height direction. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
[Industrial applications]
The present invention relates to a transfer device in an image forming apparatus. More specifically, the present invention relates to a belt device used in a transfer device.
[0002]
[Prior art]
Typical methods of forming a color image include a direct transfer method in which toner images of different colors formed on a plurality of photoconductors are transferred while being directly superimposed on transfer paper, and a toner of different colors formed on a plurality of photoconductors. There is an intermediate transfer method in which an image is transferred while being superimposed on an intermediate transfer member, and then transferred collectively to transfer paper. Since a plurality of photoconductors are arranged side by side so as to face a transfer paper or an intermediate transfer body, it is called a tandem system, and yellow (Y), magenta (M), cyan (C), and black (K) are provided for each photoconductor. An electrophotographic process such as formation and development of an electrostatic latent image is executed for each color, and the image is transferred onto a running transfer paper in the direct transfer system, or onto a running intermediate transfer body in the intermediate transfer system.
[0003]
In a tandem type color image forming apparatus using each of these methods, an endless belt running while supporting a transfer paper is received in a direct transfer method, and an image is received from a photoconductor in an intermediate transfer method. It is common to employ an endless belt to carry. Then, an image forming unit including four photoconductors is arranged side by side on one running side of the belt. As described above, in the belt, the surface facing the image carrier, such as the photoconductor, is referred to as the front surface for convenience, and the opposite surface is referred to as the back surface.
In the tandem-type color image forming apparatus, it is important to accurately overlap toner images of respective colors in order to prevent occurrence of color misregistration.
[0004]
When the number of photoreceptors is increased, the size of the mechanical device is increased, but the peripheral length of the endless belt is inevitably increased, and there is a problem that the tension of the belt is easily loosened. Generally, in order to apply tension to the belt, a roller called a tension roller is applied from the back surface of the belt, and tension is applied to the belt by a pressing spring or the like.
FIG. 7 is a schematic diagram of a belt unit showing how to apply tension of a conventional endless belt.
In the figure, reference numeral 10 denotes an endless belt, 11 denotes a driving roller, 12, 15, 16, and 17 denote support rollers, A denotes a running direction of the belt, and Y, M, C, and K denote colors.
[0005]
The support roller 16 has a role of a tension roller. Hereinafter, when it is distinguished from the others, it is simply referred to as a tension roller 16.
The reason why the tension roller 16 is applied from the back side of the belt is that the front surface is in contact with the photoreceptor, so that the belt surface is not much damaged. Therefore, the endless belt is folded by the drive roller 11 from the side where the photoconductors are lined up and moves to the position on the opposite side, whereupon the tension roller portion jumps out on the side opposite to the side where the photoconductors are present. Height H ₁ Is the height H of the top of the drive roller which is essential for the function. ₀ And the belt unit becomes larger in the height direction. Here, the height refers to a height in a vertical direction from a belt surface with which a plurality of photoconductors are in contact. The belt surface with which a plurality of photoconductors are in contact is referred to as a reference surface for convenience.
In the current situation where miniaturization of the entire mechanical device is required, miniaturization must be achieved for each unit.
[0006]
When tension is applied to the belt by the tension roller, the opening angle θ of the belt on both sides of the tension roller must be set to a value smaller than 180 ° in order to obtain stable tension. The figure shows an example of about 150 °.
If the tension roller is applied from the front surface of the belt, in order to apply the same tension, the tension roller is located at the position 16 'in the drawing, and is too close to the primary transfer roller. Failure occurs.
Further, when the number of the photoconductors is plural, the resistance during the running of the endless belt is increased, so that the load is applied to the driving side. Winding angle B around drive roller 11 ₁ Otherwise, slip occurs with the endless belt, and correct transfer cannot be performed.
[0007]
[Problems to be solved by the invention]
Provided is a belt device in which the height of a belt unit is reduced to reduce the size of the device, and furthermore, the winding angle of the belt around a drive roller is increased to obtain a stable belt drive.
[0008]
[Means for Solving the Problems]
According to the first aspect of the present invention, the surface is in contact with a plurality of image carriers arranged substantially linearly to form a reference surface, and the back surface is hung over a drive roller and a plurality of support rollers. In the endless belt driven to rotate in the direction, the endless belt is in contact with the front surface facing the side opposite to the side on which the image bearing member is arranged, and curves the endless belt in a direction approaching the reference surface side. It is characterized by having an application member.
[0009]
According to the second aspect of the present invention, in the belt device according to the first aspect, the bending imparting member is a support that is disposed adjacent to the downstream of the driving roller in the moving direction of the endless belt among the plurality of support rollers. It is characterized by being arranged between a roller and the driving roller.
According to the third aspect of the present invention, in the belt device according to the second aspect, a height of the top of the support roller disposed adjacent to the downstream side of the drive roller from the reference surface is a top of the drive roller. Is not higher than the height from the reference plane.
[0010]
According to a fourth aspect of the present invention, in the belt device according to the second or third aspect, the bending member also serves as a tension member.
According to a fifth aspect of the present invention, in the belt device according to the second or third aspect, the support roller disposed adjacent to and downstream of the drive roller is a tension roller.
[0011]
According to a sixth aspect of the present invention, in the belt device according to any one of the first to fifth aspects, the bending imparting member is detachable or movable in a direction for releasing the bending of the endless belt. And
According to a seventh aspect of the present invention, in the belt device according to any one of the first to sixth aspects, the bending member is fixed to the belt device at least during use of the device, and the endless belt is fixed to the bending device. It is characterized by sliding with respect to a member.
[0012]
According to an eighth aspect of the present invention, in the belt device according to the seventh aspect, at least a surface of the bending imparting member is made of a member having a low friction coefficient.
According to a ninth aspect of the present invention, in the belt device according to any one of the first to sixth aspects, the bending applying member is a rotatable bending roller.
[0013]
According to a tenth aspect of the present invention, in the belt device according to the ninth aspect, the height of the top of the bending roller from the reference surface is not higher than the height of the top of the drive roller from the reference surface. It is characterized by.
According to an eleventh aspect of the present invention, in the belt device according to the ninth or tenth aspect, the bending roller is a cleaning member or a cleaning auxiliary member.
[0014]
According to a twelfth aspect of the present invention, in the belt device according to the tenth aspect, a bias applying unit is connected to the bending member.
According to a thirteenth aspect of the present invention, in the belt device according to the twelfth aspect, the bias applying unit has a bias polarity switching unit, and the toner is held after the toner is held by the bias polarity switching by the switching unit. Is released.
[0015]
According to a fourteenth aspect of the present invention, in the belt device according to any one of the first to thirteenth aspects, at least a surface of the bending imparting member is an elastic body.
According to a fifteenth aspect of the present invention, in the belt device according to any one of the first to fourteenth aspects, the bending imparting member has a transfer belt deviation adjusting means.
[0016]
In the belt device according to the sixteenth aspect, in the belt device according to the fifteenth aspect, the deviation adjusting unit is a unit that inserts a spacer having a cutout on one side from a center hole in a mounting screw portion of the bending applying unit. It is characterized by.
According to a seventeenth aspect of the present invention, in the belt device according to the sixteenth aspect, the spacer is a plurality of types of spacers prepared in advance and having different thicknesses.
[0017]
In the belt device according to the eighteenth aspect, in the belt device according to the sixteenth or seventeenth aspect, the deviation adjusting means is provided at two locations provided on the belt device for attaching both ends in the longitudinal direction of the bending imparting means. One of the reference planes is set to be always lower than the other even if a manufacturing error is included.
According to a nineteenth aspect of the present invention, there is provided a transfer device including the belt device according to any one of the first to eighteenth aspects.
According to a twentieth aspect of the present invention, there is provided an image forming apparatus having the transfer device according to the nineteenth aspect.
[0018]
Embodiment
FIG. 1 is a schematic diagram of a belt unit of an indirect transfer system for explaining an embodiment of the present invention.
In the figure, reference numeral 1 denotes a plurality of photosensitive members as an image carrier, 10 denotes an endless belt, 11 denotes a driving roller, 12, 15, and 17 support rollers, 14 a bending member, 16 a tension roller, 20 Denotes a primary transfer roller, 21 denotes a secondary transfer roller, 28 denotes a pair of registration rollers, and 30 denotes a fixing device. Symbols Y, M, C, and K indicate colors, and indicate yellow, magenta, cyan, and black, respectively.
FIG. 1 is basically the same as FIG. 7, but is particularly different in that the height of the belt unit is reduced due to the presence of the bending imparting member 14.
[0019]
In this way, even if the opening angle θ of the belt with respect to the tension roller 16 is substantially the same as that of FIG. ₂ Is the aforementioned angle B in the illustrated example. ₁ About 50% larger. In addition, the height H of the top of the tension roller from the reference surface is ₁ Is the height H of the top of the drive roller from the reference plane. ₀ Can be less than or equal to
In the present configuration, the curving member is described as being between the driving roller 11 and the tension roller 16, but in principle, the driving roller is adjacent to the driving roller on the downstream side of the driving roller in the belt traveling direction inside the belt. As long as the rollers are arranged, they need not be tension rollers.
[0020]
The operation of FIG. 1 will be briefly described.
The photoconductor drums 1Y to 1K are projected with color-separated images by an exposure device (not shown) to form latent images, and are visualized by a developing device (not shown). Each visual image for each color is sequentially transferred after being positioned on the belt 10 by the primary transfer roller 20 and becomes a full-color image. Is further secondary-transferred to transfer paper sent at the same transfer timing. Here, the transfer paper carrying the image is fixed by the fixing device 30.
[0021]
The bending member 14 is disposed between the driving roller 11 and the tension roller 16 and is fixed to the belt unit main body. Height H of the top of the drive roller from the reference plane ₀ Is almost inevitably determined by the configuration of the apparatus, but the height H of the top of the tension roller from the reference plane is ₁ There are some degrees of freedom in the settings. Height H of the top of the tension roller 16 from the reference plane ₁ Varies slightly depending on the tension of the belt 10, but the height H of the top of the drive roller from the reference plane is ₀ It is good to set as follows. As a result, the height of the belt unit falls within the minimum height that is necessarily determined in the configuration.
[0022]
Since the bending imparting members 14 come into contact with the surface of the belt and slide with each other, there is a possibility that the belt surface may be damaged if the friction is large. Therefore, even if a material such as a metal plate is used for the main body of the bending imparting member 14, at least a member having a low friction coefficient is used for a contact surface with the belt 10.
[0023]
Unintended foreign matter may adhere to the belt surface. If the curving member 14 is made of a hard material, the foreign matter may separate from the belt surface and continue to slide on the curving member 14 to damage the belt surface. In order to avoid this, it is preferable that the surface of the bending member 14 has elasticity. Then, the foreign matter passes under the curving member 14 to reach the cleaning device, where it is removed.
By replacing the roller 16 in the drawing with a fixed position roller and disposing the pressing member 14a on the bending applying member 14 as shown by the broken line in the drawing, the bending applying member 14 can also serve as a tension member. Easy to do.
[0024]
In an apparatus using a plurality of photoconductors, the circumferential length of the belt is inevitably increased, making attachment and detachment difficult.
The bending imparting member 14 can be configured such that the bending action on the belt 10 can be released regardless of whether the bending imparting member 14 is also used as a tension member. When it is necessary to remove the belt 10 from the belt unit, it is common to loosen the belt by moving the tension roller 16 in the configuration shown in FIG. 7, but in the configuration shown in FIG. Alternatively, a method in which the belt 10 is loosened by moving the bending imparting member 14 can also be adopted. If the length of the belt portion included in the curved portion between the two rollers with respect to the linear distance from the drive roller 11 to the tension roller 16 is 20 mm or more, attachment and detachment becomes very easy.
[0025]
FIG. 2 is a diagram for explaining another embodiment.
In the figure, reference numeral 18 denotes a bias applying means.
The basic configuration of FIG. 2 is the same as that of FIG. 1, except that the bending imparting member 14 has a rotatable roller shape. This is called a bending roller.
Since the bending roller 14 does not slide on the belt 10, it is not necessary to particularly stick to a low friction coefficient as a material of the roller surface. However, in order to prevent the belt surface from being damaged, a hard material should be avoided. It is better to use an elastic body such as a sponge.
[0026]
The bending roller 14 can be grounded via the bias applying means 18. When a bias having a polarity opposite to the polarity of the toner for image formation is applied to the curving roller 14, the toner remaining on the belt can be attracted to the roller surface. Therefore, the bending roller 14 can function as a cleaning unit for the belt 10. The toner adsorbed on the roller surface can be removed from the surface of the curving roller 14 using a cleaning device (not shown). Thus, there is no need to separately provide a cleaning roller, and the configuration can be simplified.
[0027]
Otherwise, at the time of post-rotation after the end of image formation or at the time of pre-rotation before the start of image formation, the bias polarity by the bias applying means 18 is switched to the same polarity as the toner polarity, and the toner is discharged onto the belt. Alternatively, the belt 10 may be removed by a cleaning unit provided in advance. Alternatively, the toner discharged onto the belt may be again adsorbed to the photoconductor using switching of a bias or the like, and may be removed by a cleaning device on the photoconductor. In these cases, the curving roller 14 does not need to have a cleaning device by itself, and thus serves as a cleaning auxiliary means.
[0028]
In general, if the parallelism of a driving roller, a supporting roller, and the like is not good, a belt is generated, which may damage the end of the belt. For this reason, various methods have been used, such as a method in which the deviation is automatically corrected by devising the roller shape, and a method in which the deviation is detected, the inclination of one of the rollers is corrected, and the deviation is returned. The simplest method is a method in which the deviation of the belt is checked at the time of assembly adjustment, and the inclination or the like of one of the rollers is adjusted and fixed so that the deviation does not occur.
When the belt is bent inward as in the present invention, the deviation of the belt caused by the bending roller tends to be larger than that of the other rollers. Therefore, in the present invention, the deviation is prevented by adjusting the inclination of the bending roller 14.
[0029]
FIG. 3 is a diagram for explaining an embodiment for preventing deviation.
In the figure, reference numerals 41 and 42 denote unit substrates, 43 denotes a roller holder, 44 and 45 denote fastening portions, and 46 denotes a plurality of spacers, respectively.
2A is a side view, FIG. 2B is a front view, and FIG. 1C is a plan view of a spacer.
In the present embodiment, deviation prevention is achieved by clamping one or more of a plurality of types of spacers prepared in advance and having different thicknesses, between the mounting portions.
The mounting position of the spacer is sandwiched between one of the fastening portions 44 and 45, in which the roller height is too low.
[0030]
However, for example, in the case where the fastening portion 45 is located at a position where it is difficult to put a hand on the back side in the longitudinal direction of the bending imparting means, the fastening portion 45 is fixed after being tightened, and even if manufacturing errors are included. By setting the mounting reference surface 41a of the unit substrate 41 lower than the mounting reference surface 42a of the other unit substrate 42 so that the roller height on the front-side fastening portion 44 side is always lower, the fastening portion 44 It is sufficient to sandwich the spacer 46 only on the side of.
The spacer 46 has a notch 46a with a central hole through which the screw passes loosely, so that it can be inserted as long as there is a gap corresponding to the plate thickness of the spacer 46 without removing the screw.
[0031]
Even if the fastening portion 45 is in a fixed state, a gap enough to sandwich the spacer 46 can be easily formed by bending of the member or the like.
As described above, the deviation preventing means has been described in the case of the roller, but almost the same configuration can be adopted also in the case of the fixed bending applying means 14 shown in FIG.
[0032]
FIG. 4 is a schematic view of a direct transfer type belt unit for explaining still another embodiment of the present invention.
In the figure, reference numeral 19 denotes a transfer bias applying unit.
In the operation of the present embodiment, unlike the embodiment shown in FIG. 1, a transfer paper (not shown) enters from the lower right, passes between the surface of the belt 10 and the photoconductor 1, and is formed on the photoconductor. The visible image is directly transferred to the transfer paper. The images of the respective photoconductors 1 are superimposed on transfer paper, and come out from the upper left as a full-color image.
[0033]
Also in the present embodiment, the arrangement of the bending imparting member 14 is the same as the arrangement shown in FIGS. That is, the bending imparting member 14 may be a fixed roller as shown in FIG. 1, a roller for bending as shown in FIG. 2, or a roller which also serves as a tension member. And between them. The roller supported from the inside adjacent to the drive roller may be a tension roller or a support roller other than the tension roller.
Also in the case of the present embodiment, if the height of the top of the tension roller from the reference surface is set to be equal to or less than the height of the top of the drive roller from the reference surface, the height of the belt unit is the minimum that is inevitably determined in the configuration. It can be kept at a minimum height.
[0034]
【Example】
FIG. 5 is a diagram illustrating an example in which the configuration of the embodiment illustrated in FIG. 1 is incorporated in an image forming apparatus.
In the figure, reference numeral 2 denotes a photoconductor cleaning device, 3 denotes a charging device, 4 denotes an exposure device, 5 denotes a developing device, 10 denotes a primary transfer belt, 25 denotes a belt cleaning device, 26 denotes a paper feeding device, and 27 denotes a feeding device. Paper rollers, 29 is a paper feed guide plate, 31 is a paper discharge guide plate, 32 is a paper discharge roller pair, 40 is a paper discharge stacker unit, 100 is a secondary transfer belt, 111 is a belt drive roller, 112 is a belt support roller, 113 and 120 are secondary transfer rollers, 250 is a belt cleaning device, and P is a transfer paper, respectively.
[0035]
The operation of the image forming apparatus shown in FIG. 5 will be briefly described.
In the initial state, no image is formed on the photoconductor 1, the primary transfer belt 10, and the secondary transfer belt 100. It is assumed that a single-sided image or a double-sided image is instructed from an external operation device (not shown). The photoconductors 1Y to 1K start rotating, and perform the following image formation at predetermined timings. The description will be made by taking the photoconductor 1Y as an example.
[0036]
The surface of the photoconductor 1Y is uniformly charged to a predetermined polarity by the charging device 3. The exposure device 4 irradiates the surface of the photoreceptor with a laser beam modulated with information on the yellow color of the image, and forms an electrostatic latent image on the surface of the photoreceptor. The electrostatic latent image is visualized by the developing device 5 to become a Y toner image. The primary transfer belt 10 is in contact with the photoreceptor 1Y and moves synchronously while being pressed by the primary transfer roller 20 to form a transfer nip. The Y toner image is transferred to the primary transfer belt 10 by applying a bias having a polarity opposite to that of the toner to the primary transfer roller 20 at the timing when the Y toner image on the photoreceptor 1Y reaches the transfer nip position. Let it.
[0037]
As the primary transfer belt moves, the magenta color image formed through the same process as described above is synchronized with the timing at which the Y toner image reaches the nip position formed between the photoconductor 1M and the primary transfer belt. The M toner image reaches the nip position. Both toner images are superimposed on each other with high precision and continue to move in the direction of the photoconductor 1C. In a similar process, cyan and black toner images are superimposed to form a full-color image on the primary transfer belt 10.
[0038]
When the instruction is a one-sided image forming instruction, one transfer sheet P is taken out by a sheet feeding roller 27 of a sheet feeding device 26, guided by a sheet feeding guide plate 29, and reaches a registration roller 28. The transfer paper P is sent out in synchronization with the image on the primary transfer belt, and passes through a transfer nip formed between the drive roller 11 and the secondary transfer belt 100 when the drive roller 11 and the transfer roller The image is transferred onto the transfer paper P by the transfer bias applied during 113. The image of the transfer sheet P is fixed by the fixing device 30, and the transfer sheet P is discharged to the discharge stacker unit 40 with the image forming surface down by the discharge roller pair 32.
[0039]
After the transfer, the photosensitive member 1 is scraped off of the remaining toner by the cleaning device 2 to prepare for the next charging. The toner remaining on the belt of the primary transfer belt after the transfer is scraped off by the cleaning device 25 to prepare for the next image formation.
[0040]
When a double-sided image formation is instructed, it is assumed that the image formed in the above-described process is, for example, an image on the back side, and the transfer from the primary transfer belt 10 to the secondary transfer belt 100 is performed first. . The transfer process is basically the same as the above-described transfer to the transfer paper P, but the bias level is appropriately changed. At this time, the cleaning device 250 is in an inoperative state.
When the full-color image on the front surface is formed on the primary transfer belt 10 as in the above-described process, the transfer paper P waiting at the position of the registration roller is synchronized with the image to perform the secondary transfer. It is sent to the nip.
[0041]
The image on the primary transfer belt 10 is transferred to one side of the transfer paper P by the transfer bias applied between the drive roller 11 and the transfer roller 113, and the transfer paper P is further moved between the drive roller 11 and the transfer roller 120. The image on the secondary transfer belt 100 is transferred to the other surface of the transfer paper P by the reverse transfer bias applied to the transfer paper P.
Hereinafter, the sheet is discharged to the sheet discharge stacker section 40 via the fixing device 30 in the same manner as described above. However, since a downwardly directed front surface is a front surface formed later, a plurality of pages are discharged. Even when the double-sided image is formed, the page order is correctly arranged.
[0042]
In this embodiment, the height of the top of the cleaning opposing roller 13 is higher than the height of the top of the drive roller 11. This is because, in order to dispose the cleaning device 25, a portion where the primary transfer belt 10 is convex upward is required. Even in this case, if the curving roller 14 is not used, the convex portion necessary for the cleaning device 25 cannot be secured unless the cleaning opposing roller 13 is provided further above.
[0043]
In this embodiment, the bending roller 14 also serves as a tension roller. In a normal use state, a force is applied to the bending roller 14 to press the belt inward. However, when attaching and detaching the belt unit, the position of the bending roller 14 can be largely changed as shown by an arrow A. It has become. Due to the movement, the primary transfer belt is largely loosened and can be removed from the belt unit.
[0044]
FIG. 6 is a diagram illustrating an example in which the configuration of the embodiment illustrated in FIG. 4 is incorporated in an image forming apparatus.
In the figure, reference numeral 10 denotes an endless belt.
This image forming apparatus is a direct transfer type. When there is an instruction to form an image, one sheet of transfer paper P is sent out from the paper feeding device 26 toward the registration roller 28. The photoreceptor 1 starts rotating, and the image formation starts at the same timing for each color. The transfer paper P waiting on the registration roller 28 is attracted and sent to the endless belt 10 by, for example, electrostatic force or the like at the timing when the Y toner image is formed, and is directly transferred from the photoconductor 1Y to the transfer paper P. The toner image is transferred. The transfer paper P continues to move toward the photoconductor 1M, and the M toner image, the C toner image, and the K toner image, each of which is timed, are successively superimposed on the Y toner image to form a full-color image.
[0045]
The transfer paper P on which all the transfer is completed has a full-color image fixed on the transfer paper P by the fixing device 30, and is discharged by the discharge roller pair 32 to the discharge stacker unit 40 with the image side down.
After the transfer, the photoreceptor 1 is scraped off of the remaining toner by the cleaning device 2 to prepare for the next image formation. The toner scattered on the belt is scraped off by the cleaning device 25 on the endless belt after the transfer of the transfer paper, and the cleaning device 25 prepares for the next image formation.
[0046]
In this embodiment, the cleaning device 25 is disposed at the position of the belt driving roller 11. This is because the endless belt is in the most convex state at this position and the cleaning device can be easily installed. The cleaning device may be provided at the position as shown in FIG. 5, that is, at the position of the tension roller 16. In that case, it is preferable that the tension member also serves as the bending roller 14.
Similar to the image forming apparatus shown in FIG. 5, the position of the curving roller 14 may be made movable for attaching and detaching the belt unit.
[0047]
【The invention's effect】
ADVANTAGE OF THE INVENTION According to this invention, the height of a belt unit can be made small, maintaining a stable belt driving | running and attaching / detaching a belt easily. When a bending roller is used in the present invention, the device can be prevented from becoming complicated by also using a tension member or a cleaning device.
[Brief description of the drawings]
FIG. 1 is a schematic diagram of a belt unit of an indirect transfer system for describing an embodiment of the present invention.
FIG. 2 is a diagram for explaining another embodiment.
FIG. 3 is a diagram for explaining an embodiment of deviation prevention.
FIG. 4 is a schematic view of a direct transfer type belt unit for explaining still another embodiment of the present invention.
FIG. 5 is a diagram illustrating an example in which the configuration of the embodiment illustrated in FIG. 1 is incorporated in an image forming apparatus.
FIG. 6 is a diagram illustrating an example in which the configuration of the embodiment illustrated in FIG. 4 is incorporated in an image forming apparatus.
FIG. 7 is a schematic diagram of a belt unit showing how to apply tension of a conventional endless belt.
[Explanation of symbols]
1 Photoconductor
2 Cleaning device
3 Charging device
4 Exposure equipment
5 Developing device
10 Endless belt, primary transfer belt
11 Drive roller
12 Support rollers
14 Bending member, bending roller
16 tension roller

Claims (20)

An endless belt whose front surface is in contact with a plurality of image carriers arranged substantially linearly to form a reference surface, and whose back surface is hung over a drive roller and a plurality of support rollers and is driven to rotate in one direction. In the above, it is characterized in that it has a bending imparting member that bends the endless belt in a direction in which it comes into contact with the front surface facing the side opposite to the side where the image carrier is arranged and approaches the reference surface side. Belt device. 2. The belt device according to claim 1, wherein the bending imparting member includes a support roller, which is disposed adjacent to a downstream side of the drive roller in a moving direction of the endless belt among the plurality of support rollers, and the drive roller. 3. A belt device interposed between the belt devices. 3. The belt device according to claim 2, wherein a height of the top of the support roller disposed adjacent to the downstream side of the drive roller from the reference surface is higher than a height of the top of the drive roller from the reference surface. 4. A belt device characterized by not being high. 4. The belt device according to claim 2, wherein the bending member also serves as a tension member. The belt device according to claim 2, wherein the support roller disposed adjacent to and downstream of the drive roller is a tension roller. The belt device according to any one of claims 1 to 5, wherein the curving member is detachable or movable in a direction in which the curving of the endless belt is released. The belt device according to any one of claims 1 to 6, wherein the bending member is fixed to the belt device at least during use of the device, and the endless belt slides with respect to the bending member. A belt device characterized by the above-mentioned. The belt device according to claim 7, wherein at least a surface of the bending imparting member is made of a member having a low coefficient of friction. The belt device according to claim 1, wherein the bending applying member is a rotatable bending roller. 10. The belt device according to claim 9, wherein the height of the top of the bending roller from the reference surface is not higher than the height of the top of the drive roller from the reference surface. The belt device according to claim 9, wherein the bending roller is a cleaning member or a cleaning auxiliary member. The belt device according to claim 10, wherein a bias applying unit is connected to the bending member. 13. The belt device according to claim 12, wherein the bias applying unit has a bias polarity switching unit, and the bias polarity switching by the switching unit can release the toner after holding the toner. And belt device. The belt device according to claim 1, wherein at least a surface of the bending applying member is an elastic body. 15. The belt device according to claim 1, wherein the curving member includes a transfer belt deviation adjusting unit. 16. 16. The belt device according to claim 15, wherein the deviation adjusting unit is a unit that inserts a spacer having a notch on one side from a center hole in a mounting screw portion of the bending applying unit. 17. The belt device according to claim 16, wherein the spacer is a plurality of spacers having a plurality of different thicknesses prepared in advance. 18. The belt device according to claim 16, wherein the deviation adjusting unit adjusts one of two mounting reference planes provided on the belt device to reduce a manufacturing error in order to attach longitudinal ends of the bending applying unit. A belt device characterized in that the belt device is always set lower than the other even if it is included. A transfer device comprising the belt device according to any one of claims 1 to 18. An image forming apparatus comprising the transfer device according to claim 19.

Images