JPH10104998A - Image carrying belt unit device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To regularly deep a roller for laying an image carrying belt in the state having parallelism in the initial assembling by providing a second suspending means for suspending a roller support unit frame to an image forming device body. SOLUTION: Both pins 37, 38 constituting a first suspending means are fitted to holes 47, 48 of a body side plate 41, and a pin 39 constituting a second suspending means is rotatably fitted to the hole 49a of a unit attaching and detaching plate 49. A roller support unit frame 440 and an image carrying belt 20, in its turn, are positioned and suspended to both the side plates 41, 42 of an image forming device body. Each roller 31-35 is preliminarily installed to the frame 40 with a required parallel precision. Thus, even if the rigidity of ht image forming device body or the body side plates 41, 42 and the like and the support precision of the unit device 20 to the body side plates are not enhanced as in the past, an intermediate transfer belt 3 can be stably traveled.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an endless belt for carrying and transporting a toner image, a plurality of rollers which stretch the belt and include at least one roller for driving the rotation of the belt, and a belt. A roller support unit frame that is disposed in the internal space and rotatably supports the plurality of rollers, and the roller support unit frame rotatably supports one end side of the plurality of rollers in the axial direction. A roller supporting frame portion, a roller supporting frame portion rotatably supporting the other end side of the plurality of rollers in the axial direction, and a connecting frame portion connecting both roller supporting frame portions in the axial direction of the rollers. And an image carrying belt unit of the image forming apparatus.

[0002]

2. Description of the Related Art An image forming apparatus provided with the above-mentioned image carrying belt unit has been conventionally known, and an endless belt is constructed in various modes. For example, the endless belt is configured as an intermediate transfer belt on which a toner image formed on a latent image carrier is transferred. In particular, when the image forming apparatus is a color image forming apparatus, a plurality of endless belts are formed on the intermediate transfer belt. Are superimposed and transferred, and the toner image is transferred to a final transfer material. In addition, the endless belt may be configured as a photoreceptor belt. In this case, a toner image is formed on the photoreceptor belt and is transferred to an intermediate transfer belt or a final transfer material. Alternatively, the endless belt may be configured as a transfer belt that carries and conveys a transfer material. In this case, a toner image is formed on the transfer material on the transfer belt. In this case, there are a case where a single color toner image is formed on the transfer material and a case where a plurality of color toner images are transferred in an overlapping manner.

When an endless belt is formed as an intermediate transfer belt or a photoreceptor belt, a toner image is directly carried on the surface of the belt, but is constituted as a transfer belt carrying and transferring a transfer material. At this time, the toner image is not directly formed on the surface of the belt, and the belt carries the transfer material on which the toner image is formed. The belt intermittently carries and transports the toner image.

The endless belt is constructed in various forms as described above, but in any case, the toner image is directly or indirectly carried and conveyed. When the image forming operation is performed while being driven, if the belt meanders, the toner image on the belt is blurred and the image quality is deteriorated. In particular, if the photosensitive belt or the intermediate transfer belt used in the color image forming apparatus meanders, a color shift occurs in the color toner image on the belt, and the image quality is remarkably deteriorated.

Therefore, various devices for preventing the meandering of the belt have been proposed and put into practical use. For example, JP-A-5-294494 or JP-A-6-294494
As disclosed in, for example, Japanese Patent No. 278894, a step is provided at each end in the width direction of the belt, and an axial end of a roller that stretches the belt is abutted against the step to maintain the straight running of the belt. A device has been proposed. According to this, the belt can travel straight with high accuracy with a relatively simple configuration. A configuration is also known in which a non-stop flange is provided at an axial end of the roller, and the belt is prevented from meandering by abutting the widthwise end of the belt against the flange.

The image carrying belt unit of the type described at the beginning is positioned and supported at a predetermined position with respect to the main body of the image forming apparatus. In this state, the endless belt is driven. The main body side plate supporting the image carrying belt unit device is generally made of metal such as steel or aluminum, or made of various resins.
Since it is not a completely rigid body, a slight distortion is generated following the plane distortion of the installation floor of the image forming apparatus main body. When such a distortion occurs in the main body side plate, the image carrying belt unit device is also distorted so as to be twisted, thereby deteriorating the parallelism between the plurality of rollers that stretch the belt. Also, when the mechanical accuracy of the main body of the image forming apparatus in which the image carrying belt unit is loaded is low, the parallelism of the rollers of the unit is reduced.

[0007] When the parallelism of the plurality of rollers is reduced as described above, a biasing force in the width direction is generated on the belt. The belt is generally driven to rotate by one of the stretching rollers. If the rollers stretching the belt are not parallel to each other, a biasing force acts on the belt in the roller axial direction. This offset force is also referred to as a lateral displacement force or thrust.

The above-mentioned deviation force or thrust is substantially proportional to the amount of deviation in the parallelism of the rollers.
In this case, the end in the width direction of the belt hits the stopper flange provided on the roller, or the step provided on the end of the belt hits the roller, and the belt does not move further in the axial direction. However, when the degree of parallelism of the rollers is further deviated, the thrust in the axial direction of the belt is increased, and rubbing noise is generated at the step stopper portion. In some cases, axial buckling of the belt may occur.

For this reason, conventionally, in order to maintain the parallel accuracy of the roller for stretching the belt to the required accuracy, the mechanical accuracy of the image carrying belt unit loading section of the image forming apparatus main body has been improved, The rigidity of the image forming apparatus main body is increased, and the roller support unit frame of the image carrying belt unit is firmly fixed to the image forming apparatus main body.

According to such a conventional configuration, even if the floor surface of the image forming apparatus main body is distorted, it is possible to prevent the image forming apparatus main body from being largely distorted, so that the parallelism of the rollers can be maintained substantially stably. It is possible to run the belt with good accuracy. However, on the other hand, as the rigidity of the image forming apparatus body increases, the weight of the image forming apparatus increases. Further, since the image forming apparatus main body is considerably large, the processing cost for maintaining the image forming apparatus with high accuracy is increased, or the maintainability of the image carrying belt unit is deteriorated.

[0011]

SUMMARY OF THE INVENTION It is an object of the present invention to install an image forming apparatus main body without increasing the rigidity of the image forming apparatus main body and the mechanical accuracy of an image carrying belt unit loading section as in the prior art. It is an object of the present invention to provide an image carrying belt unit device of the type described at the beginning, in which a roller for stretching an image carrying belt can always be maintained in a state of parallelism at the time of initial assembly without being affected by flatness of a floor surface. is there.

[0012]

According to the present invention, in order to achieve the above object, in the image carrying belt unit described at the beginning, a roller supporting unit frame is provided on one of the two roller supporting frame portions. First suspension means for suspending the roller support unit frame with respect to the image forming apparatus main body so as to be positioned and mounted at a predetermined position with respect to the forming apparatus main body, and a roller support unit is provided on the other frame portion. A second frame that suspends the roller supporting unit frame with respect to the image forming apparatus main body such that the position of the frame with respect to the image forming apparatus main body is regulated and the frame is supported so as to be rotatable with respect to the image forming apparatus main body. There is proposed an image carrying belt unit device provided with the above suspending means (claim 1).

At this time, in the configuration according to the first aspect, an impact external force acting on the image carrying belt unit is provided between the roller supporting frame provided with the second suspension means and the image forming apparatus main body. It is advantageous to provide a damping means for absorbing the pressure (claim 2).

In the image forming apparatus according to the first aspect of the present invention, an impact is applied between the roller supporting frame provided with the second suspension means and the image forming apparatus main body during the image forming operation. It is advantageous to provide a frictional force generating means for applying a frictional force to the image carrying belt unit device to prevent the image carrying belt unit device from being twisted when an external force is applied (claim 3).

Further, in the configuration according to the first aspect, between the roller supporting frame provided with the second suspension means and the image forming apparatus main body, the torsional deformation of the roller supporting unit frame during the image forming operation is prevented. Therefore, it is advantageous to fix the unit frame to the main body of the image forming apparatus and interpose locking means for releasing the fixing during a non-image forming operation.

According to a fourth aspect of the present invention, in the image forming operation, the locking means fixes the roller supporting frame provided with the second suspension means to the image forming apparatus main body during the image forming operation. So that it can sometimes be unlocked,
It is advantageous if it is constituted by a roller support frame provided with the second suspension means and a locking screw attached to the image forming apparatus main body.

Further, in the configuration according to the fourth aspect, the locking means is provided between the roller supporting frame portion provided with the second suspension means and the image forming apparatus main body, and the roller supporting unit frame is twisted. It is advantageous to include a torsional deformation restricting device for preventing deformation and a control device for executing the torsional deformation restricting by the torsional deformation restricting device during the image forming operation and releasing the restriction during the non-image forming operation. Item 6).

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a schematic structural view of an image forming apparatus having an image carrying belt unit according to an embodiment of the present invention. The image forming apparatus 100 shown in FIG. 1 configured as a printer or the like is a full-color image forming apparatus, and the image forming apparatus includes cyan, magenta, yellow, and black (hereinafter referred to as C,
M, Y, and K).
A full-color image having a recording dot density of 1/16 mm or 1/24 mm is formed and output on transfer paper as an example of the final transfer material in both main scanning and sub-scanning. The selection of the recording dot density is specified in advance by a mode selection command.

Here, when the image forming operation of the present image forming apparatus is started, first, a drum-shaped photosensitive member 1 as an example of a latent image carrier is driven to rotate counterclockwise in FIG. The intermediate transfer belt 3, which is disposed obliquely from the right to the lower side in FIG. 1 of the photoreceptor 1, is driven to rotate clockwise in FIG. The intermediate transfer belt 3 forms an example of an endless belt.

As the photosensitive member 1 and the intermediate transfer belt 3 rotate, a C toner image, an M toner image,
A toner image and a K toner image are sequentially formed, and toner images of respective colors are superimposed and transferred on the intermediate transfer belt 3 in the order of C, M, Y, and K, and finally on the intermediate transfer belt 3. A full-color image is formed.

To explain this point in more detail,
First, the formation of the C toner image is performed as follows.

The charging scorotron 5 uniformly charges the photosensitive member 1 to a negative charge of -700 V by corona discharge. Subsequently, the laser diode 6 detects the photosensitive member 1 based on the C signal.
Is subjected to raster exposure. A recording signal for forming a toner image is input from the SCS1 terminal 7S. The laser drive circuit 6DV, which is a recording control circuit, controls the light emission of the laser diode 6 for each input pixel based on the recording signal.

The recording signal is area-modulated by a 4-bit value per pixel. Specifically, at the time of the highest C density pixel, laser light is emitted for the entire main scanning width, and at the time of a white pixel, no light is emitted. In the case of an intermediate density signal, light is emitted for a time proportional to the density data. It is like that.

When the photoreceptor 1 is exposed to the raster image in this way, the exposed portion of the photoreceptor 1 that is initially uniformly charged loses the charge proportional to the amount of exposure light, and the electrostatic latent An image is formed.

The toner in the developing section 8C of the developing device 8 is negatively charged by stirring with the ferrite carrier, and the cyan developing roller 8CR of the developing device 8 is not shown with respect to the metal base layer of the photoreceptor 1. The power supply means is biased to a potential at which a negative DC potential and an AC are superimposed. As a result, no toner adheres to the portion of the photoconductor 1 where the charge remains, and the C toner is adsorbed to the portion having no charge, that is, the exposed portion, and a C toner image similar to the latent image is formed. You.

When the toner image thus formed on the photoreceptor 1 reaches a position facing a primary transfer corotron 9 which is an example of a transfer device as the photoreceptor 1 rotates, the toner image is transferred to the photoreceptor 1. The primary transfer corotron 9 performs corona transfer to the intermediate transfer belt 3 that is in contact with and is driven at a synchronous speed. A small amount of untransferred residual toner on the photoconductor 1 is cleaned by the cleaning device 12 in preparation for reuse of the photoconductor 1. The collected toner is stored in a waste toner tank (not shown) via a collection pipe (not shown).

Next, prior to performing the M image forming raster exposure based on the M signal, the developing device 8 is rotated counterclockwise in FIG. 1 to make the M developing roller 8MR face the photosensitive member 1. Next, the leading position of the previously formed C toner image is detected by the leading end detecting means 13, and a request signal REQ is sent again to the signal source, "Send recording M image data after a predetermined time". The request signal is issued at a time when the image position detecting means 13 detects a registration (registration) C toner mark image (not shown) slightly ahead of the effective C toner image in the previous process. You. Further, instead of the C toner mark image, a method in which a permanent mark is previously attached to the intermediate transfer belt may be used.

If the M signal is sent in exact synchronization with the request signal, M image exposure, development, and primary transfer are performed, and accurate color plate matching with the original existing C toner image, that is, The M toner image is correctly overlapped with the C toner image on the intermediate transfer belt 3.

As described above, when the M raster image is exposed on the photoconductor 1, the photoconductor 1 initially charged uniformly.
In the exposed portion, the charge proportional to the exposure light amount disappears, and an electrostatic latent image is formed on the photoreceptor 1.

The M toner in the developing section 8M of the developing device 8 is charged to a negative polarity, and the developing roller 8MR of the main developing section 8M is charged.
The upper developer is in contact with the photoreceptor 1 and is biased to the same potential as in the C development. Therefore, the toner does not adhere to the portion of the photoconductor 1 where the charge remains, and the M toner is attracted to the portion exposed by the M signal, thereby forming an M toner image similar to the electrostatic latent image. This M toner image is also transferred onto the intermediate transfer belt 3 so as to overlap the C toner image.

Similarly, the developing units 8Y, 8Y,
By the 8K developing rollers 8YR and 8KR, a Y toner image and a K toner image are sequentially formed on the photoconductor 1, and the Y toner image is formed on the C and M toner images on the intermediate transfer belt 3, and the K toner image is formed on the intermediate transfer belt 3. The image is superimposed on the C, M, and Y toner images and transferred onto the intermediate transfer belt 3. The full-color image on the intermediate transfer belt 3 formed by rotating at least four times in this manner is transferred to the secondary transfer portion 14 in due course.

On the other hand, at the time when the image formation is started, the transfer paper 19 is supplied to three feeding units, that is, the paper feeding cassette unit 15.
A, any of the feed rollers 16A, 16B or the pair of transport rollers 16C is fed out from one of the manually inserted paper feed tray section 15B and the external feed port 15C, or fed by the transport action, and Waiting at the nip. When the leading end of the toner image on the intermediate transfer belt 3 approaches the secondary transfer roller 18, the registration roller pair 17 is driven such that the leading end of the transfer paper 19 coincides with the leading end of the image, and the full-color image on the intermediate transfer belt 3. And the transfer paper 29 are registered.

In this way, the transfer paper 19 passes between the secondary transfer roller 18 connected to the positive potential power supply and the intermediate transfer belt 3 while being superimposed on the full-color image on the intermediate transfer belt 3. At this time, the transfer paper 19 is charged to a positive charge by the transfer current, and most of the full-color image is transferred.
Transcribed above.

Subsequently, the transfer paper 19 is transferred to the secondary transfer roller 1.
When passing through a static elimination core (not shown) connected to a grounding source located near the left side of the transfer sheet 8, the transfer sheet discharges electric charges, and the attraction force between the intermediate transfer belt 3 and the transfer sheet 19 almost disappears. . Eventually, the weight of the transfer paper 19 exceeds the attraction force, and the transfer paper 19 separates from the intermediate transfer belt 3 and moves onto the transport belt 21.

A small amount of untransferred residual toner on the intermediate transfer belt 3 is scraped off by the cleaning blade 23 of the cleaning device 22 in preparation for reuse of the belt 3, and the surface of the belt 3 is cleaned. The toner collected here is also stored in a waste toner tank (not shown) via a collection pipe. When the toner image on the intermediate transfer belt 3 before being transferred to the transfer paper 19 passes through the cleaning blade 23, the blade 23 separates from the intermediate transfer belt 3, and when cleaning the belt surface, the blade 23 It comes into contact with the surface of the intermediate transfer belt 3.

The transfer paper carrying the toner image is transported by the transport belt 2
1 to the fixing device 24. At this time, the heated fixing roller 24A applies heat and pressure to the transfer paper in a nip portion with the backup roller 24B, whereby the toner is melted, and the image is fixed in the fibers of the transfer paper, thereby fixing the final image. Complete. The completed print is then sent out of the image forming apparatus main body by the discharge roller pair 26.

In the case of double-sided printing, the switching claw 12
7, the switching roller 27 is moved to the right and pressed against the opposing transport roller 28 to guide the transfer paper, and the transfer paper is once inverted by a reversing device (not shown). At 29, it is led to the automatic paper feed cassette 15A for both-side printing. The transfer paper 19 copied at this time is stacked with the copy side up, and
It is prepared for refeeding for surface printing.

The intermediate transfer belt 3 has a plurality of rollers 31,
It is stretched around 32, 33, 34, 35. As shown in FIG.
The gear 36 is fixed to one axial end of the roller shaft 31A. The rotation of the drive motor 4 shown in FIG.
The power is transmitted to the gear 36 via a gear system (not shown), and the roller 31 is driven to rotate. By the rotation of the roller 31, the intermediate transfer belt 3 is driven to rotate clockwise in FIG.

The roller 31 is a roller for driving the intermediate transfer belt 3 to rotate. The belt 3 is composed of a plurality of rollers 3 including at least such a roller for rotation.
1,32,33,34,35. In addition,
The roller 32 is a roller that applies tension to the intermediate transfer belt 3. That is, the bearing 11 is movably fitted into a roller support unit frame 40 described later, and the spring 25
When the roller 32 comes into pressure contact with the inner surface of the intermediate transfer belt 3 via the bearing 11 with the force described above, the belt 3 is stretched. The tension applying mechanism is also provided at the opposite roller end.

Here, the intermediate transfer belt 3 is an example of a configuration of an endless image carrying belt that carries and conveys an image (a full-color image in this example). As shown in FIG. 2, a roller supporting unit frame 4 is formed in the internal space.
0 is arranged.

This roller support unit frame 40 is
A roller support frame portion 40A that rotatably supports five rollers 31, 32, 33, 34, and 35, and rotatably supports one end of each roller, and rotatable at the other end. , And connecting frame portions 40C and 40D for integrally connecting both roller supporting frame portions in the axial direction of the roller. The plurality of rollers 32, 33, 34, 35 are supported by the roller support unit frame 40 substantially in parallel with each other. The connecting frame 40C is an upper frame, and the connecting frame 40D is a lower frame.

The belt 3, the frame 40, and the plurality of rollers 32 to 35 constitute the image carrying belt unit 20 which is integrally assembled. That is, the image carrying belt unit device 20 of the image forming apparatus according to the present embodiment includes:
An endless belt 3 that carries and transports the toner image, and a plurality of rollers 31, 32, 33, 3 that stretch the belt 3 and include at least one roller 31 for driving the rotation of the belt 3.
4 and 35, and a roller support unit frame 40 that is disposed in the internal space of the belt 3 and rotatably supports the plurality of rollers, and the roller support unit frame includes an axial direction of the plurality of rollers 31 to 35. Roller support frame portion 40 rotatably supporting one end side of
A, and a roller support frame portion 4 that rotatably supports the other end of the plurality of rollers 31 to 35 in the axial direction.
0B and connecting frame portions 40C and 40D connecting the roller supporting frame portions 40A and 40B in the axial direction of the rollers.

Here, the image forming apparatus 100 shown in FIG.
Of the image forming apparatus main body 10
1 is the rear side, and FIG. 1 shows the inside of the image forming apparatus body 10 as viewed from the front side. The image forming apparatus main body 10 forms a housing of the image forming apparatus 100, and as shown in FIG. 2, a front main body side plate 42 and a rear main body side plate 4 arranged in parallel with each other.
The image carrying belt unit 20 is disposed between the main body side plates 41 and 42. An opening 42A is formed in the front main body side plate 42, and the image carrying belt unit device 20 is attached to and detached from the image forming apparatus main body 10 through the opening 42A. The unit main body side plate 42 is attached to the unit attaching / detaching plate 4 by screws 43,43.
9 is detachably fixed to the side plate 42, and when the image carrying belt unit device 20 is attached to and detached from the image forming apparatus main body 10, the unit attaching / detaching plate 49 is detached from the main body side plate 42. The unit attaching / detaching plate 49 is attached to the main body side plate 4.
2, a part of the image forming apparatus main body 10 is configured.

The roller support unit frame 40 is provided on one of the two roller support frame portions 40A, 40B shown in FIG. 2, for example, on the rear roller support frame portion 40A, with the image forming apparatus main body 10 (see FIG. 2). First suspension means are provided as pins 37 and 38 for suspending the roller support unit frame 40 with respect to the image forming apparatus main body so as to be positioned and mounted at a predetermined position with respect to 1). . In addition, a roller support unit frame 40 is provided on the other roller support frame portion 40B.
A pin 39 for suspending the roller support unit frame 40 with respect to the image forming apparatus main body so that the position with respect to the image forming apparatus main body 10 is regulated and is rotatably supported with respect to the image forming apparatus main body 10. A second suspension means is provided. The first and second suspension means of the present example are arranged in parallel with the rollers 31 to 35 so that each roller supporting frame portion 40A. The pins 37 to 39 are fixed to 40B.

Here, two round holes 47 and 48 are formed in the one main body side plate 41 on the rear side shown in FIG. Then, the two pins 3 constituting the first suspension means
The pins 37 and 38 are integrally protruded from different positions of one roller support frame 40A, respectively.
38 is fitted into the holes 47 and 48 of the main body side plate 41 without rattling. On the other hand, one pin 39 constituting the second suspension means is connected to the other roller support frame portion 4.
0B, and is rotatably fitted into a round hole 49a provided in the unit attaching / detaching plate 49 without rattling. In this state, the unit attaching / detaching plate 49 holds the two screws 4 inserted through the holes 49c, 49c provided therein.
3 and 43, it is integrally fixed to the main body side plate 42 on the front side. The roller support unit frame 40 is made of, for example, an extruded aluminum material, and has a torsional rigidity that allows only a slight torsional deformation with respect to a disturbance torsional moment during a normal image forming process.

Both pins 37, 3 constituting the first suspension means
8 is fitted into the holes 47 and 48 of the main body side plate 41, and the pin 39 constituting the second suspension means is rotatably fitted into the hole 49a of the unit attaching / detaching plate 49. The belt unit device 20 includes two side plates 41 of the image forming apparatus main body 10,
Positioned with respect to 42 and suspended.

The two pins 37 and 38 and the pin 39 are
The positional relationship is shown in FIG.
The image carrier belt unit device 20 is positioned in the vertical and horizontal directions in the figure at the predetermined position of the inclination angle shown in FIG. 1 by fitting the 38 into the holes 47 and 48, respectively. That is, the image carrying belt unit device 20 is positioned at a position where the intermediate transfer belt 3 properly carries and conveys an image. Further, by fitting the pin 39 into the hole 49a (FIG. 2), the positioning of the entire image carrying belt unit device 20 at the above-described position is guaranteed, and as described later,
When the image forming apparatus main body 10 is distorted as a whole, the entirety of the image carrying belt unit apparatus 20 includes the pins 29 and the holes 49a.
Can be pivotally displaced with the fitting portion of the fulcrum as a fulcrum. The image carrying belt unit device 20 of this embodiment is suspended on side plates 41 and 42 on the image forming apparatus main body side in a three-point support system.

FIG. 3 is a partial longitudinal sectional view of the roller 31 of the image carrying belt unit 20. In the figure, inside the both ends of the intermediate transfer belt 3 in the roller axial direction, strip-shaped step portions 3a and 3b projecting inward and formed around the entire circumference of the belt 3 are provided for limiting the belt detent. Is provided. At each end of the roller 31 in the axial direction, notch-shaped steps 31a and 31b having a depth corresponding to the height of the steps 3a and 3b are provided over the entire circumference of the roller 31. ing.

The rollers 31 to 35 which stretch the intermediate transfer belt 3 are out of parallel, or there is a difference in circumferential length between one end and the other end of the intermediate transfer belt 3 in the axial direction. In this case, the intermediate transfer belt 3 that is driven to rotate is subjected to an approaching force in the direction of arrow a or b in FIG. In practice, some manufacturing errors cannot be avoided, and in many cases, the intermediate transfer belt 3 is moved to one side and eventually the belt step 3a.
And the roller step 31a or the belt step 3b and the roller step 31b are in contact with each other.

When the belt biasing force (thrust) is not so large, the distance between the intermediate transfer belt 3 and the roller 31 is
The roller in the belt winding portion slides in the axial direction, and thereafter, stable belt running is continued. On the other hand, when the deviation of the parallelism between the rollers becomes large and the biasing force of the belt 3 increases, the step 3a or 3b at the belt end strongly comes into contact with the roller step 31a or 31b. When the shear strength of the step portion 3a or 3b is exceeded, the portion breaks, and the belt body eventually breaks.

The intermediate transfer belt 3 of this embodiment has a circumference of 502 m.
m, the width is about 340 mm, but the allowable roller parallelism at this time is at most about 0.3 mm,
If it exceeds this, one of the belt ends 3a and 3b is broken. Further, even if it is not broken, the action between the steps 3a and 31a or 3
A squeak sound is caused between b and 31b. In order to avoid such a problem, it has been found that it is desirable to maintain the roller parallel accuracy of about 0.2 mm or less. The degree of parallelism of the rollers is, as shown in an exaggerated manner in FIG. 9, the amount of displacement between the two rollers R1 and R2 when one end of the two rollers is matched. The smaller the amount of deviation, the higher the degree of parallelism. When the degree of parallelism is zero, the rollers R1 and R2 are completely parallel.

As described above, if the floor on which the main body of the image forming apparatus is installed is distorted, the main body of the image forming apparatus is distorted so as to be entirely twisted. May be twisted, and the parallelism between the rollers may be deviated as described above. Also, if the mechanical accuracy of the image carrying belt unit loading portion of the image forming apparatus main body is low, the parallelism between the rollers may be degraded due to this.

Therefore, conventionally, in order to maintain such roller parallel accuracy, the mechanical accuracy of the image carrying belt unit mounting portion of the image forming apparatus main body is increased, and the image forming apparatus main body, particularly, the side plate of the image forming apparatus main body is improved. The rigidity is increased, and the roller supporting unit frame of the image carrying belt unit is firmly fixed to the main body side plate. According to such a conventional configuration, even if the installation floor of the image forming apparatus main body is slightly distorted, the parallelism of the rollers can be maintained substantially stably, and good belt running can be ensured. However, the increased rigidity of the main body of the image forming apparatus causes an increase in the total mass of the image forming apparatus, and the main body of the image forming apparatus is considerably large. There is a problem that it is bulky and hinders the maintainability of the image carrying belt unit device.

In view of the above, if the weight of the image forming apparatus is reduced by making the main body side plate of the image forming apparatus main body of low rigidity, when the horizontal surface of the floor on which the image forming apparatus main body is installed is poor, the image is formed. The side plate of the forming apparatus main body is distorted, the parallelism of each roller for stretching the belt is deteriorated, the belt is shifted, and the obtained image is blurred. Especially,
In a color image forming apparatus, a color shift occurs, and the image quality is remarkably deteriorated.

On the other hand, in the present embodiment, as described above, the rollers 31 to 35 are mounted on the roller support unit frame 40 shown in FIG. The belt unit device 20 is supported at three points on the main body side plates 41 and 42.

By doing so, the rigidity of the image forming apparatus main body 10, that is, the main body side plates 41 and 42, and the like are improved.
The intermediate transfer belt 3 can be supported without increasing the accuracy of supporting the image carrying belt unit 20 with respect to the main body side plate as in the related art.
Can be run stably.

For example, when the image forming apparatus is installed on an uneven floor, the image forming apparatus main body 10 is distorted due to its own weight. It is rather common that the flatness of the floor in the installation area of the image forming apparatus main body is deviated by about 1 mm.

At this time, in the apparatus of the present embodiment, one of the roller support frame portions 40A is provided with two spaced apart pins constituting the first suspension means, and the rear body side plate 41 is provided on the rear side.
Are fitted without looseness in the holes 47 and 48 of
The connection state becomes strong, and the roller supporting frame portion 40A is distorted together with the side plate 41 constituting the image forming apparatus main body.

However, the other roller support frame 40
B has only one pin 39 protruding therefrom, and since this pin 39 is rotatably supported on a unit mounting / detaching plate 49 of the image forming apparatus main body, the above-described roller supporting frame portion is provided. When the distortion of 40A occurs, the roller support unit frame 40 is pivotally displaced about the single pin 39 by an amount corresponding to the distortion. As a result, a large force for distorting the image carrying belt unit 20 itself does not act on the image carrying belt unit 20 itself, and the plurality of rollers of the image carrying belt unit 20 maintain the state of parallelism at the time of initial assembly. .

Conventionally, the roller supporting unit frame is firmly fixed to the image forming apparatus main body in order to prevent distortion of the image carrying belt unit apparatus. Therefore, the external force based on this is directly transmitted to the roller supporting unit frame, and the image carrying belt unit device may be distorted. In this example, the idea that the image carrying belt unit is firmly fixed to the image forming apparatus main body as in the related art is abandoned, and the image carrying belt unit 20 is rotated according to the distortion of the image forming apparatus main body 10. Thus, the image carrying belt unit 20 itself is prevented from being distorted.

As described above, the image carrying belt unit 2
Even after the rotation of the roller support unit frame 0, the position of the roller support unit frame 40 is correctly regulated by the three pins 37, 38, and 39 with respect to the image forming apparatus main body 10, and the roller support unit frame 40 is correctly positioned. The same applies to the case where the mechanical accuracy of the image carrying belt unit loading portion of the image forming apparatus main body is somewhat poor, and the parallelism of each roller does not greatly degrade.

The roller support unit frame 40
Has a shape considerably smaller than that of the image forming apparatus main body 10, and it is easy to maintain the rigidity of the roller support unit frame 40 itself and its precision to the required rigidity and precision.

As described above, since the modularized image carrying belt unit device 20 of this embodiment is supported on the image forming apparatus main body side by the three-point support system, the floor of the floor on which the image forming apparatus main body is installed is mounted. Regardless of the flatness or the mechanical accuracy of the support of the image carrying belt unit with respect to the image forming apparatus main body, the image carrying belt unit 2
The parallelism of the 0 roller can be maintained in the initial assembled state.

A configuration in which the pin 39 shown in FIG. 2 is directly suspended from the hole provided in the main body side plate 42 instead of the unit attaching / detaching plate 49 may be adopted, and the same applies to the following embodiments. Configuration can be adopted.

The structure and operation described above are specific examples corresponding to the image carrying belt unit according to the first aspect. With this configuration, the above-described excellent operation and effect can be obtained. However, on the other hand, the other roller support frame portion 40B of the image carrying belt unit device 20
Is rotatably displaceable with respect to the image forming apparatus main body by the pins 39 constituting the second suspension means. That is, when a shocking external force acts, the image carrying belt unit device 20 is torsionally deformed. The rear side of the roller support unit frame 40 is fixed to the main body side plate 41 by two pins 37 and 38, and the front side thereof is rotatably displaceably supported by one pin 39 with respect to the image forming apparatus main body. Therefore, when a disturbance acts on the image carrying belt unit device 20, the roller supporting unit frame 40 is rotationally displaced on the front side while the rear side is fixed, and the image supporting belt unit device 2 is displaced.
The whole of 0 undergoes torsional deformation.

If such a torsional deformation occurs in the image carrying belt unit device 20, the parallelism between the rollers is disturbed, and the intermediate transfer belt 3 vibrates, and the toner image formed on the surface thereof is blurred. Or a color shift occurs in the color image, and the image quality is significantly deteriorated. Factors for applying an external force to the image carrying belt unit device 20 by impact include, for example, at the start of an image forming operation,
A shock when the intermediate transfer belt 3 starts running or a shock when the cleaning blade 23 shown in FIG. Such a disturbance is caused by a difference in rotational force from a gear 36 (FIG. 2) for driving the roller 31 of the intermediate transfer belt 3 or a difference in the presence or absence of an external force when the cleaning blade 23 comes into contact with or separates from the intermediate transfer belt 3. It acts as a load fluctuation of the rotation of the belt 3.

Therefore, in a second specific example corresponding to the image carrying belt unit device according to the second aspect, a roller provided with a second suspension means in addition to the configuration shown in FIGS. Damping means is provided between the support frame portion and the image forming apparatus main body to absorb a shocking external force acting on the image carrying belt unit. A dashpot can be used as such a damping means, an example of which is shown in FIG.

In FIG. 4, a roller supporting frame portion 40B provided with a pin 39, which is an example of the configuration of the second suspension means, is shown in FIG.
A dashpot 44 acting between the image carrying belt unit device 20 and the main body of the image forming apparatus is connected to the dashpot 44. The dashpot 44 generates a predetermined drag in proportion to the moving speed of the object. Dashpot 44
Is mainly composed of a fixed cylinder 44A and a movable piston 44B.

The frame 4 at the end of the fixed cylinder 44A
Pin 46 is fitted into a hole 45 provided in 4A _1, and, the pin 46 is secured to the body side plate 42 (FIG. 2). The end of the fixed cylinder 44A is
It is connected to the side plate 42 of the image forming apparatus main body so as to be rotatable therearound.

On the other hand, a pin 51 is rotatably attached to the movable piston 44B so as to be orthogonal to the movable piston 44B, and the pin 51 is press-fitted and fixed to the roller support frame portion 40B. The pin 51 is installed so as to be separated from the pin 39 serving as the second suspension means by an appropriate distance R1, and the dash pot 44 is substantially perpendicular to a straight line connecting the pin 39 and the pin 51. It is arranged in.

The movable piston 44B of the dash pot 44
And the cylinder 44A are filled with a fluid having a predetermined viscosity, and the fluid moves through an internal small flow path as the movable piston 44B reciprocates. The frictional drag caused by the movement of the fluid is set to be substantially proportional to the moving speed V of the movable piston 44B. This proportionality constant is assumed to be K, and the roller support unit frame 40
However, when it is assumed that the motor rotates (rotates) at a rotational angular velocity of ω, the resistance moment against this is “KωR1”.

As described above, in the image carrying belt unit device 20, the rear side, that is, the main body side plate 41 side is suspended on the main body side plate 41 side with the two pins 37 and 38, and the front side, that is, the main body side plate 42 ( The side of FIG. 2) is suspended on the unit attaching / detaching plate 49 side with one pin 39,
A dash pot 44 is connected between the dash pot 44 and the side plate 42 of the image forming apparatus main body.

Therefore, during the image forming operation, some disturbance acts on the image carrying belt unit device 20, and
When the torsional moment acts on the rear side, the rear side is suspended by the two pins 37 and 38, so that the front side tends to cause torsional deformation around the fitting portion between the pin 39 and the hole 49a. However, when the disturbance torsional moment acts steeply, the drag of the dash pot 44 is large, so that the amount of torsional deformation of the image carrying belt unit device 20 is kept small, and the deformation is negligible.
For this reason, it is possible to prevent the parallelism of the rollers from being greatly deviated or the intermediate transfer belt 3 from vibrating violently. The damping means composed of the dash pot 44 absorbs an impact external force acting on the image carrying belt unit device 20, prevents torsional deformation of the image carrying belt unit device 20, prevents vibration of the intermediate transfer belt 3, Shake of the toner image formed here and occurrence of color misregistration of the color image can be prevented. In this manner, the image bearing belt unit apparatus 20 continues to maintain a state substantially equal to the original static roller arrangement.

On the other hand, when the image forming apparatus is moved on a floor surface with poor flatness, the deformation of the image forming apparatus main body 10 acts on the image carrying belt unit apparatus 20 via the dashpot 44. I do. However, in such a case, since the speed of the external force applied to the image carrying belt unit 20 is extremely low, there is almost no drag of the dash pot 44 and the image carrying belt unit 20
Is generally equivalent to three-point support. The result is the same as the state without the dashpot 44, and the operation of the configuration shown in FIGS. 1 to 3 can be achieved as it is, and the state where the original static roller arrangement is substantially maintained is maintained.

In any case, the image bearing belt unit 2
0 can absorb the disturbance torsional moment acting directly on the roller, can suppress the deviation of the roller parallelism and the vibration of the image carrying belt unit device, and even if the image forming device is distorted due to the deviation of the flatness of the floor surface, etc. Without being affected by this, the intermediate transfer belt 3 can run stably without changing the parallelism of the rollers. This is particularly effective when a relatively high-speed color image forming apparatus on which a large disturbance torsional moment is apt to act is provided with the image carrying belt unit having the damping means as described above.

In addition to the dash pot using a viscous fluid, an air damper utilizing the compression of air and the flow thereof can be used as the damping means. Dashpots and air dampers are examples of dampers utilizing the flow of fluid.
Further, a magnetically coupled magnetic damper or the like may be used as the damping means.

Further, in the above-described configuration shown in FIGS. 1 to 3, instead of or together with the above-described damping means,
When a shocking external force acts on the image carrying belt unit during the image forming operation between the roller supporting frame provided with the second suspension means and the image forming apparatus main body, the image carrying belt unit becomes A frictional force generating means for applying a frictional force for preventing the torsional deformation to the image carrying belt unit may be provided. This is a specific example corresponding to the image carrying belt unit device according to the third aspect.

For example, as shown in FIG. 5, a roller support frame portion 40B provided with a pin 39 as a second suspension means.
Further, a frictional force generating means 50, which acts between the image carrying belt unit device 20 and the main body of the image forming apparatus and includes a friction washer 53, a compression coil spring 54, a stepped screw 55, and the like, is provided. The frictional force generating means 50 prevents torsional deformation of the image carrying belt unit device 20 when an impact external force is applied thereto.

The stepped screw 55 sandwiches the unit attaching / detaching plate 49, the friction washer 53 and the compression coil spring 54 in the stepped portion between the screw portion and the screw head, and the screw portion is formed in the screw hole of the roller support frame portion 40B. Screw into 56.
FIG. 6 shows an assembled state of the frictional force generating means 50.

The length of the stepped portion of the stepped screw 55 is such that the compression coil spring 54 is compressed by a predetermined amount, and the diameter thereof is the same as that of the arc-shaped long hole 49 b formed in the unit attaching / detaching plate 49. The width is slightly smaller than the diameter of the hole 53 a of the friction washer 53. Also, the unit detachable plate 4
Nine arc-shaped long holes 49b are located at positions separated by R2 from the axis of the pin 39 (also the center of the hole 49a), and have a radius R2 centered on the axis. Has become.

It is now assumed that the image carrying belt unit 20
On the other hand, a torsion motion is forcibly given around the fitting portion between the pin 39 and the hole 49a. In this case, the friction washer 53 and the unit attaching / detaching plate 49 slip while mutually slipping each other. Move relatively. Here, the friction coefficient between the friction washer 53 and the unit attaching / detaching plate 49 is μ,
Assuming that the pressing force of the compression coil spring 54 is F, when the disturbance torsional moment is larger than μFR2, the friction washer 53 and the unit attaching / detaching plate 49 slip with each other,
Do not slip when small. Thereafter, the friction washer 53
The contact part between the unit and the unit attachment / detachment plate 49
That.

The image carrying belt unit 20 is locked on the side plate 41 of the image forming apparatus main body by two pins 37 and 38 on the rear side. In addition, one pin 39 on the front side
And the friction washer 53 described above, and is locked to the main body side plate 42 (FIG. 2) via the unit attaching / detaching plate 49.
Therefore, if any disturbance, that is, a shocking external force acts on the image carrying belt unit device 20 during the image forming operation and a torsional moment acts on the device 20, the rear side is suspended by the two pins 37 and 38. Because it is locked,
The near side tends to cause torsional deformation around the fitting portion between the pin 39 and the hole 49a.

However, the disturbance torsional moment M
Is smaller than the reaction moment μFR2 caused by the frictional drag between the friction washer 53 and the unit attaching / detaching plate 49, the torsional deformation of the image carrying belt unit device 20 is prevented. The reaction moment μFR2 due to the frictional drag at the frictional portion is set to be larger than the disturbance torsional moment M acting on the image carrying belt unit device 20 when the cleaning blade 23 comes into contact with or separates from the intermediate transfer belt 3.

Therefore, in such a case, since the reaction moment due to the frictional force at the frictional portion becomes larger than the disturbance torsional moment M, the torsional deformation of the image carrying belt unit device 20 is prevented, and the device is an original static roller. It will continue to maintain the same state as the array. As described above, the frictional force generating means 50 provided between the roller supporting frame portion 40B provided with the second suspension means and the image forming apparatus main body 10 causes the image carrying belt unit apparatus 20 to perform the image forming operation. When a shocking external force acts on the image bearing belt unit 20, a frictional force for preventing the image bearing belt unit 20 from being twisted is applied.

On the other hand, considering the case where the image forming apparatus is moved on a floor having poor planar accuracy, in such a case, the deformation of the image forming apparatus main body is caused by the frictional force generating means 50 and the image is deformed. It acts on the carrier belt unit device 20 in a twisting manner. The force acting on the frictional portion at this time is proportional to the product of the torsional rigidity of the roller support unit frame 40 and the amount of deformation of the image forming apparatus main body.

The torsional rigidity of the roller support unit frame 40 shown in FIG. 5 is increased to some extent, and when the image forming apparatus main body is deformed, a torsional moment due to an external force applied to the image carrying belt unit apparatus 20 is generated by friction. In order to exceed the reaction moment μFR2 due to drag,
By setting the frictional force at the frictional portion, when distortion occurs in the image forming apparatus main body, slip occurs at the frictional portion. That is, when the image forming apparatus main body is deformed, the image carrying belt unit device 20 is substantially equivalent to the three-point support shown in FIGS. 1 to 3. Therefore, the state which is substantially equal to that of the original static roller arrangement is maintained.

In any case, in the present embodiment, when a disturbance acts directly on the image carrying belt unit device 20 due to the contact or separation of the cleaning member of the cleaning device, the frictional portion does not slip and the image carrying belt does not slip. Since the belt unit device 20 is firmly fixed and its torsional deformation is prevented, each roller of the image carrying belt unit device can be maintained in an initial assembled state, and the image forming apparatus can be formed on a floor surface with poor planar accuracy. When the main body is moved and the image forming apparatus main body is distorted, a slip occurs at a frictional portion, so that the influence of the distortion of the image forming apparatus main body is not transmitted to the image carrying belt unit apparatus and is assembled to the image carrying belt unit apparatus. Therefore, each of the rollers can be maintained in the initial assembled state.

The frictional force generating means 50 can absorb a sudden disturbance acting on the image carrying belt unit device 20, and if the image forming apparatus main body is distorted due to irregularities in the floor or the like, the influence of the distortion is eliminated. The parallel accuracy of each roller can be maintained in the initial assembly state without being transmitted to the image carrying belt unit device 20, so that deviation is less likely to occur during belt running, and the belt can run stably. From such a point, it is particularly advantageous to apply the present configuration to a relatively high-speed color image forming apparatus or the like in which a large disturbance easily acts.

In the present embodiment, similarly to the embodiment shown in FIG. 4, while taking advantage of the three-point support system, the three-point supported image carrying belt unit 20 is used to execute an image forming process. In this case, even when a disturbance torsional moment acts, the device can be hardly deformed.

Further, in this embodiment, a disk brake system in which a frictional force is generated by applying a force in the axial direction of a roller which stretches the intermediate transfer belt 3 is employed as the frictional force generating means. A so-called radial brake system that generates a frictional force by applying a force in a linear direction may be adopted. Further, in this embodiment, a coil spring is used as the pressing means for generating the frictional force, but a magnet may be used instead. With such a magnet,
There is an advantage that the image carrying belt unit device 20 can be easily attached to and detached from the image forming apparatus main body.

In the specific example shown in FIGS. 1 to 3, the roller supporting unit 40B provided with the pin 39 as the second suspension means and the roller supporting unit during the image forming operation are provided between the roller supporting frame 40B and the image forming apparatus main body. In order to prevent torsional deformation of the frame 40, the unit frame 40 may be fixed to the image forming apparatus main body 10 and locking means for releasing the fixing during non-image forming operation may be provided.
When a sudden external force acts on the image carrying belt unit device 20, the image carrying belt unit device can be prevented from being twisted. This is a configuration corresponding to the image carrying belt unit device according to the fourth aspect, and FIG. 7 shows an example thereof.

In FIG. 7, the rotation displacement of the image carrying belt unit device 20 (between the roller supporting frame portion 40B provided with the pin 39 as the second suspension means) and the image forming apparatus main body 10 (FIG. 1). A locking means comprising a locking screw 57 for fixing the roller support unit frame 40 and releasing the fixing so that the rotation of the pin 39 and the hole 49a around the fitting portion between the pin 39 and the hole 49a becomes impossible. It is interposed.

The locking screw 57 prevents twisting deformation of the image carrying belt unit device 20, and is inserted through an arc-shaped long hole 49b provided in the unit attaching / detaching plate 49. Unit frame 40
Is screwed into a screw hole 56 provided in the roller support frame portion 40B. The elongated hole 49b is formed in an arc shape centering on the pin 39.

Here, when the locking screw 57 is loosened,
The operation is exactly the same as that of the configuration shown in FIG. That is, the image carrying belt unit device 20 is supported at three points. On the other hand, in a state where the locking screw 57 is tightened, the image carrying belt unit device 20 is maintained while maintaining the shape of the three-point support by the three pins 37, 38, and 39.
Is a side plate 4 on the image forming apparatus main body side that cannot be twisted.
1 and 42 are firmly fixed. That is, four points are supported. Therefore, even if a disturbance torsional moment acts directly on the image carrying belt unit device 20 during the image forming operation, the device is extremely unlikely to be torsionally deformed. Further, when the image forming apparatus main body is distorted due to, for example, an irregular floor, the locking screw 57 is used.
Is loosened once and then retightened, the image carrying belt unit device 20 can be returned to the original state without twist.

That is, the image carrying belt unit 20
The roller support unit frame 40 has a predetermined torsional elasticity. When the locking screw 57 is loosened, the roller support unit frame 40 is supported at three points, and the torsional elasticity of the original roller support unit frame (torsion deformation). State). By this return, the parallel accuracy of each roller is maintained at the parallel accuracy at the time of initial assembly, the belt is less likely to be shifted during the image forming operation, and the belt can be stably run. Further, when the image forming apparatus is moved to a different floor, the locking screw 57 is similarly loosened and then tightened again to restore the image carrying belt unit apparatus 20 to the initial assembly state. Is possible.

In any case, in this embodiment, during the image forming operation, the image carrying belt unit device 20 is fixed to the image forming apparatus main body side by two points at each of the front and rear sides, so that the image forming apparatus main body is securely fixed. Side, the device is extremely unlikely to be deformed against disturbances (disturbances such as fluctuations in the rotational load of the belt) that directly act on the image carrying belt unit device during image formation. If the image forming apparatus main body is distorted due to irregularities in the floor or the like, the locking screw 57 is loosened to the original three-point support system, and then tightened again, so that the image-carrying belt unit apparatus can be used. Can be easily restored to the original initial state (the initial roller parallel state). In the present embodiment, the image carrying belt unit device has a three-point support system,
It is possible to freely adjust to both the four-point support type.

As described above, in the specific example shown in FIG.
The locking means fixes the roller support frame portion 40B provided with the pin 39 as the second suspension means to the image forming apparatus main body during the image forming operation, and releases the fixing during the non-image forming operation. It is composed of a roller support frame 40B provided with a second suspension means and a locking screw 57 attached to the image forming apparatus main body. Such a configuration is a specific example corresponding to claim 5.

The above-mentioned locking means is provided between the roller supporting frame portion 40B provided with the pin 39 serving as the second suspension means and the image forming apparatus main body, and prevents the roller supporting unit frame 40 from being twisted. It is also possible to provide a torsional deformation restricting device for preventing, and a control device for executing the torsional deformation restriction by the torsional deformation restricting device during the image forming operation and canceling the restriction during the non-image forming operation. This is a configuration corresponding to the image carrying belt unit device according to the sixth aspect. FIG. 8 shows a specific example.

In FIG. 8, a movable iron piece 61 for restricting torsional deformation of the roller support unit frame 40 is provided between the roller support frame portion 40B provided with the pins 39 as the second suspension means and the image forming apparatus main body. And an electromagnet 62, and a control device 59 for selectively controlling the torsional deformation by the restricting device 58 and canceling the restriction.

Roller support frame 4 of movable iron piece 61
A pin 51 is rotatably locked at the end near 0B,
One end side of the pin 51 is a roller support frame portion 40B.
Press fit. The pin 51 is connected to the main body side plate 42.
It is provided at a position separated by an appropriate distance R3 from the pin 39 supported by (FIG. 2), and the direction of the movable iron piece 61 is substantially perpendicular to the straight line connecting the pins 39 and 51.
A movable iron piece 61 is provided.

A flat portion 61a is formed on the movable iron piece 61, and a magnetic path of the electromagnet 62 is formed along the flat portion 61a. When the electromagnet 62 is not energized, the movable iron piece 61 is guided by guide means (not shown) so as to have a slight gap with the electromagnet. Electromagnet 6
2 is fixed to the image forming apparatus main body side.

During the image forming operation, the electromagnet 62 is excited. At this time, the movable iron piece 61 is attracted to the electromagnet and comes into close contact with the electromagnet 62. In such a state, the roller support unit frame 40 and the image forming apparatus main body side are fixed, so that even if a disturbance torsional moment acts on the roller support unit frame 40, the torsional deformation of the unit frame 40 is prevented. You.

The control device 59 is configured as a control circuit including a drive circuit for the electromagnet 62. The control device 59 excites the electromagnet 62 during an image forming operation and cancels the excitation during a non-image forming operation. As described above, the torsional deformation restricting device 58 restricts the torsional deformation of the image carrying belt unit device 20, and the control device 59 biases the electromagnet 62 of the torsional deformation restricting device 58 during the image forming operation. And the device 5
8 to control the torsion deformation of the image carrying belt unit device 20 during non-image forming operation, by deenergizing the electromagnet 62 of the torsion deformation restricting device 58 to release the fixation between the electromagnet 62 and the movable iron piece 61; The torsion deformation regulation of the image carrying belt unit device 20 by the regulating device 58 is released.

Therefore, also in this embodiment, the same operation as in the configuration shown in FIG. 2 is performed during the non-image forming operation. On the other hand, during the image forming operation, the electromagnet 62 is excited, and the movable iron piece 61 is fixedly held by the electromagnet 62 by magnetic force. At this time, the roller support unit frame 40
Means that both the front and rear frame portions 40B and 40A are 2
The state is locked point by point, and the state is firmly fixed to the side plates 41 and 42 of the image forming apparatus main body.
That is, the image carrying belt unit device 20 is supported at four points. Therefore, even when a disturbance torsional moment such as a belt load fluctuation acts directly on the image carrying belt unit device 20 during the image forming operation, the image carrying belt unit device is not substantially torsionally deformed.

Further, even when a distortion occurs in the main body of the image forming apparatus due to an irregular floor or the like, the influence of the distortion is not transmitted to the side of the image carrying belt unit. Even if the image forming apparatus main body is moved on the floor surface during the image forming operation, at the end of the image forming cycle, due to the torsional elasticity of the roller supporting unit frame 40, the original state of the unit (not torsional deformed). State). Therefore, in a high-speed color image forming apparatus having an extremely large disturbance, belt deviation or the like is less likely to occur during execution of an image forming process, and stable belt running can be performed.

In the present embodiment, the three-point support system and the four-point support system can be freely adjusted in the same manner as in the embodiment shown in FIG. You can do it.

The image carrying belt unit having the intermediate transfer belt for transferring the toner image from the latent image carrier has been described above. The present invention is directed to an image carrying belt unit having an endless belt made of a photosensitive belt. Alternatively, the present invention can be applied to an image carrying belt unit using a belt that carries and conveys a transfer material such as transfer paper.

[0109]

According to the structure of the first aspect, even if the rigidity of the main body of the image forming apparatus is not remarkably increased as in the prior art,
Regardless of the flatness of the floor on which the image forming apparatus is installed, it is possible to always maintain the state of parallelism at the time of the initial assembly of the roller for stretching the image carrying belt. In addition, since stable running of the belt can be expected, the durability of the belt can be improved. Further, since it is not necessary to increase the rigidity of the image forming apparatus main body as in the related art, an image provided with the image carrying belt unit device can be provided. An increase in the weight of the forming apparatus can be avoided.

According to the second aspect of the present invention, the torsional moment acting on the image carrying belt unit can be absorbed by the damping means, so that the image carrying due to the disturbance acting on the image carrying belt unit during the image forming operation. Since the belt unit can be prevented from being twisted and deformed, and the parallelism of the rollers can be prevented and the belt can be prevented from vibrating, a high-quality image can be formed on the belt.

According to the third aspect of the present invention, the torsional moment acting on the image carrying belt unit can be absorbed by the frictional force generating means, so that a disturbance acts on the image carrying belt unit during the image forming operation. Even so, it is possible to prevent the image carrying belt unit from being twisted and deformed, and to prevent the roller from being out of parallel and the belt from being vibrated.

According to the fourth aspect of the present invention, even if a disturbance torsion moment acts on the image carrying belt unit during the image forming operation, the image carrying belt unit can be prevented from being torsionally deformed, and the installation floor can be suppressed. Even when the image forming apparatus main body is distorted due to an irregular surface or the like, the image carrying belt unit can be easily restored to the original state without deformation.

According to the structure of the fifth aspect, the above-mentioned effects can be achieved by an extremely simple structure.

According to the configuration of the sixth aspect, the control means controls the biasing of the torsional deformation restricting device for restricting the torsional deformation of the image carrying belt unit device during the image forming operation, and controls the urging during the non-image forming operation. Since the torsional deformation restricting device is deenergized, even if a disturbance torsional moment acts on the image carrying belt unit during the image forming operation, the torsional deformation of the device can be suppressed. Even if the forming apparatus main body is distorted, the influence can be prevented from being exerted on the side of the image carrying belt unit apparatus, and the rollers for stretching the belt can be maintained at the parallelism at the time of initial assembly.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of an image forming apparatus including an image carrying belt unit according to an embodiment of the present invention.

FIG. 2 is a perspective view showing the image carrying belt unit according to the embodiment of the present invention, together with a side plate of an image forming apparatus main body.

FIG. 3 is a cross-sectional view illustrating an image bearing belt unit device portion where the driving roller illustrated in FIG. 2 is located.

FIG. 4 is a perspective view showing a specific example provided with a damping unit.

FIG. 5 is a perspective view showing a specific example provided with a frictional force generating means.

FIG. 6 is a sectional view of the frictional force generating means shown in FIG.

FIG. 7 is a perspective view showing a specific example in which a locking screw is provided.

FIG. 8 is a perspective view showing a specific example in which a torsional deformation restricting device and a device for controlling the same are provided.

FIG. 9 is a diagram illustrating the parallelism of rollers.

[Explanation of symbols]

 3 Belt 10 Image forming apparatus main body 20 Image carrying belt unit apparatus 31 Roller 32 Roller 33 Roller 34 Roller 35 Roller 40 Roller support unit frame 40A Roller support frame section 40B Roller support frame section 40C Connection frame section 40D Connection frame section 50 Friction force generation Means 58 Torsional deformation restricting device 57 Locking screw 59 Control device 100 Image forming device

Claims (6)

[Claims] An endless belt that carries and conveys a toner image, a plurality of rollers that stretch the belt, and includes at least one roller for driving the rotation of the belt, and are disposed in an internal space of the belt. A roller support unit frame rotatably supporting the plurality of rollers, and the roller support unit frame rotatably supports one end side of the plurality of rollers in the axial direction; and An image of an image forming apparatus including a roller supporting frame portion rotatably supporting the other end side in the axial direction of the plurality of rollers, and a connecting frame portion connecting both roller supporting frame portions in the axial direction of the rollers. In the carrying belt unit device, a roller supporting unit frame is provided on one of the two roller supporting frame portions with respect to the image forming apparatus main body. First suspension means for suspending the roller support unit frame with respect to the image forming apparatus main body so as to be positioned and mounted at a predetermined position is provided, and the roller support unit frame is provided with an image on the other frame portion. A second suspending means for suspending the roller support unit frame with respect to the image forming apparatus main body so that the position with respect to the image forming apparatus main body is regulated and is rotatably supported with respect to the image forming apparatus main body; An image carrying belt unit device provided. 2. An image forming apparatus according to claim 1, wherein a damping means for absorbing a shocking external force acting on the image carrying belt unit is provided between the roller supporting frame provided with the second suspension means and the image forming apparatus main body. 2. The image carrying belt unit device according to 1. 3. When an impact external force acts on the image carrying belt unit during an image forming operation between the roller supporting frame provided with the second suspension means and the image forming apparatus main body, the image is formed. 2. The image carrying belt unit according to claim 1, further comprising a frictional force generating means for applying a frictional force to the image carrying belt unit to prevent the carrying belt unit from being twisted. 4. An image forming apparatus according to claim 1, wherein said unit frame is provided between said roller supporting frame provided with said second suspension means and said image forming apparatus main body so as to prevent torsional deformation of said roller supporting unit frame during an image forming operation. 2. The image carrying belt unit according to claim 1, further comprising a locking means fixed to the main body and capable of releasing the fixing during a non-image forming operation. 5. The image forming apparatus according to claim 1, wherein the locking unit fixes the roller support frame provided with the second suspension unit to the image forming apparatus main body during the image forming operation, and releases the fixing during the non-image forming operation. 5. The image carrying belt unit according to claim 4, further comprising a roller support frame provided with a second suspension means and a locking screw attached to the image forming apparatus main body. 6. The torsional deformation control for preventing torsional deformation of the roller support unit frame, wherein the locking means is provided between the roller support frame portion provided with the second suspension means and the image forming apparatus main body. 5. The image carrying belt unit according to claim 4, further comprising an apparatus, and a control device for executing the torsional deformation restriction by the torsional deformation restricting device during the image forming operation and releasing the restriction during the non-image forming operation.