JP2003149951A - Transfer belt meander prevention device and image forming device using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent meander of a belt by a simple structure. SOLUTION: The device has a roller main body 53 over which a transfer belt 62 is wrapped, a pair of fixed flanges 51 and 52 disposed on both sides of the roller main body, a flange portion 51c formed on one of the fixed flanges 51 in such a manner as to project from the peripheral face of the roller main body, and a slide flange 57 disposed on the other flange 52 in such a manner as to freely slide. The device also has a spring 59 that presses the slide flange to the other fixed flange, and a flange portion 57c formed on the slide flange in such a manner as to project from the peripheral face of the roller main body. Both edges of the transfer belt 62 are controlled by the flange portion 51c of the one of the fixed flanges 51 and the flange portion 57c of the slide flange 57.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention provides an image forming station having a charging means and a developing means around an image carrier for each color along a transfer belt, and the transfer belt is passed through each station. The present invention relates to a tandem-type image forming apparatus, and more particularly to a transfer belt meandering prevention apparatus and an image forming apparatus using the same.

[0002]

2. Description of the Related Art The above-mentioned tandem type image forming apparatus is roughly classified and a plurality of image forming stations are arranged in a row.
The recording paper is electrostatically attracted to the conveyor belt, and the recording paper is sequentially brought into contact with each station while being conveyed, and electrostatic transfer force is applied between the station and the recording paper to record a toner image of a plurality of colors. A paper transport method that overlays colors while directly transferring to paper, and multiple image forming stations are arranged in rows.
While the intermediate transfer belt made of a dielectric material is brought into contact with each station and conveyed, the toner image formed at each station is sequentially primary-transferred by applying electrostatic transfer force between the station and the intermediate transfer belt. Then, two types of methods are employed: an intermediate transfer method in which colors are superposed on the intermediate transfer belt, and then secondary transfer is collectively performed from the intermediate transfer belt to the recording paper.

The above-mentioned paper transport system requires means (rollers and brushes) for attracting the recording paper to the transport belt and a high-voltage power supply, but the intermediate transfer system does not require these means and power supply. In the paper transport method, it is necessary to strictly control the transfer bias applied to each image transfer section according to the size, thickness, and type of recording paper, but in the intermediate transfer method, resistance is applied regardless of these factors of the recording paper. The primary transfer of the toner image is performed on the intermediate transfer belt having a constant thickness, surface roughness, and then the secondary transfer is collectively performed on the recording paper. It suffices to manage the transfer conditions as described above, and therefore the intermediate transfer method has many advantages.

[0004]

By the way, in either the intermediate transfer system or the paper transport system, the color superposition accuracy is improved by the meandering of the intermediate transfer belt or the paper transport belt (hereinafter, both are collectively referred to as a transfer belt). There is a problem that the image quality deteriorates and the image quality deteriorates. The meandering of the belt occurs due to a difference in circumferential length between both side surfaces of the belt in the belt forming process, a variation in material of the belt, parallelism between the driving roller and the driven roller, and the like.

Conventionally, various devices for restricting the meandering of the belt have been proposed, but each has a problem that the structure is complicated.

The present invention solves the above-mentioned conventional problems, and provides a transfer belt meandering preventive device capable of preventing the belt meandering with a simple structure, and an image forming apparatus using the same. With the goal.

[0007]

In order to achieve the above object, an image forming apparatus according to claim 1 of the present invention is provided with a roller body around which a transfer belt is wound, and arranged on both sides of the roller body. A pair of fixed flanges, a flange portion formed on one of the fixed flanges so as to project from the outer peripheral surface of the roller body, a sliding flange slidably disposed on the other fixed flange, and A spring for urging the moving flange toward the other fixed flange, and a flange portion formed on the sliding flange so as to project from the outer peripheral surface of the roller body, and both the one fixed flange and the sliding flange are provided. The transfer belt is regulated at both ends by flange portions, and the invention according to claim 2 is characterized in that, in claim 1, the fitting concave portion formed on the other fixed flange and the sliding flange. And a fitting convex portion formed on,
The fitting convex portion is fitted in the fitting concave portion, and at the same time, a part of the spring is embedded in the other fixing flange, and the invention according to claim 3, One of the fixing flanges is formed of a non-conductive, high-sliding resin, the other fixing flange is formed of a conductive, high-sliding resin, and the other fixing flange is grounded. According to a fourth aspect of the invention, in the first aspect, the sliding flange and the spring are mounted on at least one of a driving roller and a driven roller. In claim 4, the sliding flange and the spring are mounted on a driven roller, and the diameter of the driven roller is larger than the diameter of the driving roller.
The invention according to claim 1, wherein the transfer belt is a belt formed by an extrusion molding method, and an extrusion mark is formed along an inner peripheral surface of the belt. 1 is characterized in that the transfer belt is a belt formed by a centrifugal forming method, and a low friction material layer is formed on the back surface of the belt, and the invention according to claim 8 is the belt center portion according to claim 7. According to the invention of claim 9, an image forming station in which a charging unit and a developing unit are arranged around the image carrier is provided for each color along the transfer belt. In a tandem type image forming apparatus that forms a color image by passing the transfer belt through each image forming station, the transfer belt is stretched between a driving roller and a driven roller. The transfer belt meandering prevention device according to any one of claims 1 to 8 is used for at least one of the driving roller and the driven roller. The transfer belt is a paper transport belt or an intermediate transfer belt.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. 1 and 2 show an example of an image forming apparatus to which the present invention is applied. FIG. 1 is a schematic cross-sectional view showing the overall configuration, and FIG. 2 is an enlarged view of a main part of FIG. This example is the above-described intermediate transfer type image forming apparatus.

In FIG. 1, the image forming apparatus 1 of this example is
It has a housing 2, a paper discharge tray 2 a formed on the upper part of the housing 2, and a door body 3 which is openably and closably mounted on the front surface of the housing 2. Inside the housing 2, a control unit 4, a power supply unit 5, An exposure unit (exposure unit) 6, an image forming unit 7, a cooling unit 8 including a blower fan, a transfer belt unit 9, and a sheet feeding unit 10 are provided, and a paper transport unit 11 is provided in the door 3. There is. Each unit is configured to be attachable to and detachable from the main body, and is configured such that it can be integrally removed for repair or replacement during maintenance or the like.

The transfer belt unit 9 includes a drive roller 12 disposed below the housing 2 and driven to rotate by a drive source (not shown), and a driven roller 13 disposed obliquely above the drive roller 12. The intermediate transfer belt 14 which is stretched between the rollers and is driven to circulate in the direction of the arrow (counterclockwise) in the drawing, and the cleaning unit 15 which contacts the surface of the intermediate transfer belt 14, and the driven roller 13 and the intermediate transfer belt. 14 is disposed in a direction inclined to the left side in the drawing with respect to the drive roller 12. As a result, when the intermediate transfer belt 14 is driven, the belt surface 14a in which the belt conveying direction Y faces downward is located below, and the belt surface 14b in which the conveying direction faces upward is located above. In the present embodiment, the belt surface 14a is a belt tension surface (image pulled by the drive roller 12) when the belt is driven, and the belt surface 14b is a belt slack surface when the belt is driven.

The drive roller 12 also serves as a backup roller for a secondary transfer roller 39 described later. As shown in FIG. 2, the peripheral surface of the driving roller 12 has a thickness of about 3 mm,
A rubber layer 12a having a volume resistivity of 10 ⁵ Ω · cm or less is formed, and by being grounded via a metal shaft,
It is used as a conductive path of the secondary transfer bias supplied through the secondary transfer roller 39. By thus providing the driving roller 12 with the rubber layer 12a having high friction and shock absorption, it is difficult for the shock when the recording medium enters the secondary transfer portion to be transmitted to the intermediate transfer belt 14, resulting in deterioration of image quality. Can be prevented.

Further, in this embodiment, the diameter of the driving roller 12 is smaller than the diameter of the driven roller 13. As a result, the recording paper after the secondary transfer can be easily separated by the elastic force of the recording paper itself. Further, the driven roller 13 is also used as a backup roller of the cleaning means 15 described later.

The cleaning means 15 is provided on the side of the belt surface 14a facing downward in the conveying direction. As shown in FIG. 2, a cleaning blade 15a for removing the toner remaining on the surface of the intermediate transfer belt 14 after the secondary transfer,
The cleaning blade 15a is provided with a toner conveying member 15b for conveying the collected toner, and the cleaning blade 15a is in contact with the intermediate transfer belt 14 at a portion where the intermediate transfer belt 14 is wound around the driven roller 13.

Further, on the back surface of the intermediate transfer belt 14, a primary transfer member 16 composed of a leaf spring electrode is provided so as to face an image carrier 17 of each of image forming stations Y, M, C and K described later.
Is abutted by its elastic force, and a transfer bias is applied to the primary transfer member 16.

The image forming unit 7 includes image forming stations Y (for yellow), M (for magenta), C (for cyan), and K (black) for forming a plurality of (four in this embodiment) images of different colors. 2), as shown in detail in FIG. 2, each of the image forming stations Y, M, C, and K has an image carrier 17 composed of a photosensitive drum and an image carrier 1 respectively.
7 is provided with a charging unit 19 and a developing unit 20 which are arranged around the periphery 7 and are composed of a corona charging unit. The image forming stations Y, M, C, K may be arranged in any order.

The image forming stations Y, M,
The C and K image carriers 17 are brought into contact with the belt surface 14a of the intermediate transfer belt 14 which faces downward in the conveying direction, and as a result, the respective image forming stations Y, M, C and K are also moved relative to the drive roller 12. It is arranged in a direction inclined to the left side in the figure. The image carrier 17, as shown by the arrow in the figure,
The intermediate transfer belt 14 is rotationally driven in the conveying direction. The intermediate transfer belt 14 may be arranged in a direction inclined to the right side in the figure with respect to the drive roller 12. In that case,
The belt transport direction Y is opposite and the belt surface facing downward in the transport direction is 14b.

The exposing means 6 is arranged in a space formed obliquely below the image forming unit 7 arranged obliquely, and the control unit 4 and the power supply unit 5 are arranged in the space above the exposing means 6. Has been done. Further, a paper feeding unit 10 is arranged at the bottom of the housing 2 below the exposure means 6. Since the control unit 4 and the power supply unit 5 are arranged adjacent to the exposure unit 6, the installation space can be made smaller than in the case where they are arranged in parallel with the frame supporting the device parts.

As shown in FIG. 1, the exposure means 6 includes a polygon mirror motor 21, a polygon mirror 22, and a single f-.
A θ lens 23 and a reflection mirror 24 are arranged, and further four folding mirrors 25 for the scanning light paths are arranged above the reflection mirror 24 so that the scanning light paths of the respective colors are parallel to the belt surface 14a. Three folding mirrors 25 are arranged in the scanning optical path so that the scanning optical path reflected by the folding mirror 25 is irradiated to the image carrier 17.

By providing the folding mirror 25 in this way, the scanning optical path can be bent and the height of the exposure means 6 can be lowered, thus achieving compactness. The folding mirror 25 is arranged so that the scanning optical paths of the image forming stations Y, M, C, and K to the image carrier 17 have the same length.

In the exposure means 6 having the above structure,
An image signal corresponding to each color is modulated and formed from the polygon mirror 22 based on a common data clock frequency, and is emitted. The image signal passes through the f-θ lens 23, the reflection mirror 24, and the folding mirror 25, and then the image forming stations Y and M. ，
The C and K image carriers 17 are irradiated and a latent image is formed.

In this embodiment, by arranging the scanning optical system below the apparatus, the vibration of the scanning optical system due to the vibration given to the frame supporting the apparatus by the drive system of the image forming means can be minimized. It is possible to prevent deterioration of image quality.

A cooling means 8 comprising a blower fan is provided on the side surface of the housing 2, and external air is introduced in the direction of the arrow shown in the figure to cool the exposure means 6, the control unit 4 and the power supply unit 5. The air taken into the apparatus from the rear side of the recording paper P conveyance direction or the width direction of the recording paper P conveyance direction is guided to the vicinity of the polygon motor 21, and further,
Since the cooling passage is formed to lead the control unit 4 and the power supply unit 5 to the outside of the apparatus, the temperature rise of the polygon motor 21 is suppressed, the deterioration of the image quality is prevented, and the life of the polygon motor 21 is extended. I have to.

Next, the details of the developing means 20 will be described with reference to FIG.
The image forming station Y will be described as a representative. In this example, the image stations Y, M, C, and K are arranged in an oblique direction, and the image carrier 17 includes the intermediate transfer belt 14.
The toner storage container 26 is arranged obliquely downward due to the contact with the belt surface 14a facing downward in the conveyance direction. Therefore, the developing unit 20 has a special configuration.

That is, the developing means 20 includes a toner storage container 26 for storing toner (hatched portion in the drawing), and a toner storage portion 27 formed in the toner storage container 26.
And the toner stirring member 2 disposed in the toner storage unit 27.
9, a partition member 30 formed in the upper part of the toner storage portion 27, a toner supply roller 31 disposed above the partition member 30, and a toner supply roller 31 provided on the partition member 30 and abutting against the toner supply roller 31. The flexible blade 32 includes a developing roller 33 arranged to come into contact with the toner supply roller 31 and the image carrier 17, and a regulation blade 34 brought into contact with the developing roller 33.

The image carrier 17 is rotated in the conveying direction of the intermediate transfer belt 14, and the developing roller 33 and the supply roller 31 are rotated.
Is rotationally driven in the direction opposite to the rotational direction of the image carrier 17, while the stirring member 29 is rotationally driven in the direction opposite to the rotational direction of the supply roller 31. The toner stirred and carried up by the stirring member 29 in the toner storage unit 27 is supplied to the toner supply roller 31 along the upper surface of the partition member 30, and the supplied toner is rubbed against the flexible blade 32 and supplied. It is supplied to the surface of the developing roller 33 by the mechanical adhesive force to the uneven surface portion of the roller 31 and the adhesive force due to the electric power of friction. The toner supplied to the developing roller 33 is regulated by the regulating blade 34 into a coating layer having a predetermined thickness, and the thinned toner layer is conveyed to the image carrier 17 and is developed by the developing roller 33 and the image carrier 17.
The image carrier 1 at and around the nip portion formed by the contact
The latent image portion 7 is developed.

In this embodiment, the developing roller 33, the toner supply roller 31, and the contact portion of the developing roller 33 and the regulating blade 34 on the side facing the image carrier 17 are not buried in the toner in the toner storage portion 27. There is. With this configuration, it is possible to prevent fluctuation of the contact pressure of the regulation blade 34 with respect to the developing roller 33 due to the reduction of the stored toner, and at the same time, the regulation blade 34 causes the developing roller 3
Since the excess toner scraped off from No. 3 drops to the toner storage unit 27, filming of the developing roller 33 can be prevented.

The contact portion between the developing roller 33 and the regulating blade 34 is located below the contact position between the supply roller 31 and the developing roller 33, and the supply roller 31 causes the developing roller 3 to move.
3 is provided to the toner storage portion 27 below the developing means, and the excess toner that has not been transferred to the developing roller 33 and the excess toner that has been regulated and removed from the developing roller 33 by the regulation blade 34 is provided. The toner returned to is agitated with the toner in the toner storage portion 27 by the agitating member 29, and is again supplied to the toner introducing portion near the supply roller 31 by the agitating member 29. Therefore, the surplus toner is dropped to the lower portion without being jammed in the rubbing portion between the supply roller 31 and the developing roller 33 or the contact portion between the developing roller 33 and the regulating blade 34 to stir the toner in the toner storage portion 27. It is possible to prevent the deterioration of the toner in the developing means from gradually progressing and to cause a sudden change in image quality immediately after the replacement of the developing means.

Returning to FIG. 1, the paper feed unit 10 comprises a paper feed cassette 35 in which recording media P are stacked and held, and a pickup roller 36 for feeding the recording media P one by one from the paper feed cassette 35. There is.

The paper transport unit 11 includes a pair of gate rollers 3 for defining the timing of feeding the recording medium P to the secondary transfer portion.
7 (one roller is provided on the housing 2 side)
A secondary transfer roller 39 as a secondary transfer unit that is pressed against the drive roller 12 and the intermediate transfer belt 14, a main recording medium conveyance path 38, a fixing unit 40, and a discharge roller pair 4
1 and double-sided printing conveyance path 42.

The fixing means 40 has a heating element such as a halogen heater built in at least one of the fixing means 40, and the fixing roller pair 4 is rotatable.
0a and pressing means for pressing at least one roller of the fixing roller pair 40a to the other side to press the secondary image secondarily transferred to the sheet material onto the recording medium P. The secondary image secondarily transferred to the fixing roller pair 40a
The toner is fixed on the recording medium at a predetermined temperature in the nip portion formed by. In the present embodiment, the fixing unit 40 is arranged in a space formed diagonally above the belt surface 14b that is upward in the conveying direction of the transfer belt, in other words, in a space on the opposite side of the transfer belt from the image forming station. This makes it possible to reduce heat transfer to the exposure unit 6, the intermediate transfer belt 14, and the image forming unit, and to reduce the frequency of color misregistration correction operation for each color. In particular, the exposure unit 6 is located at the farthest position from the fixing unit 40, and the displacement of the scanning optical system component due to heat can be minimized, and the color shift can be prevented.

In this example, since the intermediate transfer belt 14 is arranged in the direction inclined with respect to the driving roller 12, a wide space is created in the right space in the drawing, and the fixing means 40 is arranged in that space. The heat generated by the fixing unit 40 is
It is possible to prevent the exposure unit 6, the intermediate transfer belt 14 and the image forming stations Y, M, C and K located on the left side from being transmitted. Further, since the exposure unit 6 can be arranged in the space on the lower left side of the image forming unit 7, the vibration of the scanning optical system of the exposure unit 6 due to the vibration given to the housing 2 by the drive system of the image forming means is minimized. Therefore, it is possible to suppress the deterioration of the image quality.

Further, in this embodiment, the primary transfer efficiency is increased (about 100) by using the spherical toner.
%), Cleaning means for collecting the primary transfer residual toner is not installed on each image carrier 17. This allows
Each image carrier 17 including a photosensitive drum having a diameter of 30 mm or less
Can be arranged close to each other, and the device can be downsized.

Further, since the cleaning means is not installed, the corona charging means 19 is adopted as the charging means. When the charging means is a roller, a small amount of the primary transfer residual toner existing on the image carrier 17 is accumulated on the roller to cause charging failure, but the corona charging means 19 which is a non-contact charging means. The toner is less likely to adhere to the toner, and the occurrence of poor charging can be prevented.

The outline of the operation of the entire image forming apparatus as described above is as follows. (1) When a print command signal (image forming signal) from a host computer or the like (not shown) (personal computer or the like) is input to the control unit 4 of the image forming apparatus 1, each of the image forming stations Y, M, C, and K. The image carrier 17, each roller of the developing device 20, and the intermediate transfer belt 14 are rotationally driven. (2) The outer peripheral surface of the image carrier 17 is uniformly charged by the charging means 19. (3) The exposure unit 6 selectively exposes the outer peripheral surface of the image carrier 17 uniformly charged in each of the image forming stations Y, M, C, and K in accordance with the image information of each color. An electrostatic latent image is formed. (4) The toner images of the electrostatic latent images formed on the respective image carriers 17 are developed by the developing means 20. (5) A primary transfer voltage having a polarity opposite to the charging polarity of toner is applied to the primary transfer member 16 of the intermediate transfer belt 14, and the toner image formed on the image carrier 17 is transferred to the intermediate transfer belt at the primary transfer portion. Along with the movement of 14, the images are sequentially transferred and superposed on the intermediate transfer belt 14. (7) Intermediate transfer belt 14 to which this primary image is primarily transferred
The recording medium P stored in the paper feeding cassette 35 is fed to the secondary transfer roller 39 via the pair of registration rollers 37 in synchronization with the movement of the sheet. (8) The primary transfer image is synchronously merged with the recording medium at the secondary transfer portion, and the primary transfer image is generated by the secondary transfer roller 39 pressed toward the drive roller 12 of the intermediate transfer belt 14 by a pressing mechanism (not shown). A bias having a polarity opposite to that of the transfer image is applied, and the primary transfer image formed on the intermediate transfer belt 14 is secondarily transferred to the recording medium that is synchronously fed. (9) The untransferred toner in the secondary transfer is conveyed toward the driven roller 13 and is scraped off by the cleaning means 15 arranged facing the roller 13, and the intermediate transfer belt 14 is refreshed. Then, the above cycle can be repeated again. (10) The toner image on the recording medium is fixed by passing the recording medium through the fixing means 40, and then the recording medium is directed to a predetermined position (when it is not double-sided printing, it is directed to the discharge tray 2a and double-sided printing). In the case of (2), it is conveyed toward the double-sided printing conveyance path 42).

FIG. 3 is a schematic cross-sectional view showing another example of the image forming apparatus to which the present invention is applied and showing the entire structure. It should be noted that the same components as those in the example of FIG. This example is an example of the above-described paper conveyance system, and the paper conveyance belt 43 is used instead of the intermediate transfer belt 14 in FIG.

In this example, a transfer unit 9 and a paper transport unit 11 are provided in the door body 3. The transfer unit 9 is disposed above the housing 2, and is driven by a drive source (not shown) so as to rotate, and a driven roller 13 and a backup roller 44 which are disposed obliquely below the drive roller 12, and these three. A paper conveying belt 43 that is stretched around a book roller and is circulated and driven in the direction of the arrow (clockwise direction) in the figure, and a cleaning unit 15 that faces the backup roller 44 and contacts the surface of the paper conveying belt 43 The roller 12 and the paper transport belt 43 are arranged in a direction inclined to the left side in the figure with respect to the driven roller 13. As a result, the belt tension side (the side pulled by the drive roller 12) 43a when the paper transport belt 43 is driven is positioned below, and the belt slack side 43b is positioned above.

A transfer member 45 formed of a leaf spring electrode is brought into contact with the back surface of the paper transport belt 43 by its elastic force so as to face the image carrier 17 of each of the image forming stations Y, M, C and K. A transfer bias is applied to the transfer member 45. Then, the image forming stations Y, M, C, K
The image bearing member 17 of the paper conveyance belt 43 is on the belt tension side 43 of the paper conveyance belt 43.
As a result, the image forming stations Y, M, C, and K are also arranged in a direction inclined to the left side with respect to the driven roller 13 in the drawing.

Next, the transfer belt meandering prevention device of the present invention will be described. FIG. 4 is a sectional view showing the first embodiment.

The driven roller 13 is a fixed shaft 50 made of metal.
And a pair of fixed flanges 51 and 52 rotatably arranged on both sides of the fixed shaft 50, and a cylindrical aluminum roller body 53 fixed between the fixed flanges 51 and 52. The fixed shaft 50 penetrates between the left and right frames 54, 54 of the transfer belt unit and is fixed by a nut 55.

The fixing flanges 51 and 52 are provided on the roller body 5.
3, one of the fixing flanges 51 is made of a non-conductive and highly slidable resin (for example, polyacetal), and the other fixing flange 52 is electrically conductive and has a high sliding property. Fixed shaft 50 molded with flexible resin
Is grounded. This makes it possible to easily remove the electric charge remaining on the belt and the electric charge generated by the friction between the back surface of the belt and the roller surface. Further, one fixing flange 51 is made non-conductive, and the other one having a small material volume. By using the fixed flange 52 as a conductive bearing, the use of an expensive conductive material can be suppressed as much as possible.

The fixing flanges 51 and 52 have a shaft portion 51.
a, 52a, large-diameter roller fixing portions 51b, 52b connected to the shaft portions 51a, 52a, and the roller fixing portion 51.
b, a flange portion 51 extending in the radial direction on the outer end portion of 52b
c and 52c are formed, and both ends of the roller body 53 are fitted to the roller fixing portions 51b and 52b, and are fixed to the roller fixing portions 51b and 52b and the flange portions 51c and 52c.

The flange portion 51c of the one fixed flange 51 is projected from the outer peripheral surface of the roller body 53, and the flange portion 52c of the other fixed flange 52 is flush with the outer peripheral surface of the roller body 53. It is configured. Then, the shaft portions 51a, 52a of the fixed flanges 51, 52
Are rotatably mounted on the left and right frames via bearings 56, 56.

On the other fixing flange 52, a ring-shaped fitting recess 5 is formed around the shaft portion 52a in the roller fixing portion 52b.
2d is formed, and the sliding flange 57 is fitted in the fitting recess 52d. The sliding flange 57 includes a tubular fitting protrusion 57a fitted in the fitting recess 52d,
A through hole 57b formed in the fitting convex portion 57a and a flange portion 57c radially formed on the outer end portion of the fitting convex portion 57a.
And the through hole 57b of the fitting convex portion 57a is provided in the shaft portion 52a.
The fitting convex portion 57a is fitted into the fitting concave portion 52d. A spring 59 is provided inside the fitting protrusion 57a.
One end of the spring seat 59 abuts the other end of the spring 59.
And is fixed to the shaft portion 52a by the ring 61.
As a result, a part of the spring 59 is fixed to the fixing flange 52.
By embedding it in the inside, the span between the frames 54, 54 can be shortened, and the size in the width direction of the device can be shortened and the size can be reduced.

Then, the transfer belt 62 (the intermediate transfer belt 14 in FIG. 1 or the paper transport belt 43 in FIG. 3) is wound around the outer circumference of the roller body 53, and one end portion of the side surface of the transfer belt 62 has a fixed flange. The flange portion 51 c of the sliding flange 57 is abutted against the flange portion 51 c of the sliding flange 57. As a result, the transfer belt 62
, The sliding flange 57 slides in the fitting recess 52d by the elastic force of the spring 59, causing one end of the transfer belt 62 to slide and the other end always to the fixed flange. Since the flange portion 51c of 51 is brought into contact with and regulated, the belt can be prevented from meandering.

In this embodiment, a method is adopted in which the left and right ends of the meandering of the belt are regulated by being sandwiched between the flange portion 51c of the fixed flange 51 and the flange portion 57c of the sliding flange 57. The following two points are important in this method. (1) To reduce the frictional force between the back surface of the belt 62 and the surface of the roller main body 53.
To position the belt end with the flange 51c of
It is necessary to smoothly propagate the urging force of the sliding flange 57 to the fixed flange 51 side. When the frictional force between the back surface of the belt 62 and the surface of the roller body 53 is high, it is difficult for the biasing force of the sliding flange 57 to smoothly propagate toward the fixed flange 51 side.
If the urging force of the fixed flange 51 to the flange portion 51c is excessively increased, belt wrinkling occurs in a direction orthogonal to the urging force (radial direction of the roller), and the meandering regulation cannot be performed, and a crack occurs at the belt end portion. It may damage the belt. Therefore, it is necessary to make the material of the belt itself or the material of the back surface have a low friction, or to provide a surface having a low friction on the roller surface. (2) The belt is not deformed or damaged by the urging force applied to the fixed flange 51. Of the rollers that stretch the belt, the amount of the belt wound around the roller that regulates the meandering is set to be larger than that of the other rollers. By making the portion where the end portion of the belt is restricted into a semi-cylindrical shape, it is possible to improve the strength of the belt against the urging force to the fixed flange 51. In addition, both flange portions 51
Since the belt end portion repeatedly abutting between c and 57c is apt to crack, only the belt end portion is thickened or reinforced by another member. It is also possible to increase the material rigidity of the belt (making the material of the belt highly rigid, or constructing the belt in a sandwich structure with a highly rigid member such as metal), but in order to stretch the belt into a desired shape. This is not preferable because the tension becomes large, the driving load increases, and if the belt is stopped for a long time, the belt will bend around the roller (creep).

Next, a method of manufacturing a belt for obtaining the characteristics (1) and (2) will be described. Generally, as a method of manufacturing a seamless (seamless) belt,
There are an extrusion molding method and a centrifugal molding method, and contrivances in each manufacturing method will be described below.

FIG. 5 is a diagram for explaining a method of manufacturing a belt by an extrusion molding method. A thermoplastic resin is extruded into a cylindrical shape by a ring die 70, and a desired width W is obtained after the extruding.
The belt 62 is manufactured by cutting the belt 62. During this extrusion molding, fine uneven protrusions 62a are formed along the inner peripheral surface of the belt. On the other hand, the roller main body 53 shown in FIG. 4 is formed with processing marks (cutting marks or polishing marks) in the circumferential direction of the roller.

Therefore, the belt 62 is connected to the roller main body 53.
When stretched over, the extrusion trace 62a is in a direction orthogonal to the processing trace, and the extrusion trace 62a and the processing trace do not interfere with each other. Therefore, the propagation of the urging force by the sliding flange 57 is not hindered, and The frictional force on the surface of the roller body 53 can be reduced.

6A and 6B are views for explaining a method of manufacturing a belt by a centrifugal molding method. FIG. 6A is a sectional view showing the entire structure including a mold, and FIG. 6B is a sectional view of FIG. FIG. 6C is an enlarged cross-sectional view of part B, FIG. 6C is a cross-sectional view of the manufactured belt, and FIG.

As shown in FIG. 6A, liquid resin or rubber material is poured into the inner circumference of the rotating cylindrical mold 71, and the belt 6
Unlike the extrusion molding, it is possible to manufacture a belt having a multilayer structure by sequentially injecting resins and rubbers having different properties. In this example, as shown in FIG. 6B, a fluorine-containing resin 62b for ensuring the cleaning property of the belt surface, a urethane rubber 62c as a core material, and a fluorine-containing resin 62d for reducing the friction on the back surface of the belt. Are sequentially injected to form a belt having a three-layer structure. Further, near the both ends of the cylindrical mold 71, a large diameter portion 71a having a diameter larger than that of the central portion and a tapered surface 71b for smoothing the flow of material to the large diameter portion 71a are provided. A belt having both ends thicker than the center can be easily manufactured. Then, as shown in FIG. (C), both ends of the centrifugally molded belt are cut into desired dimensions to obtain a belt that can be mounted on the roller body 53 as shown in FIG. (D). You can

If the end portion of the belt is made thicker than necessary, the above-mentioned bending and the cracks generated when the end portion is rotated for a long time are generated. Therefore, the thickness of the end portion of the belt is approximately twice the thickness of the central portion of the belt or less. Need to For example, when the belt central portion is 200 μm, the belt end portion is 400 μm or less.

As is clear from the above description, according to this embodiment, the roller body around which the transfer belt is wound, the pair of fixing flanges arranged on both sides of the roller body, and the one fixing flange. A flange portion formed to protrude from the outer peripheral surface of the roller body, a sliding flange slidably disposed on the other fixed flange, and the sliding flange urged to the other fixed flange. A spring and a flange portion formed on the sliding flange so as to project from the outer peripheral surface of the roller body are provided, and both end portions of the transfer belt are regulated by both the fixed flange and the sliding flange. With this configuration, the belt can be prevented from meandering with a simple structure.

Although the embodiments of the present invention have been described above, the present invention is not limited to these, and conventionally known or well-known techniques can be replaced or added as necessary.

For example, in the above-described embodiment, the meandering prevention device is provided on the driven roller 13 side in FIGS. 1 and 3, but it may be provided on the drive roller 12 side or on both rollers. It may be provided, or
A plurality of driven rollers may be installed and provided respectively. However, in the image forming apparatus of FIGS. 1 and 3, the diameter of the driven roller 13 is larger than the diameter of the driving roller 12. Therefore, if a meandering preventive device is provided on the driven roller 13 side, a fixed flange having a large diameter can be obtained. Since the restriction is performed by 51 and the sliding flange 57, the meandering can be prevented more effectively.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view showing an overall configuration, which is an example of an image forming apparatus to which the present invention is applied.

FIG. 2 is an enlarged view of a main part of FIG.

FIG. 3 is a schematic cross-sectional view showing another example of an image forming apparatus to which the present invention is applied and showing the overall configuration.

FIG. 4 is a first embodiment of a transfer belt meandering prevention device according to the present invention.
It is sectional drawing which shows embodiment.

FIG. 5 is a diagram illustrating a method for manufacturing a belt by an extrusion molding method according to the present invention.

6A and 6B are views for explaining a method of manufacturing a belt by a centrifugal molding method according to the present invention, in which FIG. 6A is a cross-sectional view showing the entire configuration including a mold, and FIG. 2B is an enlarged cross-sectional view of the portion B, FIG. 6C is a cross-sectional view of the manufactured belt, and FIG.

[Explanation of symbols]

12 ... Drive roller 13 ... driven roller 14 ... Intermediate transfer belt (transfer belt) 17 ... Image bearing member 19 ... Charging means 20 ... Developing means 43 ... Paper transport belt (transfer belt) 51 ... One fixed flange 51c ... flange 52 ... the other fixed flange 52d ... fitting recess 53 ... roller body 57 ... Sliding flange 57a ... Fitting convex portion 57c ... Flange part 59 ... Spring 62 ... Transfer belt

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Yujiro Nomura             Seiko, 3-3-3 Yamato, Suwa City, Nagano Prefecture             -In Epson Corporation F-term (reference) 2H030 AB02 BB42                 2H071 CA01 CA05 DA09 DA16 EA18                 2H072 AB07 BA12 CA01 CA02 CA05                       CB09 JA03                 2H200 FA04 GA12 GA23 GA44 GA47                       GB43 GB44 JA02 JB07 JB32                       JB42 JB43 JB45 JB46 JB47                       JC04 JC07 JC12 JC13 JC15                       JC17 KA01 KA12 LA25 LB02                       LB13 LC00 MA02 MB01 MC05                 3F049 AA10 BB11 LA01 LB03

Claims (10)

[Claims] 1. A roller main body around which a transfer belt is wound, a pair of fixing flanges arranged on both sides of the roller main body, and one fixing flange formed so as to protrude from an outer peripheral surface of the roller main body. Flange part, a sliding flange slidably arranged on the other fixed flange, a spring for urging the sliding flange to the other fixed flange, and an outer peripheral surface of the roller body on the sliding flange. A transfer belt meandering prevention device, comprising: a flange portion formed so as to project further; and both end portions of the transfer belt being regulated by both of the one fixed flange and the sliding flange. 2. A fitting recess formed on the other fixed flange and a fitting projection formed on the sliding flange, wherein the fitting projection is fitted into the fitting recess. The transfer belt meandering prevention device according to claim 1, wherein a part of the spring is embedded in the other fixing flange. 3. One of the fixing flanges is made of a non-conductive and highly slidable resin, and the other fixing flange is made of a conductive and highly slidable resin. The transfer belt meandering prevention device according to claim 1, which is grounded. 4. The transfer belt meandering prevention device according to claim 1, wherein the sliding flange and the spring are mounted on at least one of a driving roller and a driven roller. 5. The transfer belt meandering preventing apparatus according to claim 4, wherein the sliding flange and the spring are mounted on a driven roller, and the diameter of the driven roller is larger than the diameter of the driving roller. 6. The meandering prevention of a transfer belt according to claim 1, wherein the transfer belt is a belt formed by an extrusion molding method, and an extrusion mark is formed along the inner peripheral surface of the belt. apparatus. 7. The transfer belt meandering prevention device according to claim 1, wherein the transfer belt is a belt formed by a centrifugal molding method, and a low friction material layer is formed on the back surface of the belt. 8. The meandering preventive device for a transfer belt according to claim 7, wherein both ends of the transfer belt are thicker than the central part of the belt. 9. An image forming station in which a charging unit and a developing unit are arranged around an image carrier is provided for each color along a transfer belt, and a color image is formed by passing the transfer belt to each image forming station. 9. In a tandem type image forming apparatus, the transfer belt is stretched between a driving roller and a driven roller, and at least one of the driving roller and the driven roller is a transfer belt meandering prevention device according to claim 1. An image forming apparatus characterized by using. 10. The image forming apparatus according to claim 9, wherein the transfer belt is a paper transport belt or an intermediate transfer belt.