JP2002006644A - Transfer device and image forming device having the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve adherence between a transfer material and an image carrier in a transfer device which has three rolls respectively supported by support bodies at their ends so as to rotate freely and a transfer belt driven by being wound around the rolls and which passes a transfer material between the transfer belt and an image carrier, thereby transferring a toner image on the image carrier to the transfer material. SOLUTION: The roll support member 26 is provided for supporting the longitudinal intermediate portion of each of the rolls 16, 17, and 18 from the inside of the transfer belt 22.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to at least three rollers each having a longitudinal end rotatably supported by a support, and an endless transfer belt wound around these rollers and driven to travel. While the transfer material is pressed against the surface of the image carrier by the transfer belt portion between two rollers adjacent to each other along the moving direction of the transfer belt,
A transfer device for passing a transfer material between the transfer belt portion and an image carrier to electrostatically transfer a toner image formed on the image carrier to the transfer material, and an image forming apparatus having the transfer device Related to the device.

[0002]

2. Description of the Related Art Electronic copiers, facsimile machines, printers,
An image forming apparatus of the above type configured as a plotter or a multifunction machine having at least two of these functions and a transfer apparatus therefor have been conventionally known (JP-A-6-35).
No. 338). In this type of transfer device, the transfer belt is supported by at least three rollers, so that the torsional rigidity of the entire transfer device can be increased as compared with a transfer device in which the transfer belt is wound around two rollers. ,
The transfer material conveyed between the transfer belt and the image carrier can be easily brought into uniform contact with the surface of the image carrier.

However, a large tensile force is applied to the transfer belt wound around the plurality of rollers, and the transfer belt strongly presses the plurality of rollers. They are elastically deformed in directions approaching each other. When the roller bends in this way, the transfer material conveyed between the transfer belt and the image carrier does not adhere to the surface of the image carrier, and a transfer failure of the toner image occurs. In particular, in an image forming apparatus that can use a wide transfer material, for example, a transfer material having a width of 450 mm or more, the rollers of the transfer device become longer. The portions are largely bent in the direction in which they approach each other, and the adhesion between the transfer material and the image carrier is reduced.

[0004] As described above, the transfer device in which the transfer belt is wound around at least three rollers has a transfer material on the surface of the image carrier, as compared with the transfer device in which the transfer belt is wound around two rollers. Although it is easy to adhere, especially when the length of the roller is long, the deflection of the roller increases,
The effect of bringing the transfer material into close contact with the surface of the image carrier with uniform pressure over the entire width direction cannot be sufficiently exhibited.

[0005]

SUMMARY OF THE INVENTION A first object of the present invention is to make it possible to bring a transfer material into close contact with a surface of an image carrier more uniformly than before, and to obtain the effect of using at least three rollers. Is to provide a transfer device of the type described at the beginning, which can sufficiently exhibit the following.

A second object of the present invention is to provide an image forming apparatus provided with the above-described transfer device.

[0007]

According to the present invention, there is provided a transfer apparatus of the type described at the outset wherein at least one roller supporting a longitudinally intermediate portion of said at least three rollers. A transfer device is provided, comprising a support member, wherein the roller support member has a bearing surface for rotatably supporting each roller from inside the transfer belt (claim 1).

In this case, it is advantageous that the roller support member is supported by a fixed support shaft that penetrates a hole formed in the roller support member.

Further, in the transfer device according to the present invention, at least one of the two rollers adjacent to each other is supported by the fixed support shaft so as to eliminate bending due to its own weight or reduce the amount of bending. Advantageously, one roller support presses the two adjacent rollers upwards (claim 3).

Further, in the transfer device according to any one of claims 1 to 3, at least the two rollers adjacent to each other along the movement direction of the transfer belt are provided with a core shaft made of a rigid body, and A plurality of elastic members mounted around a shaft and positioned adjacent to each other in a longitudinal direction of the roller in contact with each other, and a part of the roller support member does not contact the transfer belt. In this state, it is particularly advantageous that the elastic member is elastically deformed and enters between adjacent elastic members, and the bearing surface of the roller supporting member contacts the core shaft to support the core shaft ( Claim 4).

In the transfer device according to the fourth aspect, the radially inner portions of the ends of the elastic members adjacent to each other are cut out in a ring shape, and a part of the roller support member enters the cutout. Is advantageous (claim 5).

Further, in order to achieve the second object, the present invention comprises a transfer device according to any one of claims 1 to 5, and an image forming means for forming a toner image on an image carrier. An image forming apparatus characterized by the following is proposed.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described, and the above-mentioned disadvantages will be more specifically clarified with reference to the drawings.

FIG. 1 is a schematic view showing a part of an image forming apparatus. The image forming apparatus shown in FIG. 1 includes an image carrier 1 and an image forming means 2 for forming a toner image on the image carrier. Transfer device 3, a feeding device 4 for feeding a transfer material to a transfer position between the transfer device 3 and the image carrier 1, and a fixing device 5 for fixing a toner image on the transfer material. I have. First, the configuration and operation of the image carrier 1 and the image forming means 2 for forming a toner image on the surface thereof will be clarified.

The image carrier 1 shown as an example here is configured as a drum-shaped photosensitive member that is driven to rotate counterclockwise. The surface of the image carrier 1 is uniformly charged to a predetermined polarity by a charging device 6, and the charged surface is irradiated with a light-modulated laser beam L emitted from an exposure device 7 configured as an optical writing unit. As a result, an electrostatic latent image is formed on the surface of the image carrier. This latent image is visualized as a toner image by the developing device 8. The developing device 8 shown here has a developing roller 9 that carries and conveys the developer while rotating clockwise, and the toner in the conveyed developer forms an electrostatic latent image on the surface of the image carrier. The latent image is visualized by moving electrostatically. As the developer, in addition to a powdery two-component developer having a toner and a carrier,
A powdery one-component developer without a carrier, a liquid developer, or the like can be used. The toner image thus formed on the surface of the image carrier is transferred onto a transfer material by the transfer device 3 as described later, and the transfer residual toner adhering to the surface of the image carrier after the transfer of the toner image is cleaned. It is scraped off by the cleaning member 11 of the apparatus 10. The surface of the image carrier 1 whose surface has been cleaned is irradiated with light from the static eliminator 12, and its surface potential is initialized.

As described above, the image forming means of this embodiment includes a charging device 6 for charging the image carrier 1, an exposure device 7 for exposing the charged surface to form an electrostatic latent image, and an It has a developing device 8 for visualizing the image as a toner image, a cleaning device 10 for cleaning the surface of the image carrier after the transfer of the toner image, and a static eliminator 12 provided as necessary. It is well known that an appropriate image forming means can be adopted.

On the other hand, the feeding device 4 includes a pair of registration rollers 13 for feeding a transfer material P such as transfer paper at a predetermined timing.
The transfer material P sent out by the registration roller pair 13 passes through a transfer position between the image carrier 1 and the transfer device 3, and the toner image formed on the surface of the image carrier at this time is transferred. It is transferred to the surface of the material P. The image forming apparatus of the present embodiment is configured to transfer a toner image to a wide transfer material having a width of 450 mm or more. Such an image forming apparatus is also called a wide-width machine.

The transfer material having passed the transfer position then passes between the fixing roller 14 and the pressure roller 15 of the fixing device 5, and at this time, a toner image is fixed on the transfer material by the action of heat and pressure. The transfer material that has passed through the fixing device 5 is discharged outside the image forming apparatus main body and stacked.

FIG. 2 is an enlarged view of the transfer device 3, and FIG. 3 is a perspective view thereof. The transfer device 3 shown in these figures
It has three rollers 16, 17, and 18 arranged substantially parallel to each other in the direction of transport of the transfer material P (FIG. 1), that is, the direction substantially perpendicular to the direction of movement of the surface of the image carrier. 16, 17 and 18 have respective ends in the longitudinal direction,
As shown in FIG. 3, it is rotatably supported by supports 19 and 20 formed of a side plate of the transfer device 3 or a side plate of the image forming apparatus main body. FIG. 3 shows each of the rollers 16, 17, 18
And a state in which a fixed support shaft 21 described later is detached from the supports 19 and 20. In the example shown, three rollers 1
Although 6, 17, and 18 are used, four or more rollers can be used. In short, the transfer device has at least three rollers.

[0020] a plurality of rollers 16, 17, 18 described above are endless transfer belt 22 is wound, the transfer belt 22, for example a volume resistivity of 10 ⁶ to 1
Among the approximately 0 ¹⁴ Ω · cm consisting of resistor. Three rollers 1
At least one of the rollers 6, 17, and 18, for example, the roller 18 is configured as a driving roller, and the roller 18 is rotated clockwise by a motor (not shown). The vehicle is driven to travel in the A direction.

The three rollers 16, 17, 18 are spaced apart from each other so as to form a vertex of a triangle, and are adjacent to each other along the moving direction A of the transfer belt 22. 17, the transfer belt portion 23 is pressed against the surface of the image carrier, and the transfer belt portion 23 has a predetermined width (nip width) in the moving direction A of the transfer belt 22.
With N, it is in pressure contact with the surface of the image carrier 1. Also,
To the roller 17, a transfer voltage having a polarity opposite to the toner charging polarity of the toner image formed on the surface of the image carrier is applied.

As described above, the transfer material P sent out by the registration roller pair 13 is conveyed to the transfer position between the transfer belt portion 23 and the image carrier 1 while being carried on the transfer belt portion 23. You. At this time, the transfer material P is
The toner image on the surface of the image carrier is statically transferred onto the transfer material P because the transfer belt 23 presses the roller 17 to press the surface of the image carrier 1 and presses the roller 17 with the above-described transfer voltage. The toner image is transferred electrically to the transfer material P. As described above, the transfer device 3 includes the transfer belt 2
Two rollers 1 adjacent to each other along the moving direction A
While the transfer material P is pressed against the surface of the image carrier 1 by the transfer belt portion 23 between the transfer belts 6 and 17, the transfer material P is passed between the transfer belt portion 23 and the image carrier 1 so that the transfer material P Is electrostatically transferred onto the transfer material.

A cleaning blade 24 is pressed against the surface of the transfer belt portion that comes into contact with the roller 18, and the toner transferred from the image bearing member 1 to the surface of the transfer belt 22 is scraped off by the cleaning blade 24. Is done. The scraped toner falls into a toner receiver 25 arranged below the transfer belt 22, and the dropped toner is stored in a predetermined place.

Instead of configuring the roller 17 as a bias roller to which a transfer voltage is applied, a dedicated bias roller that contacts the surface of the transfer belt 22 may be provided. Instead of using such a bias roller, a corona discharger or a transfer brush is provided inside the transfer belt, and a transfer voltage is applied thereto to transfer the toner image on the image carrier onto the transfer material. You can also. Further, even when the image carrier is configured as an intermediate transfer body on which a toner image is primarily transferred from a photoconductor, the toner image on the image carrier is transferred onto a transfer material by the transfer device having the above-described configuration. The next transfer can be performed.

The above-described transfer device 3 includes three rollers 16,
Since the transfer belt 22 is supported by the transfer belts 17 and 18, the torsional rigidity of the entire transfer device can be increased as described above. However, a large tensile force is applied to the transfer belt 22, and the transfer belt 22 As shown by an arrow F in FIG. 2, the rollers 16, 17, 18 are pressed with a large force.

For this reason, in the conventional transfer apparatus of this type, the central portions in the longitudinal direction of the plurality of rollers bend in directions approaching each other, whereby the transfer material conveyed between the transfer belt and the image bearing member is moved. There is a possibility that the adhesion between the central portion in the width direction and the image carrier is reduced, and the transfer efficiency of the toner image is reduced. In the case of a wide-width machine capable of using a transfer material having a width of 450 mm or more, since the length of the roller is also long, the amount of deflection of the central portion in the longitudinal direction of the roller is particularly large, and the transfer efficiency of the toner image is likely to be reduced. Become. Also, in a wide-width machine, the paper wound in a roll is pulled out,
In many cases, a sheet-like transfer material obtained by cutting the transfer material is used. However, since the transfer material is curled by being wound, the transfer material is fed between the image carrier and the transfer belt to transfer the toner image. At this time, the adhesion between the transfer material and the image carrier is remarkably reduced, and there is inevitably the possibility that an image may be missing particularly at the front and rear ends of the transfer material. For this reason,
Conventionally, it has been difficult to adopt a transfer device in which a transfer belt is wound around a plurality of rollers in a wide-width machine.

In the transfer device 3 of the present embodiment, in order to eliminate the above-mentioned conventional disadvantage, as shown in FIGS. A supporting roller support member 26 is provided. The roller support member 26 is made of a highly rigid material such as a metal or a hard resin, and as shown in FIG.
7 has a plurality of arms 28 radially protruding therefrom, and the distal end of each arm 28 has, as clearly shown in FIG.
It is configured as an arc-shaped bearing surface 29 that can be in close contact with the peripheral surfaces of the rollers 16, 17, and 18. The roller support member 26 is located inside the transfer belt 22, and each bearing surface 29 of each roller 16, 1 from the inside of the transfer belt 22.
7, 18 are rotatably supported. The roller support member 26 shown in FIG. 2 to FIG.
Not in contact with The roller supporting member 26 is a roller 1
6, 17, 18, that is, at an appropriate position between the two supports 19, 20, as shown in FIG. 4, at the center of the rollers 16, 17, 18 in the longitudinal direction. Advantageously, they are arranged. In addition, since each bearing surface 29 is a portion that rotatably supports each of the rollers 16, 17, and 18, it is preferable to process the bearing surface 29 so that the frictional resistance of the bearing surface is reduced. Further, the bearing surface 29 may be configured by embedding a slide bearing. The number of the roller support members 26 may be plural, and the number can be set as appropriate (see FIG. 8).

As mentioned above, the transfer device must have at least three
The roller includes at least one roller support member that supports a longitudinal intermediate portion of the roller, and the roller support member has a bearing surface that rotatably supports each roller from the inside of the transfer belt. By providing such a roller support member 26, the rollers 16, 17, and 18 are supported from the inside of the transfer belt 22 by the roller support member 26.
Even if a large force is applied in the direction indicated by arrow F in FIG. 2 from FIG. 2, the rollers 16, 17, 18 are prevented from bending toward each other due to the force, or the amount of deflection is minimized. Can be small. As a result, the transfer material P conveyed between the transfer belt 22 and the image carrier 1 can be brought into close contact with the image carrier 1 over the entire width thereof with a uniform pressure, and the transfer failure of the toner image can be reduced. Generation can be prevented. Roller support member 26
Does not contact the transfer belt 22, the transfer belt 22 is damaged by the roller support member 26,
There is no danger that the transfer belt will undulate.

The rollers 16, 17, and 18 receive the external force from the transfer belt 22, and also tend to bend in the direction in which the central portion in the longitudinal direction projects downward due to the weight of the rollers themselves. Belt portion 23 pressed against image carrier 1
Assuming that the amount of deflection of the two rollers 16 and 17 that support the roller due to their own weight increases, the adhesion between the transfer material P and the image carrier 1 also decreases. In particular, in a wide-width machine, the length of the roller is long and its weight is also large, so that the amount of deflection due to its own weight may be large.

Therefore, in the transfer device 3 of this embodiment, in order to prevent the above-mentioned problem, a hole 30 is formed in the central portion 27 of the roller support member 26, and the fixed support shaft 21 penetrates the hole 30. Each end of the fixed support shaft 21 in the longitudinal direction is supported by each of the supports 19 and 29 as shown in FIGS. Thereby, the roller support member 2
6 is firmly supported by the fixed support shaft 21. The fixed support shaft 21 extends substantially parallel to each of the rollers 16, 17, and 18, and each end of the fixed support shaft 21 is
It is fixedly fixed to 9, 20 or rotatably supported. Further, the fixed support shaft 21 that penetrates the hole 30 of the roller support member 26 may be fixed to the roller support member 26, or may simply be penetrated through the hole 30.

As described above, since the roller support member 26 is supported by the fixed support shaft 21 penetrating the hole 30 formed in the roller support member 26, the roller support member 26 moves the two rollers 16 and 17 down. From the side, these rollers 1
6, 17 can be prevented from bending due to its own weight, or the amount of bending can be suppressed to a very small amount. Thus, the effect of bringing the transfer material P into close contact with the image carrier 1 over the entire width direction can be further enhanced.

The weight of the fixed support shaft 21 and the load from the rollers 16, 17 and the roller support member 26 act on the fixed support shaft 21, but if the fixed support shaft 21 is largely bent by this, the above-mentioned effects can be sufficiently achieved. It cannot be demonstrated. Accordingly, the bending rigidity of the fixed support shaft 21 is reduced by the roller 1.
It is preferable to set the flexural rigidity to be larger than the flexural rigidities of Nos. 6 and 17.

Assuming that the rollers 16 and 17 do not bend downward due to their own weights,
As shown in FIG. 7, a central portion in the longitudinal direction of FIG.
17 can be configured to be pressed upward by the roller support member 26. According to this configuration, the own weight acts on each of the rollers 16 and 17, and therefore, in actuality,
These rollers 16 and 17 are bent and deformed downward from the state shown by the solid line in FIG. 7, and as shown by the chain line in FIG.
A state in which no deflection occurs. The rollers 16, 17 are pressed by the roller supporting member 26 and lifted upward by the amount of bending when the rollers 16, 17 are bent and deformed by their own weights, and the deflection of the rollers 16, 17 due to their own weight is corrected.

In the example shown in FIG. 7, the rollers 16 and 17 are pressed upward by one roller supporting member 26,
The deflection of the rollers 16 and 17 due to their own weight is corrected.
17 may be configured to be pressed upward. Also, the rollers 16 and 17 are not fixed at all by the weight of the rollers 16 and 17 but by the roller support member 26 so that the amount of deflection is reduced.
7 may be configured to be pressed upward.

FIG. 7 shows a state in which the fixed support shaft 21 and the roller 18 are not bent and deformed.
As the rollers 16 and 17 are brought into the state shown by the chain line, the fixed support shaft 21 and the roller 18 are bent downward from the state shown in FIG. This is the same in FIG.

As shown in FIG. 8, three rollers 1
Roller support members 26 are provided at the longitudinal central portions of the rollers 6, 17, 18 and at the respective longitudinal ends of the rollers 16, 17, 18 with respect to the central portions, respectively. When a member having a shape is used,
Hole 30 in roller support member 26 located at the end of the roller
9 is formed at the position shown by the solid line in FIG. 9, and the hole 30 of the roller support member 26 located at the center portion side of the roller is, as shown by the broken line in FIG. 8 can also be formed at a lower position, and the fixed support shaft 21 can be penetrated through the holes 30 of the roller support members 26 as shown in FIG. According to this configuration, the rollers 16, 1
Assuming that the roller 7 does not bend due to its own weight, the central portions in the longitudinal direction of the two rollers 16 and 17 are pressed upward by the central roller supporting member 26, and are shown by solid lines in FIG. As shown in FIG.
Actually, the rollers 16 and 17 are subjected to their own weight, so that the rollers 16 and 17 are in a straight state without bending as shown by a chain line in FIG. In this case as well, the rollers 16 and 17 may be configured so that they do not bend due to their own weights, or the rollers 16 and 17 may be simply pressed by the roller support member 26 so that the amount of bending is reduced.

As described above, the two adjacent rollers 16 and 17 supporting the transfer belt portion 23 pressed against the surface of the image carrier 1 are prevented from bending due to their own weight, or the amount of the bending is reduced. Further, at least one roller support member 26 supported by the fixed support shaft 21 presses the two adjacent rollers 16 and 17 upward. With this configuration,
Transfer Material P Conveyed Between Transfer Belt 22 and Image Carrier 1
Can be evenly adhered to the surface of the image carrier over the entire width direction to further enhance the effect of preventing the occurrence of transfer failure of the toner image.

The three rollers 16, 17, 18
When the transfer device 3 is configured by using the roller 1, not only can the torsional rigidity of the entire transfer device be increased, but also the rollers 1
A large space is defined inside the transfer belt 22 wrapped around the transfer belts 6, 17, and 18, and the roller support member 26 and the fixed support shaft 21 are disposed therein to firmly support the rollers 16, 17, and 18. Becomes possible. For example, as shown in FIG. 17, the transfer belt 2 is attached to two rollers 16A and 17A.
Assuming that the transfer device 3A is formed by winding the transfer belt 2A around the transfer belt 22A, the internal space defined by the transfer belt 22A becomes narrower, and the image carrier 1A is pressed against the transfer belt portion 23A, so that the transfer belt portion 23A Since the sheet is bent, the space inside the transfer belt 22A becomes narrower.
For this reason, the diameter of the fixed support shaft 21A arranged in this space cannot be increased, and the fixed support shaft 21A cannot firmly support the roller support member 26A, and eventually the rollers 16A and 17A. On the other hand, as shown in FIG. 2, when three rollers 16, 17, and 18 are used, a large space can be secured inside the transfer belt 22, so that the diameter of the fixed support shaft 21 disposed in this space is increased. Can be set large, so that the roller supporting member 26 and thus the rollers 16, 17, 18 can be firmly held.

By the way, as shown in FIG. 2, the transfer belt portion 23 pressed against the image carrier 1 is as flat as possible so as to be able to contact the surface of the image carrier with a uniform pressure. Is preferred. Therefore, these rollers 1
As shown in FIG. 10, the core shafts 3 and 6 are made of a rigid body.
1 and an elastic member 32 mounted around it. Since the transfer belt 22 is wound around the surface of the elastic member 32 of the rollers 16 and 17, the flatness of the transfer belt portion 23 is improved. The elastic member 32 is made of, for example, an elastic material such as rubber or foam. Further, the elastic member 32 can be made of a conductive material. Further, the elastic member 32 is made of a material having a large friction coefficient with respect to the transfer belt 22 so that the slip between the rollers 16 and 17 and the transfer belt 22 is reduced. It is preferable to configure.

At this time, if the elastic member 32 is composed of one member that covers the core shaft 31, the roller supporting member 26
The roller 16 and 17 must be supported by bringing the bearing surface 29 of the elastic member 32 into contact with the outer surface of the elastic member 32. However, as described above, the elastic member 3 is
If the support member 2 is supported, since the coefficient of friction of the elastic member 32 is large, the support stability of the rollers 16 and 17 is impaired.

Therefore, the rollers 16 and 17 shown in FIGS. 10 and 11 have a plurality of adjacent elastic members 32 in contact with each other in the longitudinal direction of the rollers 16 and 17.
Each elastic member 32 is formed in a cylindrical shape having a center hole 34 through which the core shaft 31 passes. 11 and FIG.
As shown in FIG. 2, between the elastic members 32 adjacent to each other,
Part of the roller support member 26, that is, its bearing surface 29
A portion near (FIG. 6) elastically deforms the elastic member 32 and enters, and the bearing surface 29 contacts the core shaft 31 to support the core shaft 31. Also in this case, the roller supporting member 26 does not come into contact with the transfer belt 22, and the transfer belt 22 is not damaged by the roller supporting member 26.

As can be seen from FIG. 11, the transfer belt 22 is in contact with a portion 33 of the elastic member other than the elastic member portion into which the roller supporting member 26 has entered. Since the ends of the elastic members 32 adjacent to each other are in contact with each other, the transfer belt 22 is supported by the portion 33, and the problem that the transfer belt 22 is locally depressed can be prevented.

The structure shown in FIGS. 10 and 11 can be adopted for the roller 18 shown in FIG. In short, at least two rollers 16 and 17 adjacent to each other along the moving direction of the transfer belt 22 are fixed to the core shaft 3 made of a rigid body.
And a plurality of elastic members 32 mounted around the core shaft 31 and positioned adjacent to each other in the longitudinal direction of the rollers 16 and 17 in contact with each other. In a state where a part of the elastic member 32 is not in contact with the transfer belt 22, the elastic member 32 is elastically deformed and enters between the elastic members 32 adjacent to each other.
6 is configured so that the bearing surface 29 contacts the core shaft 31 to support the core shaft 31.

At this time, as shown in FIGS. 11 and 13,
The radially inner portions of the elastic member end portions 32 adjacent to each other are cut in an annular shape, and a part of the roller support member 26, that is, a portion in the vicinity of the bearing surface 29 enters into the cut portion 35. With this configuration, since the outer peripheral portion of the longitudinal end of the elastic member 32 is formed thin, when a part of the roller support member 26 enters between the elastic members 32 adjacent to each other, the elastic member 32 As shown in FIG. 5, the elastic member 3 which is elastically deformed without difficulty and comes into contact with the transfer belt 22 is formed.
The second portion 33 quickly and elastically returns to its original form, and can stably hold the transfer belt 22 while maintaining the transfer belt 22 in a flat state.

As shown in FIGS. 14 and 15, the outer ring of the ball bearing 36 is fixed to the tip of each arm 28 of the roller supporting member 26, and the inner ring is connected to the rollers 16, 17, 1.
8 can be fitted to the small diameter portion 37. In this case, the inner peripheral surface of the inner ring forms the bearing surface 29 of the rollers 16, 17, and 18. More specifically, each roller 16, 1
7 and 18 are constituted by a small-diameter shaft 38 and an outer cylinder 39 fitted and fixed to the small-diameter shaft 38 with a gap in the longitudinal direction of the roller.
6 is fitted to the small-diameter shaft 38, and
Are fitted and fixed. In the case of this example, as shown in FIG. 15, a part of the outer peripheral surface of the outer ring of the ball bearing 36 comes into contact with the inner surface of the transfer belt 22, thereby damaging the transfer belt 22 or waving the transfer belt 22. There is no fear that it can be done.

Also, when the ball bearing 36 is used, as shown in FIG.
And a part of the roller supporting member 26, that is, a ball bearing 36.
Is inserted between adjacent elastic members 32, a part of the elastic member 32 is elastically deformed, and a portion 33 of the elastic member 32 with which the transfer belt 22 comes into contact is elastically restored. . In this case, the entire roller supporting member 26 does not contact the transfer belt 22.

The present invention should not be limited to the configuration of the embodiment described above, but may be modified in various ways.

[0048]

According to the first aspect of the present invention, since the roller supporting member for supporting at least three rollers from the inside of the transfer belt is provided, it is possible to prevent these rollers from being largely bent by the force received from the transfer belt. Thus, the transfer material can be uniformly brought into close contact with the image carrier, and the occurrence of defective transfer of the toner image from the image carrier to the transfer material can be suppressed.

According to the second aspect of the present invention, since the deflection of the roller due to its own weight can be suppressed, the above-described effect can be further ensured.

According to the third aspect of the present invention, since the roller supporting member presses two adjacent rollers upward, the effect of the second aspect of the present invention can be further ensured. can do.

According to the fourth aspect of the invention, the flatness of the transfer belt portion facing the image carrier can be improved,
Moreover, each roller can be reliably supported by the roller support member.

According to the fifth aspect of the present invention, the radially outer portions of the ends of the elastic members adjacent to each other can be easily elastically deformed and easily returned to elasticity. The member can be elastically deformed, and the portion of the elastic member with which the transfer belt abuts can be quickly flattened to hold the transfer belt in a stable state.

According to the sixth aspect of the present invention, it is possible to provide an image forming apparatus having the above effects.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram illustrating an example of an image forming apparatus.

FIG. 2 is a front view of the transfer device.

FIG. 3 is a perspective view showing a roller, a transfer belt, and a fixed support shaft separated from a support.

FIG. 4 is a schematic side view of the transfer device with a transfer belt removed.

FIG. 5 is a front view of a roller supporting member.

FIG. 6 is a perspective view showing a bearing surface of a roller support member.

FIG. 7 is a diagram illustrating functions of a roller support member and a fixed support shaft.

FIG. 8 is a diagram illustrating functions of a roller support member and a fixed support shaft.

FIG. 9 is a diagram illustrating positions of holes formed in a roller support member.

FIG. 10 is a perspective view of a roller including a core shaft and an elastic member.

11 is a cross-sectional view showing a state where a roller supporting member is inserted between elastic members of the roller shown in FIG.

FIG. 12 is a perspective view showing a state where a roller supporting member is inserted between elastic members of the roller shown in FIG.

FIG. 13 is a perspective view showing an end of an elastic member.

FIG. 14 is a perspective view showing another example of the roller support member.

FIG. 15 is a partial cross-sectional view showing a state where the roller is supported by the roller support member shown in FIG.

16 is a partial cross-sectional view showing a state where a roller having an elastic member is supported by the roller support member shown in FIG.

FIG. 17 is a front view illustrating a problem of the transfer device in which the transfer belt is wound around two rollers.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 image carrier 2 image forming means 3 transfer device 16 roller 17 roller 18 roller 19 support 20 support 21 fixed support shaft 22 transfer belt 23 transfer belt portion 26 roller support member 29 bearing surface 30 hole 31 core shaft 32 elastic member 35 Notch A Moving direction P Transfer material

Continued on the front page F-term (reference) 2H032 AA01 AA14 BA01 BA11 BA18 BA19 BA23 2H071 BA03 CA01 CA05 DA09 DA15 DA21 DA26 3J103 AA02 AA13 AA17 AA21 BA41 BA43 CA52 DA05 FA18 GA57 GA58 GA60 HA03 HA11 HA12 HA20 HA53

Claims (6)

[Claims] 1. An endless transfer belt having at least three rollers rotatably supported by a support at each longitudinal end thereof, and an endless transfer belt wound around these rollers and driven to run. The transfer material passes between the transfer belt portion and the image carrier while the transfer material is pressed against the surface of the image carrier by the transfer belt portion between two rollers adjacent to each other along the moving direction of the transfer belt. A transfer device for electrostatically transferring the toner image formed on the image carrier onto a transfer material, comprising at least one roller support member for supporting a longitudinally intermediate portion of the at least three rollers. And a roller support member having a bearing surface for rotatably supporting each roller from the inside of the transfer belt. 2. The transfer device according to claim 1, wherein the roller support member is supported by a fixed support shaft that penetrates a hole formed in the roller support member. 3. At least one roller support member supported by the fixed support shaft is adjacent to each other so as to eliminate deflection of the two adjacent rollers due to their own weight or reduce the amount of deflection. 3. The transfer device according to claim 2, wherein the two rollers are pressed upward. 4. At least the two rollers adjacent to each other along the direction of movement of the transfer belt are provided with a core shaft made of a rigid body, and are mounted around the core shaft, and are mutually separated in the longitudinal direction of the roller. A plurality of elastic members positioned adjacent to each other in a contact state, and a part of the roller support member is disposed between the elastic members adjacent to each other while not in contact with the transfer belt. 4. The transfer device according to claim 1, wherein the transfer device is elastically deformed and enters, and a bearing surface of a roller support member contacts the core shaft to support the core shaft. 5. The transfer device according to claim 4, wherein radially inner portions of the ends of the elastic members adjacent to each other are cut out in an annular shape, and a part of the roller support member enters the cutout. 6. An image forming apparatus comprising: the transfer device according to claim 1; and image forming means for forming a toner image on an image carrier.