JPH02212869A - toner transfer device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

Detailed Description of the Invention (a) Industrial Application Field The present invention includes an intermediate transfer belt made of a photoreceptor having photoconductivity and a dielectric material. The present invention relates to an improvement in a toner transfer device (hereinafter referred to as a 2nd toner transfer device) that transfers toner on an intermediate transfer belt to paper in an image forming apparatus that transfers to paper.

fb) Prior Art Some second toner transfer devices that transfer toner on an intermediate transfer belt onto paper use a transfer roller. The intermediate transfer belt is stretched between rollers including a backup roller, and the transfer roller is brought into pressure contact with or separated from the backup roller (intermediate transfer belt). In other words, under normal conditions, the transfer roller is separated from the backup roller, but when the paper is fed, it moves in the direction of pressing against the backup roller and the paper is sandwiched between the bank amplifier roller and the transfer roller.Toner transfer is performed in this state. be exposed.

(C) Problem to be Solved by the Invention However, when the conventional transfer roller is brought into pressure contact with the bank up roller, an air gap condition occurs at the center in the axial direction as shown in FIG. In some cases, the value was significantly lower than that of the previous section. The transfer roller is supported by support parts at both ends of the shaft, and the rotation of the support parts moves the transfer roller in a pressure contact direction or a pressure release direction. Therefore, the pressure contact force at both ends becomes large, but an air gap state occurs at the center portion, making it impossible to obtain a sufficient pressure contact force.

Further, in the conventional device, a biasing member for biasing the transfer roller in the pressure direction is provided near the shaft that rotatably supports the support portion. Therefore, it is difficult to obtain a strong biasing force, and if this biasing force is even slightly different between the axial ends (front end and rear end), the pressure contact force distribution in the axial direction of the transfer roller will be uneven. Sometimes I ended up leaving. This pressure distribution is also affected by the assembly precision of the backup roller and transfer roller. For example, in conventional equipment, if the front and rear ends of the roller are misaligned by 0.4 fins, the pressure difference between the front and rear ends will exceed the allowable range. Ta. However, it is difficult to make the positional deviation between the front and rear ends less than 0.4 square inches, and assembly is extremely difficult.

An object of the present invention is to provide a 2r+d toner transfer device that can alleviate pressure distribution unevenness by improving the shape of the bank unroller, the transfer roller support portion, and the like.

(Means for Solving Problem d1) A second toner transfer device according to claim 1 of the present invention transfers toner on an intermediate transfer belt stretched between rollers including a backup roller to the banks of the intermediate transfer belt via the intermediate transfer belt. In a device that transfers images onto paper using a transfer roller placed opposite to an up roller, the surface layer of the backup roller is made of an insulating rubber material, and the diameter of the approximately central portion in the axial direction is larger than the diameter of both ends. It is characterized by a large crown shape.

In the 2nd) toner transfer device according to claim 2, the toner on an intermediate transfer belt stretched between rollers including a back-up roller is transferred to a transfer roller disposed opposite to the backup roller via the intermediate transfer belt. In an apparatus for transferring data onto a paper using The present invention is characterized in that a biasing member for biasing the support portion toward the side where the transfer roller is pressed toward the bank-up roller is provided at a portion substantially farthest from the shaft in the support portion.

(e) Effect In the 2nd) toner transfer device according to claim 1 of the present invention, even if the bank up roller is distorted when the transfer roller is pressed into contact with the transfer roller, since the diameter of the central portion is made large, the air gear state is maintained in the central portion. Since this does not occur, it is possible to prevent the pressure contact force from decreasing in the central portion. Furthermore, the surface layer of the backup roller is made of an insulating rubber material, which can alleviate uneven pressure distribution.

Further, in the device according to claim 2, since the biasing member is provided at the substantially farthest part from the shaft, the maximum biasing force can be exerted at the support part, and the pressure contact force in the axial direction can be alleviated. For example, even if the positional accuracy in the axial direction is somewhat poor, if the biasing force becomes strong, it can be alleviated and the pressure distribution difference can be alleviated.

(f) Embodiment FIG. 7 is a schematic front view of a full-color copying machine equipped with a 2nd) toner transfer device.

On the top of the copying machine body is a document table 1 made of transparent glass.
is provided. A document A to be copied is placed on the document table 1 with the document surface facing downward.

A light source 2a, mirrors 2b to 2f,
An optical device including a lens 2g and a filter 2h is provided. The optical device scans the original A on the original platen 1,
The reflected light is guided to a belt-shaped photoreceptor 3. Note that the filter 2h separates the reflected light from the document into red, green, and red colors during full-color image formation.
It separates the color into the primary color of blue and allows any of them to pass through.

The photoreceptor belt 3 includes a photoconductive layer whose resistance value decreases when irradiated with light. The photosensitive belt 3 is stretched between a driving roller 3a and a driven roller 3b. A driving force is transmitted to the driving roller 3a from a main motor (not shown), and the driving roller 3a is rotated in the direction of the arrow in the drawing. Around the photoreceptor belt 3, there are a charger 31, a blank lamp 32, developing devices 33 to 35,
Intermediate transfer device 4, cleaning device 36, static elimination lamp 3
7 are arranged in the above order. The developing device 33 stores yellow toner, the developing device 34 stores magenta toner, and the developing device 35 stores cyan toner.

With these configurations, the procedure for forming a toner image on the photoreceptor belt 3 is almost the same as that of a conventional electrophotographic image forming apparatus, and the reflected light of the document is reflected onto the photoreceptor belt 3 charged by the charger 31. A latent image is formed by the irradiation, and the latent image is developed by the developing devices 33 to 35. The toner image formed on the photoreceptor belt 3 is once transferred to an intermediate transfer device 4, and then transferred to a sheet of paper. Note that the developing devices 33 to 35 are connected to the filter 2 during image formation.
A device that stores toner of a complementary color to the light reflected from the document that is transmitted by the light transmitted by h is activated. For example, when blue light is transmitted, a developing device 33 that stores yellow toner is activated to produce yellow toner. form an image.

The intermediate transfer device 4 includes an intermediate transfer belt 5 stretched between a driving roller 5a, a driven roller 5b, and a backup roller 50.
．． 1st toner transfer device R6, 2nd) toner transfer device 7,
It is equipped with a peeling plate 8 and a cleaning device 9.

The toner image formed on the photoreceptor belt 3 is transferred to the intermediate transfer belt 5 by the 1st toner transfer device 6, and then transferred to the paper fed from the paper tray 9a or 9b on the right side of the copying machine main body. Ru. Note that the yellow image, magenta image, and cyan image formed on the photoreceptor belt 3 are superimposed on the intermediate transfer belt 5, and then transferred to paper as a full-color image. The paper onto which the full-color image has been transferred is fixed in the fixing device 10 and then ejected from the main body of the copying machine.

The configuration of the intermediate transfer device 4 will be described in detail below.

FIG. 1 is a diagram showing the configuration of an intermediate transfer section.

The intermediate transfer belt 5 is made of a sheet material having a dielectric material.For example, the intermediate transfer belt 5 is made of polycarbonate whose resistance has been adjusted by dispersing carbon black.According to experiments conducted by the present inventors, the intermediate transfer belt 5 is resistance is almost 1
0? It is desirable to have an IQ of about 11Ω. If the resistance value is high, the toner holding ability will be too strong and transfer failure will occur during 2nd transfer (transfer of toner from intermediate transfer belt 5 to paper).To prevent this, 1.
After the first transfer (toner transfer from the photoreceptor belt 3 to the intermediate transfer belt 5), it is necessary to install a device to remove static electricity.Also, if the resistance value is too low, a sufficient transfer electric field cannot be obtained during the second transfer, and the transfer This is because defects occur, and to prevent this, it is necessary to increase the capacity of the transfer power source.

As described above, the intermediate transfer belt 5 is stretched between the drive roller 5as, the driven roller 5b, and the bank up roller 50. The driving roller 5a is, for example, a roller having a diameter of 50 m-0 and having a conductive rubber layer as a surface layer, and is driven by being connected to a main motor (not shown). The driven roller 5b is, for example, a roller made of aluminum and has a diameter of approximately 42 mm, and the backup roller 5C is a roller having a diameter of approximately 25 m and has an insulating rubber layer provided as a surface layer. Driven roller 5b
is biased in a direction that applies tension to the intermediate transfer belt 5 by a biasing mechanism (not shown). The photoreceptor belt 3 is in pressure contact with the intermediate transfer belt 5 stretched between the rollers in this manner between the driving roller 5a and the driven roller 5b. In reality, a drive roller 3a with a photoreceptor belt 3 stretched thereon is pressed against an intermediate transfer belt 5, and the intermediate transfer belt 5 drives the drive roller 5a, driven roller 5b, backer/knob roller 5C, and photoreceptor belt. A tension is applied by the roller 3a. A 1st) toner transfer device 6 is disposed at a pressure contact portion between the intermediate transfer belt 5 and the photoreceptor belt 3. FIG. 2 is an external view of the ISt toner transfer device.

1st) The toner transfer device is made of metal such as stainless steel,
Two 1st transfer rollers 5 with a diameter of about 8111, for example.
a, 6b. 1st transfer roller 6a, 6
b is freely supported by the support portion 61 and is in pressure contact with the intermediate transfer belt 5 from the inner surface side of the intermediate transfer belt 5. Therefore, the first transfer rollers 6a and 6b easily rotate following the rotation of the intermediate transfer belt 5. 62 is a connector for applying voltage to the 1st transfer rollers 6a and 6b, and it connects a charge of opposite polarity to the toner (+ in this case) to 1.
It is applied to the st transfer rollers 5a and 5b. The position at which the first transfer roller 6a6b contacts the intermediate transfer belt is set as follows.

PL is the point at which the intermediate transfer belt 5 and the photoreceptor belt 3 separate.
, P! Then, the distance d=1 outward from that point
The positions are approximately 0 to 1511. Further, from the state in which the intermediate transfer belt 5 is stretched between the rollers 5a to 5C and 3a, the intermediate transfer belt 5 is moved a distance flp toward the roller 3a.
= 0.5 to 1.5 mm. As a result, the intermediate transfer belt 5 does not come into contact with the drive roller 3a of the photoreceptor belt, and the intermediate transfer belt 5 is lightly pressed toward the photoreceptor belt 3, so that the 1st transfer can be performed satisfactorily.

2nd) The toner transfer device 7 includes a 2nd transfer roller 7a. The 2nd transfer roller 7a is supported so as to be movable in the vertical direction by a moving mechanism as shown in FIG.

When the 2nd transfer roller 7a moves upward, the 2nd transfer roller 7a comes into pressure contact with the backup roller 5C via the intermediate transfer belt 5.

The timing of the upward movement of the 2nd transfer roller 7a is when the paper is fed between the intermediate transfer belt 5 and the 2nd transfer roller 7a, and the paper is transferred between the intermediate transfer belt 5 and the 2nd transfer roller 7a. The toner is transferred to the paper by sandwiching the paper. Hereinafter, the moving mechanism of the 2nd transfer roller will be explained in detail with reference to FIG. In addition, Figure 4 (A) is 2
nd is a front view of the transfer roller support section, and FIG. 2B is a right side view thereof.

The 2nd transfer roller 7a is rotatably supported by support parts 71 and 71 provided at both ends in the axial direction.A shaft 72 is provided on the right side of the 2nd transfer roller 7a, and the support part 71 is It rotates in the directions of arrows B and C in the figure. A cam 73 is provided on the right side of this shaft 72, and a spring 74 is further provided on the right side. The support portion 71 is rotated in the direction of arrow B or C by the rotation of the cam 73, and when it is rotated in the direction of arrow B, it is pressed against the backup roller 5C. At this time, an upward biasing force is applied to the support portion 71 by the spring 74, and the second transfer roller 7a is pressed against the backup roller 5C. This spring 74
is provided on the support portion 71 at the farthest position from the shaft 72. Therefore, upward biasing force can be obtained most efficiently, and sufficient biasing force can be applied separately to each end in the axial direction.

Note that 74' in the figure indicates the position of a conventional spring. By providing the spring 74 at the farthest point from the shaft 72, the maximum biasing force can be exerted on this support portion 7E.For example, when the spring is provided at the position 74', 2r+d transfer Roller 7a
Even if the front and back positional deviation of 2r+d transfer roller 7a was 0.4m, uneven pressure occurred at the front and rear ends during pressure contact, but by installing the spring at position 74, the front and rear positional deviation of 2r+d transfer roller 7a was 0.8m. Even if there was, it was alleviated during pressure welding, and we were able to obtain almost uniform pressure at the front and back. In addition, the conventional 74' position requires a considerable amount of time and effort because the space for installation is very narrow. However, as in this embodiment, the farthest part from the shaft 72, that is, the support part 7
If a subring is provided near the end of 1, the work space for installation will become wider and work efficiency will be improved.

A facing electrode roller 73 is provided on the inner surface of the intermediate transfer belt near the backup roller 5C.The facing electrode roller 73 is made of a metal material such as stainless steel. This facing electrode roller 73 is grounded and acts as an electrode facing the 2nd transfer roller 710. Also, this installation position is from the pressure contact point P between the backup roller 5 and the 2nd transfer roller 71 to the driven roller 5b side (intermediate transfer bell) 5c.
approximately the distance R1-AO~18 (upstream side in the direction of rotation)
It is in a position that is considered a favorite. The facing electrode roller 73 is arranged to lightly contact the inner surface of the intermediate transfer belt 5 and to be freely rotatable. When the toner is transferred from the intermediate transfer belt 5C to the paper, an electric field is generated between the 2nd transfer roller 71 and the facing electrode roller 73, and the toner having the opposite polarity to the voltage applied to the 2nd transfer roller 71 is transferred to the 2nd transfer roller 71 side. It is drawn and transferred to paper. At this time, the facing electrode roller 73 rotates following the rotation of the intermediate transfer belt 50. Therefore, problems such as the inner surface of the intermediate transfer belt 5 being scraped by the facing electrode roller 73 and the powder of the scraped intermediate transfer belt being fused to the facing electrode roller and causing a transfer defect do not occur.

By the way, the center part of the bank unroller 5c is made of a relatively hard material such as steel to prevent pressure distortion.
The surface layer is made of an insulating material having a resistance of, for example, about 10"-10. Specifically, silicone rubber or the like is used as the insulating material. The backup roller 5c is made of an insulating material having a resistance of about 10"-10. It has a crown shape in which the diameter at both ends is larger than the diameter at the center.The backup roller 5c
The shape of is not limited to that shown in the figure,
The shape may be set depending on how pressure is applied between the cm2nd transfer rollers 71. By forming the bank up roller 5c into a round shape like this, it becomes possible to obtain uniform pressure in the axial direction when the 2rid transfer roller 71 comes into pressure contact with the bank up roller 5C. 5 and 6 are bank up rollers 5C2
These are diagrams showing the distribution state of pressure contact force in the axial direction when pressure is applied between the nd transfer rollers 71, and FIG. 5 shows when the 2nd transfer roller of this embodiment is used, and FIG. Each shows the state when the transfer roller is used. The center of the 2nd transfer roller shown in FIG. 5 is made of aluminum, and the insulating rubber portion is flat in the axial direction. In this experiment, points ■ to ■ were taken every 5all in the axial direction at the pressure contact part of the back unroller 5 cm and the 2nd transfer roller 71, each having an axial length of 25 Cs, and a strip-shaped sheet was inserted between these parts to control both rollers. The force required to make pressure contact and pull out the sheet was investigated. The sheet used had a thickness of 40 μm, a width of 10 mm, and a length of 50 m. In addition, as can be seen from Figure 0, where the force applied between both rollers is varied in five stages (1) to (5), in conventional equipment, as the load between the rollers increases, the pressure distribution in the axial direction becomes uneven. While the pressurizing force at the center is weak, the device of this embodiment can obtain substantially uniform pressure in the axial direction. Therefore, when an image is formed, a transfer error does not occur in the axial direction, and a high-quality image can be obtained.

The intermediate transfer device 4 is configured almost as described above.
The peeling plate 8 is for peeling the paper from the intermediate transfer belt 5, and the cleaning device 9 is for peeling the paper from the intermediate transfer belt 5.
This is to remove the toner remaining on the top.

An experiment was conducted to form a full-color image using the copying machine described above. The intermediate transfer belt 5 is 10' to 10', and the voltages applied to the lsL transfer rollers 6a and 6b during the 1st transfer are: yellow: 600V1 magenta: 600V
V, cyan: 1000V. Note that this transfer voltage is changed because the charging characteristics of the toner differ depending on the pigment contained in the toner, but it is generally 40%.
Good 1st transfer can be performed with an applied voltage of 0 to 1ooovO.*lsL If the transfer voltage is too high, the potential of the toner layer on the intermediate transfer belt becomes high, causing the toner images to overlap on the intermediate transfer heald. Sometimes the toners repel each other, causing image defects. Further, the 2nd transfer voltage was approximately 1.6 V, and good 2nd transfer could be performed.

(Effects of the Phantom Invention As described above, according to the device of the present invention shown in claim 1.2, it is possible to alleviate the air gap condition in the center or increase the biasing force at the end of the shaft of the transfer roller in the axial direction. By alleviating the difference in pressure contact force between the front and rear ends, uneven pressure distribution in the axial direction can be alleviated, and the occurrence of uneven toner transfer can be prevented. Figure 2 shows a configuration that has the advantage of being able to alleviate uneven pressure distribution at the front and rear ends simply by changing the position.
is a right side view, FIG. 5 is a diagram showing the state of pressure distribution in the axial direction of the bank up roller in this embodiment, FIG. 6 is a diagram showing the state of pressure distribution in the axial direction of the conventional backup roller, and FIG. FIG. 7 is a schematic front view of a copying machine equipped with a 2nd) toner transfer device, and FIG. 8 is a diagram showing a distorted state of a bank up roller in a conventional 2nd) toner transfer device.

5-Intermediate transfer belt, 5C-Backup roller, ? −
2nd toner transfer device, 7a 2nd transfer roller, 7
1-support part, 72-shaft, 73-cam, 74-spring.

[Brief explanation of the drawing]

Claims (1)

[Claims] (1) A toner transfer device that transfers toner on an intermediate transfer belt stretched between rollers including a backup roller onto a sheet of paper using a transfer roller disposed opposite to the backup roller via the intermediate transfer belt, A toner transfer device characterized in that the surface layer of the backup roller is made of an insulating rubber material, and has a crown shape in which a diameter at an approximately central portion in an axial direction is larger than a diameter at both ends. (2) A toner transfer device that transfers toner on an intermediate transfer belt stretched between rollers including a backup roller onto a sheet of paper using a transfer roller disposed opposite to the backup roller via the intermediate transfer belt, A support part that rotatably supports the transfer roller at both ends in the axial direction is rotatably supported in a direction in which the transfer roller moves up and down using a shaft as a fulcrum, and a support part that supports the transfer roller rotatably at both ends in the axial direction is provided at a substantially farthest part from the shaft in the support part. 1. A toner transfer device comprising a biasing member that biases a support portion toward a side where the transfer roller is pressed toward a backup roller.