JPH05158361A - Electrophotographic device - Google Patents

Abstract

PURPOSE:To prevent a photosensitive body from being damaged because the surface of an image carrier directly comes in contact with a rotary transfer member or a transfer material by always making the surface of the image carrier opposed to the surface of the rotary transfer member at a specified distance apart by a gap regulating member. CONSTITUTION:A transfer roller 3 consisting of a sponge roller or a rubber roller is pressed to the photosensitive body 1 by a spring 5 to press-contact with a gap regulating member 8, and it is opposed to the photosensitive body 1 at a distance (d) apart. When the photosensitive body 1 is driven and a toner image reaches a transfer part, voltage having a reverse polarity to toner is impressed on the roller 3. Meanwhile, the transfer material fed from a paper feeding part to the transfer part passes between the photosensitive body 1 and the roller 3, and the toner image is transferred by the roller 3. By keeping the distance (d) between the photosensitive body 1 and the roller 3 about 100mum in the case that the radius of the photosensitive body 1 is 15mm and the radius of the member 8 is 15.1mm, the high-quality image without the staining of a back surface or irregularities in the image is obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic apparatus such as a copying machine, a printer or a facsimile which develops an electrostatic latent image on a drum or belt-shaped photosensitive member with toner and transfers it onto a transfer material.

[0002]

2. Description of the Related Art In recent years, a drum-shaped or belt-shaped photosensitive member (or intermediate transfer member) and a transfer roller are brought into pressure contact with each other to form a pressure contact nip portion between the photosensitive member and the transfer roller, and a transfer material is passed through the nip portion. An electrophotographic apparatus configured to transfer a toner image on a photoconductor to a transfer material has been devised.
However, in the above configuration, since the transfer roller is in contact with the photoconductor, the transfer roller is contaminated by the toner when it is transferred to a transfer material having a width narrower than the toner image formed on the photoconductor. As a result, there is a problem that the following transfer material is soiled and the back side of the paper is soiled. Further, there is a problem that not only the photoconductor is damaged by the contact with the transfer roller, but also the photoconductor may be dielectrically broken down by the transfer voltage applied to the transfer roller. In order to solve such a problem, proposals have already been made in JP-A-63-316076 and JP-A-1-316774.

A conventional electrophotographic apparatus will be described below. FIG. 6 is a side view of a transfer portion of a conventional electrophotographic apparatus, and FIG. 7 is a sectional view taken along the line DD of FIG. In FIG. 6, reference numeral 1 denotes a photoconductor having a photoconductive layer coated on an aluminum tube. Reference numerals 2 are flanges press-fitted to both ends of the photoconductor 1. The flange 2 supports rotation of the photoconductor and
A driving force from a driving source (not shown) is transmitted to the photoconductor 1 or is transmitted to other parts. 3 is a transfer roller supported by a shaft 4 and has an Asker C hardness of 20 to 40
A conductive rubber or sponge is used.
Reference numeral 5 denotes a spring that biases the transfer roller 2 toward the photoconductor 1, and is supported by the support 6. Reference numeral 7 denotes a regulation roller, which is attached to the shaft 4 near both ends of the transfer roller 3 and is in contact with the non-image portion of the photoconductor 1. The radius of the regulation roller 7 is larger than the radius of the transfer roller 3 by d. Therefore, the transfer roller 3 biased by the spring 5 is essentially opposed to the photoconductor 1 by the distance d by the regulation roller 7.

In the above structure, the toner image formed on the photoconductor 1 by the well-known electrophotographic process is transferred to the photoconductor 1 and the transfer roller 3 by the transfer roller 3 to which a voltage having a polarity opposite to that of the toner image is applied. Is transferred to a transfer material (not shown) that has passed the interval d of. Even if the transfer material is
Even if the transfer roller 3 is narrower than the toner image formed on the photoconductor 1, the transfer roller 3 is not in contact with the photoconductor 1 so that the transfer roller 3 is not contaminated by the toner. Backside dirt is no longer generated.

[0005]

However, in the above-mentioned conventional structure, since the distance between the shaft of the transfer roller and the photoconductor is determined by the regulation roller, the distance between the surface of the transfer roller and the photoconductor is the radius of the transfer roller. It is affected by the error of and the total runout error in the radial direction. As described above, since soft rubber or sponge is used for the conventional transfer roller, the total deviation error in the radial direction is very large, and when the transfer roller rotates, the distance between the transfer roller and the photoconductor largely varies. ..

FIG. 8 is a sectional view taken along the line EE in FIG. In FIG. 8, R1 is the radius of the transfer roller design value, and R2 is
Is an actual average radius including the radius error δ1 in the design radius R1, and R3 is an actual radius at an arbitrary position including the actual average radius R2 including δ2 in the radial direction. Further, R4 is a radius of the regulation roller (a radius error of the regulation roller and a total deflection error in the radial direction also influence, but since it is smaller than other errors, it is ignored here).

Assuming that the distance between the photosensitive member and the transfer roller surface is d, the design value should be d = R4-R1, but the actual distance d'is d '= R4- (R1 + δ1 + δ2) = R4- It becomes R3.

Therefore, when the radius error δ1 and the total radial deflection δ2 are large, the distance d varies greatly. Interval d
If the variation occurs, the electric field between the photoconductor and the transfer material changes,
This affects the transfer efficiency, which causes uneven density in the paper leading direction. Further, when the variation of the distance d becomes large, the photosensitive member and a part of the transfer roller surface come into contact with each other as shown in FIG. 8, and the transfer roller surface becomes dirty, causing the above-mentioned problems. That is, in order to maintain good image quality, it is necessary to maintain an appropriate distance d, but in the above configuration, it was necessary to control the accuracy of the transfer roller very strictly. Specifically, considering the transfer performance and the thickness of the toner layer, the distance d between the transfer roller and the photoconductor is 50 to 15
About 0 μm is desirable. However, in order to satisfy this, for example, considering the dimensional tolerance of the regulation roller, the radial tolerance of the transfer roller is ± 20 μm, and the total radial deflection tolerance is 20 μm.
Must be: Considering the hardness of the transfer roller, this precision is technically quite difficult, which not only increases the cost of the transfer roller but also has a serious problem in mass productivity.

Further, the regulation roller needs to be brought into contact with the non-image portion of the photoconductor, and the axial length of the photoconductor needs to be considerably longer than that of the transfer roller.

Further, the belt-shaped photoconductor is very liable to be damaged, and the damage tends to spread if a part of the photoconductor is damaged. In addition to not being able to maintain the proper distance between the transfer rollers, there is a problem in that streaks occur in the image due to scratches on the photoconductor and the image quality is degraded.

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above problems and to provide an electrophotographic apparatus having a stable image quality by properly maintaining the distance between the photoconductor and the transfer roller with a simple structure.

[0012]

In order to achieve the above object, the present invention provides an image carrier having a toner image on its surface, and the image carrier at a position where the toner image of the image carrier is transferred to a transfer material. A rotary transfer member having a generatrix parallel to the surface of the image carrier, and an interval regulating member projecting from the surface of the image carrier by a predetermined dimension and contacting the generatrix of the rotary transfer member at the transfer position of the toner image on the image carrier. Is to have.

[0013]

According to the present invention, the surface of the image carrier and the surface of the rotary transfer member are always separated from each other by a predetermined dimension by the distance regulating member, so that the surface of the image carrier and the surface of the rotary transfer member are constituted. Can be maintained with high accuracy, and since the surface of the image carrier does not directly contact the rotary transfer member or transfer material, the photoconductor is not damaged. Further, unlike the conventional example, a regulation roller for regulating the interval is unnecessary, so that the cost can be reduced accordingly.

[0014]

【Example】

(Embodiment 1) Hereinafter, a first embodiment of the present invention will be described with reference to FIGS.

FIG. 1 is a side view of a transfer portion of an electrophotographic apparatus according to the first embodiment of the present invention, and FIG. 2 is a sectional view taken along the line A--A of FIG. In FIG. 1, 1 to 6 have already been described in the conventional example, and therefore will be omitted. Reference numeral 8 denotes an interval restricting portion provided on a part of the flange 2 made of polycarbonate, the radius of which is larger than the radius of the photoconductor 1 by an interval d. The transfer roller 3 is a sponge roller or a rubber roller having a resistance value of about 10 ⁶ Ω · cm to 10 ¹⁰ Ω · cm and a hardness of 30 to 60 degrees. The transfer roller 3 is urged toward the photoconductor 1 by a spring 5, is pressed against the interval regulating portion 8 and faces the photoconductor 1 with a distance d therebetween.

In the above structure, a toner image is formed on the photoconductor 1 by a well-known electrophotographic process. When the photoconductor 1 is driven by the flange 2 and the toner image reaches the transfer portion, a voltage having a polarity opposite to that of the toner is applied to the transfer roller 3. On the other hand, the transfer material (not shown) sent from the paper feeding unit (not shown) to the transfer unit is the photosensitive member 1 and the transfer roller 3.
And the toner image is transferred by the transfer roller 3. By the way, the toner image formed on the photoconductor 1 has a thickness of about 10 to 20 μm, and considering the undulation in the axial direction of the transfer roller, the design value of the distance d between the photoconductor 1 and the transfer roller 3 is at least It is necessary to provide 50 μm or more. If the distance d is too wide, the electric field between the photoconductor 1 and the transfer material will be weakened, and the transfer efficiency will be reduced. Therefore, it is desirable that the distance d be 150 μm or less. In the experiment, the radius of the photoconductor 1 is set to 15 mm, and the radius of the space regulation unit 8 is set to 1
The distance between the photoconductor 1 and the transfer roller 3 is about 10 mm.
The image was kept at 0 μm, and a good image without back stain and without image distortion was obtained.

FIG. 3 is a sectional view taken along the line BB of FIG. In FIG. 3, R1 is a radius of a design value of the transfer roller 3, R2 is an actual average radius of the transfer roller 3, and R3 is an actual radius of the transfer roller 3 at an arbitrary position including a circumferential runout error. Since the transfer roller 3 is always urged toward the photoconductor 1, the surface of the transfer roller 3 is in contact with the interval regulating portion 8 as shown in the figure, and even if R3 changes, the transfer roller 3 is transferred to the photoconductor 1. The distance d on the surface of the roller 3 does not change and is kept constant.

(Second Embodiment) A second embodiment of the present invention will be described below with reference to FIG.

FIG. 4 is a side view of the transfer portion of the electrophotographic apparatus according to the second embodiment of the present invention, and FIG. 5 is a sectional view taken along the line CC of FIG. Since 3 to 6 in FIG. 4 have already been described in the conventional example, description thereof will be omitted. Reference numeral 9 is a seamless intermediate transfer belt made of polycarbonate and having a thickness of 150 μm, and 10 is a first support roller that supports the rotation of the intermediate transfer belt 9. Reference numeral 11 denotes a gap control portion provided on a part of the first support roller 10 and has a radius larger than the polar radius of the intermediate transfer belt 9 formed by the first support roller 10 by a gap d. The transfer roller 3 biased by the spring 5 is
It is in pressure contact with the interval regulating portion 11 and faces the intermediate transfer belt 9 with a distance d therebetween. 12 and 13 are the second and third respectively
The support roller supports the rotation of the intermediate transfer belt 9 together with the first support roller 10, and transmits the driving force from a driving source (not shown) to the intermediate transfer belt 9 or transmits the driving force to other parts. .

In the above structure, a color toner image is formed on the photosensitive belt (not shown) by a well-known color electrophotographic process. The color toner image is electrostatically transferred from the photosensitive belt to the intermediate transfer belt 9. When the color toner image on the intermediate transfer belt 9 reaches the transfer portion,
A voltage having a polarity opposite to that of the toner is applied to the transfer roller 3.
On the other hand, the transfer material (not shown) sent from the paper feeding unit (not shown) to the transfer unit is the intermediate transfer belt 9 and the transfer roller 3.
And a color toner image is transferred by the transfer roller 3 at this time.

[0021]

As is apparent from the above embodiments, according to the present invention, the surface of the image bearing member and the surface of the rotary transfer member are always separated by a predetermined dimension by the distance regulating member. The distance between the surface of the body and the surface of the rotary transfer member can be maintained with high accuracy, and therefore the transfer efficiency is stable, and an electrophotographic apparatus with excellent image quality can always be provided.

Further, since the surface of the image carrier does not come into direct contact with the rotary transfer member or transfer material, the photosensitive member is not damaged and stable image quality can be maintained for a long period of time.

Further, since the interval regulating member is also used as the flange portion of the drum-shaped image bearing member or the flange portion of the supporting roller of the belt-shaped image bearing member, the surface of the image bearing member and the rotary transfer member can be easily processed. The accuracy of the distance from the surface can be improved, and since no regulation roller is required, the number of parts and assembling steps can be shortened.

[Brief description of drawings]

FIG. 1 is a side view of a transfer portion of an electrophotographic apparatus according to a first exemplary embodiment of the present invention.

FIG. 2 is a sectional view taken along the line AA of FIG.

3 is an enlarged cross-sectional view taken along the line BB of FIG.

FIG. 4 is a side view of a transfer portion of the electrophotographic apparatus according to the second exemplary embodiment of the present invention.

5 is a cross-sectional view taken along the line CC of FIG.

FIG. 6 is a side view of a transfer section of a conventional electrophotographic apparatus.

7 is a sectional view taken along the line DD in FIG.

8 is an enlarged sectional view taken along the line EE in FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Photoconductor (image carrier) 2 Flange 3 Transfer roller (rotary transfer member) 4 Rotating shaft 5 Spring 6 Support 8 Space regulation part 9 Intermediate transfer belt (image carrier) 10 First support roller 11 Space regulation part d Photosensitive Distance between body and transfer roller R1 Designed radius of transfer roller R2 Actual average radius of transfer roller R3 Actual radius of transfer roller at any position

Claims (6)

[Claims] 1. An image carrier having a toner image on its surface, a rotary transfer member having a generatrix parallel to the surface of the image carrier at a position where the toner image of the image carrier is transferred to a transfer material, and the image. An electrophotographic apparatus having a distance regulating member that protrudes from the surface of the image carrier at a transfer position of the toner image on the carrier by a predetermined dimension and contacts the generatrix of the rotary transfer member. 2. The electrophotographic apparatus according to claim 1, wherein the image carrier has a drum shape. 3. The electrophotographic apparatus according to claim 1, wherein the image carrier has a belt shape. 4. The electrophotographic apparatus according to claim 1, wherein the rotation shaft of the rotary transfer member is pressed against the space regulating member by an elastic member. 5. The electrophotographic apparatus according to claim 1, wherein the interval regulating member is a disk-shaped flange having a diameter larger than the diameter of the drum-shaped image bearing member. 6. The electrophotographic apparatus according to claim 1, wherein the distance regulating member is a disk-shaped flange having a diameter larger than a diameter of the supporting roller of the belt-shaped image carrier.