JPH11338270A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent leak from occurring between an image carrier and an intermediate transfer belt and to improve image quality by respectively providing guard members made of insulating material between an image carrier and both ends of the intermediate transfer belt at a primary transfer part. SOLUTION: A thin guard members 5k made of the insulating material are respectively provided between a photoreceptor drum 1 positioned at non-image area parts at both ends of an intermediate transfer belt 5a and the belt 5a at the primary transfer part. The thickness of the member 5k is about 0.3 mm. The member 5k is integrally formed on an exterior member 5j covering over the surface of the belt 5a. Thus, the leak is prevented from occurring between the drum 1 and the conductive base layer of the belt 5a at the time of primary transfer, so that an excellent image is stably obtained. By providing an insulating and light transmissive patch member on a hole for detecting the beginning of image writing at the non-image area part of the belt 5a, the leak is prevented from occurring and the excellent 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 image forming apparatus such as a copying machine or a printer for forming an image using an electrophotographic system, and more particularly to a toner image temporarily transferred from an image carrier to a transfer material. The present invention relates to an image forming apparatus provided with an intermediate transfer member for performing secondary transfer.

[0002]

2. Description of the Related Art A toner image formed on a rotating drum-type electrophotographic photosensitive member (hereinafter, referred to as a photosensitive drum) as an image carrier is temporarily primary-transferred onto an intermediate transfer member and then transferred to the intermediate transfer member. An image forming apparatus of a type in which a toner image is secondarily transferred to a transfer material by a secondary transfer member to form an image,
A color image forming apparatus or a multi-color image forming apparatus or a multi-color image forming apparatus that sequentially outputs a plurality of component color images of the color image information or the multi-color image information and outputs an image formed by combining and reproducing the color image or the multi-color image. This is effective as an image forming apparatus having a forming function and multicolor image formation.

When an endless belt-like film or rubber transfer belt (hereinafter, referred to as an intermediate transfer belt) is used as an intermediate transfer member of the above-described image forming apparatus, the intermediate transfer belt is stretched by a plurality of rollers. . In an image forming apparatus provided with an intermediate transfer belt, a primary transfer unit has a primary transfer roller that comes into contact with a photosensitive drum via the intermediate transfer belt.

In the case of an intermediate transfer belt using a rubber belt, a belt composed of a coating layer of an insulating layer on the surface and a base layer of a non-insulating layer on the inner side is used. One or more detection holes are formed in the image area to detect the timing of writing an image.

[0005]

In the image forming apparatus having the above-mentioned intermediate transfer belt, a high-voltage bias is separately applied to the photosensitive drum and the primary transfer roller in the primary transfer section. For this reason, when the toner image on the photosensitive drum is primarily transferred onto the intermediate transfer belt, a leak occurs between the surface of the photosensitive drum and the base layer of the non-insulating layer of the intermediate transfer belt, causing image defects. Was.

Further, similarly, the detection holes for the image writing timing provided on the intermediate transfer belt are also used for the primary transfer.
The rotation of the intermediate transfer belt causes a leak between the intermediate transfer belt and the photosensitive drum when passing through the primary transfer section, causing image defects.

[0007]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention provides a primary transfer unit for a toner image formed on an image carrier, which is primarily transferred to an intermediate transfer member. In an image forming apparatus that forms an image by secondary transferring an image to a transfer material in a secondary transfer unit, the intermediate transfer body is an endless belt-shaped intermediate transfer belt, and the image carrier in the primary transfer unit is A guard member made of an insulating material is provided between both ends of the intermediate transfer belt.

The intermediate transfer belt has an image writing detection hole through which light for detection is transmitted in a non-image area on an end side thereof, and the guard member is provided between the image writing detection hole and the intermediate transfer belt. It is characterized by protruding toward the center of the belt.

Further, the toner image formed on the image carrier is primarily transferred to an intermediate transfer member at a primary transfer portion, and the toner image on the intermediate transfer member is secondarily transferred to a transfer material at a secondary transfer portion. In the image forming apparatus for forming an image, the intermediate transfer body is an endless belt-shaped intermediate transfer belt, and the intermediate transfer belt has an image writing detection hole in a non-image area on an end side thereof, A light transmitting patch member made of an insulating material is provided on the image writing detection hole.

(Operation) According to the configuration of the present invention, the leak between the image carrier and the intermediate transfer belt at the primary transfer portion can be prevented by the guard member. Further, a leak between the image carrier and the intermediate transfer belt at the primary transfer portion can be prevented by a transparent patch member made of an insulating material provided on the image writing detection hole formed in the intermediate transfer belt. it can.

[0011]

Embodiments of the present invention will be described below with reference to the drawings.

<First Embodiment> FIG. 1 shows an image forming apparatus provided with an intermediate transfer belt according to a first embodiment of the present invention (a full-color laser beam printer in the present embodiment).
It is a longitudinal cross-sectional view which shows schematic structure of.

The image forming apparatus A shown in FIG. 1 includes a rotating drum type photosensitive drum 1. The photosensitive drum 1 is driven to rotate in a direction indicated by an arrow R1 by a driving unit (not shown).

Around the photosensitive drum 1, a charging device 2 for uniformly charging the surface of the photosensitive drum 1, an exposure device 3 for irradiating a laser beam based on image information to form an electrostatic latent image on the photosensitive drum 1, A developing device 4 for applying toner to the electrostatic latent image to develop the toner image as a toner image; an intermediate transfer body unit 5 for secondary-transferring the toner image once primary-transferred from the photosensitive drum 1 to a transfer material; A cleaning device 6 and the like for removing transfer residual toner remaining on the surface of the drum 1 are provided.

The photosensitive drum 1, the charging device 2, and the cleaning device 6 form a process cartridge B integrally formed as a cartridge, and can be attached to and detached from the apparatus main body 13.

In the apparatus main body 13, a transfer material S such as paper is
And a fixing device 8 for fixing the toner image to the transfer material S after the secondary transfer, and the like.

The photosensitive drum 1 has, for example, an organic photoconductor layer (O) on the outer peripheral surface of an aluminum cylinder having a diameter of about 47 mm.
PC photoreceptor) is applied, and both ends are rotatably supported by a support member, and a driving force from a driving unit (not shown) is transmitted to one end, thereby forming an arrow R1. It is driven to rotate in the direction.

The charging device 2 may be of a contact charging type. In this case, the charging member is a conductive roller formed in a roller shape. The roller is brought into contact with the surface of the photosensitive drum 1 and a charging bias voltage is applied to the roller by a power supply (not shown). This is to uniformly charge the surface of the photosensitive drum 1.

The exposure device 3 has a polygon mirror 3a, and the polygon mirror 3a is irradiated with image light corresponding to an image signal from a laser diode (not shown). The polygon mirror 3a is a scanner motor (not shown)
Is rotated at high speed, and the reflected image light is selectively exposed to the charged surface of the photosensitive drum 1 via the imaging lens 3b, the reflection mirror 3c, and the like to form an electrostatic latent image. I have.

The developing device 4 contains a rotating member 4A rotatable around an axis 4d and four developing devices mounted thereon, that is, toners of yellow, magenta, cyan, and black, respectively. Developing units 4Y, 4M, 4C,
4Bk.

When developing the electrostatic latent image on the photosensitive drum 1,
A predetermined developing device of a color to be attached to the electrostatic latent image is arranged at a developing position. That is, the predetermined developing device is stopped at the developing position facing the photosensitive drum 1 by the index rotation of the rotating body 4A, and the developing sleeve 4b of the developing device faces the photosensitive drum 1 with a small gap (about 300 μm). After the positioning, the electrostatic latent image on the photosensitive drum 1 is developed.

This development is performed as follows. The toner in the container of the developing device corresponding to the color to be developed is sent to the application roller 4a by a feed mechanism, and the rotating application roller 4 is rotated.
a and a toner setting blade 4c, a thin layer of toner is applied to the outer periphery of the rotating developing sleeve 4b, and a charge is applied to the toner (friction charging). This developing sleeve 4b
By applying a developing bias between the electrostatic latent image and the photosensitive drum 1 on which the electrostatic latent image is formed, a toner image is attached to the electrostatic latent image and developed as a toner image.

Each of the developing units 4Y, 4M, 4C, 4Bk
The developing sleeve 4b is connected to a high-voltage power supply (not shown) for developing each color provided in the apparatus main body 13 when each developing device is arranged at the developing position. Is selectively applied with a voltage. Each developing unit 4
Y, 4M, 4C, and 4Bk are configured to be detachable from the rotator 4A, and the rotator 4A is detachable from the apparatus main body 13.

The intermediate transfer unit 5 transfers a plurality of toner images, which are primary-transferred from the photosensitive drum 1 in order of each color and are superimposed, onto the transfer material S collectively. The intermediate transfer unit 5 includes an endless belt-shaped intermediate transfer belt 5a that runs in the direction of arrow R5.

The intermediate transfer belt 5a has a circumference of about 440 mm.
And is stretched by a driving roller 5b, a secondary transfer facing roller 5c, and a driven roller 5d.

The intermediate transfer member unit 5 includes a photosensitive drum 1
A primary transfer roller (pressing roller) 5g for transferring the toner image formed thereon onto the intermediate transfer belt 5a is provided.
Further, a secondary transfer roller 5n for secondary-transferring the toner image primarily transferred to the intermediate transfer belt 5a to the transfer material S is provided on the apparatus main body 13 side.

At a predetermined position outside the intermediate transfer belt 5a, there is provided a cleaning unit 5e which can be brought into contact with and separated from the intermediate transfer belt 5a. Is removed. The cleaning unit 5e connects the charging roller 5f to the intermediate transfer belt 5a.
, So that a charge of a polarity opposite to that at the time of transfer is imparted to the toner. The toner having the opposite polarity charge is applied to the photosensitive drum 1
And then collected by the cleaning device 6 for the photosensitive drum 1. The method of cleaning the intermediate transfer belt 5a is not limited to the electrostatic cleaning described above, but may be a mechanical method such as a blade or a fur brush, or a method using both of them.

After the toner developed on the photosensitive drum 1 by the developing device 4 is primarily transferred to the intermediate transfer belt 5a, the cleaning device 6 removes so-called untransferred toner remaining on the surface of the photosensitive drum 1 without being primary-transferred. Is what you do. In the cleaning device 6 shown in FIG. 1, the transfer residual toner is accumulated in the cleaning container 11.

The feeding / conveying means 7 includes a sheet feeding cassette 7 in which a plurality of transfer materials S are stored and which is loaded in a lower portion of the apparatus main body 13.
The transfer material S is supplied to a transfer nip between the intermediate transfer belt 5a and the secondary transfer roller 5n, and the transfer material S after the secondary transfer is transported to the fixing device 8 by the transport belt 12.

At the time of image formation, a pickup roller (half-moon roller) 7e, a feed roller 7f,
The retard roller 7g and the transport roller pair 7b are driven and rotated in accordance with the image forming operation to separate and feed the transfer material S in the paper feed cassette 7a one by one, while being guided by the guide plate 7c and by the registration roller pair 7d. The sheet is fed to the transfer nip between the intermediate transfer belt 5a and the secondary transfer roller 5n in synchronization with the image writing position.

The fixing device 8 fixes a plurality of toner images secondary-transferred onto the transfer material S, and applies heat and pressure to the transfer material S by pressing against a driving and rotating fixing roller 8b. And a pressure roller 8a. A heater (not shown) is provided inside each of the pressing roller 8a and the fixing roller 8b. The transfer material S to which the toner image has been transferred by the fixing device 8 is conveyed by a fixing roller 8b and is applied heat and pressure by a pressure roller 8a, so that the toner image is fixed on the surface of the transfer material S.

Next, an image forming operation of the image forming apparatus A having the above configuration will be described.

First, the photosensitive drum 1 is rotated in the direction of arrow R1 in synchronization with the rotation of the intermediate transfer belt 5a, and the surface of the photosensitive drum 1 is uniformly charged by the charging device 2, and the light of the black image is exposed by the exposure device 3. Irradiation,
A black electrostatic latent image is formed on the photosensitive drum 1. At the same time as the formation of the electrostatic latent image, the developing device 4 is driven to place the black developing device 4Bk at the developing position, and the photosensitive drum 1
A high-voltage bias having the same polarity and substantially the same potential as the charging polarity is applied to cause the black toner to adhere to the electrostatic latent image for development. Then, a high-voltage bias having a polarity opposite to that of the toner is applied to the primary transfer roller (pressing roller) 5g to primary-transfer the black toner image on the photosensitive drum 1 onto the intermediate transfer belt 5a.

When the primary transfer of the black toner image is completed as described above, the next developing unit rotates and is positioned at the developing position facing the photosensitive drum 1, and the magenta, cyan, and cyan toners are moved in the same manner as in the case of black. Then, formation, development, and primary transfer of the electrostatic latent image are sequentially performed for each color of yellow, and four color toner images are superimposed on the intermediate transfer belt 5a.

During this time, the secondary transfer roller 5n is separated from the intermediate transfer belt 5a and is in a non-contact state, and the charging roller 5f of the cleaning unit 5e is also separated from the intermediate transfer belt 5a and is in a non-contact state. Then, the intermediate transfer belt 5
a after completion of the formation of the four color toner images on the secondary transfer roller 5n
Is pressed against the intermediate transfer belt 5a, and the transfer material S which has been waiting at the registration roller pair 7d is sent out in synchronization with the rotation of the intermediate transfer belt 5a.

The transfer material S on which the toner image has been secondarily transferred collectively is transported by the transport belt 12 to the fixing device 8, and the toner image is transferred between the pressing roller 8a and the fixing roller 8b. After fixing on the sheet S by heating and pressing, the sheet S is ejected to the sheet ejection tray 10 by the sheet ejection roller pairs 9a, 9b, 9c.

Next, the structure of the intermediate transfer belt 5a according to the present embodiment will be described in detail.

As shown in FIG. 2, the intermediate transfer belt 5a is formed by forming an insulating coat layer 5a1 on a conductive base layer 5a2. As described above, at the time of the primary transfer, different high-voltage biases are applied to the photosensitive drum 1 and the primary transfer roller 5g, respectively, and as shown in FIG. 3, the photosensitive drum 1 abuts via the intermediate transfer belt 5a.
And both ends N of the primary transfer portion N between the primary transfer roller 5g
At 1 and N2, a leak occurs between the photosensitive drum 1 and the base layer 5a2 of the intermediate transfer belt 5a, which causes an image defect.

Therefore, in the present invention, as shown in FIG.
A thin guard member 5k made of an insulating material is provided between the photosensitive drum 1 and the intermediate transfer belt 5a, which are located in the non-image area on both sides of the intermediate transfer belt 5a of the primary transfer portion N. The thickness of the guard member 5k is about 0.3 mm. As shown in FIG. 4, the guard member 5k is formed integrally with an exterior member 5j that covers the surface of the intermediate transfer belt 5a. An image writing detection hole (not shown) is formed in the non-image area of the intermediate transfer belt 5a.

As described above, in the present embodiment, the guard member 5k made of an insulating material is provided between the intermediate transfer belt 5a and the photosensitive drum 1 located in the non-image area on both sides of the intermediate transfer belt 5a of the primary transfer portion N. Is provided, it is possible to prevent the occurrence of a leak between the photosensitive drum 1 and the conductive base layer 5a2 of the intermediate transfer belt 5a during the primary transfer, and to obtain a stable and good image.

<Second Embodiment> FIG. 5 is a perspective view showing a main part of an intermediate transfer unit of an image forming apparatus according to the present embodiment. The same members as those of the image forming apparatus according to the first embodiment shown in FIGS. 1 to 4 are denoted by the same reference numerals, and overlapping description will be omitted.

In this embodiment, the image writing detection hole 5 formed in the non-image area at the side end of the intermediate transfer belt 5a is used.
h, an insulating and light-transmitting patch member (for example, an insulating film) 5i is provided.

As described above, in the present embodiment, the insulating and light-transmitting patch member 5i is provided on the image writing detection hole 5h of the intermediate transfer belt 5a. Leakage is prevented between the conductive base layers 5a2 of the belt 5a, and a good image can be stably obtained.

<Embodiment 3> FIG. 6 is a perspective view showing a main part of an intermediate transfer unit of an image forming apparatus according to the present embodiment. Note that the first embodiment shown in FIGS.
The same members as those of the image forming apparatus according to the second embodiment shown in FIG. 5 are denoted by the same reference numerals, and overlapping description will be omitted.

In the present embodiment, similar to the first embodiment,
A guard member 5k made of an insulating material provided between the photosensitive drum 1 and the intermediate transfer belt 5a located at the non-image area on both sides of the intermediate transfer belt 5a of the primary transfer section N; Write start detection hole 5
h, the distance L1 from the inner surface of the guard member 5k to the side end surface of the intermediate transfer belt 5a and the image writing detection hole 5
h to the side end surface of the intermediate transfer belt 5a.
The guard member 5k and the image writing detection hole 5h are provided so that L2>L1> L2, and the width L3 of the guard member 5k and the width L4 of the image writing detection hole 5h are L3> L.
4, a guard member 5k and an image writing detection hole 5h were provided.

As described above, in this embodiment, the distance L1 from the inner surface of the intermediate transfer belt 5a to the side end surface of the guard member 5k is made longer than the distance L2 from the inner surface to the side end surface of the image writing detection hole 5h. And the width L of the guard member 5k
3 is made longer than the width L4 of the image writing detection hole 5h, as in the second embodiment.
h, the photosensitive drum 1 and the intermediate transfer belt 5 a
Is prevented from occurring between the conductive base layers 5a2, and a good image can be stably obtained.

[0047]

As described above, according to the present invention,
During the primary transfer, it is possible to prevent the occurrence of a leak between the image carrier and the intermediate transfer belt at the primary transfer section, and to form a good image.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram illustrating an image forming apparatus according to a first embodiment of the present invention.

FIG. 2 is a sectional view showing the vicinity of a primary transfer section of the image forming apparatus according to the first embodiment of the present invention;

FIG. 3 is a perspective view showing an intermediate transfer unit of the image forming apparatus according to Embodiment 1 of the present invention.

FIG. 4 is a perspective view showing an intermediate transfer unit provided with a guard member of the image forming apparatus according to Embodiment 1 of the present invention.

FIG. 5 is a perspective view showing an intermediate transfer unit in which a patch member is provided on an image writing detection hole of the image forming apparatus according to Embodiment 2 of the present invention.

FIG. 6 is a perspective view showing an intermediate transfer unit provided with a guard member of the image forming apparatus according to Embodiment 3 of the present invention.

[Explanation of symbols]

 Reference Signs List 1 photosensitive drum (image carrier) 2 charging member 3 exposure device 4 developing device 5 intermediate transfer unit 5a intermediate transfer belt (intermediate transfer member) 5a1 coat layer 5a2 base layer 5g primary transfer roller 5h image writing detection hole 5i patch member 5j exterior member 5k Guard member 8 Fixing device 13 Main body of device

Claims (3)

[Claims] 1. A toner image formed on an image carrier is primarily transferred to an intermediate transfer member at a primary transfer portion, and the toner image on the intermediate transfer member is secondarily transferred to a transfer material at a secondary transfer portion. In the image forming apparatus for forming an image, the intermediate transfer body is an endless belt-shaped intermediate transfer belt, and an insulating material is provided between the image carrier and both ends of the intermediate transfer belt in a primary transfer unit. An image forming apparatus comprising: a guard member; 2. The intermediate transfer belt has an image writing detection hole in a non-image area on the end side thereof, and the guard member projects from the image writing detection hole toward the center of the intermediate transfer belt. The image forming apparatus according to claim 1. 3. The toner image formed on the image carrier is primarily transferred to an intermediate transfer member at a primary transfer portion, and the toner image on the intermediate transfer member is secondarily transferred to a transfer material at a secondary transfer portion. In the image forming apparatus, the intermediate transfer body is an endless belt-shaped intermediate transfer belt, and the intermediate transfer belt is an image writing detection device in which light for detection is transmitted to a non-image area on an end side thereof. An image forming apparatus comprising: a hole; and a light transmitting patch member made of an insulating material provided on the image writing detection hole.