JPH0651627A - Image forming device - Google Patents

Abstract

PURPOSE:To stably secure gaps between developing sleeves and a photosensitive body with high accuracy, to eliminate the complicated adjustment of the gaps, and to attain assembling only with inexpensive parts by abutting development backup members on the rear surface of a belt-like photosensitive body. CONSTITUTION:A belt 1 on which the belt-like photosensitive body is applied is disposed between turnable rollers 2 and 3 and carried clockwise in a tension state by the drive of the turnable roller 2. Four roller-like development backup members 40 are rubbed on the inner periphery of the belt 1. The development backup members 40 are oppositely arranged on four developing units 8-11 installed in the vicinity of the outer periphery of the belt-like photosensitive body, respectively. On the other hand, the belt-like photosensitive body on the outer periphery of the belt 1 is always kept at the position of constant relation with the surface of the development backup member 40, during carrying. Then, the outer peripheries of the bearing members of the developing sleeves 8A-11A of the developing units 8-11 are directly pressed on the development backup member 40, so that the gaps between the belt-like photosensitive body and the developing sleeves 8A-11A are kept constant.

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 for forming a toner image on a belt-shaped photosensitive member by an electrophotographic method and transferring the toner image on a transfer material to obtain an image.

[0002]

2. Description of the Related Art Many methods and apparatuses have been proposed for obtaining a color image using electrophotography. For example, JP-A-61
As disclosed in Japanese Unexamined Patent Publication No. 100770, a latent image is formed and developed on a photosensitive drum, which is an image carrier, according to the number of separated colors of an original image, and the latent image is transferred to a transfer drum each time the image is developed. There is a method in which a multicolor image is formed on the surface and then transferred onto a recording paper to obtain a color copy.

Further, a method of obtaining a color image by repeatedly forming a latent image on the photosensitive drum according to the number of separated colors of the original image and developing with a color toner, superimposing the color toner image on the photosensitive drum and then transferring it. There is. The basic process for forming this multicolor image is disclosed in Japanese Patent Application Laid-Open No. 60-75850 by the present applicant.
No. 60-76766, No. 60-95456, No. 60-95458, No. 60-158475, and JP-A-3-78770.

As for the image forming body, a belt-shaped photoconductor in which a photoconductor is applied or vapor-deposited on a flexible belt is proposed in addition to the photoconductor drum whose photoconductor is applied or vapor-deposited on the peripheral surface of the drum. Has been done. Since the shape of the belt-shaped photosensitive member is determined by stretching it between rotating rollers including a driving roller, it is effective when the space is effectively used to form a color image forming apparatus having a compact shape. Further, the belt-shaped photoconductor has a great advantage over the drum photoconductor in that no abutting roller is required.

[0005]

FIG. 9 is a diagram showing a schematic structure of a conventional image forming apparatus using a belt-shaped photoreceptor.

An endless belt 1 having a belt-shaped photoconductor applied or vapor-deposited on one surface is stretched around rotating rollers 2 and 3 and conveyed. The development backup member 4 is provided on the inner surface of the belt 1.
Is fixed to the device body. The back surface of the belt 1 is rubbed against the backup member 4. Areas unnecessary for image formation are formed in the backup member 4 as concave portions. Developing unit 8, 9,
10, 11 developing sleeves 8A, 9A, 10A, 11
A has a predetermined gap with the belt-shaped photoreceptor 1.

The conventional development backup member 4 is a continuous single component as shown in FIG. This is because of the performance of the image forming apparatus, the belt-shaped photoreceptor and the developing sleeves 8A, 9A,
It is necessary to make the gap between 10A and 11A to have a machining accuracy of 500 ± 10μ, but such a large part is warped or twisted and cannot be dealt with by a normal machining method.

Therefore, it has been considered to perform ultra-precision processing only at a portion facing the developing units 8, 9, 10, and 11.
The manufacturing cost is extremely high. Since the cartridge or the main body of the image forming apparatus is used to determine the positional relationship between the facing position and the developing device, there is a drawback that the position of the ultra-precision portion or the position of the developing device varies.

Further, if the photoconductor cartridge has a developing device, it is still good because the developing device can be fixed to the photoconductor cartridge after the position adjustment, but this is not practical because the weight of the cartridge becomes heavy. In the case where the developing device is configured separately, there is a drawback that the gap between the developing sleeve and the photoconductor cannot be secured stably due to the variation because the position is determined by the main body of the apparatus.

The present invention has been made in view of the above points, and it is possible to stably secure the gap between the developing sleeve and the photosensitive member with high precision, and the troublesome adjustment of the gap is unnecessary. An object of the present invention is to provide an image forming apparatus that can maintain the assembly accuracy only by itself.

[0011]

In order to solve the above-mentioned problems, the present invention provides a plurality of belt-shaped photoconductors which are stretched and moved between two rotating rollers arranged in the lateral direction on the lower peripheral edge thereof. In an image forming apparatus in which developing devices are opposed to each other, a roller-shaped developing backup member is brought into contact with the back surface of the belt-shaped photoconductor so as to face the plurality of developing devices.

Further, the outer peripheral surface of the bearing member of the developing sleeve of the developing unit is directly pressed against the developing backup member to keep the gap between the belt-shaped photosensitive member and the developing sleeve constant.

Further, the outer peripheral surface of the bearing member of the developing sleeve of the developing device is directly pressed against the developing backup member, the outer peripheral surface of the bearing member or the developing backup member is made of an insulating material, and development is performed by a bias voltage applied to the developing device. An electric field is formed between the sleeve and the belt-shaped photoconductor.

The outer peripheral surface of the bearing member of the developing sleeve is pressed against the developing backup member via the resin casing for holding the bearing member so that the gap between the belt-shaped photosensitive member and the developing sleeve is kept constant and the belt is held. An electric field is obtained between the photosensitive member and the developing sleeve.

Further, the invention is characterized in that a developing backup member is inserted or sandwiched in a resin casing for holding a bearing member of a developing sleeve of a developing device to maintain a constant gap between the photoconductor and the developing sleeve.

Further, the invention is characterized in that a connection member is provided for directly connecting the development backup member and the development sleeve shaft or the bearing member thereof, or the development casing.

[0017]

By configuring the developing backup member used in the image forming apparatus of the present invention as described above, the gap between the developing sleeve and the belt-shaped photoreceptor can be secured and maintained with high accuracy and extremely easily.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the drawings.

FIG. 8 is a view showing the schematic arrangement of the image forming apparatus of the present invention.

In FIG. 8, a belt 1 coated with a belt-shaped photosensitive member is provided between rotating rollers 2 and 3 and is conveyed in a clockwise tensioned state by driving the rotating roller 2.

Four roller-shaped development backup members 40 rub against the inner peripheral surface of the belt 1. The development backup member 40 is arranged so as to face each of four developing devices provided near the outer periphery of the belt-shaped photoreceptor.

Further, the belt-shaped photosensitive member on the outer peripheral surface of the belt 1 is always kept in a constant relation position with respect to the surface of the developing backup member 40 during conveyance, and constitutes a stable image forming surface.

6 is a scorotron charger as a charging means, and 7
Is a laser writing system unit as an image exposing means, 8 to 1
Reference numeral 1 denotes a developing device, which is a plurality of developing means for accommodating a developer of a specific color, and these image forming means are arranged at positions facing the development backup member 40 of the belt 1.

The developing devices 8, 9, 10 and 11 contain, for example, yellow, magenta, cyan and black developers, respectively, and developing sleeves 8A, 9A, which keep a predetermined distance from the belt-shaped photoreceptor. 10A and 11A are provided, and the latent image on the photoconductor is visualized by a non-contact developing method.

Reference numeral 12 is a transfer device, 12A is a static eliminator, and 13 is a cleaning device, which is a blade 1 of the cleaning device 13.
3A and the toner conveying roller 13B are kept at a position apart from the surface of the photoconductor belt 1 during image formation and are pressed against the surface of the photoconductor belt 1 only during cleaning after image transfer.

1 and 2 are a perspective view and an end view showing the relational arrangement between the developing backup member and the developing sleeve used in the image forming apparatus of the present invention.

In FIGS. 1 and 2, the developing backup member 40 has a roller shape, and although not shown, a step for positioning is provided at the end portion thereof, and a fixing screw is provided at the end surface thereof, and the main body (of the image forming apparatus) is provided. The main body) or the photoconductor cartridge casing 5 is fixed. It is generally known that the roller shape can be processed with higher precision than the flat plate shape by a processing technique such as cylindrical grinding.

The shafts 14 at both ends of the developing sleeve 8A are supported by the photosensitive cartridge casing 5 via bearings 15 such as ball bearings. In FIGS. 1 and 2, the developing backup member 40 is in direct contact with the bearing 15, but the bearing 15 is embedded in the casing 5 so that the developing backup member 40 can be attached to the outer periphery of the bearing 15 by the casing 5.
You may make it contact via.

At this time, (bearing outer diameter)-(developing sleeve outer diameter) = (gap G between belt-shaped photosensitive member and developing sleeve) × 2
If + (belt-shaped photosensitive member thickness), the development backup member, the bearing, and the development sleeve all have a cylindrical shape that can be processed with high precision. The gap G between the belt-shaped photosensitive member and the developing sleeve 8A is, for example, 500 ± 5.
It can be maintained with extremely high accuracy of 10 μm.

By making the outer peripheral surface of the above-mentioned developing backup member 40 or the bearing 15 in contact with the developing backup member 40 insulative, a developing bias can be easily applied by the conventional method to generate an electric field between the photosensitive member and the developing sleeve. In fact, the latent image can be revealed.

FIG. 7 is a schematic view showing the relationship between the developing backup member and the belt-shaped photoreceptor in the present invention.

As described above, the developing backup member 40 used in the present invention has a roller shape. Therefore, in FIG. 7, considering the X direction positional allowance (dimension in the drawing) of the developing device (b). As shown in the figure, the development backup member 40
When the radius R is large, the X-direction position allowance of the developing device also increases, but the space of the developing device in the vertical direction (y direction in FIG. 7) increases.

In order to make the entire machine compact,
When the roller diameter R of the development backup member 40 is reduced as shown in FIG. 7A, the position allowance of the developing device in the x direction decreases. Therefore, maintaining the positional relationship between the developing device and the developing backup member in the x direction with high accuracy is essential when making a compact machine.

FIG. 6 shows a plurality of development backup members 40.
It is a schematic diagram showing arrangement of each backup member to the belt-like photoconductor when A to 40D are used in order.

In FIG. 6, the member 40B between the member 40A and the member 40C for giving a tension to the photosensitive member is always outside the tangent line between the members 40A and 40C, and similarly, the member 40B and the member 40D are the same. The member 40C in between is
It must be located outside the tangent line between the members 40B and 40D. Further, as the amount of protrusion to the outside of the tangent line increases, the amount of wrapping of the belt-shaped photosensitive member with respect to the member 40, that is, the length of the contact line increases, and x of the developing device increases.
Although the allowable amount of the directional position increases, a large space in the y direction is required. Specific values of the X-direction position allowance are, for example, when the diameter of the developing backup member 40 is 18 mm, the step between the developing backup members is 1 mm, and the distance between the developing backup members is about 50 mm, the allowable amount of the position of the developing device is It is ± 0.25 mm or less.

FIGS. 3 and 4 are schematic views showing means for securing the relative position of the developing sleeve and the developing backup member.

In order to solve such a problem, FIG.
An example as shown in FIG. 4 was considered. In the embodiment of FIG. 3, the casing 5 holding the bearing 15 of the developing sleeve is extended so as to sandwich the developing backup member 40, and the notch 16 for positioning it is provided. This makes it possible to secure and maintain the accuracy of the gap G between the photoconductor and the developing sleeve. At this time, a part 5A of the casing is inserted between the photoconductor and the developing sleeve, but this part is a small part in terms of area, and only this part is extremely high when the casing is processed. There is no serious problem in producing precision. A positioning hole 17 may be provided instead of the cutout portion 16 (FIG. 4).

FIG. 5 is a front view of a connecting member 18 for connecting the developing backup member and the shaft of the developing sleeve or its bearing, or the casing.

By manufacturing such a connecting member 18 with high precision, the gap G between the developing sleeve and the photoconductor can be accurately maintained. In this method, since the connecting member 18 itself is a small component, precision machining is easier than in the case of machining the casing shown in FIGS.

[0040]

As described above, the present invention has the above-mentioned structure. Therefore, in the image forming apparatus, a highly accurate gap between the developing sleeve and the belt-shaped photosensitive member can be manufactured by an inexpensive part and easily assembled, and the part can be easily assembled. It is possible to obtain the excellent effect that the accuracy can be maintained even after the maintenance and replacement of. As a result, an image forming apparatus that can always obtain a high quality image is provided.

[Brief description of drawings]

FIG. 1 is a perspective view showing a schematic relationship between a developing backup member and a developing sleeve used in an image forming apparatus of the present invention.

FIG. 2 is a side view showing a schematic relationship arrangement of a developing backup member and a developing sleeve used in the image forming apparatus of the present invention.

FIG. 3 is a side view showing a means for ensuring the arrangement of the developing backup member and the developing sleeve used in the image forming apparatus of the present invention.

FIG. 4 is a side view showing a means for ensuring the arrangement of the developing backup member and the developing sleeve used in the image forming apparatus of the present invention.

FIG. 5 is a side view showing a means for ensuring the arrangement of the developing backup member and the developing sleeve used in the image forming apparatus of the present invention.

FIG. 6 is a schematic view showing a contact state between a belt-shaped photosensitive member and a plurality of development backup members in the image forming apparatus of the present invention.

FIG. 7 is a schematic view showing a contact state between a belt-shaped photoreceptor and a development backup member in the image forming apparatus of the present invention,
(A) shows the case where the diameter of the development backup member is small, and (b) shows the case where it is large.

FIG. 8 is a diagram showing a schematic configuration of an entire image forming apparatus of the present invention.

FIG. 9 is a schematic diagram showing the overall schematic configuration of a conventional image forming apparatus.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Belt-shaped photoreceptor 2 Rotating roller 3 Rotating roller 8-11 Developing device 8A-11A Developing sleeve 40 Development backup member G Gap between photosensitive body and developing sleeve

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display location G03G 21/00 118

Claims (6)

[Claims] 1. An image forming apparatus in which a plurality of developing devices are arranged facing each other on a lower peripheral edge of a belt-shaped photosensitive member which is stretched and moved between two rotating rollers arranged in a lateral direction, An image forming apparatus, characterized in that a roller-shaped developing backup member is brought into contact with the back surface of the belt-shaped photoconductor so as to face a plurality of developing devices. 2. The gap between the belt-shaped photoreceptor and the developing sleeve is kept constant by directly pressing the outer peripheral surface of the bearing member of the developing sleeve of the developing device against the developing backup member. The image forming apparatus described. 3. The outer peripheral surface of the bearing member of the developing sleeve of the developing device is directly pressed against the developing backup member, the outer peripheral surface of the bearing member or the developing backup member is made of an insulating material, and development is performed by a bias voltage applied to the developing device. The image forming apparatus according to claim 1, wherein an electric field is formed between the sleeve and the belt-shaped photoreceptor. 4. A bearing member for a developing sleeve is pressed against a developing backup member via a resin casing for holding the bearing member so as to maintain a constant gap between the belt-shaped photoreceptor and the developing sleeve and to expose the developing sleeve. The image forming apparatus according to claim 1, wherein an electric field is obtained between the body and the developing sleeve. 5. A developing backup member is inserted or sandwiched in a resin casing for holding a bearing member of a developing sleeve of a developing device to maintain a constant gap between the belt-shaped photoconductor and the developing sleeve. 1. The image forming apparatus according to 1. 6. The image forming apparatus according to claim 1, further comprising a connecting member for directly connecting the developing backup member and the developing sleeve shaft or the bearing member thereof, or the developing casing.