JPS62231975A - Electrophotographic recorder - Google Patents

Abstract

PURPOSE:To keep a developing gap constant by providing directly a ring-shaped spacer member on one of a photosensitive drum or a developing roller, in a position of the outside of both ends of an image forming position of the photosensitive drum, and pressing this spacer member against the outside peripheral surface of the other side. CONSTITUTION:At the time of development, the outside periphery of a developing roller 4 is pressed against a ring-shaped spacer member 10, and a developing gap (strictly speaking, it is different by a size difference of the outside surface of a photosensitive layer and the outside surface of both ends of a conductive base body) of only a portion prescribed by thickness of the ring-shaped spacer member 10 is held between the photosensitive layer 3 and the developing roller 4. In this state, by a rotation of the developing roller 4, a toner on its outside peripheral surface is supplied to a photosensitive drum 1. As for the ring-shaped spacer member 10 which is used in this case, a resin film which has been formed endlessly, for instance, an endless polyester film is suitable.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an electrophotographic recording apparatus of the type using a powder developer.

Conventional technology An electrophotographic recording device consists of a photosensitive drum having a photosensitive layer on its surface, a charger and an exposure device placed around the photosensitive drum.

It has a developing device, a transfer device 2 separator, a fixing device, a cleaning device, etc., and the surface of the photosensitive drum is
It is uniformly charged with a charger, then exposed with an exposure device to form an electrostatic latent image, and a developer (toner) is applied to this latent image to make it visible, and this toner image is recorded. Image recording is performed through a process in which the recording paper is transferred onto paper, and then the recording paper is separated from the photosensitive drum, sent to a fixing device, fixed, and discharged.The developing device in such an electrophotographic recording device generally includes a developing roller. Fig. 4 shows a conventional photosensitive drum and developing device, in which the photosensitive drum 1 has a cylindrical conductive base 2 made of a conductive material such as aluminum, and the outer circumferential surface of the base excluding both ends is A developing roller 4 is provided with a photosensitive layer 3 to maintain a constant gap (development gap) with respect to the photosensitive drum l, and applies toner 5 held on the surface of the developing roller 4 to the photosensitive drum l. Here, the developing roller 4 is connected to the photosensitive layer 3 of the photosensitive drum 1.
A spacer ring 7 having an outer diameter larger than the outer diameter of the developing roller by a predetermined size is attached to the shaft 6 supporting the developing roller 4 in order to maintain a constant gap between the spacer ring 7 and the photosensitive drum. By pressing against the outer peripheral surface of the conductive substrate 2 of 1, a predetermined gap is maintained between the photosensitive drum 1 and the developing roller 4. This spacer ring 7 is generally formed by combining a resin ring 8 made of resin such as Duracon and a bearing 9.

Problems to be Solved by the Invention However, with such a configuration, density unevenness tends to occur in the image in the vertical direction (recording paper running direction), and this density unevenness is particularly large in a system using a -component developer. There was a problem.

The above problem arises for the following reasons. That is, since the spacer ring is a combination of a bearing and a resin ring, the deviation of the outer periphery of each of the two components is accumulated and appears as a deflection of the outer periphery of the spacer ring. especially,
It is difficult to improve the machining accuracy of the resin ring used as an insulating part due to the material, and when it is finally attached to the shaft of the developing roller as a spacer ring, the outer circumference can only be photographed to a maximum of about 0.05 mm. . Furthermore, since the discrepancy of the outer periphery of the developing roller with respect to the shafts at both ends of the developing roller to which the spacer ring is attached is added as a factor for variation in the developing gap, the final variation in the developing gap can be as much as 0.07 to 0.10. turn into.

This is a relatively small problem when there are several development gaps, such as in a system that uses a two-component developer, but in a system that uses a -component developer, the development gap is generally narrow (,0, In many cases, the range is 20 to 0.50, and the variation in the development gap due to the aforementioned fluctuation of the outer periphery directly appears as unevenness in the degree of R of the image.

However, even if processing accuracy were to be improved, it would still result in higher costs. Of course, this also applies to bearings.

The present invention was made in view of the above-mentioned problems, and it is difficult to achieve machining accuracy and it is difficult to use bearings.

It is an object of the present invention to provide an electrophotographic recording device equipped with a photosensitive drum and a developing roller, in which a developing gear can be easily and accurately set without using a spacer ring which is expensive to use. .

Means for Solving the Problems In order to solve the above-mentioned problems, the present invention provides a method of applying a method to the outer circumferential surface of at least one of the photosensitive drum and the developing roller, at a position outside both ends of the image forming position of the photosensitive drum. A ring-shaped spacer member is provided, and the development gap is held constant by pressing this spacer member against the outer peripheral surface of the other party.

According to the present invention, the spacer member is provided directly on the outer circumferential surface of the photosensitive drum or the developing roller, so even if the photosensitive drum or the developing roller itself shakes, the developing gap is hardly affected by the wobbling. Fluctuations in the development gap occur only due to unevenness in the thickness of the spacer member, and by manufacturing the spacer member with a uniform thickness, it is possible to make the development gap uniform. Furthermore, compared to a conventional spacer ring consisting of a bearing and a resin ring, the structure is simpler and costs can be reduced.

Real ellipse example Hereinafter, the present invention will be described in detail as shown in the drawings.

FIG. 1 is a plan view showing a photosensitive drum and a developing roller used in an electrophotographic recording apparatus according to an embodiment of the present invention, and FIG. 2 is a perspective view of the photosensitive drum. In the figure, 1 is a photosensitive drum, and a photosensitive layer 3 is placed on a conductive base 2 made of a conductive material such as aluminum, except for both ends of the base 2.
is provided. A ring-shaped spacer member 10 made of an insulating material and having a thickness equal to a desired development gap is provided on the outer peripheral surface of the conductive substrate 2 located outside both ends of the photosensitive layer 3. On the other hand, the developing roller 4 disposed opposite the photosensitive drum 1 is formed to have a width longer than the width for supplying the toner 5, so that the ring-shaped spacer member IO attached to the outer circumferential surface of the photosensitive drum 1 directly contacts and hangs. There is. Thus, during development, the outer periphery of the developing roller 4 is pressed against the ring-shaped spacer member 10, and the photosensitive layer 3 and the developing roller 4 are
A developing gap defined by the thickness of the ring-shaped spacer member 10 (strictly speaking, it differs by the dimensional difference between the outer surface of the photosensitive layer and the outer surfaces of both ends of the conductive substrate) is maintained between the two. As the developing roller 4 rotates, the toner 5 on the outer circumferential surface of the developing roller 4 is supplied to the photosensitive drum 1 .

The ring-shaped spacer member 10 used here is as follows:
An endless resin film, such as an endless polyester film, is suitable.

This endless polyester film is produced by Hokushin Kogyo Co., Ltd. under the trade name 2 Polyester Belt (Material;
What is sold as t r e +, ) J can be used. Such an endless resin film can be used in this state by simply stretching it and attaching it to the outer circumference of the photosensitive drum 1, and it is tightly attached and fixed to the outer circumferential surface of the photosensitive drum 1 by its own shrinkage force. Therefore, it is extremely easy to attach, and there is no need to use adhesive or the like. In addition, the thickness of the endless resin film can be easily adjusted to high precision during manufacturing. For example, in the above-mentioned polyester belt,
The thickness accuracy is ±5 μm [i]. Therefore, fluctuations in the developing gap during rotation of the photosensitive drum 1 and the developing roller 4 are extremely small, and fluctuations in the developing gap that would cause unevenness in image density do not occur. Furthermore, polyester film has sufficient abrasion resistance, so when the photosensitive drum and the developing roller rotate in the same direction in the developing section, the rotational speed (peripheral speed) of the photosensitive drum 1 and the developing roller 4 is intentionally controlled. There is no need to match the circumferential speed of the photosensitive drum l.

FIG. 3 shows a modification of the photosensitive drum used in the present invention. This photosensitive drum IA also has two conductive substrates and a photosensitive layer 3, but a small diameter portion is formed at both ends of the two conductive substrates, and a ring-shaped spacer member 10 is formed in this small diameter portion.
A is attached, and a flange 11 is attached to the outside thereof. The other configurations are similar to those in FIG. In this embodiment, the spacer member 10A is housed in a groove formed by the small diameter portions at both ends of the conductive base member and the 7 flange 11, so that the spacer member 10A does not come off during use and can be kept in position. This has the advantage that no deviation occurs.

FIG. 4 shows still another modification of the photosensitive drum. This photosensitive drum IB has a cylindrical base 12 made of an insulating material such as glass fiber reinforced resin, and a conductive layer 13 made of a conductive resin, etc., except for both ends thereof, and a photosensitive layer 14 on top of the cylindrical base 12. was formed. The outer circumferential surface 15 of the substrate on the outside of both ends of the photosensitive layer 14 is formed to have a diameter larger than that of the photosensitive layer 14, and the outer circumferential surface 15 of the substrate and the photosensitive layer 14 are formed to have a diameter larger than that of the photosensitive layer 14.
The distance from the outer surface is the same as a predetermined development gap. In this embodiment, the outer circumferential surface 15 of the base body constitutes a ring-shaped spacer member, and similarly to the embodiments shown in FIGS. 1 and 3, it contacts the outer circumferential surface of the developing roller 4 and is photosensitive. It serves to maintain a predetermined development gap between layer 14 and the development roller.

In the above embodiments, ring-shaped spacer members are provided at both ends of the photosensitive drum, but instead of this, for example, in FIG. A ring-shaped spacer member made of a film or the like may be attached and pressed against the outer surface of the conductive substrate at both ends of the photosensitive drum.

It goes without saying that the developer that can be used in the present invention may be magnetic or non-magnetic.

Effects of the Invention As is clear from the above description, the present invention provides a ring-shaped spacer member directly on either the photosensitive drum or the developing roller at a position outside both ends of the image forming position of the photosensitive drum. By holding the development gap constant by pressing the member against the outer circumferential surface of the other side, the gap can be easily maintained constant with high precision.Furthermore, the simple structure eliminates high costs. This has the effect of not causing any problems.

[Brief explanation of drawings]

FIG. 1 is a partially sectional plan view showing a photosensitive drum and a developing roller of an electrophotographic recording apparatus according to an embodiment of the present invention, FIG. 2 is a perspective view of the photosensitive drum in the above embodiment, and FIG. 3 is a photosensitive drum. FIG. 4 is a sectional view showing another modification of the photosensitive drum, and FIG. 5 is a perspective view showing a photosensitive dome and a developing roller of a conventional electrophotographic recording apparatus. DESCRIPTION OF SYMBOLS 1... Photosensitive drum, 2... Conductive substrate, 3... Photosensitive layer, 4... Developing roller, 5... Toner, lo...
・Ring-shaped spacer member.

Claims (4)

[Claims] (1) A photosensitive drum having a cylindrical outer peripheral surface with a photosensitive layer;
a developing roller that applies developer to the surface of the photosensitive drum, and at least one of the photosensitive drum and the developing roller is arranged on an outer circumferential surface located outside both ends of the image forming position of the photosensitive drum, and on the outer circumferential surface of the other one. An electrophotographic recording device comprising a ring-shaped spacer member made of an electrically insulating material and in contact with the other. (2) An endless type in which the photosensitive drum has a cylindrical conductive base and a photosensitive layer provided on the surface of the conductive base, and ring-shaped spacer members are attached to the outer circumferential surface of both ends of the conductive base. 2. The electrophotographic recording device according to claim 1, wherein the electrophotographic recording device is made of film. (3) The electrophotographic recording apparatus according to claim 1 or 2, wherein the ring-shaped spacer member is an endless polyester film. (4) The photosensitive drum has a cylindrical insulating base, a conductive layer formed on the outer peripheral surface of the insulating base excluding both ends, and a photosensitive layer formed on the conductive layer, and An electrophotographic recording device characterized in that a ring-shaped spacer member is formed at both ends of an insulating substrate.