JPS63304279A - Image forming device - Google Patents

Abstract

PURPOSE:To equalize the pressure at the time of development and to maintain a prescribed developing gap by a min. load by constituting the titled device in such a manner that force acts always in the direction where a photosensitive drum and spacing member are pressurized in the contact parts of both at the time of development and both are detached by a pulling means at the time of non-development. CONSTITUTION:This device has the spacing member 6 which maintains the specified spacing of a developer carrier 2 and a turning means which turns around a fulcrum 7. The device is so constituted that the force acts always in the direction where the latent image carrier 1 and the spacing member 6 are pressurized in the contact part of both at the time of the development and both are parted by a pulling means at the time of the non-development. The rotating directions of both the photosensitive drum 1 and a sleeve 2, the relative positions thereof, and the turning fulcrum position of the developing device are so determined that the sleeve 2 is kept pressurized at all times to the drum 1 by means of the spacing member 6. The fluctuations in the forces of right and left springs are thereby eliminated, by which the load fluctuation is decreased and the uniform developing gap is stably maintained.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to an image forming apparatus for visualizing an electrostatic latent image on a latent image carrier in electrophotography.

Conventional Technology The gap between the latent image carrier and the developer carrier in the electrophotographic process is one of the most important conditions for obtaining good images. In the past, the latent image carrier and the developing device were attached by adjusting their positions to obtain a predetermined gap, but this required a lot of time for adjustment.

The developing device proposed to solve the above problems is as follows:
For example, there is one disclosed in Japanese Unexamined Patent Publication No. 55-111973, and an outline thereof is shown in FIG.

In FIG. 3, 100 is a latent image carrier (hereinafter referred to as a photosensitive drum), and 103 is a developer carrier (hereinafter referred to as a sleeve).
, 105 are gap holding members, and are configured to apply force to the photosensitive drum 100 in the direction in which the sleeve 103 is separated via the gap holding member 105 during development. 1
08 and 109 are pressure springs, and in order to improve the meshing between the drum drive gear 101 and the gear 104, the drive side spring 108 is made stronger than the opposite side spring 109. Further, 106 is a bottle, and 107 is a support.

In the developing device configured as above, the photosensitive drum 100 and the sleeve 103 rotate in the direction of the arrow,
The sleeve 103 is pressed against the photosensitive drum 100 by springs 108 and 109 to maintain a constant gap and perform development.

Problems to be Solved by the Invention However, in the above example, since the structure is such that a force is applied in the direction in which the sleeve 103 separates from the photosensitive drum 100, the springs 108 and 109 are strengthened in order to maintain a constant developing gap. 100 photosensitive drums with great force
It is necessary to press the photosensitive drum 1.
There were problems such as damaging the 00 and causing jitter due to load fluctuations.

Means for solving the problems and the technical means of the present invention for solving the above-mentioned problems is that during development, a force is always applied in the direction in which the photosensitive drum and the gap holding member are pressurized at the abutting portions of the two. The structure is such that it is detached by a traction means during development.

action The effect of this technical means is as follows.

That is, during development, the photosensitive drum and the sleeve are rotating at a constant speed, and the direction of rotation of both the photosensitive drum and the sleeve is such that the sleeve is always pressurized against the photosensitive drum via the gap holding member; relative position,
The rotational fulcrum position of the developing device is determined. Therefore, there is no need to press the gap holding member against the photosensitive drum with a large force, and there is no variation in the force of the left and right springs as in the conventional example shown in FIG. The development gap can be maintained stably. As a result, it is possible to obtain a good image without damaging the photosensitive drum and eliminating jitter.

Furthermore, during non-development, the developing device can be easily removed using a pulling means such as a lever or a spring in a small amount of space around the rotational fulcrum of the developing device itself.

Embodiment FIG. 1 shows an example in which the image forming apparatus of the present invention is used in an electrophotographic copying machine. 1 (hereinafter referred to as photosensitive drum) with a development gap of 100 to 200 μm. However, the gap holding member 6 is a cylindrical spacer link having a larger diameter than the sleeve 2, and is attached coaxially with the sleeve 2.

FIG. 2 is a diagram showing the driving state of the photosensitive drum 1 and the sleeve 2, in which 11 is a drum drive gear, 12 is a sleeve drive gear, and the sleeve drive gear 12 and the photosensitive drum 1 are attached concentrically to the sleeve 22. Drum drive gears 11, which are attached concentrically, mesh with each other to transmit power. A one-component magnetic developer 10 (hereinafter simply referred to as toner) is housed in the hopper 9, and is positively charged by the fur brush 3 and supplied to the cylindrical sleeve 2 in this example, and then to the blade 4. The image forming apparatus of this embodiment is configured as described above, and according to experiments conducted by the inventor, a thin layer of toner is formed on the sleeve 2 by controlling the layer thickness to a constant value. 2 and the photosensitive drum 1 rotate in the direction shown in FIG. 3, and the angle formed by the horizontal line and the line connecting the center of the photosensitive drum 1 and the center of the sleeve 2 is 0° when viewed counterclockwise from the horizontal line, θ≦7.
00 and by selecting an appropriate rotational fulcrum position of the developing device, it was observed that a force always acts in the direction in which the sleeve 2 comes into pressure contact with the photosensitive drum through the gap holding member 6 at the contact portion between the two. It was done.

In this case, at both ends of the photosensitive drum 1 and the sleeve 2,
a drum drive gear 11 installed concentrically with the photosensitive drum 1;
It is desirable to provide a sleeve drive gear 12 that is attached concentrically to the sleeve 2 to balance the left and right sides, and in order to obtain good images, the photosensitive drum 1 and sleeve 2 are rotated at a certain speed during development. It is necessary to be present. Further, the separation lever 8 is connected to the photosensitive drum 1.
This is for bringing the sleeve 2 into contact with a part of the body of the developing device, and it rotates in the direction of the arrow by controlling mechanisms such as cams and solenoids with electrical pulses. The sleeve 2 is rotated in a direction that separates it from the photosensitive drum 1 during non-development, and moves away from the transparent body 9 during development without applying any force.
Further, the rotational fulcrum 7 is located below the line connecting the centers of the photosensitive drum 1 and the sleeve 2, and the developing device does not occupy space around this fulcrum 7 both during development and non-development. It can be rotated.

When developing under the above conditions, the force is applied uniformly, and therefore a constant development gap can be maintained and development can be performed in a state with little load fluctuation.

Next, a second embodiment of the present invention will be described.

FIG. 4 shows a second embodiment of the present invention, in which spring force is used during separation. In order to avoid complication, the same numbers have been given to the same parts. In FIG.
A drum drive gear 11 and a sleeve drive gear 12, which are attached to both ends of the photosensitive drum 1 and the sleeve 2 and are opposed to each other with a developing gap of 00 μm, mesh with each other and rotate in the direction indicated by the arrow. However, the positional relationship between the photosensitive drum 1 and the sleeve 2 is the same as that described in the first embodiment.

As a result, a pressing force (FIG. 4F) is applied to the photosensitive drum 1 as explained in the first embodiment, and the sleeve 2 is applied to the photosensitive drum 1.
are pressed together via the gap holding member 6. At this time, spring 1
3 may be effective depending on the degree of pressure of the sleeve 2 against the photosensitive drum 1 via the gap holding member 6. Further, during non-development, a separation spring 14 serving as a traction means operates to separate the developing device from its own pivot point 7. When the sleeve 2 is pressed into contact with the photosensitive drum 1 again via the gap holding member 6, the separation spring 14 engages the drum drive gear 11 attached to the photosensitive drum 1 and the sleeve drive gear 12 attached to the sleeve 2. It is clear that by adopting zero or more configurations that serve as a cushion and smooth the connection, the same effect as the first embodiment of the present invention can be obtained.

Effects of the Invention According to the present invention, pressure is applied evenly during development and a predetermined development gap can be maintained with a minimum load.
This has great practical effects, such as preventing jitter and obtaining good images, as well as reducing the force applied to the photosensitive drum, thereby preventing damage to the photosensitive drum.

[Brief explanation of the drawing]

113!1 is a principle diagram of the developing device in the first embodiment of the present invention, FIG. 2 is a plan view of a part of the same device, FIG. 3 is a diagram for explaining the same device, and FIG. 4 is the invention of the present invention. FIG. 5 is a perspective view of a developing device in a conventional example. 1. Photosensitive drum 2. Sleeve 6. Gap holding member 7. Rotation fulcrum 8. Separation lever 11.
・Drum drive gear 12...Sleeve drive gear 13...
Spring 14... Name of separation spring agent Patent attorney Toshio Nakao 1 person 1 - Front drum 2 - Sleeve 3 - F1 - Drag 4... Zlade 6 - M1iFIF member 7 - Times U 1 color 8 - Separation lever 9 --- Main horn V- Toyner No. 1ff1 No. 2 Fig. m-a tom 701-Drum fitting 41 +r-El image 5 103-Sleeve set...-Gima Fig. 4 1- 1! J light drum? -Sleeve 6-Gap protection hemorrhoid material 7-times! 7zuk. 9-Honhorn V- 13-Pa Half+4-Half between the wrinkles Figure 5

Claims (4)

[Claims] (1) A latent image carrier, a developer carrier, a gap holding member that maintains a constant gap between the latent image carrier and the developer carrier, and a rotating means that rotates about a fulcrum. An image characterized in that, during development, a force always acts in a direction in which the latent image carrier and the gap holding member are pressurized at their abutting portions, and are separated by a traction means during non-development. Forming device. (2) The image forming apparatus according to claim 1, wherein the gap holding member is a cylindrical body that is held concentrically with the developer carrier and has a larger diameter than the developer carrier. (3) The image forming apparatus according to claim 1 or 2, wherein the traction means is a lever that rotates around a fulcrum. (4) The image forming apparatus according to item 1, 2, or 3, wherein the traction means is constituted by a member to which a spring force acts when detached.