JPS6336338Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an image forming apparatus used, for example, as an electrophotographic copying machine.

Generally, electrophotographic copying machines are equipped with a toner density control device that controls the density of toner and a surface potential control device that controls the surface potential of the photoreceptor, and the operation of these devices stabilizes the image quality and density. There is.

However, in the past, there was no way to know if the developer had deteriorated, and if the developer deteriorated and the image density decreased, a large amount of toner was replenished, or the surface potential of the photoreceptor was raised to maintain the image density to a predetermined level. In the former case, a large amount of toner may fall off, staining the inside of the copying machine and adversely affecting image quality, and in the latter case, fogging may occur due to an increase in residual potential. There was a problem.

This invention was made with attention to the above circumstances,
The purpose of this is to provide an image forming device that displays the deterioration of the developer so that it is not necessary to replenish a large amount of toner or to increase the surface potential of the photoreceptor when the image quality and density decreases. This is what we are trying to provide.

Hereinafter, one embodiment of the present invention will be described based on the drawings. In the figure, reference numeral 1 denotes a document table that is movably installed on the top surface of the copying machine.
is placed on the document 2, and the cover 3 is placed over the document 2. Further, a black portion 4 is provided at one end of the back surface of the document table 1 . On the other hand, a photoreceptor 5 is provided in the center of the main body of the copying machine, and around the photoreceptor 5, a charger 6, a developing device 7 as a toner supply means,
Transfer, static elimination chargers 8 and 9, and static elimination lamp 10 are provided. Reference numeral 11 denotes a detection circuit for detecting the surface potential of the photoconductor 5 charged by the charging charge 6, and the detection circuit 11 sets the surface potential of the photoconductor 5 to a constant value according to the detected value. A surface potential control circuit 12 is connected thereto. Further, the developing device 7 is provided with a toner concentration control device 13 that controls the toner concentration of the developer 7a made of toner and carrier to a constant value.

On the other hand, between the developing device 7 and the transfer charger 8, light-emitting and light-receiving elements 15 constituting a detection means 14 for detecting the image density of the black portion 4,
16 are arranged. The light emitting element 15 emits light when the image of the black portion 4 arrives, and stops emitting light when the image of the black portion 4 passes. Further, the light receiving element 16 is the light emitting element 15.
Reflected light from the black portion 4 is detected only during the light emission period. This light receiving element 16 is connected to a detection circuit 18 via an amplifier circuit 17, and this detection circuit 18 is connected to a discrimination circuit 1 as a concentration discrimination means.
9. Furthermore, display means 20 is connected. Also,
The discrimination circuit 19 includes the surface potential control device 12.
and a toner concentration control device 13 are connected. The discrimination circuit 19 stores in advance a voltage to be outputted as a constant image density of the black portion 4, and detects the image density of the image each time one cycle of copying is performed on the original 2. The image density of the image is calculated.

Note that 21 is an exposure system consisting of an exposure lamp 22, a reflecting mirror 23, a lens 24, and a reflecting mirror 25.

In the above-described configuration, when the charging charger 6 charges the surface of the photoreceptor 5 and rotates it, and also irradiates light from the exposure lamp 22 to move the document table 1, first, the document table 1 is moved.
Light is irradiated onto the black part 4 at the tip of the holder and reflected,
As shown by the arrow, the light is reflected by the reflecting mirror 23 and then guided to the reflecting mirror 25 via the lens 24, and after being reflected by the reflecting mirror 25, it is irradiated onto the photoreceptor 5. As a result, an electrostatic latent image corresponding to the black portion 4 is formed on the photoreceptor 5, and this electrostatic latent image is visualized by being supplied with developer 7a in the developing device 7. The surface potential of the photoreceptor 5 is always controlled to be constant by a surface potential control device, and the developing device 7 is controlled by a toner specific concentration control device 13.
Therefore, the specific toner density is constantly controlled to be constant. The developed image formed on the photoreceptor 5 is exposed to light by the light emitting element 15 which emits light when the developed image arrives and stops emitting light when the developed image has passed by a synchronization circuit (not shown). Then, the reflected light from the imager due to the light emission of the light emitting element 15 is received by the light receiving element 16 and sent to the detection circuit 18 via the amplifier circuit 17.If the carrier of the developer 7a is not deteriorated, The output voltage becomes the reference concentration voltage a as shown in FIG.
If it has deteriorated, the concentration voltage will be reduced b. This reduced concentration voltage b is sent to the discrimination circuit 19 and subtracted from the reference concentration voltage a, and when the output voltage after the subtraction exceeds the allowable level as shown in FIG. 3, it is displayed by the display means 20. That will happen.

In this way, if the image density decreases due to deterioration of the carrier in the developer 7, the display means 20 will display the result, so the surface potential of the photoreceptor 5 may be increased or a large amount of toner may be There is no risk of replenishing the image density and correcting the image density.

As explained above, the present invention uses the display means to indicate when the developer has deteriorated, so it is possible to replenish a large amount of toner without knowing the deterioration of the developer, and to increase the surface potential of the photoreceptor. The developer can be replaced without increasing the amount of toner, and fogging and toner dropping can be prevented from occurring.

Further, the density detection means and the density difference determination means can be used as a detection means for detecting deterioration of the developer, and there is no need for a separate means for detecting deterioration of the developer, resulting in a simplified structure and low cost.

Further, since deterioration of the developer is detected by detecting the density of toner attached to the photoreceptor, there is an advantage that detection accuracy is excellent.

Furthermore, since the toner concentration is detected and the deterioration of the developer is determined prior to the image forming operation, it is possible to reliably form an image using a normal developer during image formation.

[Brief explanation of the drawing]

The drawings show one embodiment of the present invention; Fig. 1 is a block diagram showing a part of an electronic copying machine, Fig. 2 is a graph showing the output voltage of the detection circuit, and Fig. 3 is the output of the discrimination circuit. It is a graph diagram showing voltage. 5...Photoreceptor, 7...Developing device (toner supply means),
7a... Toner, 13... Toner density control means, 1
4, 18...Concentration detection means, 19...Discrimination circuit (concentration difference discrimination means), 20...Display means.

Claims (1)

[Scope of utility model registration request] In an image forming apparatus that performs an image forming operation by supplying toner to a photoreceptor, there is provided a toner supply means for supplying toner to the photoreceptor prior to the image forming operation, and a toner supply means for removing toner attached to the photoreceptor. a concentration detection means for detecting concentration; a concentration difference determination means for determining whether a difference between the concentration detected by the concentration detection means and a reference concentration is within an allowable level; toner concentration control means for controlling the toner concentration to a constant level when the discrimination means determines that the density difference is outside an allowable level; and display means for displaying the determination result when the discrimination means determines that the density difference is outside an allowable level. An image forming apparatus comprising: