JPH0335263A - Developing device - Google Patents

Abstract

PURPOSE:To control the density of a final image by changing the abutting pressure of a layer thickness control member and the abutting pressure of a supplying roller corresponding to the detected concentration of toner adhering on a photosensitive drum. CONSTITUTION:The device is provided with an image density control means M8 for changing the abutting pressure of the layer thickness control member M4 and the abutting pressure of the supplying roller M3 against an developing roller M2 corresponding to the output of a means M7 for detecting the concentration of the toner adhering on the photosensitive drum M1. By controlling the abutting pressure of the layer thickness control member M4 against the developing roller M2, the thickness of the toner and the electrostatic charging quantity of the toner on the developing roller M2 are controlled, and by controlling the abutting pressure of the supplying roller M3 against the developing roller M2, the toner concentration on the developing roller M2 is controlled. Thus, the density of the final image on the photosensitive drum M1 is controlled.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electrostatic developing device used in copying machines, printers, etc., and particularly to a method for controlling the density of toner on a photoreceptor drum (for example, a photoreceptor drum). It's about control.

In the conventional pinch strain electrostatic developing device, a developed image is obtained by transferring toner carried on a developing roller to an electrostatic latent image formed on a photoreceptor drum. By transferring this developed image onto paper or the like, it becomes possible to copy a manuscript or print out an arbitrary figure. Here, since the density of the toner on the photoreceptor drum is directly related to the print or image density on the copied or printed paper, accurate control of the toner density on the photoreceptor drum is desired.

Such developing devices include a one-component type and a two-component type, depending on the type of developer used. - In the component type, only the toner to be transferred onto paper or the like is used, and in the two-component type, a mixture of toner and powder called a carrier is used.

In either method, the thickness of the toner carried on the developing roller affects the density of the toner on the photoreceptor drum. A method was used to perform feedback control by detecting the height of the toner and moving a layer thickness regulating member (doctor blade) according to the detected value so that the height of the toner on the developing roller remained constant (for example, 1986-18
(Japanese Patent No. 2073 discloses such a technique regarding a printer using a magnetic latent image forming method).

In the old one-command-type developing device, the toner moves to the surface of the developing roller at the contact point between the supply roller and the developing roller and is charged by friction. Due to friction with the doctor blade that regulates the toner layer, the entire surface of the developing roller is triboelectrically charged.

In such a one-component type developing device, the amount of toner transferred to the photoreceptor drum also depends on the toner charge amount and toner packing density. It is not possible to sufficiently control the density of the copied or printed image (!i) by simply regulating the toner height. And the amount of charge on the toner also changes, and as a result,
Image density changes.

SUMMARY OF THE INVENTION An object of the present invention is to solve these problems and provide a one-component type developing device in which the density of a final image can be accurately and arbitrarily controlled.

In order to achieve the above object, the developing device of the present invention includes a first
As shown in the figure, photoreceptor drum old and photoreceptor drum Ml
a developing roller gate 2 that is provided in parallel with and carries the toner to be transferred to the photoreceptor drum Ml; and a supply roller gate that is provided parallel to and in contact with the developing roller gate 2 and that carries the toner that is to be transferred to the developing roller gate 2. 3, and a layer thickness regulating member M4 that comes into contact with the rotating developing roller gate 2 and makes the thickness of the toner carried on the developing roller M2 uniform. means M5 for controlling the contact pressure on the developing roller gate 2; means M6 for controlling the contact pressure of the supply roller gate 3 on the developing roller label; and means M for detecting the adhesion density of toner on the photoreceptor drum Ml.
7, and an image density control means for changing the contact pressure of the layer thickness regulating member and the contact pressure of the supply roller according to the detected toner adhesion density.

The toner adhesion density detection means M7 detects the density of the toner on the photoreceptor drum Ml, and sends a signal corresponding to the adhesion density between the image density control means. Based on this, the contact pressure of the layer thickness regulating member to the developing roller gate 2 and the contact pressure of the supply roller to the developing roller gate 2 are controlled so that the toner concentration on the photoreceptor drum becomes a predetermined value. .

By controlling the contact pressure of the layer thickness regulating member M4 to the developing roller gate 2, the toner thickness on the developing roller M2 and the amount of toner charge are controlled, and the contact thickness of the old supply roller to the developing roller gate 2 is controlled. By controlling , the density of toner on the developing roller gate 2 can be controlled. Therefore, by comprehensively controlling these circumferential contact pressures between the image density control means,
It is possible to control the adhesion density of toner on the photoreceptor drum, that is, the density of the final image.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 2 is a schematic diagram of an image recording section of a toner-type electrostatic copying machine using a developing device according to the present invention.

The image recording section is arranged around the photoconductor drum l in order in the rotational direction: a main charging section 2, a developing device 6, a transfer section 7, a separation section 8, a toner density sensor 9, and a drum cleaning section lO.
and a static eliminator 11 are arranged. A space serving as an exposure section 3 is provided between the main charging medium 2 and the developing device 6.

The drum l is usually an aluminum or aluminum alloy cylinder coated with a photoconductive material (e.g., a vapor-deposited selenium compound, etc.). The main charger 2 is composed of a charge wire 2a made of a tungsten wire stretched in the axial direction of the drum 1 close to the surface thereof, and a case 2b surrounding the back thereof. The developing device 6 includes a toner cartridge 4, a toner hopper 12, and a toner supply roller 1.
3, a supply roller 14, a developing roller 15, and a doctor blade 20. Both the transfer section 7 and the separation section 8 have substantially the same structure as the main charger 2.

The toner concentration sensor 9 is an optical sensor that uses a light emitting part and a light receiving part, and detects the toner layer carried on the drum 1 by irradiating light onto the surface of the drum 1 and detecting the intensity of the reflected light. Detect concentration.

The drum cleaning section 10 includes a rubber blade 17 for scraping off toner powder on the drum surface. The static eliminator 11 includes a static eliminator lamp 1.
g.

The structure of this developing device 6 will be explained in detail with reference to FIG.

In the doctor blade 20 , an elastic plate 23 is fixed to a support member 22 that freely rotates around a shaft 21 , and a contact member 24 attached to the tip of the elastic plate 23 contacts the surface of the developing roller 15 . Arm 2 fixed to support member 22
A first cam 27 that is rotatable about a shaft 26 is in contact with 5, and this first cam 27 is rotated by a small angle by a motor (not shown).

On the other hand, the bearing of the rotating shaft (not shown) of the supply roller 14 has
A press plate 30 is in contact with the press plate 30, and a second cam 32 rotatable about a shaft 31 is in contact with the press plate 30.

This second cam 32 is also rotated by a small angle by a motor (not shown).

This copying machine is controlled by a control device mainly composed of a microcomputer, of which only the configuration of the portion related to the present invention is shown in FIG. This control device 40 includes a CPU 41. It is composed of a RAM 42, a ROM 43, an input/output ink face (Ilo) 44, and a pass line 45 connecting these. This l1044 includes the above-mentioned toner concentration sensor 9 and the first and second cams 27.
．． A motor 46,47 is connected to rotate the motor 32.

Next, the normal copying operation of this copying machine will be explained.

When the copying operation is started, the drum 1 rotates clockwise in FIG. 2 at a constant speed, and the photoreceptor layer on its surface is charged to a predetermined potential by the main charger 2. The image of the document passing through the narrow slit is recorded as a latent image on the charged photoreceptor layer of the drum 1 at each slit width in the exposure section 3.

In the developing device 6, the latent image on the photoreceptor layer is developed into a visible image using toner powder in the following manner. The toner powder that has come down from the toner cartridge 4 through the hopper 12 and the toner supply roller 13 is frictionally charged while moving to the surface of the development roller 15 at the contact portion between the supply roller 14 and the development roller 15. Furthermore, the toner powder is caused by friction between the surface of the developing roller 15 and the doctor blade 20 that regulates the toner layer.
The entire surface of the developing roller 15 is charged by N friction.

A predetermined bias voltage is applied to the developing roller 15, and due to the potential difference between the developing roller 15 and the drum 1, toner is transferred to the drum 1, thereby developing the latent image on the drum 1.

The toner-based image is transferred in the transfer section 7 onto the cover 5 that is supplied one by one by a pair of registration rollers 16. The discharge wire of the separating section 8 is connected to the drum 1 by alternating current (AC).
An electric field is applied to separate the gills 5 electrostatically attached to the drum l. In this way, a copy of the original can be obtained on the paper 5. After the paper 5 is separated, the toner powder remaining on the drum surface is scraped off by a rubber blade 17 in a cleaning section 10, and the photoreceptor layer on the drum 1 is irradiated with a static elimination lamp 18 in a static elimination section 11 to eliminate static electricity. Ru.

The above is the operation during normal copying, but in the copying apparatus of this embodiment, in order to keep the density of the copied image constant, the control device 40 performs the processing shown in the flowchart of FIG. The program for this process is stored in the ROM 43, and is executed when the copying machine is turned on, when the preheat mode is released, or when the aging process is performed. When this routine starts, the rotation of the photoreceptor drum 1 is first started by the stelaph 11, and the photoreceptor of the drum 1 is charged by the main charger 2. At the same time, the operation of the developing device 6 is started,
The supply roller 14, developing roller 15, etc. also start rotating. Furthermore, the operation of the cleaning section 10 and the static eliminating section 11 is also started. However, in this process, the photoreceptor is not exposed in the exposure section 3, so in the developing device 6, the drum l is transferred from the developing roller 15.
The amount of toner transferred to is maximum. After that, the toner adhesion density in the area where the toner has been transferred is detected by the steno knob I2,
The corresponding signal St is manually generated. In step 13, it is determined whether this input signal is within a predetermined range 5L-32, and if it is within the predetermined range, the process of this routine is ended without any further adjustment.

If the toner concentration signal St is lower than the lower limit value S1 of the predetermined range, that is, if the toner adhesion density on the drum 1 is too high than the predetermined range, the motor 46 is
the first cam 27 and the second cam 32 by the motor 47.
are each rotated by a predetermined small angle to bring the doctor blade 20 into stronger contact with the developing roller 15 and to weaken the contact force of the supply roller 14 with the developing roller 15. By doing this, the amount of toner transferred from the supply roller 14 to the developing roller 15 is reduced, and the thickness of the toner adhering to the developing roller 15 is also strongly regulated by the doctor blade 20 and reduced. Further, since the amount of toner charge due to friction between the contact member 24 of the doctor blade 20 and the developing roller 15 increases, the amount of toner transferred from the developing roller 15 to the photoreceptor drum 1 decreases.

If the toner concentration 1 word St is higher than the upper limit value S2 of the predetermined range, the operation completely opposite to the above is performed in step I4.

After adjusting the contact force between the doctor blade 20 and the supply roller 14 in step 14 or 15, step
Return to step 2, check the toner density, and check the toner density signal S.
Adjustment is continued until t falls within the predetermined range S1 to S2. After adjusting the density of the toner layer on the photosensitive drum 1 to be within a predetermined range as described above, a lamp or the like is used to notify that normal copying work is possible. Thereby, after starting normal copying work, a copied image with a predetermined density can always be stably obtained. Of course, S2 to the predetermined range Sl
can be arbitrarily changed using a switch or the like, and can be adjusted to any concentration desired by the operator.

As described in detail, according to the present invention, in order to control both the contact pressure between the developing roller and the layer thickness regulating member (doctor blade) and the contact pressure between the developing roller and the supply roller, the developing roller In addition to the above toner thickness, toner density and toner charge amount can also be comprehensively controlled, and the toner density on the photoreceptor drum can be accurately controlled to any value. Therefore,
The density of the final image (copy, printout image) can be precisely controlled to any value.

[Brief explanation of drawings]

Fig. 1 is a diagram corresponding to the claims of the present invention, Fig. 2 is a schematic configuration diagram of an electrostatic copying machine that is an embodiment of the invention, Fig. 3 is a configuration diagram of its developing device, and Fig. 4 is a block diagram of a control device. FIG. 5 is a flowchart of the image density adjustment process executed by the control device. l...Photosensitive drum 3...Exposure section 5...Gi 7...Transfer section 9...Density sensor 11...Static elimination section 15...Developing roller 20...Doctor blade 2 ... Main charger 4 ... Toner cartridge 6 ... Developing device 8 ... Separation section 10 ... Cleaning section 14 ... Supply roller 16 ... Registration roller rad 27.32 ... Cam application Hitosanda Kogyo Co., Ltd. Figure 1 Funeral map Figure 4

Claims (1)

[Scope of Claims] A photosensitive drum; a developing roller that is provided parallel to the photosensitive drum and carries toner to be transferred to the photosensitive drum; and a developing roller that is provided parallel to and in contact with the developing roller and that transfers toner to the developing roller. It comes into contact with the supply roller that carries the toner and the rotating developing roller,
A developing device comprising: a layer thickness regulating member that uniformizes the thickness of the toner carried on the developing roller, further comprising means for controlling the contact pressure of the layer thickness regulating member against the developing roller; and a developing device of the supply roller. means for controlling the contact pressure against the roller; means for detecting the toner adhesion density on the photoreceptor drum; and means for controlling the layer thickness regulating member contact pressure and the supply roller contact pressure in accordance with the detected toner adhesion density. A developing device comprising: image density control means for changing image density.