JPH05107922A - Dry developing device - Google Patents

Abstract

PURPOSE:To prevent toner from being scattered from the bearing parts, etc., of various rotational members in a developing device and to prevent the density of a developed image from lowering because the powder pressure of the toner near the surface of a developing roller becomes excessive in the case of developing a latent image whose area of a toner adhesion part is comparatively small and whose toner consumption is comparatively low. CONSTITUTION:A strain sensor 20 for detecting a bend amount, which detects pressure applied to a scraper 6, is provided. It detects the powder pressure of the toner near the surface of the developing roller 3 by utilizing that the scraper 6 is pressured and bent by the pressure from the toner which is pushed into an area surrounded by the developing roller 3, a supply roller 4, a doctor roller 5 and the scraper 6. Then, the rotation of an agitator 8 in a toner cartridge 2b is controlled in accordance with the bend amount detected by the sensor 20.

Description

Detailed Description of the Invention

[0001]

[Field of Industrial Application] A dry developing device used in an image forming apparatus such as a copying machine, a facsimile, and a printer.
Specifically, it relates to control of toner powder pressure in the dry developing device.

[0002]

2. Description of the Related Art Conventionally, as a dry developing apparatus of this type, for example, one shown in FIG. 3 is known. In FIG. 3, reference numeral 1 denotes a photoconductor drum which is an image carrier, and around the photoconductor drum 1, for example, a charging device, an exposure device, and a transfer device (not shown) for executing an electrophotographic process are shown. Then, the photoconductor drum 1 is provided with a facing arrangement), a cleaning device, a charge eliminating device, and the like. And
A dry developing device 2 is arranged between the exposure device and the transfer device so as to face the surface of the photosensitive drum 1. This dry developing device 2 rotates a developing roller 3, which is a developer bearing member provided in an opening facing the surface of the photoconductor drum 1, in the clockwise direction of the arrow so that powder toner (hereinafter , Toner) is supplied to develop an electrostatic latent image which is a latent image formed on the surface of the photosensitive drum 1.

The dry developing device 2 of this example forms a developing device 2a forming a developing chamber in which the developing roller 3 is provided, and a toner containing chamber containing non-magnetic toner to be replenished into the developing device 2a. It is composed of a toner cartridge 2b. In the developing device 2a, in addition to the developing roller 3, a supply roller 4 for frictionally charging and electrostatically adhering toner on the surface of the developing roller 3, and the amount of toner on the surface of the developing roller 3 are regulated to a predetermined value. Doctor roller 5, which is a thinning member that reduces the thickness of the doctor roller 5, scraper 6 that is a plate-shaped member that removes toner on the surface of the doctor roller 5, and the developing roller 3, the replenishing roller 4, and the doctor roller 5 described above. A sub-agitator 9, which is a conveying unit and a stirring unit that conveys the toner and also stirs the toner, is provided in a region surrounded by the scraper 6 and the toner cartridge 2b.
An agitator 8 which is a conveying means for discharging the stored toner is provided inside.

In the above structure, the developing roller 3, the replenishing roller 4, the doctor roller 5, the sub-agitator 9 and the agitator 8 are each driven to rotate in the clockwise direction of the arrow so that the thin toner layer formed on the surface of the developing roller 3 becomes a photosensitive member. Drum 1
By facing the surface, the electrostatic latent image formed on the surface of the photoconductor drum 1 is developed. Here, conventionally, the agitator 8 and the sub-agitator 9 were always driven at a constant speed to convey a constant amount of toner near the surface of the developing roller 3.

[0005]

However, according to the above configuration, when the area of the toner adhering portion in the electrostatic latent image formed on the photosensitive drum 1 is relatively small and the toner consumption is relatively small, In some cases, toner may be scattered from the bearings of various rotating members in the developing device 2a or the density of the developed image may be reduced.

This is due to the following reason. That is, the amount of toner adhering to and consumed by the electrostatic latent image on the surface of the photosensitive drum 1 is the area of the toner adhering portion of the electrostatic latent image formed on the surface of the photosensitive drum 1 (the total area of the image is constant. In some cases, it depends on the image area ratio, which is the area of the toner adhesion portion. However, as described above, the agitator 8 and the sub-agitator 9 are always driven at a constant speed to convey a constant amount of toner near the surface of the developing roller 3. Therefore, when the area of the toner adhesion portion in the electrostatic latent image formed on the photoconductor drum 1 is relatively small and the toner consumption amount is relatively small,
A larger amount of toner than the consumed toner will be transported to the vicinity of the surface of the developing roller 3. For this reason, the toner is pushed in the vicinity of the surface of the developing roller, for example, in the area A shaded in FIG. In addition, the toner is hardened in the area A, which causes defective replenishment to the surface of the developing roller 3, or the toner layer once formed on the surface of the developing roller 3 by the replenishing roller 4 is destroyed, and The toner supply to the surface of the drum 1 becomes defective and the density of the developed image becomes insufficient.

The present invention has been made in view of the above problems, and it is an object of the present invention to prevent the powder pressure of toner near the surface of the developer carrying member in the developing device from becoming excessively high. A dry developing device is provided.

[0008]

In order to achieve the above object, the present invention provides a dry developing apparatus for supplying powder toner to a latent image formed on an image carrier by a developer carrier.
Toner conveying means for conveying toner to the vicinity of the surface of the developer carrier, powder pressure detecting means for detecting the powder pressure of the powder toner near the surface of the developer carrier, and development based on the detection result of the powder pressure detecting means The present invention is characterized in that a conveyance amount adjusting means for adjusting the toner conveyance amount to the vicinity of the surface of the agent carrier is provided. Here, the carrying amount adjusting means may be configured to adjust the carrying force of the toner carrying means, and the width of the toner carrying path from the toner carrying means to the surface of the developer carrying member may be adjusted. You may comprise using the means to change. Further, in the dry developing device having a thinning member for thinning the powder toner on the surface of the developer carrying member and a plate-shaped member for stripping the powder toner off the surface of the thinning member, The powder pressure detection means can be configured using a detection element that detects the pressure applied to the plate-shaped member. Further, a dry chamber is provided in which a developing chamber provided with the developer carrying member and a toner containing chamber containing toner to be supplied to the developing chamber are formed, and a stirring means for stirring powder toner is provided in the developing chamber. In the developing device, the powder pressure detection means can be configured by using a detection element that detects the stirring torque of the stirring means.

[0009]

According to the present invention, the powder pressure detecting means for detecting the powder pressure of the powder toner in the vicinity of the surface of the developer carrier is detected. Then, based on this detection result, when the detected powder pressure is high, the amount of toner conveyed to the vicinity of the surface of the developer carrier is reduced by the conveying amount adjusting means, whereby the surface of the developer carrier in the developing device is reduced. It prevents the powder pressure of the toner in the vicinity from becoming excessively high. Here, in the dry developing device having a thinning member for thinning the powder toner on the surface of the developer carrying member and a plate-shaped member for stripping the powder toner from the surface of the thinning member, Since the plate-shaped member is arranged near the surface of the image carrier, the powder pressure of the toner near the surface of the image carrier is applied to the plate-shaped member. Therefore, the pressure applied to the plate-shaped member is detected to detect the image carrier. The powder pressure of the powder toner near the surface can be detected. Further, a dry chamber is provided in which a developing chamber provided with the developer carrying member and a toner containing chamber containing toner to be supplied to the developing chamber are formed, and a stirring means for stirring powder toner is provided in the developing chamber. In the developing device, the agitation torque of the agitation means changes depending on the powder pressure of the powder toner near the surface of the developer carrying member. Therefore, by detecting this agitation torque, the powder pressure of the powder toner near the surface of the image bearing member is detected. Can be detected.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the present invention is applied to a dry developing device of an electrophotographic copying machine (hereinafter referred to as a copying machine) which is an image forming apparatus will be described below. FIG. 1A is a front view showing a schematic configuration of the dry developing device according to this embodiment. The dry developing device 2 has basically the same configuration as the dry developing device shown in FIG. 3 described above, and includes a developing device 2a forming a developing chamber in which a developing roller 3 as a developer carrying member is provided, and a developing device 2a. It is configured with a toner cartridge 2b that forms a toner storage chamber that stores a non-magnetic toner to be supplied into the developing device 2a. Further, like the device shown in FIG.
In addition to the developing roller 3, a replenishing roller 4, a doctor roller 5 that is a thinning member, a scraper 6 that is a plate-shaped member, and a sub-agitator 9 that is a conveying unit and a stirring unit are provided inside the developing roller 3. Further, inside the toner cartridge 2b, an agitator 8 which is a conveying means is provided.

Here, the developing roller 3 can be constituted by an elastic roller whose surface can be deformed by an external pressure. In this case, the elastic layer is made of NBR type or urethane type having a rubber hardness of 30 to 50 degrees (JISA). It can be formed of rubber.
A voltage of, for example, minus 500 V is applied to the developing roller 3 as a developing bias. Further, as the replenishing roller 4, a conductive urethane foam roller can be used, and a voltage of, for example, −600 V is applied to this. Further, the doctor roller 5 is arranged so as to contact the lower part of the developing roller 3. The doctor roller 5 is driven so as to move in the opposite direction at the contact portion with the surface of the developing roller 3, and a voltage of, for example, −600 V is applied. This ensures sufficient charging of the toner. Further, as the doctor roller 5, a hard roller made of metal such as stainless steel or hard resin can be used. Further, the doctor roller 5 is replaced with the developing roller 5
In order to press the roller against, the roller end portion is urged toward the developing roller 5 side by urging means such as a compression coil spring, a torsion coil spring, a leaf spring, and a disc spring. The urging force of the urging means is appropriately set based on the required density of the developed image, the rotatable torque of the developing roller 3, and the like. In this example, a compression coil spring with a weight of 800 g on each side is used. Further, the toner cartridge 2b is configured to be detachably attached to the developing device 2a, whereby
It can be used as a replaceable toner cartridge 2b.

With only the construction described above, the amount of toner conveyed by the replenishing roller 4 to the surface of the developing roller 3 is set to a large value so as not to be insufficient even if the amount of toner consumption changes slightly due to the electrostatic latent image. Excessive toner on the surface of the developing roller 3 is scraped off by the doctor roller 5, so that the toner is always pushed into the area surrounded by the developing roller 3, the replenishing roller 4, the doctor roller 5 and the scraper 6. Further, since the toner is conveyed from the toner cartridge 2b to the developing device 2a by the agitator 8, the powder pressure of the toner in the vicinity of the surface of the developing roller 3 becomes excessive, which may cause the above-mentioned trouble.

Therefore, in this embodiment, as shown in FIG.
As shown in (1), a strain sensor 20 for detecting the amount of deflection for detecting the pressure applied to the scraper 6 is provided. This is because the scraper 6 is pressed and deflected by the pressure from the toner pressed into the area surrounded by the developing roller 3, the replenishing roller 4, the doctor roller 5 and the scraper 6, and the toner near the surface of the developing roller 3 is bent. The powder pressure is detected. Then, according to the amount of deflection detected by the strain sensor 20, the agitator 8 in the toner cartridge 2b is
Is controlled to adjust the toner conveyance amount into the developing device 2a so that the toner amount in the developing device 2a does not become too large.

More specifically, for example, as shown in FIG. 1C, the strain sensor 20 is attached to the scraper 6 substantially at the center in the longitudinal direction. And this strain sensor 2
The output of 0 is input to the control unit 21, and the control unit 21 determines whether or not the amount of deflection of the scraper 6 exceeds a predetermined limit value, and when it exceeds the limit value of the drive system to the agitator 8. A control signal is output to the clutch 22 provided in the above to interrupt this, and the rotation of the agitator 8 normally rotating at, for example, 10 ppm is stopped. Detection of the amount of deflection by the strain sensor 20 and switching of clutch ON / OFF based on the detection result are repeatedly executed. Figure 1 (b)
Is a flowchart showing an example of such control.
The cycle of this repetition should be set so that the toner in the developing device 2a will not run short even if a black image is copied after the clutch is disengaged and the rotation of the agitator 8 is stopped. Is desirable. In other words, once the clutch is disengaged, if it becomes less than or equal to the above limit value, this is promptly detected, the clutch is connected and the rotation of the agitator 8 is restarted, and development is also performed by copying an all-black image. It is desirable to set the cycle to such an extent that the toner in the container 2a will not run short.

In this example, the strain sensor 20 which detects the amount of deflection of the scraper 6 is used to detect the pressure applied to the scraper 6, but other pressure sensors may be used instead. Further, a pressure sensor may be arranged at any place as long as the powder pressure of the toner near the surface of the developing roller 3 can be detected.

Further, as shown in FIG. 2A, the developing device 2
A torque sensor 23 for detecting the torque of the sub-agitator 9 provided in a may be provided, and the clutch 22 of the agitator may be controlled by the output of the torque sensor 23. This is the developing roller 3 and the replenishing roller 4.
The powder pressure of the toner in the vicinity of the surface of the developing roller 3 is detected by increasing the torque of the sub-agitator 9 with the toner pushed into the area surrounded by the doctor roller 5 and the scraper 6. Also in this example, FIG.
As shown in, the torque sensor 23 determines whether or not the torque exceeds a predetermined limit value, and when it exceeds, a control signal is sent to the clutch 22 provided in the drive system to the agitator 8. The output is cut off and the rotation of the agitator 8 is stopped. Detection of the amount of deflection by the strain sensor 20 and clutch ON / O based on the detection result
FF switching is repeatedly executed. The developing roller 3
When the amount of toner near the surface also affects the drive torque of the agitator 8 in the toner cartridge 2b, it is possible to detect the drive torque of the agitator 8 instead of detecting the drive torque of the sub-agitator 9. However, since the drive torque of the agitator 8 depends on the remaining amount of toner in the toner cartridge 2b, it is better to detect the drive torque of the sub-agitator 9 in the developing device 2a as in the above example. Accurate detection is possible.

As described above, according to this embodiment, it is possible to prevent the powder pressure of the toner near the surface of the developing roller 3 from becoming excessively large.
Toner is excessively pushed into the area surrounded by the developing roller 3, the replenishing roller 4, the doctor roller 5, and the scraper 6, and the amount of toner becomes excessive, resulting in toner scattering and insufficient density of the developed image. Can be prevented.

In each of the above examples, the toner conveyance amount to the surface side of the developing roller 3 is adjusted by controlling the rotation or non-rotation of the agitator 8, but instead of this, the pressure applied to the scraper 6 and the like. The rotation speed of the agitator 8 may be switched in multiple stages according to the size of the.

Further, by switching the rotation state of the sub-agitator 9 provided in the developing device 2a while keeping the agitator 8 in the toner cartridge 2b in the rotation state,
When the toner transportation to the vicinity of the surface of the developing roller 3 can be controlled, instead of controlling the rotation state of the agitator 8, the rotation state of the sub-agitator 9 can be controlled while the agitator 8 is kept in the rotation state. good.

Further, for example, a movable partition plate that can change the width of the toner transport path from the toner cartridge 2b to the surface of the developing roller 3 in the developing device 2a is provided. The toner conveyance amount to the surface side of the developing roller 3 may be adjusted by position control.

Although the above embodiment uses a non-magnetic one-component developer, the present invention can be applied to a dry developing device using a magnetic one-component developer.

[0022]

According to the present invention, the powder pressure detecting means for detecting the powder pressure of the powder toner in the vicinity of the surface of the developer carrying member detects it.
Based on this detection result, when the detected powder pressure is large, the amount of toner conveyed to the vicinity of the surface of the developer carrying member is reduced by the conveying amount adjusting means, and as a result, near the surface of the developer carrying member in the developing device. Since the powder pressure of the toner is prevented from becoming excessively high, the powder pressure of the powder toner in the vicinity of the surface of the image carrier is excessively increased, so that the toner from the bearings of the various rotating members in the developing device, etc. There is an excellent effect that the problem of 1) can be prevented and a good developed image can be obtained.

[Brief description of drawings]

FIG. 1A is a front view showing a schematic configuration of a dry developing device according to an embodiment, FIG. 1B is a control flowchart of the dry developing device, and FIG. 1C is a bottom view of the dry developing device in the vicinity of a scraper.

FIG. 2A is a front view showing a schematic configuration of a dry developing device according to a modified example, and FIG. 2B is a control flowchart of the dry developing device.

FIG. 3 is a front view showing a schematic configuration of a dry developing device according to a conventional example.

[Explanation of symbols]

1 photoconductor drum, 2 dry developing device 2a developing device, 2b toner cartridge 3 developing roller, 4 replenishing roller 5 doctor roller, 6 scraper 8 agitator, 9 sub-agitator 20 strain sensor, 21 control section 22 clutch, 23 torque sensor

Claims (3)

[Claims] 1. A dry developing device for supplying a powder toner to a latent image formed on an image bearing member by a developer bearing member, and a toner feeding means for feeding the toner near the surface of the developer bearing member, and a developer. Powder pressure detecting means for detecting the powder pressure of the powder toner near the surface of the carrier, and carrying amount adjusting means for adjusting the toner carrying amount to the surface of the developer carrier based on the detection result of the powder pressure detecting means. A dry developing device characterized by being provided with. 2. A thinning member for thinning the powder toner on the surface of the developer carrying member, and a plate-like member for stripping the powder toner from the surface of the thinning member. In the dry developing device, the powder pressure detecting means is constituted by using a detecting element for detecting the pressure applied to the plate member.
Dry developing device. 3. A developing chamber provided with the developer carrying member and a toner containing chamber containing the toner to be supplied to the developing chamber are formed, and a stirring means for stirring the powder toner is provided in the developing chamber. The dry developing device according to claim 1, wherein the powder pressure detection means is configured by using a detection element that detects a stirring torque of the stirring means.
Dry developing device.