JPH07253716A - Developing device - Google Patents

Abstract

PURPOSE:To eliminate the need of forming a pattern or a dot in the conventional manner and to realize rapid control by detecting a toner amount on a developing roller according to the potential of a toner layer before thinning a layer and controlling a toner thin layer or a developing condition. CONSTITUTION:A surface potential detector 6 is arranged around the developing roller 1 between a supply roller 2 and a layer thinning blade 3 to measure the surface potential of the toner layer on the roller 1. Since residual potential is hardly generated on the roller 1 having a surface layer whose resistance is equal to or under medium resistance, the measured value by the detector 6 is regarded as the potential of the toner layer. In order to obtain the desirable toner density of a copied image in such a case, the potential of the toner layer is controlled to be within the range of -37V to -48V. Namely, when the measured value is <=-37V, the blade pressure by the blade 3 is weakened and when it is #>=-48V, the blade pressure is strengthened. The blade pressure is controlled by deviating the position of the blade 3.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a developing device used in an image forming apparatus such as a copying machine, a facsimile, and a laser printer, and more particularly to a developing device using a one-component developer.

[0002]

2. Description of the Related Art Generally, an electrophotographic image forming apparatus prints by the following process. That is, the surface of the photoconductor is uniformly charged by the charging charger, and an electrostatic latent image as image information is formed on the surface by light irradiation by the optical system.
Then, when the electrostatic latent image passes through a position opposite to the developing device, the latent image is visualized by toner adhesion, and the latent image is superposed on the conveyed recording paper at a timing, and the toner is transferred using a transfer charger. The image is transferred onto recording paper. The transferred toner image is fixed on the recording paper by passing through the fixing device.

In the developing process in this series of processes, there are a mode using a so-called two-component developer composed of a carrier and a toner and a mode using a so-called one-component developer not using a carrier. Regardless of which developer is used, control of the toner concentration is essential for maintaining the desired image quality of the copied image. However, in particular, in the case of a two-component developer, the toner component of the developer is consumed each time the development is repeated due to its configuration, and the ratio to the carrier component changes. Features are often used. For example, in JP-A-59-232375,
It is stated that the toner concentration of the developer is detected based on the change in the inductance of the electromagnetic coil around the magnetic core arranged near the developing sleeve, which varies depending on the mixing ratio of the magnetic carriers. Also, JP-A-62-99
In Japanese Patent No. 773, the content of the magnetic carrier increases as the toner concentration in the developer decreases, and the thickness of the layer of the developer adhering to the surface of the developing sleeve changes. It is assumed that the lower limit of the toner density is when the contact occurs.

Since these toner concentration detecting methods utilize the change in the ratio of the toner component and the carrier component in the developer, they cannot be applied to the toner concentration detection in a one-component developer.

Further, Japanese Utility Model Application Laid-Open No. 55-4403 discloses that the toner density is detected by forming a large number of linear stripes or circular dots having a uniform optical density on the photosensitive surface. Japanese Unexamined Patent Publication (Kokai) No. 60-83975 discloses that the toner density is detected by forming a reference pattern image on the photosensitive surface and detecting the level and width of the image by a pulse signal obtained by scanning the reference pattern image. ing.

[0006]

Since these toner concentration detecting methods detect the toner after being separated from the carrier, they can also be applied to the toner concentration detection in a one-component developer. . However, since the toner image is once formed on the photosensitive surface, the toner is consumed excessively. In recent years, there has been a strong demand for reducing the running cost of image forming apparatuses and the like, and such waste must be avoided as much as possible.

The present invention provides a developing device capable of avoiding excessive consumption of toner by forming a reference pattern image or a dot image in detecting toner density as in the prior art, and capable of quick control. The task is to do.

[0008]

In order to solve the above-mentioned problems, a developing device according to the present invention comprises, in one aspect, a developer carrying member, a developer supplying member and a developer layer thinning member,
In a developing device using a one-component developer, a contact area with the developer supply member in the vicinity of the surface of the developer carrying member,
A means for detecting the surface potential of the developer layer on the surface of the developer carrying member is arranged between the contact area with the developer layer thinning member and the developer layer thinning member of the developer layer thinning member is detected according to the detected surface potential. The contact pressure on the developer carrying member is controlled.

Toner characteristics are easily affected by temperature and humidity as an external environment, and thus the toner adhesion amount on the developing roller fluctuates. The present invention intends to control the toner density by utilizing this variation amount.

Further, application means for applying different bias potentials to the developer carrying member and the developer supplying member are provided, and a contact area with the developer supplying member near the surface of the developer carrying member A means for detecting the surface potential of the developer layer on the surface of the developer carrying member is arranged between the area for contacting the agent thinning member, and the developer carrying member and the developer supplying member according to the detected surface potential. Even if a potential difference is applied between the above and the above, the above problem can be solved.

Alternatively, in the vicinity of the surface of the developer carrying member,
A means for detecting the surface potential of the developer layer on the surface of the developer carrying member is disposed between the contact area with the developer supply member and the contact area with the developer thinning member, and the detected surface potential is adjusted. Even if the developing bias potential applied to the developer carrying member is controlled accordingly, the above problem can be solved.

Further, between the contact area with the developer supplying member and the contact area with the developer thinning member near the surface of the developer carrying member, the developer layer surface potential on the surface of the developer carrying member. It is also possible to solve the above-mentioned problems by disposing a means for detecting and changing the rotational speed of at least one of the developer carrying member and the developer supplying member according to the detected surface potential.

[0013]

In FIG. 3, which shows a developing device using a toner as a one-component developer, the toner conveyed by the conveying member 4 is uniformly replenished on the supply roller 2 in the longitudinal direction.
The toner is frictionally charged between the developing roller 1 and the supply roller 2 which rotate with a linear velocity difference between them, and electrostatically adheres to the developing roller 1. As the developing roller 1 rotates in the direction of the arrow, the adhered toner layer is pressed by the thinning blade 3 to be smoothed to a desired thin layer, and the charging potential of the photosensitive member and the developing roller are opposed to the photosensitive member 7. It is used for development by the potential difference between the developing bias potentials. The toner and the like scraped off by the blade 3 are processed by the toner collecting member 5.

In such a structure, how the toner adhesion amount on the developing roller 1 changes as the blade pressure of the thinning blade 3 changes, and the change of the blade pressure changes the toner amount on the developing roller 1. An experiment on how the charge amount is affected is shown in FIGS. 4 and 5. That is, as the blade pressure increases, the toner adhesion amount decreases, while the charge amount increases. Examining the relationship between the toner adhesion amount and the charge amount that change in this way and the toner layer surface potential before passing through the thin layer blade, (a) and (b) of FIG.
As shown in. That is, the toner charge amount greatly changes in a certain narrow range and changes gently in the other range with respect to the change of the toner layer surface potential, while the toner adhesion amount changes substantially evenly. Therefore, it is possible to control the toner adhesion amount directly connected to the toner concentration or the development amount by using the toner layer surface potential. For example, the corresponding toner adhesion amount can be recognized by detecting the surface potential of the toner layer before thinning, and the blade pressure for obtaining the adhesion amount can also be obtained from the correlation shown in FIG. In order to control the toner concentration to a desired value, the blade pressure may be adjusted according to the detected surface potential.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The details of the present invention will be described based on the embodiments shown in the drawings.

In FIG. 1 showing a first configuration example, toner is transported by a toner transport member 4 and is uniformly replenished in the longitudinal direction onto a supply roller 2 made of, for example, a conductive urethane sponge. The toner is frictionally charged between the developing roller 1 and the supply roller 2 which rotate with a linear velocity difference between them,
It electrostatically adheres to the developing roller 1. The developing roller 1
Is formed of a single dielectric layer of 10 ¹² Ω · cm or less,
A developing bias is applied to the developing roller 1 and the supply roller 2. As the developing roller 1 rotates in the direction of the arrow, the adhered toner layer is pressed by the thinning blade 3 made of urethane rubber to have a desired thickness,
Contact development is performed at a position facing a PC (Organic photo-conductor) belt photoreceptor 7. The toner and the like scraped off by the blade 3 are processed by the toner collecting member 5.

A surface potential detector 6 known per se is arranged around the developing roller 1 between the supply roller 2 and the thinning blade 3 to measure the surface potential of the toner layer on the roller 1.
Since the residual potential hardly occurs in the developing roller 1 having the surface layer having a medium resistance or less, the value measured by the detector 6 can be regarded as the potential of the toner layer. At this time, in this embodiment, it is preferable that the toner layer potential is within the range of -37V to -48V in order to obtain the preferable toner density of the copied image. Decrease the blade pressure at the blade and increase the blade pressure at -48V or higher.

As can be seen from FIG. 1, such control of the blade pressure is performed by shifting the position of the thinning blade 3. A member that supports and is integrated with the blade 3 is configured to be slidable by rotation of a blade pressure control member (control roller) 8. When increasing the blade pressure, the control member 8 is rotated to move in the direction of the arrow. When the blade 3 is moved and conversely the blade pressure is lowered, the blade 3 is retracted.

Such an adjustment can be made as necessary during the operation of the apparatus. Therefore, by adjusting the blade pressure according to the detected surface potential, the toner adhesion amount is always maintained within a certain range. Therefore, a stable copy image can be formed.

In FIG. 2 showing the second structural example, the process itself in which the toner conveyed by the conveying member 4 is subjected to contact development at a position facing the belt photosensitive member 7 is substantially the same as the first structural example. The same reference numeral is given to the same component for the sake of simplification of description, and the description thereof will be omitted. Bias potentials BIAS1 and BIAS2 are separately applied to the developing roller 1 and the supply roller 2.

As in the first configuration example, in order to obtain a preferable toner density of the copied image, the surface potential of the toner layer of the roller 1 which is regarded as the toner layer potential is -37V to -48V.
It is preferable that the measured value falls within the range of, for example, the measured value is -3.
In the case of 7 V or less, a sufficient toner adhesion amount is obtained on the developing roller. Therefore, | BIAS1-BIAS2 | = 100 to 1
Control is performed so that it becomes 50V. For example, in the case of reversal development using negatively charged toner, | BIAS1 | <| B
IAS2 |

As a third configuration example, referring to FIG.
The toner conveyed by the conveying member 4 is transferred to the belt photosensitive member 7.
The process itself that is used for contact development at a position opposed to is substantially the same as that of the first configuration example.
A surface potential detector 6 known per se is arranged around the developing roller 1 between the thinning blade 3 and the thinning blade 3 to measure the surface potential of the toner layer on the roller 1.

As in the first configuration example, in order to obtain a preferable toner density of the copied image, the surface potential of the toner layer of the roller 1 which is regarded as the toner layer potential is -37V to -48V.
It is preferable that the amount of toner adhered to the developing roller is reduced when the measured value is −37 V or less. Therefore, the developing bias is changed in the direction of increasing the developing potential. And develop. If the surface potential is −48 V or more, the toner may be over-supplied, which may cause an undesired situation such as scumming. Therefore, the developing bias is adjusted to lower the developing potential to reduce the developing amount. Control to reduce.

As a further different control, the configuration itself is the third.
If the measured value of the surface potential of the developing roller is -37 V or less, it is considered that the toner adhesion amount on the developing roller is reduced. Controls to increase the rotation speed of. Further, in the case of −48V or higher, in order to reduce the developing potential, the rotation number of the developing roller is increased or the rotation number of the supply roller is decreased to control the development amount.

[0025]

According to the present invention, since the toner amount on the developing roller is detected by the toner layer potential before thinning, and the toner thin layer or developing condition is controlled, it is necessary to form a conventional pattern or dot. It is possible to prevent wasteful waste of toner and enable quick control. Further, since the detector can be completely housed in the developing device from its installation position, there is an advantage that the degree of freedom in the position of the photoconductor is large without forming a protrusion on the outside.

According to the developing device of claim 1 or 2, the toner adhesion amount on the developing roller is controlled, and according to the developing device of claim 3 or 4, the developing amount is controlled. As a result, the above-mentioned effects are exhibited.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of a developing device of a first configuration example according to the present invention.

FIG. 2 is a schematic configuration diagram of a developing device of a second configuration example according to the present invention.

FIG. 3 is a schematic configuration diagram of a developing device that uses toner that is a one-component developer.

FIG. 4 is a graph showing the relationship between blade pressure and toner adhesion amount.

FIG. 5 is a graph showing the relationship between blade pressure and toner charge amount.

6A and 6B show the relationship between the toner layer potential before thinning, the toner adhesion amount, and the toner charge amount. FIG. 6A illustrates the relationship between the potential and the adhesion amount, and FIG. 6B illustrates the potential and charge amount. It is a graph which shows a relationship.

[Explanation of symbols]

 1 Development Roller 2 Supply Roller 3 Thinning Blade 4 Toner Conveying Member 5 Toner Collection Member 6 Surface Potential Detector 7 Photosensitive Body 8 Blade Pressure Control Member

Claims (4)

[Claims] 1. A developing device having a developer carrying member, a developer supplying member, and a developer layer thinning member, and using a one-component developer, wherein the developer near the surface of the developer carrying member. A means for detecting the surface potential of the developer layer on the surface of the developer carrying member is disposed between the contact area with the supply member and the contact area with the developer thinning member. A developing device, wherein a contact pressure of a developer layer thinning member with respect to a developer carrying member is controlled. 2. In a developing device having a developer carrying member, a developer supplying member, and a developer layer thinning member, and using a one-component developer, the developer carrying member and the developer supplying member are different from each other. Application means for applying a bias potential is provided, and the developer carrying member is provided between the contact area with the developer supplying member and the contact area with the developer thinning member near the surface of the developer carrying member. A developing device, characterized in that means for detecting the surface potential of the developer layer on the surface of the member is arranged, and a potential difference is applied between the developer carrying member and the developer supplying member according to the detected surface potential. 3. A developing device having a developer carrying member, a developer supplying member, and a developer layer thinning member, and using a one-component developer, wherein the developer near the surface of the developer carrying member. A means for detecting the surface potential of the developer layer on the surface of the developer carrying member is disposed between the contact area with the supply member and the contact area with the developer thinning member. A developing device which controls a developing bias potential applied to a developer carrying member. 4. A developing device having a developer carrying member, a developer supplying member, and a developer layer thinning member, and using a one-component developer, wherein the developer near the surface of the developer carrying member. A means for detecting the surface potential of the developer layer on the surface of the developer carrying member is disposed between the contact area with the supply member and the contact area with the developer thinning member. A developing device, wherein the number of revolutions of at least one of a developer carrying member and a developer supplying member is changed.