JPH0194368A - Developing device - Google Patents

Abstract

PURPOSE:To secure the degree of freedom for the scattering of toner particles in a development area and to prevent a decrease in concentration by allowing the toner particles to receive attractive force against contacting pressure to magnetic particles. CONSTITUTION:When development is carried out under such conditions that the potential of an electrostatic latent image on an image carrier is, for example, 200-600V, the gap of the development area 5 is 300mum, and the development speed is 270mm/sec, a developer 4 whose layer thickness is uniformed by a leveling member 9 is excited with a bias voltage 11 applied to the leveling member 9. This bias voltage 11 is a DC voltage having the opposite polarity from toner particles, so the degree of freedom of the toner particles is secured because of the attractive force operating against the contact pressure to the magnetic particles which is received from the leveling member 9. The toner particles are therefore scattered actively without decreasing in its flowability, so the concentration in the development area 5 is prevented from decreasing.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a developing device in a recording device such as an electrostatic recording device, and in particular, a developer carried on a developer carrier provided close to an image carrier. The present invention relates to a contact type two-component developing device in which the developer is maintained in a layered state in a non-contact state in a developing section.

(Advances and Problems with Conventional Techniques) Conventionally, this type of developing device has developed by applying an alternating electric field to the developing gap between the developer carrier and the image carrier. The smaller the development gap, the better the development performance, so in order to make the developer layer non-contact with the image carrier, it is necessary to reduce the code thickness of the developer layer. In order to meet this requirement, by setting the development position to be the area corresponding to the two poles of the fixed magnet in the developer carrier, the ears of the developer layer held by the magnetic lines of force use the area where the lines of magnetic force lie as the development area. Devices and the like that make it easier to obtain non-contact conditions have recently been disclosed in Japanese Patent Laid-Open Nos. 59-91453, 60-14263, and 60-176069.

However, the above-mentioned devices have a drawback that if the thickness of the developer layer in the developing section is uneven, the unevenness may cause slight density unevenness.

Therefore, an attempt has been made to solve this problem by using a leveling plate made of an elastic member disclosed in Japanese Patent Application Laid-Open No. 54-43038.

However, when a leveling plate is used, pressure is applied so that the toner particles in the developer layer are brought into close contact with the magnetic particles, resulting in a decrease in the fluidity of the toner particles. It will no longer fly. For this reason, there is a problem in that the density of toner particles decreases, making it difficult to obtain a harmonious and clear image.

(Means for Solving the Problems) The present invention is intended to solve the above-mentioned problems, and its purpose is to improve the flight efficiency of toner particles without reducing the fluidity of the toner particles even when a leveling plate is used. It is an object of the present invention to provide a developing device which prevents a decrease in density and obtains a well-balanced and clear image.

In order to achieve the above-mentioned object, the present invention forms a development area in the vicinity of the image carrier, has a fixed magnet inside, and mixes toner particles and magnet particles on the outer peripheral surface. a rotating developer carrier carrying a two-component developer; a regulating member disposed with a predetermined gap between the two-component developer layer and regulating the layer thickness of the two-component developer layer; A developing device comprising: a leveling member that is in pressure contact with the outer circumferential surface of the developer carrier and levels the two-component developer layer at a position downstream of the regulating member in the rotational direction of the developer carrier; The magnet is set so that the space between two adjacent different magnetic poles is located in the development area, and the leveling member is disposed between approximately the center of the development area and the regulating member, A direct current voltage having a polarity opposite to the charged polarity of the toner particles is applied to the charging member as a bias voltage.

(Example) Hereinafter, the present invention will be described in detail based on FIGS. 1 and 2 of the accompanying drawings.

In the first embodiment shown in FIG. 1, a rotating developer carrier 2 (hereinafter referred to as a developing sleeve) rotating in the direction of arrow B is arranged close to an image carrier L rotating in the direction of arrow B. It is set up.

The developing sleeve 2 is housed in a housing 6 formed into a cylinder and having an opening at the top, and is applied with a developing bias voltage 7, which is a DC voltage superimposed with an AC voltage at a frequency of 130 Ov and 3500 flz, for example. .

This developing sleeve 2 has a fixed magnet 3 inside it,
A two-component developer 4 (hereinafter referred to as "developer"), which is a mixture of toner particles and magnetic particles, is supported on the outer peripheral surface of the developing sleeve 2.

The fixed magnet 3 is formed in a cylindrical shape, and has magnetic poles N s, S , N 4. from the upstream side to the downstream side in the rotational direction of the developing sleeve 2, that is, in the direction B. N3 and S2 are formed sequentially. Both magnetic poles N and S have a development pole magnetic force of 1200 Gauss, and the center of magnetic pole N1 becomes the upstream development pole, and the interpole angle between this and the paired magnetic pole SI is set to 70 degrees. A developing area 5 is formed in a portion of the developing sleeve 2 within the range that is close to the photosensitive tram 1 .

On the other hand, the developer 4 supported on the outer circumferential surface of the developing sleeve 2 by the fixed magnet 3 is, for example, styrene with a particle size of 2 to 5 pm,
It is formed by mixing acrylic or suspension polymerized toner particles with magnetic particles having a particle size of 30 to 50 gm manufactured by Toyo Ink KK, for example.

A regulating member 8 is provided to regulate the layer thickness of the developer 4. This regulating member 8 is provided on the inner wall of the housing 6 facing the upstream position of the developing sleeve 2 in the rotational direction, and is formed to create a constant gap S between it and the outer circumferential surface of the developing sleeve 2. A leveling member 9 is provided to make the layer surface of the thus regulated developer 4 uniform.

The leveling member 9 is made of a conductive elastic member, for example, urethane rubber with carbon added thereto, or a thin metal plate of about 0.2 mm thick, such as phosphorescent copper or non-magnetic stainless steel. It is completely insulated from the sleeve 2. This leveling member 9 is disposed between approximately the center of the developing area 5 and the regulating member 8, one end thereof is attached to an insulating member 10 installed on the regulating member 8 side of the housing 6, and the other end is attached to an insulating member 10 installed on the regulating member 8 side of the housing 6. It is considered a free end. This free end faces the developing area 5 side and is formed to elastically abut on the developing sleeve 2 at a position approximately 5 degrees downstream from the magnetic pole N, for example. The leveling member 9 is charged with a voltage of about 50 to 500 V with a polarity opposite to that of the toner particles carried on the developing sleeve 2.
A bias voltage 11 consisting of a DC voltage is applied.

Reference numeral 12 and 13 denote a conveying screw for the developer 4, which is housed in the lower part of the housing synchronizer and is configured to rotate in the directions of arrows C and D to convey the developer 4 to the outer circumferential surface of the developing sleeve 2. .

Next, the operation of the embodiment configured as described above will be explained.

In the developing device having such a configuration, for example, the electrostatic latent image potential of the image carrier is set to about 200 to 600 V, the development gap of the development area 5 is set to 3001 Lm, and the development speed is set to 270 mm/sec.
When development is performed under conditions such as c, the developer 4 that has passed through the leveling member 9 and whose layer thickness has been made uniform is excited by the bias voltage 11 applied to the leveling member 9. Since this bias voltage 11 is a DC voltage with a polarity opposite to that of the toner particles, the toner particles have a degree of freedom due to the attractive force that acts against the pressure applied to the magnetic particles by the leveling member 9. be done. Therefore, the fluidity of the toner particles does not decrease and the toner particles can fly actively, so that no decrease in density occurs in the development area 5.

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

This embodiment is characterized in that the bias voltage applied to the leveling member is a DC voltage superimposed with an AC voltage, thereby adding a developer stirring action to the suction action similar to that of the previous embodiment. There is. Therefore, the bias voltage 14 is, for example, a DC voltage of about 300V, and the voltage applied to the developing sleeve 2 described in the previous embodiment: 1:100V (amplitude value).
Frequency: +500 [1z AC voltage is superimposed.

Therefore, the developer 4 is stirred by the vibratory suction force, the mixing ratio is made uniform, and moreover, the amount of toner particles that maintains an appropriate density flies into the development area 5.

(Effects of the Invention) The present invention has a structure in which a bias voltage having a polarity opposite to that of the charged polarity of the toner particles is applied to the leveling member, thereby applying an attractive force to the toner particles that counteracts the adhesion force to the magnetic particles. As a result, the degree of freedom for the flight of toner particles in the development area is ensured, and as a result, a decrease in density is prevented and a harmonious and clear image with increased image density is obtained.

In this way, the reliability of the developing device can be improved by -1.

[Brief explanation of the drawing]

FIG. 1 is a vertical cross-sectional view showing a schematic configuration of a device according to a first embodiment of the present invention, and FIG. 2 is a vertical cross-sectional view showing a schematic configuration of a device according to a second embodiment of the present invention. ■・・・・・・・・・・・・Image carrier 2・・・・・・・・・Rotating developer carrier (developing sleeve) 3・・・・・・・・・・・・・・・・Fixed magnet 4...Developer 5...Development area 9...Leveling plate 11 .14...Bias' as a positive power source Patent applicant Patent attorney representing Canon Co., Ltd.
Toru Fujioka Figure 1 Figure 2

Claims (2)

[Claims] (1) A rotary development system in which a development area is formed in the vicinity of the image carrier, and a two-component developer having a fixed magnet inside and a mixture of toner particles and magnet particles is supported on the outer peripheral surface. a regulating member disposed with a certain gap between the developer carrier and the rotating developer carrier to regulate the layer thickness of the two-component developer layer; In the developing device, a leveling member is provided at a position downstream of the regulating member and is pressed against the outer circumferential surface of the developer carrier to level the two-component developer layer. The leveling member is disposed between approximately the center of the developing area and the regulating member, and the leveling member is configured to control the charging of the toner particles. A developing device characterized in that a DC voltage of opposite polarity is applied as a bias voltage. (2) The developing device according to claim (1), wherein the bias voltage is formed by superimposing an alternating current voltage on a direct current voltage having a polarity opposite to the charging polarity of the toner particles.