JP2002268380A - Developing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a developing device which prevents the occurrence of abnormal images. SOLUTION: A developing device 103 is provided with a developing roller 210, which is rotated when an image is formed to supply single-component toner to a photosensitive belt 100, a doctor roller 230, which is brought into contact with the developing roller 210 to make the toner on the developing roller 210 into a thin layer of a certain amount of toner, and a sealing member 250 which moves close to the developing roller 210 to seal the toner on the developing roller 210, and the doctor roller 230 is rotated together with the developing roller 210, when the developing roller 210 is rotated in the direction opposite to the rotation direction or image formation, when the image is not formed. The sealing member 250 is provided with a high friction part 250a and a low-friction part 250b which differ in friction coefficients, and the low- friction part 250b of the sealing member 250 is brought into contact with the developing roller 210, when the developing rollers 210 is rotated at the image formation, and the high-friction part 250a of the seal member 250 is brought into contact with the developing roller, when the developing roller 210 is rotated in the opposite direction, when the image is not being formed.

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 for an image forming apparatus such as a printer, a copying machine, a facsimile, and the like.

[0002]

2. Description of the Related Art In a one-component developing apparatus of this type, a toner layer regulating member frictionally charges toner supplied from a supply roller to a developing roller at a nip portion between the toner layer regulating member and the developing roller, and a fixed amount of toner is provided. Form a toner layer. As the toner layer regulating member, a regulating blade is generally used, and a hard roller having a developing roller made of metal or resin has elasticity such as urethane rubber,
Conversely, when the base material has elasticity such as rubber as a developing roller, a metal blade or the like is used.

The one-component developing device has an advantage that it can be constructed at a low cost because it does not require a carrier or a toner density sensor as compared with a two-component developing device. However, since the regulating blade is pressed against the developing roller,
Over time, the surface is scraped and the chargeability deteriorates, and accordingly the charge of the toner decreases, causing background contamination, and the reproducibility of minute dots is reduced. Further, the toner staying in the developing nip portion is melted by frictional heat generated between the rotating developing roller and the blade to form a toner mass, and white streaks are generated by the toner mass. Therefore, it has been difficult to extend the life of the developing device.

To solve such a problem, a developing device using a roller-shaped regulating roller instead of the regulating blade has been proposed. The regulating roller forms a toner layer having a predetermined thickness on the developing roller by coming into contact with the developing roller carrying the toner. In addition, by rotating the regulating roller, the same portion of the surface of the regulating roller is prevented from contacting the developing roller, so that the surface of the regulating roller does not wear over time, and the same as when using a blade. This prevents the surface from being constantly worn and the toner from staying in the nip.

[0005]

However, when the developing roller rotates in the reverse direction to the rotation during image formation during non-image formation, the toner supplied from the supply roller onto the developing roller loses the toner of the developing roller. It only passes through the sealing member to be sealed, and a thick toner layer may be formed on the developing roller due to poor charging. Even if the thick toner layer having poor charging is thinned by the regulating roller due to the rotation of the developing roller at the time of development, the amount of frictional charge of the toner is reduced, and an abnormal image such as background contamination occurs. There is.

Accordingly, an object of the present invention is to provide a developing device capable of preventing occurrence of an abnormal image.

[0007]

According to a first aspect of the present invention, there is provided a developing roller for supplying a one-component toner to an image carrier by rotating at the time of forming an image, and contacting the developing roller to remove toner of the developing roller. A toner layer regulating roller that reduces the thickness to a certain amount, and a seal member that seals the toner of the developing roller. When the developing roller rotates in a direction opposite to the rotation direction at the time of non-image formation, the toner A developing device in which the layer regulating roller rotates together with the developing roller, wherein the seal member is
It has a high friction portion and a low friction portion having different friction coefficients, and when the developing roller rotates during image formation, the low friction portion of the seal member contacts the developing roller, and the developing roller rotates in the opposite direction during non-image formation. In some cases, the high friction portion of the seal member contacts the developing roller.

According to the first aspect of the present invention, during development, when the developing roller is rotating, the low-friction portion of the seal member comes into contact with the developing roller, thereby suppressing scraping of toner by the seal member. If the developing roller rotates in the reverse direction during development, the high friction portion of the seal member comes into contact with the developing roller, and the high friction portion scrapes off the toner on the developing roller to form a poorly charged toner layer on the developing roller. Therefore, occurrence of an abnormal image such as background dirt can be prevented. Further, when the developing roller is rotated in the reverse direction, the contact surface of the toner layer regulating roller with the developing roller is changed by rotating the toner layer regulating roller together with the developing roller, and the same surface of the toner layer regulating roller is constantly worn. Therefore, the life of the toner layer regulating roller can be extended.

According to a second aspect of the present invention, in the first aspect, the seal member has a film shape, the high friction portion is provided integrally on one surface of the seal member, and the low friction portion is provided. Is provided integrally on the other surface of the seal member.

[0010] According to the second aspect of the present invention, the first aspect is provided.
In addition to the same operation and effect as the invention described in the above, since the high friction portion and the low friction portion are integrated with the seal member,
The size can be reduced.

According to a third aspect of the present invention, in the second aspect of the present invention, the developing roller supplies the toner to the image carrier by an image area carrying the toner, and a seal is provided outside the image area. A resistance member having a higher coefficient of friction than the member is provided.

According to the third aspect of the present invention, the second aspect is provided.
In addition to the same effects as the invention described in the above, the distal end of the seal member moves along the rotation direction of the developing roller due to the frictional force with the resistance member, so that the high frictional portion and the low frictional portion of the seal member are formed. Switching can be performed, and there is no need to separately provide a member for switching between the high friction portion and the low friction portion of the seal member. Therefore, further downsizing and cost reduction can be achieved.

According to a fourth aspect of the present invention, in the first aspect, the seal member has a roller shape, and the high friction portion and the low friction portion are integrally provided on the roller surface. Features.

According to the fourth aspect of the present invention, the first aspect is provided.
In addition to the same operation and effect as the invention described in (1), the seal can be simplified by forming the seal member into a roller shape.

[0015]

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings. FIG. 1 is a configuration diagram schematically showing a color laser printer to which the present invention is applied. As shown in FIG. 1, a color laser printer 10 generally includes a photoconductor unit 101 having a photoconductor belt 100, a writing unit 102 for forming an electrostatic latent image on the photoconductor belt 100, and a photoconductor belt 100. A developing device 103 that supplies a component toner to visualize the electrostatic latent image on the photoreceptor belt 100 as a toner image, an intermediate transfer unit 104 having an intermediate transfer belt 108, a paper feeding device 105 that feeds transfer paper, Intermediate transfer belt 10
8 is provided with a paper transfer device 106 for transferring the toner image primarily transferred to the transfer paper, and a fixing device 107 for fixing the toner image on the transfer paper by heat and pressure.

The photoreceptor belt 10 of the photoreceptor unit 101
0, a charger 1 for charging the photosensitive belt 100
10, each developing cartridge 130a of the developing device 103,
130b, 130c, 130d and a photoconductor cleaning device 150 are arranged. An organic photosensitive layer is formed on the surface of the photoreceptor belt 100, and the photoreceptor belt 100 is uniformly charged by applying a high voltage to the charger 110.

The color laser printer 10 converts color image information, for example, a color image signal from a computer into an optical signal, and uses a laser to emit black (hereinafter, referred to as Bk), cyan (hereinafter, referred to as C), magenta (hereinafter, referred to as C). M
Optical writing corresponding to image signals of yellow (hereinafter referred to as Y) through the writing unit 102,
An electrostatic latent image is formed on the photoreceptor belt 100.

This electrostatic latent image is formed by Bk, which has toner charged with a charge opposite to that of the electrostatic latent image on the photosensitive belt 100,
Each of the developing cartridges 130a, 130
The toner is developed by electrostatically adsorbing the charged toner by b, 130c, and 130d. In the present embodiment,
The developing cartridge 130a has Bk toner, the developing cartridge 103b has C toner, the developing cartridge 130c has M toner, and has a developing cartridge 130d.

Intermediate transfer belt 108 and photosensitive belt 10
In the contact portion 0, a charge opposite to that of the toner is applied to the intermediate transfer belt 108 so that the intermediate transfer belt 108
The toner image is transferred onto the top. This operation is performed four times by each of the developing cartridges 130 a, 130 b, 130 c, and 130 d to form a four-color superimposed image on the intermediate transfer belt 108. 106 transfer roller 121
Is transferred by applying a charge opposite to that of the toner. The transfer paper is transported to the fixing device 107, and the fixing device 107 melts and fixes the toner image.

Next, referring to FIG. 2, a description will be given of a developing cartridge 130a for developing with Bk toner.
When immersed in the other developing cartridges 130b, 130c, and 130d, the configuration is substantially the same as that of the Bk developing cartridge, and the description thereof is omitted.

As shown in FIG. 2, the developing cartridge 13
0a indicates that the toner of Bk is transferred from the first transport paddle 241 to the second
The toner is filled up to the third transport paddle 243 via the transport paddle 242, and the transport paddles 241, 242, 243 rotate in the direction of the arrow to send out toner forward (to the left in FIG. 2).

In the present embodiment, each transport paddle 241,
Reference numerals 242 and 243 are formed of a soft material such as polypropylene, and have elasticity. The elasticity allows the toner to be securely brought into close contact with the inner wall of the developing cartridge 130a. Thereafter, the toner is transported by the first transport paddle 241 to the supply roller 220 made of foamed polyurethane, and subsequently supplied from the supply roller 220 to the developing roller 210. Further, the toner supplied to the developing roller 210 is a doctor roller (toner layer regulating roller).
At 230, the electrostatic latent image formed on the photoconductor 100 is developed and visualized by being thinned to a predetermined thickness while being charged.

Since the outer diameters of the doctor roller 230 and the developing roller 210 change due to environmental fluctuations, the doctor roller 230 is attached to the developing roller 210 by a spring 231 provided on a bearing 233 of the doctor roller 230 to absorb the change. Pressed toward. still,
The toner scraped off by the doctor roller 230 travels along the inclination inside the developing cartridge, and
Is returned to.

The developing cartridge 130a comes into contact with the photosensitive member 100 by rotation of a contact / separation cam (not shown) at the rear of the apparatus during image formation (see FIG. 2), and separates during non-image formation. A spring (not shown) separates the photosensitive member 100 from the photosensitive member 100 (see FIG. 4), and the developing cartridge 130a can selectively contact the photosensitive member 100.

At the end of the doctor roller 230, a one-way clutch and a housing into which the one-way clutch is press-fitted are formed.
When the developing roller 210 rotates forward during image formation, the one-way clutch is locked and the doctor roller 230 is prevented from rotating along with the developing roller, and the toner of the developing roller 210 is thinned to a certain amount.

In a state where the developing cartridge 130a is separated from the photosensitive belt 100 at the time of non-image formation, the rotation direction shown in FIG. 4 is opposite to the rotation direction at the time of image formation shown in FIG. The doctor roller 230 is rotated in the direction of the arrow in FIG. 4 by rotating the developing roller 210 in the reverse direction and rotating the doctor roller 230 pressed by the spring 231 against the developing roller 210.

As described above, when the developing roller 210 is rotated in the reverse direction, the doctor roller 230 rotates together with the developing roller 210, thereby changing the contact surface of the doctor roller 210 with the developing roller 210.
0 can be prevented from being constantly worn, so that the life of the doctor roller 210 can be extended.

A film-shaped sealing member 250 for sealing the toner of the developing roller 210 is provided above the developing roller 210 to prevent the toner from blowing out to the photosensitive belt 100. The front and back of the seal member 250 have different friction coefficients, and in the present embodiment, the seal member 25
0, the surface on the supply roller 220 side has a high friction portion 250 provided with a member having a high friction coefficient (for example, rubber or the like).
a, and a low friction portion 250b provided with a member having a low friction coefficient (for example, fluorine or the like) is formed on the back surface on the photosensitive belt 100 side.

In this embodiment, the high friction portion 250a and the low friction portion 250b are formed integrally with the sheet member 250 by applying rubber to the front surface of the seal member 250 and applying fluorine to the back surface. The sheet member 250
The high friction portion 250a and the low friction portion 250b may be formed by attaching a sheet made of rubber on the surface of the above and sticking a sheet made of fluorine on the back surface.

In this embodiment, as shown in FIG. 3, the non-image areas R and R outside the image area (area where the developing roller 210 carries toner) G of the developing roller 210 Resistance member 211 such as rubber having a high friction coefficient
Is applied. Therefore, the tip of the seal member 250 moves in the rotation direction of the developing roller 210 due to the frictional force between the tip of the seal member 250 and the resistance member 211, and the high friction portion 250 of the seal member 250 with respect to the developing roller 210.
a and the low friction portion 250b are switched over.

As described above, the high friction portion 250a and the low friction portion 250b of the seal member 25 with respect to the developing roller 210
Can be switched without separately using a solenoid or the like, so that downsizing and cost reduction can be achieved.

The low friction portion 250a of the seal member 250
As shown in FIG. 2, when the developing roller 210 is rotating forward during image formation, the developing roller 210 is in contact with the developing roller 210, and the scraping of toner from the developing roller 210 is suppressed.

On the other hand, the high friction portion 250 of the seal member 250
FIG. 4A illustrates a developing roller 210 during non-image formation, as shown in FIG.
When the roller is rotating in the reverse direction, it is in contact with the developing roller 210, and scrapes off the toner from the developing roller 210 to prevent a thick toner layer from being generated due to poor charging. Thereby, occurrence of an abnormal image such as background dirt can be prevented.

Next, another embodiment will be described. In the description, the same parts as those described above are denoted by the same reference numerals, and the description thereof will be omitted.

FIG. 5 is a sectional view showing a developing cartridge according to the second embodiment. In the second embodiment, a roller-shaped seal member 251 is provided instead of the film-shaped seal member 250, and a high friction portion 251a and a low friction portion 251b are provided on the roller surface as in the first embodiment. This is different from the first embodiment.

As shown in FIG. 5, during image formation, when the developing roller 210 is rotating forward,
The low friction portion 251 b of 51 is in contact with the developing roller 210. When the developing roller 210 rotates in the reverse direction during non-image formation, the seal member 251 rotates by a predetermined angle to rotate the high friction portion 2.
51 a comes into contact with the developing roller 210. Note that reference numeral 252 in the figure is a seal member for sealing the toner blowout above the seal member 251.
Since the seal member 251 has a roller shape, the seal formed by the seal member 251, the developing roller 210 and the doctor roller 230 can be simplified.

The present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the gist of the present invention. For example, in the present embodiment, the high friction portion 2
Although rubber is used for 50a and fluorine is provided for the low friction portion 250b, the material is not particularly limited as long as members having different friction coefficients are provided on the front and back of the film-shaped sealing member 250.

Although the present invention has been applied to the color printer 10, the present invention is not limited to this. Get the effect.

[0039]

According to the first aspect of the present invention, during development, when the developing roller is rotating, the low friction portion of the seal member comes into contact with the developing roller, thereby suppressing scraping of the toner by the seal member. If the developing roller rotates in the reverse direction during non-development, the high friction portion of the seal member comes into contact with the developing roller, and the high friction portion scrapes off the toner on the developing roller. Since formation can be prevented, occurrence of an abnormal image such as background dirt can be prevented. Also, when the developing roller rotates in the reverse direction, the toner layer regulating roller rotates together with the developing roller,
Since the contact surface of the toner layer regulating roller with the developing roller is changed, it is possible to prevent the same surface of the toner layer regulating roller from being constantly worn, so that the life of the toner layer regulating roller can be extended.

According to the second aspect of the invention, the same effects as those of the first aspect of the invention can be obtained, and the high friction portion and the low friction portion are integrated with the seal member, so that the size can be reduced.

According to the third aspect of the invention, the same effect as that of the second aspect of the invention is obtained, and the tip of the seal member moves along the rotation direction of the developing roller due to the frictional force with the resistance member. This makes it possible to switch between the high friction portion and the low friction portion of the seal member, and it is not necessary to separately provide a member for switching between the high friction portion and the low friction portion of the seal member. And cost can be reduced.

According to the fourth aspect of the present invention, the same effects as those of the first aspect of the invention can be obtained, and the sealing can be simplified and the configuration can be simplified by forming the sealing member in a roller shape.

[Brief description of the drawings]

FIG. 1 is a configuration diagram schematically showing a color laser printer to which the present invention is applied.

FIG. 2 is a sectional view schematically showing a developing cartridge.

FIG. 3 is a plan view showing a developing roller and a seal member.

FIG. 4 is a cross-sectional view illustrating the operation of the developing cartridge during non-image formation.

FIG. 5 is a sectional view showing a developing cartridge according to a second embodiment.

[Explanation of symbols]

 Reference Signs List 10 color laser printer (image forming apparatus) 100 photoreceptor belt (image carrier) 210 developing roller 211 resistive member 230 doctor roller (toner layer regulating roller) 250 film-shaped seal member 250a, 251a high friction portion 251 roller-shaped seal member 250b, 251b Low friction part G Image area R Non-image area

Claims (4)

[Claims] A developing roller for supplying a one-component toner to an image carrier by rotating at the time of image formation; a toner layer regulating roller for contacting the developing roller to reduce the toner of the developing roller to a constant amount; A sealing member for sealing the toner of the developing roller, wherein the toner layer regulating roller rotates together with the developing roller when the developing roller rotates in a direction opposite to the rotation direction during non-image formation. The seal member includes a high friction portion and a low friction portion having different friction coefficients, and when the developing roller rotates during image formation, the low friction portion of the seal member contacts the development roller, and when the image is not formed, When the developing roller rotates in the opposite direction, the high friction portion of the seal member contacts the developing roller. 2. The sealing member has a film shape, the high friction portion is provided integrally on one surface of the sealing member, and the low friction portion is provided integrally on the other surface of the sealing member. The developing device according to claim 1, wherein: 3. The developing roller supplies toner to the image carrier through an image area supporting the toner, and a resistive member having a higher friction coefficient than the seal member is provided outside the image area. The developing device according to claim 2, wherein: 4. The seal member has a roller shape.
The developing device according to claim 1, wherein a high friction portion and a low friction portion are integrally provided on a roller surface.