JP2003280367A - Developing device and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent a toner from cohering or adhering at the contact part between a developer carrier and a developer regulation member and to make development fast while switching a plurality of developing units. <P>SOLUTION: A developing device having a plurality of developing units 5 which develop a latent image on an image carrier 6 by using a developer carrier 11 is provided with a means 50 which positions the developing unit to be used for development at a developing operation position and positions developing units not used for the development at standby positions. Each developing unit has a supply means 12 which supplies a developer to the developer carrier, a developer regulation member 14 which regulates a developer layer on the developer carrier by bringing a part of the surface into contact with the developer carrier and can switch surface parts to come into contact with the developer carrier by surface movement, and a surface moving means which performs the surface movement. Then the surface movement by the surface moving means is carried out at the standby positions. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

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

[0002]

2. Description of the Related Art Conventionally, as a developing device of this type, a developing device using a regulating blade as a developer regulating member for regulating the amount of the developer carried on a developer carrying member such as a developing roller has been widely used. . It has been proposed to use a regulation roller instead of this regulation blade (Japanese Patent Laid-Open No. 60-10).
3373 gazette and JP-A-11-84867 gazette). For example, Japanese Patent Laid-Open No. 11-84867 discloses the following. "In the above-mentioned conventional non-magnetic one-component developing device for an electrophotographic apparatus, since toner is charged by friction of a member, the stress on the toner increases as the printing speed increases, so that the developing roller 5 and the toner regulating blade 7 are separated from each other. The toner agglomerates at the contact portion of the toner, and finally the toner adheres to the surface of the toner regulating blade 7. Further, in the fixing step,
In order to prevent the offset phenomenon in which the toner on the paper is transferred to the surface of the heat roller 22, the cohesiveness of the toner is increased even if a wax of low molecular weight such as polyethylene or polypropylene that is sufficiently melted when heated is added to the toner. Let
It has the same problem. SUMMARY OF THE INVENTION It is an object of the present invention to provide a non-magnetic one-component developing device capable of forming a high quality image even when the printing speed of an electrophotographic device and the fixing offset phenomenon are prevented. In order to solve this problem, the non-magnetic one-component developing device of the present invention supplies a toner to the developing roller which forms a non-magnetic one-component toner layer on the surface and the developing roller which is disposed in contact with the developing roller. It consists of a toner supply roller composed of a conductive member and a toner regulation roller that regulates the toner on the developing roller to form a thin layer, and allows the toner to adhere to the electrostatic latent image on the electrostatic latent image carrier. A non-magnetic one-component developing device for visualizing, wherein the toner regulation roller is stationary during development and is rotated at a predetermined timing during non-development. According to the non-magnetic single-component developing device of the present invention, even when the printing speed is increased and the offset phenomenon of the fixing portion is prevented, the aggregation and sticking of toner is prevented at the contact portion between the developing roller and the toner regulating member. , You can get high quality images. "

[0003]

The inventors of the present invention, like the one proposed in the above-mentioned Japanese Patent Application Laid-Open No. 11-84867, make the toner regulating roller stationary during development and rotate at a predetermined timing during non-development. It was examined to use the developing device to be used as the developing device of the next developing device. That is, the present invention is applicable to a developing device of a developing device having means for locating a developing device of the plurality of developing devices, which is used for developing, at the developing operation position, and for arranging a developing device not used for development at the retracted position. investigated. The developing operation position is a position where the developer carrier of the developing device comes into contact with or approaches the surface of the latent image carrier. The retracted position is a position separated from the surface of the latent image carrier as compared with the developing operation position. However,
When applied to such a developing device, it has been found that the following problems may occur depending on the setting of the specific timing for rotating the toner regulating roller. Figure 3
(A) shows an example of a specific timing setting. The timing of non-rotation of the developing roller, the timing of non-rotation of the toner regulating roller (doctor roller), and the timing of movement of the developing device (developing unit) between the developing operation position (contact) and the retracted position (separation) are shown. There is. In this example, after the development is completed and the rotation of the developing roller is stopped, the toner regulating roller is rotated while the developing device itself is in the developing operation position. With this setting, the rotation of the toner regulation roller is stopped and the developing device is moved to the retracted position, and the next developing device is moved to the developing operation position to form a color image. The timing at which development can be started is delayed accordingly. For this reason,
It has been found that the developing operation while switching the developing device to be used takes time, which in turn may reduce the image forming speed of the image forming apparatus.

The above is the case where the roller-shaped regulating member is used. Even if other shapes such as a belt shape or a swinging member shape instead of a roller shape, as long as it is a developer regulating member capable of switching the surface portion that comes into contact with the developer carrier by surface movement,
Similar problems can occur. And, it is considered that the same effect as that of the above-mentioned JP-A No. 11-84867 can be obtained if it is a developer regulating member capable of switching the surface portion in contact with the developer carrier by the surface movement. That is, it is considered that the toner can be prevented from aggregating and sticking at the contact portion between the developer carrying member such as the developing roller and the developer regulating member, and a high quality image can be obtained.

The above publication only describes the following regarding the timing. “The reason why fogging occurs when the toner regulating roller 27 rotates during development is that the relative velocity of the contact portion between the developing roller 5 and the toner regulating roller 27 increases due to the rotation of the toner regulating roller 27, which causes the mechanical It can be considered that the toner 10 deteriorates with time due to an increase in dynamic stress, that is, it is necessary to shorten the time for which the toner regulation roller 27 rotates as much as possible. Since the thin layer state of the toner on the developing roller 5 is different when stationary, it is optimal to rotate the toner regulating roller 27 during non-developing as in the present invention. Although the toner regulating roller 27 is always rotated at some times, it is not always necessary to rotate it depending on the system, and at a predetermined timing during non-developing. The period to may be rotated. "

The present invention has been made in view of the above background. A purpose of the invention is to provide a developing device capable of speeding up development while switching a plurality of developing devices while preventing aggregation and sticking of toner at a contact portion between a developer carrying member and a developer regulating member. An image forming apparatus is provided.

[0007]

In order to achieve the above-mentioned object, the invention of claim 1 is a developing device having a plurality of developing devices for developing a latent image on an image carrier by using a developer carrier. A developing device which is used for developing among the plurality of developing devices and is located at a developing operation position where the developer carrying member comes into contact with or comes close to the surface of the latent image carrying member, and which is not used for developing Is provided at a retracted position separated from the surface of the latent image carrier relative to the developing operation position, and as the developing device, a supply means for supplying a developer to the developer carrier and a part of the surface. A developer regulating member capable of contacting the developer bearing member to regulate the developer layer on the developer bearing member and switching the surface portion in contact with the developer bearing member by surface movement, A developing device having a surface moving means for moving the surface is used. The surface movement by the surface moving means is characterized in that it has configured to perform above the retracted position. According to the invention of claim 2, an image carrier, a latent image forming means for forming a latent image on the image carrier, and a plurality of developing devices for developing the latent image on the image carrier by using a developer carrier. An image forming apparatus including a developing device having a developing device having the above-mentioned structure, wherein the developing device according to claim 1 is used as the developing device. In the present invention, since the surface movement by the surface moving means is performed at the retracted position, unlike the case where the surface movement is performed at the developing operation position, the developing operation position is moved to the retracted position until the surface movement is completed. You don't have to wait for a move. Therefore, as compared with the case where the surface movement by the surface moving means is performed at the developing operation position, the developing device to be used can be switched more quickly.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment in which the present invention is applied to a color laser printer (hereinafter referred to as "printer") as an image forming apparatus having four developing devices will be described below. FIG. 1 is a front view showing a schematic configuration of a printer according to this embodiment. This printer includes a photoconductor belt 1 as a latent image carrier that is wound around a plurality of support rollers. The photoconductor belt 1 is indicated by an arrow A in the figure.
It is driven to rotate clockwise as indicated by, and around it, the charger 3, the optical writing unit 4, and the four developing devices 5Bk, 5 are provided.
A developing device 5 including C, 5M and 5Y is provided.
Further, an intermediate transfer belt 6 as an intermediate transfer member, a photoconductor cleaning device 7 and the like are also arranged. Photoconductor belt 1
An organic photosensitive layer is formed on the surface of the.

When the image forming operation (printing operation) is executed by the printer, a high voltage is applied to the charger 3 so that the photosensitive belt 1 is uniformly charged. Then, color image information, for example, a color image signal sent from an external computer is converted into an optical writing signal by an image signal processing unit (not shown) and sent to the optical writing unit 4. In the optical writing unit 4, a laser as a light source (not shown) is controlled based on the optical writing signal. As a result, Black (Bk), Cyan (C), and
Optical writing corresponding to the image signals of nta (M) and Yellow (Y) is performed. Light from this laser is applied to the photosensitive belt 1 via the polygon mirror 8, the f / θ lens 9 and the reflection mirror 10, and an electrostatic latent image is formed on the photosensitive belt 1.

The electrostatic latent image on the photoconductor belt 1 is developed for each color by the developing devices 5Bk, 5C, 5M and 5Y each having toner of each color charged with an electric charge having a polarity opposite to that of the latent image. To be done. As a result, a toner image is formed on the photosensitive belt 1 for each color.

At the contact portion between the photosensitive belt 1 and the intermediate transfer belt 6, by applying an electric charge having a polarity opposite to that of the toner to the intermediate transfer belt 6, the toner image on the photosensitive belt 1 is transferred onto the intermediate transfer belt 6. Is transcribed to. By repeating this toner image formation and transfer operation four times, a four-color superposed color toner image is formed on the intermediate transfer belt 6.
The color toner image on the intermediate transfer belt 6 is transferred by a paper transfer roller 43 as a secondary transfer member onto a transfer paper as a recording material sent from a paper feed cassette 40 or a manual feed tray 41 by a transport roller pair 42. To be done. The transfer paper on which the color toner image has been transferred is fixed by the fixing roller pair 44.
And the toner image is fused and fixed.

Next, each developing device of the developing device 5 according to this embodiment will be described with reference to FIG. Although FIG. 2 illustrates the black developing device 50BK as an example, other developing devices have the same structure. The developing device according to the present embodiment is a one-component developing type developing device using a non-magnetic one-component toner (hereinafter referred to as toner). Each developing device has a developing container 10 having an opening toward the photoconductor belt 1, a developing roller 11 as a developer carrying member, and a toner supply roller 12 for supplying toner onto the developing roller 11. . It also has conveyance paddles 17a, 17b, 17c for sending the toner stored in the toner storage portions 18a, 18b, 18c in the developing container 10 to the supply roller 12 side, and a regulation roller 14 as a developer regulation member. This regulation roller 1
As will be described later, 1 can switch the surface portion in contact with the developing roller 11 by the surface movement by rotation.

A part of the developing roller 11 is exposed from the opening of the developing container 10 and is rotatably installed in a counterclockwise direction at a predetermined linear velocity so that the toner is carried on the roller surface to form the photosensitive belt 1. The latent image on the photoconductor belt 1 is developed by carrying the latent image on the photoconductor belt 1. In this embodiment, a metal roller is used as the developing roller 12. The toner supply roller 12 is in contact with the developing roller 11 with a predetermined pressure and is rotatably installed in the counterclockwise direction of the arrow.
The surface portion is composed of polyurethane foam. Further, the toner supply roller 12 includes a toner regulating blade 1
3 is brought into contact with the developing roller 11, and the amount of toner supplied to the developing roller 11 is regulated. Each of the transport paddles 17 is rotatably installed in the counterclockwise direction of the arrow, and the toner is sent to the supply roller 12 side by this rotation. As a material of each of the transport paddles, for example, a soft and elastic material such as polypropylene can be used, and by utilizing the elasticity, the toner rotates reliably in a state of being brought into close contact with the inner wall of the developing container 10 to reliably transport the toner.

The regulation roller 14 regulates the toner on the developing roller 11 to a predetermined layer thickness, and frictionally charges the toner by slidingly contacting the toner.
The toner charged on the developing roller 11 develops the electrostatic latent image on the photosensitive belt 1. In this embodiment, urethane rubber coated with resin is used as the material of the surface portion of the regulation roller 14. Further, a regulation roller cleaning blade 16 is in contact with the regulation roller 14, so that the surface of the regulation roller 14 that has passed the contact portion with the developing roller 11 is cleaned.

Further, in the illustrated example, a spring 19 is provided as an urging means for absorbing a change in outer diameters of the developing roller 11 and the regulating roller 14 due to environmental changes such as humidity, and the regulating roller 14 is used as the developing roller 11. Pressurized against.

A cam 50, which is independently rotatable, is in contact with a side end portion (left side in the drawing) of each developing device 5. The rotation of the cam 50 causes the photosensitive belt 1 to be in a non-developed state.
And the contacting / separating operation is performed such that the developing roller 11 moves to the developing position where the developing roller 11 comes into contact with the photosensitive belt 1 prior to the developing. Then, the photosensitive belt 1
When developing the above electrostatic latent image, the corresponding developing device moves to the developing position where it contacts the photosensitive belt 1. For example, when an electrostatic latent image of Bk is formed on the photoconductor belt 1, the cam 50Bk located at the rear part of the developing device 5Bk is rotated 180 degrees by a drive control unit (not shown), and the developing device 5Bk is driven by the photoconductor. It is pushed out to the belt 1 side. As a result, the developing roller 11Bk moves to the developing position where it contacts the photosensitive belt 1. Other color developing devices 5C, 5M, 5Y
When developing with, the corresponding cams 50C, 50
The M and 50Y are driven to rotate.

Further, the printer of the present embodiment is provided with a control means for rotating the regulating roller 14 in accordance with the movement operation of each developing device 5, that is, the switching operation of the used developing device. FIG. 3B is a timing chart according to this embodiment. The timing of non-rotation of the developing roller 11, the timing of non-rotation of the regulating roller (doctor roller) 14, and the timing of movement of the developing device (developing unit) between the developing operation position (contact) and the retracted position (separation) are shown. ing. In this example, after the development is completed and the rotation of the developing roller 11 is stopped, the developing device is immediately moved to the retracted position. Then, the regulation roller 1 is moved to the retracted position.
Rotate 4 The rotation of the regulation roller 14 is, for example, 9
Do it 0 times. As described above, after each developing device is moved from the developing operation position to the retracted position, the regulating roller 14 of the developing device is rotated. As can be seen from the comparison with FIG. 3A, if the rotation time of the developing roller, that is, the developing time is the same, the contact time of the developing device, that is, the developing operation is performed in this embodiment for a time t. Time can be shortened at the position. In the developing device 5 of the present embodiment in which the photosensitive belt 1 is provided with a total of four developing devices for each color, in the case of forming a color image using these four colors, the development of the other colors is performed during the development of one color. The container cannot be brought into contact with the photosensitive belt 1.
Therefore, it takes 4 hours in total while forming the four color toner images.
The time can be shortened by t.

As a mechanism for rotationally driving the hand regulating roller 14 according to the movement of the developing device as described above, for example, only the regulating roller 14 is independently rotated by using a clutch, and the developing roller 11 is separated from the photoconductor. Sometimes only that clutch is turned on and off independently. A drive source different from the developing roller 10 may be prepared as a drive source for driving and supplying the regulating roller 14 via the clutch, or may be used also as the developing roller 10. However, when the developing roller 11 is also used, a clutch is provided between the dual-purpose drive source and the developing roller 14 in order to prevent toner scattering due to the rotation of the developing roller 11 with the rotation of the regulating roller 14 at the retracted position. Then, at the retracted position, it is desirable to cut off the drive transmission to the developing roller 14 side. Of course,
Instead of using such a clutch, a direct drive motor may be provided and the rotation of the regulation roller 14 may be controlled by turning the motor on and off. A surface moving unit is configured by a control unit that drives and controls the clutch, the direct drive motor, and the like, and the clutch, the drive source, and the direct drive motor according to the timing regarding the movement control of the developing device 5.

Further, a rotation stopping force may be exerted when the regulating roller 14 is stopped during the developing operation at the developing operation position. For example, as the clutch, a one-way clutch that transmits drive only in a direction in which the surface of the regulation roller 14 moves in the direction opposite to the direction of movement of the surface of the developing roller 11 at the contact portion with the developing roller 11 is used. If such a configuration that exerts the rotation stopping force is exerted, the regulation roller 14 does not crawl around the developing roller 14 during development, and it is possible to exert the functions of sufficient triboelectrification for the toner and the layer thickness regulation.

As described above, according to the present embodiment, the regulation roller 14 is rotated by the predetermined angle only during the non-development,
As compared with the case where the roller is constantly rotated during development, the regulation roller 14
It is possible to reduce the power consumption for rotationally driving. During development, the developing roller 11 and the regulation roller 14
Abut with and stopped. As a result, the driving torque of the developing roller 11 is reduced as compared with the case where both rollers contact each other while rotating in the counter direction during development.
It is possible to suppress the fluctuation of the rotation speed of the developing roller 11 due to the increase of the driving torque. Therefore, it is possible to prevent the occurrence of image density unevenness due to this variation. Further, since the regulation roller 14 can be intermittently rotated by a predetermined angle, it is possible to prevent the same portion of the regulation roller 14 surface from being always in contact with the developing roller 11. As a result, it is possible to prevent the surface of the regulation roller 14 from being abraded with time, and to extend the life of the regulation roller 14. Further, it is possible to prevent the deterioration of the charging ability of the toner due to this abrasion, and to prevent the occurrence of background stains on the non-image area and the deterioration of the reproducibility of minute dots due to insufficient charging of the toner.

[0021]

According to the first and second aspects of the present invention, toner is prevented from aggregating and adhering at the contact portion between the developer carrying member and the developer regulating member, and development is performed by switching a plurality of developing devices. There is an excellent effect that it is possible to speed up.

[Brief description of drawings]

FIG. 1 is a front view showing a schematic configuration of a printer according to an embodiment.

FIG. 2 is a schematic configuration diagram of a developing device in the embodiment.

FIG. 3A is a timing chart according to a comparative example.
(B) is a timing chart according to the embodiment.

[Explanation of symbols]

1 photoconductor belt 3 charger 4 Optical writing unit 5 Development device 6 Intermediate transfer belt 7 Photoconductor cleaning device 10 developer container 11 Developing roller 12 Toner supply roller 13 Toner regulation blade 14 Regulation roller 14a rotating shaft 16 Regulation roller cleaning blade 17 Transport paddle 18 Toner container 19 spring 40 paper cassettes 41 bypass tray 42 pairs of transport rollers 43 paper transfer roller 44 fixing roller 50 cams

   ─────────────────────────────────────────────────── ─── Continued front page    F-term (reference) 2H077 AB03 AB18 AC03 AC04 AD06                       AD14 AD17 AD23 AE03 BA01                       DB25 EA14 GA13                 2H300 EB02 EB08 EB13 EC02 EC05                       EF08 EG02 EH16 EH25 EJ09                       EJ13 EJ25 EJ45 EJ47 EK03                       EL07 GG29 GG43 HH23 HH24                       HH32 HH33 QQ10 QQ16 TT06

Claims (2)

[Claims] 1. A developing device having a plurality of developing devices for developing a latent image on an image bearing member by using a developer bearing member, wherein the developing device used for developing among the plurality of developing devices is the developing device. The developer carrier, which is located at a developing operation position where the agent carrier comes into contact with or comes close to the surface of the latent image carrier, and a developing device which is not used for the development is separated from the surface of the latent image carrier at a retracted position. And a means for locating
A supply means for supplying a developer to the developer carrying member, a part of the surface of the developer carrying member is brought into contact with the developer carrying member to regulate the developer layer on the developer carrying member, and the development is carried out by surface movement. A developing device having a developer regulating member capable of switching the surface portion in contact with the agent carrier and surface moving means for moving the surface is used, and the surface moving by the surface moving means is performed at the retracted position. And a developing device. 2. An image carrier, a latent image forming means for forming a latent image on the image carrier, and a plurality of developing devices for developing the latent image on the image carrier using a developer carrier. An image forming apparatus including a developing device, wherein the developing device is the image forming device.
An image forming apparatus using the developing device of.