JP2007079322A - Developing device, process cartridge and image forming apparatus having the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a developing device preventing pressure variation of developer applied to a developer regulation member without increasing costs by a complicated developer pressure control means and in which image unevenness by developer unevenness on a developer carrier is eliminated, even when the developer is arranged above the image carrier. <P>SOLUTION: The developing device 100 has: the developer carrier 102; a developer storage part 101; a developer supply means 104; a developer stirring member 105; and the developer regulation member 103 which regulates the developer supplied on the developer carrier 102 to a predetermined amount, in which the developer storage part 101 is arranged above the developer carrier 102, and a contact part between the developer storage part 101 and the developer regulation member 103 is almost right above the developer carrier 102. The developing device 100 has a developer powder pressure prevention member 109 which prevents the pressure variation of the developer applied to the developer regulation member 103, and the developer powder pressure prevention means 109 is provided on an upper part of the developer regulation member 103. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a one-component developing device employed in an image forming apparatus such as a copying machine, a facsimile machine, or a printer.

Conventionally, a one-component developing device has been widely used as one of developing devices used in an electrophotographic image forming apparatus. The developing device used for this has a horizontal structure in which the developer is installed horizontally with respect to the image carrier, and the developer is transported in the horizontal direction from the hopper chamber in the developing device with a stirring blade and supplied to the developer carrier. There are many. Generally, this horizontal type developing device has a good dispersibility and a good image uniformity because the developer moving direction is different from the gravity direction.
In the case of an image forming apparatus that forms a color image by synthesizing 3 to 4 color images, it is necessary to arrange 3 to 4 developing units including a latent image carrier, and the entire apparatus is made compact and developed. In order to secure the capacity of the agent, it is preferable to arrange the developing units horizontally rather than vertically. Further, in order to arrange the developing units horizontally and make the entire image forming apparatus compact, it is necessary to adopt a so-called vertical structure in which the hopper is arranged above the developing unit.

However, when development is performed using such a vertical developing device as a one-component developing device, the developer is supplied onto the developing carrier due to the remaining amount of the developer, tightening of the developer due to standing, and rotation of the stirring member. The pressure applied to the regulating member that regulates the developer to a predetermined amount fluctuates, causing density changes and image unevenness in the developed image.
For this reason, in the developing device having a vertical structure, a hopper unit and a developing unit are divided so that the developer pressure applied to the regulating member does not change, and a device for supplying the developer from the hopper unit to the developing unit is provided, When a developer sensor is provided in the developing portion and the developer in the developing portion is reduced, a means for supplying the developer from the hopper portion is required, which causes an increase in cost.

In view of the above problems, as a conventional technique in which the development apparatus has been improved, for example, a retention inhibitor that prevents the toner core from staying on the upstream side of the press contact portion with the developer layer thickness regulating member is provided. A one-component developing device (for example, refer to Patent Document 1) is disclosed in which a layer thickness regulating member is a rigid member whose nip width with a developing roller is in point contact with the rotation direction of the developing roller.
Further, in a developing device containing a one-component developer arranged downward from above with respect to the image carrier, a support for supporting the weight pressure of the developer at a position close to the developer carrier of the developing device. A developing device (see, for example, Patent Document 2) in which members are installed is disclosed. In addition, a developing device that transports developer using magnetic force without providing a plurality of developer regulating members as in the prior art, and in which the developer regulating member is installed with a gap in the developing roller (for example, Patent Documents) 3) is disclosed.

JP-A-10-031358 Japanese Patent Application Laid-Open No. 2002-221853 JP 09-329954 A

  The present invention has been made in view of the above-described problems. Even if the developing device is arranged on the image carrier in a different configuration from the conventional developer regulating methods of Patent Documents 1 to 3, the present invention is complicated. A developer device that can prevent a change in the pressure of the developer applied to the developer regulating member without incurring high cost by a simple developer pressure control means, and eliminates image unevenness due to developer unevenness on the developer carrier, It is an object of the present invention to provide a process cartridge and an image forming apparatus provided with the same.

The features of the present invention, which is a means for solving the above problems, are listed below.
The developing device of the present invention is provided so as to be rotatable in contact with the developer carrier, a developer carrier that is rotatably provided opposite to the latent image carrier, a developer container that contains the developer, and the developer carrier. A developer supplying means for supplying the developer onto the developer carrying member, and a developer accommodating portion rotatably provided in the developer accommodating portion, wherein the developer in the developer accommodating portion is stirred and circulated, and the developer is provided on the developer supplying means. A developer agitating member that contacts the developer carrying member, and a developer regulating member that regulates the developer supplied onto the developer carrying member to a predetermined amount, and the developer accommodating portion In the developing device that is disposed above the developer carrying member and the contact portion between the developer containing portion and the developer regulating member is located almost directly above the developer carrying member, the developing device is connected to the developer regulating member. A developer powder pressure blocking member for preventing a pressure change of the applied developer, and the developer Wherein said providing the developer powder pressure blocking member at the top of the braking member.
The developing device of the present invention is characterized in that the developer regulating member is a metal thin plate.
The developing device of the present invention is characterized in that the developer regulating member is a thin rubber plate.
In the developing device of the present invention, the position of the tip of the developer powder pressure blocking member is the same as the position of the tip of the developer regulating member, or the position of the tip of the developer powder pressure blocking member is the developer. The distance from the front end of the developer regulating member to the developer powder pressure blocking member is made short before the position of the front end of the regulating member.
The developing device of the present invention is characterized in that the tip of the developer powder pressure blocking member has a thin shape.
The developing device of the present invention is characterized in that the developer powder pressure blocking member is integrally formed with a case of the developer accommodating portion.
In addition, a process cartridge according to the present invention includes at least the developing device described above, and is detachable from the image forming apparatus.
Further, an image forming apparatus of the present invention includes at least the developing device described above.

  As described above, according to the developing device of the present invention, by providing the developer powder pressure blocking member that supports the self-weight pressure of the developer above the regulating member, the change in pressure applied to the regulating member is reduced, and the image It is possible to eliminate uneven developer coating on the carrier and prevent image unevenness. Further, by reducing the area of the developer's own pressure applied to the regulating member by making the distance from the leading end of the regulating member to the developer powder pressure blocking member the same or smaller, the pressure of the regulating member can be reduced, and the development The deterioration of the agent can be suppressed. Further, by thinning the tip of the developer powder pressure blocking member, it is possible to eliminate stagnation of the developer at the tip of the regulating member due to its own weight, suppress rapid deterioration of the retained developer, and eliminate image unevenness.

  The best mode for carrying out the present invention will be described below with reference to the drawings. Note that it is easy for a person skilled in the art to make other embodiments by changing or correcting the present invention within the scope of the claims, and these changes and modifications are included in the scope of the claims. The following description is an example of the best mode of the present invention, and does not limit the scope of the claims.

FIG. 1 shows an electrophotographic copying apparatus as an image forming apparatus used in an embodiment of the present invention. In FIG. 1, an image forming apparatus 1 includes an exposure unit 2, process cartridges 3Y, 3C, 3M, and 3Bk, a transfer device 4, a photosensitive drum 5, a charging roller 6, a developing roller 12Y, and the like. A transfer device 4 is disposed below each process cartridge 3Y, 3C, 3M, 3Bk. The transfer device 4 includes an intermediate transfer belt 19, primary transfer rollers 20Y, 20C, 20M, and 20Bk, a secondary transfer roller 21, and a transfer belt cleaning unit 22.
The exposure unit 2 exposes image information to the photosensitive drum 5 to form an electrostatic latent image. For the exposure means 2, a laser beam scanner using a laser diode, an LED, or the like is used. Below the exposure means 2, each process cartridge 3Y, 3C, 3M, 3Bk is arranged.
Each process cartridge 3Y, 3C, 3M, 3Bk has a non-magnetic one-component developer (hereinafter referred to as toner) color stored therein (yellow for 3Y, cyan for 3C, magenta for 3M, black for 3Bk). Except for the above, each is configured in the same manner, and is detachably attached to the main body of the image forming apparatus 1 by a stopper (not shown).
Four process cartridges 3 are arranged in parallel in the moving direction of the intermediate transfer belt 19 and form visible images in the order of yellow Y, cyan C, magenta M, and black Bk.

The intermediate transfer belt 19 is stretched around a drive roller 23 and driven rollers 24, 25, and 26, and is moved in the direction indicated by the arrow in FIG. 1 when the drive roller 23 is rotationally driven by a drive motor (not shown). Is done. The intermediate transfer belt 19 is disposed in such a manner that the surface thereof abuts against the surface of each of the photosensitive drums 5Y, 5C, 5M, and 5Bk.
Primary transfer rollers 20Y, 20C, 20M, and 20Bk are disposed at positions facing the respective photosensitive drums 5Y, 5C, 5M, and 5Bk via the intermediate transfer belt 19. The primary transfer rollers 20Y, 20C, 20M, and 20Bk are respectively connected to the photosensitive drums 5Y, 5C, 5M, and 5Bk.
The photosensitive drums 5Y, 5C are each supported by a predetermined primary transfer bias voltage applied to each primary transfer roller 20Y, 20C, 20M, 20Bk from a high voltage power source (not shown). , 5M, and 5Bk, the toner images formed on the surface of the intermediate transfer belt 19 are successively transferred onto the surface of the intermediate transfer belt 19 to form a full-color image.
The secondary transfer roller 21 is rotatably supported on the main body of the image forming apparatus 1 and is disposed in pressure contact with the drive roller 23. A predetermined secondary transfer bias voltage is applied to the secondary transfer roller 21 from a high voltage power source (not shown). As a result, the full-color image formed on the intermediate transfer belt 19 is transferred to the paper 27 as a transfer material fed toward the pressure contact portion between the secondary transfer roller 21 and the drive roller 23. The paper 27 to which the image has been transferred is fixed on the image transferred by a fixing device (not shown) and then discharged onto a predetermined paper discharge tray (not shown). Further, the toner that cannot be transferred onto the paper 27 by the secondary transfer roller 21 and remains on the intermediate transfer belt 19 is collected by the transfer belt cleaning means 22.

A developing device in which a developer powder pressure blocking member is provided above the developer regulating member, which is a characteristic part of the present invention, will be described below with reference to FIGS.
FIG. 2 is a cross-sectional view of a process cartridge including a developing device in which a developer powder pressure blocking member is provided above the developer regulating member. Each process cartridge 3 has a structure in which the photosensitive drum 5, the charging roller 6, the developing device 100, and the photosensitive member cleaning means 7 are integrally coupled. Each process cartridge 3 is configured to be detachably exchangeable with the image forming apparatus 1 by releasing the stopper.
The photosensitive drum 5 rotates in the arrow direction at a peripheral speed of 150 mm / sec.
The charging roller 6 is in pressure contact with the surface of the photosensitive drum 5 and is driven to rotate by the rotation of the photosensitive drum 5. A predetermined bias is applied to the charging roller 6 by a high voltage power source (not shown), and the surface of the photosensitive drum 5 is charged to −500V.
The photoconductor cleaning means 7 cleans the transfer residual toner on the surface of the photoconductor drum 5.
The developing device 100 is one-component contact development, and visualizes the electrostatic latent image on the photosensitive drum 5 as a toner image. A predetermined developing bias is supplied to the developing device 100 from a high voltage power source (not shown).

Next, the developing device of the present invention will be described in detail.
The developing device 100 includes a toner accommodating chamber 101 that is a developer accommodating portion, a developing roller 102 that is a developer carrying member, a developer regulating member 103 provided in contact with the developing roller 102, and a supply roller 104. The The developing device 100 of the present invention has a vertical structure in which the toner storage chamber 101 is disposed above the developing roller 102, and a developer powder pressure blocking member that supports the developer's own pressure above the developer regulating member 103. 109 is arranged.
The developing roller 102 is disposed in contact with the photosensitive drum 5 and is applied with a predetermined developing bias from a high voltage power source (not shown). In the present embodiment, the developing roller 102 is disposed in contact with the photosensitive drum 5, but may be disposed in a non-contact manner.
A toner agitation member 105 is provided in the toner storage chamber 101, and the stored toner flows by rotating in a counterclockwise direction to promote the drop in the direction of the supply roller 104. The surface of the supply roller 104 is covered with a foam material having a structure having pores (cells), so that the toner adhesion amount on the supply roller 104 is secured and the pressure is concentrated at the contact portion with the developing roller 102. Toner deterioration is prevented. In addition, a conductive material containing carbon fine particles is used as the foam material, and the electric resistance value is set to 10 ³ to 10 ¹³ Ω. A supply bias having a value offset in the same direction as the charging polarity of the toner with respect to the developing bias is applied to the supply roller 104. This supply bias acts in the direction in which the precharged toner is pressed against the developing roller 102 at the contact portion with the developing roller 102. The supply roller 104 rotates counterclockwise to apply and supply the toner adhered to the surface to the surface of the developing roller 102.
As the developing roller 102, a roller coated with an elastic rubber layer 106 is used, and a surface coat layer 107 made of a material that is easily charged to a polarity opposite to that of the toner is provided on the surface. The elastic rubber layer 106 is set to a hardness of 50 degrees or less according to JIS-A in order to keep the contact state with the photosensitive drum 5 uniform, and further has an electrical resistance of 10 ³ to 10 ¹⁰ Ω to act a developing bias. Set to resistance value. The surface roughness Ra is set to 0.2 to 2.0 μm, and a necessary amount of toner is held on the surface. The developing roller 102 rotates in the counterclockwise direction, and conveys the toner held on the surface to a position facing the developer regulating member 103 and the photosensitive drum 5.

  The developer regulating member 103 is made of a metal leaf spring material such as SUS or phosphor bronze, and the free end is brought into contact with the surface of the developing roller 102 with a pressing force of 10 to 70 N / m, and passes under the pressure. The toner is thinned and charged by triboelectric charging. Further, in order to assist frictional charging, the developer regulating member 103 is applied with a regulating bias having a value offset in the same direction as the toner charging polarity with respect to the developing bias.

The photosensitive drum 5 rotates in the clockwise direction. Therefore, the surface of the developing roller 102 moves in the same direction as the traveling direction of the photosensitive drum 5 at a position facing the photosensitive drum 5.
The thinned toner is conveyed to a position facing the photosensitive drum 5 by the rotation of the developing roller 102 and is formed by the developing bias applied to the developing roller 102 and the electrostatic latent image on the photosensitive drum 5. In accordance with the latent image electric field, it moves to the surface of the photosensitive drum 5 and is developed.
A seal seal 108 is provided in contact with the developing roller 102 at a portion where the toner remaining on the developing roller 102 without being developed on the photosensitive drum 5 returns to the toner containing chamber 101 again. It is sealed so as not to leak out of the developing device.

  By adopting such a configuration of the developing device, even if the developing device 100 is disposed above the photosensitive drum 5, the developer powder pressure is prevented without increasing the cost by complicated developer pressure control means. The member 109 can prevent a change in the pressure of the developer applied to the developer regulating member 103 and can eliminate unevenness of the developer on the developing roller 102.

Another object of the present invention is to reduce the pressure of the developer regulating member 103 against the developing roller 102 by reducing the area of the developer's own pressure applied to the developer regulating member 103. It is to suppress the deterioration of the developer and eliminate the occurrence of developer unevenness.
Therefore, in the developing device 100 of the present invention, the position of the tip of the developer powder pressure blocking member 109 is made the same as the position of the tip of the developer regulating member 103 or the position of the tip of the developer powder pressure blocking member 109 is developed. The distance from the front end of the developer regulating member 103 to the developer powder pressure blocking member 109 is made short before the position of the front end of the developer regulating member 103.

Table 1 shows the results of confirming the occurrence of streaky image unevenness and image unevenness by changing the conditions of the pressing force and the distance from the front end of the developer regulating member 103 to the front end of the developer powder pressure blocking member 109. The developer regulating member 103 was brought into contact with the surface of the developing roller 102 at the free end side with a pressing force of 12 N / m, 23 N / m, 53 N / m, and 106 N / m. As the distance from the leading end of the developer regulating member 103 to the developer powder pressure blocking member 109 becomes 6 mm, 3 mm, and 0 mm starting from the leading end of the developer regulating member 103, the occurrence of image unevenness is suppressed. However, when the tip of the developer powder pressure blocking member 109 exceeds the tip of the developer regulating member 103 by 2 mm, streaky image unevenness occurred.

  FIG. 3 shows an example in which the developer powder pressure blocking member is integrated with the case of the toner storage chamber. The developer powder pressure blocking member 109 can prevent a change in the pressure of the developer applied to the developer regulating member 103 without incurring an increase in cost with a simple configuration, and eliminate uneven developer on the developing roller 102. Can do.

FIG. 4 shows an example in which the tip of the developer powder pressure blocking member has a thin shape.
An object of the present invention is to cause image unevenness due to streaky developer coat unevenness on the developing roller 102 due to retention of the developer at the tip of the developer regulating member 103 caused by a decrease in developer fluidity in a high humidity environment. Is to prevent.
Therefore, the developing device 100 of the present invention eliminates the retention of the developer at the tip of the developer regulating member 103 by thinning the tip of the developer powder pressure blocking member 109 that supports the pressure due to the weight of the developer. The rapid deterioration of the staying developer was suppressed, and the occurrence of streaky image unevenness was prevented.

Table 2 shows the results of confirming the occurrence of streaky image unevenness after printing 10,000 sheets in a high temperature and high humidity environment of 30 ° C./80%.

1 is a schematic front view of an electrophotographic copying apparatus as an image forming apparatus employing an embodiment of the present invention. FIG. 4 is a cross-sectional view of a process cartridge including a developing device in which a developer powder pressure blocking member is provided on the developer regulating member. An example in which the developer powder pressure blocking member is configured integrally with the case of the toner storage chamber is shown. An example in which the tip of the developer powder pressure blocking member is made thin is shown.

Explanation of symbols

1 Image forming device (electrophotographic copying machine)
2 Exposure means 3Y, 3C, 3M, 3Bk Process cartridge 4 Transfer device 5Y, 5C, 5M, 5Bk Image carrier (photosensitive drum)
6Y, 6C, 6M, 6Bk Charging rollers 7Y, 7C, 7M, 7Bk Photoconductor cleaning means 8Y, 8C, 8M, 8Bk Developing devices 12Y, 12C, 12M, 12Bk Developer carrier (developing roller)
14Y, 14C, 14M, 14Bk Developer supply member (supply roller)
19 Intermediate transfer belts 20Y, 20C, 20M, 20Bk Primary transfer roller 21 Secondary transfer roller 22 Transfer belt cleaning means 23 Drive rollers 24, 25, 26 Followed roller 27 Paper 100 Developing device 101 Toner storage chamber (developer storage section)
102 Developing roller (developer carrier)
103 developer regulating member 104 supply roller (developer supply means)
105 Toner stirring member (developer stirring member)
106 Elastic rubber layer 107 Surface coating layer 108 Sealing seal 109 Developer powder pressure blocking member

Claims (8)

A developer carrying member rotatably provided to face the latent image carrying member;
A developer accommodating portion for accommodating the developer;
A developer supply means that is rotatably provided in contact with the developer carrier, and that supplies the developer onto the developer carrier;
A developer agitating member that is rotatably provided in the developer accommodating portion, agitates and circulates the developer in the developer accommodating portion, and supplies the developer onto the developer supplying means;
A developer regulating member provided in contact with the developer carrying member and regulating the developer supplied on the developer carrying member to a predetermined amount;
In the developing device in which the developer accommodating portion is disposed above the developer carrying member, and the contact portion between the developer containing portion and the developer regulating member is positioned almost directly above the developer carrying member.
The developing device includes a developer powder pressure blocking member that prevents a change in pressure of the developer applied to the developer regulating member, and the developer powder pressure blocking member is provided above the developer regulating member. A developing device. The developing device according to claim 1, wherein the developer regulating member is a metal thin plate. The developing device according to claim 1, wherein the developer regulating member is a thin rubber plate. In the developing device, the position of the tip of the developer powder pressure blocking member is the same as the position of the tip of the developer regulating member, or the position of the tip of the developer powder pressure blocking member is set to the tip of the developer regulating member. 4. The developing device according to claim 1, wherein a distance from a tip of the developer regulating member to the developer powder pressure blocking member is reduced before the position of the developing device. 5. The developing device according to claim 1, wherein a tip of the developer powder pressure blocking member has a thin shape. The developing device according to claim 1, wherein the developer powder pressure blocking member is configured integrally with a case of the developer accommodating portion. A process cartridge comprising at least the developing device according to claim 1, wherein the process cartridge is detachable from the image forming apparatus. An image forming apparatus comprising at least the developing device according to claim 1.

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