JP2002169375A - Developing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a developing device capable of preventing toner from being melted on a layer thickness regulating roller and a developing roller even in the case of using the toner whose melting point and glass transition temperature are low and capable of performing excellent development with little secular change as a developing device for forming a specified toner thin layer by bringing the layer thickness regulating roller into contact with the developing roller. SOLUTION: This device is provided with the developing roller to carry the toner while rotating in a specified direction, the layer thickness regulating roller to form the toner thin layer on the developing roller by rotating in a direction opposite to the rotating direction of the developing roller or in a forward direction, and a cooling means to cool the layer thickness regulating roller. Especially, the cooling means is constituted of a heat conduction member arranged to come into contact with the layer thickness regulating roller and a Peltier element arranged to cool the heat conduction member.

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 copying machine or a printer, and more particularly to a method for forming a uniform thin layer of toner on an elastic developing roller. And a developing device that develops an electrostatic latent image formed on the image carrier by bringing the electrostatic latent image into contact with the surface of the image carrier to visualize the image.

[0002]

2. Description of the Related Art Generally, an image forming apparatus of this type forms an electrostatic latent image on an image carrier such as an electrophotographic photosensitive member, and then develops the electrostatic latent image by providing a developer. Visualize. As the developer, a one-component developer composed of a single toner or a two-component developer composed of a toner and a carrier carrying the toner is mainly known, and various development systems suitable for them are developed and proposed. .

In particular, the performance of a one-component developer (hereinafter simply referred to as a toner or a one-component toner) has been remarkably developed. Toners having further improved performance as compared with toners produced by the conventional manufacturing method have been developed, and accordingly, use in actual machines has been rapidly expanding.

[0004] For example, as one of developing devices using non-magnetic one-component toner, a conductive or semiconductive elastic developing roller is used in contact with an image carrier, and a thin toner layer is formed on the surface of the developing roller. A contact-type developing device is known in which a toner is formed and then the toner is pressed against the surface of an image carrier to perform development.

[0005] In such an apparatus, forming a uniform thin layer of toner on the developing roller is one of the important conditions for good development, and therefore, various methods are required to form a uniform thin layer. Means have been proposed.

A device using a doctor blade is known as one of the typical ones. In this apparatus, the thickness of the toner passing between the blade and the developing roller is reduced by bringing the tip of the blade into pressure contact with or close to the peripheral surface of the developing roller to form a thin layer. Toner accumulation or sticking occurs at the leading end entrance side, and the pressure contact force of the blade and the gap between the blade and the developing roller change, which may hinder the formation of a uniform thin toner layer.

In view of this, there has been proposed an apparatus in which a layer thickness regulating roller is disposed in pressure contact with the surface of a developing roller instead of a blade to form a thin layer with toner passing between the rollers. In such an apparatus, the layer thickness regulating roller is rotated in a direction opposite to the rotation direction of the developing roller, or in a forward direction at a different speed, but considerably high temperature frictional heat is generated due to the contact between the layer thickness regulating roller and the developing roller. In some cases, this heat causes the toner to locally melt and fuse to the surface of the layer thickness regulating roller or the developing roller.

In particular, with the increase in process speed, 40
There is a tendency to use a toner having a low melting point such as ~ 80 ° C (for example, a polymerized toner using a low softening point substance) or a low glass transition temperature, but the frictional heat between the layer thickness regulating roller and the developing roller is locally increased. In some cases, the melting point or the glass transition temperature of the toner is low. Such fusing causes streaks and unevenness in the toner layer on the developing roller, thereby hindering good development.

Further, since the developing roller made of an elastic material such as rubber has a high coefficient of thermal expansion, its diameter is apt to change due to a change in ambient temperature, and the contact nip width between the image carrier and the developing roller depends on the temperature. And may adversely affect the formed image.

[0010]

SUMMARY OF THE INVENTION The present invention has been made in view of the above points, and has been developed in view of the fact that even when a toner having a low melting point and a low glass transition temperature is used, the toner is fused to the layer thickness regulating roller and the developing roller. It is an object of the present invention to provide a developing device capable of preventing adhesion and performing good development with little change over time.

[0011]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention provides a developing roller which rotates in a predetermined direction to carry toner, and a developing roller which rotates in a direction opposite to the rotating direction of the developing roller or in a forward direction. It is characterized by having a layer thickness regulating roller for forming a thin layer of toner on the roller, and cooling means for cooling the layer thickness regulating roller. Still further, in addition to the above, there is provided a scraping member for scraping off the toner attached to the layer thickness regulating roller.

In particular, the cooling means includes a heat conducting member arranged in contact with the layer thickness regulating roller, and a Peltier element arranged to cool the heat conducting member. Further, the heat conducting member is made of a metal member arranged to be in contact with the longitudinal direction of the layer thickness regulating roller. The Peltier element is provided with a plurality of heat dissipating fins directly or indirectly on its heat generating surface, and further provided with a blower for cooling the fins.

Preferably, the heat conducting member has a closed space therein, and a liquid or gas for promoting heat conduction is sealed in the space. The developing roller is, for example, an elastic roller, and the layer thickness regulating roller is a metal roller.

Still further, according to the present invention, there is provided a developing roller which rotates in a predetermined direction and supplies toner to an electrostatic latent image formed on the surface of an image carrier, and a developing roller at a position upstream of a toner supply position to the image carrier. A layer thickness regulating roller provided in contact with the developing roller and rotatable in a direction opposite to the rotating direction of the developing roller or in a forward direction, and a layer thickness regulating roller for regulating the toner on the developing roller to a thin layer; A scraping member provided in contact with the layer thickness regulating roller for scraping off toner adhered to the layer thickness regulating roller, and a heat transfer member provided in contact with the layer thickness regulating roller at a position upstream of the contact position with the developing roller. A Peltier element arranged directly or indirectly to cool the heat conduction member; a plurality of radiating fins provided directly or indirectly on a heat generating surface of the Peltier element; And having a blower for cooling the.

[0015]

Preferred embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a schematic configuration diagram of a developing device to which the present invention is applied. In the figure, reference numeral 1 denotes a drum-shaped image carrier which rotates in a direction indicated by an arrow A, that is, a clockwise direction, and has a configuration in which an electrophotographic photosensitive member is provided on a surface of a drum-shaped substrate such as aluminum. As such an electrophotographic photosensitive member, an organic photosensitive member or an amorphous silicon photosensitive member can be used.

Although not shown, an eraser lamp for erasing the residual charges on the image carrier 1 according to the rotation direction A of the image carrier 1 is provided around the image carrier 1, and an image after erasing the residual charges. A charging device for uniformly charging the surface of the carrier 1 to a specific polarity, forming an electrostatic latent image on the surface of the image carrier 1 by projecting digital light information on the surface of the uniformly charged image carrier 1 An exposure device such as an LED head, a developing device 2 that supplies a powder toner to the surface of the image carrier 1 on which the electrostatic latent image is formed, and converts the electrostatic latent image into a toner image; And a transfer device for transferring paper from a paper to a transfer material such as paper. The configuration of these devices around the image carrier is the developing device 2
Except for, a known configuration may be used.

The developing device 2 includes a developing container 3 containing a non-magnetic one-component toner manufactured by a polymerization method or a pulverization method.
An elastic developing roller 4 disposed in the developing container 3 so as to press a part of its peripheral surface against the surface of the image carrier; and provided in contact with the developing roller 4 behind the developing roller 4. A supply roller 6 for supplying the toner in the developing container 3 to the developing roller 4, and a thin layer of the toner adhering to the peripheral surface of the developing roller 4 which is disposed in contact with the developing roller 4 with an appropriate pressure. And a layer thickness regulating roller 7 to be formed. Although not shown, the developing roller 4, the supply roller 6, and the layer thickness regulating roller 5 are connected to an appropriate bias power source, and a bias voltage having an optimum value is applied to promote transfer of toner to each roller. Have been.

The developing roller 4 has a length substantially equal to the length of the image carrier 1, extends in a direction substantially parallel to the axis of the image carrier 1, and faces the image carrier 1 of the developing container 3. A portion of the peripheral surface is exposed from the opening 8 to the image carrier 1 side, and is provided so as to come into contact with the surface of the image carrier 1 with an appropriate nip width (contact width). The developing roller 4 rotates at substantially the same speed as the image carrier 1 in the forward direction (counterclockwise direction B) with the rotation of the image carrier 1.

The amount of toner contained in the developing container 3 is
For example, the amount is such that the head of the supply roller 6 is exposed, and a remaining amount sensor (not shown) provided on the rear wall of the developing container 3
Accordingly, the amount is constantly monitored, and when the amount becomes smaller than the predetermined amount, an instruction signal is issued to supply fresh toner from the toner cartridge 8.

The structure of the developing roller 4 will be described. The developing roller 4 has a conductive central shaft 11 to which a bias is applied.
, An elastic intermediate layer 12 is formed around the intermediate layer 12, and an elastic surface layer 13 is further formed on the outer periphery of the intermediate layer 12. Although not limited, for example, the intermediate layer 12 and the surface layer 13
Are made to have different electrical properties such that the intermediate layer 12 has a relatively high electrical resistance and the surface layer 13 has a relatively low electrical resistance. Further, the developing roller 4
Is not limited to the above-described two-layer structure, but may be a single-layer structure or a three- or more-layer structure. As a material of the developing roller 4, in addition to a single layer of silicon rubber, the intermediate layer 12 having a two-layer structure is made of a porous foam having elasticity such as NBR rubber (acrylonitrile butadiene copolymer rubber) or urethane rubber. May be an elastic body such as urethane rubber.

The supply roller 6 located behind the developing roller 4 is arranged so as to extend in parallel with the axis of the developing roller 4, and is in contact with the developing roller 4 over substantially the entire length. The supply roller 6 is made of, for example, a urethane rubber foam mixed with fine carbon powder, and is opposed to the rotation direction of the developing roller 4 while contacting the developing roller 4 with a predetermined pressure, that is, a counterclockwise direction. To supply the toner in the developing container 3 to the developing roller 4 and charge the toner on the developing roller 4 by frictional charging. Reference numeral 14 denotes a stirring blade that rotates clockwise to stir the toner in the developing container 3 and conveys the toner to the supply roller 6.

The toner supplied onto the developing roller 4 by the supply roller 6 is carried to the layer thickness regulating roller 7 as the developing roller 4 rotates. The layer thickness regulating roller 7 includes the developing roller 4
A roller made of a conductive or semi-conductive metal or the like having substantially the same length as that of a roller made of a metal or the like, or a roller made of such a metal or the like coated with a material having good toner release properties such as Teflon (registered trademark); or The roller has a configuration in which a suitable elastic outer layer is provided on the peripheral surface of the roller made of metal or the like. The layer thickness regulating roller 7 is positioned so as to contact the elastic developing roller 4 with an appropriate pressure over substantially the entire length in the axial direction, and at a suitable speed in a direction opposite to the rotation direction of the developing roller 4, that is, in a counterclockwise direction. It is provided to rotate. With such a configuration, when the toner on the developing roller 4 passes through the layer pressure regulating roller 7, only a part of the toner passes through the layer thickness regulating roller 7, whereby a uniform thin toner layer is formed. The layer thickness regulating roller 7 may rotate in the forward direction with respect to the rotation direction of the developing roller 4.

Reference numeral 16 denotes a removing blade serving as a toner scraping member disposed such that the leading end thereof comes into contact with or presses against the peripheral surface of the layer thickness regulating roller 7. This serves to scrape off excess toner adhered to the peripheral surface of the layer thickness regulating roller 7 from the layer thickness regulating roller 7.

The layer thickness regulating roller 7 is a very useful means for forming a thin layer of toner as described above.
The member 1 that is pressed against or scraped off against the developing roller 4
Since the pressure contact portions 6 are configured to be in pressure contact with each other, frictional heat is generated in the pressure contact portions or the rubbing portions. This heat locally melts the toner attached thereto because it becomes a considerably high temperature. This melting causes local fusion of the toner to the layer thickness regulating roller 7, the developing roller 4, or the scraping member 16, thereby preventing the formation of a uniform thin layer of the toner.

Reference numeral 20 denotes a cooling means for cooling the layer thickness regulating roller 7. The cooling means 20 basically includes a plate-shaped heat conducting member 21 arranged in contact with the peripheral surface of the layer thickness regulating roller 7, and a Peltier element 22 arranged to cool the heat conducting member 21. .

The heat conducting member 21 is used to transmit the cooling effect of the Peltier element 22 to the developing roller 4 in a favorable manner.
It is made of a material having good thermal conductivity such as metal, and generally includes a blade portion 21a and a case portion 21b.
As shown particularly in FIG. 2, the blade 21 a is provided so that its abdomen abuts or presses against the peripheral surface of the layer thickness regulating roller over substantially the entire length of the layer thickness regulating roller 7 in the longitudinal direction. The case portion 21b is provided substantially in close contact with the blade portion 21b at a position above the blade portion 21b. The case portion 21b extends so as to be in contact with almost the entire length of the blade portion 21a, and has a closed space 21c therein, and a liquid for promoting heat conduction (thermal cooling) is provided in the space 21c. Alternatively, a gas such as water is sealed.

On the side of the heat transfer member 21 opposite to the case portion 21b of the blade portion 21a, a Peltier element 22 constituting a cooling source is provided with an adhesive or the like such that its cooling surface is in close contact with the surface of the blade portion 21a. It is glued. The Peltier device 22 has a well-known structure in which two different types of P-type and N-type semiconductors are joined together by metal electrodes and a plurality of the semiconductors are sandwiched between ceramics. This causes a physical phenomenon in which the other side warms. For convenience, the side from which such heat is deprived is called the "cooling surface" and the side that gets warm is called the "heat generating surface".
That. Thereby, when the Peltier device 22 operates,
Due to the cooling effect, the blade portion 21a abutting on the cooling effect
Is cooled by the action of the liquid or gas in the case portion 21b and the blade portion 21a is cooled.
The layer thickness regulating roller 7 which is transmitted to the front end side and is in contact therewith is cooled from the peripheral surface side.

A plurality of radiating fins 23 are provided directly or indirectly on the heat generating surface of the Peltier element 22 on the side opposite to the cooling surface to assist heat radiation of the heat generating surface of the Peltier element. A duct 25 is provided so as to surround the radiating fins 23, and a fan such as a fan blows warm air in the duct 25 out of the machine from one open end of the duct 25 so that the radiating fins 23 are positively propelled. Is preferably cooled.

[0029]

As described above, according to the present invention, in a developing apparatus for forming a thin layer of toner on a developing roller using a layer thickness regulating roller, a toner is applied to a layer thickness regulating roller, a developing roller or a toner scraping member. Can be prevented, and a good toner thin layer can be continuously formed. In particular, by using a Peltier element as the cooling means, it is possible to suitably reduce the size of the apparatus.

[Brief description of the drawings]

FIG. 1 is a schematic side sectional view of a developing device according to the present invention.

FIG. 2 is a cross-sectional perspective view of the developing device according to the present invention with a part thereof omitted;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Image carrier 2 Developing device 4 Developing roller 7 Layer thickness regulating roller 20 Cooling means 21 Heat conduction member 22 Peltier element

Claims (9)

[Claims] A developing roller that rotates in a predetermined direction to convey toner; and a layer thickness regulating roller that forms a thin layer of toner on the developing roller by rotating in a direction opposite to the rotating direction of the developing roller or in a forward direction. And a cooling means for cooling the layer thickness regulating roller. 2. A developing roller which rotates in a predetermined direction to carry toner, and a layer thickness regulating roller which rotates in a direction opposite to the rotating direction of the developing roller or in a forward direction to form a thin layer of toner on the developing roller. A developing unit, comprising: a removing unit that removes toner attached to the layer thickness regulating roller; and a cooling unit that cools the layer thickness regulating roller. 3. The cooling device according to claim 1, wherein the cooling means is a heat conducting member arranged in contact with the layer thickness regulating roller, and a Peltier element arranged to cool the heat conducting member. 3. The developing device according to 2. 4. The developing device according to claim 3, wherein the heat conductive member is a metal member arranged so as to contact the layer thickness regulating roller over substantially the entire length of the layer thickness regulating roller in the longitudinal direction. 5. The heat conduction member according to claim 3, wherein the heat conduction member has a closed internal space, and a liquid or a gas for promoting heat conduction is sealed in the internal space. Developing device. 6. The developing roller is an elastic roller,
The developing device according to claim 1, wherein the layer thickness regulating roller is a rigid roller. 7. The Peltier device is arranged such that a cooling surface thereof is in contact with the heat conductive member, and a plurality of heat radiation fins are provided directly or indirectly on a heat generation surface of the Peltier device. The developing device according to claim 2, further comprising a blower for cooling the fin. 8. A developing roller which rotates in a predetermined direction and supplies toner to an electrostatic latent image formed on the surface of the image carrier, and comes into contact with the developing roller at a position upstream of a toner supply position to the image carrier. A layer thickness regulating roller provided rotatably in a direction opposite to the rotation direction of the developing roller or in a forward direction to regulate the toner on the developing roller to a thin layer; and a layer thickness regulating roller at a downstream position of a contact position with the developing roller. A scraping member provided to contact the layer thickness regulating roller and scraping off toner adhered to the layer thickness regulating roller; a heat conducting member arranged in contact with the layer thickness regulating roller at a position upstream of a contact position with the developing roller; A Peltier element directly or indirectly arranged to cool the member, a plurality of radiating fins provided directly or indirectly on the heat generating surface of the Peltier element, and a feeder for cooling the radiating fin. A developing device comprising a blower. 9. The device according to claim 8, wherein the member is made of a metal member having a space closed inside, and a liquid or gas for promoting heat conduction is sealed in the space. Developing device.