KR20040005148A - apparatus for maintaining a developing gap in a developing device - Google Patents

Abstract

PURPOSE: An apparatus for maintaining a developing gap of a developing device is provided to stably obtain good toner images and improve the durability of an image forming system. CONSTITUTION: An apparatus for maintaining a developing gap of a developing device includes a developing gap determining member(130) and a spacer(120). The developing gap determining member is set at both sides of a photoconductive drum(104) of an image forming system. At least a part of the developing gap determining member has a diameter larger than the diameter of the photoconductive drum by a predetermined developing gap. The spacer is placed at both sides of a developing roller(105) of the image forming system and rotated being engaged with the part of the developing gap determining member. The diameter of the spacer is identical to the diameter of the developing roller. The spacer is integrated with the developing roller. The developing gap determining member is formed of a nonconductive material.

Description

Apparatus for maintaining a developing gap in a developing device}

The present invention relates to a developing apparatus for developing an electrostatic latent image formed on a consultation body (hereinafter referred to as a photosensitive drum), such as a photosensitive drum, used in an office apparatus using an electrophotographic method such as a laser beam printer, a facsimile, a digital copying machine, or the like as a toner image. More particularly, the present invention relates to a developing gap holding device of a developing machine which maintains a constant and stable interval between a developer conveying body such as a developing roller (hereinafter referred to as a developing roller) and a photosensitive drum.

In general, an image forming apparatus using an electrophotographic method such as a laser beam printer, an LED printer, a facsimile, a digital copier, or the like is used to print an image signal according to a digital signal input from a computer or a scanner to a paper, which is a printing medium, through a series of image forming processes. Performs the function of printing in the form of a visible image.

In this printing process, the developing device constituting the image forming apparatus receives a digital image signal as an optical signal, forms an electrostatic latent image on the photosensitive drum, and uses a toner of a predetermined color on the electrostatic latent image formed on the photosensitive drum. The developer thus formed is attached and developed into a toner image. The developed toner image is transferred to a printing paper, fixed, and discharged to the outside of the image forming apparatus.

Referring to FIG. 1, a general image forming apparatus 1 performing an image forming process for printing as described above is schematically illustrated.

The image forming apparatus 1 includes a paper feeder unit 10 on which paper is loaded, a conveyer unit (not shown) for transferring paper from the paper feeder unit 10, and a laser scanning unit for forming an electrostatic latent image on the photosensitive drum. (Laser scanning unit: LSU) 40, a developing device unit 30 for supplying a developer to an electrostatic latent image formed on the photosensitive drum to develop a toner image and then forming a toner image on the paper conveyed by the transfer device unit, And a fixing device unit (not shown) for fixing the toner image formed on the paper with a constant heat and pressure, and a discharge device unit 50 for discharging the paper on which the toner image is fixed.

The developing unit 30 has an electrical characteristic on the surface of the photosensitive drum 4 while rotating in engagement with the photosensitive drum 4 and the photosensitive drum 4 which form an electrostatic latent image by the LSU 40 using the potential characteristics of the surface. A developing roller for attaching a developer 8 made of toner of a predetermined color to an electrostatic latent image formed on the photosensitive drum 4 so that the charging roller 2 and the photosensitive drum 4 rotate to face each other while forming a visible image. (5), the developer feeding roller 6, which is rotated in engagement with the developing roller 5, and supplies the developer 8 to the developing roller 5, and transfers the developer 8 to the developer supply roller 6; The remaining developer 8 remaining on the surface of the developer supply bar 12, the developer layer regulating member 7 for controlling the developer layer formation of the developing roller 5, and the photosensitive drum 4 after one cycle of rotation. ) And a cleaner 11 having a cleaning blade 16 for removing.

Referring to the operation of the image forming apparatus 1 configured as described above, first, the surface of the photosensitive drum 4 is uniformly charged with a constant voltage through the charging roller 2 by the controller.

Thereafter, the LSU 40 converts the digital signal inputted from the computer or the scanner into the optical signal 3 in the form of a laser beam through a laser diode and scans the photosensitive drum 4, thus, the photosensitive drum 3 The latent electrostatic image is formed on the surface.

On the other hand, the developer (8) is supplied to the developer supply roller (6) by the developer supply bar (12), moves to the developer roller (5), and is adsorbed.

The developer 8 adsorbed on the surface of the developing roller 5 is conveyed to the developing gap g formed by the photosensitive drum 4 and the developing roller 5 as the developing roller 5 rotates (Fig. 2A). . At this time, the developer 8 is held as a toner layer having a constant thickness on the surface of the developing roller 5 by the developer layer regulating member 7 provided above the developing roller 5.

Then, as the photosensitive drum 4 rotates, the developer 8 moves to the surface of the photosensitive drum 4 by the potential difference between the electrostatic latent image on the photosensitive drum 4 and the surface of the developing roller 5. The latent latent image formed on the surface of the photosensitive drum 4 is developed as a toner image in the form of a visible image.

On the other hand, when the paper 13 conveyed by the conveying device section enters between the photosensitive drum 4 on which the toner image is formed and the transfer roller 9 disposed below, the transfer roller 9 is attached to the photosensitive drum 4. The attached toner image is transferred onto the sheet 13.

Thereafter, the photosensitive drum 4 continues to rotate, and the cleaning blade 16 removes the developer 8 remaining on the surface of the photosensitive drum 4 so that the photosensitive drum 4 again forms an electrostatic latent image. To be able. At this time, the paper 13 on which the image has been transferred is fixed by a fixing device unit for fixing the toner image with heat and pressure, and then discharged out of the machine by the discharge device unit 50, and a series of printing processes are completed.

However, such an image forming apparatus 1 attaches the developer 8 to the electrostatic latent image of the photosensitive drum 4 so as to maintain the development quality uniformly and stably in the process of developing the toner image. It is important to maintain a constant developing gap g between and the developing roller 5.

To this end, as shown in FIG. 2A, the image forming apparatus 1 is a developing gap holding device, and has an outer diameter larger than the outer diameter of the developing roller 5 at a both ends of the developing roller 5 by a predetermined developing gap g. A spacer 20 made of plastic material is provided. At this time, the spacer 20 is in contact with the photosensitive layer 4a of the photosensitive drum 4 at a constant pressure so that the developing roller 5 and the photosensitive drum 4 always maintain a constant developing gap g without shaking. Doing.

However, when the spacer 20 is in contact with the photosensitive layer 4a of the photosensitive drum 4 at a constant pressure in this manner, the spacer 20 is exposed to the photosensitive drum when the spacer 20 and the photosensitive drum 4 rotate together. It is easy to wear or damage the photosensitive layer 4a of (4), which causes a problem that the photosensitive layer 4a is peeled off. This phenomenon occurs more severely when the peripheral speed of the developing roller 5 is faster than the peripheral speed of the photosensitive drum 4 in order to increase the image density. When the photosensitive layer 4a is peeled off in this way, the developing gap g formed between the developing roller 5 and the photosensitive drum 4 during driving becomes non-uniform, thereby causing image defects such as image stains. .

In order to prevent such a problem, US Patent No. 5,610,690 discloses that the photosensitive layer 4a in contact with the spacer 20 contains a lubricating resin powder containing fluorine atoms in order to increase the lubricity and wear resistance of the photosensitive layer 4a. Although the method has been proposed, this method has a problem in that the problem that the photosensitive layer 4a is peeled off during long-term repeated contact between the spacer 20 and the photosensitive layer 4a cannot be completely prevented.

Alternatively, as shown in FIG. 2B, a method of forming a non-photosensitive layer 4b separated from the photosensitive layer 4a 'on the photosensitive drum 4' and contacting the spacer 20 'with it is considered. As can be seen, this method is difficult to clean even if the developer 8 adheres to and accumulates by the electrostatic force on the non-photosensitive layer 4b located at the same height as the photosensitive layer 4a '. Image defects are likely to occur in the portion of the photosensitive layer 4a '. In addition, there is a problem in that the manufacturing cost is increased by adding a step of peeling a part of the photosensitive layer 4a 'to form the non-photosensitive layer 4b when the photosensitive drum 4' is manufactured.

The present invention has been made to solve the above problems, the object of the present invention is not only easy to manufacture at low cost, but also to improve the durability and excellent toner without problems such as peeling off due to damage of the photosensitive layer of the photosensitive drum The present invention provides a developing gap holding device of a developing device capable of stably obtaining an image.

1 is a schematic diagram of a general image forming apparatus.

2A and 2B are front and perspective views illustrating examples of a developing gap holding device of a conventional image forming apparatus.

3 is an exploded front view of a developing gap holding device of a developing device according to a preferred embodiment of the present invention;

4 is a front view of the developing gap holding device shown in FIG.

* Description of the symbols for the main parts of the drawings *

1: Image forming apparatus 4, 4 ', 104: Photosensitive drum

5, 105: developing roller 10: paper feeding unit

20, 20 ', 120: spacer 30: developing unit

40: laser scanning unit 50: ejection unit

100: developing gap holding device 130: developing gap determining member

132: fixed part 134: developing gap determination part

136: support

In order to solve the above problems, the present invention provides a visual contact image by attaching a developer to an electrostatic latent image formed on the counseling member while rotating against the counseling member to form an electrostatic latent image using the potential characteristics of the surface, and the counseling member. A developing apparatus comprising a developer conveying member, wherein the developing gap determining member is provided at both ends of the counseling member, and has a developing gap determining member having an outer diameter at least partially larger than the outer diameter of the counseling member. Provided is a developing gap holding device for a developing device including a spacer installed at both ends of the developer conveying member so as to rotate in engagement with a portion thereof.

In a preferred embodiment, the outer diameter of the spacer is the same as the outer diameter of the developer carrier. Optionally, the developer carrier and the spacer may be integrally formed. In this case, the developer carrier and the spacer are preferably made of rubber.

In addition, the developing gap determining member is preferably made of a non-conductive material.

Hereinafter, the developing gap holding device of the developing device according to the preferred embodiment of the present invention will be described in detail with reference to the accompanying drawings.

Referring to FIG. 3, there is illustrated a developing gap maintaining apparatus 100 of the present invention applied to the developing apparatus 30 of the general image forming apparatus 1 as shown in FIG.

The developing gap holding device 100 of the present invention includes a developing gap determining member 130 provided at both ends of the photosensitive drum 104 and provided with a developing gap g (FIG. 4), and a developing gap determining member 130. And spacers 120 provided at both ends of the developing roller 105 so as to rotate in engagement with each other.

The developing gap determining member 130 is provided with a fixing portion 132 and a developing gap g configured to have an outer diameter approximately the same as the inner diameter of the photosensitive drum 104 so as to be tightly fitted inside the photosensitive drum 104. The developing gap determining unit 134 having an outer diameter larger than the outer diameter of the photosensitive drum 104 by a predetermined development gap g, and the spacer 120 when the photosensitive drum 104 is combined with the developing roller 105. It consists of two flanges each consisting of support parts 136 supporting from the side. Each flange is forcibly fitted to both ends of the photosensitive drum 104 via the fixing portion 132.

The flange is preferably formed of a non-conductive plastic material such as polycarbonate (PC), polyacetal (POM) or the like.

In addition, the photosensitive drum 104 is composed of a metal pipe such as aluminum and a photosensitive layer 104a coated on the outer surface of the metal tube to a thickness of 10-30 μm.

The spacer 120 is engaged with the developing gap determining unit 134 of the developing gap determining member 130 attached to both ends of the photosensitive drum 104 when the photosensitive drum 104 and the developing roller 105 rotate to face each other. It consists of two small rollers fitted to the developing roller shaft 122 separately from the developing roller 105 at both ends of the developing roller 105 so as to rotate while forming a constant developing gap g. Each small roller has the same outer diameter as that of the developing roller 105.

In addition, the small roller constituting the spacer 120 is formed of a metal, a plastic having excellent wear resistance, or rubber. At this time, the developing roller 105 may be made of a metal such as aluminum, or rubber having an elastic force.

Optionally, the developing roller 105 and the spacer 120 may be integrally formed without forming each other separately. In this case, the developing roller 105 and the spacer 120 are preferably made of rubber.

As described above, the developing gap maintaining apparatus 100 of the present invention includes a developing gap determining member 130 in which a developing gap g between the developing roller 105 and the photosensitive drum 104 is coupled to both ends of the photosensitive drum 104. Is determined by the size of the outer diameter of the developing gap determining unit 134. That is, the developing gap determining member 130 increases the outer diameter of the developing gap determining unit 134 by the developing gap g than the outer diameter of the photosensitive drum 104 including the photosensitive layer 104a, thereby developing the developing roller 105. The constant developing gap g is maintained by making contact with the spacers 120 provided at both ends of the substrate at a constant pressure.

Therefore, even if the photosensitive drum 104 manufactured by a general manufacturing process in which the photosensitive layer 104a is not peeled off at both ends of the photosensitive drum 104 is used, the spacer 120 is formed in the developing gap (as in the conventional developing gap holding device). g) By not contacting the photosensitive drum 104 for maintenance, the problem that the photosensitive layer 104a is damaged and peeled off can be prevented.

In addition, since the material of the developing gap determining member 130 in contact with the spacer 120 is non-conductive, the developer may be prevented from adhering to the developer due to electrostatic force, thereby preventing an image defect due to contamination of the spacer 120. You can prevent it.

In addition, when the developer amount per unit area (M / A) formed in the developing roller 105 is 0.6 mg / cm 3 or more, and a rubber roller is used as the developing roller 105, the development roller 105 and the photosensitive drum 104 are formed. The line speed ratio may be 1: 1, and the spacer 120 may be integrally formed without the need for forming the developing roller 105 separately. Therefore, when the developing roller 105 rotates to face the photosensitive drum 104 with each other, it is possible to prevent the problem that the developing gap g remains unstable according to the mechanical dimensional accuracy of the spacer 120.

The operation of the developing gap maintaining apparatus 100 and the image forming apparatus employing the same according to the present invention configured as described above are the same as those described with reference to FIG.

As described above, the developing gap holding device of the developing device of the present invention can be easily manufactured at low cost as well as to increase durability by using a developing gap determining flange that can be easily coupled to the photosensitive drum. It provides an effect of stably obtaining an excellent toner image without problems such as peeling off due to damage to the photosensitive layer.

In addition, when the developing roller is formed of rubber integrally with the spacer, when the developing roller rotates opposite to the photosensitive drum, the developing gap is unstable according to the mechanical dimensional accuracy of the spacer, thereby preventing stable image density. You can get it.

In the above, specific preferred embodiments of the present invention have been illustrated and described. However, the present invention is not limited to the above-described embodiments, and various modifications and variations can be made by any person having ordinary skill in the art without departing from the gist of the present invention as claimed in the claims. It will be possible.

Claims (5)

A counseling member for forming an electrostatic latent image using a potential characteristic of the surface, and a developer conveying member for attaching a developer to the electrostatic latent image formed on the counseling member while rotating against the counseling member to form a visible image; In the developing device of the electrophotographic image forming apparatus, A developing gap determining member installed at both ends of the counseling member, the developing gap determining member having an outer diameter at least partially larger than the outer diameter of the counseling member; And And a spacer provided at both ends of the developer conveying member so as to rotate in engagement with the portion of the developing gap determining member. The developing gap holding apparatus of the developing device according to claim 1, wherein an outer diameter of the spacer is the same as an outer diameter of the developer carrier. The apparatus of claim 2, wherein the spacer is integrally formed with the developer carrier. The developing gap holding device of the developing device according to claim 3, wherein the developer conveying member and the spacer are made of rubber. 6. The developing gap holding device of a developing device according to claim 2 or 5, wherein said developing gap determining member is made of a non-conductive material.