JPH04240880A - Developing roll in image forming device - Google Patents

Abstract

PURPOSE:To prevent the fault in picture quality even if a distance DRS between a developing roll and a photosensitive drum is made narrow and to securely achieve a miniaturized, high-speed device by employing a small-sized sleeve with grooves. CONSTITUTION:The cross section of the groove 1006a of the sleeve 1006 is almost a rectangular shape, and the following inequalities are set: (1) 2L1>=L2 and 0.7mm<=L2<=1.2mm and (2) (3/4)D2<=D1, where L1 is the width of a groove 1006a, L2 is a distance between the outer periphery of the sleeve 1006 in two adjacent grooves 1006a and the outer periphery of the photosensitive drum 51, D1 is a distance between the outer periphery of the sleeve 1006 and that of the photosensitive drum 51, (that is, DRS), and D2 is a distance between the bottom of the groove 1006a and the outer periphery of the photosensitive drum 51. Thus, the amount that developer is carried is made constant and stable irrespective of the groove 1006a.

Description

[Detailed description of the invention]

0001

[Field of Industrial Application] The present invention relates to a developing roll in a developing machine for conveying and supplying a developer to visualize an electrostatic image on a latent image carrier, and in particular to a mag roll and the outer periphery of the mag roll. The present invention relates to a magnetic developing roll, which is rotatably disposed on a sleeve and has an axial groove formed therein.

0002

2. Description of the Related Art In a copying machine, an image is formed as an electrostatic image on a latent image carrier, and this electrostatic image is made visible by a developing machine. In that case, a toner is generally used to create a visible image in a developing machine. Conventionally, such a developing machine is equipped with a magnetic developing roll consisting of a mag roll and a sleeve rotatably disposed around the outer periphery of the mag roll and having grooves formed in the axial direction. , a two-component developer consisting of toner and a magnetic carrier is attracted onto the sleeve by the magnetism of the mag roll, and this developer is conveyed to the developing main pole of the developing roll facing the photoreceptor. The toner is applied to the photosensitive drum from the pole. In that case, conventionally, the distance DRS between the developing roll and the photosensitive drum has been set to around 1.0 mm even in the case of a narrow setting.

0003

[Problems to be Solved by the Invention] In recent years, various image forming apparatuses such as copying machines have been designed to handle large amounts of information quickly with a small installation space. There is a growing demand for smaller size and faster speed. Therefore, it is desirable for the developing machine to be as compact as possible and to have high developing performance, and for this reason, efforts are being made to further narrow the distance DRS between the developing roll and the photosensitive drum to around 0.5 mm. ing.

However, when a conventional grooved sleeve is used, groove marks appear on the developed image, resulting in image quality defects. The present invention was made in view of such problems, and its purpose is to prevent image quality defects even if the distance DRS between the developing roll and the photosensitive drum is narrowed by using a small grooved sleeve. It is an object of the present invention to provide a developing roll for an image forming apparatus that can reliably cope with the increase in size and speed without causing problems.

[0005]

[Means for Solving the Problems and Their Effects] In order to solve the above-mentioned problems, the developing roll of the present invention includes a magnetic roll, a magnetic roll that covers the outer periphery of the magnetic roll and is rotatably provided, and a plurality of developing rolls arranged in the groove direction. consisting of a sleeve with a groove formed therein, sleeve outer diameter ≦35mm, sleeve thickness≦1.0mm
, process speed≧200 mm/sec, and speed ratio≧1.2. Furthermore, the groove width is L1, the distance between two adjacent grooves is L2, and the distance between the outer peripheral surface of the sleeve and the outer peripheral surface of the photosensitive drum between the two adjacent grooves is D1.
And when the distance between the bottom of the groove and the outer peripheral surface of the photosensitive drum is D2, the groove of the sleeve should be (1) 2L1≧L2 and 0.7mm≦L2≦1.2mm.
(2) (3/4) D2≦D1 is set. By setting in this way, the conveyance amount of the developer becomes almost constant and stable regardless of the groove, groove marks do not appear on the developed image, and the image quality becomes good. In other words, the developing machine has high developing performance, and can be made smaller and faster.

[0006]

Embodiments Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a schematic sectional view of a color copying machine to which an embodiment of the present invention is applied. As shown in FIG. 1, the color copying machine 1 includes a main body 2, a platen 3 provided on the top side of the main body 2 and on which an original (not shown) is placed, and a platen 3 provided below the platen 3 for placing the original. An image information reading section 4 that reads image information, an image forming device 5 that receives signals from the image information reading section 4 and forms a predetermined image, and an image formed on the image forming device 5 that is a transfer medium. paper 6
a transfer unit 7 that transfers the toner image to the paper 6; a paper supply unit 8 and a paper transport unit 9 that supply and transport the paper 6; a fixing device 10 that fixes the toner image transferred to the paper 6 by the image forming device 5;
It is comprised of a discharge tray 11 that receives paper 6 on which a toner image is fixed.

The image forming apparatus 5 includes a photosensitive drum 51 and a first developing means 5 disposed adjacent to the photosensitive drum 51.
2 and a second developing means 53. First developing means 5
2 is a developing device having a two-component developer for color;
Further, the second developing means 53 is a developing device having a black two-component developer. Both of these developing means 52 and 53 are moved in directions toward and away from the photosensitive drum 51 by retract mechanisms (not shown) disposed corresponding to the respective developing means.

As shown in FIG. 2, the second developing means 53 develops the second latent image formed on the photosensitive drum 51, and broadly speaking, the second developing means 53 is an opening provided at one end of the housing 1001. A developing roll 1002 (developer carrier) having a part of its outer peripheral surface exposed outside the housing 1001 , a developer stirring means 1003 disposed inside the housing 1001 on the back side of the developing roll 1002 , and a developing roll 100 .
The trimmer plate 1004 (hereinafter also referred to as a trimmer) is attached to the top plate of the housing 1001 above the developing roller 1002 and regulates the height of the magnetic brush of the developer formed on the developing roll 1002. Developing roll 1
Tracking rolls (not shown) are rotatably provided on the outside of both ends of 002, and when this tracking roll comes into contact with the photosensitive drum 51, the developing roll 10
02 and the photosensitive drum 51 is maintained.

On the other hand, the stirring means 1003
The first auger 10 is arranged in the same axial direction as 002.
07 and a second auger 1008, and a partition plate 1009 erected on the housing 1001 to separate these two augers. 1st auger 1007
The rotating directions of the second auger 1008 and the second auger 1008 are determined so that the developer conveying directions are opposite to each other. Further, at both ends of the partition plate 1009, there is a region where the first auger 1007 is arranged (hereinafter referred to as a first stirring path 1010) and a region where the second auger 1007 is disposed.
008 (hereinafter referred to as the second stirring path 1011) is provided, so that the flow of the first stirring path 1010→second stirring path 1011→first stirring path 1010 is provided. The developer is circulated.

Furthermore, a developing roll 1002 and stirring means 10
03, there are a plurality of blades 1012a parallel to the axial direction.
A paddle wheel 1012 is provided. As the paddle wheel 1012 rotates, the developing roll 1
A means 100 for forcibly stirring the developer peeled off from 002
3, the developer is mixed and agitated by a stirring means 1003 and is continuously supplied to a developing roll 1002. A toner supply device 1020 is disposed above the first auger 1007 in the housing 1001 . New toner is supplied from this toner supply device 1020, and this toner is stirred with carrier by stirring means 1003 to form a developer.

As shown in FIGS. 2 and 3, the developing roll 1
002 is a device in which a cylindrical sleeve 1006 made of aluminum is disposed and is rotatable concentrically so as to cover the outer circumference of a fixedly supported substantially cylindrical magnetic member (also referred to as a mag roll) 1005. 1005
A magnetic brush of developer is formed on the sleeve 1006 by the magnetic force, and as the sleeve 1006 rotates, the magnetic brush is transported to a developing area facing the photosensitive drum 51. Photosensitive drum 51 and developing roll 100
The distance DRS between 2 and 2 is set as described later. The sleeve 1006 to which the present invention is directed has an outer diameter of 35 mm or less and a thickness of 1.0 mm or less. Further, the process speed of the developing machine is 200 mm/sec or more, and the speed ratio of the circumferential speed of the sleeve 1006 to the process speed is 1.2 or more.

The mag roll 1005 includes a peeling pole N1 for peeling off (picking off) the developer on the sleeve 1006 after development is completed, and a peeling pole N1 for picking up new developer.
an adsorption pole N2 for transporting the developer adsorbed onto the sleeve 1006; transport poles S3 and N3 for transporting the developer adsorbed onto the sleeve 1006; and a main development pole S1 for supplying toner of the transported developer toward the photosensitive drum 51. A plurality of magnetic poles of S2 are provided in this order counterclockwise.

In the developing roll 1002 of the present embodiment having such a magnetic pole arrangement, magnetic poles of different magnetic properties are alternately arranged in a sequence of attraction pole N2→transport pole S3→transport pole N.
The developer is held on the surface of the sleeve 1006 between 3 → main developing poles S1 and S2 → attraction pole N1, while the developer is held on the sleeve 1006 between stripping pole N1 and attraction pole N2 where magnetic poles of the same magnetic properties are arranged adjacently. It is designed to be peeled off from 1006.

By the way, as is clear from FIG. 3, the sleeve 1006 of the developing roll 1002 has a large number of axial grooves 1006a formed at equal intervals on its outer peripheral surface. As shown in FIG. 4, these grooves 1006a have a substantially rectangular cross section, and the width of the grooves 1006a is L1, which is the distance between the outer circumference of the sleeve 1006 and the outer circumference of the photosensitive drum 51 between two adjacent grooves 1006a. L2 is the distance between the outer peripheral surface of the sleeve 1006 and the outer peripheral surface of the photosensitive drum 51, D1 (that is, DRS) is the distance between the bottom of the groove 1006a and the outer peripheral surface of the photosensitive drum 51. Assuming D2, (1) 2L1≧L2 and 0.7mm≦L2≦1.2mm
(2) (3/4) D2≦D1 is set.

In this way, the groove 1006 of the sleeve 1006
By setting a and DRS, the conveyance amount of the developer becomes almost constant and stable, almost regardless of the groove 1006a. As a result, groove marks no longer appear on the developed image, resulting in improved image quality and the developing machine having high developing performance. Therefore, the developing machine can be made even smaller and faster.

[0016] To explain the reason for this setting, tests have shown that, for example, when L2 = 1.0 mm,
A relationship as shown in FIG. 5 was obtained between L1 and the developer conveyance amount. As is clear from Figure 5, L1 is 0.5m
It can be seen that when the amount is equal to or more than m, the amount of developer conveyed is almost at its maximum and stable. Therefore, by setting 2L1≧L2, a stable developer conveyance amount can be achieved.

Further, as a result of the test, the relationship between L2, developer conveyance amount, and sleeve deflection was as shown in FIG. 6. As is clear from FIG. 6, the stable state in which the amount of developer conveyed is approximately the maximum and the swing of the sleeve 1006 is small is when L2 is between 0.7 mm and 1.2 mm. Therefore, 0.7mm≦L
By setting 2≦1.2 mm, it is possible to maintain a stable developer conveyance amount and to reduce the swing of the sleeve 1006.

Furthermore, the relationship between D1 and the groove mark grade was as shown in FIG. 7 as a result of a test when D2 was 1.0 mm. The term "groove mark" as used herein refers to a groove mark that appears on a copy, especially a groove mark that appears on a slid. As is clear from Fig. 7, the groove mark grade is within the permissible range up to G1, that is, D
It can be seen that when 1=0.75 mm or more, the groove mark hardly appears. Therefore, (3/4)D2≦D
By setting it to 1, the influence of the groove can be eliminated.

Although the above-mentioned embodiment describes the case where the present invention is applied to a color copying machine, the present invention can also be applied to a developing roll of a developing machine in a black-and-white copying machine or other image forming apparatuses. can do. Further, in the above embodiment, the main developing pole is composed of two magnetic poles S1 and S2 of the same polarity, but the present invention can also be applied to a developing roll in which the main developing pole is composed of one magnetic pole S1. Needless to say.

[0020]

As is clear from the above explanation, according to the present invention, the amount of developer conveyed can be kept almost constant and stable, almost regardless of the groove of the sleeve.
Groove marks no longer appear on the developed image, resulting in good image quality. In other words, the developing machine has high developing performance, and can be made smaller and faster.

[Brief explanation of the drawing]

FIG. 1 is a schematic sectional view of a color copying machine to which an embodiment of the present invention is applied.

FIG. 2 is an enlarged sectional view of the developing means of this color copying machine.

FIG. 3 is a perspective view schematically showing the relationship between a developing roll and a photosensitive drum.

FIG. 4 is a diagram showing the dimensions of the groove in the sleeve and the distance between the sleeve and the photosensitive drum.

FIG. 5 is a diagram showing the relationship between the width L1 of the groove and the amount of developer conveyed.

FIG. 6 is a diagram showing the relationship between the distance L2 between the outer circumferential surface of the sleeve and the outer circumferential surface of the photosensitive drum between two adjacent grooves, the amount of developer conveyed, and the deflection of the sleeve.

FIG. 7 is a diagram showing the relationship between the distance D1 between the outer circumferential surface of the sleeve and the outer circumferential surface of the photosensitive drum and the groove mark grade.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1... Color copying machine, 5... Image forming device, 51... Photosensitive drum, 52... First developing means, 53... Second developing means, 100
2...Developing roll, 1005...Mag roll, 1006...Sleeve, 1006a...Groove, L1...Groove width, L2...Distance between the outer circumferential surface of the sleeve and the outer circumferential surface of the photosensitive drum between two adjacent grooves, D1... Distance between the outer peripheral surface of the sleeve and the outer peripheral surface of the photosensitive drum, D2...Distance between the bottom of the groove and the outer peripheral surface of the photosensitive drum

Claims (1)

[Claims] [Claim 1] Consisting of a magnetic roll and a sleeve that covers the outer periphery of the magnetic roll and is rotatably provided and has a plurality of grooves formed in the groove direction, the sleeve magnetically attracts developer and supplies it to the photosensitive drum. A developing roll that performs development, the sleeve outer diameter ≦35 mm, the sleeve thickness ≦1.0 mm,
Process speed≧200mm/sec, speed ratio≧
1.2 In the developing roll of the image forming apparatus, the groove width is L1, the distance between two adjacent grooves is L2, and the distance between the outer peripheral surface of the sleeve and the outer peripheral surface of the photosensitive drum between the two adjacent grooves is If D1 is the distance between the bottom of the groove and the outer peripheral surface of the photosensitive drum, then (1) 2L1≧L2 and 0.7mm≦L2≦1.2mm
(2) (3/4) A developing roll in an image forming apparatus, characterized in that D2≦D1.