JP6743464B2 - Developer carrier, developing device, process cartridge, and image forming apparatus - Google Patents

Description

The present invention relates to a developer carrier, a developing device, a process cartridge, and an image forming apparatus.

Conventionally, as a developing device for forming an electrophotographic image, a two-component developer composed of toner and a magnetic carrier is carried on a developer carrier, and a magnetic pole is fixed by a fixed magnetic pole arranged inside the developer carrier. It is known that a brush is formed and development is performed. In such a developing device, after the layer thickness of the developer layer formed on the developer carrier is regulated by a developer regulating member such as a doctor blade, the developer carried on the surface of the developer layer is regulated. By the movement of the surface, it is conveyed to the developing area facing the latent image carrier. Here, in order to satisfactorily convey the developer, the surface of the developer carrier has a shape change such as irregularities, grooves, and depressions.

When the developer is conveyed, the surface of the developer carrier is subjected to frictional stress from both the developer regulating member and the latent image carrier. Due to this frictional stress, shape changes such as irregularities, grooves, and dents formed on the surface of the developer carrying member are worn out, and the developer carrying force is reduced, so that a predetermined amount of developer cannot be carried. was there. When the developer carrying force is reduced, the amount of developer drawn up is reduced, and thus the developing ability is reduced. When the developing ability is lowered, the toner density is increased to compensate for the lowered ability, but this causes a problem of toner scattering. The toner scattering pollutes the inside of the apparatus and causes so-called toner loss, which is an abnormal image in which toner is dropped on the paper.

In particular, due to the recent high-speed image formation and the long life of the apparatus, the developer carrier in the developing device is required to have a long rotational speed and a long life, and the developer carrier is durable against surface abrasion. Is required. Therefore, there is known a technique for preventing abrasion by coating a dimple-shaped depression (for example, refer to "Patent Document 1"). Compared with blasting, which is a general surface roughening process, this technology is configured so that one recess becomes larger by shaving in the shape of a dimple, and the carrying force does not easily decrease even when worn. There is. Further, as long as the coating is not abraded, abrasion of the edge portion can be prevented, so that it can be said to have high durability.

However, the above-mentioned technique has a problem in that the edge portion is easily worn because stress concentrates on the edge portion of the depression. As a result, there is a problem that it is insufficient for further speeding up and extending the life.
The present invention solves the above-mentioned problems, can cope with high speed and long life, has excellent durability against surface abrasion, and can prevent the occurrence of troubles such as toner scattering and toner falling. The purpose is to provide the body.

The invention according to claim 1 carries a developer having a carrier and a toner and rotates in a predetermined direction, and a diamond-like carbon coating is formed on a stainless sprayed layer on the surface carrying the developer . The ten-point average roughness of the surface is 30 to 80 μm, and Δq is 0.4 to 0.6 .

According to the present invention, since the abrasion resistance is better than that of the conventional developing sleeve, the transportability of the developer carrying member is not deteriorated, and the occurrence of abnormal images and the like is prevented and the reliability is improved. It is possible to provide a developer carrier capable of

1 is a schematic front view of an image forming apparatus to which an embodiment of the present invention can be applied. 1 is a schematic diagram of a developing device to which an embodiment of the present invention can be applied. It is a schematic diagram of a developing device used for another example of one embodiment of the present invention. FIG. 1 is a schematic view of a main part of a developing device used in an embodiment of the present invention. FIG. 3 is a schematic view of a main part of a surface of a developing sleeve used in one embodiment of the present invention. FIG. 6 is a diagram showing a relationship between a traveling distance and a surface roughness when a coating layer of the developing sleeve used in the embodiment of the present invention is changed. FIG. 6 is a diagram showing a relationship between a traveling distance and an angle of surface irregularities when the coating layer of the developing sleeve used in the embodiment of the present invention is changed. FIG. 6 is a diagram showing a relationship between the surface roughness of the developing sleeve used in the embodiment of the present invention and the amount of developer pumped up. FIG. 6 is a diagram showing the relationship between the surface roughness and the shake of the developing sleeve used in the embodiment of the present invention.

FIG. 1 shows an image forming apparatus to which an embodiment of the present invention can be applied. In the figure, the image forming apparatus has a sheet feeding table 4 in which a sheet-shaped transfer sheet S is stored inside the apparatus main body 1. An image forming unit 2 in which a plurality of image forming units 3Y, 3M, 3C and 3K are arranged in parallel is provided inside the apparatus main body 1. The subscripts Y, M, C and K attached to the reference numerals respectively indicate yellow, magenta, cyan and black.

An endless belt-shaped intermediate transfer belt 30 which is stretched around a plurality of support rollers and the like is provided at a substantially central portion of the apparatus main body 1 so as to be capable of traveling in a clockwise direction. Above the intermediate transfer belt 30, the image forming units 3 are arranged in parallel along the traveling direction thereof, and the tandem type image forming unit 2 is formed. Each image forming unit 3 has a photoconductor drum 20Y, 20M, 20C, 20K as a latent image carrier for carrying a toner image of each color of yellow, magenta, cyan and black.

An exposure device 100 is arranged above the image forming unit 2. As the exposure apparatus 100, an optical scanning type exposure apparatus can be used. The optical scanning type exposure apparatus includes, for example, four light sources (semiconductor laser, semiconductor laser array, multi-beam light source, etc.), a coupling optical system, a common optical deflector (polygon mirror, etc.), and four scanning connection systems. It is composed of an image optical system and the like. Then, each photoconductor drum 20 is exposed by the exposure device 100 according to the image information of each color of yellow, magenta, cyan, and black, and an electrostatic latent image is formed on the outer peripheral surface of each photoconductor drum 20.

Around the photoconductor drums 20, charging devices 23Y, 23M, 23C and 23K that uniformly charge the photoconductor drums 20 prior to exposure, and electrostatic latent images formed by the exposure device 100 are developed with toner of each color. The developing devices 22Y, 22M, 22C and 22K are provided. Further, cleaning devices 24Y, 24M, 24C, and 24K that remove the transfer residual toner on each photoconductor drum 20 are arranged around each photoconductor drum 20. Further, around each photoconductor drum 20, primary transfer rollers 25Y, 25M, 25C, 25K that primarily transfer the toner image from each photoconductor drum 20 to the intermediate transfer belt 30 are disposed. Each primary transfer roller 25 is arranged to face each corresponding photoconductor drum 20 via the intermediate transfer belt 30.

Of the plurality of rollers that support the intermediate transfer belt 30, the support roller 26a is a drive roller that drives the intermediate transfer belt 30 to travel, and is connected to a motor via a drive transmission mechanism such as a gear, belt, or pulley (not shown). There is. When a black monochromatic image is formed on the intermediate transfer belt 30, a supporting mechanism 26a and a supporting roller 26b other than the primary transfer roller 25K, primary transfer rollers 25Y, 25M, 25C, etc. are formed by a moving mechanism (not shown). Move downward. As a result, the intermediate transfer belt 30 is separated from the photoconductor drums 20Y, 20M, and 20C.

A secondary transfer device 31 is disposed on the side facing the image forming unit 2 via the intermediate transfer belt 30. The secondary transfer device 31 presses the secondary transfer roller 31 a from the front side of the intermediate transfer belt 30 to the secondary transfer counter roller 31 b that is a support roller of the intermediate transfer belt 30. The secondary transfer device 31 applies a transfer bias between the secondary transfer roller 31a and the secondary transfer counter roller 31b to form a transfer electric field, thereby transferring the image on the intermediate transfer belt 30 as a recording medium. It is transferred onto the paper S. A fixing device 50 that fixes the image on the transfer sheet S to the transfer sheet S by heat and pressure is disposed on the downstream side of the secondary transfer device 31 in the transfer sheet conveying direction. The fixing device 50 includes a fixing roller 52 having a heating unit (a heater, a lamp, an electromagnetic induction type heating device, etc.) (not shown), and a pressure roller 51 that is in pressure contact with the fixing roller 52. The transfer sheet S on which the image is transferred by the secondary transfer device 31 is sent to the fixing device 50 by the conveyor belt 32 supported by the rollers 32a and 32b. Instead of the transport belt 32, a fixed guide member, a transport roller, or a transport roller may be used.

When image data is sent to the apparatus main body 1 and an image formation start signal is received, the support roller 26a is rotated in the image forming section 2 and the intermediate transfer belt 30 is driven to run clockwise in FIG. At the same time, in each image forming unit 3, each photoconductor drum 20 rotates counterclockwise, and each charging device 23 charges and the exposure device 100 performs exposure. Next, a development process using each color toner in each development device 22 is performed, and a single color image of yellow, magenta, cyan, and black is formed on each photoconductor drum 20. Then, in accordance with the running of the intermediate transfer belt 30, each primary color image on each photoconductor drum 20 is superposed and transferred onto the intermediate transfer belt 30 by each primary transfer roller 25, whereby the full-color toner is transferred onto the intermediate transfer belt 30. An image is formed.

On the other hand, the transfer paper S is fed from the paper feed cassette 4a in the paper feed table 4 in accordance with the above-mentioned image forming operation, and the fed transfer paper S is guided to the paper feed path 40 to the registration roller pair 41. It is hit and it is suspended. Then, the registration roller pair 41 is rotationally driven at the timing when the image on the intermediate transfer belt 30 reaches the secondary transfer device 31. As a result, the transfer paper S is fed between the intermediate transfer belt 30 and the secondary transfer device 31, and the full-color toner image on the intermediate transfer belt 30 is collectively transferred onto the transfer paper S. The transfer sheet S on which the image has been transferred is sent to the fixing device 50 by the conveyor belt 32, and after the image is fixed by heat and pressure in the fixing device 50, the transfer sheet S is discharged to the outside by the discharge roller 42 and discharged. Stacked on the tray 43.

The toner remaining on the surface of each photoconductor drum 20 after the image transfer is removed by each cleaning device 24. The toner remaining on the surface of the intermediate transfer belt 30 after the image transfer is removed by a belt cleaning device (not shown). After this cleaning step, the image forming apparatus prepares for another image formation by the image forming unit 2.

Above the exposure device 100, toner bottles 10Y, 10M, 10C, and 10K filled with yellow, magenta, cyan, and black color toners are disposed. Each toner bottle 10 is detachably attached to the apparatus main body 1, and each color toner is supplied to each corresponding developing device 22 by a toner replenishing device. Each toner bottle 10 is a consumable item that is replaced when the toner inside is consumed, and is removed from the apparatus main body 1 and replaced when all the toner is consumed.
An operation unit 60 is arranged on the upper part of the apparatus body 1. The operation unit 60 is connected to the apparatus body 1 by an interface (not shown), and a user inputs an operation to the apparatus body 1 by a key input from the operation unit 60.

FIG. 2 shows an example of the developing device 22 to which the embodiment of the present invention can be applied. The developing device 22 has developing rollers 27, 28 which are developer carrying members, three screws 9, 14, 11, a regulating blade 12, a case 29 for accommodating these. Each of the developing rollers 27 and 28 has a rotatable sleeve and a plurality of magnets fixedly arranged therein. The rotating shafts 16, 17, 13 of the screws 9, 14, 11 are provided so as to be parallel to the photosensitive drum 20, respectively. Further, a third screw (stirring screw) 11 is arranged at a position between the first screw (supply screw) 9 arranged above and the second screw (recovery screw) 14 arranged below. It is set up. Each of the screws 9, 14, 11 is rotated by a driving force from a driving source (not shown), and agitates and conveys the developer in the developing device 22.

The screw 9 supplies the developer to the developing roller 27 while stirring and conveying the developer. The sleeve of the developing roller 27 rotating in the clockwise direction holds the supplied developer by magnetic force and forms a magnetic brush on the outer peripheral surface thereof. The regulation blade 12 regulates the height of the formed magnetic brush and returns the regulated developer to the screw 9. The developer, which is not supplied to the developing roller 27 and is agitated and conveyed to the downstream position of the screw 9 on the left side in FIG. 2C, moves due to the retention and drops from the opening N3 to the periphery of the screw 14. The developer that has passed through the regulation blade 12 visualizes the electrostatic latent image on the photoconductor drum 20, moves to the developing roller 28, and again visualizes the electrostatic latent image on the photoconductor drum 20. The developer whose toner concentration has decreased due to development is collected from the developing roller 28 by stirring and conveying the screw 14, and is conveyed to the downstream position on the left side of the screw 14 in FIG. 2C.

Each developer conveyed to the downstream position of the screw 14 moves to the screw 11 through the opening N1 due to a certain amount of staying. The moved developer is conveyed to the downstream position, which is the right side in FIG. 2C, by stirring and conveying the screw 11 together with the toner replenished from the replenishing port N4. The stirring and transport of the developer by the screw 11 is performed by a partition wall 15 provided so that other screws do not coexist with the developer being stirred and transported in the width of the image area where the photosensitive drum 20 forms an electrostatic latent image. It is performed in a shut-off state.

FIG. 3 shows another example of the developing device to which the embodiment of the present invention can be applied. The developing device 33 is different from the above-described developing device 22 only in that the screw 18 is used in place of the screw 11, and the other configurations are the same. The screw 18 has an upstream end 13A of the rotating shaft 13 provided at the same height as the lower screw 14 and a downstream end 13B provided at the same height as the upper screw 9. The developer whose toner concentration has decreased due to the development is collected by the stirring and conveying of the screw 14, and is conveyed to the position downstream of the screw 14. The developer transported to the downstream position of the screw 14 moves to the end portion 13A side of the screw 18 through the opening N1 due to the retention of the downstream position. The moved developer is agitated and conveyed by the screw 18 while being blocked by the partition wall 15 so as not to be mixed with the developer agitated and conveyed by the toner replenished from the replenishment port N4, and the end portion 13B side is provided. Be transported to. The developer transported to the periphery of the end portion 13B moves to the screw 9 through the opening N2 due to the retention. The developer moved to the screw 9 is supplied to the developing roller 27.

FIG. 4 shows a developing device 22 used in one embodiment of the present invention. The developing device used in this embodiment may be the developing device 33. In this embodiment, the sleeves of the developing rollers 27 and 28 are coated with tetrahedral amorphous carbon (ta-C) layers, respectively. Tetrahedral amorphous carbon (ta-C), which is one of a plurality of variations of diamond-like carbon (DLC), has an electrical resistivity of 10 ⁹ to 10 ¹⁴ Ω·cm.

The developing sleeve has a cylindrical shape, and has an outer diameter of about 17 to 18 mm and an axial length of about 300 to 350 mm. The developing sleeve encloses a magnet roller (not shown) and is rotatable about its axis, and is rotated so that its inner peripheral surface faces the fixed magnetic pole in order. The developing sleeve is made of a non-magnetic material such as aluminum alloy, brass, stainless steel, and conductive resin. In this embodiment, stainless steel, particularly SUS303, SUS304, SUS316, is used.

FIG. 5 shows a developing sleeve used in this embodiment. As described above, the developing sleeve 61 having a cylindrical shape is made of stainless steel, and the stainless sprayed layer 62 is formed on the surface thereof. The stainless steel sprayed layer 62 is a layer that is hard and is not easily worn because it is made of stainless steel because it is formed by injecting melted stainless steel to form irregularities on the surface of the developing sleeve 61. As described above, in recent years, high-speed image forming operation and long life of the image forming apparatus are required. Therefore, the developing apparatus is also required to have high durability, and the surface is simply sprayed with stainless steel. A developing sleeve is insufficient, and it is desired to further improve wear resistance.

In order to solve the above-mentioned problems, there is known a technique of improving wear resistance and durability by coating titanium nitride (TiN) on the stainless steel sprayed layer 62. However, it has been experimentally proved that the titanium nitride coating does not sufficiently prolong the life due to the speeding up of the image forming operation. Therefore, the present inventors coated the surface of the developing sleeve 61 with a coating of tetrahedral amorphous carbon (TAC) (hereinafter, referred to as “TAC coating”) 63 formed by a vacuum arc deposition method instead of the titanium nitride coating. Then, an experiment was conducted using this developing sleeve 61. Here, the thickness of the TAC coating 63 is 1 to 3 μm.

FIG. 6 shows the relationship between the traveling distance of the developing sleeve 61 and its ten-point average surface roughness Rz in the above-described experiment. As shown in FIG. 6, it was found that the surface roughness of the TAC coat did not decrease with time as compared with the TiN coat. Therefore, by using the developing sleeve 61 having the TAC coating 63, the abrasion resistance is better than that of the conventional developing sleeve, so that the developer carrying force of the developing rollers 27 and 28 does not decrease, and an abnormal image or the like is generated. It is possible to provide the developing rollers 27 and 28 capable of preventing the occurrence of the above and improving the reliability.

FIG. 7 shows the angles of irregularities on the surface of the developing sleeve 61 described above. Here, Δq is the average of the squared values of the angles of the line segments that connect the start point and the end point of the measurement curve in this section, dividing the measurement curve in the horizontal direction at regular intervals ΔX (the vertical direction at this time is ΔYi). Obtained and say the square root of the value. That is, Δq is

Therefore, the inclination angle is calculated by tan-1(ΔYi/ΔX).

Δq is an index representing the angle of the unevenness, but it has been found that Δq, which becomes small when the surface is worn, is preferably 0.4 to 0.6. FIG. 7 is a diagram showing the amount of change in Δq depending on the type of coat. From the results shown in FIG. 7, the TAC coat having the change amount of Δq of +0.03 to −0.03 is Δq as compared with the TiN coat having the change amount of Δq of 0 to −0.16. It can be seen that the wear does not decrease and the wear is small. Therefore, since the surface of the developing sleeve 61 is not worn, the developer transporting force of the developing rollers 27, 28 does not decrease, and it is possible to prevent the occurrence of abnormal images and improve the reliability of the developing rollers 27, 28. Can be provided.

In the case of the two-stage developing roller shown in this embodiment, the developer and the developing roller 27 are slid by the regulating blade 12 arranged only with respect to the developing roller 27 located on the upstream side in the rotation direction of the photosensitive drum 20. It has been found that the friction of the developing roller 27 promotes the abrasion of the developing roller 27 as compared with the developing roller 28 located on the downstream side in the rotation direction of the photoconductor drum 20 due to the friction. Therefore, it is desirable to improve the abrasion resistance of the developing roller 27 as compared with the developing roller 28.

FIG. 8 shows the relationship between the surface roughness Rz of the developing sleeve and the developer scooping amount ρ. As is clear from FIG. 8, the lower the surface roughness, the slower the decrease of ρ. This means that, rather than being excellent in wear resistance, it means that when the same amount of wear is used, rough (large peaks) has less effect on transportability than rough (small peaks). There is. That is, when Rz 70 μm is worn by the same amount as Rz 35 μm, the decrease in ρ can be smaller. Further, it has been known that the thermal spraying of stainless steel affects the runout of the developing sleeve, and the runout becomes worse as the surface roughness becomes rougher. When the runout becomes worse, unevenness of the pitch of the developing sleeve per revolution occurs. The sensitivity to the unevenness of one pitch due to the shake of the developing sleeve is the result shown in FIG.

With the above configuration, by making the surface roughness of the developing roller 27 rougher than that of the developing roller 28, it is possible to reduce the deterioration of the developer transportability on the roller surface and prevent the occurrence of abnormal images and the like. It is possible to provide the developing devices 22 and 33 that can improve reliability. Further, with the above configuration, it is possible to reduce the decrease in ρ and prevent the occurrence of unevenness in the pitch of one round. If the difference in the surface properties between the developing rollers 27 and 28 is too large, the developer carrying force is affected. Therefore, the surface properties of the developing rollers 27 and 28 are preferably 10 to 30 μm in Rz.

In the above-described embodiment, an example is shown in which each photosensitive drum 20, each charging device 23 as a charging unit, each cleaning device 24 as a cleaning unit, and each developing device 22, 33 are separately provided in the apparatus main body 1. .. However, the present invention may constitute a process cartridge in which the developing devices 22 and 33 are integrally provided with at least one of the photosensitive drums 20, the charging devices 23, and the cleaning devices 24. In this case, the constructed process cartridge is detachably attached to the apparatus main body 1.

In the above-described embodiment, the transfer paper S is shown as the recording medium on which the image is formed. The transfer paper S is not limited to recording paper, and includes thick paper, postcards, envelopes, plain paper, thin paper, coated paper (coated paper or art paper), tracing paper, and the like. As the recording medium other than the paper, any material such as an OHP sheet, an OHP film, and a resin film may be used as long as it is a sheet-shaped substance capable of forming an image.

Although the preferred embodiments of the present invention have been described above, the present invention is not limited to the above-described specific embodiments, and unless otherwise specified in the above description, the invention is described in the claims. Various modifications and changes can be made within the scope of the present invention.
For example, the image forming apparatus to which the present invention is applied is not limited to the above-described type image forming apparatus, and may be another type of image forming apparatus. That is, the image forming apparatus to which the present invention is applied may be a printer, a facsimile alone, or a complex machine thereof, or a complex machine such as a monochrome machine or a color machine. In addition, the image forming apparatus to which the present invention is applied may be an image forming apparatus used for forming an electric circuit or an image forming apparatus used for forming a predetermined image in the field of biotechnology.
The effects described in the embodiments of the present invention only list the most suitable effects that occur from the present invention, and the effects according to the present invention are not limited to those described in the embodiments of the present invention. ..

20 Latent image carrier (photosensitive drum)
22, 33 developing device 27 developer carrier (developing roller)
28 developer carrier (developing roller)
62 stainless steel sprayed layer 63 TAC coating

Japanese Patent No. 55341212

Claims (8)

It carries a developer having a carrier and toner and rotates in a predetermined direction,
A film of diamond-like carbon is formed on the stainless steel sprayed layer on the surface supporting the developer, the ten-point average roughness of the surface is 30 to 80 μm, and Δq is 0.4 to 0.6. Developer carrier. The developer carrier according to claim 1,
The developer carrier, wherein the diamond-like carbon is tetrahedral amorphous carbon . 3. A plurality of developer carrying bodies for supplying a developer to a rotatable latent image carrying body, wherein at least one of the plurality of developer carrying bodies is the developer carrying body according to claim 1. Developing device . The developing device according to claim 3,
3. The developing device according to claim 1, wherein among the plurality of developer carrying bodies, only the developer carrying body located on the upstream side in the rotation direction of the latent image carrying body is the developer carrying body according to claim 1 . The developing device according to claim 3 or 4 ,
Of the plurality of developer carrying members, the surface roughness of the developer carrying member located on the upstream side in the rotation direction of the latent image carrying member has a surface roughness of the developer carrying member located on the downstream side in the rotation direction of the latent image carrying member. A developing device characterized by being rougher than the surface roughness . A process cartridge comprising: the developing device according to claim 3 ; and at least the latent image carrier . An image forming apparatus comprising the developing device according to claim 3 . An image forming apparatus comprising the process cartridge according to claim 6 .

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