JP2019159235A - Developing device and image forming apparatus - Google Patents

Abstract

To provide a developing device that can prevent troubles due to variations in surface state of rollers and a belt member, while achieving a reduction in size of an image forming apparatus body and a reduction in cost.SOLUTION: A developing device 100 comprises: a roller-like developer carrier 11 that is in contact with an image carrier 21 at a predetermined pressure; a support 12 that rotatably supports the developer carrier 11; and a support shaft 30 that rotatably supports the support 12 so that the developer carrier 11 can contact/separate from the image carrier 21, wherein the support shaft 30 is located within ±5° with respect to the tangent of the surface of the developer carrier 11 at a contact part A where the developer carrier 11 is in contact with the image carrier 21.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a developing device and an image forming apparatus.

  In various rollers and belt members used in an electrophotographic image forming apparatus, the surface state changes over time due to filming of toner and paper powder. Such a change in the surface state may cause various problems such as a noise due to rubbing and a torque increase due to an increase in sliding load.

In order to solve such a problem, a technique for applying a lubricant to the surface of the photoconductor (see, for example, Patent Document 1) has been proposed for the purpose of preventing fusion of toner and external additives to the surface of the photoconductor. .
However, in the above-described technique, a lubricant application unit that applies a lubricant to the surface of the photoreceptor is required, and a space for laying out the lubricant application unit in the image forming apparatus main body is required. It is difficult to reduce the size of the main body. In addition, there is a problem that it is difficult to reduce the cost due to the component cost.

  SUMMARY OF THE INVENTION An object of the present invention is to suppress problems caused by fluctuations in the surface state of a roller or a belt member while realizing a reduction in size and cost of an image forming apparatus main body.

  In order to achieve the above object, the present invention provides a roller-shaped developer carrier that abuts an image carrier at a predetermined pressure, a support that rotatably supports the developer carrier, and the developer carrier. And a support shaft that rotatably supports the support so that the image carrier can be contacted and separated from the image carrier, and the support shaft is a contact portion where the developer carrier abuts the image carrier. The developing device is located within ± 5 ° with respect to the tangent to the surface of the developer carrying member.

  According to the present invention, it is possible to suppress problems caused by fluctuations in the surface state of the roller and the belt member while realizing a reduction in size and cost of the image forming apparatus main body.

1 is a schematic view of an example of an image forming apparatus including a developing device according to the present invention. It is a front sectional view of an example of a developing device according to the present invention. FIG. 3 is a diagram illustrating an example of an arrangement of support shafts provided in the developing device illustrated in FIG. 2. FIG. 3 is a diagram illustrating a method for measuring a dynamic friction coefficient between an image carrier and a developer carrier provided in the developing device illustrated in FIG. 2.

  FIG. 1 shows an example of an image forming apparatus 500 including a process cartridge 100 as a developing device according to the present invention, and FIG. 2 shows an example of a process cartridge 100. The image forming apparatus 500 is a full color printer using four color toners of yellow (Y), cyan (C), magenta (M), and black (K), and a full color copier having an equivalent image forming function.

  As shown in FIG. 1, the image forming apparatus 500 includes four process cartridges 100Y, 100M, 100C, and 100K that perform image formation with respective color toners. Since the configuration and operation of each of the process cartridges 100Y, 100M, 100C, and 100K are substantially the same, the process cartridge 100 will be described with the symbols (Y, M, C, and K) indicating colors omitted.

As shown in FIG. 2, a process cartridge 100 includes a photosensitive unit 20 having a photosensitive member 21 as an image carrier, and a developing roller 11 as a roller-like developer carrier that contacts the photosensitive member 21 with a predetermined pressure. And a developing section 10 having The photosensitive member 21 is driven to rotate clockwise in the drawing, and the developing roller 11 is driven to rotate counterclockwise in the drawing at a linear velocity higher than the linear velocity of the photosensitive member 21.
The developing unit 10 includes a first support 12 as a support that rotatably supports the developing roller 11. The first support 12 has a connecting portion 12a to which a toner cartridge 105 described later is connected.
The developing unit 10 includes a toner supply roller 13 and a regulating blade 14 that are disposed around the developing roller 11.

The photoconductor unit 20 has a second support 22 that supports the photoconductor 21 rotatably. As shown in FIG. 2, the second support 22 has a portion that overlaps the first support 12 as indicated by a broken line when the process cartridge 100 is viewed from the front.
The photoconductor unit 20 includes a charging roller 23 and a cleaning blade 24 disposed around the photoconductor 21.

The process cartridge 100 includes a support shaft 30 that rotatably supports the first support 12 on the main body of the image forming apparatus 500 so that the developing roller 11 can come into contact with and separate from the photoreceptor 21. The support shaft 30 is provided so as to communicate with the portions of the first support 12 and the second support 22 indicated by broken lines, and the developing unit 10 and the photosensitive unit 20 form an image integrally. It can be removed from the device 500.
The process cartridge 100 includes a spring 40 as a pressure member that brings the developing roller 11 into contact with the photosensitive member 21 with a predetermined pressure.

As shown in FIG. 1, the image forming apparatus 500 includes exposure apparatuses 101Y, 101M, 101C, and 101K disposed above the respective photoreceptors 21.
The image forming apparatus 500 includes an intermediate transfer belt 102 disposed below the four process cartridges 100Y, 100M, 100C, and 100K.
The image forming apparatus 500 includes primary transfer rollers 103Y, 103M, 103C, and 103K as primary transfer units, which are disposed so as to face the respective photoreceptors 21 with the intermediate transfer belt 102 interposed therebetween.
The image forming apparatus 500 includes a toner sensor 104 provided to face the intermediate transfer belt 102.
The image forming apparatus 500 includes toner cartridges 105Y, 105M, 105C, and 105K that supply toner into the first support 12 from the connecting portion 12a.

The image forming apparatus 500 includes a paper feed cassette 106 at the bottom. For example, a sheet is fed from the sheet feeding cassette 106 as a sheet.
The image forming apparatus 500 includes a secondary transfer roller 109 that forms a secondary transfer portion in contact with the intermediate transfer belt 102.
The image forming apparatus 500 includes a fixing unit 110 that fixes an image on a sheet on which an image is transferred by a secondary transfer unit.
The image forming apparatus 500 includes a paper discharge unit 112 that discharges paper on which an image has been fixed by the fixing unit 110.

In each process cartridge 100, the photosensitive member 21 is driven to rotate clockwise in the drawing, and the surface of the photosensitive member 21 is uniformly charged to a predetermined polarity by the charging roller 23. Next, an electrostatic latent image is formed on the photosensitive member 21 by irradiating the charged surface with a light-modulated laser beam emitted from the exposure apparatus 101.
The toner stored on the first support 12 is conveyed to the developing roller 11 by the toner supply roller 13, and the toner conveyed onto the developing roller 11 is regulated to a uniform thickness by the regulating blade 14. . The toner held on the developing roller 11 is attracted to the electrostatic latent image on the photosensitive member 21 due to a potential difference between the developing roller 11 and the photosensitive member 21. That is, the electrostatic latent image on the photosensitive member 21 is developed with toner applied from the developing roller 11 and visualized as a toner image.

The yellow, cyan, magenta, and black color toner images formed by the process cartridges 100 are sequentially superimposed and transferred onto the intermediate transfer belt 102. The toner images of the respective colors transferred onto the intermediate transfer belt 102 are adjusted so as to be transferred at an appropriate timing by the toner sensor 104 at a certain fixed job interval.
The toner that is not transferred to the intermediate transfer belt 102 and remains on the photoreceptor 21 is collected by the cleaning blade 24. When the toner remaining amount detection unit provided in the first support 12 detects that the remaining amount of toner in each first support 12 falls below a certain threshold, a certain amount of toner is transferred from the toner cartridge 105. Is supplied.

On the other hand, the sheet fed from the sheet feeding cassette 106 by the sheet feeding roller 107 is conveyed toward the registration roller pair 108. The paper that has been stopped by being abutted against the registration roller pair 108 is sent out from the registration roller pair 108 at a timing with the toner image on the intermediate transfer belt 102, and the secondary transfer roller 109 and the intermediate transfer belt 102 are connected to each other. It is sent to the secondary transfer section that comes into contact.
Since a voltage having a polarity opposite to the charging polarity of the toner is applied to the secondary transfer roller 109, a superimposed toner image, for example, a full color image on the intermediate transfer belt 102 is transferred onto the sheet. The sheet on which the toner image has been transferred is conveyed to the fixing unit 110 where the toner is fixed on the sheet by heat and pressure. The sheet on which the toner image has been fixed is discharged out of the apparatus, that is, outside the image forming apparatus 500 by the paper discharge roller 111, and is discharged to the paper discharge unit 112.

As described above, the developing roller 11 is pressed against the photosensitive member 21 by the spring 40 so as to be rotatable about the support shaft 30 as a fulcrum. In FIG. 2, an arrow F indicates the spring pressure by the spring 40.
In addition to the spring pressure F, the forces that may act as a pressing force for pressing the developing roller 11 against the photosensitive member 21 include the own weight W of the developing unit 10, the sealing pressure S of the connecting portion 12a, the photosensitive member 21 and the developing. A frictional force P generated when the roller 11 has a linear speed difference is considered.

  When the pressing force fluctuates, various problems such as a noise due to rubbing and a torque increase due to an increase in the sliding load may occur. Therefore, it is desirable that the pressing force be constant. For this reason, it is necessary to prevent the force that easily fluctuates from acting as a pressing force.

  Each of the above-described forces F, W, S, and P acts on the photosensitive member 21 by a moment force corresponding to the distance between the point of action of each force and the support shaft 30, that is, the arm length, as a pressing force. Since the moment force is the product of each force and the arm length, the shorter the arm length, the smaller the moment force. That is, as the arm length is shorter, the pressing force is less likely to be affected by fluctuations in each force. In addition, if the direction of the force and the direction of the arm length are parallel, the influence of the force on the pressing force is zero. Therefore, for easily changing force, the arm length is shortened or the direction of the force is The support shaft 30 is preferably arranged so that the direction of the arm length is parallel to the arm length.

  The arm length of the spring pressure F is desirably as long as possible in order to bring the developing roller 11 into full contact with the photoreceptor 21. That is, the spring 40 and the support shaft 30 are preferably arranged as far apart as possible. In order to suppress variation in moment, it is desirable to use a spring 40 having as small a variation in spring pressure F as possible. In general, there are many springs with a variation in spring pressure of about ± 10%, but in this embodiment, a spring of about ± 5% was used.

  The magnitude of the frictional force P varies depending on the type of developing roller, photoreceptor and toner used. Even in a system using the same developing roller, photoconductor, and toner, changes in the surface condition over time due to wear on the developing roller surface layer, toner filming, etc., the color type of the toner, and the external additives on the toner surface The frictional force P varies greatly due to peeling or the like. In order to cope with such fluctuations, that is, to prevent the influence of fluctuations in the frictional force P from being exerted on the pressing force, the support shaft 30 is preferably disposed on the line of action of the frictional force P. In other words, the support shaft 30 is preferably arranged on the tangent line of the surface of the developing roller 21 in the contact portion A where the developing roller 11 contacts the photoreceptor 21.

  Table 1 shows whether or not a failure occurs when the installation angle of the support shaft 30 is swung around the contact portion A. In Table 1, “Initial” means that the developing roller and the photosensitive member in the initial state are used, and “Durability (after printing 10 kp sheets)” means that the developing roller and the photosensitive member after printing 10 kp sheets are used. Show. In FIG. 3, the installation angle of the support shaft 30 is based on the tangent line of the surface of the developing roller 21 at the contact portion A, and the counterclockwise direction in FIG. It is. ○ indicates that there was no problem, and x indicates that there was a problem.

  When the installation angle of the support shaft 30 is set to the plus side, the moment due to the frictional force P acts in a direction in which the developing roller 11 is separated from the photoreceptor 21. For this reason, the developing roller 11 may not make full width contact with the photosensitive member 21, and an image defect in which a part of the image is whitened, that is, a whiteout image may occur. As shown in the case where the installation angle of the support shaft 30 is set to 7.5 °, the margin of the white image is different for each color, and when the initial state and the durability are compared, the developing roller surface layer is smoothed by the durability. As a result, the margin during endurance was higher than the initial state.

  When the installation angle of the support shaft 30 is set to the minus side, the moment due to the frictional force P acts in a direction to push the developing roller 11 into the photosensitive member 21. For this reason, the frictional load between the developing roller 11 and the photosensitive member 21 increases, and the torque may exceed the allowable value. As shown in the case where the installation angle of the support shaft 30 is −8 °, when comparing the initial state and the durability state, the margin in the durability state is lower than that in the initial state. When the installation angle of the support shaft 30 was further set to the minus side, various problems occurred due to the increased pressing force regardless of the initial state and durability.

As shown in Table 1, no trouble occurred when the installation angle of the support shaft 30 was set to -5 ° to + 5 °. For this reason, in consideration of time-dependent deterioration due to manufacturing errors, friction, and the like, in this embodiment, as shown in FIG. 3, the support shaft 30 is ± 5 with respect to the tangent to the surface of the developing roller 11 at the contact portion A. Arranged to be located within °.
Note that the tangent to the surface of the developing roller 11 at the contact portion A is a tangent when it is assumed that the peripheral surface of the developing roller 11 has an ideal arc shape.

Since the own weight W of the developing unit 10 may vary depending on the remaining amount of toner and the like, the support shaft 30 may be disposed on an extension line of the action line of the own weight W of the developing unit 10. That is, as shown in FIG. 2, the support shaft 30 may be disposed so as to be positioned on a vertical line passing through the center of gravity of the developing unit 10.
Similarly, with respect to the sealing pressure S of the connecting portion 12a, the support shaft 30 may be disposed so as to be positioned on a vertical line passing through the connecting portion 12a.
In the present embodiment, the installation angle of the support shaft 30 can take a range of approximately −3 ° to + 3 ° with reference to a vertical line passing through the center of gravity of the developing unit 10 or a vertical line passing through the connecting portion 12a due to component tolerances. However, no problems occurred in this range.

In this embodiment, the confirmation was made when the dynamic friction coefficient between the developing roller 11 and the photosensitive member 21 was 0.5 or more. FIG. 4 shows a method for measuring the dynamic friction coefficient μ.
First, in the image forming apparatus 500, a toner thin layer is formed on the surface layer of the developing roller 11. Next, the developing roller 11 on which the toner thin layer is formed is held by the measuring device so as not to rotate. Then, the weight is suspended around one end of the sheet material coated with the photosensitive layer and wound around the developing roller 11, and the other end is pulled with a digital force gauge at a constant speed. The dynamic friction coefficient μ is theoretically obtained from the weight load B and the digital force gauge reading A by the following formula (Euler belt method).

  As described above, the rotation directions of the photosensitive member 21 and the developing roller 11 are opposite to each other. Table 2 shows whether or not a problem occurs when the linear speed ratio of the developing roller 11 to the photosensitive member 21 is varied. ○ indicates that there was no failure, and Δ or × indicates that there was a failure.

When the linear velocity ratio of the developing roller 11 to the photosensitive member 21 is set to 0.9 or 1.0, the amount of toner to be attached to the electrostatic latent image on the photosensitive member 21 cannot be attached, so The concentration could not be satisfied.
In addition, when the ratio of the linear velocity of the developing roller 11 to the photosensitive member 21 is 1.7 or more, the amount of heat generated by sliding between the photosensitive member 21 and the developing roller 11 increases and slightly exceeds the target temperature of the process cartridge 100. I have. As a problem that is assumed when the amount of heat generated is large, there is a possibility that a vertical streak image is generated when the toner melts and adheres to the regulating blade 14 or the like. In the experiment, the defect did not appear as a vertical streak image.
As shown in Table 2, no trouble occurred when the linear speed ratio of the developing roller 11 to the photosensitive member 21 was set to 1.1 to 1.6. The linear speed ratio was 1.1 or more and 1.6 or less.

  The preferred embodiments of the present invention have been described above. However, the present invention is not limited to the specific embodiments, and the present invention described in the claims is not specifically limited by the above description. Various modifications and changes are possible within the scope of the above.

  The effects described in the embodiments of the present invention are only the most preferable effects resulting from the present invention, and the effects of the present invention are limited to those described in the embodiments of the present invention. is not.

DESCRIPTION OF SYMBOLS 10 Development part 11 Developer support body, developing roller 12 Support body, 1st support body 12a Connection part 13 Toner supply roller 14 Control blade 20 Photoconductor unit 21 Photoconductor 22 2nd support body 23 Charging roller 24 Cleaning blade 30 Support shaft 40 Pressure member, spring 100 Developing device, process cartridge 500 Image forming apparatus A Abutting portion F Spring pressure P Friction force S Seal pressure W Weight of developing portion

JP 2002-55580 A

Claims (7)

A roller-shaped developer carrier that contacts the image carrier at a predetermined pressure;
A support that rotatably supports the developer carrier;
A support shaft that rotatably supports the support so that the developer-carrying member can come into contact with and separate from the image carrier;
The developing device is a developing device in which the support shaft is located within ± 5 ° with respect to a tangent line of the surface of the developer carrier at a contact portion where the developer carrier contacts the image carrier. The developing device according to claim 1,
A developing unit including the developer carrier and the support;
The developing device according to claim 1, wherein the support shaft is located on a vertical line passing through the center of gravity of the developing unit. The developing device according to claim 1 or 2,
The support has a connecting portion to which a toner cartridge is connected,
The developing device, wherein the support shaft is positioned on a vertical line passing through the connecting portion. The developing device according to any one of claims 1 to 3,
A developing device, wherein a coefficient of dynamic friction between the image carrier and the developer carrier is 0.5 or more. In the developing device according to any one of claims 1 to 4,
A developing device characterized in that a linear velocity ratio of the developer carrier to the image carrier is 1.1 or more and 1.6 or less. The developing device according to any one of claims 1 to 5,
A developing device comprising the image carrier.   An image forming apparatus comprising the developing device according to claim 1.

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