JP2001281993A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To surely carry out abutting and separating in rotation of a developing roll. SOLUTION: In the image forming device carrying out multicolor developing by plural developing devices loaded to a rotating body 15, a member to be engaged 32 that is fixed to a shaft of the developing roll 19 of each developing device, an engaging member 34 that is installed to be able to be separated from and brought into contact with the member to be engaged, a developing roll driving means 27 rotating the engaging member and a press member 42 to press the engaging member to the member to be engaged in the front and the back of a developing position are provided.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as a copying machine, a printer, a facsimile, etc. using an electrophotographic method. Related to the device.

[0002]

2. Description of the Related Art As an image forming apparatus using electrophotography, electrostatic latent images of a plurality of colors are sequentially formed on a photoreceptor, and the electrostatic latent images are sequentially developed into toner images of respective colors by a rotary developing device. There is a method in which each color toner image is superimposedly transferred on an intermediate transfer medium, and a full-color toner image transferred on the intermediate transfer medium is transferred to a transfer material and then fixed.

In the above rotary developing device, a rotating body is provided opposite to a photoreceptor, and a plurality of developing devices (yellow, cyan, magenta, and black developing devices) are mounted in the rotating body, and the rotating body is rotated. Thus, one of the plurality of developing devices is selectively brought into contact with the developing position of the photoconductor, and the developing roller in the developing device is rotated and a developing bias is applied, thereby developing the electrostatic latent image with toner. Like that.

In the above-mentioned rotary developing device, when the developing roller in contact with the developing position of the photoreceptor is rotated, if the developing rollers of other developing units are also rotated, deterioration of toner, scattering, and color mixing may occur. This causes an increase in load torque in a single drive means, which leads to an increase in power consumption and an increase in cost due to an increase in the size of the motor as the drive means. Therefore, a method is employed in which only the developing roller that is in contact with the developing position of the photoconductor is rotated (for example, Japanese Patent Application Laid-Open No. 9-101675).

FIG. 7A is a perspective view of a main part showing the above-mentioned conventional system, and FIG. 7B is a sectional view taken along the line BB of FIG. 7A. A driven gear 52 (52a to 52d) connected to the rotating shaft of each developing roller is provided on one side surface of the rotating body 50, while the driving force of the driving motor 51 is transmitted to the pulleys 53 and 54 and the transmission gears. Drive gear 5 via belt 55
When the one of the developing rollers reaches the developing position, the driven gear 52 and the driving gear 56 mesh with each other, and the rotation of the driving motor 51 is transmitted to the developing roller. The power supply brush 62 that contacts each developing roller is provided on one side surface of the rotating body 50.
(62a to 62d) are provided, while the image forming apparatus main body 64 is provided with a power supply plate 63 connected to a developing bias power supply, and one of the developing rollers reaches the developing position. At this point, the power supply plate 63 is configured to be brought into contact with the power supply brush 62 and a developing bias is applied to the developing roller.

[0006]

In a rotary developing device, a developing roller comes into contact with or separates from a photoreceptor. The toner on the surface of the developing roller is scraped by the contact force, so that the surface of the developing roller is exposed, and the photoconductor layer of the photoconductor is damaged. Therefore, it is necessary to always rotate the developing roller so as to make uniform contact with the photosensitive member with the toner layer interposed (hereinafter referred to as rotating contact and separation of the developing roller). However, in the above-described conventional method, power can be transmitted only within the range of contact or separation between the driving gear 56 and the non-driving gear 52, so that the developing roller abuts on the photosensitive member without sufficiently rotating. Alternatively, there is a problem that there is a risk of separation.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned conventional problems, and an object of the present invention is to provide an image forming apparatus capable of reliably performing rotation contact and separation of a developing roller.

[0008]

According to a first aspect of the present invention, there is provided an image forming apparatus, comprising: a plurality of developing devices mounted on a rotating body; An engaged member fixed to a developing roller shaft of each developing device, an engaging member disposed detachably from the engaged member, a developing roller driving unit for rotating the engaging member, A pressing member that presses the engaging member toward the engaged member before and after the developing position is provided. The invention according to claim 2, wherein the engaging member includes a plurality of engaging members. A mating blade is formed, and a plurality of engaging grooves with which the engaging blade is engaged are formed in the engaged member. The developing roller driving means is formed on the outer periphery of each engagement member. Characterized in that a sun gear which is meshed with the Ya, invention of claim 3, wherein, in any one of claims 1 to 3, wherein the pressing member is characterized by pressing the engaging member by a spring.

[0009]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is an overall configuration diagram showing an example of an image forming apparatus to which the present invention is applied. Although this image forming apparatus is a color electrophotographic printer capable of forming a full-color image with four color toners, the present invention is not limited to this. Applicable to forming equipment.

In the case body 2 of the image forming apparatus 1, a photosensitive member 3 as a latent image carrier is disposed. Photoconductor 3
Has a belt-shaped conductive substrate and a photosensitive layer formed on the surface thereof, and is driven to rotate in a direction indicated by an arrow by driving means (not shown). Around the photosensitive member 3, a charging device 4 for uniformly charging the photosensitive member 3 along its rotation direction, an exposure device 5 for forming an electrostatic latent image on the photosensitive member 3, A rotary developing device 6 for developing an electrostatic latent image,
An intermediate transfer drum 7 and a photoreceptor cleaner 8 for transferring a single-color toner image formed on the photoreceptor 1 are provided. A secondary transfer roller 9 for transferring a full-color image on a recording medium (paper or the like), a fixing device 10 for fixing the toner image transferred on the recording medium, and a transfer drum cleaner 11 are provided. . Reference numeral 12 denotes a paper feed tray for storing a recording medium, and reference numeral 13 denotes a recording medium transport path.

The rotary developing device 6 comprises a yellow developing device 6Y, a cyan developing device 6C, a magenta developing device 6M, and a black developing device 6K rotatable. These developing devices 6Y, 6C, 6M , 6K, only the developing roller of one developing unit can selectively contact the photosensitive member 3 for each rotation of the photosensitive member 3. Each developing device has a toner cartridge 1 containing a respective toner.
4 is connected to supply toner.

The operation of the image forming apparatus having the above configuration will be described. When an image forming signal is input from a computer (not shown), the photosensitive member 3, the developing roller of the developing device 6, and the intermediate transfer drum 7 are driven to rotate, and first, the outer peripheral surface of the photosensitive member 3 is uniformly charged by the charging device 4. The outer peripheral surface of the charged and uniformly charged photoconductor 3 is selectively exposed by the exposure device 5 in accordance with the image information of the first color (for example, yellow) to form a yellow electrostatic latent image. You.

The developing unit 6Y for yellow rotates to contact the developing roller at the position of the latent image formed on the photoconductor 3, whereby the yellow electrostatic latent image toner image is formed on the photoconductor 3. Then, the toner image formed on the photoconductor 3 is transferred onto the intermediate transfer drum 7. At this time, the secondary transfer roller 9 is separated from the intermediate transfer drum 7. After the toner remaining on the photoreceptor 3 is removed by the photoreceptor cleaner 8, the surface of the photoreceptor 3
A removes electricity.

The above processing is repeated for the second, third, and fourth colors of the image forming signal, and the latent image formation, development, and transfer by one rotation of the photosensitive member 3 and the intermediate transfer drum 7 are repeated. Four color toner images corresponding to the contents of the image forming signals are superimposed and transferred on the intermediate transfer drum 7. When the full-color image reaches the secondary transfer roller 9, a recording medium (transfer paper) is supplied to the secondary transfer roller 9 from the transport path 13.
Is pressed against the intermediate transfer drum 7 and a secondary transfer voltage is applied, so that the full-color toner image on the intermediate transfer drum 7 is transferred onto a recording medium. The toner image transferred onto the recording medium is heated and pressed by the fixing device 10 and fixed. The toner remaining on the intermediate transfer drum 7 is removed by the transfer drum cleaner 11.

FIGS. 2 to 6 show one embodiment of the image forming apparatus of the present invention.
FIG. 2 shows an embodiment, and FIG.
FIG. 3 is an enlarged perspective view showing a main part of FIG. 2, and FIG.
3 is a sectional view of FIG. 3, FIG. 5 is an exploded perspective view of the coupling mechanism 31 of FIG. 3, and FIG. 6 is a plan view of a main part viewed from a direction B in FIG. Note that the same configuration is denoted by the same reference numeral in each drawing, and description thereof may be omitted.

In FIG. 2, the rotary developing device 6 has a rotating body 15 composed of a housing, and rotating shafts 16 are provided on both side surfaces of the rotating body 15, and the rotating shaft 16 is rotatable on front and rear support plates 17. It is installed. Rotating body 15
Inside, four sets of developing rollers 19 and regulating blades 20 are arranged along the outer periphery. The developing roller 19 is a means for transporting toner as a developer,
Is a means for pressing the developing roller 19 to form a thin toner layer. Four toner replenishing units 21 are mounted on one side of the rotating body 15, and these toner replenishing units 21 are respectively connected to the toner cartridges 14 by toner replenishing tubes 22.
(FIG. 1).

In FIGS. 3 and 4, a driven gear 23 is provided on the rotating body 15 on the side opposite to the toner replenishing section 21. The driven gear 23 is connected to the support plate 17 via a transmission gear 24 and a driving gear 25. It is connected to a fixed rotating body driving motor 26. A drive gear (sun gear) 27 composed of a helical gear is rotatably mounted on the rotation shaft 16 supported by the support plate 17, and the drive gear 27 is connected to a developing roller driving motor 30 via a transmission gear 29. Have been. On the other hand, on the drive gear 27 side of the four developing rollers 19, a coupling mechanism 31 is mounted on the developing roller shaft 19a. In the present invention, the developing roller driving motor 30, the transmission gear 29 and the driving gear 27 are collectively referred to as developing roller driving means.

The coupling mechanism 31 includes the developing roller shaft 1
The engaged member 32 fixed to the fixing roller 9a and the developing roller shaft 19
a, and a spring 33 is provided between the engaged member 32 and the engaging member 34. The engaging member 34 includes a plurality of engaging blades 3.
5, a plurality of engagement grooves 36 with which the plurality of blades 35 are engaged are formed in the engaged member 32. A helical gear is formed on the outer periphery of the engaging member 34, and is meshed with the helical gear of the drive gear 27. Also,
A truncated cone-shaped pressing surface 37 is formed on the outer end of the engaging member 34.

As shown in FIG. 5, the engaging blade 35 of the engaging member 34 has an engaging surface 3 extending axially from a bottom surface 35a.
5b and a sliding surface 35d extending in an arc from the leading edge 35c of the engagement surface 35b to the bottom surface 35a. on the other hand,
The engagement groove 36 of the engaged member 32 includes an engagement surface 36b extending in the axial direction from the top surface 36a, and a sliding surface 36d extending from the bottom of the engagement surface 35b to the top surface 36a in an arc shape. The engagement groove 36 is formed continuously through a leading edge 36c of the engagement surface 36b. With this configuration, the engagement member 34
Is pressed in the Y direction while rotating in the X direction, the sliding surface 35d of the engaging blade 35 is
6D, the engagement surface 35b and the engagement surface 36b are engaged, and the rotation of the engagement member 34 is transmitted to the engaged member 32.

A coupling drive mechanism 39 is attached to the support plate 17 at a position facing the rotation locus of the engagement member 34 of the coupling mechanism 31. The coupling drive mechanism 39 includes a support frame 40 fixed to the support plate 17, and a pressing member 42 supported by the support frame 40 so as to be swingable by a shaft 41.
A pressing piece 43 is provided on the coupling mechanism 31 side, and the other end of the pressing member 42 is fixed to the support frame 40 via a spring 44. With this configuration, the pressing member 4
The second pressing piece 43 is constantly urged toward the engaging member 34.

As shown in FIG. 6, the pressing piece 43 provided on the pressing member 42 is formed to have an arcuate width, and the width is a line connecting the center C of the rotating body 15 and the developing position. It has angles α and β with respect to P. With this configuration,
The engaging member 34 and the engaged member 32 are engaged at a position before the angle P with respect to the line P of the developing position, and the developing roller 19 is rotated and brought into contact with the photoreceptor. , Angle β
Can be separated from the photoreceptor while the developing roller 19 is rotated to the position.

The operation of the image forming apparatus of the present invention having the above configuration will be described. When the development cycle is completed, the rotator 15 is rotated by the rotator driving motor 26, and the developing unit 19 is on standby at a retracted position where none of the developing rollers 19 of the respective developing units contact the photosensitive member 3.

When an electrostatic latent image is formed on the photoreceptor 3 and the developing cycle starts, the rotating body driving motor 26 and the developing roller driving motor 30 are driven at a predetermined timing. The engaging member 34 of each developing roller 19 revolves around the drive gear 27 by the rotation of the rotating body 15 and rotates by itself by the drive gear 27. At this time, as shown by an arrow A in FIG. The joining member 34 is pushed outward by the spring 33, and the engaging blade 35 is retracted from the engaging groove 36. Therefore, in this state, the rotation of the engaging member 34 is not transmitted to the developing roller 19 via the engaged member 32.

When the engaging member 34 of the developing roller 19 involved in the development rotates to the position of the pressing piece 43 of the coupling drive mechanism 39, the pressing piece 43 presses the pressing surface 47 of the engaging member 34. As a result, the engaging member 34 is
As a result, the rotating blade 15 is stopped at the developing position in a state where the engaging blade 35 enters the engaging groove 36 and both are engaged with each other. At this time, as described in FIG. 6, since the coupling mechanism 31 is engaged immediately before the rotating body 15 stops at the developing position,
The developing roller 19 can be rotated. Then, the rotation of the engaging member 34 is transmitted to the developing roller 19, and the electrostatic latent image on the photoconductor 3 is developed. When the development is completed, the rotating body 15 rotates, but immediately thereafter, the coupling mechanism 31 is engaged, so that the developing roller 19 can be separated from the photosensitive member without stopping, and the rotation of the developing roller can be stopped. Separation can be reliably performed.

The engaging blade 35 and the engaging groove 36
In the process where the coupling is repeatedly performed, the leading edges 35c and 36c of the two collide with a small probability,
As a result, there is a problem that the engaging blade 35 or the pressing piece 43 is broken. In order to solve this, a spring 44 for urging the pressing piece 43 in the retreating direction is provided in the coupling drive mechanism 39 so that the pressing piece 43 is retracted when an edge contact occurs. Further, by engaging the drive gear 27 and the outer periphery of the engagement member 34 with a helical gear, the engagement member 34 can easily escape in the direction of the pressing piece 43 when an edge contact occurs due to an axial thrust. I have.

[0026]

As is apparent from the above description, according to the present invention, the developing roller can be rotated immediately before the rotating body stops at the developing position, and the developing roller can be stopped after the development is completed. The rotating member can be separated from the photosensitive member without any contact, and the rotation contact and separation of the developing roller can be reliably performed.

[Brief description of the drawings]

FIG. 1 is an overall configuration diagram illustrating an example of an image forming apparatus to which the present invention is applied.

FIG. 2 is a perspective view of the rotary developing device of FIG. 1, showing one embodiment of the image forming apparatus of the present invention.

FIG. 3 is an enlarged perspective view showing a main part of FIG. 2;

FIG. 4 is a sectional view of FIG. 3;

FIG. 5 is an exploded perspective view of the coupling mechanism of FIG. 3;

FIG. 6 is a plan view of a main part viewed from a direction B in FIG. 4;

7 (A) is a perspective view of a main part showing a conventional rotary developing device, and FIG. 7 (B) is a cross-sectional view taken along line BB of FIG. 7 (A).

[Explanation of symbols]

 6 rotary developing device 15 rotating body 19 developing roller 19a developing roller shaft 27 sun gear (developing roller driving means) 32 engaged member 34 engaging member 35 engaging blade 36 engaging groove 42 Pressing member 44 ... Spring

Claims (4)

[Claims] In an image forming apparatus for performing multicolor development by a plurality of developing devices mounted on a rotating body, an engaged member fixed to a developing roller shaft of each developing device and a separated member are disposed on the engaged member. An engaging member disposed so as to be contactable, a developing roller driving means for rotating the engaging member, and a pressing member for pressing the engaging member toward the engaged member before and after the developing position. Characteristic image forming apparatus. 2. A plurality of engaging blades are formed on the engaging member, and a plurality of engaging grooves with which the engaging blades are engaged are formed on the engaged member. The image forming apparatus according to claim 1. 3. An image forming apparatus according to claim 1, wherein said developing roller driving means is a sun gear meshed with a gear formed on an outer periphery of each engaging member. 4. An image forming apparatus according to claim 1, wherein said pressing member presses said engaging member by a spring.