JP3651578B2 - Image forming apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an image forming apparatus such as a copying machine, a printer, and a fax machine that uses electrophotography, and more particularly to an image forming apparatus that performs multicolor development using a plurality of developing units mounted on a rotating body.
[0002]
[Prior art]
As an image forming apparatus using electrophotography, an electrostatic latent image of a plurality of colors is sequentially formed on a photosensitive member, and the electrostatic latent image is sequentially developed into each color toner image by a rotary developing device. There is a system in which the image is transferred onto a transfer medium, transferred, a full color toner image transferred onto the intermediate transfer medium is transferred to a transfer material, and then fixed.
[0003]
The rotary developing device is provided with a rotating body facing the photoreceptor, and a plurality of developing units (yellow, cyan, magenta, black developing units) are mounted in the rotating body, and the rotating body is rotated and moved. The electrostatic latent image is developed with toner by selectively bringing one of the plurality of developing units into contact with the developing position of the photosensitive member, rotating the developing roller in the developing unit and applying a developing bias. Yes.
[0004]
In the rotary developing device, when the developing roller in contact with the developing position of the photosensitive member is rotated, if the developing roller of another developing device is also rotated, it causes toner deterioration, scattering, and color mixing. In addition, the load torque increases in a single drive means, which increases the power consumption and increases the cost of the motor as the drive means. Therefore, a system is adopted in which only the developing roller in contact with the developing position of the photosensitive member is rotated (for example, JP-A-9-101675).
[0005]
FIG. 7A is a perspective view showing a main part of the conventional method, and FIG. 7B is a cross-sectional view taken along line BB in FIG. 7A. Driven gears 52 (52a to 52d) connected to the rotation shafts of the developing rollers are disposed on one side 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. It is transmitted to the drive gear 56 via the belt 55, and the driven gear 52 engages with the drive gear 56 when any of the developing rollers reaches the developing position, and the drive motor 51 rotates. Is transmitted to the developing roller, and a power supply brush 62 (62a to 62d) that is in contact with each developing roller is disposed on one side surface of the rotating body 50. On the other hand, the image forming apparatus The main body 64 is provided with a power feeding plate 63 connected to a developing bias power source. When any one of the developing rollers reaches the developing position, the power feeding plate 63 is brought into contact with the power feeding brush 62, and Bias is configured to be applied to the developing roller.
[0006]
[Problems to be solved by the invention]
By the way, in the rotary developing device, the developing roller contacts and separates from the photosensitive member, but when the developing roller comes into contact with the photosensitive member in a stopped state, the toner on the surface of the developing roller is scraped by the contact force with the photosensitive member. As a result, the surface of the developing roller is exposed and the photosensitive layer of the photosensitive member is damaged. Therefore, it is necessary to rotate the developing roller so that the toner layer is equidistantly contacted with the toner layer (hereinafter referred to as rotating contact of the developing roller). However, in the above-described conventional system, power can be transmitted only within the range of operation in which the driving gear 56 and the non-driving gear 52 are in contact with or separated from each other, so that the developing roller does not sufficiently rotate and contacts the photosensitive member. Or it has the problem that there exists a possibility of separating.
[0007]
SUMMARY An advantage of some aspects of the invention is that it provides an image forming apparatus capable of reliably rotating and contacting a developing roller.
[0008]
[Means for Solving the Problems]
In order to achieve the above object, an image forming apparatus according to the present invention is an engagement device fixed to a developing roller shaft of each developing device in an image forming device that performs multicolor development by a plurality of developing devices mounted on a rotating body. And a developing roller driving means for rotating the engaging member, and the developing roller driving means is a sun gear comprising a helical gear. A helical gear meshing with the sun gear of the developing roller driving means is formed on the outer periphery of each engaging member, and the engaging member is engaged with the developing roller driving means while maintaining the meshing state. And a pressing member that presses the engaging member toward the engaged member. The pressing member is swingably attached to a fixed support plate and is provided with a spring that presses the engaging member. To do.
In the image forming apparatus of the present invention, the engagement member is formed with a plurality of engagement blades, and the engaged member is formed with a plurality of engagement grooves with which the engagement blades are engaged. It is characterized by that.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described 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. The image forming apparatus is a color electrophotographic printer capable of forming a full color image with four colors of toner, but the present invention is not limited to this, and all color images using electrophotography are used. It can be applied to a forming apparatus.
[0010]
In the case main body 2 of the image forming apparatus 1, a photoconductor 3 which is a latent image carrier is disposed. The photoreceptor 3 has a belt-like conductive base material and a photosensitive layer formed on the surface thereof, and is driven to rotate in the direction of the arrow shown by a driving means (not shown). Around the photoconductor 3, a charging device 4 for uniformly charging the photoconductor 3 along the rotation direction, an exposure device 5 for forming an electrostatic latent image on the photoconductor 3, a static A rotary developing device 6 for developing an electrostatic latent image, an intermediate transfer drum 7 for transferring a monochromatic toner image formed on the photosensitive member 1, and a photosensitive member cleaner 8 are disposed. In the periphery, a secondary transfer roller 9 for transferring a four-color full-color image formed on the intermediate transfer drum 7 onto a recording medium (paper or the like), and a fixing for fixing the toner image transferred onto the recording medium. An apparatus 10 and a transfer drum cleaner 11 are provided. Reference numeral 12 denotes a paper feed tray for storing the recording medium, and 13 denotes a recording medium conveyance path.
[0011]
The rotary developing device 6 is configured such that a yellow developing unit 6Y, a cyan developing unit 6C, a magenta developing unit 6M, and a black developing unit 6K are rotatable, and these developing units 6Y, 6C, 6M, 6K In addition, only the developing roller of one developing device is selectively brought into contact with the photosensitive member 3 every rotation of the photosensitive member 3. Each developing device is connected to a toner cartridge 14 in which each toner is accommodated so as to supply toner.
[0012]
The operation of the image forming apparatus having the above configuration will be described. When an image forming signal from a computer (not shown) is input, the photosensitive member 3, the developing roller of the developing device 6 and the intermediate transfer drum 7 are rotationally driven. First, the outer peripheral surface of the photosensitive member 3 is uniformly made by the charging device 4. The exposure device 5 selectively exposes the charged and uniformly charged outer peripheral surface of the photoreceptor 3 in accordance with image information of the first color (for example, yellow) to form a yellow electrostatic latent image. The
[0013]
At the position of the latent image formed on the photoreceptor 3, the yellow developing device 6 </ b> Y rotates and the developing roller comes into contact therewith, whereby a yellow electrostatic latent image toner image is formed on the photoreceptor 3. Next, the toner image formed on the photoreceptor 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 photosensitive member 3 is removed by the photosensitive member cleaner 8, the surface of the photosensitive member 3 is discharged by the discharging unit 8A.
[0014]
In response to the second color, the third color, and the fourth color of the image formation signal, the above processing repeats latent image formation, development, and transfer by one rotation of the photosensitive member 3 and the intermediate transfer drum 7, and the image formation signal Four color toner images corresponding to the contents of the toner image are superimposed and transferred on the intermediate transfer drum 7. Then, at the timing when this full-color image reaches the secondary transfer roller 9, the recording medium (transfer paper) is supplied from the conveyance path 13 to the secondary transfer roller 9, and at this time, the secondary transfer roller 9 is transferred to the intermediate transfer drum 7. When pressed, a secondary transfer voltage is applied, and the full-color toner image on the intermediate transfer drum 7 is transferred onto the recording medium. The toner image transferred onto the recording medium is fixed by being heated and pressed by the fixing device 10. The toner remaining on the intermediate transfer drum 7 is removed by the transfer drum cleaner 11.
[0015]
2 to 6 show one embodiment of the image forming apparatus of the present invention, FIG. 2 is a perspective view of the rotary developing device 6 of FIG. 1, and FIG. 3 is an enlarged perspective view showing the main part of FIG. 4 is a cross-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 the main part seen from the direction B of FIG. In addition, about the same structure between each drawing, the same number may be attached | subjected and description may be abbreviate | omitted.
[0016]
In FIG. 2, the rotary developing device 6 has a rotating body 15 formed of a housing. A rotating shaft 16 is provided on both side surfaces of the rotating body 15, and the rotating shaft 16 is rotatably attached to the front and rear support plates 17. Yes. In the rotating body 15, four sets of the developing roller 19 and the regulating blade 20 are disposed along the outer periphery thereof. The developing roller 19 is a means for conveying toner as a developer, and the regulating blade 20 is a means for forming a thin toner layer by being pressed against the developing roller 19. Four toner replenishing portions 21 are mounted on one side of the rotating body 15, and these toner replenishing portions 21 are connected to the respective toner cartridges 14 (FIG. 1) by toner replenishing tubes 22.
[0017]
3 and 4, a driven gear 23 is provided on the opposite side of the rotating body 15 from the toner replenishing portion 21, and the driven gear 23 is fixed to the support plate 17 via a transmission gear 24 and a driving gear 25. The rotating body driving motor 26 is connected. A drive gear (sun gear) 27 formed of a helical gear is rotatably mounted on the rotary 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. Has 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.
[0018]
The coupling mechanism 31 includes an engaged member 32 fixed to the developing roller shaft 19a, and an engaging member 34 slidably disposed on the developing roller shaft 19a, and is engaged with the engaged member 32. A spring 33 is provided between the members 34. The engaging member 34 is provided with a plurality of engaging blades 35, and the engaged member 32 is formed with a plurality of engaging grooves 36 with which the plurality of blades 35 are engaged. A helical gear is formed on the outer periphery of the engaging member 34 and meshed with the helical gear of the drive gear 27. A frustoconical pressing surface 37 is formed at the outer end of the engaging member 34.
[0019]
As shown in FIG. 5, the engagement blade 35 of the engagement member 34 includes an engagement surface 35b extending in the axial direction from the bottom surface 35a, and a sliding surface extending from the tip edge 35c of the engagement surface 35b to the bottom surface 35a in an arc shape. 35d. 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. Four engagement grooves 36 are formed continuously via the leading edge 36c of the engagement surface 36b. With this configuration, when the engaging member 34 is pressed in the Y direction while rotating in the X direction in the figure, the sliding surface 35d of the engaging blade 35 is inserted while sliding on the sliding surface 36d of the engaging groove 36. Then, the engagement surface 35 b and the engagement surface 36 b are engaged, and the rotation of the engagement member 34 is transmitted to the engaged member 32.
[0020]
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 that is fixed to the support plate 17 and a pressing member 42 that is swingably supported by the support frame 40 by a shaft 41, and presses the pressing member 42 toward the coupling mechanism 31. A piece 43 is provided, 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 piece 43 of the pressing member 42 is always biased toward the engaging member 34.
[0021]
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 relative to a line P connecting the center C of the rotating body 15 and the developing position. And have angles α and β. With this configuration, the engaging member 34 and the engaged member 32 are engaged with each other at a position that is an angle α before the developing position line P, and the developing roller 19 is rotated and brought into contact with the photosensitive member. At the end of development, the developing roller 19 can be moved away from the photoreceptor while being rotated to the position of the angle β.
[0022]
The operation of the image forming apparatus of the present invention having the above configuration will be described. When the developing cycle is completed, the rotating body 15 is rotated by the rotating body driving motor 26, and the developing roller 19 of each developing device is on standby at a retracted position where the developing roller 19 does not contact the photoreceptor 3.
[0023]
When an electrostatic latent image is formed on the photosensitive member 3 and a development cycle starts, the rotary member 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 driving gear 27 by the rotation of the rotating body 15 and rotates by the driving gear 27 itself. At this time, as shown by an arrow A in FIG. The joint member 34 is pushed outward by the spring 33, and the engagement blade 35 is retracted from the engagement 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.
[0024]
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 pressed against the engaged member 32 against the spring 33, and as a result, the rotating body 15 is developed in a state where the engaging blade 35 enters the engaging groove 36 and is engaged. Stop at position. At this time, as described with reference to 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 photoreceptor 3 is developed. When the development is completed, the rotating body 15 rotates. Immediately after that, since the coupling mechanism 31 is engaged, the developing roller 19 can be separated from the photoreceptor without stopping, and the developing roller can be rotated. Separation and contact can be performed reliably.
[0025]
By the way, in the process in which the coupling between the engagement blade 35 and the engagement groove 36 is repeatedly performed, the leading edges 35c and 36c of the both collide with a slight probability. As a result, the engagement blade 35 or the pressing piece 43 There is a problem of being damaged. In order to solve this, a spring 44 that urges the pressing piece 43 in the retracting direction is provided in the coupling drive mechanism 39 so that the pressing piece 43 is retracted when the edge hit occurs. Further, by engaging the outer periphery of the drive gear 27 and 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 hit occurs due to axial thrust. Yes.
[0026]
【The invention's effect】
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 rotating body can be exposed to light without stopping the developing roller after completion of development. The developer roller can be separated from the body, and the rotating contact of the developing roller can be reliably performed.
[Brief description of the drawings]
FIG. 1 is an overall configuration diagram showing 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 an embodiment of the image forming apparatus of the present invention.
FIG. 3 is an enlarged perspective view showing a main part of FIG. 2;
4 is a cross-sectional view of FIG.
5 is an exploded perspective view of the coupling mechanism of FIG. 3. FIG.
6 is a plan view of a main part when viewed from a direction B in FIG. 4;
7A is a perspective view of a main part of a conventional rotary developing device, and FIG. 7B is a cross-sectional view taken along line BB in FIG. 7A.
[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 (2)

In an image forming apparatus that performs multi-color development using a plurality of developing units mounted on a rotating body, an engaged member fixed to a developing roller shaft of each developing unit and a member that is detachable from the engaged member An engaging member, a developing roller driving unit for rotating the engaging member, and the developing roller driving unit is a sun gear formed of a helical gear, and the developing roller driving unit is disposed on an outer periphery of each engaging member. A helical gear that meshes with the sun gear, and the engagement member presses the engagement member toward the engaged member before and after the development position while maintaining engagement with the developing roller driving means. An image forming apparatus , wherein the pressing member is swingably attached to a fixed support plate and provided with a spring that presses the engaging member .   2. The engagement member is formed with a plurality of engagement blades, and the engaged member is formed with a plurality of engagement grooves with which the engagement blades are engaged. Image forming apparatus.

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