JP2004258353A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus that decreases the level of uneven pitch occurring on an image by realizing stable engagement of gears in the middle of each gear tooth width, thereby preventing minute vibration which occurs when the gears engage with each other. <P>SOLUTION: The drive unit disposed in the main body of the image forming apparatus or a drive means in a process cartridge drives one or more image carriers. In the drive unit or the drive means, the teeth faces of the gears 47 of an image carrier drive gear train which drives the image carrier have the shape of a crown. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an electrophotographic image forming apparatus such as a color copying machine or a color printer, and relates to prevention of print position deviation and pitch unevenness when forming a multicolor image on a recording medium.
[0002]
[Prior art]
In recent years, the demand for a color electrophotographic image forming apparatus capable of forming a color image has been increasing, and (1) low running cost, (2) small space, (3) low power, (4) high image quality, It is expected that a color image forming apparatus capable of achieving the six items of (5) high speed and (6) improvement of operability will be introduced.
[0003]
Among them, (6) a method for providing a technique for providing a high-quality color image while (5) increasing the speed while simplifying the operability, and providing a color image forming apparatus with yellow, There is a system in which four photosensitive drums are arranged in parallel using four process cartridges of magenta, cyan, and black to form an image, thereby improving operability and increasing speed.
This method is called a tandem type or a four-drum type color image forming apparatus.
[0004]
Also in this method, (4) as a factor that hinders improvement in image quality, a minute vibration generated by engagement of a driving gear train for driving the photosensitive drum causes uneven rotation of the photosensitive drum, resulting in pitch unevenness on an image. There is a problem of appearing.
[0005]
To cope with this, the drive gear for driving the photosensitive drum should have a large diameter to reduce the pitch of the pitch unevenness generated on the image, or the number of reduction steps of the drive gear train for driving the photosensitive drum should be one. There has been an improvement method such as limiting the meshing frequency generated in the above to one to make pitch unevenness less noticeable.
[0006]
[Problems to be solved by the invention]
However, in the case of the above-mentioned conventional technology, the following problems have occurred.
[0007]
That is, the above-described conventional configuration does not reduce the cause of the fundamental pitch unevenness, but aims at making the generated pitch unevenness less noticeable. A poor level of pitch unevenness may occur on an image due to an increase in meshing vibration due to deterioration of durability.
[0008]
The large-diameter gear configuration has an effect of making initial pitch unevenness less noticeable, but simply reduces the pitch of the pitch unevenness generated on the image (increases the gear meshing frequency) to obtain a visible image at the conventional image observation distance. In an image forming apparatus capable of outputting color photographic images and the like with higher image quality because the purpose is to make the sensitivity or less, the user holds the output color photographic image in his hand, which is longer than the conventional image observation distance. Since the output image is determined at a short observation distance, the pitch (frequency), which is lower than the visible sensitivity in the conventional configuration, may deteriorate the user's impression and cause a complaint.
[0009]
Further, in the single-stage reduction configuration, it is necessary to reduce the number of teeth as much as possible by directly cutting the rotating metal shaft of a driving source such as a motor in order to increase the reduction ratio. Since the large-diameter gear of the mold directly meshes with the gear, at the end of the life of the image forming apparatus, the tooth surface of the large-diameter gear of the mold wears due to durability, and the vibration due to the meshing of the gear increases. There was a problem of getting worse.
[0010]
The present invention has been made in order to solve the above-mentioned problems of the prior art, and an object thereof is to realize a stable meshing by a central portion of a tooth width of a gear, and to reduce a minute vibration generated at the time of meshing. An object of the present invention is to provide an image forming apparatus that suppresses the occurrence of a pitch unevenness level on an image while suppressing the occurrence.
[0011]
[Means for Solving the Problems]
In order to solve the above problems, the present invention has the following means.
[0012]
That is, the image forming apparatus of the present invention is an image forming apparatus that drives one or a plurality of image carriers, an image that drives the image carriers in a driving unit provided in the image forming apparatus main body, or a driving unit in a process cartridge. The gear tooth surface of the carrier drive gear train is formed in a crowning shape.
[0013]
Further, the image forming apparatus of the present invention transmits a drive to each rotation drive unit of the charging unit and the developing unit of a process cartridge having a charging unit and a developing unit acting on one or a plurality of image carriers. In a driving unit provided in the image forming apparatus main body or a driving unit in the process cartridge, a gear tooth surface of the charging unit driving gear train or the developing unit driving gear train for driving the charging unit or the developing unit. It features a crowning shape.
[0014]
Further, the image forming apparatus according to the present invention includes a driving unit provided in the main body of the image forming apparatus or a driving unit in the intermediate transfer body unit for driving an intermediate transfer body for sequentially transferring the respective color toner images on the image carrier in a superimposed manner. , Wherein a gear tooth surface of an intermediate transfer member driving gear train for driving the intermediate transfer member has a crowning shape.
[0015]
Still further, in the image forming apparatus of the present invention, a configuration is also exemplified in which each gear of the image carrier driving gear train, the charging unit driving gear train, the developing unit driving gear train, and the intermediate transfer body driving gear train is a helical gear. it can.
[0016]
Furthermore, in the image forming apparatus of the present invention, in the image carrier driving gear train, the charging unit driving gear train, the developing unit driving gear train, and the intermediate transfer body driving gear train, gear tooth surfaces of all gears are changed. A configuration having a crowning shape can also be exemplified.
[0017]
Still further, in the image forming apparatus of the present invention, in the image carrier driving gear train, the charging unit driving gear train, the developing unit driving gear train, and the intermediate transfer body driving gear train, at least one of the gear pairs meshing with each other. A configuration in which the gear tooth surface of the gear is crowned can also be exemplified.
[0018]
For example, an image forming apparatus that drives each of image forming units such as a photoconductor drum, a charging unit acting on the photoconductor drum, a developing unit, and an intermediate transfer body that sequentially transfers the respective color toner images on the photoconductor drum in an overlapping manner. The gear tooth surfaces of the drive gear train in the drive unit provided in the main body or the drive means in the process cartridge and in the intermediate transfer body unit are formed in a crowning shape. The crowning of the gear tooth surfaces has a remarkable effect when the drive gear train for driving each of the image forming units is constituted by a helical gear.
[0019]
When the helical gear meshes, one end in the tooth width direction of the gear contacts the mating gear and starts meshing, and the other end separates from the mating gear and ends the meshing. (See FIG. 6 (c)), an impact vibration occurs, which is transmitted directly to the photoreceptor drum, and noticeable pitch unevenness occurs on the image.
[0020]
Therefore, if the tooth surface of the gear is formed into a crowning shape (see FIG. 6D), both ends of the tooth width become smaller than the center part, so that the normal gear starts contacting for a short time at the beginning of meshing. The timing is later than the timing, and at the end of the meshing, the separation becomes earlier by a very short time, so that stable meshing by the central part of the gear tooth width can be realized, and the occurrence of minute vibration generated at the time of meshing is suppressed and the image is reduced. It becomes possible to reduce the pitch unevenness level generated above.
[0021]
At this time, the meshing ratio is slightly reduced by forming the gear tooth surface into a crowning shape as described above. However, the reduction is slight, and if the meshing ratio is sufficiently secured in advance, it can be reduced on the image. There is no adverse effect on the pitch unevenness level.
[0022]
In addition, the crowning of the gear tooth surface is stabilized by the central portion of the gear tooth width as described above, even when the parallelism between the shafts is slightly deviated due to the inclination of the crimping shaft of the gear or the deterioration of the flatness of the sheet metal, as described above. Since the meshing can be realized, the effect of suppressing the generation of the minute vibration by keeping the meshing smooth can be expected.
[0023]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. However, the dimensions, materials, shapes, relative arrangements, and the like of the components described in this embodiment are not intended to limit the technical scope of the present invention to them unless otherwise specified. Not something.
[0024]
(First embodiment)
[Overall Description of Image Forming Apparatus]
First, the overall configuration of the image forming apparatus will be schematically described with reference to FIG.
[0025]
FIG. 1 is an explanatory diagram of the overall configuration of a laser printer, which is an embodiment of a color image forming apparatus.
[0026]
As shown in the overall configuration diagram of FIG. 1, the color laser printer includes an image forming unit having image carriers 1Y, 1M, 1C, and 1K that rotate at a constant speed for each color of Y, M, C, and Bk, and a color developing unit. And an intermediate transfer member that holds the color image that has been developed and transferred by the image forming unit and is transferred to the transfer material 2 fed from the feeding unit. The transfer material 2 on which the color image has been transferred is then transported to a fixing unit to fix the color image on the transfer material, and is discharged to a discharge unit on the upper surface of the apparatus by a discharge roller. The four color developing units are configured to be individually detachable from the printer main body.
[0027]
Next, the configuration of each section of the image forming apparatus will be sequentially described in detail.
[0028]
[Image carrier]
The image carriers (photosensitive drums) 1Y, 1M, 1C, and 1K are integrally formed with containers 3Y, 3M, 3C, and 3K of developing device holders, and the developing units 4Y, 4M, 4C, and 4K are attached to the printer body. Are detachably supported, and the unit can be easily replaced in accordance with the life of the image carriers 1Y,. The image carriers (photosensitive drums) 1Y,... According to the present embodiment are formed by coating an organic photoconductor layer on the outside of an aluminum cylinder, and are rotatable on containers 3Y,. It is supported by. Also, by transmitting the driving force of a driving motor (not shown) to one end on the rear side in the drawing, the image carriers 1Y,... Are rotated counterclockwise in the drawing in accordance with the image forming operation.
[0029]
[Charging means]
The charging means 5Y, 5M, 5C, and 5K use an injection charging method, and uniformly charge the surface of the image carriers 1Y,.
[0030]
[Exposure means]
Exposure to the image carriers 1Y,... Is performed from the scanner units 6Y, 6M, 6C, 6K. That is, when an image signal is given to a laser diode, the laser diode irradiates image light corresponding to the image signal to the polygon mirrors 6Ya,. The polygon mirror 6a is rotated at a high speed by a scanner motor, and the image light reflected by the polygon mirrors 6Ya,... Selectively exposes the surfaces of the image carriers 1Y,. As a result, an electrostatic latent image is formed on the image carrier.
[0031]
[Developing means]
The developing means is composed of four developing devices 4Y, 4M, 4C, and 4K capable of developing respective colors of yellow, magenta, cyan, and black in order to visualize the electrostatic latent image. Each of the four color developing units 4Y, 4M, 4C, and 4K has sleeves 3YS, 3MS, 3CS, and 3KS arranged at a small distance from the image carrier 1 at positions opposed to the image carriers 1Y,. A visible image is formed by each color toner on the body 1Y,.
[0032]
The developing devices 4Y,... Of each color feed the toner in the container by a feeding mechanism, and the outer periphery of the sleeve 3S is rotated in a clockwise direction in the drawing by mixing the powder obtained by mixing the toner (non-magnetic) and the developer (magnetic) with the outer periphery of the sleeve 3S. Coat. After that, the toner in the powder is developed with the toner corresponding to the electrostatic latent images of the image carriers 1Y,.
[0033]
[Intermediate transfer member]
During the color image forming operation, the intermediate transfer member 9 rotates clockwise in the figure in synchronization with the outer peripheral speed of the image carriers 1Y,... In order to multiplex transfer the toner image on the image carrier 1 visualized by each developing device. Further, the intermediate transfer body 9 that has undergone the multiple transfer simultaneously transfers the toner images of the respective colors on the intermediate transfer body onto the transfer material 2 by sandwiching and transporting the transfer material 2 with the secondary transfer roller 10 to which a voltage is applied.
[0034]
The intermediate transfer body 9 according to the present embodiment is formed of a resin belt having a circumference of about 1000 mm, and is stretched around three axes of a driving roller 9a, a secondary transfer facing roller 9b, and a tension roller 9c. Even if a load is applied to both ends by a spring 9e, even if the circumference of the intermediate transfer belt 9 changes due to temperature and humidity in the main body or a change in diameter, the amount of change can be absorbed. The intermediate transfer body 9 is supported by a main body with a driving roller as a fulcrum. By transmitting a driving force of a driving motor (not shown) to one end on the rear side of the drawing to the driving roller, the intermediate transfer body 9 is moved according to an image forming operation. It is made to rotate around. Further, the intermediate transfer member 9 can be easily attached to and detached from the front in the figure.
[0035]
[Paper feed unit]
The paper feeding unit feeds the transfer material to the image forming unit, and includes a cassette 7 containing a plurality of transfer materials 2 and a paper feed roller 8a, a feed roller 8b, a retard roller 8c for preventing double feed, a paper feed. It mainly comprises a guide 8d and a registration roller 8e. At the time of image formation, the paper feed roller 8a is driven and rotated in accordance with the image forming operation, separates and feeds the transfer material 2 in the cassette 7 one by one, is guided by the guide plate 8d, and is registered via the transport roller. 8e. During the image forming operation, the registration roller 8e performs a non-rotating operation of keeping the transfer material 2 stationary and a rotating operation of transporting the transfer material 2 toward the intermediate transfer body in a predetermined sequence, and performs the next process, transfer. The image at the time of the process and the transfer material 2 are aligned.
[0036]
[Transfer section]
The transfer section includes a swingable transfer roller 10. The transfer roller 10 is formed by winding a metal shaft with a medium-resistance foamed elastic body, is movable up and down in the figure, and is driven. While forming the four-color toner image on the intermediate transfer member 9, that is, until the toner image on the intermediate transfer member 9 reaches the secondary transfer portion, transfer is performed as shown by a dotted line in the drawing so as not to disturb the image. The roller 10 is located below and is separated from the intermediate transfer body 9.
[0037]
Thereafter, the transfer roller 10 is pressed by a cam member (not shown) at an upper position indicated by a solid line in the drawing, that is, at a predetermined pressure to the intermediate transfer body 9 via the transfer material 2 in accordance with the timing of transferring the color image to the transfer material 2. Can be At this time, a bias is applied to the transfer roller 10 at the same time, and the toner image on the intermediate transfer body 9 is transferred to the transfer material 2. Here, since the intermediate transfer member 9 and the transfer roller 10 are driven respectively, the transfer material 2 sandwiched between the two is transferred at a predetermined speed in the left direction in the drawing at the same time as the transfer process is performed. Is sent to the fixing device.
[0038]
[Intermediate transfer body cleaning unit]
The intermediate transfer member cleaning unit 14 includes a cleaning blade 12a, a pressure spring 12e for pressing the cleaning blade 12a against the intermediate transfer member 9, a fur brush 13, and a cleaner container 14a for holding these.
[0039]
The fur brush 13 is formed of rayon yarn and removes the charge of the toner image that has not been transferred on the intermediate transfer member after the secondary transfer. The fur brush 13 is rotated at a constant peripheral speed in the opposite direction (clockwise) with respect to the intermediate transfer body 9 by transmitting the driving force of a driving motor (not shown) to one end in the front of the drawing. Note that a tension roller 9c is disposed as a backup roller at a portion facing the fur brush 13.
[0040]
The material of the cleaning blade 12a is urethane rubber, which is affixed to the metal plate 12b, and is pressed against the intermediate transfer body 9 at a predetermined angle by a pressure spring 12e about a shaft 12d held by a cleaner container 14a as a rotation center. The intermediate transfer member 9 can be uniformly contacted. In addition, a tension roller 9c is disposed as a backup roller at a portion facing the cleaning blade 12a, and the cleaning blade 12a is configured to be able to contact the intermediate transfer member 9 with a predetermined contact pressure. At the point where the cleaning blade 12a comes into contact, the toner image removed by the fur brush 13 is scraped off the intermediate transfer member 9 and the intermediate transfer member 9 is cleaned.
[0041]
The discharged toner scraped off by the cleaning blade 12a is collected in a cleaner container 14a, and is discharged via a relay hose 24 separately disposed in the main body by a screw 14b disposed at the lowermost portion of the cleaner container 12a. Sent to and collected. The screw 14b is rotated in the conveying direction of the screw by transmitting the driving force of a driving motor (not shown) to one end on the rear side in the figure.
[0042]
[Fixing section]
The fixing section 17 fixes the toner image formed on the transfer material 2 via the intermediate transfer member 9 to the toner image formed by the developing means, and transfers heat to the transfer material 2 as shown in FIG. The fixing roller 18 includes a fixing roller 18 for applying toner and a pressure roller 19 for pressing the transfer material 2 against the fixing roller 18. Each roller is a hollow roller and has a heater (not shown) inside, and is driven to rotate and transfer simultaneously. It is configured to transport the material 2. That is, the transfer material 2 holding the toner image is conveyed by the fixing roller 18 and the pressure roller 19 and heat and pressure are applied to fix the toner to the transfer material 2.
[0043]
[Image forming operation]
Next, an operation when image formation is performed by the apparatus configured as described above will be described.
[0044]
First, the paper feed roller 8a shown in FIG. 1 is rotated to separate one transfer material 2 in the paper feed cassette 1 and transport it to the registration roller 8e.
[0045]
On the other hand, the image carriers 1Y,... And the intermediate transfer member 9 rotate at predetermined outer peripheral speeds V (hereinafter, referred to as process speeds) in the directions indicated by arrows.
[0046]
When an arbitrary point on the outer periphery of the illustrated intermediate transfer body reaches the position shown in FIG. S, the image carrier 1 whose surface is uniformly charged by the charging means receives laser exposure at the position shown in E to form an image. The distance a from the exposure position E of the image carrier 1 to the contact portion T1 with the intermediate transfer member 9 in the counterclockwise direction is equal to the distance b from the point S to the point T1 on the intermediate transfer member 9 in the counterclockwise direction. At the beginning of writing and the point S on the intermediate transfer member 9 coincide with the position of T1. That is, an image is formed counterclockwise on the intermediate transfer member 9 with the point S as a tip.
[0047]
1: Formation of yellow image
The scanner unit 6Y irradiates a yellow image with a laser to form a yellow latent image on the image carrier 1Y. Simultaneously with the formation of the latent image, the yellow developing device 4Y is driven to apply a voltage having the same polarity and substantially the same potential as the charging polarity of the image carrier 1Y so that the yellow toner adheres to the latent image on the image carrier 1. Perform development. At the same time, the yellow toner image on the image carrier 1Y is primarily transferred to the outer periphery of the intermediate transfer member 9 at a first transfer position T1Y slightly downstream of the developing section. At this time, a voltage having a characteristic reverse to that of the yellow toner is applied to the intermediate transfer member 9 to perform primary transfer.
[0048]
When the image to be formed is A3 size, the length is 420 mm, and the image is formed from the outer periphery S point of the intermediate transfer body 9 to the L1 point.
[0049]
2: Magenta image formation
Next, when one point S (the tip of the yellow image) on the outer periphery of the intermediate transfer member 9 comes to the position of S 'in the drawing, the magenta image laser irradiation is similarly started by the scanner section 6M, and the image carrier 1M is made in the same manner as yellow. The magenta toner image is developed on the upper latent image, and the magenta toner image on the image carrier 1M is transferred onto the intermediate transfer member 9 at the first transfer position T1M.
[0050]
3: formation of cyan image
Next, when one point S (the leading end of the yellow and magenta images) on the outer periphery of the intermediate transfer member 9 comes to the position of S ″ in the drawing, the laser irradiation of the cyan image is similarly started by the scanner unit 6C, and the image carrier is similarly operated in the magenta manner. A cyan toner image is developed on the latent image on 1C, and the cyan toner image on the image carrier 1C is transferred onto the intermediate transfer member 9 at the first transfer position T1C so as to overlap the yellow and magenta toner images.
[0051]
4: Black image formation
Next, when one point S (the leading end of the yellow / magenta / cyan image) on the outer periphery of the intermediate transfer member 9 reaches the position of S ′ ″ in the drawing, similarly, laser irradiation of the black image is started by the scanner unit 6K, and the same as in the case of cyan. As a result, a black toner image is developed on the latent image on the image carrier 1 and the black toner image on the image carrier 1K is further transferred onto the intermediate transfer member 9 at the first transfer position T1K.
[0052]
As described above, the latent image formation, development, and toner transfer to the intermediate transfer member 9 are performed at the respective primary transfer positions T1Y, T1M, T1C, and T1K in the order of yellow, magenta, cyan, and black. , Magenta, cyan, and black toners to form a full-color image.
[0053]
Before the transfer of the black toner to the intermediate transfer member 9 is completed, that is, the image front end S of the intermediate transfer member 9 which has completed the first transfer of the fourth color black toner to form a full-color image is transferred to the secondary transfer portion T2. Before the transfer, the transfer material 2 that has been waiting by the above-described registration roller is started to be conveyed at an appropriate timing.
[0054]
At the time of image formation of each color on the above-described four-color intermediate transfer body 9, the transfer roller 10, which waits downward and is not in contact with the intermediate transfer body 9, is simultaneously moved upward by a cam (not shown) to transfer material. 2 at the second transfer portion T2 of the intermediate transfer member 9 and simultaneously applying a bias having a characteristic reverse to that of the toner to the transfer roller 10, thereby simultaneously transferring four colors of the full-color image on the intermediate transfer member 9 to the transfer material 2 at a stretch. I do.
[0055]
The transfer material 2 having passed through the second transfer portion T2 is peeled off from the intermediate transfer member 9 and is conveyed to the fixing portion 17, where the toner is fixed. The sheet is discharged face down, and the image forming operation ends.
[0056]
Next, the configuration of the main part of the present invention will be described with reference to FIGS.
[0057]
FIG. 2 is a diagram illustrating a state in which the process cartridge 100 is mounted on the image forming apparatus main body.
[0058]
The process cartridge 100 is a cartridge in which an image carrier (hereinafter, referred to as a photosensitive drum) 1 and process means (a charger and a developing device) acting on the photosensitive drum are integrally formed into a cartridge. It is removable.
[0059]
A guide rail (not shown) is provided in the image forming apparatus main body along the mounting / removing direction of the process cartridge 100, and the user inserts the process cartridge 100 along the guide rail.
[0060]
A drive unit 103 for driving the plurality of photosensitive drums 1 is positioned and fixed outside a frame (rear side plate) 101 on the back side of the main body of the image forming apparatus on the back side in the insertion direction of the process cartridge 100.
[0061]
3 and 4 are views for explaining the drive unit 103. FIG.
In the drive unit 103, drive units 103Y, 103M, 103C, and 103Bk for driving the photosensitive drums 1 of Y, M, C, and Bk are accurately positioned and fixed on a drive frame 104, respectively. Further, a drum motor 45 fixed to each drive unit for each color, a pinion 46 fixed to the motor shaft of the motor 45, and an intermediate gear 47 meshed with the pinion 46 and the large gear 48 and rotatably supported, , A large gear 48, a drum drive shaft 49 fixed to the large gear 48 and having a substantially spherical positioning portion 57 formed at the end thereof, a bearing 51 supporting the drum drive shaft 49, and a triangular coupling 52. Have.
[0062]
The bearing 51 supports the drum drive shaft 49 so as not to move in the axial direction. Further, a rotary encoder 53 is provided coaxially with the center axis of the opposite end of the drum drive shaft 49, and a rotation detecting means 54 (two places) for detecting rotation fluctuation of the drum drive shaft 49 by the rotary encoder 53. ) Are accurately installed at 180 ° opposed positions about the center axis of the drum drive shaft 49.
[0063]
By detecting the rotation fluctuation of one rotation of the photosensitive drum 1 by these rotation detecting means and controlling the next rotation of the drum motor 45 by a driving signal which cancels the rotation fluctuation, the rotation fluctuation of the drum driving shaft of each color is minimized. Can be kept to a minimum.
[0064]
Here, two positioning pins 105 are fixed on the opposite side of the gear portion on the drive frame 104, and their positions are coaxial (y = 0) with the central axes of the photosensitive drums 1 of the respective colors. The positioning pin (first reference axis) 105a on the Bk side is also a reference in the x direction of the drive frame 104 (x = 0), and the drive unit 103 uses the positioning pin (first reference axis) 105a as a reference for the rear side plate of the main body. It is fixed to 101 by screws or the like.
[0065]
A drum drive shaft 49 for driving the photosensitive drum 1 of each color is attached with high precision in both the x direction and the y direction with reference to the positioning pin (first reference axis) 105a. By fixing the process cartridge to the main body rear plate 101 with reference to the first reference axis 105a, the center axis of the photosensitive drum 1 of each color fits with the drum drive shaft 49 when the user inserts the process cartridge into the main body. Thus, the positioning is accurately performed based on the positioning pin (first reference axis) 105a.
[0066]
Further, as shown in FIG. 2, a reference hole 106 is provided in the rear plate 101 of the main body to fit the positioning pin 105 of the drive unit 103 with high accuracy. The center of the first reference hole 106a fitted to the first reference shaft 105a of the drive unit 103 is the origin (x = 0, y = 0) of the rear plate 101, and all parts on the rear plate 101 are the first reference. It is configured based on the hole 106a. The first reference hole 106a is accurately fitted to the first reference shaft 105a in both the x direction and the y direction to position the drive unit 103, but the second reference hole 106b into which the second reference shaft 105b is inserted is in the x direction. , And is fitted and positioned with the second reference shaft 105b only in the y direction.
[0067]
Next, a connection configuration between the photosensitive drum 1 and the drive unit 103 will be described with reference to FIGS.
[0068]
The triangular coupling concave portion 52 has a hole serving as a twisted regular triangular prism, and is axially disengaged from the triangular coupling convex portion 37 formed on the flange 60 at the end of the photosensitive drum 1.
[0069]
When the triangular coupling convex portion 37 and the triangular coupling concave portion 52 are fitted, the ridge of the twisted regular triangular prism of the triangular coupling convex portion 37 comes into contact with the twisted triangular prism surface of the triangular coupling concave portion 52, thereby forming the triangular coupling. The ring convex portion 37 and the triangular coupling concave portion 52 are aligned, and their rotation centers coincide with each other.
[0070]
At this time, the drum drive shaft 49 and the triangular coupling recess 52 are provided with circumferential play that can be slightly moved. Further, in the above description, the position of the triangular coupling 52 is determined at a position most moved to the process cartridge side, and the triangular coupling 52 is supported so as to be retractable against the urging force of the return spring 62.
[0071]
Further, a fitting hole 61 is formed at the center of the shaft of the flange 60 at the end of the photosensitive drum 1, and the center thereof coincides with the rotation center of the triangular coupling convex portion 37 and the triangular coupling concave portion 52.
[0072]
When the user attaches the process cartridge 100 to the image forming apparatus main body, the photosensitive drum 1 is connected to the triangular coupling recess 52 on the image forming apparatus main body side at the same time as the fitting hole 61 on the flange 60. A substantially spherical positioning portion 57 provided at the tip of the drum drive shaft 49 on the image forming apparatus main body side is inserted and fitted into the drum drive shaft 49 to position and fix the drum drive shaft 49 on the image forming apparatus main body. And the axis of the photosensitive drum are arranged on the same straight line. In this embodiment, the fitting relationship between the fitting hole 61 and the positioning portion 57 is such that the gap is 20 μm or less.
[0073]
When the triangular phase of the triangular coupling convex portion 37 and the triangular coupling concave portion 52 do not match, and the triangular coupling is not connected, the end face of the triangular coupling convex portion 37 becomes the mouth of the triangular coupling concave portion 52. And the triangular coupling 52 is retracted toward the drive unit 103 against the urging force of the return spring 62. After the process cartridge 100 is mounted, the connection is instantaneous when the triangular coupling convex portion 37 and the triangular coupling concave portion 52 have the same triangular phase during the pre-rotation of the image forming apparatus main body.
[0074]
Further, a step 63 is provided on the drum drive shaft 49, and the drive-side end face of the triangular coupling protrusion 37 at the end of the photosensitive drum 1 inserted into the end face of the step 63 is abutted. The positioning and fixing of the photosensitive drum 1 in the axial direction (thrust direction) are simultaneously performed.
[0075]
As described above, the drive unit 103 and the photosensitive drum 1 are engaged with each other by the triangular coupling concave portion 52 and the triangular coupling convex portion 37, and furthermore, the tip spherical positioning portion 57 of the drum driving shaft 49 is formed by the flange 60. By fitting into the upper fitting hole 61, the positioning and fixing can be performed with high accuracy, and the rotational driving force of the drum motor 45 as a driving source is transmitted to the photosensitive drum 1 with high accuracy.
[0076]
Here, the pinion 46, the intermediate gear 47, and the large gear 48 that transmit the rotational force from the drum motor 45, which is the driving source, to the drum driving shaft 49 use a module 0.5 and a helical gear having a twist angle of 20 °, respectively. Each gear tooth surface is not an ideal tooth trace shape as shown in FIGS. 6 (a) and 8 (a), but a crowning shape as shown in FIGS. 6 (d) and 8 (b) by injection molding. Sometimes intentionally formed.
[0077]
At present, in the current state of normal injection molding, even if the tooth trace shape of the gear tooth surface is molded aiming at an ideal shape as shown in FIG. 6A, a certain amount of the tooth trace shape error (FIG. a) in b) to (d) occurs. For example, even in a gear in which a tooth trace shape error falls within a certain range, as shown in FIG. 6C, the central portion of the tooth width of the gear is closed, and the tooth traces at both ends are shifted to the convex side. In this case, a small impact vibration is generated at the start and end of the meshing of the gear, and is transmitted directly to the photosensitive drum, so that remarkable pitch unevenness occurs on the image.
[0078]
That is, both gears start to mesh with each other at a point c-1 in FIG. 7A, but at this time, both ends (solid line in FIG. 7A) of the tooth trace shape shown in FIG. At point b-1 in FIG. 7 (a) (the point where the central portion of FIG. 6 (c) is engaged), the gear tooth surfaces are momentarily out of contact (see FIG. 7 (a)). In the transition from the point c-1 to the point b-1), impact vibration occurs when passing through the step portion of the gear tooth trace. The same impact vibration occurs at the transition from point b-1 to point d-1 in FIG. 7A where both tooth surfaces are separated.
[0079]
On the other hand, FIG. 7B shows the meshing of a gear having a crowning shape formed on the tooth surface as shown in FIG. 6D. The point c-2 in the figure is the point at which the two gears start to mesh with each other. At this moment, the ends of the tooth traces are rounded by crowning, so the two gears are not yet in contact, but immediately after this, Gears begin to engage.
[0080]
Thereafter, the gear can stably engage at the center portion of the gear tooth trace until immediately before the point d-2 where the meshing is separated through the point b-2, so that the impact vibration when passing through the step portion of the gear tooth trace is achieved. Does not occur and pitch unevenness does not deteriorate. At this time, the meshing ratio is slightly reduced by forming the gear tooth surface into a crowning shape as described above. However, the reduction is slight, and if the meshing ratio is sufficiently ensured in advance, it can be reduced on the image. There is no adverse effect on the pitch unevenness level.
[0081]
Also, even when the tooth traces at both ends of the tooth width are not deviated (see FIG. 6 (a)), when the crimping shaft is tilted or the flatness of the sheet metal whose shaft is crimped is poor, the parallelism between the gear shafts may be reduced. As described above, at the start of meshing or at the end of meshing, a small impact vibration occurs and pitch unevenness occurs on the image as described above.
[0082]
This is because, when the gear is tilted, the end of the gear tooth surface may come into contact with one side to increase the impact, or the uneven wear may occur to increase the minute vibration.
[0083]
On the other hand, the crowning of the gear tooth surface can realize a stable meshing by the central portion of the tooth width of the gear as described above, so that the effect of keeping the meshing smooth and suppressing the generation of minute vibration can be expected. . Deterioration of the parallelism between the shafts causes pitch unevenness not only in the helical gear but also in the spur gear, so that the crowning of the gear tooth surface is effective even in an image forming drive train using the spur gear.
[0084]
The effectiveness of the crowning of the gear tooth surface in the image forming gear train described above can be confirmed by the evaluation as shown in FIG. FIG. 9 shows a horizontal line image (for example, a two-dot horizontal line or a three-dot space) output as an actual image, and FFT analysis of unevenness in pitch intervals between the output horizontal lines.
[0085]
FIG. 9 (a) is a measurement using a gear molded aiming at an ideal shape as shown in FIG. 6 (a), and FIG. 9 (b) is a graph of the intermediate gear 47 and the large gear 48 in FIG. It is a result measured using a crowning gear. In the case of the present embodiment, the meshing frequency generated by the meshing between the intermediate gear 47 and the large gear 48 is about 114.4 Hz. It can be confirmed that the minute vibration is reduced and no pitch unevenness occurs on the image.
[0086]
(Second embodiment)
10 and 11 show a second embodiment. In the second embodiment, since the configuration of the image forming apparatus and the configuration of the developing apparatus are the same as those of the first embodiment, the same components are denoted by the same reference numerals, and the description thereof will be simplified. The characteristic configuration of will be described.
[0087]
In the first embodiment, in the drive gear train for driving the photosensitive drum 1, the case where the gear tooth surface is formed in a crowning shape has been described. However, similarly, the charging unit, the developing unit, and the intermediate unit that act on the photosensitive drum 1 The same effect can be expected in a drive gear train for driving another image forming unit such as a transfer body.
[0088]
FIGS. 10 and 11 are diagrams showing an embodiment in the case where a running gear is used for the intermediate transfer body drive train.
[0089]
FIG. 10 is a diagram showing the relationship between the intermediate transfer unit 9, the drive unit 103, and the process cartridge 100. The intermediate transfer unit 9 is configured such that a coupling 127 provided on a drive roller shaft for driving an intermediate transfer belt is driven. The drive is transmitted by engaging with a drive coupling 124 provided in the unit 103.
[0090]
FIG. 11 is a diagram illustrating a driving unit 103 that drives the intermediate transfer unit 9.
[0091]
The intermediate transfer body unit driving unit 103ITB includes a fixed motor 119, a pinion 120 fixed to a motor shaft, an intermediate gear 121 rotatably supported by meshing with the pinion 120 and the large gear 122, a large gear 122, and a large gear. A drive shaft 125 is fixed to the drive shaft 122, the bearing 51 supports the drive shaft 125, and a drive coupling 124. The bearing 51 supports the drive shaft 125 so as not to move in the axial direction.
[0092]
The drive coupling 124 is supported in the coupling holder 123 so as to be movable in the thrust direction along the drive shaft 125, and is urged toward the intermediate transfer member by a return spring (not shown).
[0093]
Here, the pinion 120, the intermediate gear 121, and the large gear 122 that transmit the rotational force from the motor 119, which is the drive source, to the drive shaft 125 use a module 0.5 and a helical gear with a torsion angle of 20 °, respectively. The gear tooth surface is not an ideal tooth trace shape as shown in FIGS. 6 (a) and 8 (a), but a crowning shape as shown in FIGS. 6 (d) and 8 (b) at the time of injection molding. It is formed.
[0094]
As a result, as described above in the first embodiment, the gear teeth can be stably meshed at the central portion of the tooth width in the gear tooth trace, so that an impact vibration is generated when the gear tooth trace passes through the stepped portion. In addition, since the speed fluctuation of the intermediate transfer unit 9 is minimized, the pitch unevenness does not deteriorate in the output image.
[0095]
In the present embodiment, a full-color copying machine is cited as an example of the configuration of the image forming apparatus. However, the present invention is not limited to this, and may include a printer, a facsimile, and a monochrome copying machine. Is also applicable.
[0096]
Further, as the image forming unit, an electrophotographic image forming unit, an ink jet type image forming unit, a bubble jet (registered trademark) type image forming unit, and the like can be applied, but the image forming unit is not limited thereto. Alternatively, a thermal transfer recording method, a thermal recording method, or a wire dot can be applied.
[0097]
【The invention's effect】
As described above, in the present invention, the image forming unit such as the photosensitive drum, the charging unit and the developing unit acting on the photosensitive drum, and the intermediate transfer body for sequentially transferring the respective color toner images on the photosensitive drum in a superimposed manner Each of the driving units provided in the main body of the image forming apparatus, or the driving gear train of the driving means in the process cartridge and the intermediate transfer unit has a toothed surface of a crown. If the tooth surface of the gear is formed in a crowning shape (see FIGS. 6D and 8B), both ends of the tooth width become smaller than the center portion. The timing is later than the timing of starting the contact, and at the end of the engagement, the separation is advanced by a very short time. In addition, it is possible to suppress the impact caused by the irregularity of the tooth traces at both ends of the gear and to realize stable meshing at the center of the gear tooth width. Can be reduced.
[0098]
At this time, the meshing ratio is slightly reduced by forming the gear tooth surface into a crowning shape as described above. However, the reduction is slight, and if the meshing ratio is sufficiently secured in advance, it can be reduced on the image. There is no adverse effect on the pitch unevenness level.
[0099]
In addition, the crowning of the gear tooth surface is stabilized by the central portion of the gear tooth width as described above, even when the parallelism between the shafts is slightly deviated due to the inclination of the crimping shaft of the gear or the deterioration of the flatness of the sheet metal, as described above. Since the meshing can be realized, the effect of suppressing the generation of the minute vibration by keeping the meshing smooth can be expected.
[Brief description of the drawings]
FIG. 1 is a longitudinal sectional view showing an overall configuration of a color laser printer (image forming apparatus) to which the present invention is applied, according to first and second embodiments.
FIG. 2 is a perspective view illustrating a configuration according to a first embodiment in a color laser printer (image forming apparatus) to which the present invention is applied.
FIG. 3 is a unit configuration diagram showing a configuration of a drive unit according to a first embodiment in a color laser printer (image forming apparatus) to which the present invention is applied.
FIG. 4 is a detailed view showing a configuration of a drive unit according to the first embodiment in a color laser printer (image forming apparatus) to which the present invention is applied.
FIG. 5 is a configuration diagram illustrating a connection mode between a drive unit and a photosensitive drum according to the first embodiment in a color laser printer (image forming apparatus) to which the present invention is applied.
FIG. 6 is a detailed view illustrating a shape of a gear tooth surface of a drive unit according to the first and second embodiments in a color laser printer (image forming apparatus) to which the present invention is applied.
FIG. 7 is a detailed diagram illustrating a meshing state of gears of a drive unit according to the first and second embodiments in a color laser printer (image forming apparatus) to which the present invention is applied.
FIG. 8 is a detailed diagram illustrating the shape of the gear tooth surface of the drive unit according to the first and second embodiments in the color laser printer (image forming apparatus) to which the present invention is applied.
FIG. 9 is a graph illustrating the effect of reducing minute vibrations due to meshing of gears of a drive unit according to the first and second embodiments in a color laser printer (image forming apparatus) to which the present invention is applied.
FIG. 10 is a perspective view illustrating a configuration according to a second embodiment in a color laser printer (image forming apparatus) to which the present invention has been applied.
FIG. 11 is a unit configuration diagram showing a configuration of a drive unit according to a second embodiment in a color laser printer (image forming apparatus) to which the present invention is applied.
[Explanation of symbols]
1 Photoconductor drum
9 Intermediate transfer member
10 Secondary transfer roller
17 Fixing device
20, 21, 22 discharge roller pair
37 Triangular coupling protrusion
45, 119 motor
46, 120 Motor pinion
47, 121 Intermediate gear
48, 122 Large gear
49, 125 drive shaft
51 bearing
52 Triangular coupling
53 Rotary encoder
54 rotation detection means
57 Positioning unit
60 flange
61 Mating hole
62 return spring
63 Step
64 Drum through shaft
100 process cartridge
101 Rear panel
102 Front panel
103 drive unit
104 drive frame
104a bending part
105 Positioning pin (reference axis)
106 Reference hole
107 CRG opening / closing lid
108 Side plate hinge bearing
109, 110 Front reference
111 Open / close lid hinge axis
112 Front reference hole receiver
113 CRG Receiving
114 Mating hole
115 Scanner plate
116 Scanner unit (image exposure means)
123 coupling holder
124 drive coupling
127 coupling

Claims (6)

Driving one or a plurality of image carriers, a driving unit provided in the image forming apparatus main body, or a driving unit in a process cartridge,
An image forming apparatus, wherein a gear tooth surface of an image carrier driving gear train for driving the image carrier has a crowning shape. A drive unit provided in an image forming apparatus main body, which transmits a drive to each rotation drive unit of the charging unit and the developing unit of a process cartridge having a charging unit and a developing unit acting on one or a plurality of image carriers. Or in the driving means in the process cartridge,
An image forming apparatus, wherein a gear tooth surface of the charging unit driving gear train or the developing unit driving gear train for driving the charging unit or the developing unit has a crowning shape. A driving unit provided in the image forming apparatus main body or a driving unit in the intermediate transfer body unit for driving an intermediate transfer body for sequentially transferring the respective color toner images on the image carrier in a superimposed manner,
An image forming apparatus, wherein a gear tooth surface of an intermediate transfer member driving gear train for driving the intermediate transfer member has a crowning shape. 4. The gears of the image carrier driving gear train, the charging unit driving gear train, the developing unit driving gear train, and the intermediate transfer body driving gear train are helical gears. 5. The image forming apparatus as described in the above. In the image carrier drive gear train, the charging unit drive gear train, the developing unit drive gear train, and the intermediate transfer body drive gear train,
The image forming apparatus according to any one of claims 1 to 4, wherein the gear tooth surfaces of all the gears have a crowning shape. In the image carrier drive gear train, the charging unit drive gear train, the developing unit drive gear train, and the intermediate transfer body drive gear train,
5. The image forming apparatus according to claim 1, wherein at least one of the gear teeth of the pair of gears meshing with each other has a crowned shape.

Images