JP2002189383A - Image carrier driving device and image forming device using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the distortion of an image transferred from an image carrier. SOLUTION: The image carrier 1 driving device for driving the cylindrical image carrier 1 to rotate it is provided with a driven member 4 which is constituted by integrally forming a gear part 2 with formed engagement teeth 2a with a swelling part 3 having an outside diameter equal to the pitch circle PC of the gear part 2 and swelling from the side part of the gear part 2, and also, the swelling part 3 is engaged with a recessed part 1a having an inside diameter equal to the outside diameter of the swelling part 3 and formed in the side part of the image carrier 1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a driving device for driving an image carrier, and more particularly to a driving device for an image carrier having a cylindrical shape and an improvement of an image forming apparatus using the same.

[0002]

2. Description of the Related Art As a conventional image forming apparatus, for example, a tandem-type image forming apparatus is used to form toner images of respective color components of yellow (Y), magenta (M), cyan (C), and black (K). The image forming units are arranged in parallel, and each color component toner image formed by each image forming unit is multiplex-transferred to a recording material such as paper via an intermediate transfer body such as an intermediate transfer belt or directly. Is already known. In this type of image forming apparatus, an image forming unit is for forming an image by, for example, an electrophotographic method, and includes an image carrier such as a photosensitive drum. As a driving device for the photosensitive drum of this type, a driven gear attached to a rotating shaft of the photosensitive drum, a driving gear meshed with the driven gear and transmitting a driving force from a driving source such as a motor. And those with

[0003]

In this type of image forming apparatus, the above-mentioned driven gear and the rotating shaft of the photosensitive drum have an error in manufacturing, so that the center of rotation is slightly shifted from the true center. As a result, even if the driving speed is kept constant, the rotation speed of the photosensitive drum fluctuates. Then, the rotation speed of the photosensitive drum is different between the exposure position and the transfer position, and there is a problem that the transferred image is expanded and contracted. Further, when such a speed variation occurs in each photosensitive drum of the image forming apparatus, the transfer position of each color component toner image transferred onto the intermediate transfer body or the recording material is shifted, and the image quality is deteriorated due to the color shift. There was also a problem that would be.

Therefore, in order to solve such a problem,
For example, Japanese Patent Application Laid-Open No. 9-184993 discloses a method for accurately positioning a surface position of a photosensitive drum corresponding to a writing position of an exposure device and simultaneously reducing the influence of eccentricity of the photosensitive drum. There has been proposed a configuration in which a portion is pressed against a positioning roll and the driving force is transmitted via a universal coupling. Also, Japanese Patent No. 2677566 (JP-A-1-96664).
In the method, the driven gears provided on the support shaft of the photosensitive drum are simultaneously driven by a plurality of drive gears, and the exposure position and the transfer position are set at positions corresponding to the positions where the plurality of gears are disposed. A technique has been proposed in which the rotation speed of the photosensitive drum at the exposure position and the transfer position is made equal.

However, in the former prior art, there is a problem that the drive system becomes complicated and expensive. When applied to a tandem-type image forming apparatus, there has been a technical problem that it is difficult to make the angular velocity fluctuations in each photosensitive drum the same.
On the other hand, in the latter prior art as well, there were technical problems that the drive system became complicated and expensive, and that it was difficult to make the rotational speeds of a plurality of drive gears the same.

[0006] Among the above-mentioned technical problems, the adverse effect caused by the speed fluctuation caused by the eccentricity of the image carrier is described below.
The present invention is not limited to the tandem type image forming apparatus, but similarly occurs in other types of image forming apparatuses.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned technical problems, and a drive device for an image carrier capable of preventing distortion of an image transferred from the image carrier, and a driving apparatus using the same. And an image forming apparatus.

[0008]

That is, according to the present invention, as shown in FIG. 1, there is provided a driving device for an image carrier 1 which rotationally drives an image carrier 1 having a cylindrical shape.
a driven portion integrally formed with a gear portion 2 formed with a and a bulging portion 3 bulging at the side portion of the gear portion 2 with the same outer diameter as the pitch circle PC of the gear portion 2. A member 4 is provided, and the bulging portion 3 is fitted into a concave portion 1a provided on a side portion of the image carrier 1 and having the same inner diameter as the bulging portion 3. .

In such technical means, examples of the image carrier 1 include a photoreceptor, a dielectric, and an intermediate transfer member used in a copying machine, a printer, and the like.

The bulging portion 3 is provided on the image carrier 1.
Is fitted into a concave portion 1a having the same inner diameter as the bulging portion 3 on its side.

Further, in the invention in which the driving device of the image carrier according to the present invention is applied to a so-called tandem type image forming apparatus, a plurality of image forming units are arranged in parallel along the moving path of the intermediate transfer body or the recording material. Each image forming unit is provided with an image carrier on which each color component image is carried, and each color component image formed on the image carrier of each image forming unit is recorded on a recording material via an intermediate transfer member or In an image forming apparatus for direct transfer, each of the image carriers is provided with an image carrier driving device according to claim 1 and a gear portion between adjacent driven members. A transmission gear meshing with both gear portions is arranged, and further, each driven member and each transmission gear are arranged so that the maximum eccentric position of each gear portion and the maximum eccentric position of each transmission gear face each other. It is characterized by the following.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail based on an embodiment shown in the accompanying drawings. FIG. 2 shows a schematic configuration of an embodiment of an image forming apparatus to which the present invention is applied. In FIG. 1, the image forming apparatus according to the present embodiment includes a plurality of image forming units 100 (specifically, 10
0Y, 100M, 100C, and 100K), an intermediate transfer belt 110 as an intermediate transfer body for sequentially transferring (primary transfer) and holding each color component toner image T formed by each image forming unit 100, and on the intermediate transfer belt 110. The image forming apparatus includes a batch transfer device 120 for batch-transferring (secondary transfer) the transferred superimposed images onto a sheet P as a recording material, and a fixing device 150 for fixing the batch-transferred toner image T onto the sheet P. is there.

In this embodiment, an image forming unit 100 for each color component (specifically, 100K, 100Y,
00M, 100C) are photosensitive drums 101 (specifically, 101K, 1K, 1K) as image carriers rotating in the direction of arrow A.
01Y, 101M, and 101C), the uniform charging device 102 (specifically, 1
02K, 102Y, 102M, and 102C), a laser exposure apparatus 1 for writing an electrostatic latent image on the photosensitive drum 101
03 (specifically, 103K, 103Y, 103M, 10
3C, a developing device 104 (specifically, a laser beam is represented by a symbol Bm in the drawing), in which each color component toner is stored and an electrostatic latent image on the photosensitive drum 101 is visualized.
K, 104Y, 104M, 104C), and a drum cleaner 106 (specifically, 106K, 106Y, 106M, 1C) for cleaning the photosensitive drum 101 after passing through the transfer area.
06C) are sequentially arranged. Then, each photosensitive drum 101 and the intermediate transfer belt 1
At the primary transfer position where the transfer roller 10 faces the primary transfer roller 105 (specifically, 105K, 105Y, 105Y)
M, 105C).

Further, the intermediate transfer belt 110 is wound around a plurality of (four in the present embodiment) support rolls 111 to 114. In this embodiment, the support roll 111 is As drive roll 110,
When the support roll 112 is a driven roll, the support roll 11
As a steering roll 3 is arranged to be tiltable,
Further, the support roll 114 is used as a backup roll of the batch transfer device 120 as described later.

Further, a collective transfer device 120 is provided at a collective transfer position (secondary transfer position) of the intermediate transfer belt 110 facing the transport path of the paper P. In the present embodiment,
A secondary transfer roll 115 that is pressed against the toner image bearing surface of the intermediate transfer belt 110 and a counter roll (backup roll) 114 that is disposed on the back side of the intermediate transfer belt 110 and forms a counter electrode of the secondary transfer roll 115. And A roll cleaner 121 is provided on the peripheral surface of the secondary transfer roll 115, and an electrode roll (not shown) is in contact with the backup roll 114 to supply power. Further, a belt cleaner 141 for removing residual toner on the intermediate transfer belt 110 is provided downstream of the collective transfer device 120.

Further, in the present embodiment, the sheet transport system feeds the sheet P from the sheet tray 116 to the feed roll 1.
The sheet P is sent out to the secondary transfer position at a predetermined timing, and the sheet P after the secondary transfer is
To be transported to Reference numeral 118 denotes a transport roll provided in the paper transport path, and reference numeral 119 denotes a registration roll (registration roll).

FIG. 3 shows a drive system for rotating each photosensitive drum 101. In the present embodiment, the driven gear 201 (specifically, 201K, 201Y, 201M,
01C), and the driven gear 201K,
A transmission gear 202a is provided between the driven gears 201Y.
A transmission gear 202b is provided between the driven gear 2 and the driven gear 2M.
A transmission gear 202c is disposed between 01M and 201C so as to mesh with each driven gear 201, respectively. In the present embodiment, the pitch circle of each driven gear 201 and each transmission gear 202 is set to the same diameter. Reference numeral 210 denotes a drive motor, which sequentially transmits a driving force to driven gears 201K to 201C via a gear 211. Here, in the present embodiment, a driven gear 201 manufactured in the same lot is used,
Further, the transmission gear 202 manufactured in the same lot is used. Therefore, each driven gear 201K-20K
1C are similarly eccentric, and each transmission gear 202 is also similarly eccentric.

FIG. 4 shows the driven gear 201. In the present embodiment, the driven gear 2
01 is a gear portion 221 having a gear tooth surface formed thereon, and a rotating shaft 222 provided at a central portion outside the gear portion 221.
And a bulging portion 223 provided inside the gear portion 221.
And

Here, the bulging portion 223 is
It has the same diameter as one pitch circle PC. Further, as shown in FIG. 5, the diameter of the bulging portion 223 is the same as the inner diameter of the cylindrical photosensitive drum 101, and
The driven gear 201 and the photosensitive drum 101 are integrally rotated by fitting the photosensitive drum 101 with the driven gear 201. In addition, in FIG.
It is assumed that it is formed at a position displaced from the true center for manufacturing reasons (error range allowed for manufacturing).

FIG. 6 shows the arrangement of the driven gears 201 and the transmission gears 202. In the figure, the symbol ▼ indicates a position where the radius of rotation r is the largest due to the eccentricity.
And the transmission gears 202 are arranged such that the corresponding portions of the transmission gears 202 face downward.

Next, an image forming process of the color image forming apparatus according to the present embodiment will be described. Now, when a start switch (not shown) is turned on, a predetermined image forming process is executed. More specifically, for example, when the color image forming apparatus is configured as a digital color copying machine, a document set on a document table (not shown) is read by a color image reading device, and the read signal is read by an image signal processing unit. , And temporarily stores the digital image signals in a memory. Based on the stored digital image signals of four colors (K, Y, M, and C), toner images of each color are formed. .

That is, the image forming unit 1 according to the digital image signal of each color inputted from the image signal processing means.
00 (specifically, 100K, 100Y, 100M, 10
0C) are respectively driven. Then, each image forming unit 1
At 00, the laser exposure device 103 writes an electrostatic latent image corresponding to the digital signal on the photosensitive drum 101 uniformly charged by the uniform charging device 102. Then, each of these electrostatic latent images is developed by the developing device 104 containing the toner of each color to form the toner image T of each color. When this color image forming apparatus is configured as a device such as a printer, it is only necessary to form toner images of each color based on an image signal input to the image signal processing means from the outside.

The toner image T formed on each of the photosensitive drums 101 is intermediately transferred from the photosensitive drum 101 by each of the primary transfer rolls 105 at a primary transfer position where each of the photosensitive drums 101 and the intermediate transfer belt 110 are in contact with each other. The images are sequentially transferred to the surface of the belt 110.

The toner image T primarily transferred onto the intermediate transfer belt 110 in this manner is superimposed on the intermediate transfer belt 110, and is conveyed to the secondary transfer position with the rotation of the intermediate transfer belt 110.

On the other hand, the paper P is carried out of the paper tray 116 by the feed roll 117, and the paper P is supplied to the secondary transfer position at a predetermined timing, and is fed between the secondary transfer roll 115 and the intermediate transfer belt 110. It is sandwiched.

Then, at the secondary transfer position, the toner image T carried on the intermediate transfer belt 110 is collectively transferred onto the paper P by the action of the transfer electric field formed between the secondary transfer roll 115 and the backup roll 114. Transcribed. The sheet P to which the toner image T has been transferred is conveyed to the fixing device 150, where the toner image T is fixed. On the other hand, the toner remaining on the intermediate transfer belt 110 after the secondary transfer is cleaned by the belt cleaner 141.

In the above-described series of processes, each photosensitive drum 101 is driven to rotate by a drive motor 210. Here, in the present embodiment, the photosensitive drum 101
(For example, the photosensitive drum 101K) and the driven gear 201
(For example, the driven gear 201K) is directly connected via the bulging portion 223, and the pitch circle PC of the gear portion 221 and the diameter of the bulging portion 223 are set to be the same. Therefore, the eccentricities of the driven gear 201K and the photosensitive drum 101K are completely the same. Then, as shown in FIG. 7A, the moving speed V at the position P1 where the turning radius r is large.
Is always VP1 as shown in FIG. 7 (b), while the moving speed V at the position P2 where the turning radius r is small is always VP2. Therefore, the moving speed V at the exposure position and the transfer position is always constant at an arbitrary position on the photosensitive drum 101K, and even if the speed fluctuates due to the eccentricity of the photosensitive drum 101K, the moving speed V is transferred onto the intermediate transfer belt 110. There is no occurrence of a situation in which the image expands or contracts (distortion of the image).

Further, in the present embodiment, as described above, since each driven gear 201 and each transmission gear 202 have the same diameter, the same positions of the gears are always in contact with each other. As shown in FIG. 6, since the positions where the rotational radii r of the driven gears 201 and the transmission gears 202 are the largest are directed downward, the adjacent driven gears 201 and the transmission gears The gears 202 are denoted by ▼, respectively.
The parts indicated by are in contact with each other.

Further, in the present embodiment, the driven gear 20
1 are used in the same lot, and the transmission gears 202 are used in the same lot, so that each driven gear 201 and each transmission gear 202
As shown in FIG. 8, the rotational radii (radius a and radius a ', radius b and radius b', and radius c and radius c ') are always in contact with each other. Then, since the feed-side radius is equal to the feed-side radius, the rotational radius r is constant, and the driven gears 201 rotate at the same angular speed from the transmitted speed V = r · ω.

Here, when each of the transmission gears 202 is manufactured in the same lot as the driven gear 201 and is arranged upside down with respect to the driven gear 201, each driven gear 201 and each FIG. 9 shows the state of the speed fluctuation ΔV of the transmission gear 202. In this case, since the driven gear 201 and the transmission gear 202 exhibit completely opposite speed fluctuation characteristics, the color unevenness of a single color due to the variation of the angular velocity becomes equal in each photosensitive drum 101, so that each photosensitive drum 101 becomes equal. Color misregistration can be prevented by adjusting the phases of the image writing timing (exposure timing) on the drum 101.

In the present embodiment, each driven gear 20
1 and each transmission gear 202 are arranged in a straight line,
However, the present invention is not limited to this. For example, zigzags may be provided as shown in FIG. However, in such a case, the diameters of the driven gears 201 and the transmission gears 202 are the same, and the positions where the rotation radius r of each gear is the maximum (the position indicated by the symbol ▼) are opposed to each other. It is necessary to arrange.

In the present embodiment, the driven gear 20
The gear 211 is provided below the 1K, and driving is performed from the transfer position side. However, the present invention is not limited to this.
For example, the driven gear 201K is driven from the exposure position side.
Needless to say, it may be driven from above.

Example The present inventor conducted an investigation on the positional variation of each photosensitive drum 101 using the image forming apparatus described in the first embodiment. In this investigation, encoders were attached to the ends of the respective photosensitive drums 101, and the position fluctuations were calculated by integrating the outputs from the encoders. The results are shown in FIGS. In the figure, POINT on the horizontal axis represents a measurement point, and 2500 POINTs correspond to one rotation of the photosensitive drum 101. FIG. 11 (b)
Is a partially enlarged view of FIG.
T: Refer to the part enclosed by the ellipse). As can be seen, in the image forming apparatus according to the present embodiment, Y, M, C,
It can be understood that all the colors of K show the same fluctuation tendency, the magnitude of the position fluctuation itself is small, and the difference in the deviation between the colors is extremely small.

In the image forming apparatus described in the first embodiment, the present inventor has used a conventional type (gear pitch of gear) as each driven gear 201 and each transmission gear 202 of each photosensitive drum 101. (Designed without considering the outer diameter of the photosensitive drum 201) was used as a comparative example, and the position variation of each photosensitive drum 201 was similarly investigated. The result is shown in FIG. As can be seen, in the image forming apparatus according to the comparative example, although the Y, M, C, and K colors all have the same fluctuation tendency, the magnitude of the positional fluctuation is significantly larger than that of the embodiment, It is understood that the difference between the deviations is extremely large. In FIG. 12, the reason why the position fluctuation increases in the order of K <Y <M <C is that the driving force from the driving motor 210 is K → Y → M → C
This is considered to be because the influence of the eccentricity of each driven gear 201 and each transmission gear 202 is sequentially amplified and transmitted.

[0035]

As described above, according to the present invention,
By setting the eccentricity of the image carrier and the eccentricity of the driven member for rotating the same to always keep the moving speed of an arbitrary position on the surface of the image carrier constant, the distortion of the image transferred from the image carrier is reduced. Can be prevented.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing an outline of the present invention.

FIG. 2 is a schematic view of an embodiment of an image forming apparatus to which an image carrier driving device according to the present invention is applied.

FIG. 3 is a schematic diagram of a photosensitive drum and a drive system thereof.

FIG. 4 is an explanatory diagram of a driven gear of the photosensitive drum.

FIG. 5 is an explanatory diagram of a photosensitive drum and a driven gear.

FIG. 6 is an explanatory diagram illustrating a method of disposing a driven gear and a transmission gear.

FIGS. 7A and 7B are explanatory diagrams illustrating the relationship between the eccentricity of the photosensitive drum and the moving speed.

FIG. 8 is an explanatory diagram showing a correlation between a driven gear and a transmission gear.

FIG. 9 is a graph showing a relationship between speed fluctuations of a driven gear and a transmission gear.

FIG. 10 is an explanatory diagram illustrating another example of a method of disposing a driven gear and a transmission gear.

FIGS. 11A and 11B are graphs showing position fluctuations of each photosensitive drum in the example.

FIG. 12 is a graph showing a position variation of each photosensitive drum in a comparative example.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Image carrier, 2 ... Gear part, 2a ... Meshing teeth, 3 ... Swelling part, 4 ... Driven member

Continued on the front page F-term (reference) 2H030 AA01 AA07 AB02 BB42 BB44 BB71 2H035 CA07 CB04 CD07 CD14 CG03 2H071 BA04 BA20 BA27 CA02 CA05 DA02 DA06 DA08 DA13 DA15 DA26 EA18 3J009 DA16 DA20 EA04 EA05 EA11 EA21 EA21

Claims (2)

[Claims] 1. A driving device for an image carrier which rotationally drives an image carrier having a cylindrical shape, comprising: a gear portion provided with meshing teeth; and a pitch circle of the gear portion on a side portion of the gear portion. A driven member integrally formed with a swelling portion having the same outer diameter and swelling, wherein the swelling portion is formed on a side portion of the image carrier in the same manner as the swelling portion. A driving device, wherein the driving device is fitted into a concave portion provided with an inner diameter. 2. A plurality of image forming units are arranged in parallel along a moving path of an intermediate transfer body or a recording material, and each image forming unit is provided with an image carrier on which each color component image is carried. 2. The image forming apparatus according to claim 1, wherein each color component image formed on the image carrier of each image forming unit is transferred to a recording material via an intermediate transfer member or directly. A drive device for the carrier is provided, and between the gear portions of the adjacent driven members, a transmission gear meshing with both gear portions is disposed, and further, the maximum eccentric position of each gear portion An image forming apparatus, wherein each driven member and each transmission gear are disposed such that the maximum eccentric position of each transmission gear faces each other.