JP2002372825A - Color image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce uneven rotation and color slurring by reducing unstable load acting on the driving gear of an image carrier and reducing the unstable movement of each monochrome toner image carrier. SOLUTION: The driving gears 51 of the monochrome toner image carriers 21 (KCMY) successively transferring toner images to a circularly driven belt 13 and intermediate gears 52 are arranged in a line where motive power is not branched, and the center of rotation 52a of the gear 52 is arranged at a position other than on a line SL linking the centers of rotation 51a of the gears 51 with each other. At least the image carrier 21 and the gear 51 are unitized.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a color image forming apparatus. More specifically, a plurality of single-color toner image carriers are arranged on the intermediate transfer belt or the recording medium transport belt that is driven in a circulating manner, and different colors are applied to the recording medium transported by the intermediate transfer belt or the recording medium transport belt. The present invention relates to a so-called tandem type color image forming apparatus for sequentially transferring toner images by a single-color toner image carrier to form a color image. In particular, the present invention relates to a drive system for rotating the single-color toner image carrier.

[0002]

2. Description of the Related Art Conventionally, as a tandem type color image forming apparatus, for example, an apparatus as shown in FIG. 8 is known (Japanese Patent Laid-Open No. 61-156159). As shown in FIG. 1A, the color image forming apparatus includes a recording medium transport belt 1 that is driven in a circulating manner, and three (yellow (Y) and magenta) arranged with respect to the recording medium transport belt 1. Photoconductors 2Y, 2M, and 2C as monochromatic toner image carriers (for three colors of (M) and cyan (C)), and a gear train 3 that rotationally drives these monochromatic toner image carriers (see FIG. (B)) And sequentially transfers and records the toner images by the three single-color toner image carriers 2Y, 2M, and 2C onto the recording medium P supplied by the paper feed roller 4 and transported by the recording medium transport belt 1. A color image is formed on the medium P. A drive gear 3a (Y, C, M) is provided at an end of each of the single-color toner image carriers 2Y, 2M, and 2C. An intermediate gear 3 is provided between the drive gears 3a (Y, C, M).
b, 3b, and these drive gears 3a (Y,
C, M) and the intermediate gears 3b, 3b are arranged in one row to form a gear train 3. A driving gear 3a (Y) located at the end of the gear train 3 is meshed with a drive source gear 5a that is driven to rotate by the motor 5, whereby the single-color toner image carrier 2 ( Y, M, and C) are rotationally driven. Thus, the driving gear 3a
By arranging the (Y, C, M) and the intermediate gears 3b, 3b in one row, it is possible to rotationally drive each monochromatic toner image carrier 2 (Y, C, M) with a minimum number of gears. Becomes

[0003]

In the conventional apparatus described above, as shown in FIG. 8B, the rotation center of the driving gear 3a (Y, C, M) in the gear train 3 and the intermediate gear 3b 3b are arranged on the straight line SL, the following problem occurs. That is, the drive gear 3a and the intermediate gear 3b may be larger than desired dimensions because there are manufacturing errors in the drive gear 3a and the intermediate gear 3b, and the drive gear 3a and the intermediate gear 3b expand due to an increase in the temperature inside the apparatus. . In such a situation, if the rotation center of the driving gear 3a (Y, C, M) and the rotation center of the intermediate gears 3b, 3b are arranged on a straight line SL, the gear 3a, When 3b becomes larger than the desired size, the gears 3a and 3b
It is compressed in the L direction and receives an unstable load. Such an unstable load, particularly an unstable load acting on the drive gear 3a, is generated by each of the monochromatic toner image carriers 2 (Y,
C, M) are unstablely moved in the direction of the straight line SL, causing rotation unevenness and color misregistration, and consequently image quality deterioration.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems, reduce the above-mentioned unstable load, reduce the unstable movement of each monochromatic toner image carrier, and reduce rotation unevenness and color shift. It is another object of the present invention to provide a color image forming apparatus capable of improving the image quality.

[0005]

According to another aspect of the present invention, there is provided a color image forming apparatus, comprising: an intermediate transfer belt or a recording medium transport belt driven by circulation; A plurality of single-color toner image carriers, and a gear train in which a drive gear that rotationally drives these single-color toner image carriers and an intermediate gear that is arranged between the drive gears are arranged in a single row, A color image forming apparatus for sequentially transferring toner images by the plurality of single-color toner image carriers to a recording medium conveyed by the intermediate transfer belt or a recording medium conveyance belt, wherein The rotation center is arranged at a position other than on a line connecting the rotation centers of the drive gears arranged on both sides of the intermediate gear. According to a second aspect of the present invention, there is provided the color image forming apparatus as described in the first aspect, wherein the intermediate gear is engaged with driving gears disposed on both sides of the intermediate gear to rotate the two driving gears. It is characterized by being movable in a direction orthogonal to a line connecting the centers. According to a third aspect of the present invention, in the color image forming apparatus according to the second aspect, the intermediate gear is urged by an elastic member toward a line connecting the rotation centers of the two drive gears. It is characterized by being. In the color image forming apparatus according to a fourth aspect, in the color image forming apparatus according to the second aspect, the intermediate gear is rotatably supported by inserting a shaft through a hole provided at the center thereof. A gap is formed between the inner peripheral surface and the outer peripheral surface of the shaft. A color image forming apparatus according to claim 5, wherein in the color image forming apparatus according to any one of claims 1 to 4, the plurality of single-color toner image carriers and a driving gear thereof are provided on a common frame. It is supported and configured as a unit. A color image forming apparatus according to a sixth aspect is the color image forming apparatus according to the fifth aspect, wherein the intermediate gear is further supported by the common frame and configured as a unit.

[0006]

According to the first aspect of the present invention, there is provided a color image forming apparatus, comprising: an intermediate transfer belt or a recording medium transport belt that is driven in a circulating manner; And a drive gear for rotating and driving these single-color toner image carriers, and a gear train in which intermediate gears arranged between the drive gears are arranged in a line, and are conveyed by the intermediate transfer belt or the recording medium conveyance belt. A color image forming apparatus for sequentially transferring toner images by the plurality of single-color toner image carriers to a recording medium, wherein rotation centers of intermediate gears in the gear train are arranged on both sides of the intermediate gears. According to the color image forming apparatus of the present invention, the driving gear is disposed at a position other than on a line connecting the rotation centers of the driving gears. Even if the intermediate gear becomes larger than a desired size due to its manufacturing error or expansion due to an increase in the temperature inside the apparatus, the drive gear is still connected to the line connecting its rotation centers (the aforementioned line SL). In the (corresponding line) direction, there is no direct compression. Therefore, the unstable load acting on the drive gear in the linear direction is reduced, and the unstable movement of each monochromatic toner image carrier is also reduced. As a result, according to the color image forming apparatus of the first aspect,
Rotation unevenness and color shift of each single-color toner image carrier are reduced, and the image quality is improved. According to the color image forming apparatus of the second aspect, in the color image forming apparatus of the first aspect,
The intermediate gear is movable in a direction orthogonal to a line connecting the rotation centers of the two drive gears while being engaged with the drive gears disposed on both sides of the intermediate gear. Or, even if the intermediate gear becomes larger than a desired size due to its manufacturing error or expansion due to an increase in the temperature inside the apparatus, the intermediate gear is engaged with the driving gears disposed on both sides of the intermediate gear. Therefore, the drive gear moves (runs away) in a direction orthogonal to a line connecting the rotation centers of the two drive gears. Therefore, the unstable load acting on the drive gear in the linear direction is further reduced, and the unstable movement of each monochromatic toner image carrier is further reduced. As a result, the rotational unevenness of each monochromatic toner image carrier is reduced. And color shift are further reduced, and the image quality is further improved. According to the color image forming apparatus of the third aspect, in the color image forming apparatus of the second aspect, the intermediate gear is urged by an elastic member toward a line connecting the rotation centers of the two drive gears. Therefore, the meshing between the intermediate gear and the drive gear and the movement of the intermediate gear in the direction orthogonal to the line connecting the rotation centers of both drive gears are smoothly performed. According to the color image forming apparatus of the fourth aspect, in the color image forming apparatus of the second aspect, the intermediate gear is rotatably supported by inserting a shaft into a hole provided at the center thereof, Since a gap is formed between the inner peripheral surface of the hole and the outer peripheral surface of the shaft, the intermediate gear has an amount corresponding to this gap in a direction orthogonal to a line connecting the rotation centers of the two drive gears. It is possible to move without depending on the urging force of the elastic member. Therefore, according to this configuration, the unstable load acting on the driving gear in the linear direction is significantly reduced, and the unstable movement of each monochromatic toner image carrier is also significantly reduced. As a result, each monochromatic toner The rotation unevenness and color shift of the image carrier are further reduced, and the image quality is further improved. According to the color image forming apparatus of the fifth aspect, in the color image forming apparatus of any one of the first to fourth aspects, the plurality of single-color toner image carriers and a driving gear thereof are common. Since the unit is supported by the frame and configured as a unit, a plurality of single-color toner image carriers can be collectively attached to and detached from the apparatus main body, thereby improving maintainability. Further, the following operation and effect can be obtained. That is, in order to reliably and smoothly engage the intermediate gear with the drive gears disposed on both sides of the intermediate gear, the pitch diameter of the intermediate gear is increased to some extent (to such an extent that the engagement is reliably and smoothly performed. However, for example, as shown in FIG. 8B, the rotation center of the driving gear (3a) and the rotation center of the intermediate gear (3b) in the gear train are aligned with each other (see FIG. 8B). SL), when the pitch circle diameter of the intermediate gear is increased, the interval (L) between the rotation centers of the drive gears also increases. For this reason, for example, as shown in FIG. 8B, in a gear train in which the rotation center of the drive gear (3a) and the rotation center of the intermediate gear (3b) are arranged on a straight line (SL), If this is to be unitized, the unit will have a large width in the direction of the interval (L). FIG.
As shown in (b), when the rotation center of the driving gear (3a) and the rotation center of the intermediate gear (3b) in the gear train are arranged on a straight line (SL), the intermediate gear It is extremely difficult to provide (3b) on the apparatus body side without incorporating it into a unit. Intermediate gear (3
If b) is provided on the apparatus main body side, it becomes extremely difficult to engage the drive gear (3a) on the unit side with the intermediate gear (3b) on the apparatus main body side when attaching and detaching the unit. Therefore, as shown in FIG. 8B, the rotation center of the drive gear (3a) and the intermediate gear (3
In the case where the rotation center of (b) is arranged on a straight line (SL), if an attempt is made to unitize a plurality of monochromatic toner image carriers and their driving gears, an intermediate gear (3) is used.
There is also a drawback that b) must be incorporated in the unit, and as a result, the unit becomes larger. On the other hand, according to the color image forming apparatus of the fifth aspect, the rotation center of the intermediate gear in the gear train is not on a line connecting the rotation centers of the drive gears disposed on both sides of the intermediate gear. , The distance between the rotation centers of the drive gears can be shortened accordingly. Therefore, according to the color image forming apparatus of the fifth aspect, the unit can be made compact, and as a result, the entire apparatus can be downsized. According to the color image forming apparatus of the sixth aspect, in the color image forming apparatus of the fifth aspect, the intermediate gear is also supported by the common frame and configured as a unit. An effect can be obtained. That is, the drive gears and the intermediate gears are supported by a common frame together with the plurality of single-color toner image carriers to form a unit, so that a reliable and smooth meshing state between each drive gear and the intermediate gears is ensured. Thus, smooth and reliable rotation of each monochromatic toner image carrier is ensured. Further, even if the intermediate gear is incorporated in the unit, the rotation center of the intermediate gear in the gear train is arranged at a position other than on a line connecting the rotation centers of the drive gears arranged on both sides of the intermediate gear. Therefore, the unit can be made compact as described above.

[0007]

Embodiments of the present invention will be described below with reference to the drawings. <First Embodiment> FIG. 1 is a schematic front view showing a first embodiment of a color image forming apparatus according to the present invention, and FIG. 2 is a front view showing a driving system of a single color toner image carrier. .

As shown in FIG. 1, this color image forming apparatus comprises an intermediate transfer belt which is stretched around a driving roller 10, a driven roller 11, and a tension roller 12 and is driven to circulate in the direction shown by an arrow (counterclockwise). 13 and a plurality (four) of monochromatic toner image forming means 20 (K, C, M, Y) arranged on the intermediate transfer belt 13. Monochromatic toner image forming means 2
The toner images of 0 are sequentially transferred by individual transfer members (transfer blades shown in the figure) 31, 32, 33, and 34. Each transfer portion (primary transfer portion) is denoted by T1K, T1C, T1M, and T1Y.

The single-color toner image forming means includes 20 (K) for black, 20 (C) for cyan, 20 (M) for magenta, and 20 (Y) for yellow.
And are arranged. These monochromatic toner image forming means 20
(K, C, M, Y) are a photosensitive member 21 having a photosensitive layer on the outer peripheral surface as a monochromatic toner image carrier, and a charging unit as a charging unit for uniformly charging the outer peripheral surface of the photosensitive member 21. A charging roller 22; an exposing unit 23 for selectively exposing the outer peripheral surface uniformly charged by the charging roller 22 to form an electrostatic latent image; and an electrostatic latent image formed by the exposing unit 23 Developing roller 24 as developing means for applying a toner as a developer to the image to form a visible image (toner image)
Cleaning means for removing toner remaining on the surface of the photoconductor 21 after the toner image developed by the developing roller 24 is transferred to the intermediate transfer belt 13 which is an intermediate transfer body (primary transfer object) And a cleaning blade 25.

The primary transfer is sequentially performed on the intermediate transfer belt 13,
The full-color toner image sequentially superimposed on the intermediate transfer belt 13 is secondarily transferred to a recording medium P such as a sheet in a secondary transfer section T2, and passes through a fixing roller pair 41 serving as a fixing section. The sheet is fixed on the sheet P, and is discharged by a sheet discharge roller pair 42 onto a sheet discharge tray 48 formed at the upper part of the case of the apparatus main body 40.

Reference numeral 43 denotes a paper feed cassette on which a large number of recording media P are stacked and held; 44, a pickup roller for feeding the recording media P one by one from the paper feed cassette 43; and 45, a pickup roller to the secondary transfer unit T2. A pair of gate rollers defining the supply timing of the recording medium P, 46 is a secondary transfer roller as a secondary transfer member forming a secondary transfer portion T2 with the intermediate transfer belt 13, and 47 is an intermediate transfer roller after secondary transfer. Transfer belt 13
A cleaning blade as cleaning means for removing the toner remaining on the surface of the cleaning blade.

As shown in FIG. 2, this image forming apparatus comprises:
An image carrier driving gear train 50 for driving each monochromatic toner image carrier 21 (K, C, M, Y) is provided.
A drive source gear 61 driven by a motor 60 is driven via two reduction gears 62 and 63. The gear train 50 includes the single-color toner image carriers 21 (K, C, M,
The drive gears 51 (K, C, and K) fixed to the end of Y) (see FIG. 3) and rotationally drive the respective monochrome toner image carriers 21.
M, Y) and an intermediate gear 52 (C, M, Y) disposed between these drive gears 51 (K, C, M, Y).
The drive gear 51 (K, C, M, Y) and the intermediate gear 52
(C, M, Y) is the one with no branch in the power transmission path.
They are arranged in rows (in a staggered manner in one row). That is, the drive source gear 61 is driven by being fixed to the output shaft of the motor 60, and the drive source gear 61 is connected to the reduction gear 6.
The image carrier 21K is rotationally driven by the engagement of the drive gear 51K via the gears 2 and 63, and the gear 51K
The image carrier 21C is rotationally driven by the driving gear 51C meshing with the driving gear 51C via the intermediate gear 52C and the driving gear 51M via the intermediate gear 52M.
Are engaged with each other to rotate the image carrier 21M. The drive gear 51Y meshes with the gear 51M via the intermediate gear 52Y, so that the image carrier 21M is rotated.
Y is driven to rotate. As is clear from this, and as is clear from FIGS. 3 and 1, a driving gear 51 for yellow and an image carrier 21Y are arranged at the final end of the driving path.

As shown in FIG. 2, the rotation center 52a of the intermediate gear 52 in the drive gear train 50 is
Positions other than on the line SL connecting the rotation centers of the drive gears 51 disposed on both sides of the drive gear 51 (positions shifted from the line SL)
Are located in The line SL is a line extending in the arrangement direction of the plurality of monochrome toner image carriers 21 (K, C, M, Y), and is a primary transfer portion T1K, T1C, T1M, T1Y.
It is a line basically parallel to the line connecting.

As shown in FIG. 3, a plurality of monochromatic toner image carriers 21 (K, C, M, Y) and a driving gear 51 thereof
(K, C, M, Y) and the intermediate gear 52 (C, M,
Y) is supported by the common frame 70 and the unit 71
Is configured as The intermediate gear 52 (C, M,
Y) may be supported by a frame (not shown) on the apparatus body side without being supported by the frame 70 of the unit 71. In FIG. 3, reference numeral 72 denotes a bearing rotatably supporting the shaft 21a of the image carrier 21, and reference numeral 73 denotes a shaft rotatably supporting the intermediate gear 52. As shown in FIG. 4, the image bearing member 21 includes a shaft 21b fixed to a frame 70.
May be rotatably supported.

As is apparent from FIG. 1, a secondary transfer portion T2 for transferring a color toner image from the intermediate transfer belt 13 to the recording medium P is formed at a portion where the intermediate transfer belt 13 is wound around the driven roller 11. And the recording medium P
Pass through the secondary transfer portion T2 from below to above. The cleaning blade 47 for removing the residual toner remaining on the intermediate transfer belt 13 after the secondary transfer is provided on the intermediate transfer belt 1 to the driven roller 11.
3 is in contact with the intermediate transfer belt 13 at the winding portion.

According to the above-described color image forming apparatus, the following functions and effects can be obtained. (A) The intermediate transfer belt 13 that is driven to be circulated, a plurality of single-color toner image carriers 21 (K, C, M, and Y) arranged on the intermediate transfer belt 13, and these single-color toner image carriers 21 And a gear train 50 in which an intermediate gear 52 arranged in a row is arranged in a row with respect to the intermediate transfer belt 13. Is a color image forming apparatus for sequentially transferring toner images by the intermediate gear 52 in the gear train 50.
(For example, 52 (c)), the rotation center 51 of the drive gear 51 (for example, 51 (K), 51 (C)) disposed on both sides.
a, it is arranged at a position other than on the line SL connecting the a.
Even if the first and / or intermediate gear 52 becomes larger than a desired size due to a manufacturing error thereof or expansion due to an increase in the temperature inside the apparatus, the driving gear 51 is moved in the direction of the line SL connecting the rotation centers 51a. Is not directly pressed (cosine component (Fig. 2
Pressure). Therefore, the unstable load acting on the drive gear 51 in the direction of the line SL is reduced (reduced to the cosine component), and the unstable movement of each monochromatic toner image carrier 21 is also reduced. As a result, according to the color image forming apparatus, the rotation unevenness and color shift of each monochrome toner image carrier 21 are reduced, and the image quality is improved. (B) Since the plurality of single-color toner image carriers 21 and the drive gear 51 thereof are supported by a common frame 70 and are configured as a unit 71, the plurality of single-color toner image carriers 21 are collectively assembled into an apparatus body. 1 can be attached and detached as shown by an arrow X in FIG. 1, for example, thereby improving maintainability. Further, the following operation and effect can be obtained. That is, in order to reliably and smoothly engage the intermediate gear 52 with the drive gears 52 disposed on both sides of the intermediate gear 52, the pitch diameter of the intermediate gear 52 is increased to some extent (to such an extent that the engagement is surely and smoothly performed). It is necessary to increase the number of teeth by increasing the number of teeth), for example, as shown in FIG.
When the rotation center of the drive gear (3a) and the rotation center of the intermediate gear (3b) in the gear train are arranged on a straight line (SL), when the pitch circle diameter of the intermediate gear is increased,
The distance (L) between the rotation centers of the drive gears also increases. For this reason, for example, as shown in FIG. 8B, in a gear train in which the rotation center of the drive gear (3a) and the rotation center of the intermediate gear (3b) are arranged on a straight line (SL), If this is to be unitized, the unit will have a large width in the direction of the interval (L). As shown in FIG. 8B, the rotation center of the drive gear (3a) in the gear train and the intermediate gear (3b)
It is extremely difficult to provide the intermediate gear (3b) on the apparatus main body side without incorporating the intermediate gear (3b) into the unit when the rotation center is arranged on a straight line (SL). This is because if the intermediate gear (3b) is provided on the apparatus main body side, it becomes extremely difficult to engage the drive gear (3a) on the unit side with the intermediate gear (3b) on the apparatus main body side when attaching and detaching the unit. Therefore, as shown in FIG. 8B, the rotation center of the driving gear (3a) and the rotation center of the intermediate gear (3b) in the gear train are arranged on a straight line (SL). If a plurality of single-color toner image carriers and their driving gears are to be unitized, the intermediate gear (3b) must be incorporated into the unit, and as a result, the unit is further increased in size. On the other hand, according to the color image forming apparatus of this embodiment, the rotation centers 52a of the intermediate gears 52 in the gear train 50 connect the rotation centers of the drive gears 51 arranged on both sides of the intermediate gears. Since it is arranged at a position other than on the line SL, it is possible to shorten the distance L1 (see FIG. 2) between the rotation centers 51a of the drive gear 51 accordingly. Therefore, according to the color image forming apparatus of this embodiment, the unit 71 can be made compact, and as a result, the entire apparatus can be downsized. (C) Further, in this embodiment, the intermediate gear 52 is also supported by the common frame 70 and is configured as the unit 71, so that the following operation and effect can be further obtained.
That is, together with the plurality of monochrome toner image carriers 21,
Since the drive gear 51 and the intermediate gear 52 are supported by the common frame 70 and configured as a unit 71, each drive gear 51 and the intermediate gear 52 are compared with a case where the intermediate gear 52 is arranged on the apparatus main body side. Is ensured, and the smooth and reliable rotation of each monochromatic toner image carrier 21 is ensured. Also, the intermediate gear 5
2 is incorporated in the unit 71, the rotation center 52a of the intermediate gear 52 in the gear train 50 is located at a position other than the line SL connecting the rotation centers of the drive gears disposed on both sides of the intermediate gear. Therefore, the unit 71 can be made compact as described above.

(D) A driving gear 51Y for yellow and an image carrier 21Y are provided at the last end of the driving path by the gear train 50.
Are arranged, so that the color misregistration is less noticeable, as described below, and the image quality of the entire color image is further improved. That is, as shown in the prior art shown in FIG.
In the case where the gear train for driving the first gear train is formed in one row, the color () formed by the image carrier located at the last stage of the drive path is due to the accumulation of the manufacturing error of each gear constituting the gear train. In the prior art shown in FIG. 8, cyan (in this embodiment, yellow) is the most likely to cause color shift. In such a situation, in the related art shown in FIG. 8, the image carrier 2 (C) for cyan, which is a relatively conspicuous color, is arranged at the last stage of the driving path, and therefore, is superimposed on the recording medium. In such a state, the deviation of the cyan image is conspicuous, and as a result, there is a disadvantage that the image quality of the entire color image is reduced. On the other hand, according to the color image forming apparatus of this embodiment, at the final end of the drive path by the gear train 50, the drive gear 51Y and the image carrier 21Y for yellow, whose color itself is relatively inconspicuous, are arranged. Therefore, the deviation of the yellow image in a state where the yellow image is superimposed on the recording medium P is less noticeable, and as a result, the image quality of the entire color image is further improved. In this embodiment, the drive gear 51K and the image carrier 2 for black, in which the color itself is relatively conspicuous, are used.
Since 1K is disposed at the start end of the drive path by the gear train 50 where color shift is least likely to occur, the image quality of the entire color image is further improved.

<Second Embodiment> FIG. 5 is a partially omitted front view showing a main part of a driving system of a monochromatic toner image carrier in a color image forming apparatus according to a second embodiment of the present invention. In FIG. 5, the same or corresponding portions as those in the first embodiment are denoted by the same reference numerals. This embodiment is different from the first embodiment in that the intermediate gears 52 are engaged with the drive gears 51 arranged on both sides of the intermediate gear 52, and the rotation centers of the two drive gears 51 are connected to each other. This point is configured to be movable in a direction (vertical direction in FIG. 5) orthogonal to the line SL connecting, and the other points are the same. The intermediate gear 52 in this embodiment is urged F by an elastic member (in this case, a tension spring) 74 toward the line SL. 53 is a supporting member for supporting the shaft end 52b of the intermediate gear 52,
Since the tension spring 74 is stretched between the support member 53 and the spring hooking portion 75 provided on the frame 70, the intermediate gear 52 is urged toward the line SL by the force F.
Have been. According to this embodiment, the following operation and effect can be obtained in addition to the operation and effect obtained by the first embodiment. (E) The intermediate gear 52 is engaged with the drive gears 51 disposed on both sides of the intermediate gear, and
Since the drive gear 51 and / or the intermediate gear 52 can move in a direction orthogonal to the line SL connecting the rotation centers of the first and second rotation centers, the desired size of the drive gear 51 and / or the intermediate gear 52 is increased due to a manufacturing error or expansion due to an increase in the temperature inside the apparatus. Even if it becomes larger, the intermediate gear 52 moves (runs away) in a direction orthogonal to the line SL in a state where the intermediate gear 52 meshes with the drive gears 51 arranged on both sides of the intermediate gear 52.
Therefore, the unstable load acting on the drive gear 51 in the direction of the line SL is further reduced, and the unstable movement of each monochrome toner image carrier 21 is further reduced. As a result, each monochrome toner image carrier 21 is further reduced, and the image quality is further improved. (F) Since the intermediate gear 52 is urged by the elastic member 74 toward the line SL, the engagement between the intermediate gear 52 and the drive gear 51 and the line S of the intermediate gear 52 are performed.
The movement in the direction orthogonal to L is smoothly performed.

<Third Embodiment> FIG. 6 is a partially omitted front view showing a main part of a driving system of a single color toner image carrier in a color image forming apparatus according to a third embodiment of the present invention. In FIG. 6, the same or corresponding parts as those in the first embodiment are denoted by the same reference numerals. In FIG. 6, the intermediate gear 52 (M) and the driving gears 51 on both sides thereof are shown.
(C) and (M) are drawn as representatives. This embodiment is different from the first embodiment in that the intermediate gear 52
Can be moved in a direction (vertical direction in FIG. 5) orthogonal to a line SL connecting the rotation centers of the two drive gears 51 in a state in which the drive gears 51 are engaged with the drive gears 51 disposed on both sides of the intermediate gear 52. It is in the point that it is configured, and the other points remain unchanged. Intermediate gear 52 in this embodiment
Is rotatably supported by inserting a shaft 73 into a hole 52d provided at the center thereof, and the inner peripheral surface 52e of the hole 52d is
The clearance C is formed between the shaft SL and the outer peripheral surface 73a of the shaft 73, so that the shaft C is movable in a direction perpendicular to the line SL (a vertical direction in FIG. 5).

As shown in FIG. 6 (a), when the operation of the apparatus is stopped and power is not transmitted by the gear train 50, the intermediate gear 52 is provided with an inner peripheral surface 52e of the hole 52d.
Is moved down by its own weight so as to contact the shaft 73,
The pitch circle 52p and the pitch circle 51p of the drive gear 51 are slightly separated (to such an extent that meshing of the teeth of the intermediate gear 52 and the drive gear 51 does not become impossible). On the other hand, as shown in FIG. 6B, when the apparatus operates and power is transmitted by the drive gear train 50, the intermediate gear 52 (in this case, 52 (M)) is located upstream of the power transmission system. In response to the driving force F1 from the driving gear 51 (in this case, 51 (C)) and the driving reaction force R1 from the downstream driving gear 51 (in this case, 51 (M)), both driving gears 51 (C) ( M)
(In the direction toward the line SL and upward in the drawing), and the two drive gears 51 (C) and (M) are securely engaged to transmit power. In this state, a gap C is formed between the inner peripheral surface 52e of the hole 52d of the intermediate gear 52 and the outer peripheral surface 73a of the shaft 73 in a substantially ring shape. The operation of the device is stopped and the drive gear train 50 is stopped.
When the power transmission by is stopped, the state returns to the state shown in FIG.

According to this embodiment, the following operation and effect can be obtained in addition to the operation and effect obtained by the first embodiment. (G) The intermediate gear 52 is engaged with the drive gears 51 disposed on both sides of the intermediate gear, and
The drive gear 51 and / or the intermediate gear 52 can move in a direction orthogonal to the line SL connecting the rotation centers of the first and second rotation centers without depending on the biasing force of the elastic member (for example, the tension spring 74). Even if the size becomes larger than a desired size due to a manufacturing error or expansion due to a rise in the temperature inside the apparatus, the above-mentioned state is maintained in a state where the intermediate gear 52 meshes with the drive gears 51 arranged on both sides of the intermediate gear 52. It moves (runs away) in the direction orthogonal to the line SL without receiving the urging force of the elastic member. Therefore, the unstable load acting on the drive gear 51 in the direction of the line SL is further reduced, and the unstable movement of each monochrome toner image carrier 21 is further reduced. As a result, each monochrome toner image carrier 21 is further reduced, and the image quality is further improved. That is, in this embodiment, the intermediate gear 52 is rotatably supported by inserting the shaft 73 into a hole 52d provided in the center thereof, and the inner peripheral surface 52e of the hole 52d and the outer peripheral surface 73a of the shaft 73.
The intermediate gear 52 receives the urging force of the elastic member in a direction orthogonal to the line SL connecting the rotation centers of the two drive gears 51 by the amount of the gap C. It can be moved without acting on the drive gear 51,
The unstable load in the direction of the line SL is significantly reduced, and the unstable movement of each monochrome toner image carrier 21 is also significantly reduced. As a result, the rotation unevenness and color shift of each monochrome toner image carrier are further reduced. As a result, the image quality is further improved. (H) Unlike the second and second embodiments, no urging member is required, so that the number of components is reduced and the structure is simplified.

<Fourth Embodiment> FIG. 7 is a schematic front view showing a color image forming apparatus according to a fourth embodiment of the present invention. In the figure, the same or corresponding parts as those in the first to third embodiments are denoted by the same reference numerals. This embodiment differs from the first to third embodiments in that the belt is replaced with the intermediate transfer belt 13 and
Recording medium transport belt 14 that holds and transports recording medium P
The recording medium P held by the recording medium transport belt 14 is provided with a plurality of single-color toner image forming units 20.
(K, C, M, Y) toner image by individual transfer means 3
The point is that the images are sequentially transferred in steps 1 to 34, and the other points remain unchanged. In the figure, 49a is a gate roller pair 45.
A recording medium suction roller 49 for holding the recording medium P from the recording medium conveyance belt 14 is provided. Reference numeral 49 b is a separation roller for separating the recording medium P from the recording medium conveyance belt 14 and supplying the recording medium P to the fixing roller pair 41. According to such an embodiment, the same operation and effect as those of the above-described first to third embodiments can be obtained. The toner images formed by the plurality of monochrome toner image forming units 20 (K, C, M, and Y) are sequentially transferred to the recording medium P held on the recording medium transport belt 14 by the individual transfer units 31 to 34. The only difference is what you did.

Although the embodiment of the present invention has been described above, the present invention is not limited to the above embodiment, and can be appropriately modified and implemented within the scope of the present invention.

[0024]

According to any of the color image forming apparatuses of the first to sixth aspects, the unstable load acting on the driving gear is reduced, and the unstable movement of each monochromatic toner image carrier is reduced. Rotation unevenness and color shift of the single-color toner image carrier are reduced, and the image quality is improved. Further, according to the color image forming apparatus of the present invention, the unstable load acting on the drive gear is further reduced, and the unstable movement of each monochromatic toner image carrier is further reduced. The rotation unevenness and color shift of the toner image carrier are further reduced, and the image quality is further improved. According to the color image forming apparatus of the third aspect, the engagement between the intermediate gear and the drive gear, and the engagement of the intermediate gear,
The movement in the direction orthogonal to the line connecting the centers of rotation of the two drive gears is smoothly performed. According to the color image forming apparatus of the present invention, the unstable load acting on the drive gear is significantly reduced, and the unstable movement of each single-color toner image carrier is also significantly reduced. The rotation unevenness and color shift of the image carrier are further reduced, and the image quality is further improved. According to the color image forming apparatus of the fifth aspect, a plurality of single-color toner image carriers can be collectively attached to and detached from the apparatus main body, thereby improving the maintainability and making the unit compact. It is possible to reduce the size of the entire device. According to the color image forming apparatus of the present invention, the smooth and stable meshing state between each drive gear and the intermediate gear is ensured, the smooth and reliable rotation of each monochromatic toner image carrier is ensured, and the unit is compact. Can be

[0025]

[Brief description of the drawings]

FIG. 1 is a schematic front view showing a first embodiment of a color image forming apparatus according to the present invention.

FIG. 2 is a front view showing a driving system of a monochromatic toner image carrier.

FIG. 3 is a partially cutaway plan view of a unit and a gear train.

FIG. 4 is a partially cut-away plan view of the modification.

FIG. 5 is a partially omitted front view showing a main part of a driving system of a single color toner image carrier in a color image forming apparatus according to a second embodiment of the present invention.

FIG. 6 is a partially omitted front view showing a main part of a driving system of a monochromatic toner image carrier in a color image forming apparatus according to a third embodiment of the present invention.

FIG. 7 is a schematic front view showing a fourth embodiment of the color image forming apparatus according to the present invention.

FIGS. 8A and 8B are explanatory diagrams of a conventional technique.

[Explanation of symbols]

 P Recording medium 13 Intermediate transfer belt 14 Recording medium transport belt 21 Monochromatic toner image carrier 50 Gear train 51 Drive gear 51a Center of rotation SL line 52 Intermediate gear 52a Center of rotation 52d Hole 52e Inner peripheral surface 70 Frame 71 Unit 74 Tension spring (elasticity) Member) 73 shaft 73a Outer peripheral surface C gap

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2H030 AA01 AA06 AA07 AB02 BB02 BB42 2H035 CA07 CB04 CD05 CD07 CD14 CG03 2H071 AA03 AA20 BA04 BA14 BA20 BA27 CA02 CA05 DA15 DA26 EA18

Claims (6)

[Claims] An intermediate transfer belt or a recording medium transport belt that is driven in a circulating manner; a plurality of single-color toner image carriers disposed on the intermediate transfer belt or the recording medium transport belt; A drive gear that is driven to rotate, and a gear train in which intermediate gears arranged between the drive gears are arranged in a single row. A color image forming apparatus for sequentially transferring toner images by a single-color toner image carrier, wherein rotation centers of intermediate gears in the gear train connect rotation centers of driving gears disposed on both sides of the intermediate gear. A color image forming apparatus, wherein the color image forming apparatus is arranged at a position other than on an elliptical line. 2. The method according to claim 1, wherein the intermediate gear is movable in a direction orthogonal to a line connecting the rotation centers of the two drive gears in a state in which the intermediate gear meshes with drive gears disposed on both sides of the intermediate gear. The color image forming apparatus according to claim 1, wherein: 3. The color image forming apparatus according to claim 2, wherein the intermediate gear is urged by an elastic member toward a line connecting the rotation centers of the two drive gears. 4. The intermediate gear is rotatably supported by inserting a shaft into a hole provided at the center thereof, and a gap is formed between an inner peripheral surface of the hole and an outer peripheral surface of the shaft. 3. The color image forming apparatus according to claim 2, wherein: 5. The unit according to claim 1, wherein the plurality of single-color toner image carriers and a driving gear thereof are supported by a common frame to form a unit. The color image forming apparatus as described in the above. 6. The color image forming apparatus according to claim 5, wherein said intermediate gear is also supported by said common frame and configured as a unit.