JP3141800B2 - Drive system for image forming apparatus - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a drive system for an image forming apparatus employing an electrophotographic system or the like,
The present invention relates to an improvement in a drive system for synchronously driving each image bearing drum, assuming an image forming apparatus of a type in which a plurality of image bearing drums are arranged in parallel.

[0002]

2. Description of the Related Art As a conventional color image forming apparatus, for example, a plurality of image forming units (for example, adopting an electrophotographic system) are arranged on a paper transporting path along a horizontal direction, and move along the paper transporting path. A so-called tandem type in which a toner image is sequentially transferred from each of the image forming units to a sheet to be formed and a color image is formed on the sheet is known. As a paper transport system of this type of color image forming apparatus, each image forming unit is provided with a transfer roll that comes into contact with a photosensitive drum for carrying an image, and the photosensitive drum and the transfer roll perform a paper transport operation. Transfer roll transfer method (for example, Japanese Patent Laid-Open No. 7-319254)
Or a belt transport system in which a paper transport belt that circulates and moves along a paper transport path is provided, and the paper transport belt is configured to hold paper, for example, by electrostatic attraction (see, for example, JP-A-5-53412). Gazette) has already been proposed. Further, regarding the arrangement structure of each image forming unit of this type of color image forming apparatus, a horizontal type in which a plurality of image forming units are arranged in a horizontal direction with respect to a paper transport path along a horizontal direction (for example, Japanese Patent Laid-Open -53412
Japanese Patent Application Laid-Open No. 7-287455, and a vertical type in which a plurality of image forming units are arranged in a vertical direction on a paper transport path along the vertical direction (for example, see Japanese Patent Application Laid-Open No. 7-287455).

Further, as a conventional photosensitive drum drive system, a rotatable guide roller is fixedly arranged between each photosensitive drum, and a flat belt is mounted on the outer peripheral surface of each photosensitive drum outside the image forming area and the guide roller. Have been proposed, in which a single drive motor drives a flat belt to synchronously drive each photosensitive drum with a frictional force between the outer peripheral surface of each photosensitive drum and the flat belt. (For example, JP-A-7-319254).

[0004]

However, in such a photosensitive drum drive system, the driving force is transmitted to the photosensitive drum by a frictional force between the outer peripheral surface of the photosensitive drum and the flat belt. Therefore, in order to drive the flat belt without slipping, the friction coefficient between the photosensitive drum and the flat belt must be increased or the tensile force (tension force) of the flat belt must be increased. For this reason, it is extremely difficult to drive each photosensitive drum with high accuracy.In addition, when the flat belt is driven, the tensile force of the flat belt gradually decreases from the tight side of the flat belt to the loose side. The torque resistance of the body drum (corresponding to the slip resistance of the flat belt) also gradually decreases from the tight side to the loose side. Therefore, there is a technical problem that the transfer condition of the toner image on each photosensitive drum is likely to be ununiform, and accordingly, the color image is likely to be misregistrated.

SUMMARY OF THE INVENTION The present invention has been made to solve the above technical problems, and always synchronizes the surface speeds of a plurality of image bearing drums accurately to obtain a good color image without color shift. And a driving system for the image forming apparatus.

[0006]

That is, the present invention provides:
As shown in FIG. 1, a plurality of image bearing drums 1 (for example, 1a
1d), a rotating body 2 (for example, 2a to 2d), which is arranged opposite to the outer peripheral surface of the end of each image carrying drum 1 and is swingable, and a plurality of image carrying drums. The endless belt 3 includes an endless belt 3 wrapped around a drum 1 and a plurality of rotating bodies 2, and a drive source 4 for applying a driving force to the endless belt 3.
Are sequentially wound around the outer peripheral surface of the end of the image bearing drum 1 through the space between the outer periphery of each rotating body 2 and the end of the image bearing drum 1 facing the rotating body 2, and the endless belt 3 Each rotating body 2 swings toward the image bearing drum 1 by the driving force,
The image carrier drum 1 is driven by being pressed against the image carrier drum 1 so as to sandwich the endless belt 3 with the end of the image carrier drum 1.

In such technical means, as an image forming apparatus to which the present invention is applied, if a plurality of image bearing drums 1 are arranged in parallel, a paper transport system (transfer roll system, paper transport belt, Method) or the arrangement direction of the image bearing drum 1 may be appropriately selected. The image bearing drum 1 may be any as long as it can carry an image such as a toner image, and an appropriate material such as a photoconductor or a dielectric may be selected according to the type of the latent image forming means.

Further, in the present invention, the end of the image bearing drum 1 around which the endless belt 3 is wound is defined as the outer peripheral surface of the image bearing drum 1 (in addition to the outer peripheral surface of the image bearing drum 1 itself, the outer peripheral surface of the drum). And a cylindrical body coaxial with the rotation axis of the image bearing drum 1. Here, from the viewpoint of effectively suppressing the slip of the endless belt 3, the outer peripheral surface of the end of the image bearing drum 1 may be formed as a friction resistance surface, or the end outer belt 3 may be in contact with the end of the image bearing drum 1. Preferably, the contact surface is formed as a frictional resistance surface.

Further, in a mode in which a cylindrical body coaxial with the rotation axis of the image bearing drum 1 is used as an end of the image bearing drum 1 around which the endless belt 3 is wound, the contact area of the endless belt 3 is reduced. From the viewpoint of ensuring a large amount and reliably transmitting the driving force, it is preferable to use a flange having a diameter larger than the outer diameter of the image bearing drum 1 as the cylindrical body, and further minimize an eccentric error of the flange. From the viewpoint, it is preferable that the flange is positioned concentrically by the outer diameter of the image bearing drum 1.

[0010] Further, as a structure for bridging the endless belt 3, one endless belt 3 is attached to the image bearing drum 1.
Or two endless belts 3 may be wound around one end or both ends of the image bearing drum 1. Here, in a mode in which the two endless belts 3 are stretched, from the viewpoint of making the torque resistance of the image bearing drums 1 the same, one of the two endless belts 3 is placed on the most upstream image side in the process direction. It is preferable that the other end of the image bearing drum 1d, which is the most downstream side in the process direction, be stretched so that the carrying drum 1a is on the tight side.

Further, as the oscillating rotating body 2, one oscillating rotating body 2 per one image carrying drum may be provided, or one oscillating rotating body 2 per one image carrying drum may be provided. Two movable rotors 2 may be disposed, or one pivotable rotor 2 may be disposed and fixed to the downstream side of the endless belt 3 of the pivotable rotor 2 in the traveling direction. An idler may be provided. Here, from the viewpoint of increasing the winding angle of the endless belt 3 around the image bearing drum 1 and securing the contact area, one swingable rotating body 2 per image bearing drum
Is preferable, or an embodiment including one swingable rotating body 2 and a fixed idler is preferable.

Further, as the swingable rotator 2,
For example, an idler with an arm having one end as a swing fulcrum may be used, or an idler whose rotation axis moves along a long hole.

The drive source 4 generally has a driving pulley around which the endless belt 3 is wound, but is not limited to this as long as it applies a driving force to the endless belt 3. In particular, from the viewpoint of reliably transmitting the driving force from the driving source 4 to the endless belt 3, a slip suppressing means for the endless belt 3 may be added to the driving pulley of the driving source 4, or the driving pulley may be connected to the driving pulley. It is preferable to provide a plurality of them, or to form the peripheral surface of the driving pulley of the drive source 4 as a frictional resistance surface. Here, the method of forming the friction resistance surface is performed by coating a high friction material or performing sandblasting.

Further, in the mode in which the two endless belts 3 are stretched over, the two endless belts 3 may be driven by different driving sources 4, but from the viewpoint of making the traveling speeds of both endless belts 3 the same. Drive source 4 having a single driving pulley for driving two endless belts 3
It is preferable to use

The outer peripheral length of the driving pulley of the driving source 4 around which the endless belt 3 is wound may be appropriately selected. However, from the viewpoint of reducing the influence of the eccentricity error of the driving pulley, the endless belt may be used. It is preferable that the distance 3 is set to a value substantially equal to an integral number of the travel distance of the endless belt 3 when the outer peripheral surface of the image bearing drum 1 is moved by the transfer position pitch distance.

Further, the material of the endless belt 3 may be appropriately selected, but from the viewpoint of effectively preventing the speed fluctuation due to the elongation of the endless belt 3, it is preferable to use a metal belt with a small elongation. . When such a metal belt is used, from the viewpoint of ensuring a frictional force between the image bearing drum 1 and the driving pulley of the driving source 4, the outer peripheral surface of the end portion of the image bearing drum 1 of the metal belt, It is preferable to form a coating layer made of an abrasion-resistant material on the metal belt surface of the drive source 4 which is in contact with the peripheral surface of the driving pulley.

Further, from the viewpoint of preventing a decrease in frictional resistance between the endless belt 3 and the contacted member due to the adhesion of dirt such as toner, a belt cleaner for cleaning the surface of the endless belt 3 may be added. preferable.

From the viewpoint of maintaining good operability when attaching and detaching the process cartridge in which the image bearing drum 1 and the like are incorporated, for example, the swingable rotating body 2 has one end serving as a swing fulcrum. It is preferable that an idler with an arm be used, and a winding roller that absorbs slack of the endless belt 3 when the idler with the arm is retracted from the image bearing drum 1 be added to the arm.

Further, from the viewpoint of effectively avoiding the situation where the endless belt 3 is extremely loosened when the process cartridge in which the image bearing drum 1 or the like is incorporated is not mounted, it is necessary when the endless belt 3 is driven. It is preferable to include a main tension applying mechanism that applies the main tension and an auxiliary tension applying mechanism that always applies an auxiliary tension smaller than the main tension so that the endless belt 3 does not loosen.

Further, from the viewpoint of effectively preventing belt damage due to slippage between the endless belt 3 and the driving pulley of the drive source 4 when applying the final tension to the endless belt 3, Belt 3
It has a main tension applying mechanism for applying a main tension required at the time of driving, and when applying the main tension to the endless belt 3, the driving pulley of the drive source 4 is operated in a normal operation state in conjunction with the operation of applying the main tension. It is preferable to provide a low-speed rotation mechanism that can rotate at a lower speed.

Next, the operation of the above technical means will be described. In FIG. 1, an endless belt 3 has a rotatable rotating body 2 (2a to 2d) and each image bearing drum 1 which can swing.
When the driving force from the driving source 4 is transmitted to the endless belt 3, the image bearing drums 1 are synchronously rotated by the driving force of the endless belt 3. At this time, each swingable rotating body 2 is
The angle at which the endless belt 3 is wound around each of the image bearing drums 1 is increased, and further, the endless belt 3 is pressed against the image bearing drum 1 and nipped with the image bearing drum 1 at a predetermined pressure. For this reason, a large contact area between the image bearing drum 1 and the endless belt 3 is secured, and even if the final tension of the endless belt 3 is not increased,
The pressing force between the image bearing drum 1 and the endless belt 3 is additionally applied, and the frictional force between the image bearing drum 1 and the endless belt 3 is sufficiently ensured. Further, since the swingable rotator 2 can be separated from the image bearing drum 1, the operation of attaching and detaching the process cartridge in which the image bearing drum and the like are incorporated is easily performed.

[0022]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail based on an embodiment shown in the accompanying drawings. First Embodiment FIG. 2 shows a first embodiment of a color image forming apparatus to which the present invention is applied. In the figure, the color image forming apparatus vertically arranges image forming units 22 (specifically, 22a to 22d) of four colors (yellow, magenta, cyan, and black) in a main body housing 21 in a vertical direction. A paper feed cassette 23 for accommodating supply paper is disposed below the paper feed cassette 23, and a paper feed path serving as a paper feed path from the paper feed cassette 23 is provided at a location corresponding to each image forming unit 22. The road 24 is arranged vertically.

In this embodiment, the image forming units 22 (22a to 22d) form toner images for yellow, magenta, cyan, and black in order from the upstream side of the paper transport path 24. , A process cartridge 30, a laser exposure device 40, and a transfer roll 50. Here, the process cartridge 30
In particular, as shown in FIG. 3, a photosensitive drum 31, a charging roll 32 for previously charging the photosensitive drum 31, and the laser exposure device 40 on the charged photosensitive drum 31.
The developing unit 33 for developing the electrostatic latent image formed by exposure with the corresponding color toner and the cleaner 34 for removing the residual toner on the photosensitive drum 31 are integrally formed into a cartridge.

In the present embodiment, the developing device 33 is provided below the photosensitive drum 31 and has a developing housing 331 extending in the lateral direction.
1 accommodates a developer containing a predetermined color toner (one-component developer composed of a non-magnetic developer or a magnetic developer), and a pair of developer agitating members 332 is provided in a developing housing 331. Further, a developing roll 333 is provided at an opening of the developing housing 331 facing the photosensitive drum 31.
, A developer supply member 334 for supplying the developer in the developing housing 331 to the developing roll 333 side is disposed near the developing roll 333, and further, the developer is supplied onto the developing roll 333. Is provided with a developer layer thickness regulating member 335 whose layer thickness is regulated. On the other hand, the cleaner 34 is disposed above the photosensitive drum 31 and has a cleaner housing 341 extending in the lateral direction. The cleaner housing 341 is provided at a position facing the photosensitive drum 31 for scraping residual toner. A blade 342 is provided.

In particular, in this embodiment, since the developing housing 331 for storing the developer and the cleaner housing 341 for collecting the residual toner are extended in the horizontal direction, the respective housing spaces are secured. The vertical dimension of the process cartridge 30 is set to be short.

The laser exposure device 40 includes a case 41
A semiconductor laser (not shown), a polygon mirror 42, an imaging lens 43 and mirrors 44 and 45 are stored therein, and light from the semiconductor laser (not shown) is deflected and scanned by the polygon mirror 42. The optical image is guided to an exposure point on the photosensitive drum 31 via the light source 45. In the present embodiment, since the case 41 extends in the horizontal direction, its vertical dimension is set to be short.

Further, in the present embodiment, the left side of the main body housing 21 in the figure is covered with an openable / closable main body cover 21a, and a transfer roll 50 is provided separately from the process cartridge 30 on the main body cover 21a side. When the main body cover 21a is closed, the photosensitive drum 31 of the process cartridge 30 is brought into contact with the photosensitive drum 31 and is driven to rotate substantially in synchronization with the photosensitive drum 31. Then, a predetermined transfer electric field is applied to the transfer roll 50, so that a transfer force to the transfer roll 50 side is applied to the toner image on the photosensitive drum 31.

Further, in this embodiment, as shown in FIGS. 2 and 4, the feed cassette 23 is provided with a feed roll 61 for sending out paper at a predetermined timing.
A nip transport roll 62 on the entrance side is provided in the paper transport path 24 located between the feed roll 61 and the transfer portion of the uppermost stream image forming unit 22a, and an optical paper passage sensor is provided downstream of the nip transport roll 62. 63 are provided. In the present embodiment, the paper passage sensor 63 detects the leading edge of the paper, and based on the detection timing, for example, the laser exposure device 40 of each image forming unit 22.
The writing timing of the electrostatic latent image is controlled.

Further, a fixing device 64 is provided in the sheet transport path 24 located on the downstream side of the most downstream image forming unit 22d. The fixing device 64 is composed of a heating roll 641 and a pressure belt 642 that comes into surface contact with the heating roll 641 in a wide nip area. In this embodiment, the fixing device 64 also functions as a nip transport roll 65 on the exit side. Further, a discharge roll 66 for discharging the paper is provided on the downstream side of the fixing device 64, and the discharged paper is stored in a storage tray 67 formed above the main body housing 21.

In this embodiment, as shown in FIG. 4, the distance between the entrance nip transport roll 62 and the exit nip transport roll 65 is L, and each image forming unit 2
A, the interval between the uppermost image forming unit 22a and the entrance nip transport roll 62 is B, and the interval between the most downstream image forming unit 22d and the exit nip transport roll 65 is A. C, the length of the paper (not shown) of the standard use size (JIS A4 size in this embodiment) in the transport direction is S (not shown), and the minimum use size (JIS A6 size postcard in this embodiment) Assuming that the length of the sheet having the size S in the transport direction is S ′ (not shown), the following relational expression is established. S> L = 3A + B + C S ′> 2A, A + B, A + C

Further, in the present embodiment, each image forming unit 22 is located on the front side of the most upstream image forming unit 22a.
a to 22d, and behind the most downstream image forming unit 22d, a paper guide 7 for regulating the movement locus of the paper.
1 to 75 are provided. Here, the paper guides 71 to 71 located on the front side of the image forming units 22a to 22d.
74, a taper guide surface 76 slightly upwardly to the right with respect to the vertical line is formed. The taper guide surface 76 extends in a direction in which the back surface including the leading end of the sheet to be transferred and conveyed always contacts. The paper is adjusted so that the paper moves toward the nip area between the drum 31 and the transfer roll 50 while making contact, and the leading end of the paper abuts on the photosensitive drum 31 side before the nip area. Further, in the present embodiment, the paper guide 75 on the rear side of the most downstream image forming unit 22d is divided into two, and the taper guide surface 77 slightly rises to the left with respect to the vertical line, and the fixing device is connected thereto. An arcuate guide surface 78 is formed toward the nip area of the fixing device 64 so that the leading end of the sheet passing through the most downstream image forming unit 22d is guided to the nip area of the fixing device 64 without curling.

Next, a description will be given of a photosensitive drum drive system used in the color image forming apparatus according to the present embodiment. FIG. 5 schematically shows a photosensitive drum drive system according to the present embodiment, and FIG. 6 is a perspective view of a main part thereof. 5 and 6, the photosensitive drum drive system includes an outer peripheral surface of the end of the photosensitive drum 31 of each of the image forming units 22 (specifically, 22a to 22d). (Equivalent to the outer peripheral surface)
Of the swingable arm-equipped idler 100 (specifically, 100a to 100a)
d). Here, idler with arm 100
Has an idler pulley 103 rotatably supported on a free end side of an arm 101 having one end as a swing fulcrum 102. In this embodiment, the swing fulcrum 1 of the arm 101 is provided.
02 is the center of the photosensitive drum 31 and the idler pulley 103
Is set in a direction substantially orthogonal to a straight line connecting the rotation center of the first and second rotations. Further, in the present embodiment, a coating layer (for example, diamond coat) 90 (see FIG. 6) of a high friction material is formed on the outer peripheral surface of the end of the photosensitive drum 31 with which the idler with arm 100 contacts.

Further, the driving system has a driving pulley 110 which is drivingly connected to a driving motor as a driving source. The endless belt 120 wound around the driving pulley 110 is driven by a plurality of driven pulleys 111 to 113, The idler with arm 100 and the photosensitive drums 31 are sequentially extended. In the present embodiment, for example, a rubber-coated belt having Kepler as a core body is used as the endless belt 120, and the driving pulley 110
A coating layer (for example, a diamond coat) made of a high-friction material (not shown) is formed on the outer peripheral surface of the substrate. On the other hand, the driven pulley 111 is disposed in contact with the driving pulley 110, and the driven pulley 112 is disposed further above the most downstream photosensitive drum 31 (image forming unit 22d) to apply a predetermined tension to the endless belt 120. The driven pulley 113 is disposed below the uppermost-stream photosensitive drum 31 (image forming unit 22a). still,
In the present embodiment, the tension applying mechanism 114
As shown in FIG. 6, a driven pulley (tension pulley) 112 is swingably supported by a swing arm 115, and the driven pulley 112 is urged in a predetermined direction by an urging spring 116. Also applies tension.

In particular, in the present embodiment, the endless belt 120 is wound about two thirds of the outer peripheral surface of the idler pulley 103 of each idler with arm 100, and
The photosensitive drum 31 is wound about two-thirds of the outer peripheral surface of the end portion thereof, passing between the idler pulley 103 and the photosensitive drum 31.

Next, the operation of the photosensitive drum drive system and the color image forming apparatus according to the present embodiment will be described. In the present embodiment, the drive system for the photosensitive drum operates as follows. In FIG. 5, when an unillustrated image forming start switch is turned on, first, the driving pulley 110 rotates to transmit a predetermined driving force to the endless belt 120, and the endless belt 120 starts circulating and rotating in the direction of the arrow in the figure. At this time, the idler with arm 100 around which the endless belt 120 is wound is shown in FIG.
Works like That is, the idler with arm 100
Of the idler pulley 103 by the driving force of the endless belt 120, F1 (meaning the vector acting in the direction in the figure with the magnitude of | F1 |) and F2 (acting in the direction of the figure with the magnitude of | F2 | An external force (meaning vector) acts on the center axis of the idler pulley 103, and a resultant force of F1 + F2 acts on the center axis of the idler pulley 103. Then, as a resultant force of the resultant force F1 + F2 ,
F (auxiliary tension) acts on the idler pulley 103 toward the center of the photosensitive drum 31, and the idler pulley 103 is pressed against the photosensitive drum 31, and clamps the endless belt 120 at a predetermined pressure. In this state, since the endless belt 120 is wound over a wide area of about 2/3 of the outer peripheral surface of the end of each photosensitive drum 31, the endless belt 120 and the photosensitive drum 31
The frictional force between the endless belt 1
Reference numeral 20 synchronizes the surface peripheral speed of the photosensitive drum 31 without slipping.

Accordingly, the transfer roll 50 arranged in contact with the photosensitive drum 31 rotates following the photosensitive drum 31. On the other hand, if an image forming start switch (not shown) is pressed, the sheet (for example, the sheet of the standard use size: the length S in the transport direction) in the sheet cassette 23 is sent out by the feed roll 61 and then the leading end of the sheet Reaches the nip transport roll 62 on the entrance side. Then, the paper is nip-conveyed by the entrance-side nip conveyance roll 62, and sequentially enters the transfer portions of the image forming units 22 a to 22 d in the paper conveyance path 24. At this time, since the paper transport speed is kept constant by the entrance-side nip transport roll 62, the paper passing speed at the transfer site of each of the image forming units 22a to 22d is kept constant. In addition, the span A between the transfer sites of the image forming units 22a to 22d and the span B between the entrance-side nip transport roll 62 and the transfer site of the most upstream image forming unit 22a are set for the standard size paper. Since it is set to be sufficiently short, the vicinity of the leading end of the sheet entering the transfer portion of each of the image forming units 22a to 22d is close to the entrance nip transport roll 62 or the transfer nip portion of the front image forming units 22a to 22c (photosensitive). Nip portion between body drum 31 and transfer roll 50)
, And the position of the leading end of the sheet entering the transfer portion of each of the image forming units 22a to 22d is stabilized accordingly. For this reason, each of the image forming units 22a to 22a
Since the 2d image cycle and the timing at which the sheet enters the transfer area are kept constant, there is no shift in the transfer position of each color toner image, and there is no color shift and color unevenness in the color image.

When the leading end of the sheet reaches the fixing device 64 (exit side nip conveying roll 65) and is nipped, at this stage, the sheet is supplied to both the entrance side nip conveying roll 62 and the exit side nip conveying roll 65. Nip transport. Thereafter, as the paper is conveyed, the nip operation by the entrance-side nip conveyance roll 62 is released, but the paper is still nip-conveyed by the exit-side nip conveyance roll 65, and therefore still moves at a constant conveyance speed. I do. For this reason, the passing speed of the sheet at the transfer site of each of the image forming units 22a to 22d is always kept constant. Thereafter, when the sheet has passed through the fixing device 64, the sheet on which the unfixed toner image has been fixed is transferred through the discharge roll 66 to the storage tray 67.
(See FIG. 2). In such an operation process, it is confirmed that a color image free from color misregistration and color unevenness is obtained with respect to the paper of the standard use size.

In this embodiment, since the idler with arm 100 can swing about the swing fulcrum 102, the idler with arm 100 is opened after the body cover 21a of the body housing 21 is opened. Drum 3
When the photosensitive drum 31 is swung in the direction away from the photosensitive drum 31, the process cartridge
0 can be detached from the opening on the side of the main body cover 21a. In a mode in which a space for attaching and detaching the process cartridge 30 cannot be secured at the opening on the side of the main body cover 21a, a space for attaching and detaching the process cartridge 30 may be secured in a direction perpendicular to the paper surface.

Here, as a modification of the present embodiment, as shown in FIG. 8, for example, a pair of idlers with arms 104 (specifically, 104a to 104a) are provided on the outer peripheral surface of the end of each photosensitive drum 31. 104d), 105 (specifically, 10
5a to 105d) may be arranged to face each other.
Each of the idlers with arms 104 and 105 has a mode in which an idler pulley 103 is rotatably supported on a free end of an arm 101 having one end as a swing fulcrum 102.
In this embodiment, a pair of idlers with arms 104,
When each idler pulley 103 of 105 is made smaller and both idler pulleys 103 are arranged close to each other, the endless belt for the outer peripheral surface of the end portion of the photosensitive drum 31 is compared with the mode using one idler with arm 100. It is possible to secure a larger winding angle of the roller 120, and accordingly, a larger contact area between the endless belt 120 and the outer peripheral surface of the end of the photosensitive drum 31 is secured. Further, since both the pair of idlers with arms 104 and 105 are pressed against the photosensitive drum 31 side, the pressing force for pressing and holding the endless belt 120 increases as compared with the mode using the idler with one arm 100. Therefore, in the present modification, the frictional force between the photosensitive drum 31 and the endless belt 120 is more reliably ensured as compared with the mode using one idler with arm 100.

As another modification of the present embodiment, as shown in FIG. 9, for example, one idler with an arm is provided on the outer peripheral surface of the end of each photosensitive drum 31 on the upstream side in the running direction of the endless belt 120. 104 (specifically, 104a-
104d) and a fixed idler (an idler pulley whose rotation axis position is fixed) 106 downstream of the photosensitive drum 31 in the running direction of the endless belt 120.
(Specifically, 106a to 106d) are arranged to face each other. Even in this mode, the idler with arm 104
Of the idler pulley 103 and the fixed idler 106, and the idler pulley 103 and the fixed idler 10
6 can be secured closer to the end outer peripheral surface of the photosensitive drum 31 than in the case of using the idler 100 with one arm. , That much,
A larger contact area between the endless belt 120 and the outer peripheral surface of the end of the photosensitive drum 31 is ensured. Therefore, in the present modification, the frictional force between the photosensitive drum 31 and the endless belt 120 is more reliably ensured as compared with the mode using one idler with arm 100, and the idler with both arms is further improved. Compared with the embodiment using 104 and 105, the structure is simplified because the number of movable members is reduced.
8 and 9, the same components as those of the first embodiment are denoted by the same reference numerals as those of the first embodiment, and the detailed description thereof will be omitted.

Second Embodiment FIG. 10 is an explanatory diagram showing an outline of a second embodiment of a photosensitive drum drive system applied to a tandem type color image forming apparatus. In the figure, the drive system of the photosensitive drum is substantially the same as that of the first embodiment (FIG. 5), but different from the first embodiment, a driven pulley 111 arranged in contact with the driving pulley 110 (see FIG. 5). Instead, the idler with arm 130 is used as the slip suppression mechanism. The idler with arm 130 has an idler pulley 133 rotatably supported on a free end of an arm 131 having one end serving as a swing fulcrum 132. The idler pulley 133 is arranged in contact with the driving pulley 110.

According to the present embodiment, when a tension force T in the direction of the arrow is applied to the tension pulley 112 and the endless belt 120 is pulled, the idler with arm 130 is pressed against the driving pulley 110, and the driving pulley 110 and the idler with arm are pressed. 130 and the endless belt 12
0 is held at a predetermined pressing force (indicated by F in FIG. 10), and the idler pulley 133 of the idler with arm 130 is more strongly pressed via the endless belt 120 by the driving force of the driving pulley 110 itself. In addition, the slip between the driving pulley 110 and the endless belt 120 is effectively suppressed.

A drive system for a photosensitive drum according to a modification of the present embodiment is substantially the same as the modification of the first embodiment (see FIG. 8) as shown in FIG. 11, for example. Unlike the modification of the first embodiment, the driving pulley 1
Instead of the driven pulley 111 (see FIG. 8) arranged in contact with 10, a pair of idlers 134 and 135 with arms are used. Idler 13 with a pair of arms
4, 135 is an arm 13 having one end serving as a swing fulcrum 132.
An idler pulley 133 is rotatably supported at one free end, and each idler pulley 133 is arranged in contact with the driving pulley 110.

According to this modification, if the idler pulleys 133 of the pair of idlers with arms 134 and 135 are made smaller and both idler pulleys 133 are arranged close to each other, one idler with arm 130 is used. Compared with the aspect, it is possible to secure a larger winding angle of the endless belt 120 with respect to the outer peripheral surface of the driving pulley 110, and accordingly, the contact area between the endless belt 120 and the outer peripheral surface of the driving pulley 110 is increased. Many are secured. Further, a pair of idlers with arms 134 and 13 is provided.
5 is pressed against the driving pulley 110, so that the pressing force for pressing and holding the endless belt 120 is increased as compared with the mode using one idler with arm 130. Therefore, in the present modified embodiment, the frictional force between the driving pulley 110 and the endless belt 120 is more reliably ensured as compared with the mode using one idler with arm 130, and between the two. Slip is more reliably suppressed.

Further, as still another modification of the present embodiment, for example, a modification of the first embodiment (see FIG. 9)
However, unlike this modified embodiment, an idler with arm 134 is disposed in contact with the driving pulley 110 on the upstream side in the traveling direction of the endless belt 120, and a fixed idler (not shown) is provided on the downstream side in the traveling direction of the endless belt 120. ) May be arranged in contact. Note that components similar to those of the first embodiment and its modifications are denoted by the same reference numerals, and a detailed description thereof will be omitted. The same applies to the following embodiments.

Third Embodiment FIG. 12 is an explanatory diagram showing an outline of a third embodiment of a photosensitive drum drive system applied to a tandem type color image forming apparatus. In the figure, the drive system of the photosensitive drum is substantially the same as, for example, the first embodiment (FIG. 5), but different from the first embodiment, a plurality of driving pulleys 117 and 118 are provided as drive sources, and each of them is provided. Drive pulley 117,
Idler 13 with arm as slip suppression mechanism 118
0 is used. In the present embodiment, for example, a driving force from a single driving motor is separated and transmitted to the driving pulleys 117 and 118 by a transmission gear.

According to the present embodiment, the driving force from the two driving pulleys 117 and 118 is transmitted to the endless belt 120, and furthermore, the tension pulling force 112 is applied to the tension pulley 112 in the direction of the arrow.
12, the idlers with arms 130 and 131 are pressed against the respective driving pulleys 117 and 118, and the endless belt 120 is pressed between the driving pulleys 117 and 118 and the idlers with arm 130 and 131 with a predetermined pressing force (FIG. 12).
(Shown as middle F1 and F2), and the idlers 130 and 131 with arms are also driven by the driving pulleys 117 and 118 via the endless belt 120 by their own driving force.
Is pressed more strongly, the slip between the driving pulley 110 and the endless belt 120 is effectively suppressed, and the endless belt 120 is reliably circulated by the driving force from the driving pulleys 117 and 118 without slipping. Rotate.

In the present embodiment, one idler with arm 130 is arranged in contact with each of the driving pulleys 117 and 118. However, the present invention is not limited to this. For example, each of the driving pulleys 117 and 118 is provided. In addition, as a slip suppression mechanism, two armed idlers are placed in contact with each other,
Alternatively, the idlers with arms may be arranged in contact with the driving pulleys 117 and 118 on the upstream side in the traveling direction of the endless belt 120, and the fixed idlers may be arranged in contact on the downstream side in the traveling direction of the endless belt 120. Of course.

Fourth Embodiment FIG. 13 shows a fourth embodiment of a photosensitive drum drive system applied to a tandem type color image forming apparatus. In the figure, the drive system of the photoconductor drum is substantially the same as that of the second embodiment, but unlike the second embodiment, the outer peripheral surface of the end portion of the photoconductor drum 31 around which the endless belt 120 is wound is a photosensitive drum. The photosensitive drum 31 is not an outer peripheral surface but a cylindrical flange 140 having a diameter larger than the outer diameter of the photosensitive drum 31. This cylindrical flange 140 is particularly useful in FIG.
As shown in FIGS. 4A and 4B, a male ring portion 141 having a wedge-shaped cross section is formed on the inner peripheral edge of the cylindrical flange 140 by being press-fitted to the outer peripheral surface of the photosensitive drum 31. The part 141 is wedge-engaged with the wedge-shaped female ring 142,
Further, the cylindrical flange 140 is fixed by a stopper 143 such as a bolt.
And the female ring 142 are integrally connected. Furthermore,
A coating layer (for example, diamond coat) 144 made of a high friction material is formed on the outer peripheral surface of the flange 140.

Therefore, in the present embodiment, since the endless belt 120 is wound around the outer peripheral surface of the flange having a diameter larger than the outer diameter of the photosensitive drum 31, the photosensitive drum 3
Endless belt 1 compared to the mode using the outer peripheral surface of
20 has a large contact area, and the frictional resistance increases due to the presence of the coating layer 144 having a high friction coefficient. For this reason, a large frictional force between the endless belt 120 and the outer peripheral surface of the end of the photosensitive drum 31 is ensured, and the transmission of the driving force to the photosensitive drum 31 by the endless belt 120 is more reliably performed. Will be Further, in the present embodiment, since the flange 140 is positioned at the outer diameter of the photosensitive drum 31, the flange 140
Is set to be coaxial with the photosensitive drum 31, and the outer peripheral surface of the flange 140 hardly contains an eccentric error.

Fifth Embodiment FIG. 15 shows a fifth embodiment of a photosensitive drum drive system applied to a tandem type color image forming apparatus. Unlike the first to fourth embodiments, the photoconductor drum driving system according to the present embodiment has one driving pulley 110 that is drivingly connected to a driving motor as a driving source, and is wound around the driving pulley 110. Two endless belts 12
1, 122 is a plurality of driven pulleys 151 to 157,
Each idler with arm 161 (specifically, 161a to 161a
1d), 162 (specifically, 162a to 162d) and each photosensitive drum 31.

More specifically, in the present embodiment, the two endless belts 121 and 122 are arranged along the outer peripheral surface of one end of the photosensitive drum 31 (in the present embodiment, the outer peripheral surface of the photosensitive drum 31). Is being passed over,
The driving pulley 110 has two endless belts 121, 1
22 having a width dimension that is equal to or greater than the sum of the width dimensions of 22.
A coating layer (for example, a diamond coat) made of a high friction material (not shown) is formed on the outer peripheral surface of one end of the photosensitive drum 31 around which the endless belts 121 and 122 are wound and the outer peripheral surface of the driving pulley 110. On the other hand, the driven pulleys 151 and 154 are arranged in contact with opposing portions connected by the diameter of the driving pulley 110, and the driven pulleys 152 and 155 are further disposed on the most downstream photosensitive drum 31 (image forming unit 22d). The driven pulleys 153, 156, and 157 are disposed above the photosensitive drum 31 (image forming unit 22a) on the most upstream side. In the present embodiment, the driven pulleys 152 and 156 (or 157) function as tension pulleys.

Further, idlers with arms 161 and 162 are provided at opposing portions connected by the diameter of each photosensitive drum 31.
Are arranged in contact. These idlers with arms 16
The idler pulley 103 is rotatably supported on the free end of the arm 101 having one end serving as the swing fulcrum 102. In the present embodiment, the idler with one arm 161 is an idler pulley 103. , Whereas the other idler with arm 162 has the swing fulcrum 102 positioned below the idler pulley 103.

In this embodiment, one endless belt 121 is wound about two-thirds of the outer peripheral surface of the idler pulley 103 of the idler 161 with each arm from the driving pulley 110 via the tension pulley 152. , Passing between the idler pulley 103 and the photosensitive drum 31, approximately two-thirds of the outer peripheral surface of the end of the photosensitive drum 31.
It is wound to the extent, and is further circulated to the driving pulley 110 via the driven pulleys 153 and 151. The other endless belt 122 is wound about two-thirds of the outer peripheral surface of the idler pulley 103 of each idler with arm 162 from the driving pulley 110 via the driven pulley 157 and the tension pulley 156, and then the endless belt 122 is connected to the idler pulley 103. The photosensitive drum 31 is wound around approximately ／ of the outer peripheral surface at the end of the photosensitive drum 31, and is circulated to the driving pulley 110 via driven pulleys 155 and 154.

In particular, in the present embodiment, the tension pulleys 152 and 156 are disposed vertically and separately, and one endless belt 121 is the photosensitive drum 31 (image forming unit 22d) on the most downstream side in the process direction. And the other endless belt 122
Is wound so that the photosensitive drum 31 (image forming unit 22a) on the most upstream side in the process direction is on the tight side.

Therefore, according to the present embodiment, the two endless belts 121 and 122 are
0, both endless belts 12
The running speed of 1,122 is kept the same. Further, the driving force from the driving pulley 110 is applied to each endless belt 12.
1, 122, each endless belt 12
Idlers 161 with arms wound around 1,122
162 are pressed against the photosensitive drum 31, and the endless belts 121 and 122 press the photosensitive drum 31 with a predetermined pressure. For this reason, the endless belt 12
A sufficient frictional force between the endless belts 121 and 122 and the photosensitive drum 31 is secured.
By the second driving force, the photosensitive drum 31 is reliably rotated synchronously.

Further, in the present embodiment, one of the two endless belts 121 and 122 has the photosensitive drum 31 on the most upstream side in the process direction on the tension side, and the other has the most end in the process direction. Downstream photosensitive drum 31
Is set to be on the tension side, so that the torque resistance (slip resistance) of all the photosensitive drums of the image forming units 22a to 22d is kept substantially the same after the combination,
Compared with a mode using one endless belt, it is possible to further suppress the color shift of the transferred image.

That is, as shown in FIGS. 15 and 18, one endless belt 121 and each photosensitive drum 3
1 (image forming units 22a to 22d), each photosensitive drum 31 has an axial load FK based on the acting forces F1 and F2 applied to the endless belt 121 (the photosensitive drum 31 of the image forming unit 22d). Action), axial load FY (acting on the photosensitive drum 31 of the image forming unit 22c), axial load FM (acting on the photosensitive drum 31 of the image forming unit 22b), axial load FC (image forming unit 2).
2a) occurs on the photosensitive drum 31 of FIG. At this time, since a tension force is applied to the tension pulley 152, the axial load increases toward the upstream side in the process direction (FC>FM>FY> FK), and as shown in FIG. As shown in FIG. 20, the transfer image of the color component on the downstream side in the process direction is likely to be misregistered due to belt slip, as shown in FIG. On the other hand, when the other endless belt 122 is bridged between the photosensitive drums 31 (image forming units 22a to 22d), an axial load based on the acting force on the endless belt 122 is applied to each photosensitive drum 31. Since the tension force is applied to the tension pulley 156 on the endless belt 122, the axial load increases toward the downstream side in the process direction (F
C <FM <FY <FK), the slip ratio increases toward the upstream side in the process direction, and the registration of the transferred image of the color component on the upstream side in the process direction is easily shifted due to belt slip. Therefore, in the present embodiment, since the stepwise decreasing tendency of the tension force of the endless belts 121 and 122 has an opposite relationship, the torque resistance (slip resistance) of each photosensitive drum 31 is stepwise. The tendency to decrease is offset each other, and the torque resistance of each photosensitive drum 31 is kept substantially the same.

In the present embodiment, the two endless belts 121 and 122 are wound around the outer peripheral surface of one end of the photosensitive drum 31. However, the present invention is not limited to this. 31 may be wound around the outer peripheral surfaces at both ends. In this embodiment, the bending moment acting on the photosensitive drum 31 in the axial direction is reduced by the tension on the endless belts 121 and 122.

Sixth Embodiment FIG. 21 shows a sixth embodiment of a photosensitive drum drive system applied to a tandem type color image forming apparatus. In the figure, the drive system of the photosensitive drum is substantially the same as that of the first embodiment, but is different from the first embodiment (see FIG. 5) in that the frame 1 is replaced with the idler 100 with arm.
The long hole 171 (specifically, 171a-17)
1d) along with the idler 172 (specifically,
172d) is swung. Also in the present embodiment, when the tension acts on the endless belt 120, the swingable idler 172 is pressed against the photosensitive drum 31 side, and the endless belt 120 is sandwiched between the photosensitive drum 31. Form 1
In substantially the same manner as described above, the photosensitive drum 31 is reliably rotated by the endless belt 120 at the synchronous peripheral speed.

Embodiment 7 The drive system of the photosensitive drum according to the present embodiment is substantially the same as that of Embodiment 1, but is different from Embodiment 1 in that the endless belt 120 is a metal belt, for example, a stainless steel. It uses a belt. If a metal belt of this type is used, color shift due to elongation of the endless belt 120 can be reduced. In order to confirm this, four belts A (a rubber belt having a polyethylene core), B (a rubber belt having a Kepler core), C (a narrow stainless steel belt), and D (a stainless steel belt) as shown in FIG. When the color misregistration due to the belt elongation with respect to the image length was examined using (wide belt), the result shown in FIG. 22 was obtained. According to the figure, a metal belt (C,
It can be seen that D) is very good with regard to color shift.

In this embodiment, a coating layer made of a wear-resistant material (for example, urethane) is formed on the surface of the metal belt. Therefore, the frictional force between the endless belt 120, the photosensitive drum 31, and the driving pulley 110 increases, and the endless belt 12
0 abrasion resistance is improved.

Eighth Embodiment FIG. 24 shows an eighth embodiment of a photosensitive drum drive system applied to a tandem type color image forming apparatus. The drive system of the photosensitive drum according to the present embodiment is substantially the same as that of the first embodiment. However, unlike the first embodiment, the circumference L1 of the driving pulley 110 is an integer of the span L2 between the photosensitive drums 31. One-fifth, in this embodiment, is set to 1. According to the present embodiment, as shown in FIG. 25, even if the surface speed of the driving pulley 110 has a periodic speed fluctuation, each of the photosensitive drums C, M, Y, and
K, that is, 31 (image forming units 22a to 22d)
Can be synchronized for all colors.

Ninth Embodiment FIG. 26 shows a photosensitive drum driving system according to a ninth embodiment applied to a tandem type color image forming apparatus. In the figure, the drive system of the photosensitive drum is substantially the same as the modified embodiment of Embodiment 1 (see FIG. 8), but different from the modified embodiment, a belt cleaner 180 for cleaning the surface of the endless belt 120 is used. For example, the driven pulley 113
This is added to the part opposite to. Here, as the belt cleaner 180, a blade, a brush, or the like may be appropriately selected.

According to the present embodiment, even if dirt such as toner adheres to the surface of endless belt 120,
Since the cleaning is performed by the belt cleaner 180, a situation where the friction coefficient between the endless belt 120 and the driving pulley 110, the idler pulley 103 of the armed idlers 104 and 105, etc. is reduced is effectively avoided. In the present embodiment, the belt cleaner 180 cleans only one side of the endless belt 120, but it may clean both sides of the endless belt 120.

Embodiment 10 FIG. 27 shows Embodiment 10 of a photosensitive drum drive system applied to a tandem type color image forming apparatus.
In the figure, the drive system of the photosensitive drum is substantially the same as that of the first embodiment, but differs from the first embodiment in that the arm 101 of the armed idler 100 is extended to the opposite side across the swing fulcrum 102. A winding roller 192 is provided on the extension 191, and when the idler with arm 100 is retracted from the photosensitive drum 31, the endless belt 120 is pushed down by the winding roller 192, and
It is designed to absorb 20 slacks. FIGS. 28 and 29 show a process of absorbing the slack of the endless belt 120 by the winding roller 192 according to the present embodiment.

According to the present embodiment, when the idler with arm 100 (for example, 100d) is retracted from the photosensitive drum 31 (for example, the image forming unit 22d), FIG.
As shown in FIGS. 8 and 29, the endless belt 120 wound around the photosensitive drum 31 actively pushes out the photosensitive drum 31 because the winding roller 192 winds up the slack of the endless belt 120. The detachment operation of the process cartridge 30 incorporating the drum 31 and the like is easily executed.

Eleventh Embodiment FIG. 30 shows an eleventh embodiment of a photosensitive drum drive system applied to a tandem type color image forming apparatus.
In the figure, the drive system of the photosensitive drum is substantially the same as that of the tenth embodiment, but different from the tenth embodiment.
The endless belt 120 includes a main tension applying mechanism 200 for applying a predetermined main tension (main tension force) to the endless belt 120, and an auxiliary tension applying mechanism 201 for applying an auxiliary tension (auxiliary tension force) weaker than the main tension to the endless belt 120. ing. In the present embodiment, the tension applying mechanism 200
A support frame 230 in the main body housing is provided with an engaging arm 204 coaxially with a swing fulcrum 203 of a swing arm 202 on which the tension pulley 112 is swingably supported.
The support frame 230 is provided with an advancing / retracting rod 206 which advances / retreats in accordance with the operation of the lock arm 205, and the advancing / retreating rod 206 advances when the lock arm 205 is locked (operation of pushing down from a solid line position to an imaginary line position) to engage the engaging arm 204 , The swing posture of the swing arm 202 is changed, and the position of the tension pulley 112 is moved to the main tension position. Note that reference numeral 20
7 is a return spring for returning the advance / retreat rod 206 to a predetermined position when the lock by the lock arm 205 is released.
Reference numeral 1 denotes a photosensitive drum 31 provided on the support frame 230.
And a positioning plate for positioning a process cartridge in which the process cartridge is incorporated. Also, the auxiliary tension applying mechanism 201
The biasing spring 20 is attached to one end of the swing arm 202.
8, the swing arm 202 is balanced in a predetermined posture, and a predetermined auxiliary tension is applied to the endless belt 120.

According to the present embodiment, since the endless belt 120 is always pulled by the auxiliary tension by the auxiliary tension applying mechanism 201, even when the process cartridge 30 is not mounted, the endless belt 120 is pulled.
Unnecessarily loosening is effectively avoided.

Embodiment 12 FIGS. 31 and 32 show Embodiment 1 of a photosensitive drum drive system applied to a tandem type color image forming apparatus.
2 is shown. In the figure, the drive system of the photosensitive drum is substantially the same as that of the tenth embodiment,
Unlike this, the transmission gear 221 is provided coaxially with the driving pulley 110, and the transmission gear 221 is meshed with the pinion 222. On the other hand, the main body housing 21 is provided with an openable / closable main body cover 21a, and the main body cover 21a is opened. A movable rack 223 is provided at a position where the movable rack 223 is engaged with the pinion 222 when the pinion 222 is closed later.
3 are engaged with the rack guides 226 and 227 having a predetermined groove locus, and when the main cover 21a is completely closed and the tension is applied to the endless belt 120, the movable rack 223 is It is retracted from the meshing position with the pinion 222. In the present embodiment, the tension pulley 1
Numeral 12 is supported by a swing arm 202 so as to be swingable, and an engagement arm 204 is coaxial with a swing fulcrum 203 of the swing arm 202.
Are protruded, and the engagement protrusion 2 formed on the main body cover 21a is provided.
10 abuts on the engagement arm 204, changes the posture of the swing arm 202, and applies this tension to the endless belt 120.

According to the present embodiment, the main body cover 21a
Is gradually closed from the open position, the engagement protrusion 210 pushes the engagement arm 204 and the endless belt 120 is closed.
Is given this tension. In such an operation process, since the movable rack 223 meshes with the pinion 222 and rotates the driving pulley 110 at a lower speed than in the normal operation state, the driving force from the driving pulley 110 is transmitted to the endless belt 120, 120 circulates slowly. For this reason, at the time of this tension applying operation, slippage due to slack between the endless belt 120 and the driving pulley 110 can be prevented, and belt damage does not occur.

[0072]

As described above, according to the present invention,
By using a swingable rotating body, a large contact area between the image bearing drum and the endless belt can be ensured, and the distance between the image bearing drum and the endless belt can be increased without increasing the tension of the endless belt. Of the image bearing drum and the endless belt to ensure sufficient frictional force between the endless belt and each image bearing drum without applying excessive tension to the endless belt. Can be prevented, and the image bearing drums can always be accurately and rotationally synchronized, so that a good color image without color shift can be obtained. Further, by separating the swingable rotating body from the image bearing drum, the operation for attaching and detaching the process cartridge in which the image bearing drum and the like are incorporated can be easily realized.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing a drive system of an image forming apparatus according to the present invention.

FIG. 2 is an explanatory diagram illustrating an outline of the color image forming apparatus according to the first embodiment;

FIG. 3 is an explanatory diagram illustrating details of an image forming unit used in the first embodiment.

FIG. 4 is an explanatory diagram showing details of a paper transport system used in the first embodiment.

FIG. 5 is an explanatory diagram showing an outline of a photoconductor drum driving system used in the first embodiment.

FIG. 6 is a perspective view of a main part thereof.

FIG. 7 is an explanatory view showing the operation of an idler with an arm.

FIG. 8 is an explanatory diagram illustrating an outline of a photoconductor drum driving system according to a modification of the first embodiment.

FIG. 9 is an explanatory diagram showing an outline of a photosensitive drum drive system according to another modification of the first embodiment.

FIG. 10 is an explanatory diagram showing an outline of a photoconductor drum driving system according to a second embodiment.

FIG. 11 is an explanatory diagram showing an outline of a photosensitive drum drive system according to a modification of the second embodiment.

FIG. 12 is an explanatory diagram illustrating an outline of a photoconductor drum driving system according to a third embodiment;

FIG. 13 is an explanatory diagram showing an outline of a photosensitive drum drive system according to a fourth embodiment.

14A is a perspective view showing a main part of the fourth embodiment, and FIG. 14B is an explanatory sectional view thereof.

FIG. 15 is an explanatory diagram showing an outline of a photosensitive drum drive system according to a fifth embodiment.

FIG. 16 is a view as viewed in the direction of the arrow in FIG. 15;

FIG. 17 is an explanatory view corresponding to FIG. 16 showing a modification of the fifth embodiment.

FIG. 18 is an explanatory diagram showing a change in a shaft load acting on each photosensitive drum in a structure for bridging one endless belt and each photosensitive drum.

FIG. 19 is an explanatory diagram showing a relationship between slip increase rates of respective color components.

FIG. 20 is an explanatory diagram illustrating a change in a transferred image according to a slip increase rate of each color component.

FIG. 21 is an explanatory diagram showing an outline of a photosensitive drum drive system according to a sixth embodiment.

FIG. 22 is a graph showing a relationship between an image length and a color shift due to belt elongation for a metal belt and other materials used in the seventh embodiment.

FIG. 23 is an explanatory diagram showing each material shown in FIG. 22.

FIG. 24 is an explanatory diagram showing an outline of a photoconductor drum driving system according to an eighth embodiment.

FIG. 25 is an explanatory diagram showing a state of synchronization of the photosensitive drum surface speed.

FIG. 26 is an explanatory diagram showing an outline of a photosensitive drum drive system according to a ninth embodiment.

FIG. 27 is an explanatory diagram showing an outline of a photoconductor drum driving system according to a tenth embodiment.

FIG. 28 is an explanatory diagram showing an operation process of the photosensitive drum drive system according to the tenth embodiment.

FIG. 29 is an explanatory diagram showing an operation process of the photosensitive drum drive system according to the tenth embodiment.

FIG. 30 is an explanatory diagram showing an outline of a photosensitive drum drive system according to an eleventh embodiment.

FIG. 31 is an explanatory diagram showing an outline of a photosensitive drum drive system according to a twelfth embodiment.

FIG. 32 is an explanatory diagram showing an operation state when the main body cover of the twelfth embodiment is closed.

[Explanation of symbols]

1 (1a to 1d) ... image bearing drum, 2 (2a to 2d) ...
Rotating body, 3 ... endless belt, 4 ... drive source, 21a ...
Body cover, 22 (22a to 22d) image forming unit 31, photoconductor drum, 100, 104, 105 idler with arm, 106 fixed idler, 110, 11
7, 118: driving pulley, 120, 121, 122: endless belt, 130, 134, 135: idler with arm, 140: flange, 171: long hole, 172: idler, 180: belt cleaner, 192: winding roller, 200 ... this tension applying mechanism, 201 ... auxiliary tension applying mechanism, 221 ... transmission gear, 222 ... pinion, 223 ...
Movable rack, 224, 225 ... pin, 226, 227 ...
Rack guide

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-7-92761 (JP, A) JP-A-7-140755 (JP, A) JP-A-4-149475 (JP, A) JP-A-9-97 146325 (JP, A) JP-A-9-114171 (JP, A) JP-A-10-111586 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G03G 13/01 G03G 15 / 01-15/01 117 G03G 15/00 550

Claims (28)

(57) [Claims] 1. A plurality of image bearing drums (1: 1a to 1d)
Are arranged in parallel with each other, and a rotatable rotator (2: 2a to 2d) arranged opposite to the outer peripheral surface of the end of each image bearing drum (1), and a plurality of image bearing drums (1) and an endless belt (3) wound around a plurality of rotating bodies (2); and a drive source (4) for applying a driving force to the endless belt (3). It is sequentially wound around the outer periphery of the end of the image bearing drum (1) passing from the outer periphery of each rotating body (2) to the end of the image bearing drum (1) opposed to the rotating body (2). The rotating body (2) swings toward the image bearing drum (1) by the driving force of the endless belt (3), and pinches the endless belt (3) with the end of the image bearing drum (1). The image bearing drum (1) is pressed against the image bearing drum (1) And a driving system for the image forming apparatus. 2. The image bearing drum (1) according to claim 1, wherein the outer peripheral surface of the end of the image bearing drum (1) around which the endless belt (3) is wound is the outer peripheral surface of the image bearing drum (1). Drive system for the image forming apparatus. 3. An image bearing drum (1) around which an endless belt (3) is wound, wherein an outer peripheral surface of an end portion of the image bearing drum (1) or a cylindrical body coaxial with a rotation axis. A driving system for an image forming apparatus, wherein the driving system is an outer peripheral surface. 4. The image bearing drum (1) according to claim 3, wherein an end of the image bearing drum (1) around which the endless belt (3) is wound has a larger diameter than an outer diameter of the image bearing drum (1). A driving system for an image forming apparatus, wherein the driving system is a flange. 5. A drive system for an image forming apparatus according to claim 4, wherein the flange is positioned concentrically by an outer diameter of the image bearing drum. 6. An image forming apparatus according to claim 1, wherein an outer peripheral surface of an end portion of the image bearing drum on which the endless belt is wound is a friction resistance surface. system. 7. A driving system for an image forming apparatus according to claim 1, wherein one endless belt (3) is stretched around one end of the image bearing drum (1). 8. An image forming apparatus according to claim 1, wherein two endless belts are wound around one end or both ends of the image bearing drum. system. 9. The image forming apparatus according to claim 8, wherein one of the two endless belts (3) is such that the image carrier drum (1a) on the most upstream side in the process direction is on the tight side, and the other is in the process direction. A driving system for an image forming apparatus, wherein the lowermost image bearing drum (1d) is stretched so as to be on the tight side. 10. A drive system for an image forming apparatus according to claim 1, wherein one rotating body (2) capable of swinging is provided per image bearing drum (1). 11. A driving system for an image forming apparatus according to claim 1, wherein two oscillating rotating members (2) are arranged for each image bearing drum (1). 12. An endless belt for an oscillating rotating body (2) according to claim 1, wherein one oscillating rotating body (2) is arranged per image bearing drum (1). (3) A drive system for an image forming apparatus, wherein a fixed idler is disposed downstream in the traveling direction. 13. A driving system for an image forming apparatus according to claim 1, wherein the rotating body is an idler with an arm having one end as a swing fulcrum. 14. The drive system according to claim 1, wherein the rotating body is an idler whose rotation axis moves along the elongated hole. 15. The drive source (4) according to claim 1, wherein the driving source (4) has a driving pulley around which an endless belt (3) is wound, and the driving pulley has an endless belt (3).
A drive system for an image forming apparatus, characterized by adding a slip suppressing means for the image forming apparatus. 16. A driving system for an image forming apparatus according to claim 15, wherein said slip suppressing means is obtained by adding a swingable idler to a driving pulley. 17. An image forming apparatus according to claim 15, wherein said slip suppressing means is provided with a swingable idler in the upstream and downstream directions in the running direction of the endless belt of the driving pulley. Drive system. 18. The slip restraining means according to claim 15, wherein a slidable idler is added on the upstream side in the running direction of the endless belt of the driving pulley, and a fixed idler is added on the downstream side. Drive system of the image forming apparatus. 19. The drive system according to claim 1, wherein the drive source has a plurality of driving pulleys around which the endless belt is wound. 20. The device according to claim 1, wherein two endless belts (3) are wound around one or both ends of the image bearing drum (1), and the driving source (4) is provided with two driving belts. A driving system for an image forming apparatus, comprising a single driving pulley for driving an endless belt (3). 21. A driving system for an image forming apparatus according to claim 1, wherein a peripheral surface of a driving pulley of a driving source (4) around which the endless belt (3) is wound is a frictional resistance surface. . 22. The outer peripheral surface of the driving pulley of the drive source (4) around which the endless belt (3) is wound, the endless belt (3) being the outer peripheral surface of the image bearing drum (1). A driving amount of the endless belt (1) when the image forming apparatus is moved by the transfer position pitch distance. 23. The drive system according to claim 1, wherein the endless belt is a metal belt. 24. The endless belt (3) according to claim 1, wherein the endless belt (3) is a metal belt, and an outer peripheral surface of an end portion of the image bearing drum (1) of the metal belt, and a driving force of a drive source (4). A drive system for an image forming apparatus, wherein a coating layer made of an abrasion-resistant material is formed on a metal belt surface on a side contacting a pulley peripheral surface. 25. The drive system of an image forming apparatus according to claim 1, further comprising a belt cleaner for cleaning a surface of the endless belt (3). 26. The apparatus according to claim 1, wherein the swingable rotator is an idler with an arm having one end as a swing fulcrum, and the idler with an arm has an image bearing drum. A drive system for an image forming apparatus, further comprising a take-up roller for absorbing slack of the endless belt (3) when retreating from (1). 27. An apparatus according to claim 1, further comprising a main tension applying mechanism for applying a main tension required when the endless belt is driven, and an auxiliary force smaller than the main tension so that the endless belt is not loosened. A driving system for an image forming apparatus, comprising: an auxiliary tension applying mechanism for applying tension. 28. The endless belt (3) according to claim 1, further comprising a main tension applying mechanism for applying a main tension required when the endless belt (3) is driven. A drive system for an image forming apparatus, comprising: a low-speed rotation mechanism that rotates a driving pulley of a drive source (4) at a lower speed than in a normal operation state in conjunction with an operation of applying the tension.