JPH10221910A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming device which prevents transfer irregularity and color slippage and improves image quality. SOLUTION: The driving force generated by a single motor 78 is distributed to a fixing roller, each photoreceptive drum, and a drive roller 52 for a transfer belt 51 via worms 74, 39K, 39Y, 39M, 39C, and 74H attached to a worm shaft 73 and worm wheels 65, 39K, 39Y, 39M, 39C, and 59, thereby rotating and driving each of them.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as a color copying machine or a color laser printer, and more particularly to a so-called tandem type image forming apparatus in which a plurality of image forming means are arranged along a conveying surface of a recording sheet. Related to the device.

[0002]

2. Description of the Related Art In a color copying machine, a recording sheet is transported by a transporting device comprising a transporting belt stretched by a plurality of rollers, and the recording sheet is arranged along the transporting path.
By rotating the photoreceptor drums, the toner images formed on the drums, consisting of cyan, magenta, yellow, and black, are sequentially transferred to a recording sheet to be conveyed, and a color image is formed by superimposing the respective colors. The tandem type to be formed is often used.

In such a tandem type color copying machine,
If the transfer positions of the respective photoconductor drums are shifted, a color shift occurs. To prevent this, it is necessary to strictly match the peripheral speed of all the photoconductor drums with the moving speed of the transport belt.

[0004]

However, in a conventional tandem-type color copying machine, there is no tandem-type color copying machine in which four photosensitive drums are driven by one motor and the peripheral speeds of the photosensitive drums are matched. However, since the motor is driven by a separate motor from the conveying device, the peripheral speed of the photosensitive drum or the moving speed of the conveying belt can be adjusted to the target speed if only one of the two motors slightly deviates from the target rotational speed. , The peripheral speed of the photosensitive drum does not match the moving speed of the conveyor belt, and a color shift occurs.

In order to solve this problem, the driven belt is driven in a state where each photosensitive drum is brought into contact with the transport belt, and the driven drum is driven by the driven belt to form an image. Has been devised. In such a tandem-type color copying machine, the transfer belt is pressed against the photosensitive drum by a pressing plate, and the driving force of the transfer belt is reliably transmitted to the photosensitive drum, and the photosensitive drum is driven by the transfer belt. The moving speed of the conveyor belt and the peripheral speed of each photosensitive drum
The color shift is prevented.

However, in the case of the above-mentioned conventional driven-type copying machine, the transfer charger must be disposed immediately below the image forming area of each photosensitive drum via a conveyor belt, so that the pressing force is limited. The location pressed by the plate is limited to the non-image forming areas at both ends of each photosensitive drum. Therefore, most of the power transmission from the conveyor belt to each photosensitive drum is performed at the contact portion between each end of each photosensitive drum and the conveyor belt. Is applied, and the tension applied to the transport belt in the transport direction is significantly different between the center portion and both end portions.

[0007] Since the conveyor belt is usually formed of an elastic member such as a resin film, the belt is deformed due to the unevenness of the tension, and loses its planarity.
As a result, the contact between the recording sheet and the photosensitive drum at each transfer position becomes non-uniform, causing uneven transfer of the toner image (hereinafter, referred to as “transfer unevenness”), thereby deteriorating the reproduced image. was there.

In view of the above problems, it is an object of the present invention to provide an image forming apparatus capable of preventing color misregistration without causing transfer unevenness.

[0009]

To achieve the above object, an image forming apparatus according to the present invention conveys a recording sheet to a plurality of image forming means arranged along a conveying path by a sheet conveying means. In an image forming apparatus that forms an image by
The image forming means and the sheet conveying means are driven by distributing the power of the same drive source by a power transmission means.

The image forming apparatus further includes a fixing unit for fixing an image on the recording sheet while feeding the recording sheet by a heated fixing roller, and the power transmission unit includes a fixing unit for fixing the image to the fixing unit. The power is also distributed to drive the fixing unit. Further, the power transmission means distributes the power of the drive source to each means by a worm rotated by the drive source and a worm wheel attached to the drive shaft of each means and meshing with the worm. It is characterized by the following.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an embodiment of an image forming apparatus according to the present invention will be described with reference to a case where the present invention is applied to a digital full-color copying machine. FIG. 1 shows a front view of the digital full-color copying machine (hereinafter, simply referred to as "copying machine").

This copying machine is a so-called tandem-type copying machine, which is configured such that a sheet cassette 41 set removably in a right side wall 11 of a housing 10 and a left side wall 1 of the housing.
2, a conveyor belt 51 is horizontally installed in the lower space of the housing up to the paper discharge tray 650 attached in an outwardly protruding posture, and a plurality of conveyor belts are provided on the conveyor belt 51 along the belt longitudinal direction (in the example shown in the drawing). 4) imaging units 3C, 3M, 3Y, 3K
The image forming units transfer the toner images of the respective color components onto the recording sheet while conveying the recording sheet S by the conveyance belt 51, and form a color image by superimposing the respective colors.

An image reader unit 10 is provided at an upper part of the housing 10.
0, the original image optically read here is subjected to required image processing by the image processing unit 150, and each color of Y (yellow), M (magenta), C (cyan), and K (black) is After being decomposed into components, the laser diodes 21C to 21K of the optical units 2C to 2K arranged above the image forming units 3C to 3K are optically modulated and driven based on each color component signal. The modulated laser light is applied to polygon mirrors 22C-2.
While being scanned in the main scanning direction at 2K, they are introduced into the image forming units 3C to 3K of the corresponding color components. The image forming units 3C to 3K are provided around the photosensitive drums 31C to 31K with a charger, a developing machine, and the like around the photosensitive drums 31C to 31K. The electrostatic latent image is formed as a toner image by a developing machine, that is, an image is formed by a so-called electrostatic copying method. Incidentally, the developing machines of the respective image forming units supply C, M, Y, and K toners as developing agents to the photosensitive drums corresponding to the light modulation color components of the optical units 2C to 2K.

Transfer chargers 54C to 54C are provided at positions directly below the photosensitive drums of the image forming units 3C to 3K via a conveyor belt.
K is provided so that the toner image on the surface of the photosensitive drum is transferred to the recording sheet S on the transport belt 51. As shown in FIG. 2 (b), the transport belt 51 is stretched between a driving roller 52 and a driven roller 51, and the rotating shafts 52S and 51S of the two rollers are connected to the front side plate 55 and the rear side plate 5 respectively.
6 and the front plate 55 of the frame constituted by the stays 57 and 58
It is rotatably attached to the rear side plate 56 via a bearing (not shown). A worm wheel 5 is provided at an end of the rotation shaft 52S of the drive roller 52 on the front plate 55 side.
9 is fixed. The transport belt 51 is made of PET.
(Polyethylene terephthalate) material.
The drive roller 52 is formed by polishing the surface of a material such as neoprene rubber. In some cases, the surface of the drive roller 52 is roughened in order to make the coefficient of friction with the transport belt 51 an appropriate value. I do. The driven roller 51 may be made of a metal material such as aluminum in addition to neoprene rubber.

Referring back to FIG. 1, the recording sheet S is fed from the paper feed cassette 41 to the transport belt 51 of the transport belt device 500 having the above-described configuration in synchronization with the image forming operation of the photosensitive drums 32C to 32K. The paper is fed by a paper feed mechanism such as a paper feed roller 42 and a timing roller 43. The fed recording sheet S is charged by the suction charger 550, is suctioned by the conveyance belt 51, and is conveyed by the conveyance path 555.
Along the photoconductor drums 32C to 32K to a transfer position below. At this transfer position, the transport belt 51
The toner images formed on the photosensitive drums 32C to 32K are sequentially transferred onto the recording sheet S by the electrostatic force of the transfer chargers 54C to 54K installed on the back of the recording sheet S. The sheet is conveyed to the fixing device 600 by the conveying belt 51. The fixing device 600 includes a pair of fixing rollers 61 and 62. A heater (not shown) is provided inside the upper fixing roller 61, and the recording sheet S on which the toner image has been transferred is conveyed. Then, the recording sheet S is nipped between the rotating fixing rollers 61 and 62, and is further fed forward while being pressed against the recording sheet S. In this process, the recording sheet S
The toner particles on the surface fuse and adhere to the sheet, are fixed, and are discharged onto the paper discharge tray 650.

As shown in FIG. 2A, each of the image forming units 3C to 3K is housed in a housing 310.
Unitized. Such a unit facilitates maintenance such as maintenance and inspection. Each photosensitive drum 32C to 32K of the image forming unit 300
The rotating shafts 38C to 38K of FIG. 1 are rotatably attached to the front plate 311 and the rear plate 312 of the housing 310 via bearings (not shown).
Worm wheels 39 </ b> C to 39 </ b> K are fixed to end portions of the front plate 311 side.

FIG. 3 shows a state where the image forming unit 300, the conveying belt device 500, the fixing device 600 and the drive motor 78 are assembled. Note that the fixing device 600 is also unitized by housing the fixing rollers 61 and 62 in the housing 610. The rotation shaft 61S of the fixing rollers 61 and 62,
62S is rotatably attached to the front plate 63 and the rear plate 64 of the housing 610 via a bearing (not shown), and a worm wheel 65 is attached to an end of the rotation shaft 61S on the front plate 63 side. Has been fixed.

As shown in FIG.
An image forming unit 300 is mounted on the image forming apparatus, and a fixing device 600 is arranged beside the image forming unit 300. Worm wheel 65,
Between 39K-39C and the worm wheel 59, there is provided a worm shaft 73 rotatably mounted via brackets (not shown) on brackets 71, 72 mounted on the housing of the copying machine or the like. I have. The worm shaft 73 is provided with worms 74T, 74K to 74C and 74H at respective positions facing the worm wheels 65, 39K to 39C and 59, respectively, and the worm wheel and the worm facing each other are meshed. (Hereinafter, a pair of a worm and a worm wheel is referred to as a "worm gear.") A pulley 75 is attached to an end of the worm shaft 73 on the bracket 72 side.
Is fixed, and a timing belt 78 is stretched between the pulley 75 and the other two pulleys 76 and 77. A drive shaft of a motor 78 is attached to the pulley 77. Each worm gear is set such that when the worm shaft 73 is turned in the direction of arrow e, each worm wheel is turned in the direction of arrow f or g.

In the above configuration, when the motor 78 is rotated in the direction of arrow h, the timing belt 78
Through the pulley 75, the worm shaft 73 is rotated in the direction of arrow e, and each worm 74T, 74K to 74C, 74H
Worm wheels 65, 39K to 39 corresponding to
C, 59 are rotated in the direction of arrow f or g, and the fixing roller 61, the photosensitive drum 32, and the drive roller 52 are rotated in the directions of arrows j, a, and b, respectively (FIG. 1). That is, the power generated by the motor 78 is distributed by each worm and each worm wheel, and the fixing roller 61, the photosensitive drum 32, and the driving roller 52 are driven. In this manner, the power of one motor 78 is distributed to fix the fixing roller 61, the photosensitive drum 32,
Since the driving roller 52 is driven, even if the rotation speed of the motor 78 fluctuates from the target value due to fluctuations in the power supply voltage or the like, the peripheral speed of the fixing roller 61 and the photosensitive drum 32 and the movement of the driving roller 52 The speed also fluctuates in the same manner, and the consistency between the peripheral speed and the moving speed is maintained, so that no color shift occurs.

The fixing roller 61 and the photosensitive drums 32C, 32M, 32M, 32M, and 32K are moved so that the peripheral speeds of the fixing roller 61 and the photosensitive drums 32C, 32M, 32Y, and 32K are equal to the moving speed of the surface of the conveyor belt 51. 32Y, 32K
In consideration of the diameter of the worm gear, the diameter of the drive roller 52, the thickness of the transport belt 51, and the like, the reduction ratio of each worm gear is determined. Preferably, the radius of the fixing roller 61, the radius of each of the photosensitive drums 32C, 32M, 32Y, 32K, the radius of the drive roller 52, and the length obtained by adding the thickness of the transport belt 52 in a stretched state are all the same. The same parts are used for each worm and each worm wheel. By doing so, the cost can be reduced by sharing the parts. Also, in this case,
Instead of providing a worm for each worm wheel, a single worm having a length capable of engaging with all worm wheels may be used. Thereby, there is an advantage that the rigidity of the worm shaft is increased.

As described above, according to the image forming apparatus of the present embodiment, the image forming unit (photosensitive drum) and the transport belt device (transport belt) are driven by one drive source (motor). Therefore, unlike in the conventional case where each unit is driven by a separate drive source, the peripheral speed of the photosensitive drum and the moving speed of the conveyor belt are prevented from being inconsistent, and color shift is prevented. be able to.

Further, a fixing device (fixing roller)
Is driven by the same drive source as the image forming unit (photosensitive drum) and the transport belt device (transport belt), so that the peripheral speed of the fixing roller matches the peripheral speed of the photosensitive drum and the transport speed of the transport belt. As a result, the quality of the finished image can be improved. That is, the toner particles before being fixed are in a very unstable state such that they peel off as soon as they are touched, and when the fixing roller is slowed down, the sending speed is too fast than the receiving speed. In this case, the recording sheet may be bent, and the toner particles on the recording sheet may be more easily peeled off. On the other hand, if the peripheral speed of the fixing roller is higher than the peripheral speed of the photosensitive drum and the moving speed of the transport belt, the recording sheet may be pulled and the image being formed may be disturbed. However, according to the present invention, since the peripheral speed of the fixing roller, the peripheral speed of the photosensitive drum, and the moving speed of the transport belt are the same,
This is because such a situation can be avoided.

Further, an image forming unit (photosensitive drum),
Since the transport belt device (transport belt) and the fixing device (fixing roller) are driven by one drive source (motor), the peripheral speed of the photosensitive drum and the fixing roller can be adjusted simply by adjusting the rotation speed of one motor. The drive adjustment can be facilitated such that all of the speed and the moving speed of the conveyor belt can be adjusted.

Further, since the worm gear is used in the final power transmission section, the generated vibration is minute, so that the adverse effect of the vibration on the photosensitive drum, the conveying belt and the fixing roller can be prevented, and the quality of the finished image can be reduced. improves.
Furthermore, since a large reduction ratio can be obtained with the worm gear, the number of parts can be reduced as compared with the case where other mechanisms are used, and thus the structure can be simplified, and there is an advantage that a failure is less likely to occur. There is.

[0025]

As described above, according to the image forming apparatus of the present invention, the power of the same driving source is distributed to drive the plurality of image forming means and the sheet conveying means. It is possible to prevent color misregistration caused when the image forming means and the sheet conveying means are driven by separate driving sources, and almost no power is transferred between the image forming means and the sheet conveying means. Since there is no transfer, uneven transfer or the like does not occur as in the case where the image forming means is driven by the conventional sheet conveying means.

Further, the power of the same drive source is also distributed to the fixing unit, and the fixing unit is driven. Therefore, the conveying speed of the recording sheet in the image forming unit and the sheet conveying unit and the conveyance of the recording sheet in the fixing unit. It is possible to easily match the speed, and it is possible to prevent the finished image from deteriorating due to the mismatch between the two speeds, and to improve the image quality.

Further, since the power of the same drive source is distributed between the worm and the worm wheel to drive each unit, the power is generated during power transmission (distribution) as compared with the case where other units are used. Vibration is reduced, and it is possible to prevent a decrease in image quality due to vibration of the power transmission system.

[Brief description of the drawings]

FIG. 1 is a diagram showing an entire configuration of a digital full-color copying machine to which an image forming apparatus according to the present invention is applied.

FIG. 2 is a perspective view showing the appearance of an image forming section and a transport / transfer section of the copying machine.

FIG. 3 is a perspective view showing a state where an image forming unit, a conveying / transferring unit, a fixing unit, and the like of the copying machine are assembled.

[Explanation of symbols]

32K, 32Y, 32M, 32C Photoreceptor drums 39K, 39Y, 39M, 39C, 59, 65 Worm wheel 51 Conveying belt 52 Drive roller 53 Follower roller 61, 62 Fixing roller 74T, 74K, 74Y, 74M, 74C, 74H Worm 78 Motor 300 imaging unit 500 transport belt device 600 fixing device

Continued on the front page (72) Inventor Masanori Murakami 2-3-13 Azuchicho, Chuo-ku, Osaka-shi, Osaka Inside Osaka International Building Minolta Co., Ltd. (72) Inventor Hideyuki Kurahashi 2-chome, Azuchi-cho, Chuo-ku, Osaka-shi, Osaka No. 13 Osaka International Building Minolta Co., Ltd.

Claims (3)

[Claims] An image forming apparatus configured to convey a recording sheet to a plurality of image forming units disposed along a conveying path to form an image by conveying the recording sheet by the sheet conveying unit; An image forming apparatus, wherein the power of the same drive source is distributed and driven by a power transmission means. 2. The image forming apparatus further comprises: a fixing unit that fixes an image on the recording sheet while feeding the recording sheet by a heated fixing roller; 2. The image forming apparatus according to claim 1, wherein the power is also distributed to drive the fixing unit. 3. The power transmission means includes: a worm rotated by the drive source; and a worm wheel attached to a drive shaft of each of the means and meshing with the worm to supply the power of the drive source to each of the means. The image forming apparatus according to claim 1, wherein the image is distributed to the image forming apparatus.