JPH11102096A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming device capable of reducing the color smear of an image, making drive sources common and the miniaturization of a device main body. SOLUTION: In an image forming device provided with photoreceptive drums (image carriers) 11a-11d on which images are formed, a carrying belt 31 for holding/carrying recording paper (transfer material) to transferring positions opposite to the photoreceptive drums 11a-11d, oscillatory wave motors (first drive sources) 52a-52d for rotationally driving the drums 11a-11d and an oscillatory wave motor (second drive source) 60 for rotationally driving the carrying belt 31, the oscillatory wave motors 52a-52d and 60 are separately arranged a part from the sides opposite to each other holding a carrying path for carrying the recording paper.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an image forming apparatus such as a full-color or mono-color copying machine or printer.

[0002]

2. Description of the Related Art An image forming apparatus employing an electrophotographic recording method forms a latent image on a photosensitive drum as an image carrier using light, magnetism, electric charge, and the like, and develops the latent image to form a toner. An image forming unit that visualizes the image, a transfer material conveying unit that conveys the transfer material to a transfer position of the image forming unit, and a fixing unit that fixes the toner image on the transfer material that has received the transfer of the toner image at the transfer position. Have.

As the transfer material transporting means, a transfer material transporting belt having a transfer material transporting belt is used from the viewpoint of transportability, and an image forming section of each color is formed on the transporting belt along the belt. Be placed. A transfer material such as a recording sheet is held on a transport belt by electrostatic attraction, and is sequentially transported to a transfer position of an image forming unit for each color by rotation of the transport belt, and further transported to a fixing device.

[0004] The transport belt is stretched over and supported by one driving roller and at least two driven rollers.
An endlessly rotating transfer material conveying means is constituted. In order to prevent the transport belt from being slackened between the driving roller and the driven roller, the transport belt is devised so as to be stretched with a constant force, whereby the transport belt is moved at a constant speed from the most downstream side of the image forming portion on the most upstream side. To the image forming unit on the side.

[0005] The transfer material, which is attracted and held on the conveyor belt and conveyed to the transfer position of each image forming unit, sequentially receives toner images of each color formed on the image carrier of each image forming unit. It is transferred by being superimposed. Then, the transfer material to which the toner images of each color have been transferred is output as a full-color print image by undergoing color mixing and fixing of the toner images of each color in the fixing device.

In a conventional image forming apparatus, a single DC is used as a drive source for a photosensitive drum and a conveyor belt.
In general, the photosensitive drum and the conveyor belt are driven collectively by using a motor or the like. However, even when the photosensitive drum and the conveyor belt are driven by separate DC motors or the like, one surface of the apparatus housing may be used. There were multiple motors on the side.
That is, a plurality of motors are arranged close to one side when viewed from the transfer material conveyance path.

FIG. 3 is a plan view of a main part of an image forming apparatus for forming a full-color image by arranging four photosensitive drums in parallel and transporting a transfer material under each photosensitive drum by a transport belt and superimposing toner of each color.

In FIG. 3, 101a, 101b, 10
Reference numerals 1c and 101d denote photosensitive drums, each having a front end having a pin 103 supported on a front plate 102 of the apparatus main body.
a, 103b, 103c, and 103d rotatably supported. Also, the photosensitive drums 101a to 101a
The other end of the vibration wave motors 106 a, 106 b, 1 supported by the rear side plate 104 and the motor support 105.
Drive shafts 107a, 107 extending from 06c, 106d
b, 107c, and 107d are supported so that the rotational driving force is transmitted.

Reference numeral 111 denotes a transport belt, 112 denotes a driving roller, and 113 denotes a driven roller. The driving roller 112 is rotatably supported by a pin 114 whose front end is supported by the front plate 102. Then, the driving roller 112
The other end of the vibration wave motor 11 supported on the rear side plate 104
The drive shaft 116 is supported by a drive shaft 116 extending from the drive shaft 5 so that the rotational drive force is transmitted.

[0010] In particular, high precision is required for superimposing toner images of respective colors on a full-color copying machine, a printer and the like. Therefore, as shown in FIG. 3, the vibration wave motor 106 has a characteristic that a high rotation accuracy is secured and the rotation accuracy is hardly deteriorated even when a disturbance such as a load change occurs.
a to 106d for each of the photosensitive drums 101a to 101d and the transport belt 111.
There is a need to directly connect 7a to 107d.

[0011]

However, in the above-mentioned conventional image forming apparatus, the vibration wave motors 106a to 106d and 115, which are driving sources, are disposed close to one surface of the apparatus housing. There were the following problems.

1. The heat generated by the vibration wave motors 106a to 106d is biased toward one surface of the apparatus, the temperature of the apparatus body is not uniform, and the front plate 1 supporting the photosensitive drums 101a to 101d is not uniform.
A remarkable difference occurs between the 02 side and the rear plate 104 side. In particular, the vibration wave motor generates a large amount of heat with respect to the work amount as compared with a DC motor or the like due to its characteristics, so that a measure for increasing the temperature becomes particularly important.

Conventionally, vibration wave motors 106a to 106d
The temperature on the side of the rear side plate 104 where the light is concentrated rises, and the thermal expansion amount also increases.
01a to 101d are inclined in a C-shape, and the deviation (that is, the color deviation) of each color toner image in the transfer paper conveyance direction (sub-scanning direction).
Becomes large.

2. The rotational directions of the vibration wave motors 106a to 106d for directly driving the photosensitive drums 101a to 101d and the vibration wave motor 115 for directly driving the drive roller 112 are opposite to each other.

The fact that the diameters of the photosensitive drums 101a to 101d and the diameter of the drive roller 112 are the same and can be driven at the same number of rotations, and that only the rotation direction is different, prevents the use of common components including the motor control circuit. It becomes a factor.

3. In order to arrange the vibration wave motors 106a to 106d for directly driving the photosensitive drums 101a to 101d and the vibration wave motor 115 for directly driving the drive roller 112, the vibration wave motors 106a to 106d, 1
Due to the size of 15 itself, the distance L to be approached is naturally limited. Photosensitive drums 101a to 101d and drive roller 1
The vibration wave motors 106a to 106a
6d, 115, the photosensitive drum 1
01a to 101d and the drive roller 112 must be arranged at a predetermined distance from each other, which has been an obstacle to downsizing the apparatus.

The present invention has been made in view of the above problems, and an object thereof is to provide an image forming apparatus in which color misregistration of an image is small, a drive source can be shared, and the apparatus body can be downsized. Is to provide.

[0018]

In order to achieve the above object, according to the present invention, at least one image carrier on which an image is formed and a transfer material are held and opposed to the image carrier. The first driving source in an image forming apparatus including a transport belt that transports the image carrier to a transfer position, a first drive source that rotationally drives the image carrier, and a second drive source that rotationally drives the transport belt. And the second drive source are separately disposed on opposite sides of a transport path for transporting the transfer material.

According to a second aspect of the present invention, in the first aspect of the present invention, the first driving source is disposed directly coaxially with the image carrier, and the second driving source is connected to the second driving source. It is characterized in that it is disposed directly coaxially with the drive roller of the transport belt.

Therefore, according to the present invention, the heat generated by the first drive source for driving the image carrier to rotate and the heat generated by the second drive source for driving the transfer belt to rotate are separated from each other across the transfer material transfer path. Because of the occurrence, the temperature rise of the structure that defines the parallelism between the image carriers is substantially uniform on both sides supporting the image carriers,
High parallelism is secured in the image carrier, and a high-quality image with little color shift can be obtained.

Further, by setting the rotation direction and the number of rotations of the first and second drive sources to be the same, the drive sources can be shared.

Further, despite the fact that the first drive source and the second drive source are directly connected on the same axis of the image carrier and the drive roller of the conveyance belt, respectively, the first drive source and the second drive source are arranged. Since the drive sources are separately arranged on opposite sides of the transfer material conveyance path, the drive roller of the image carrier and the conveyance belt can be arranged close to each other without being restricted by the external shape of the drive source. Thus, the size of the image forming apparatus can be reduced.

[0023]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

First, the configuration of a color image forming apparatus according to the present invention will be described with reference to FIG.

FIG. 2 is a cross-sectional view of the color image forming apparatus. The image output section 1P of the present color image forming apparatus is roughly divided into an image forming section 10 (four stations a, b, c, and d are arranged side by side. , The configuration is the same), a paper feed unit 20, a transfer material transport unit 30, a fixing unit 40, and a control unit (not shown).

The image forming section 10 is configured as follows.

Photosensitive drums 11a to 11 as image carriers
d is pivotally supported at its center and is driven to rotate in the direction of the arrow.
Primary chargers 12a to 12d, optical systems 13a to
3d and developing devices 14a to 14d are arranged.

The primary chargers 12a to 12d apply charges of a uniform charge amount to the surfaces of the photosensitive drums 11a to 11d, respectively. Next, a light beam such as a laser beam modulated according to a recording image signal by the optical systems 13a to 13d is exposed on the photosensitive drums 11a to 11d, thereby forming an electrostatic latent image thereon.

By the way, the developing devices 14a to 14d contain four color toners of yellow, cyan, magenta and black, respectively.
The electrostatic latent images formed on the respective photosensitive drums 11a to 11d are developed by bringing them closer to the photosensitive drums 11a to 11d to visualize them as toner images.
On the downstream side of the image transfer area, the toner remaining on the photosensitive drums 11a to 11d without being transferred to the recording paper P is scraped off by the cleaning devices 15a to 15d to clean the surfaces of the photosensitive drums 11a to 11d.

Through the above-described processes, image formation by each toner is sequentially performed.

On the other hand, the paper feeding unit 20 includes a cassette 21 for storing the recording paper P, a pickup roller 22 for feeding out the recording paper P one by one from the cassette 21,
Paper feed rollers 23a and 23b for feeding the recording paper P sent from the pickup roller 22 to the registration roller rollers 25a and 25b, a paper feed guide 24, and the recording paper P are fed in accordance with the image forming timing of the image forming unit 10. Registration rollers 25a for sending out to the unit 30,
25b and a guide 26 for guiding the recording paper P to the transfer / conveyance unit 30.

Next, the transfer and transport unit 30 will be described in detail.

The recording paper holding sheet 31a is wound around a plurality of rollers 32, 33, and 34 to form the transfer belt 31.
The material of the recording paper holding sheet 31a is, for example, PE.
T (polyethylene terephthalate), PVdF (polyvinylidene fluoride) or the like is used.

Reference numeral 32 denotes a driving roller, and 33 denotes a driven roller. An image transfer plane A is provided between these two rollers 32 and 33.
Is formed, and the image transfer plane A and the photosensitive drums 11a to 11a are formed.
The distance between 11d is about 1 mm. Belt drive roller 3
Numeral 2 is to coat the surface of the metal roller with rubber (urethane or chloroprene) having a thickness of several mm to prevent slippage with the transfer belt 31. Reference numeral 34 denotes a tension roller for appropriately applying tension to the transfer belt 31.

At a position where the recording paper P sent from the registration rollers 25a, 25b enters the transfer belt 31, an attraction charging device 27 is disposed, and each of the photosensitive drums 11a to 11d and the transfer belt 31 on the downstream side are arranged. In the opposed image transfer area, transfer charging blades 35a to 35d located on the back side of the transfer belt 31 are arranged. Each of the transfer charging blades 35a to 35d can be pressed and separated from the photosensitive drums 11a to 11d by a mechanism (not shown). At the time of pressing, the transfer belt 31 is lifted and the transfer belt 31 is moved to the photosensitive drums 11a to 11d. And good image transfer is performed by pressing with appropriate pressure.

Further, a charging / discharging charger 36 for separation / discharging is disposed slightly upstream of the driving roller 32, and a charging / discharging charger 3 for imparting uniform charge to the surface of the transfer belt 31 is provided downstream thereof.
7. A brush roller 38 for cleaning the recording paper holding surface of the transfer belt 31 is provided.

Next, the fixing unit 40 will be described.

The fixing unit 40 includes a fixing roller 41A having a heat source such as a halogen heater therein and a pressing roller 41B pressed against the fixing roller 41A (the pressing roller 41B may also have a heat source). , Both rollers 41
An entrance guide 43 for guiding the recording paper P to the nip portion of each of the rollers A and 41B, an inner discharge roller 44 and an outer discharge roller 45 for further guiding the recording paper P discharged from the rollers 41A and 41B outside the apparatus. It is composed of The distance between the fixing roller 41A and the belt driving roller 32 is set to 100 mm or less.

The control unit is composed of the above units 10 and 2
It includes a control board 50 for controlling the operation of the mechanisms in the units 0, 30, and 40, and the like.

Next, the operation of the present color image forming apparatus will be described.

When the image forming operation start signal is issued, first, the recording paper P is sent out from the cassette 21 by the pickup roller 22 one by one. And the paper feed roller 2
The recording paper P is guided between the paper feed guides 24 by 3a and 23b and is conveyed to registration rollers 25a and 25b. At this time, the registration rollers 25a and 25b are stopped, and the leading end of the recording paper P is
B hits the nip.

Thereafter, the registration rollers 25a and 25a are synchronized with the timing at which the image forming section 10 starts forming an image.
5b starts rotation. The registration roller 25
The rotation timing of the transfer paper P and the photosensitive drum 11a
The timing is set so that the toner image on the image No. to 11d exactly matches the image transfer area.

Thus, the recording paper P is moved by the driving roller 32 of the transfer belt 31.
a, the recording paper P comes into contact with the suction charger 27.
Is electrostatically attracted onto the transfer belt 31 by the Coulomb force. The transfer belt 31 rotates in synchronization with the photosensitive drums 11a to 11d, and the recording paper P is conveyed to the first image transfer area while being held thereon. There, the transfer charging blade 35 pressurized at the start of the sequence.
A high voltage is applied to a in accordance with the timing at which the recording paper P passes. Then, the photosensitive drum 1 is formed by the above-described process.
The toner images formed on 1a to 11d are transferred onto the surface of the recording paper P, and thereafter, the recording paper P is further conveyed to the next transfer image area. In this case, the image formation is performed with a delay corresponding to the time required for the recording paper P to be conveyed between the stations a and b. become.

Hereinafter, the same steps are repeated, and the recording paper P
Eventually, four color toner images are multiplex-transferred.

When the multiple transfer is completed, the adsorbing force between the recording sheet P and the recording sheet holding sheet 31a is reduced by the operation of the separating / discharging charger 36 in the separation section. P is separated from the transfer belt 31.

Recording paper P separated from transfer belt 31
Is accurately guided by the entrance guide 43 to the nip portion between the fixing roller 41A and the pressure roller 41B. And
The toner image is fixed on the surface of the recording paper P by the heat of the rollers 41A and 41B and the pressure of the nip.

Thereafter, the recording paper P is transferred to the inner and outer discharge rollers 44,
It is conveyed by 45 and discharged out of the machine. The pressure of the transfer charging blades 35a to 35d is released, and the transfer belt 3
The sequence ends with 1 being separated from the photosensitive drums 11a to 11d. This is done by minimizing external forces acting on the photosensitive drums 11a to 11d as much as possible.
This is for protecting a to 11d.

Next, a characteristic portion of the present invention will be described with reference to FIG.

FIG. 1 is a perspective view showing the positional relationship between the photosensitive drums 11a to 11d, the transfer belt 31, and the vibration wave motors 52a to 52d, which are characteristic parts of the present invention.

In FIG. 1, reference numeral 51 denotes a rear side plate of the main body of the apparatus. The rear side plate 51 is provided with vibration wave motors 52a, 52b, 52c, 52d for holes formed at a predetermined pitch.
Are fitted and attached. Incidentally, 53a, 53b,
53c and 53d are output shafts of the vibration wave motors 52a to 52d.

The photosensitive drums 11a to 11d are fitted to the output shafts 52a to 52d so as to be accurately positioned and to directly transmit a rotational driving force.

A front plate 54 is disposed at a position facing the rear plate 51 with the photosensitive drums 11a to 11d interposed therebetween.
A common centering plate 55 is fixed to the front side plate 54. On the outer surface of the common centering plate 55, an individual centering plate 56 is provided.
a, 56b, 56c and 56d are arranged, and the photosensitive drums 11a to 11d are provided on these individual centering plates 56a to 56d.
Drum shafts 57a, 57b, 57c for pivotally supporting the other end of the
57d is attached. And the individual centering plate 5
The positions of the photosensitive drums 6a to 56d are finely adjusted so that the photosensitive drums 11a to 11d are accurately parallel to the common centering plate 55, and are fixed by screws 58a, 58b, 58c, and 58d.

In FIG. 1, reference numeral 30 denotes a transfer / transport unit, 31 denotes a transfer belt, 32 denotes a driving roller, 33 denotes a driven roller, and 34 denotes a tension roller.

One end of the drive roller 32 is fitted to a ball bearing 59 fitted and fixed to the rear plate 51 to be accurately positioned and rotatably supported.
An output shaft 61 of a vibration wave motor 60 is fitted to the other end of the drive roller 32 so that the rotational driving force of the vibration wave motor 60 is directly transmitted to the drive roller 32. The specifications of the vibration wave motor 60 are exactly the same as those of the vibration wave motors 52a to 52d, and the rotation direction and the number of rotations are the same.

The vibration wave motor 60 is connected to the motor support plate 6.
2 and the motor support plate 62 is attached to the front side plate 54.
Are positioned and fitted by pins 63 and 64. Therefore, the drive roller 32 is connected to the photosensitive drums 11a to 11a.
It is positioned parallel to d and driven to rotate.

As described above, in the present embodiment,
The heat generated by the vibration wave motors 52a to 52d that rotationally drive the photosensitive drums 11a to 11d and the heat generated by the vibration wave motor 60 that rotationally drives the transport belt 31 are generated with the transport path of the recording paper P interposed therebetween. The temperature rises of the rear side plate 51 and the common centering plate 55 that define the parallelism between the photoconductive drums 11a to 11d are substantially equal on both sides supporting the photosensitive drums 11a to 11d, and a high parallelism is secured on the photosensitive drums 11a to 11d. A high-quality image with little displacement can be obtained.

The vibration wave motors 52a to 52d and the vibration wave motor
0 can be shared.

Further, the vibration wave motors 52a to 52d and the vibration wave motor 60 are arranged directly coaxially with the photosensitive drums 11a to 11d and the driving roller 32 of the conveyor belt 31, respectively. 52d and the vibration wave motor 60 are separately disposed on the side facing each other across the conveyance path of the recording paper P, so that the vibration wave motors 52a to 52d
The photosensitive drums 11a to 11d and the drive roller 32 of the conveyor belt 31 can be arranged close to each other without being restricted by the outer shape of the vibration wave motor 60, and the size of the image forming apparatus can be reduced.

[0059]

As is apparent from the above description, according to the present invention, at least one image carrier on which an image is formed and a transfer material are held and transferred to a transfer position facing the image carrier. A transport belt for transporting, a first drive source for rotationally driving the image carrier, and a second drive source for rotationally driving the transport belt.
Since the first driving source and the second driving source are separately disposed on opposite sides of a transport path for transporting the transfer material in the image forming apparatus having the This makes it possible to obtain a high-quality image with less noise, and to achieve an effect of realizing a common drive source and downsizing of the apparatus main body.

[Brief description of the drawings]

FIG. 1 is a perspective view of a main part of a color image forming apparatus according to the present invention.

FIG. 2 is a sectional view of the color image forming apparatus according to the present invention.

FIG. 3 is a plan view of a main part of a conventional color image forming apparatus.

[Explanation of symbols]

 11a to 11d Photosensitive drum (image carrier) 31 Transfer belt 32 Drive roller 52a to 52d Vibration wave motor (first drive source) 60 Vibration wave motor (first drive source) P Recording paper (transfer material)

Claims (2)

[Claims] An at least one image carrier on which an image is formed; a transport belt for holding a transfer material and transporting the transport material to a transfer position facing the image carrier; 1. An image forming apparatus comprising: a first drive source and a second drive source that rotationally drives the transport belt, wherein the first drive source and the second drive source face each other across a transport path that transports a transfer material. An image forming apparatus, wherein the image forming apparatuses are separately disposed on a side of the image forming apparatus. 2. The image forming apparatus according to claim 1, wherein the first driving source is directly connected coaxially to the image carrier, and the second driving source is directly connected coaxially to a driving roller of the transport belt. The image forming apparatus according to claim 1, wherein: