JP2000259009A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming device excellent in the positioning accuracy of a transfer unit to an image forming part even though the transfer unit can be separated, pulled out and detached from a device main body. SOLUTION: As for a driving roller 32, both ends of a driving roller shaft 32a are supported by a frame 39 through bearing holders 39c and 39d. The bearing holder 39c is fitted in the fitting part 18a of an inner side positioning holder 18, so that the holder 18 is positioned on a main body rear side plate 18b. Both fitting parts 18a and 18b are guaranteed about concentricity. The fitting part 62b of a transfer positioning holder 62 also functions to position a driving motor base 65. A transfer motor 17 is positioned and fixed by the fitting hole of the base 65. The fitting hole is guaranteed about concentricity with a fitting part 62a for the holder 62 and the holder 39d. Thus, the motor 17 and the roller shaft 32a are accurately coaxially arranged.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention generally relates to a method of forming a visible image (toner image) on an image carrier by an electrophotographic recording method or an electrostatic recording method, and transferring the toner image to a transfer material to obtain an image. The present invention relates to an image forming apparatus, and more particularly to an image forming apparatus that conveys a transfer material with a conveying belt, 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 system 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 image. An image forming unit for visualizing the image, a transfer material conveying unit for conveying the transfer material to a transfer position of the image forming unit (hereinafter, referred to as a “transfer unit”), and a toner image transferred onto the transfer material at the transfer position And fixing means for fixing the image.

As the transfer unit, a belt-like transfer member, that is, a transfer member provided with a transfer material transfer belt, is used from the viewpoint of transferability, and the image forming sections of each color are arranged along the transfer belt. . The transfer material, that is, the recording paper, is held on the transport belt by electrostatic attraction, and is sequentially transported by the rotation of the transport belt to the transfer position of the image forming unit for each color and further to the fixing unit.

The above-mentioned transport belt is stretched around one driving roller and at least one driven roller, and is stretched.
It is supported and configured to rotate endlessly. Between the driving roller and the driven roller, the conveyance belt is devised so as to be stretched with a constant force, and by arranging the driving roller downstream in the conveyance direction, the conveyance belt on the side facing the image forming unit does not slack. It is devised as follows.

[0005] As a result, the conveyor belt is driven at a constant speed.
It is guaranteed that the image forming unit moves from the most upstream image forming unit to the most downstream image forming unit.

The drive roller is driven by a transfer drive motor disposed in the transfer unit via a timing belt.

On the recording paper sucked and held on the conveyor belt and conveyed to the transfer position of each image forming unit, the toner images of each color formed on the photosensitive drum of each image forming unit are sequentially arranged. It is transferred by being superimposed.

Further, the transfer unit is structured so as to be able to be pulled out at the time of jam clearance or maintenance, so that when the transfer unit is pulled out, the image forming section and the conveyor belt can be pivotally moved, for example, around a drive roller. Be composed.

The transfer unit can be detached from the main body of the image forming apparatus during maintenance of the transfer unit itself.

The recording paper onto which the toner images of each color have been transferred is mixed by the heat (and pressure) in a fixing unit arranged close to the downstream side of the transport belt in the transport direction and mixed with the toner images of each color by the heat (and pressure). The fixing is performed, and a full-color print image is formed.

[0011]

However, the above-described image forming apparatus has the following problems.

(1) If the positional accuracy between the image forming section and the transfer unit is not ensured, a good transfer state cannot be obtained and an image defect occurs.

Further, in the above-mentioned image forming apparatus, the transfer unit can swing and can be pulled out in consideration of maintainability.
In addition, due to the removable structure, the positioning with respect to the apparatus main body is inferior to the case where the transfer unit is fixed, and a good image may not be obtained in some cases.

In order to solve this problem, the center of oscillation of the transfer unit is used as a drive roller shaft, and the center of oscillation is used as a positioning portion with respect to the apparatus main body. It is known that can be prevented as much as possible.

(2) If the conveyor belt is not driven at a stable speed, image defects such as image expansion and contraction and color shift occur.

However, in the above image forming apparatus, the driving roller is driven by the transfer driving motor provided in the transfer unit via the timing belt, so that the speed of the transport belt is limited by the eccentricity of the pulley on the driving motor shaft. And is affected by the eccentricity of the pulley on the drive roller shaft, and fluctuates in these rotation cycles.

Therefore, the transport belt cannot be transported at a constant speed, and image defects such as expansion and contraction of images and color shift may occur.

In order to solve this problem, a vibration wave motor having a characteristic that a high rotation speed is secured and the rotation accuracy is hardly deteriorated even when subjected to disturbances such as load fluctuations, is directly connected coaxially with the drive roller. A so-called direct drive configuration has been proposed.

However, in this configuration, since the drive roller and the vibration wave motor are integrated, it becomes difficult to make the transfer unit a positioning portion of the drive roller shaft relative to the apparatus main body as described in (1) above. The positional accuracy between the image forming unit and the transfer unit cannot be obtained, and a good image cannot be obtained.

Accordingly, a main object of the present invention is to provide an image forming apparatus having good positioning accuracy with respect to an image forming section even when the transfer unit can be separated, pulled out, and removed from the image forming apparatus main body. That is.

Another object of the present invention is to provide an image forming apparatus capable of driving a transfer belt of a transfer unit at a stable speed.

[0022]

The above object is achieved by an image forming apparatus according to the present invention. In summary, the present invention provides:
A unit having a drive source, a driven body, drive transmission means for transmitting drive from the drive source to the driven body, and a plurality of positioning means, wherein the plurality of positioning means connect the unit to the image forming apparatus. In the image forming apparatus serving as a means for positioning the main body, at least one of the plurality of positioning means is located between the driving source and the driven body.

It is preferable that the drive source, the driven body, the drive transmission means, and the positioning means are on the same axis, and the unit is swingable about the axis.

According to another aspect of the present invention, there is provided at least one image carrier on which a toner image is formed, and holding a transfer material to which the toner image on the image carrier is transferred,
An endlessly rotating transport belt that transports to a transfer position facing the image carrier, a driving roller that supports and drives the transport belt, and at least one driven roller that stretches the transport belt together with the drive roller; A drive motor that drives the drive roller, a drive transmission unit that coaxially connects the drive roller and the drive motor, and a transfer unit that has a plurality of positioning units. In the image forming apparatus which is a unit for positioning the transfer unit in the image forming apparatus main body, the transfer unit is swingable around a center axis of the driving roller, and at least one of the positioning units is An image forming apparatus, which is coaxial with a driving roller, and is located between the driving roller and the driving motor. It is subjected.

[0025]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an image forming apparatus according to the present invention will be described in more detail with reference to the drawings.

First, an embodiment of the image forming apparatus according to the present invention will be specifically described with reference to FIG. The image forming apparatus of the present embodiment is described as a color image forming apparatus in which the image forming method is an electrophotographic method and a plurality of image forming units considered to be particularly effective for the present invention are arranged in parallel. I do.

In FIG. 1, the image output unit 1P is roughly composed of an image forming unit 10, a paper feed unit 20, a transfer and transport unit 30, a fixing unit 40, and a control unit (not shown). The image forming section 10 has four stations a, b, c, and d arranged side by side. The configuration of each of the stations a to d is the same, and has photosensitive drums 11a, 11b, 11c, and 11d as image carriers. The primary charger 12a12 faces the outer peripheral surface in the rotational direction.
b, 12c, 12d, optical systems 13a, 13b, 13c,
13d, developing devices 14a, 14b, 14c, 14d, and cleaning devices 15a, 15b, 15c, 15d
It has.

The developing devices 14a to 14d store developers (hereinafter, referred to as "toners") of four colors of yellow, cyan, magenta, and black, respectively.

Here, the configuration and functions of the station a will be described. The center of the photosensitive drum 11a is pivotally supported, and is driven to rotate in the direction of the arrow. In the primary charger 12a, a charge of a uniform charge amount is given to the surface of the photosensitive drum 11a. Next, a light beam such as a laser beam modulated according to a recording image signal is exposed on the photosensitive drum 11a by the optical system 13a, thereby forming an electrostatic latent image thereon.

Further, the electrostatic latent image is visualized as a yellow toner image by a developing device 14a containing, for example, yellow toner.

On the downstream side of the image transfer area Ta, the cleaning device 15a cleans the drum surface by scraping off the toner remaining on the photosensitive drum 11a without being transferred to the recording paper P as a transfer material.

The above-described process is performed in the other stations b, c, and d, and the image formation using the other toners is sequentially performed.

The paper feed unit 20 is a cassette 21 for storing the recording paper P, and feeds one recording paper P from the cassette 21.
Pickup roller 22 for feeding out each sheet, paper feed rollers 23a and 23b for conveying recording paper P sent out from pickup roller 22, and paper feed guide 2
4, registration rollers 25a and 25b for sending the recording paper P to the transfer unit 30 in accordance with the image forming timing of the image forming unit, and a suction guide 26 for guiding the recording paper P to the transfer unit 30.

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

As shown in FIG. 2, the transfer unit 30 includes a transport belt 31, a belt driving roller 32 over which the transport belt 31 is wound, a driven roller 33, and a tension roller for applying an appropriate tension to the transport belt 31. 3
4. Further, transfer blades 35a, 35b, 35c, 35
d, frame 3 supporting transfer blades 35a to 35d
9. Drive motor 17 as drive source for driving belt drive roller 32 shown in FIG.
Is constituted by a support base 65 for supporting the.

Referring again to FIG. 1, the transport belt 31 is made of, for example, PET (polyethylene terephthalate) or PVdF (polyvinylidene fluoride).

An image transfer plane A is formed between the belt driving roller 32 and the driven roller 33 by the transport belt 31. At this time, the transport belt 31 and the photosensitive drums 11a to 11a to
The distance 11d is only slightly (about 1 mm) apart.

An attraction charger 27 is disposed at a position where the recording paper P sent from the registration rollers 25a and 25b enters the conveyor belt 31, and each of the photosensitive drums 11a to 11 downstream thereof is disposed.
d and image transfer areas Ta and T where the conveyor belt 31 faces
Transfer charging blades 35a to 35d are disposed behind the conveyor belt 31 at b, Tc, and Td.

The transfer charging blades 35a to 35d can be pressed against and separated from the photosensitive drums 11a to 11d by a mechanism (not shown). Good image transfer is performed by being pressed against an appropriate pressure.

The recording paper P is located slightly upstream of the drive roller 32.
A charger 36 for separating and removing the electricity is disposed, and a downstream of the charger 36 is a charge removing charger 37 for giving a uniform charge to the surface of the transport belt 31 and a brush roller 38 for cleaning the transport belt 31. Is provided.

The fixing unit 40 includes a fixing roller 41 a having a heat source such as a halogen heater therein, and a fixing roller 4.
A pressure roller 41b (which may also be provided with a heat source) for pressing the recording paper 1a, an entrance guide 43 for guiding the recording paper P to a nip portion of the roller pair, and a discharge roller 41b discharged from the roller pair The paper discharge roller 44 and the external discharge roller 45 for further guiding the recording paper P to the outside of the apparatus.

Next, a further explanation will be given in accordance with the operation of the apparatus.

When the image forming operation start signal is issued, first, the recording paper P is fed out of the cassette 21 by the pickup roller 22 one by one. And the recording paper P is
The sheet is guided between the sheet feeding guides 24 by the sheet feeding rollers 23a and 23b, and is conveyed to the 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
Hit the nip.

Thereafter, the registration rollers 25a, 2b are synchronized with the timing at which the image forming section 1P starts forming an image.
5b starts rotating. The rotation timing is set so that the recording paper P and the toner image on the photosensitive drum 11a exactly coincide in the image transfer area.

When the recording paper P enters and comes into contact with the transport belt 31 moving by the drive roller 32, the recording paper P is electrostatically attracted by the Coulomb force generated on the transport belt 31 by the action of the attraction charger 27.

The conveyor belt 31 is provided with photosensitive drums 11a to 11a.
The recording paper P is conveyed to the first image transfer area Ta while being held thereon in synchronization with d. In this case, a high voltage is applied to the transfer charging blade 35a pressurized at the start of the sequence in accordance with the passage timing of the recording paper P.

Then, the toner image formed on the photosensitive drum 11a by the above-described process is transferred onto the surface of the recording paper P, and thereafter, the recording paper P is further conveyed to the next image forming area Tb. Here, image formation is performed with a delay of the time required for the recording paper P to be transported between the stations a and b, and the next toner image is transferred by registering the registration on the previous image. Become.

Thereafter, the same steps are repeated, so that four color toner images are transferred onto the recording paper P in a multiplex manner.

When the operation is completed, the adsorbing force between the recording paper P and the conveyor belt 31 is reduced by the operation of the charge removing charger 36 in the separation unit, and the recording paper P is separated from the conveyor belt 31 by the curvature of the driving roller 32 that follows. To separate.

The recording paper P separated from the conveyor belt 31 is accurately guided by the entrance guide 43 to the fixing roller nip.

The toner image is fixed on the surface of the recording paper P by the heat of the roller pair 41a and 41b and the pressure of the nip. Thereafter, the recording paper P is conveyed by the inner and outer discharge rollers 44 and 45, and the recording paper P is discharged onto a tray 46 outside the apparatus.

The transfer blades 35a to 35d are released from the pressure, and the recording material holding sheet 31b is moved from the photosensitive drums 11a to 11d.
The sequence ends with the distance from d. This is to protect the photosensitive drums 11a to 11d by preventing external forces from acting thereon as much as possible.

Next, features of the present invention will be described.

The transfer unit 30 is generally provided with the transfer unit 3 in consideration of the operability at the time of jam clearance and maintenance.
0 can be pulled out of the apparatus main body. However, the conveyor belt 31 is used for the photosensitive drums 11a to 11
Since the conveyor belt 31 is in contact with the photosensitive drum 11a, the conveyor belt 31 needs to be once separated from the photosensitive drums 11a to 11d and then pulled out.

As described above, the transfer unit 30 is stretched by the belt drive roller 32, the driven roller 33, the tension roller 34, the transfer blades 35a to 35d, the transfer unit frame 39 supporting these, and the rollers. And a drive motor 17 that drives the drive roller 32 and a drive motor base 65 that supports the drive motor 17. The drive roller 32 swings around the photosensitive drums 11 a to 11 d. The photosensitive drum 11
It is configured to be able to be pulled out to the near side in a state separated from a to 11d.

More specifically, when the transfer unit 30 is brought into contact with the photosensitive drums 11a to 11d as shown in FIG.
2 at a position facing the photosensitive drum 1
The projection 39a of the transfer unit frame 39 is fixed to the abutting portion 110 on the side of 1a to 11d by abutting.

Further, as shown in FIG.
When 0 is separated from the photosensitive drums 11a to 11d,
The pressurizing swing cam 55 is automatically or manually rotated by a drive source or a handle (not shown), and the pressurizing means 54 is turned in the pressure releasing direction, so that the protrusion 39 b of the transfer frame 39 is placed on the transfer unit support 52. Place and separate / hold.

Next, a detailed configuration around the driving roller will be described with reference to FIGS.

The driving roller 32 has a cylindrical bearing holder 39 having both ends of the driving roller shaft 32a fixed to bearings 39e, 39e and a transfer unit frame 39.
It is supported on the transfer unit frame 39 via c and 39d.

The outer peripheral portion of the bearing holder 39c is fitted to the fitting portion 18a of the rear positioning holder 18 on the main body side. The rear positioning holder 18 is positioned at the fitting portion 18b with respect to the main body rear plate 2a. Both fitting portions 18a, 18
b is guaranteed coaxiality. Therefore, the main body rear side plate 2a and the drive roller 32 are accurately positioned with respect to the back side.

At this time, positioning pins 51a, 51b projecting from the transfer support frame 51 in the front-rear direction with respect to the apparatus main body.
Is actually performed via the positioning pieces 2c and 2d. The positioning pieces 2c and 2d are movably supported with respect to the main body front side plate 2b.

The positioning pieces 2c and 2d are fixed in a state where the transfer unit positioning holes 51c of the transfer support frame 51 are directly positioned with respect to the main body front side plate 2b by a positioning jig (not shown) in an assembling process. With this positioning method, the relationship between the transfer unit positioning hole 51c and the main body is equivalent to the relationship between the fitting portion 18b of the back side positioning holder 18 directly positioned on the main body rear plate 2a and the main body. Therefore, the main body and the drive roller 32 are accurately positioned with respect to the front side similarly to the back side.

On the other hand, the fitting portion 6 of the transfer positioning holder 62
2b also serves to position the drive motor base 65. The transfer motor 17 is positioned and fixed by a fitting hole 65b of the drive motor base 65. The coaxiality of the fitting hole 65b of the drive motor base 65 with the fitting portion 62a of the transfer positioning holder 62 and the bearing holder 39d is guaranteed. Therefore, the transfer motor 17 and the drive roller shaft 32a are coaxially arranged with high precision. Transfer motor 17 and drive roller shaft 32a
Are connected by a coupling 64 without play in the rotational direction.

The positioning in the direction in which the transfer unit 30 is pulled out (front-rear direction) is performed as follows. In the transfer support frame 51, a magnet catch 51e is fixed near the bearing holder 39 on the back side. A magnet 18c is fixed to the rear positioning holder 18 corresponding to the magnet catch 51e. When the magnet catch 51e is attracted to the magnet 18c, the transfer support frame 51 is fixed to the main body in the front-rear direction.

On the other hand, the transfer unit 30
2 and is positioned in the front-rear direction as follows. Transfer positioning holder 62 and bearing holder 39d
Is a contact member 63 provided on the coupling 64 side.
Are disposed on the side of the belt drive roller 32 so as to be sandwiched by a stopper 61 movable in the axial direction. still,
The transfer positioning holder 62 and the drive motor base 65 are integrated beforehand.

In this state, the transfer positioning holder 62 is abutted against the abutting member 63 by the stopper 61, and the stopper 61 is fixed in the axial direction by a screw or the like. As a result, the transfer unit frame 39 via the drive roller 32
Then, the drive motor base 65 is fixed without play in the front-rear direction.

By coupling the drive motor base 65 to the transfer support frame 51, the transfer unit 30 is positioned with respect to the main body in the front-rear direction.

As shown in FIG. 5, when the transfer unit 30 is pulled out to the near side, the drive roller 32 side is connected to the transfer unit 30 via the transfer support frame 51 integrated with the movable side of the slide rail 56. Are supported by the slide rail 56. The slide rail 56 is provided on the front side plate 2 of the main body.
b and the rear side plate 2a are fixed to a left connecting plate 58a.

The driven roller 33 side of the transfer frame 39 is placed on a transfer unit support 52 fixed to the movable side of the slide rail 57, and the guide portions 52a, 52b and the projecting portion 39b of the transfer frame 39 engage. . As described above, the slide rail 57 includes the main body front side plate 2b and the rear side plate 2b.
a is connected to a right connecting plate 58b that connects a.

The transfer unit 30 is pulled out by holding a handle 51 d integral with the transfer unit support frame 51.
It is operated by pulling over the magnetic force of the magnet 18c.

Next, an operation of removing the transfer unit 30 from the main body will be described with reference to FIG.

The transfer unit 30 releases the coupling between the drive motor base 65 and the transfer support frame 51 and moves it toward the near side (downward in the figure), so that the bearing holder 39c is also separated from the transfer support frame 51, and Can be uncoupled.

As shown in FIG. 7, the transfer unit positioning hole 51c of the transfer support frame 51 has a notch 51f.
(See FIG. 6).

Therefore, the transfer unit 30 can be completely removed from the main body by lifting the transfer unit 30 upward in the vertical direction of the main body at the position of the transfer unit 30 shown in FIG.

With the above configuration, even if the transfer unit 30 can be separated, pulled out, and removed from the apparatus main body, accurate positioning of the transfer unit 30 with respect to the apparatus main body is achieved, and an image defect due to poor transfer can be prevented.

Further, since the belt drive roller 32 is coaxial with the drive motor 17 and is driven directly without the use of a timing belt or gears, the belt speed is constant and expansion and contraction of images and color shift are suppressed. Can be

Further, the following items are given as effects unique to the present embodiment.

In the present embodiment, the center axis 32a of the belt driving roller 32 coincides with the positioning with respect to the main body.
Since the positioning is performed via the bearing holders 39c and 39d fixed to the transfer unit frame 39 so that the coaxiality with the center axis 32a of the belt drive roller 32 is ensured, the weight of the transfer unit 30 is reduced by the drive roller shaft 32a. Therefore, it is possible to prevent the rotation accuracy from deteriorating due to the deflection of the drive roller shaft 32a.

Further, as in this embodiment, the transfer unit 3
In the case where 0 can be pulled out, conventionally, the side from which the transfer unit 30 is drawn out is not allowed to have a shield on the projection surface of the transfer unit 30. Therefore, the position of the side to be drawn out (front side) can be used as the drive shaft itself. Therefore, the driving roller position accuracy is reduced by one step. However, according to this embodiment,
Since the jig is adjusted in advance by the main body of the drive roller positioning portion on the front side, the same accuracy as that on the back side can be secured on the front side.

[0080]

As is apparent from the above description, according to the image forming apparatus of the present invention, at least one of the plurality of positioning means for positioning the unit in the image forming apparatus main body includes a driving source and a driven source. By being located between the image forming apparatus and the body, even when the unit can be separated, pulled out, or removed from the image forming apparatus main body, the positioning accuracy with the image forming unit can be improved, and a high-quality image can be obtained. Obtainable.

Further, the transfer unit is swingable about the center axis of the drive roller, and at least one of a plurality of positioning means for positioning the transfer unit with respect to the image forming apparatus main body is connected to the drive roller. Since the transfer unit is coaxial and located between the drive roller and the drive motor, even if the transfer unit can be separated, pulled out, or removed from the image forming apparatus main body, the positioning accuracy with the image forming unit can be improved. The transfer belt of the transfer unit can be driven at a stable speed, so that a high-quality image can be obtained. The operability of the unit can be improved.

[Brief description of the drawings]

FIG. 1 is an overall configuration diagram showing an embodiment of a color image forming apparatus according to the present invention.

FIG. 2 is a front sectional view showing a transfer unit in contact with a photosensitive drum.

FIG. 3 is a front sectional view showing a transfer unit separated from a photosensitive drum.

FIG. 4 is a cross-sectional view from above showing the transfer unit positioned in the apparatus main body and its periphery.

FIG. 5 is a top sectional view showing the transfer unit and its periphery when the transfer unit is pulled out to the near side from the state of FIG. 4;

FIG. 6 is a top sectional view showing the transfer unit removed from the apparatus main body and its periphery.

FIG. 7 is a front view showing a transfer unit and its periphery.

[Explanation of symbols]

2a Main body rear side plate 2b Main body front side plate 11a, 11b, 11c, 11d Photosensitive drum (image carrier) 17 Drive motor (drive source) 18 Back side positioning holder (positioning means) 31 Transport belt 32 Drive roller (driven body) 32a Drive roller shaft (drive transmission means) 33 Followed rollers 39c, 39d Bearing holder 51 Transfer support frame 62 Positioning holder (positioning means)

Claims (3)

[Claims] A unit having a drive source, a driven body, a drive transmission unit for transmitting drive from the drive source to the driven body, and a plurality of positioning units, wherein the plurality of positioning units are An image forming apparatus for positioning a unit in an image forming apparatus main body, wherein at least one of the plurality of positioning means is located between the driving source and the driven body. Forming equipment. 2. The drive source, the driven body, the drive transmission means, and the positioning means are on the same axis,
The image forming apparatus according to claim 1, wherein the unit is swingable about the axis. 3. An image forming apparatus comprising: at least one image carrier on which a toner image is formed; and holding a transfer material onto which the toner image is transferred on the image carrier, at a transfer position facing the image carrier. An endlessly rotating conveying belt for conveying, a driving roller for supporting and driving the conveying belt, at least one driven roller for stretching the conveying belt together with the driving roller, and a driving motor for driving the driving roller; And a transfer unit having a drive transmission unit coaxially connecting the drive roller and the drive motor, and a plurality of positioning units, wherein the plurality of positioning units position the transfer unit with respect to the image forming apparatus main body. In the image forming apparatus, the transfer unit is swingable about a central axis of the driving roller, Both One is on the drive roller coaxially, and an image forming apparatus, characterized in that located between the drive motor and the drive roller.