JP2001125391A - Color image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the cracking of an electrostatic transfer belt and the peeling of a patch and to control the rotating speed of the electrostatic transfer belt to be constant while restraining the rising of production cost. SOLUTION: A line 33 having a distance L being the periphery of a photoreceptor drum 1 is formed on the drum 1 by toner development, and transferred to the electrostatic transfer belt 11. Then, the distance L of the line 33 is temporally measured by a sensor 29 previously provided around the belt 11 so as to control the revolving speed of a driving motor 31 for the belt 11. Namely, the speed of the belt 11 is controlled.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic color image forming apparatus such as a color copying machine or a color printer.

[0002]

2. Description of the Related Art Conventionally, a tandem type image forming apparatus has
Horizontally arranged yellow, magenta, cyan,
A latent image is sequentially formed on an image carrier, which is four photosensitive members for black, by optical writing, the latent image is formed into a toner image (developed image), the toner image is transferred to a transfer material, and the transferred image is formed. Heat-fixed to transfer material.

The transfer material is conveyed by a pair of rollers called a pair of registration rollers to an attraction portion of a transfer device at an image transfer timing, and the attraction portion statically contacts the surface of an electrostatic transfer belt as a transfer material carrier. It is electrically attracted and sequentially conveyed to the image transfer section.

The electrostatic transfer belt is an endless belt in the form of a film having a uniform surface resistance, is stretched by a plurality of rollers including a driving roller, and is sandwiched between respective photosensitive members and a transfer roller to form an image transfer portion.

Further, the position of the electrostatic transfer belt in the width direction of the transfer material is regulated by the apparatus main body by a rib for regulating the displacement provided on the back surface thereof, and is circulated in the transfer material transport direction by the driving roller. Here, in order to keep the transfer material transport speed constant and prevent image defects, it is necessary to keep the rotation speed of the electrostatic transfer belt constant. Therefore, conventionally, as shown in FIG.
One or more are opened, the time is measured by a sensor 129 serving as a detecting means, and the rotation speed of the drive motor 131 connected to the drive roller 113 is controlled to keep the rotation speed of the electrostatic transfer belt 111 constant. Control was taking place.

[0006] Then, the transfer material conveyed from the pair of registration rollers is pressed and applied with a suction voltage by a suction roller which comes into contact with the surface of the electrostatic transfer belt, thereby electrostatically attracting the surface of the electrostatic transfer belt to transfer the image. To the department. As a result, the transfer material is maintained at a constant vertical and horizontal position.
The images are sequentially conveyed to the image transfer units at the locations where image formation is performed.

[0007]

However, as in the above-described conventional example, the reference hole 130 is provided in the electrostatic transfer belt 111, and the sensor 129 detects the reference hole 130, whereby the rotation of the drive motor 131 of the electrostatic transfer belt 111 is performed. In the method of controlling the number, the manufacturing cost is increased by the step of forming the reference hole 130, and the electrostatic transfer belt 1 is
There was a problem that cracking of the eleventh and peeling of the patch 132 stuck on the upper surface of the reference hole 130 occurred.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a color image forming apparatus capable of controlling the rotation speed of a transfer material carrier to be constant while preventing the transfer material carrier from cracking and peeling off patches while suppressing an increase in manufacturing cost. It is to be.

[0009]

The above object is achieved by a color image forming apparatus according to the present invention. In summary, the present invention forms an electrostatic latent image on each of a plurality of image carriers, develops the electrostatic latent image as a developed image with a developer of a predetermined corresponding color, and transfers the transfer material to the plurality of image carriers. In a color image forming apparatus for transferring a developed image to a transfer material by transferring the developed image to a transfer material a plurality of times to obtain a multicolor image, transferring the developed image on the image carrier to the image carrier. A color image forming apparatus is characterized in that the image is transferred to a transfer material carrier, the transferred image is detected by a detecting unit, and a driving unit of the transfer material carrier is controlled based on the detection result.

Preferably, the transfer image is transferred to a non-image area of the transfer material carrier. It is preferable that the transfer image is transferred at one circumferential interval of the image carrier.

[0011]

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

First, the overall configuration of the color image forming apparatus of the present embodiment will be schematically described with reference to FIG. FIG. 1 shows a four-color full-color laser beam printer 100 which is an embodiment of a color image forming apparatus.

As shown in FIG. 1, a color laser beam printer 100 according to the present embodiment has four color laser beam printers arranged in a horizontal direction.
Photoconductors (hereinafter, referred to as "photoconductor drums") 1a, 1b, 1c, and 1d as image carriers are provided. The photosensitive drums 1a to 1d are driven to rotate clockwise in FIG. 1 by driving means (not shown). Photoconductor drums 1a to 1
d, a charging device 2a, 2b, 2c, 2d for uniformly charging the surfaces of the photosensitive drums 1a to 1d in order according to the rotation direction, and irradiating a laser beam based on image information to the photosensitive drums Scanner units 3a, 3b, 3c, and 3d for forming electrostatic latent images on drums 1a to 1d; developing devices 4a, 4b, 4c, and 4d for attaching toner to the electrostatic latent images and developing them as toner images; Drums 1a-1
d, an electrostatic transfer device 5 for transferring the toner image on the transfer material S, and cleaning devices 6a, 6b, 6 for removing transfer residual toner remaining on the surfaces of the photosensitive drums 1a to 1d after the transfer.
c, 6d, etc. are provided.

The photosensitive drums 1a to 1d, charging devices 2a to 2d, developing devices 4a to 4d, and cleaning devices 6a to 6d for removing toner are integrally formed as process cartridges 7a, 7b, 7c. ,
7d, and a full-color laser beam printer 10
0 is detachable.

Hereinafter, each of the above components will be described in detail. Since each component has the same configuration, the description will be omitted by omitting the suffix (alphabet) of the reference numeral indicating each component.

The photosensitive drum 1 has, for example, an organic photoconductor layer (OP) on the outer peripheral surface of an aluminum cylinder having a diameter of 30 mm.
C photoreceptor). The photosensitive drum 1 is rotatably supported at both ends by supporting members (not shown), and a driving force from a driving motor (not shown) is transmitted to one end thereof, so that the photosensitive drum 1 rotates clockwise in the drawing. Is driven to rotate.

The charging device 2 may be of a contact charging type. The charging member is a conductive roller formed in a roller shape. The roller is brought into contact with the surface of the photosensitive drum 1 and a power source (not shown) is attached to the roller.
By applying a charging bias voltage, the surface of the photosensitive drum 1 is uniformly charged.

The scanner unit 3 is disposed substantially in the vertical direction of the photosensitive drum 1, and emits image light corresponding to an image signal by a laser diode (not shown) to a scanner motor (not shown).
Polygon mirror 9 (9a, 9a)
b, 9c, 9d). The image light reflected by the polygon mirror 9 is transmitted to the imaging lens 10 (10a, 10b, 1).
0c, 10d) to selectively expose the charged surface of the photosensitive drum 1 to form an electrostatic latent image.

Each of the developing devices 4 (4a, 4b, 4c, 4d) is composed of a developing device containing a toner of each color of yellow, magenta, cyan, and black. At the time of developing the electrostatic latent image on the photosensitive drum 1, the toner in the developing container of the corresponding developing unit is sent to the application rollers 4a1, 4b1, 4c1, and 4d1 by the feeding mechanism, and the developing sleeves 4a2, 4b2, and 4c2 which rotate. A thin layer of toner is applied to the outer periphery of 4d2, and a charge is applied to the toner (frictional charging).

By applying a developing bias between the developing sleeves 4a2 to 4d2 and the photosensitive drums 1a to 1d on which the electrostatic latent images are formed, toner adheres to the electrostatic latent images to form toner images ( (Developed image).

After the toner developed on the photosensitive drum 1 by the developing device 4 is transferred to the transfer material S, the cleaning device 6 removes so-called untransferred toner remaining on the surface of the photosensitive drum 1 without being transferred. I do.

The electrostatic transfer device 5 includes an electrostatic transfer belt 11 which is a transfer material carrier circulating and moving so as to face all the photosensitive drums 1a to 1d. The electrostatic transfer belt 11 is formed of a film-like member having a volume resistivity of 10 ¹² Ω · cm or less and a thickness of about 150 μm. The electrostatic transfer belt 11 is supported by rollers on four axes in the vertical direction, and circulates so that the transfer material S is electrostatically attracted to the outer peripheral surface on the upper side in the drawing and the transfer material S comes into contact with the photosensitive drum 1. I do. Thereby, the transfer material S is transferred to the electrostatic transfer belt 1.
1, the toner image on the photosensitive drum 1 is sequentially transferred.

Contacting the inside of the electrostatic transfer belt 11,
Transfer roller 1 corresponding to four photosensitive drums 1a to 1d
2 (12a, 12b, 12c, 12d) are juxtaposed.
The transfer roller 12 is connected to a transfer bias power supply (not shown), and faces the photosensitive drum 1 to form a transfer section. Then, a positive charge is applied from the transfer roller 12 to the transfer material S via the electrostatic transfer belt 11, and an electric field generated by the charge causes the transfer material S in contact with the photosensitive drum 1 to be in contact with the transfer material S.
Then, the negative toner image on the photosensitive drum 1 is transferred.

The electrostatic transfer belt 11 has a circumference of about 700 mm,
The driving roller 13 and the driven roller 1 have a thickness of 150 μm.
4a, 14b, and a tension roller 15, and are wound around four rollers, and rotate counterclockwise in the figure. This allows
The toner image on the photosensitive drum 1 is transferred while the transfer material S is conveyed from the driven roller 14a side to the drive roller 13 side by circulating the electrostatic transfer belt 11 described above.

The rollers 26, 27 and 28 provided between the transfer rollers 12a to 12d are electrostatically driven so that the transfer material S adsorbed and carried on the electrostatic transfer belt 11 is brought into contact with the respective photosensitive drums 1a to 1d. This is a push-up roller that pushes up the transfer belt 11 to the photosensitive drum 1 side.

The paper feed unit 16 feeds and conveys the transfer material S to the image forming unit. A plurality of transfer materials S are stored in a paper feed cassette 17. At the time of image formation, a paper feed roller (half-moon roller) 18 and a registration roller pair 19 are driven and rotated in accordance with the image forming operation to separate and feed the transfer material S in the paper feed cassette 17 one by one and to transfer the transfer material S to the leading end. Is stopped once after hitting the pair of registration rollers 19, and after forming a loop, the rotation of the electrostatic transfer belt 11 and the image writing position are synchronized, and the sheet is re-fed to the electrostatic transfer belt 11 by the pair of registration rollers 19. To go.

The fixing unit 20 fixes a plurality of toner images (transferred images) transferred to the transfer material S. The fixing unit 20 heats and pressures the transfer material S by pressing the heating roller 21 which is driven and rotated. And a pressure roller 22 for applying the pressure.

That is, the transfer material S onto which the toner image on the photosensitive drum 1 has been transferred is conveyed by the fixing roller pairs 21 and 22 while passing through the fixing unit 20 and is also conveyed by the fixing roller pair 2.
Heat and pressure are applied by 1,22. Thus, the toner images of a plurality of colors are fixed on the surface of the transfer material S.

Next, the image forming operation of the above-described image forming apparatus will be described.

The transfer material S is separated and fed one by one from the paper feeding unit 16 and once stops after hitting the registration roller pair 19 to form a loop. The photosensitive drum 1 is rotated clockwise in the figure in synchronization with the rotation of the electrostatic transfer belt 11, and the transfer material S waiting by the registration roller pair 19 is transferred to the toner image on the peripheral surface of the uppermost photosensitive drum 1 a. When the leading end of the sheet is rotated to a point facing the electrostatic transfer belt 11, the sheet is re-fed to the electrostatic transfer belt 11 so that the printing start position of the transfer material S matches the point.

On the other hand, the surface of each photosensitive drum 1 is uniformly charged by the charging device 2, and the peripheral surface of the photosensitive drum 1 is exposed by the scanner unit 3 in accordance with an image signal, so that the peripheral surface of the photosensitive drum 1 is exposed. To form an electrostatic latent image. The developing roller 4a2 applies a voltage of the same polarity and substantially the same potential as the charging polarity of the photosensitive drum 1a so that the yellow toner adheres to the electrostatic latent image on the photosensitive drum 1a, and adheres the yellow toner to the electrostatic latent image. And develop.

The suction roller 8 and the driven roller 14a hold the re-fed transfer material S together with the electrostatic transfer belt 11, and the suction roller 8 electrostatically attracts and presses the transfer material S to the electrostatic transfer belt 11. The transfer material S is transported while being transferred. The leading end of the transfer material S is conveyed by the driven rotation roller 14a and the suction roller 8 and is stuck to the electrostatic transfer belt 11 even after leaving the holding portion. The sheet is transported to the uppermost transfer section to be formed. After that, since electrostatic attraction occurs due to the electric field of the transfer portion between the electrostatic transfer belt 11 and the transfer material S,
The transfer material S is sequentially conveyed to the next transfer section along the electrostatic transfer belt 11.

While being conveyed in this manner, the transfer material S
By applying a voltage from each of the transfer rollers 12a, 12b, 12c, and 12d, the toner image on each photosensitive drum 1 is sequentially transferred.

The transfer material S to which the four color toner images have been transferred is
Drive roller 13 separates from electrostatic transfer belt 11,
After reaching the fixing device 20, the transfer material S is thermally fixed on the toner image, and then is discharged outside the apparatus by a discharge roller 24 and a discharge roller 25.

Next, the control of the speed of the electrostatic transfer belt in this embodiment will be described in detail with reference to FIGS.

FIG. 2 is an enlarged view of the electrostatic transfer device 5. The electrostatic transfer belt 11 is rotated in the direction of the arrow by the driving roller 13. However, the transport speed of the transfer material S changes due to the speed unevenness of the electrostatic transfer belt 11 due to the eccentricity of the drive roller 13, the speed increase of the electrostatic transfer belt 11 due to the expansion of the diameter of the drive roller 1 due to the temperature rise in the apparatus, and the like. It causes image unevenness and color shift.

As a countermeasure, as described with reference to FIG. 4, the accuracy of the diameter of the driving roller 113 is increased.
One or more reference holes 130 are provided in the electrostatic transfer belt 111, and the number of reference holes 130 is measured by a sensor 129 to control the number of rotations of a drive motor 131 that drives the drive roller 113 to rotate. Price increase due to process, crack due to stress concentration on reference hole 130,
There was a problem such as peeling of the patch 132 stuck on the upper surface of the reference hole 130.

Therefore, in this embodiment, as shown in FIG. 3, a line 33 having an interval L around the photosensitive drum 1 is formed on the photosensitive drum 1 by toner development and transferred to the electrostatic transfer belt 11. Then, a sensor (such as a density detection sensor) 29 provided beforehand around the electrostatic transfer belt 11 measures the interval L between the lines 33 and controls the number of rotations of the drive motor 31 of the electrostatic transfer belt 11. That is, the speed of the electrostatic transfer belt 11 is controlled.

By adopting such a configuration, there is no increase in the price of the device, no crack in the reference hole, and no peeling of the patch.
The speed of the electrostatic transfer belt 11 can be kept constant, that is, the transfer speed of the transfer material can be kept constant, and image defects such as image unevenness and color shift can be prevented.

In the image forming step, an image may be transferred by providing a minute gap between the photosensitive drum and the transfer material on the electrostatic transfer belt.

[0041]

As is apparent from the above description, according to the color image forming apparatus of the present invention, the developed image on the image carrier is transferred to the transfer material carrier, and the transferred image is detected by the detecting means. By controlling the driving means of the transfer material carrier based on the detection result, it is possible to prevent the transfer material carrier from cracking and peeling off the patches while suppressing an increase in manufacturing cost, and to reduce the rotational speed of the transfer material carrier. Can be controlled to be constant.
Therefore, economic efficiency can be improved and a high-quality image can be obtained.

[Brief description of the drawings]

FIG. 1 is a configuration diagram illustrating a color image forming apparatus according to an embodiment.

FIG. 2 is an enlarged view showing an electrostatic transfer device in the color image forming apparatus of FIG.

FIG. 3 is an explanatory diagram showing a conventional electrostatic transfer belt speed control unit.

FIG. 4 is an explanatory diagram illustrating a speed control unit of the electrostatic transfer belt according to the present exemplary embodiment.

[Description of Signs] 1 Photosensitive drum (image carrier) 11 Electrostatic transfer belt (transfer material carrier) 29 Sensor (detection unit) 31 Drive motor (drive unit)

Claims (3)

[Claims] An electrostatic latent image is formed on each of a plurality of image carriers, and the electrostatic latent image is developed as a developed image with a developer of a predetermined corresponding color. A color image forming apparatus that transports the developed image to the transfer material at a body position and transfers the developed image to the transfer material a plurality of times to obtain a multicolor image; Transfer to the body,
A color image forming apparatus, wherein the transfer image is detected by a detection unit, and a driving unit of the transfer material carrier is controlled based on the detection result. 2. The color image forming apparatus according to claim 1, wherein the transfer image is transferred to a non-image area of the transfer material carrier. 3. The color image forming apparatus according to claim 1, wherein the transfer image is transferred at one circumferential interval of the image carrier.