JPH04114178A - Electrophotographic printer - Google Patents

Abstract

PURPOSE:To obtain the electrophotographic printer with high precision in carrying of the photosensitive body belt by making exposure width of an exposure head be an integral multiple of an outer periphery length of a belt drive roll. CONSTITUTION:Either both the outer periphery length of a belt driving roll 9 and the exposure width of the exposure head are matched or the exposure width of the exposure head is made to be the integral multiple of the outer periphery length of the driving roll 9. For example, a radius of the belt driving roll 9 and the outer periphery length of the roll is matched with the exposure width of the exposure head 2. Because of this, even when the belt driving roll 9 is eccentric, since one exposure width is equivalent to one rotation of the belt driving roll 9, an exposure range is always formed a distance of one rotation of the belt driving roll 9 apart in the following exposure scanning, and spacing between the exposure range is prevented from being inaccurate. Thus, accurate control of the photosensitive body carrying quantity can be carried out.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to an electrophotographic printer, and particularly to a photoreceptor conveying mechanism thereof.

[Conventional technology]

In conventional electrophotographic printers, a method is widely used in which a laser beam emitted by a laser light source is deflected using a rotating polygon mirror, and modulated while scanning over a photoreceptor to expose a predetermined position (for example, Kaisho 63-21081
5, Japanese Patent Publication No. 62-210819).

On the other hand, it is also possible to use a head having a plurality of LED elements to scan an intermittently rotating photoconductor, selectively lighting up each LED element, and performing image exposure (
For example, Utility Model Application Publication No. 1-208160). According to this configuration,
The light source and photoreceptor can be placed close to each other, making it possible to downsize the device.

Furthermore, as the present inventors have already proposed (Japanese Patent Application No. 2-41941), while the photoconductor is continuously conveyed at a constant speed, the head is moved in the photoconductor conveyance direction at the same speed as the conveyance speed. It can be configured to move, simultaneously scan in a direction perpendicular to the transport direction, and perform exposure.

According to this configuration, the image forming process is performed continuously,
Stable image formation is possible.

[Problem to be solved by the invention]

In the apparatus proposed by the present inventors, the conveyance operation of the photoreceptor and the scanning speed of the exposure head are performed in synchronization. Furthermore, if the exposure width of the exposure head is H1, the transport speed of the photoconductor is V, and the amount of storage required for the reciprocating operation of the exposure head is T, then by satisfying the relationship H=TXV, the photoconductor can be covered without gaps. Can be exposed to light.

However, at this time, if the conveyance amount of the photoreceptor is not managed with high precision, subsequent exposure scans may result in image exposure that overlaps the edges of the previously exposed area, or conversely, unexposed areas may be created. The problem arises. In particular, when the photoreceptor is formed into a belt, it becomes difficult to control the conveyance amount of the photoreceptor with high precision due to the bending of the shaft of the drive roller and eccentricity of the center of rotation.

An object of the present invention is to solve this problem beforehand and to realize an electrophotographic printer that can accurately control the amount of photoreceptor conveyance.

[Means to solve the problem]

The electrophotographic printer of the present invention is an electrophotographic printer that has a photoreceptor made of a photoconductor belt that is conveyed in a predetermined direction by a belt drive roller, and an exposure means that exposes the photoreceptor to form an image. The exposure means includes a plurality of light emitting sources that can selectively control light emission, and scans exposure with a predetermined exposure width in a direction perpendicular to the conveying direction of the photoreceptor, and also in the conveying direction of the photoreceptor. ,
The present invention is characterized in that it comprises an exposure head that moves at the same speed as the conveyance speed of the photoreceptor, and that the exposure width of the exposure head is an integral multiple of the outer circumferential length of the drive roller of the photoreceptor.

〔Example〕

Next, examples of the present invention will be described. FIG. 1 is a perspective view of a printer showing one embodiment of the present invention. An exposure head 2, a charging device 3, a developing device 4, a cleaner device 5,
A transfer device 6 is arranged. A charging device 3 consisting of a corotron charger charges the photoreceptor belt 1 to a predetermined potential.

The developing device 4 rubs the photoreceptor belt 1 with a charged powder toner, attaches the toner according to the electrostatic latent image, and visualizes this. The transfer device 6 is composed of a corotron charger, and creates a potential difference between it and the conductive layer of the photoreceptor belt 1 to perform toner image transfer. That is, the charged toner interposed between the recording paper 26 and the photoreceptor belt 1 is attracted and adhered to the recording paper 26 by electrostatic force. The cleaner device 5 presses the elastic plate 5a against the photoreceptor belt 1 to remove the remaining toner after transfer. The eraser lamp 10 uses −-like light irradiation to
Perform latent image erasure.

The exposure head 2 is guided by a guide shaft 25 and scans the photoreceptor belt 1 while maintaining a constant distance from the surface of the photoreceptor belt, and a carriage drive wire 23 is driven by a motor to cause it to reciprocate. . The head 2 is provided with wiring 22 for driving the LED elements. The photoreceptor belt 1 is conveyed by a belt drive roller 9. When the exposure head 2 moves in the direction of the arrow A, the guide shaft 25 is aligned with the photoconductor conveying direction so that it moves in this direction at the same speed as the moving speed of the photoconductor belt 1 in the direction of the arrow B. It is installed at a certain angle.

The structure of the exposure head 2 is shown in FIG. The exposure head 2 includes a light emitting substrate 36, a carriage 31, an imaging lens 33, and a casing (not shown) that covers these.

The carriage 31 has an integrated bearing 35, is guided by the guide shaft 25, and is movably supported. As shown in FIG. 3, the light emitting board 36 includes 128 LEDs arranged in a straight line at a pitch of 1/300 inch in the conveyance direction of the photoreceptor belt 1, and forming light sources that can independently control light emission. An LED chip 42 having an array of elements 45 (partially shown in the figure) and a dry fly C41 for driving,
It is configured by being mounted on a printed circuit board 43 with printed wiring and connected. The imaging lens 33 is an array of a plurality of self-focusing type gradient index lenses, and is an LE lens.
An equal-strength standing image of the D array is formed on the surface of the photoreceptor belt 1.

Next, the printing operation will be explained using FIG. 1. The photoreceptor belt 1 is charged by the charging device 3 while being conveyed in the direction of arrow B. Next, the exposure head 2 selectively eliminates the static electricity on the exposed portion to approximately Ov, thereby forming an electrostatic latent image. That is, the exposure head 2 performs exposure during the scanning operation in the direction of arrow A, and does not perform exposure during the return operation in the direction opposite to arrow A. Exposure head 2, photoreceptor belt 1 during exposure operation
is being transported at a constant speed. These control methods use conventional techniques used in printers and the like.

At the same time as the photoreceptor belt 1 is rotated in the direction of arrow B,
The exposure head 2 scans along the guide shaft 25 described above.

The exposure head 2 has a pitch of 1/300 inch, 128
The LED elements 45 are arranged on a straight line in a direction that coincides with the conveying direction of the photoreceptor belt 1. The outer circumferential speed of the photoreceptor belt 1 is V=21.7 mm/s, and the photoreceptor belt 1 rotates at a constant speed. The exposure head 1 reciprocates for a time T=500 ms. That is, during one scanning operation time, the photoreceptor belt 1 moves by a distance corresponding to the effective exposure length (exposure width) of the exposure head 2, H = 10.8 mm, so the relationship H = VXT is satisfied. has been done. Therefore, the photoreceptor belt 1 can be scanned in a stripe pattern without gaps by continuous exposure head scanning operations.

The electrostatic latent image thus formed is developed by the developing device 4 and transferred onto the recording paper 26 by the transfer device 6, thereby forming an image on the paper.

FIG. 4 shows the exposed area on the recording paper 26 that has undergone the transfer process. Since the exposure head 2 obliquely scans the photoreceptor belt 1, the exposure area formed in one scanning process is a striped area perpendicular to the conveying direction of the photoreceptor belt 1. Therefore, after being transferred onto the recording paper 26, the exposure area 27 formed by the first penetrating scan is formed in a stripe shape with a width H in a direction parallel to the edge 26a of the recording paper. Further, the exposure area 28 formed by the second exposure scan and the exposure area 29 formed by the third exposure scan are parallel to each other on the recording paper 26.
It is formed so that it fills in without any gaps.

In this embodiment, the photoreceptor belt 1 is conveyed by a belt drive roller 9 that is directly connected to a motor 8 . Although the outer diameter of mechanical parts such as rollers can be manufactured with high precision, the shaft is likely to be bent or the center of rotation may be eccentric. However, the positional accuracy of the formed dots required of the printer is, for example, about ±20 μm from the viewpoint of maintaining image quality.

When the outer circumferential length of the belt drive roller 9 is different from the effective exposure length (that is, the exposure width H), in order to convey the photoreceptor belt 1 by a predetermined amount, it is determined from the designed radius of the belt drive roller 9. It is necessary to provide a predetermined rotation angle. In this case, if there is eccentricity, the actual roller radius is changing, which causes an error in the conveyance amount expressed as (roller radius) x (rotation angle for a predetermined time) x π/360. For this reason, it is difficult to ensure the above-mentioned dot position accuracy. Therefore, in the apparatus of this embodiment, the radius of the belt drive roller 9 was set to 1.72 mm, and the outer peripheral length of the roller (approximately 10.8 mm) was made to match the exposure width of the exposure head 2, 10.8 mm. Therefore, even if the belt drive roller 9 is eccentric, one exposure width corresponds to one revolution of the belt drive roller 9, so
During the subsequent exposure scan, an exposure area is formed at a distance corresponding to one revolution of the belt drive roller 9. Therefore, the exposure area interval will not become inaccurate. In addition, the above effect can be obtained not only when the outer circumferential length of the belt drive roller 9 and the exposure width of the exposure head are the same, but also when the exposure width of the exposure head is 1 and an integral multiple of the outer circumference length of the belt drive roller 9. In some cases, the same can be obtained.

〔Effect of the invention〕

According to the present invention, since the exposure width of the exposure head is an integral multiple of the outer circumferential length of the belt drive roller, the conveyance amount of the photoreceptor belt can be controlled with high precision without being affected by the eccentricity of the belt drive roller. Therefore, it is possible to realize an electrophotographic printer with high photoreceptor belt conveyance accuracy.

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing the configuration of a printer showing an embodiment of the present invention. FIG. 2 is a perspective view showing the configuration of an exposure head used in a printer that is an embodiment of the present invention. FIG. 3 is a perspective view showing the structure of a light emitting board used in a printer that is an embodiment of the present invention. FIG. 4 is a diagram illustrating the state of image formation on recording paper in the printer of the present invention. Guide shaft Recording paper Carriage Imaging lens Light emitting board LED chip LED element Applicant Seiko Epson Co., Ltd. Agent Patent attorney Kizobe Suzuki and 1 other person Photoreceptor belt exposure Rad motor belt drive port - La Φ: 2r'',: Figure 3

Claims (1)

[Scope of Claims] An electrophotographic printer comprising a photoconductor made of a photoconductor belt conveyed in a predetermined direction by a belt drive roller, and an exposure means for exposing the photoconductor to form an image. , the exposure means is equipped with a plurality of light emitting sources that can selectively control light emission, and performs exposure scanning with a predetermined exposure width in a direction perpendicular to the transport direction of the photoreceptor, and also in the transport direction of the photoreceptor.
An electrophotographic printer comprising an exposure head that moves at the same speed as the conveyance speed of the photoreceptor, and the exposure width of the exposure head is an integral multiple of the outer circumference length of the drive roller of the photoreceptor. .