JPH03287182A - Electrophotographic printer - Google Patents

Abstract

PURPOSE:To obtain this electrophotographic printer having high-resolution by having a proper different height according to the curve of an image-forming face with respect to a plane where an exposing source is intersected orthogonally with the optical axis of an image-forming optical system. CONSTITUTION:Scanning is curvedly carried out by an exposing head 2 along a guiding shaft 25 while a photosensitive drum 1 is rotated in the direction of the arrow 10, so that the photosensitive drum 1 is scanned in the direction parallel to the shaft of the photosensitive drum in relative relation to the photosensitive drum 1. The image forming face 41 of an exposing part on the photosensitive drum 1 is a cylindrical one, and an LED element line 34 is formed on the curved face so as to form an image on the image-forming surface, with respect to the image forming face. Therefore, all LED elements form the images on the photosensitive drum 1 in a focusing state, and expose them. Thus, the printer having the high resolution is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an electrophotographic printer, and more particularly to an exposure device that performs image exposure on a photoreceptor.

[Prior Art] 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, Japanese Patent Application Laid-Open No. 63-210815).

On the other hand, an exposure head in which a plurality of LED elements are arranged linearly is used to perform image exposure of the LED element array using an imaging optical system, and while continuously rotating the cylindrical photoreceptor, exposure is performed in the direction of this rotation axis. A configuration in which the head scans can also be used. According to this configuration, the light source and the photoreceptor can be placed close to each other, making it possible to downsize the device.

[Problems to be Solved by the Invention] In the above configuration, since the imaging surface is a curved surface for the light emitting part on a plane perpendicular to the optical axis, it is not possible to expose all the LED elements in a focused state, and the cost is high. The problem has been that a high-resolution printer has not been realized.

An object of the present invention is to solve this problem and realize a high resolution printer.

[Means for Solving the Problems] The electrophotographic printer of the present invention includes a photoreceptor made of a photoconductor,
In electrophotographic blinking, which has an exposure means and a development means, and in which a charged photoreceptor is image-exposed by the exposure means to form an electrostatic latent image, and the electrostatic latent image is formed into a sinusoidal image by the development means, the photoreceptor has a curvature in the exposed part. The exposure means has a plurality of light emitting members that can be selectively modulated and an imaging optical system, and is supported so as to be movable relative to the photoreceptor, and the light emitting member is connected to the imaging optical system. With respect to the plane perpendicular to the optical axis direction of the system,
It is characterized in that it has different heights and is configured such that the exposure means performs image exposure on a predetermined position on the photoreceptor.

〔Example〕

Next, the present invention will be explained based on examples. FIG. 1 is a sectional view of a printer showing an embodiment of the present invention. An exposure head 2, a charging device 3, a developing device 4, a cleaner device 5, and a transfer device 6 are arranged around a photosensitive drum 1, which is constructed by applying a photoconductive layer to the outer periphery of a metal drum. The charging device 3 is a roller made of conductive rubber, which is brought into contact with the photosensitive drum 1 while applying a potential to perform contact charging. The developing device 4 rubs the surface of the photoreceptor 1 with charged powder toner, adheres the toner in accordance with the electrostatic latent image, and visualizes the toner. The transfer device 6 is composed of a conductive roller, which creates a potential difference between the photoreceptor drum 1 and the metal drum, and attracts and adheres the charged toner interposed between the photoreceptor drum 1 and the recording paper toward the recording paper using electrostatic force. Then, the toner image is transferred. The cleaner device 5 presses an elastic plate against the photosensitive drum 1 to remove residual toner after transfer.

Furthermore, it is comprised of a paper feeding device 7 for storing recording paper, a fixing device 9 for thermally fixing toner on the recording paper, and a paper discharge tray 8 for storing the recording paper after printing.

The structure of the exposure head 2, which is the exposure means, is shown in FIGS. 3(a) and 3(b).
). The exposure head 2 includes a light emitting substrate 36 and a carriage 3
1. Consists of an imaging lens 33 and a cover (not shown). The carriage 31 has a structure in which a bearing 35 is integrated and guided by a guide shaft, which will be described later. The light emitting board 36 is a board with a wiring pattern, and the lighting can be controlled independently.
LE having an LED element row 34 consisting of LED elements
D chip 32 and driver IC 33 that drives it
0 is installed. The LED element rows 34 are arranged in a direction perpendicular to the axis of the photoreceptor drum l. The surface of the LED chip 32 having the LED elements is a curved surface, and each LED element is formed on the surface at a different height. This LED light is imaged by an imaging lens 33 on the outer peripheral surface of the photoreceptor drum. The photosensitive drum 1 is cylindrical with a diameter of 30 mm, and the imaging lens 33 is a glass lens with a focal length of 10 mm and a numerical aperture of 05. On the optical axis, the distance between the lens and the light source is 20 mm, and the distance between the lens and the photosensitive drum surface is 20 mm. It is set.

The relationship among the exposure head 2, photosensitive drum 1, and guide shaft 25 is shown in FIG. The exposure head 2 scans over the photoreceptor drum 1 in a substantially spiral manner, and the exposure head 2 scans the photoreceptor drum 1 with one exposure scanning operation.
Expose the top in stripes. The exposure head 2 is a guide shaft 2
The carriage driving wire 23 is driven by a motor 24 to perform reciprocating motion on the photosensitive drum 1 while being guided by a motor 24 to scan the photosensitive drum 1 while maintaining a constant distance from the outer periphery of the photosensitive drum. The exposure head 2 is provided with wiring 22 for driving a light source.

The guide shaft 25 is formed into a substantially spiral shape so that when the head 2 moves in the direction of the arrow 20, it also moves in the rotational direction at the same speed as the rotational speed of the photosensitive drum 1 in the direction of the arrow 10.

Next, the printing operation will be explained using FIGS. 1 and 2. While rotating the photoreceptor drum 1, the surface of the photoreceptor drum 1 is charged by bringing it into contact with a charging device 3 to which a high voltage is applied. Next, the exposure head 2 selectively removes the charge and forms an electrostatic latent image. That is, by scanning a curve along the guide shaft 25 while rotating the photoreceptor drum 1 in the direction of the arrow 10, the photoreceptor drum 1 is rotated in a direction parallel to the photoreceptor drum axis relative to the photoreceptor drum 1. 1 is scanned. L
Sixty-four ED elements are arranged at a pitch of 1/300 inch, and in order to form an 1:1 inverted image on the photoreceptor by the imaging lens 33, they are placed on the photoreceptor drum l with a width of about 5.5 mm along the drum axis. Expose parallel striped areas. The outer peripheral speed of the photoreceptor drum 1 is constant rotation at 11 mm/s.

The length of exposure in the circumferential direction on the photoreceptor drum 1 made by the exposure head 2 is 5.5 mm, and the reciprocating spiral scanning operation is performed for about 500 m5. In other words, since the photoreceptor drum 1 moves by a distance corresponding to the head's effective exposure length (5.5 mm) during the scanning operation time, the photoreceptor drum 1 is moved without any gaps in the next scanning operation of the exposure head 2. Can be exposed to light.

The configuration of the optical system is shown in FIG. The image forming surface 41 of the exposure section on the photoreceptor drum l is a cylindrical surface. On the other hand, the LED element array 34 is formed on a curved surface so as to form an image on the image forming surface. For this reason, all the LED elements form an image on the photosensitive drum 1 in a focused state and expose the image.

The electrostatic latent image thus formed is developed by a well-known electrophotographic process, transferred to recording paper, fixed, and stored in the paper discharge tray 8.

A second embodiment is shown in FIG. The figure shows L on the light emitting board.
The ED chip configuration is shown. In the first embodiment, the LED elements are formed on a curved surface, but all the LED elements
There is no need for the D elements to be formed on planes of different heights. Each LED element is provided on a stepped surface at an appropriate height, and multiple LED elements are provided on the same surface within the allowable depth of focus to achieve the necessary MTF characteristics required for the optical system. You can also do it like this. In this example, six L
An LED chip 51 having an ED element 52 is provided on a common light emitting substrate 53 provided with a step.

A third embodiment is shown in FIG. The figure shows the LE on the light emitting board.
FIG. 3 is a cross-sectional view showing a D-chip configuration. Common light emitting board 61
4 LEs with 64 LED elements each on top of
The D chip 62 is provided on a surface inclined with respect to a surface perpendicular to the optical axis 63.

[Effects of the Invention] According to the above configuration of the present invention, the exposure source has different heights with respect to the plane perpendicular to the optical axis of the imaging optical system depending on the curved surface of the imaging surface. This has the effect that all the LED elements can be exposed in a focused state, and a high-resolution electrophotographic printer can be realized. This also has the effect of realizing a printer with high image quality.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing the configuration of a printer showing an embodiment of the present invention. FIG. 2 is a perspective view showing the structure of a peripheral portion of a photoreceptor of a printer showing an embodiment of the present invention. FIGS. 3(a) and 3(b) are diagrams showing the configuration of an exposure head used in a printer showing an embodiment of the present invention. FIG. 4 is a diagram illustrating the configuration of the exposure optical system. FIG. 5 shows an LED of an exposure head showing another embodiment of the present invention.
A diagram showing chip arrangement. FIG. 6 is a diagram showing the arrangement of LED chips in an exposure head showing still another embodiment of the present invention. 1 ・ 2 ・ 25 ・ 32° 33 ・ 34 ・ 36 ・ 52 ・ 53, Photoreceptor drum Exposure head guide shaft LED chip Imaging lens LED element array Light emitting board LED element common board and above

Claims (1)

[Claims] It has a photoreceptor made of a photoconductor, an exposure means, and a developing means,
In an electrophotographic printer in which the charged photoreceptor is imagewise exposed by the exposure means to form an electrostatic latent image and visualized by the developing means, the photoreceptor has a curvature at the exposed portion, and the exposure means has a curvature. It has a plurality of light emitting members that can selectively control modulation and an imaging optical system, is supported so as to be movable relative to the photoreceptor, and the light emitting member is arranged in the optical axis direction of the imaging optical system. have different heights with respect to orthogonal planes,
An electrophotographic printer characterized in that the exposure means performs image exposure on a predetermined position on the photoreceptor.