JPH0421877A - Electrophotographic printer - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to an electrophotographic printer.

[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 Publication).

On the other hand, it is also possible to scan by running a plurality of LED elements arranged on a straight line. In this method, while the photoreceptor is continuously running, an exposure head is run in a direction perpendicular to the running direction, and the image-forming optical system performs image exposure of the LED element.

According to this structure, the light source and the photoreceptor can be placed close to each other,
It is possible to downsize the device.

[Problem to be solved by the invention]

With the configuration of the prior art described above, multilevel density gradation control is difficult. In other words, in both methods, it is difficult to control the amount of light emitted by the light source, so the dot size is controlled by the lighting time to give pseudo gradation, and the density value is directly multivalued controlled. That was difficult.

An object of the present invention is to solve this problem and realize an electrophotographic printer capable of multi-level density control.

[Means to solve the problem]

The electrophotographic printer of the present invention includes a photoconductor made of a photoconductor, an exposure device, and a developing device, and the charged photoconductor is imagewise exposed by the exposure device to form an electrostatic latent image, which is then developed by the developing device. In an electrophotographic printer that generates images, the exposure device includes a light emitting member having a plurality of light emitting sources that can selectively control light emission, and continuously transports the photoreceptor, while continuously conveying the photoreceptor. , image exposure is carried out by causing a desired light emitting source to emit light, and is characterized in that it is constructed such that the same location on the photoreceptor is exposed by a plurality of the light emitting sources.

〔Example〕

Next, the present invention will be explained based on examples.

FIG. 2 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 , a transfer device 6 is placed. The charging device 3 is a roller made of conductive rubber, which is brought into contact with the photoreceptor drum 1 while applying a potential to perform contact charging. The developing device 4 rubs the surface of the photoreceptor drum 1 with charged powder toner, adheres the toner according to 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 the charged toner interposed between the photoreceptor drum 1 and the photoreceptor drum 1 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.

FIG. 4 shows members around the photosensitive drum 1. As shown in FIG. The exposure head 2 is guided by a guide shaft 25 and is attached to the photoreceptor drum 1.
The top is scanned while keeping a constant distance from the outer periphery of the photoreceptor drum.

The carriage driving wire 23 is driven by a motor 24 to make it reciprocate. The positions of both the exposure head 2 and the photoreceptor 1 are detected, and the speed of each is controlled by changing slightly from a constant value as necessary, so that the scanning is performed so that a predetermined position of the photoreceptor 1 is exposed. Control behavior. The head 2 is provided with wiring 22 for driving the LED elements. The guide shaft 25 is formed into a 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.

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. A bearing 35 integrated with the carriage 31 is connected to the guide shaft 25.
(shown in FIG. 4) and is movably supported. As shown in FIG. 1, the light emitting board 36 is constructed by mounting an LED chip 42 and a driver IC 41 on a printed circuit board 43 provided with printed wiring.

The LED chips 42 include 64 LED elements 45 per row, which are arranged in a straight line at a pitch of 1/300 inch in a direction perpendicular to the photoreceptor drum axis and can be independently lit.
It has LED element rows 46 and 47 having . That is, 128
LED elements. The imaging lens 33 forms an equilateral inverted image of the LED element rows 46 and 47 on the photoreceptor drum 1.

Next, the printing operation will be explained using FIG. 2. While rotating the photoreceptor drum 1 in the direction of the arrow 10, the photoreceptor drum 1 is brought into contact with the charging device 3 to which a high voltage is applied, and the surface photoconductive layer of the photoreceptor drum 1 is brought into contact with the metal drum of the photoreceptor drum 1.
Charge to -600V. Next, the exposure head 2 selectively removes the charge and forms an electrostatic latent image. While rotating the photosensitive drum 1 in the direction of the arrow 10, the guide shaft 25 described above is rotated.
The exposure head 2 scans a curve along the curve. Exposure head 2
As explained earlier, 64 light-emitting parts per row are arranged in a straight line in a direction perpendicular to the photoreceptor drum axis at a pitch of 1/300 inch, and one-on-one, inverted images are formed. An image is formed on the photosensitive drum by the image lens 33. The outer peripheral speed of the photoreceptor drum is constant rotation at 11 mm/s. One reciprocating operation of the exposure head is performed over 500 m5. In other words, during one scanning operation time, the effective exposure length of the head (5.5 m
Since the photoreceptor drum is rotated by a distance corresponding to m), the photoreceptor drum can be scanned in a stripe pattern without gaps in the next exposure head scanning operation.

In this configuration, the LED element arrays 46 and 47 each scan and expose the same location on the photoreceptor drum 1. First, the first LED element array 47 scans, and then the subsequent second LED element array 46 scans after a certain period of time. Therefore, the same location is exposed twice. The exposed portion performs three-value density control by controlling each LED element in ◯N/◯FF. In other words, three types of control are possible: one LED is ON, two LEDs are ON, and all LEDs are OFF.The surface potential of the exposed area is determined according to each exposure light amount, and the surface potential is The amount of adhered toner is determined accordingly. Therefore, the adhering toner can be controlled and image density can be controlled.

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

Next, a second embodiment will be explained using FIG. 5. In the figure, an exposure head 54 is placed around the photoreceptor drum 51.
is placed. Components other than the exposure head 54 are the same as in the previous embodiment and are not shown. Exposure head 5
An LED chip 53 is mounted on the substrate 52 of No. 4. On the LED chip 53, there are 2560 LEs per row.
LED element rows 55 and 56 consisting of D elements are provided.

The images of the LED element rows 55 and 56 are formed on the photoreceptor 51 by the gradient index lens array 57 and exposed. Since the two rows of LED elements 55 and 56 expose the same part of the photoreceptor drum 51 at a certain time interval, three-value density control is performed by ○N/○FF control of each of these LED elements. I do.

That is, the amount of exposure light can be controlled in three stages: when the LED element array scans twice, when the exposure is performed only once, when the exposure is performed twice, and when the exposure is not performed at all. This allows the surface potential after exposure neutralization to be determined by the surface potential of the unexposed part (potential obtained by the charging process), the surface potential of the exposed part (the surface potential approximately the same as that of the metal drum of the photoreceptor drum 1), and These intermediate surface potentials can be controlled in three stages. By controlling the amount of attached toner depending on these surface potentials, 3
Step-by-step concentration control becomes possible.

A third embodiment is shown in FIG. In the figure, an exposure head 69 is arranged around a photosensitive drum 610 times. Components other than the exposure head 69 are the same as in the previous embodiment and are not shown. Substrates 64 and 65 of exposure head 69
On top, LED chips 66 and 67 are mounted. L.E.
There are 2560 LEs on each D chip 66.67.
An LED element array (not shown) consisting of D elements is provided. The image of this LED element row is captured at the same location 68 on the photoreceptor 61 by the refractive index gradient lens array 62, 63.
image and expose. 0N10 of each of these LED elements
Performs three-value density control using FF control. In this case, since the corresponding LED elements that expose the same area are lit at the same timing, there is no need to set a time difference in the lighting timing, which simplifies circuit configuration and control, and eliminates deviations in the exposure position. It has the following advantages.

In addition, in the configuration of the present invention, as shown in FIG. 7, the exposure portions formed by the first LED element row 46 and the second LED element row 47 are arranged so that the irradiated areas are staggered with respect to each other, It is also possible to configure two dots 71 and 72 to correspond to one dot. In this case, the area can be controlled in two stages to perform pseudo multilevel density gradation control.

Furthermore, by performing exposure using only one of the two LED element arrays, exposure with a resolution of ], /2 can be achieved. That is, an electrophotographic printer whose resolution can be variably controlled can be realized in the same device.

Further, according to this configuration, the light emitting energy per unit area of the LED element 45 only needs to be such that the sum of the two exposure amounts reaches a predetermined exposure amount of the photoconductive layer of the photosensitive drum 1. Therefore, even if the exposure head 2 is scanned at high speed, the necessary exposure energy can be obtained, and there is also the effect that recording can be performed at a higher speed than when using one row of LED elements.

In addition, although the above-mentioned Example showed the case where it comprised by two LED element rows, it is also possible to set it as the structure of multiple rows, such as 3 rows and 4 rows.

〔Effect of the invention〕

According to the above configuration of the present invention, since the photoreceptor is exposed by multiple exposure operations, the amount of exposure light can be multivalued controlled using a light source with a constant amount of light while keeping the area of the exposed portion constant. As a result, it is possible to realize an electrophotographic printer capable of multi-level density control. Furthermore, in order to perform image exposure by multiple exposure operations, a single row of light sources is used.
It also has the effect that a high-speed electrophotographic printer can be realized compared to the case of single exposure.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the configuration of a light emitting board used in a printer showing one embodiment of the present invention. FIG. 2 is a sectional view showing the configuration of a printer showing an embodiment of the present invention. FIG. 3 is a diagram showing the configuration of an exposure head used in a printer showing an embodiment of the present invention. FIG. 4 is a perspective view showing the structure of a peripheral portion of a photoreceptor of a printer showing an embodiment of the present invention. FIG. 5 is a perspective view showing the structure of a peripheral portion of a photoreceptor of a printer showing another embodiment of the present invention. FIG. 6 is a side view showing the configuration of a peripheral portion of a photoreceptor of a printer showing still another embodiment of the present invention. FIG. 7 is a diagram showing the arrangement of exposed parts, showing an embodiment of the present invention. Photosensitive drum exposure head 51.61 58.69 Carriage imaging lens light emitting substrate 52.66.67 54 LED element 47.55.56 1. 2, 42. 45, /I6, LED chip LED element row 52.64.65 Substrate 57. 62. Lens array or above Applicant Seiko Epson Co., Ltd. Agent Patent attorney Kizobe Suzuki and 1 other person

Claims (1)

[Claims] It has a photoreceptor made of a photoconductor, an exposure device, and a development device,
In an electrophotographic printer that performs image exposure on a charged photoconductor using an exposure device to form an electrostatic latent image and visualize it using a developing device, the exposure device includes a plurality of light emitting sources that can selectively control light emission. The device is equipped with a light-emitting member having a light-emitting member, and performs image exposure by causing a desired light-emitting source to emit light at a predetermined position on the photoreceptor while continuously conveying the photoreceptor. An electrophotographic printer characterized in that it is configured to expose the same place on the body.