JPH04130391A - Image forming device - Google Patents

Abstract

PURPOSE:To form a good-quality image with extremely little color slurring by detecting the position of the leading edge of a photosensitive paper on a carrying belt and deciding exposure start timing based on a position signal and a beam detection signal. CONSTITUTION:The leading edge of the photosensitive paper 20 on the carrying belt 10 shields light emitted from an LED 12 at the position of a slit 14a, and a paper leading edge signal is inputted in a timing adjuster. Since the beam detection signal is outputted to an exposing device, the paper 20 is accurately exposed from the position of its leading edge. Thereafter, the paper 20 passes a developing electrode and fed to a stop roller after an electrostatic latent image on the surface thereof is visualized. After removing excess developer remaining on the surface, the excess developer adhering to the outer peripheral surface of the belt 10 is removed, and a stage for one color is completed. At a following stage, the exposure start timing is deviated by taking the position of the leading edge of the photosensitive paper 20 as reference, and exposure is always performed in the same timing.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an image forming apparatus, and more specifically, it charges a photosensitive paper on a conveyor belt that is controlled to move at a constant speed and performs laser scanning exposure. The present invention relates to an image forming apparatus that forms an electrostatic latent image using a method and then supplies a developer to the electrostatic latent image to obtain a visible image.

[Prior Art] Conventionally, in a wet color image forming apparatus, as shown in FIG.
0 is rotatably supported by two drums lla and llb. The following devices are provided in order at positions facing the outer peripheral surface of the conveyor belt 10. First, above the conveyor belt 10, there is a corona charger 41 that applies an electrostatic charge to the photosensitive paper 20 to charge it, and the photosensitive paper 20 charged by the corona charger 41 is exposed to light to form an electrostatic latent image. An exposure device 42 for forming is installed. Further, below the conveyor belt 10, there is a front bath roller 43 that contacts the photosensitive paper 20 to prevent scumming with the front bath liquid, and a developing device 44 that develops the photosensitive paper 20 moistened with the front bath liquid with a developer. (
44Y, 44M, 44C, 44B) and conveyor belt 10
A conveyor belt cleaning device 45 for removing excess developer and fixed/stacked toner adhering to the outer peripheral surface of the conveyor belt cleaning device 45
is located. Furthermore, a static eliminator 46 is provided behind the conveyor belt cleaning device 45 for removing the electric charge remaining on the photosensitive paper 20 after development.

The developing device 44 is composed of a developing electrode 30 that faces the photosensitive paper 20 and supplies a developer, and an aperture roller 31 that removes excess developer adhering to the surface of the photosensitive paper 20. The number of developing solutions required for the copying machine (four in this conventional example) are arranged below the conveyor belt 10.

As shown in the figure, each developing device 44 can be sequentially raised and lowered to a position where the developing electrode 3o faces the conveyor belt 1o with a slight distance therebetween.

At this time, the squeezing roller 31 is pressed against the lower surface of the conveyor belt 10.

Next, the operation of the wet color image forming apparatus will be explained.

Photosensitive paper 20 is fed to the conveyor belt 10 from a paper feeder (not shown), and the photosensitive paper 20 is held on the outer peripheral surface of the conveyor belt 10 . In this state, the drums lla and l
lb is rotated by a drive device (not shown) to move the conveyor belt 10 in the direction of the arrow, and at the same time, the photosensitive paper 20 is first charged with an electrostatic charge applied to its surface by the corona charger 41. After this, the photoreceptor 20 is exposed to the exposure device 4.
After an electrostatic latent image is formed on the surface by 2, the surface is wetted with a pre-bath liquid by a pre-bath roller 43. Subsequently, when the photosensitive paper 20 passes through the developing electrode 30, it is developed with a developer and the electrostatic latent image is visualized. After development, excess developer remaining on the surface of the photosensitive paper 20 is removed and collected by a squeeze roller 31. Furthermore, the charge remaining on the surface of the photosensitive paper 2o is removed by a static eliminator 46, and then the photosensitive paper 2o is moved to the next color process.

A color image can be obtained by repeating the above image forming process as many times as necessary. Furthermore, the start and end timings of each operation in the above steps are determined by detecting detection holes provided in the conveyor belt using a photointerrupter.

[Problems to be Solved by the Invention] However, in the conventional apparatus described above, while the conveyor belt goes around the drum, it is repeatedly bent and flattened along the drum. However, since the exposure timing is determined by detecting the position of the conveyor belt, if the conveyor belt is rotated multiple times and images are sequentially created for each color, color misalignment will occur on the photosensitive paper. There was a problem.

The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide an image forming apparatus that can obtain high-quality images with extremely little color shift.

[Means for Solving the Problems] In order to achieve this object, the image forming apparatus of the present invention includes a position detecting means for detecting the leading edge position of the photosensitive paper on the conveyor belt, and a photosensitive paper obtained by the position detecting means. The apparatus includes timing control means for determining exposure start (sub-scanning) timing based on a paper leading edge position signal and a beam detect signal from a polygon laser scanner unit.

[Operation] In the image forming apparatus of the present invention having the above configuration, the position detection means detects the position of the leading edge of the photosensitive paper on the conveyor belt.

The timing control means determines the exposure start (sub-scanning) timing based on the leading edge position signal of the photosensitive paper obtained by the position detecting means and the beam detect signal of the polygon laser scanner unit.

[Example] Hereinafter, an example in which the present invention is embodied in a wet color image forming apparatus will be described with reference to the drawings.

The structure of the wet color image forming apparatus is the same as that of the conventional example explained using FIG. 3, so the explanation will be omitted, and in this embodiment, the same names and symbols will be used for explanation.

FIG. 1 is a block diagram of an exposure start timing control circuit, and a paper leading edge signal and a beam detect signal of a polygon laser scanner unit are input to a timing adjuster 2, which is a timing control means of the present invention. Further, the timing adjuster 2 includes an exposure device 42 that exposes the photosensitive paper 20 charged by the charger 41 to form an electrostatic latent image.
is connected.

FIG. 2 is a partially enlarged view of the wet color image forming apparatus.
An LED 12 is arranged on the lower side of the conveyor belt 10, and a slit plate 14 having a slit 14a on the upper side and a light receiving element 15 are arranged in a straight line, and the light emitted from the LED 12 is provided on a part of the conveyor belt. The light is configured to pass through the light transmission hole 13 and the slit 14a of the slit plate 14, and enter the light receiving element 15. The LED 12, the light transmitting hole 13, the slit plate 14, and the light receiving element 15 constitute a position detection means for detecting the leading edge position of the photosensitive paper and outputting a paper leading edge signal. Further, the position detecting means is the exposure device 4.
2, it is arranged immediately before the position where the photosensitive paper 20 is exposed.

Further, the light transmitting hole 13 is connected to the conveyor belt 10 at the leading edge position of the paper.
The hole has a diameter larger than the amount of deviation.

Next, the image forming operation of the wet color image forming apparatus in this embodiment will be explained.

When the leading edge of the photosensitive paper 20 held on the outer peripheral surface of the conveying belt 10 comes to the position of the slit 14a of the slit plate 14 as the conveying belt 10 rotates and blocks the light from the LED 12, the paper leading edge signal is adjusted in timing. is input to device 2. The timing adjuster 2 converts the beam detect signal of the first polygon laser scanner unit after the paper leading edge signal is input into an exposure reference timing signal (
It is output to the exposure device 42 as the exposure start timing).

Therefore, exposure is performed accurately from the leading edge position of the paper.

Photosensitive paper 20 exposed at a precise position by exposure device 42
Thereafter, the electrostatic latent image on the surface of the photosensitive paper 20 is visualized by passing through the developing electrode 30 and sent to the aperture roller 31 .

After removing the excess developer remaining on the surface of the photosensitive paper 20, the aperture roller 31 separates from the outer peripheral surface of the conveyor belt 10 as the developing device is transferred to the next process. When the squeezing roller 31 separates from the conveyor belt 10, the excess developer attached to the outer circumferential surface of the conveyor belt 10 is removed by the conveyor belt cleaning device 45, and the process for one color is completed.

Similarly, in the next process, by shifting the exposure start (sub-scanning) timing based on the leading edge position of the photosensitive paper 20, exposure is always performed at the same timing even if the paper edge position deviates relative to the conveyor belt. .

The present invention is not limited to the embodiments detailed above, and various changes can be made without departing from the spirit thereof. For example, it is also effective in a dry image forming apparatus that uses a powder developer.

[Effects of the Invention] As is clear from the detailed description above, according to the present invention, even if the relative positions of the belt and the photosensitive paper on the belt shift during the process, color shift when three or four colors are superimposed can be prevented. can be extremely reduced and high quality images can be obtained.

[Brief explanation of the drawing]

1 to 2 show embodiments embodying the present invention. FIG. 1 is a block diagram of an exposure start timing control circuit, and FIG. 2 is a part of a wet color image forming apparatus. The enlarged view, FIG. 3, is an overall schematic side view of a conventional wet color image forming apparatus. 2 ・ ・ 3 ・ ・ 12 ・ 13 ・ 14 ・ 15 ・ Phase difference detector timing adjuster Exposure device ED Light transmission hole slit light receiving element

Claims (1)

[Claims] 1. After forming an electrostatic latent image by charging a photosensitive paper on a conveyor belt that is controlled to move at a constant speed and performing laser scanning exposure, a developer is applied to the electrostatic latent image. An image forming apparatus that obtains a visible image by supplying the photosensitive paper to the conveyor belt includes a position detection means for detecting the leading edge position of the photosensitive paper on the conveyor belt, and a leading edge position signal of the photosensitive paper obtained by the position detection means and a beam of a laser scanner unit. An image forming apparatus comprising: timing control means for determining exposure start timing based on a detect signal.