JP2003186256A - Image forming device for electrophotographic device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide image detecting means for an electrophotographic device, which accurately detect a pattern image for alignment adjustment formed on an image carrier and make it possible to obtain more satisfactory accuracy of color superimposition. <P>SOLUTION: The image forming device has optical sensors disposed opposite the front and back of a recording medium in order to detect measurement pattern images in separate colors formed on the front and back of the recording medium by a recorder. The image forming device also has the two image detecting means disposed opposite the corresponding optical sensors and are composed of gap rollers which move the recording medium into the arbitrary effective detection range of the optical sensors. The device further has an arithmetic means which calculates an amount of misalignment of the measurement pattern image in each color based upon the detection result of the corresponding detecting means, and an adjusting means that adjusts, based upon the amount of misalignment, the timing of the emission of light to the image carrier by the recorder. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multicolor image forming apparatus of an electrophotographic apparatus in which a plurality of recording devices are arranged on both sides of a recording medium and images of plural colors are transferred to both sides of the same recording medium. is there.

[0002]

2. Description of the Related Art FIG. 1 is a schematic view of a multicolor image forming apparatus of an electrophotographic apparatus for transferring images of a plurality of colors on both surfaces of the same recording medium in a multiple transfer manner. In FIG. 1, the image carrier 3 that forms a toner image by the electrophotographic process is rotated at a constant speed in the direction of arrow a. The image carrier 3 passes under the charger 4 arranged so as to face its surface,
The surface is uniformly charged. An electrostatic latent image is formed on the surface of the image carrier 3 that is uniformly charged by the light emitted from the exposure unit 5 that is turned on according to the print information signal supplied from the information processing device, and A developing device 6 arranged so as to face each other and having a developing function of adhering fine powder toner to the surface of the image carrier 3 by the electrostatic force of the electrostatic latent image.
As a result, a toner image is formed on the surface of the image carrier 3.

The recording apparatus having the above-described structure has, for example, a total of 8 black and magenta, yellow, and cyan colors along the conveyance direction of the recording medium 1 and on both sides of the recording medium 1.
Individually arranged. The recording medium 1 is nipped and conveyed at a constant speed by a pair of conveying rollers 2 which are in pressure contact with each other. The recording medium 1 comes into contact with the surface of each image carrier 3 so as to transfer the toner image onto the surface thereof. At this time, the transport speed of the recording medium 1 and the transport speed of the image carrier 3 are equal. The toner image formed differently on the surface of the image carrier 3 is transferred to the surface of the recording medium 1 by the transfer device 7 which gives a charge having a polarity opposite to that of the toner image to the back surface of the recording medium 1 which is in contact with the surface of the image carrier 3. Transfer (transcription)
To do. Then, the recording medium 1 having the toner image transferred on its surface
However, the toner image is fused and fixed on the recording medium 1 by passing through the fixing device 9 having a heating function.

When superposing images of different colors on the same position on the recording medium 1, the image bearing of the recording device (for example, the recording device A2 in FIG. 1) on the downstream side with respect to the conveying direction of the recording medium. The timing of irradiating light to form an electrostatic latent image on the body 3 (hereinafter referred to as exposure timing) is recorded with respect to the exposure timing of a recording device (for example, the recording device A1 in FIG. 1) on the upstream side. This can be realized by delaying the distance L between the transfer points of the devices by the time t0 spent for the recording medium 1 to move.

However, since the distance L between transfer points has a variation of ± ΔL due to an error during assembly, the time t0 during which the recording medium moves between the transfer points also has an error of ± Δt. In addition, since the distance M from the exposure point to the transfer point also varies, even if an image of different color is superimposed on the recording medium 1 at the exposure timing as described above, a positional deviation occurs, This causes deterioration of image quality. Therefore, in the conventional image forming apparatus, the following adjustment and control are performed in order to obtain good color matching accuracy.

An optical sensor 8 is installed on the front surface and the back surface of the recording medium 1 by a plurality of recording devices so as to face the recording medium 1 with measurement pattern images for each color.
a and 8b are read, and based on the result, the shift amount of the measurement pattern image for each color is calculated by the calculation means 10,
Further, by adjusting the exposure timing of the image carrier 3 of each recording device by the adjusting means 11 based on the deviation amount, good color matching accuracy on the recording medium 1 is obtained.

[0007]

When the measurement pattern image is detected by the optical sensors 8a and 8b which are installed to face the recording medium 1 on which the measurement pattern image is formed, the recording medium 1 of the recording medium 1 is detected. Occasionally, the gap between the recording medium 1 and the optical sensors 8a and 8b may fluctuate due to fluttering or the like, and accurate detection may not be possible. In the worst case, the recording medium 1 comes into contact with the surfaces of the optical sensors 8a and 8b, and the measurement pattern image is destroyed.

An object of the present invention is to provide an electrophotographic apparatus capable of accurately detecting a measurement pattern image by keeping the gap between the recording medium and the optical sensor constant, and obtaining a better color matching accuracy. To provide the image detection means.

[0009]

The above object is to face a recording medium in order to detect a pattern image for measurement for each color formed on both the front surface and the back surface of the recording medium by a recording device. Optical sensors installed on the front surface and the back surface respectively, and installed facing the optical sensor, and
Two image detection means composed of gap rollers for moving the recording medium within an arbitrary effective detection range of the optical sensor, and a measurement pattern image for each color based on the detection result of the image detection means. This is achieved by having an arithmetic means for calculating the deviation amount and an adjusting means for adjusting the timing of irradiating the image carrier of the recording apparatus with light based on the deviation amount.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. FIG. 2 shows a main part of the present invention. In FIG. 2, the gap roller 13a (or 13b) is
Supported by two arms 14a (or 14b),
Optical sensor 8a (or 8b) via the recording medium 1
It is installed to face. Optical sensor 8a
(Or 8b) is arranged at a position which is farther from the effective detection range of the optical sensor 8a, that is, the gap required for the alignment adjustment operation with respect to the recording medium 1. The shaft of the gap roller 13a (or 13b) is connected to the gap roller moving motor 12a (or 1
Eccentric cam 15a attached to the shaft axis of 2b)
(Or 15b), and the gap roller moving motor 12a (or 12b) rotates so that the gap roller moving motor 12a can move in a direction approaching the optical sensor 8a (or 8b). Two sets of this mechanism are provided to detect the measurement pattern images on the front surface and the back surface of the recording medium, respectively.

The operation when the electrophotographic apparatus is powered on and shifts to the adjusting operation in the above configuration will be described with reference to FIGS. 3 and 4. First, in order to align the surface side of the recording medium 1, first, the gap roller moving motor 12a is driven to move the gap roller 13a in the f direction.
It is held at the position A so as to be within the effective detection range of a. In this way, the fluttering of the recording medium 1 can be suppressed by bringing the recording medium 1 into contact with the optical sensor 8a, and the measurement pattern image transferred onto the recording medium 1 is accurately read. It becomes possible. At this time, the other gap roller 13b is held at a position B away from the optical sensor 8b so as not to contact the recording medium 1. Gap roller 13
This is because when b comes into contact with the recording medium 1, the measurement pattern image formed on the recording medium 1 is rubbed and destroyed. When the adjustment operation on the front side is completed, next, the recording medium 1
To align the back side of the gap roller 1
3a and 13b respectively move to the positions as shown in FIG. 4 so that fluttering of the recording medium 1 can be suppressed as in the case of the front surface side, and the measurement pattern image can be accurately measured by the optical sensor 8b. It becomes possible to read.

During normal printing operation, the gap rollers 13a and 13b are held at the position B where they do not contact the recording medium 1 to destroy the toner images formed on both sides of the recording medium 1. Absent.

[0013]

As described above, according to the present invention, it is possible to accurately detect the measurement pattern images formed on both sides of the recording medium, and to obtain better toner image alignment accuracy. It is possible to provide image detection means for an electrophotographic apparatus.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing an overall configuration of a multiple image forming apparatus of an electrophotographic apparatus.

FIG. 2 is a schematic diagram showing a configuration of an image detecting means which is a main part of the present invention.

FIG. 3 is an explanatory diagram of a position adjustment adjustment operation on the front surface side of the recording medium according to the present invention.

FIG. 4 is an explanatory diagram of a position adjustment adjustment operation on the front surface side of the recording medium according to the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Recording medium, 2 ... Conveying roller, 3 ... Image carrier, 4 ... Charging device, 5 ... Exposure part, 6 ... Developing device, 7 ... Transfer device, 8a,
8b ... Optical sensor, 9 ... Fixing device, 10 ... Computing means,
11 ... Adjusting means, 12a, 12b ... Gap roller moving motor, 13a, 13b ... Gap roller, 14a,
14b ... Arm, 15a, 15b ... Eccentric cam.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Satoshi Aida             Hitachiko, 1060 Takeda, Hitachinaka City, Ibaraki Prefecture             Machine Co., Ltd. F-term (reference) 2H027 DA09 DC01 DE02 DE09 DE10                       EA18 EC03 ED04 ED06 ZA07                 2H028 BA16 BB06                 2H030 AA01 AB02 AD06 BB02 BB16                       BB21 BB43 BB56

Claims (2)

[Claims] 1. An image carrier, charging means for uniformly charging the surface of the image carrier, exposing means for irradiating the image carrier with light according to image information, and electrostatic means for the image carrier. A plurality of recording devices each having a developing unit that develops a latent image and forms a toner image are provided along a conveyance path of a recording medium that is nipped and conveyed by a pair of conveyance rollers that are in pressure contact with each other and on both sides of the recording medium. In a multicolor image forming apparatus in which toner images of different colors are separately arranged and sequentially superimposed on both surfaces of the recording medium, for each color formed on both the front surface and the back surface of the recording medium by the recording apparatus. Optical sensors installed on the front surface and the back surface of the recording medium so as to detect a pattern image, and an optical sensor installed opposite the optical sensor and effective for the optical sensor. The recording medium within the detection range Based on the two image detecting means composed of a gap roller for moving the image, a calculating means for calculating the deviation amount of the measurement pattern image for each color based on the detection result of the image detecting means, and the deviation amount. A multicolor image forming apparatus of an electrophotographic apparatus, comprising: an adjusting unit that adjusts a timing of irradiating the image carrier of the recording apparatus with light. 2. The gap roller is moved and held at a position where the recording medium is pressed against the optical sensor only in the adjustment operation, and the gap between the recording medium and the optical sensor surface is made constant. 2. The multicolor image forming apparatus of an electrophotographic apparatus according to claim 1, wherein the multicolor image forming apparatus is held and is moved / held at a position where it is kept away from the optical sensor during normal printing operation and does not come into contact with the recording medium.