JPH0966626A - Color image forming equipment - Google Patents

Abstract

(57) [Summary] [Purpose] A color image forming apparatus that maintains printing quality and reduces costs. An FG detector that detects a predetermined rotation position of a scanner motor 2 that drives a polygon mirror 1 that scans a photosensitive drum with a laser beam, and relational data between the detection position of the FG detector and the rotation position of the polygon mirror 1. Has a memory 4 for storing the data, and outputs a scanning control signal based on the detection of the FG detector and the data stored in the memory 4 to form a color image.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technical field of a color image forming apparatus for sequentially transferring a plurality of color visible images sequentially formed on an image carrier on a transfer material so as to be transferred.

[0002]

2. Description of the Related Art In recent years, color printers have been used as various means of expression for users. In particular, color laser printers are attracting attention because they have quietness, high printing quality, and high-speed printing. FIG. 3 is an explanatory diagram of the configuration of the color laser printer, and the color image recording operation of the conventional apparatus will be described with reference to FIG.

The photosensitive drum 4 is charged to a predetermined polarity and a predetermined voltage by the charger 3, and the recording paper P stored in the cassette 5 is moved by the paper feed roller 6 at a predetermined timing.
Paper is fed one by one. When the leading edge of the recording paper P is detected by the leading edge detector 7, the image signal VDO for one page is output to the semiconductor laser diode 8 and the image signal VD is output.
The laser light controlled by O is emitted toward the polygon mirror 1 which is rotationally driven by the scanner motor 2. The emitted laser light is horizontally scanned on the photosensitive drum 4 by the polygon mirror 1, the lens 9 and the mirror 10. Further, when the laser beam L is emitted, the signal detected by the photodetector 11 arranged on the scanning axis is output as the beam detect signal BD which becomes the horizontal synchronizing signal. As a result, the laser beam L scans and exposes the photosensitive drum 4 in synchronization with the beam detect signal BD, and a first electrostatic latent image is formed. Next, the developing device 12M develops the first electrostatic latent image to form a magenta first toner image on the photosensitive drum 4. On the other hand, immediately before the recording paper P reaches the transfer start position, a predetermined transfer bias voltage having a polarity opposite to that of the toner is applied to the transfer drum 14, the first toner image is transferred to the recording paper P, and at the same time, the recording paper P is transferred. Transfer drum 1
4 is electrostatically adsorbed. After the transfer is completed, the photosensitive drum 4
The untransferred toner image remaining on the sheet is scraped off by the cleaner 13.

Next, a laser beam L is formed on the photosensitive drum 4.
Thus, a second electrostatic latent image is formed, the formed second electrostatic latent image is developed by the developing device 12C, and a cyan second toner image is formed on the photosensitive drum 4. This second toner image is transferred onto the recording paper P in accordance with the position of the first toner image previously transferred onto the recording paper P.

In the same manner, a third electrostatic latent image is formed on the photosensitive drum 4, the formed electrostatic latent image is developed by the developing device 12Y, and the yellow toner image is similarly aligned and recorded on the recording paper. Transcribed to P. Subsequently, in the same manner as described above, development is performed by the developing device 12BK, and the black toner image is transferred to the recording paper P.

After that, the recording paper P on which the four color toner images are transferred facilitates the separation of the recording paper P by the separation claws 15 and reduces the air discharge at the time of separation, so that the recording paper P accumulates thereon. The electric charge is removed by the charger 16. And
When the leading edge of the recording paper P approaches the separating claw position, the separating claw 15 approaches the transfer drum 14 at a predetermined timing and contacts the surface thereof, and the contact state is maintained. As a result, the recording paper P is separated from its leading end. When the trailing end of the recording paper P is separated, the separation claw 15 separates from the transfer drum 14 and retreats to its original position. Then, the separated recording paper P is fixed by the fixing device 17 and is discharged to the discharge tray 18.

Next, the operation of the laser beam scanning device will be described with reference to the block diagram of FIG. The reference clock from the reference oscillator 19 is divided by the frequency divider 20, and the scanner motor 2 controls the control circuit 21 (shown in the figure) so that the phase difference between the divided clock and the feedback signal from the scanner motor 2 becomes a predetermined phase difference. No built-in known phase control circuit)
Is rotated at a constant speed.

On the other hand, the transfer drum 14 is rotated at a constant speed by a drive motor (not shown), and the recording paper P on the transfer drum 14 is transferred.
Is detected by the detector 7, and the vertical synchronization signal VSY is detected.
The NC is output to the image generator 22. Vertical synchronization signal V
The image signal VDO is sequentially transmitted to the laser 8 in synchronization with the beam detect signal BD after SYNC.

[0009]

However, in the above-mentioned conventional example, a light receiving element such as a photo interrupter is required to detect the BD signal which is a horizontal synchronizing signal for image printing.

As means for solving such a problem,
There is a method to generate a pseudo BD signal from the output of the crystal oscillator, but the shape and distortion of the polygon mirror are different,
In addition, there is a problem in that since rotation occurs at a high speed, uneven rotation occurs, so that a horizontal shift occurs except during ideal rotation.

The present invention has been made to solve the above problems, and an object of the present invention is to provide a color image forming apparatus capable of suppressing the cost without deteriorating the printing quality.

[0012]

Therefore, according to the present invention, a laser beam modulated in accordance with an image signal is polarized by a rotating polygon mirror and is guided to an image carrier to optically scan the image carrier. An optical scanning unit, a developing unit for developing the latent image formed on the image carrier by the optical scanning unit with a recording material of a plurality of colors, a transfer material transporting unit for supporting and transporting the transfer material, and the developing unit. A color image forming apparatus having a transfer means for transferring the obtained visible image to the same transfer material after each color development, and a first detecting means for detecting a predetermined rotational position of a motor for driving the rotary polygon mirror, Second detection means for detecting the rotational position of the rotary polygon mirror, time difference measurement means for measuring the time difference between the output signal from the first detection means and the output signal from the second detection means, and the time difference measurement means When measured Storage means for storing the difference, and synchronization output means the time difference stored in the storage means from the time of detection of said first detection means outputs a pseudo BD signal Once arrived,
The above object is achieved by a color image forming apparatus including a control unit for controlling image formation by using a pseudo BD signal output from the synchronization output unit as a horizontal synchronization signal. .

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention relates to an optical scanning means for polarizing a laser beam printer modulated according to an image signal by means of a rotary polygon mirror and guiding it to an image carrier to optically scan the image carrier. A developing means for developing the latent image formed on the image carrier by the optical scanning means with a recording material of a plurality of colors, a transfer support for supporting and conveying the transfer material, and a visible light obtained by the developing means group. In a color image forming apparatus having a transfer means for transferring an image to the same transfer material after each color development, a first detecting means for detecting a predetermined position of a motor for driving the rotating polygon mirror and a position of the rotating polygon mirror are detected. Second detecting means, a time difference measuring means for measuring a time difference between the output signal from the first detecting means and the output signal from the second detecting means, and a storage means for storing a result measured by the time difference measuring means. When The result stored in the storage means,
It is composed of synchronous output means for outputting in synchronization with the result of the first detection means.

According to the present invention, the predetermined position of the rotary polygon mirror is detected by the first detecting means, and a pseudo horizontal synchronizing signal is generated when the time stored in the storage means has elapsed to perform control.

[0015]

Embodiments of the present invention will now be described in detail with reference to the drawings.

FIG. 1 is a block diagram showing the configuration of a characteristic control portion of an embodiment of the present invention, and FIG. 2 is a time chart for explaining a pseudo BD signal. Since the mechanical structure is similar to that of the conventional example shown in FIG. 3, the illustration thereof is omitted, and the characteristic structure of the color image forming apparatus of the embodiment will be described below with reference to FIGS. 1 and 2.

Reference numeral 1 is a polygon mirror, 2 is a scanner motor, 3 is an FG signal detector, 4 is a memory, 5 is a BD signal generating circuit, and 6 is a scanner motor driving circuit.

In the configuration of the FG detector 3, the Hall element reacts with the magnetic substance installed in the scanner motor and outputs a signal. This output signal is the FG signal.

When the scanner motor 2 rotates, one FG signal is obtained every rotation by the FG detector 3 provided at a predetermined position of the scanner motor.

According to the prior art, the time difference from the FG signal to the BD signal obtained by receiving the horizontal scanning start point of the laser light is defined as t, and when there are n surfaces, t1, for each surface.
Let t2, ..., Tn (see FIG. 2). The values unique to each polygon mirror from t1 to tn are stored in advance in the memory 4
To memorize it. In this embodiment, the above steps are not included,
The obtained memory is used for a control circuit.

The BD signal generation circuit 5 which is a feature of this embodiment
When a FG detector 3 detects an FG signal, a timer starts measuring time, and a pulse is generated when t1 elapses. When t2 has passed from the FG signal, a pulse is generated again,
Similarly, a pulse is generated when t3, t4, ..., Tn have elapsed. When n pulses are generated and the FG signal is detected, the timer is reset, the measurement is restarted from that point, and pulses are similarly generated after t1 to tn. The pulse train generated here is equal to the BD signal of the conventional technique and serves as a horizontal synchronizing signal for image printing.

[0022]

As described above, according to the present invention,
Since it is not necessary to use a detecting means such as a photo interrupter for the horizontal synchronizing signal of an image as in the conventional case, there is an effect that a cost can be reduced and a color image can be formed with good printing quality.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a color image forming apparatus that is an embodiment of the present invention.

FIG. 2 is a time chart illustrating a pseudo BD signal.

FIG. 3 is a diagram illustrating a configuration of a conventional color image forming apparatus.

FIG. 4 is a block diagram showing a configuration of each unit of a conventional color image forming apparatus.

[Explanation of symbols]

 1 polygon mirror 2 scanner motor 3 FG detector 4 memory 5 BD signal generation circuit 6 scanner motor drive circuit 8 semiconductor diode 11 photodetector 19 reference oscillator 20 frequency divider 21 motor control circuit 22 image generator

Claims (1)

[Claims] 1. A light scanning means for polarizing a laser beam modulated in accordance with an image signal by a rotating polygon mirror and guiding it to an image carrier to optically scan the image carrier, and the optical scanning means for scanning the image carrier. Developing means for developing the latent image formed on the image bearing member with a recording material of a plurality of colors, transfer material conveying means for supporting and conveying the transfer material, and the visible image obtained by the developing means is the same after each color development. A color image forming apparatus having a transfer means for transferring onto a transfer material, the first detecting means for detecting a predetermined rotation position of a motor for driving the rotary polygon mirror, and the first detection means for detecting a rotation position of the rotary polygon mirror. Two detection means,
A time difference measuring means for measuring a time difference between an output signal from the first detecting means and an output signal from the second detecting means, a storage means for storing the time difference measured by the time difference measuring means, and the first detecting means When the time difference stored in the storage means has come from the time of detection, the synchronous output means for outputting the pseudo BD signal, and the control for controlling the image formation by using the pseudo BD signal output by the synchronous output means as the horizontal synchronous signal And a color image forming apparatus.