JPH11227250A - Apparatus and method for forming image - Google Patents

Abstract

PROBLEM TO BE SOLVED: To generate copy images of high quality at high speed without the need of setting a new synchronous control means by controlling a first reference clock signal for driving a polygon motor and a second reference clock signal for forming images by the same reference clock signal. SOLUTION: A scan start reference signal (BD signal used as a horizontal synchronous signal) is generated by a laser light of a polygon mirror 103 reflected for every screen. A cycle of the BD signals is determined by a rotational cycle of the polygon mirror 103. The polygon mirror 103 is coupled to a rotary shaft of a polygon motor 111 which is a pulse motor, and the polygon motor 111 is driven by a control circuit 112. The polygon motor control circuit 112 feeds back in the PLL, inputting a polygon motor rotation control clock 122 obtained by dividing a clock signal generated from a reference clock 120 as an external rotation control signal by a frequency divider 121.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus provided with a scanning device using a laser, and relates to a digital electrophotographic system for charging, exposing and developing a photosensitive medium and transferring the image to a recording medium or an intermediate transfer member. Image forming apparatus and method.

[0002]

2. Description of the Related Art Conventionally, in an image forming apparatus for forming an image by an electrophotographic system, a laser beam is scanned on a photoreceptor, and the intensity of the laser beam and the lighting time for each pixel are changed according to the value of an input signal. Modulation forms an electrostatic latent image on the photoreceptor. The electrostatic latent image on the photoreceptor is developed by a developing device and transferred to a recording medium, fixed, or transferred once to an intermediate transfer member, and then transferred and fixed to the recording medium. Becomes

A laser beam emitted from a laser light emitting element is reflected by a rotating and driven polygon mirror to perform scanning.

Conventionally, a polygon motor that drives a polygon mirror that drives a polygon mirror for scanning a laser and an image clock that is a reference signal that drives a laser to form an image operate asynchronously with each other. Therefore, it is necessary to control the phase between the BD signal, which is the writing position reference signal in the main scanning direction, and the image clock in a predetermined relationship. Conventionally, the following method has been proposed for this synchronization control method.

A first method is to use a BD signal as a reset signal for an oscillation source of an image clock. This will be described with reference to FIG.

A source clock signal generated by a crystal oscillator or the like 1000 is temporarily input to a clock generator 2000 such as a multiplier constituted by a PLL (phase comparator) and the output is used as an image clock. An example in which the BD signal is a reset signal of the clock generator will be described with reference to FIG.

Before the BD signal is input, the source clock signal which is the input of the clock generator and the image clock signal which is the output are the same signal. When the BD signal is input, the PLL in the clock generator is reset, and the oscillation of the image clock stops for a predetermined time. FIG. 2 shows an example in which the clock generator 2000 is reset at the rise of the BD signal and the oscillation stops. Then, the image clock is output after a predetermined time (synchronization control period).
In this case, the synchronization control time of the clock generator 2000 is the same for each reset input, and after the synchronization control time, the image clock is output at a fixed phase with the BD signal.

A second method is a means for inputting a BD signal to a flip-flop and using the BD signal resynchronized with a clock obtained by multiplying the image clock as a horizontal writing reference signal. FIG. 3 shows a circuit configuration of the second method.

[0009]

However, in the case of the first method, an image clock is not output unless a predetermined time has elapsed after the input of the BD signal. Therefore, there is a drawback that the waiting time until the writing of the image is increased, and it is difficult to speed up the image forming time.

In the second method, as shown in FIG. 4, the synchronized BD signal has a variation of one clock cycle of the multiplied clock compared to the timing of the original BD signal. become. If the multiplication factor is sufficiently increased, the variation will be reduced, but there are restrictions on the circuit operation,
There is a limit in increasing the frequency of the clock. Therefore, there is a disadvantage that it is difficult to improve the quality of the formed image.

In view of the above, an object of the present invention is to provide an image forming apparatus and method capable of contributing to an improvement in image quality and an improvement in image forming speed.

[0012]

In order to achieve the above object, a first aspect of the present invention is a reference clock signal generating means for generating a reference clock signal in an image forming apparatus for forming an image by an electrophotographic method. And control means for controlling the rotation of the polygon motor based on the first reference clock signal; and image forming means for performing image formation based on the second reference clock signal, wherein the first reference clock signal and the second reference A clock signal is generated from the reference clock signal.

According to a second aspect of the present invention, in the image forming apparatus according to the first aspect, there is further provided a first signal generating means for generating the first reference clock signal by dividing the frequency of the reference clock signal, The control means controls the BD signal and the first reference clock signal so as to have a predetermined phase relationship.

According to a third aspect of the present invention, in the image forming apparatus according to the second aspect, the second signal generating means is separate from the first signal generating means, and wherein the second reference clock signal is used as the reference clock signal. There is further provided a second signal generating means for generating the signal by dividing the signal, wherein a dividing ratio for creating the first reference clock signal is different from a dividing ratio for creating the second reference clock signal. It is characterized by the following.

According to a fourth aspect of the present invention, in the image forming apparatus according to the first aspect, there is further provided a first signal generating means for generating the first reference clock signal by dividing the reference clock signal, The control means controls the FG signal of the polygon motor and the first reference clock signal so as to have a predetermined phase relationship.

According to a fifth aspect of the present invention, in the image forming apparatus according to the fourth aspect, the number m of faces of the polygon mirror to be driven by the polygon motor and the number of pulses of the FG signal generated during one rotation of the polygon motor. The relationship with n

[0017]

When m / n = N (N is an integer), an image is formed using all the surfaces of the polygon mirror, and

[0018]

## EQU6 ## When m / n ≠ N, an image is formed using the same surface of the polygon mirror.

According to a sixth aspect of the present invention, there is provided an image forming method for forming an image by electrophotography, wherein a reference clock signal is generated, a rotation of a polygon motor is controlled based on the first reference clock signal, and a second reference clock signal is generated. Forming an image based on the first reference clock signal and the second
A reference clock signal is created from the reference clock signal.

According to a seventh aspect of the present invention, in the image forming method according to the sixth aspect, the first reference clock signal is created by dividing the reference clock signal, and a BD signal and the first reference clock signal are generated. Is controlled so that a predetermined phase relationship is established between the two.

According to an eighth aspect of the present invention, in the image forming method according to the seventh aspect, the second reference clock signal different from the first reference clock signal is created by dividing the frequency of the reference clock signal. The frequency division ratio for generating the first reference clock signal is different from the frequency division ratio for generating the second reference clock signal.

According to a ninth aspect of the present invention, in the image forming method according to the sixth aspect, the first reference clock signal is created by dividing the frequency of the reference clock signal, and the FG signal of the polygon motor and the FG signal are generated. It is characterized in that control is performed so as to have a predetermined phase relationship with one reference clock signal.

According to a tenth aspect of the present invention, in the image forming method according to the ninth aspect, the number m of faces of the polygon mirror to be driven by the polygon motor and the number of pulses of the FG signal generated during one rotation of the polygon motor. The relationship with n

[0024]

When m / n = N (N is an integer), an image is formed using all surfaces of the polygon mirror, and

[0025]

## EQU8 ## When m / n ≠ N, an image is formed using the same surface of the polygon mirror.

[0026]

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

(Embodiment 1) FIG. 8 is a schematic sectional view of a color image forming apparatus according to an embodiment of the present invention.

This embodiment has a digital color image reader section at the top and a digital color image printer section at the bottom. In the reader section, the original 30 is placed on an original platen glass 31 and is exposed and scanned by an exposure lamp 32, so that a reflected light image from the original 30 is condensed on a full color sensor 34 by a lens 33, and a color separation image signal is output. Get. The color-separated image signal is processed by a video processing unit (not shown) through an amplifier circuit (not shown) and sent to a printer unit.

In the printer section, a photosensitive drum 1 as an image carrier is rotatably supported in the direction of an arrow. A pre-exposure lamp 11, a corona charger 2, a laser exposure optical system 3, and a potential sensor 12 are provided around the photosensitive drum 1. , Four developing units 4y, 4c, 4m, 4Bk of different colors, and a drum light amount detecting unit 1
3. The transfer device 5 and the cleaning device 6 are arranged.

In the laser exposure optical system 3, an image signal from the reader unit is converted into an optical signal by a laser output unit (not shown), and the converted laser light is converted into a polygon mirror 3a.
And is projected on the surface of the photosensitive drum 1 through the lens 3b and the mirror 3c.

When forming an image on the printer unit, the photosensitive drum 1
Is rotated in the direction of the arrow to uniformly charge the photosensitive drum 1 after charging by the pre-exposure lamp 11 by the charger 2, and irradiate the light image E for each separation color to form a latent image.

Next, a predetermined developing device is operated to develop the latent image on the photosensitive drum 1 to form a toner image on the photosensitive drum 1 using a resin as a base. The developing device has an eccentric cam 24.
The operations of y, 24c, 24m, and 24Bk make it possible to selectively approach the photosensitive drum 1 in accordance with each separation color.

Further, the toner image on the photosensitive drum 1 is
The recording material is transferred from a recording material cassette 7 to a recording material supplied to a position facing the photosensitive drum 1 via a transfer system and a transfer device 5. In the present embodiment, the transfer device 5 includes a transfer drum 5a, a transfer charger 5b, and an adsorption charger 5 for electrostatically adsorbing a recording material.
A recording material carrying sheet made of a dielectric material is provided on an opening area of a peripheral surface of a transfer drum 5a which is rotatably driven and has a suction roller 5g, an inner charger 5d, and an outer charger 5e opposed to the transfer roller 5c. 5f is integrally extended in a cylindrical shape. The recording material supporting sheet 5f uses a dielectric sheet such as a polycarbonate film.

As the transfer device in the form of a drum, that is, the transfer drum 5a is rotated, the toner image on the photosensitive drum is transferred by the transfer charger 5b onto the recording material carried on the recording material carrying sheet 5f.

As described above, a desired number of color images are transferred to the recording material sucked and conveyed to the recording material carrying sheet 5f to form a full-color image.

In the case of forming a full-color image, when the transfer of the toner images of the four colors is completed in this way, the recording material is separated from the transfer drum 5a by the action of the separating claw 8a, the separating push-up roller 8b and the separating charger 5h. Roller fixing device 9
The paper is discharged to the tray 10 via the. On the other hand, after the transfer, the photosensitive drum 1 is subjected to the image forming process again after the residual toner on the surface is cleaned by the cleaning device 6.

When forming images on both sides of a recording material,
Immediately after the fixing device 9 is ejected, the conveyance path switching guide 19 is driven, and once guided to the reversing path 21a via the conveyance vertical path 20, the rear end of the reversing roller 21b is moved forward by the reverse rotation of the reversing roller 21b. And is retracted in the direction opposite to the direction in which the sheet is fed, and stored in the intermediate tray 22. Thereafter, an image is formed on the other surface again by the above-described image forming step.

Further, in order to prevent scattering of powder on the recording material carrying sheet 5f of the transfer drum 5a and adhesion of oil on the recording material, etc., the fur brush 14 and the fur brush via the recording material carrying sheet 5f are used. The cleaning is performed by the action of the backup brush 15 facing the oil removal roller 16 and the backup brush 17 facing the oil removal roller 16 via the oil removal roller 16 and the recording material carrying sheet 5f. Such cleaning is performed before or after image formation, and at any time when a jam (paper jam) occurs.

In this embodiment, the gap between the recording material carrying sheet 5a and the photosensitive drum 1 is reduced by operating the eccentric cam 25 at a desired timing and operating the cam follower 5i integrated with the transfer drum 5a. The configuration can be set arbitrarily. For example, during standby or when the power is off, the interval between the transfer drum and the photosensitive drum is increased.

FIG. 1 is a schematic view of a portion for forming, developing and transferring a latent image by laser irradiation of the color image forming apparatus in the present embodiment. The surface of the photosensitive drum 101 is uniformly charged by a charging device (not shown), and the laser light source 1 is charged.
02 and the photosensitive drum 10
1 is exposed to form an electrostatic latent image corresponding to the image information. The laser beam scans on the photosensitive drum 101 via the polygon mirror 103 and the f-θ lens 104. At one end of the photosensitive drum 101, a BD sensor 105, which is a photo sensor, is arranged. The laser beam reflected on each surface of the polygon mirror 103 is used as a reference signal for starting scanning (used as a horizontal synchronization signal and called a BD signal). ). Therefore, the period of the BD signal is the polygon mirror 103
Can be determined by the rotation cycle. Polygon mirror 10
Numeral 3 is connected to a rotation axis of a polygon motor 111 which is a pulse motor, and the pulse motor 111 is driven by a control circuit 112 thereof. The polygon motor control circuit 112 performs feedback of the PLL system, and inputs a polygon motor rotation control clock 122 obtained by dividing a clock signal generated from the reference clock 120 by a frequency divider 121 as an external rotation control signal.

A transfer drum 106 and a developing device for each developing color (not shown) are provided around the photosensitive drum 101, and the toner image developed by the developing device is recorded on a recording sheet 107 held by the transfer drum 106. The image is transferred by a transfer unit (not shown) at the transfer position. A mark 109b indicating a reference position is provided at an end of the transfer drum 106, and a sensor 109a is disposed at a predetermined reference position on the movement locus of the mark. The passing time of the sheet at the reference position can be known from the output itop signal 110 from the sensor 109a. The transfer drum 106 is connected to a rotation shaft of a drum drive motor 114 which is a pulse motor, and the drum drive motor (pulse motor) 114 is driven by a control circuit 115 thereof. The control circuit 115
LL feedback is performed, and the reference clock is stored internally.

The outputs of these sensors, that is, the BD signal and the itop signal are supplied to the image writing timing control circuit 1.
At the corrected timing, the image signal which is also input to the image writing timing control circuit 131 is applied to the photosensitive drum 101 as laser modulated light.
An image clock 125 serving as a reference for the image signal is generated by dividing the frequency of a clock signal generated from an external reference clock 120 by a frequency divider 123.

The polygon motor driving motor 111 is
A BD signal is input to detect a rotation speed, and is controlled by a control circuit of a PLL drive system. That is, the reference clock is frequency-divided to an appropriate frequency, and the motor is driven so as to eliminate the deviation of the frequency pulse from the BD signal.

(Embodiment 2) In the first embodiment, the BD signal is used as the rotation detection signal of the polygon mirror 111, but the FG signal (pulse signal indicating the number of rotations) 52 is used instead.
The same effect can be obtained even if 5 is used. FIG. 5 shows the configuration, except for the above, and the description is omitted.

When the FG signal is used, the following condition occurs on the surface of the polygon mirror to be irradiated with the laser beam, depending on the relationship between the number of surfaces of the polygon mirror 103 and the number of FG pulses generated per rotation of the polygon mirror 103.

First, the number m of polygon faces and the number n of FG pulses are

[0047]

In the case of m / n = N (N: integer), it is possible to form an image by using all the surfaces irradiated with the laser. FIG. 6 shows an example in which, when the number of FG pulses generated per rotation is four, an image is formed using all surfaces using an eight-sided polygon mirror. Also, in this case, every other plane (eg, first, third, fifth, seventh), every third plane (eg, first, fifth), or a predetermined one plane is used every other rotation. The same effect can be obtained by doing so.

Second, the number m of polygon faces and the number n of FG pulses
But

[0049]

In the case of m / n ≠ N (N: an integer), an image can be formed using one predetermined surface for one rotation of the polygon mirror. Fig. 7 shows an 8-sided polygon mirror with 1
In the case where the number of FG pulses generated per rotation is 3, an example in which image formation is performed by one rotation and using only the first surface is shown.
In this case, it is apparent that the same surface selected at the start of image formation may be used until the end of image formation.

[0050]

As described above, according to the first to tenth aspects of the present invention, the first reference clock signal for driving the polygon motor and the second reference clock signal for image formation are the same reference clock signal. , The second reference clock signal, the so-called image clock, and the BD signal have a synchronous relationship from the time of generation, so that it is not necessary to newly provide a synchronization control means, and a high-speed, high-quality copy image can be generated. it can.

Further, since the first and second reference clock signals that are different from each other are generated from the same reference clock signal, it is possible to arbitrarily create suitable synchronization signals having different periods. Furthermore, the frequency of performing image formation using the same surface of the polygon mirror increases, and uniform image quality can be provided.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a control circuit of a first conventional control method.

FIG. 2 is a timing chart for explaining a first conventional control method.

FIG. 3 is a circuit diagram showing a control circuit of a second control method of a conventional example.

FIG. 4 is a timing chart for explaining a circuit operation of a conventional example.

FIG. 5 is a configuration diagram schematically illustrating a system configuration according to a second embodiment of the present invention.

FIG. 6 is an explanatory diagram showing the contents of drive control of a polygon mirror according to Embodiment 2 of the present invention.

FIG. 7 is an explanatory diagram showing the contents of drive control of a polygon mirror according to Embodiment 2 of the present invention.

FIG. 8 is a cross-sectional view schematically showing a mechanical structure according to the embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1, 101 Photosensitive drum 2 (Corona) charging device 3 Laser exposure optical system 5 Transfer device 6 Cleaning device 7 Recording material cassette 9 Fixing device 10 Tray 12 Potential sensor 13 Drum light amount detecting means 31 Platen glass 32 Exposure lamp 33 Lens 34 Color Sensor 102 Laser light source 103 Polygon mirror 106 Transfer drum 111 Pulse motor 114 Drum drive motor 112 (Polygon motor) control circuit 120 Reference clock 121, 123 Divider

Claims (10)

[Claims] 1. An image forming apparatus for forming an image by an electrophotographic method, comprising: a reference clock signal generating means for generating a reference clock signal; a control means for controlling rotation of a polygon motor based on a first reference clock signal; (2) An image forming apparatus, comprising: an image forming unit configured to form an image based on a reference clock signal, wherein the first reference clock signal and the second reference clock signal are created from the reference clock signal. 2. The image forming apparatus according to claim 1, further comprising: first signal generating means for generating said first reference clock signal by dividing said reference clock signal, wherein said control means is a BD. An image forming apparatus, wherein control is performed such that a signal and the first reference clock signal have a predetermined phase relationship. 3. The image forming apparatus according to claim 2, wherein said second signal generating means is separate from said first signal generating means, and divides said second reference clock signal by said reference clock signal. And a frequency dividing ratio for generating the first reference clock signal is different from a frequency dividing ratio for generating the second reference clock signal. Image forming device. 4. The image forming apparatus according to claim 1, further comprising: first signal generating means for generating said first reference clock signal by dividing said reference clock signal, wherein said control means includes: An image forming apparatus, wherein control is performed such that a predetermined phase relationship is established between an FG signal of a polygon motor and the first reference clock signal. 5. The image forming apparatus according to claim 4, wherein the relationship between the number m of surfaces of the polygon mirror to be driven by the polygon motor and the number n of pulses of the FG signal generated during one rotation of the polygon motor is determined. When m / n = N (N is an integer), image formation is performed using all surfaces of the polygon mirror, and when m / n ≠ N, the polygon is formed. An image forming apparatus for forming an image using the same surface of a mirror. 6. An image forming method for forming an image by an electrophotographic method, wherein a reference clock signal is generated, rotation of a polygon motor is controlled based on a first reference clock signal, and image formation is performed based on a second reference clock signal. Forming the first reference clock signal and the second reference clock signal from the reference clock signal. 7. The image forming method according to claim 6, wherein the first reference clock signal is created by dividing the reference clock signal, and a predetermined interval is provided between a BD signal and the first reference clock signal. An image forming method characterized by performing control so as to have a phase relationship of: 8. The image forming method according to claim 7, wherein the second reference clock signal different from the first reference clock signal is created by dividing the reference clock signal, and the first reference clock signal is generated. An image forming method, wherein a frequency division ratio for generating a clock signal is different from a frequency division ratio for generating the second reference clock signal. 9. The image forming method according to claim 6, wherein the first reference clock signal is generated by dividing the reference clock signal, and the FG signal of the polygon motor and the first reference clock signal are generated. An image forming method for controlling the image forming apparatus to have a predetermined phase relationship. 10. The image forming method according to claim 9, wherein the relationship between the number m of surfaces of the polygon mirror to be driven by the polygon motor and the number n of pulses of the FG signal generated during one rotation of the polygon motor is determined. When m / n = N (N is an integer), image formation is performed using all surfaces of the polygon mirror, and when m / n ≠ N, the polygon is formed. An image forming method, wherein an image is formed using the same surface of a mirror.