JPH0949974A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To simplify the control concerning image-forming. SOLUTION: Polygon mirrors respectively rotated by respective polygon motors are constituted in the same specification. In the case where respective polygon motor drivers 60BK, 60C, 60M and 60Y control the revolving speed of the respective polygon motors according to the same reference frequency signal (control signal) and any of the respective polygon motors attains normal revolving speed within a specified time, only image-forming in a color corresponding to the polygon motor which attains the normal revolving speed is permitted. In the case where any of the polygon motors does not attain the normal revolving speed within the specified time, such error information that abnormality occurs in the polygon motor which does not attain the normal revolving speed, is displayed. It is acceptable to inhibit all image-forming during a period till attaining the normal revolving speed from respectively starting the rotation of the polygon motors.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention uses a polygon mirror rotated by a plurality of polygon motors to periodically deflect laser beams emitted from a plurality of semiconductor lasers to scan a photosensitive member. The present invention relates to an image forming apparatus that forms an image of a plurality of colors.

[0002]

2. Description of the Related Art In recent years, image forming apparatuses such as digital two-color (for example, black and red) copying machines, digital color copying machines, and printers (including those in which a controller is connected to a digital color copying machine) have gained considerable momentum. It is becoming popular in the market.

Among these, the digital color copying machine is
Generally, the lower surface (image surface) of a document is scanned to read R (red), G (green), and B (blue) image data, and the image data is BK (black), M (magenta), and Y (yellow). , C (cyan) image data, and a polygon mirror rotated by a polygon motor is used to periodically deflect the laser beam emitted from the semiconductor laser in accordance with the image data of four colors, so that the photosensitive member A body drum or a photoconductor belt) is scanned to form an image of each color.

That is, since electrostatic latent images are sequentially formed on the surface of the photosensitive member by exposure scanning with a laser beam, toner is attached to each of the electrostatic latent images by a developing unit of a corresponding color to visualize it. And each toner image is sequentially transferred onto a transfer drum or a transfer belt, which is disposed so as to face the photoconductor, and a color copy is obtained.

In such a digital color copying machine, since an image forming (image forming) operation is required for the number of colors, the speed of the entire system must be increased in order to increase the number of copies. However, increasing the speed of the system requires not only the improvement of the developing ability but also the speed of the writing system and the image processing system for modulating the laser beam, which is a technically difficult problem.

On the other hand, when the image forming unit (photoreceptor or the like) corresponding to four colors is provided, the system speed can be suppressed and a large number of copies can be made.
In order to realize such a system, a plurality of polygon mirrors are rotated by one polygon motor, and laser beams emitted from a plurality of semiconductor lasers are periodically deflected by using the respective polygon mirrors. A type in which four-color image formation is performed by scanning each of the photoconductors is conceivable. According to this, the time required to form the latent images of four colors is 1/4 of the type of one image forming unit.

Further, the four polygon mirrors are rotated by the four polygon motors, and the laser beams emitted from the four semiconductor lasers are periodically deflected using the respective polygon mirrors to scan the respective photoconductors. A type in which four-color image formation is performed is conceivable. This has a merit that a small-sized polygon mirror (having a small moment of inertia) can be used as compared with a type in which four polygon mirrors are rotated by one polygon motor, so that high-speed exposure scanning can be performed.

[0008]

However, on the other hand, since there are four polygon motors, the synchronous control of writing and the image formation such as control (processing method) when an abnormality occurs in any of the polygon motors are involved. There was a problem that control became complicated. The present invention has been made in view of the above points, and it is an object of the present invention to simplify control related to image formation in an image forming apparatus including a plurality of polygon motors, which are expected to become popular in the future.

[0009]

In order to achieve the above-mentioned object, the present invention uses a polygon mirror rotated by a plurality of polygon motors to periodically emit laser beams emitted from a plurality of semiconductor lasers. In an image forming apparatus for deflecting and scanning each photoconductor to form an image of a plurality of colors, a plurality of motor control means for controlling the number of revolutions of each polygon motor by the same control signal are provided, and each polygon mirror. Are configured with the same specifications.

Further, it is preferable to provide means for inhibiting all image formation from the start of rotation of each polygon motor until the steady rotation speed is reached. Further, it is preferable to provide a means for displaying error information when one of the polygon motors does not reach the steady rotation speed within a predetermined time. In this case, if one of the polygon motors does not reach the steady speed within a predetermined time, error information indicating that an abnormality has occurred in the polygon motor that has not reached the steady speed is displayed. Is desirable.

Alternatively, when any one of the polygon motors reaches the steady rotation speed within a predetermined time, a means is provided for permitting only the image formation of the color corresponding to the polygon motor having reached the steady rotation speed. You may do it.

[0012]

Embodiments of the present invention will be specifically described below with reference to the drawings. FIG. 2 is a schematic configuration diagram showing an example of a mechanical section of a digital color copying machine embodying the present invention.

This digital color copying machine includes a scanner 1 for reading an image of an original, an image processing section 2 for performing color conversion processing on the image data read by the scanner 1, and each color from the image processing section 2. The printer 3 performs an image forming operation according to the image data and various driving signals and forms an image on the transfer paper.

A document pressing plate (not shown) is provided on the upper portion of the scanner 1, and the document is set on the contact glass 4 by opening the document pressing plate upward.
By closing the document pressing plate, the document can be fixed at the set position.

When a start key (not shown) is pressed in that state, the scanner 1 starts image reading of the original on the contact glass 4. That is, the illumination lamps 5, 5
The carriage integrated with the first mirror 6 is reciprocally moved in the horizontal direction to optically scan (scan) the lower surface (image surface) of the document set on the contact glass 4.

As a result, the reflected light image from the original surface is reflected by the first mirror 6, the second mirror 7, the third mirror 8 and the lens 9.
Is incident on the dichroic prism 10 via the light source, and is split into light of three types of wavelengths of R (red), G (green), and B (blue), and each color sensor 11R (red) corresponding to each wavelength light. Images), 11G (for green), and 11B (for blue).

Each color sensor 11R, 11G, 11B
Converts the formed reflected light image into R, G, B image data (image signal) and outputs the image data to the image processing unit 2. The image processing unit 2 colors the R, G, B image data. After conversion processing, BK (black), C (cyan), M (magenta),
The image data is converted into Y (yellow) image data, and each image data is sent to the laser writing unit of the printer 3.

The laser writing unit has polygon mirrors 13BK, 13C and 13 rotated by four polygon motors 12BK, 12C, 12M and 12Y, respectively.
Laser beams emitted from four semiconductor lasers (not shown) are periodically deflected by using M and 13Y to scan on the photoconductor drums 14BK, 14C, 14M and 14Y. Here, each polygon mirror 13BK, 13
C, 13M, and 13Y have the same specifications (number of surfaces, radius, surface accuracy, etc.).

Around the photoconductor drum 14BK for the BK of the printer 3, for example, known portions such as a charging charger 15BK, a developing device 16BK, a transfer charger 17BK, etc. for executing an image forming process are provided. Photoreceptor drum 1 by charging charger 15BK
The surface of 4BK is uniformly charged, and a laser beam from the polygon mirror 13BK is irradiated onto the surface of the 4BK for exposure to form an electrostatic latent image of a BK optical image thereon, and then toner is attached by the developing device 16BK. To visualize.

Other C, M, Y photoconductor drums 14C,
Similarly, around 14M and 14Y, the charging chargers 15C and 15C for executing the image forming process, respectively.
M, 15Y, developing devices 16C, 16M, 16Y, transfer chargers 17C, 17M, 17Y and the like are provided. In this embodiment, the negative / positive development process method (reversal development process method) is adopted.

In the printer 3, the paper feed cassettes 19 are removably attached to the upper and lower two stages on the side surface, and the transfer papers housed in the paper feed cassettes 19 are provided in the upper portions of the paper feed end sides from any of the paper feed cassettes. The paper roller 18 feeds the paper, and the registration roller pair 20 sends the paper to the transfer / transport belt 21 at a predetermined timing.

The transfer / conveyance belt 21 is formed of a dielectric film such as polyester or a rubber material such as urethane, and is charged by a belt charger 24 provided on the surface thereof so as to adsorb the transfer paper. Then, the transfer paper sent by the pair of registration rollers 20 is electrostatically adsorbed on the surface of the belt and is accurately carried at a predetermined carrying speed.

The transfer paper conveyed by the transfer / conveyance belt 21 is sequentially sent to the photoconductor drums 14BK, 14C, 14M, 14Y on which toner images are formed, and the transfer chargers 17BK, 17C, 17
The toner images are sequentially transferred by M and 17Y. The transfer sheet onto which the toner image (image) has been transferred is fixed by the fixing roller 22 and is discharged by a discharge roller 23 to a discharge tray or the like (not shown) outside the apparatus.

3 and 4 are block diagrams showing an example of the configuration of the control system of the printer 3. In this printer 3, 40 is a CPU (central processing unit), ROM, RAM,
It is a main control unit using a microcomputer including I / O and controls the printer 3 as a whole.

On the input side of the main control section 40, a paper discharge sensor 41 for detecting the discharge of the transfer paper to the outside of the machine, a paper end sensor 42 for detecting the presence or absence of the transfer paper in the paper feed cassette 19, and a register. A registration sensor 43 for controlling the sheet feeding to the roller pair 20, a cassette size sensor 44 for detecting the cassette size, and photo sensors 45BK, 45C for detecting the densities of the toners BK, C, M and Y, respectively.
45M and 45Y are connected.

At the output side of the main controller 40, a charging high voltage power source 48 for applying a charging voltage to each of the charging charges 15BK, 15C, 15M and 15Y, and a transfer charger 1.
Transfer high voltage power supply 49 for applying transfer voltage to 7BK, 17C, 17M and 17Y, and belt charge removal charger 4
A belt charge removal high-voltage power supply 50 that applies a charge removal voltage to 7 and a heater control unit 52 that controls the energization of the heaters 51, 51 provided in the fixing roller 22 are connected.

Further, the main motor 53 is rotated and the photosensitive drums 14BK, 14C, 14M, 14Y,
Transfer / transport belt 21 and toner supply roller 29B
DC for rotating K, 29C, 29M, 29Y, etc.
A DC motor driver 55 that drives the motor 54 is connected.

Further, the image data (video data) from the image processing unit 2 is fetched, and the semiconductor lasers 57BK, 57C, 57M and 57Y for the respective colors are passed through the LD driver 58.
ON / OFF control is performed, and the polygon motors 12BK, 12C, 12M and 12Y are respectively passed through the polygon motor drivers 60BK, 60C, 60M and 60Y.
A video control unit 56 for controlling ON / OFF and rotation speed is connected.

Furthermore, the developing devices 16BK, 16C,
A developing bias high-voltage power supply 61 for applying a developing bias voltage to the developing sleeves 26BK, 26C, 26M, and 26Y provided in 16M and 16Y, respectively, and a developing device 16
Toner supply rollers 29BK, 29C, 29M, and 29Y provided in BK, 16C, 16M, and 16Y, respectively.
Replenishment bias high voltage power supply 6 for applying replenishment bias voltage to
2 and toner replenishing rollers 29BK, 29C, 29M, 2
The clutches 63BK, 63C, 63M, 63Y for transmitting the power of the DC motor 54 are connected to 9Y.

Further, the main control section 40 is connected with an operation panel 65 constituted by a key switch for inputting various information and a display for displaying various information including error information described later. There is.

FIG. 5 shows a polygon motor driver 60BK.
3 is a block diagram showing a configuration example of FIG. Note that the other polygon motor drivers 60C, 60M, and 60Y have the same configuration as that in FIG. 5, and therefore their illustration and description are omitted. The polygon motor driver 60BK is a PLL (Phase Locked Loop)
This is a rotation speed control device for the polygon motor 12BK to which control is applied.

In this polygon motor driver 60BK, the power amplification section 71 is started from the main control section 40 via the video control section 56 and a start signal (for example, a high level signal) is sent.
When is input, a predetermined electric power is applied to the polygon motor 12BK to start rotation. Then, the signal FG generated from the frequency generator 70BK attached to the polygon motor 12BK is detected, and the rotation speed (rotation speed) of the polygon motor driver 60BK is controlled to a steady rotation speed (target rotation speed).

That is, the signal FG generated from the frequency generator 70BK is amplified and shaped by the shaping unit 72.
The signal is amplified and shaped by and is output as a frequency signal ft. The phase comparison unit 73 compares the phase with the reference frequency signal fs input from the video control unit 56 to detect the phase difference (including lead and lag), and the detection thereof. The signal is output as an error signal. Further, since this error signal has a pulse shape, it is smoothed by the low-pass filter 74 (phase difference φ → voltage V).
I do.

On the other hand, if the rotation speed of the polygon motor driver 60BK is controlled simply by phase comparison, even if the reference frequency signal fs and the frequency signal ft do not match (for example, even when fs = 2 · ft), the If the phase difference is small, the error signal output from the phase comparison unit 73 is small,
Since the phase is locked, F for monitoring the frequency
The frequency signal f from the amplification / shaping unit 72 in the −V conversion unit 75
The voltage t is converted into a voltage, which is compared with the voltage Es corresponding to the reference frequency, and a voltage signal corresponding to the difference is output as an error signal.

Then, in the mixing section 76, the low-pass filter 7
4 and the error signal from the FV converter 75 are summed, and the power amplifier 71 supplies the polygon motor 12BK with electric power according to the calculated value, and the rotation speed thereof is set to a steady rotation speed. Control. Further, the mixing unit 76 outputs a lock signal (for example, a high level signal) to the video control unit 56 when the calculated value becomes “0”, that is, when the rotation speed of the polygon motor 12BK reaches the steady rotation speed. .

According to the polygon motor driver 60BK of this feedback system, since the polygon motor 12BK rotates in principle in synchronization with the reference frequency signal fs,
If the stability of the reference frequency is increased, the polygon motor 12BK can be rotated with a rotation accuracy similar to that.

FIG. 1 is a block diagram showing an example of a main part of a control unit of the printer 3. The video control unit 56 includes a reference oscillator 80, and generates a reference frequency signal fs from the reference oscillator 80 to generate the polygon motor drivers 60BK, 60C, 6 respectively.
Input to 0M and 60Y. That is, each polygon motor 1
The rotation speeds of 2BK, 12C, 12M, and 12Y are controlled by the same reference frequency signal fs (control signal).

Further, the steady rotation judging section 81 constituted by an AND gate is provided, and when all the lock signals from the respective polygon motor drivers 60BK, 60C, 60M and 60Y become high level "H" (all polygons Only when the motors 12BK, 12C, 12M, and 12Y have reached the normal rotation speed), the polygon error signal to the main controller 40 and the LD driver 58 is set to "H".

FIG. 6 is a flow chart showing an example of control according to the present invention by the main control section 40. In this routine, a start key (not shown) on the operation panel 65 is pressed, and a start signal is sent to each of the polygon motor drivers 60BK, 60C, 60M, and 60Y via the video control unit 56 to start rotation. It is called by the main routine and started, and the timer is started first.

Thereafter, when the time t measured by the timer reaches a predetermined time ta, which is set in advance, the timer is reset, and subsequently it is judged whether or not the polygon error signal from the video controller 56 is at the high level "H". If it is "H" (all polygon motors 12BK, 12C, 12M, 1
All image formation is permitted (when 2Y reaches a steady rotation speed). That is, each semiconductor laser 57BK, 57C, 5
Allows laser writing and image forming system operation by 7M and 57Y.

If the polygon error signal from the video control unit 56 is not at the high level "H" (when any of the polygon motors 12BK, 12C, 12M and 12Y has not reached the steady speed). , Operation panel 6
After displaying error information indicating that an abnormality has occurred in the polygon motor which has not reached the steady-state rotation speed on the display unit 5, it is determined whether or not the start key on the operation panel 65 has been pressed.

Then, if the start key is not pressed, it is judged whether or not the clear key is pressed. If it is not pressed, the process returns to the judgment whether or not the start key is pressed. When the clear key is pressed, the process directly returns to the main routine, and when the start key is pressed, only the image formation of the color corresponding to the polygon motor that has reached the steady rotation speed is permitted. , Return to the main routine.

As described above, in the digital color copying machine of this embodiment, each polygon mirror 13BK, 13C, 1 is used.
3M and 13Y have the same specifications, and each polygon motor driver 60BK, 60C, 60M, 60Y controls the rotation speed of each polygon motor 12BK, 12C, 12M, 12Y by the same reference frequency signal fs (control signal). Therefore, the control related to image formation is simplified,
Moreover, the occurrence of color misregistration in the color image is eliminated, and a stable high-quality image can be obtained.

Further, each polygon motor 12BK, 12
When any one of C, 12M, and 12Y reaches the steady rotation speed within a predetermined time, only the image formation of the color corresponding to the polygon motor having reached the steady rotation speed is permitted. Even if the motor fails and a full-color image cannot be obtained, a color image corresponding to a normal polygon motor can always be obtained.

Further, each polygon motor 12BK, 12
There are variations in the rise of C, 12M, 12Y,
Even if an abnormality does not occur in each of the motors, all of them do not reach the steady speed at the same time, so by prohibiting image formation until the time required for all of the motors to reach the steady speed is reached, It is possible to prevent the photosensitive drum from being exposed with an extra laser beam, suppress unexpected image forming operation of the image forming system, and minimize the consumption of parts of each unit.

Furthermore, each polygon motor 12BK,
If any of the 12C, 12M, and 12Y does not reach the steady rotation speed within the predetermined time, error information indicating that an abnormality has occurred in the polygon motor that has not reached the steady rotation speed is displayed. The operator knows that an abnormality has occurred in the polygon motor and can immediately contact a service person. Moreover, there is an effect that it is possible to save the trouble of finding a polygon motor in which an abnormality has occurred by a service person who has arrived at the site, and shorten the work time required for replacing the polygon motor.

Alternatively, since the operator can confirm the image color corresponding to the normal polygon motor by looking at the above-mentioned error information and then perform the image formation of that color, the image formation of an undesired color is performed. You can avoid that.

In the digital color copying machine of this embodiment, the polygon motors 12BK, 12C, 12M,
When any of the 12Y reaches the steady rotation speed within a predetermined time, only the image formation of the color corresponding to the polygon motor that has reached the steady rotation speed is allowed.
It is also possible to prohibit all image formation from the start of rotation of each of the polygon motors 12BK, 12C, 12M and 12Y until the steady rotation speed is reached.

Further, each polygon motor 12BK, 12
If any of C, 12M, and 12Y does not reach the steady rotation speed within a predetermined time, the information indicating that the color image corresponding to the polygon motor that has not reached the steady rotation speed cannot be formed or the steady rotation is performed. Information indicating that the image formation of the color corresponding to the polygon motor which has reached the maximum number can be performed may be displayed on the display of the operation panel 65.

The embodiments in which the present invention is applied to a digital color copying machine have been described above. However, the present invention is not limited to this, and an electrophotographic apparatus such as a laser color printer, a digital color facsimile apparatus, or a multi-function machine integrating them is used. It can be applied to an image forming apparatus using the method.

[0051]

As described above, according to the image forming apparatus of the present invention, the control relating to image formation can be simplified.

[Brief description of drawings]

FIG. 1 is a block diagram showing an example of main parts of a control unit of a printer 3 shown in FIG.

FIG. 2 is a schematic configuration diagram showing an example of a mechanical section of a digital color copying machine embodying the present invention.

3 is a block diagram showing a configuration example of a part of a control system of the printer 3 shown in FIG.

FIG. 4 is a block diagram showing the remaining configuration example.

5 is a block diagram showing a configuration example of a polygon motor driver 60BK of FIG.

6 is a flow chart showing an example of control according to the present invention by a main control unit 40 of FIG.

[Explanation of symbols]

1: Scanner 3: Printer 12BK, 12C, 12M, 12Y: Polygon motor 13BK, 13C, 13M, 13Y: Polygon mirror 14BK, 14C, 14M, 14Y: Photosensitive drum 15BK, 15C, 15M, 15Y: Charger charger 16BK, 16C , 16M, 16Y: Developing device 17BK, 17C, 17M, 17Y: Transfer charger 40: Main control unit 56: Video control unit 60BK, 60C, 60M, 60Y: Polygon motor driver 65: Operation panel 80: Reference oscillator 81: Steady rotation Judgment part

Claims (5)

[Claims] 1. An image of a plurality of colors is obtained by periodically deflecting laser beams emitted from a plurality of semiconductor lasers by using respective polygon mirrors rotated by a plurality of polygon motors and scanning the respective photoreceptors. In an image forming apparatus for forming an image, a plurality of motor control means for controlling the number of revolutions of each polygon motor by the same control signal are provided, and each polygon mirror has the same specifications. apparatus. 2. The image forming apparatus according to claim 1, wherein
An image forming apparatus comprising means for prohibiting all image formation from the start of rotation of each of the polygon motors to a steady rotation speed. 3. The image forming apparatus according to claim 2,
An image forming apparatus comprising means for displaying error information when one of the polygon motors does not reach a steady rotation speed within a predetermined time. 4. The image forming apparatus according to claim 3, wherein
When any one of the polygon motors does not reach the steady rotation speed within a predetermined time, means for displaying error information indicating that an abnormality has occurred in the polygon motor that has not reached the steady rotation speed is provided. An image forming apparatus characterized by the above. 5. The image forming apparatus according to claim 1,
When any one of the polygon motors reaches a steady rotation speed within a predetermined time, means for permitting only image formation of a color corresponding to the polygon motor having reached the steady rotation speed is provided. Image forming apparatus.