JPH09267513A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make it possible to shorten the lighting time of a laser in starting a scanner motor by eliminating the lighting of a laser beam for a predetermined time from the start of driving a rotary polygonal mirror, and accelerating the rotating speed of the mirror. SOLUTION: A CPU 54 notifies the occurrence of image forming failure to a controller when it senses the H level of the output signal 6 of a flip-flop 48 from a video signal 53 from the controller even only once during the operation, sets the output signal 78 to an L level so that a scanner motor 21 does not run away to fix the driving voltage applied to the motor 21. The rising time of the motor 21 is predicted, and the failure is sensed before arriving at the specified times to prevent the run-away of the motor 21 and the feedback of the rotating speed by the main scanning synchronization BD signal 55 from a printer starts to predict the start, and hence the lighting time of the laser can be shortened.

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 which forms an image in an electrophotographic system by scanning a laser beam.

[0002]

2. Description of the Related Art Conventionally, in an image forming apparatus that scans a laser beam on a photosensitive drum to form an image forming apparatus, that is, in an image forming apparatus that employs an electrophotographic method, the scanning speed of the laser beam is controlled by a scanner. It is controlled by using the tack pulse of the motor. The scanner motor is a motor that rotationally drives a rotary polygon mirror that deflects a laser beam.

There is also known an image forming apparatus configured to control the scanning speed of a laser beam using a main scanning synchronization signal.

[0004]

However, in the above-mentioned conventional example, since the scanning pulse of the laser beam is controlled by using the tack pulse of the scanner motor, there are the following problems.

[0005] 1. A circuit for shaping the tack pulse waveform is required.

[0006] 2. Since the tack pulse is generated by the electromagnetic induction of the motor, it is vulnerable to external noise.

Further, when the scanning speed of the laser beam is controlled using the main scanning synchronization signal, the laser continues to be lit until the scanner motor reaches the specified rotation, thereby shortening the life of the laser and If the main scanning synchronization signal is not output due to a laser failure or the like due to this, there is a drawback that the scanner motor rotates at an abnormally high speed.

Therefore, a first object of the present invention is to provide an image forming apparatus capable of shortening the lighting time of the laser at the time of starting the scanner motor.

A second object of the present invention is to provide an image forming apparatus capable of detecting a failure of a scanner motor before it becomes abnormally high speed rotation due to a failure of a laser.

[0010]

In order to achieve such an object, the invention of claim 1 is an image forming apparatus for forming an image by an electrophotographic method using a laser beam,
A rotary polygon mirror driving means for rotating and driving a rotary polygon mirror for deflecting and scanning the laser beam; a sync signal generating means for generating a sync signal for detecting the laser beam at a predetermined position and notifying a scanning timing; The counting means for counting the cycle of the synchronizing signal, the rotation speed control means for controlling the rotation speed of the rotary polygon mirror so that the cycle counted by the counting means becomes a predetermined scanning cycle, and the driving of the rotary polygon mirror. A start-up control unit that accelerates the rotation speed of the rotary polygon mirror by turning off the laser beam for a predetermined time from the start is provided.

According to a second aspect of the present invention, in the image forming apparatus according to the first aspect, from the start of driving the rotary polygon mirror until the period of the synchronizing signal counted by the counting means reaches a predetermined scanning period. Rising time counting means for counting the rising time, storage means for storing the counted rising time, and time changing means for changing the predetermined time during which the next laser is not turned on according to the stored rising time Is characterized by.

According to a third aspect of the present invention, in the image forming apparatus according to the first aspect, means for counting an elapsed time from when the driving of the rotary polygon mirror is stopped until the next driving is started, and the elapsed time. And a means for changing a predetermined time during which the laser of the next startup control means is not turned on according to the stored elapsed time.

According to a fourth aspect of the present invention, in the image forming apparatus according to the first aspect, the laser is turned on at predetermined intervals until a predetermined time elapses after the current supplied to the rotary polygon mirror driving means is cut off. It further comprises: counting means for counting the cycle of the synchronization signal; storage means for storing the counted cycle; and time changing means for changing the predetermined time during which the next laser is not turned on by the stored cycle. And

According to a fifth aspect of the present invention, in an image forming apparatus for forming an image by an electrophotographic method using a laser beam, a rotary polygon mirror for deflecting and scanning the laser beam is driven to rotate according to an applied voltage. The polygon mirror driving means, the synchronization signal generating means for generating a synchronization signal for detecting the laser beam at a predetermined position and notifying the scanning timing, the counting means for counting the period of the synchronization signal, and the counting means. A rotation speed control means for controlling the rotation speed of the rotary polygon mirror so that the counted cycle becomes a predetermined scanning cycle; a judgment means for judging whether the cycle counted by the counting means is within a predetermined scanning cycle range; When the determining unit determines that the period is outside the predetermined scanning period range during formation, until the synchronizing signal is generated again by the synchronizing signal generating unit. The voltage applied to the serial rotary polygon mirror drive means, characterized in that a voltage holding means for holding the value of the time of the said judgment.

According to a sixth aspect of the present invention, in an image forming apparatus for forming an image by an electrophotographic method using a laser beam, a rotary polygon mirror that deflects and scans the laser beam is driven to rotate according to an applied voltage. The polygon mirror driving means, the synchronization signal generating means for generating a synchronization signal for detecting the laser beam at a predetermined position and notifying the scanning timing, the counting means for counting the period of the synchronization signal, and the counting means. A rotation speed control means for controlling the rotation speed of the rotary polygon mirror so that the counted cycle becomes a predetermined scanning cycle; a judgment means for judging whether the cycle counted by the counting means is within a predetermined scanning cycle range; The voltage applied to the rotary polygon mirror driving means is applied to the rotary polygon mirror driving means for the first predetermined time until the synchronization signal is generated after the first predetermined time from the start of driving the rotary polygon mirror. The voltage holding means for holding the value at the excessive time point and the time for holding the voltage by the voltage holding means are counted, and when the voltage holding time reaches the second predetermined time or more, the voltage is supplied to the rotary polygon mirror driving means. And a cutoff unit that cuts off the electric current.

According to a seventh aspect of the invention, in the image forming apparatus according to the sixth aspect, the rising time from the start of driving of the rotary polygon mirror until the period of the synchronizing signal reaches a predetermined scanning period is counted. It is characterized by further comprising time counting means, storage means for storing the counted rising time, and changing means for changing the first predetermined time by the stored rising time.

According to an eighth aspect of the present invention, in the image forming apparatus according to the sixth aspect, counting means for counting the elapsed time from the stop of the driving of the rotary polygon mirror to the start of the next driving, Storage means for storing the counted elapsed time,
It is characterized by further comprising changing means for changing the first predetermined time according to the stored elapsed time.

According to a ninth aspect of the present invention, in the image forming apparatus according to the sixth aspect, the laser is turned on at predetermined intervals until a predetermined time elapses after the current supplied to the rotary polygon mirror driving means is cut off. It is characterized by further comprising counting means for counting the cycle of the synchronization signal, storage means for storing the counted cycle, and changing means for changing the first predetermined time according to the stored cycle.

According to a tenth aspect of the present invention, in an image forming apparatus for forming an image by an electrophotographic method using a laser beam, scanning means for scanning the laser beam, and scanning by detecting the laser beam at a predetermined position. Sync signal generating means for generating a sync signal for notifying the timing, first counting means for counting the cycle of the sync signal, and control means for controlling acceleration / deceleration of the scanning speed of the laser beam by the measured cycle. A second counting means for counting the time during which the control means continuously controls the scanning speed for acceleration, and a stop means for stopping the acceleration control when the measured time is longer than a predetermined time. Is characterized by.

According to an eleventh aspect of the invention, in the image forming apparatus according to the tenth aspect, a change is made to change a predetermined time for stopping the acceleration control before and after the scanning speed of the laser beam reaches a predetermined speed. It is characterized by further comprising means.

According to a twelfth aspect of the present invention, in an image forming apparatus for forming an image by an electrophotographic method using a laser beam, scanning means for scanning the laser beam, and scanning by detecting the laser beam at a predetermined position. Sync signal generating means for generating a sync signal for notifying timing, counting means for counting the cycle of the sync signal, control means for accelerating and decelerating the scanning speed of the laser beam according to the measured cycle, The control means includes a counting means for counting the time during which the scanning speed is continuously decelerated and controlled, and a stop control means for stopping the deceleration control when the measured time is longer than a predetermined time. To do.

According to a thirteenth aspect of the present invention, in the image forming apparatus according to the twelfth aspect, a change is made to change a predetermined time for stopping the deceleration control before and after the scanning speed of the laser beam reaches a predetermined speed. It is characterized by further comprising means.

[0023]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described in detail below with reference to the drawings.

(First Embodiment) FIG. 1 shows a schematic structure of a laser beam printer to which the present invention is applied. In FIG. 1, after the power is turned on, the printer 1 checks internal conditions such as whether the temperature of the fixing device 12 has become appropriate, whether the paper 13 is loaded in the paper cassette 14, and the like. (Not shown). In the printable state, the controller sends a print start command to the printer 1 as necessary to start the print operation.

Since this embodiment is an electrophotographic (electrostatic copying) printer using a laser (generally called a laser beam printer), first of all, a pre-exposure lamp 8, a charger 2 and a transfer device 6 are used. Turn on. Further, by rotating the photosensitive drum 2, the surface potential of the photosensitive drum 2 is initialized, and at the same time, the rotating mirror (rotating polygonal mirror) 30.
To start rotating. When the photoconductor drum 2 is initialized and the rotation of the rotary mirror 30 is stabilized, the paper feed roller 9
Thus, the paper 13 is fed from the paper cassette 14, and when the leading edge of the paper reaches the registration roller 10, the paper is once stopped and stands by.

In this state, the printer 1 requests the controller to send a sub-scanning direction synchronizing signal (VSYNC signal), and in response to this, the controller sends the VSYNC signal and the main scanning direction synchronizing signal (BD) from the printer 1. Image signal (video signal) in synchronization with the signal). The laser light reflected by the rotating mirror 30 forms an optical image on the photosensitive drum 2 by the lens system 17 and the mirror 16. The optical image is then developed by the developing device 5 to become a toner image. By driving the registration rollers 10, the transfer device 6 transfers the toner image to the paper whose front end is aligned with the toner image, is conveyed, and the fixing device 12 fixes the toner image and discharges it to the tray 15.

Next, the control of the scanner and the main scanning direction synchronizing signal (BD signal) will be described with reference to FIG.

FIG. 2 shows the configuration of the control system related to the scanner control and the main scanning direction synchronizing signal of this embodiment. When a print operation is instructed by the controller in FIG. 2, the CPU 54 first performs a failure detection process and a scanner motor start-up process, which will be described later. When the scanner motor 21 that rotationally drives the rotating mirror 30 reaches the specified rotation, the laser light emitted from the semiconductor laser 24 is shaped by the coupling lens 22 and then reflected by the rotating mirror 30 rotating by the scanner motor 21. After passing through the fθ lens 23, the light is periodically received by the photodiode 25.

The signal photoelectrically converted by the photodiode 25 is amplified by the amplifier 27, and shaped by the waveform shaping circuit 20 into a pulse waveform (BD signal 55). In order to obtain the timing used for the print control, the clock output (10 MHz in this embodiment) of the reference oscillator 72 is counted so that B
The 16-bit counter 73 that counts the generation period of the D signal 55 clears the count value by the BD signal 55.

The latch 74 is a circuit for holding the generation period of the BD signal 55 of 16-bit data, and the gate of the AND circuit 76 is opened (CPU of the AND circuit 76).
When the input from 54 is the H level), the LD input becomes the H level by the BD signal 55 and the value (DB input value) immediately before the count value of the counter 73 is cleared is captured and held.

The data (DA input) from the CPU 54 has priority over the DB input when the S input is at H level, and the write signal 83 from the CPU 54 is the OR circuit 82.
It is taken in by making the LD input connected via the H level. The output of the latch 74 is converted by the digital / analog (D / A) conversion circuit 100 into an analog DC voltage signal according to the count value, input to the motor drive circuit 75, and applied to the scanner motor 21. In this way, a servo system that controls the rotation speed of the scanner motor 21 by adjusting the voltage applied to the scanner motor 21 according to the cycle of the BD signal 55 is configured.

If the BD signal 55, which will be described later, is normally output in a prescribed cycle and the BD signal 55 is normal, the CPU 54 determines that the scanner motor 21 is stable, and the above-described printing operation is performed. When the video signal 53 is input from the controller, the video signal 53 is amplified by the video amplifier 26 and the semiconductor laser 24
Drive. The laser light emitted from the semiconductor laser 24 passes through the above-mentioned optical path, is reflected by the rotating mirror 30, and f
The photosensitive drum 2 is scanned through the θ lens 23.

In such a case, since the video signal 53 is of a system in which a dot signal is generated in synchronization with the horizontal deflection scanning of the laser light, it is notified that the laser light has reached a predetermined position. , I.e., a sync signal is required to inform the scan timing. As such a synchronization signal, the signal from the photodiode 25 described above is amplified by the amplifier 27, shaped into a pulse waveform by the waveform shaping circuit 20, and BD.
It is output as a signal 55.

Next, the other blocks in FIG. 2 will be described.

Reference numeral 32 denotes a counter, which counts the clock 65 from the clock generator 33 to obtain 10
The bit count value is output to the comparators 40 to 45, and is reset when the output 60 of the OR circuit 31 becomes H level. 34 to 39 are 1
In the 0-bit shift register, a numerical value converted into the count value of the clock 65 is set by the CPU 54, and its output is output to the counter 32 by the comparators 40 to 45.
Is compared to the output of

Comparators 40 to 45 bring their outputs to H level when their inputs are equal. 47-50
Are set / reset type JK flip-flops, each of which is a clock input (C
The Q output becomes H level in synchronization with K), and when the K input is at H level, the Q output becomes L level in synchronization with the clock input.

Reference numeral 54 is a CPU for controlling the entire apparatus, which receives information such as resolution and paper size 71 from the register 34.
Various controls are performed such as determining a numerical value to be set in 39 to 39 and setting it in each register. The CPU 54 also includes a ROM for storing control programs and data, a RAM as a working area, and the like.

Next, the operation of checking the cycle of the BD signal will be described. Data that is slightly smaller than the count value output by the counter 32 is set in the shift register 35 each time the BD signal 55 is output when the scanner motor 21 is rotating normally. This data is the BD signal 55
This is the shortest period data in the range that does not affect the image even if the period of is shortened.

Therefore, the comparator 41 compares the data set in the shift register 35 with the output of the counter 32, and when the output of the counter 32 becomes equal to the set data, sets the output signal 64 to the H level. As a result, the flip-flop 47 sets the output signal 66 to the H level in synchronization with the clock 65. Therefore AND circuit 2
8 can transmit the BD signal 55 output from the waveform shaping circuit 20 to the pulse synchronizer 29. Therefore, even if the BD signal 55 having a shorter synchronization than the data set in the shift register 35 is input, it is not transmitted to the pulse synchronizer 29 and the BD signal 55 is ignored.

Here, when the laser light detection signal from the photodiode 25 is input, the pulse synchronizer 2
The counter 32 is reset via 9. At the same time, the flip-flops 47 and 48 are reset, and their outputs 66 and 67 become L level.

On the other hand, the shift register 34 is set with data a little larger than the count value output by the counter 32 each time the BD signal 55 is output when the scanner motor 21 is rotating normally. This data is the longest cycle data in a range that does not affect the image even if the cycle of the BD signal 55 is long. Therefore, the comparator 4
0 outputs an H level when the BD signal 55 is not output although the counter 32 has the above-mentioned data.

As a result, the output signal 67 of the flip-flop 48 becomes H level in synchronization with the clock 65, so that the output of the OR circuit 31 also becomes H level and the counter 31.
Is cleared. Further, since the output of the OR circuit 31 is connected to the reset input of the flip-flop 48,
The flip-flop 48 sets the output to the L level when the next clock 65 is input. CPU 54 is a flip-flop 48
The H level of the output signal 67 is detected to determine that the BD signal 55 is abnormal.

Here, when the CPU 54 detects the H level of the output signal 67 of the above-mentioned flip-flop 48 even during scanning of the video signal 53 from the controller,
The controller is notified that an image formation failure has occurred, and the output voltage 78 is set to the L level so that the scanner motor 21 does not run away and the drive voltage applied to the scanner motor 21 is fixed. Here, if the BD signal 55 is input again after the output signal 78 is set to the L level and before the failure is detected by the failure detection to be described later, the CPU 54 returns the output signal 78 to the H level and the speed of the scanner motor 21. Restart control.

Next, start-up processing and CP at start-up
The failure detection process of U54 will be described with reference to the flowcharts of FIGS. 3 and 4.

In the failure detection process shown in FIG. 3, in step S101, the CPU 54 causes the data line 7 to output the value of the latch 74 holding the 16-bit BD signal cycle count value.
7, the value is set to a value corresponding to twice the normal cycle, the output signal 78 is set to the L level, and the data in the latch 74 is fixed. In step S102, the output signal 79 is changed to H
By setting the level, the driving of the scanner motor 21 is started by the motor drive circuit 75. In step S103,
The timer 1 inside the CPU 54 which counts up after 3 seconds is set. In step S104, timer 1
Waits for counting up, and when counting up, moves to S105.

At step S105, the output signal 80 is changed to H level.
The laser 24 is turned on by setting the level. Step S
At 106, the CPU 5 that counts up after 1 second
The internal timer 2 of 4 is set. In step S107, it is determined whether the timer 2 has counted up. If the timer 2 has counted up, the process proceeds to step S109, and if not, the process proceeds to step S108.

In step S108, it is determined whether or not the BD signal 55 is input, and if it is input, step S11.
If the BD signal 55 is not input within 1 second, it is determined that there is a failure, and the process proceeds to step S109. In step S109, the controller is notified of the occurrence of a failure of the scanner motor / optical system, the driving of the scanner motor is stopped, and the printing operation is also stopped. Since the normal operation of the scanner motor / optical system is confirmed by the determination in step S108, the speed of the scanner motor can be normally controlled by the BD signal 55. Therefore, in step S110, the value of the latch 74 is set to the normal cycle time as an initial process. The laser 24 is turned off by setting it to a corresponding value, setting the output signal 78 to the L level, fixing the data in the latch 74, and setting the output signal 80 to the L level.

In step S111, the timer 3 inside the CPU 54 which counts up after 2 seconds is set. In step S112, wait for the timer 3 to count up, and if the timer 3 counts up, step S113
Move to In step S113, the laser 24 is turned on by setting the output signal 80 to the H level, and the output signal 7
The speed control of the scanner motor 21 is started by setting 8 to the H level. In step S114, the timer 4 inside the CPU 54 that counts up after 10 seconds is set. In step S115, it is determined whether the timer 4 has counted up. If the timer 4 has counted up, the process proceeds to step S117, and if not, the process proceeds to step S116. In step S116, it is determined whether or not the L level of the output signal 67 of the flip-flop 48 is detected. If it is detected three times consecutively for each input of the BD signal 55, the process proceeds to step S118, and if not detected, step S117. Move on to. In step S117, the controller is notified of a failure of the scanner motor, the driving of the scanner motor is stopped, and the printing operation is stopped. In step S118, since the control by the BD signal 55 can be normally performed, the output signal 80 is set to the L level to stop the forced lighting of the laser 24 and the scanner motor 2
It is determined that 1 has reached the specified rotation.

Next, the failure detection process will be described with reference to the flowchart of FIG.

The CPU 54 executes the failure detection process shown in FIG.
It is performed every time the D signal 55 is input. In FIG. 5, step S2
01 detects the input of the BD signal 55, and the CPU 54 fetches and stores the output 81 of the latch 74, that is, the generation period of the BD signal. In step S202, the CPU 54
The speed of the scanner motor by comparing the count data (data 1) corresponding to the maximum time within the range that does not affect the image of the BD signal cycle stored in the internal ROM with the input data stored in step S201. Determines whether is accelerating or decelerating. If the input data is larger, it is determined that the scanner motor is under acceleration control, and the process proceeds to step S204. If the input data is smaller, the process proceeds to step S203. In step S204, it is determined whether the acceleration / deceleration flag on the RAM in the CPU 54 indicating acceleration / deceleration is 0 (acceleration). If the acceleration / deceleration flag is 0, step S2 is performed.
05, and if the acceleration / deceleration flag is 1, step S20
Go to 6. In step S205, the value of the counter buffer for counting the number of acceleration / deceleration prepared in the RAM is set to 1
Add and move to step S212.

In step S206, the value of the counter buffer is set to 0. In step S207, the acceleration / deceleration flag is set to 0 indicating that the vehicle is accelerating, and the process proceeds to step S212.
In step S203, the count data (data 2) corresponding to the minimum time in the range that does not affect the image of the BD signal cycle stored in the ROM is compared with the input data stored in step S201, and the input data If it is smaller, it is determined that the deceleration control is being performed, and the process proceeds to step S208.

If the input data is larger, step S2
Move to 12. In step S208, the acceleration / deceleration flag is 1
If the acceleration / deceleration flag is 1, the process proceeds to step S209, and if the acceleration / deceleration flag is 0, the process proceeds to step S210. In step S209,
The value of the counter buffer is incremented by 1, and the process proceeds to step S212. In step S210, the value of the counter buffer is set to 0.
Set to. In step S211, the acceleration / deceleration flag is set to 1 indicating that the vehicle is decelerating, and the process proceeds to step S212.

In step S212, it is determined whether or not the startup process of the scanner motor is in progress.
If it is not being processed, the process proceeds to step S214. In step S213, since the startup process of the scanner motor is being performed, the value of the counter buffer is returned to 0 and the process is completed. In step S214, it is determined whether the value of the counter buffer is 6 or more. If it is 6 or more, the process proceeds to step S215, and if it is less than 6, the process ends. Step S
At 215, the controller is notified of a failure of the scanner motor, the driving of the scanner motor is stopped, and the printing operation is stopped.

As described above, by sharing the BD signal as the feedback signal for controlling the speed of the scanner motor, the circuit for producing the tack pulse of the scanner motor can be omitted, and the feedback signal can be detected by the laser light. By doing so, noise resistance can also be improved.

Further, by predicting the rise time of the scanner motor and detecting the failure before the specified rotation is reached, runaway of the scanner motor is prevented, and the feedback of the rotation speed by the BD signal is also predicted and started. Therefore, there is an effect that the lighting time of the laser can be shortened.

(Second Embodiment) In a printer having the same configuration as that of the first embodiment, the time required for the previous startup process of the scanner motor 21 (from the start of driving the scanner until it is determined that the specified rotation has been reached) Time) and measure CPU5
It stores in RAM in 4. If the data is less than 8 seconds, set the time for timer 1 from 3 seconds to 2 seconds
ec and the time set in the timer 3 is changed from 2 sec to 1 sec. Data is 8 seconds or more and 10 seconds
If less, the current values of both timer 1 and timer 3 are set. If the data is 10 sec or more, the time set in the timer 1 is changed from 3 sec to 4 sec, and the time set in the timer 3 is changed from 2 sec to 3 sec.

As described above, by changing the timer value of the current rising control according to the time required for the previous rising control, the time for turning on the laser at the rising of the scanner motor can be shortened.

(Third Embodiment) In a printer having the same configuration as that of the first embodiment, the print processing is terminated and the driving of the scanner motor 21 is stopped (the output signal 79 of the CPU 54 is set to L).
The CPU 54 counts the elapsed time from the setting of the level) to the start of the driving of the scanner motor, and then the CP
The counted time is stored in the RAM in U54. If the data is less than 10 sec at the start of the next print, the time set in timer 1 is set from 3 sec to 0 sec.
In addition, the time set in the timer 3 is from 2 seconds to 1 s.
Change to ec. If the data is 10 seconds or more and less than 20 seconds, set the timer 1 time from 3 seconds to 1
sec, and the time set in the timer 3 is changed from 2 sec to 1.5 sec. If the data is 20 seconds or more, both timer 1 and timer 3 are set to the current values.

As described above, the laser value is changed when the scanner motor starts up by changing the timer value for the current start-up control according to the elapsed time after the printing process is completed and the driving of the scanner motor 21 is stopped. The lighting time can be shortened.

(Fourth Embodiment) In a printer having the same configuration as that of the first embodiment, the print processing is completed and the driving of the scanner motor 21 is stopped (the output signal 79 of the CPU 54 is set to L).
Even if the current supplied to the scanner motor 21 is cut off by setting the level to 0.
The laser 24 is forcibly turned on for 1 sec (the output signal 80 of the CPU 54 is set to the H level for 0.1 sec), the period of the BD signal 55 is measured by the counter 73 and the latch 74, and the value of the data 81 is stored in the RAM. If 0.1
When the BD signal 55 can be obtained only once or less during the sec, this process ends.

At the start of the next print, the stored data 8
If the time corresponding to the count value of 1 is less than 10 msec, the time set in timer 1 is changed from 3 sec to 0 sec.
c, and the time set in timer 3 from 2 sec to 1
Change to sec. If the time corresponding to the count value of the stored data 81 is 10 msec or more and less than 50 msec, the time set in the timer 1 is 3 sec to 1 sec.
Further, the time set in the timer 3 is changed from 2 sec to 1.
Change to 5 seconds. If the time corresponding to the count value of the stored data 81 is 50 msec or more, timer 1,
Both the timer 3 and the current value are set.

As described above, the period of the BD signal is measured with a certain time even after the printing process is finished and the driving of the scanner motor 21 is stopped, and the timer value of the current rising control is obtained from the data. By changing the, the time to turn on the laser at the time of starting the scanner motor can be shortened.

[0063]

As described above, in the inventions of claims 1 to 4, it is necessary to turn on the laser beam from the start of the rotational driving of the rotary polygon mirror until the constant rotation speed is reached. The inventor notices that this is not the case, and prevents the laser from being consumed by not turning on the laser beam for a predetermined time during this period. Further, by varying the time during which the laser beam is not lit depending on the rising time, the stopping time, etc. of the rotary polygon mirror, it is possible to cope with changes in performance of the laser over time.

In the inventions of claims 5 to 9, attention is paid to the fact that the period of the synchronizing signal created from the laser beam corresponds to the rotating speed of the rotary polygon mirror, and an abnormality in the rotating speed is detected using this synchronizing signal. However, by keeping the rotation speed at the time of the abnormality detection, the runaway of the rotary polygon mirror is prevented.

According to the tenth and twelfth aspects of the invention, the acceleration / deceleration control for the scanning of the laser beam is performed by the cycle of the synchronizing signal, and the abnormality is detected by the acceleration / deceleration control time, and the control is stopped.

According to the eleventh and thirteenth aspects of the present invention, the abnormality detection accuracy is improved by changing the threshold value used for abnormality detection before and after the laser beam reaches the predetermined speed.

[Brief description of drawings]

FIG. 1 is a schematic sectional view showing a schematic configuration of an embodiment of the present invention.

FIG. 2 is a block diagram showing a control system of an embodiment of the present invention.

FIG. 3 is a flowchart showing the control contents of the embodiment of the present invention.

FIG. 4 is a flowchart showing the control contents of the embodiment of the present invention.

FIG. 5 is a flowchart showing the control contents of the embodiment of the present invention.

[Explanation of symbols]

 1 Printer 2 Photosensitive Drum 73 Counter 74 Latch 100 D / A Converter

Claims (13)

[Claims] 1. An image forming apparatus for forming an image by an electrophotographic method using a laser beam, comprising: a rotary polygon mirror driving means for rotating and driving a rotary polygon mirror for deflecting and scanning the laser beam; A synchronizing signal generating means for generating a synchronizing signal for notifying the scanning timing by detecting at a predetermined position, a counting means for counting the period of the synchronizing signal, and a cycle counted by the counting means becomes a predetermined scanning cycle. And a rotation speed control means for controlling the rotation speed of the rotary polygon mirror, and to accelerate the rotation speed of the rotary polygon mirror by turning off the laser beam for a predetermined time after starting the driving of the rotary polygon mirror. An image forming apparatus comprising a start-up control unit. 2. The image forming apparatus according to claim 1, wherein the rising time from the start of driving of the rotary polygon mirror until the period of the synchronizing signal counted by the counting means reaches a predetermined scanning period is counted. Rise time counting means,
An image forming apparatus further comprising: a storage unit that stores the counted rise time, and a time changing unit that changes the predetermined time during which the next laser is not turned on according to the stored rise time. 3. The image forming apparatus according to claim 1, further comprising: a unit that counts an elapsed time from when the rotary polygon mirror is stopped to be driven next, and a unit that stores the elapsed time. An image forming apparatus, comprising means for changing a predetermined time during which the laser of the startup control means for the next time is not turned on according to the stored elapsed time. 4. The image forming apparatus according to claim 1, wherein the laser is turned on at predetermined intervals until a predetermined time elapses after the current supplied to the rotary polygon mirror driving means is cut off, and the cycle of the synchronization signal is changed. An image forming apparatus further comprising: counting means for counting, storage means for storing the counted cycle, and time changing means for changing the predetermined time during which the next laser is not turned on according to the stored cycle. . 5. An image forming apparatus for forming an image by an electrophotographic method using a laser beam, comprising: a rotary polygon mirror driving means for rotating and driving a rotary polygon mirror for deflecting and scanning the laser beam according to an applied voltage. A synchronization signal generating means for generating a synchronization signal for detecting the laser beam at a predetermined position and notifying a scanning timing; a counting means for counting a cycle of the synchronization signal; and a cycle counted by the counting means is predetermined. Rotation speed control means for controlling the rotation speed of the rotary polygon mirror so that it becomes a scanning cycle, judgment means for judging whether or not the cycle counted by the counting means is within a predetermined scanning cycle range, and the cycle during image formation. When the discriminating means discriminates that is outside the predetermined scanning cycle range, the rotary polygon mirror is until the synchronizing signal is regenerated by the synchronizing signal generating means. An image forming apparatus comprising: a voltage holding unit that holds the voltage applied to the driving unit at the value at the time of the determination. 6. An image forming apparatus for forming an image by an electrophotographic method using a laser beam, comprising: a rotary polygon mirror driving means for rotating and driving a rotary polygon mirror for deflecting and scanning the laser beam according to an applied voltage. A synchronization signal generating means for generating a synchronization signal for detecting the laser beam at a predetermined position and notifying a scanning timing; a counting means for counting a cycle of the synchronization signal; and a cycle counted by the counting means is predetermined. Rotation speed control means for controlling the rotation speed of the rotary polygon mirror so as to have a scanning cycle, judgment means for judging whether the cycle counted by the counting means is within a predetermined scanning cycle range, and driving of the rotary polygon mirror. After the first predetermined time from the start of the operation, the voltage applied to the rotary polygon mirror driving means is set to the value at the time when the first predetermined time elapses until the synchronization signal is generated. The voltage holding means for holding and the time during which the voltage is held by the voltage holding means are counted, and the current supplied to the rotary polygon mirror driving means is cut off when the voltage holding time reaches a second predetermined time or more. An image forming apparatus comprising: a blocking unit. 7. The image forming apparatus according to claim 6, wherein time counting means for counting a rising time from the start of driving of the rotary polygon mirror until the cycle of the synchronizing signal reaches a predetermined scanning cycle, An image forming apparatus further comprising: a storage unit that stores the counted rising time, and a changing unit that changes the first predetermined time according to the stored rising time. 8. The image forming apparatus according to claim 6, wherein the counting means counts an elapsed time from when the driving of the rotary polygon mirror is stopped until the next driving is started, and the counted elapsed time. An image forming apparatus further comprising: a storage unit that stores the change, and a change unit that changes the first predetermined time period according to the stored elapsed time. 9. The image forming apparatus according to claim 6, wherein the laser is turned on at predetermined intervals until the predetermined time elapses after the current supplied to the rotary polygon mirror driving means is cut off, and the cycle of the synchronization signal is changed. An image forming apparatus, further comprising: counting means for counting, storage means for storing the counted cycle, and changing means for changing the first predetermined time in accordance with the stored cycle. 10. An image forming apparatus for forming an image by an electrophotographic method using a laser beam, for scanning means for scanning the laser beam, and for notifying the scanning timing by detecting the laser beam at a predetermined position. A synchronization signal generating means for generating a synchronization signal, a first counting means for counting the cycle of the synchronization signal, a control means for accelerating / decelerating the scanning speed of the laser beam according to the measured cycle, and the control means. An image comprising a second counting means for counting the time during which the scanning speed is continuously accelerated and a stopping means for stopping the acceleration control when the measured time is longer than a predetermined time. Forming equipment. 11. The image forming apparatus according to claim 10, further comprising a changing unit that changes a predetermined time for stopping the acceleration control before and after the scanning speed of the laser beam reaches a predetermined speed. An image forming apparatus characterized by the above. 12. An image forming apparatus for forming an image by an electrophotographic method using a laser beam, for scanning means for scanning the laser beam, and for notifying the scanning timing by detecting the laser beam at a predetermined position. Sync signal generating means for generating a sync signal, a counting means for counting the cycle of the sync signal, a control means for accelerating and decelerating the scanning speed of the laser beam according to the measured cycle, and the control means for scanning. An image forming apparatus comprising: a counting unit that counts a time during which the speed is continuously controlled to be decelerated, and a stop control unit that stops the deceleration control when the measured time is longer than a predetermined time. 13. The image forming apparatus according to claim 12, further comprising a changing unit that changes a predetermined time for stopping the deceleration control before and after the scanning speed of the laser beam reaches a predetermined speed. An image forming apparatus characterized by the above.