JPH05313084A - Image forming device - Google Patents

Abstract

PURPOSE:To reduce a burden to a microcomputer without degrading a control characteristic by detecting only whether a horizontal synchronous signal is in a specified period or not after detecting that a scanner motor is rotating at a specified speed. CONSTITUTION:When driving of a scanner motor 19 is indicated from a microcomputer 20 by means of a scanner driving signal/SCNON, the scanner motor 19 rotates while using an oscillation period corresponding to image recording density as it standard. A scanner tack signal SCNTA proportional to the number of revolutions is inputted to the microcomputer 20. The microcomputer 20 measures the period, and detects that a rotary polygon mirror, that is, the scanner motor 19 is rotating at a specified speed. Afterward, since a horizontal synchronous signal BDO can be detected in a specified period, a judgment is made only on whether the horizontal synchronous signal BDO is put in the specified period, and the scanner motor 19 is controlled without checking up the number of revolutions.

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 for drawing an image by scanning a laser beam on a photosensitive member using a rotary polygon mirror.

[0002]

2. Description of the Related Art A conventional image forming apparatus of this type turns on / off a laser based on pixel information with respect to a polygonal mirror mounted on a rotary shaft of a scanner motor rotating at a constant speed. An image is formed by causing the modulated laser light to enter and scanning the photosensitive drum.

Therefore, during the formation of the image operation, the scanner tack signal proportional to the rotation speed of the scanner motor causes
It is always determined that the scanner motor is rotating at the specified speed. Further, a laser beam reflected by a fixed mirror (BD mirror) provided in the optical path of the laser beam is received to generate a horizontal synchronizing signal, and scanning for one line is performed in synchronization with this horizontal synchronizing signal. Since the writing start position of the image in the horizontal direction is determined by, it is always configured to determine whether or not the horizontal synchronization signal is generated at the specified cycle.

[0004]

However, in the above-mentioned conventional example, since the rotation speed of the scanner motor is continuously detected even after the horizontal synchronization signal reaches the specified synchronization, the microcomputer controlling the apparatus is controlled. There was a drawback that the load on the was increased.

Therefore, in view of the above points, an object of the present invention is to provide an image forming apparatus which simplifies the rotation control mode of the scanner motor without degrading the control characteristics and reduces the load on the microcomputer. is there.

[0006]

The present invention relates to an image forming apparatus for drawing an image on a photosensitive member by deflecting laser light emitted from a semiconductor laser by a rotary polygon mirror composed of a plurality of mirror surfaces. A rotation holding means for holding the rotation speed of the polygon mirror at a specified rotation speed, a rotation detection means for detecting that the rotation polygon means has become a specified rotation by the rotation holding means, and a laser reflected by the rotation polygon mirror. Timing signal generating means for receiving a light at a non-image portion and generating a writing timing signal of laser light for horizontally scanning the photoconductor; timing detecting means for detecting that the timing signal has reached a prescribed cycle; While the timing detection means is detecting that the write start timing signal has reached the specified period, the rotation polygon mirror by the rotation detection means is detected. The regulation revolution detection is obtained and a control means for stopping.

[0007]

According to the present invention, after detecting that the rotary polygon mirror, that is, the scanner motor is rotating at the specified number of revolutions, the horizontal synchronizing signal can be detected at the specified period. Control is performed only to determine whether or not is the specified cycle, and not to check the rotation speed of the scanner motor.

[0008]

EXAMPLES Examples of the present invention will be described in detail below.

Embodiment 1 FIG. 1 is a diagram showing the configuration of a laser beam printer according to an embodiment of the present invention. In the figure, reference numeral 1 denotes a paper feed tray on which the set recording paper P is placed. Two
Is a paper feed roller, and a recording paper P placed on the paper feed tray 1 is driven by driving a paper feed solenoid (not shown).
Is fed into the machine by pressing the roller pad 4.

A paper feed pad 3 presses the fed recording paper P against the paper feed roller 2. 5 is a paper feed sensor,
Detects whether the leading edge of the fed paper has passed. Reference numeral 6 denotes a photosensitive drum, which is scanned by a rotary polygon mirror 8 which is rotated at a prescribed rotation speed by a scanner motor 19 with laser light modulated according to image information, and an electrostatic latent image is formed on the surface thereof. ..

Reference numeral 7 denotes a charging roller, which negatively and uniformly charges the surface of the photosensitive drum 6. A developing roller 9 develops an electrostatic latent image on the photosensitive drum 6 into a toner image by a well-known reversal developing method. A transfer roller 10 transfers the toner image developed on the photosensitive drum 6 to the recording paper P fed by being positively charged.

Reference numeral 11 denotes a paper discharge roller, which is a paper discharge tray 12
Then, the recording paper P is discharged. 13 is a front door.

A fixing unit 17 includes a fixing heater 1.
4, a heating roller 16 and a pressure roller 15, and the toner image transferred to the recording paper P is fixed to the recording paper P by heat and pressure.

Reference numeral 18 denotes a paper ejection sensor, which detects that there is a recording paper at the paper ejection port by pushing up a paper ejection sensor lever (not shown) by the recording paper P ejected by the paper ejection roller 11.

FIG. 2 is a block diagram showing the main control section of this embodiment. In the figure, 19 is a scanner motor and its driver circuit,
When the driving of the scanner motor is instructed from 0 by the scanner drive signal (/ SCNON), the scanner motor is rotated based on the oscillation cycle corresponding to the image recording density.
When the scanner motor rotates, a scanner tack signal (SCNTAC) proportional to the number of rotations of the scanner motor is input to the microcomputer 20.

The microcomputer 20 includes a horizontal synchronizing signal check logic circuit, which will be described later, and the like.
Each part is controlled comprehensively based on the control program stored in M.

Reference numeral 21 is a D / A conversion circuit. Reference numeral 22 denotes a voltage / current conversion circuit, which converts the voltage received from the microcomputer 20 via the D / A conversion circuit 21 into a current so as to obtain a set light amount, and supplies the current to the laser diode 27.

Reference numeral 23 is an AND circuit, and 24 is an AND circuit 23.
Voltage / current conversion circuit 2 only when the output of the
2 is a current switch circuit that enables the current from 2 to be supplied to the laser 27. 25 is a photodiode,
The back beam of the laser 27 is detected.

Reference numeral 26 is an A / D conversion circuit, which converts the output of the photodiode 25 into digital data and supplies it to the microcomputer 20.

Reference numeral 28 is a folding mirror. Reference numeral 29 denotes a light receiving circuit, which sends a beam detect signal (BDi) to the microcomputer 20 when receiving the laser beam reflected by the folding mirror 28.

FIG. 3 is a block diagram of the horizontal synchronizing signal checking logic portion of this embodiment. In the figure, 30
33 are 10-bit registers. 34 counts the basic clock from the clock generator 39 to 1
It is a counter that outputs a 0-bit count value to the comparators 35 to 38, and the count value is reset to 0 when the output of the OR circuit 46 is at the “L” level.

Reference numerals 35 to 38 are comparators, which compare the count value of the counter 34 with the values of the respective registers 30 to 33, and when they match the count value, set the output to "H" level.

A clock generator 39 outputs a reference clock corresponding to the image recording density. 40 is O
R circuits, 41 to 43 are JK flip-flops, and 44 is an AND circuit. Reference numeral 45 is a pulse synchronizer for synchronizing the input from the AND circuit 44 with the reference clock, and the output (BDO) of only one clock of the first reference clock after the output of the AND circuit 44 becomes "H". It becomes "H" level. 47 is a NOR circuit.

Next, a normal printing operation in the laser beam printer configured as described above will be described.

When a controller (not shown) receives code data of an image from a host computer or the like, the code data is developed into video data which is pixel information, and a print start command (PRINT) is sent to the microcomputer 20.

As a result, the microcomputer 20 raises the internal temperature of the fixing device 17 to a temperature sufficient for fixing the toner image on the recording paper P. At the same time, a horizontal scanning control task, which will be described later, is activated, it is confirmed that the horizontal synchronizing signal has reached a predetermined cycle, a main motor (not shown) is driven, and a high voltage is applied to the charging roller 7.

When the charged photosensitive drum 6 reaches the position of the developing roller 9, a high voltage is also applied to the developing roller 9 to uniformly charge at least one round of the photosensitive drum 6.

After the photosensitive drum 6 is uniformly charged, the sheet feeding solenoid (not shown) is driven to feed the recording sheet P on the sheet feeding tray 1. When the leading edge of the fed recording paper P reaches the paper feed sensor 5, the microcomputer 20 sends a vertical synchronization signal to the controller, and a high voltage is applied to the transfer roller at the timing when the recording paper P reaches the transfer roller 10. To do.

The controller synchronizes the video data (VID) with the vertical synchronizing signal and the horizontal synchronizing signal (BDO).
EO) to the microcomputer 20. The microcomputer 20 outputs the video data (VIDEO) sent from the controller to / VDOUT, and the current switch circuit 24 turns on / off the laser 27.

As a result, the laser beam based on the video data scans the photosensitive drum 6 via the rotary polygon mirror 8 to form an electrostatic latent image.

The formed electrostatic latent image is developed into a toner image by the developing roller 9 and transferred onto the recording paper P by the transfer roller 10. The transferred toner image is heated by the fixing device 17.
It is pressurized, fixed on the recording paper P, and ejected to the paper ejection tray 12 by the paper ejection roller 11.

FIG. 4 is a flow chart of an event interruption process for detecting whether or not the number of rotations of the scanner motor 19 is the specified number of rotations.

This event interrupt processing is performed by the scanner tack signal (SCN) input to the microcomputer 20.
It is generated at each rising edge of (TAC) and measures the period of the scanner tack signal to detect the number of rotations of the scanner motor 19, and the respective processes will be described below.

In step S101, for example, the increment operation of the timer counter that is incremented every 1 microsecond is stopped.

In step S102, the count value of the timer counter is compared with the maximum allowable value of the period of the scanner tack signal when the scanner motor 19 is rotating at the specified rotation speed. If the count value is large, step S103 is performed.
If the count value is small, the process proceeds to step S104.

In step S103, the scanner ready flag for judging whether or not the scanner motor 19 is rotating in the specified manner in the horizontal scanning control task processing described later is turned off.
Set to (0).

In step S104, the count value of the timer counter is compared with the allowable minimum value of the period of the scanner tack signal when the scanner motor 19 is rotating normally. If the count value is small, the process proceeds to step S103. Is larger, the process proceeds to step S105.

In step S105, the scanner ready flag is turned ON (1).

In step S106, the count value of the timer counter is set to "0".

In step S107, the increment operation of the timer counter is restarted.

By performing the above processing, the period of the scanner tack signal is measured by the count value using the timer counter at each rising edge of the scanner tack signal,
The scanner motor has reached the specified number of revolutions for horizontal scanning control task processing by turning on the scanner ready flag only while the count value is between the allowable minimum value and the allowable maximum value of the scanner tack signal. Let me know.

FIG. 5 is a flow chart of the horizontal scanning control task processing in this embodiment.

Upon receiving the print start command, the microcomputer 20 activates this task to rotate the scanner motor 19, send a horizontal synchronizing signal to the controller, and perform error processing. The respective processes will be described below.

In step S201, it is permitted to perform an event interrupt process that occurs in synchronization with the rising edge of the scanner tack signal from the scanner motor 19 described above.

In step S202, the scanner motor 19 is started by setting the scanner drive signal (/ SCNON) to "L" level.

In step S203, the scanner motor 1
In order to detect the failure of item 9, a timer that counts up after t ₁ seconds is set.

In step S204, it is determined from the state of the scanner ready flag from the event interruption process whether or not the number of rotations of the scanner motor 19 is the specified number of rotations, and the scanner ready flag is OFF, that is, the scanner motor 19 Is not rotating as specified, step S
When the scanner ready flag is ON, that is, when the scanner motor 19 is in the specified rotation, the process proceeds to step S207.

In step S205, step S203
It is determined whether or not the t ₁ second timer set in step ₁ has counted up, and if not, step S2
Returning to 04, if the count is up, it is determined that the scanner motor has failed, and the process proceeds to step S206.

In step S206, the scanner drive signal (/ SCNON) is set to "H" level to stop the scanner motor 19, notify the controller of the scanner motor failure, and stop this task.

In step S207, the scanner motor 1
When it is determined that 9 is rotating normally at the specified rotation, event interrupt processing synchronized with the rising edge of the scanner tack signal is prohibited from being performed, and detection of the number of rotations of the scanner motor 19 is stopped.

In step S208, as the laser APC processing, the L _ON signal shown in FIG. 3 is set to the “H” level, and the NOR circuit 47 causes the laser lighting signal (/ MLO).
N) is set to "L" level and the AND circuit 2 shown in FIG.
The output of 3 is set to "L" level. As a result, the switch of the current switch circuit 24 is turned on, the current is supplied to the laser 27, and the laser is turned on.

At this time, the microcomputer 20
The output of the photodiode 25 corresponding to the light amount of the laser is received via the A / D converter 26, and the D / A converter 2 is set so that the data (light amount) becomes the target light amount.
The voltage is increased or decreased via 1 to change the current value supplied to the laser 27, and the laser light amount is adjusted to the target value.

When the laser light amount reaches the target value, the laser AP
C processing is stopped, the L _ON signal is set to “H” level, the laser is turned off, and it is determined whether or not the horizontal synchronizing signal can be generated at the specified cycle. Set the value in the synchronization check register 30,
The value corresponding to the allowable maximum time is set to the synchronization check register 31.
Set to.

Further, in order to generate the horizontal synchronizing signal, the laser light must be incident on the light receiving circuit 29 without fail.
In order to set N to "L" level and turn on the laser 27, a count value corresponding to a predetermined time from the previous horizontal synchronizing signal is set in the laser on register, and the time when the laser light scans the light receiving circuit 29 from the horizontal synchronizing signal. The count value corresponding to is set in the laser off register 32. When these values are set and the pulse from the light receiving circuit 29 is input to the beam detect signal (BDi), the rising edge of the pulse causes the clock generator 39 to output the horizontal synchronizing signal (BDO) output from the pulse synchronizer 45. A pulse (“H” level) for one cycle of the clock obtained in step 1 is output.

This pulse resets the counter 34 and restarts counting from 0. When the count value of the counter 34 becomes equal to the value set in the synchronization check register 30, the output of the comparator 35 becomes "H" level, and the BD ready signal (BDRDY) output from the JK flip-flop 41 at the next clock. Becomes "H" level.

After that, when the rising edge of the next beam detect signal (BDi) is detected before the count value reaches the value set in the synchronization check register 31, the BD ready signal (BDRDY) remains at "H" level. Become.
Conversely, when the count value becomes equal to the value set in the synchronization check register 31, the output of the comparator 36 becomes "H" level and the BD ready signal (BDRDY) returns to "L" level at the next clock.

Therefore, the beam detect signal (BD
When i) is detected in a cycle longer than the value set in the sync check counter 30 and shorter than the value set in the sync check register 31, the BD ready signal becomes "H" level.

In step S209, a timer that counts up after t ₂ seconds is set in order to detect a failure of the circuit for generating the horizontal synchronizing signal and the optical system (hereinafter referred to as horizontal scanning system).

In step S210, a BD ready signal (BDR) indicating that the horizontal synchronizing signal has a specified cycle is generated.
DY) is at "H" level,
If the "H" level, that is, the horizontal synchronizing signal has the specified cycle, the process proceeds to step S213, and if the "L" level remains, the process proceeds to step S211.

In step S211, step S209
It is determined whether or not the t ₂ second timer set in step 1 has counted up, and if not, step S2
Returning to step 10, if the count is up, it is determined that the horizontal scanning system has failed, and the process proceeds to step S212.

In step S212, the scanner drive signal (/ SCNON) is set to the "H" level to stop the scanner motor 19, notify the controller of the horizontal scanning system failure, and stop this task.

In step S213, since it has been confirmed that the horizontal synchronizing signal is output to the controller at the specified cycle, the paper feed permission flag for permitting the paper feed operation in another task is set.

In step S214, it is determined whether or not the horizontal synchronizing signal is always normally output during the printing operation.
It is determined that the ready signal (BDRDY) is at the "H" level. If the BD ready signal is at the "H" level, it is determined that the horizontal synchronizing signal is normal, and the process proceeds to step S216. When the BD ready signal goes to "L" level,
If there is a problem with the horizontal sync signal, step S
Move to 215.

In step S215, the scanner motor 19
Then, the paper feed permission flag is reset to prohibit feeding of the next page, the controller is notified that there is a problem with the horizontal synchronizing signal, and this task is stopped.

In step S216, it is determined whether the print operation is in progress or the print start command for the next page is not sent. If yes, the process returns to step S214. If not, the paper feed permission flag is reset and the scanner motor is operated. Stop 19 and stop this task.

As described above, the scanner motor 19
After detecting that the horizontal rotation signal is rotating for the specified period, it is possible to reduce the load on the microcomputer 20 by detecting only that the horizontal synchronizing signal has the specified cycle.

Embodiment 2 FIG. 6 is a flow chart showing the horizontal scanning control task processing in another embodiment of the present invention. Note that this embodiment has the same configuration as the printer of Embodiment 1 described above. Therefore, the description thereof is omitted.

In FIG. 6, except for step S318,
Processing similar to that of each step at the same position shown in FIG. 5 is performed.

In step S314, when the BD ready signal (BDRDY) becomes "L" level, it is determined that there is a problem with the horizontal synchronizing signal, and the process proceeds to step S317.
In step S317, the paper feed permission flag is reset, the paper feed for the next page is prohibited, the controller is notified that there is a problem in the horizontal synchronizing signal, the BD error flag is set, and the process returns to step S301.

Returning to step S301, the event interruption is permitted again, the number of rotations of the scanner motor 19 is started to be checked, and the failure of the scanner motor is judged.

If it is determined in steps S304 and S305 that the scanner motor 19 is defective, the process proceeds to step S306, the scanner motor 19 is stopped, and the controller is informed that the scanner motor is defective.
Stop this task.

If it is determined in step S304 that the scanner motor is rotating normally, the laser APC process is performed again, and in steps S310 and S311, the failure detection of the horizontal scanning system is performed.

In steps S310 and S311, it is determined that the horizontal scanning system has failed. If it is determined that the horizontal scanning system has failed, the process proceeds to step S312 and the scanner motor 19 is stopped.
Notify the controller that the horizontal scanning system is faulty,
Stop this task.

In step S310, the BD ready signal (BD
RDY) becomes “H” level and it is determined that the horizontal synchronizing signal is normal, the process proceeds to step S318, it is determined whether the BD error flag is set, and if the BD error flag is set, That is, when the BD ready flag is set to the “L” level during the previous printing operation and the BD error processing is being performed, this task is stopped.

As described above, when a problem occurs in the horizontal synchronizing signal during the printing operation, the failure cause of the scanner motor 19 and the horizontal scanning system can be checked again by checking the failure. If no failure is found in the recheck, the BD error flag is cleared by an instruction from the controller, so that a minor error can be automatically recovered by the printer.

[0076]

As described above, according to the present invention, after detecting that the scanner motor for rotating the rotary polygon mirror makes the specified rotation, the horizontal synchronizing signal has the specified cycle. I try to detect only things,
The burden on the microcomputer can be reduced without degrading the control characteristics.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a laser beam printer according to an embodiment of the present invention.

FIG. 2 is a block diagram showing a main control unit according to an embodiment of the present invention.

FIG. 3 is a circuit diagram showing a logic unit for checking a horizontal synchronizing signal in an embodiment of the present invention.

FIG. 4 is a flowchart showing event interrupt processing according to an embodiment of the present invention.

FIG. 5 is a flowchart showing horizontal scanning control task processing according to an embodiment of the present invention.

FIG. 6 is a flowchart showing horizontal scanning control task processing according to another embodiment of the present invention.

[Explanation of symbols]

 6 Photosensitive drum 8 Rotating polygon mirror 19 Scanner motor 20 Microcomputer 21 D / A converter 22 Voltage / current conversion circuit 23 AND circuit 24 Current switch 25 Photodiode 26 A / D converter 27 Laser diode 28 Folding mirror 29 Light receiving circuit

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hideki Suzuki 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc.

Claims (1)

[Claims] 1. An image forming apparatus for drawing an image on a photosensitive member by deflecting laser light emitted from a semiconductor laser by a rotating polygon mirror composed of a plurality of mirror surfaces, wherein a rotation speed of the rotating polygon mirror is regulated. Rotation holding means for holding the number of rotations, rotation detection means for detecting that the rotation polygon has become a specified rotation by the rotation holding means, and laser light reflected by the rotation polygon mirror is received by a non-image portion. Timing signal generating means for generating a writing timing signal of a laser beam for horizontally scanning the photoconductor, a timing detecting means for detecting that the timing signal has reached a prescribed cycle, and the writing timing signal by the timing detecting means. Is detected at the specified period, the specified rotation detection of the rotary polygon mirror by the rotation detection means is stopped. An image forming apparatus characterized by including a that control means.