JP2002067377A - Image forming device and its controlling method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrophotographic type laser beam printer and the like which can do automatic adjustment of quantity of light of laser during acceleration of a scanner motor, can fast complete an operation to initialize a photosensitive body, and can improve a first print time. SOLUTION: Rotational drive and the number of rotations of the scanner motor 31 are detected by a scanner motor drive circuit 32, and quantity of light of a laser diode 14 is controlled by a laser drive circuit 13. When printing operation starts, the quantity of light of the laser is set lower than the quantity of light after the scanner motor 31 reaches a regular number of rotations until the scanner motor 31 reaches the regular number of rotations.

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 forming an image by scanning a light beam on a photoreceptor such as a laser beam printer, and a control method thereof.

[0002]

2. Description of the Related Art In a laser beam printer which is an electrophotographic image forming apparatus, when a printing operation is instructed by a video controller 3 shown in FIG. 2, an engine controller 12 activates a scanner motor 31. When the scanner motor 31 reaches the specified rotation speed, / SC
The NRDY signal becomes L. Engine controller 12
Detects that the scanner motor 31 has reached the specified number of revolutions based on the / SCNRDY signal, forcibly drives the semiconductor laser diode 14, and performs automatic light amount adjustment control (APC
Control). Hereinafter, APC will be described.

A laser driving circuit 13 automatically adjusts a laser light amount to a specified light amount.
atic power control circuit; hereinafter AP
C circuit). FIG. 3 shows a configuration example of the APC circuit.

[0004] The APC circuit controls the current of the laser diode 14 so as to keep the photocurrent of the photodiode 35 receiving the laser light constant. At the time of printing an image, a means for storing a set value is necessary in order to keep the current value of the laser diode 14 controlled constant. As a means for storing the set value, a capacitor for normal hold is used. .

The holding capacitor is used in a sample and hold circuit, and this circuit is operated in a sample state at the time of APC, and charges the holding capacitor until the laser light amount reaches a value corresponding to a specified light amount. Therefore, at the time of APC, the laser must be turned on for a longer time than the hold capacitor is charged. On the other hand, the operation in the hold state is at the time of image formation, and the laser is caused to emit light with a specified light amount based on the voltage value of the hold capacitor.

The laser light emitted from the laser diode 14 is shaped by a coupling lens 33, reflected by a polygon mirror 15 rotated by a scanner motor 31, and periodically reflected by a photodiode 35 through an fθ lens 34. Hit. The signal from the photodiode 35 is amplified by an amplifier (amplifier) 36, shaped into a pulse waveform by a waveform shaping circuit 37, and then input to the engine controller 12 as a horizontal synchronization signal. Scanner motor 31
Is rotating at the specified rotation, the engine controller 12 periodically turns on the laser in synchronization with the horizontal synchronization signal, so that the laser can be turned on only in the non-image area near the photodiode 35.

After the APC is completed, the engine controller 12 turns on the semiconductor laser only in the non-image area near the photodiode 35 as described above. In the image area, the video signal input from the video controller 3 turns the laser diode 14 on. It will be in a driving state. After this state, the engine controller 12 starts initialization of the photoconductor surface. After the initialization of the photoreceptor surface is completed, the engine unit starts a printing operation and feeds paper.

At this time, the paper taken out one by one from the paper feed cassette 27 shown in FIG. 1 by the paper feed roller 28 is conveyed, and when the leading end of the paper reaches the TOP sensor 26, the vertical synchronization is transmitted to the video controller 3. Can be Then, the video controller 3 sends out an image signal (BD signal) in synchronization with the BD signal. The image signal input to the engine controller 12 is created in the laser drive circuit 13, where ON / OFF of the laser diode 14 is controlled. The laser light 17 emitted from the laser diode 14 is deflected by the polygon mirror 15 to become scanning light in the longitudinal direction of the photosensitive drum 19,
Is projected onto the photosensitive drum 19 via the.

The photosensitive drum 19 rotates in the direction of the arrow in FIG. 1 and is primarily charged by a primary charger 18 and then receives an exposure corresponding to ON / OFF of a laser beam 17, so that the surface of the photosensitive drum 19 An electrostatic latent image is formed. And
After the colored charged particles (referred to as toner) are applied by the developing device 20 and a visualized image is obtained, the visualized image is transferred to a sheet as a recording medium by the transfer charger 21. The transfer residual toner is wiped off from the surface of the photosensitive drum 19 by the cleaning device 22, and the photosensitive drum 19 prepares for the next image forming process.

On the other hand, the paper on which the unfixed toner image is placed is passed through a fixing device 23, where a permanent fixed image is obtained.
As a final print, the paper is discharged out of the machine in the direction of the arrow in the figure. The arrows in FIG. 1 indicate the feed trajectory of the sheet taken out of the sheet cassette 27 and conveyed.

[0011]

However, in the above-described conventional image forming apparatus, the speed at which the laser scans the surface of the photoreceptor during startup of the scanner motor is slower than during image formation. However, it is also exposed to relatively strong light. Therefore, the APC operation is started after the scanner motor reaches the specified rotation, or the APC operation is started.
It is necessary to charge the photoreceptor surface for a longer time so that the effects of exposure to strong light after completion are eliminated. Therefore, it takes a long time for the process initialization operation, and it is difficult to reduce the first print time.

SUMMARY OF THE INVENTION The present invention has been made in consideration of the above-described problems, and it is an object of the present invention to prevent the photosensitive member surface from being relatively exposed to light even when the rotation of a scanner motor is slow. It is an object of the present invention to provide an image forming apparatus capable of eliminating the waiting time at the time of process initialization, completing the process initialization in a shorter time, and shortening the first print time, and a control method thereof.

[0013]

An image forming apparatus and a control method therefor according to the present invention are configured as follows.

(1) An image forming apparatus for forming an image by scanning a light beam on a photoreceptor, comprising: a scanner motor for rotating the reflector for reflecting the light beam to scan on the photoreceptor; Light amount adjusting means for adjusting the light amount of the light beam, and detecting means for detecting the number of rotations of the scanner motor, and the scanner motor adjusts the light amount of the light beam until the scanner motor reaches a predetermined number of rotations. The light amount is set to be lower than the light amount after reaching a predetermined number of rotations.

(2) In the above (1), the light amount of the light beam is determined according to the rotation speed of the scanner motor.

(3) In the above (1), the light amount of the light beam is determined according to the rotation speed of the motor for rotating the photosensitive member.

(4) In the above (1), a detecting means for detecting the scanning reference position of the light beam is provided, and the light amount of the light beam is set for each scanning of one line.

(5) In any one of the above (1) to (4), a charging means for uniformly charging the photosensitive member is provided, and the uniformly charged photosensitive member is scanned with a light beam. .

(6) A method of controlling an image forming apparatus for forming an image by scanning a light beam on a photosensitive member, wherein the reflecting member is rotated to reflect the light beam and scan the photosensitive member. The number of revolutions of the scanner motor is detected, and the light amount of the light beam is set to be lower than the light amount after the scanner motor reaches the predetermined number of revolutions until the scanner motor reaches the predetermined number of revolutions.

(7) In the above (6), the light amount of the light beam is determined according to the rotation speed of the scanner motor.

(8) In the above (6), the light amount of the light beam is determined according to the rotation speed of the motor for rotating the photosensitive member.

(9) In the above (6), the scanning reference position of the light beam is detected, and the light amount of the light beam is set for each scanning of one line.

(10) In any one of the above (6) to (9), the photosensitive member uniformly charged by the charging means is scanned with a light beam.

[0024]

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

(Embodiment 1) FIG. 1 is a configuration diagram of an electrophotographic laser beam printer to which the present invention is applied, and FIG. 2 is a block diagram showing a configuration of a control system thereof. The same applies to the present embodiment, and a duplicate description will be omitted.

In FIG. 1, reference numeral 1 denotes a control unit for transmitting a video signal, and an I / F with a host computer.
(Interface) It has a circuit 2, a video controller 3, and an operation unit 4. The video controller 3 develops an electric signal, which is code data input from a host computer (not shown), into a dot image and stores it in a memory inside the video controller. After that, it is returned as a video signal to the engine unit 11 having the printer engine. Each element of the engine unit 11 is controlled by an engine controller 12, and exchange of video signals with the control unit 1 is also performed via the engine controller 12.

Reference numeral 13 denotes a laser driving circuit for driving a semiconductor laser diode 14, reference numeral 15 denotes a polygon mirror (reflector) for reflecting laser light (light beam) to scan the photosensitive drum, and reference numeral 16 denotes a fixed mirror. Then, the laser beam 17 is guided to the photosensitive drum 19 whose surface is uniformly charged by the primary charger 18.

Reference numeral 20 denotes a developing device, 21 denotes a transfer charger, 22 denotes a cleaning device, 23 denotes a heater 24 and a pressure roller 25.
The fixing device 26 has a T for detecting the leading end of the sheet fed from the sheet feeding cassette 27 by the sheet feeding roller 28.
This is an OP sensor, and the sheet is conveyed in the direction of the arrow in the figure.

In FIG. 2, reference numeral 31 denotes a scanner motor for rotating the polygon mirror 15, and reference numeral 32 denotes a scanner motor drive circuit, which has a detecting means for detecting the number of rotations of the scanner motor 31. 33 is a laser diode 14
A coupling lens for shaping the laser light from the lens, 34 an fθ lens (condensing means) for condensing the laser light, 35 a photodiode serving as a beam position detecting means, 36 an amplifier for amplifying the output of the photodiode 35, 37 Is a waveform shaping circuit, 38 is a BD signal generating circuit in the engine controller 12, and 39 is a CPU.

In the above configuration, when the apparatus is in a printable state, the video controller 3 gives an instruction to start printing to the engine controller 12 as necessary, thereby starting a printing operation.

When the printing operation is started, the engine controller 12 starts the main motor (not shown) and the scanner motor 31. The main motor drives all the driving units related to sheet conveyance, such as the photosensitive drum 19 and the sheet feeding motor 28. Engine controller 12
Means that the speed of the main motor has exceeded the specified speed and the photosensitive drum 1
After 9 rotates at the specified speed, the laser is forcibly turned on,
APC control is started.

FIG. 3 is a block diagram showing the configuration of the laser drive circuit 13.

In FIG. 3, reference numeral 41 denotes a photodiode as a laser light amount detecting means for detecting the amount of light emitted from the laser diode 14 as a light beam emitting means; 42, a semi-fixed resistor (light amount adjusting means) for adjusting the laser light amount; 43 is a differential amplifier for converting the current value of the photodiode 41 together with the semi-fixed resistor 42 to a voltage value, and 44 is a sample and hold circuit for controlling charge / discharge as a sample and hold operation. A mode switching control signal (referred to as an S / H control signal) is input.

An amplifier gain switching circuit 45 determines the output voltage of the linear amplifier 46, and receives a control signal (PCHG signal) for switching the gain. 47 is a reference voltage source used for controlling the output, and 48 is the laser diode 1
4 is a switching constant current source, and 49 is a switching circuit for turning on / off the laser diode 14.
An N / OFF control signal (referred to as an image data signal) is input. 50 is a load resistor for flowing a current instead of the laser diode 14 when the laser diode 14 is OFF, 51 is a constant current source for biasing the laser diode 14, 52 is a resistor for setting a bias current value, and 53 is a switching current. Value setting resistors, 54 and 55 are reference resistors for determining the reference gain of the amplifier gain switching circuit 46, and 56 is a sample and hold device for storing a set value for keeping the controlled current value of the laser diode 14 constant. It is a capacitor.

The APC control of the laser diode 14 is in a state called a sample mode in the system using the sample and hold circuit 44. In practice, the sample mode is designated by an S / H control signal from the engine controller 12, and the engine controller The switching circuit 49 is switched so that the laser diode 14 is forcibly turned on by the image data signal from the controller 12. When the laser diode 14 is ON, current-voltage conversion is performed by the semi-fixed resistor 42 and the differential amplifier 43 on the output current from the photodiode 41 that generates a current proportional to the amount of laser light emitted. The output voltage from the differential amplifier 43 is compared with the voltage of the reference voltage source 47 by the linear amplifier 46, and the sample-hold circuit 4
Reference numeral 4 denotes charging and discharging of the sample and hold capacitor 56.

That is, when the amount of light emitted from the laser diode 14 is small, the output voltage of the differential amplifier 43 becomes lower than the reference voltage of the reference voltage source 47, so that the sample and hold circuit 44 supplies a current to the sample and hold capacitor 56. , The charging voltage of the capacitor 56 is increased. When the voltage of the sample and hold capacitor 56 increases, the current value of the switching constant current source 48 increases, and the current flowing through the laser diode 14 increases to increase the amount of laser light. Then, the sample-and-hold capacitor 56 is charged until the output voltage of the differential amplifier 43 becomes equal to the reference voltage of the reference voltage source 47.

The laser diode 14 has a portion called an LED light-emitting region and a laser light-emitting region. In order to increase the ON / OFF switching speed of the laser diode 14, the laser diode 14 does not reach the laser light-emitting region and has a LE.
A means is provided for supplying a current to the maximum of the D light emitting region, and the current value is set by the bias constant current source 51.

Conversely, if the amount of light emitted from the laser diode 14 is large, the output voltage of the differential amplifier 43
Sample and hold circuit 4
4 discharges the capacitor 56 for sample and hold. When the voltage of the sample and hold capacitor 56 decreases, the current value of the switching constant current source 48 decreases, and the current flowing through the laser diode 14 decreases, thereby reducing the amount of laser emission. And the differential amplifier 43
Is discharged until the output voltage becomes equal to the reference voltage of the reference voltage source 47.

Since the light quantity of the laser diode 14 is substantially proportional to the sample-and-hold capacitor 56, the amplifier gain switching circuit 45 controls the linear amplifier 4
By controlling the output voltage of No. 6, it is also possible to change the charging voltage of the sample and hold capacitor 56 to change the amount of laser light. For example, if the gain of the linear amplifier 46 is doubled, the laser light amount is also doubled.

When the APC control is started, the engine controller 12 uses the PCHG signal to set the laser light amount to be smaller than that at the time of image formation. In this embodiment, the light amount is set to a half of that during image formation. Further, the engine controller 12 includes a sample and hold capacitor 56.
The APC control is performed for a time necessary for charging the laser, and after the light amount adjustment is completed, the laser is stopped, and an initialization process around the photosensitive drum described below is started.

That is, the primary charger 18 charges the photosensitive drum 19 one or more times. At the same time, the photosensitive drum 19
Where the charged portion of the sheet passed the transfer charger 21,
A voltage is applied to the transfer charger 21 and the constant current control is performed for one or more rounds of the transfer charger 21. Then, the resistance characteristic of the transfer charger 21 is obtained, and the voltage applied to the transfer charger 21 when the image is transferred to the paper is determined. When the above two operations are completed, the initialization process around the photosensitive drum is completed.

Further, the engine controller 12 outputs / S
When it is detected from the CNRDY signal that the scanner motor 31 has reached the specified number of revolutions, the laser is emitted only in the non-image area in synchronization with the BD signal, and the gain of the linear amplifier 46 is doubled using the PCHG signal. In this way, the laser light amount is doubled to prepare for image formation. FIG. 4 shows the relationship between the number of rotations of the scanner motor 31 and the amount of laser light at this time.

Then, the engine controller 12 determines that the scanner motor 31 has reached the specified number of revolutions, that the initialization process of the photosensitive portion of the photosensitive drum 19 has been completed,
When it is detected that the temperature of the fixing device 23 has reached the specified temperature, the paper is fed one by one from the paper feed cassette 27 by the paper feed roller 28 to perform the printing operation. Subsequent operations are the same as those of the above-described conventional example, and thus description thereof is omitted.

As described above, in the present embodiment, the laser drive circuit 13 is configured to be capable of performing APC control with a plurality of light amounts according to an instruction from the engine controller 12, and the scanner motor 31 is controlled to a specified (predetermined) rotation speed. Until the light amount reaches, the laser light amount is set lower than that during image formation. In this manner, even when the rotation of the scanner motor 31 is slow, it is possible to prevent the photosensitive drum surface from being relatively exposed more strongly than during image formation. Therefore,
The waiting time during the process initialization can be eliminated, the process initialization can be completed in a shorter time, and the first print time can be reduced.

FIG. 7 shows the operation of the above embodiment. The control processing shown in this flowchart is executed by the engine controller 12 of the engine unit 11 according to a program stored in advance.

The video controller 3 of the control unit 1
Sends a video signal and gives a print instruction (S1), and activates the scanner motor 31, the main motor and the fixing device 213 (S2). When the rotation speed (rotation speed) of the main motor for driving the photosensitive drum or the like reaches a predetermined specified value (S3), the laser is turned on (S4),
While performing the above-mentioned APC control (S5), an initialization process around the photosensitive drum is executed (S6).

When the number of revolutions of the scanner motor 31 reaches the specified value (S7), the photosensitive drum 19 is exposed by emitting laser light (S8). If the temperature of the fixing unit 23 has reached the specified value (S9), the sheet cassette 2
7 is fed (S10), and printing is performed (S1).
1).

(Embodiment 2) Next, a second embodiment of the present invention will be described. Since the configuration and basic operation of the printer of the present embodiment are the same as those of the first embodiment, the description of the overlapping parts will be omitted.

When the printing operation is started, the engine controller 12 starts the main motor and the scanner motor 31 (not shown). Then, after the main motor reaches the specified speed or more and the photosensitive drum 19 rotates at the specified speed,
The laser is forcibly turned on and APC control is started. At this time, the light amount of the laser is set as small as possible. However, it is necessary that the light amount is equal to or larger than the light amount that can be detected by the photodiode 35.

The engine controller 12 controls the above AP
At the same time as performing the C control, the scanning speed of the laser beam on the photosensitive drum 19 is determined by detecting the period of the BD signal,
The laser light amount is determined so that the light amount per unit area does not become larger than that during image formation. For example, if the period of the BD signal is one half of the prescribed period during image formation, the laser light amount is also set to one half. And the scanner motor 3
Until 1 reaches the specified number of revolutions, such laser light amount control is performed, and laser light emission is continued. FIG. 5 shows the relationship between the number of rotations of the scanner motor 31 and the amount of laser light at this time.

By doing so, the scanner motor 3
Even if the laser is forcibly turned on during acceleration of the photosensitive drum 19,
Of the process can be minimized, and the process initialization control can be performed quickly.

(Embodiment 3) Next, a third embodiment of the present invention will be described. Since the configuration and basic operation of the printer of the present embodiment are the same as those of the first embodiment, the description of the overlapping parts will be omitted.

When the printing operation is started, the engine controller 12 controls the main motor and the scanner motor 31.
Start In this embodiment, the engine controller 12
The motor gradually accelerates from low speed over time to reduce the torque at the time of starting the main motor (slow-up control). If the slow-up control time of this motor is long and the scanner motor 31 reaches the specified number of revolutions first, the laser light amount is controlled as follows.

The engine controller 12 determines the speed of the photosensitive drum 19 in the sub-scanning direction from the rotation speed of the main motor, and determines the amount of laser light so that the amount of light per unit area on the photosensitive drum does not become larger than that during image formation. decide. For example, if the speed of the main motor is half that during image formation, the laser light amount is also set to half. Such control of the laser light amount is performed until the main motor reaches the specified rotation speed. FIG. 6 shows the relationship between the speed of the main motor and the amount of laser light at this time.

By doing so, even if the laser is forcibly turned on during acceleration of the main motor, the influence on the photosensitive drum 19 can be minimized, and the process initialization control can be performed quickly.

[0056]

As described above, according to the present invention,
Even when the rotation of the scanner motor is slow, the surface of the photoconductor can be prevented from being relatively exposed compared to the time of image formation, eliminating waiting time when initializing the process and completing the process initialization in a shorter time. As a result, the first print time can be reduced.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a laser beam printer to which the present invention is applied.

FIG. 2 is a block diagram showing a configuration of a control system according to the embodiment.

FIG. 3 is a block diagram illustrating a configuration of a laser driving circuit according to an embodiment.

FIG. 4 is a diagram illustrating a scanner motor speed and a laser light amount according to the first embodiment.

FIG. 5 is a diagram illustrating a scanner motor speed and a laser light amount according to a second embodiment.

FIG. 6 is a diagram illustrating a main motor speed and a laser light amount according to a third embodiment.

FIG. 7 is a flowchart showing the operation of the first embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Control part 2 I / F circuit 3 Video controller 4 Operation part 11 Engine part 12 Engine controller 13 Laser drive circuit 14 Laser diode 15 Polygon mirror (reflector) 16 Mirror 17 Laser light 18 Primary charger 19 Photosensitive drum 20 Developer 21 Transfer charger 22 Cleaning device 23 Fixing device 24 Heater 25 Pressure roller 26 TOP sensor 27 Paper cassette 28 Paper feed roller 31 Scanner motor 32 Scanner motor drive circuit (detection means) 33 Coupling lens 34 fθ lens (light collecting means) 35 Photodiode (beam position detecting means) 36 Amplifier 38 BD signal generating circuit 39 CPU 41 Photodiode 42 Semi-fixed resistor (light amount adjusting means)

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H04N 1/113 H04N 1/04 104A 5C071 / 23 103 F term (Reference) 2C362 AA54 AA56 AA64 AA68 BA32 CB60 CB80 2H045 AA53 CB42 CB61 2H076 AB05 DA04 DA17 DA22 DA43 2H110 CD12 5C072 AA03 BA03 HA02 HA13 HB02 HB04 HB08 HB15 XA05 5C074 AA12 BB03 BB26 CC22 CC26 DD08 EE02 EE05 GG02 GG04

Claims (10)

[Claims] 1. An image forming apparatus for forming an image by scanning a light beam on a photoconductor, comprising: a scanner motor for rotating a reflector for reflecting the light beam to scan the photoconductor; The scanner motor includes a light amount adjusting unit that adjusts a light amount of the light beam, and a detecting unit that detects a rotation speed of the scanner motor. The scanner motor controls the light amount of the light beam until the scanner motor reaches a predetermined rotation speed. An image forming apparatus, wherein the light amount is set lower than the light amount after the number of rotations is reached. 2. The image forming apparatus according to claim 1, wherein a light amount of the light beam is determined according to a rotation speed of the scanner motor. 3. The image forming apparatus according to claim 1, wherein the light amount of the light beam is determined according to a rotation speed of a motor that rotates the photosensitive member. 4. The image forming apparatus according to claim 1, further comprising detecting means for detecting a scanning reference position of the light beam, wherein the light amount of the light beam is set for each scanning of one line. 5. The image forming apparatus according to claim 1, further comprising a charging unit configured to uniformly charge the photosensitive member, and scanning the uniformly charged photosensitive member with a light beam. . 6. A method for controlling an image forming apparatus for forming an image by scanning a light beam on a photosensitive member, wherein the scanner rotates a reflector for reflecting the light beam and scanning the photosensitive member. The number of rotations of the motor is detected, and the light amount of the light beam is set to be lower than the light amount after the scanner motor reaches the predetermined number of revolutions until the scanner motor reaches the predetermined number of revolutions. A method for controlling an image forming apparatus. 7. The control method according to claim 6, wherein the light amount of the light beam is determined according to the rotation speed of the scanner motor. 8. The control method for an image forming apparatus according to claim 6, wherein the light amount of the light beam is determined according to a rotation speed of a motor for rotating the photosensitive member. 9. The method according to claim 6, wherein a scanning reference position of the light beam is detected, and a light amount of the light beam is set for each scanning of one line. 10. The control method for an image forming apparatus according to claim 6, wherein the photosensitive member uniformly charged by the charging means is scanned with a light beam.