JPH10133136A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent irradiation of a photoreceptor with an unnecessary laser beam other than image data. SOLUTION: A scanner motor 27 is driven at maximum acceleration by printing start instruction, the period T of a Hall signal HS generated by the rotation of the scanner motor 27 is simultaneously monitored, a laser beam is emitted when the period T becomes shorter than (t) and a photoelectric convertion signal PC at this time is detected. When a second photoelectric conversion signal PC is detected, the emission of a laser beam is stopped, the period T of the photoelectric conversion signal PC at this time is measured, the emission is controlled so as to emit a laser beam on a place other than the image printing area of a photo-receptor drum. On the other hand, the photoelectric conversion signal PC is also inputted to a motor rotation control circuit 22, the scanner motor 27 driven with the maximum acceleration reaches an originally prescribed number of revolution, initialization of the photoreceptor drum is finished, thereafter, transfer of papers is started when the temp. of a fixation device reaches the prescribed temp. and printing operation is started by receiving a video signal.

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 used in an electrophotographic process such as a laser printer and capable of controlling a laser diode.

[0002]

2. Description of the Related Art FIG. 7 shows a configuration of a conventional scanner unit used in an image forming apparatus such as a laser printer.
Are arranged, and the polygon mirror 2 is connected to the scanner motor 3. An imaging lens 4 and a return mirror 5 are arranged in the reflection direction of the polygon mirror 2, and a photoconductor 6 is arranged in the reflection direction of the return mirror 5. Further, a photoelectric converter 7 is arranged near the imaging lens 4.

[0003] Laser light from a laser diode 1 is reflected by a polygon mirror 2 rotating at a high speed by a scanner motor 3, and is irradiated on a photoreceptor 6 via an imaging lens 4 and a return mirror 5. Also, polygon mirror 2
A part of the laser light reflected by the light enters the photoelectric converter 7 so that the timing of scanning can be determined.

FIG. 8 is a block diagram of a first conventional drive unit for the laser diode 1 and the scanner motor 3. The output of the CPU 10 is a rotation speed control circuit 11, a motor drive circuit 12, and a laser diode 1 for the scanner motor 3. The output of the frequency generator 14 is connected to the rotation speed control circuit 11,
The output of the rotation speed control circuit 11 is connected to a motor drive circuit 12. The output of the motor drive circuit 12 is connected to the scanner motor 3, and the output of the laser drive circuit 13 is connected to the laser diode 1.

The rotation speed control circuit 11 includes a scanner motor 3
The pulse signal generated from the frequency generator 14 in accordance with the rotation speed of the motor 10 is compared with a reference clock signal SC output from the CPU 10, and a rotation speed control signal RS is output to the motor drive circuit 12. The rotation speed of the scanner motor 3 is controlled by the drive signal MD. The laser drive circuit 13 controls on / off of the laser diode 1 by a laser drive signal LD from the CPU 10 in accordance with image data from an external device (not shown).

FIG. 9 shows a configuration diagram of a second conventional drive unit. A rotation speed control circuit 11 'is added to a CPU 10', and a rotation speed control signal RS and a rotation speed control signal RS, which are signals from the rotation speed control circuit 11 ', are provided. The motor drive signal MD is connected to the motor drive circuit 13, and the output of the motor drive circuit 13 is connected to the scanner motor 3, and the rotation speed control circuit 11 '
Is connected to the BD signal BD from the photoelectric converter 7.
The laser drive signal LD from the CPU 10 'is connected to the laser drive circuit 14,
The output of 4 is connected to the laser diode 1.

In this case, as the speed control method of the scanner motor 3, the image writing position is determined by utilizing the time during which the laser light is input to the photoelectric converter 7 depending on the speed of the scanner motor 3. A BD control method that controls the speed of the scanner motor 3 using an output signal from the photoelectric converter 7 is used. By doing so, the configuration of the motor drive circuit 13 can be simplified by omitting the frequency generator 14, and a low-cost scanner motor drive unit can be configured.

[0008]

However, in the above-described speed detection method using the photoelectric converter 7 of the second conventional example, the laser light must be emitted at the same time as the rotation of the scanner motor 3 is started. In addition, even before the rotation of the scanner motor 3 is stabilized or when image data is not input, a problem occurs that the laser beam scans the photoconductor 6 and adversely affects the photoconductor 6 itself and an image.

An object of the present invention is to solve the above-mentioned problems,
An object of the present invention is to provide an image forming apparatus for preventing unnecessary laser light other than image data from being irradiated on a photosensitive member.

[0010]

According to a first aspect of the present invention, there is provided an image forming apparatus comprising: a laser diode, a polygon mirror, a scanner motor for rotating the polygon mirror, and a rotor of the scanner motor. Rotation detection means for detecting a magnetic field change due to rotation of the provided magnet,
A photosensitive drum having a photosensitive body on its surface and rotating around a cylindrical axis, and a charging mechanism for charging the photosensitive drum, wherein a light beam emitted from the laser diode is transmitted to the shaft on the photosensitive drum by the polygon mirror. An image forming apparatus that forms a latent image by scanning in the direction to form an image by an electrophotographic process, wherein a light beam from the laser diode is reflected on the polygon mirror and is arranged on a predetermined optical axis for scanning. A rotation speed detection mechanism that detects a rotation speed of the scanner motor based on a signal from the photoelectric converter, and a rotation speed control mechanism that holds the rotation speed obtained from the rotation speed detection mechanism at a desired value. When the rotation detecting means detects a predetermined rotation speed or more, the light emission of the laser diode is permitted.

According to a second aspect of the present invention, there is provided an image forming apparatus comprising: a laser diode; a polygon mirror; a scanner motor for rotating the polygon mirror; a photosensitive drum having a photosensitive member on its surface and rotating about a cylindrical axis; An image forming apparatus that forms a latent image by scanning a light beam emitted from the laser diode in the axial direction on the photosensitive drum by the polygon mirror, and forms an image by an electrophotographic process. In the forming apparatus, a photoelectric converter arranged on a predetermined optical axis for scanning by reflecting a light beam from the laser diode on the polygon mirror, and a rotation detecting a rotation speed of the scanner motor based on a signal from the photoelectric converter. A speed detection mechanism, and a rotation speed control mechanism that holds a rotation speed obtained from the rotation speed detection mechanism at a desired value, When the rotation speed obtained by the rotation speed detection mechanism is equal to or lower than a reference speed set lower than a desired value, the light emission amount of the laser diode is reduced or the light emission of the laser diode is stopped. I do.

According to a third aspect of the present invention, there is provided an image forming apparatus comprising: a laser diode; a polygon mirror; a scanner motor for rotating the polygon mirror; a photosensitive drum having a photosensitive member on its surface and rotating about a cylindrical axis; An image forming apparatus that forms a latent image by scanning a light beam emitted from the laser diode in the axial direction on the photosensitive drum by the polygon mirror, and forms an image by an electrophotographic process. In the forming apparatus, a photoelectric converter arranged on a predetermined optical axis for scanning by reflecting a light beam from the laser diode on the polygon mirror, and a rotation detecting a rotation speed of the scanner motor based on a signal from the photoelectric converter. A speed detection mechanism, a rotation speed control mechanism for maintaining the rotation speed obtained from the rotation speed detection mechanism at a desired value, and a temperature detection mechanism. The laser diode starts emitting light with a delay from the rotation start time of the scanner motor, and when the temperature obtained by the temperature detection mechanism is low, the light emission start time of the laser diode and the scanner motor Is characterized by extending the rotation start time.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail with reference to the embodiments shown in FIGS. FIG. 1 shows a block diagram of the first embodiment. In a sequence control section 20 for controlling a sequence of an image forming apparatus, a sequence control circuit 21 and a motor rotation control circuit 22 are provided. The circuit 21 is attached to a CPU that controls the operation timing of each drive system of the image forming apparatus, and is connected to a reference signal SS from a motor rotation control circuit 22 that controls the rotation speed of the scanner motor 27 to be constant.

The acceleration signal AP from the motor rotation control circuit 22
The deceleration signal DP is connected to a motor drive circuit 24 in the motor drive unit 23. The output of the motor drive circuit 24 is connected to a brushless scanner motor 27 including a three-phase coil 25 and three two-pole Hall sensors 26. . The output of one of the three Hall sensors 26 is connected to a comparator 28 in a motor drive circuit 24, and the output of the comparator 28 is used in the motor drive circuit 24.
The hall signal HS is connected to the sequence control circuit 21.

An output of the sequence control circuit 21 and an external video signal VS are connected to respective input terminals of an OR gate 29 provided in the sequence control section 20, and a laser-on signal LN of the OR gate 29 outputs laser light. The laser driving circuit 30 is connected to a laser driving circuit 30 including an APC circuit for lighting at a constant light amount.
1 connected. The photoelectric conversion signal PC from the light amount converter 33 including the photodiode 32 is connected to the sequence control circuit 21 and the motor rotation control circuit 22.

The sequence controller 20 includes a motor driver 23
Signal HS from the photoelectric converter 33, the reference signal SS for setting the number of rotations to the motor rotation control circuit 22, and the laser drive circuit 30 for detecting the photoelectric conversion signal PC. The laser on LN signal is output.

The motor rotation control circuit 22 uses the photoelectric conversion signal PC from the light emission amount converter 33 as a feedback signal indicating the actual rotation speed, and controls the rotation speed of the scanner motor 27 to be constant. That is, it is determined whether the actual rotation speed is slower than the predetermined rotation speed from the difference between the cycle of the reference signal SS from the sequence control circuit 21 and the period of the photoelectric conversion signal PC, and the acceleration signal AP and the deceleration are sent to the motor drive circuit 24 accordingly. A signal DP is output, and by this operation, the rotation speed of the scanner motor 27 is controlled so as to always be a predetermined rotation speed. Sequence control circuit 2
A signal for emitting laser light at a predetermined timing and a video signal VD, which is print data input from the outside, are ORed in order to detect the photoelectric conversion signal PC output from No. 1.
The logical product of the gate 29 is output to the laser drive circuit 30 as a laser-on signal LN.

The output of one Hall sensor of the scanner motor 27 is subjected to waveform shaping via a comparator 28, and then used by the motor drive circuit 24 and sent to the sequence control circuit 21 as a Hall signal HS indicating the number of revolutions. Is output. The laser drive circuit 30 drives a laser light source 31 to record image information on a photoreceptor (not shown), and controls blinking of the laser light according to on / off of a laser on signal LN. The photoelectric converter 33 outputs a photoelectric conversion signal PC serving as a horizontal synchronization signal at the time of recording image data on the photosensitive drum, and the laser light emitted from the laser light source 31 receives the photoelectric conversion signal PC.
Is detected by irradiating a photodiode 32 provided therein, and the detected signal is converted to a photoelectric converter 33.
, And is output to the sequence control circuit 21 and the motor rotation control circuit 22 as a photoelectric conversion signal PC.

FIG. 2 is a flowchart, and FIG. 3 is a timing chart. The image forming apparatus starts its operation in response to an instruction from a sequence controller 20 for processing print data. The print data processing in the sequence control unit 20 is completed, and the video signal VS, which is image data to the image forming apparatus, is output.
Is output, an instruction to start the printing process is output to the image forming apparatus in step S1. In the image forming apparatus, the photosensitive drum is initialized, the rotation of the scanner motor 27 is started, the amount of emitted laser light is set, the fixing device is started to a predetermined temperature,
Operations such as pickup of recording paper are started.

When an instruction to start printing is given, the motor rotation control circuit 22 first outputs an acceleration signal AP for starting rotation of the scanner motor 27 in step S2, and starts the scanner motor 27 at the maximum acceleration. At the same time, the sequence control circuit 21 monitors the period T of the hall signal HS generated by the rotation of the scanner motor 27 in step S3.
The cycle T gradually decreases with an increase in the number of revolutions of the scanner motor 27, and when the cycle T becomes shorter than t, the step T
In S4, the laser light source 31 emits a laser beam according to the laser ON signal LN from the OR gate 29. Step S5
The photoelectric conversion signal PC is detected by the sequence control circuit 21 by the emission of the laser light, and the second photoelectric conversion signal is further output.
The laser light source 31 continues to emit light until a PC is detected.

Upon detection of the second photoelectric conversion signal PC, the laser light source 31 stops emitting light, and the cycle of the photoelectric conversion signal PC at the time of detection is measured. The light emission of the laser light source 31 for detecting the third photoelectric conversion signal PC is predicted from the previously measured cycle T, and from this prediction, the laser light source 31 emits light at a location other than the image printing area of the photosensitive drum. Is controlled. Hereinafter, by repeating the same operation, the photoelectric conversion signal PC is continuously detected.

On the other hand, the detected photoelectric conversion signal PC is also input to the motor rotation control circuit 22 in step S6, and the scanner motor 27 which has been driven at the maximum acceleration until then is input.
Is the scanner motor 27 according to the input of the photoelectric conversion signal PC.
Is formed, the original rotation control is activated. Thereafter, when the scanner motor 27 reaches a predetermined number of revolutions, the initialization of the photosensitive drum is completed, and the temperature of the fixing device reaches a predetermined temperature, the sheet starts to be conveyed, receives a video signal, and starts a printing operation.

FIG. 4 shows the configuration of the second embodiment. A polygon mirror 41 is fixed to a scanner motor 40, a laser light source 42 for irradiating a laser beam toward the polygon mirror 41, and reflection from the polygon mirror 41. A photoelectric converter 43 for receiving light is provided.

The laser light source 42 has a laser driving circuit 4
4 is connected, and the photoelectric conversion signal PC from the photoelectric converter 43 is connected to the discriminator 45 and the timing generation circuit 46. The output of the discriminator 45 is connected to the scanner motor 40 and the comparator 47 as an acceleration / deceleration pulse AD, the output of the timing generation circuit 46 is connected to one input of an AND gate 48 as the forced light emission signal FL, and the other input signal is The discriminator 45 is connected to the scanner motor 40 as a motor-on signal MN. The output of the AND gate 48 is OR gate 4
9 is connected to one input terminal, the other input terminal of the OR gate 49 receives the data video signal VS, and the output of the OR gate 49 is connected to the input of one AND gate 50. The other input terminal is connected to the laser enable signal LE from the converter 47, and the output of the AND gate 50 is connected to the laser drive circuit 44 as a laser lighting signal LN.

The polygon mirror 41 includes a scanner motor 40
, And the laser light emitted from the laser light source 42 scans on a photosensitive drum (not shown). Also, in order to detect this scanning timing,
When the polygon mirror 41 reaches a specific angle, the laser beam enters the photoelectric converter 43. The laser light source 42 is driven by a laser driving circuit 44, and the on / off of the laser light source 42 is controlled by a laser lighting signal LN input to the laser driving circuit 44. The output of the photoelectric converter 43 is input to an image data output device (not shown) and is used for output control of image data. The photoelectric converter 43 is also used for detecting the rotation speed of the scanner motor 40 and has a reference clock (not shown). Input to the discriminator 45, and sends an acceleration / deceleration pulse AD to the scanner motor 40,
The rotation speed of the scanner motor 40 is maintained at a desired constant value.

The photoelectric converter 43 includes a laser light source 42
Is turned on, the output of the photoelectric converter 43 is input to the timing generation circuit 46. Then, at the time when the polygon mirror 41 is at a specific angle, the forced emission signal is output to turn on the laser light source 42. Generate FL. Further, the acceleration / deceleration pulse AD of the discriminator 45 is input to the comparator 47, and the laser enable signal LE is set to “false” so that the laser light source 42 is not turned on until the acceleration pulse width becomes equal to or less than a predetermined time.

FIG. 5 shows a third embodiment in which the output of the OR gate 49 is directly used as the laser lighting signal LN without using the AND gate 50 in FIG.
, And the output of the comparator 47 is directly connected to the laser drive circuit 44 as a power down signal PD. Thus, the laser drive circuit 44 can control the emission intensity of the laser light by an external signal.

This embodiment operates by the same operation as that of the second embodiment, and until the acceleration pulse width of the acceleration / deceleration pulse AD of the discriminator 45 input to the comparator 47 becomes equal to or less than a predetermined time. , The power down signal PD is set to “true”, and this power down signal PD is input to the laser drive circuit 44,
During "true", the laser emission intensity is reduced.

FIG. 6 shows a fourth embodiment. In this embodiment, a delay circuit 50 is provided without using the comparator 47, and temperature data from a temperature detector (not shown) is connected to the delay circuit 50. Further, the motor-on signal MN is connected to the discriminator 45 and the delay circuit 50. Also, A in FIG.
The ND gate 48 is not used, the delay circuit 50 is connected to one input terminal of the AND gate 50 by the laser enable signal LE, and the forced light emission signal FL of the timing generation circuit 46 is directly connected to one of the OR gates 49. Connected to input terminal. The temperature detector may use a thermistor used for controlling the temperature of the fixing device, which is indispensable for the electrophotographic process, or may be provided separately.

In this embodiment, the motor operates in the same manner as in the second embodiment, and the motor-on signal MN input to the delay circuit 50 is delayed and output as the laser enable signal LE.
The delay circuit 50 can change the delay time by an external signal. The output from the temperature detector is used as a signal for changing the delay time of the delay circuit 50.
Since the delay time is input to 0 and the detected temperature is lower, the delay time is longer, so that the time when the laser enable signal LE becomes “true” after the scanner motor 40 is turned on becomes longer as the detected temperature is lower.

[0031]

As described above, in the image forming apparatus according to the first aspect of the present invention, when the rotation of the scanner motor is started, the laser light source is not turned on until the rotation speed becomes equal to or higher than a predetermined speed. Unnecessary laser light irradiation to the drum is reduced, and unnecessary turning on of the laser light source is prevented.

The image forming apparatus according to the second aspect of the present invention reduces unnecessary laser light to the photosensitive drum by lowering the emission intensity of laser light until the rotation speed of the scanner motor starts to be higher than a predetermined speed. Reduce the light irradiation intensity.

The image forming apparatus according to the third aspect of the present invention focuses on the fact that, for example, in a scanner motor using oil SGB, the lower the temperature, the slower the rotation speed rises. The irradiation intensity of unnecessary laser light to the drum is reduced, and unnecessary lighting of laser light is prevented.

[Brief description of the drawings]

FIG. 1 is a block circuit configuration diagram of a first embodiment.

FIG. 2 is a timing chart.

FIG. 3 is a flowchart.

FIG. 4 is a configuration diagram of a second embodiment.

FIG. 5 is a configuration diagram of a third embodiment.

FIG. 6 is a configuration diagram of a fourth embodiment.

FIG. 7 is a configuration diagram of a conventional scanner unit.

FIG. 8 is a configuration diagram of a first conventional driving circuit.

FIG. 9 is a configuration diagram of a drive circuit of a second conventional example.

[Explanation of symbols]

 Reference Signs List 20 sequence control unit 21 sequence control circuit 22 motor rotation control circuit 23 motor drive unit 24 motor drive circuit 27, 40 scanner motor 31, 42 laser light source 32 photodiode 33, 43 photoelectric converter 41 polygon mirror 44 laser drive circuit 45 discriminator 46 timing generation circuit 47 comparator 50 delay circuit

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification code FI H04N 1/113

Claims (3)

[Claims] 1. A laser diode, a polygon mirror, a scanner motor for rotating the polygon mirror,
Rotation detecting means for detecting a magnetic field change due to rotation of a magnet provided on a rotor of the scanner motor, a photosensitive drum having a photosensitive body on its surface and rotating about a cylindrical axis, and a charging mechanism for charging the photosensitive drum; An image forming apparatus that scans a light beam emitted from the laser diode in the axial direction on the photosensitive drum by the polygon mirror to form a latent image and forms an image by an electrophotographic process. A photoelectric converter that is arranged on a predetermined optical axis that scans by reflecting the light beam on the polygon mirror,
A rotation speed detection mechanism that detects the rotation speed of the scanner motor by a signal from the photoelectric converter, and a rotation speed control mechanism that holds the rotation speed obtained from the rotation speed detection mechanism at a desired value, An image forming apparatus, wherein the laser diode is allowed to emit light when the rotation detecting means detects a predetermined rotation speed or more. 2. A laser diode, a polygon mirror, a scanner motor for rotating the polygon mirror,
A photosensitive drum having a photosensitive body on its surface and rotating around a cylindrical axis, and a charging mechanism for charging the photosensitive drum, wherein a light beam emitted from the laser diode is transmitted to the shaft on the photosensitive drum by the polygon mirror. An image forming apparatus that forms a latent image by scanning in the direction to form an image by an electrophotographic process, wherein a light beam from the laser diode is reflected on the polygon mirror and is arranged on a predetermined optical axis for scanning. A rotation speed detection mechanism that detects a rotation speed of the scanner motor based on a signal from the photoelectric converter, and a rotation speed control mechanism that holds the rotation speed obtained from the rotation speed detection mechanism at a desired value. If the rotation speed obtained by the rotation speed detection mechanism is equal to or lower than a reference speed set lower than a desired value, the light emission amount of the laser diode is reduced. Or the image forming apparatus characterized by stopping the emission of the laser diode causes. 3. A laser diode, a polygon mirror, a scanner motor for rotating the polygon mirror,
A photosensitive drum having a photosensitive body on its surface and rotating around a cylindrical axis, and a charging mechanism for charging the photosensitive drum, wherein a light beam emitted from the laser diode is transmitted to the shaft on the photosensitive drum by the polygon mirror. An image forming apparatus that forms a latent image by scanning in the direction to form an image by an electrophotographic process, wherein a light beam from the laser diode is reflected on the polygon mirror and is arranged on a predetermined optical axis for scanning. A rotation speed detection mechanism for detecting a rotation speed of the scanner motor based on a signal from the photoelectric converter, a rotation speed control mechanism for holding the rotation speed obtained from the rotation speed detection mechanism at a desired value, And the laser diode starts emitting light with a delay from the rotation start time of the scanner motor, and the temperature obtained by the temperature detection mechanism is provided. At low image forming apparatus characterized by extending the light emission start time and rotation start time of the scanner motor of the laser diode.