JPH09183251A - Image forming device and image forming method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize a scanner motor driving control system which is hard to be influenced by a noise and to form a stable image. SOLUTION: A scanner motor drives to rotate a rotational polygon mirror that deflects a laser beam for forming an image by scanning it on a photosensitive body. A scanner motor control section 2 controls the scanner motor so that the rotating speed of the rotational polygon mirror is controlled in a prescribed range. A driver 3 of the scanner motor and the scanner motor control section 2 are connected with two electric wires 2A, 2B. The scanner motor control section 2 instructs the driver 3 to be in the accelerating, decelerating or neutral condition by a combination of levels of a first signal S5 and a second signal S6 outputted to the electric wires 2A, 2B.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laser beam printer or the like which scans a photosensitive member with a laser beam modulated by an image signal to form an image, and more particularly, to rotate a rotary polygon mirror for deflecting the laser beam. The present invention relates to an image forming apparatus and an image forming method with improved speed control.

[0002]

2. Description of the Related Art A motor constituting a laser scanning portion of a laser beam printer, which is a kind of printer, is required to have a high rotational speed accuracy.

FIG. 1 is a perspective view showing the structure of a main part of a conventional laser beam printer, and FIG. 2 is a side view thereof.

An image signal (VDO signal) 101 is input to the laser unit 102. Reference numeral 103 is a laser beam that is on / off modulated by the laser unit 102. Reference numeral 104 denotes a scanner motor, which causes the rotating polygon mirror (polygon mirror) 105 to steadily rotate. 106
Is an image forming lens, and is a photosensitive drum 108 which is a surface to be scanned with a laser beam 107 deflected by a polygon mirror.
Focus on the top. Therefore, the laser beam 107 modulated by the image signal 101 is horizontally scanned (scanning in the main scanning direction) on the photosensitive drum 108.

Reference numeral 109 is a beam detection port, which receives a laser beam from a slit-shaped entrance. The laser beam entering from this entrance is guided to the photoelectric conversion element 111 through the inside of the optical fiber 110. Photoelectric conversion element 11
The laser beam converted into an electric signal by 1 is amplified by an amplifier circuit (not shown) and then becomes a horizontal synchronizing signal (hereinafter, referred to as BD signal). Reference numeral 112 denotes a recording paper, and the latent image formed on the photosensitive drum 108 is visualized by the developing device 123 shown in FIG. 2 to become a toner image, which is transferred to the recording paper 112 by the transfer device 120. The recording paper 112 on which the toner image is transferred is the fixing device 1 shown in FIG.
The sheet is fixed by the sheet 21, and the sheet is discharged from the sheet discharging unit 122.

Next, a conventional control circuit and drive circuit (scanner motor drive control system) for the scanner motor 104 will be described with reference to FIGS. 9 and 10.

FIG. 9 is a block diagram showing the configuration of the scanner motor drive control system, and FIG. 10 is a timing chart of the signals shown in FIG. Printer engine control unit 201
The scanner motor control unit 202 and the scanner motor control unit 202 are configured by different integrated circuits.

The printer engine controller 201 outputs a clock CK having a cycle corresponding to the resolution of image formation to the scanner motor controller 202 via an electric wire. Clock CK
Is divided by the second frequency divider 203 in the scanner motor control unit 202 into 1 / 2n cycles. On the other hand, the scanner motor 10
The rotation speed of No. 4 is converted by the rotation speed detector 205 into a rectangular wave S11 according to the rotation speed. The signal S11 from the rotation speed detector 205 is used as the scanner motor control unit 2
02, and is divided by a first frequency divider 206 therein into 1 /
The frequency is divided into 2m cycles.

Reference numerals 207 and 208 denote a rising pulse generator and a falling pulse generator. These pulse generators 207 and 208 generate pulses S13 and S14 at the rising and falling timings of the divided signal S12.
Is output. A first counter 209 counts the number of clocks divided by the second divider 203 by a predetermined number.

The first counter 209 has a rising pulse S.
Counting is started from the time when 13 is input, and the high-level output signal S15 is output during that time. Similarly, the second counter 210 starts counting from the time when the falling pulse S14 is input, and outputs the high-level output signal S16 during that time (see FIG. 10).

A signal S17 obtained by synthesizing the output signals S15 and S16 of these two counters 209 and 210 by the waveform synthesizer 211 is output to the scanner motor driver 212 via the electric wire 17. The signal S17 has three states of high level (H), low level (L) and high impedance as shown in Table 1 below. High level, low level, and high impedance mean acceleration, neutral, and deceleration, respectively. Neutral is to maintain the current speed. In response to this signal S17, the driver 212
Controls the rotation speed of the scanner motor 104.

[0012]

[Table 1] That is, when the rotation speed of the scanner motor 204 is lower than the target speed, the signal S17 is set to a high level to instruct acceleration, and when the rotation speed is higher than the target speed, a low level is output. Instruct to decelerate. Further, within the target rotation speed range, the signal S17 is set to high impedance to instruct the speed maintenance (neutral). The scanner motor driver 212 includes the scanner motor controller 2
02 from the signal S17 to the integrator 2 in the driver 212
12A is integrated, and a voltage corresponding to the signal S17 is supplied to the scanner motor 204 to rotate it.

The scanner motor driver 212 and the scanner motor control unit 202 are each formed of an integrated circuit, and the scanner motor driver 212 and the scanner motor control unit 202 are connected by one electric wire (wire) 17.

[0014]

However, the above-mentioned conventional scanner motor drive control system has the following problems.

First, the electric wire 17 is more susceptible to noise than in other integrated circuits. Further, when the rotational speed is maintained as it is, that is, when neither acceleration nor deceleration is performed, the scanner motor control unit 202 causes the scanner motor driver 2 to
The signal S17 output to 12 has a high impedance, but this high impedance state is easily affected by small noise. Therefore, the scanner motor 104 may malfunction, which may affect image formation.

Further, the printer engine control circuit 201
Since the clock CK from is output to the scanner motor control unit 202 through the electric wire, noise is generated from the electric wire due to the clock, and thus a noise generation prevention circuit is necessary.

Further, when the resolution of the image to be formed is switched by a command from the outside of the printer, the switching speed is not sufficiently satisfactory.

In view of the above-mentioned conventional problems, the present invention provides a scanner motor drive control system which is not easily affected by noise and provides an image forming apparatus and an image forming method capable of performing stable image formation. To aim. Another object of the present invention is to provide an image forming apparatus and an image forming method capable of quickly switching the image resolution.

[0019]

In order to achieve the above object, an image forming apparatus according to a first aspect of the present invention scans a photoconductor with a laser beam modulated by an image signal to form an image. Forming means, driving means for rotationally driving the rotary polygon mirror for deflecting the laser beam, and control means for controlling the driving means to control the rotational speed of the rotary polygon mirror within a predetermined range. In the image forming apparatus having the above, a first signal line and a second signal line for connecting the control unit and the driving unit are provided, and the control unit connects the first signal line and the second signal line to each other. First to output respectively
By the combination of the signal level of the second signal and the signal level of
The driving means is configured to instruct acceleration, deceleration, and a neutral state.

An image forming apparatus according to a second aspect of the present invention is the image forming apparatus according to the first aspect, in which the acceleration state is set when the first signal is at a high level and the second signal is at a low level. Is at a low level and the second signal is at a high level, a deceleration state is set, when both the first signal and the second signal are at a low level, or the first signal and the second signal are Both indicate a neutral state when they are at a high level.

An image forming apparatus according to a third aspect of the present invention is the image forming apparatus according to the first aspect, wherein the first signal is in an accelerating state when the first signal is at a low level and the second signal is at a high level. Is at a high level and the second signal is at a low level, a deceleration state is set, when both the first signal and the second signal are at a low level, or when the first signal and the second signal are Both indicate a neutral state when they are at a high level.

An image forming apparatus according to a fourth aspect of the present invention comprises an image forming means for forming an image by scanning a photoconductor with a laser beam modulated by an image signal, and a rotary multifaceted for deflecting the laser beam. An image forming apparatus comprising: a drive unit that rotationally drives a mirror; and a control unit that controls the drive unit to control the rotational speed of the rotary polygon mirror within a predetermined range, wherein the control unit and the drive unit are provided. A first signal line and a second signal line that connect to each other, and the control means outputs a first signal and a second signal to the first signal line and the second signal line, respectively. A combination of levels is used to instruct the drive means to perform acceleration, deceleration, and a neutral state, and the rotation speed of the rotary polygon mirror is changed from a predetermined first rotation speed to a first rotation by an external command. Than speed In the case of changing the rotation speed to a second rotation speed, the deceleration state is forced to the driving means for a certain time so that the rotation speed of the rotary polygon mirror falls within a predetermined range including the second rotation speed. It is designed to be directed.

An image forming apparatus according to a fifth aspect of the present invention comprises an image forming means for forming an image by scanning a photoconductor with a laser beam modulated by an image signal, and a rotary multifaceted for deflecting the laser beam. An image forming apparatus comprising: a drive unit that rotationally drives a mirror; and a control unit that controls the drive unit to control the rotational speed of the rotary polygon mirror within a predetermined range, wherein the control unit and the drive unit are provided. A first signal line and a second signal line that connect to each other, and the control means outputs a first signal and a second signal to the first signal line and the second signal line, respectively. A combination of levels is used to instruct the drive means to accelerate, decelerate or neutral, and when the first or second signal line is broken, the drive means is prohibited from being in an accelerated state. When disconnection It is provided with a prohibiting means.

In an image forming apparatus according to a sixth aspect of the present invention, in the above fifth aspect, the control means sets the acceleration state when the first signal is at a low level and the second signal is at a high level, A configuration in which a deceleration state is instructed when the first signal is at a high level and the second signal is at a low level, and a neutral state is instructed when the first and second signals are both at a low level or a high level. It is the one.

According to a seventh aspect of the present invention, in the fifth or sixth aspect of the invention, the disconnection acceleration inhibiting means includes a pull-up resistor connected to the first signal line.
And a pull-down resistor connected to the second signal line.

In the image forming apparatus according to an eighth aspect of the present invention, in the fifth or sixth aspect of the invention, the acceleration inhibiting means at the time of disconnection includes a first current detecting means for detecting a current of the first signal line. The first and second drive circuits are provided in the drive means, and when the first current detection means detects that no current is flowing in the first signal line, the drive means is not accelerated. The configuration is such that the level of the signal line is controlled.

According to a ninth aspect of the present invention, in the eighth aspect of the present invention, the acceleration inhibiting means at the time of disconnection is such that no current flows through the first signal line by the first current detecting means. When the first signal line is set to the high level and the second signal line is set to the low level, the deceleration state is set, and when the first and second signal lines are set to the high level, the neutral state is set. In the image forming apparatus according to the tenth invention, which is configured to control the driving means so as to achieve the above, in the fifth or sixth invention, the disconnection acceleration inhibiting means is the second invention. When the second current detecting means detects that no current is flowing in the second signal line, the driving means includes second current detecting means for detecting the current of the signal line. Accelerating means Is obtained by the configuration for controlling the level of said first and second signal lines so as not to.

According to an eleventh aspect of the invention, in the tenth aspect of the invention, the disconnection acceleration inhibiting means is
When the second current detecting means detects that no current is flowing in the second signal line, decelerates when the first signal line is set to the high level and the second signal line is set to the low level. In this state, when the first and second signal lines are both brought to a low level, the drive means is controlled so as to be in a neutral state.

In the image forming method according to the twelfth aspect of the invention, drive means for rotationally driving a rotary polygon mirror for deflecting a laser beam modulated by an image signal, and the rotary polygon mirror are controlled by controlling the drive means. In the image forming method of forming an image by scanning the photoconductor with the laser beam, using an image forming apparatus having a control unit for controlling the rotation speed of the device within a predetermined range, the control unit and the driving unit are provided. A first signal line and a second signal line that connect to each other are provided, and a combination of the signal levels of the first signal and the second signal output to the first signal line and the second signal line, respectively. And a speed control process for instructing the driving means to accelerate, decelerate or neutral state, and the first signal line or the second signal line.
When the signal line is disconnected, the disconnection acceleration prohibition process for prohibiting the drive means from being in an accelerated state is executed.

The image forming method according to the thirteenth invention is the image forming method according to the twelfth invention, wherein the speed instruction processing is performed when the first signal is at a low level and the second signal is at a high level. , Indicating a deceleration state when the first signal is at a high level and the second signal is at a low level, and indicating a neutral state when both the first and second signals are at a low level or a high level It was done like this.

In the image forming method of the fourteenth invention, in the twelfth or thirteenth invention, a pull-up resistor is connected to the first signal line and a pull-down resistor is connected to the second signal line. The disconnection acceleration inhibition process is performed by using the pull-up resistor and the pull-down resistor.

In the image forming method of the fifteenth invention, in the twelfth or thirteenth invention, a first current detecting means for detecting a current of the first signal line is provided in the driving means. In the disconnection acceleration prohibition process, when the first current detecting unit detects that no current is flowing in the first signal line, the first and the second units are configured so as not to bring the driving unit into an accelerating state. The signal level of the second signal line is controlled.

In the image forming method according to the sixteenth invention, in the above-mentioned fifteenth invention, the acceleration prohibition process at the time of disconnection is:
When the first current detecting means detects that no current is flowing through the first signal line, the first signal line is decelerated when the first signal line is set to the high level and the second signal line is set to the low level. In this state, the driving means is controlled so as to be in a neutral state when both the first and second signal lines are set to the high level.

In the image forming method of the seventeenth invention, in the twelfth or thirteenth invention, the acceleration prohibition process at the time of disconnection includes a second current detecting means for detecting a current of the second signal line. It is provided in the driving means, and when the second current detecting means detects that no current is flowing in the second signal line, the first and the first and second driving means are arranged so as not to bring the driving means into an accelerating state. The signal level of the second signal line is controlled.

An image forming method according to an eighteenth invention is the image forming method according to the seventeenth invention, wherein the acceleration inhibiting process at the time of disconnection is:
When the second current detecting means detects that no current is flowing in the second signal line, decelerates when the first signal line is set to the high level and the second signal line is set to the low level. In this state, the driving means is controlled so as to be in a neutral state when both the first and second signal lines are at a low level.

[0036]

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

The mechanical structure of the laser beam printer according to the embodiment of the present invention is the same as that shown in FIGS.

FIG. 3 is a block diagram showing the configuration of the scanner motor drive control system according to the first embodiment of the present invention.

1 is a printer engine control circuit,
The output is connected to the scanner motor control unit 2 that controls the rotation speed of the rotary polygon mirror within a predetermined range. Further, the output of the scanner motor control unit 2 is input to the scanner motor driver 3 via the two electric wires (wires) 2A and 2B. The scanner motor control unit 2 and the scanner motor driver 3 are respectively configured by different integrated circuits. The scanner motor control unit 2 and the printer engine control circuit 1 are both logic circuits and are configured as one integrated circuit 100.

The scanner motor driver 3 drives the scanner motor 104, the rotation speed of the scanner motor 104 is detected by the rotation speed detector 5, and the detection signal S1 is sent through the signal line 5A to the scanner motor controller 2 To be fed back to.

The printer engine controller 1 outputs a clock CK having a cycle corresponding to the resolution of image formation to the scanner motor controller 2. In the present embodiment, the output of the clock CK does not go through the electric wire (in one integrated circuit), so that noise generation can be suppressed. The clock CK is divided by the second frequency divider 21 in the scanner motor control unit 2 into 1 / 2n cycles (for example, 1/8 cycle).

On the other hand, the rotation speed of the scanner motor 104 is converted by the rotation speed detector 5 into a rectangular wave signal S1 corresponding to the rotation speed. The waveform of the rectangular wave signal S1 has a long cycle when the rotation speed of the scanner motor 4 is slow, and a short cycle when the rotation speed is fast. The signal S1 from the speed detector 5 is sent to the scanner motor controller 2, and the first frequency divider 22 in the scanner motor controller 2 provides a 1/2 m cycle (for example, 1 / m).
It is divided into two cycles. Further, in the scanner motor control unit 2, a rising pulse generator 23, a falling pulse generator 24, a first counter 25, and a second counter 26.
Among them, the pulse generators 23 and 24 respectively output the pulses S3 and S4 at the rising and falling timings of the signal S2 divided by the first frequency divider 22 (see FIG. 4).

The first counter 25 counts the number of clocks CK divided by the second divider 21 by a predetermined number, and starts counting from the time when the rising pulse S3 is input, and during that time. , And outputs a low level output signal S5 (see FIG. 4). When the count value reaches the determined number, the output signal S5 is set to the high level. Similarly, the second counter 26 starts counting from the time when the falling pulse S4 is input, and outputs the high-level output signal S6 during that time (see FIG. 4). When the count value reaches the determined number, the output signal S6 is set to the low level.

The output signal (first signal) S5 of the first counter 25 and the output signal (second signal) S6 of the second counter 26 are two electric wires as output signals from the scanner motor control section 2. It is transmitted to the scanner motor driver 3 via 2A and 2B. These two signals S5
The states transmitted to the scanner motor driver 3 by S6 are as shown in Table 2.

[0045]

[Table 2] That is, when both the first signal S5 and the second signal S6 are low level, the acceleration state is
When both signals S6 of 1 are high level, the deceleration state is indicated.
Further, when the first signal S5 is low level and the second signal S6 is high level, or when the first signal S5 is high level and the second signal S6 is low level, neither neutralization nor acceleration is performed. It represents the state.

In the scanner motor driver 3, the waveform synthesizer 31 waveform-synthesizes the first and second signals S5 and S6, and the voltage level converter 33 generates a voltage according to the waveform level through the integrator 32. This is supplied to the scanner motor 4.

As described above, in the case where the command from the scanner motor control unit 2 is transmitted to the scanner motor driver 3 which is composed of an integrated circuit different from the scanner motor control unit 2, it is transmitted via the signal lines 2A and 2B. As shown in Table 2 above, the two signals S5 and S6 are combined and sent. Therefore, when instructing the neutral state, it is not necessary to use the high impedance state as in the conventional case, and the device is not easily affected by noise. Can be configured to.

Further, according to this configuration, since the instruction of acceleration and deceleration is given by a combination of one of the signals S5 and S6 being high level and the other being low level, it is affected by noise as shown below. Hateful.

FIG. 5 shows an acceleration instruction (S5 = H, S6 = L).
6 is a diagram showing waveforms of the first and second signals S5 and S6 when noise is present on the first and second signal lines 2A and 2B while outputting the signal to the scanner motor driver 3. FIG. .

As shown in the figure, both the first and second signals S5 and S6 are instantaneously brought to a high level due to noise. That is, as can be seen from Table 2, the speed maintenance instruction is given instantaneously, and the rotation speed of the scanner motor 104 is neither accelerated nor decelerated. If S5 = H and S6 = H, an acceleration instruction is given. If S5 = L and S6 = L, a deceleration instruction is given.
= H, S6 = L or S5 = L, S6 = H, if the speed maintenance (neutral) instruction is configured, when noise is received during the deceleration instruction, an acceleration instruction is issued, and the speed is reduced. Flapping and not stable.

As described above, the relationship between the signals S5 and S6 of this embodiment and acceleration, deceleration, and speed maintenance can suppress the influence of noise as much as possible. The relationship shown in Table 3 may be used to obtain the same effect.

[0052]

[Table 3] To obtain the output of Table 3, the first counter 25 and the second counter 25
The output of the counter 26 may be set to a value opposite to the above.

In this embodiment, the printer engine control circuit 1 and the scanner motor control unit 2 are integrated into one integrated circuit 100.
Therefore, it is possible to suppress the noise generation of the clock CK.

Further, since the integrated circuit 100 can be manufactured at a cost which does not substantially replace the cost of the integrated circuit of the printer engine control circuit 201 which has been conventionally manufactured.
The cost can be saved by cutting the manufacturing cost of the conventional scanner motor control unit 202. Then, the integrated circuit 100 and the scanner motor driver 3 are connected by two electric wires, and when the signals of the two electric wires are different from each other, an instruction to accelerate or decelerate, and an instruction to maintain the speed when they are the same is configured. Therefore, it is possible to suppress the rotation speed of the motor 104 from becoming inaccurate or the rotation speed flickering due to noise from the outside with a simple configuration as much as possible.

When the resolution of the image formed by the above laser beam printer is switched, particularly when changing from high level resolution to low resolution, the rotation speed of the scanner motor 4 is changed to
The first rotation speed is reduced to the second rotation speed slower than the first rotation speed. For example, when the resolution is switched from 600 dpi to 300 dpi, the rotation speed of the scanner motor 4 is switched from the normal rotation speed (first rotation speed) to half the rotation speed (second rotation speed).

In the present embodiment, when a command to switch the resolution is issued from the outside of the printer, the above-mentioned scanner motor drive control system is forced to carry out the first and second signals S5 and S5 for a predetermined time. The combination of S6 is set to the deceleration state. By forcibly decelerating the scanner motor 4 in this way, the resolution can be switched faster.

Next, as another embodiment of the present invention, FIG.
A configuration will be described in which the motor 104 does not run away when either or both of the electric wires 2A and 2B of FIG.

FIG. 6 is a block diagram showing a structure for preventing the motor from running away in the structure for instructing the relationship shown in Table 3 above.

When the first electric wire 2A is broken, the scanner motor board 30 is set so as to set the first signal S5 to the high level.
The pull-up resistor 34A is connected to the signal line 2A above. Accordingly, when the second signal S6 is at the high level, the neutral state can be obtained, and when the second signal S6 is at the low level, the deceleration state can be achieved.
Can be prevented from running out of control and reaching an abnormal speed.

Similarly, when the second electric wire 2B is disconnected, the pull-down resistor 34B is connected to the signal line 2B on the scanner motor substrate 30 so that the second signal S6 is set to the low level.
Are connected. Accordingly, when the first signal S5 is at the low level, the neutral state can be obtained, and when the first signal S5 is at the high level, the deceleration state can be obtained.
It is possible to prevent the motor 104 from running out of control and reaching an abnormal speed.

When both the electric wires 2A and 2B are broken, the signal S5 becomes high level and the signal S6 becomes low level, so that the deceleration state can be achieved. As described above, the motor 104 does not run away under any non-conduction state.

In the case of the configuration of Table 2 described above, if the pull-down resistor is connected to the electric wire 2A and the pull-up resistor is connected to the electric wire 2B, the runaway of the motor 104 can be prevented in the same manner as described above.

FIG. 7 is a block diagram showing a configuration in which the positions of the pull-up resistor and the pull-down resistor are outside the scanner motor driver 3 and inside the scanner motor board. FIG. 8 shows that the first current detector 35A is provided in the motor driver 3.
It is a block diagram which shows the structure which provided the said 2nd electric current detector 35B.

In the first current detector 35A, the first signal S
The current of 5 is detected. Then, when it is detected that no current flows in the first signal line 2A, it is determined that a normal signal is not transmitted, and the waveform synthesizer 31 is set to the deceleration state or the neutral state. The waveforms are combined, the voltage corresponding to the waveform level is converted through the integrator 32 into the voltage level of the motor 104 by the voltage level converter 33, and the voltage is supplied to the motor 104.

Similarly, in the second current detector 35B,
The current of the first signal S6 is detected. Then, when it is detected that no current flows in the second signal line 2B, it is determined that a normal signal is not transmitted, and the waveform synthesizer 31 is set to the deceleration state or the neutral state. The waveforms are combined, the voltage corresponding to the waveform level is converted through the integrator 32 into the voltage level of the motor 104 by the voltage level converter 33, and the voltage is supplied to the motor 104. As a result, runaway of the motor 104 can be prevented.

[0066]

As described above in detail, according to the first aspect of the invention, it is possible to realize a device that is not easily affected by noise with a simple structure without requiring an extra circuit such as a noise generation prevention circuit. it can. As a result, uneven rotation of the scanner motor due to noise can be reduced, and stable image formation can be performed.

According to the second invention, the influence of noise can be further suppressed, and the effect of the first invention can be made remarkable.

According to the third invention, the influence of noise can be further suppressed, and the effect of the first invention can be made remarkable.

According to the fourth aspect of the invention, when the rotation speed of the rotary polygon mirror is changed from the predetermined first rotation speed to the second rotation speed by the external command, the driving means is operated for a certain period of time. Since the deceleration state is forcibly instructed, it is possible to switch the resolution of the image faster, for example.

According to the fifth and twelfth aspects of the present invention, since the disconnection acceleration prohibition means for prohibiting the driving means from being in the acceleration state when the first or second signal is disconnected is provided, noise is reduced. It is possible to reduce uneven rotation of the driving unit (for example, the scanner motor) caused by the above, and it is possible to prevent abnormal rotation of the scanner motor without newly passing through the signal line.
As a result, the rotation of the scanner motor is always stable, and high-quality image formation is possible.

According to the sixth and thirteenth inventions, the influence of noise can be further suppressed, and the effect of the fifth invention can be made remarkable.

According to the seventh and fourteenth inventions, in the fifth or sixth invention, it is possible to realize the acceleration inhibiting means at the time of disconnection with a simple structure.

According to the eighth and fifteenth inventions, abnormal rotation of the scanner motor at the time of disconnection can be prevented easily and accurately.

According to the ninth and sixteenth inventions, the abnormal rotation of the scanner motor at the time of disconnection can be easily and accurately prevented.

According to the tenth and seventeenth aspects, the abnormal rotation of the scanner motor at the time of disconnection can be prevented easily and accurately.

According to the eleventh and eighteenth inventions, abnormal rotation of the scanner motor at the time of disconnection can be prevented simply and accurately.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a main configuration of a laser beam printer.

FIG. 2 is a sectional view of a laser beam printer.

FIG. 3 is a block diagram showing a configuration of a scanner motor drive control system of the first embodiment.

4 is a timing chart of signals in the circuit of FIG.

FIG. 5 is a diagram showing a state where noise is placed on the electric wires 2A and 2B.

FIG. 6 is a block diagram showing a configuration of a scanner motor drive control system of another embodiment.

FIG. 7 is a block diagram showing a configuration of a scanner motor drive control system of another embodiment.

FIG. 8 is a block diagram showing a configuration of a scanner motor drive control system of another embodiment.

FIG. 9 is a block diagram showing a configuration of a conventional scanner motor drive control system.

10 is a timing chart of signals in the circuit of FIG.

[Explanation of symbols]

 1 Printer Engine Control Circuit 2 Scanner Motor Control Section 2A, 2B Electric Wire 3 Scanner Motor Driver 5 Rotational Speed Detector 21 Second Frequency Divider 22 First Frequency Divider 23 Rising Pulse Generator 24 Falling Pulse Generator 25 First Counter 26 second counter 30 scanner motor substrate 31 waveform synthesizer 32 integrator 33 voltage level converter 34A pull-up resistor 34B pull-down resistor 35A first current detector 35B second current detector 104 scanner motor S5 first signal S6 second Signal of

Claims (18)

[Claims] 1. An image forming unit for scanning an image on a photosensitive member by a laser beam modulated by an image signal to form an image, and a driving unit for rotationally driving a rotary polygon mirror for deflecting the laser beam. An image forming apparatus comprising: a control unit that controls the drive unit to control the rotation speed of the rotary polygon mirror within a predetermined range, and a first signal line that connects the control unit and the drive unit. A second signal line is provided, and the control unit controls the drive unit by combining the signal levels of the first signal and the second signal output to the first signal line and the second signal line, respectively. An image forming apparatus having a structure for instructing acceleration, deceleration, and a neutral state. 2. An accelerating state when the first signal is at a high level and the second signal is at a low level, and a deceleration is performed when the first signal is at a low level and the second signal is at a high level. A state indicating a neutral state when both the first signal and the second signal are at a low level, or when both the first signal and the second signal are at a high level. The image forming apparatus according to claim 1. 3. An acceleration state when the first signal is at a low level and the second signal is at a high level, and a deceleration is performed when the first signal is at a high level and the second signal is at a low level. A state indicating a neutral state when both the first signal and the second signal are at a low level, or when both the first signal and the second signal are at a high level. The image forming apparatus according to claim 1. 4. An image forming means for forming an image by scanning a photoconductor with a laser beam modulated by an image signal, and a driving means for rotationally driving a rotary polygon mirror for deflecting the laser beam. An image forming apparatus comprising: a control unit that controls the drive unit to control the rotation speed of the rotary polygon mirror within a predetermined range, and a first signal line that connects the control unit and the drive unit. A second signal line is provided, and the control unit controls the drive unit by combining the signal levels of the first signal and the second signal output to the first signal line and the second signal line, respectively. On the other hand, a configuration in which acceleration, deceleration, and a neutral state are instructed, and the rotation speed of the rotary polygon mirror is set from a predetermined first rotation speed to a second rotation speed lower than the first rotation speed by an external command Place to change to Therefore, the deceleration state is forcibly instructed to the drive means for a certain period of time so that the rotation speed of the rotary polygon mirror falls within a predetermined range including the second rotation speed. A characteristic image forming apparatus. 5. An image forming means for forming an image by scanning a photoconductor with a laser beam modulated by an image signal, and a driving means for rotationally driving a rotary polygon mirror for deflecting the laser beam. An image forming apparatus comprising: a control unit that controls the drive unit to control the rotation speed of the rotary polygon mirror within a predetermined range, and a first signal line that connects the control unit and the drive unit. A second signal line is provided, and the control unit controls the drive unit by combining the signal levels of the first signal and the second signal output to the first signal line and the second signal line, respectively. On the other hand, a structure for instructing acceleration, deceleration or neutral state is provided, and further, a disconnection acceleration prohibition means for prohibiting the drive means from being in an acceleration state when the first or second signal line is disconnected is provided. Characterized by Image forming apparatus. 6. The control means is in an acceleration state when the first signal is at a low level and the second signal is at a high level, and the control means sets the first signal at a high level and the second signal is at a high level. The image forming apparatus according to claim 5, wherein the deceleration state is instructed when the level is low, and the neutral state is instructed when both the first and second signals are low or high. 7. The disconnection acceleration prohibition means comprises a pull-up resistor connected to the first signal line and a pull-down resistor connected to the second signal line. The image forming apparatus according to claim 5 or 6. 8. The disconnection acceleration prohibition means has a first current detection means for detecting a current of the first signal line in the drive means, and the first current detection means allows the first current detection means to detect the first current. 6. When it is detected that no current is flowing through the signal line, the levels of the first and second signal lines are controlled so as not to bring the driving means into an accelerating state. Alternatively, the image forming apparatus according to claim 6. 9. The disconnection acceleration prohibiting means sets the first signal line to a high level when the first current detecting means detects that no current flows in the first signal line. The driving means is controlled so as to be in a decelerating state when the second signal line is at a low level, and in a neutral state when both the first and second signal lines are at a high level. The image forming apparatus according to claim 8. 10. The disconnection acceleration prohibition means has a second current detection means for detecting a current of the second signal line in the drive means, and the second current detection means allows the second current detection means to detect the second current. 6. When it is detected that no current is flowing through the signal line, the levels of the first and second signal lines are controlled so as not to bring the driving means into an accelerating state. Alternatively, the image forming apparatus according to claim 6. 11. The disconnection acceleration prohibition unit sets the first signal line to a high level when the second current detection unit detects that no current is flowing in the second signal line. The driving means is controlled so as to be in a decelerating state when the second signal line is at a low level, and in a neutral state when both the first and second signal lines are at a low level. The image forming apparatus according to claim 10. 12. A drive means for rotationally driving a rotary polygon mirror for deflecting a laser beam modulated by an image signal, and controlling the drive means to keep the rotational speed of the rotary polygon mirror within a predetermined range. Using an image forming apparatus having a control means for controlling, scanning the photoconductor with the laser beam,
In an image forming method for forming an image, a first signal line and a second signal line for connecting the control unit and the driving unit are provided, and the first signal line and the second signal line are connected to the first signal line and the second signal line. A speed control process for instructing the drive means to accelerate, decelerate or neutral state by a combination of the signal levels of the first signal and the second signal output respectively, and the first signal line or the second signal line. An image forming method, characterized in that when a signal line is broken, an acceleration prohibition process at the time of breaking is prohibited to prohibit the driving means from being in an accelerating state. 13. The speed instructing process includes an accelerating state when the first signal is at a low level and the second signal is at a high level, and the first signal is at a high level and the second signal is at a high level. 13. The image forming method according to claim 12, wherein the deceleration state is instructed when is low level, and the neutral state is instructed when both the first and second signals are low level or high level. 14. A pull-up resistor is connected to the first signal line,
14. The image according to claim 12, wherein a pull-down resistor is connected to the second signal line, and the acceleration prohibition process at the time of disconnection is performed using the pull-up resistor and the pull-down resistor. Forming method. 15. A first current detecting means for detecting a current of the first signal line is provided in the driving means, and the wire-breakage acceleration prohibition process is performed by the first current detecting means. 13. The level of the first and second signal lines is controlled so that the driving means is not accelerated when it is detected that no current is flowing through the first signal line. Item 14. The image forming method according to Item 13. 16. The acceleration prohibition process during disconnection sets the first signal line to a high level when the first current detecting unit detects that no current is flowing through the first signal line. The driving means is controlled so as to be in a deceleration state when the second signal line is at a low level, and in a neutral state when both of the first and second signal lines are at a high level. Item 16. The image forming method according to Item 15. 17. The acceleration prohibition process at the time of disconnection is provided with a second current detection means for detecting a current of the second signal line in the drive means, and the second current detection means is used to perform the second current detection means. 13. The level of the first and second signal lines is controlled so that the driving means is not accelerated when it is detected that no current is flowing through the second signal line. Item 14. The image forming method according to Item 13. 18. The disconnection acceleration prohibition process sets the first signal line to a high level when the second current detecting unit detects that no current is flowing in the second signal line. The driving means is controlled so as to be in a deceleration state when the second signal line is at a low level, and to be in a neutral state when both the first and second signal lines are at a low level. Item 18. The image forming method according to Item 17.