JPH09297839A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the image forming device which can stop a scanner at a target position by performing speed reduction control over the scanner at its speed reduction time even if a DC servomotor enters a heat generating state. SOLUTION: A microcontroller 5 inputs a PWM signal with a duty ratio corresponding to the scanning speed of the scanner from a PWM generator 4 to MOS FETs 33 and 34 driving the DC servomotor 1, which rotates at a specific rotating speed to move the scanner reciprocally and read a document image, and at the time of return acceleration of the scanner, the microcontroller 5 corrects the duty ratio of the PWM signal at the return speed reduction time of the scanner with the speed of the scanner at a position of a specific distance. Consequently, the scanner stops accurately at a specific position under invariably high-precision speed reduction control at the speed reduction time of the scanner even if the DC servomotor 1 enters a heat generating state, and stable image formation which is not affected by the heat generation of the DC servomotor is performed.

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 that reciprocates a scanner by using a DC servo motor.

[0002]

2. Description of the Related Art In an image forming apparatus such as a copying machine, an original placed on a contact glass is irradiated with light from a light source while scanning a scanner, and reflected light from the original image is captured as image data. An exposure process is performed by forming an image on the image carrier.

In order to drive this scanner scanning, D
In an image forming apparatus that drives a scanner using a C servo motor, a DC servo motor is connected to four MOS FETs that switch the armature current so as to form an H bridge, and a motor drive circuit is configured. Then, each MOS / FET of the motor drive circuit is connected to the four output terminals of the drive selection circuit connected to the two output terminals of the microcontroller for controlling the overall operation, and the whole is configured by a microcomputer. Then, four logical value signals are output to the two output terminals, and four states of forward rotation, reverse rotation, stop, and brake are set in the motor drive circuit by the logically intelligent signal,
It controls the rotation of the DC servo motor.

In this case, the rotation speed of the DC servo motor is detected by the rotary encoder, the difference value between the detected rotation speed and the preset rotation speed is monitored, and the motor drive circuit is based on this difference value. The duty ratio of the PWM signal input to is changed to control the rotation speed of the DC servo motor to a preset rotation speed.

■

In the above-described conventional scanner drive, when the scanner is continuously operated, the heat generation of the DC servo motor causes the winding resistance value of the motor to change, which causes a change in the width of the predetermined PWM. , The current flowing through the DC servo motor decreases. When the current flowing through the DC servo motor decreases in this way, the torque of the DC servo motor decreases and a predetermined acceleration cannot be obtained in the acceleration region of the DC motor, and in particular, the deceleration at the return of the scanner deviates from the target value. As a result, the stop position of the scanner is displaced.

The present invention has been made in view of the present situation of scanner control of an image forming apparatus as described above, and an object thereof is to achieve high accuracy when decelerating the scanner even when the DC servo motor is in a heat generating state. An object of the present invention is to provide an image forming apparatus capable of controlling deceleration and stopping a scanner at a target position.

[0007]

In order to achieve the above object, the invention according to claim 1 is a scanner for reading image data from an original image, a driving means for reciprocating the scanner by a DC servo motor, and An image forming apparatus, comprising: a control unit that controls the operation of the DC servo motor by switching the servo loop gain of the DC servo motor according to the scanning speed of the scanner, and is set in advance when the return acceleration of the scanner is performed. Based on the speed of the scanner at the position of the predetermined distance, the servo loop gain during return deceleration of the scanner is corrected, and stop control means for stopping the scanner at a fixed position is provided. .

[0008] Similarly, to achieve the above object, the invention according to claim 2 is a scanner for reading image data from an original image, a driving means for reciprocating the scanner by a DC servo motor, and a scanning speed of the scanner. In response to the,
An image forming apparatus comprising: a control unit that switches the servo loop gain of the DC servo motor to control the operation of the DC servo motor, wherein the scanner sets a predetermined distance set in advance when the scanner accelerates the return. Stop control means for correcting the servo loop gain during deceleration of the return of the scanner based on the passing time and stopping the scanner at a fixed position.

Similarly, in order to achieve the above object, the invention according to claim 3 is different from the invention according to claim 1 or 2 in that the encoder outputs a pulse signal according to the rotation of the DC servo motor. Is provided, and the calculation of the preset predetermined distance is performed by counting the output signals of the encoder.

Similarly, in order to achieve the above object, the invention according to claim 4 is different from the invention according to claim 3, in that a frequency dividing means for dividing an output signal of the encoder and a return start of the scanner are started. At the same time, a clearing means for clearing the frequency dividing means is provided.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION

[First Embodiment] A first embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a circuit diagram showing the configuration of the present embodiment, FIG. 2 is a velocity diagram showing the operation of the present embodiment, and FIG. 3 is a characteristic diagram showing the scanner return operation of the present embodiment.

In the present embodiment, as shown in FIG. 1, a microcontroller 5 for controlling the overall operation is arranged, and the microcontroller 5 has output terminals P0, P1 and An address data bus output terminal P5 for outputting a PWM command signal, output terminals P3, P4 for outputting a frequency division control signal, an input terminal INT for inputting a motor control interrupt signal, and a motor rotation direction detection signal are input. The input terminal P2 is provided.

An inverting circuit 25 is provided at the output terminals P0 and P1.
a, 25b, AND circuits 26a, 26b, level conversion circuits 27a, 27b, 28a, 28b, and an output terminal P
A drive selection circuit 30 that transmits a logical value signal input from 0 and P1 and a PWM signal based on the logical value signal is connected. In addition, the DC servo motor 1 is equipped with MOS / FE
A motor drive circuit 35 in which T31 to 34 are connected to form an H bridge is arranged, and output terminals t1 to t4 of the drive selection circuit 30 are M of the drive selection circuit of the motor drive circuit 35.
It is connected to OS-FET31-34, respectively.

At the output terminal P5 of the address data bus of the microcontroller 5, the PWM generator 4 is connected to the output terminal P5.
3, P4, the input terminal INT, the frequency divider 3 to the input terminal P
Flip-flops 36 are respectively connected to 2 and PW
The output terminal of the M generator 4 is connected to one input terminal of each of the AND circuits 26a and 26b, and the output terminal of the rotary encoder 2 that detects the rotation speed of the DC servomotor 1 is the frequency divider 3 and the flip-flop 36. Are connected to the input terminals of.

The output terminal P0 is connected to the level conversion circuit 2
8a and the input terminal of the inverting circuit 25a, and the output terminal of the level conversion circuit 28a is connected to the output terminal t1 via a resistor.
And the output terminal of the inverting circuit 25a is connected to the other input terminal of the AND circuit 26a.
The output terminal of is connected to the output terminal t3 via the level conversion circuit 27a. Similarly, the output terminal P1 is connected to the input terminals of the level conversion circuit 28b and the inverting circuit 25b, the output terminal of the level conversion circuit 28b is connected to the output terminal t2 via a resistor, and the output terminal of the inverting circuit 25b is , AND circuit 26b is connected to the other input terminal of A,
The output terminal of the ND circuit 26b is connected to the output terminal t4 via the level conversion circuit 27b.

Further, in the present embodiment, the microcontroller 5 detects the speed of the scanner at a position of a predetermined distance set in advance at the time of return acceleration of the scanner, compares it with the reference speed, and obtains a comparison signal. To
A correction data output means for inputting the correction data to the PWM generator 4 is provided.

The driving operation of the scanner of this embodiment having such a configuration will be described. In the present embodiment, as shown in FIG. 2, when the image forming operation is started, the control gain is set to G1 during the rising time T1, and the scanner is accelerated from the stopped state to the document scanning speed to scan. Time T2
During this period, the control gain is set to G2, and the scanner is scanned at a constant document scanning speed. After the end of this scan, the control gain is set to G3 during the inversion time T3, and the scanner is stopped after the inversion time T3, but the control gain is set to G4 during the return rise time T4. The scanner is accelerated in the reverse direction from the stopped state to the return speed, the control gain is set to G5 at the return time T5, the scanner returns at a high speed, and the control gain is set to G6 at the deceleration time T6. After the deceleration time T6, the vehicle is stopped and the same operation is repeated after the stop time T7.

This operation will be described in detail. When the DC servomotor 1 rotates in the normal direction, the logical value of the signal at the output terminal P0 is set to "1" and the logical value of the signal at the output terminal P1 is set to "0". It In this state, the logical value of the signal at the output terminal of the inverting circuit 25a is "0", so the logical value of the signal at the other input terminal of the AND circuit 26a is "0", and the AND
Even if the PWM signal is applied to one input terminal of the circuit 26a, no signal is output from the output terminal of the level conversion circuit 27a, and the MOS • FET 33 is turned off. At this time, since the output terminal of the level conversion circuit 28a is an open collector output, the gate voltage and the source voltage of the MOS.FET 31 become equal, and the MOS.FET 31 is turned off.

The logical value of the signal at the output terminal of the inverting circuit 25b is "1" and the logical value of the signal at the other input terminal of the AND circuit 26b is "1".
When a PWM signal is applied to one input terminal of
The logical value of the signal at the output terminal of the circuit 26b becomes "1" corresponding to the duty ratio of the PWM signal, a predetermined signal is output at the output terminal of the level conversion circuit 27b, and the MOS / F
The ET 34 is turned on. At this time, the level conversion circuit 2
The output terminal of 8b becomes GND level, and MOSFET3
Since the gate voltage of 2 is lower than the source voltage, the MOS • FET 32 is turned on.

As described above, when the logical value of the signal at the output terminal P0 is set to "1" and the logical value of the signal at the output terminal P1 is set to "0", the MOS FETs 32 and 34 are turned on.
The MOS • FETs 31 and 33 are turned off, a current flows in the DC servo motor 1 in the normal rotation direction, and the DC servo motor 1 rotates in the normal direction.

Next, at the time of reverse rotation of the DC servo motor 1,
The logical value of the signal at the output terminal P0 becomes "0", and the output terminal P1
The logical value of the signal is set to "1". In this state,
Since the logical value of the signal at the output terminal of the inverting circuit 25a is "1", the logical value of the signal at the other input terminal of the AND circuit 26a is "1", and the PWM signal is applied to one input terminal of the AND circuit 26a. When applied, the logical value of the signal at the output terminal of the AND circuit 26a becomes "1" corresponding to the duty ratio of the PWM signal, a predetermined signal is output at the output terminal of the level conversion circuit 27a, and the MOS-FET 33 Is ON
State. At this time, the output terminal of the level conversion circuit 28a becomes GND level, the gate voltage of the MOS.FET 31 becomes lower than the source voltage, and the MOS.FET 31 becomes O.
The state becomes the N state.

The logical value of the signal at the output terminal of the inverting circuit 25b becomes "0", and the logical value of the signal at the other input terminal of the AND circuit 26b becomes "0".
Even if the PWM signal is applied to one input terminal of 6b, no signal is output from the output terminal of the level conversion circuit 27b, and the MOS • FET 34 is turned off. This time,
Since the output terminal of the level conversion circuit 28b is an open collector output, the gate voltage and the source voltage of the MOS.FET 32 become equal, and the MOS.FET 32 is turned off.

As described above, when the logical value of the signal at the output terminal P0 is set to "0" and the logical value of the signal at the output terminal P1 is set to "1", the MOS FETs 31 and 33 are turned on.
The MOS • FETs 32 and 34 are turned off, a current flows in the reverse direction in the DC servo motor 1, and the DC servo motor 1 reversely rotates.

When the logical values of the signals at the output terminals of the output terminals P0 and P1 are both set to "1", the logical value of the signal at the output terminal of the inverting circuit 25a becomes "0".
Since the MOS • FET 33 is turned off and the output terminal of the level conversion circuit 28a is an open collector output, it is MO.
The gate voltage and the source voltage of the S-FET 31 become equal, and the MOS-FET 31 is turned off. This time,
Since the logical value of the signal at the output terminal of the inverting circuit 25b is "0", the MOS.FET 34 is in the OFF state, and the output terminal of the level conversion circuit 28b is an open collector output, so the gate voltage and source voltage of the MOS.FET 32 are set. Are equal to each other, and the MOS • FET 32 is turned off.

In this way, when the logical values of the signals at the output terminals of the output terminals P0 and P1 are both set to "1", M
All the OS-FETs 31 to 34 are turned off, and DC
The servo motor 1 is stopped.

In the normal rotation and reverse rotation operations of the DC servo motor 1 thus performed, the rotary encoder 2 outputs an encoder signal for detecting the rotation of the DC servo motor 1, and the encoder signal is used as the frequency divider 3. And is input to the microcontroller 5 as an interrupt signal, and the encoder signal is also divided by the flip-flop 36.
The rotation direction detection signal is input to the microcontroller 5 from the flip-flop 36.

Then, the microcontroller 5 inputs a PWM command signal to the PWM generator 4 based on the deviation of the scanner speed from the target speed, and the DC servo motor 1
Control.

On the other hand, in the microcontroller 5, in order to cope with the change in the winding resistance due to the heat generation of the DC servo motor, the correction data output means calculates the correction data based on the input interrupt signal. FIG. 3 is a characteristic diagram showing the scanner return operation of the present embodiment, and the solid line curve in the figure is the initial characteristic curve C1 of the motor.
The curve indicated by the dotted line is the characteristic curve C when the motor heats up.
2. TR is a return area of the scanner.

In the present embodiment, during return acceleration of the scanner, as shown in the figure, a preset predetermined distance L is detected, and the scanner speed V1 at the obtained predetermined distance L position is detected. The scanner speed V1 is compared with a preset reference speed V0, and the obtained correction signal Δ is PWM
The PWM signal is input to the generator 4, and a PWM signal corrected based on the correction signal Δ is output from the PWM generator 4.

Therefore, according to the present embodiment, even if the DC servomotor 1 is heated and the resistance value of the winding changes due to the continuous drive operation of the scanner, the predetermined value at the time of the return acceleration of the scanner caused by this is generated. The scanner speed V1 at the distance L position is detected and compared with the reference speed V0 of the obtained scanner signal, the correction signal Δ is input to the PWM generator 4, and the PWM generator 4 outputs the correction signal Δ based on the correction signal Δ. Since the corrected PWM signal is output and the DC servo motor 1 is driven by the corrected PWM signal, even when the DC servo motor 1 is in a heat generation state, the scanner is always controlled with high accuracy during deceleration of the scanner. As a result, it is possible to accurately stop at a predetermined position, and stable image formation is performed without being affected by heat generation of the DC servo motor.

[Second Embodiment] A second embodiment of the present invention will be described with reference to FIG. FIG. 4 is a circuit diagram showing the configuration of this embodiment.

In the present embodiment, as shown in FIG. 4, the PW in the first embodiment already described with reference to FIG. 1 is used.
Instead of the M generator 4, the output terminal P of the address data bus
5, the digital-analog converter 16 is connected, the output terminal of the digital-analog converter 16 is connected to the non-inverting input terminal of the operational amplifier 19, and the output terminal of the operational amplifier 19 is the non-inverting input terminal of the comparator 21. The output terminal of the triangular wave generator 20 is connected to the inverting input terminal of the comparator 21. The output terminal of the comparator 21 is connected to one input terminal of each of the AND circuits 26a and 26b.

In the motor drive circuit 35, the MO
Connection point between S / FET33 and MOS / FET34 and GN
A current detection resistor 17 for detecting a current flowing through the DC servomotor 1 is connected between D and the MOS • FETs 33, 34.
The connection point between the current detection resistor 17 and the current detection resistor 17 is connected to the non-inverting input terminal of the operational amplifier 18, and the output terminal of the operational amplifier 18 is connected to the inverting input terminal of the operational amplifier 19.

Then, in the present embodiment, the microcontroller 5 detects, based on the encoder signal, the time during which the scanner passes the preset predetermined distance during the return acceleration of the scanner and compares it with the reference time. A correction speed signal output means for calculating the correction speed signal and outputting it to the digital-analog converter 16 is provided.

The configuration of the other parts of this embodiment is the same as that of the first embodiment already described with reference to FIG.

The operation of this embodiment having such a configuration will be described. In the present embodiment, the armature current of the DC servo motor 1 is detected by the current detection resistor 17, and the current detection signal is input to the non-inverting input terminal of the operational amplifier 18,
The current detection signal output from the operational amplifier 18 is input to the inverting input terminal of the operational amplifier 19. Operational amplifier 19
The reference current signal is input from the microcontroller 5 to the non-inverting input terminal of the comparator 5 via the digital-analog converter 16, and the output signal of the operational amplifier 19 is input to one input terminal of the comparator 21 and the other input terminal. The output signal of the triangular wave generator 20 input to the terminal is compared.

Then, the PWM signal of the duty ratio corresponding to the reference current value from the microcontroller 5 is output from the comparator 21 and input to the AND circuits 26a and 26b, which has already been described in the first embodiment. Like D
The rotation control of the C servo motor 1 is performed. This control
Operational amplifiers 18, 19, comparator 21, and triangular wave generator 2
With 0, the rotation speed of the DC servo motor 1 is quickly set to the speed corresponding to the reference current from the microcontroller 5 based on the current value of the DC servo motor 1,
Speed control with good responsiveness is performed.

On the other hand, in the microcontroller 5, the correction data output means calculates the correction data corresponding to the heat generation of the DC servomotor based on the input interrupt signal. In this case, the correction data output means detects the time required for the scanner to pass the predetermined distance set in advance, and compares the time with the reference time to determine the change in the winding resistance value due to the heat generation of the DC servo motor 1. The corresponding corrected speed signal is calculated, and the corrected speed signal is input to the digital-analog converter 16.

In this way, in this embodiment, the microcontroller 5 outputs a reference current signal for causing the scanner to perform a predetermined reciprocating movement, and the heat generation of the DC servo motor 1 causes a change in the winding resistance value. If so, the current feedback works so as to correct the torque decrease due to the resistance change, and the correction speed signal is further output. Therefore, the DC servo motor 1
Even when the heat is generated, the scanner can be decelerated with high accuracy at the time of decelerating the scanner and can be accurately stopped at a predetermined position, and stable image formation can be performed without being affected by the heat generated by the DC servo motor. Be seen. Further, in the present embodiment, the control is performed by the operational amplifiers 18 and 19, the comparator 21, and the triangular wave generator 20 based on the current value of the DC servo motor 1, so that the rotation speed of the DC servo motor 1 is instantaneous. Is set to be responsive.

The present invention is not limited to the above-described embodiments. For example, a clear means for clearing the frequency divider at the start of the return of the scanner is provided for each of the embodiments. , Prevent the deviation of divided pulse,
It is also possible to adopt a configuration in which highly accurate distance measurement is performed. Further, when the scanner return is accelerated, the servo loop gain during the return deceleration of the scanner is corrected based on the speed change amount of the scanner at a position of a preset predetermined distance, and the scanner is stopped at a fixed position. Is also possible.

[0041]

According to the first aspect of the present invention, the scanner that reads the image data from the original image is reciprocated by the DC servo motor by the driving means, and the DC servo motor is controlled by the control means according to the scanning speed of the scanner. In the image forming apparatus in which the operation of the DC servo motor is controlled by switching the servo loop gain of the scanner, the stop control means causes the scanner to be controlled by the stop control means based on the speed of the scanner at a position of a predetermined distance set at the time of return acceleration of the scanner. Since the servo loop gain at the time of deceleration of the return is corrected, even if the DC servo motor is in a heat generation state, the scanner can be decelerated with high precision at the time of deceleration of the scanner, and the scanner can be accurately stopped at a predetermined position. As a result, stable image formation is performed without being affected by the heat generated by the DC servo motor.

According to the second aspect of the present invention, the scanner that reads the image data from the original image by the driving means is D
In the image forming apparatus in which the servomotor is reciprocally moved by the C servomotor, the servo loop gain of the DC servomotor is switched by the control means according to the scanning speed of the scanner, and the operation of the DC servomotor is controlled, the return acceleration of the scanner is accelerated. Sometimes, the stop control means corrects the servo loop gain during return deceleration of the scanner on the basis of the time for which the scanner passes a preset distance. The deceleration of the scanner can always be controlled with high accuracy to accurately stop the scanner at a predetermined position, and stable image formation can be performed without being affected by heat generated by the DC servo motor.

According to the invention of claim 3, in addition to the effect obtained by the invention of claim 1 or 2, DC
An encoder that outputs a pulse signal according to the rotation of the servo motor is provided, and a predetermined distance that is set in advance is calculated by counting the output signals of the encoder. It becomes possible to calculate the set predetermined distance.

According to the invention of claim 4, in addition to the effect obtained by the invention of claim 3, the output signal of the encoder is used without being divided, so that the servo loop gain is corrected. It is possible to calculate a predetermined distance set in advance with high accuracy.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing a configuration of a first exemplary embodiment of the present invention.

FIG. 2 is a velocity diagram showing the operation of the same embodiment.

FIG. 3 is a characteristic diagram showing a scanner return operation of the same embodiment.

FIG. 4 is a circuit diagram showing a configuration of a second exemplary embodiment of the present invention.

[Explanation of symbols]

 1 DC Servo Motor 2 Rotary Encoder 3 Divider 4 PWM Generator 5 Microcontroller 16 Digital-Analog Converter 17 Current Detection Resistor 18, 19 Operational Amplifier 20 Triangular Wave Generator 21 Comparator 30 Drive Selection Circuit 31-34 MOS ・ FET 35 Motor drive circuit

Claims (4)

[Claims] 1. A scanner for reading image data from an original image, a driving means for reciprocating the scanner by a DC servo motor, and a servo loop gain of the DC servo motor being switched according to a scanning speed of the scanner, An image forming apparatus comprising: a control unit for controlling the operation of the DC servo motor, wherein when the scanner is accelerated for return, the scanner is decelerated for return based on the speed of the scanner at a position of a predetermined distance set in advance. 2. An image forming apparatus comprising: stop control means for correcting the servo loop gain and stopping the scanner at a fixed position. 2. A scanner for reading image data from an original image, a driving means for reciprocating the scanner by a DC servo motor, and a servo loop gain of the DC servo motor being switched according to a scanning speed of the scanner, An image forming apparatus comprising: a control unit for controlling the operation of the DC servo motor, wherein the scanner decelerates the return speed of the scanner based on the time during which the scanner passes a predetermined distance when the scanner accelerates the return operation. An image forming apparatus comprising: a stop control unit that corrects the servo loop gain at the time and stops the scanner at a fixed position. 3. The image forming apparatus according to claim 1, further comprising an encoder that outputs a pulse signal according to the rotation of the DC servomotor, and counts the output signal of the encoder. An image forming apparatus, wherein the preset predetermined distance is calculated. 4. The image forming apparatus according to claim 3, further comprising frequency dividing means for dividing the output signal of the encoder and clear means for clearing the frequency dividing means when the scanner starts returning. An image forming apparatus characterized by being provided.