JP3405594B2 - Servo control device for scanner motor - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a servo control device for a DC servo motor that drives a scanner of a copying machine or a printer, and more particularly to improving the accuracy of a document reading start position.

[0002]

2. Description of the Related Art For example, in a slit exposure type copying machine, an original having an image surface facing down is placed on a contact glass, and the projected image read by scanning the image surface with a scanner is placed on a photoconductor. An image is formed and a copied image is obtained.
The rotation speed and rotation direction of the DC servo motor that drives this scanner are determined by a predetermined speed diagram and the number of feedback pulses and feedback obtained from the output of the encoder attached to the servo motor. Depending on the feedback pulse frequency
The volume gain is switched and controlled. Servomo
As shown in FIG. 7, the velocity diagram for controlling the rotation of the rotor is divided into a scan operation and a return operation. In FIG. 7, t ₁ is the rise time, t ₂ is the time for scanning at a constant speed, t ₃ is the reversal time, t ₄ is the rise time during the return operation, and t ₅ is the time during the return operation. constant speed time, t ₆ the deceleration time, t ₇ shows the stop control time, G ₁ ~G ₇ the difference at each operation step - shows the loop gain - Bol. As shown in the figure,
During the period of the rising time t ₁ and the rising time t ₄ and the deceleration time t ₆ during the return operation, the servo gain is increased,
The responsiveness of the control system is improved so that it can follow sudden speed changes.

In order to obtain a good copy image without blur when driving the scanner while controlling the servomotor based on this velocity diagram and reading a document, the scanner for reading the image has a constant velocity. After that, it is necessary to start reading the original. For that purpose, the run-up distance until the scanner starts up at a constant speed is required, but because the downsizing of copying machines and the like is required, the run-up distance until the scanner starts up at a constant speed is limited to, for example, about 20 mm. The current situation is that the run-up distance cannot be taken too long. Since the approach distance is fixed in this way, when the speed diagram for controlling the rotation speed and the rotation direction of the DC servomotor that drives the scanner is changed to increase the reading speed of the scanner. In this case, the acceleration at the time of rising of the scanner is changed so that the speed becomes constant during a fixed rising distance.

Further, when the functions such as the enlargement copy and the reduction copy are used, the change of the velocity diagram becomes larger.
That is, as shown in FIG. 8, it is necessary to increase the acceleration a ₃ at the start of the reduction copy more than the acceleration a ₂ at the start of the expansion copy, and at the rise of the expansion copy and the reduction copy. The amount of change in acceleration changes to about 1/2 to 4 times the acceleration a ₁ of the standard ₁ × copy. For this reason, the servo gain of the control system is changed according to the velocity diagram determined for each of the same-size copy, the enlargement copy, and the reduction copy to stabilize the operation.

[0005]

However, the temperature of the servo motor driving the scanner rises during operation, and the torque characteristic deteriorates due to this temperature rise, so the responsiveness also deteriorates. Therefore, even if the servo motor is controlled by a predetermined servo gain, the target acceleration cannot be obtained at the time of rising, and when the temperature rises from T to T ₁ , as shown in FIG. As shown, from a ₁ (T) to a ₁ (T
It will change to ₁ ). Due to this change in acceleration, the start-up time t ₁ changes, the time t ₁ (T) required for the scanner to reach the leading edge of the document changes to t ₁ (T ₁ ), and the reading start position of the document changes. Therefore, it is difficult to obtain a uniform copy image.

Further, the rise time also changes depending on the load of each device and variations in applied voltage.

The present invention has been made in order to solve the above disadvantages, and it is possible to solve the above problems regardless of the temperature change of the servo motor.
It is an object of the present invention to provide a servo control device for a scanner motor that can perform appropriate speed control.

[0008]

A servo control device for a scanner motor according to the present invention has an arithmetic processing section, a motor temperature measuring section, and a start timing correcting section. It calculates and outputs the control signals of the rotation speed and rotation direction of the DC servo motor that drives the scanner, and outputs a predetermined speed diagram and the encoder attached to the servo motor. The control temperature is calculated by switching the servo gain according to the number of feedback pulses and the feedback pulse frequency obtained from the motor temperature measurement section. The start timing correction unit changes the start timing of the servo motor according to the detected temperature of the servo motor and sends it to the arithmetic processing unit.

It is desirable to have a gain correction unit that corrects the servo gain according to the detected temperature of the servo motor and sends it to the arithmetic processing unit.

Further, the start timing correction section has a rise time detection section for detecting the rise time of the motor based on the number of feedback pulses and the frequency of the feedback pulse obtained from the output of the encoder. It is advisable to correct the start timing of the servo motor changed according to the temperature of the servo motor according to the rise time of the motor.

Further, the start timing corrected according to the rise time is stored in correspondence with the temperature of the motor, and the start timing correction section is provided for the starter of the servo motor.
The start timing may be determined by the corrected start timing stored in accordance with the temperature of the servo motor.

[0012]

In the present invention, the winding temperature of the servo motor successively detected by the motor temperature measuring section is sent to the start timing correcting section of the control section. The start timing correction unit changes the start timing of the servo motor according to the temperature of the sent servo motor and sends it to the arithmetic processing unit. The arithmetic processing unit controls the start-up time of the servo motor according to the sent start timing, changes the start position of the constant speed operation for reading the original, and makes the original reading start position constant.

Further, the servo mode detected by the gain correction unit
The servo gain is corrected according to the temperature of the motor and sent to the arithmetic processing section, and the rotation speed of the servo motor is controlled by the corrected servo gain according to the temperature of the servo motor. Then
Even if the responsiveness of the servo motor decreases due to the temperature rise, the servo motor can be stably driven at a predetermined velocity diagram.

Further, in the rise time detection section, the number of feedback pulses and the frequency of the feedback pulse obtained from the output of the encoder for detecting the number of revolutions of the servo motor change the load pulse and the voltage. The rise time of the motor is detected. Correct the start timing of the servo motor that is changed according to the temperature of the servo motor according to the changing rising time, and change the reading start position of the document due to variations in load and voltage. prevent.

Further, the start timing corrected according to the rise time is stored in association with the temperature of the motor, and the start timing correction unit calculates the start timing of the servo motor. The start timing determined with reference to the corrected start timing stored at the time of determination can easily obtain a more stable start timing.

[0016]

1 is a block diagram showing the configuration of an embodiment of the present invention. As shown in the figure, for example, a control device for controlling the rotation speed of a DC servo motor 1 for driving a scanner of a copying machine is provided in advance with the same magnification operation, enlargement operation, and reduction operation during the operation of the scanner. A speed command unit 2 for outputting a determined speed diagram, a central processing unit (CPU) 3, a PWM generator 4, a base drive unit 5, and a drive unit 6.
And an encoder 7 for detecting the rotation speed of the servo motor 1.
And a temperature sensor 8 having a thermistor for detecting the surface temperature of the servomotor 1, for example.

As shown in the block diagram of FIG. 2, the CPU 3 has an arithmetic processing unit 31, a timer unit 32, and a gain correction unit 3.
3. A start timing correction unit 34 is provided. The timer unit 32 is an encoder for detecting the number of revolutions of the servo motor 1.
The feedback pulse frequency f is detected from the feedback pulse train input from the frequency divider 7 via the frequency divider 9 and sent to the arithmetic processing unit 31. The gain correction unit 33 detects the servo gain determined by each speed diagram from the speed command unit 2 according to the same-magnification operation, the expansion operation, and the reduction operation by the temperature sensor 8. It is corrected according to the temperature of and is sent to the arithmetic processing unit 31. The start timing correction unit 34 sets the start timing of the control signal of the servo motor according to the detected temperature of the servo motor 1, and the arithmetic processing unit 31.
Send to. The arithmetic processing unit 31 includes a velocity diagram sent from the velocity command unit 2, a control constant, that is, a servo gain corrected by the gain correction unit 33, an encoder 7 and a frequency divider 9.
The start timing sent from the start timing correction unit 34 by performing proportional / integral calculation with the feedback pulse number n input via the feedback pulse frequency f sent from the timer unit 32. To output.

The PWM generator 4 pulse-width modulates the control signal output from the arithmetic processor 31 to generate and output a PWM signal. The base drive unit 5 has level shifts 51, 5
2 and AND elements 53 and 54, and a control signal output from the arithmetic processing unit 31 and a P output from the PWM generating unit 4.
The drive unit 6 is controlled by the WM signal. The drive unit 6 has a plurality of FETs 61 and drives the servo motor 1.

The operation of the control device constructed as above will be described with reference to the flow chart of FIG.

When the copying machine is powered on and in a standby state, the temperature of the servo motor 1 is constantly detected by the temperature sensor 8 and input to the CPU 3 (step S1). In this state, when the operation state of any one of the 1: 1 copy, the enlargement copy and the reduction copy and the enlargement ratio or the reduction ratio are designated to read and copy the document, the operation designated by the speed command unit 2 is performed. The velocity diagram shown in FIG. 7 according to the state is sent to the arithmetic processing unit 31 and the gain correction unit 33 of the CPU 3 (step S
2). Gain correction unit 33 the rise time of the velocity diagrams t ₁ sent, a certain deceleration time t _2, the inversion time t _3, Rita - down startup time during operation t _4, Rita - down constant speed during operation time t ₅ , deceleration time t ₆ and stop control time t ₇ during each process
Loop gain G ₁ ~G ₇ predefined motor - motor temperature versus control constant characteristics and detected by the temperature sensor 8 sequentially sent by that service - Vomo - corrected based on the temperature of the motor 1, the operation steps of the corrected The optimum servo gain for each is sent to the arithmetic processing unit 31 (step S3). Also, the start timing correction unit 34 starts the start timing of the control signal for driving the servo motor 1 from the characteristics of the motor temperature and the start timing which are determined in advance according to the reading start position of the document. Is changed and set based on the temperature of the servo motor 1 detected by the temperature sensor 8 and sent to the arithmetic processing section 31 (step S4).
When the copy-to-key is pressed (step S5), the arithmetic processing unit 31 receives from the velocity curve being input at that time, the optimum servo gain corrected by the gain correction unit 33, and the encoder 7. The control signal is proportionally and integratedly calculated by the feedback pulse number n input via the frequency divider 9 and the feedback pulse frequency f sent from the timer unit 32 (step S6). Thereafter, the arithmetic processing unit 31 receives the copy start signal, and then the start timing correction unit 3
After the start timing input from 4 has passed (step S7), the calculated control signal is sent to the base drive unit 5
To the PWM generation circuit to start the copy operation (step S7).

For example, when the temperature of the servo motor 1 is T, as shown in FIG. 4, the rising acceleration a when the start timing t ₀ (T) elapses after the copy start signal is input. _{At 1} (T), rotation of the servo motor 31 is started and the servo motor 31 is rotated.
When the temperature of the body motor ₁ is T ₁ which is higher than T, in order to compensate for the deterioration of the torque characteristics due to the temperature rise of the servo motor 31, after the copy start signal is input. When the start timing t ₀ (T ₁ ) shorter than the start timing t ₀ (T) at the temperature T elapses, the rotation of the servo motor 31 is started at the rising acceleration a ₁ (T ₁ ). To do. However, acceleration a ₁ (T ₁ ) <acceleration a ₁ (T).
Since the start timing is changed according to the temperature of the servo motor 31 as described above, as shown in FIG. 4, the scanner always reaches the original reading start position after the operation at a constant speed, and uneven scanning occurs. You can get no image. Also,
Although the responsiveness of the servo motor 31 is deteriorated due to the temperature rise, the servo motor 31 is used with an optimum servo gain in which the servo gain is increased in accordance with the temperature rise of the servo motor 31. Since the rotation of the motor 31 is controlled, the servo motor 31 can be stably rotated at a predetermined velocity diagram. When the copying of the required number of originals is completed in this way, the copying operation is completed and the standby state is set (step S
9).

In the above embodiment, the rotation start of the servo motor 31 is controlled at the start timing set according to the temperature of the servo motor 31, but the servo motor 31 is controlled. The start timing set according to the temperature of 31 may be corrected by the actual rising time of the servo motor 31.

For example, as shown in the block diagram of FIG.
PU3 is provided with a rise time detecting section 35, and the servo motor 31 at that time is determined by the number of feedback pulses and the feedback pulse frequency obtained from the output of the encoder 7.
Detect the rise time of. The detected actual rising time is sent to the start timing correction section 34, and the servo mode is adjusted.
The start timing set based on the temperature of data 1 is corrected.

In the case of this embodiment, the flow chart of FIG.
As shown in FIG. 7C, the temperature of the servo motor 1 is detected by the temperature sensor 8 and is input to the CPU 3 in the standby state after the power of the copying machine is turned on (step S11). When the operation state when reading a document in this state is designated (step S12), the service during each step of the velocity diagram in the gain correction unit 33 - Bol - loop gain G ₁ ~G ₇ the service - Vomo - motor 1 Is corrected on the basis of the temperature and the corrected optimum servo gain for each operation process is sent to the arithmetic processing unit 31 (step S1).
3), the start timing correction unit 34 operates the servo motor 1
The start timing of the control signal for driving is set based on the temperature of the servo motor 1 detected by the temperature sensor 8 and sent to the arithmetic processing section 31 (step S14). Arithmetic processing unit 3
1 is when the copy start key is pressed (step S1
5) Controlled by the input velocity diagram, the optimum servo gain corrected by the gain correction unit 33, and the feedback pulse number n and the feedback pulse frequency f obtained from the output of the encoder 7. The signal is divided by minutes (step S16). After that, when the start timing input from the start timing correction unit 34 elapses after the copy start signal is input, the arithmetic processing unit 31 determines whether the original reading start position is appropriate or not. The control signal corresponding to is output for one scan to rotate the servo motor 31 (steps SS17, 18). Servo motor 31
Is rotated by one scan, the rise time detection unit 35 obtains the feedback pulse number n obtained from the output of the encoder 7.
Then, the rise time of the servo motor 31 at that time is detected by the feedback pulse frequency f and sent to the start timing correction unit 34 (step S19). On the other hand, the arithmetic processing unit 31 determines the moving position of the scanner based on the feedback pulse number n and the feedback pulse frequency f obtained from the output of the encoder 7 when the servo motor 31 rotates for one scan. The moving speed is calculated and the servo motor 31
Stands up and confirms whether or not the original reading start position has been reached during a constant speed operation (step S20). When the scanner reaches the original reading start position and the servo motor 31 has not reached the constant speed operation, the arithmetic processing section 31 sets the start timing correction section 34 to the start timing correction section 34.
Command to correct the timing. Upon receiving this command, the start timing correction unit 34 corrects the start timing set based on the temperature of the servo motor 1 with the actual rise time at that time sent from the rise time detection unit 35. The corrected start timing is sent to the arithmetic processing unit 31 (step S21). After that, the arithmetic processing unit 31 starts the copying operation in accordance with the sent start timing and the calculated control signal (step S22). When the copying of the required number of originals is completed, the copying operation is ended and the standby state is established. (Step S23).

By correcting the start timing set based on the temperature of the servo motor 1 in this way with the rising time of the servo motor 31 obtained during the actual copying,
It is possible to prevent the reading start position of the document from fluctuating due to variations in load and voltage.

In the above embodiment, the actual rise time of the servo motor is detected each time a copy is made, and it is determined whether or not the servo motor 31 has risen to reach the original reading start position during a constant speed operation. The case of confirming and correcting the start timing set based on the temperature of the servo motor 1 has been described. However, when the start timing is corrected according to the actual rise time, the start timing is corrected each time. The SRAM 3 is provided with the start timing corresponding to the temperature of the servo motor 31.
Remember in 6. Then, the start timing correction section 34 determines the start timing by referring to the corrected start timing stored in the SRAM 36 when determining the start timing of the servo motor 31. May be. By storing the corrected start timing in the SRAM 36 in association with the temperature of the servo motor 31, a more stable start timing can be easily obtained.

[0027]

As described above, according to the present invention, the start timing of the servo motor is changed according to the temperature of the servo motor, which is detected successively, at the start of the rise of the servo motor. Since the scanner is controlled to drive the servo motor, the scanner can always reach the original reading start position after a constant speed operation, and a high-quality image without uneven reading can be obtained.

The servo gain is corrected according to the detected temperature of the servo motor, and the rotation speed of the servo motor is controlled with the optimum servo gain. Even if the responsiveness of the motor decreases due to the temperature rise, it can be stably driven at a predetermined velocity diagram, and a uniform image can always be obtained. It can be rotated.

Further, the servo motor which changes due to variations in load, voltage, etc. by the feedback pulse number and the feedback pulse frequency obtained from the output of the encoder for detecting the rotational speed of the servo motor. The actual rise time of the motor is detected, and the start timing of the servo motor set according to the temperature of the servo motor is corrected by the detected rise time. It is possible to prevent the reading start position of the document from changing.

Further, the start timing corrected in accordance with the rise time is stored in association with the temperature of the motor, and the start timing correction section stores the start timing of the servo motor. By determining the start timing with reference to the corrected start timing stored at the time of determination, a more stable start timing can be easily obtained.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of an embodiment of the present invention.

FIG. 2 is a block diagram showing a configuration of a CPU of the above embodiment.

FIG. 3 is a flowchart showing the operation of the above embodiment.

FIG. 4 is a velocity characteristic diagram showing the operation of the above embodiment.

FIG. 5 is a block diagram showing a configuration of a CPU of another embodiment.

FIG. 6 is a flowchart showing the operation of another embodiment.

FIG. 7 is a velocity diagram showing operating characteristics of a servo motor.

FIG. 8 is a change characteristic diagram of acceleration when the servo motor rises.

FIG. 9 is a characteristic diagram of changes in acceleration depending on the temperature of the servo motor.

[Explanation of symbols]

1 Servo motor 2 Speed command section 3 Central processing unit (CPU) 4 PWM generator 7 Encoder 8 Temperature sensor 31 arithmetic processing unit 32 Timer section 33 Gain correction section 34 Start Timing Correction Unit 35 Rise time detector 36 SRAM

─────────────────────────────────────────────────── ─── Continuation of front page (58) Fields surveyed (Int.Cl. ⁷ , DB name) H02P 5/00-5/26 H02P 7/00-7/34 G05B 19/05 G05D 13/62

Claims (4)

(57) [Claims] 1. An arithmetic processing unit, a motor temperature measuring unit, and a start timing correction unit, wherein the arithmetic processing unit is a control signal of a rotation speed and a rotation direction of a DC servo motor for driving a scanner. Is calculated and output, and the speed is determined according to the number of feedback pulses and the frequency of the feedback pulses obtained from the output of the encoder attached to the servomotor. The control signal is calculated by switching the volume gain, the motor temperature measuring unit detects the winding temperature of the servo motor, and the start timing correction unit responds to the detected temperature of the servo motor. A servo control device for a scanner motor, wherein start timing of the servo motor is set and sent to an arithmetic processing unit. 2. A servo controller for a scanner motor according to claim 1, further comprising a gain correcting section for correcting the servo gain according to the detected temperature of the servo motor and sending it to the arithmetic processing section. . 3. The start timing correction section has a rise time detection section for detecting the rise time of the motor based on the number of feedback pulses and the frequency of the feedback pulse obtained from the output of the encoder. 3. A servo controller for a scanner motor according to claim 1, wherein the start timing of the servo motor set in accordance with the temperature of the servo motor is corrected in accordance with the rise time of the motor. . 4. A star corrected according to the rise time.
The start timing is stored in association with the temperature of the motor, and the start timing correction unit stores the corrected start timing of the servo motor according to the temperature of the servo motor. A servo control device for a scanner motor according to claim 3, wherein the servo control device is determined by the timing.