JP2002291290A - System for controlling drive of stepping motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce unnecessary power consumption, vibrations, noises and unevenness in revolutions by adding a very simple circuit to a system for controlling drive of a stepping motor. SOLUTION: A drive signal having an appropriately set frequency undergoes appropriate current amplification by a driver 2, so as to be supplied to a coil of the stepping motor 1. Feedback control is exercised so that an output current of a driver 2 can be equal to a target current. A revolution detection signal having a frequency proportional to an actual rotational speed of the stepping motor 1 is generated. The drive signal is compared with the revolution detection signal. Consequently, the longer the phase of the revolution detection signal is delayed with respect to the revolution detection signal when the stepper motor 1 runs in synchronization with the driving signal, the greater the target current is made.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a drive control system for a stepper motor which is frequently used in OA equipment such as a copying machine and a printer, and more specifically, to reduce unnecessary power consumption and to reduce rotational unevenness and vibration. The present invention relates to technical improvements for reducing noise.

[0002]

2. Description of the Related Art As is well known, in OA equipment such as a copying machine and a printer, many servo mechanisms are incorporated, and a stepper motor is frequently used as a drive source of the servo mechanisms. The stepper motor is a motor that is very easy to use because the control of the rotational speed and the control of the rotational position can be realized by open-loop control, so that the configuration of the control system is simplified.

[0003]

The speed and position of the stepper motor can be controlled by the open loop control only in a range where the stepper motor is rotated in synchronization with the drive signal without step-out. is there. And
In order to rotate the stepper motor synchronously so as not to lose synchronism, the stepper motor must be operated with a drive signal frequency below a certain value.

The upper limit frequency varies depending on the load of the stepper motor. In a situation where the load of the stepper motor changes within a certain range and the rotation speed of the stepper motor also changes within a certain range, be careful not to lose synchronization even when the load of the stepper motor is maximum and the rotation speed is maximum. In other words, the value of the stepper motor drive current is increased, and drive is performed so as to generate a rotational torque corresponding to the load. Thus, the drive control system of the stepper motor is designed.

However, in this case, when the rotational speed is not so high and the motor load increases and decreases, if the load becomes relatively small, an excessively large current is supplied to the motor coil and an excessively large rotational torque is generated. You are doing. This means that unnecessary motor drive power is consumed. In addition, due to excessive torque, torque ripple increases, which tends to cause uneven rotation, vibration, and noise.

SUMMARY OF THE INVENTION The present invention has been made in view of the above background, and an object of the present invention is to solve the above-described problems and to add a very simple circuit system to a stepper motor drive control system. An object of the present invention is to provide a drive control system for a stepper motor that can reduce unnecessary power consumption and reduce uneven rotation, vibration, and noise.

[0007]

In order to achieve the above object, a drive control system for a stepper motor according to the present invention comprises a stepper motor which amplifies current of a drive signal of an appropriately set frequency by a driver. A drive control system for a stepper motor for supplying a coil with a current feedback control system for performing feedback control so that an output current value of the driver becomes equal to a target current value; and a frequency proportional to an actual rotation speed of the stepper motor. A rotation detection system that generates the rotation detection signal of the above, and comparing the drive signal with the rotation detection signal, the rotation detection signal when the stepper motor is rotating in synchronization with the drive signal is used as a reference. A drive current control system that increases the target current value as the phase of the rotation detection signal lags behind. It was and.

In this system, the rotation detection system may include an encoder coupled to an output shaft of the stepper motor, or may include an encoder coupled to a rotation system of a load mechanism driven by the stepper motor. Can also be taken.

According to the present invention, when the rotation of the stepper motor tends to be delayed due to an increase in the motor load or the like, the phase of the rotation detection signal is delayed with respect to the drive signal. The drive current control system detects this, and increases the target current value corresponding to the phase delay. As a result, the output current of the driver increases, the torque of the stepper motor increases, and the operation returns to the fully synchronized operation state.

On the other hand, when the rotation phase of the stepper motor tends to advance due to a decrease in the motor load or the like, the phase of the rotation detection signal advances with respect to the drive signal. Output current becomes smaller.
Therefore, excessive torque of the stepper motor is reduced.

[0011]

FIG. 1 shows the principle configuration of a preferred embodiment of a drive control system for a stepper motor according to the present invention. The stepper motor 1 of this example is a two-phase motor, and includes two systems of drivers 2 for A-phase and B-phase. The drive signal generator 3 outputs a drive signal having an appropriately set frequency. This drive signal is supplied to the A-phase and B-phase drivers 2 via the phase switching unit 4. The driver 2 appropriately amplifies the drive signal and supplies the current to the coil of the stepper motor 1.

The driver 2 has a current feedback control system for performing feedback control so that the output current value becomes equal to the target current value. That is, the output current value is detected by the current detection unit 5, and the detected value X and a target current value Y described later are used.
Are compared by the current comparing unit 6, and the output current value of the driver 2 is controlled so that the detected value X becomes equal to the target current value Y.

An encoder 7 is coupled to an output shaft of the stepper motor 1 or a mechanism driven by the stepper motor 1, and outputs a rotation detection signal having a frequency proportional to the rotation speed of the stepper motor 1 from the encoder 7. . This rotation detection signal is divided or multiplied by the frequency converter 8 and shaped into a rectangular wave. The rotation detection signal N that has passed through the frequency converter 8 is input to the phase comparator 9.

The drive signal output from the drive signal generator 3 is also input to the frequency converter 10, where it is divided or multiplied and shaped into a rectangular wave. Frequency converter 10
Is input to the phase comparator 9. When the stepper motor 1 is rotating completely in synchronization with the drive signal, the components are set so that the frequency and phase of the rotation detection signal N input to the phase comparator 9 and the drive signal M match. .

The above-mentioned target current value Y is output from the phase comparator 9. As described above, in the fully synchronous operation state in which the frequency and phase of the rotation detection signal N and the drive signal M match, the target current value Y output from the phase comparison unit 9 is kept at the previous value.

When the rotation of the stepper motor 1 tends to be delayed due to an increase in the motor load or the like, the phase of the rotation detection signal N is delayed with respect to the drive signal M. In this case, the target current value Y output from the phase comparison unit 9 increases in accordance with the phase delay, the output current of the driver 2 increases, and therefore the torque of the stepper motor 1 increases, and the state of the fully synchronized operation is established. Return.

On the other hand, when the rotation phase of the stepper motor 1 is slightly advanced due to a decrease in the motor load or the like, the phase of the rotation detection signal N is advanced with respect to the drive signal M. In this case, the target current value Y output from the phase comparator 9 becomes smaller, the output current of the driver 2 becomes smaller, and the excessive torque of the stepper motor 1 is reduced. In this way, the stepper motor 1 is driven with the minimum current for keeping the stepper motor 1 in a completely synchronized operation state.

In the stepper motor application mechanism illustrated in FIG. 2, a pulley belt mechanism is connected to the stepper motor 1, whereby the block 11 is driven to reciprocate.
A linear encoder is constituted by a sensor 12 attached to the block 11 and a linear scale 13 attached to a fixed member. This linear encoder is a main part of the rotation detection system described above.

In the motor application mechanism illustrated in FIG. 3, a gear mechanism is connected to the stepper motor 1, whereby the paper feed roller 14 is driven to rotate. A rotary encoder is constituted by a circular scale 15 attached to the shaft of the roller 14 and a sensor 16 attached to a fixed member. This rotary encoder is a main part of the above-described rotation detection system.

[0020]

According to the present invention, the speed and the position of the stepper motor are controlled by the basic open-loop control, but the drive current is minimized in order to maintain the fully synchronized operation state by the control. Since a local feedback control system is added, unnecessary power consumption can be reduced and rotation unevenness, vibration, and noise can be reduced without using a very complicated control system.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a principle configuration of a drive control system for a stepper motor according to an embodiment of the present invention.

FIG. 2 is a diagram showing an example of a motor application mechanism to which the present invention is applied.

FIG. 3 is a diagram showing another example of the motor application mechanism.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Stepper motor 2 Driver 3 Drive signal generation part 4 Phase switching part 5 Current detection part 6 Current comparison part 7 Encoder 8 Frequency conversion part 9 Phase comparison part 10 Frequency conversion part 11 Block 12 Sensor 13 Linear scale 14 Paper feed roller 15 Circular scale 16 Sensor

 ────────────────────────────────────────────────── ─── Continued from the front page (72) Inventor Shigeki Miyachi 5-36-11 Shimbashi, Minato-ku, Tokyo FDC Corporation F-term (reference) 2C480 CA01 CA02 CA44 CB03 CB34 EA12 EA22 EA27 5H580 AA05 BB01 BB02 BB07 CA12 CB03 FA02 FA04 HH02 HH22

Claims (3)

[Claims] 1. A drive control system for a stepper motor, wherein a drive signal of an appropriately set frequency is appropriately amplified by a driver and supplied to a coil of the stepper motor, wherein the output current value of the driver is a target current value. A current feedback control system for performing feedback control so as to be equal to; a rotation detection system for generating a rotation detection signal having a frequency proportional to the actual rotation speed of the stepper motor; and comparing the drive signal and the rotation detection signal. so,
A drive current control system that, based on the rotation detection signal when the stepper motor is rotating in synchronization with the drive signal, increases the target current value as the phase of the rotation detection signal is delayed. And a stepper motor drive control system. 2. The stepper motor drive control system according to claim 1, wherein the rotation detection system includes an encoder coupled to an output shaft of the stepper motor. 3. The drive control system for a stepper motor according to claim 1, wherein the rotation detection system includes an encoder coupled to a final stage rotation system of a load mechanism driven by the stepper motor. .