JPH02151298A - Stepping motor driving device - Google Patents

Abstract

PURPOSE:To suppress vibration and speed variation caused by the vibration by detecting the stepout of a stepping motor, and automatically setting a driving voltage of the motor to a low voltage immediately before the stepout on the basis of its detection information. CONSTITUTION:Since the driving speed of a stepping motor 101 is different according to a copying magnification, a torque necessary for the stepping motor 101 is also different according to the copying magnification. Thus, before copying, the stepping motor 101 is moved at a speed responsive to the designated copying magnification. If a controller 105 detects a stepout by the output 104 of a stepout detector 103 at that time, the controller 105 sends a control signal 107 to a voltage varying unit 108 to raise the motor driving voltage 109 from the voltage varying unit 108, for example, by approx. 1V. However, if it does not detect the stepout, the controller 105 lowers the voltage 109, for example, by approx. 1V through the voltage varying unit 108 and finds the value of the motor driving voltage immediately before the stepout.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a stepping motor drive device for driving a stepping motor.

(Prior Art) Conventionally, the driving voltage for driving a stepping motor is set to a constant voltage with sufficient margin to account for load fluctuations such as mechanical variations in the load and changes over time.

However, in constant voltage driving, which is one driving method of a stepping motor, two voltage sources 402 are used as shown in FIG.
, 403 are switched by a voltage switching signal 401 depending on when the stepping motor is accelerating or at constant speed, when it is stopped or running, or when it is at low speed or high speed. Note that 201 is a motor winding, and 106 is a stepping motor driver control signal.

On the other hand, constant current chimipper driving, which is a common driving method for stepping motors, makes it possible to increase the torque of the stepping motor during high-speed rotation compared to the above-mentioned constant voltage driving.

FIG. 2 shows the principle of constant current chopper drive. As shown in FIG. 2, this drive method extracts the current flowing through the motor winding 201 as a motor current detection voltage 208 using a current detection resistor 202.
08 is the reference voltage (2) generated by the reference voltage generator 203.
The voltage comparison circuit 204 compares the oscillation wave (approximately 0 KHz) 207 with the voltage comparison circuit 204, and depending on the comparison result, the switching transistor 206 is turned on and off using the pulse width modulation signal of the PWM (pulse width modulation) control circuit, thereby controlling the motor windings. The motor driving voltage applied to the motor winding 201 is turned on and off to maintain a constant current flowing through the motor winding 201.

The relationship between the motor drive voltage and the current flowing through the motor windings during constant current chopper driving is, for example, as shown in FIG. 3(A). As shown in this figure, if the voltage is constant, the rise and fall characteristics of the current flowing through the motor winding 201 are as follows:
It is determined by a time constant determined by the inductance and resistance value of the motor winding 201. For this reason, it is common to drive the stepping motor by applying a sufficiently high voltage to it so that step-out due to a delay in startup does not occur.

[Problem to be solved by the invention]

However, the current waveform during this drive is as shown in Figure 3 (A
) shows a waveform in which the current value changes finely.

This change in current appears as mechanical vibration in the stepping motor. Therefore, for example, when a stepping motor is used as a drive source for a document reading device of a copying machine, vibrations of the stepping motor may appear on the image.

However, if the driving voltage is lowered, the rise of the current becomes slower as shown in FIG. 3(B), so the current waveform becomes smoother, making it possible to reduce the vibration of the stepping motor. Furthermore, it would be very effective if the voltage could be lowered to the point where the stepping motor is on the verge of losing synchronization.

In view of the above-mentioned points, an object of the present invention is to provide a stepping motor drive device that automatically sets the stepping motor drive'BJ voltage to a voltage on the verge of losing synchronization, thereby allowing the stepping motor to be used in a state with the least amount of vibration. Our goal is to provide the following.

[Means to solve the problem]

In order to achieve such an object, the present invention includes step-out detection means for detecting step-out of the stepping motor based on a change in rotational speed of the stepping motor or a change in motor current, and a step-out detection means for detecting step-out of the stepping motor based on the detection output of the step-out detection means. The present invention is characterized by comprising a control means for setting the driving voltage of the stepping motor low within a range that does not step out, and a voltage variable means for varying the driving voltage of the stepping motor to a voltage value set by the control means.

(Function) With the above configuration, the present invention detects step-out of the stepping motor and automatically sets the driving voltage of the stepping motor to a low voltage just before step-out based on the detected information. , it is possible to suppress stepping motor vibration and accompanying speed fluctuations without step-out.

(Example) Hereinafter, an example of the present invention will be described in detail with reference to the drawings.

A. First Embodiment FIG. 1 shows a schematic configuration of an embodiment in which a stepping motor to which the present invention is applied is used as a drive source for a document reading device of a copying machine.

In FIG. 1, a stepping motor 101 moves and scans a contact type sensor 102 for reading a document via a timing belt 112. stepping motor 1
For example, a rotary encoder or the like is attached to the rotor No. 01 as a tax adjustment detection device 103, and the output 104 of this step-out detection device 103 is sent to the control value fff105. The stepping motor 101 is driven by an excitation signal 111 from a stepping motor driver 110 as shown in FIG. 2, and the stepping motor driver 11G is controlled by a control signal 106 from a control device 105.

Further, a motor drive voltage 109 applied to the stepping motor 101 and the stepping motor driver 110 is varied by a voltage variable device 108 in accordance with a control signal 107 from the control device 105.

In the case of a copying machine, since the driving speed of the stepping motor 101 differs depending on the copying magnification, the torque required by the stepping motor 101 also differs depending on the copying magnification.

Therefore, before copying, if the stepping motor 101 is moved at a speed corresponding to the specified copying magnification, and the control device 105 detects a step-out from the output 104 of the step-out detection device 103, the control device 105 operates the voltage variable device A control signal 107 is sent to 108 to increase the motor drive voltage 1G9 from the voltage variable device 108 by, for example, 1 (v). but,
If step-out is not detected, the control device 105 switches the voltage variable device 1
The voltage 109 is lowered, for example, by 1 (V) via the voltage 109, and the value of the motor drive voltage that is on the verge of losing synchronization is found.

In this way, in this embodiment, since the motor drive voltage is controlled to be as low as possible within the range that does not cause step-out, the vibration of the stepping motor during document reading and the accompanying speed unevenness of the stepping motor are reduced, and the image quality can be improved.

B. Second embodiment FIG. 5 shows a circuit configuration of another embodiment of the present invention.

As shown in FIG. 5, the step-out detection device 103 of this embodiment detects the peak value of the motor current detection voltage 208 with a peak value detector 503, and uses this peak value and the peak value reference voltage generator 501 to detect the peak value of the motor current detection voltage 208. Step-out is detected by comparing the output peak value reference voltage with the comparator 502.

When the stepping motor 101 steps out, the current waveform is disturbed and the peak value of the motor current 208 changes significantly over time compared to normal times. By comparing, it becomes possible to detect step-out.

The output 104 of the comparator 502 is sent to the control device 105, and depending on this output 104, the voltage variable device 108
The stepping motor drive voltage 109 and the stepping motor 101 can be controlled via. Out-of-step detection using the above drive method uses the current detection resistor 202 that is originally in the constant current control circuit, so there is no need to use a rotary encoder, and step-out detection can be easily performed without increasing manufacturing costs. becomes.

(Effects of the Invention) As explained above, according to the present invention, step-out of the stepping motor is detected, and based on the detected information, the driving voltage of the stepping motor is automatically reduced to a low voltage just before step-out. Since this setting is made, it is possible to suppress vibrations of the stepping motor and accompanying speed fluctuations without step-out.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing a schematic circuit configuration of a drive system of a document reading device embodying the present invention; FIG. 2 is a circuit diagram showing a circuit configuration of a stepping motor driver using constant current tip drive in FIG. 1; Figures 3 (A) and (B) are characteristic diagrams showing the relationship between motor drive voltage and motor current during constant current chopper drive, and Figure 4 shows an example of the circuit configuration of a conventional two-voltage switching constant voltage drive system. FIG. 5 is a circuit diagram showing a circuit configuration of another embodiment of the present invention. ...Stepping motor, ...Contact type sensor, ...Step-out detection device, ...Control device, ...Voltage variable device, ...Stepping motor driver, ...Motor winding, 202. ...Resistor for current detection, 203...Reference voltage generator, 204.502...Voltage comparison circuit, 205...PWM control circuit, 206...Switching transistor for voltage on/off, 501... - Peak value reference voltage generator, 503...Peak value detector.

Claims (1)

[Scope of Claims] Step-out detection means for detecting step-out of the stepping motor due to a change in rotational speed of the stepping motor or a change in motor current; and a step-out detection means for detecting step-out of the stepping motor based on a detection output of the step-out detection means. A stepping motor comprising: a control means for setting the drive voltage of the stepping motor to a low value within a range; and a voltage variable means for varying the drive voltage of the stepping motor to a voltage value set by the control means. Drive device.