JP3200477B2 - Method for suppressing vibration of stepping motor and its driving circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a driving method and a driving circuit capable of effectively suppressing vibration during rotation of a stepping motor.

[0002]

2. Description of the Related Art Since a stepping motor performs step driving, it is unavoidable to generate vibration during driving. On the other hand, various devices equipped with a stepping motor are continually becoming lighter and more precise, and the vibration generated when the stepping motor is driven has a negative effect on the accuracy of the device itself. It is the present situation that the basic characteristics possessed have been questioned as a serious problem.

[0003] A stepping motor is basically driven stepwise every time a pulse is input. Various types of stepping motors, such as a three-phase machine to an eight-phase machine, are used according to the purpose. For example, in a 4-5-phase drive system of a 5-phase pulse motor, a method of connecting excitation phases is used. Standard, pentagon, and star systems have been proposed.

FIG . 5 shows a first conventional example, which is a pentagon connection type circuit in which a 5-phase pulse motor is driven by a total of 10 switching transistors in a set of two. Briefly describing this conventional example, each motor coil (A) to 5-phase pulse motor (M)
(E), the starting end and the end are sequentially connected to form an annular pentagon connection, and switching means (Tr1) to (Tr10) are separately connected to these several connection points, respectively, and the switching means ( (Tr1) to (Tr10) are sequentially turned on according to the sequence.
By turning it off, step driving is executed.

Next, problems in the conventional control method will be described. (i1) is a supply current, which is supplied from the switching circuit (SC) composed of the chopper (Q1), the diode (D1) and the reactor (L1) to the capacitor (C1),
(C1) charges this. The charge charged in the capacitor (C1) is defined by the DV voltage.

[0006] (i2) is discharged by the capacitor (C1),
The rotor is step-driven by the exciting current flowing through the motor coils (A) to (E) via the switching means of the motor drive circuit (DC). That is, the capacitor (C1) is repeatedly charged and discharged. The switching means (Tr1) to (Tr10) control the exciting current (i2) generated at the time of this discharge, so that the stepping motor (M) is step-driven.

(I3) is generated by the electromotive force of the motor coil when the motor is driven, and the protection diode of the motor drive circuit is used.
Capacitor (C1) and sense resistor (R) via (PD1) to (PD10)
As described in 1), it is a surplus current circulating in the motor drive circuit in the reverse direction.

As can be seen from FIG . 5 , a motor drive circuit (DC)
Are connected to the ground side. In this way, connect the lower diode (PD2) to ground (GND).
Side, the (i1 + i3) current flows through the sense resistor (R1). Then, the voltage (V1) of the sense resistor (R1) generated by the current (i1 + i3) and the reference voltage are compared with a comparator (AMP).
Compare (1) and (PWM) so that (i1 + i3) current is constant
What is controlled is a conventional control method.

Now, when the motor rotates, the stepping motor
When (M) vibrates, the exciting current (i) of the motor coils (A) to (D)
2) and the ratio of surplus current (i3) changes. To suppress vibration, it is important to keep the ratio between the exciting current (i2) and the surplus current (i3) constant at all times. Therefore, the exciting current (i2) and the surplus current (i3)
If the DV voltage is controlled so as to keep the ratio of the constant, the vibration of the stepping motor (M) can be suppressed.

Since the exciting current (i2) is a current supplied from the capacitor (C1) to the motor drive circuit (DC), it is necessary to increase / decrease the DV voltage to proportionally control the increase / decrease of the exciting current (i2). Can be done. However, since the surplus current (i3) is a current generated by the electromotive force of the motor coils (A) to (D), when the surplus current (i3) increases due to vibration, the increased surplus current (i3) decreases. In order to achieve this, the DV voltage must be increased, and if it decreases, the excess current
In order to increase (i3), it is necessary to lower the DV voltage so that the electromotive force of the motor coils (A) to (D) lasts long, and the surplus current (i3) is inversely proportional to the rise and fall of the DV voltage. In a relationship.

In the conventional circuit of FIG . 5, the (i1 + i3) current is detected by the sense resistor (R1) as described above. Then, when vibration occurs in the stepping motor (M) in this conventional circuit, the surplus current (i3) fluctuates as described above. However, when the surplus current (i3) increases, the total current (i1 + i3) increases, Sense resistor sensing this (R1)
, The DV voltage is lowered in order to keep the (i1 + i3) current constant, and control is performed so that the total amount of the (i1 + i3) current becomes constant.

However, as described above, the surplus current (i3) is a current generated by the electromotive force of the motor coils (A) to (D). Therefore, to reduce the surplus current (i3), the DV voltage must be increased. In order to increase the surplus current (i3), the DV voltage must be reduced.
There is a serious problem that the DV voltage is controlled in a direction opposite to the direction in which (i3) is to be controlled, resulting in amplification of vibration.

FIG. 6 shows the stepping motor (M) shown in FIG.
7 is an example in which the star connection is used, and FIG. 7 is an example in which the excitation circuit is bipolar connection. However, in any case, the problem still remains.

[0014]

The problem to be solved by the present invention is as follows.
An object of the present invention is to enable control so that the ratio between the exciting current and the surplus current is always kept constant even when vibration occurs in the motor.

[0015]

A first aspect of the present invention is the first aspect.
Invention method, "stepping motor at a supply current (i1)
Charges the drive capacitor (C1) and charges the charged capacitor
The excitation current (i2) generated by discharging (C1) is switched.
The stepping motor (M) is controlled by
Drive method of stepping motor (M) for step drive
In step drive, the motor coils (A) to (E)
The surplus current (i3) generated by the force is subtracted from the exciting current (i2).
Current (i2-i3) and the supply current (i1)
And the surplus current (i3) is subtracted from the excitation current (i2).
The sum of the subtracted current (i2-i3) and the supply current (i1) is constant (i1
+ I2−i3) so that the stepping motor (M)
Controlling the drive voltage that controls the step drive current
It is a sign . " Thereby, when the surplus current (i3) increases or decreases due to the vibration of the stepping motor (M),
The current control by raising and lowering the drive voltage (DV voltage) for controlling the step drive current matches the increase / decrease direction of the excess current (i3)
The surplus current (i3) can be controlled by current control by raising and lowering the DV voltage.
And the ratio of the exciting current (i2) and the current can be controlled without losing the ratio. As a result, the vibration of the motor can be effectively suppressed.

A first embodiment of the first invention circuit according to claim 2 is composed of a DC power supply (1) for charging a stepping motor driving capacitor (C1), a DC power supply (1) for charging the supply current (i1), A capacitor (C1) that drives the stepping motor (M) with the exciting current (i2) generated by discharging, and a drive circuit (DC) that switches the exciting current (i2) to step-drive the stepping motor (M) And one end is ground (G
ND), the other end is connected to the capacitor (C1), the first sense resistor (R1), the capacitor (C1) and the drive circuit (DC)
A second sense resistor (R2) connected between the first sense resistor (R1) and the sum (V1 + 2) of the voltages of the first sense resistor (R1) and the second sense resistor (R2) connected in series, and a reference voltage. The first sense resistor (R
The sum of (1) and the current flowing through the second sense resistor (R2) (i1 + i2-i3)
And a control unit (CO) that controls so as to keep the constant. ” This allows the control method to be realized.

A second embodiment of the first invention circuit according to the third aspect is described as follows. In the vibration suppression circuit for a stepping motor, when the circuit is connected between the second sense resistor (R2) and the control unit (CO). It is characterized by having a peak hold circuit (PH) having a constant. " As a result, only the frequency component of the voltage fluctuation of the second sense resistor (R2) can be effectively detected, and the vibration control can be more effectively performed.

According to a fourth aspect of the present invention, there is provided a vibration suppression circuit for a stepping motor according to the second or third aspect , wherein the switching element of the drive circuit is an FET. As a result, a parasitic diode inside the FET can be used, and an external diode is unnecessary as in the case of using a transistor, and the number of components can be reduced.

[0020]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. In the present embodiment, a five-phase stepping motor (M) is used as a representative example, and the circuit to be applied will be described focusing on the first embodiment of the second invention circuit. However, the present invention is not limited to this.
Further, description of parts shown in the conventional example will be omitted.

FIG. 1 shows an example in which windings (A) to (E) of a pulse motor are pentagon-connected. The output stage transistors (Tr1) to (Tr10) as switching means are (Tr1) (Tr2), (Tr
3) Divided into 5 sets of (Tr4), (Tr5) (Tr6), (Tr7) (Tr8), (Tr9) (Tr10) To form a drive circuit. Winding (A) to (E)
The connection section of this series connected output stage transistors (Tr1) (Tr2), (Tr3) (Tr4), (Tr5) (Tr6), (Tr7) (Tr8),
It is connected to the connection between (Tr9) and (Tr10).

(R1) is a first sense resistor which is connected to the capacitor (C1).
It is connected in series between the (−) side and the ground (GED),
(R2) is the second sense resistor, the output side of the drive circuit and the capacitor
It is connected in series between the (-) side of (C1). (AMP1) is a comparator, which includes a first sense resistor (R1) and a second sense resistor (R1).
Compare the sum of the voltage of 2) with the reference voltage and calculate the current (i1 + i2-i3)
(PWM) is controlled so that is constant. (PD1) to (PD10) are output stage transistors (Tr1) to (Tr10)
Is an external protection diode connected in parallel.

In FIG. 1, similarly to the conventional example, the current (i1) is a supply current for raising and lowering the DV voltage and charging the capacitor (C1), and the current (i2) is obtained by discharging the capacitor (C1). The generated exciting current for driving the stepping motor is circulated as a capacitor (C1), a drive circuit, and a second sense resistor (R2) as shown by a broken line in the figure. Current
(i3) is also a surplus current (i3) generated by the electromotive force of the motor as described above, but since the circuit configuration is different from the conventional example, the surplus current (i3) is a capacitor (C1) via a diode of the drive circuit. , The second sense resistor (R2), and the driving circuit. As a result, the exciting current (i
The current (i2-i3) obtained by subtracting the surplus current (i3) from 2) flows. The comparator (AMP1) compares the sum (V1 + 2) of the voltages of the first and second sense resistors (R1, 2) with the reference voltage so that the current (i1 + i2-i3) becomes constant ( PWM) control.

Here, when the motor vibrates, the ratio between the exciting current (i2) flowing through the motor coil and the surplus current (i3) changes. However, in the circuit of the present invention, the current flowing through the second sense resistor (R2) is (i2-i3), and when the surplus current (i3) increases due to vibration, the current (i2-i3) decreases, and the second sense resistor (R2) )
Voltage decreases. The comparator (AMP1) detects this voltage drop and raises / lowers the DV voltage to keep the current (i2-i3) flowing through the second sense resistor (R2) constant. The increase in the DV voltage acts in the direction of decreasing the surplus current (i3), and is controlled in the direction in which the current (i2-i3) is kept constant. Conversely, if the surplus current (i3) decreases due to vibration, the DV voltage will decrease, but this will work in a direction to increase the surplus current (i3).

Since the circuit according to the present invention is a constant current circuit, when the exciting current (i2) increases, the motor coils (A) to (A)
(E) has a function of reducing the exciting current (i2) flowing therethrough so as to keep it constant, so that the DV voltage is controlled to be reduced. Conversely, when the exciting current (i2) decreases, the DV voltage is increased to increase the exciting current (i2) to a constant value. Then, as described above, DV
Decreasing the voltage increases the surplus current (i3),
Increasing the DV voltage reduces the surplus current (i3). That is, when the surplus current (i3) increases due to vibration, the second
Control is performed such that the detection level of the sense resistor (R2) decreases, the DV voltage increases, and the surplus current (i3) decreases. Conversely, when the surplus current (i3) decreases, the detection level of the second sense resistor (R2) increases, so that the DV voltage decreases and the electromotive force of the motor lasts longer. As a result, the surplus current (i3) increases. Will be. That is, the increase / decrease of the surplus current (i3) and the rise / fall of the DV voltage are in inverse proportion, and the rise / fall of the DV voltage causes the surplus current
Control of (i3) becomes possible.

As a result, even if vibration occurs in the motor, the DV
Excitation current (i2) and surplus current (i3) can be controlled by raising and lowering the voltage, and it does not promote vibration by DV voltage control as in the conventional example. Can be suppressed.

The voltage fluctuation of the vibration component detected by the second sense resistor (R2) has a long period of several milliseconds,
When a peak hold circuit (PH) having a time constant connected between the second sense resistor (R2) and the control unit (CO) is provided, (PWM) control is performed with a waveform connecting the peak values. Vibration control becomes easier.

Also, a case has been described in which the switching element of the drive circuit (DC) is a transistor, and an external protection diode is connected in parallel with the transistor.
It is also possible to use ET, which allows the use of a parasitic diode inside the FET, eliminating the need for an external diode as in the case of using a transistor, and reducing the number of parts. .

Further, the motor connection method is not limited to the pentagon method, and it is needless to say that the motor connection method can be applied to the star connection method as shown in FIG. 3 and the bipolar standard connection method as shown in FIG.

[0030]

[Effect] Since the present invention is configured as described above, even if vibration occurs when the stepping motor is driven, control is performed without losing the ratio of the excess current (i3) and the exciting current (i2) by raising and lowering the DV voltage. Therefore, there is an advantage that the vibration of the motor can be effectively suppressed.

[Brief description of the drawings]

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

FIG. 2 is a circuit diagram of a second embodiment of the present invention .

FIG. 3 shows a star connection type step according to the first embodiment of the present invention .
Circuit diagram using ping motor

FIG. 4 In the first embodiment of the present invention, the standard connection type
Circuit diagram using a stepping motor

FIG. 5 is a circuit diagram of a conventional example.

FIG. 6 shows a conventional example of FIG .
Circuit diagram using motor

FIG. 7 shows a step of a standard connection method in the conventional example of FIG .
Circuit diagram using ping motor

[Explanation of symbols]

A, B, C, D, E ... Motor coil (Tr1) ~ (Tr1
0) Switching means (i1) Supply current (C1) Drive capacitor (i2) Excitation current (M) Stepping motor (i2-i3) Excessive current (i3) is subtracted from excitation current (i2) Current

Claims (4)

(57) [Claims] 1. A stepping motor driving method in which a stepping motor driving capacitor is charged with a supply current and an exciting current generated by discharging the charged capacitor is switching-controlled to step-drive the stepping motor. The current obtained by subtracting the surplus current generated by the electromotive force of the motor coil during the step drive from the exciting current and the supply current are separately sensed, and the sum of the current obtained by subtracting the surplus current from the exciting current and the supply current is provided. stepping so they become constant, you and controlling the drive voltage for controlling the step driving current of the stepping motor
Vibration suppression method. 2. A DC power source for charging a capacitor for driving a stepping motor, a capacitor for driving a stepping motor with an exciting current generated by charging and discharging the supply current, and a stepping device for switching the exciting current to perform stepping. A drive circuit for step-driving the motor, a first sense resistor having one end connected to the ground and the other end connected to a capacitor, and a second sense resistor connected between the capacitor and the drive circuit; And a control unit configured to compare the reference voltage with the sum of the voltages of the first and second sense resistors and control the sum of the currents flowing through the first and second sense resistors to be constant. A vibration suppression circuit for a stepping motor, characterized in that: 3. The vibration of a stepping motor according to claim 2 , further comprising a peak hold circuit having a time constant connected between the second sense resistor and the control unit. Suppression circuit. 4. A vibration suppressing circuit for a stepping motor according to claim 2 , wherein the switching element of the drive circuit is an FET.