JPH11235092A - Torque control method of stepping motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a torque control method of a stepping motor smoothly performing operation in the region of a load torque larger than at ordinary time or in a load having the direction of rotation. SOLUTION: When a command pulse in accordance with a drive quantity of a load is input to a microcomputer 1, it generates a pulse of desired frequency so as to drive by an arbitrary pulse rate of torquespeed characteristic, the pulse is distributed to two-phase excitation in a drive (distribution) circuit 2 and supplied to a drive winding of a stepping motor 3. In this way, the stepping motor 3 step drives the load 4 so as to obtain a prescribed drive quantity. Torque of the load 4 during being driven is detected in a torque detector 5 and fed back to the microcomputer 1, when the torque is increased above a value at ordinary operation time, the microcomputer automatically reduces a frequency of the generated pulse supplied to the drive (distribution) circuit 2. As a result, output torque is increased of the stepping motor 3, stable operation is continued regardless of an increase of torque of the load.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a torque control method for a stepping motor driven by two-phase excitation.

[0002]

2. Description of the Related Art A stepping motor is widely used for control and operation of various electric devices because a rotation angle with respect to one pulse is constant and a rotation angle corresponding to the number of input pulses can be obtained. The excitation method in the stepping motor includes a one-phase excitation method, a two-phase excitation method,
A two-phase excitation system is known.

[0003] The one-phase excitation system energizes only one phase of a motor coil in order. In a certain period, there is a coil in which no current flows at all, and the conductor utilization of the motor decreases. However, there is a disadvantage that the generated torque is reduced. The two-phase excitation method is a method in which two coils of A-phase and B-phase are excited at the same time, and has an advantage that the torque is large and the vibration at the time of stepping is small. In the 1-2-phase excitation method, one-phase excitation and two-phase excitation are alternately repeated, so that half of the basic step angle can be stopped, fluctuations in generated torque can be reduced, and vibration and vibration can be reduced. Noise can be reduced.

Normally, a stepping motor is used as a motor for opening and closing the variable flow valve for controlling hot water in the air conditioner with hot water, but the torque when the variable flow valve is opened is larger than the torque when it is closed. Since it is required, a stepping motor having an output capacity that can be driven by a 1-2-phase excitation method when closed, and driven by a two-phase excitation method when opened to cope with a large output torque when opened has already been proposed. The applicant has proposed.

However, in the case where a stepping motor driven and driven at a constant pulse rate by a two-phase excitation method at the time of opening and closing at the time of opening and closing is used as a motor for opening and closing the flow rate variable valve for hot water control because of the simplicity of the drive circuit. Is that, even if a smooth operation is achieved when the variable flow rate valve is closed, the two-phase excitation does not open or cannot perform a smooth operation in the middle for a large torque at the time of opening, There were times when I couldn't respond enough.

[0006]

SUMMARY OF THE INVENTION Accordingly, the present invention provides a driving method using a two-phase-excited stepping motor.
Provided is a stepping motor torque control method that enables smooth operation in a region where the load torque is larger than normal or a load having a rotation direction, such as a flow control valve for hot water control of an air conditioner or the like. With the goal.

[0007]

According to a first aspect of the present invention, there is provided a torque control method for a stepping motor, in which a step frequency is varied in accordance with a magnitude of a load torque in a two-phase excitation drive of the stepping motor. It is achieved by doing.

Thus, even if the load torque slightly exceeds the output torque of the stepping motor at the frequency of the normal operation and driving becomes difficult, the driving frequency of the stepping motor is reduced and the output torque of the motor is increased. By operating in the frequency domain, reliable driving can be ensured.

According to a second aspect of the present invention, there is provided a torque control method for a stepping motor. In the two-phase excitation driving of the stepping motor, the step frequency is reduced by reducing the step frequency in the direction of the large load torque in the forward rotation and the reverse rotation. It is achieved by doing.

In this way, if the rotation direction in which the load torque is large is known in advance, even if the load torque in the rotation direction slightly exceeds the output torque of the stepping motor at the frequency of the normal operation, driving is difficult, In the rotation direction, the driving frequency of the stepping motor is reduced and the motor is driven in a frequency range in which the output torque of the motor increases, so that reliable driving can be secured.

According to a third aspect of the present invention, there is provided a torque control method for a stepping motor. In the two-phase excitation driving of the stepping motor for driving a variable flow valve, the step frequency is reduced when the variable flow valve having a large load torque is opened. This is achieved by adjusting the torque.

Thus, when the torque of the variable flow rate valve is large when the valve is in the open state, the load torque in the opening direction of the valve slightly exceeds the output torque of the stepping motor at the frequency of the normal operation, and driving is difficult. Even in the case of the opening direction of the valve, the variable flow rate valve can be reliably driven and opened by reducing the driving frequency of the stepping motor and operating in the frequency region where the output torque of the motor increases.

According to a fourth aspect of the present invention, in the two-phase excitation driving of the stepping motor for driving the variable flow valve, the opening of the variable flow valve is detected and the variable flow valve is not opened. This is sometimes achieved by reducing the step frequency and adjusting the torque.

In this manner, when it is detected that the torque of the variable flow valve does not open because the torque of the variable flow valve slightly exceeds the output torque of the stepping motor at the frequency of the normal operation, the drive frequency of the stepping motor is reduced. By operating in a frequency range in which the output torque of the motor increases, the variable flow rate valve can be reliably driven and opened.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS As shown in FIG. 2, the torque-speed characteristics of a two-phase excitation type stepping motor used in the present invention are as follows. Is as at the time of pull-in indicated by a solid line. The torque-speed characteristics from the high-speed operation to the stop of the load are as shown at the time of pull-out indicated by the dotted line.

As can be seen from FIG. 2, in this type of stepping motor, the output torque increases as the pulse rate decreases, and the torque characteristics from the stop of the motor to the start of driving to high-speed operation are almost 100 pp.
The torque is further increased at a pulse rate lower than s. In the torque-speed characteristics from the high-speed operation of the load to the stop, the tendency is more remarkable.

When the load torque increases, for example,
The above-mentioned case corresponds to the driving of opening the flow rate variable valve for hot water control.
Since the operation is performed at about 25 pps, if the valve cannot be opened or smooth operation cannot be performed in the middle, the driving rate can be reduced by reducing the pulse rate to about 50 pps and the torque can be adjusted so that a large driving torque can be secured. Thus, the opening operation of the valve can be smoothly and reliably achieved.

Next, an embodiment of the present invention will be described with reference to FIGS. 1 (A) and 1 (B). In FIG. 1A, reference numeral 1 denotes a microcomputer which receives a command pulse corresponding to a drive amount and generates a variable frequency pulse, and 2 denotes a drive which distributes a drive pulse to two-phase excitation and supplies the pulse to a drive winding ( Distribution) circuit,
Reference numeral 3 denotes a stepping motor for driving a load 4, and reference numeral 5 denotes a load torque detector.

First, when a command pulse corresponding to the drive amount of the load is input to the microcomputer 1, the microcomputer 1 drives the microcomputer 1 at an arbitrary pulse rate of the torque-speed characteristic indicated by the solid line in FIG.
Generates a pulse of a desired frequency and generates a drive (distribution) circuit 2
The pulse is distributed to the two-phase excitation and supplied to the drive winding of the stepping motor 1. This allows the stepping motor 1
Drives stepwise so that the load 4 has a predetermined drive amount.

Here, the torque of the load 4 being driven is detected by the torque detector 5 and fed back to the microcomputer 1, and if the torque becomes larger than the value during normal operation, the microcomputer 1 automatically changes the frequency of the generated pulse. The power is reduced and supplied to the drive (distribution) circuit 2. As a result, the stepping motor 1 increases the output torque and continues the stable operation regardless of the increase in the load torque.

In the case where the operation of the load 4 performs normal rotation or reverse rotation, and the magnitude of torque at the time of normal rotation or reverse rotation is different, the torque detector 5 detects the normal rotation or reverse rotation. By outputting the signal to the microcomputer 1, the microcomputer 1 automatically reduces the frequency of the generated pulse and supplies it to the drive (distribution) circuit 2 in the case of the rotation direction in which the torque is large. As a result, the stepping motor 1 increases the output torque and continues the stable operation regardless of the increase in the load torque.

Next, an embodiment in which the present invention is applied to a hot water control flow rate variable valve as a load will be described with reference to FIG. 1 (B). In the figure, the same components as those in FIG. 1A are denoted by the same reference numerals, and description thereof will be omitted. Reference numeral 6 denotes a flow rate variable valve for controlling hot water as a load, and reference numeral 7 denotes a valve opening detector.

First, when a command pulse corresponding to the opening amount of the load flow variable valve 6 is input to the microcomputer 1, an arbitrary pulse rate (normally 12 pulses) of the torque-speed characteristic indicated by the solid line in FIG.
The microcomputer 1 is driven at a desired 125
drive (distribution) circuit 2 that generates a pulse having a frequency of pps
The pulse is distributed to the two-phase excitation and supplied to the drive winding of the stepping motor 1. This allows the stepping motor 1
Is step-driven so that the flow rate variable valve 6 has a predetermined opening degree.

Here, the open state of the variable flow rate valve 6 being driven is detected by the valve opening detector 7 and fed back to the microcomputer 1, and if the valve opening detector 7 detects that the valve is not open. Then, the microcomputer 1 automatically reduces the frequency of the generated pulse and supplies it to the drive (distribution) circuit 2. As a result, the stepping motor 1 drives the variable flow rate valve 6 by increasing the output torque, and continues a stable operation such that the variable flow rate valve 6 is reliably opened in response to the increase in the torque of the variable flow rate valve 6. .

In still another embodiment, since the flow rate variable valve for hot water control may require a larger torque when opened than when closed, a command pulse corresponding to the amount of opening is supplied to the microcomputer 1. At the same time, the microcomputer 1 determines that the variable flow rate valve 6 is in the open mode, and the microcomputer 1 automatically reduces the frequency of the generated pulse and supplies it to the drive (distribution) circuit 2. Can also be adopted. As a result, the stepping motor 1 drives the variable flow rate valve 6 by increasing the output torque, and continues a stable operation with an output corresponding to the torque of the variable flow rate valve 6.

If the determination that the hot water control flow rate variable valve 6 is in the open state is made by the valve opening detector 7 without detecting the command pulse, if the valve opening degree detector 7 detects that the valve is going to be operated in the opening direction, the determination is made. The microcomputer 1 may automatically reduce the frequency of the generated pulse by a signal and supply the generated pulse to the drive (distribution) circuit 2.

[0027]

As described above, the method for controlling the torque of a stepping motor according to the present invention can be used even if the load torque slightly exceeds the output torque of the stepping motor at the frequency of the normal operation and driving becomes difficult. If the drive frequency of the stepping motor is reduced, and the rotational direction of the load torque is known in advance, the load torque in the rotational direction slightly exceeds the output torque of the stepper motor at the frequency of normal operation. Is difficult,
In the rotation direction, the driving frequency of the stepping motor is reduced and the motor is driven in a frequency range in which the output torque of the motor increases, so that reliable driving can be secured.

Further, when the load is a hot water control flow rate variable valve, when the torque of the flow rate variable valve is large when the valve is in the open state, the load torque in the valve opening direction is increased by the stepping motor at the frequency of normal operation. Even if the output torque of the stepping motor slightly exceeds the driving torque, the driving frequency of the stepping motor is reduced when the valve is in the opening direction. By operating in a frequency range where the driving frequency is reduced and the output torque of the motor increases, the variable flow rate valve can be reliably driven and opened.

[Brief description of the drawings]

FIG. 1 shows an embodiment of the present invention.

FIG. 2 shows torque of a two-phase excitation type stepping motor.
Speed characteristics.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Microcomputer 2 Drive (distribution) circuit 3 Stepping motor 4 Load 5 Torque detector 6 Flow rate variable valve for hot water control 7 Valve opening detector

Claims (4)

[Claims] 1. A torque control method for a stepping motor, wherein the stepping motor is controlled in a two-phase excitation mode by varying a step frequency according to the magnitude of a load torque. 2. A torque control method for a stepping motor, comprising: in a two-phase excitation driving of a stepping motor, in a rotation direction in which a load torque in forward rotation and reverse rotation is large, a step frequency is reduced to adjust the torque. 3. The torque control of a stepping motor, characterized in that in a two-phase excitation drive of a stepping motor for driving a variable flow valve, when the variable flow valve with a large load torque is open, the step frequency is reduced to adjust the torque. Method. 4. The two-phase excitation driving of a stepping motor for driving a variable flow rate valve, wherein an opening of the variable flow rate valve is detected, and when the variable flow rate valve does not open, the step frequency is reduced to adjust the torque. To control the torque of a stepping motor.