JPH07194195A - Controller for stepping motor - Google Patents

Abstract

PURPOSE:To make the output shaft of a stepping motor to smoothly rotate when the output shaft is rotated from the outside. CONSTITUTION:A controller for stepping motor is provided with a constant- frequency signal generating means 5E which generates drive timing of a constant frequency higher than a self-starting frequency of a stepping motor and a stop control means 5 which controls the drive of the motor by successively exciting the motor in accordance with the drive timing of a constant frequency while the motor keeps a standstill.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a stepping motor control device for releasing a holding force generated when a stepping motor is stopped.

[0002]

2. Description of the Related Art One of the features of stepping motors is the generation of static torque. That is, the stepping motor can be used by generating a holding force.

There are two types of static torque generation, and it is known as follows. One is called a holding torque, which refers to a torque generated when the motor shaft is rotated from the outside while a certain phase of the stepping motor is excited and the position is opposed to the rotation. The second is known as detent torque, and in a type in which a permanent magnet is used for the rotor of a stepping motor, a force to stay in a fixed position is generated even in a non-excited state. Torque is called detent torque.

When the holding force of the stepping motor is used, there are cases where the rotor in the rotating state is stopped and cases where the holding force of the stepping motor is used as a resistance force when the rotor is operated from the outside during the stop. . The latter is, for example, a case where it is used for holding the position of a printing paper feeding mechanism as shown in FIG.

In FIG. 3, a sheet 2 wound around a platen 1 is conveyed by a stepping motor 3 and aligned with a predetermined position to be printed by a predetermined printing means (not shown). At this time, it is necessary to hold the platen 1 so that the paper 2 does not shift. Also, for some reason,
It is necessary to resist even when a force is applied to the sheet 2 from the outside and the stepping motor 3 is operated.

On the other hand, the knob 4 is for manually moving the sheet 2, and is used when the sheet 2 is set or ejected. When using knob 4, stepping motor 3
It is necessary that the static torque of is weak and the rotation operation becomes smooth. Therefore, when operating the knob, the holding torque was reduced or the excitation was turned off to zero.

[0007]

In the above-mentioned conventional example,
To reduce the holding force while the stepping motor is stopped, reduce the holding torque, or
Even if the excitation is turned off, if the detent torque is strong, smooth movement may be hindered when the stepping motor is operated from the outside, and a solution means has been demanded. In recent years, the performance of the magnet used for the rotor of the stepping motor has been improved, and the one having a strong attractive force has been used, so that the detent torque becomes stronger and becomes more remarkable.

It is an object of the present invention to provide a stepping motor control device capable of smooth movement when operating the output shaft of the stepping motor from the outside.

[0009]

In order to achieve the above object, the present invention provides a stepping motor control device with signal generating means for generating drive timing of a frequency exceeding a self-starting frequency, and operation stoppage at that frequency. And a stop control unit for driving the windings of the stepping motor in a fixed order by exciting.

[0010]

Therefore, according to the present invention, when the stepping motor is operated from the outside, the windings of the stepping motor are excited and switched in a fixed order to apparently disperse the force for staying in the fixed position. . Furthermore, by using a frequency that exceeds the self-starting frequency at which the rotor of the stepping motor cannot be rotated by itself as the excitation switching frequency, the rotor remains in a freely rotatable state. You will be able to make smooth movements according to the operation you perform.

[0011]

FIG. 1 is a block diagram of a stepping motor control device showing an embodiment of the present invention. In this block diagram, the stepping motor 1 is connected to a drive circuit 2 and is supplied with electric power by a power supply 3. The control circuit 4 is an excitation signal output circuit that distributes a pulse train of an input signal, for example, the drive signal E to each phase of the stepping motor to excite the winding of the stepping motor in a fixed order.

A feature of the present invention is to have a stop control means 5 surrounded by a broken line in FIG. The stop control means 5 has an oscillation signal source 5E having a constant frequency and changeover switches 5a, 5b, 5c and 5d. This changeover switch inputs the pulse train of the drive signal E in the conventional manner to the control circuit 4, or executes the operation of the present invention.
Whether or not the constant frequency signal D from the oscillation signal source 5E having a constant oscillation frequency exceeding the self-starting frequency is input to the control circuit 4 is performed. The changeover switches 5a and 5b are AND elements,
Similarly, 5C is an inverter element, and 5d is an OR element. The switching is performed by inputting the stop signal C by a control means (not shown) such as software processing or processing according to the sensor output signal.

FIG. 2 is a timing chart of each signal showing the states before and after the input of the stop signal C. The case where the two-phase excitation method is adopted as the predetermined excitation sequence is shown. Drive timing a pulses P1, P2, P3, P4, P
5, P6 and P7 are input signals of the control circuit 4.
This input signal causes the control circuit 4 to drive the drive circuit. Output to drive the stepping motor. At this time, the stop signal C is at high level.

When the pulse P5 of the drive timing a is output and the stepping motor is stopped, the stop signal C becomes low level and the constant frequency signal D from the oscillation signal source 5E.
Is input to the control circuit 4. Here again, each excitation signal is generated based on the two-phase excitation method.

When the stop signal C returns to the high level, the switching of the excitation signal is stopped and the next drive timing a
The drive is restarted after waiting for the pulse P6.

The state of the stop section in which the stop signal C changes from the high level to the low level and the constant frequency signal D from the oscillation signal source 5E is input to the control circuit 4 will be described. Control circuit 4
Then, as in the conventional example, the input signal is distributed according to the phases of the stepping motor, and the excitation signals (the two-phase excitation signals) for exciting the respective phases in a fixed order are output to the drive circuit 2. When the drive circuit 2 receives the excitation signal from the control circuit 4, it enables each winding of the stepping motor 1 to be excited in a predetermined order.
When the power supply 3 is applied to the drive circuit 2, each winding is excited and a holding torque is generated in each winding. However, the excitation of each winding has a constant frequency, especially because the cycle exceeds the self-starting frequency, the rotor cannot rotate by itself, and the holding torque generated in each winding balances the rotor as a whole. Becomes Therefore, when the rotor is rotated from the outside, there is no force to stay at a specific position, and therefore smooth rotation is possible.

When there is no output from the power source 3, only the detent torque of the stepping motor 1 acts to keep the rotor in a fixed position. However, when the rotor is attempted to rotate from the outside, electromotive force generated due to rotational displacement is generated in each winding, and excitation switching is performed in a fixed order. The resulting holding torque balances the rotor and reduces the effect of detent torque. Therefore, the rotor can be smoothly rotated even when the detent torque is generated without the output of the power supply 3.

The order of excitation switching is not limited to a specific one as long as the rotor can be balanced. Therefore, the well-known one-phase excitation, two-phase excitation or 1-2-phase excitation sequence remains unchanged. Available. Moreover, the balanced rotor can move smoothly both clockwise and counterclockwise regardless of the excitation sequence.

In this embodiment, the constant frequency signal D, which is easy to generate, is input from the oscillation signal source 5E to the control circuit 4, but instead of the constant frequency signal D, a frequency exceeding the self-starting frequency is used. The same effect can be obtained even if the frequency changes. Therefore, the oscillating signal source 5E may be created by a software process having a different configuration in addition to the hardware configuration. Further, in this embodiment, the stepping motor is driven to attract the excitation sequence (two-phase excitation method) immediately before the stop, but it is determined that the predetermined excitation sequence, for example, the one-phase excitation method is output. Similar effects can be obtained by switching the output.

FIG. 4 is a block diagram of a stepping motor control device showing a different embodiment of the present invention. In this block diagram, the stepping motor 1 is connected to an NPN type transistor 20 and further supplied with power from a power source 3 via a PNP type transistor 17.
When the type transistor 17 is turned off by the control circuit 11 via the voltage drop resistor 16 and the control transistor 15, a voltage lower than the voltage of the power supply 3 is passed through the voltage dividing resistor 19 and the backflow prevention diode 18. Supplied. The control circuit 11 receives various control signals from the CPU (central processing unit) 13 via the bus 14 which is a signal line, and the windings of the stepping motor 1 are arranged in a fixed order corresponding to each phase of the stepping motor 1. It is an excitation signal output circuit for exciting. The control circuit 11 is for driving and stopping the stepping motor. On the other hand, the oscillation excitation unit 12 is a CPU
Upon receiving the control signal from the stepping motor 13, the windings of the stepping motor are excited in a fixed order at a frequency exceeding the self-starting frequency and in a predetermined excitation sequence while the operation of the stepping motor is stopped. Oscillation excitation unit 12
When there is an output of the control circuit 11, the excitation state output from the control circuit 11 is maintained.
A low-level signal that turns off the
The P-transistor 17 is turned off, and the power supply 3 is a diode 18
Power through. What is characteristic of the different embodiment of the present invention shown in FIG. 4 is that it has an OR element 10 surrounded by a broken line in FIG. The OR element 10 is an NPN transistor 2 that turns on and off each winding of the stepping motor 1.
It is connected to 0 to form a gate action, while accepting an excitation signal for driving and stopping the stepping motor 1, and while the operation is stopped, the oscillation exciting unit 12 keeps the excitation state selected for the stop. The excitation signal is received and superimposed and output.

[0021]

As described above, according to the present invention, when the output shaft of the stopped stepping motor is to be rotated from the outside, the conventional control circuit excites a constant cycle exceeding the self-starting frequency. By applying the switching signal, the rotor can be operated smoothly. Therefore, in a printer, a copying machine, or the like that uses a stepping motor for the paper feeding mechanism, the force for pulling out the paper becomes weak when a paper jam error occurs, and the recovery process can be performed quickly.
Further, in a device in which an accident has occurred in the driven object of the stepping motor, the detent torque can be apparently erased, and the stepping motor can be freely rotated to minimize damage. Further, the present invention has the advantage that it can be applied regardless of the type of stepping motor. Therefore, the stepping motor can be easily incorporated in the stepping motor control drive circuit part in devices such as printers, plotters, and robots in which the stepping motor is used.

Even in a drive circuit that holds the excitation torque and generates the holding torque when the stepping motor is stopped, the holding torque is apparently reduced by superimposing the excitation switching signal with a cycle exceeding the self-starting frequency. Then, the rotor can be operated smoothly.

[Brief description of drawings]

FIG. 1 is a block diagram of a stepping motor control device according to the present invention.

FIG. 2 is a timing chart of control signals according to the present invention.

FIG. 3 is a printing paper feed mechanism to which the present invention is applied.

FIG. 4 is a different block diagram of a stepping motor control device according to the present invention.

[Explanation of symbols]

 1 Stepping Motor 2 Drive Circuit 3 Power Supply 4 Control Circuit 5a Changeover Switch 5b Changeover Switch 5C Changeover Switch 5d Changeover Switch 5E Oscillation Signal Source 10 OR Element 11 Control Circuit 12 Oscillation Excitation Section 13 CPU 14 Bus 15 Control Transistor 16 Voltage Drop Resistor 17 PNP type transistor 18 Diode 19 Voltage dividing resistor 20 NPN type transistor

Claims (4)

[Claims] 1. A stepping motor control device for driving and stopping one phase or a plurality of phases selected in a predetermined excitation sequence among a plurality of windings in sequence according to predetermined drive timing. A signal generating means for generating a drive timing of a frequency exceeding the self-starting frequency, and a stop control means for sequentially exciting and controlling the drive according to the drive timing of the frequency in a predetermined excitation sequence during operation stop, A stepping motor control device comprising: 2. A stepping motor control device for driving and stopping one phase or a plurality of phases selected in a predetermined excitation sequence among a plurality of windings in sequence according to a predetermined drive timing. A constant frequency signal generating means for generating a drive timing of a constant frequency exceeding the self-starting frequency, and a stop for controlling the drive by sequentially exciting according to the drive timing of the constant frequency in a predetermined excitation sequence while the operation is stopped. A stepping motor control device comprising: a control unit. 3. A stepping motor control device for driving and stopping by sequentially exciting one phase or a plurality of phases selected in a predetermined excitation sequence among a plurality of phases of winding in accordance with a predetermined drive timing. A constant frequency signal generating means for generating a drive timing of a constant frequency exceeding a self-starting frequency; and a stop control means for sequentially exciting and controlling the drive in accordance with the drive timing of the constant frequency in the excitation sequence while the operation is stopped. And a stepping motor control device. 4. A stepping motor control device for driving and stopping by sequentially exciting one phase or a plurality of phases selected in a predetermined excitation sequence among a plurality of windings in accordance with a predetermined drive timing. A constant frequency signal generating means for generating a drive timing of a constant frequency exceeding the self-starting frequency, and a predetermined excitation sequence while maintaining the excitation state selected when the operation is stopped during the operation stop, A stepping motor control device comprising: stop control means for sequentially applying excitation in a superimposed manner according to frequency drive timing to control drive.