JPH052000Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Field of Industrial Application] This invention relates to a step motor drive device that is provided with interphase capacitors between each of a pair of excitation coils of a four-phase step motor that are not simultaneously excited. .

[Prior Art] Conventionally, in this type of step motor drive device, there has been one in which an interphase capacitor is provided between a pair of excitation coils that are not excited at the same time. These interphase capacitors reduce rotor vibration by absorbing the induced current generated in one excitation coil when it switches from an energized state to a de-energized state.

[Problems to be Solved by the Invention] When a battery consisting of a primary battery or a secondary battery is used as a power source for driving a step motor, the power supply voltage decreases over a long period of time. When the power supply voltage is high, such as immediately after battery replacement or charging, a large induced current proportional to the power supply voltage flows through the excitation coil that switches from the energized state to the de-energized state. Since this induced current causes the rotor to vibrate, there have conventionally been methods to reduce rotor vibration by absorbing the induced current using an interphase capacitor. but,
When the power supply voltage decreases due to long-term use of the battery, the excitation current flowing through the excitation coil causes the interphase capacitor to switch from the de-energized state to the energized state, even though the induced current becomes relatively small. As a result, the step response of the motor deteriorates, and even the motor sometimes loses synchronization.

Furthermore, since the induced current is inversely proportional to the frequency of the drive signal supplied to the excitation coil, the interphase capacitor acts to absorb the induced current when the motor speed is slow. However, as the speed of the step motor increases, the rise of the excitation current is delayed by the interphase capacitors, which deteriorates the step response of the motor, even though the induced current decreases.

[Purpose of the invention] Therefore, the present invention was devised to solve the problems of the conventional technology. It is an object of the present invention to provide a step motor drive device that is free from motor step-out, vibration, noise, etc. even when the motor is moved, and has good responsiveness.

[Means for Solving the Problems] In order to achieve the above-mentioned object, the step motor driving device of the present invention uses an interphase capacitor provided between a pair of excitation coils that are not simultaneously excited. , a switch connected in series with the interphase capacitor and always closed, and a voltage detector that detects that the battery voltage is lower than a set level and outputs a detection signal indicating that.
A speed detector that detects that the speed of the phase step motor is faster than a predetermined speed and outputs a detection signal indicating this, and a speed detector that is connected to the voltage detector and the speed detector and outputs a detection signal from at least one of both detectors. and control means for opening the switch when the output is output.

[Function] When the power supply voltage for driving the step motor decreases or the speed of the step motor increases, the rise of the excitation current is delayed and the step response becomes poor. Therefore, either the voltage detector detects that the battery voltage is lower than the set level and outputs a detection signal, or the speed detector detects that the step motor speed is higher than the predetermined speed and outputs a detection signal. , the control means opens the switch. This allows the excitation current to rise quickly and improves step response.

[Embodiment] An embodiment of the step motor drive device of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing the configuration of the drive device of this embodiment.
A program for driving 0 and a driving pulse generator are built-in. An external device 16 and a step motor drive circuit 12 are connected to the control section 14, and the control section 14 causes the step motor drive circuit 12 to drive the step motor drive circuit 12 based on a drive command signal regarding the drive direction and drive amount from the external device 16. Outputs drive pulses according to direction and drive speed.

A voltage detector 22 is connected to the control section 14, and the voltage detector 22 detects the voltage of the battery 18, which is a power source for driving the step motor 10, and when the power supply voltage is lower than a predetermined voltage, the control section 22 is connected. 1
The detection signal is output to 4. The predetermined voltage is the lowest voltage at which sufficient step responsiveness can be obtained to stably drive the step motor 10, and is set in advance. Further, a speed detector 20 is connected to the control unit 14, and the speed detector 20
detects the speed of the step motor 10 by detecting the frequency of the drive pulse output from the control section 14, and outputs a detection signal to the control section 14 when the detected speed is faster than a predetermined speed. The predetermined speed is the highest speed at which sufficient step responsiveness can be obtained to stably drive the step motor 10, and is set in advance.

The step motor drive circuit 12 having transistors Tr1 to Tr4 shown in FIG.
The four types of driving pulses output from the transistor Tr are sequentially input to the base terminals 31 to 34.
By controlling ON-OFF of Tr1 to Tr4,
The excitation coils A to D of the four-phase step motor 10 are excited. One end side of the excitation coils A to D is commonly connected and connected to a power supply Vcc, and the other end side is connected to the collector terminals of transistors Tr1 to Tr4, respectively. In addition, the transistor
The emitter terminals of Tr1 to Tr4 are connected in common and then grounded.

Between a pair of excitation coils A and B and C and D, which are not excited at the same time, that is, excitation coil A
and the common connection point between the transistor Tr1 and the common connection point between the excitation coil B and the transistor Tr2,
and a common connection point between excitation coil C and transistor Tr3, and excitation coil D and transistor Tr4.
between the common connection points of the two interphase capacitors, respectively.
4a and 24b are connected. A switch 26 is connected to each interphase capacitor 24a and 24b.
The switches 26a and 26b are connected in series, and the switches 26a and 26b are normally closed. In addition, switches 26a, 26
An electromagnetic relay 28 is the actuating means for each of b.
is connected to the control unit 14 and switches 26a and 26b, and when a switch open signal or a close signal from the control unit 14 is input, the switch 2
6a and 26b are opened or closed. Note that the control section 14 and the electromagnetic relay 28 constitute a control means of the present invention.

Here, the action of the interphase capacitors 24a, 24b when the switches 26a, 26b are closed will be described in the case of 2-2 phase excitation as shown in FIG. The excitation state is from a to b in Fig. 3.
At the moment of switching to
from OFF to OFF, transistor Tr2 from OFF to ON
Therefore, the excitation current I1 flowing through the excitation coil A is cut off, and the excitation current I2 starts flowing through the excitation coil B. At this time, the interphase capacitor 24a is
The exciting coil B side changes from positive potential to zero potential, and the exciting coil A side changes from zero potential to negative potential. The next moment,
A back electromotive force is generated in the exciting coil A to maintain the excited state, and an induced current flows in the forward direction. Furthermore, at the next instant, an induced current flows in the opposite direction to maintain the de-energized state, and in this way, the induced current is
The current flows alternately in the forward and reverse directions, and the amount of current gradually decreases. A similar induced current is generated in the excitation coil B, and these induced currents flow alternately in both forward and reverse directions like an alternating current, so that they can pass through the interphase capacitor 24a. The interphase capacitor 24a is charged until the excitation coil A side changes from a negative potential to a positive potential, so a circulating current i due to an induced current flows in the direction of the arrow during that time. That is, the interphase capacitor 24a absorbs a portion of the induced current, and a portion of the exciting current I2 is also absorbed by the induced current, so that the rise of the exciting current I2 is delayed. Therefore, if the power supply voltage is high and the step motor 1
When the speed of 0 is slow, there is a lot of induced current, so
The interphase capacitor 24a absorbs the induced current, thereby reducing vibration of the rotor due to the induced current. Moreover, the interphase capacitor 24b has the same function as the interphase capacitor 24a.

The operation of the step motor drive device having the above configuration will be explained.

FIG. 4 shows a step motor drive subroutine. When a drive command signal is supplied to the control section 14 from the external device 16, the program moves to the step motor drive subroutine according to the program within the control section 14. First, in step S1, the voltage detector 22 detects the voltage of the battery 18, which is a power source. step
In S2, if the power supply voltage is higher than the predetermined voltage, the process moves to step S3, and if the power supply voltage is lower than the predetermined voltage, the voltage detector 22 outputs a detection signal to the control section 14, and the process moves to step S6. Move to. In step S6, a switch opening signal is sent from the control section 14 to the electromagnetic relay 28, the electromagnetic relay 28 opens the switches 26a and 26b, and the process moves to step S7. Also, in step S3,
A speed detector 20 detects the speed of the step motor 10. In step S4, if the detected speed is faster than the predetermined speed, the speed detector 2
0 outputs a detection signal to the control section 14 and the process moves to step S6, and if the detected speed is slower than the predetermined speed, the process moves to step S5. In step S5, a switch close signal is sent from the control section 14 to the electromagnetic relay 28, the electromagnetic relay 28 closes the switches 26a and 26b, and the process moves to step S7. At step S7, the step motor 10 is rotated by a predetermined amount of steps in the designated direction at the designated speed, and the process advances to step S8. In step S8,
To continue driving the step motor 10, return to step S1; to stop driving the step motor 10, return to the main routine until the next drive command signal is input to the control unit 14 from the external device 16. stand by.

With the above operation, the voltage of the battery 18, which is the power source, is equal to or higher than the predetermined voltage, and the step motor 10
If the speed of
Since 6a and 26b are closed, the interphase capacitor 2
4a and 26b can absorb the induced current and reduce vibration of the rotor. Further, when the voltage of the battery 18 is below a predetermined voltage or the speed of the step motor is above a predetermined speed, the switches 26a and 26b are opened, so that the step is stopped without delay in the rise of the excitation current caused by the interphase capacitors 24a and 24b. Responsiveness can be improved.

Note that the present invention is not limited to the embodiments detailed above, and various changes can be made without departing from the spirit thereof.

[Effects of the invention] As is clear from the detailed description above, according to the step motor drive device of the invention, the step motor drive device of the present invention has a step motor drive device that is connected in series with the interphase capacitors provided between each pair of excitation coils that are not simultaneously excited. By providing a switch connected to the motor and controlling the switch, the step response is improved even when the voltage of the battery that drives the step motor fluctuates or when the motor speed is changed to a slow speed. It is also possible to reduce synchronization, vibration, noise, etc.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of a step motor drive device that embodies this invention, and FIG. 2 is a circuit diagram showing the step motor and its drive circuit.
FIG. 3 is a time chart for 2-2 phase excitation of the step motor, and FIG. 4 is a step motor drive subroutine. 10...Step motor, 12...Step motor drive circuit, 14...Control unit, 18...Battery, 20...Speed detector, 22...Voltage detector,
24a, 24b... interphase capacitor, 26a, 2
6b...Switch, 28...Electromagnetic relay.

Claims (1)

[Claims for Utility Model Registration] In a drive device for driving a four-phase step motor 10 with a battery 18, the drive device includes a pair of excitation coils A, B, C, and D that are not simultaneously excited. interphase capacitors 24a, 24b provided between the two, and switches 26a, 26 connected in series with the interphase capacitors 24a, 24b and normally closed.
b; a voltage detector 22 that detects that the voltage of the battery 18 is lower than a set level and outputs a detection signal indicating that; and a voltage detector 22 that detects that the voltage of the battery 18 is lower than a set level and outputs a detection signal indicating that; a speed detector 20 that detects and outputs a detection signal indicating that; and a speed detector 20 that is connected to the voltage detector 22 and the speed detector 20, and when a detection signal is output from at least one of both detectors, the switch 26a ,26b
1. A step motor drive device characterized by comprising control means 14 and 28 for opening the step motor.