JPH0833367A - Drive control device of ultrasonic motor - Google Patents

Abstract

PURPOSE:To prevent temperature drop while the drive of an ultrasonic motor is at halt in a state where a still torque can be obtained. CONSTITUTION:A temperature sensor 17 detects the temperature around an ultrasonic motor 1, the detection signal T is compared with a reference value Tr by temperature comparison 18, and the comparison result is outputted to a switch control 25. The switch control part 25 connects switches 14 and 15 to terminals 14c and 15c when T is smaller than Tr and at the same time turns on a switch 20. A synchronization switcher 22 alternately switches a switch 21 for every one period of one signal of bi-phase signals outputted from a phase-shifting circuit 13 and supplies an AC signal alternately to a pair of piezoelectric bodies 2a and 2b of the ultrasonic motor 1, thus increasing the temperature of the ultrasonic motor 1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a drive control device for an ultrasonic motor.

[0002]

2. Description of the Related Art For example, in various card processing devices for reading and writing information on a magnetic card, as a drive source for card transportation and head movement, there is no magnetism in place of a conventional DC motor, and it is small but large. Ultrasonic motors that can obtain torque are being used.

An ultrasonic motor generally comprises a stator composed of a pair of piezoelectric bodies each of which is composed of a plurality of piezoelectric elements, and a mover arranged on the surface of the stator. When a two-phase AC signal with a phase difference of 90 degrees is supplied to the piezoelectric body of, a traveling wave is generated on the surface of the stator,
The traveling wave moves the mover in a predetermined direction.

The drive control device for driving such an ultrasonic motor supplies a two-phase drive signal having a 90-degree phase difference to the stator of the ultrasonic motor only when the motor needs to be driven. There is.

However, the piezoelectric body forming the stator of the ultrasonic motor can obtain a traveling wave with a large amplitude at room temperature (about 15 ° C), but a large amplitude at a low temperature (about 0 ° C). It is not possible to expect stable operation in an environment where the ambient temperature is low.

As a technique for solving this, in Japanese Patent Laid-Open No. 2-114869, an in-phase AC signal with no phase difference is constantly supplied to an ultrasonic motor during a motor stop period to reduce the temperature of the motor. Techniques to prevent are disclosed.

[0007]

However, in the method for constantly supplying the in-phase AC signal during the stop period as described above, a standing wave is generated on almost the entire surface of the stator of the ultrasonic motor during the stop period. It always occurs and the standing wave eliminates the frictional force between the stator and the mover, and the static torque of the motor is used as various regulation forces (for example, the force that regulates overrun of cards and heads). I can not do it.

Further, the method of constantly supplying the AC signals of the same phase during the stop period as described above has a problem that the power consumption increases and the life of the motor becomes extremely short.

The present invention solves this problem, uses the static torque of the motor, consumes less power, and enables stable driving of the motor at low temperatures without extremely shortening the life of the motor. An object of the present invention is to provide a drive control device for a sound wave motor.

[0010]

In order to solve the above-mentioned problems, a drive control device for an ultrasonic motor according to the present invention provides a phase difference for a plurality of piezoelectric bodies constituting a stator of the ultrasonic motor. In a drive control device for an ultrasonic motor that supplies a certain multi-phase drive signal to drive the ultrasonic motor, an AC signal having a predetermined frequency is supplied to the ultrasonic motor during a drive stop period of the ultrasonic motor. AC signal supply means for sequentially supplying to the piezoelectric body every predetermined period is provided.

[0011]

Thus, in the drive control apparatus for an ultrasonic motor according to the present invention, in the drive stop period of the ultrasonic motor, an AC signal of a predetermined frequency is used instead of the multi-phase drive signal. Are sequentially supplied to the plurality of piezoelectric bodies constituting the above for each predetermined period, and the signal supply prevents the temperature of the ultrasonic motor from decreasing.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows the configuration of a drive control device 10 according to an embodiment for controlling the drive of a rotary ultrasonic motor 1 used as a drive source for a card or a magnetic head of a card processing device.

This drive control device 10 includes an ultrasonic motor 1
To supply a two-phase drive signal to the frequency controller 1
1, a voltage controlled oscillator 12, a phase shift circuit 13, and a power amplifier 16. The frequency controller 11 outputs a control voltage having a magnitude corresponding to the speed designation signal to the voltage controlled oscillator 12.

The voltage controlled oscillator 12 includes a frequency control unit 11
A signal having a frequency corresponding to the control voltage output from is output to the phase shift circuit 13. The phase shift circuit 13 receives the signal output from the voltage controlled oscillator 12, and receives a two-phase signal φ1 having a 90-degree phase difference of a frequency corresponding to the frequency of this signal,
Output φ2. The phase shift circuit 13 is configured to digitally divide the frequency of the signal output from the voltage controlled oscillator 12 and output a two-phase AC signal having a phase difference of 90 degrees.

The two-phase signals output from the phase shift circuit 13 are input to the power amplifier 16 via the switches 14 and 15. The switches 14 and 15 are interlocked with each other under the control of the switch control unit 25 described later, and the power amplifier 16
Terminals 14a, 15a connected to the terminal 14b,
15b and one of the terminals 14c and 15c, which is a two-phase signal φ1 output from the phase shift circuit 13.
φ2 is the terminals 14b, 1 of the switches 14, 15 respectively
It is connected to 5b.

The signals respectively amplified by the power amplifier 16 are supplied to the pair of piezoelectric bodies 2a and 2b constituting the stator of the ultrasonic motor 1 as drive signals or signals for keeping the motor warm. .

A temperature sensor 17 is arranged close to the ultrasonic motor 1. The temperature sensor 17 outputs a signal T corresponding to the temperature around the ultrasonic motor 1 to the temperature comparator 18.

The temperature comparator 18 constitutes the temperature comparing means of this embodiment, and the magnitude of the reference value Tr preset in the reference temperature setting device 19 and the output signal T from the temperature sensor 17 is determined. After comparison, the comparison result is output to the switch control unit 25 described later. The reference temperature setting device 19 includes
For example, the same value as the magnitude of the signal output from the temperature sensor 17 when the temperature is 15 ° C. is preset as the reference value Tr.

Further, one of the two phase signals φ1 and φ2 output from the phase shift circuit 13 is input to the terminal 21a of the switch 21 via the switch 20 which is opened / closed by the switch controller 25. ing. Switch 21
21b and 21c of the switch are terminals 1 of the switches 14 and 15.
4c and 15c, respectively, and the terminal 21a
Are connected to terminals 21b, 2 by a synchronous switching device 22 described later.
1c is alternately connected to connect the signal φ1 to the switch 14,
It outputs to 15 terminals 14c and 15c alternately.

The synchronization switch 22 includes switches 14, 15 and
The AC signal supply means of this embodiment is constituted together with 20, 21 and a switch control section 25 which will be described later, and one period (α) of the signal φ1 is synchronized with the signal φ1.
The switch 21 is switched every time.

The switch control unit 25 controls the switches 14, 15 and 20 in response to a drive request signal from the outside (another control unit in the card processing device or the like) and the comparison result of the temperature comparator 18. .

FIG. 2 is a flow chart showing the processing procedure of the switch control unit 25. The operation of the drive control device 10 according to the embodiment will be described below based on this flowchart.

When the card processing device is powered on and the drive control device 10 is powered on, the switch control unit 25 connects the switches 14 and 15 to the terminals 14c and 15c and turns off the switch 20. After initializing the state, the comparison result of the temperature comparator 18 is judged (S
1-3). Here, the ambient temperature of the ultrasonic motor 1 is 15
If it is lower than ° C and it is determined that T is smaller than Tr, the switch 20 is turned on (S4).

By turning on the switch 20, the signal φ1 is applied to the terminals 14a and 15a of the switches 14 and 15.
Will be output in sequence (alternately in this case) for each one cycle (α), and the ultrasonic motor 1 will receive the signal φ1 as shown in FIGS. 3 (a) and 3 (b). The amplified AC signals A1 and A2 are alternately output every one cycle.

For this reason, a standing wave is alternately generated in the pair of piezoelectric bodies 2a and 2b forming the stator of the ultrasonic motor 1, and the standing wave causes the motor to generate heat. Output also increases.

When the switch 20 is on, the temperature sensor 1
7 is maintained until the reference value Tr is reached, and when the output signal T reaches Tr, the switch 20 is turned off, it is determined that the drive request signal is on, and when the drive request signal is off, T Is determined to be lower than the reference value Tr (S5-7).

When T becomes lower than the reference value Tr, the switch 20 is turned on and the temperature of the ultrasonic motor 1 is maintained at the reference temperature of 15 ° C. (S8).

When T is equal to or larger than the reference value Tr, or when the drive request signal is turned on when the switch 20 is turned on and the AC signal is alternately supplied to the ultrasonic motor 1, switch control is performed. The part 25 includes the switch 14,
15 is switched to the terminals 14b and 15b, and the phase shift circuit 1
The two-phase signals φ1 and φ2 from 3 are input to the power amplifier 16 as they are, and the pair of piezoelectric bodies 2a and 2b of the stator of the ultrasonic motor 1 are connected to the pair of piezoelectric bodies 2a and 2b as shown in FIGS. 90
The drive signals D1 and D2 having a phase difference of 100 degrees are supplied (S
9).

By the supply of this drive signal, a traveling wave is generated on the surface of the stator of the ultrasonic motor 1, and the traveling wave rotates a mover (not shown) to convey a card or to move the magnetic head. A move is made.

At this time, since the motor is driven from a state where the temperature is sufficiently high, a stable carrying operation can be performed.

This driving is performed until the drive request signal is turned off. When the drive request signal is turned off, the switches 14 and 15 are switched to the terminals 14c and 15c (S10, 11), and the process returns to step S5. Then, the supply of the signal to the ultrasonic motor 1 is stopped until the next drive request signal is turned on or the temperature of the motor is lowered.

Since the temperature of the motor immediately after the driving is stopped has risen to the reference temperature or higher due to the driving, the state in which no signal is supplied to the motor continues for a while, and the driving request signal is not turned on during that time. Temperature becomes lower than the reference temperature, switch 20 turns on again (S
8) The alternating signal is alternately supplied to maintain the motor temperature at the reference temperature.

As described above, during the period in which the signal supply to the motor is stopped, a strong frictional force is generated between the stator and the mover of the motor, and a large static torque can be obtained. However, even when alternating signals are alternately supplied to the pair of piezoelectric bodies 2a and 2b in order to maintain the temperature of the motor, a standing wave is not always generated in one of the piezoelectric bodies. Large static torque can be obtained. Therefore, the static torque can regulate the movement of the card and the head after the driving is stopped.

Further, in order to maintain the temperature of the motor, the AC signal is alternately supplied to the pair of piezoelectric bodies 2a and 2b, so that the power consumption thereof is small and the life of the motor is greatly shortened. Can also be prevented.

[0035]

Other Embodiments In the above embodiment, one of two phase signals for driving the motor is sequentially supplied to the pair of piezoelectric bodies of the motor for a predetermined period in order to maintain the temperature when the motor is stopped. However, this is not a limitation of the present invention. For example, as shown in FIG.
Two switches that can be opened and closed independently between and
1, 32 are provided, and by the AC signal supply control unit 33, 2
The one switch 31, 32 may be switched to the simultaneous off state, the simultaneous on state, and the alternate on state.

Further, the method of alternately supplying the AC signal during the drive stop period of the motor is not limited to the method shown in this embodiment and FIG. 5, but a switch may be provided on the output side of the power amplifier or may be moved. Various methods can be used by using a gate circuit in the phase circuit.

Further, not only the alternating signal is alternately supplied every one cycle as in the above-described embodiment, a non-supply time during which the alternating signal is not supplied to all the piezoelectric bodies may be provided each time during the switching.

Further, an AC signal (not only a sine wave but also a triangular wave or a rectangular wave) generated on the basis of a signal other than the two-phase signals φ1 and φ2 for driving the motor may be applied to a pair of stators. You may make it supply to a piezoelectric body.

Further, in the above-described embodiment, the AC signal obtained by amplifying the signal φ1 for maintaining the temperature is supplied for each one cycle in synchronization with the signal φ1, but a plurality of signals φ1 (or φ2) are supplied. The signals may be supplied for each cycle, or a timer circuit may be used to switch signals at a timing asynchronous with the signal φ1.

Further, in the above embodiment, the frequency of the drive signal supplied when the motor is driven is the same as the frequency of the AC signal supplied when the drive is stopped, but the traveling wave generated on the surface of the stator of the ultrasonic motor is the same. And the amplitude of the standing wave depends on the frequency of the supply signal, so that the control voltage output from the frequency control unit 11 during the drive stop period is set to a voltage different from that during the drive stop period and is generated during the drive stop period. The amplitude of the standing wave may be smaller than the amplitude of the traveling wave during driving.

In the above embodiment, the frequency control unit 1
Although the two-phase drive signals are supplied to the ultrasonic motor by the voltage control oscillator 12, the phase shift circuit 13, and the power amplifier 16, the microcomputer directly generates the two-phase signals and the power amplifier 16 Output to the temperature sensor 17 in this case.
The output of is converted into a digital value by the A / D converter,
This digital value may be input to the microcomputer to perform the same processing as the temperature comparator 18, the reference temperature setting device 19, the synchronous switching device 22 and the switch control unit 25.

Further, in the above-described embodiment, the alternating-current signal is alternately supplied to the piezoelectric body to the rotary ultrasonic motor in which the stator is composed of two (one pair) piezoelectric bodies. Even in the case of a drive control device that drives an ultrasonic motor having a stator composed of three or more piezoelectric bodies, the same effect as described above can be obtained if AC signals are sequentially supplied to a plurality of piezoelectric bodies, for example, one cycle at a time. To be Further, the present invention can be similarly applied to a device that controls the drive of an ultrasonic motor in which a mover moves linearly.

[0043]

As described above, the drive control device for an ultrasonic motor according to the present invention sequentially supplies an alternating current signal to a plurality of piezoelectric bodies forming a stator of the ultrasonic motor for a predetermined period. As a result, the temperature is prevented from decreasing during the motor stop period, so a much larger static torque can be obtained compared to the case where signals are supplied to multiple piezoelectric bodies at the same time. Can be regulated, power consumption can be reduced, and the life of the motor can be prevented from being extremely shortened.

[Brief description of drawings]

FIG. 1 is a block diagram showing the configuration of an embodiment of the present invention.

FIG. 2 is a flowchart showing a processing procedure of a main part of one embodiment.

FIG. 3 is a diagram showing signals supplied to a motor when the motor is stopped.

FIG. 4 is a diagram showing signals supplied to a motor during driving.

FIG. 5 is a principal block diagram for explaining another embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Ultrasonic motor 2a, 2b Piezoelectric body 10 Drive control device 11 Frequency control part 12 Voltage control oscillator 13 Phase shift circuit 14, 15 switch 16 Power amplifier 17 Temperature sensor 18 Temperature comparator 19 Reference temperature setting device 20, 21 Switch 22 Synchronization Changeover device 25 Switch control unit

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[Procedure amendment]

[Submission date] September 8, 1994

[Procedure Amendment 1]

[Document name to be corrected] Drawing

[Correction target item name] All drawings

[Correction method] Change

[Correction content]

[Figure 3]

[Figure 4]

FIG.

[Fig. 2]

[Figure 5]

Claims (2)

[Claims] 1. A driving method for an ultrasonic motor for driving the ultrasonic motor by supplying multi-phase driving signals having a phase difference to a plurality of piezoelectric bodies forming a stator of the ultrasonic motor. In the control device, an AC signal supply means for supplying an AC signal of a predetermined frequency to the plurality of piezoelectric bodies of the ultrasonic motor in sequence for a predetermined period during the drive stop period of the ultrasonic motor is provided. Ultrasonic motor drive controller. 2. A temperature sensor for detecting the temperature of the ultrasonic motor, and a temperature comparison means for comparing the temperature detected by the temperature sensor with a predetermined reference temperature. The AC signal supply means comprises: Receiving the comparison result of the temperature comparison means, sequentially supplying an AC signal of a predetermined frequency to a plurality of piezoelectric bodies of the ultrasonic motor for a predetermined period until the temperature of the ultrasonic motor reaches the reference temperature. The drive control device of the ultrasonic motor according to claim 1.