JPH02151284A - Drive controller for ultrasonic motor - Google Patents

Abstract

PURPOSE:To escape an ultrasonic motor rapidly from a vibration deviating state and to recover it to a normal vibrating state by altering the applied pressure of a rotor by an actuator if the ultrasonic motor becomes the vibration deviating state. CONSTITUTION:When a high frequency voltage is supplied from a power supply circuit 20 to a piezoelectric element 1b, the piezoelectric element 1b is vibrated to form a traveling vibration wave at an elastic element 1a. When a rotor 2 is brought into pressure contact with a stator 1 in which the traveling vibration wave is generated by a pressurizing unit 100, the rotor 2 is rotated by a frictional drive while vibrating. When a vibration deviating state discrimination circuit 40 judges the vibration deviating state, it inputs a vibration deviating state signal to a vibration recovering unit 50. The vibration recovering unit 50 elongates or contracts a piezoelectric actuator 51 by its drive circuit 52 to alter an applied pressure by an energizing member 6 thereby to vary the resonance characteristic of an ultrasonic motor MT. Thus, the ultrasonic motor MT is recovered from the vibration deviating state to a normal vibrating state.

Description

DETAILED DESCRIPTION OF THE INVENTION A. Field of Industrial Application The present invention relates to a drive control device for an ultrasonic motor that drives a rotor using progressive vibration waves generated in an elastic body by a piezoelectric body.

B. Conventional technology A progressive vibration wave type ultrasonic motor is disclosed in Japanese Patent Application Laid-Open No. 59-111.
As also disclosed in Publication No. 609.

By applying an alternating current voltage to the piezoelectric body, a progressive vibration wave is generated in the elastic body to which the piezoelectric body is attached without causing bending vibration in the piezoelectric body, and the rotor is brought into pressurized contact with this elastic body to drive the rotor by friction. It's a motor.

This ultrasonic motor has the following characteristics: IEICE Journal Vol. 1.7
0. No, 7. As shown in pP717-pp720 July 1987 issue, there is a characteristic that when the load exceeds the rated value, it deviates from resonance and stops. If the motor stops in such a state, the phase difference between the input voltage and the monitor voltage (voltage generated by the deformation of the piezoelectric body) deviates from the value during normal rotation, and the stator hardly vibrates. In this specification, such a state is referred to as a vibration deviation state. Therefore, a progressive vibration wave type ultrasonic motor is inevitably equipped with a limiter against overload due to such characteristics. If the motor deviates from the normal resonance state, the normal driving point is reset by taking measures such as: (1) removing the load, and (2) shifting the drive frequency to a restart frequency higher than the resonance frequency.

Problems to be Solved by the C0 Invention By the way, ultrasonic motors with such characteristics are susceptible to load fluctuations due to changes in temperature, humidity, changes in pressurizing force, or changes in the viscosity of the lubricating oil inside the bearings. , it is easy to fall into a vibration deviation state, and as a result, there is a possibility of a sudden stop, resulting in low operation reliability.Furthermore, in order to escape from a vibration deviation state, it is necessary to take the measures described in 7. It is necessary to reset the settings, and it takes time to recover to normal state. Also, considering the case of releasing the load,
In an actual product, a clutch mechanism and the like are required, resulting in a large and complicated device.

A technical object of the present invention is to easily recover from a vibration deviation state to a normal vibration state without removing the load.

To explain with FIG. 1 and FIG. 2 showing an example of means for solving the problem,
The drive control device according to the present invention includes a stator 1 that generates progressive vibration waves in an elastic body 1a by excitation of a piezoelectric body 1b, and a stator 1 that is pressed into contact with the stator 1 by a pressurizing means 100 and is driven by the progressive vibration waves. The ultrasonic motor MT is used for drive control of an ultrasonic motor MT having a rotor 2.

The pressurizing means 100 of the drive control device according to the present invention has an actuator 51 that adjusts the pressurizing force. Then, in order to excite the piezoelectric body 1b, at least a pair of frequency voltages having different phases are applied to the piezoelectric body 1b (1!). source circuit 20;
Discrimination means 4o for determining the vibration deviation state of the stator 1;
Adjustment means 5 for adjusting the pressure applied by the actuator 51
o, and when the determining means 40 determines that the vibration deviation state is present, the adjusting means 50 controls the actuator 51 to change the pressurizing force of the pressurizing means 100, thereby solving the above-mentioned technical problem. .

The vibration deviation state determination means 40 includes: (1) applied voltage value detection means for detecting the voltage value of the frequency voltage applied to the piezoelectric body 1b;
■Rotation speed detection means for detecting the rotation speed of the ultrasonic motor MT, ■Monitor voltage value detection means for detecting the monitor voltage generated as the piezoelectric body 1b deforms, and ■Frequency voltage applied to the piezoelectric body 1b. and a phase difference detection means for detecting the phase difference between the voltage and the monitor voltage.

If it is detected that the frequency voltage is above a predetermined value, the rotation speed is zero, the monitor voltage is below a predetermined value, and the phase difference is below a predetermined value, it is determined that the vibration deviation state is occurring. It is preferable to

When the E6 action vibration deviation state is determined, the actuator 51 changes the pressing force on the rotor 2. Due to this.

The ultrasonic motor can quickly recover to its normal vibration state.

In the above-mentioned sections and section E, which describe the present invention in detail, figures of embodiments are used to make the present invention easier to understand, but the present invention is not limited to the embodiments.

F. Example An embodiment of the present invention will be described with reference to FIGS. 1 to 7.

First, the ultrasonic motor will be explained with reference to FIG. In FIG. 2, the stator 1 includes a ring-shaped elastic body 1a and a ring-shaped piezoelectric body 1b bonded to the ring-shaped elastic body 1a.
It consists of The elastic body 1a includes a rotor 2, which will be described later.
A comb-shaped groove is formed on the contact surface side. A flange-shaped support member 1c is formed on the stator 1 and protrudes in the radial direction from near the neutral axis thereof, and the support member 1c is bonded to a ring-shaped stator support member 3 having an inner diameter approximately equal to the outer diameter of the stator 1. be supported. The outer edge of the stator support member 3 is sandwiched between the installation tube 4 and the fixed tube 5, so that the stator 1 is installed in the installation tube 4. Note that the fixed tube 5 is screwed onto the installation tube 4.

On the other hand, the rotor 2 is composed of a ring-shaped rotor base material 2a and a slider material 2b bonded to the rotor base material 2a. A support member 2C that extends from the vicinity of the neutral axis and receives pressure is integrally formed on the rotor base material 2a. This rotor 2 is installed inside the installation tube 4 and is brought into pressure contact with the elastic body 1a of the stator 1 installed in the installation tube 4. That is, the pressing force from the urging member 6 is transferred to the pressure transmitting member 7.
is transmitted to the rotor 2 via the rotor 2, whereby the rotor 2 comes into pressure contact with the elastic body 1a. The ball bearing 8 reduces the rotational resistance between the pressurizing force transmitting member 7 and the rotor 2 during this pressurizing contact.

The pressing force applied by the biasing member 6 can be changed by expanding and contracting an actuator 51 made of, for example, a laminated piezoelectric body. This piezoelectric actuator 51 is held by a fixed tube 9 screwed into the installation tube 4, and expands and contracts by controlling the applied voltage to adjust the biasing force of the biasing member 6.
Change the rotor pressure. Here, the biasing member 6, the pressing force transmission member 7, the fixed cylinder 9, and the piezoelectric actuator S1
The pressurizing device 100 is configured as follows. In place of the piezoelectric type, an electromagnetic or hydraulic type 7-cut unit may be used.

FIG. 1 is a block diagram of a drive control device for an ultrasonic motor configured as described above. The drive control device includes a power supply circuit 20 that generates a high frequency voltage to be applied to the ultrasonic motor MT, and a rotation speed detector 3 that detects the rotation speed of the ultrasonic motor MT.
0 and a vibration deviation state determination circuit (
(discrimination means) 40, and a vibration recovery device (adjustment means) 50 for changing the pressurizing force of the rotor 2.

The power supply circuit 20 includes a high frequency signal generator 21.

The output of the high frequency signal generator 21 is branched into two.

One is input to the amplifier 22, and the other is input to the phase shifter 23. The phase shifter 23 changes the phase of one input voltage to the other input voltage according to the rotational direction of the ultrasonic motor MT.
After being shifted by 2 or −π/2, the signal is input to the amplifier 24. High frequency voltage V i output from both tank width transducers 22 and 24
na and Vinb are input to the piezoelectric body 1b of the ultrasonic motor.

Piezoelectric body 1b affixed to stator 1 of ultrasonic motor MT
As shown in FIG.
, 1b-G, and lb-M are provided.

Electrodes 1b-L and 1b-R are connected to amplifiers 22, 24, respectively, electrodes 1b-G are grounded, and electrodes 1b-M are connected to a vibration deviation state determination circuit 40.

Note that here, the frequency of the voltage input from the power supply circuit 20 to the electrodes 1b-L and 1b-R is referred to as a power supply frequency.

Regarding the positional relationship of electrodes in an ultrasonic motor, the polarization state under the electrodes, etc., there are many documents such as 1st Nikkei Mechanical, February 28, 1983 issue, pages 44-49, Japanese Patent Application Laid-Open No. 59-204476, etc. Since this method is well known, its explanation will be omitted here.

The electrodes 1b-M are portions to which no input voltage is applied, and a voltage Vm (referred to as monitor voltage Vm) corresponding to the vibration amplitude of the stator 1 can be detected from the piezoelectric body 1b in this portion. This is due to the piezoelectric phenomenon of the piezoelectric body 1b, and the detailed rules are disclosed in Japanese Patent Laid-Open No. 59-204477, so the explanation will be omitted. As described above, this monitor voltage Vm is input to the vibration deviation state determination circuit 40 and used for detecting the vibration deviation state.

The rotation speed detector 30 detects the rotation of the ultrasonic motor MT and outputs a rotation speed signal R and a direction signal CW/CCV, and each of the rotation speed signal R2 and direction signal CW/CCV is sent to the vibration deviation state determination circuit 4o. Wired to input.

The vibration deviation state determination circuit 40 receives the input rotation speed signal R.
Two-way signal CW/CCW, input voltage Vina, V
inb, the vibration deviation state of the ultrasonic motor MT is detected using the monitor voltage Vm, and a signal indicating the vibration deviation state (referred to as a vibration deviation state signal) is input to the vibration recovery device 50.

Here, the configuration of the vibration deviation state determination circuit 40 will be explained with reference to FIG.

The vibration deviation state determination circuit 40 receives a direction signal CW/CCW.
an input voltage selection circuit 41 that selects either one of the input voltages V ina or V inb; and an input voltage selection circuit 41 that outputs a signal indicating the phase difference between one of the input voltages selected by the input voltage selection circuit 41 and the monitor voltage Vm. A phase difference output circuit 42, an F/V converter 43 that converts the rotation speed signal R into a voltage value, a monitor voltage converter 44 that converts the monitor voltage Vm into a DC voltage, and the output of the monitor voltage converter 44 as a reference. A comparator 45-1 that compares the voltage, an input voltage converter 46 that converts the input voltage selected by the input voltage selection circuit 41 into a DC voltage, and a comparator that compares the output of the input voltage converter 46 with a reference voltage. 45-2 and phase difference output circuit 42
a comparator 45-3 for comparing the output of F/V with a reference voltage;
Comparator 45-4 that compares the output of converter 43 with a reference voltage
and a vibration deviation state determination signal generation circuit 47 that determines the vibration deviation state based on the comparison result signals of the comparators 45-1 to 45-4 and outputs a vibration deviation state signal.

The vibration deviation state determination signal generation circuit 47 can be configured in the form of software, for example, as shown in FIG.

In FIG. 4, in step S1, it is determined whether the input voltage Vin is the set value based on the signal of the comparator 45-2. If it is the set value, the process proceeds to step S2, and in step S1, the input voltage Vin is If it is determined that is not the set value, the transmission of the vibration deviation state signal is stopped in step S7.

In step S2, the number of rotations is determined based on the signal from the comparator 45-4, and if no rotation is detected, the process proceeds to step S3. Further, in step S2, if rotation is recognized by the signal from the comparator 45-4, the process proceeds to step S7, and the transmission of the vibration deviation J source signal is stopped. In step S3, it is determined based on the signal from the comparator 45-1 whether the monitor voltage Vm exceeds the set value, and if the monitor voltage Vm does not exceed the set value, the process proceeds to step S4. In step S3, if the monitor voltage Vm exceeds the set value, step S3
Proceed to step 7 and stop transmitting the vibration deviation state signal. In step S4, it is determined whether the phase difference is within the set conditions based on the signal of the comparator 45-3, and if this step S4 is negative, a vibration deviation state signal is transmitted in step S5, and the phase difference If it is within the setting conditions and step S4 is affirmed, the process proceeds to step S7 and the transmission of the vibration deviation state signal is stopped. If it is determined in step S6 that the procedure is finished, this procedure is finished, and if it is not finished, step S6 is again carried out.
Return to 1.

As shown in FIG. 1, the vibration recovery device 50 includes the piezoelectric actuator 51 and the piezoelectric actuator 5 described above.
1 drive circuit 52, and a vibration deviation state determination circuit 4.
When the vibration deviation state signal from 0 is input to the drive circuit 52, the piezoelectric actuator 51 is driven and the pressurizing force of the rotor 2 is changed.

Here, when the pressing force is changed, the resonance characteristics of the ultrasonic motor MT change as shown in FIG. 7. In Figure 7, the horizontal axis shows the power supply frequency f, and the vertical axis shows the monitor voltage Vm.
A solid line FH shows a resonance characteristic diagram when the pressing force is high, and a dashed-dotted line FL shows a resonance characteristic diagram when the pressing force is low. It can be seen from this figure that the resonance characteristics of the ultrasonic motor MT change by changing the pressing force.

Next, the operation of the first embodiment will be explained.

When a high frequency voltage is supplied to the piezoelectric body 1b by the lt source circuit 20 shown in FIG. 1, the piezoelectric body 1b vibrates and progressive vibration waves are formed in the elastic body 1a. When the rotor 2 is brought into pressure contact with the stator 1 in which the progressive vibration waves are generated by the pressurizing device 100, the rotor 2 is rotated by friction drive while vibrating.

Here, the input voltages V ina and V inb during rotation are
, monitor voltage Vm will be explained with reference to FIG. FIG. 5(a) shows the case where the rotor 2 rotates in the clockwise direction CW, and FIG. 5(b) shows the case when the rotor 2 rotates in the counterclockwise direction CCW.
3, the phase is +π/2. It is shifted by -π/2. The monitor voltage Vm has a phase difference of about π/2 from Vina in FIG. 5(a), and about −π/2 from V inb in FIG. 5(b).
It has a phase difference of

If the ultrasonic motor falls into a state of vibration deviation due to load fluctuations due to changes in temperature, humidity, pressurizing force, viscosity of lubricating oil, etc., there will be no change in the input voltages Vina and Vinb, but the number of revolutions will increase. When R becomes zero, as shown in Figure 6,
The monitor voltage Vm also decreases significantly, and the phase difference with the input voltage also changes significantly. When the vibration deviation state determination circuit 40 determines that the vibration deviation state is based on these parameters,
A vibration deviation state signal is input to the vibration recovery device 50. The vibration recovery device 50 changes the pressing force applied by the biasing member 6 by expanding or contracting the piezoelectric actuator 51 using its drive circuit 52. As a result, the resonance characteristics of the ultrasonic motor MT change as explained with reference to FIG. 7, and the ultrasonic motor MT recovers from the vibration deviation state to the normal vibration state.

The supporting member 3 of the stator 1, which will explain the second embodiment of the present invention with reference to FIG. The stator 1 is held between the fixed cylinder 62 and the stator 1 at f.
f[It is installed inside the cylinder 4 so that it can move in the axial direction. The protrusion 61a of the movable cylinder 61 fits into the straight groove 4a of the installation cylinder 4, and the stator 1 cannot rotate with respect to the installation cylinder 4. In addition, a retaining cylinder 63 is screwed onto the installation cylinder 4.
A plurality of piezoelectric actuators 64 are installed to support the stator 1 so as to be movable in the axial direction. On the other hand, in this embodiment, the biasing member 6 and the pressing force transmission member 7 are interposed between the fixed cylinder 65 screwed into the installation cylinder 4 and the bearing 8, so that the actuator 64 can be expanded and contracted. By doing so, the pressing force by the biasing member 6 is changed.

Then, as in the first embodiment, when a vibration deviation state is determined, the piezoelectric actuator 64 is driven to change the pressing force, and the resonance characteristics of the ultrasonic motor MT are changed to normalize the ultrasonic motor MT. This is to restore the vibration state to normal. The other configurations are completely the same as those in the first embodiment, and their explanation will be omitted.

Note that also in this embodiment, the piezoelectric actuator 64
The actuator may be an electromagnetic type or a pressure type actuator.

Furthermore, in the above, ■The input voltage is equal to the set value.■The rotation speed of the rotor 2 is not zero.■The monitor voltage Vm is below the set value.■The phase difference between the input voltage and the monitor voltage Vm is below the predetermined value. It was determined that the vibration deviation state occurred when all of the following conditions were true, but simply, when ■, ■, ■ hold, or ■, ■, ■
The vibration deviation state may be determined when the following is true.

G0 Effects of the Invention According to the present invention, when the ultrasonic motor enters a state of vibration deviation due to load fluctuations due to changes in temperature, humidity, changes in pressurizing force, changes in the viscosity of lubricating oil, etc., the actuator By simply changing the pressurizing force, the ultrasonic motor can quickly escape from the vibration deviation state and return to the normal vibration state, making it possible to provide a highly reliable ultrasonic motor.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the overall configuration of the present invention. FIG. 2 is a sectional view of the ultrasonic motor according to the first embodiment of the present invention. FIG. 3 is a block diagram showing details of the vibration deviation state determination circuit. FIG. 4 is a flowchart showing the operation of the vibration deviation state determination signal generation circuit. FIG. 5 is a diagram showing the relationship between the input voltage of the ultrasonic motor and the monitor voltage Vm. FIG. 6 is a diagram showing changes in the monitor voltage Vm in a normal state and in a vibration deviation state. FIG. 7 is a graph showing the relationship between power supply frequency and monitor voltage. FIG. 8 is a sectional view showing the ultrasonic motor of the second embodiment. 1: Stator 2: Rotor 3: Support member 4: Installation cylinder 5: Fixed cylinder 6: Biasing member 7: Pressure force transmission member 8: Bearing 9: Fixed @
30: Rotation speed detector 40/Vibration deviation state determination circuit 50: Vibration recovery device 51.64: Piezoelectric actuator 1oO: Pressure device

Claims (1)

[Scope of Claims] 1) A stator that generates progressive vibration waves in an elastic body by excitation of a piezoelectric body, and a rotor that is brought into pressure contact with the stator by a pressure means and is driven by the progressive vibration waves. In the drive control device, the drive control device is used for drive control of an ultrasonic motor, and includes a power supply circuit that applies at least a pair of frequency voltages having different phases to the piezoelectric body in order to excite the piezoelectric body, The drive control device includes an actuator that adjusts a pressing force, and the drive control device includes a determining unit that determines whether the stator is in a vibration deviation state, and an adjusting unit that adjusts the pressing force by the actuator, and the determining unit determines whether the vibration deviation is A drive control device for an ultrasonic motor, characterized in that when it is determined that the state is the same, the adjusting means controls the actuator to change the pressing force of the pressing means. 2) The vibration deviation state determining means includes: applied voltage detection means for detecting a frequency voltage applied to the piezoelectric body; monitor voltage detection means for detecting a monitor voltage generated as the piezoelectric body deforms; A phase difference detection means for detecting a phase difference between a frequency voltage applied to the piezoelectric body and the monitor voltage is provided, and when it is detected that the phase difference is outside a predetermined range, the discrimination means detects a vibration deviation state. 2. The drive control device for an ultrasonic motor according to claim 1, wherein the ultrasonic motor drive control device determines that: 3) The vibration deviation state determining means includes: applied voltage value detection means for detecting the applied voltage value of the frequency voltage applied to the piezoelectric body; rotation speed detection means for detecting the rotation speed of the ultrasonic motor; and monitor voltage value detection means for detecting the voltage value of the monitor voltage generated as the piezoelectric body deforms, and each of these detection means detects whether the frequency voltage is a predetermined value or more and whether the rotation speed is zero or not. 2. The drive control device for an ultrasonic motor according to claim 1, wherein the determining means determines that the vibration deviation state exists when it is detected that the monitor voltage is equal to or lower than a predetermined value. 4) The vibration deviation state determining means includes: applied voltage value detection means for detecting the voltage value of a frequency voltage applied to the piezoelectric body; rotation speed detection means for detecting the rotation speed of the ultrasonic motor; It is equipped with phase difference detection means for detecting a phase difference between a frequency voltage applied to the body and the monitor voltage, and each of these detection means detects whether the frequency voltage is a predetermined value or more and whether the rotation speed is zero or not. 2. The drive control device for an ultrasonic motor according to claim 1, wherein the determining means determines that the vibration deviation state exists when it is detected that the phase difference is equal to or less than a predetermined value.