JP2979542B2 - Drive control device for vibration motor - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a drive control device for an ultrasonic motor that drives a rotor by a progressive vibration wave generated in an elastic body by a piezoelectric body.

B. Prior Art A progressive vibration wave type ultrasonic motor is disclosed in
As disclosed in Japanese Patent Application Laid-Open Publication No. H10-209, an alternating voltage is applied to a piezoelectric body to cause bending vibration in the piezoelectric body, and a progressive vibration wave is generated in the elastic body to which the piezoelectric body is attached, so that the elastic body This is a motor that frictionally drives the rotor by applying pressure to the rotor.

This ultrasonic motor includes IEICE journal Vo1.70, N
o.7, pp717-pp720 As shown in the July 1987 issue, there is a characteristic that when the load exceeds the rated value, it deviates from resonance and stops. If you stop in such a state,
The phase difference between the input voltage and the monitor voltage (voltage generated by deformation of the piezoelectric body) deviates from the value at the time of normal rotation, and the vibration of the stator is almost eliminated. In this specification, such a state is referred to as a vibration deviation state. Therefore, the progressive vibration wave type ultrasonic motor inevitably has a limiter for overload due to such characteristics, but once it deviates from the resonance state, the load is released in order to return to the normal resonance state. Then, the drive frequency is reset to a normal drive point by taking measures such as shifting the drive frequency to a restart frequency higher than the resonance frequency.

C. Problems to be Solved by the Invention By the way, an ultrasonic motor having such characteristics is subject to a change in load due to changes in temperature, humidity, pressure, or viscosity of lubricating oil in a bearing. It is easy to fall into a vibration deviating state, and as a result, it may stop suddenly, resulting in low reliability of operation. In addition, in order to escape from the vibration departure state, it is necessary to reset the drive frequency to the normal drive frequency by performing the above-described measures, and it takes time to recover to the normal state. In addition, when the load is released, an actual product requires a clutch mechanism and the like, 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 releasing a load.

D. Means for Solving the Problems To be described with reference to FIGS. 1 to 3 showing one embodiment, a drive control device according to the present invention is a stator that generates a vibration wave on an elastic body 1a by exciting a piezoelectric body 1b. 1 and a driving control device used for driving control of a vibration motor including a moving body 2 that is pressed against the stator 1 by a pressing means and driven by a vibration wave. By providing the vibration state detecting means 40 to be detected and the adjusting means 50 for adjusting the pressing force applied between the moving body 2 and the stator 1 according to the detection result by the vibration state detecting means 40, The problem is solved.

The vibration state detecting means 40 according to the second aspect of the present invention is an input voltage detecting means for detecting an input voltage applied to the piezoelectric body 1b.
46 and a rotational speed detecting means 30 for detecting the rotational speed of the vibration motor
And a monitor voltage detecting means 44 for detecting a monitor voltage taken out of the piezoelectric body 1b.The adjusting means 50 controls the input voltage to the input voltage set value, the rotational speed of the vibration motor to be zero, and the monitor voltage to be When the monitor voltage is less than a predetermined monitor voltage set value, the pressure applied between the moving body 2 and the stator 1 is changed.

The vibration state detecting means of the invention according to claim 3 is an input voltage detecting means for detecting an input voltage applied to the piezoelectric body 1b.
46 and a rotational speed detecting means 30 for detecting the rotational speed of the vibration motor
A monitor voltage detecting means 44 for detecting a monitor voltage taken out of the piezoelectric body 1b, and a phase difference detecting means 42 for detecting a phase difference between an input voltage applied to the piezoelectric body 1b and a monitor voltage taken out of the piezoelectric body 1b. When the input voltage is the input voltage set value, the rotation speed of the vibration motor is zero, and the phase difference is equal to or less than a predetermined value, the adjusting means 50 It is characterized in that the pressing force applied in between is changed.

E. Function When the vibration departure state is determined, the pressing force of the moving body 2 is adjusted by the adjusting means 50. As a result, the vibration actuator immediately recovers to the normal vibration state.

In the above sections D and E for describing the configuration of the present invention, the drawings of the embodiments are used for easy understanding of the present invention, but the present invention is not limited to the embodiments.

F. Embodiment An embodiment of the present invention will be described with reference to FIGS.

First, the ultrasonic motor will be described with reference to FIG.
In FIG. 2, the stator 1 is composed of a ring-shaped elastic body 1a and a ring-shaped piezoelectric body 1b adhered to the ring-shaped elastic body 1a. In the elastic body 1a, a comb-shaped groove is formed on a contact surface side with the rotor 2 described later. The stator 1 is formed with a flange-shaped support member 1c that protrudes radially from near the neutral axis, and the support member 1c is
Is adhered and supported on a ring-shaped stator support member 3 having an inner diameter substantially equal to the outer diameter of the ring. The outer edge of the stator support member 3 is sandwiched between the installation cylinder 4 and the fixed cylinder 5, whereby the stator 1 is installed on the installation cylinder 4. Note that the fixed cylinder 5 is screwed to the installation cylinder 4.

On the other hand, the rotor 2 includes a ring-shaped rotor base material 2a and a slider material 2b adhered to the rotor base material 2a. A supporting member 2c that extends from the vicinity of the neutral shaft and receives pressure is integrally formed with the rotor base material 2a. The rotor 2 is installed inside the installation cylinder 4, and is brought into pressure contact with the elastic body 1 a of the stator 1 installed in the installation cylinder 4. That is, the pressing force of the urging member 6 is transmitted to the rotor 2 via the pressure transmitting member 7, whereby the rotor 2 comes into pressure contact with the elastic body 1a. The ball bearing 8 reduces the resistance of the rotation of the pressure transmitting member 7 and the rotor 2 during the pressurized contact.

The pressing force of the urging member 6 can be changed by, for example, expansion and contraction of an actuator 51 composed of a laminated piezoelectric body. The piezoelectric actuator 51 is held by a fixed cylinder 9 screwed to the installation cylinder 4 and expands and contracts by controlling the applied voltage to adjust the urging force of the urging member 6 and change the rotor pressing force. I do. Here, the urging member 6, the pressing force transmitting member 7, the fixed cylinder 9, and the piezoelectric actuator 51 constitute a pressurizing device 100. An electromagnetic or hydraulic actuator may be used instead of the piezoelectric actuator.

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 applied to the ultrasonic motor MT,
A rotation speed detector 30 for detecting the rotation speed of the ultrasonic motor MT,
The apparatus includes a vibration departure state determination circuit (determination means) 40 for detecting a vibration departure state, and a vibration recovery device (adjustment means) 50 for changing the pressure of the rotor 2.

The power supply circuit 20 includes a high-frequency signal generator 21, and the output of the high-frequency signal generator 21 is branched into two, one of which is connected to an amplifier 22.
The other is input to each phase shifter 23. The phase shifter 23 shifts the phase of the other input voltage by + π / 2 or −π / 2 with respect to one input voltage in accordance with the rotation direction of the ultrasonic motor MT, and then inputs the phase to the amplifier 24. The high-frequency voltages Vina and Vinb output from the amplifiers 22 and 24 are input to the piezoelectric body 1b of the ultrasonic motor.

As shown in FIG. 1, 1b-L, 1b-R, 1b-G, 1b are provided on the surface of the piezoelectric body 1b adhered to the stator 1 of the ultrasonic motor MT.
-M four electrodes are provided. Electrodes 1b-L, 1b-R
Are connected to the amplifiers 22 and 24, respectively, the electrode 1b-G is grounded, and the electrode 1b-M is connected to the vibration departure state determination circuit 40. Here, the electrodes 1b-L, 1b-
The frequency of the voltage input to the R from the power supply circuit 20 is called a power supply frequency.

Regarding the positional relationship of the electrodes and the polarization state under the electrodes in the ultrasonic motor, see Nikkei Mechanical February 28, 1983
Many documents including pages 44 to 49, and JP-A-59-2044
Since it is publicly known from Japanese Patent Publication No. 76 and the like, its description is omitted here.

The electrode 1b-M is a portion to which no input voltage is applied, and a voltage Vm (referred to as a 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, the details of which are disclosed in JP-A-59-204477, and the description thereof will be omitted. As described above, the monitor voltage Vm is input to the vibration departure state determination circuit 40 and used for detecting the vibration departure 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 / CCW.
Each of the direction signals CW / CCW is connected so as to be input to the vibration departure state determination circuit 40.

The vibration departure state determination circuit 40 receives the input rotation speed signal R,
The vibration deviation state of the ultrasonic motor MT is detected based on the direction signal CW / CCW, the input voltages Vina, Vinb, and 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. I do.

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

The vibration departure state determination circuit 40 includes an input voltage selection circuit 41 that selects one of the input voltages Vina and Vinb based on the direction signal CW / CCW, and one of the input voltage and the monitor voltage selected by the input voltage selection circuit 41. A phase difference output circuit 42 that outputs a signal indicating a phase difference of Vm, an F / V converter 43 that converts the rotation speed signal R into a voltage value, and a monitor voltage converter 44 that converts the monitor voltage Vm into a DC voltage. A comparator 45-1 for comparing the output of the monitor voltage converter 44 with a reference voltage; an input voltage converter 46 for converting the input voltage selected by the input voltage selection circuit 41 into a DC voltage; A comparator 45-2 comparing the output of 46 with the reference voltage, a comparator 45-3 comparing the output of the phase difference output circuit 42 with the reference voltage, and comparing the output of the F / V converter 43 with the reference voltage. The comparator 45-4 and the comparator 45-1
And a vibration departure state determination signal generation circuit 47 which outputs a vibration departure state signal by determining a vibration departure state based on each comparison result signal of .about.45-4.

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

In FIG. 4, in a step S1, it is determined whether or not the input voltage Vin is a set value based on a signal of the comparator 45-2. If the set value is the set value, the process proceeds to a step S2. Is not the set value, the transmission of the vibration departure state signal is stopped in step S7. Step S2
Then, the rotation speed is determined based on the signal of the comparator 45-4, and if the rotation is not recognized, the process proceeds to step S3. Further, in step S2, if rotation is recognized by the signal of the comparator 45-4, the process proceeds to step S7, and the transmission of the vibration deviation state signal is stopped. In step S3, the monitor voltage is applied to the signal of the comparator 45-1.
It is determined whether Vm has exceeded the set value. If the monitor voltage Vm has not exceeded the set value, the process proceeds to step S4. Steps
In S3, when the monitor voltage Vm exceeds the set value, the process proceeds to Step S7, and the transmission of the vibration departure state signal is stopped. In step S4, it is determined whether or not the phase difference is within the set condition based on the signal of the comparator 45-3. If step S4 is denied, in step S5, a vibration departure state signal is transmitted, and If the phase difference is within the set conditions, step S4
If affirmative, the process proceeds to step S7 to stop transmitting the vibration departure state signal. If it is determined in step S6 that the process is to be terminated, the procedure is terminated.
Return to

As shown in FIG. 1, the vibration recovery device 50 includes the above-described piezoelectric actuator 51 and a drive circuit 52 for the piezoelectric actuator 51. A vibration departure state signal is input to the drive circuit 52 from the vibration departure state determination circuit 40. Then, the piezoelectric actuator 51 is driven, and the pressing 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. FIG. 7 shows the power supply frequency f on the horizontal axis and the monitor voltage Vm on the vertical axis. The solid line FH shows the resonance characteristic diagram when the applied pressure is high.
Shows a resonance characteristic diagram when the pressing force is low. From this figure, it can be seen that changing the pressing force changes the resonance characteristics of the ultrasonic motor MT.

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

When a high-frequency voltage is supplied to the piezoelectric body 1b by the power supply circuit 20 shown in FIG. 1, the piezoelectric body 1b vibrates and a progressive vibration wave is formed on the elastic body 1a. When the rotor 2 is brought into pressure contact with the stator 1 in which the traveling vibration wave is generated by the pressure device 100, the rotor 2 is rotated by friction driving while vibrating.

Here, the relationship between the input voltages Vina, Vinb and the monitor voltage Vm during rotation will be described with reference to FIG. FIG. 5 (a) shows the rotor 2
Rotate in the clockwise direction CW, and (b) shows the case of rotating in the counterclockwise rotation term CCW. The input voltages Vina and Vinb are shifted in phase by + π / 2 and −π / 2 by the phase shifter 23. The monitor voltage Vm has a phase difference of approximately π / 2 from Vina in FIG. 5A, and has a phase difference of approximately −π / 2 with Vinb in FIG. 5B. If the load changes due to changes in temperature and humidity, changes in pressure, changes in the viscosity of lubricating oil, etc., and the ultrasonic motor falls into a vibration deviation state, the input voltages Vina and Vinb do not change, but the rotation speed signal R Becomes zero, and as shown in FIG. 6, the monitor voltage Vm also significantly decreases, and the phase difference from the input voltage greatly changes. When the vibration departure state determination circuit 40 determines that the state is a vibration departure state based on these parameters, the vibration departure state signal is input to the vibration recovery device 50. Vibration recovery device
Reference numeral 50 changes the pressing force of the urging member 6 by extending or contracting the piezoelectric actuator 51 by its drive circuit 52. As a result, the resonance characteristics of the ultrasonic motor MT change as described with reference to FIG. 7, and the ultrasonic motor MT recovers from the vibration deviation state to the normal vibration state.

 A second embodiment of the present invention will be described with reference to FIG.

The support member 3 of the stator 1 includes a movable cylinder 61 slidably inserted into the installation cylinder 4 and a fixed cylinder 62 screwed to the movable cylinder 61.
, Whereby the stator 1 is slidably installed in the installation cylinder 4 in the axial direction. The protrusion 61 a of the movable cylinder 61 is fitted in the straight groove 4 a of the installation cylinder 4, and the stator 1 cannot rotate with respect to the installation cylinder 4. Also,
A piezoelectric actuator is attached to the holding cylinder 63 screwed to the installation cylinder 4.
64 are provided, and support the stator 1 movably in the axial direction. On the other hand, in this embodiment, the urging member 6 and the pressing force transmitting member 7 are interposed between the fixed cylinder 65 screwed to the installation cylinder 4 and the bearing 8, and therefore, the actuator 64 is expanded and contracted. By doing so, the pressing force by the urging member 6 is changed.

Then, as in the first embodiment, when the vibration departure 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. To recover to a vibrating state. The other configuration is completely the same as that of the first embodiment, and the description is omitted. In this embodiment, the piezoelectric actuator 64 may be an electromagnetic actuator or a hydraulic actuator.

In the above, the input voltage is equal to the set value, the rotation speed of the rotor 2 is zero, the monitor voltage Vm is less than the set value, and the phase difference between the input voltage and the monitor voltage Vm is equal to or less than a predetermined value. Is determined to be the vibration departure state when is established, but simply, when is established, or
May be determined as the vibration departure state.

G. Effects of the Invention According to the present invention, changes in temperature and humidity, changes in pressure,
If a load fluctuation occurs due to a change in the viscosity of the lubricating oil and the vibration actuator is in a vibration deviation state, the vibration actuator can quickly escape from the vibration deviation state by simply changing the pressing force of the moving body by the adjusting means. And a highly reliable vibration actuator that can recover to a normal vibration state.

[Brief description of the drawings]

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 departure state determination circuit. FIG. 4 is a flowchart showing the operation of the vibration departure 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 a change in monitor voltage Vm in a normal state and in a state of deviation from vibration. FIG. 7 is a graph showing the relationship between the power supply frequency and the monitor voltage. FIG. 8 is a sectional view showing an ultrasonic motor according to the second embodiment. 1: Stator, 2: Rotor 3: Support member, 4: Installation cylinder 5: Fixed cylinder, 6: Biasing member 7: Pressure transmission member, 8: Bearing 9: Fixed cylinder, 30: Rotation speed detector 40: Vibration Departure state judgment circuit 50: Vibration recovery device 51, 64: Piezoelectric actuator 100: Pressurizing device

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-2-111274 (JP, A) JP-A-63-56178 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) H02N 2/14

Claims (3)

(57) [Claims] 1. A vibration motor driving apparatus comprising: a stator for generating a vibration wave on an elastic body by excitation of a piezoelectric body; and a moving body which is pressed against the stator by a pressing means and driven by the vibration wave. In a drive control device used for control, a vibration state detection unit that detects a vibration state of the vibration motor, and a pressing force applied between the moving body and the stator according to a detection result by the vibration state detection unit. A drive control device for a vibration motor, comprising: an adjusting means for adjusting. 2. The vibration state detection means includes: an input voltage detection means for detecting an input voltage applied to the piezoelectric body; a rotation speed detection means for detecting a rotation speed of the vibration motor; Monitor voltage detection means for detecting a monitor voltage to be detected, wherein the adjustment means is such that the input voltage is an input voltage set value, the number of revolutions of the vibration motor is zero, and the monitor voltage is a predetermined monitor voltage. If it is less than the set value,
The drive control device for a vibration motor according to claim 1, wherein a pressure applied between the moving body and the stator is changed. 3. The vibration state detection means includes: an input voltage detection means for detecting an input voltage applied to the piezoelectric body; a rotation speed detection means for detecting a rotation speed of the vibration motor; Monitor voltage detection means for detecting a monitor voltage to be detected, and phase difference detection means for detecting a phase difference between an input voltage applied to the piezoelectric body and a monitor voltage taken out of the piezoelectric body. When the input voltage is an input voltage set value, the number of revolutions of the vibration motor is zero, and the phase difference is equal to or less than a predetermined value, a pressure applied between the moving body and the stator is reduced. The drive control device for a vibration motor according to claim 1, wherein the drive control device is changed.