JPH07303383A - Ultrasonic vibrator and its driving method - Google Patents

Abstract

PURPOSE:To always stably drive an ultrasonic vibrator by preventing the damage and separation of a temperature detecting element caused by ultrasonic vibrations and, at the same time, preventing the superposition of the AC voltage applied across a piezoelectric element upon the output of the temperature detecting element and correcting the variation of the resonance frequency of a vibrator caused by the ambient temperature of the vibrator or by the heat generated from the vibrator itself. CONSTITUTION:In an ultrasonic vibrator 10 which generates ultrasonic vibrations by applying an AC voltage across a piezoelectric element 12 fixed to an elastic body 11, a temperature detecting element is fitted to a holding member which holds the vibrator 10.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a device, such as an ultrasonic motor, for applying an AC voltage to an electromechanical energy conversion element to generate ultrasonic vibration and driving the ultrasonic vibration by using this as an energy source.

[0002]

2. Description of the Related Art A piezoelectric element is fixed to an elastic body to form a vibrator, and the temperature of the ultrasonic vibrator when ultrasonic vibration is generated by applying an AC voltage to the piezoelectric element is detected. As a technique for adjusting the frequency of the AC voltage, a driving method of an ultrasonic motor disclosed in Japanese Patent Laid-Open No. 1-264579 is known.

As shown in FIG. 9, a temperature sensor is directly attached to a vibrator, and the output voltage of the temperature sensor is VFC.
By changing the output frequency of the (voltage-frequency converter), it is possible to drive at a frequency that matches the temperature change of the resonance frequency of the vibrator.

[0004]

However, in the above-mentioned prior art, when the temperature detecting element is fixed to the vibrator in order to correct the change in the resonance frequency due to the ambient temperature of the vibrator or the heat generation of the vibrator itself, the piezoelectric element is There is a problem in that the AC voltage applied to is superimposed on the output of the temperature detection element as noise, and accurate temperature measurement cannot be performed. There is also a problem that the temperature detecting element may be damaged by the ultrasonic vibration and the adhesive agent to which the temperature detecting element is fixed may be peeled off.

The present invention has been made in view of the above problems, and prevents the temperature detecting element from being damaged or peeled off due to ultrasonic vibration, and the AC voltage applied to the piezoelectric element is superimposed on the output of the temperature detecting element as noise. The present invention provides an ultrasonic transducer and a method of driving the ultrasonic transducer, which can prevent the occurrence of the above-mentioned problems, and can correct the variation of the resonance frequency of the transducer due to the ambient temperature of the transducer and the heat generated by the transducer itself to always stably drive the transducer. The purpose is to

[0006]

In order to achieve the above object, an ultrasonic vibrator of the present invention according to claim 1 comprises an elastic body and an electro-mechanical energy conversion element fixed to the elastic body, In the ultrasonic vibrator for applying an AC voltage to the electro-mechanical energy conversion element to generate ultrasonic vibration, a temperature detecting element is attached to a holding member that holds the ultrasonic vibrator.

In the ultrasonic vibrator of the present invention according to claim 2, the holding member is electrically conductive and is grounded to a reference potential.

Further, in the ultrasonic vibrator driving method of the present invention according to claim 3, the AC voltage applied to the electro-mechanical energy conversion element is controlled according to the temperature detected by the temperature detection element.

[0009]

In the ultrasonic vibrator according to the first aspect, the ultrasonic vibration generated by the vibrator is less likely to be transmitted to the temperature detecting element.

In the ultrasonic oscillator according to the second aspect, the temperature detecting element is prevented from being influenced by the high frequency noise caused by the oscillator drive voltage.

In the method of driving the ultrasonic vibrator according to the third aspect, the ultrasonic vibrator can always be driven at the driving frequency corresponding to the temperature change of the resonance frequency of the vibrator.

Embodiments of an ultrasonic oscillator and a driving method thereof according to the present invention will be described below with reference to the accompanying drawings. In the description of the drawings, the same elements will be denoted by the same reference symbols, without redundant description.

[0013]

First Embodiment First, a first embodiment of the present invention will be described with reference to FIGS. In addition, Example 1 below is an application of the present invention to the ultrasonic transducer disclosed in Japanese Patent Application No. 4-321096 previously proposed by the present inventor.

As shown in FIG. 1, the ultrasonic transducer 10 has an elastic body 11 in which two laminated piezoelectric elements 12 are sandwiched by two holding members 13 in the laminating direction, and fixed by screws 14 and an adhesive. Two sliding members 15 are provided on the lower surface of the body 11.
It is configured by bonding. A holding pin 16 is attached to the common node of the longitudinal vibration and the bending vibration of the vibrator 10.

Next, as shown in FIG. 2, an ultrasonic linear motor 20 is constructed using this vibrator 10. Oscillator 10
Are held by being sandwiched by two holding plates 21 from both sides via holding pins 16. The holding plate 21 is fixed at its upper end to a holding plate fixing member 22 by a screw 23, and a linear bush 24 is planted upward in the holding plate fixing member 22. And this linear bush 24
Is adapted to move linearly in the vertical direction along the axis 25.

Here, the shaft 25 is planted downward from the lower end surface of the shaft fixing member 26.
6 is fixed to the base 27 with screws 26a. A tap penetrating in the up-down direction is cut in a substantially central portion of the shaft fixing member 26, and a pressing screw 28 is screwed therein. A pressing spring 29 is interposed between the lower end surface of the screw portion of the pressing screw 28 and the holding plate fixing member 22.

On the other hand, a linear guide 32, which is a driven member, is fixed to the base 27 by a fixing member 30 with screws 31, and a sliding member 34 is adhered to a moving portion 33 of the linear guide 32. There is.

A thermistor 40 as a temperature detecting element is adhered to the holding plate 21. As shown in FIG. 3, the temperature detection result by the thermistor 40 is converted by the control signal generation circuit 41 into a control voltage for controlling the output frequency of the VCO (voltage controlled oscillator) 42, and one output of the VCO 42 is converted into a power amplifier. The power is amplified by 44 and applied to one piezoelectric element 12 of the linear motor 20, and the output of the other is given a phase difference of ± 90 degrees by the phase shifter 43, and then power amplified by the power amplifier 45 to obtain the linear motor 20. Is applied to the other piezoelectric element 12.

Next, the operation of the ultrasonic transducer of the present embodiment having the above structure will be described. By appropriately adjusting the dimensions of the ultrasonic transducer 10 and applying an AC voltage to the piezoelectric element 12,
The longitudinal resonance vibration shown in FIG. 5A and the bending resonance vibration shown in FIG. 5B are simultaneously generated. When the phase difference between the voltages applied to the two piezoelectric elements 12 is appropriately adjusted, the longitudinal vibration and the bending vibration are combined, and elliptical vibration is generated at the antinode of the bending vibration. A sliding member 15 for taking out the elliptical vibration output is fixed at this position. When the driven member is brought into contact with the elliptical vibration, the vibrator and the driven member relatively move, as is known.

The voltage applied to the piezoelectric element 12 is an AC voltage having a frequency that matches the resonance frequencies of the longitudinal vibration and the bending vibration of the ultrasonic vibrator 10, and the phase difference between the two AC voltages is one of the piezoelectric elements. While the other is +90
The ultrasonic linear motor 20 is driven by setting the degree. Further, when the phase difference is set to −90 degrees, the moving direction of the ultrasonic linear motor 20 is reversed.

Next, FIG. 4 shows the measurement result of the temperature change of the resonance frequency of the vibrator 10. The resonance frequency decreases as the temperature rises, and the optimum drive frequency of the ultrasonic linear motor 20 also changes. Therefore, the driving device shown in FIG. 3 measures the temperature so that the driving frequency is always optimum.

Further, regarding the ultrasonic vibration leakage from the ultrasonic vibrator 10 of the holding plate 21 and the temperature difference between the vibrator 10 and the holding plate 21, the holding pin 16 has longitudinal vibration and bending as described above. Since it is mounted at a node position common to the vibration, the vibration transmission can be minimized, and the thermistor 40 can detect the temperature of the vibrator 10 by placing the thermistor 40 close to the holding pin 16. In order to further reduce the temperature detection error, it is preferable to fix the thermistor 40 to the holding pin 16.

According to this embodiment, when the driving frequency of the vibrator is determined by detecting the temperature, the temperature detecting element is attached to the holding plate of the vibrator so that the temperature detecting element can be operated by the ultrasonic vibration generated by the vibrator. It is possible to prevent breakage and peeling of the adhesive.

[0024]

Second Embodiment Next, a second embodiment of the present invention will be described with reference to FIGS. As shown in the drawing, in this embodiment, the holding pin 16 of the same vibrator 10 as in FIG. 1 is contacted from above the V-shaped notch of the vibrator holding member 51 covering the vibrator 10. The vibrator holding member 51 is fixed to the base 57 by a screw 52 from a portion having a V-shaped notch to a holding portion via a hinge. With this hinge as the center, the holding member 51
Has a degree of freedom only in the substantially vertical direction.

Above the vibrator holding member 51, the pressing mechanism holding member 55 is fixed to the base 57 with screws 56. A tap penetrating in the up-down direction is cut in a substantially central portion of the pressing mechanism holding member 55, and a pressing screw 54 is screwed into the tap. Between the lower end surface of the screw portion of the pressing screw 54 and the vibrator holding member 51, the pressing spring 5
3 is interposed.

On the other hand, a linear guide 62, which is a driven member, is fixed to the base 57 with a fixing member 60 fixed by screws 61. A sliding member 64 is adhered to the moving portion 63 of the guide 62. Here, the oscillator holding member 51 is made of a conductive material such as stainless steel, and is grounded to a predetermined reference potential.

The thermistor 7 is used as the temperature detecting element.
As shown in FIG. 7, the temperature detection result by the thermistor 70 is converted into a voltage signal by the thermistor circuit 71 and then input to the microcomputer 73 via the A / D converter 72. The microcomputer 73 controls an oscillator 74 that generates a two-phase signal having a phase difference of 90 degrees by its program. Oscillator 7
One output of No. 4 is power-amplified by the power amplifier 75 to drive one piezoelectric element 12 of the linear motor 50, and the oscillator 7
The other output of No. 4 is power-amplified by the power amplifier 76, and drives the other piezoelectric element 12 of the linear motor 50.

Next, the operation of the ultrasonic transducer of the present embodiment having the above structure will be described. Since the operations of the vibrator 10 and the linear motor 50 are the same as those in the first embodiment, the description thereof will be omitted.

The measurement result by the thermistor 70 is processed by the microcomputer 73 as shown in FIG. That is, if the temperature is within a predetermined temperature range after sampling the temperature data, the optimum driving frequency is calculated from the temperature data, and then the oscillation frequency of the oscillator 74 is updated. On the other hand, when the sampling temperature is out of the predetermined range, alarm processing for stopping the output of the oscillator is performed to prevent the piezoelectric element 12 from being damaged by the heat generated by the vibrator 10 itself.

The vibrator holding member 51 covers most of the vibrator 10 including the piezoelectric element 12 and is grounded, so that the vibrator holding member 51 also has an electromagnetic shield effect on a high frequency voltage when the piezoelectric element 12 is driven.

According to the present embodiment, in addition to the effect of the first embodiment, the holding member covers most of the vibrator including the piezoelectric element, so that the holding member has an electromagnetic shield effect and the temperature detecting element vibrates. There is an advantage that it is not affected by high frequency noise caused by the child drive voltage.

[0032]

As described above, according to the ultrasonic vibrator of the present invention and the driving method thereof, it is possible to prevent the temperature detecting element from being damaged or peeled off due to the ultrasonic vibration. Also,
It is possible to prevent the AC voltage applied to the piezoelectric element from being superimposed on the output of the temperature detection element as noise. Then, changes in the resonance frequency of the vibrator due to the ambient temperature of the vibrator or heat generated by the vibrator itself can be corrected, and stable driving can always be performed.

[Brief description of drawings]

FIG. 1 is a perspective view showing an ultrasonic transducer according to a first embodiment of the present invention.

FIG. 2 is a front view showing the ultrasonic linear motor according to the first embodiment of the present invention.

FIG. 3 is a block diagram showing a drive circuit for the ultrasonic transducer according to the first embodiment of the present invention.

FIG. 4 is a graph showing a relationship between a temperature of a vibrator and a resonance frequency.

FIG. 5 is a diagram schematically showing a vibration mode of a vibrator.

FIG. 6 is a perspective view showing an ultrasonic linear motor according to a second embodiment of the present invention.

FIG. 7 is a block diagram showing a drive circuit for an ultrasonic transducer according to a second embodiment of the present invention.

FIG. 8 is a flowchart showing a control operation of the second embodiment.

FIG. 9 is a diagram illustrating a conventional technique.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Ultrasonic vibrator 11 Elastic body 12 Piezoelectric element 13 Holding member 14 Screw 15 Sliding member 16 Holding pin 20 Ultrasonic linear motor 21 Holding plate 22 Holding plate fixing member 23 Screw 24 Linear bush 25 Shaft 26 Shaft fixing member 27 Base 28 Pressure screw 29 Pressure spring 30 Fixing member 31 Screw 32 Linear guide 33 Moving part 34 Sliding member 40 Thermistor 41 Control signal generating circuit 42 VCO 43 Phase shifter 44 Power amplifier 45 Power amplifier

Claims (3)

[Claims] 1. An ultrasonic transducer comprising an elastic body and an electro-mechanical energy conversion element fixed to the elastic body, wherein an alternating voltage is applied to the electro-mechanical energy conversion element to generate ultrasonic vibration. An ultrasonic vibrator, wherein a temperature detecting element is attached to a holding member that holds the ultrasonic vibrator. 2. The ultrasonic transducer according to claim 1, wherein the holding member is conductive and is grounded to a reference potential. 3. A method of driving an ultrasonic transducer, comprising controlling an AC voltage applied to the electromechanical energy conversion element according to a temperature detected by the temperature detection element.