JPH04161078A - Driver for standing wave ultrasonic motor - Google Patents

Abstract

PURPOSE:To prevent driving speed and driving efficiency from lowering due to temperature rise by providing a temperature detecting means and means for controlling each frequency signal input to an ultrasonic oscillator in response to a detection signal from the temperature detecting means. CONSTITUTION:A frequency signal output from an oscillator 41 is split through a phase shifter 2 into two voltage signals having different phases which are then applied through amplifiers 43a, 43b on the electrode 26 of a first piezoelectric element 22 and the electrodes 27a, 27b of second piezoelectric elements 23a, 23b in order to drive an ultrasonic motor 30. Resilient body 21 of the ultrasonic oscillator 11 is provided with a thermocouple 50 connected with an operating circuit 51 and the frequency signal of the oscillator 41 is controlled in response to a detected temperature. Variation of resonance frequency due to temperature rise of the ultrasonic oscillator 11 is detected through the thermocouple 50 and the operating circuit 51 controls each frequency signal input to the ultrasonic oscillator.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a driving device for a standing wave type ultrasonic motor using ultrasonic vibration energy as a driving source, and in particular to miniaturization and high efficiency of the driving circuit. This relates to improvements for.

[Conventional technology]

In recent years, various types of ultrasonic motors have been developed that utilize the high-frequency mechanical vibration energy of an ultrasonic vibrator and use the relative frictional force between the object and the object as a driving source, and research on their application is actively underway.

This type of ultrasonic motor is, for example, equipped with a compound vibrator excited by resonance vibration in two directions that are substantially orthogonal to each other, and a drive device that applies a required high-frequency vibration to the compound vibrator. , a target object such as a movable element is pressed against the composite vibrator, and a thrust is generated by the relative frictional force caused by this pressing force to perform the required relative movement between the movable elements. This is a drive device designed to allow

[Problems to be Solved by the Invention] However, in the conventional ultrasonic motor configured in this way, the influence of the temperature rise of frictional heat generated while driving the ultrasonic vibrator by the drive device and the rise of the ambient temperature. There is a problem in that the resonant frequency of the ultrasonic transducer changes due to temperature changes such as 1. In particular, in ultrasonic motors that use a compound vibrator that is excited by resonant vibrations in two directions that are substantially orthogonal to each other, the resonant frequency diversion becomes large, and it is not possible to maintain the required speed just by adjusting the drive frequency. It was something I couldn't get.

This invention was made in order to improve each of these problems in conventional ultrasonic motors, and its purpose is to improve the temperature rise in a driving device for a standing wave type ultrasonic motor. Therefore, it is possible to prevent a decrease in drive speed and drive efficiency caused by the above.

[Means for Solving the Problem] In order to achieve the above object, a driving device for a standing wave type ultrasonic motor according to the present invention provides a driving device for a standing wave type ultrasonic motor according to the present invention. Has an ultrasonic vibrator,
In a driving device for a standing wave type ultrasonic motor that causes the ultrasonic vibrator to resonate and vibrate using different frequency signals having different phases, detecting the temperature of the ultrasonic vibrator,
The ultrasonic transducer includes at least a temperature detection means for outputting a signal corresponding to the detected temperature, and a frequency control means for controlling each frequency signal input to the ultrasonic transducer in response to a detection signal of the temperature detection means. It is characterized by its composition.

Further, in the driving device for the standing wave type ultrasonic motor,
The present invention is characterized in that it includes a resonant frequency adjusting means for controlling the resonant frequency signal of at least one of the two directions of vibration to match the resonant frequency signal of the other.

[Function J] In the standing wave type ultrasonic motor drive device having the above configuration,
By detecting the temperature of the ultrasonic transducer by the temperature detection means and outputting a signal corresponding to the detected temperature, the frequency control means can control each frequency signal input to the ultrasonic transducer, and as a result, the ultrasonic This makes it possible to prevent the drive speed and drive efficiency of the ultrasonic motor from decreasing due to a rise in the temperature of the vibrator.

In addition, in the case of multiple vibrations excited in the ultrasonic transducer, in response to changes in the resonant frequency caused by temperature rise, the resonant frequency adjustment means is used to reduce the number of vibrations in two directions (one resonant frequency signal to the other). Since the resonant frequency signal of both vibrations is controlled to match the resonant frequency signal, the resonant frequencies of both vibrations can always be made to match.

〔Example〕

EMBODIMENT OF THE INVENTION Hereinafter, one embodiment of a driving device for a standing wave type ultrasonic motor according to the present invention will be described in detail with reference to FIGS. 1 to 8.

An example of the standing wave type ultrasonic motor in this embodiment is, for example, Japanese Patent Application No. 1-468 filed by the applicant earlier.
The present invention may be a standing wave type ultrasonic motor using an ultrasonic vibrator including a mechanical resonator as proposed in the specification and drawings attached to the No. 66 application.

FIG. 1 is a plan view schematically showing the general configuration of a standing wave type ultrasonic motor according to the existing proposal.

In the device configuration of the standing wave type ultrasonic motor shown in FIG. 1, the ultrasonic vibrator 11 applies bending vibration to the upper surface portion of the elastic body 21 having a rectangular prism shape along the longitudinal direction. A first piezoelectric body 22 for excitation is mounted, and on each left and right side surface that is substantially orthogonal to this mounting surface, second piezoelectric bodies 22 for exciting longitudinal vibration in the elastic body 21 are provided. Piezoelectric body 23a.

23b is attached to each.

Further, the center portions of both longitudinal sides of the elastic body 21 are connected to a base 25 via fixing bolts 24a and 24b, respectively.
a, 25b side, the elastic body 21 itself also serves as a grounding pole, and each of these fixing bolts 24a, 24
It is grounded to the bases 25a and 25b via the electrodes 25a and 25b, and furthermore, an electrode 26 is attached to the upper surface of the first piezoelectric body 22, and an electrode 26 is attached to the upper surface of each of the second piezoelectric bodies 23a and 23b. In addition, electrodes 27a and 27b are attached to each of the first piezoelectric electrodes 26. Input terminals are taken out from each of the second piezoelectric electrodes 27a and 27b, respectively.

As for the elastic body 21, both free ends in the thickness direction bend in a secondary mode at a predetermined frequency f, and both free ends in the length direction vibrate in a first order mode at the same frequency f. The shape and dimensions of each part are adjusted so that it can vibrate vertically.

In general, the resonance frequency of longitudinal vibration propagating in an elastic body depends on the length of the elastic body, and the resonance frequency of bending vibration in the thickness direction of the elastic body depends on the length of the elastic body. , and is known to depend on thickness; in these respects,
It is extremely easy to obtain the elastic body 21 that acts as described above, and a detailed explanation thereof will be omitted.

Next, the operation of the ultrasonic transducer 11 with the above configuration will be described.

First, when an alternating current voltage of frequency f is applied to the first piezoelectric body 22 to cause it to vibrate, the elastic body 21 resonates in the secondary mode of bending vibration, and a standing wave is excited. Similarly, when an AC voltage of frequency f is applied to each of the second piezoelectric bodies 23a and 23b to cause it to vibrate, the elastic body 21 resonates in the primary mode of longitudinal vibration, and a standing wave is excited. . That is, in the elastic body 21, the portion corresponding to the fixed position by each fixing bolt 24a, 24b becomes a node of each standing wave.

Also, at this time, these first piezoelectric bodies 22. When adjusting the amplitude and phase of the voltage applied to each of the second piezoelectric bodies 23a and 23b, the elastic body 21 is Therefore, it is possible to generate approximately elliptic vibrations having an arbitrary shape.

In the case of this embodiment, the elastic body 21 is excited with a first-order mode of longitudinal vibration and a second-order mode of bending vibration,
Although we have described the ultrasonic transducer 11 that generates vibrations in the shape of an elliptical motion by synthesizing them, the mode of the vibrations is not limited to this. In addition to combining various vibrations such as bending vibration, shear vibration, and torsional vibration, it is also effective to use higher-order modes.

Next, the basic operation of an ultrasonic motor that effectively utilizes the ultrasonic transducer 11 having the above configuration will be described with reference to FIGS. 2 and 3.

FIGS. 2(a) to 2d) are operation explanatory diagrams showing the operation of the ultrasonic transducer 11 at each stage, and here, in order to facilitate understanding, the form of each operation is explained briefly. This is a somewhat exaggerated representation.

In the device configuration shown in FIG. 2, the ultrasonic motor 30 is
Driving elements 32, 32 are formed at the lower parts of both ends that provide the maximum amplitude of the ultrasonic transducer 11, and each of these driving elements 32, 32 is formed relative to the rail portion 34, which is a second elastic body. are arranged so that they can come into contact with each other.

FIG. 3 also shows the first piezoelectric body 22 of the ultrasonic vibrator 11 constituting the ultrasonic motor 30. and each second piezoelectric body 23
FIG. 4 is an explanatory diagram showing voltage waveforms of input drive signals applied to each of a and 23b.

In the ultrasonic motor 30 shown in FIG. 2, when the ultrasonic vibrator 11 is excited by applying the AC drive signal shown in FIG. )
The required driving force is generated by repeating longitudinal vibration and bending vibration as shown in d).

That is, by adjusting the phases of both the longitudinal and 9-bending vibrations in the ultrasonic transducer 11, when the first longitudinal vibration shown in FIG. 32 is pressed against the rail part 34, and when it expands over time, it is expanded in that state as shown in FIG. , the drive tube 32 corresponding to the right side is pressed against the rail portion 34, and when it is extended over time, it is extended in that state as shown in FIG. By repeating this sequentially, each driving element 32 receives a driving force due to frictional force at the time when it comes into pressure contact with these rail parts 34, and a thrust force is generated in the same direction shown by arrows A and H.

The speed of the ultrasonic transducer 11 at this time can be adjusted arbitrarily by the voltage and phase of the input drive signal, and the driving direction can also be adjusted arbitrarily by the phase. Can be set. In addition, although the case where the ultrasonic transducer 11 side is used as a movable element has been described in this S, it is also possible to conversely use the rail portion 34 side as a movable element.

Next, the configuration and details of the operation of a driving device for a standing wave type ultrasonic motor according to an embodiment of the present invention are shown in FIG.
and Fig. 5 will be described.

FIG. 4 is a configuration diagram showing an outline of a driving device for a standing wave type ultrasonic motor according to this embodiment, and FIG. 5 is an explanatory diagram showing the relationship between resonance frequency and temperature in the same driving device. .

In the device configuration according to the embodiment in FIG. 4, a driving device 40 for a standing wave type ultrasonic motor has an oscillator 41, and the frequency signal output of the oscillator 41 is outputted in a phase shifter 42 with a different phase. After being converted into two voltage signals, these voltage signals are passed through amplifiers 43a and 43b to the electrodes 26. and each second piezoelectric body 23a, 2
3b is applied to the electrodes 27a and 27b, and in this way the ultrasonic motor 30 described above is driven. Also,
On the other hand, a thermocouple 5 is attached to the elastic body 21 of the ultrasonic transducer 11 as a temperature detection means for measuring the surface temperature of the elastic body 21.
0 is attached, and the temperature information detected by the thermocouple 50 is used as a frequency control means, in this case,
is input to the arithmetic circuit 51, and by the arithmetic circuit 51,
The frequency signal of the oscillator 41 and, by extension, the frequency signal input to the ultrasonic transducer 11 can be controlled in accordance with the detected temperature.

Regarding the relationship between the resonant frequency f and the temperature T in the ultrasonic motor 30, as shown in the resonant frequency f vs. temperature characteristic shown in FIG. The frequency decreases, and even though this ultrasonic motor 30 can operate with high efficiency, most of the loss becomes frictional heat on the sliding surface and the ultrasonic vibration This causes a change in the temperature of the child 11.

Therefore, in the embodiment configuration shown in FIG.
By controlling the driving frequency of the ultrasonic transducer 11 in accordance with the temperature change according to the actual measurement results as shown in the figure, the driving efficiency due to the temperature rise can be improved.

This makes it possible to effectively and effectively prevent a reduction in drive speed.

On the other hand, especially in the ultrasonic motor 30 using an ultrasonic vibrator that excites resonance vibrations in multiple directions, the resonance frequency difference between these multiple vibrations changes with temperature changes. As a result, the driving efficiency and driving speed of the ultrasonic motor 30 are significantly reduced, as described above.

Therefore, in this embodiment, a resonance frequency adjustment means is separately provided in order to control and eliminate the resonance frequency difference caused by the temperature rise in the plurality of vibrations.

In this embodiment, as a method of controlling the resonance frequency, for example, Japanese Patent Application No. 1-468 related to the applicant's earlier application
The control method proposed in the specification and drawings attached to the application No. 68 can be used, and according to this control method, only the resonant frequency of one of the vibrations in two directions orthogonal to each other is controlled by the resonance frequency of one vibration in the other direction. can be controlled according to the resonant frequency of

Next, the structure using a separate resonant frequency adjusting means in the driving device for the standing wave type ultrasonic motor according to this embodiment and details of the operation will be described with reference to FIGS. 6 to 8.

FIG. 6 is a block diagram showing an outline of a driving device for a standing wave type ultrasonic motor to which an example of the frequency adjustment means is applied, and FIGS. 7 and 8 are diagrams showing the frequency adjustment means of the same device. FIG. 3 is an explanatory diagram showing an equivalent circuit and a relationship between resonance frequency and inductance.

In the configuration of the embodiment shown in FIG. 6, °C controls the resonance frequency of one of the approximately orthogonal two-directional vibrations excited in the ultrasonic transducer 11, in this case, for example, longitudinal vibration. As a frequency adjustment means for this purpose, a control piezoelectric element 60 is attached to the longitudinal vibration node of the ultrasonic transducer 11, and this is connected to the arithmetic circuit 51 via a variable inductance coil 61. On the other hand, the inductance value of the variable inductance coil 61 can be controlled by the arithmetic circuit 51.

In this case, an equivalent circuit of the control piezoelectric element 60 and the variable inductance coil 61 can be expressed as shown in FIG. That is, the control piezoelectric element 60 is represented by a capacitor C1, a four-terminal constant M having a force coefficient as a parameter, and a capacitor C2, to which a variable inductance coil 61 is connected in parallel.

Further, in this case, since the control piezoelectric element 60 is attached to the longitudinal vibration node of the ultrasonic transducer 11, it can control only the resonance frequency of the longitudinal vibration, and the actual measurement results can be This is shown in FIG. 8, which shows the correlation between the resonant frequency and the variable inductance coil 61.

That is, in this case, the variable inductance coil 61
As parallel anti-resonance occurs in the capacitor C7 of the control piezoelectric element 60, the elasticity of the control piezoelectric element 60 increases.

The temperature dependence of each resonance frequency of the longitudinal vibration and bending vibration excited in the ultrasonic transducer 11 as shown in FIG. 5 is measured independently in advance. Therefore, in this case, the resonant frequency difference will increase in response to the temperature rise of the ultrasonic transducer 11 detected by the thermocouple 50, but at this time, the arithmetic circuit 51 will:
A signal is output to change the inductance of the variable inductance coil 61, and as a result, only the resonant frequency of the longitudinal vibration among the above-mentioned vibrations is changed. This allows the resonance frequencies to always be kept the same.

In addition, in the above embodiment, the case where a thermocouple is used as the temperature detection means of the ultrasonic transducer is described as an example.
The method is not limited to this, and there are nine other possible methods, such as using a semiconductor element whose internal resistance is temperature dependent.

Furthermore, in the above embodiments, a prismatic composite resonator was used as an example of the elastic body of the ultrasonic transducer, but the invention is not limited to this. It is also possible to use similar resonators having various shapes such as an annular shape, a cylindrical shape, etc., and although a piezoelectric material is used as an excitation source for an elastic body in the embodiment, it is also possible to convert electrical energy into mechanical energy. Other elements that can be converted into 1 For example, a magnetostrictive element can be used, and its shape may be various shapes such as a disk shape, a laminated shape, etc. in addition to a flat plate shape.

〔Effect of the invention〕

As described in detail above, according to the present invention, the ultrasonic transducer is provided with an ultrasonic transducer excited with at least two vibrations in directions substantially orthogonal to each other, and the ultrasonic transducer is stimulated by each frequency signal having a different phase. In a driving device for a standing wave type ultrasonic motor that causes resonance vibration by Since the structure includes a frequency control means for controlling each frequency signal input to the ultrasonic transducer in accordance with the signal, the temperature detection means detects the temperature of the ultrasonic transducer and generates a signal corresponding to the detected temperature. By using the output, each frequency signal input to the ultrasonic transducer can be controlled by the frequency control means, and as a result,
It is possible to effectively and effectively prevent a decrease in the drive speed and drive efficiency of the ultrasonic motor due to a rise in the temperature of the ultrasonic vibrator, and also to reduce the vibration in two directions excited by the ultrasonic vibrator. , a small number of resonant frequency signals. of each vibration in two directions.

It has an excellent feature that at least one resonant frequency signal can be matched with the other resonant frequency signal, and thereby effective driving can be performed.

[Brief explanation of drawings]

FIG. 1 is a plan view schematically showing the general configuration of a standing wave type ultrasonic motor applied to the present invention, and FIGS. 2(a) to 2d) are ultrasonic FIG. 3 is an explanatory diagram showing the operation of the sonic vibrator at each stage, and FIG. 3 is an explanatory diagram showing the voltage waveform of the input drive signal applied to the piezoelectric body of the composite vibrator. Further, FIG. 4 is a configuration diagram showing an outline of the driving device for the standing wave type ultrasonic motor according to this embodiment, and FIG. 5 is an explanatory diagram showing the relationship between the resonant frequency and temperature in the same driving device. Fig. 6 is a block diagram showing an outline of a driving device for a standing wave type ultrasonic motor to which an example of the above frequency adjusting means is applied, and Figs. 7 and 8 are equivalent circuits of the frequency adjusting means of the above device, and resonance FIG. 3 is an explanatory diagram showing the relationship between frequency and inductance. 11... Composite vibrator, 21... Elastic body, 22
and 23a, 23b...first and second piezoelectric bodies, 24a, 24b...fixing bolts, 25a, 25
b = = base, 26 and 27a, 27b ---- electrode, 30...
・Ultrasonic motor, 32...driver, 34...rail section, 40...drive circuit, 41...oscillator, 42...phase shifter, 43a, 43b =
= Amplifier, 50...Thermocouple (temperature detection means), 51... Arithmetic circuit (frequency control means), 60, 61... Piezoelectric element for control, variable inductance coil (frequency adjustment means). Patent applicant: Brother Industries, Ltd. Patent attorney
Kimi Tateno - Figure 1 Figure 3 Figure 2 (Q) (b) // l--Rhythm (C) (d) Figure 4 145 Temperature T of the ultrasonic transducer Figure 6 61 Inryo 8 figure

Claims (2)

[Claims] (1) A standing wave that has an ultrasonic vibrator that is excited with at least two vibrations in directions that are substantially perpendicular to each other, and that causes the ultrasonic vibrator to resonate and vibrate with each frequency signal having a different phase. A drive device for an ultrasonic motor includes: a temperature detection means for detecting the temperature of the ultrasonic vibrator and outputting a signal corresponding to the detected temperature; 1. A driving device for a standing wave type ultrasonic motor, comprising at least a frequency control means for controlling each frequency signal input to a vibrator. (2) The driving device for a standing wave type ultrasonic motor according to claim 1, wherein resonance frequency adjustment is performed to control a resonance frequency signal of at least one of the vibrations in the two directions to match a resonance frequency signal of the other resonance frequency. 1. A driving device for a standing wave type ultrasonic motor, comprising: means.