JP3192028B2 - Ultrasonic motor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultrasonic motor, and more particularly, to an ultrasonic motor driven by two electro-mechanical energy conversion elements fixed to an elastic body.

[0002]

2. Description of the Related Art A piezoelectric element, which is two electro-mechanical energy conversion elements fixed to an elastic body, is used as a drive source to generate longitudinal vibration and bending vibration in the elastic body. Conventionally, an ultrasonic linear motor including an ultrasonic oscillator that generates vibration and a driven member that is pressed by a part of the ultrasonic oscillator and moves relatively to the ultrasonic oscillator has conventionally been various types. An example of such a device is proposed in Japanese Patent Application No.
No. 321096.

As shown in FIG. 12, the ultrasonic vibrator described in the specification attached to this application has two laminated piezoelectric elements 53 and 54 on an elastic body 52 and a holding member 5 in the laminating direction.
The elastic members 54 are sandwiched and fixed by the members 5, 56, 57, and a plurality of sliding members 58, 59 are adhered to the lower surface of the elastic body 54.

As shown in FIG. 13, a linear guide 60 and a guide rail 6
1, the sliding members 58 and 59 are mounted on the driving plate 67 while being held by the holding frame 62, the screw 63, the pressing force adjusting screw 64, the spring 65, and the vibrator holding member 66 so as to be able to move linearly in the left-right direction. An ultrasonic linear motor is configured by pressing so as to make frictional contact.

[0005] The driving method of this ultrasonic linear motor is as follows. When an alternating voltage is applied to the laminated piezoelectric elements 53 and 54 by appropriately adjusting the dimensions of the ultrasonic vibrator, the resonance longitudinal vibration shown in FIG. 14A and the resonance bending vibration shown in FIG. Occurs at the same time. When the phase difference between the voltages applied to the two stacked piezoelectric elements 53 and 54 is appropriately adjusted, the longitudinal vibration and the bending vibration are combined, and an elliptical vibration is generated at the antinode position of the bending vibration. Thereby, the sliding members 58 and 59 fixed at the positions where the elliptical motion is performed,
A driving force is generated between the sliding members 58 and 59 and the sliding plate 67 in contact with the sliding members.

More specifically, the voltages applied to the laminated piezoelectric elements 53 and 54 are more specifically described.
54, an alternating voltage of about 10 Vp-p having a frequency corresponding to the resonance frequency of the longitudinal vibration and the bending vibration of the ultrasonic transducer, wherein a phase difference between two alternating voltages is applied to one of the laminated piezoelectric elements. The other is set to +90 degrees to drive the ultrasonic linear motor, while the phase difference is set to -9.
By setting it to 0 degree, the moving direction of the ultrasonic linear motor is reversed.

However, when a voltage of about 10 Vp-p is applied to the above-mentioned laminated piezoelectric element, the heat generated by the internal friction of the elastic body is large, so that the temperature of the elastic body reaches about 60 ° C. during driving. There was a case. For this reason, the adhesive and the like used for joining the members of the ultrasonic vibrator are likely to be deteriorated due to a rapid thermal change. Also, when this ultrasonic linear motor is used in a precision positioning device, the heat of the ultrasonic vibrator is transmitted to the components of the positioning device, causing thermal expansion, which may reduce the positioning accuracy. was there. Furthermore, the conversion efficiency of electro-mechanical energy of the ultrasonic linear motor is 10
%. In addition, in order to optimize the vibration state of the ultrasonic vibrator, it is necessary to separately install a sensor that detects the vibration state of the piezoelectric element, etc., which hinders miniaturization and adds extra cost. Had become.

[0008]

As described above, in the conventional ultrasonic motor, the conversion efficiency of electric-mechanical energy is 1 unit.
In some cases, the electrical energy that is low, such as about 0%, and is not converted to mechanical energy, becomes heat and degrades the adhesive and the like.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has as its object to provide an ultrasonic motor having high conversion efficiency of electric-mechanical energy and capable of reducing unnecessary heat generation.

[0010]

In order to achieve the above object, a first ultrasonic motor according to the present invention comprises: an elastic body;
Two electrical each oscillation direction is fixed to the elastic body so as to be parallel to - and mechanical energy conversion element, and a driven member which is pressed by the elastic member, the two electro - into mechanical energy conversion element each by generating longitudinal vibration and the bending vibration in the elastic member by applying an alternating voltage, in the ultrasonic motor for driving the driven member, the two electric - to mechanical energy conversion element, ultrasonic
Electro-mechanical energy forward of the wave oscillator
The amplitudes of the AC voltages applied to the respective elements are made different so that the voltage amplitudes of the energy conversion elements are increased , and the phases are inverted and the difference between the amplitudes is inverted .
Further, the second ultrasonic motor according to the present invention includes an elastic body,
Two electro-mechanical energies fixed integrally to an elastic body
A conversion element and a driven member pressed by the elastic body.
The AC voltage is applied to the electromechanical energy conversion element.
Longitudinal vibration and bending vibration
To the ultrasonic motor that drives the driven member
Further comprising an inductor, wherein the electro-mechanical energy is
AC voltage is applied to one of the
To the above-mentioned inductor
It is configured to drive the driven member by connecting
It is characterized by having.

[0011]

An AC voltage is applied to each of the two electro-mechanical energy conversion elements to generate longitudinal vibration and bending vibration in the elastic body to drive the driven member. -The amplitudes of the AC voltages applied to the mechanical energy conversion elements are made different from each other to invert the phase and the amplitude difference.

[0012]

Embodiments of the present invention will be described below with reference to the drawings. 1 to 4 show a first embodiment of the present invention. As shown in FIG. 1, an oscillator 1 generates an alternating voltage, and its output is branched into two. One of the branch outputs is input to an amplifier 3 whose voltage amplification factor can be switched, and is power-amplified by the amplifier 3 before being applied to a laminated piezoelectric element 5.
The other of the branch outputs is input to the phase shifter 2, the phase is shifted by +90 degrees or -90 degrees, and the power is amplified by another amplifier 4 capable of switching the voltage amplification factor. The voltage is applied to the element 6.

In the phase shifter 2, the phase shift amount is changed from +90 degrees to -90 degrees or from -90 degrees to +90 degrees.
At the time of switching, the amplitudes of the output voltages of the power amplifier 3 and the power amplifier 4 are switched in two stages in conjunction with the switching. More specifically, when one of the amplifiers has a large voltage amplitude (H state), the other amplifier has a small voltage amplitude (L state).

As shown in FIG. 2, the ultrasonic vibrator sandwiches the laminated piezoelectric elements 5 and 6 with respect to an elastic body 35,
The sliding members 36 and 37 are fixed to the lower end surfaces thereof, and are pressed against a driving plate 38 as a driven member via the sliding members 36 and 37 by a holding and pressing mechanism (not shown) to The acoustic linear motor 21 is constituted. In such a configuration, with respect to the traveling direction of the ultrasonic vibrator,
It is configured such that the laminated piezoelectric element on the front side has a larger voltage amplitude than the laminated piezoelectric element on the rear side. That is, in FIG. 2, for example, when the ultrasonic transducer advances to the right, the multilayer piezoelectric element 6 is in the H state and the multilayer piezoelectric element 5 is in the L state, and when it advances to the left, the opposite is true. .

Next, the operation of the first embodiment will be described. FIGS. 3A and 3B show an example of the measurement results of the speed and the power / mechanical energy conversion efficiency with respect to the load thrust.

This measurement was performed as shown in FIG. That is, a load is applied to the ultrasonic linear motor 21 via the pulley 22 by the weight 23, and the moving time between the two sensors 24 and 25 arranged in parallel at a predetermined interval along the moving direction is measured. In this way, the moving speed was obtained, and the efficiency was obtained from the relationship among power, speed, and load at this time.

FIG. 3A shows a case where the voltage amplitude in the H state is 10 Vp-p, and a voltage amplitude in the L state is 6 Vp-p. FIG. Motor 21
The case where the voltage amplitude applied to the two laminated piezoelectric elements 5 and 6 is the same 10 Vp-p irrespective of the moving direction of.

As is clear from the measurement results, FIG.
3A is larger than the speed characteristic with respect to the thrust shown in FIG. 3A, but the maximum value of the electric-mechanical energy conversion efficiency is larger than that shown in FIG. It is about 1/2. Since the energy loss at this time is mainly converted to heat, the heat generation in FIG. 3A is smaller.

According to the first embodiment, the conversion efficiency of the electro-mechanical energy of the ultrasonic linear motor can be improved, the power consumption can be reduced, and unnecessary heat generation can be suppressed. Therefore, adverse effects such as thermal expansion due to heat generation can be reduced.

FIGS. 5 to 8 show a second embodiment of the present invention. In the second embodiment, the first
The description of the same parts as those of the embodiment will be omitted, and only different points will be mainly described. As shown in FIG. 5, after the alternating voltage output of the oscillator 7 is power-amplified by the amplifier 8, the voltage is switched by the switching means 10 composed of, for example, two interlocking switches, etc. Power is applied to the element 12. These two stacked piezoelectric elements 11 and 12 are connected to the inductor 9 when power is not supplied from the amplifier 8.

The multilayer piezoelectric elements 11 and 12 and the inductor 9 are arranged so that the electrical resonance frequency of the LC matches the output frequency of the oscillator 7, that is, the driving frequency of the ultrasonic vibrator. The capacitance and inductance of 11 and 12 are determined.

As shown in FIG. 6, the ultrasonic vibrator has a structure in which the laminated piezoelectric elements 11 and 12 are sandwiched between elastic bodies 26 and sliding members 36 and 37 are fixed to lower end surfaces thereof. The driving plate 38 is moved through the sliding members 36 and 37.
The ultrasonic linear motor 21 is configured to be pressed by a holding and pressing mechanism (not shown). In such a configuration, the laminated piezoelectric element on the front side with respect to the traveling direction of the ultrasonic transducer is connected to the amplifier 8, and the laminated piezoelectric element on the rear side is connected to the inductor 9.

Next, the operation of the second embodiment will be described. The ultrasonic linear motor according to the second embodiment operates even when only the alternating voltage is applied to only one of the two laminated piezoelectric elements, which will be described below with reference to the measurement results. .

When an alternating voltage was applied to only one of the stacked piezoelectric elements of the ultrasonic vibrator, the vibration state was observed using two vibrometers 29 and 30 and an oscilloscope 31, as shown in FIG.

First, when a voltage is applied only to the laminated piezoelectric element 11, a vibration as shown in FIG. 7A is observed, and the Lissajous becomes as shown in FIG. 7B, and an elliptic motion occurs. You can see that it is. Further, when a voltage is applied only to the multilayer piezoelectric element 12, a vibration as shown in FIG. 7 (C) is observed, and the Lissajous becomes as shown in FIG. 7 (D). It can be seen that an elliptical motion in the rotation direction opposite to that in the case where. When the driving plate 38 is brought into pressure contact with the sliding members 36 and 37 provided in the portion performing the elliptical motion as shown in FIG. 6, the ultrasonic vibrator and the driving plate 38 relatively move. It is known that the moving direction of is determined by the rotation direction of the elliptical motion.

Next, the state when the inductor 9 is connected to the electric terminal of the laminated piezoelectric element on which no voltage is applied will be described. When an alternating voltage is applied to one of the laminated piezoelectric elements to excite the ultrasonic transducer, the other laminated piezoelectric element is also displaced (deformed) and a voltage is generated by the piezoelectric effect. At this time, when the inductor 9 is connected to the electric terminal of the multilayer piezoelectric element, for example, when the multilayer piezoelectric element is compressed, a current flows from the multilayer piezoelectric element to the inductor 9, and the current flows through the inductor 9. It is temporarily stored as magnetic energy in the inductor 9.

Next, when the phase of the vibration changes with the passage of time and the multilayer piezoelectric element expands, the polarity of the voltage of the electric terminal of the multilayer piezoelectric element is inverted, and the energy stored in the inductor 9 is reduced. It flows through the laminated piezoelectric element as electric energy (current). In this case, compared with the case where the electric terminals are opened, the stiffness of the multilayer piezoelectric element is reduced, and the displacement amplitude of the multilayer piezoelectric element when mechanical vibration is applied from the outside increases. That is, since the laminated piezoelectric element and the inductor 9 are electrically resonated, the vibration efficiency is further increased.

According to the second embodiment, the above-described first embodiment
In addition to having substantially the same effects as the embodiment, the driving of the ultrasonic linear motor can be performed with a single-phase alternating voltage, and the driving device is simplified. Further, the thrust of the ultrasonic linear motor can be increased by connecting an inductor to an electric terminal of the laminated piezoelectric element to which no alternating voltage is applied to generate electric resonance.

FIGS. 9 to 11 show a third embodiment of the present invention. In the third embodiment, description of the same parts as those in the first and second embodiments will be omitted, and only different points will be mainly described. As shown in FIG. 9, the alternating voltage output of the oscillator 13 is power-amplified by the amplifier 14, and then switched to the laminated piezoelectric elements 17 and 18 by the switching means 15 composed of, for example, two interlocking switches. Are respectively applied. In a state where power is not supplied from the amplifier 14, the two stacked piezoelectric elements 17 and 18 are input to the control amount determining means 16 of the oscillator 13, and the control means 16 controls the voltage or frequency control amount of the oscillator 13. It is determined and controlled.

Another example of the configuration shown in FIG. 9 is shown in FIGS. FIG. 10 shows an example in which an inductor 19 is provided between the control amount determining means 16 and the switching means 15 and the voltage across the inductor 19 is measured.
FIG. 11 shows an example in which an inductor 19 is provided between the control amount determining means 16 and the switching means 15, and the current flowing through the inductor 19 is measured from the voltage across the resistor 20. These examples are examples in which the inductor connection in the second embodiment is performed and the sensor function is provided at the same time.

Next, the operation of the third embodiment will be described. The ultrasonic linear motor according to the third embodiment can be driven even when an alternating voltage is applied to only one of the two stacked piezoelectric elements 17 and 18 as in the second embodiment. Can be. Further, when an alternating voltage is applied to one of the laminated piezoelectric elements, the ultrasonic transducer vibrates due to the inverse piezoelectric effect, and an electromotive force is generated in the other laminated piezoelectric element due to the vibration of the ultrasonic transducer. At this time, the amplitude of the vibration is substantially proportional to the amplitude of the generated voltage, so that the laminated piezoelectric element to which the alternating voltage is not applied can be used as a sensor for detecting the vibration state of the ultrasonic transducer. Then, the control amount determination means 16 determines the control amount of the output voltage amplitude or frequency of the oscillator 13 so that the vibration state is always constant, and performs control so as to obtain the optimum vibration.

According to the third embodiment, the same effects as those of the first and second embodiments can be obtained, and the vibration state of the ultrasonic vibrator can be controlled by controlling the voltage of the driving multilayer piezoelectric element. Since it can be detected by the laminated piezoelectric element on the side where no voltage is applied, there is no need to provide a special sensor for detecting vibration.
Using this, the vibration state can be controlled in a closed loop.

[0033]

As described above, according to the present invention, it is possible to provide an ultrasonic motor having high conversion efficiency of electric-mechanical energy and capable of reducing unnecessary heat generation.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an electric circuit portion of an ultrasonic motor according to a first embodiment of the present invention.

FIG. 2 is a side view showing the ultrasonic motor according to the first embodiment.

FIG. 3 shows the relationship between speed and efficiency with respect to thrust of the ultrasonic motor of the first embodiment. (A) When different voltages are applied to two laminated piezoelectric elements, (B) two laminated piezoelectric elements FIG. 3 is a diagram showing a case where a voltage equal to is applied.

FIG. 4 is a side view showing a configuration for measuring the relationship between speed and efficiency with respect to thrust of the ultrasonic motor of the first embodiment.

FIG. 5 is a block diagram showing an electric circuit portion of an ultrasonic motor according to a second embodiment of the present invention.

FIG. 6 is a side view showing the ultrasonic motor according to the second embodiment.

FIG. 7 is a diagram showing vibration of an ultrasonic transducer measured by the vibrometer of the second embodiment.

FIG. 8 is a side view showing a configuration for measuring the vibration of the ultrasonic transducer of the second embodiment.

FIG. 9 is a block diagram showing an electric circuit portion of an ultrasonic motor according to a third embodiment of the present invention.

FIG. 10 is a block diagram showing another example of the electric circuit portion of the ultrasonic motor according to the third embodiment.

FIG. 11 is a block diagram showing still another example of the electric circuit portion of the ultrasonic motor according to the third embodiment.

FIG. 12 is a perspective view showing a conventional ultrasonic transducer.

FIG. 13 is a side view showing an ultrasonic linear motor constituted by using the ultrasonic transducer shown in FIG. 12;

FIG. 14 (A) shows the ultrasonic transducer shown in FIG.
FIG. 3 is a diagram showing a resonance longitudinal vibration state and FIG.

[Explanation of symbols]

 1, 7, 13 oscillator 2 phaser 3, 4, 8, 14 amplifier 5, 6, 11, 12, 17, 18 laminated piezoelectric element 9, 19 inductor 10, 15 switching means 20 resistance 26, 35 ... elastic body 36, 37 ... sliding member 38 ... drive plate

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Yoshihisa Taniguchi 2-43-2 Hatagaya, Shibuya-ku, Tokyo Inside Olympus Optical Co., Ltd. (56) References JP-A-4-190684 (JP, A) JP-A-3-61237 (JP, A) JP-A-3-239171 (JP, A) JP-A-63-141680 (JP, A) JP-A-3-273876 (JP, A) (58) Fields investigated (Int .Cl. ⁷ , DB name) H02N 2/00

Claims (2)

(57) [Claims] 1. An elastic body and its vibration direction are parallel to each other.
So as it fixed two electricity to the elastic body - and mechanical energy conversion element, and a driven member which is pressed by the elastic member, the two electrical - applying each AC voltage to mechanical energy conversion element In the ultrasonic motor that drives the driven member by generating longitudinal vibration and bending vibration in the elastic body, the two electro-mechanical energy conversion elements are driven by ultrasonic vibration.
Electro-mechanical energy on the forward side of the moving direction of the rotor
An ultrasonic motor characterized in that there is a difference between the amplitudes of AC voltages to be applied so as to increase the voltage amplitude of the conversion element, and the phases are inverted and the difference in amplitude is inverted. 2. An elastic body, and an elastic body integrally fixed to the elastic body.
One of electro - and mechanical energy conversion element, and a driven member which is pressed by the elastic member, the electro - to generate longitudinal vibration and the bending vibration in the elastic member by applying an AC voltage to mechanical energy conversion element An ultrasonic motor for driving the driven member, further comprising an inductor, applying an AC voltage to one of the electro-mechanical energy conversion elements, and connecting the other electro-mechanical energy conversion element to the inductor; An ultrasonic motor configured to drive the driven member.