JPH06197574A - Actuator utilizing acoustic radiation pressure - Google Patents

Abstract

PURPOSE:To increase the output of the actuator by making acoustic waves to be repeatedly reflected multiple times between a mobile and fixed reflecting bodies and superimposing generated forces upon the mobile reflecting body by utilizing acoustic reflection pressures. CONSTITUTION:Acoustic waves generated when a vibrator is vibrated hit a mobile reflecting plate 42 after passing through a window 43 opened in a fixed reflecting body 43 and reflected waves from the plate 42 hit the plate 43 except a window 43a opened in the plate 43. Thereafter, the ultrasonic beam changes the direction upon hitting the reflecting surface 45a of a reflecting casing 45 after repeatedly reflected multiple times between the plates 42 and 43 and are again repeatedly reflected multiple times between the plates 42 and 43. Because of the effect of acoustic reflection pressures caused by the multiple reflection, the mobile reflecting plate 42 is moved against the force of a coil spring 40 by a driving source which is the force generated in the plate 42 and the output of this actuator can be increased.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an energy conversion device, and can be used for an actuator that operates using acoustic radiation pressure, which is one of the effects associated with sound wave generation, as a drive source.

[0002]

2. Description of the Related Art Conventionally, as this type of energy conversion device, one disclosed in Japanese Patent Application Laid-Open No. 2-41677 has been known. This is provided with a stator composed of a vibrator and an elastic body, a rotor arranged on the stator and composed of a friction material and an elastic body contacting the stator, and a spring means for pressing the rotor toward the stator. Of the traveling wave of the stator caused by the vibration of the rotor causes an elliptical locus motion at an arbitrary point on the surface of the elastic body of the stator, and the frictional force between the stator and the rotor caused by the motion causes the traveling wave to generate in the rotor. It is movable in the opposite direction.

However, in the above-mentioned energy conversion device, the vibration energy generated on the surface of the elastic body is converted into mechanical work through frictional force, so that the members are worn or damaged, the durability is deteriorated, and the life is shortened. Have the drawback to
Furthermore, since a vibration displacement of about several μm is used, high processing accuracy is required, and since highly accurate and highly reliable bonding technology is required as a means for fixing the vibrator to the elastic body, productivity is also poor. there were.

Therefore, the applicant of the present invention comprises a vibrating body which generates a sound wave in a medium, and a movable body which is arranged on the progress of the sound wave generated from the vibrating body and is movable by acoustic radiation pressure accompanying the progress of the sound wave. We invented an actuator that utilizes acoustic radiation pressure. According to this, the vibrating body generates a sound wave in the medium. This sound wave propagates in the medium and hits the movable body. The movable body receives acoustic radiation pressure generated as the sound waves travel. Therefore, the movable body receives a force in the traveling direction of the sound wave and moves. According to this technique, since the vibration energy of the vibrating body is transmitted to the movable body as acoustic energy through the medium, problems such as wear and damage due to friction do not occur.

FIG. 21 shows a rotary actuator utilizing this acoustic radiation pressure. This is the rotor 73
3a is provided, a vibrating body 72 is provided in the housing 74, a sound wave is generated in the medium by the vibrating body 72, and the rotor 73 is rotated by acoustic radiation pressure generated as the sound wave progresses.

[0006]

However, the force received by the movable body is extremely small because the sound wave hits the movable body only once, which is disadvantageous in achieving high output and high efficiency.

Therefore, the present applicant has made it a first object to further increase the output and the efficiency of the actuator.

Further, since the output intensity of the sound wave is consumed to excite the surface acoustic wave of the solid surface at a certain incident angle with respect to the movable body and the fixed reflector, there is a problem that the acoustic energy of the reflected wave is attenuated. .

Therefore, a second object of the present invention is to prevent the acoustic energy from being attenuated by the surface acoustic waves.

[0010]

In order to solve the above-mentioned first problem, in the invention of claim 1, the sound wave emitted by hitting the movable body is reflected by the fixed body arranged in the traveling direction of the once reflected sound wave. , The movable body is applied again, and this is repeated, and the force generated in the movable body due to the effect of acoustic radiation pressure is superimposed and amplified. That is, it is configured that a larger force is applied to the movable body by multiple reflection of sound waves between the movable body and the fixed body.

Further, in the invention of claim 2, further,
The incident angles of the sound waves to the movable body and the fixed body were set to be equal to or larger than the total reflection angle of the sound waves of the medium and the movable body and the total reflection angle of the medium and the fixed body, respectively.

In order to confront the second problem, claim 3
In the invention, the incident angle of the sound wave to the movable body and the fixed body is further set to a region excluding the angle which is a condition for exciting the surface acoustic wave of the solid surface.

[0013]

The movable body is moved by the radiation pressure from the sound field generated in the medium by driving the vibrating body. Radiation pressure is related to the energy density of sound waves and the reflection, transmission, and absorption of sound waves generated between movable bodies.

FIG. 1 shows the force exerted by the radiation pressure on an object placed in an infinite plane traveling wave sound field in which the energy density of the sound wave is E. Rubber is typically used as the absorber, but in most cases, this corresponds to the case of a partial reflector having a sound wave intensity reflectance of R. The reflectance is related to the acoustic impedances Z1 and Z2 of the acoustic medium and the object,

[0015]

[Equation 1]

Thus, about 90% of water and SUS, water and A
It becomes about 70% at l. In the case of using the reflection, if the sound wave is made into a beam and is multiple-reflected between the fixed reflectors as shown in FIG. 2, the force acting on the object due to the acoustic radiation pressure can be superimposed, and a larger force can be applied to the object. Can be given. FIG. 4 shows a force (radiation pressure) F exerted on an object larger than its cross section by a beam sound wave having an output W (watt) sound velocity V.

The actual radiation pressure is as complicated as the sound field distribution, but in the case of a liquid sound field medium, the half angle is about 2 to 3 ° or less at about 1 MHz or more, and it becomes a beam shape. It can be practically approximated to a plane traveling wave. For example, φ2
Approximately φ6 from a disk-shaped oscillator of 0 mm and 1.7 MHz
It becomes a beam-shaped plane wave of about mm. On the other hand, it is not practical because the attenuation is high in a high frequency band, and the attenuation distance is 10 MHz or more and the attenuation distance is several tens cm or less in the liquid. Therefore, in the case of a liquid sound field medium, the frequency band is 1 to 10 MHz.
Is desirable.

As a sound wave radiating medium, a liquid can supply an acoustic power higher than that of gas by three digits or more.

In the case of PZT (titanate-zirconate-lead), the allowable acoustic power to be put into water is about 800 W / cm ^2.
On the other hand, only about 0.2 W / cm ² of acoustic power can be applied to the air. As described above, as the radiation medium of the sound wave, the liquid has a stronger radiation pressure than the gas. However, even a liquid that absorbs and attenuates sound waves is not suitable as a radiation medium. In addition, since most of the energy of the vibrator can be introduced into the liquid by the configuration in which one surface of the vibrator is liquid and the other surface is gas, the electroacoustic conversion efficiency in that case reaches 90% or more.

As described above, according to the invention of claim 1,
By applying an acoustic radiation pressure obtained by optimally setting the acoustic frequency by using an appropriate liquid as a sound field medium, it is possible to solve the first problem and realize an actuator having features not present in conventional methods. Become.

Next, the force F generated in the reflector in the multiple reflection system of the parallel reflector shown in FIG.

[0022]

[Equation 2]

It becomes f is the generated force per beam and is equal to the force received by the perfect absorber.

Since the reflectance R is R <1, the value of F converges when n → ∞,

[0025]

[Equation 3]

This shows the limit of force amplification in the case of multiple reflection with reflectance R, and F is 8 of f in water and SUS.
Water and Al are only about three times. 5 and 6 show the relationship between the number of reflections and the attenuation rate of acoustic output intensity, and the number of reflections and the amplification factor of force in the case of water and SUS and water and tungsten.

Although the combination of the medium and the object with R = 1 does not exist in the natural world, the incident angle θi from the medium to the object is
This problem can be solved by setting the total reflection angle to be larger than the total reflection angle determined by the medium and the object. FIG. 7 shows medium I to object II
Shows the relationship between the incidence, reflection, and refraction of sound waves. Incident angle θi
The relationship between the refraction angle θt and

[0028]

[Equation 4]

It is shown by. C ₁ is the speed of sound in the medium, and C ₂ is the speed of sound in the object. Here, the condition of θt = 90 ° is the condition of total reflection, and the incident angle θc at that time is called the total reflection angle or the critical angle,

[0030]

[Equation 5]

There is a relationship of 14.8 between water and SUS.
And 13.7 ° for water and Al.

As described above, by setting the incident angle θi and the total reflection angle θc or more, a system close to R = 1 can be realized, and the problem of attenuation of acoustic energy due to the influence of the reflection angle R is solved. can do.

Therefore, according to the second aspect of the present invention, by setting the incident angle of the sound wave to the movable body and the fixed body to be equal to or more than the total reflection angle, it is possible to suppress the attenuation of the acoustic energy due to the reflection and the multiple reflection. The effect of force amplification can be further enhanced, and the output of the actuator can be further enhanced.

Next, FIG. 20 shows the conditions for exciting surface acoustic waves on the solid surface by sound waves. When the surface wave advances in AC while the plane wave (sound wave) advances in BC, the surface acoustic wave is excited because the plane wave and the surface wave are in phase with each other. Incident angle θs at this time
Is

[0035]

[Equation 6]

It is represented by C ₁ is the speed of sound of the medium, Cs is the speed of the solid surface wave, and θs is about 33 for water and SUS.
It becomes °. At an incident angle near this point, the surface acoustic wave is excited and the output of the reflected wave is attenuated. Therefore, the incident angle is θ
By setting the area other than near s, the attenuation of the acoustic energy of the reflected wave due to the excitation of the surface acoustic wave can be suppressed.

Therefore, according to the third aspect of the present invention, the surface elasticity is set by setting the incident angle of the sound wave to the movable body and the fixed body to an area excluding the angle which is a condition for exciting the surface acoustic wave of the solid surface. It is possible to suppress the attenuation of the acoustic energy of the reflected wave due to the wave excitation, and to further enhance the force amplification effect due to the multiple reflection.

[0038]

Embodiments of the present invention will be described below with reference to the drawings.

8 to 10 show a first embodiment of the present invention, which is an actuator for converting the vibration of the vibrating body into the linear motion of the movable body.

The housing 44 has a cylindrical portion 44a forming a cylindrical hollow portion 50, and a hole 44b extending obliquely from a bottom surface 44c of the hollow portion 50. The fixed reflection plate 43 is fixed to the bottom surface 44c. The fixed reflector 43 has a hole 4
A window 43a is provided in a portion corresponding to the center of 4b.
A movable reflection plate 42 is provided parallel to the fixed reflection plate 43 so as to be slidable in the cylindrical portion 44a. The movable reflector 42 has a guide 42a extending toward the bottom surface 44c. The guide 42a is fitted in a hole 44d provided in the housing 44. Both ends of the coil spring 40 are fixed to the bottom of the hole 44d and the end of the guide 42a, respectively. A reflection casing 45 is sandwiched between the fixed reflection plate 43 and the movable reflection plate 42. The inner surface of the reflective casing 45 is hollowed out in a polygonal shape. The inner surface of the reflective casing 45 is formed as a reflective surface 45a. A disc-shaped ultrasonic beam generator 41 is fixed to the housing 44 at one end of the hole 44b. A liquid medium 49 is filled in the space formed by the one side of the ultrasonic beam generator 41, the hole 44d, the fixed reflection plate 43, the reflection casing 45, and the movable reflection plate 42. On the other side of the ultrasonic beam generator 41, the cap 47 is provided on the housing 4
4 and forms a closed air chamber 48. Lead wire 24 extending from the ultrasonic beam generator 41
The a and 24b pass through the inside of the air chamber 48 and extend to the outside of the housing 44 via the bush 46.

The structure of the ultrasonic beam generator 41 is shown in FIGS.
13 shows. The disk-shaped vibrator 20 is supported by a rubber bush 21 along with a positive electrode 22 and a negative electrode 23. As shown in FIG. 12, the oscillator 20 has a negative electrode 20b on the outer edge on the gas chamber side and a positive electrode 20a on the center on the gas chamber side.
Equipped with. As shown in FIG. 13, the negative electrode 23 includes a ring-shaped portion 23a and a terminal 23b. The ring-shaped portion 23 a of the negative electrode 23 is in contact with the negative electrode 20 b on the outer edge of the vibrator 20. The end of the lead wire 24b is soldered to the terminal 23b of the negative electrode 23. The positive electrode 22 includes a ring-shaped portion 22a, a terminal 22b and a spring-shaped contact 22c. The ring-shaped portion 22 a of the positive electrode 22 is the oscillator 20.
It is placed in parallel with and without contact. Terminal 22 of positive electrode 22
The end of the lead wire 24a is soldered to b. The spring contact 22c of the positive electrode 22 is formed so as to come into contact with the positive electrode 20a at the substantially center of the vibrator 20. The oscillator 20 can be vibrated to generate a sound wave having a desired frequency by controlling the voltage and / or current applied to the lead wires 24a and 24b. It should be noted that with the above-mentioned configuration, high frequency vibration can be generated.

The electrodes 2a and 2b of the vibrator 20 are the sound field medium 4
In order to prevent the deterioration of the vibrator 20 due to the permeation of No. 9 and to improve the wear resistance of the contact bonding surface with the contact connected to the control circuit, a dense film is formed by the vacuum thin film manufacturing method. A CVD method may be used instead of the vacuum thin film method.

In the vibrator 20, the traveling direction of the sound wave generated by the vibration passes through the window 43a provided in the fixed reflection plate 43, hits the movable reflection plate 42, and the movable reflection plate 4 is moved.
The window 43a in which the reflected wave from 2 is provided on the fixed reflection plate 43
It is arranged in such a way that it hits the part excluding.

The reflection casing 45 has a polygonal angle so that the beam-like sound waves generated from the oscillator 20 are reflected and the input wave and the reflected wave do not overlap each other.

In the present embodiment, the vibrator 20 has a P
Made of ZT (titanate-zirconate-lead), thickness 1.2m
A ceramic piezoelectric vibrator with a vertical resonance frequency of 1.7 MHz and a diameter of about 20 mm is used.

The entire reflective casing 45 may be made of a reflective material such as SUS and the inner surface may be the reflective surface 45a, or only the portion facing the inner surface may be made of the reflective material. The fixed reflecting plate 43 and the movable reflecting plate 42 may be entirely made of a reflecting material, but only the emitting surface may be made of a reflecting material.

In the first embodiment, the vibrator 20 generates a beam-like ultrasonic wave in the central axis direction. The sound wave generated by the vibration of the vibrator 20 passes through the window 43a provided in the fixed reflection plate 43, hits the movable reflection plate 42, and the reflected wave except the window 43a provided in the fixed reflection plate 43. Hit After that, the ultrasonic beam repeatedly multiple-reflects between the movable reflection plate 42 and the fixed reflection plate 43, hits the reflection surface 45a of the reflection casing 45, changes its direction, and is further multiplexed between the movable reflection plate 42 and the fixed reflection plate 43. Repeat reflection. Due to the effect of acoustic radiation pressure due to this multiple reflection, the movable reflecting plate 42 moves against the force of the coil spring 40 by using the force generated in the movable reflecting plate 42 as a driving source.

The actuator of the first embodiment is used by immersing it in a liquid. When this actuator is used in the atmosphere, the movable reflecting plate 42 and the end of the cylindrical portion 44a of the housing 44 are connected by rubber or bellows, and the medium side is sealed. A medium supply means for supplying a medium that is a liquid with the movement may be provided.

When used in the air, the air chamber 4
The sealing of 8 becomes unnecessary.

In the first embodiment, the reflecting surfaces of the multiple reflections are not located at the same place, and the reflected beam is a traveling path of the sound wave that does not return to the vibration source.

In the first embodiment, the movable reflecting plate 42 is used.
And the fixed reflection plate 43 are made of the same material and are arranged in parallel, and the incident angle of the first sound wave on the movable reflection plate 42 is determined by the medium and the movable reflection plate, and by the medium and the fixed reflection plate. The ultrasonic beam generation unit 41 is arranged so that it is larger than the larger one of the reflection angles. Thereby, the attenuation of acoustic energy due to reflection can be suppressed, and the effect of force amplification due to multiple reflection can be further enhanced.

14 to 16 show a second embodiment of the present invention, which is an actuator for converting the vibration of the vibrating body into the rotational movement of the movable body.

The housing 54 is provided with a chamber 54a having a substantially rhombic cross section in which a medium 55 is enclosed. A star-shaped rotor 52 is rotatably supported in the chamber 54a. A hole 54b extending obliquely in the vertical direction from a rhombic surface is provided at the vertical end of the housing 54.

Further, the fixed reflecting plate 53 is fixed along the rhombic surface. The fixed reflection plate 53 is provided so as not to block the portion that abuts the center of the hole 54b. A disc-shaped ultrasonic beam generator 51 is fixed to the housing 54 at one end of the hole 54b. A medium 55 is filled in a space formed by one side of the ultrasonic beam generator 51, the hole 54b, the fixed reflection plate 53, and the rhombic inner surface of the housing 54. The cap 57 is provided on the other side of the ultrasonic beam generator 51.
Are fixed to the housing 54 to form a closed air chamber 58. The lead wire 60 extending from the ultrasonic beam generator 51 passes through the inside of the air chamber 58 and the bush 56.
Through to the outside of the housing 54.

The ultrasonic beam generator 51 is the same as the ultrasonic beam generator 41 of the first embodiment shown in FIGS.

The ultrasonic beam generator 51 has a housing 54.
One is provided for each part corresponding to the side of the rhombus of
Each of the ultrasonic beam generators 51a, 51b, 51
c and 51d are caps 57a, 57b and 57, respectively.
It is fixed by c and 57d. When the pair of ultrasonic beam generators 51a and 51c provided on the opposite sides of the rhombus of the housing 54 are driven, the rotor 52 can be rotated clockwise. Further, by driving the ultrasonic beam generators 51b and 51d, the rotor 52 can be rotated counterclockwise.

The ultrasonic beam 59 generated from the ultrasonic beam generating section 51 hits the surface of the rotor 52 made of a sound wave reflecting material, is reflected, and goes toward the fixed reflecting plate 53. The ultrasonic beam reflected by the fixed reflection plate 53 is again reflected by the rotor 52.
Towards the reflective surface. In this way, the ultrasonic beam is transmitted to the rotor 5
Multiple reflection occurs between the second reflecting surface and the fixed reflecting plate 53 (see FIGS. 17 and 18). The force generated in the rotor 52 by the effect of acoustic radiation pressure due to multiple reflection is used as a drive source in the rotor 52.
Rotates. The frequency of multiple reflection differs depending on the rotational position of the rotor in the second embodiment, but FIG. 18 shows the positional relationship between the rotor and the fixed reflection plate when the force generated by multiple reflection becomes maximum.

When used in the same liquid as the acoustic wave medium 55, it is not necessary to seal the medium 55 in the housing 54, but the air chamber 58 needs to be airtight.

In the second embodiment, the fixed reflection plate 53 has a flat plate shape. However, when the rotor 52 rotates by a predetermined angle from the rotation position shown in FIG. 15, the reflected sound waves gradually deviate from the fixed reflection plate 53, and the multiple reflection occurs. The number of reflections is reduced.
If the reflected wave adversely affects the rotation, the sound wave may be generated in pulses and synchronized with the rotation of the rotor 52. In this case, the sound wave is emitted at a position where the plane of the rotor 52 and the fixed reflection plate 53 are parallel to each other.

Further, as shown in FIG. 19, the fixed reflection plate may be a curved surface so that the reflected wave from the fixed reflection plate always strikes a straight line on the plane of the rotor 52. The fixed reflection plate is processed into a shape that always returns the sound wave that has arrived from the rotor in the arrival direction when viewed in a plane perpendicular to the axis of the rotor. Since the incident wave and the reflected wave on the fixed reflector deviate from the axial direction of the rotor, a standing wave is not generated.

Also in the second embodiment, the reflecting surfaces of the multiple reflections are not located at the same place, and the reflected beam is a traveling path of the sound wave which does not return to the vibration source.

In the second embodiment, the rotor 52 and the fixed reflection plate 53 are made of the same material, and the rotor 52 and the fixed reflection plate 53 are used.
When parallel to each other, the angle of incidence of the first sound wave on the reflection surface of the rotor is greater than or equal to the larger of the total reflection angle determined by the medium and rotor material and the total reflection angle determined by the medium and reflector material. Therefore, the ultrasonic beam generator 51 is arranged so as not to excite the active surface acoustic waves. This allows
Attenuation of acoustic energy due to reflection can be suppressed,
The effect of force amplification by multiple reflection can be further enhanced.

[0063]

According to the first aspect of the present invention, sound waves are multiple-reflected between the movable reflector and the fixed reflector, and the forces generated in the movable body by the acoustic radiation pressure are superposed, so that a larger driving force can be obtained. Since the force is applied to the movable body, the output of the actuator can be made higher.

According to the second aspect of the invention, the attenuation of acoustic energy due to reflection can be suppressed, the effect of force amplification due to multiple reflection can be further enhanced, and the output of the actuator can be further enhanced.

According to the invention of claim 3, the incident angle of the sound wave to the movable body and the fixed body is set to a region excluding the angle which is a condition for exciting the surface acoustic wave of the solid surface, and thus the surface acoustic wave It is possible to suppress the attenuation of the acoustic energy of the reflected wave due to the excitation and further enhance the effect of the force amplification due to the multiple reflection.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing radiation pressure in a perfect absorber, a perfect reflector and a partial reflector.

FIG. 2 is an explanatory diagram showing a state of multiple reflection of sound waves.

FIG. 3 is an explanatory diagram showing a state of multiple reflection of sound waves.

FIG. 4 is an explanatory diagram showing radiation pressure in a perfect absorber, a perfect reflector and a partial reflector.

FIG. 5 is a graph showing the relationship between the number of reflections and the intensity attenuation rate.

FIG. 6 is a graph showing the relationship between the number of reflections and the radiation power amplification factor.

FIG. 7 is an explanatory diagram showing states of an incident wave, a reflected wave, and a transmitted wave.

FIG. 8 is a sectional view of the first embodiment of the present invention.

FIG. 9 is a sectional view of the first embodiment of the present invention.

FIG. 10 is a side view of the first embodiment of the present invention.

FIG. 11 is a cross-sectional view of an ultrasonic beam generator of the present invention.

FIG. 12 is a cross-sectional view and a top view of a vibrator of the present invention.

FIG. 13 is a perspective view of a vibrator and electrodes of the present invention.

FIG. 14 is a partial sectional view of a second embodiment of the present invention.

FIG. 15 is a sectional view of a second embodiment of the present invention.

FIG. 16 is a sectional view of a second embodiment of the present invention.

FIG. 17 is an operation explanatory diagram of the second embodiment of the present invention.

FIG. 18 is an operation explanatory diagram of the second embodiment of the present invention.

FIG. 19 is an operation explanatory view of a modified example of the second embodiment of the present invention.

FIG. 20 is an explanatory diagram showing conditions for generating surface acoustic waves.

FIG. 21 is a sectional view of a conventional actuator.

[Explanation of symbols]

20 vibrator 20a positive electrode 20b negative electrode 21 rubber bush 22 positive electrode 22a ring-shaped portion 22b terminal 22c spring-like contact 23 negative electrode 23a ring-shaped portion 23b terminals 24a, 24b
Lead wire 40 Coil spring 41 Ultrasonic beam generation part 42 Movable reflection plate 42a Guide 43 Fixed reflection plate 43a Window 44 Housing 44a Cylindrical part 44b Hole 44c Bottom surface 44d hole 45 Reflection casing 45a Reflection surface 46 Bush 47 Cap 48 Air chamber 49 Medium 50 Hollow part 51 Ultrasonic beam generating part 51a, 51b, 51c, 51d Ultrasonic beam generating part 52 Rotor 53 Fixed reflection plate 54 Housing 54a chamber 54b Hole 55 Medium 56 Bush 57, 57a, 57b, 57c, 57d Cap 58 Air chamber 59 Ultrasonic beam 60 Lead wire 71 Housing 72 Vibrating body 73 Rotor 73a Blade 74 Housing

Claims (3)

[Claims] 1. A vibrating body which generates a sound wave in a medium, a movable body which is arranged in a traveling direction of the sound wave generated from the vibrating body and which is moved by acoustic radiation pressure accompanying the progress of the sound wave, and a discharge from the vibrating body. And a fixed body for receiving a sound wave reflected from the movable body and using acoustic radiation pressure as a drive source, wherein the movable body and the fixed body serve as a sound wave reflecting material, and the sound wave is fixed to the movable body. An actuator utilizing acoustic radiation pressure, which is characterized by multiple reflection between bodies. 2. The incident angle of the sound wave to the movable body and the fixed body is set to be equal to or more than the total reflection angle of the sound wave of the medium and the movable body and the total reflection angle of the medium and the fixed body, respectively. An actuator utilizing acoustic radiation pressure according to claim 1. 3. An incident angle of a sound wave to the movable body and the fixed body is configured in a region excluding an angle which is a condition for exciting a surface acoustic wave on the surface of the movable body and the surface of the fixed body. An actuator utilizing acoustic radiation pressure according to claim 1.