CA1208269A

CA1208269A - Motor device utilizing ultrasonic oscillation

Info

Publication number: CA1208269A
Application number: CA000421908A
Authority: CA
Inventors: Toshiiku Sashida
Original assignee: Individual
Current assignee: Individual
Priority date: 1982-02-25
Filing date: 1983-02-18
Publication date: 1986-07-22
Also published as: FR2522216A1; DE3306755A1; IT8319758A0; DE3306755C2; FR2522216B1; BR8300874A; GB2120462A; US4562374A; IT1169116B; NL8300700A; CH665511A5; GB8304897D0; ES520082A0; ES8402734A1; GB2120462B; USRE33390E

Abstract

ABSTRACT

A motor device utilizing ultrasonic oscillation, which comprises an ultrasonic oscillator including an elastic body and one or more piezoelectric, electrostriction or magne-tostriction elements assembled in or on the elastic body, and a movable body movable in a fixed direction. A portion of the ultrasonic oscillator and a portion of the movable body are held pressed against each other. A progressive wave, which is generated on the surface of the elastic member and constituted by a longitudinal wave and a trans-verse wave, is converted to a uni-directional motion of the movable body.

Description

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FIELDS OF THE INVENTION
This invention relates to a motor device, in which a progressive wave produced on the surface of an ultrasonic oscillator is converted into a uni-directional motion of a movable body held pressed against the oscillator.

DESCRIPTION OF THE PRIOR ART
Prior art motor devices of various types used for a variety of purposes mostly utilize electromagnetic forces as their drive source. The size, weight and torgue of these devices, however, are limited by the material used. More particularly, the factors noted above are determined by the magnetic properties of the material used, and a device which is designed beyond the properties of the material cannot provide driving torgue.
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SUMMARY OF THE INVENTION
An object of the invention is to provide a small-size and light-weight motor device, in which high oscillation energy of an ultrasonic wave is converted to rotational or translational motion.
A more specific object of the invention is to provide a motor device, which utilizes a progressive wave produced on the surface of an ultrasonic oscillator including an elastic body and one or more pie~oelectric, electrostriction or magnetrostriction elements assembled therein or thereon.

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Fig. 1 is a fragmentary perspective view for explaining the operational principles underlying the invention;
Fig. 2 is a sectional view showing an embodiment of the 5invention;
~c; tl~dr Fig. 3 is a side view showing an osi~ a-tor;
Fig. 4 is a schematic sectional view taken along line A-A in Fig. 3;
Fig 5 is a side view showing an example of,~ressure 10adjustment mechanism;
Fig. 6 is a view for explaining elastic oscillation of the oscillator;
Fig. 7 illustrates the state of contact between oscillator and rotor;
15 Fig. 8A is a sectional view showing a different embodi-ment of the invention;
Fig. 8B is a schematic sectional view taken along line A-A in Fig. 8A;
FigO 9 illustrates the state of contact between 20oscillator and rotor;
Fig. 10A is a sectional view showing a further embodi-ment of the invention;
Fig. 10B is a schematic view showing the arrangement of piezoelectric member electrodes;
25 Fig. 11 is a perspective view showing a further embo-diment of the invention;

12(~8~6~3 1 Fig. 12 is a view showing a method of generating a uni-directional surface wave used for the embodiment of Fig. 12;
Fig. 13 is a view showing a linear motor using an endless elastic member;
Fig. 14A is a view showing a linear motor using a loop structure including couplers;
Fig. 14B is a view showing a linear motor using a loop structure including resonators;
Fig. 15 is a view showing a linear motor using a single linear elastic member and two oscillators;
Fig. 16 is a view showing an electrode arrangement for - producing a progressive wave on a rod-like elastic member with a piezoelectric member;
Fig. 17 and 19 are views showing the modiflcation of the arrangement of Fig. 16; and Fig. 18 is a view showing an electrode arrangement for producing a progressive wave on a rod-like elastic ~ember with oscillators.

DETAILED DESCRIPTION OF THE INVENTION
0 ~w~t~he operational principles and some preferred embodiments of the motor device according to the invention will be described with reference to the drawingsO Fig. 1 is a fragmentary perspective view illustrating the operational principles underlying the invention. There is shown an &df e,~c~pJe, elastic body,~e-~q., a metal, along the surface la of which is propagated a progressive wave, shown in an exaggerated ~2~

1 form, which is constituted b~ a longitudinal wave and a transverse wave~ Primarily, the progressive wave is a sur-face wave called Rayleigh wave. The existence ~f a wave propagated along the surface of an elastic body is made clear.
Elastic waves propagated through solids include longitudinal waves and transverse waves. Longitudinal and transverse waves can exist in a solid independently, but they are com-plicatedly combined in a complex manner at the surface according to boundary conditions thereof.
A Rayleigh wave can be produced by placing an oscillator, which can undergo longitudinal or transverse oscillation, on a medium plate and tapping the surface of the plate.
A surface wave can be observed at a position considerably spaced apart from the source of oscillation when the plate surface is tapped in whatever manner~ Alternatively, the progressive wave is produced due to elastic oscillation of a bar-like tor plate-like) elastic body. In this case, the wave is propagated along the surface o~ the body with the formation of elliptical particle trajectories having longi-tudinal and transverse components 90 degrees out of phasewith each other. In another case, thè progressive wave is a longitudinal wave propagated along the surface of a bar-like (or plate-like) elastic body. In this case, a trans-verse wave based on the Poisson ratio appears on the surface of the elastic body. Again in this case particle trajectories having longitudinal and transverse components 90 degrees out of phase with each other are formed.

1 In Fig. 1, no oscilla~ion source is shown, but only the state of propagation of the Rayreigh wave is shown. Here, a mass point B, for instance, is executing motion along an elliptical trajectory Q, which has a transverse component amplitude a (in the vertical directions) and a longitudinal component amplitude b (in the horizontal directions), in the direction of arrow M. The progressive wave is being propa-gated at the speed U of sound. In the state of Fig. 1, all points on the surface la of the elastic body are executing an identical motion. If a free body 2 is pressed against the surface la of the elastic body 1 in this state, the body

2 is in contact with the elastic body 1 only at the tops A, A'.... of the progressive wave.
Since the tops A, A'.... are moving in the direction of arrow M at an oscillation speed of v = 2~f b (wheref is the oscillation freguency), the free body 2 is driven in the direction of arrow N by the frictional forces between it and the elastic body 1.
The motor device according to the invention is based on the driving of a movable body with a progressive wave as discussed above, and it will now be described in conjunction with some preferred embodiments thereof. Fig. 2 is a sec-tional view showing one embodiment of the invention. A
casing 11 accommodates a cylindrical elastic oscillator 13, which has its node portion supported by a support 12.
The oscillator 13 has a tapered outer periphery 13a formed 6~
1 substantially in a central portion along its length.
The casing 11 also accommodates a rotor 14 which serves as a moving body. The rotor 14 has a tapered inner peripheral surface which is pressed agains-t the tapered outer peripheral surface 13a of the oscillator 13.
The rotor 14 is supported for axial movement on a shaft 15. Torque is transmitted from the rotor 14 to the shaft 15 via a pressure adjustment mechanism 16. The pressure adjustment mechanism 16 will be described later in detail with reference to Fig. 5. The shaft 15 is journalled in bearings 17.
The ~sclllator 13 includes electrostriction or piezoelectric elements 18 and 19 which are assembled as its i~termediate section and serve as a source of a progressive wave. Fig. 3 shows a side view of the oscillator 13, and Fig. 4 shows a section taken along line A-A in Fig~3. The electrostriction or piezoelectric elements 18 and 19 are capable o~ axial elongation and contraction as shown by arrows in Fig. 3. An electrode assembly 20 is sandwiched between the elements 18 and 19. The electrostriction or piezoelectric elements and the electrodes of the electrode assembly are arranged in a manner as shown in Fig.4. A
pair of diametrically opposed electrodes a and b are con-nected to a terminal 21. Another pair of electrodes c and d, which are also diametrically opposed, are connected to a terminal 22. Portions of the electrostriction or ~ i '~''^ .

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1 piezoelectric elements which are diametrically opposed to each other are adapted to undergo elongation or contraction in opposite directions. More particularly, portions o~ the electrostriction or piezoelectric elements 18 and 19 which are in contact with the electrode a are adapted to undergo expansion while their portions in contact with the electrode b are adapted to undergo contraction. Likewise, their por-tions in contact with the electrode d are adapted to und~ergo elongation while their portions in contact with the electrode c are adapted to undergo contraction.
Fig. 5 is a sectional view showing a specific example of the pressure adjustment mechanism 16 mentioned above.
The illustrated example is an automatic pressure adjustment mechanism. The mechanism includes a pair of special cams 23 and 24, which have opposed cam surfaces each consisting of a plurality of V-shaped valley portions arranged side by side, and steel balls 25 each received in each pair of V-shaped portions of the opposed cam surfaces. When there is no load, each steel ball is located to correspond to the bottom of the associated pair V-shaped valley portions. As torque is increased with applicatîon of load, the steel balls are displaced to force apart the opposed cam surfaces, thus generating an axial pressure. In this way, torque is transmitted from the rotor 14 to the shaft 15.
With the above construction, the oscillator 13 is caused to undergo elastic oscillation as shown in Fig. 6 by ~...

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l applying a high frequency voltage between it and the ter-minal 21, to which the electrodes a and b are connected as shown in Fig. 4. In the primar,v oscillation state as shown in Fig. 6, a central point B constitutes the loop while points H and K constitute the nodes of the oscillation. By applying a high frequency voltage which is 90 degrees out of phase with respect to the voltage applied to the electrodes a and b between the oscillator 13 and the other terminal 22, which is connected to the other electrodes c and d, an oscillation which is shifted in phase with respect to the afore-mentioned oscillation with the loop at the point B in the vertical direction (i.e., in the direction perpendicular to the plane of the Figure) is induced. The resultant wave of the longitudinal and transverse waves that are artifi-cially produced in the above manner constitutes rotating circular oscillation.
Figs. 7A to 7D show the state of contact between the outer periphery of the central portion 13b of the oscillator 13, which constitutes the loop of the oscillation, and the corresponding inner periphery 14a of the rotor 14 for indi-vidual quarters of one cycle. The inner periphery of the rotor 14 is in contact with the loop of the wave on the side of the oscillator 13, and the point of contacts completes one excursion along the inner periphery l~a of the rotor 14 for éach cycle. The speed of the mass point constituting the loop of the wave is proportional to the amplitude of the --` lZ(~
oscillation, and is oE the order of 0 to several m/sec. The oscillation generated on the side of the oscillator is con-verted into torque on the side of the rotor with the move-ment of the contact point for the following reason.
Comparing the circumferential length of the inner periphery 14a of the rotor 14 and that of the corresponding outer periphery 13b of the oscillator 13, the former is greater than the latter as is apparent from Fig. 7. When the contact point alters, the rotor 14 is thus shlfted with respect to the oscillator 13 by an amount corresponding to the difference between the circumferential lengths of the two. This amount of shift is taken out as rotation.
The dlrection of rotation can be reversed by inverting the phase of the high Erequency voltage applied to the electrodes a and b or c and d.
Fig. 8A i5 a sectional view showing a different embodi-ment of the invention, and Fig. 8B is a schematic sectional representation of the same taken along line A-A in Fig. 8A.
This embodiment comprises a ring-like elastic oscillator 33 accommoda-ted in a casing 31 and supported by a support. The ring-like el~stic oscillator 33 has a tapered lnner periphery 33a, which is in contact with a correspondlng outer periphery of rotor 34. The rotor 34 is supported for axial movement on a shaft 35. Torque is transmitted from the rotor 34 to the shaft 35 via a pressure adjustment mechanism 36, which has the same construction as that shown ,i ~ .

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1 in Fig. 5. Designated at 37 is an electrostriction or piezoelectric element, and at 38 bearings. As shown in Fig.
8B, in which the casing 31 is not shown, the electrostric-tion or piezoelectric element 37 is secured to the outer periphery of the ring-like elastic oscillator 33 which is an elastic body. The element is polarized such that it can undergo elongation and contraction in the directions of arrows, and it is provided with electrodes a to h. The electrodes a to d are connected to a terminal 39, while the electrodes e to h are connected to a terminal 40.
When a high frequency voltage is applied between the terminal 39 and the oscillator 33 while a high frequency voltaqe 90 degrees out of phase is applied between the ter-minal 40 and the oscillator 33, the oscillator 33 i9 caused to undergo bimorph type elastic oscillation. The frequency of this elastic oscillation is given as ~ _ E h2 n2 (n2 _ 1)2 - 24(1- ~2) ~a~ n2 ~ 1 where E is Young's modulus, ~is the Poisson ratio, a is the radius of the center circle, h is the peripheral wall thickness, n is the order number of the elastic oscillation, and fis the density of the material.
In this embodiment is n = 2, and Figs. 9A to 9D show the state of contact between the inner periphery of the rotor oscillator and the outer periphery of the rotor 34 for individual quarters of one cycle. The point of contact bet-~Z~ 6~
1 ween the oscillator and rotor constitutes the loop of the wave. The loop completes one half excursion for each cycle of oscillation. The oscillation generated on the oscillator 33 is transmitted as torgue to the rotor 34 with the move-ment of the contact point as discussed earlier in connectionwith Fig. 7.
Fig. lOA is a sectional view showing a further embodi-ment of the invention, and Fig. lOB is a view showing the arxangement of electrodes provided on a piezoelectric member. In this embodiment, high frequency voltages 90 degrees out of phase from each other, which are provided from respective independent circuits, are applied to respec-tive electrode terminals a and b to excite the piezoelectric member 52. An elastic ring 51 can undergo bimorph oscilla-tion to produce a surface wave as the resultant of a longi-tudinal wave and a transverse wave, the surface wave being propagated along the surface 51a of the elastic ring Sl~ A
rotor 53 which is held pressed against this surface receives the driving torgue. The electrode arrangement and polariza-tion of the piezoelectric member are shown in Fig. lOB.Here, the pitch of the electrode arrangement is set to one half the wavelength of the surface wave, and the polariza-tion of the piezoelectric member is shown as plus and minus signs (electrode groups A and B being shifted in position by an amount corresponding to a quarter of the wavelength).
The individual terminals a and b are connected to terminals 3L2~

1 a and b of respective distinct circults. With the above construction, by applying high frequency voltages 90 degrees out of phase from each other to the respective terminals a and b, a progressive wave is formed on the surface of the elastic ring 51.
Fig. 11 shows a further embodiment of the invention applied to a linear motor, in which ultrasonic oscillation is converted to translational motion. As is shown, elastic members 62 are held pressed against the surface o~ a plate-like member 61. A piezoelectric member 63 is cemented to part of the surface of each elastic member 62. A surface /2 ,~h wave (or ~y-r~i-gh wave) thus can be produced on the elastic member 62. The elastic member 62 has smoothly curved ends 62a so that the surface wave can be propagated along the surface of the elastic member 62 continuously to cause move-ment of the plate-like member 61 in the direction of arrow W.
Fig. 12 shows a method of generating a uni-directional surface wave used for the preceding embodiment. A plurality of electrodes 92 are cemented to the surface of a piezoelectric member 91 and are connected through three dif-ferent circuits to a phase shifter 93. By applying high frequency voltages with respective phases of 0, 120 and 240 degrees to the respective circuits, a uni-directional sur-face wave can be generated on the piezoelectric member 91.
Fig. 13 shows a modification of the previous embodiment 1 of Fig. 11. Here, a plate-like member 72 is held pressed against the surface of an endless bar-like elastic member 71~ A plurality of piezoelectric members 73 are secured to other part of the elastic member 71. With this construc-tion, the endless bar-like elastic member 71 can be caused to undergo elastic oscillation to generate a wave. ~he wave h~ is propagated and circulated ~ progressive wave along the elastic member 71.
Fig. 14A shows a further example of the linear motor.
Here, two bar-like elastic members 76 and 77 are secured to each other by couplers 78 and 79. Plate-like members 80 are held pressed against the bar-like elastic member 76~ A
plurality of piezoelectric members 81 is secured to the other abar-like elastic member 77. With this construction, the piezoelectric members 81 can cause elastic oscillation of the bar-like elastic member 77. The progressive wave thus produced is converted to a longitudinal oscillation of the coupler ~ provided at one end of the elastic member 77.
This longitudinal oscillation is converted to elastic oscillation of the bar-like elastic member 76 to be propa-gated as progressive wave along the bar-like elastic member 76. This progressive wave is transmitted back to the bar-like elastic member 76 through the coupler 79.
Fig. 14B shows a further example of the linear motor.
Here, two bar-like elastic members 76 and 77 are secured to each other by resonators 82 and 83. Plate-like members~80 ., lZI)~269 are held pressed against the bar-like elastic member 76. A
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plurality of piezoelectric members 81 are ~er-ve~ to the other bar-like elastic member 77. With this construction, the piezoelectric members 81 can cause elastic oscillation of the bar-like elastic member 77, and the progressive wave thus produced is converted to a longitudinal oscillation o the resonator 88 provided at one end of the bar-like elastic member 77. The longitudinal oscillation is converted to elastic oscillation of the bar-like elastic member 76 to be propagated as progressive wave along the bar-like elastic member 76. This progressive wave is transmitted back to the bar-like elastic member 77 through the resonator 83.
The coupler and resonator as mentioned above are dif-ferent in their function as follows.
The coupler serves to convert the elastic oscillation of the bar-like elastic member into longitudinal oscillation or vice versa. Its material and dimensions are restricted ~ C~'lS~ ~' e, by *e~ust-i-ca-l~impedance matching problems. However, its shape is simple so that its size reduction and cost reduc-tion can be readily obtained.
The resonator, while it serves the same role as the coupler, permits comparatively free selection of the acoustic impedance matching and has higher oscillation energy transmission capacity. However, its shape is compli-cated, and it is necessary to match its characteristic fre-quency to the oscillation frequency of the oscillation source. For the above reasons, it is rather expensive.
Fig. 15 shows a further example of the linear motor.
Here, plate-like members 89 are held pressed against the surface of a bar-like elastic member 86, to which oscilla-tors 87 and 88 are coupled. With this construction, the oscillator 87 can cause elastic oscillation of the bar-like elastic member 86. The oscillator 88 absorbs the oscilla-tion of the progressive wave thus produced and converts it to electric energy to be recovered or fed back to the oscillator 87, Fig. 16 shows a further embodiment,in which a piezoelectric member 87 is secured to a bar-like (or plate-like) elastic member 96. The piezoelectric member 87 is provided with electrodes which are connected to distinct circuits (A and B). The piezoelectric member is polarized with respect to the elastic member 96 in opposite directions of arrows M and M' perpendicular to the plane o~ paper for every quarter of the wavelength. By applying high frequency voltages 90 degrees out of phase with each other to the respective electrode groups A and B, the bar-like elastic member 96 is caused to undergo elastic oscillation to pro-duce a uni-directional progressive wave.
Fig; 17 and 19 show modifications of the embodiment of Fig. 16. Here, electrode groups A' and B' for respective piezoelectric members 97a and 97b are provided in separate positions. The piezoelectric members 97a and 97b are 12~)8~ 3 i polarized in opposite directions of arrows M and M' for every half one half of the wavelength. The piezoelectric members ~7a and 97b are spaced apart or staggered center-to-center by a distance corresponding to l/4 plus n/2 ~n being an integral number) of the wavelength.
Fig. 18 shows a ferther modification of the embodiment of Fig. 16. Here, two oscillators 98 and 99 are secured to a bar-like (or plate-like) elastic member 96 via respective couplers lO0 and 101. The oscillators 98 and 99 are again spaced apart center-to-center by a distance corresponding to l/4 plus n/2 (n being an integral number) of the wavelength.
By applying high frequency voltages '~0 degrees out of phase with one another to the respective oscillators 98 and 99, the bar-like elastic member 96 is caused to undergo elastic oscillation to produce a uni-directional progressive wave.
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While the above embodiments ~ concerned with oscillators including or consisting of piexoelectric ele-ments, these elements may be replaced with electrostriction or magnetostriction elements.
As has been described in the foregoing in connection with the operational principles and some preferred embodi-ments, the motor device accordiny to the invention, unlike the prior art motor devices of various types, utilizes ultrasonic oscillation, i.e., a progressive wave produced on the surface of an elastic body by a piezoelectric, electrostriction or magnetostriction element assembled as 38X:~
oscillator in or on the elastic body. More particularly, the device makes use of a revolutional system of producing a progressive wave where particle trajectories are elliptical with high oscillation energy of an ultrasonic wave and con-verting the progressive wave into rotational or transla-tional motion of a moving body. The motor device thus can provide high driving torque while it is small in size and light in weight, so that it can find very extensive applica-tions.

Claims

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A motor device utilising ultrasonic oscillation com-prising:
an ultrasonic oscillator including an elastic member provided with one or more transducer elements capable of producing a progressive wave on the surface of said member; and a movable body having a portion in contact with a portion of said elastic member and movable in a fixed direction, wherein a progressive wave produced on the surface of said elastic member and having longitudinal and transverse components is converted to uni-directional motion of said movable body.

2. A motor device according to claim 1, in which a plurality of such elements is arranged to produce a Rayleigh wave on the surface of said elastic body.

3. A motor device according to claim 1, in which a plu-rality of such elements is arranged to cause elastic oscillation of the elastic member to produce said pro-gressive wave on the surface of said elastic member.

4. A motor device according to claim 1, in which a plurality of such elements is arranged to cause said elastic member to produce a longitudinal wave component, said transverse component being produced according to Poisson's ratio of said elastic member.

5. A motor device according to claim 1, wherein said movable body is a cylindrical rotor held in contact with said ultrasonic oscillator, the progressive wave produced on the surface of said ultrasonic oscillator being converted to uni-directional rotational motion of said rotor.

6. A motor device according to claim 5, wherein a central portion of said ultrasonic oscillator is held in contact with an inner peripheral portion of said rotor.

7. A motor device according to claim 6, wherein the central portion of said ultrasonic oscillator has a tapered outer periphery, the device further comprising a shaft, said rotor being supported for axial movement on said shaft, and a pressure adjustment mechanism for trans-mitting torque from said rotor to said shaft.

8. A motor device according to claim 7, in which the inner peripheral portion of said rotor defines an open end, the shaft extending through an opposite end of the rotor and the ultrasonic oscillator, and having an end region supported in a bearing.

9. A motor device according to claim 1, wherein said ultrasonic oscillator includes a pair of such elements with an electrode assembly sandwiched therebetween in an inter-mediate section of said elastic member.

10. A motor device according to claim 1, wherein said element or elements is/are capable of expansion and con-traction in an axial direction.

11. A motor device according to claim 9 or 10, wherein said electrode assembly has two or more electrode pairs arranged around the periphery of a circle, each pair con-sisting of diametrically opposed electrodes, the electrodes in each pair being connected to respective independent terminals, diametrically opposed portions of said elements being thereby capable of being expanded and contracted respectively..

12. A motor device utilizing ultrasonic oscillation according to claim 1, in which said ultrasonic oscillator is a ring-like oscillator having a tapered inner periphery the outer periphery of said ring-like oscillator being provided with such an element, in which said movable body is a cylindrical rotor having an outer periphery held pressed against said tapered inner periphery of said ring-like oscillator, and which further comprises a shaft, said rotor being supported for axial movement on said shaft, and a pressure adjustment mechanism for transmitting torque from said rotor to said shaft.

13. A motor device according to claim 12, wherein the outer periphery of said ring-like oscillator is provided with a circumferentially polarized element as said such element.

14. A motor device according to claim 1, wherein said ultrasonic oscillator includes a ring-like elastic member with one or more such elements assembled in or on said ring-like elastic member and connected to two or more distinct circuits, and said movable body is a rotor disposed in and held pressed against said ring-like elastic member, a progressive wave produced on the surface of said ring-like elastic member and constituted by a longi-tudinal wave and a transverse wave being converted to uni-directional rotational motion of said rotor.

15. A motor device according to claim 14, which further comprises a shaft, said rotor, ring-like elastic member and one or more such elements being disposed coaxially on said shaft in the mentioned order, a pressure adjustment mechanism, said shaft having one end supported in a bearing through said pressure adjustment mechanism, and a casing accommodating all the components.

16. A motor device utilizing ultrasonic oscillation according to claim 14, which further comprises a shaft, said rotor, ring-like elastic member and one or more such elements being disposed coaxially on said shaft in the mentioned order, and in which said ultrasonic oscillator further includes an electrode assembly provided on said elements, said electrode assembly having an even number of electrodes alternately connected to two independent terminals, the electrodes connected to one of said terminals receiving a voltage which is 90 degrees out of phase with respect to the electrodes connected to the other of said terminals.

17. A motor device according to claim 5, wherein said pressure adjustment mechanism is provided between said shaft and said rotor and has a cam and plurality of steel balls.

18. A motor device according to claim 17, wherein said pressure adjustment mechanism is an automatic pressure adjustment mechanism, which has a pair of cams having opposed cam surfaces each consisting of a succession of V-shaped portions, steel balls being received in associated V-shaped portions of the pair of cam surfaces.

19. A motor device according to claim 1, wherein said movable body is a plate-like member movable in a fixed direction, and said ultrasonic oscillator includes one or more elastic members held pressed against said plate-like member and one or more such elements secured to said elastic member or members and connected to two or more distinct circuits, high frequency voltages having different phases being applied to said respective distinct circuits to produce a progressive wave on the surface of said elastic member or members and constituted by a longitudinal wave and a transverse wave for causing translational motion of said plate-like member in said fixed direction.

20. A motor device according to claim 1, wherein said ultrasonic oscillator includes a bar-like elastic member, one or more such elements being secured to said bar-like elastic member and connected to two or more distinct circuits, and said movable member is a plate-like member

Claim 20 continued....

held pressed against a different portion of said bar-like elastic member to the portion to which said element or elements is/are secured, high frequency voltages of different phases being applied to said respective distinct circuits to generate a progressive wave constituted by a longitudinal wave and a transverse wave on the surface of said bar-like elastic member, said progressive wave being converted to a uni-directional motion of said plate-like member.

21. A motor device according to claim 20, wherein said bar-like elastic member is endless.

22. A motor device according to claim 1 or 3, wherein said ultrasonic oscillator includes two bar-like elastic members secured to each other by coupler means and a plurality of such elements secured to one of said bar-like elastic members, and said movable body is a plate-like member held pressed against the other one of said bar-like elastic members, a progressive wave generated on the surface of said bar-like elastic members and constituted by a longitudinal wave and a transverse wave being con-verted to uni-directional motion of said plate-like member.

23. A motor device according to claim 1 or 3, wherein said ultrasonic oscillator includes two bar-like elastic members secured to each other by resonator means and a plurality of such elements secured to one of said bar-like

Claim 23 continued...

elastic members, and said movable body is a plate-like member held pressed against the other one of said bar-like elastic members, a progressive wave generated on the surface of said bar-like elastic member and constituted by a longitudinal wave and a transverse wave being converted to a uni-directional motion of said plate-like member.

24. A motor device according to claim 1, 3 or 4, wherein said movable body is a plate-like member, and said ultra-sonic oscillator includes a bar-like elastic member, said plate-like member and said one or more elements being arranged on said bar-like elastic member.

25. A motor device according to claim 20, in which there is a plurality of such elements secured to one surface of said bar-like elastic member and polarised in a distinct manner for every quarter of the wavelength of a pro-gressive wave generated on the surface of said bar-like elastic member as a result of elastic oscillation thereof.

26. A motor device according to claim 20, in which there is a plurality of such elements secured to one surface of said bar-like elastic member and polarised in a distinct manner for every one half of the wavelength of a progressive wave generated on the surface of said bar-like elastic member as a result of elastic oscillation thereof, said elements being arranged with a center-to-center interval corresponding to 1/4 plus n/2 of the wavelength.

27. A motor device according to claim 20, in which there is a plurality of such elements secured to one surface of said bar-like elastic member through respective couplers and arranged with a center-to-center interval corresponding to 1/4 plus n/2 of the wavelength of a progressive wave generated on the surface of said bar-like member as a result of elastic oscillation thereof.

28. A motor device according to claim 1, wherein said ultrasonic oscillator includes an endless elastic member and a plurality of such elements secured to the surface of said endless elastic member, a progressive wave pro-duced on said endless elastic member by elastic oscillation thereof and constituted by a longitudinal wave and a transverse wave being converted into a uni-directional motion of said movable body.