United States Patent (19) 11 Patent Number: 5,066,884 Takagi Et Al

United States Patent (19) 11 Patent Number: 5,066,884 Takagi et al. 45) Date of Patent: Nov. 19, 1991

(54) ULTRASONIC MOTOR HAVING HIGH 59-111609 10/1984 Japan. DRIVE EFFICIENCY 60-96183 4/1985 Japan. 60-245482 12/1985 Japan. 75 Inventors: Tadao Takagi, Yokohama; Daisuke 0203872 9/1986 Japan ...... 310/323 Saya, Urayasu; Shigehisa Nemoto, 62-77068 3/1987 Japan . Kamagaya, all of Japan 62-247775 10/1987 Japan ...... 310/323 73 Assignee: Nikon Corporation, Tokyo, Japan 63-73887 4/1988 Japan ...... 310/323 Primary Examiner-Mark O. Budd (21) Appl. No.: 475,000 Attorney, Agent, or Firm-Shapiro and Shapiro (22) Filed: Feb. 5, 1990 (57) ABSTRACT 30 Foreign Application Priority Data An ultrasonic motor has a stator having a piezoelectric Feb. 10, 1989 JP Japan ...... 1-32085 member vibrated by a drive signal, and an elastic mem Mar. 1, 1989 JP Japan ...... 150711 ber for generating traveling vibration wave in a drive Sep. 16, 1989 JP Japan ...... 1-240375 surface thereof upon vibration of the piezoelectric Oct. 12, 1989 (JP) Japan ...... 1-265793 member, a rotor which is urged against the drive sur Dec. 21, 1989 JP Japan ...... 1.332299 face of the elastic member and is driven by the gener ated traveling vibration wave, a support member inte 51) int. C...... HO1 41/08 grally molded on the elastic member, and a fixing mem 52 U.S. Cl...... 3.10/323 ber for holding the support member. In the ultrsonic 58) Field of Search ...... ------310/323, 328 motor, one end face of the support member is formed at (56) References Cited the same level as the drive surface or the junction sur U.S. PATENT DOCUMENTS face of the elastic member, an electrode of the piezo electric member is grounded through the support mem 4,634,915 l/1987 Mukoujima et al...... 310/323 ber, a plurality of holes are regularly formed in the 4,645,964 2/1987 Hiramatsu et al...... 310/323 circumferential direction of the support member, or the 4,937,488 6/1990 Fujie et al...... 310/323 support member is fixed to the fixing member by an FOREIGN PATENT DOCUMENTS adhesive, thereby improving drive efficiency. 59-178988 1/1984 Japan. 59-213286 3/1984 Japan . 23 Claims, 8 Drawing Sheets

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5,066,884 1. 2 ture. A stator 10 is constituted by adhering an annular ULTRASONIC MOTOR HAVING HIGH DRIVE elastic member 11 and an annular piezoelectric member EFFICIENCY 12. A plurality of electrodes 13 (FIG. 11) are formed on the upper surface of the piezoelectric member 12, and BACKGROUND OF THE INVENTION electrodes 14a to 14d are also formed on its lower sur 1. Field of the Invention face. The elastic member 11 is adhered to the piezoelec The present invention relates to an ultrasonic motor tric member 12 so as to be electrically connected to all having high drive efficiency, which causes a stator to the electrodes 13. These electrodes are magnetized to generate a traveling vibration wave, thereby driving a alternately have opposite polarities. One-end portions rotor. More particularly, the present invention relates 10 of lead wires 15 and 16 are respectively soldered to the to an ultrasonic motor having high drive efficiency, electrodes 14a and 14b. An AC voltage is applied to the which causes an elastic member to generate a traveling electrodes 14a and 14b through these lead wires 15 and vibration wave upon vibration having a vibration fre 16. The other end of a lead wire 17, one end of which is quency in an ultrasonic range of a piezoelectric mem grounded, is soldered to the electrode 14c. The elec ber, thereby driving a rotor. 15 trode 14c is electrically connected to the elastic member 2. Related Background Art 11 through a conductive adhesive 18. The structure of a conventional ultrasonic motor is In the above-mentioned structure, all the electrodes disclosed in, e.g., JP-A-62-77068. FIG. 6 is a sectional 13 are grounded through the elastic member 11, the view of the ultrasonic motor. A stator 1 is constituted conductive adhesive 18, the electrode 14c, and the lead by integrally fixing a piezoelectric member 1b to an 20 wire 17. Therefore, when an AC voltage is applied to elastic member 1a. A radial support member 3 is inte the electrodes 14a and 14b, this is equivalent to apply a grally molded on an inner peripheral surface of the voltage to the widthwise direction of the piezoelectric elastic member 1a near a neutral axis of the stator 1 as a member 12. When a predetermined AC voltage is ap whole. The support member 3 has a thin plate portion plied to the electrode 14a through the lead wire 15, and 3a provided to the inner peripheral surface of the elastic 25 an AC voltage having a 90° phase difference from the member 1a, and a thick portion 3b provided on the predetermined voltage is applied to the electrode 14b peripheral edge of the thin plate portion 3a and having through the lead wire 16, the piezoelectric member 12 is a larger thickness than that of the thin plate portion 3a. A technique for integrally molding the support member vibrated by these applied voltages. Upon this vibration, to the elastic member in this manner is also disclosed in, 30 a traveling vibration wave is generated in a drive sur e.g., JP-A-59-213286. The thick portion 3b is fixed in a face 11a of the electric member 11. case 5 which receives a bearing 4. However, in this structure, the elastic member 11 and A flange portion 6a radially projects from the inner the electrode 14c are electrically connected through the periphery of the rotor 2, and a thick portion 6b is inte conductive adhesive 18 to ground the electrodes 13. grally molded on the peripheral edge of the flange por 35 Therefore, the adhesive 18 is degraded by vibration of tion 6a. A compression force by a given means (not the elastic member 11 in resulting in a grounding error shown) is applied to the thick portion 6b through a of the electrodes 13. Since ultrasonic vibration has a bearing 7, so that a lower surface 8 of the rotor 2 is high frequency, it has a peeling effect as demonstrated urged against a drive surface 1c of the elastic member in ultrasonic washing. Thus, the ground lead wire 17 1a. 40 may be directly connected to the elastic member 11 When an AC voltage is applied to the piezoelectric through a screw or the like so as not to disconnect the member 1b, the piezoelectric member 1b causes bending lead wire 17. However, undesirable vibration occurs in vibration, and a traveling vibration wave is generated in the connected portion due to the weight of the screw, the elastic member 1a. This vibration wave frictionally and as a result, smooth driving is disturbed. drives the rotor 2. The generation mechanism of the 45 In some motors, as disclosed in Japanese Patent Laid traveling vibration wave is described in detail in JP-A- Open (Kokai) No. 59-178988, a comb-like groove is 60-24.5482 and a description thereof will be omitted. formed in the drive surface of the elastic member to In the above structure, when the thick portion 3b of improve drive efficiency. the support member 3 is fixed by a pressing 40 and a As a support method of the stator, the following fixing cylinder 50 or their equivalents shown in FIG. 2, 50 methods are known: the following problems are posed. If a lower end face 3c (1) A method of supporting the stator by arranging a of the thick portion 3b of the support member 3 is not shock absorber such as a felt on the lower surface of the flat, when the thick portion 3b is fixed by the pressing 40 piezoelectric member; and the fixing cylinder 50 shown in FIG. 2, an internal (2) A method of supporting the stator by arranging a stress is generated in the elastic member 1a, thus de 55 flange-like support member extending from an outer or creasing drive efficiency of the ultrasonic motor. On the inner peripheral surface of the stator near a neutral other hand, if a junction surface 1d of the elastic mem surface and clamping the support member by fixing ber 1a contacting the piezoelectric member 1b is not members; and flat, when the piezoelectric member 1b is fixed to the (3) A method of supporting the stator by arranging a elastic member 1a, an internal stress is generated in the 60 plurality of rod-like sub vibration members radially elastic member 1a, and also decreases drive efficiency of extending from the outer or inner peripheral surface of the ultrasonic motor. As shown in FIG. 6, when the the stator near a neutral surface, and placing the distal lower end face 3c of the thick portion 3b and the junc ends of the vibration members on the support member, tion surface 1d of the elastic member a do not exist on as disclosed in Japanese Patent Laid-Open (Kokai) No. the same plane, it is almost impossible to simultaneously 65 60-96.183 (corresponding to U.S. Pat. No. 4,634,915). polish these surfaces. However, in the method (1) of supporting the stator The structure of a conventional stator is disclosed in, by the felt, the felt has poor weather resistance, and a e.g., JP-A-60-245482. FIGS. 10 and 11 show this struc drive condition largely changes due to aging of the felt, 5,066,884 3 4. resulting in poor reliability. In the method (2) of sup invar material, and a slider member of the rotor is porting the stator by the flange, since a bending strength formed of a material containing polytetrafluoroethylene of the flange portion cannot be lowered, drive effi (PTFE), thereby decreasing wear of the slider member ciency is decreased. In addition, in the method (3) of of the rotor and increasing a durability-limit rotation supporting the stator by the rod-like sub vibration mem 5 count. In addition, the slider member can be prevented bers, since a large number of rod-like sub vibration from being stuck to the elastic member due to an in members having a small width and thickness must be crease in temperature or humidity. In this manner, the arranged to have high dimensional precision, and are durability and weather resistance of the rotor are im difficult to work, resulting an expensive structure. If proved to improve drive efficiency of the ultrasonic each rod-like sub vibration member is thick, its mechan 10 notor. ical strength is increased, and the vibration of the stator In order to achieve the objects of the present inven is externally transmitted through the support member, tion, there is also provided an ultrasonic motor in which resulting in generation of noise. a first electrode is arranged on a surface of a piezoelec tric member on a side contacting an elastic member, a SUMMARY OF THE INVENTION 15 It is an object of the present invention to improve second electrode is arranged on an opposite surface, the drive efficiency of an ultrasonic motor by reducing an first electrode is grounded through the elastic member, internal stress generated in an elastic member when a and an AC voltage is applied to the second electrode to support member of the elastic member is clamped and vibrate the piezoelectric member, comprising ground fixed by fixing members. ing means for grounding the first electrode through a It is another object of the present invention to im support member integrally formed on the outer or inner prove drive efficiency of an ultrasonic motor by im peripheral surface of the elastic member. With this proving durability of a slider member of a rotor which structure, when the piezoelectric member vibrates and a is frictionally driven on an elastic member and by im traveling vibration wave is generated in the elastic proving weather resistance caused by a change in envi 25 member, a grounding error of the first electrode can be ronmental condition such as a temperature, humidity, prevented, thus improving drive efficiency of the ultra and the like. sonic motor. It is still another object of the present invention to In order to achieve the object of the present invention improve drive efficiency of an ultrasonic motor by in an ultrasonic motor of the present invention, a plural preventing a grounding error of electrodes formed on a 30 ity of holes are regularly formed in a circumferential stator caused by unnecessary vibration generated in an direction in a support member which is integrally elastic member. formed on a side surface of an elastic member. In addi It is still another object of the present invention to tion, in the ultrasonic motor of the present invention, a improve drive efficiency of an ultrasonic motor and to comb-like groove is formed in the elastic member, and prevent generation of noise by decreasing a bending 35 a plurality of holes are periodically formed in the sup strength of a support member of an elastic member to port member integrally formed on the side surface of improve a vibration condition of the elastic member. the elastic member in association with the cycle of the It is still another object of the present invention to comb-like groove. Thus, the bending strength of the improve drive efficiency of an ultrasonic motor and to support member can be decreased, and the vibration prevent generation of noise by eliminating a support condition of the elastic member is improved. Therefore, loss of a support member of an elastic member. drive efficiency of the ultrasonic motor can be im In order to achieve the above objects, according to proved, and generation of noise can be prevented. the present invention, there is provided an ultrasonic Furthermore, in order to achieve the objects of the motor having a stator consisting of a piezoelectric mem present invention, there is also provided an ultrasonic ber and an elastic member, a rotor which is brought into 45 motor in which a support member integrally arranged contact with the stator under pressure, a support mem on a side surface of an elastic member is clamped and ber for holding the stator, and a fixing member, the fixed by a pressing and a fixing cylinder, wherein the support member consisting of a thin plate portion and a support member is adhered to at least one of the press thick portion being integrally molded on an outer or ing and the fixing cylinder by an adhesive. With this inner peripheral surface of the elastic member, wherein 50 structure, the support loss of the support member can be one end face of the thick portion is formed at the same eliminated, thus improving drive efficiency of the ultra level as a drive surface or a junction surface of the sonic motor, and preventing generation of noise. elastic member with the piezoelectric member. Thus, the junction surface of the elastic member with the BRIEF DESCRIPTION OF THE DRAWINGS piezoelectric member and one end face of the thick 55 FIGS. 1 and 2 show an embodiment of an ultrasonic portion of the support member can be simultaneously motor according to the present invention, in which polished. The drive surface of the elastic member and FIG. 1 is an exploded sectional view of the motor, and the other end face of the thick portion of the support FIG. 2 is a sectional view of the motor after assembly; member can be simultaneously polished. Therefore, the FIG. 3 shows an amplitude of a vibration wave acting junction surface of the elastic member and one end face on an elastic member and a support member in the em of the thick portion, or the drive surface of the elastic bodiment shown in FIGS. 1 and 2; member and the other end face of the thick portion can FIG. 4 is a sectional view showing another embodi be kept flat. Even if the thick portion is clamped and ment of an elastic member and a support member consti fixed by the fixing members, no internal stress is gener tuting an ultrasonic motor according to the present ated in the elastic member, thus improving drive effi 65 invention; ciency of an ultrasonic motor. FIG. 5 is a sectional view showing another embodi In order to achieve the objects of the present inven ment of an ultrasonic motor according to the present tion, the elastic member of the stator is formed of an invention; 5,066,884 5 6 FIG. 6 is a sectional view showing a structure of a the rotor base 21. A lower surface P6 of the slider mem conventional ultrasonic motor; ber 22 is polished to the same flatness as that of the drive FIG. 7 is a sectional view showing still another em surface P1 after the slider member 22 is adhered to the bodiment of an ultrasonic motor according to the pres rotor base 21, so that the lower surface P6 can be in ent invention; uniform contact with the drive surface P1 of the elastic FIG. 8 is a sectional view showing another embodi member 101. ment of a stator, a support member, and a fixing member As shown in FIG. 2, after the piezoelectric member constituting the ultrasonic motor according to the pres 102 is adhered to the junction surface P2 of the elastic ent invention; member 101, the pressing 40 is threadably engaged with FIG. 9 is a sectional view showing still another em 10 the fixing cylinder 50, so that the upper and lower end bodiment of an ultrasonic motor according to the pres faces P4 and P3 of the thick portion 32 of the support ent invention; member 30 are clamped between a surface P7 of the FIGS. 10 and 11 show a structure of a conventional fixing cylinder 50 and the surface P5 of the pressing 40. stator, in which FIG. 10 is a perspective view thereof, In this case, since the lower end face P3 of the thick and FIG. 11 is a sectional view thereof; 5 portion 32 and the surface P5 of the pressing 40 have FIGS. 12 and 13 are perspective views showing an been polished, even if the surface P7 of the fixing cylin other embodiment of a rotor a stator and a support der 50, which is difficult to be polished, is merely member constituting the ultrasonic motor according to lathed, i.e., even if the surface P7 does not have high the present invention; flatness, the flatness of the drive surface P1 of the elastic FIG. 14 shows an amplitude of a vibration wave 20 member 101 will not be degraded. acting on the stator and the support member in the In this embodiment, the pressing 40 has a larger thick embodiment shown in FIG. 13; - ness than that of a surface P7 portion of the fixing cylin FIGS. 15A to 15G show patterns of a comb-like der 50, and the thick portion 32 of the support member groove and a plurality of holes formed in the elastic 30 is clamped by the pressing 40 and the fixing cylinder member and the support member in the embodiment 25 50, so that the influence of the stress acting on the elas shown in FIG. 13; and tic member 101 is determined by a contact state be FIG. 16 is a sectional view showing another structure tween the surface P5 of the pressing 40 and the surface of holes formed in the support member in the embodi P3 of the thick portion 32. ment shown in FIG. 13. The slider member 22 is adhered to the rotor base 21, 30 and the lower surface P6 of the slider member 22 is DESCRIPTION OF THE PREFERRED urged against the drive surface P1 of the elastic member EMBODIMENTS 101 by a pressing member (not shown). An embodiment of the present invention will be de When an AC voltage (drive signal) is applied to the scribed hereinafter with reference to FIGS. 1 to 3. piezoelectric member 102 in this state, the piezoelectric FIG. 1 is an exploded sectional view of an ultrasonic 35 member 102 causes bending vibration, and a traveling motor according to the present invention, and FIG. 2 is vibration wave is generated in the drive surface of the a sectional view thereof after assembly. A stator 100 is elastic member 101. Thus, the vibration wave drives the constituted by a ring-like elastic member 101, and a rotor 20. In this case, the amplitude of the vibration ring-like piezoelectric member 102 adhered to a junc wave acting on the support member 30 and the elastic tion surface P2 of the elastic member 101. A drive sur member 101 is as shown in FIG. 3. More specifically, face P1 of the elastic member 101 has a flatness toler since the thick portion 32 is fixed at a contiguous por ance of 0.5um or less by polishing. A radial flange-like tion between the thin plate portion 31 and the thick support member 30 is integrally formed on the elastic portion 32, the amplitude is almost zero, and the ampli member 101 by cutting the elastic member 101 from its tude of the thin plate portion 31 is increased as getting outer peripheral surface near a neutral surface of the 45 closer to the elastic member 101. The amplitude near stator 100 as a whole. The support member 30 has a the central portion of the elastic member 101 is maxi 0.3-mm thick thin plate portion 31 contiguous with the mum. Therefore, even if the thick portion 32 having a outer peripheral surface of the elastic member 101, and large thickness is arranged, drive efficiency of the ultra a thickportion 32 contiguous with the thin plate portion sonic motor will not be decreased as compared to that 31. The thickness of the thick portion 32 is sufficiently 50 of a conventional motor. larger than that of the thin plate portion 31. In this Since the junction surface P2 of the elastic member embodiment, a lower end face P3 of the thick portion 32 101 and the end face P3 of the thick portion 32 are at the is at the same level as the junction surface P2 of the same level, the end face P3 can be simultaneously pol elastic member 101. ished upon polishing of the junction surface P2. As a The junction surface P2 of the elastic member 101 55 result, efficiency of a polishing operation can be im must be finished to have the same flatness as that of the proved. More specifically, in polishing, a member to be drive surface P1 by polishing since it must be electri worked is polished while rotating it on a polishing plate cally connected to all the electrodes of the piezoelectric which is finished to have high flatness. In order to pol member 102 when it is adhered to the piezoelectric ish the surfaces P2 and P3 with steps, a work of a sur member 102. In this embodiment, since the junction face at a lower step is difficult and inefficient. In this surface P2 and the lower end face P3 of the thick por embodiment, since the surfaces P2 and P3 can be simul tion 32 are at the same level, the end face P3 can be taneously polished in a single polishing operation, it is simultaneously polished upon polishing of the junction very efficient as compared to a case wherein surfaces P2 surface P2. In addition, a surface P5 of the pressing 40, and P3 are worked with steps, and easy mass-produc which is brought into contact with the polished end 65 tion can be expected. face P3 is also subjected to polishing. FIG. 4 shows another embodiment wherein a thick A rotor (movable element) 20 comprises a ring portion 35 of a support member 33 also projects on the shaped rotor base 21, and a slider member 22 adhered to side of the drive surface P1 of the elastic member 101, 5,066,884 7 8 and its upper end face P40 is worked at the same level TABLE as the drive surface P1. In this case, the end face P40 can be simultaneously polished when the drive surface No. Slider Member Composition P1 is polished. In this case, the positions of the pressing Bismaeinide Triamine Resin - Kevlar Fiber Polyester Resin + Kevlar Fiber 40 and the fixing cylinder 50 are reversed to hold the Epoxy Resin -- Kevlar Fiber stator 100. More specifically, the surface P5 of the Polyamideimide Resin + PTFE (3 wt.%) + pressing 40 is in contact with the upper end face P40 of Graphite (12 wt.%) the thick portion 35. When the thick portion 35 is Ekonol E101 (70 wt.%) + PTFE (30 wt.%) PTFE (80 wt.%) + Glass Fiber (15 wt.%) + clamped by the pressing 40 and the fixing cylinder 50, Molybdenum Disulfide (5 wt.%) no internal stress is generated in the elastic member 101. 10 In the above embodiment, the support member is PTFE: Polytetrafluoroethylene formed on the outer peripheral surface of the elastic member. However, as shown in FIG. 5, a support mem TABLE 2 ber 36 may be formed on an inner peripheral surface of Maximum the elastic member 101. In this case, a thick portion 38 15 Efficiency Djurability-Limit of the support member 36 is clamped and fixed by a No. (%) Wear Rotation Count Sticking pressing 41 and a fixing cylinder 51 which are located 27.5 Large About 180,0000 m on the inner periphery of the stator 100. Reversible The material of the slider member 22 will be de Rotations 2 7.5 - m m scribed in detail below. 20 3 23.0 - m m The present applicant conducted performance tests 4. 28.1 Medium About 40,000 m about six slider members No. 1 to No. 6 shown in Table Reversible Rotations 1 upon selection of an optimal slider member therefrom. s 28.0 Very About 100,0000 Yes In this case, as the elastic member 101 constituting the Small Reversible stator 100, Fe-36Ni invar was used. In the performance 25 Rotations tests, maximum efficiency values (%) of motors were 6 27.0 Very About 800,0000 No obtained, as shown in Table 2, and it was found from the Small Reversible test results that the slider members No. 1 and No. 4 to Rotations or More No. 6 were good in efficiency at almost the same level. The present applicant conducted wear-resistance tests 30 The above test results reveal the followings. of these slider members No. 1 and No. 4 to No. 6, and The influence of the material of the slider member to obtained the results shown in Table 2. Then, it was the drive efficiency of a motor has not been clear at found that the slider members No. 5 and No. 6 were present. The slider members No. 1, No. 2, and No. 3 superior in terms of a wear level and a durability-limit contain the Kevlar fibers, and of these members, only rotation count. 35 the slider member No. 3 has poor efficiency. Therefore, The present applicant then conducted acceleration it can be estimated that the poor efficiency is not caused reaction tests of the slider members No. 5 and No. 6. by the Kevlar fiber but by a content of a polyester resin More specifically, in an ultrasonic motor, a slider mem or an epoxy resin. ber is always brought into contact with an elastic mem As can be seen from TABLE 2, in the wear resistance ber at a constant compression force. Thus, if a motor test, better test results are obtained when a material has not been operated for a long period of time, the having a low coefficient of friction is used. More specif slider member is stuck to the elastic member, and the ically, since the slider member No. 1 does not contain a motor can never be driven. In this test, in order to check material having a low coefficient of friction at all, it the presence/absence of sticking, the slider members suffers from largest wear. Although the slider member No. 5 and No. 6 were left in an atmosphere at a humid 45 No. 4 contains a material of a low frictional coefficient, ity of 90% and a temperature of 80 C. while being in i.e., PTFE, since its content is as low as 3 wt.%, the contact with the elastic members at a constant compres wear is medium. However, under a normal use condi sion force. As a result, the slider member No. 5 exhib tion, the member No. 4 can assure a sufficient wear ited a sticking reaction, while the slider member No. 6 resistance. The slider members No. 5 and No. 6 contain did not exhibit any sticking reaction and were normally 50 PTFE as high as 30 wt.% and 80 wt.%, respectively, driven after the test. Performance (efficiency) using the and hence, they assure very small wear. slider member No. 6 after all the tests was almost the In this manner, as shown in TABLE 2, the slider same as the results shown in Table 2. member can contain 3 to 100 wt.% of a material of a Finally, the present applicant conducted a test of low coefficient of friction such as PTFE to reduce combining the slider member No. 6, and a phosphor 55 wear. In addition, it can also be estimated that if a slider bronze stator and a stainless-steel (SUS301) stator. As a member comprises a material containing at least PTFE, result, it was found that the slider No. 6 was firmly drive efficiency of a motor can also be improved. stuck to the phosphor-bronze stator, and that it might or With the above examinations, an alternative material might not be stuck to the stainless-steel slider. of a fluorine resin such as a perfluoroalkoxy fluoroplas Thus, it was found that the slider member No. 6, i.e., tic (PFA) or an ethylene-tetrafluoroethylene copoly a material containing PTFE (80 wt.%)+glass fiber (15 mer (ETFE). The content of the fluoroplastic prefera wt.%)--molybdenum disulfide (5 wt.%) was most bly falls within the range of 3 to 1000 wt.%,and more suitable for the slider member. In addition, it was also preferably, is 30 wt.% or more. found that if an invar material was used as a material of As for the durability, only the slider member No. 6 is a stator combined with the slider member No. 6, the 65 much superior to other slider members, i.e., has a dura motor could be used regardless of an atmosphere (con bility-limit rotation count of 80,0000 reversible rota dition); if stainless steel was used, application conditions tions. Such superiority is caused by the fact that the must be limited. slider member No. 6 has a content of a material of a low 5,066,884 9 10 coefficient of friction (PTFE) as very high as 80 wt.%, member 12 constituting a stator 10, and second elec and also contains a lubricant material, i.e., molybdenum trodes 14a and 14b are formed on its lower surface. A disulfide. In this manner, when a slider member is conductive elastic member 11 is coupled to the piezo formed by filling above 1 to 20 wt.% of a lubricant electric member 12 so as to be electrically connected to material (molybdenum disulfide) in a base containing 50 5 the electrode 13. The electrodes 14a and 14b are con wt.% or more of a material of a low coefficient of nected to lead wires 15 and 16 in the same manner as in friction (PTFE), thus obtaining a motor having high FIGS. 10 and 11. The elastic member 11 is formed of a efficiency, wear resistance, and durability. conductive material such as phosphor bronze, stainless As for only the durability, with the above examina steel, or invar. tions, an alternative lubricant material such as carbon 10 A flange-like support member 300 radially extends may be considered in addition to molybdenum disulfide from the outer peripheral surface of the elastic member described above. The content of such a lubricant nate 11 near a neutral surface of the stator 10 as a whole by rial preferably falls within the range of 1 to 20 wt.% integral molding. The support member 300 has a thin and more preferably, is about 10 wt.% in order to attain plate portion 301 contiguous with the outer peripheral lubricity. 15 surface of the elastic member 11 and having a thickness Sticking can be reasoned by the relationship between of about 0.3 mm, and a thick portion 302 contiguous a material constituting the slider member and a stator with the thin plate portion 301. The thickness of the material. More specifically, the slider member No. 6 is thick portion 302 is sufficiently larger than that of the formed by filling an inorganic material, i.e., a glass fiber thin plate portion 301. A male thread is formed on the which originally has almost no sticking property in 20 peripheral surface of the thick portion 302, and is addition to materials free from sticking with respect to threadably engaged with a female thread formed on the a fluoroplastic (PTFE) and a lubricant material (molyb inner peripheral surface of an annular fixing member 53, denum disulfide). Since a stator employs an invar mate thereby fixing and holding the elastic member 11. The rial which is resistant against a chemical change such as other end of a lead wire 17, one end of which is rusting in combination with the above-mentioned slider 25 member, a sticking reaction never occurs when the grounded, is mounted on the upper surface of the thick slider member and the stator are combined. portion 302 by a screw 52. In combinations of the slider member No. 6 and sta A rotor 20 is constituted by adhering an annular tors of materials other than the invar material (phosphor slider member 22 to an annular rotor base 21. A flange bronze and SUS301), sticking or sticking tendency is 30 portion 21a radially projects from a portion of the rotor observed since phosphor bronze is not resistant against base 21 near a neutral surface of the rotor as a whole, a chemical change and SUS301 is also not so resistant and a support member 54 is integrally molded on the against a chemical change as compared to the invar peripheral edge of the flange portion 21a. A compres material. Sticking of the slider member No. 5 is caused sion force generated by a compression means (not by the sticking property of the EKonol E101 contained 35 shown) is transmitted to the rotor 20 through the sup therein. port member 54, thereby urging the lower surface of the As for only sticking, with the above examinations, slider member 22 against a drive surface 11a of the alternative materials of inorganic materials such as tita elastic member 11. nium oxide, potassium titanate, and the like may be used In the above structure, the electrode 13 is grounded in addition to the above composition. 40 through the elastic member 11, its support member 300, As described above, according to the embodiment of and the lead wire 17. As described above, a predeter the present invention, a slider member of a rotor driven mined AC voltage is applied to the electrodes 14a by a stator formed of a nickel-iron alloy is formed to through the lead wire 15, and an AC voltage having a contain 3 to 100 wt.% of a fluoroplastic, so that a motor 90° phase difference from the predetermined voltage is having high efficiency and wear resistance as shown in 45 applied to the electrode 14b through the lead wire 16. TABLE 2 can be provided, and is suitable for a product Upon application of these voltages, the piezoelectric which is required to be used over a long period of time. member 12 vibrates, and a traveling vibration wave is If a slider member is formed of a material containing generated on the drive surface 11a of the elastic mem a fluoroplastic (50 wt.% or more) and a lubricant mate ber 11. As a result, the rotor 20 is driven. In this case, rial (1 to 20 wt.%), a motor having high efficiency, 50 the thick portion 302 of the support member 300 is not wear resistance, and durability can be provided. vibrated since it is fixed to the fixing member 53. Furthermore, if a slider member is formed of a mate As described above, the support member 300 and the rial containing a fluoroplastic (3 to 80 wt.%), a lubri elastic member 11 are integrally formed, and the lead cant material (1 to 20 wt.%), and an inorganic material wire 17 is connected to the thick portion 302 of the (1 to 30 wt.%), a motor which has high efficiency, wear 55 support member 300 to ground the electrode 13. There resistance, and durability, and which is free from stick fore, no conductive adhesive 18 (FIG. 10) is necessary. ing between a stator and a slider member can be pro The thick portion 302 is not almost influenced by the vided. The motor is suitable for a maintenance-free vibration of the piezoelectric member 12, and does not product such as a camera. When the motor is used in a cause a grounding error due to vibration of the elastic maintenance-free product such as a camera, sticking is 60 member 11 unlike in the conventional structure. In most important in the test items. In this case, a material addition, no undesirable vibration acts on the elastic formed of only a sticking-free material such as the slider member. member No. 6 is preferable. The thick portion 302 is not always necessary to Other embodiments of the present invention will be prevent a grounding error of electrodes as an object of described below with reference to FIGS. 7 to 9. 65 the present invention. That is, the distal end of the thin FIG. 7 is a sectional view showing an ultrasonic plate portion 301 may be fixed and held by a fixing motor according to the present invention. A first elec member. In the above structure, the lead wire 17 and trode 13 is formed on an upper surface of a piezoelectric the screw 52 constitute a grounding means. 5,066,884 11 12 As shown in FIG. 8, a fixing member 55 may be compared to a case without the grooves 103, the ampli formed of a conductive material, the grounding lead tude of the vibration wave is increased, thus improving wire 17 may be fixed to the fixing member 55 by the drive efficiency of the rotor 20. screw 52, and the electrode 13 may be grounded Since the holes 312 are formed in portions of the thin through the elastic member 11, a support member 303, plate portion 310 of the support member 309, which are the fixing member 55, and the lead wire 17. located on extending lines of the comb-like grooves 103, In the above structures, the lead wire 17 is connected the following advantages are obtained. to the thick portion 302 or the fixing member 55 by the Since the portion of the elastic member 101 with the screw 52 but may be soldered thereto. A printed circuit grooves 103 serves as the bending portion of the vibra board may be used in place of the lead wire 17. In addi 10 tion wave, the portions of the thin plate portion 310 tion, the male thread is formed on the peripheral edge of located on the extending lines of the grooves 103 also the thick portion 302 or 305, and the threaded portion is serve as bending portions. Since the holes 312 are threadably engaged with the fixing member. However, formed at the bending portions, a bending strength of the thick portion 302 or 305 may be fixed to be verti these portions is decreased, and these portions can be cally clamped by a pair of fixing members. 15 easily bent, thus increasing an amplitude. This also In the above structures, the support member 300 or causes a decrease in support loss and improvement of 303 is formed on the outer peripheral surface of the drive efficiency of a motor. FIG. 14 shows vibration elastic member 11. However, as shown in FIG. 9, a amplitudes of respective portions of the stator 100 in the support member 306 may be formed on the inner pe radial direction. In FIG. 14, a curve 11 represents a case ripheral surface of the elastic member 11, and the sup 20 wherein the holes 312 are formed in the thin plate por port member may be fixed by a fixing member 56 inside tion 310, and a curve 12 represents a case wherein no the elastic member 11. holes 312 are formed. As can be seen from FIG. 14, Other embodiments of the present invention will be vibration amplitudes of respective portions with the described below with reference to FIGS. 12 to 16. holes 312 can be increased as compared to those with FIG. 12 is a perspective view of a rotor constituting 25 out holes. an ultrasonic motor according to the present invention, Since the bending strength of the support member and FIG. 13 is a perspective view of a stator constitut 309 is decreased, vibration is never externally transmit ing the ultrasonic motor according to the present inven ted through the support member 309, thus preventing tion. A stator 100 comprises a ring-like elastic member noise. In this embodiment, since the holes 312 are 101 of, e.g., phosphor bronze, stainless steel, invar, or 30 formed by etching, no residual stress is produced in the the like, and a ring-like piezoelectric member 102 ad support member 309. hered to the elastic member 101. Comb-like grooves 103 In the above structure, the holes 312 are formed at are formed at the side of a drive surface P of the elastic positions on the thin plate portion 310 on the extending member 101. lines of the comb-like grooves 103. However, the holes A flange-like support member 309 is formed inte 35 312 need only be regularly formed in the circumferen grally with the elastic member 101. The support men tial direction of the support member 309, and more ber 309 comprises a thin plate portion 310 radially pro preferably, need only be regularly formed in association jecting from the outer peripheral surface of the elastic with the wavelength component of the traveling vibra member 101 near a neutral surface of the stator 100 as a tion wave generated in the elastic member 101. If the whole, and a thick portion 311 integrally formed at the holes 312 are regularly formed in association with the distal end of the thin plate portion 310. The thick por cycle of the comb-like grooves 103, they can provide tion 311 is fixed by a fixing member (not shown). A the above-mentioned effect. FIGS. 15A to 15G show plurality of holes 312 are formed by etching in portions another embodiment of holes 312 formed in the thin of the thin plate portion 310 located on extending lines plate portion 310 in the relationship between a traveling of the comb-like grooves 103. 45 vibration wave and the comb-like grooves 103. FIG. A rotor 20 is constituted by adhering a ring-like slider 15A is a chart of a traveling vibration wave, and FIG. member 22 to a ring-like rotor base 21. A flange portion. 15B shows comb-like grooves. Eight comb-like grooves 21a radially projects from the outer peripheral surface are formed within one wavelength component of the of the rotor base 21 near a neutral surface of the rotor 20 traveling vibration wave. FIGS. 15C to 15G show thin as a whole. A support member 54 is integrally molded 50 plate portion patterns of a support member. FIG. 15C on the outer edge of the flange portion 21a. A compres shows a pattern wherein holes corresponding in number sion force generated by a compression member (not to the comb-like grooves are aligned at equal intervals shown) is transmitted to the rotor 20 through the sup in the circumferential direction so that the centers of the port member 54, thus urging a lower surface P6 of the grooves and holes coincide with each other. With this slider member 22 against the drive surface P1 of the 55 pattern, a support loss can be minimized. FIG. 15D elastic member 10. shows substantially the same pattern as in FIG. 15C The operation of this embodiment will be described except that the centers of the comb-like grooves and the below. holes do not coincide with each other. FIG. 15E show When an AC voltage is applied to the piezoelectric a pattern wherein every other holes in FIG. 15C are member 102, the piezoelectric member 102 causes bend formed. FIG. 15F shows a pattern wherein the holes are ing-vibration, and a traveling vibration wave is gener aligned in units of half wavelengths of the traveling ated in the drive surface P1 of the elastic member 101. vibration wave. FIG. 15G shows a pattern wherein The vibration wave drives the rotor 20. In this case, each hole has a modified shape other than a circle. since a portion of the elastic member 101 formed with As shown in FIG. 15G, the shape of each hole 312 is the comb-like grooves 103 has a smaller thickness than 65 not limited to a circular or rectangular shape, but may those of other portions, this portion serves as a bending be an elliptic shape or any other shapes. portion of the vibration wave. In this case, since the In the above description, the support member 309 is neutral surface of the stator 100 is located below as formed on the outer peripheral surface of the elastic 5,066,884 13 14 member 101 but may be formed on its inner peripheral between a first surface engaging said one end face of surface. Furthermore, the holes 312 are formed as said thick portion and a second surface engaging an through holes. However, the holes may be formed as opposite end face of said thick portion. recessed grooves 316, as shown in FIG. 16. That is, in 4. An ultrasonic motor according to claim 3, wherein the present invention, the hole means not only a said first surface is an external surface of a pressing through hole but also a non-through recessed groove member and said second surface is an internal surface of (FIG.16), a dimple, and the like. a fixing member. Still another embodiment of the present invention 5. An ultrasonic motor according to claim 4, wherein will be described below with reference to FIG. 2. said pressing member is threaded into said fixing mem As shown in FIG. 2, after a piezoelectric member 102 10 ber. is adhered to a junction surface P2 of an elastic member 6. An ultrasonic motor according to claim 5, wherein 101, an adhesive 400 is applied to upper and lower end the thickness of said pressing member is greater than the faces P4 and P3 of a thick portion 32 of a support mem thickness of a portion of said fixing member on which ber 30, a surface P7 of a fixing cylinder 50, and a surface said second surface is formed. P5 of a pressing 40, and the pressing 40 is threadably 15 7. An ultrasonic motor according to claim 1, wherein engaged with the fixing cylinder 50 so that the surfaces said one end face of said thick portion and the junction P7 and P4, and the surfaces P5 and P3 are brought into surface of said elastic member are simultaneously flat contact with each other. Thus, the thick portion 32 is tened so as to be formed at the same level. vertically clamped and fixed by the fixing cylinder 50 8. An ultrasonic motor according to claim 1, wherein and the pressing 40. At this time, the lower end face P3 20 each of said junction surface and said drive surface has of the thick portion 32 and the surface P5 of the pressing substantially the same degree of flatness. 40 are polished, and the adhesive between the surfaces 9. An ultrasonic motor which comprises: P7 and P4 and between the surface P5 and the end face a stator having a piezoelectric member which is vi P3 serves as a filler. Therefore, the flatness of the drive brated by a drive signal, and an elastic member, a surface P1 of the elastic member 101 will not be de 25 junction surface of which is coupled to said piezo graded. Therefore, the support member 30 integrally electric member, and which generates a traveling provided to the stator 100 is adhered to the fixing cylin vibration wave in a drive surface thereof upon der 50 and the pressing 40 and is clamped by the cylin vibration of said piezoelectric member; der 50 and the ring 40, so that a support loss can be a rotor which is urged against the drive surface of reduced and reliability can be improved. In addition, 30 said elastic member and is driven by the generated since external transmission of vibration can be pre traveling vibration wave; vented, noise can be stopped. a support member having a thin plate portion contig As shown in FIG. 5, when a support member 36 is uous with a peripheral surface of said elastic mem formed on the inner peripheral surface of an elastic ber, and a thick portion contiguous with a periph member 10, an adhesive 400 can be filled between a 35 eral edge of said thin plate portion and having a thick portion 38 and a pressing 41 and a fixing cylinder larger thickness than that of said thin plate portion, 51 when it is clamped by the pressing 41 and the fixing said support member projecting integrally from cylinder 51, thus obtaining the same effect a described said elastic member; and above. means engaging said thick portion for fixing and sup We claim: porting said support member, 1. An ultrasonic motor which comprises: wherein one end face of said thick portion is formed a stator having a piezoelectric member which is vi at the same level as said junction surface of said brated by a drive signal, and an elastic member, a elastic member, and an opposite end face of said junction surface of which is coupled to said piezo thick portion is formed at the same level as said electric member, and which generates a traveling 45 drive surface of said elastic member. vibration wave in a drive surface thereof upon 10. An ultrasonic motor according to claim 9, vibration of said piezoelectric member; wherein said support member and said elastic member a rotor which is urged against the drive surface of are integrally molded. said elastic member and is driven by the generated 11. An ultrasonic motor according to claim 9, traveling vibration wave; 50 wherein said one end face of said thick portion and said a support member having a thin plate portion contig junction surface of said elastic member are simulta uous with an outermost peripheral surface of said neously flattened, and wherein said opposite end face of elastic member, and a thick portion contiguous said thick portion and said drive surface are simulta with an outer peripheral edge of said thin plate neously flattened. portion and having a larger thickness than that of 55 12. An ultrasonic motor according to claim 9, said thin plate portion, said support member pro wherein said thin plate portion of said support member jecting integrally from said elastic member; and is contiguous with an outermost peripheral surface of means engaging said thick portion for fixing and sup said elastic member. porting said support member, 13. An ultrasonic motor which comprises: wherein one end face of said thick portion is formed 60 a stator having a piezoelectric member which is vi at the same level as the junction surface of said brated by a drive signal, and an elastic member, a elastic member. junction surface of which is coupled to said piezo 2. An ultrasonic motor according to claim 1, wherein electric member, and which generates a traveling said support member and said elastic member are inte vibration wave in a drive surface thereof upon grally molded. 65 vibration of said piezoelectric member; 3. An ultrasonic motor according to claim 1, wherein a rotor which is urged against the drive surface of said means for fixing and supporting said support mem said elastic member and is driven by the generated ber comprises means for clamping said thick portion traveling vibration wave; 5,066,884 15 16 a support member having a thin plate portion contig than the thickness of a portion of said fixing member on uous with an innermost peripheral surface of said which said second surface is formed. elastic member, and a thick portion contiguous 20. An ultrasonic motor which comprises: with an inner peripheral edge of said thin plate a stator having a piezoelectric member which is vi portion and having a larger thickness than that of 5 brated by a drive signal, and an elastic member, a said thin plate portion, said support member pro junction surface of which is coupled to said piezo jecting integrally from said elastic member; and electric member, and which generates a traveling means engaging said thick portion for fixing and sup vibration wave in a drive surface thereof upon porting said support member, vibration of said piezoelectric member; O a rotor which is urged against the drive surface of wherein one end face of said thick portion and said said elastic member and is driven by the generated junction surface of said elastic member are formed traveling vibration wave; at the same level. a support member having a thin plate portion contig 14. An ultrasonic motor according to claim 13, uous with an outermost peripheral surface of said wherein said one end face of said thick portion and said 5 elastic member, and a thick portion contiguous junction surface of said elastic member are simulta with an outer peripheral edge of said thin plate neously flattened to be formed at the same level. portion and having a larger thickness than that of 15. An ultrasonic motor according to claim 13, said thin plate portion, said support member pro wherein each of said junction surface and said drive jecting integrally from said elastic member; and surface has substantially the same degree of flatness. 20 means engaging said thick portion for fixing and Sup 16. An ultrasonic motor according to claim 13, porting said support member, wherein said means for fixing and supporting said Sup wherein said means for fixing and supporting said port member comprises means for clamping said thick support member comprises a member into which portion between a first surface engaging said one end said thick portion is threaded. face of said thick portion and a second surface engaging 25 21. An ultrasonic motor according to claim 20, an opposite end face of said thick portion. wherein each of said junction surface and said drive 17. An ultrasonic motor according to claim 16, surface has substantially the same degree of flatness. wherein said first surface is an external surface of a 22. An ultrasonic motor according to claim 20, pressing member and said second surface is an internal wherein the last-mentioned member has a flat surface surface of a fixing member. 30 engaging a flat end face of said thick portion. 18. An ultrasonic motor according to claim 17, 23. An ultrasonic motor according to claim 22, wherein said pressing member is threaded onto said wherein said end face of said thick portion and said fixing member. junction surface of said elastic member are simulta 19. An ultrasonic motor according to claim 18, neously flattened so as to be formed at the same level. wherein the thickness of said pressing member is greater 35