Patent Publication Number: US-2005127782-A1

Title: Ultrasonic motor, and electronic timepiece having ultrasonic motor

Description:
TECHNICAL FIELD  
      The present invention relates to an ultrasonic motor which includes an ultrasonic rotor formed from a base resin of thermoplastic resin. Moreover, the present invention relates to an electronic timepiece of an analog display type which has an indication wheel rotated by the rotation of an ultrasonic motor. Furthermore, the present invention relates to an electronic apparatus with an ultrasonic motor which has a power source, a source of oscillation, a controlling circuit, and an ultrasonic motor.  
     BACKGROUND ART  
      Referring to  FIG. 12 , a conventional ultrasonic motor  930  includes an ultrasonic stator  922 , an ultrasonic motor supporting member  924 , an ultrasonic motor shaft  932 , an ultrasonic rotor  934 , and an ultrasonic motor lead substrate  936 . The ultrasonic motor shaft  932  includes a guard part  932   a,  a first shaft part  932   b.  a second shaft part  932   c,  and a tip shaft part  932   d.  The ultrasonic motor supporting member  924  has a first through hole  924   a  for penetrating by the ultrasonic motor shaft  932  and a second through hole  924   b  for penetrating by a conducting pattern of the ultrasonic motor lead substrate  936 . The ultrasonic motor supporting member  924  has this first through hole  924   a  penetrated by the ultrasonic motor shaft  932 , and is adhered to the first shaft part  932   b  of the ultrasonic motor shaft  932 . In the ultrasonic motor supporting member  924 , the lower face of the ultrasonic motor supporting member  924  is abutted against the guard-part  932   a  of the ultrasonic motor shaft  932  The ultrasonic stator  922  has a central hole  922   a,  an ultrasonic stator main body  922   b,  a projection for enlarging displacement (comb teeth)  987 , and a cylindrical part  922   d.  The projection  987  is provided on the surface of the ultrasonic stator main body  922   b.  The ultrasonic stator main body  922   b  is formed from aluminum alloy. The cylindrical part  922   d  projects from the back of the ultrasonic stator main body  922   b,  and the central hole  922   a  is formed to penetrate through the cylindrical part  922   d.    
      A polarization processed piezoelectric element  802  is adhered to the,lower face of the ultrasonic stator main body  922   b.  The ultrasonic stator  922 , with the central hole  922   a  through which the ultrasonic motor shaft  932  passes, is adhered to the second shaft part  932   c  of the ultrasonic motor shaft  932 . The ultrasonic stator  922  is adhered to the ultrasonic motor shaft  932  in a condition where the outer peripheral portion of the central hole  922   a,  that is the end face of the cylindrical part  922   d,  is contacted with the upper face of the ultrasonic motor supporting member  924 .  
      The ultrasonic motor lead substrate  936  is provided in order to apply an electric signal to the electrode provided in the piezoelectric element  982 . The ultrasonic motor lead substrate  936  has a substrate main body  936   d  formed from insulating material such as polyimides, and conducting patterns  936   a  and  936   b  adhered to the substrate main body  936   d.  The face without the conducting patterns  936   a  nor  936   b  of the substrate main body  936   d  of the ultrasonic motor lead substrate  936 , is adhered onto the back face of the ultrasonic motor supporting member  924 .  
      The ultrasonic rotor  934  includes a rotating member  934   c,  a spring contacting member  934   e,  and a bearing jewel  934   f.  The ultrasonic rotor  934  is rotatably provided on the ultrasonic motor shaft  932  so that the lower face of the rotating member  934   c  contacts with the upper face of the projection  987  of the ultrasonic stator  922 . The rotating member  934   c  is formed from carbon steel. The spring contacting member  934   e  is formed from polyacetal. The bearing jewel  934   f  is formed from ruby or ceramic. The pressurizing spring  938  contacts to the top of the spring contacting member  934   e.  The ultrasonic rotor  934  is contacted under pressure against the ultrasonic stator  922  by the elastic force of the pressurizing spring  938 .  
      An ultrasonic motor driving circuit (not illustrated) generates an electric signal for driving the ultrasonic motor  930 , and this electric signal is input to the piezoelectric element  982  through the conducting patterns  936   a  and  936   b  of the ultrasonic motor lead substrate  936 . Based on this electric signal, oscillatory waves are generated in the ultrasonic stator  922  to which the piezoelectric element  982  is fixed. By this oscillating wave, the ultrasonic rotor  934 , which contacts with the ultrasonic stator  922  under pressure, rotates. Configurations of conventional ultrasonic motors and the conventional electronic timepieces of the analog display type having an ultrasonic motor, have been disclosed, for example, in Japanese Patent No. 2764123, Japanese Unexamined Patent Application, First Publication No. H05-273361, Japanese Unexamined Patent Application, First Publication No. H11-215865, Japanese Unexamined Patent Application, First Publication No. H11-281772, and the like.  
      However, in a conventional ultrasonic motor the ultrasonic rotor  934  is composed of three parts. Therefore, the process for manufacturing the ultrasonic rotor  934  is complex. Moreover, since the rotating member  934   c  is made from metal and is thus heavy, the spring power of the pressurizing spring  938  must be adjusted to be small, so that it is difficult to design the pressurizing spring  938 , In addition, since the coefficient of dynamic friction is about 0.1 to 0.4 in the natural material of polyacetal (polyoxymethylene) constituting the spring contacting member  934   e,  the spring power of the pressurizing spring  938  must be adjusted to be large, so that it is difficult to increase the wear resistance of the spring contacting member  934   e.  Moreover, since the coefficient of dynamic friction is about 0.1 to 0.4 in the natural material of polyacetal (polyoxymethylene) in the configuration of the ultrasonic rotor molded as a monolithic configuration of the polyacetal, the spring power of the pressurizing spring must be adjusted to be large. Therefore, it is difficult to increase the wear resistance of the spring contacting member, and it is difficult to increase the wear resistance of the bearing section of the ultrasonic rotor which contacts with the ultrasonic motor shaft.  
      Moreover, conventionally, in order to manufacture the ultrasonic rotor, a method where a large amount of powdery carbon black is added to the base resin has also been implemented. In the case where this ultrasonic rotor is installed in a conventional ultrasonic motor, it is necessary to lubricate the contact face of the ultrasonic rotor and the ultrasonic stator with oil to decrease the wear of the ultrasonic rotor. However, to decrease the wear of the ultrasonic rotor, it is necessary to add a large amount of carbon black to the base resin, which becomes a factor in increasing the manufacturing cost of the ultrasonic rotor. Moreover, since adhesion of the carbon black and the base resin is not good, if the ultrasonic rotor is worn even a little, there is the possibility that dust may be generated, and this dust may enter into the sliding parts of other members causing a decrease in performance of the equipment.  
      Moreover, regarding the basic characteristic of the ultrasonic motor, there is known to be the conflicting characteristic in that, if the spring power of the pressurizing spring is increased, the warm-up time becomes longer and the rotating torque of the ultrasonic motor becomes higher, while if the spring power of the pressurizing spring is decreased, the warm-up time becomes shorter and the rotating torque of the ultrasonic motor becomes lower. Therefore, in order to improve the basic characteristic of the ultrasonic motor, the spring power of the pressurizing spring must be controlled to a suitable value. Particularly, in the case where a large amount of carbon black is added to the base resin, the friction. coefficient on the surface of the ultrasonic rotor is decreased and the slipperiness in the contact face of the ultrasonic rotor and the ultrasonic stator is increased, so that it is very difficult to control the spring power of the pressurizing spring to a suitable value. In the case where the contact face of the ultrasonic rotor and ultrasonic stator is lubricated with oil, the oil deteriorates due to long term use, causing a shorter maintenance period of the equipment. Furthermore, in the case where the contact face of the ultrasonic rotor and ultrasonic stator is lubricated with oil, it is necessary to provide an oil retention construction for retaining the oil so that it is no flung out due to the impact on the equipment.  
     DISCLOSURE OF INVENTION  
      The present invention is characterized in that, in an ultrasonic motor configured such that, by applying an electric signal to an electrode provided in a polarization processed piezoelectric element, oscillating waves are generated in an ultrasonic stator to which a piezoelectric element is fixed, and an ultrasonic rotor which contacts with this ultrasonic stator under pressure is driven, the ultrasonic rotor is formed from a filler containing resin having a base resin of thermoplastic resin, and carbon filler mixed with this base resin.  
      By such a configuration, it becomes possible to realize an ultrasonic motor which is stable in rotation performance of the ultrasonic rotor, and excellent in durability performance.  
      In the present invention, preferably the base resin is selected from a group consisting of, polystyrene, polyethylene terephthalate, polycarbonate, polyacetal (polyoxymethylene), polyamide, modified polyphenylene ether, polybutylene terephthalate, polyphenylene sulfide, polyether ether ketone, and polyether imide. Furthermore, in the present invention, preferably the carbon filler is selected from a group consisting of; a monolayer carbon nanotube, a multilayer carbon nanotube, a vapor growth carbon fiber, a nanografiber, a carbon nanohorn, a cup stack type carbon nanotube, a monolayer fullerene, a multilayer fullerene, and a mixture of any one of the carbon fillers doped with boron. Moreover the present invention, in an electronic timepiece of an analog display type which has a power source, a source of oscillation, a controlling circuit, a wheel train, and a time information display member, is characterized in including: the ultrasonic motor of the above mentioned aspect of the invention, an ultrasonic motor driving circuit for driving-the ultrasonic motor, and an indication wheel rotated by rotation of the ultrasonic motor. Furthermore the present invention, in an electronic timepiece of an analog display type which has a power source, a source of oscillation, a controlling circuit, a wheel train, and a time information display member, is characterized in including: the ultrasonic motor of the above mentioned aspect of the invention; an ultrasonic motor driving circuit for driving the ultrasonic motor; and an output member which operates by rotation of the ultrasonic motor.  
      The ultrasonic motor of the present invention includes an ultrasonic rotor formed from a filler containing resin having a base resin of carbon filler mixed with a base resin. The coefficient of dynamic friction of the filler containing resin can be made more than that of a no filler resin. Therefore, in the ultrasonic motor of the present invention, the frictional property between the ultrasonic rotor and the ultrasonic stator can be stabilized. Consequently, in the ultrasonic motor of the present invention, the spring power of a “pressurizing spring” which makes the ultrasonic rotor contact with the ultrasonic stator under pressure, can be easily adjusted.  
      Moreover, in the filler containing resin the specific wear rate is significantly less than for the no filler resin. Therefore, since the ultrasonic motor of the present invention includes the ultrasonic rotor formed from the filler containing resin, wear resistance of the contact area between the ultrasonic rotor shaft and the bearing, and wear resistance of the contact area between the ultrasonic rotor and the ultrasonic stator can be increased.  
      As a result, in an electronic timepiece or an electronic device having the ultrasonic motor of the present invention, it is easy to adjust the spring power of the “pressurizing spring” which makes the ultrasonic rotor contact with the ultrasonic stator under pressure. Moreover, the durability performance of the contact area between the ultrasonic rotor shaft and the bearing, and the contact area between the ultrasonic rotor and the ultrasonic stator, becomes excellent.  
      For example, in the case where the ultrasonic rotor is molded as just the ultrasonic rotor, the coefficient of dynamic friction is about 0.1 to 0.4 in the natural material of the polyacetal (polyoxylhethylene). On the other hand, in the case where the ultrasonic rotor is molded from the filler containing resin with a polyacetal base resin filled with a carbon filler, the coefficient of dynamic friction is about 0.55 for the filler containing resin, the coefficient of dynamic friction of the filler containing resin being larger than that for the polyacetal. Consequently, in the ultrasonic motor of the present invention, the frictional property of the ultrasonic rotor and ultrasonic stator is stable. Hence it is easy to adjust the spring power of the pressurizing spring. Moreover, in the case where the ultrasonic rotor is molded as just the ultrasonic rotor, the specific wear rate is about 2.2×10 −4 mm 3 /N·km for the natural material of the polyacetal. On the other hand, in the case where the ultrasonic rotor is molded from the filler containing resin with the polyacetal base resin filled with a carbon filler, the specific wear rate is about 3.3×10 −9 mm 3 /N·km, the specific wear rate of the filler containing resin being much smaller than that for the natural material of the polyacetal. Consequently, the ultrasonic motor of the present invention can be manufactured so that the wear resistance of the contact area between the ultrasonic rotor bearing section and the ultrasonic rotor shaft section, and the contact area between the ultrasonic rotor and the ultrasonic stator can be increased. Moreover, in an electronic timepiece or an electronic device having the ultrasonic motor of the present invention, it is easy to adjust the spring power of the pressurizing spring, and the durability performance of the contact area between the ultrasonic rotor and the ultrasonic stator is excellent. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       FIG. 1  is a schematic cross-sectional view showing an embodiment of an ultrasonic motor of the present invention.  
       FIG. 2  is a plan view showing the appearance as seen from the obverse side, of the embodiment of the ultrasonic motor of the present invention.  
       FIG. 3  is a plan view showing the appearance as seen from the rear side, of the embodiment of the ultrasonic motor of the present invention.  
       FIG. 4  is a plan view showing an ultrasonic motor lead substrate used for the ultrasonic motor of the present invention.  
       FIG. 5  is an schematic plan view showing the appearance as seen from the obverse side, of an electronic timepiece in which the ultrasonic motor of the present invention is used, with some components omitted.  
       FIG. 6  is a schematic plan view showing the appearance as seen from the rear side, of the electronic timepiece in which the ultrasonic motor of the present invention is used, with some components omitted.  
       FIG. 7  is a block diagram showing a construction of the electronic timepiece in which the ultrasonic motor of the present invention is used.  
       FIG. 8  is a block diagram showing a configuration of a drive circuit of the ultrasonic motor of the present invention.  
       FIG. 9  is a plan view of an ultrasonic stator of the ultrasonic motor of the present invention.  
       FIG. 10  is a cross-sectional view of the ultrasonic stator of the ultrasonic motor of the present invention,  
       FIG. 11  is a fragmentary sectional view showing another construction of an electronic timepiece in which the ultrasonic motor of the present invention is used.  
       FIG. 12  is a schematic cross-sectional view of a conventional ultrasonic motor. 
    
    
     BEST MODE FOR CARRYING OUT THE INVENTION  
      (1) Ultrasonic Motor Construction  
      Referring to  FIG. 1  to  FIG. 3 , an ultrasonic motor  130  of the present invention includes; an ultrasonic stator  122 , an ultrasonic motor supporting member  124 , an ultrasonic motor shaft  132 , an ultrasonic rotor  134 , and an ultrasonic motor lead substrate  136 . The ultrasonic motor shaft  132  includes a guard part  132   a,  a first shaft part  132   b,  a second shaft part  132   c,  and a tip shaft part  132   d.    
      The ultrasonic motor supporting member  124  has a first through hole  124   a  for penetrating by the ultrasonic motor shaft  132  and a second through hole  124   b  for penetrating by the conducting pattern of the ultrasonic motor lead substrate  136 . The ultrasonic motor supporting member  124  has this first through hole  124   a  penetrated by the ultrasonic motor shaft  132 , and is adhered to the first shaft part  132   b  of the ultrasonic motor shaft  132 . In the ultrasonic motor supporting member  124 , the lower face of the ultrasonic motor supporting member  124  is abutted against the guard part  132   a  of the ultrasonic motor shaft  132 .  
      The ultrasonic stator  122  has a central hole  122   a,  an ultrasonic stator main body  122   b,  a projection for enlarging displacement (comb teeth)  817 , and a cylindrical part  122 . The projection  817  is provided on the surface of the ultrasonic stator main body  122   b.  The cylindrical part  122   d  projects from the back of the ultrasonic stator main body  122   b,  and the central hole  122   a  is formed to penetrate through the cylindrical part  122   d.  The ultrasonic stator main body  122   b  is formed from an elastic material such as aluminum alloy. A polarization processed piezoelectric element  802  is adhered to the lower face of the ultrasonic stator main body  122   b.  The ultrasonic stator  122 , with the central hole  122   a  through which the ultrasonic motor shaft  132  passes, is adhered to the second shaft part  132   c  of the ultrasonic motor shaft  132 . The ultrasonic stator  122  is adhered to the ultrasonic motor shaft  132  in a condition where the outer peripheral portion of the central hole  122   a,  that is the end face of the cylindrical part  122   d,  is contacted with the upper face of the ultrasonic motor supporting member  124 .  
      Referring to  FIG. 4 , the ultrasonic motor lead substrate  136  is provided in order to apply an electric signal to the electrode provided in the piezoelectric element  802 . The ultrasonic motor lead substrate  136  has a substrate main body  136   d  formed from insulating material such as polyimides, and conducting patterns  136   a  and  136   b  adhered to the-substrate main body  136   d.  An opening  136   c  is provided in the substrate main body  136   d.  A tip part  136   e  of the conducting pattern  136   a  and a tip part  136   f  of the conducting pattern  136   b  are arranged in the opening  136   c.  Referring to  FIG. 1  to  FIG. 3  again, the face without the conducting patterns  136   a  nor  136   b  of the substrate main body  136   d  of the ultrasonic motor lead substrate  136 , is adhered onto the back face of the ultrasonic motor supporting member  124 . Preferably the ultrasonic motor lead substrate  136  is adhered to the ultrasonic motor supporting member  124  after the ultrasonic stator  122  is adhered to the ultrasonic motor shaft  132 .  
      Next, the tip part  136   e  of the conducting pattern  13   6   a  on the ultrasonic motor lead substrate  136  is welded to an electrode  803   a  of the piezoelectric element  802 , and the tip part  136   f  of the conducting pattern  136   b  on the ultrasonic motor lead substrate  136  is welded to an electrode  803   b  of the piezoelectric element  802 . As a modified example, the tip part  136   e  of the conducting pattern  136   a  may be soldered to the electrode  803   a  of the piezoelectric element  802 , and the tip part  136   f  of the conducting pattern  136   b  may be soldered to the electrode  803   b  of the piezoelectric element  802 . The ultrasonic rotor  134  is rotatably provided with respect to the ultrasonic motor shaft  132  so that a part on the lower face may contact with the upper face of the projection  817  of the ultrasonic stator  122 . The pressurizing spring  138  contacts with the top of the spring contacting member  134   e.  The ultrasonic rotor  134  is contacted under pressure with the ultrasonic stator  122  by the elastic force of the pressurizing spring  138 .  
      The ultrasonic rotor  134  is formed from a filler containing resin with a base resin of thermoplastic resin, and carbon filler filled into this base resin. If the ultrasonic rotor  134  is formed from the filler containing resin, wear of the bearing can be effectively prevented due to the filler. Consequently, the ultrasonic motor of the present invention has excellent durability performance of the bearing, and maintenance is facilitated.  
      The base resin used in the present invention is generally polystyrene, polyethylene terephthalate, polycarbonate, polyacetal (polyoxymethylene), polyamide, modified polyphenylene ether, polybutylene terephthalate, polyphenylene sulfide, polyether ether ketone, or polyether imide. That is, in the present invention, the base resin is preferably made of a so-called general-purpose engineering plastic or a so-called super engineering plastic. In the present invention, a general-purpose engineering plastic or a super engineering plastic other than the above can also be used for the base resin. It is preferable that the base resin used for the present invention is a thermoplastic resin. The carbon filler used in the present invention is generally; a monolayer carbon nanotube, a multilayer carbon nanotube, a vapor growth carbon fiber, a nanografiber, a carbon nanohorn, a cup stack type carbon nanotube, a monolayer fullerene, a multilayer fullerene, or a mixture of any one of the aforementioned carbon fillers doped with boron. Preferably the carbon filler is contained as 0.2 to 60% by weight of the total weight of the filler containing resin. Or preferably the carbon filler is contained as 0.1 to 30% by volume of the total volume of the filler containing resin.  
      Preferably the monolayer carbon nanotube has a diameter of 0.4 to 2 nm, and an aspect ratio (length/diameter) of 10 to 1000, specifically an aspect ratio of 50 to 100. The monolayer carbon nanotube is formed in a hexagon shaped netlike having -a cylindrical shape or a truncated-cone shape, and is a monolayer structure. The monolayer carbon nanotube can be obtained from Carbon Nanotechnologies Inc. (CNI) in the U.S.A. as “SWNT”.  
      Preferably the multilayer carbon nanotube has a diameter of 2 to 4 nm, and an aspect ratio of 10 to 1000, specifically an aspect ratio of 50 to 100. The multilayer carbon nanotube is formed in a hexagon shaped netlike having a cylindrical shape or a truncated-cone shape, and is a multilayer structure. The multilayer carbon nanotube can be obtained from NIKKISO as “MWNT”.  
      Such carbon nanotubes are described in “Carbon Nanotubes and Accelerated Electronic Applications” (“Nikkei Science” March, 2001 issue, pp 52-62) and “The Challenge of Nano Materials” (“Nikkei Mechanical” December, 2001 issue, pp 36-57) by P. G. Collins et. al., or the like. Moreover, the configuration and the manufacturing method of carbon fiber-containing resin composition has been disclosed for example in Japanese Unexamined Patent Application, First Publication No. 2001-200096.  
      Preferably the vapor growth carbon fiber has a diameter of 50 nm to 200 nm, and an aspect ratio of 10 to 1000, specifically an aspect ratio of 50 to 100. The vapor growth carbon fiber is formed in a hexagon shaped netlike having a cylindrical shape or a truncated-cone shape, and is a multilayer structure. The vapor growth carbon fiber can be obtained from SHOWA DENKO as “VGCF (trademark)”. The vapor growth carbon fiber has been disclosed for example in Japanese Unexamined Patent Application, First Publication No. H05-321039, Japanese Unexamined Patent Application, First Publication No. H07-150419, and Japanese Examined Patent Application, Second Publication No. H03-61768.  
      Preferably the nanografiber has an outer diameter of 2 to 500 nm, and an aspect ratio of 10 to 1000, an aspect ratio of 50 to 100 being particularly preferable. The nanografiber has an almost solid cylindrical shape. The nanografiber can obtained from ISE ELECTRON.  
      Preferably the carbon nanohorn has a diameter of 2 to 500 nm, and an aspect ratio of 10 to 1000, an aspect ratio of 50 to 100 being particularly preferable. The carbon nanohorn has an cup shape being a hexagon shaped netlike.  
      Preferably the cup stack type carbon nanotube has a shape where the carbon nanoborn is laminated into a cup shape, and an aspect ratio of 10 to 1000, an aspect ratio of 50 to 100 being particularly preferable.  
      Fullerene is a molecule which uses a carbon cluster as a parent. The definition of CAS, is that it is a molecule being a closed globular shape with 20 or more carbon atoms respectively combined with adjacent three atoms. Monolayer fullerene has a football like shape. Preferably the monolayer fullerene has a diameter of 0.1 to 500 nm. Preferably the composition of the monolayer fullerene is C60 to C540. The monolayer fullerene is for example C60, C70, and C120. The diameter of C60 is about 0.7 nm. Multilayer fullerene has a telescopic shape with the monolayer fullerene mentioned above concentrically laminated. Preferably the multilayer fullerene has a diameter of 0.1 nm to 1000 nm, a diameter of 1 nm to 500 nm being particularly preferable. Preferably the multilayer fullerene has a composition of C60 to C540. Preferably the multilayer fullerene has a configuration with for example C70 arranged on the outside of C60, and C120 arranged further on the outside of C70. Such multilayer fullerene has been described for example in “The Abundant Generation and Application to Lubricants of Onion Structured Fullerene” (“Japan Society for Precision Engineering” vol.67, No.7, 2001) by Takahiro Kakiuchi et. al.  
      Furthermore, the aforementioned carbon filler may also be made with any of the carbon fillers (a monolayer carbon nanotube, a multilayer carbon nanotube, a vapor growth carbon fiber, a nanografiber, a carbon nanohorn, a cup stack mold carbon nanotube, a monolayer fullerene, or a multilayer fullerene) doped with boron. The method of doping the carbon filler with boron is disclosed in Japanese Unexamined Patent Application, First Publication No. 2001-200096 or the like. In the method disclosed in Japanese Unexamined Patent Application, First Publication No. 2001-200096, the carbon fiber and boron manufactured by the gaseous-phase method, are mixed by a Henschel mixer type mixer, and this mixture is heat-treated at about 2300° C. in a high-frequency furnace or the like. Then, the heat-treated mixture is ground by a grinder. Next, the base resin and the ground mixture are blended at a predetermined rate, and melting and kneading carried out by an extruder in order to manufacture a pellet.  
      An ultrasonic motor driving circuit (not illustrated) generates an electric signal for driving the ultrasonic motor  130 , and this electric signal is input to the piezoelectric element  802  through the conducting patterns  136   a  and  136   b  of the ultrasonic motor lead substrate  136 . Based on this electric signal, oscillatory waves are generated in the ultrasonic stator  122  to which the piezoelectric element  802  is fixed. By this oscillating wave, the ultrasonic rotor  134 , which contacts with the ultrasonic stator  122  under pressure, rotates. When the ultrasonic motor  130  of the present invention is used for an electronic timepiece (analog electronic timepiece), the ultrasonic motor supporting member  124  is preferably fixed to the main plate  102 . In this case, the pressurizing spring  138  may be formed as a part of the components formed from an elastic material, such as a day wheel presser, a switch spring, and the like.  
      (2) Structure of Electronic Timepiece in Which Ultrasonic Motor is Used  
      Next is a description of the structure of an electronic timepiece (analog electronic timepiece) in which the ultrasonic motor  130  of the present invention is used. Referring to  FIG. 5  and  FIG. 6 , a movement  100  (machine body including the driving part) of the electronic timepiece in which the ultrasonic motor  130  of the present invention is used, is constituted by an analog electronic timepiece, and is provided with a main plate  102  constituting a base plate of the movement. A hand setting stem  104  is rotatably integrated to a hand setting stem guide hole of the main plate  102 . A dial  104  (not illustrated) is attached to the movement  100 . A switch device (not illustrated) operated by operating the hand setting stem  104 , is provided in the main plate  102 .  
      Among the both sides of the main plate  102 , a side having the dial is referred to as the “rear side” of the movement  100 , and the opposite side to the side with the dial is referred to as the “obverse side” of the movement 100. A wheel train integrated to the ” obverse side” of the movement  100  is referred to as an ” obverse wheel train”, and a wheel train integrated to the “rear side ” of the movement  100  is called a “rear wheel train”.  
      The switch device may integrated to the “obverse side” of the movement  100  or may be integrated to the “rear side” of the movement 100. The indication wheel such as a date indicator, a day of the week indicator or the like is integrated to the “rear side” of the movement  100 . The date indicator  120  is rotatably arranged in the main plate  102 . The date indicator  120  includes a date indicator wheel gear portion  120   a  and a date character print portion  120   b.  As an example of a date characters  120   c,  only “5” is shown in  FIG. 6 . The date indicator wheel gear portion  120   a  includes 31 date indicator teeth.  
      An ultrasonic motor  130  for rotating the date indicator  120  is arranged in the main plate  102 . By using the ultrasonic motor  130 , the date indicator  120  can be reliably rotated by a small number of reduction wheel trains. An intermediate date indicator driving wheel  142  is installed so that it may rotate based on the rotation of the ultrasonic rotor  134  of the ultrasonic motor  130 . A date indicator driving wheel  150  is provided so that it may rotate based on the rotation of the intermediate date indicator driving wheel  142 . The date indicator driving wheel  150  has four date feed gear parts  150   b.  The date feed gear part  150   b  is constituted to rotate the date indicator  120  by rotation of the date indicator driving wheel  150 , The indication wheel rotated by the ultrasonic motor  130  may be a date indicator, a day of the week indicator, or other kinds of wheel which display information on time or calendar, for example, a month indicator, a year indicator, a lunar age indication wheel, or the like.  
      A circuit block  172  is arranged on the obverse side of movement  100 . This circuit block  172  is provided with a circuit board  170 , an integrated circuit  210 , and a quartz oscillator  212 . The movement  100  is provided a coil block  220 , a stator  222 , and a rotor  224 . A fifth wheel-and-pinion  230  is arranged to rotate based on rotation of the rotor  224 . A fourth wheel-and-pinion  232  is arranged to rotate based on rotation of the fifth wheel-and-pinion  230 . A second hand  234  for indicating “second” is attached to the fourth wheel-and-pinion  232 . A third wheel-and-pinion  236  is arranged to rotate based on the rotation of the fourth wheel-and-pinion  232 . A minute indicator  240  is arranged to rotate based on the rotation of the third wheel-and-pinion  236 . A minute hand  242  for indicating “minute” is attached to the minute indicator  240 . A battery  250  is arranged on the circuit block  172  and a wheel train bridge  246 .  
      (3) Operation of Electronic Timepiece in Which the Ultrasonic Motor is Used  
      Next, is a description of the operation of the electronic timepiece in which the ultrasonic motor of the present invention is used.  
      Referring to  FIG. 7 , an oscillation circuit  424  outputs a reference signal. The oscillation circuit  424  includes the quartz oscillator  212  constituting a source of oscillation. The quartz oscillator  212  is oscillated at, for example, at 32,768 Hz. Based on the oscillation of the quartz oscillator  212 , a frequency dividing circuit  426  divides an output signal from the oscillation circuit  424 . A motor driving circuit  428  outputs the motor drive signal for driving a step motor based on the output signal from the frequency dividing circuit  426 . The oscillation circuit  424 , the frequency dividing circuit  426 , and the motor driving circuit  428  are incorporated in the integrated circuit  210 . When the coil block  220  inputs the motor drive signal, the stator  222  is magnetized and rotates the rotor  224 . The rotor  224  is rotated by, for example,  180  degrees per second. Based on rotation of the rotor  224 , the fourth wheel-and-pinion  232  is rotated via rotation of the fifth wheel-and-pinion  230 . The fourth wheel-and-pinion  232  is constituted to rotate once per minute. The second hand  234  is rotated integrally with the fourth wheel-and-pinion  232 .  
      The third wheel-and-pinion  236  is rotated based on rotation of the fourth wheel-and-pinion  232 . The minute indicator  240  is rotated based on rotation of the third wheel-and-pinion  236 . The minute hand  242  is rotated integrally with the minute indicator  240 . A slip mechanism (not illustrated) is provided in the minute indicator  240 . When hand is set by the slip mechanism, in a state in which the minute hand  234  is stopped, the hand setting stem  104  is rotated by which the minute hand  242  and the hour hand can be rotated. The minute indicator  240  is rotated once per hour. A minute wheel  270  is rotated based on rotation of the minute indicator  240 . An hour wheel  272  is rotated based on rotation of the minute wheel  270 . The hour wheel  272  is rotated once per  12  hours. An hour hand  274  is attached to the hour wheel  272 . The hour hand  274  is rotated integrally with the hour wheel  272 .  
      An ultrasonic motor driving circuit  310  outputs an ultrasonic motor drive signal for driving the ultrasonic motor  130  based on an output signal from the frequency dividing circuit.  426 . The ultrasonic motor driving circuit  310  incorporated in the integrated circuit  210 . The intermediate date indicator driving wheel  142  is rotated based on rotation of the ultrasonic rotor  134  of the ultrasonic motor  130 . The date indicator driving wheel  150  is rotated based on rotation of the intermediate date indicator driving wheel  142 . By rotating the date indicator driving wheel  150 , the date driving gear portion  150   b  rotates the date indicator  120 . A signal output from the ultrasonic motor driving circuit  310 , is output to rotate the date indicator  120  by one tooth per day. The date indicator  120  is constituted to be able to rotate by operating a date correction switch  330 . When the date correction switch  330  is operated, the ultrasonic motor driving circuit  310  outputs the ultrasonic motor drive signal for driving the ultrasonic motor  130 . By this constitution, indication of the date indicator  120  can be changed. The date correction switch  330  may be constituted to operate by operating the hand setting stem  104 , or may be provided with a button or the like for operating the date correction switch  330 .  
      (4) Operation of the Ultrasonic Motor  
      Next, is a description of the operation of the ultrasonic motor of the present invention.  
      Referring to  FIG. 8 , a piezoelectric element  802  formed with two sets of electrode groups  803   a  and  803   b  each including a plurality of electrodes, is bonded to one face of the ultrasonic stator  122  constituting a vibrating member of the ultrasonic motor  130 . An oscillation driving circuit  825  is connected to the electrode groups  803   a  and  803   b  of the piezoelectric element  802 . An inverter  812  serves as an inverting power amplifier for inversely amplifying an electric signal which is excitation data from one face of the piezoelectric element  802  formed with the electrode groups  803   a  and  803   b,  and an electrode  803   c  or the ultrasonic stator  122  formed on the other face. A resistor  813  is connected in parallel with the inverter  812  for stabilizing an operating point of the inverter  812 . An output terminal of the inverter  812  is connected to input terminal of two sets of buffers  811   a  and  811   b  via a resistor  814 , The output terminal of the buffer  811   a  is connected to the electrode group  803   a  of the piezoelectric element  802 . The output terminal of the buffer  811   b  is connected to the electrode group  803   b  of the piezoelectric element  802 . One end of a capacitor  815  is connected to an input terminal of the inverter  812 , and one end of a capacitor  816  is connected to the output terminal of the inverter  812  via the resistor  814 . Respective other ends of the capacitors  815  and  816  are grounded for adjusting a phase in the oscillation driving circuit  825 .  
      The inverter  812  and the buffers  811  a and  811  b are each provided with an input terminal, an output terminal, and a control terminal, and accordingly are an inverter or buffer having of a tri-state structure capable of bringing the output terminal into a high impedance state in accordance with a signal input to the control terminal. A regular/reverse signal generating device  820  outputs a regular/reverse signal for setting the rotational direction of the ultrasonic rotor  134  of the ultrasonic motor to a switching circuit  826 . Output terminals of the switching circuit  826  are respectively connected to the control terminals of the tri-state buffers  811   a  and  811   b,  and the tri-state inverter  812  of the oscillation driving circuit  825 , and makes one of the tri-state buffers  811   a  and  811   b  function as an ordinary buffer and disables the output terminal of other buffer by bringing the output terminal in a high impedance state based on output signals outputted from the regular/reverse signal generating device  820 .  
      The oscillation driving circuit  825 , the regular/reverse signal generating device  820 , and the switching circuit  826  are included in the ultrasonic motor driving circuit  310 . The ultrasonic stator  122  is driven by the tri-state buffer which is selected by the output signal from the switching circuit  826  and functions as an ordinary buffer. The ultrasonic stator  122  is driven only by the tri-state buffer permitted to function as an ordinary buffer by the switching circuit  826 , and when the tri-state buffer permitted to function as an ordinary buffer by the switching circuit  826  is exchanged by an other one, the rotational direction of the ultrasonic motor is reversed. The output terminal of the tri-state inverter can be brought into the high impedance state by the output signal from the switching circuit  826  which is outputted based on the output from the regular/reverse signal generating device  820  and when the tri-state inverter is brought into a disabled state, both of the tri-state buffers  811   a  and  811   b  are brought into the disabled state by which rotation of the ultrasonic rotor  134  of the ultrasonic motor can be stopped.  
      Referring to  FIG. 9  and  FIG. 10 , the disc-shaped piezoelectric element  802  is bonded to the plane of the disk-shaped ultrasonic stator  122  by bonding, a thin film forming process, or the like. Standing waves of two wavelengths are excited in the circumferential direction of the ultrasonic stator  122  to thereby drive to rotate the ultrasonic rotor. The piezoelectric element  802  is formed with eight-divided electrodes, which is four times the number of waves in the circumferential direction alternately arranged on one plane, so as to give a first electrode group  803   a  and second electrode group  803   b.  As shown in  FIG. 9  and  FIG. 10  these groups are subjected to a polarization treatment of (+) and (−). The first electrode group  803   a  is constituted by electrodes a 1 , a 2 , a 3 , and a 4 , and the respective electrodes are short-circuited by a first connecting device  814   a,  The second electrode group  803   b  is constituted by electrodes b 1 , b 2 , b 3 , and b 4 , and the respective electrodes are short-circuited by a second connecting device  814   b.    
      Symbols (+) and (−) in the drawing designate directions of the polarization treatment, and the polarization treatment is carried out by respectively applying positive electric fields and negative electric fields to a face of the piezoelectric element  802  bonded with the ultrasonic stator  122 . Projections (comb teeth)  817  for enlarging displacement of the ultrasonic stator and transmitting drive force from the ultrasonic stator  122  to the ultrasonic rotor  134  are provided on the surface of the ultrasonic stator  122 , at the vicinities of the boundaries the respective electrodes for every other electrode A high frequency voltage generated by the oscillation driving circuit  825  is applied to either one of the electrode groups  803   a  and  803   b  in order to excite standing waves of two wave lengths in the circumference direction of the ultrasonic stator  122 , to thereby rotate and drive the ultrasonic stator  122 . The rotational direction of the ultrasonic rotor  134  of the ultrasonic motor  130  is switched depending on which electrode group drives the ultrasonic stator  122 .  
      Preferably the ultrasonic motor  130  of the present invention is driven by the construction including the ultrasonic motor driving circuit  3   1   0 , the piezoelectric element  802 , and the ultrasonic stator  122  of the above construction. However, it may be driven by an other construction. When a counted result of 12:00 at midnight is output, the ultrasonic motor driving circuit  310  outputs an ultrasonic motor drive signal to the ultrasonic motor  130 . That is, the ultrasonic motor driving circuit  310  is configured to output an ultrasonic motor drive signal for rotating the date indicator  120  by 360°/31, that is, 1/31 rotations once a day, to the ultrasonic motor  130 . The ultrasonic motor driving circuit  310  counts “year”, “month”, “day”, and time. When the calculation result of the ultrasonic motor driving circuit  310  outputs 12:00 at midnight of an ordinary day, in correspondence with the ordinary day is outputted to the ultrasonic motor  130 . That is, the ultrasonic motor driving circuit  310  is constituted to output to the ultrasonic motor  130 , the ultrasonic motor drive signal for rotating the date indicator  120  once per day, by 360°/31, that is, by a 1/31 rotation.  
      As described above, the ultrasonic motor  130  of the present invention is provided with the ultrasonic stator  122  bonded with the piezoelectric elements  802 , and provided with the ultrasonic rotor  134  frictionally driven by oscillatory waves generated at the ultrasonic stator  122  by elongation and contraction of the piezoelectric element by inputting the ultrasonic motor drive signal. There are formed at least two sets of electrode groups each including a plurality of electrodes, on the surface of the piezoelectric element  802 . The ultrasonic motor driving circuit  310  includes at least two power amplifiers, and output terminals of the power amplifiers are respectively connected to the two sets of electrode groups of the piezoelectric element to thereby drive to excite the respective electrodes independently from each other.  
      (5) Other Structure of Electronic Timepiece in Which Ultrasonic Motor is Used  
      Next is a description of an other structure of an electronic timepiece in which the ultrasonic motor of the present invention is used.  
      Referring to  FIG. 11 , a movement  400  (machine body including the driving part) of the electronic timepiece is constituted by an analog electronic timepiece, and is provided with a main plate  402  constituting a base plate of the movement  400 . A dial  430  is attached to the movement  400 . The movement  400  has the ultrasonic motor  130 . The fourth wheel-and-pinion  410  is arranged to rotate based on rotation of the ultrasonic rotor  134 . The gear section provided in the ultrasonic rotor  134  of the ultrasonic motor  130  meshes with the gear section provided in the fourth wheel-and-pinion  410  so that the fourth wheel-and-pinion  410  can rotate based on the rotation of the ultrasonic rotor  134 . The fourth wheel-and-pinion  410  is constituted to rotate once per minute. A second hand  424  for indicating “second”, is attached to the fourth wheel-and-pinion  410 . A third wheel-and-pinion  412  is arranged to rotate based on rotation of the fourth wheel-and-pinion  410 . A minute indicator  414  is arranged to rotate based on rotation of the third wheel-and-pinion  412 . The minute indicator  414  is constituted to rotate once per hour. A minute hand  422  for indicating “minutes”, is attached to the minute indicator  414 . An hour wheel  416  is arranged to rotate based on rotation of the minute indicator  414 .  
      The hour wheel  416  is constituted to rotate once in 12 hours. An hour hand  420  for indicating “hours”, is attached to the hour wheel  416 . In the movement  400 , the construction of the other parts is similar to a conventional analog electronic timepiece.  
      Next, is a description of the operation of the movement  400 . Based on the oscillation of the quartz oscillator, a frequency dividing circuit divides an output signal from the oscillation circuit The oscillation circuit, the frequency dividing circuit, and the ultrasonic motor driving circuit (all not illustrated) are built into the integrated circuit (not illustrated). Based on the output signal from the frequency dividing circuit, the ultrasonic motor driving circuit outputs the ultrasonic motor drive signal which drives the ultrasonic motor  130 . The fourth wheel-and-pinion  410  rotates based on the rotation of the ultrasonic rotor  134  of the ultrasonic motor  130 . The fourth wheel-and-pinion  410  is constituted to rotate once per minute. The second hand  424  is rotated integrally with the fourth wheel-and-pinion  410 . The third wheel-and-pinion  412  is rotated based on rotation of the fourth wheel-and-pinion  410 . The minute indicator  414  is rotated based on rotation of the third wheel-and-pinion  412 . The minute hand  422  is rotated integrally with the minute indicator  414 . The minute indicator  414  rotates once per hour. A minute wheel (not illustrated) is rotated based on rotation of the minute indicator  414 . The hour wheel  416  is rotated based on rotation of the minute wheel. The hour wheel  416  is rotated once per  12  hours. An hour hand  420  is attached to the hour wheel  416 . The hour hand  420  is rotated integrally with the hour wheel  416 .  
      The electronic timepiece in which the ultrasonic motor of the present invention is used, may also be provided with a calendar indication wheel for indicating other data in respect of a calendar, that is, “year”, “month”, “day of the week”, “six weekdays” or the like. In this case, the calendar indication wheel may be constituted so as to be rotated by rotation of the ultrasonic motor  130  via a reduction wheel train. Or, the calendar indication wheel may be constituted so as to be rotated by rotation of the hour wheel  416  via a reduction wheel train.  
      (6) Other Embodiments  
      In the above embodiments of the present invention, the present invention was described for the embodiment of an analog electronic timepiece including one motor and one ultrasonic motor, and the embodiment of an analog electronic timepiece including one ultrasonic motor. However, the present invention may be applied to; an analog electronic timepiece including a plurality of ultrasonic motors and one motor, may be applied to an analog electronic timepiece including one ultrasonic motor and a plurality of motors, or may be applied to an analog electronic timepiece including a plurality of ultrasonic motors and a plurality of motors. In the above embodiments of the present invention, the present invention was described for a so-called “disk shaped ultrasonic motor”. However, the present invention may be applied to a so-called “toric shaped ultrasonic motor”. Furthermore, the ultrasonic motor of the present invention may be applied to an electronic apparatus with an ultrasonic motor which has a power source, a source of oscillation, a controlling circuit, and the ultrasonic motor. Examples of such electronic apparatus with an ultrasonic motor include a vibration alarm timepiece, a vibration timer, a pocket-bell (registered trademark), a pager, a transceiver, a mobile telephone, and a warning machine, and the like. In such electronic apparatus with an ultrasonic motor, output member include a diaphragm, a rotation weight, an enunciating member, n display plate, and the like, which operate by rotation of the ultrasonic motor of the present invention. Moreover, the ultrasonic motor of the present invention can be applied to a measuring instrument, a printer, imaging equipment, recording equipment, a storage equipment, and the like. In such electronic apparatus-with an ultrasonic motor, an output member may include a gear, a cam, a plate member, or the like, which operates by rotation of the ultrasonic motor of the present invention.  
      In the above embodiments of the present invention, generally the base resin is polystyrene, polyethylene terephthalate, polycarbonate, polyacetal (polyoxymethylene), polyamide, a modified polyphenylene ether, polybutylene terephthalate, polyphenylene sulfide, polyether ether ketone, or polyether imide. polyether sulphone, polyethylene, nylon 6, nylon 66, nylon 12, polypropylene, ABS plastic, or AS resin, can also be used as the base resin. Moreover, two or more kinds of the above mentioned thermoplastic resins may be mixed to use as the base resin. Furthermore, an additive (antioxidant, lubricant, plasticizer, stabilizer, bulking agent, solvent, or the like) may be blended with the base resin used in this invention.  
      Next is a description of experimental data showing the coefficient of dynamic friction and the specific wear rate of the carbon filled resin used in the above embodiments, referring to TABLE. 1 and TABLE 2. TABLE. 1 shows the coefficient of dynamic friction, the specific wear rate, and the critical PV value of polyamide resin  12  (PA12), polyacetal resin (POM), and polycarbonate resin (PC) with a carbon filler of 20% by weight added.  
      In TABLE 1, VGCF (trademark) “Vapor Grown Carbo Fiber” is a resin with carbon filler of 20% by weight added. The characteristics of non-composite material to which carbon filler has not been added (resin only, that is PA12, POM, PC itself) are shown as “Blank” for comparison.  
      The respective resins mentioned above were injection mould under the molding conditions shown in TABLE.  2 . That is, for a composite material of PA12 with carbon filler of 20% by weight added, the temperatures was 220° C. at the nozzle, 230° C. at the front section (metering section), 220° C. at the middle section (compressing section), 210° C. at the back section (supplying section), and 70° C. at the mold. For the non-composite material of PA12, the respective temperatures were 190° C., 200° C., 180° C., 170° C., and 70° C. For the composite material of POM with carbon filler of 20% by weight added, the above respective temperatures were 200° C., 210° C., 190° C., 170° C., and 60° C., and for the non-composite material of POM, the respective temperatures were 180° C., 185° C., 175° C., 165° C., and 60° C. For the composite material of PC with carbon filler of 20% by weight added, the above temperatures were 290° C., 310° C., 290° C., 270° C., and 80° C., and for the non-composite material of PC, the respective temperatures were 280° C., 290° C., 270° C., 260° C., and 80° C.  
      Here, coefficient of dynamic friction, specific wear rate (mm3/N·km), and critical PV value (kPa·m/s) denote the values when a resin piece of a predetermined shape (φ55 mm×thickness 2 mm) is slid along a copper sheet (S45C) at a speed of 0.5 m/sec while adding a face pressure of 50N.  
      These measuring methods are according to the plastic sliding wear test method (JIS K 7218 standard) (JIS: Japanese Industrial Standard).  
      In the case of polyacetal resin (POM), for the filler added material compared to the non-composite material (Blank), the coefficient of dynamic friction was about 1.5 times, and the specific wear rate was about 1/10000.  
      Incidentally, the rotating torque of the ultrasonic motor can be obtained by the following equation. 
 
Rotating torque=“spring power of pressurizing spring,”×“coefficient of dynamic friction”×“radius from ultrasonic motor rotation center to pressurizing section”. 
 
      From the above, by forming the ultrasonic rotor  134  or the like from the carbon filled polyacetal resin (POM) in the above embodiments, it was found that the rotating torque was 1.5 times that of the non-composite material (Blank), even if the spring power of the pressurizing spring was the same.  
      On the other hand, although there is no qualitative equation regarding warm-up time (response time) of ultrasonic rotors  134  or the like, it is empirically known that the more the spring power of the pressurizing spring is increased, the longer the warm-up time becomes. Therefore, by forming the ultrasonic rotor  134  or the like from the carbon filled polyacetal resin (POM) in the above embodiments, the spring power of the pressurizing spring can be decreased compared to the non-composite material (Blank) even if the rotating torque is the same, so that warm-up time can be shortened.  
      In the case of polyamide resin (PA12), for the carbon filled material compared to the non-composite material (Blank), the coefficient of dynamic friction was about 1/2, but the specific wear rate was about 1/100. Therefore, by forming the ultrasonic rotor  134  or the like from the carbon filled polyamide resin in the above embodiments, the spring power of the pressurizing spring can be about 50 times that of the non-composite material (Blank), if the durability is equal, so that the rotating torque can be increased by about 50 times. On the other hand, in the case where equal torques are obtained, the spring power of the pressurizing spring should be doubled. However since the specific wear rate is about 1/100, the durability can be about 50 times.  
      In the case of polycarbonate resin (PC), for the carbon filled material compared to the non-composite material (Blank), the coefficient of dynamic friction was about 1/2.5, but the specific wear rate quantity was about 1/3. Therefore, by forming the ultrasonic rotor  134  or the like from the carbon filled polycarbonate resin in the above embodiments, even if the spring power of the pressurizing spring is increased 3 times that of the non-composite material (Blank), the abrasion loss becomes equal to that of the non-composite material (having 1 times the spring power). Therefore, by forming the ultrasonic rotor  134  or the like from the carbon filled polyamide resin, the spring power of the pressurizing spring can be increased by more than the drop of the coefficient of dynamic friction, so that the rotating torque can be increased.  
     Industrial Applicability  
      The ultrasonic motor of the present invention includes an ultrasonic rotor formed from the filler containing resin with a base resin of carbon filler filled into a base resin. The index α (α=specific wear rate /coefficient of dynamic friction) of the filler containing resin can be decreased less than that of the no filler resin. The index a can be decreased by increasing the coefficient of dynamic friction, or decreasing the specific wear rate.  
      Now, in the case where the deflection when raising the pressurizing spring is fixed, the smaller the spring constant (spring constant=spring power/deflection), the smaller the fluctuation of the spring power with respect to the fluctuation change. Here, considering the case where the coefficient of dynamic friction is increased, since the spring power of a pressurizing spring required for generating the same rotating torque becomes smaller, the spring constant becomes small under the aforementioned condition where the deflection is constant. Therefore, stable spring power can be generated with respect to deflection fluctuation, so that the spring force of the “pressurizing spring” can be easily adjusted.  
      Moreover, considering the case where the specific wear rate of the filler containing resin is reduced, since the ultrasonic motor of the present invention includes the ultrasonic rotor formed from the filler containing resin, wear resistance of the contact area between the ultrasonic rotor shaft and the bearing, and wear resistance of the contact area between the ultrasonic rotor and the ultrasonic stator can be increased.  
      As a result, in an electronic timepiece or an electronic instrument having the ultrasonic motor of the present invention, it is easy to adjust the spring power of the “pressurizing spring” which makes the ultrasonic rotor contact with the ultrasonic stator under pressure. Moreover, the durability performance of the contact area between the ultrasonic rotor shaft and the bearing, and the contact area between the ultrasonic rotor and the ultrasonic stator, becomes excellent.  
      For example, in the case where the ultrasonic rotor is molded as just the ultrasonic rotor, the coefficient of dynamic friction is about 0.1 to 0.4 in the natural material of the polyacetal (polyoxymethylene). On the other hand, in the case where the ultrasonic rotor is molded from the filler containing resin with a polyacetal base resin filled with a carbon filler, the coefficient of dynamic friction is about 0.55 for the filler containing resin, the coefficient of dynamic friction of the filler containing resin being larger than that for the polyacetal. Consequently, in the ultrasonic motor of the present invention, the frictional property of the ultrasonic rotor and ultrasonic stator is stable. Hence it is easy to adjust the spring power of the pressurizing spring. Moreover, in the case where the ultrasonic rotor is molded as just the ultrasonic rotor, the specific wear rate is about 2.2×10 −4  mm 3 /N·km for the natural material of the polyacetal. On the other hand, in the case where the ultrasonic rotor is molded from the filler containing resin with the polyacetal base resin filled with a carbon filler, the specific wear rate is about 3.3×10 −9  mm 3 /N·km, the specific wear rate of the filler containing resin being much smaller than that for the natural material of the polyacetal. Consequently, the ultrasonic motor of the present invention can be manufactured so that the wear resistance of the contact area between the ultrasonic rotor bearing section and the ultrasonic rotor shaft section, and the contact area between the ultrasonic rotor and the ultrasonic stator can be increased. Moreover, in an electronic time piece or an electronic instrument having the ultrasonic motor of the present invention, it is easy to adjust the spring power of the pressurizing spring, and the durability performance of the contact area between the ultrasonic rotor and the ultrasonic stator is excellent.  
                               TABLE 1                                      PA12   POM   PC                                                     VGCF       VGCF       VGCF           Item   Units   20 wt %   BLANK   20 wt %   BLANK   20 wt %   BLANK                                                     Dynamic friction       0.25   0.56   0.55   0.35   0.18   0.51       coefficient       Specific wear rate   mm 3 /N · km   3.8 × 10 −13     5.2 × 10 −11     3.3 × 10 −9     2.2 × 10 −4     3.3 × 10 −8     8.1 × 10 −8         Critical PV value   kPa · m/s   1547   765(melt)   1056(melt)       1056(melt)   765(melt)                  
 
     
       
         
           
               
               
               
               
             
               
                   
                 TABLE 2 
               
             
            
               
                   
                   
               
               
                   
                   
               
               
                   
                 PA12 
                 POM 
                 PC 
               
            
           
           
               
               
               
               
               
               
               
            
               
                   
                 VGCF 
                 BLANK 
                 VGCF 
                 BLANK 
                 VGCF 
                 BLANK 
               
               
                   
               
               
                 NOZZLE 
                 220° C. 
                 190° C. 
                 200° C. 
                 180° C. 
                 290° C. 
                 280° C. 
               
               
                 FRONT SECTION 
                 230° C. 
                 200° C. 
                 210° C. 
                 185° C. 
                 310° C. 
                 290° C. 
               
               
                 MIDDLE SECTION 
                 220° C. 
                 180° C. 
                 190° C. 
                 175° C. 
                 290° C. 
                 270° C. 
               
               
                 BACK SECTION 
                 210° C. 
                 170° C. 
                 170° C. 
                 165° C. 
                 270° C. 
                 260° C. 
               
               
                 MOLD TEMP. 
                  70° C. 
                  70° C. 
                  60° C. 
                  60° C. 
                  80° C. 
                  80° C.