Abstract:
A piezoelectric transducer of a new laminated structure is provided that is easy to fabricate, produces a large amount of motive energy and has high mechanical strength. Electrodes are installed on one of the surfaces of respectively a first and a second piezoelectric element formed in a thin shape, a second piezoelectric element formed without an electrode is laminated onto the top of the surface of the first piezoelectric element having an electrode to form a laminated piece. The laminated piece is wound to form a tube or folded to form a rod. The tube or rod-shaped laminate is then baked and polarized to produce a piezoelectric transducer.

Description:
This application is based on patent application No. 10-119901 filed in Japan, the contents of which are hereby incorporated by reference. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to the structure and process of forming of piezoelectric transducer, and an actuator using the piezoelectric transducer. 
     2. Description of Related Art 
     Actuators utilizing piezoelectric transducers are highly efficient in converting electrical energy to motive energy, and generating large amounts of motive energy though being compact and lightweight. In addition, the motive energy generated by the piezoelectric transducer can be easily regulated. All of these characteristics make actuators utilizing piezoelectric transducers ideal for use in positioning and moving driven members in cameras, test instruments and other precision equipment. 
     The piezoelectric transducer which serves as the drive source used in this kind of actuator is comprised of a plurality of piezoelectric elements laminated together. This configuration allows the largest possible physical displacement in the direction of piezoelectric element thickness to be obtained in response to an applied voltage. 
     FIG.  22 ( a ) is an oblique view showing the external structure of the piezoelectric transducer comprised of a plurality of piezoelectric elements laminated together. A piezoelectric transducer  100  is comprised of a plurality of individual piezoelectric elements  101  each being about 100 micrometers thick and provided on one surface with an electrode  102 . Every other electrode  102  (between facing piezoelectric elements) is connected to a line  103  as the positive terminal while the remaining electrodes  102  are connected to the line  104  as the negative terminal as shown in FIG.  22 ( b ). Since the thickness of the piezoelectric transducer changes as a voltage is applied between the positive and negative terminals, the changes in the thickness or displacement can be transmitted through an appropriate means to drive or position the driven member. 
     FIG. 23 is a cross-sectional view showing the actuator using the piezoelectric transducer comprised of a plurality of piezoelectric element units as described above. FIG. 24 is a cross sectional view showing the friction coupling of the actuator. 
     In FIG. 23, the reference numeral  111  denotes a frame,  112 ,  113 ,  114  are support blocks and  115  is a drive shaft. The drive shaft  115  is supported by the support block  113  and the support block  114  to allow axial movement. One end of the piezoelectric transducer  100  is affixed to the support block  112  and affixed at the other end to the drive shaft  115 . The drive shaft  115  is supported to allow axial displacement (direction of arrow a and its opposite direction) in response to displacement in the direction of thickness of the piezoelectric transducer  100 . 
     The drive shaft  115  passes through a slider block  116 . An aperture  116   a  is formed, as shown in FIG. 24, in the lower part of the slider block  116  through which the drive shaft  115  passes and the lower half of the drive shaft  115  is thus exposed. In this aperture  116   a , a pad  117  is fitted to engage with the lower half of the drive shaft  115 , and a protrusion  117   a  is formed in the lower section in the pad  117  (See FIG.  24 ). The protrusion  117 a of the pad  117  is pressed upwards by a plate spring  118  and an upward force F is thus applied on the pad  117  to contact the drive shaft  115 . 
     A table  120  for placement of objects is secured to the slider block  116  with machine screws  121 . 
     In the above arrangement, the drive shaft  115  and slider block containing the pad  117  are press-contacted by the force F of the plate spring  118  and friction coupled. 
     The operation is described next. First of all, when a sawtooth waveform pulse having a gentle rising part and a steep falling part is applied to the piezoelectric transducer  100 , the gentle rising part of the drive pulse causes the piezoelectric transducer  100  to elongate, displacing in the direction of thickness, and the drive shaft  115  coupled to the piezoelectric transducer  100  also displaces slowly in the direction of the arrow “a”. The slider block  116  at this time friction coupled to the drive shaft  115  moves in the direction of the arrow “a” along with the drive shaft  15  due to the friction coupling force. 
     The steep falling part of the drive pulse causes the piezoelectric transducer  100  to contract, displacing in the direction of thickness, and the drive shaft  115  coupled to the piezoelectric transducer  100  also displaces swiftly in the opposite direction of the arrow “a”. The slider block  116  at this time friction coupled to the drive shaft  115  is effectively stopped in the current position and does not move, due to the cancelling out of the friction coupling force by the inertia of the slider block  116 . The slider block  116  and the table attached to the slider block  116  can be moved consecutively in the direction of the arrow “a” by means of consecutive application of drive pulses to the piezoelectric transducer  100 . 
     In order to move the slider block  116  and the table  120  in the opposite of the previous direction (opposite direction of arrow “a”), the sawtooth drive pulse waveform applied to the piezoelectric transducer  100  is changed and a drive pulse consisting of a steep rising part and a gentle falling part can then be applied to achieve movement in the opposite direction. 
     The above description also effectively takes into account that a sliding motion is added to the friction coupled surfaces between the slider block  116  and the drive shaft  115  whether moving in the direction of the arrow “a” or the opposite direction and objects moving in direction of the arrow “a” are also included due to the difference in drive times. 
     Among other configurations of the piezoelectric transducer is a piezoelectric transducer formed in hollow tubular shape of a single layer. FIG. 25 is a cross sectional view showing one configuration of the hollow tubular shaped single layer piezoelectric transducer  134 . In FIG. 25, an electrode  136  and an electrode  137  are formed on the outer surface of the single layer, hollow tubular piezoelectric transducer  134 , and an electrode  138  is formed on the inner surface of the hollow cylinder. 
     The single layer, hollow tubular piezoelectric transducer  134  is supported by support members  132 ,  133  installed on the right and left of a mount  131 . A slider  135  is friction coupled to the hollow tubular piezoelectric transducer  134  by an appropriate amount of frictional force. A plug  133   a  is installed to fit in with one end of the piezoelectric transducer  134  and this plug  133   a  screws into the support member  133  so that the piezoelectric transducer  134  is secured and supported by the mount  131 . 
     In this configuration, a first electrode section comprised of an electrode  136  and an electrode  138 ; and a second electrode section comprised of an electrode  137  and an electrode  138 , are both polarized beforehand in the same radial direction. When sawtooth wave pulses of mutually reverse polarities are applied to the first electrode section and the second electrode section while in this state, an elongation displacement occurs at the first electrode section and a contraction displacement occurs at the second electrode section during the gentle rising part of the sawtooth waveform pulse, and the slider  135  can move in the direction of the arrow “a”. Further, on the steep falling part of the sawtooth waveform pulse a sudden contraction displacement occurs at the first electrode section and a sudden elongation displacement occurs at the second electrode section however the inertia of the slider  135  cancels out the force of the frictional coupling with the piezoelectric transducer  134  and there is no sliding movement on their surfaces. Thus by transmitting the movement of the slider  135  to the drive section of a transducer by a suitable means, the positioning and driving of a drive member can be achieved. 
     The piezoelectric transducer of the conventional art configured as related above with a plurality of laminations of piezoelectric elements was fabricated by means of a complex process consisting of a process to install electrodes in the respective surfaces of the individual piezoelectric elements, a process to bond or adhere the laminations, and a process to wire the electrodes of each layer. These complex processes had the drawback of a high manufacturing cost. 
     Further, even though the hollow tubular shaped single layer piezoelectric transducer had the characteristic of comparatively high mechanical strength, increasing the intensity of the electrical field was required in order to increase the displacement generated by the piezoelectric element. Accordingly, when there are limitations on the voltage that can be applied to the piezoelectric element, the thickness of the piezoelectric transducer had to be reduced to raise the intensity of the electrical field. In other words, the problem arose that when increasing the displacement generated by the piezoelectric transducer was attempted, the mechanical strength of the piezoelectric transducer declined. 
     SUMMARY OF THE INVENTION 
     In view of the above mentioned problems it is therefore a purpose of the current invention to provide a piezoelectric transducer having a new laminated structure, simple to fabricate and yielding a large motive power. 
     Another object of this invention is to provide a piezoelectric transducer comprising a new laminated structure having adequate mechanical strength even if the thickness of the piezoelectric element is reduced in order to generate a large displacement by increasing the intensity of the electrical field. 
     Yet another object of this invention is to provide a new process of forming a piezoelectric transducer comprising a new laminated structure, simple to fabricate, thus allowing a drastic reduction in the complex fabrication required in the conventional art such as a process to install electrodes in the respective surfaces of the individual piezoelectric elements, a process to bond or adhere the laminations, and a process to wire the electrodes of each layer. 
     Other objects of the invention will become clear by the detailed description of the invention while referring to the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is an oblique view of the exterior of the piezoelectric transducer of the first embodiment of this invention. 
     FIG. 2 is a cross sectional view showing the piezoelectric transducer of FIG.  1 . 
     FIG. 3 is an oblique view showing the fabrication process of the piezoelectric transducer of FIG.  1 . 
     FIG. 4 is a cross sectional view showing the structure of the actuator used in the piezoelectric transducer of FIG. 
     FIG. 5 is an oblique view showing the structure of the piezoelectric transducer of the second embodiment. 
     FIG. 6 is a cross sectional view showing the structure of the actuator used in the piezoelectric transducer of FIG.  5 . 
     FIG. 7 is an oblique view showing the structure of the piezoelectric transducer of the third embodiment. 
     FIG. 8 is a cross sectional view showing the structure of the actuator used in the piezoelectric transducer of FIG.  7 . 
     FIG. 9 is an oblique view showing the structure of the piezoelectric transducer of the fourth embodiment. FIG. 10 is a cross sectional view showing the structure of the actuator used in the piezoelectric transducer of FIG.  9 . 
     FIG. 11 is an oblique view showing the fabrication process of the piezoelectric transducer of the fifth embodiment. 
     FIG. 12 is an oblique view showing the piezoelectric transducer of FIG.  11 . 
     FIG. 13 is a cross sectional view showing the structure of the actuator used in the piezoelectric transducer of FIG.  12 . 
     FIG. 14 is an oblique view showing the structure of the laminated piezoelectric element of the sixth embodiment. 
     FIG. 15 is an oblique view showing the structure of the piezoelectric transducer comprised of a folded piezoelectric element of FIG.  14 . 
     FIG. 16 is an oblique view showing another configuration of the piezoelectric transducer comprised of a folded piezoelectric element. 
     FIG. 17 is a cross sectional view illustrating the laminated structure of the piezoelectric element in FIG.  16 . 
     FIG. 18 is an oblique view showing another configuration of the piezoelectric transducer comprised of a folded piezoelectric element. 
     FIG. 19 is an oblique view shown another configuration of the laminated piezoelectric element. 
     FIG. 20 is an oblique view showing the structure of the laminated piezoelectric element of the seventh embodiment. 
     FIG. 21 is an oblique view of the exterior of the piezoelectric transducer of the seventh embodiment. 
     FIG.  22 ( a ) is an oblique view showing the structure of the piezoelectric transducer of the conventional art comprising a plurality of laminated piezoelectric elements. 
     FIG.  22 ( b ) is a side view showing the wiring of the piezoelectric transducer of the conventional art comprising a plurality of laminated piezoelectric elements. 
     FIG. 23 is a cross sectional view showing the actuator using the piezoelectric transducer of the conventional art comprising a plurality of laminated piezoelectric elements. 
     FIG. 24 is a cross sectional view showing the structure of the frictional coupling of the actuator of the conventional art in FIG.  23 . 
     FIG. 25 is a cross sectional view showing a typical structure of the hollow tubular shaped single layer piezoelectric transducer of the conventional art. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The embodiments of the present invention will next be described in detail while referring to the accompanying drawings. 
     First Embodiment 
     The piezoelectric transducer of the first embodiment of this invention is described while using FIG.  1  through FIG.  3 . FIG. 1 is an oblique view showing an external view of the piezoelectric transducer. FIG. 2 is a cross sectional view showing the piezoelectric transducer of FIG.  1 . FIG. 3 is an oblique view showing the fabrication process of the piezoelectric transducer of FIG.  1 . 
     The piezoelectric transducer as shown in FIG. 3 is first formed with two electrodes  11   a  and  12   a  on the respective surfaces of the two thin piezoelectric elements  11  and  12 , next the surface of the second piezoelectric element  12  formed without the electrode, is aligned opposite with and laminated on the surface of the first piezoelectric element  11  having the surface electrode  11   a , and then formed in a tubular shape as shown in FIG.  1  and FIG.  2 . 
     As shown in FIG. 1, when laid on each other, the end of the second piezoelectric element  12  positioned on the upper side is formed with a notch  12   b  in order to expose the electrode  11   a  of the first piezoelectric element  11  positioned on the lower side. This notch  12   b  allows a wire lead to be connected to the electrode  11   a  on the lower side of the piezoelectric element  11 . 
     The piezoelectric elements laminated on each other and wound to form a tubular shape are then normalized (baked), wire leads connected to the electrodes  11   a  and  12   a , and when a specific high DC current is applied for polarization, the fabrication of a piezoelectric transducer  10  is complete. 
     As piezoelectric materials, PZT (PbZrO 3 ·PbTiO 3 ) can be used as the main constituents of the piezoelectric elements  11  and  12 . Further, it is possible to use inorganic piezoelectric materials as the main constituents of the piezoelectric elements  11  and  12 , wherein the inorganic piezoelectric materials can be formed in prescribed shape by baking. A ceramic powder of this type is mixed with solvents, dispersants and plasticizers, and then a blade or similar tool is used to draw out the material to a specified thickness with a uniform surface. When the solvent is dried, a soft material referred to as a green sheet can be obtained. An electrode is formed on the surface of this green sheet by a means such as lithography, a desired shape formed and when normalized (baked) to a specific temperature, a piezoelectric transducer as described above can be obtained. 
     FIG. 4 is a cross sectional view showing the structure of the actuator used in the piezoelectric transducer of FIG.  1 . Here, the reference numeral  14  denotes a mount,  15 ,  16 ,  17  are a support blocks, and  18  is a drive shaft. The drive shaft  18  is supported by the support block  16  and the support block  17  to move in the axial direction (direction of arrow “a” or opposite direction) by the axial displacement occurring in the piezoelectric transducer  10 . 
     Here, the reference numeral  10  denotes a piezoelectric transducer formed in a tubular shape of two laminated thin piezoelectric elements as described above. One end of the piezoelectric transducer  10  is secured by bonding to the support block  15  and the other end is secured by bonding to the drive shaft  18 . 
     The reference numeral  19  denotes a slider block. This slider block  19  is frictionally coupled by an appropriate amount of frictional force to the drive shaft  18 . The frictional coupling is comprised of the same structure as previously described for the example of the conventional art in FIG.  24 . In other words, the drive shaft  18  runs through the slider block  19  and an aperture  19   a  is formed in the lower section of the slider block  19  through which the drive shaft  18  runs and exposes the lower half of the drive shaft  18 . Further, a pad  20  is insertably fitted to make contact in the lower half of the drive shaft  18  in the aperture  19   a . This pad  20  is pressed upwards by a plate spring not shown in the drawing, the drive shaft  18 , slider block  19  and the pad  20  are press-contacted by the force of the spring lever and frictionally coupled by an appropriate amount of frictional force. Further, the slider block  19  is coupled to a driven member such as a table not shown in the drawing. 
     This operation is the same for that previously described for the actuator in the example of the conventional art in FIG.  23 . When a sawtooth waveform pulse at a frequency of  10  kHz is applied to the electrodes  11   a  and  12   a  of the piezoelectric transducer  10 , a reciprocating vibration is generated axially at differing speeds in the piezoelectric transducer  10  and the same reciprocating vibration is also generated for the drive shaft  18 . By this process, the slider block friction coupled to the drive shaft  18  is moved in the low speed direction of vibration by means of an asymmetrical reciprocal vibration while sliding along the drive shaft and a driven member such as a table coupled to a slider block can therefore be moved. 
     Second Embodiment 
     The piezoelectric transducer of the second embodiment has functions and configuration that can be substituted for the hollow tubular shaped single layer piezoelectric transducer shown in FIG. 25 as an example of the conventional art. 
     FIG. 5 is an oblique view showing the structure of the piezoelectric transducer of the second embodiment. This piezoelectric transducer comprises a lamination of two thin piezoelectric elements  31  and  32  and a portion is wound as shown in the drawing. The finished shape is a hollow tubular shape formed from a plurality of completely wound layers. 
     A common electrode  31   a  is formed on the entire surface of the first thin piezoelectric elements  31 , and a first electrode  32   a  and a second electrode  32   b  are formed at a specified interval D on the surface of the second thin piezoelectric element  32 . Next, the non-electrode side of the second piezoelectric element  32  is positioned opposite and laminated on the common electrode  31   a  of the first thin piezoelectric elements  31  and winding performed in a plurality of wound layers to comprise the hollow tubular shaped piezoelectric transducer  30 . 
     As shown in FIG. 5, a notch  32   c  is formed on the end of the second piezoelectric element  32  positioned on the upper side during alignment for lamination in order to expose the end of the common electrode  31   a  of the first piezoelectric element  31  positioned on the lower side. A wire lead can then be connected to the common electrode  31   a  of the first piezoelectric element  31  on the lower side during alignment for lamination. 
     The piezoelectric elements configured in a wound tubular shape are normalized (baked), and wire leads connected to the first electrode  32   a , the second electrode  32   b  as well as the common electrode  31   a , and when a specified high DC current is applied across the first electrode  32   a  and common electrode  31   a  and also across the second electrode  32   b  and the common electrode  31   a , polarization occurs and the fabrication of the piezoelectric transducer  30  is complete. 
     The material and the fabrication process of the piezoelectric elements  31  and  32  is the same as previously described for the configuration of the first embodiment so the detailed description is omitted here. 
     FIG. 6 is a cross sectional view showing the structure of the actuator used in the piezoelectric transducer shown in FIG.  5 . In FIG. 6, the reference numeral  34  denotes a mount,  35 ,  36  are support blocks and both ends of the above mentioned hollow, tubular shaped piezoelectric transducer  30  are fixedly supported by the support blocks  35  and  36 . The technique used for securing and supporting the piezoelectric transducer  30  to the support blocks  35  and  36  is by fitting a plug into the end of the piezoelectric transducer  30  as shown in the previous example in FIG. 25, and screwing the plug into the support member, however other methods can be employed when suitable. A slider  37  is friction coupled on the hollow, tubular shaped piezoelectric transducer  30  by an appropriate amount of frictional force. 
     In this configuration, when a sawtooth waveform pulse is applied across the common electrode  31 a of the surface of the first piezoelectric element  31  and a first electrode  32 a of the second piezoelectric element  32  forming a first electrode section, and a sawtooth waveform pulse of reverse polarity is applied across the common electrode  31   a  of the first piezoelectric element  31  and an electrode  32   b  of the second piezoelectric element  32  forming a second electrode section, at the gentle rising part of the sawtooth waveform pulse, an elongation displacement is generated at the first electrode section and a contraction displacement is generated at the second electrode section, and the slider  37  can then move in the direction of the arrow “a”. 
     On the steep falling part of the sawtooth waveform pulse, a sudden contraction displacement occurs at the first electrode section and a sudden elongation displacement occurs at the second electrode section however the inertia of the slider  37  cancels out the force of the frictional coupling with the hollow, tubular piezoelectric transducer  30  and there is no sliding movement on their surfaces. Thus by transmitting the movement of the slider  37  to the driven member of a transducer by a suitable means, the positioning and driving of a drive member can be achieved. 
     This configuration has the advantages that an adhesive bond between the piezoelectric transducer and the drive shaft is unnecessary, assembly is simple, a large mechanical strength is obtained by the fixed support at both ends of the piezoelectric transducer and further that vibration is not prone to occur in a direction perpendicular to the axis. Additional advantages are that increasing the intensity of the electrical field is easy since each electrode in the laminated structure is thin and generating a large displacement is easy to achieve. 
     Third Embodiment 
     The piezoelectric transducer of the third embodiment has a structure similar to that previously described for the second embodiment however the structure of the third embodiment is capable of generating a larger axial displacement. 
     FIG. 7 is an oblique view showing the structure of the piezoelectric transducer of the third embodiment. Here, the piezoelectric transducer has a laminated structure comprised of two thin piezoelectric elements  41  and  42  and a portion of the structure in a wound state is shown in FIG.  7 . The finished shape is a hollow tubular shape formed from a plurality of completely wound layers. 
     A common electrode  41   a  is formed on the entire surface of the first thin piezoelectric element  41 , and a first electrode  42   a  and a second electrode  42   b  are formed at a specified interval D on the surface of the second thin piezoelectric element  42 . Next, the non-electrode side of the second piezoelectric element  42  is positioned opposite and laminated on the common electrode  41   a  of the first thin piezoelectric elements  41  and winding performed in a plurality of wound layers to comprise the hollow tubular shaped piezoelectric transducer  40 . 
     As shown in FIG. 7, a notch  42   c  is formed on the end of the second piezoelectric element  42  positioned on the upper side during alignment for lamination in order to expose the end of the common electrode  41   a  of the first piezoelectric element  41  positioned on the lower side. A wire lead can then be connected to the common electrode  41   a  of the first piezoelectric element  41  on the lower side during alignment for lamination. 
     Further, the widths hi of the first electrode  42   a  and the second electrode  42   b  on the surface of the second thin piezoelectric element  42 , are the tubular lengths in the axial direction of the first and second electrodes  42   a ,  42   b  when the piezoelectric element  41  and  42  were laminated and wound into a hollow tubular shape so that the widths hi can be formed with an electrode width larger than in the configuration of the second embodiment. Also, an extension  42   e  is formed at the center section  42   d  where the first and second electrodes  42   a ,  42   b  of the second piezoelectric element  42  are not formed, and a large size frictional coupling  42   f  is formed at the center of the piezoelectric transducer  40  when the piezoelectric elements are wound in the hollow tube shape as shown in FIG.  8 . The frictional coupling  42   f  is the section coupled by frictional force with the slider  47 . 
     The piezoelectric elements configured in a wound tubular shape are normalized (baked), wire leads connected to the electrode  41   a ,  42   a  and  42   b , and when a specified direct current high voltage is applied across the first electrode  42   a  and the common electrode  41   a  and also across the second electrode  42   b  and the common electrode  41   a , polarization is accomplished and the fabrication of the piezoelectric transducer  40  is complete. 
     The material and the fabrication process of the piezoelectric elements  41  and  42  is the same as previously described for the configuration of the first embodiment so the detailed description is omitted here. 
     FIG. 8 is a cross sectional view showing the structure of the actuator used in the piezoelectric transducer of the third embodiment. In FIG. 8, the reference numeral  44  denotes a mount,  45 ,  46  are support blocks and both ends of the above mentioned hollow, tubular shaped piezoelectric transducer  40  are fixedly supported by the support blocks  45  and  46 . The technique used for securing and supporting the piezoelectric transducer  40  to the support blocks  45  and  46  is by fitting a plug into the end of the piezoelectric transducer  40  as shown in the previous example in FIG. 25, and screwing the plug into the support member, however other methods can be employed when suitable. A slider  47  is friction coupled by an appropriate amount of frictional force to a large diameter friction coupling  42   f  formed in the center section of the piezoelectric transducer  40 . 
     In this configuration, when a sawtooth waveform pulse is applied across the common electrode  41 a on the surface of the first piezoelectric element  41  and a first electrode  42   a  of the second piezoelectric element  42  forming a first electrode section, and a sawtooth waveform pulse of reverse polarity is applied across the common electrode  41   a  of the first piezoelectric element  41  and a second electrode  42   b  of the second piezoelectric element  42  forming a second electrode section, during the gentle rising part of the sawtooth waveform pulse, an elongation displacement is generated at the first electrode section and a contraction displacement is generated at the second electrode section, and the slider  47  can then move in the direction of the arrow “a”. 
     On the steep falling part of the sawtooth waveform pulse a sudden contraction displacement occurs at the first electrode section and a sudden elongation displacement occurs at the second electrode section however the inertia of the slider  47  cancels out the force of the frictional coupling  42   f  with the hollow, tubular piezoelectric transducer element  40  and there is no sliding movement on their surfaces. Thus by transmitting the movement of the slider  47  to the driven member by a suitable means, the positioning and driving of a driven member can be achieved. 
     This configuration, besides the same items mentioned for the second embodiment has the advantages that an adhesive bond between the piezoelectric transducer and the drive shaft is unnecessary, assembly is simple, a large mechanical strength is obtained by the fixed support at both ends of the piezoelectric transducer and a further benefit that vibration is not prone to occur in a direction perpendicular to the axis. Additional advantages are that increasing the intensity of the electrical field is easy since each electrode in the laminated structure is thin and generating a large displacement is easy to achieve. 
     A still further advantage of this configuration is that a greater width hi can be obtained for the electrodes  42   a  and  42   b  than in the second embodiment of this invention, so that the drive is faster since a larger displacement can be obtained from application of the drive pulse voltage. 
     Fourth Embodiment 
     The piezoelectric transducer of the fourth embodiment is the hollow tubular piezoelectric transducer as previously described for the second embodiment however the structure is bent in the center so that an elliptical vibration can be generated in the bent section. 
     FIG. 9 is an oblique view showing the structure of the piezoelectric transducer of the fourth embodiment. Here, the piezoelectric transducer has a structure the same as previously described for the second embodiment, and a common electrode  51   a  is formed on the entire surface of the first thin piezoelectric element  51 , and a first electrode  52   a  and a second electrode  52   b  are formed at a specified interval on the surface of the second thin piezoelectric element  52 . Next, the non-electrode side of the second piezoelectric element  52  is positioned opposite and laminated on the common electrode  51   a  of the first thin piezoelectric elements  51  and winding performed in a plurality of wound layers to comprise the hollow tubular shaped piezoelectric transducer  50 . 
     As shown in FIG. 9, a notch  52   c  is formed on the end of the second piezoelectric element  52  positioned on the upper side during alignment for lamination in order to expose the end of the common electrode  51   a  of the first piezoelectric element  51  positioned on the lower side. A wire lead can then be connected to the common electrode  51   a  of the first piezoelectric element  51  on the lower side during alignment for lamination. 
     Next, the piezoelectric element is bent near the center at a bend section  53  to form the shape shown in FIG.  9  and then normalized (baked), and when wire leads connected to the common electrode  51   a , a first electrode  52   a  and a second electrode  52   b , a specific high DC current is applied and polarization occurs, the fabrication of a piezoelectric transducer  50  is complete. A suitable means such as press-contact is then used in the bend section  53  to achieve friction coupling to drive the driven member  57  not shown in the drawing (See FIG.  10 ). 
     The material and the fabrication process of the piezoelectric elements  51  and  52  is the same as previously described for the configuration of the first embodiment so the detailed description is omitted here. 
     FIG. 10 is a cross sectional view showing the structure of the actuator used in the piezoelectric transducer of the fourth embodiment. In FIG. 10, the reference numeral  54  denotes a mount,  55 ,  56  are support blocks and both ends of the above mentioned hollow, tubular shaped piezoelectric transducer  50  are fixedly supported by the support blocks  55  and  56 . 
     In this configuration, when a sine wave voltage of a certain phase is applied across the common electrode  51 a on the surface of the first piezoelectric element  41  and a first electrode  52 a of the second piezoelectric element  52  forming a first electrode section, and a sine wave voltage of a certain phase of a respectively different polarity is applied across the common electrode  51   a  of the first piezoelectric element  52  and a second electrode  52   b  of the second piezoelectric element  52  forming a second electrode section, an elliptical vibration is generated in the bend section  53  of the piezoelectric transducer  50  so that driving of the driven member  57  is accomplished by friction coupling to the bend section  53 . 
     The configuration of the fourth embodiment, just the same as previously described for the second embodiment besides requiring no bond coupling between the drive shaft and the piezoelectric transducer and having a simple assembly process, also has a large mechanical strength by way of the fixed support at both ends of the piezoelectric transducer and the further benefit that vibration is not prone to occur in a direction perpendicular to the axis. Further advantages are that increasing the intensity of the electrical field is simple since each electrode in the laminated structure is thin and generating a large displacement is easy to achieve. 
     Fifth Embodiment 
     The piezoelectric transducer of the fifth embodiment is the configuration described for the fourth embodiment achieved in two dimensions. 
     FIG. 11 is an oblique view showing the fabrication process of the piezoelectric transducer of the fifth embodiment in which a common electrode  61 a is installed on the entire surface of the square-shaped first piezoelectric element  61 , and the four electrodes consisting of a first electrode  62   a , a second electrode  62   b , a third electrode  62   c  and a fourth electrode  62   d  mutually facing respectively in  90  degree directions are formed on the surface of the second piezoelectric element  62 . 
     Next, the non-electrode side of the second piezoelectric element  62  is made to face and laminated on the common electrode  61   a  of the first piezoelectric element  61  and formed four elements  63   a - 63   d . Notches are provided between each of the elements  63   a ,  63   b ,  63   c  and  63   d . Each of these elements  63   a ,  63   b ,  63   c  and  63   d  is respectively wound to form four hollow tubular piezoelectric elements  63   a ,  63   b ,  63   c  and  63   d  at respective  90  degree angles on the same plane. These four hollow tubular piezoelectric elements  63   a ,  63   b ,  63   c  and  63   d  are joined together at a center section  63   e  of the piezoelectric transducer  60 . 
     Next, each of the four hollow tubular piezoelectric elements  63   a ,  63   b ,  63   c  and  63   d  joined together at the center section  63   e , are bent at a specified angle from the center section  63   e  as shown in FIG.  12 . The resulting structure is normalized (baked). Wire leads are connected to the first electrode  62   a  through fourth electrode  62   d , a specified high direct current voltage applied to cause polarization and the fabrication of the piezoelectric transducer  60  is now complete. A driven member  67  not shown in the figure, (See FIG. 13) is friction coupled by a suitable means such as press-contact. 
     The material and the fabrication process of the piezoelectric elements  61  and  62  is the same as previously described for the configuration of the first embodiment so the detailed description is omitted here. 
     In this configuration, the four hollow tubular piezoelectric elements  63   a ,  63   b ,  63   c  and  63   d  are positioned at 90 degree angles from each other on the same surface. In other words, the piezoelectric elements  63   a  and  63   c  are positioned along the plane of the X axis and the piezoelectric elements  63   b  and  63   d  are positioned along the plane of the Y axis so that an actuator functioning on the X and Y axes can be obtained. 
     FIG. 13 is a cross sectional view showing the structure of the XY axis actuator used in the piezoelectric transducer of the fifth embodiment and shows a cross section taken along the X axis. The configuration is exactly the same however for the Y axis direction. In FIG. 13, the reference numeral  64  denotes a mount, and a support blocks  65 ,  66  are installed at the ends of the X axis. The ends of the piezoelectric elements  63   a  and  63   c  of the piezoelectric transducer  60  are fixedly supported by the support blocks  65 ,  66 . Further, the support blocks  65 ,  66  are installed on the mount  64 , at the ends of the Y axis (not shown in drawing) and fixedly support the ends of the piezoelectric elements  63   b  and  63   d.    
     In order to obtain movement along the X axis by drive of piezoelectric elements  63   a  and  63   c , when a sine waveform voltage of a certain phase is applied to a first electrode section comprised of the common electrode  61   a  and first electrode  62   a  of a piezoelectric element  63   a , and a sine waveform voltage of a correspondingly different phase is applied to a third electrode section comprised of the third electrode  62   c  and the common electrode  61   a  of a piezoelectric element  63   c , a vibration is generated in the center section  63 e of the piezoelectric transducer  60  so that the driven member  67  frictionally coupled to the center section  63   e  is driven in the direction of the X axis. 
     In order to obtain movement along the Y axis per drive of piezoelectric elements  63   b  and  63   d , when a sine waveform voltage of a certain phase is applied to a second electrode section comprised of the common electrode  61   a  and the second electrode  62   b  of a piezoelectric element  63   b , and a sine waveform voltage of a correspondingly different phase is applied to a fourth electrode section comprised of the fourth electrode  62   d  and the common electrode  61   a  of a piezoelectric element  63   d , a vibration is generated in the center section  63   e  of the piezoelectric transducer  60  so that the driven member  67  frictionally coupled to the center section  63   e  is driven in the direction of the Y axis. 
     The configuration of the fifth embodiment, just the same as previously described for the second embodiment, besides requiring no bond coupling between the drive shaft and the piezoelectric transducer and having a simple assembly process, also has a large mechanical strength by way of the fixed support at both ends of the piezoelectric transducer and the further benefit that vibration is not prone to occur in a direction perpendicular to the axis. Further advantages are that increasing the intensity of the electrical field is simple since each electrode in the laminated structure is thin and generating a large displacement is easy to achieve. 
     Sixth Embodiment 
     In contrast to the first through fifth embodiments in which the first thin piezoelectric element and the second thin piezoelectric element were laminated together and then wound, the piezoelectric transducer of the sixth embodiment has a structure in which the first thin piezoelectric element and the second thin piezoelectric element were laminated and then folded. 
     In other words, an oblique view in FIG. 14 shows the laminated structure of the first thin piezoelectric element and the second thin piezoelectric element. In FIG. 14, a common electrode  71   a  is formed on the upper surface of the first thin piezoelectric element  71  and further, an electrode  71 b is formed on the lower surface of the piezoelectric element  71 . An electrode  72   a  is formed on the upper surface of the second thin piezoelectric element  72 . The non-electrode side of the piezoelectric element  72  faces the common electrode  71   a  of piezoelectric element  71  and is laminated and bonded on the piezoelectric element  71 . 
     FIG. 15 is an oblique view showing the structure of the piezoelectric transducer  70  comprised of laminated and then folded piezoelectric elements. The laminated piezoelectric elements are consecutively folded so that the surface is alternately positioned on the inside and outside of the laminated piece. The upper surface electrode  72   a  of the piezoelectric element  72  and the lower electrode  71   b  of the piezoelectric element  71  are then electrically connected to comprise the first electrode  73  (= 72   a + 71   b ). The resulting structure is normalized (baked). Wire leads are connected to the first electrode  73  and the common electrode  71   a , a specified high direct current voltage applied to cause polarization and the fabrication of the piezoelectric transducer  70  as shown in FIG. 15 is now complete. 
     The material and the fabrication process of the piezoelectric elements  71  and  72  is the same as previously described for the configuration of the first embodiment so the detailed description is omitted here. 
     The piezoelectric transducer  70  of the shape shown in FIG. 15 can be substituted and used in place of the piezoelectric transducer  10  as previously described for the first embodiment. 
     In other words, when a sawtooth waveform pulse of some several hundred kilohertz is applied across the common electrode  71   a  and the first electrode  73  ( 72   a  and  71   b ) of the piezoelectric transducer  70 , a reciprocating vibration of varying speeds is generated axially in the piezoelectric transducer  70 , and just the same as explained for the first embodiment, a drive shaft (not shown in the drawing) secured tothepiezoelectrictransducer 70  is madeto vibrate. A slider block friction coupled to the drive shaft is moved in the direction of the slower vibration by the asymmetrical motion from the reciprocating vibration of the drive shaft, and the driven member such as a table linked to the slider block can be moved. 
     FIG. 16 is also an oblique view showing the structure of the piezoelectric transducer  75  comprised of a thin first piezoelectric element and a thin second piezoelectric element which are laminated and then folded. 
     In the configuration of this embodiment, a common electrode  76   a  is formed on the upper surface of the thin first piezoelectric element  76 , and an electrode  76   c  and an electrode  76   d  are formed separated by a specified gap D on the lower surface of the piezoelectric element  76  as shown in the cross sectional view of the piezoelectric element in FIG.  17 . Further, an electrode  77   a  and an electrode  77   b  are formed separated by a specified gap D on the upper surface of the thin second piezoelectric element  77 . 
     The non-electrode side of the second piezoelectric element  77  faces the common electrode  76   a  of the first piezoelectric element  76  and is laminated and bonded on the piezoelectric element  76  (see FIG. 17) these laminated piezoelectric elements are consecutively folded so that their surface is alternately positioned on the inside and outside of the laminated piece (see FIG.  16 ). The upper surface electrode  77   a  of the second piezoelectric element  77  and the lower electrode  76   c  of the first piezoelectric element  76  are then electrically connected to comprise the first electrode  78  (= 77   a + 76   c ), and the electrode  77   b  of the second piezoelectric element  77  and the lower surface electrode  76   d  of the piezoelectric element  76  are electrically connected to comprise the second electrode  79 (= 77   b + 76   d ). 
     These piezoelectric elements are normalized (baked) and wire leads connected to the first electrode  78 , common electrode  76   a  and second electrode  79 . A specified high DC current is applied across the first electrode  78  and common electrode  76   a , and also across the second electrode  79  and common electrode  76   a  to cause polarization, and the fabrication of the piezoelectric transducer  75  as shown in FIG. 16 is now complete. 
     The piezoelectric transducer  75  of the shape shown in FIG. 16 can be substituted and used instead of the previously described piezoelectric transducer  30  of the second embodiment. The operation and applications are identical to those of the second embodiment so a description is omitted here. 
     FIG. 18 is also an oblique view showing the structure of the piezoelectric transducer  80  comprised of a thin first piezoelectric element and a thin second piezoelectric element which are laminated and then folded comprising a structure similar to those in FIG.  16  and FIG.  17 . 
     In the configuration of this embodiment, a common electrode  76   a  is formed on the upper surface of the thin first piezoelectric element  76 , and an electrode  76   c  and an electrode  76   d  are formed separated by a specified gap D on the lower surface of the piezoelectric element  76 . An electrode  77   a  and an electrode  77   b  are formed separated by a specified gap D on the upper surface of the thin second piezoelectric element  77 . This configuration is similar to the previous configurations in FIG.  16  and FIG.  17 . 
     However, the configuration shown in FIG. 18 differs from those in FIG.  16  and FIG.  17 . That is, the width h1 for the electrodes  76   c  and electrode  76   d  formed separated by a specified gap D on the lower surface of the first piezoelectric element  76  and the width hi between the electrodes  77   a  and  77   b  formed separated by a specified distance h1 on the upper surface of the second piezoelectric element  77  is broader than the constitution shown in FIG.  16 . Another difference is that an extension  77   e  is formed on the center section  77   d  of the second piezoelectric element  77  so that when the piezoelectric element is folded, a frictional coupling  77   f  with a large thickness can be formed in the center of the piezoelectric transducer  80 . The frictional coupling  77   f  is frictionally coupled to the slider not shown in the drawing. 
     The piezoelectric transducer  80  of the shape shown in FIG. 18 can be substituted and used instead of the previously described piezoelectric transducer  40  of the third embodiment. Though not shown in FIG. 18, a slider such as denoted by reference numeral  47  (configuration of third embodiment) of FIG. 8, is friction coupled to the friction coupling  77   f  by an appropriate amount of frictional force, and an elongation or contraction displacement of the piezoelectric transducer  80  causes frictional coupling by the friction coupling  77   f  so the slider can move in a specified direction. The operation and applications are identical to those of the third embodiment and detailed description is omitted here. 
     FIG. 19 is an oblique view showing another structure of the piezoelectric element as shown in FIG.  14 . That is, one thin piezoelectric element sheet is folded over on itself. In FIG. 19, an electrode  85   a  is formed on the front surface of that one thin piezoelectric element sheet  85  and an electrode  85   b  is formed on the rear face and this structure folded over at section  86 . In a configuration of this type, just as previously explained for the configuration in FIG. 15, there is no need for a process to form an electrical connection between the upper surface electrode  72  of the piezoelectric element  72  and the lower surface electrode  71   b  of the piezoelectric element  71 . 
     The configuration shown in FIG. 19 can of course be adapted to the piezoelectric transducers shown in FIG.  16  and FIG.  18  and is further adaptable to the piezoelectric transducers shown in FIG.  1  and FIG.  5 . 
     Seventh Embodiment 
     The piezoelectric transducer of the seventh embodiment has a hollow tubular shape transducer. 
     In FIG. 20, electrodes  92  and  93  are formed on the both side surfaces of the piezoelectric element  91 , and an insulating sheet  94  is laminated and bonded on the electrode  93 . Then, laminated sheet is wound to form a tubular shape as shown in FIG.  21 . 
     The piezoelectric element formed in tubular shape is then normalized (baked), and wire leads connected to the electrodes  92  and  93 , and when specific high DC voltage is applied for polarization, the fabrication of a piezoelectric transducer  10  is completed. 
     The material and the fabrication process of the piezoelectric element  91  is the same as previously described for the configuration of the first embodiment so the detailed description is omitted here. 
     In the above description, after the piezoelectric transducer of this invention, configured of a plurality of laminated sheets of thin piezoelectric elements has been wound in a tubular shape or folded, electrodes can be installed on the respective surfaces of each piezoelectric element, the elements laminated together and bonded, and a drastic reduction made in the former complicated process of installing wiring to the electrodes of each layer, so that not only can the cost of the fabrication process be greatly lowered but high mechanical strength is obtained even if the thickness of the individual piezoelectric elements are reduced in order to increase the intensity of the electrical field thus achieving a remarkable effect of the invention. 
     Further, a large motive power at a low voltage can be obtained from the actuator utilizing the piezoelectric transducer of this invention and an actuator having a high mechanical strength can also be provided.