Patent Publication Number: US-2020278375-A1

Title: Rotation operation detection mechanism and rotation operation detection method

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of International Patent Application No. PCT/JP2019/042517 filed on Oct. 30, 2019, which claims priority to Japanese Patent Application No. 2019-029027, filed on Feb. 21, 2019, and to Japanese Patent Application No. 2018-212638, filed on Nov. 13, 2018, the contents of each of which are incorporated herein by reference. 
    
    
     TECHNICAL FIELD 
     The present invention relates to a rotation operation detection mechanism and a rotation operation detection method for detecting rotation operation. 
     BACKGROUND 
     Patent Document 1 (identified below) discloses a waterproof structure including an outer knob and a mounting surface for the outer knob. An O-ring is fitted as a first waterproof material between the outer knob and the mounting surface of the outer knob. Further, an O-ring is fitted as a second waterproof material between the outer knob and an inner knob.
     Patent Document 1: Japanese Patent Application Laid-Open No. 6-224009.   

     In the waterproof structure of a knob portion described in Patent Document 1, the outer knob and the inner knob slide with respect to a housing. Parts such as the 0-ring rub against each other due to sliding of the outer knob and the inner knob, and friction occurs between the parts. If the outer knob and the inner knob are repeatedly operated, the parts may be deteriorated due to friction. 
     SUMMARY OF THE INVENTION 
     In view of the foregoing, it is an object of the exemplary embodiments to provide a rotation operation detection mechanism and a rotation operation detection method for detecting rotation operation, in which sliding portions are reduced. 
     A rotation operation detection mechanism according to an exemplary embodiment includes a housing, an operation surface disposed on a first main surface of the housing, an operation unit formed integrally with the housing and protruding toward the operation surface side, and a sensor that detects a stress generated on the housing when the operation unit is rotated. 
     In this configuration, the operation unit is formed integrally with the housing. When the user rotates the operation unit, the number of locations where parts rub against each other are reduced. In this configuration, since there are few locations where the operation unit slides with respect to the housing, deterioration in the parts is suppressed. 
     Moreover, a rotation operation detection method according to an exemplary embodiment includes determining that any one of a plurality of sensors, which are formed integrally with a housing, are disposed, one for each section of an operation unit divided into three or more sections, and detect a stress generated in the operation unit when the operation unit is rotated, outputs a signal of a peak of an intensity equal to or more than a predetermined threshold; storing, as a first time, a time at which a signal of the one sensor is determined to become a reference value after a signal with a peak of an intensity equal to or more than the predetermined threshold is determined to be output; storing, as a second time, a time at which any one of the plurality of sensors is determined to output a signal with a peak having an intensity equal to or more than the predetermined threshold for first time after the first time; storing, as a third time, a time at which any one of the plurality of sensors is determined to output a signal with a peak having an intensity equal to or more than the predetermined threshold and of same polarity as a peak output at the second time for first time after the second time; and determining that the operation unit receives rotation operation when signals of all the plurality of sensors are determined to exceed the predetermined threshold during a period from the first time to the third time. 
     With this configuration, whether or not the user rotates the operation unit can be determined based on the magnitude of an output from a plurality of sensors that detect a stress generated in the operation unit and a detection time. 
     According to the exemplary embodiments of the present disclosure, a rotation operation detection mechanism and a rotation operation detection method are provided that detect rotation operation with few sliding portions can be provided. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1(A)  is a perspective view of a rotation operation detection mechanism according to a first embodiment.  FIG. 1(B)  is a cross-sectional view of the rotation operation detection mechanism shown in  FIG. 1(A) . 
         FIG. 2(A)  is an enlarged cross-sectional view of a sensor shown in  FIG. 1(B) , and  FIG. 2(B)  is an exploded perspective view of the sensor according to the first embodiment. 
         FIG. 3  is a partially enlarged view for explaining a piezoelectric film according to the first embodiment. 
         FIG. 4(A)  is a diagram schematically showing a shear stress generated in a case where the user operates the rotation operation detection mechanism according to the first embodiment, and  FIG. 4(B)  is a diagram showing an output value of the sensor in a case where the user operates to rotate an operation unit or in a case where the user grips the operation unit. 
         FIGS. 5(A) to 5(C)  are diagrams for explaining the rotation operation detection mechanism according to a second embodiment. 
         FIGS. 6(A) to 6(C)  are diagrams for explaining the rotation operation detection mechanism according to a third embodiment. 
         FIGS. 7(A) to 7(C)  are diagrams for explaining the rotation operation detection mechanism according to a fourth embodiment. 
         FIGS. 8(A) and 8(B)  are diagrams for explaining the rotation operation detection mechanism according to a fifth embodiment. 
         FIGS. 9(A) and 9(B)  are diagrams for explaining the rotation operation detection mechanism according to a sixth embodiment. 
         FIG. 10(A)  is a diagram for explaining the rotation operation detection mechanism according to a seventh embodiment, and  FIG. 10(B)  is a diagram for explaining the rotation operation detection mechanism according to an eighth embodiment. 
         FIGS. 11(A) to 11(C)  are diagrams for explaining the rotation operation detection mechanism according to a ninth embodiment. 
         FIGS. 12(A) to 12(D)  are diagrams for explaining a variation of the rotation operation detection mechanism according to the first embodiment. 
         FIGS. 13(A) to 13(C)  are diagrams for explaining the rotation operation detection mechanism according to a tenth embodiment. 
         FIG. 14(A)  is a diagram schematically showing a shear stress generated in a case where the user operates the rotation operation detection mechanism according to the tenth embodiment, and  FIG. 14(B)  is a diagram showing an output value of the sensor in a case where the user operates to rotate the operation unit or in a case where the user grips the operation unit. 
         FIGS. 15(A) to 15(C)  are diagrams for explaining the rotation operation detection mechanism according to an eleventh embodiment. 
         FIGS. 16(A) to 16(C)  are diagrams for explaining the rotation operation detection mechanism according to a twelfth embodiment. 
         FIG. 17(A)  and  FIG. 17(B)  are diagrams schematically showing a shear stress generated in a case where the user operates the rotation operation detection mechanism according to the twelfth embodiment. 
         FIGS. 18(A) to 18(C)  are diagrams for explaining the rotation operation detection mechanism according to a thirteenth embodiment. 
         FIGS. 19(A) to 19(C)  are diagrams for explaining the rotation operation detection mechanism according to a fourteenth embodiment. 
         FIG. 20  is a functional block diagram of signal processing performed by the sensor, a sensor detection circuit, and a microcomputer of the rotation operation detection mechanism according to the fourteenth embodiment. 
         FIG. 21  is a graph showing a detection value of the sensor in a case where the user rotates the operation unit of the rotation operation detection mechanism according to the fourteenth embodiment to the right. 
         FIG. 22  is a graph showing a detection value of the sensor in a case where the user rotates the operation unit of the rotation operation detection mechanism according to the fourteenth embodiment to the left. 
         FIG. 23  is a graph showing a detection value of the sensor in a case where the user grips the operation unit of the rotation operation detection mechanism according to the fourteenth embodiment. 
         FIG. 24  is a flowchart showing a rotation operation detection method. 
     
    
    
     DETAILED DESCRIPTION 
     Hereinafter, a rotation operation detection mechanism and a rotation operation detection method according to an exemplary embodiment will be described with reference to the drawings. It is noted that, in each of the drawings, wirings and the like are omitted for convenience of explanation. 
       FIG. 1(A)  is a perspective view of a rotation operation detection mechanism  101  according to a first embodiment.  FIG. 1(B)  is a cross-sectional view when the rotation operation detection mechanism  101  is cut along an X-Y plane. It is noted that the rotation operation detection mechanism  101  shown in  FIGS. 1(A) and 1(B)  is merely an example of the present invention, and the present invention is not limited to this configuration and can have a shape and the like appropriately changed according to specifications. Further, in  FIG. 1(A) , for convenience of explanation, a sensor inside a housing is shown by a broken line through the housing. Hereinafter, in other drawings as well, there is a case where the sensor inside the housing is shown by a broken line through the housing. 
     As shown in  FIGS. 1(A) and 1(B) , the rotation operation detection mechanism  101  includes a substantially rectangular parallelepiped housing  10 . The housing  10  has an operation surface  11  on a first main surface  1  of the housing  10 . An operation unit  12 , an operation unit  13 , and an operation unit  14  are formed integrally with the housing  10 , and are formed to protrude from the housing  10  on the operation surface  11  side. Since the operation unit  12 , the operation unit  13 , and the operation unit  14  have similar configurations, the operation unit  12  will be described below as a representative. Hereinafter, the rotation operation detection mechanism  101  will be described with a width direction (lateral direction) of the housing  10  as an X direction, a thickness direction as a Y direction, and a length direction (vertical direction) as a Z direction. It is noted that these directions are relative to each other based on the orientation of the rotation operation detection mechanism  101 . 
     In an exemplary aspect, the housing  10  is made from a metal material, for example, aluminum, an aluminum alloy, stainless steel, or the like can be used. The operation unit  12  is formed by pressing the operation surface  11  side of the housing  10 . Note that the housing  10  and the operation unit  12  may be formed by integrally injection-molding resin or the like. Further, the housing  10  and the operation unit  12  may be made from another material as long as a shear stress is generated by rotation operation. 
     The operation unit  12  is formed continuously with the housing  10 . For this reason, the operation unit  12  hardly slides or does not slide with respect to the housing  10 . Furthermore, in a case where there is no gap between the operation unit  12  and the housing  10 , the internal space of the housing  10  is kept watertight from the outside. Further, at least the operation surface  11  is preferably formed continuously. Note that the material and shape of the housing  10  are not limited to metal and resin, and may be any as long as the housing  10  is deformed at least slightly when a force is applied. 
     The operation unit  12  has a columnar shape, and protrudes from the housing  10  on the operation surface  11  side. For this reason, the user can grip a side surface  122  of the operation unit  12  and apply a force in a direction in which the operation unit  12  rotates on an X-Z plane. Note that the operation unit  12  is not limited to a columnar shape, and may be, for example, a rectangular parallelepiped, a polygonal column such as a hexagonal column, or have a structure in which a protrusion exists on part of the circumference according to alternative aspects. 
     The operation unit  12  is formed in a hollow shape. Moreover, a sensor  15  is disposed on a back side  16  of the operation surface  11  in the operation unit  12 . Since the sensor  15  is not directly in contact with the user&#39;s hand, durability of the sensor  15  improves. 
     The sensor  15  is disposed along a circumferential direction of the operation unit  12 . The sensor  15  is attached to the operation unit  12  with, for example, an adhesive, a pressure sensitive adhesive, or the like. As will be described in detail below, the sensor  15  detects a stress generated on the housing  10  when the operation unit  12  is rotated. 
     When the user applies a force in a direction in which the operation unit  12  rotates on the X-Z plane, that is, in the circumferential direction of the operation unit  12 , the sensor  15  can detect deformation of the housing  10 . As shown, the sensor  15  is disposed along and around the side surface  122  of the operation unit  12 . When a thickness of the operation unit  12  is small, the operation unit  12  is easily deformed by a force applied by the user. In this manner, a force applied by the user is transmitted to the sensor  15  disposed on an inner side of the operation unit  12 . 
     It is noted that although the sensor  15  is disposed along and around the side surface  122  of the operation unit  12 , the configuration is not limited to this. The sensor  15  may be disposed, for example, only on part along the side surface  122  of the operation unit  12 , or may be disposed spirally on the side surface  122  of the operation unit  12  in one or more circumferences of the operation unit  12 . 
       FIG. 2(A)  is an enlarged cross-sectional view of the sensor  15  shown in  FIG. 1(B)  cut along an X-Y plane, and  FIG. 2(B)  is an exploded perspective view of the sensor  15 . Note that  FIGS. 2(A) and 2(B)  are schematic diagrams, and for convenience of explanation, the thickness and the like of each part of the sensor  15  are shown large, and a processing unit, a wiring, and the like are omitted. Further,  FIG. 2(B)  is a diagram in which the sensor  15  is extended so as to be parallel to the Y-Z plane. 
     As shown in  FIGS. 2(A) and 2(B) , the sensor  15  includes a piezoelectric film  20 , a first electrode  21 , and a second electrode  22 . Each of the piezoelectric film  20 , the first electrode  21 , and the second electrode  22  has a flat (i.e., planar) film shape. The first electrode  21  and the second electrode  22  are stacked so as to sandwich the piezoelectric film  20 , and are bonded by a first adhesive layer  24  and a second adhesive layer  25 , respectively. The first electrode  21  is a signal electrode, and the second electrode  22  is a ground electrode. It is also noted that the second electrode  22  may be a signal electrode, and the first electrode  21  may be a ground electrode in an alternative arrangement. Further, in  FIG. 2(B) , the illustration of the first adhesive layer  24  and the second adhesive layer  25  is omitted. 
     The piezoelectric film  20 , the first electrode  21 , and the second electrode  22  are each formed in a rectangular shape in plan view. When the sensor  15  is viewed in plan view from an X-axis direction, the first electrode  21  and the second electrode  22  preferably completely overlap with the piezoelectric film  20  in top view or are preferably positioned on an inner side of the piezoelectric film  20  in a plane direction. In this manner, a short circuit at an end portion of the first electrode  21  and the second electrode  22  can be suppressed. 
       FIG. 3  is a partially enlarged view for explaining the piezoelectric film  20 . The piezoelectric film  20  may be a film formed from a chiral polymer. As the chiral polymer, polylactic acid (PLA), particularly poly-L-lactic acid (PLLA), is used in the first embodiment. In the PLLA including a chiral polymer, a main chain has a helical structure. PLLA has piezoelectricity when uniaxially stretched and a molecule is oriented. Then, the uniaxially stretched PLLA is charged when a flat plate surface of the piezoelectric film  20  is extended. 
     In the first embodiment, a uniaxial stretching direction of the piezoelectric film  20  (PLLA) is a direction parallel to the Z direction which is a long side direction, as indicated by an arrow  901  in  FIG. 3 . This parallel direction includes, for example, an angle including about ±10 degrees. When the piezoelectric film  20  is extended, for example, in a direction of 45 degrees with respect to the Z direction, charges are generated. At this time, an amount of the generated charges depends on an amount of extension and a direction of extension. The piezoelectric film  20  generates a largest amount of charges when stretched in a direction of 45 degrees with respect to the uniaxial stretching direction of the piezoelectric film  20 , and does not generate an amount of charges when stretched in the same direction as the uniaxial stretching direction. It is also noted that the uniaxial stretching direction of the piezoelectric film  20  may be a direction parallel to a short side direction. 
     In PLLA, piezoelectricity is generated by orientation treatment of molecules by stretching or the like, and there is no need to perform poling treatment like other polymers such as PVDF and piezoelectric ceramics. That is, piezoelectricity of PLLA not belonging to a ferroelectric is not expressed by polarization of an ion like a ferroelectric, such as PVDF or PZT, but is derived from a helical structure which is a characteristic structure of a molecule. For this reason, pyroelectricity that is generated in other ferroelectric piezoelectric materials is not generated in the PLLA. The sensor  15 , which does not have pyroelectricity and is not affected by a temperature of a finger of the user or frictional heat, can be formed to be thin. Furthermore, a change in a piezoelectric constant is observed over time in PVDF or the like, and in some cases, a piezoelectric constant may decrease significantly; however, a piezoelectric constant of PLLA is extremely stable over time. Accordingly, extension of the piezoelectric film  20  can be detected at high sensitivity without any influence from an ambient environment. 
     As the first electrode  21  and the second electrode  22  formed on both main surfaces of the piezoelectric film  20 , an electrode based on meatal, such as aluminum and copper, can be used. Further, when the electrode is required to have transparency, the first electrode  21  and the second electrode  22  can be made from a highly transparent material such as ITO or PEDOT. By providing the first electrode  21  and the second electrode  22 , a charge generated by the piezoelectric film  20  is output to a processing unit (not shown), and is converted into a voltage in a circuit of the processing unit, so that a detected voltage value corresponding to an amount of extension is detected. When the housing  10  is deformed, the sensor  15  outputs a charge corresponding to the deformation of the housing  10  to the processing unit (not shown). 
     Hereinafter, detection of a voltage value of the sensor  15  when the user operates the operation unit  12  of the rotation operation detection mechanism  101  will be described in detail. 
       FIG. 4(A)  is a diagram schematically showing a shear stress generated when the user operates to rotate the operation unit  12  of the rotation operation detection mechanism  101 , and is a side view when the operation unit  12  is viewed from the X direction to a −X direction.  FIG. 4(B)  is a diagram showing an output value of the sensor  15  when the user operates to rotate the operation unit  12  or when the user grips the operation unit  12 . 
     When the user rotates the operation unit  12 , that is, a case where the user grips the operation unit  12  and applies a force in a direction in which the operation unit  12  rotates on the X-Z plane will be described. For example, assume a case where the user rotates the operation unit  12  counterclockwise as indicated by arrow  900  in  FIG. 1(A) . 
     As shown in  FIG. 4(A) , a shear stress as indicated by arrows  301  and  302  is generated on a side surface of the operation unit  12 . The shear stress is generated to be in a direction mainly at 45 degrees with respect to a circumferential direction of the operation unit  12 . The shear stress is generated to be in a direction mainly at 45 degrees with respect to the uniaxial stretching direction (arrow  901 ) of the piezoelectric film  20 . That is, the piezoelectric film  20  is disposed so that each shear stress (arrows  301  and  302 ) generated on the operation surface  11  when the operation unit  12  receives rotation operation is along a direction in which the sensor  15  detects the extension of the piezoelectric film  20 . Here, that the direction in which the extension of the piezoelectric film  20  is detected is along the shear stress means that the direction in which the extension of the piezoelectric film  20  is detected and the direction of the shear stress preferably form an angle of parallel±10°. Therefore, the sensor  15  outputs a voltage value according to the shear stress. It is also noted that arrows  301  and  302  represent particularly large ones of the shear stresses generated on the operation surface  11 . Shear stresses shown in a diagram described below also represent some particularly large ones of the shear stresses generated on the operation surface  11  similarly to  FIG. 4(A) . 
     In  FIG. 4(A) , the shear stress indicated by arrow  302  near the center in a vertical direction of the operation unit  12  mainly forms a direction of 45 degrees with respect to the uniaxial stretching direction (arrow  901 ). An inclination with respect to the Z direction of the shear stress indicated by arrow  301  is shown to be larger than that of the shear stress indicated by arrow  302 . This is because the piezoelectric film  20  is curved with respect to the X-axis direction, and the degree of the curving is greater on upper and lower sides in the Z-axis direction with arrow  301  than on the center with arrow  302 . 
     Further, the shear stress indicated by arrow  301  mainly forms a direction of 45 degrees with respect to the uniaxial stretching direction (i.e., arrow  901 ) of the piezoelectric film  20  that is curved with respect to the X-axis direction. Here, the thickness of arrows  301  and  302  indicates an amount of charges generated from the piezoelectric film  20 . The shear stress indicated by arrow  301  is shown to be larger than the shear stress indicated by arrow  302 , because the piezoelectric film  20  is curved with respect to the X-axis direction, and a large number of shear stresses overlap in the X-axis direction. In actuality, the shear stress is uniformly generated in the circumferential direction of the operation unit  12 . 
     Due to the deformation of the operation unit  12 , the piezoelectric film  20  is deformed. The piezoelectric film  20  generates charge, and the sensor  15  outputs a voltage as shown by a solid line in  FIG. 4(B) . On the other hand, when the user only grips the operation unit  12 , the output value of the sensor  15  is small as shown by a broken line in  FIG. 4(B) . This is because no shear stress that forms the direction of 45 degrees with respect to the uniaxial stretching direction (arrow  901 ) of the piezoelectric film  20  is generated, and no large charge is generated on the piezoelectric film  20 . Therefore, depending on the magnitude of the output from the sensor  15 , it is possible to distinguish when the user grips the operation unit  12  and when the user grips and further performs operation of rotating the operation unit  12 . 
     For example, a predetermined threshold is stored in a processing unit (not shown) in advance. The rotation operation detection mechanism  101  can distinguish that the user rotates the operation unit  12  when the magnitude of the output from the sensor  15  is equal to or greater than a predetermined threshold, and that the user only grips the operation unit  12  when the magnitude of the output from the sensor  15  is smaller than the predetermined threshold. 
     Further, as an amount of rotation of the operation unit  12  by the user is larger, the shear stress generated on the operation unit  12  is larger. The output from the sensor  15  becomes larger in proportion to an amount of rotation of the operation unit  12  by the user. Therefore, the rotation operation detection mechanism  101  can distinguish an amount of rotation of the operation unit  12  based on the magnitude of the output from the sensor  15 . 
     Further, when the user rotates the operation unit  12  counterclockwise as shown by arrow  900  in  FIG. 1(A)  has been described; however, when the user rotates the operation unit  12  in a clockwise direction opposite to arrow  900  in  FIG. 1(A) , all the shear stresses generated on the operation unit  12  are in a direction 90 degrees different as compared to the case where the user rotates the operation unit  12  counterclockwise. Therefore, the polarity of the charge generated on the piezoelectric film  20  is reversed, and the polarity of the output from the sensor  15  is reversed. Therefore, whether the user has rotated the operation unit  12  clockwise or counterclockwise can be distinguished based on the polarity of the output from the sensor  15 . 
     Hereinafter, a rotation operation detection mechanism  102  according to a second embodiment will be described.  FIG. 5(A)  is a perspective view of the rotation operation detection mechanism  102  according to the second embodiment. 
       FIG. 5(B)  is a cross-sectional view when the rotation operation detection mechanism  102  is cut along the X-Y plane.  FIG. 5(C)  is a diagram schematically showing a shear stress generated when the user operates to rotate the operation unit  12  of the rotation operation detection mechanism  102 , and is a side view of a case where the operation surface  11  is viewed from a −Y direction toward the Y direction. The rotation operation detection mechanism  102  according to the second embodiment has a substantially similar configuration to that of the first embodiment, except that the rotation operation detection mechanism  102  includes one of the operation unit  12  and the arrangement of the sensor  15  is different. Therefore, in the second embodiment, only the differences from the first embodiment will be described, and the rest will be omitted. 
     As shown in  FIGS. 5(A) and 5(B) , the rotation operation detection mechanism  102  includes one of the operation unit  12 . Note that a plurality of the operation units  12  may be provided as in the first embodiment. The sensor  15  is adhered to the back side  16  of a housing  50 . The sensor  15  is disposed on locations other than the operation unit  12  on the operation surface  11 . For this reason, the sensor  15 , which can be adhered to a flat place, is easily disposed. 
     As shown in  FIG. 5(C) , the sensor  15  is disposed along a direction parallel to the Z direction which is a tangential direction of the operation unit  12  in the circumferential direction. The operation surface  11  includes a short side  51  and a long side  52 . Since the sensor  15  is disposed along a direction parallel to the short side  51 , positioning of the sensor  15  when attached to the back side  16  of the housing  50  is easy. 
     When the user grips the operation unit  12  and applies a force in the direction in which the operation unit  12  rotates on the X-Z plane, a shear stress is generated around the operation unit  12 . Shear stresses as indicated by arrows  501 ,  502 , and  503  are generated on the operation surface  11 . Each of the shear stresses is generated so as to be mainly at 45 degrees with respect to the tangential direction of the operation unit  12 . 
     Since the sensor  15  is disposed along a direction parallel to the tangential direction of the operation unit  12 , the shear stress is mainly generated in the direction of 45 degrees with respect to the uniaxial stretching direction (arrow  901 ) of the piezoelectric film  20  of the sensor  15  as shown in  FIG. 5(C) . Therefore, the sensor  15  can output a voltage value according to the shear stress. 
     It is also noted that the sensor  15  may be disposed along a direction orthogonal to the tangential direction of the operation unit  12 . For example, there is a case where the sensor  15  shown in  FIG. 5(A)  is rotated by 90 degrees at a position where the sensor  15  is located, and is adhered along the X-axis direction. Also in this case, the shear stress is generated to be in a direction mainly at 45 degrees with respect to the uniaxial stretching direction (arrow  901 ) of the piezoelectric film  20  of the sensor  15 . Therefore, the sensor  15  outputs a large voltage value. 
     Further, when the operation unit  12  is merely gripped, the stress is mainly generated on a side surface of the operation unit  12 . For this reason, large stress is not transmitted to a location of the sensor  15  disposed on locations other than the operation unit  12  on the operation surface  11 . Therefore, the sensor  15  can detect only an amount of rotation of the operation unit  12  in the rotation operation detection mechanism  102 . For this reason, the rotation operation detection mechanism  102  can more accurately detect the rotation of the operation unit  12 . 
     Hereinafter, a rotation operation detection mechanism  103  according to a third embodiment will be described. 
       FIG. 6(A)  is a perspective view of the rotation operation detection mechanism  103  according to the third embodiment.  FIG. 6(B)  is a cross-sectional view when the rotation operation detection mechanism  103  is cut along the Y-Z plane.  FIG. 6(C)  is a diagram schematically showing a shear stress generated when the user operates to rotate the operation unit  12  of the rotation operation detection mechanism  103 , and is a side view of a case where the operation surface  11  is viewed from the −Y direction toward the Y direction. The rotation operation detection mechanism  103  according to the third embodiment has a substantially similar configuration to the second embodiment except that the arrangement of the sensor  15  is different. Therefore, in the third embodiment, only the differences from the second embodiment will be described, and the rest will be omitted. 
     As shown in  FIGS. 6(A), 6(B) and 6(C) , the sensor  15  is attached to the back side  16  of the housing  50 . End portions of the operation surface  11  are the short side  51  and the long side  52 . The sensor  15  is disposed on locations other than the operation unit  12  on the operation surface  11 . 
     The sensor  15  is disposed between the operation unit  12  and an end portion of the operation surface  11  where a shortest distance from the end portion of the operation surface  11  to the operation unit  12  is shortest. For example, when the operation unit  12  is disposed at the center of the operation surface  11 , a distance L 2  from the center of the long side  52  to the operation unit  12  is shorter than a distance L 1  from the center of the short side  51  to the operation unit  12 , and the distance L 2  between the center of the long side  52  and the operation unit  12  is shortest as compared with positions of the other end portions. In this case, the sensor  15  is disposed between the center of the long side  52  and the operation unit  12  along a direction parallel to a tangential direction of the operation unit  12  in the circumferential direction. 
     When the user grips the operation unit  12  and applies a force in the direction in which the operation unit  12  rotates on the X-Z plane, shear stresses as indicated by arrows  501 ,  502 , and  503  are generated on the operation surface  11 . An end portion of the operation surface  11  is fixed to another surface of the housing  10 . For this reason, as a distance between the operation unit  12  and an end portion of the fixed operation surface  11  becomes smaller, a larger distortion is generated between the operation unit  12  and the end portion of the operation surface  11 . Therefore, on the operation surface  11 , a greater shear stress is generated at the position indicated by arrow  502  than at the positions indicated by arrows  501  and  503 . Therefore, the sensor  15  of the rotation operation detection mechanism  103  can output a larger voltage value as compared to the rotation operation detection mechanism  102  according to the second embodiment. Therefore, the accuracy of rotation detection of the rotation operation detection mechanism  103  can be improved. 
     Hereinafter, a rotation operation detection mechanism  104  according to a fourth embodiment will be described.  FIG. 7(A)  is a perspective view of the rotation operation detection mechanism  104  according to the fourth embodiment. 
       FIG. 7(B)  is a cross-sectional view when the rotation operation detection mechanism  104  is cut along the X-Y plane.  FIG. 7(C)  is a diagram schematically showing a shear stress generated when the user operates to rotate the operation unit  12  of the rotation operation detection mechanism  104 , and is a side view of a case where the operation surface  11  is viewed from the −Y direction toward the Y direction. The rotation operation detection mechanism  104  according to the fourth embodiment has a substantially similar configuration to the second embodiment except that the arrangement of the sensor  15  is different. Therefore, in the fourth embodiment, only the differences from the second embodiment will be described, and the rest will be omitted. 
     As shown in  FIGS. 7(A) and 7(B) , the sensor  15  is disposed on the back side  16  of the housing  50  so as to extend across a boundary  71  between the operation unit  12  and the housing  50  other than the operation unit  12 . In other words, the sensor  15  is disposed so as to be continuous with the operation unit  12  and the housing  50  other than the operation unit  12  on the operation surface  11 . 
     As shown in  FIG. 7(B) , a cross section of the housing  50  has a shape that changes greatly at the boundary  71 . As shown in  FIG. 7(C) , when the user grips the operation unit  12  and applies a force in the direction in which the operation unit  12  rotates on the X-Z plane, a shear stress concentrates around the boundary  71 . For example, as indicated by arrow  504 , a larger shear stress is generated around the boundary  71  than in other portions of the operation surface  11 . Moreover, in the sensor  15 , the piezoelectric film  20  around the boundary  71  is greatly deformed. In this manner, the sensor  15  can output a larger voltage value. Therefore, the accuracy of rotation detection of the rotation operation detection mechanism  104  can be improved. 
     Hereinafter, a rotation operation detection mechanism  105  according to a fifth embodiment will be described.  FIG. 8(A)  is a side view when the rotation operation detection mechanism  105  is viewed from the −Y direction toward the Y direction.  FIG. 8(B)  is a diagram schematically showing a shear stress generated when the user operates the operation unit  12  of the rotation operation detection mechanism  105 . 
     In the exemplary aspect, the rotation operation detection mechanism  105  has a substantially similar configuration to the second embodiment except that the shape, the number, and the arrangement of the sensors are different. Therefore, in the fifth embodiment, only the differences from the second embodiment will be described, and the rest will be omitted. 
     As shown in  FIG. 8(A) , the rotation operation detection mechanism  105  includes a sensor  81 , a sensor  82 , a sensor  83 , and a sensor  84 . The sensor  81 , the sensor  82 , the sensor  83 , and the sensor  84  are each formed in a fan shape that is a 90-degree arc. The sensor  81 , the sensor  82 , the sensor  83 , and the sensor  84  are disposed in an annular shape so as to surround the operation unit  12 . Accordingly, the sensor  81 , the sensor  82 , the sensor  83 , and the sensor  84  can be disposed around the operation unit  12  without any gap. For this reason, each of the sensors (the sensor  82 , the sensor  83 , and the sensor  84 ) can completely detect the shear stress generated around the operation unit  12 . 
     The uniaxial stretching direction (arrow  901 ) of the piezoelectric film  20  in the sensor  82  and the sensor  84  is along the Z direction. A uniaxial stretching direction (arrow  902 ) of the piezoelectric film  20  in the sensor  81  and the sensor  83  is along the X direction. That is, the uniaxial stretching direction of the piezoelectric film  20  in the sensors  81 ,  82 ,  83 , and  84  is parallel or perpendicular to a tangential line of the operation unit  12 . 
     When the user grips the operation unit  12  and applies a force in the direction in which the operation unit  12  rotates on the X-Z plane, shear stresses as indicated by arrows  501  and  502  are generated on the operation surface  11  around the operation unit  12  as shown in  FIG. 8(B) . 
     The shear stresses indicated by arrows  501  and  502  form an angle of 45 degrees with respect to the uniaxial stretching direction of the piezoelectric film  20  in the sensors  81 ,  82 ,  83 , and  84 . In this manner, the sensor  81 , the sensor  82 , the sensor  83 , and the sensor  84  can output a voltage value according to the shear stress. Further, the rotation operation detection mechanism  105 , which includes a plurality of sensors, can output a larger voltage value by adding output values from the sensors. Therefore, the accuracy of rotation detection of the rotation operation detection mechanism  105  is further improved. 
     Hereinafter, a rotation operation detection mechanism  106  according to a sixth embodiment will be described.  FIG. 9(A)  is a side view when the rotation operation detection mechanism  106  is viewed from the −Y direction toward the Y direction. FIG.  9 (B) is an enlarged cross-sectional view of part of the rotation operation detection mechanism  106  shown in  FIG. 9(A)  cut along a broken line I-I. The rotation operation detection mechanism  106  has a substantially similar configuration to the fifth embodiment except that the shape of the sensor and the number of the piezoelectric films  20  are different. Therefore, in the sixth embodiment, only the differences from the fifth embodiment will be described, and the rest will be omitted. 
     As shown in  FIG. 9(A) , the rotation operation detection mechanism  106  includes a sensor  90 . The sensor  90  is formed in an O shape. The sensor  90  is disposed so as to surround the operation unit  12 . The sensor  90  includes the single O-shaped piezoelectric film  20 . The uniaxial stretching direction (arrow  902 ) of the piezoelectric film  20  in the sensor  90  is along the Z direction. Since the piezoelectric film  20  of the sensor  90  is formed as a single sheet, the trouble of adhering a plurality of the piezoelectric films  20  as in the fifth embodiment can be omitted. 
     Here, as shown in  FIG. 9(A) , the sensor  90  is shown divided into four regions (region  91 , region  92 , region  93 , and region  94 ). As shown in  FIG. 9(B) , in the sensor  90 , electrodes are divided into each region. In each region of the sensor  90 , the first electrodes  21  and the second electrodes  22  are arranged in reverse order alternately. In the region  91 , the second electrode  22  and the first electrode  21  are stacked in this order so as to sandwich the piezoelectric film  20  from the operation surface  11  side of the housing  10 . In the region  94 , the first electrode  21  and the second electrode  22  are stacked in this order so as to sandwich the piezoelectric film  20  from the housing  10  side. The region  93  is similar to the region  91 , and the region  92  is similar to the region  94 . 
     When the first electrode  21  is a signal electrode and the second electrode  22  is a ground electrode, in the region  91  and the region  93 , the first electrode  21  as a signal electrode is disposed in a direction opposite to the operation surface  11  of the piezoelectric film  20 . On the other hand, in the regions  92  and  94 , the first electrodes  21  as a signal electrode is disposed on the operation surface  11  side of the piezoelectric film  20 . When the sensor  90  receives similar deformation in the regions  91  and  93  and in the regions  94  and  92 , the piezoelectric film  20  detects charges of opposite polarities. 
     When the user grips the operation unit  12  and applies a force in the direction in which the operation unit  12  rotates in the X-Z plane, shear stresses as indicated by arrow  501  and arrow  502  are generated on the operation surface  11  around the operation unit  12  like in  FIG. 8(B) . 
     Directions of shear stresses are different between the regions  91  and  93  and the regions  94  and  92 . For this reason, different shear stresses are transmitted to the piezoelectric film  20  in the region  91  and the region  93  and in the region  94  and the region  92 . However, in the region  91  and the region  93 , and in the region  94  and the region  92 , the first electrode  21  and the second electrode  22  are arranged in reverse order. Accordingly, the sensor  90  detects charges of the same polarity from an electrode pair including the first electrode  21  and the second electrode  22  of each of the regions. Therefore, the sensor  90  can output a larger voltage value by adding output values from the electrode pair and thus the accuracy of the rotation detection of the rotation operation detection mechanism  106  is further improved. 
     It is also noted that the first electrode  21  and the second electrode  22  can be similarly arranged in the region  91  and the region  93  and in the region  94  and the region  92 . In this case, for example, charges obtained from an electrode pair including the first electrode  21  and the second electrode  22  in the region  91  and the region  93  are inverted by a processing unit (not shown). In this manner, the sensor  90  can output a larger voltage value by adding a voltage value obtained from the regions  91  and  93  and an inverted voltage value obtained from the regions  94  and  92 . 
     Hereinafter, a rotation operation detection mechanism  107  according to a seventh embodiment and a rotation operation detection mechanism  108  according to an eighth embodiment will be described.  FIG. 10(A)  is a cross-sectional view when the rotation operation detection mechanism  107  according to the seventh embodiment is cut along the X-Y plane.  FIG. 10(B)  is a cross-sectional view when the rotation operation detection mechanism  108  according to the eighth embodiment is cut along the X-Y plane. The rotation operation detection mechanism  107  according to the seventh embodiment and the rotation operation detection mechanism  108  according to the eighth embodiment have substantially similar configurations as those in the first embodiment except that the number and the shape of operation units are different. Therefore, in the seventh embodiment and the eighth embodiment, only the differences from the first embodiment will be described, and the rest will be omitted. 
     As shown in  FIG. 10(A) , the rotation operation detection mechanism  107  includes an operation unit  17 . As shown in  FIG. 10(B) , the rotation operation detection mechanism  108  includes an operation unit  18 . Part of the operation unit  17  and the operation unit  18  protrudes to the back side  16  of the operation surface  11 . 
     In the rotation operation detection mechanism  107 , the operation unit  17  includes a central portion  171  and an outer peripheral portion  172 . The central portion  171  is located on the same plane as a portion other than the operation portion  17  on the operation surface  11  side of the housing  10 . The outer peripheral portion  172  protrudes to the back side  16  of the operation surface  11  and is positioned on an inner side of the housing  10  than a portion other than the operation unit  17  on the operation surface  11  side of the housing  10 . The sensor  15  is disposed on a side surface  177  of the central portion  171 . The side surface  177  exists at a position recessed from the operation surface  11  side of the housing  10  toward an internal side of the housing  10 . For this reason, the sensor  15  disposed on the side surface  177  is hardly affected by the outside. Therefore, it is possible to prevent erroneous detection in a case of, for example, the user collides with the housing  10 . 
     In the rotation operation detection mechanism  108 , the operation unit  18  includes a central portion  181  and an outer peripheral portion  182 . The outer peripheral portion  182  protrudes on the operation surface  11  side from a portion other than the operation portion  18  on the operation surface  11  side of the housing  10 . That is, an end portion  183  of the operation unit  18  protrudes on the operation surface  11  side. The central portion  181  protrudes from the outer peripheral portion  182  toward the back side  16  of the operation surface  11 . For this reason, the strength of the end portion  183  of the operation unit  18  increases. Therefore, it is possible to prevent erroneous detection when, for example, the user collides with the end portion  183 . 
     Hereinafter, a rotation operation detection mechanism  109  according to a ninth embodiment will be described.  FIG. 11(A)  is a perspective view of the rotation operation detection mechanism  109  according to the ninth embodiment.  FIG. 11(B)  is a cross-sectional view when the rotation operation detection mechanism  109  is cut along the X-Y plane.  FIG. 11(C)  is a side view when the rotation operation detection mechanism  109  is viewed from the −Y direction toward the Y direction. The rotation operation detection mechanism  109  according to the ninth embodiment has a substantially similar configuration to that of the first embodiment except that the shape of the operation unit and the number and arrangement of sensors are different. Therefore, in the ninth embodiment, only the differences from the first embodiment will be described, and the rest will be omitted. 
     As shown in  FIGS. 11(A) to 11(C) , in the rotation operation detection mechanism  109 , an operation unit  19  has a rectangular parallelepiped shape. An end portion of the operation unit  19  has a rectangular shape having sides parallel to the Z-X direction. For this reason, a boundary  191  between the operation unit  19  and the housing  50  other than the operation unit  19  is also rectangular. 
     The rotation operation detection mechanism  109  includes a plurality of the sensors  15 . A plurality of the sensors  15  are disposed in parallel with four sides of the boundary  191 . That is, a plurality of the sensors  15  are disposed parallel to the X direction or the Z direction. In this manner, the rotation operation detection mechanism  109  can output a larger voltage value by adding output values from the sensors. Therefore, the accuracy of rotation detection of the rotation operation detection mechanism  109  is further improved. 
     Hereinafter, a variation according to the first embodiment will be described.  FIG. 12(A)  is a diagram showing a first variation,  FIG. 12(B)  is a diagram showing a second variation,  FIG. 12(C)  is a diagram showing a third variation, and  FIG. 12(D)  is a diagram showing a fourth variation. Note that  FIGS. 12(A) to 12(D)  are enlarged cross-sectional views of a portion around each operation unit cut along the X-Y plane. The first to fourth variations have substantially similar configurations to the first embodiment except that the arrangement of the sensor  15  and the shape of the operation unit are different. Therefore, in the first to fourth variations, only the differences from the first embodiment will be described, and the rest will be omitted. 
     As shown in  FIG. 12(A) , in the first variation, the sensor  15  is disposed to vertically cross the operation unit  12  when the operation unit  12  is viewed from the −Y direction toward the Y direction, that is, in plan view. For this reason, the sensor  15  can detect a shear stress generated at the boundary  71  between the operation unit  12  and the housing  10  other than the operation unit  12 . 
     As shown in  FIG. 12(B) , in the second variation, the sensor  15  is disposed from an end portion  121  of the operation unit  12  to a side surface  122 . Further, the sensor  15  is adhered to the operation surface  11  side of the housing  10 . The sensor  15  is fixed at the end portion  121  of the operation unit  12  to which no force is applied by the user. For this reason, when the user applies a force to the side surface  122 , even if the sensor  15  comes off the side surface  122 , the sensor  15 , which is fixed at the end portion  121  of the operation unit  12 , can be prevented from peeling off from the housing  10 . 
     As further shown in  FIG. 12(C) , in the third variation, the operation unit  12  has no gap. The sensor  15  is disposed so as to vertically cross the operation unit  12  in plan view, similarly to the first modification. For this reason, the sensor  15  can detect a shear stress generated at the boundary  71  between the operation unit  12  and the housing  10  other than the operation unit  12 . Further, since the sensor  15  is attached to a flat surface, the sensor  15  can be easily adhered to the housing  10 . 
     As shown in  FIG. 12(D) , in the fourth variation, the operation unit  12  has no gap. The sensor  15  is disposed so as to horizontally cross part of the operation unit  12  in plan view. For this reason, the sensor  15  can detect a shear stress generated at the boundary  71  between the operation unit  12  and the housing  10  other than the operation unit  12 . Further, since the sensor  15  is attached to a flat surface, the sensor  15  can be easily adhered to the housing  10 . 
     Hereinafter, a rotation operation detection mechanism  110  according to a tenth embodiment will be described.  FIG. 13(A)  is a perspective view of the rotation operation detection mechanism  110  according to the tenth embodiment.  FIG. 13(B)  is a cross-sectional view when the rotation operation detection mechanism  110  is cut along I-I of  FIG. 13(A) .  FIG. 13(C)  is a cross-sectional view when the rotation operation detection mechanism  110  is cut along II-II of  FIG. 13(B) .  FIGS. 13(A) to 13(C)  show only a portion around the operation unit  12  of the rotation operation detection mechanism  110 . Further,  FIG. 13(A)  shows the operation unit  12  by a broken line as transparent. The cut surface II-II of  FIG. 13(B)  is further in the Z direction than the sensor  15 .  FIG. 13(C)  shows part of a support portion  32  by a broken line and through the housing  10 . 
     The rotation operation detection mechanism  110  according to the tenth embodiment has a substantially similar configuration to that of the first embodiment, except that the rotation operation detection mechanism  110  includes a holding portion  31  and the support portion  32 , and the arrangement of the sensor  15  is different. Therefore, in the tenth embodiment, only the differences from the first embodiment will be described, and the rest will be omitted. 
     As shown in  FIGS. 13(A) to 13(C) , the rotation operation detection mechanism  110  includes the holding portion  31  and the support portion  32 . The holding portion  31  is disposed on the back side  16  of the operation surface  11  of the operation unit  12 . The support portion  32  is disposed on the back side  16  of the housing  10  on the operation surface  11 . Further, part of the support portion  32  is disposed so as to face the operation unit  12 . 
     The holding portion  31  is a flat plate shape. Both main surfaces of the holding portion  31  have a rectangular shape that is longer in the Y direction than in the X direction. A longitudinal direction of the holding portion  31  is the Y direction, and a short direction of the holding portion  31  is the X direction. The sensor  15  is disposed on one main surface of the holding portion  31 . The sensor  15  has a rectangular shape that is longer the Y direction than in the X direction. When the holding portion  31  is cut along the X-Z plane, a cross section of the holding portion  31  is rectangular. Note that the holding portion  31  only needs to be able to hold the sensor  15 , and may have a film shape with a small thickness in the Z direction. Further, the cross section of the holding portion  31  when cut along the X-Z plane is not limited to a flat plate shape, and may be, for example, a polygonal column shape or an ellipse. 
     The sensor  15  is adhered to the holding portion  31  so that the uniaxial stretching direction (arrow  901 ) is parallel to the Y direction. Note that the sensors  15  may be disposed on both main surfaces of the holding portion  31 . In this manner, an entire area of the sensor  15  becomes large, and an output of the entire sensor  15  becomes large. Further, the sensor  15  may be adhered to the holding portion  31  so that the uniaxial stretching direction (arrow  901 ) is perpendicular to the Y direction. 
     One end  30  of the holding portion  31  is fixed to the back side  16  of the operation unit  12 . The other end  33  of the holding portion  31  is fixed to the support portion  32 . The holding portion  31  is fixed by the back side  16  of the operation unit  12  and the support portion  32 . The holding portion  31  is fixed to the operation unit  12  and the support portion  32  by a publicly-known method such as a screw and an adhesive. The holding portion  31  is positioned substantially at the center of the operation unit  12 . The holding portion  31  is likely to be influenced by deformation of the operation unit  12  as compared to a case where the holding portion  31  is at a position other than the center of the operation unit  12 . For this reason, the holding portion  31  can easily catch deformation of the operation unit  12  accurately. 
     Part of the support portion  32  protrudes from the operation surface  11  to the inside of the housing  10 . In this manner, the holding portion  31  can be ensured to have a long length in the Y direction. Further, since the area of the sensor  15  disposed on the holding portion  31  is large in the Y direction, the output of the entire sensor  15  is large. Further, when the user grips the operation unit  12  and applies a force in the direction in which the operation unit  12  rotates on the X-Z plane, the holding portion  31  is more easily twisted as the length in the Y direction of the holding portion  31  is larger. Accordingly, since the deformation of the sensor  15  becomes significant, the output of the sensor  15  becomes large. Note that the support portion  32  does not need to protrude from the operation surface  11  to the inside of the housing  10 . For example, when the support portion  32  has a flat plate shape, the support portion  32  is easily formed. 
     The holding portion  31  and the support portion  32  may be formed of the same material as the housing  10 , or may be formed of a different material. The material of the holding portion  31  and the supporting portion  32  is, for example, aluminum, an aluminum alloy, stainless steel, resin, or the like. 
       FIG. 14(A)  is a diagram schematically showing a shear stress generated when the user operates the rotation operation detection mechanism  110 .  FIG. 14(B)  is a diagram showing an output value of the sensor  15  when the user operates to rotate the operation unit  12  or when the user grips the operation unit  12 . 
     As shown in  FIG. 14(A) , when the user grips the operation unit  12  and applies a force in the direction in which the operation unit  12  rotates on the X-Z plane, a force applied to the operation unit  12  is transmitted to the holding portion  31  that exists in the operation unit  12 . In this manner, a shear stress indicated by arrow  303  is generated in the holding portion  31 . The shear stress mainly forms a direction of 45 degrees with respect to the longitudinal direction (Y direction) of the holding portion  31 . 
     Since the sensor  15  is adhered to one main surface of the holding portion  31 , the shear stress indicated by arrow  303  is also generated in the sensor  15 . The sensor  15  is adhered so that the uniaxial stretching direction (arrow  901 ) of the piezoelectric film  20  is parallel to the Y direction. For this reason, the shear stress is generated to be in a direction mainly at 45 degrees with respect to the uniaxial stretching direction (arrow  901 ) of the piezoelectric film  20  of the sensor  15 . Therefore, the sensor  15  can output a voltage value according to the shear stress. Note that, even when the sensor  15  is adhered so that the uniaxial stretching direction (arrow  901 ) of the piezoelectric film  20  is perpendicular to the Y direction, a shear stress is generated to be in a direction mainly at 45 degrees with respect to the uniaxial stretching direction (arrow  901 ), and a similar effect can be obtained. 
     Due to the deformation of the piezoelectric film  20 , the sensor  15  generates charges. When the user grips the operation unit  12  and applies a force in the direction in which the operation unit  12  rotates on the X-Z plane, the sensor  15  outputs a voltage as indicated by a solid line in  FIG. 14(B) . On the other hand, when the user only grips the operation unit  12 , the operation unit  12  is only slightly deformed from the front side to the back side. In this case, the force applied to the operation unit  12  by the user is hardly transmitted to the holding portion  31 . For this reason, as indicated by a broken line in  FIG. 14(B) , an output value of the sensor  15  becomes small. Depending on the magnitude of the output from the sensor  15 , the rotation operation detection mechanism  110  can distinguish a case where the user grips the operation unit  12  and a case where the user grips and further performs operation of rotating the operation unit  12 . Therefore, the rotation operation detection mechanism  110  can more accurately detect the rotation of the operation unit  12 . 
     Hereinafter, a rotation operation detection mechanism  111  according to an eleventh embodiment will be described. 
     Specifically,  FIG. 15(A)  is a perspective view of the rotation operation detection mechanism  111  according to the eleventh embodiment.  FIG. 15(B)  is a cross-sectional view when the rotation operation detection mechanism  111  is cut along I-I in  FIG. 15(A) .  FIG. 15(C)  is a cross-sectional view when the rotation operation detection mechanism  111  is cut along II-II in  FIG. 15(B) . It should be appreciated that  FIGS. 15(A) to 15(C)  show only a portion around the operation unit  12  of the rotation operation detection mechanism  111 . Further,  FIG. 15(A)  shows the operation unit  12  by a broken line as transparent. The cut surface of  FIG. 15(B)  is further in the positive side of the Z direction than the sensor  15 . 
     The rotation operation detection mechanism  111  according to the eleventh embodiment has a substantially similar configuration to that of the tenth embodiment, except that the rotation operation detection mechanism  111  does not include the support portion  32 , and the arrangement of a holding portion  41  is different. Therefore, in the eleventh embodiment, only the differences from the tenth embodiment will be described, and the rest will be omitted. 
     As shown in  FIGS. 15(A) to 15(C) , the rotation operation detection mechanism  111  includes the holding portion  41  that has a flat plate shape, and is disposed on the back side  16  of the operation surface  11  of the operation unit  12 . The one end  30  of the holding portion  41  is connected to the back side  16  of the operation unit  12 . The other end  33  of the holding portion  41  is not fixed. End portions  34  and  35  in the X direction of the holding portion  41  are connected to the back side  16  of the operation unit  12 . That is, the holding portion  41  is fixed in three directions by the back side  16  of the operation unit  12 . Therefore, since the rotation operation detection mechanism  111  has no support portion, the structure can be simplified. 
     When the user grips the operation unit  12  and applies a force in the direction in which the operation unit  12  rotates in the X-Z plane, the deformation of the operation unit  12  is transmitted from the one end  30 , the end portion  34 , and the end portion  35  of the holding portion  41  to the holding portion  41 . In this manner, a shear stress is generated in the sensor  15  as in the case of the rotation operation detection mechanism  110 . Therefore, the rotation operation detection mechanism  111  can detect the rotation of the operation unit  12 . 
     Hereinafter, a rotation operation detection mechanism  112  according to a twelfth embodiment will be described. 
     In particular,  FIG. 16(A)  is a perspective view of the rotation operation detection mechanism  112  according to the twelfth embodiment.  FIG. 16(B)  is a partial cross-sectional view when the rotation operation detection mechanism  112  is cut along I-I in  FIG. 16(A) .  FIG. 16(C)  is a cross-sectional view when the rotation operation detection mechanism  112  is cut along II-II in  FIG. 16(B) .  FIGS. 16(A) to 16(C)  show only a portion around the operation unit  12  of the rotation operation detection mechanism  112 .  FIG. 16(A)  shows the operation unit  12  by a broken line as transparent. The cut surface of  FIG. 16(B)  is further in the positive side of the Z direction than the sensor  15 .  FIG. 16(B)  shows only the operation unit  12  and the support portion  32  in a cross-sectional view, and is a diagram as viewed from the positive side to the negative side in the Z direction. 
     The rotation operation detection mechanism  112  according to the twelfth embodiment has a substantially similar configuration to that of the tenth embodiment, except that the shapes and arrangement of a holding portion  42 , a support portion  43 , and the sensor  15  are different. Therefore, in the twelfth embodiment, only the differences from the tenth embodiment will be described, and the rest will be omitted. 
     As shown in  FIGS. 16(A) to 16(C) , the rotation operation detection mechanism  112  includes the holding portion  42  having a columnar shape. The holding portion  42  is arranged on the back side  16  of the operation surface  11  of the operation unit  12 . The one end  30  of the holding portion  42  is connected to the back side  16  of the operation unit  12 . The other end  33  of the holding portion  42  is connected to the supporting portion  43 . Note that the holding portion  42  is not limited to a columnar shape, and may be, for example, a polygonal columnar shape. 
     The support portion  43  is disposed so as to completely cover a position corresponding to the operation unit  12 . In this manner, the holding portion  42  is more firmly fixed to the housing  10 . 
     The sensor  15  is disposed on a side surface of the holding portion  42  along the circumferential direction of the operation unit  12 . The sensor  15  is adhered so as to cover the entire side surface of the holding portion  42 . In this manner, the sensor  15  can detect the deformation of the holding portion  42  completely. Further, an entire area of the sensor  15  becomes large, and an output of the entire sensor  15  becomes large. 
     Note that the sensor  15  may be disposed in part of the holding portion  42 . For example, the sensor  15  may be disposed in an upper semicircular portion in a cross section of the holding portion  42 . Further, the sensor  15  may be adhered so as to cover part of the side surface of the holding portion  42  in the Y direction. 
     The sensor  15  is adhered to the holding portion  42  so that the uniaxial stretching direction (arrow  901 ) is parallel to the Y direction. Note that the sensor  15  may adhered to the holding portion  42  so that the uniaxial stretching direction (arrow  901 ) is along the circumferential direction of the holding portion  42 . 
       FIGS. 17(A) and 17(B)  are diagrams schematically showing a shear stress generated when the user operates the rotation operation detection mechanism  112 .  FIG. 17(A)  is a diagram when viewed from the positive side in the Z direction.  FIG. 17(B)  is a diagram when viewed from the positive side in the X direction. 
     When the user grips the operation unit  12  and applies a force in the direction in which the operation unit  12  rotates in the X-Z plane, the deformation of the operation unit  12  is transmitted from the one end  30  and the other end  33  of the holding portion  42  to the holding portion  42 . As shown in  FIGS. 17(A) and 17(B) , a shear stress indicated by arrow  303  is generated in the holding portion  42 . 
     The shear stress mainly forms a direction of 45 degrees with respect to the longitudinal direction (Y direction) of the holding portion  42 . In this manner, a shear stress is generated in the sensor  15  as in the case of the rotation operation detection mechanism  110 . Therefore, the rotation operation detection mechanism  112  can detect the rotation of the operation unit  12 . In this case, the rotation direction of the operation unit  12  coincides with the rotation direction due to twisting of the holding portion  42  that generates a shear stress as indicated by arrow  303 . Therefore, the sensor  15  can detect the rotation of the operation unit  12  with higher accuracy. 
     Hereinafter, a rotation operation detection mechanism  113  according to a thirteenth embodiment will be described. 
       FIG. 18(A)  is a perspective view of the rotation operation detection mechanism  113  according to the thirteenth embodiment.  FIG. 18(B)  is a partial cross-sectional view when the rotation operation detection mechanism  113  is cut along I-I in  FIG. 18(A) .  FIG. 18(C)  is a cross-sectional view when the rotation operation detection mechanism  113  is cut along II-II in  FIG. 16(B) .  FIGS. 18(A) to 18(C)  show only a portion around the operation unit  12  of the rotation operation detection mechanism  113 .  FIG. 18(A)  shows the operation unit  12  by a broken line as transparent. The cut surface of  FIG. 18(B)  is further in the positive side of the Z direction than the sensor  15 . That is,  FIG. 18(B)  shows only the operation unit  12  and a support portion  38  in a cross-sectional view, and is a diagram as viewed from the positive side to the negative side in the Z direction. 
     The rotation operation detection mechanism  113  according to the thirteenth embodiment has a substantially similar configuration to that of the twelfth embodiment, except that the shapes of a holding portion  44  and the support portion  38 . Therefore, in the thirteenth embodiment, only the differences from the twelfth embodiment will be described, and the rest will be omitted. 
     As shown in  FIGS. 18(A) to 18(C) , the rotation operation detection mechanism  113  includes the holding portion  44  having a cylindrical shape. The holding portion  44  is hollow and has an internal space  45 . Since the holding portion  44  has the internal space  45 , the rigidity is low. The holding portion  44  is easily deformed by an external force. For this reason, a shearing force generated on a side surface of the holding portion  44  is large as compared with a case where the holding portion  44  is not hollow. Therefore, when the user grips the operation unit  12  and applies a force in the direction in which the operation unit  12  rotates in the X-Z plane, the output of the sensor  15  is large as compared to a case where the holding portion  44  is not hollow. 
     The support portion  38  has a flat plate shape not protruding from the operation surface  11  into the housing  10 . For this reason, formation of the support portion  38  is easy. 
     Hereinafter, a rotation operation detection mechanism  114  according to a fourteenth embodiment will be described. 
       FIG. 19(A)  is a perspective view of the rotation operation detection mechanism  114  according to the fourteenth embodiment.  FIG. 19(B)  is a cross-sectional view when the rotation operation detection mechanism  114  is cut along in  FIG. 19(A) .  FIG. 19(C)  is a cross-sectional view when the rotation operation detection mechanism  114  is cut along II-II in  FIG. 19(B) .  FIGS. 19(A) to 19(C)  show only a portion around the operation unit  12  of the rotation operation detection mechanism  114 .  FIG. 19(A)  shows the operation unit  12  by a broken line as transparent, and shows only part of the housing  10 . 
     The rotation operation detection mechanism  114  according to the fourteenth embodiment has a substantially similar configuration to the first embodiment except that the rotation operation detection mechanism  114  includes a plurality of sensors  151  to  156 . Therefore, in the fourteenth embodiment, only the differences from the first embodiment will be described, and the rest will be omitted. 
     As shown in  FIGS. 19(A) to 19(C) , the rotation operation detection mechanism  114  includes six of the sensors  151  to  156 , a signal processing unit  61 , and a signal detection unit  62 . The signal processing unit  61  and the signal detection unit  62  are disposed inside the housing  10 . 
     As shown, the sensors  151  to  156  are disposed on the back surface  16  of the operation surface  11  on the side surface of the operation unit  12 . The sensors  151  to  156  are disposed at regular intervals along the circumferential direction of the operation unit  12 . Six of the sensors  151  to  156  are disposed, one for each of sections obtained by dividing the side surface of the operation unit  12  into six equal parts. It is noted that the phrase “six equal parts” indicates a state in which the operation unit  12  is equally divided in the circumferential direction at a central angle of 60°. That is, the sensors are disposed in each of the sections obtained by equally dividing the side surface of the operation unit  12 . It is also noted that the number of the sensors is not limited to six as long as the number is three or more. Further, the sensors only need to be disposed in each of the sections into which the operation unit  12  is equally divided, and the intervals between the sensors do not need to be equal. Furthermore, the equal division may include an error to some extent, and may include an error of, for example, about 10°. 
       FIG. 20  is a functional block diagram of signal processing performed by six of the sensors  151  to  156  of the rotation operation detection mechanism  114 , the signal detection unit  62 , and the signal processing unit  61 . The sensors  151  to  156  are connected to the signal detection unit  62 . 
     When the user deforms the operation unit  12 , the sensors  151  to  156  corresponding to the deformed locations of the operation unit  12  generate charge. The signal detection unit  62  detects charge generated in the sensors  151  to  156 . The signal processing unit  61  inputs a detection value of the signal detection unit  62 . The signal processing unit  61  detects a voltage value detected by the signal detection unit  62  for each of the sensors  151  to  156 . That is, the signal processing unit  61  detects the magnitude of deformation of the operation unit  12  at a position corresponding to each of the sensors  151  to  156  as a load applied to the operation unit  12  by the user. 
     The signal processing unit  61  includes a storage unit (not shown), and stores a predetermined threshold set in advance. The threshold is set in each of the positive and negative polar directions. The signal processing unit  61  detects, as a peak, a voltage value output from the sensors  151  to  156  whose peak is equal to or more than the predetermined threshold. Further, the signal processing unit  61  does not detect, as a peak, a voltage value output from the sensors  151  to  156  whose peak is less than the predetermined threshold. In this manner, the signal processing unit  61  can suppress unnecessary processing for noise and the like. 
     The signal processing unit  61  stores a time at which the signal detection unit  62  detects a peak of a voltage value. In this manner, the signal processing unit  61  can store from which sensor a signal is generated at which time associated with each other. Therefore, the signal processing unit  61  can determine the order in which signals are generated for each sensor. Hereinafter, detection values from the sensors  151  to  156  when the user operates the operation unit  12  will be described. 
       FIG. 21  is a graph showing detection values of the sensors  151  to  156  when the user rotates the operation unit  12  of the rotation operation detection mechanism  114  clockwise to the right. 
       FIG. 22  is a graph showing detection values of the sensors  151  to  156  when the user rotates the operation unit  12  of the rotation operation detection mechanism  114  counterclockwise to the left. 
       FIG. 23  is a graph showing detection values of the sensors  151  to  156  when the user only grips the operation unit  12  of the rotation operation detection mechanism  114 . Note that  FIGS. 21 to 23  show examples of detection values. 
     Hereinafter, detection values from the sensors  151  to  156  when the user rotates the operation unit  12  to the right, rotates the operation unit  12  to the left, and only grips the operation unit  12  will be described in order. 
     When the user rotates the operation unit  12  to the right, the signal processing unit  61  first detects peaks of positive voltage values from the sensors  152  and  155  as shown in  FIG. 21 . Note that the signal processing unit  61  detects only a peak that exceeds a predetermined threshold in both positive and negative sides as a peak. A time at which a voltage value detected from the sensor  152  or the sensor  155  first returns to 0 V, which is a reference value, is defined as a first time (T 1 ). 
     In this case, a time at which a voltage value detected from the sensor  155  returns to 0 V is the first time (T 1 ). The signal processing unit  61  stores the first time (T 1 ). 
     The signal processing unit  61  treats a signal detected by the signal detection unit  62  after the first time (T 1 ) as the basis for determination. That is, the signal processing unit  61  treats a time before the first time (T 1 ) as the influence of the user gripping the operation unit  12  and excluding the time from the basis for determination. In this manner, erroneous determination due to the influence of the user gripping the operation unit  12  can be prevented. 
     At and after the first time (T 1 ), the signal processing unit  61  detects a peak of a first positive voltage value from the sensor  151  and the sensor  154 , and then detects a peak of a second positive voltage value from the sensor  152  and the sensor  155 . The signal processing unit  61  stores a time at which the peak of the first positive voltage value is detected from the sensors  151  and  154  as a second time (T 2 ). The signal processing unit  61  stores a time at which the peak of the second positive voltage value is detected from the sensors  152  and  155  as a third time (T 3 ). During a period (T 4  shown in  FIG. 21 ) from the first time (T 1 ) to the third time (T 3 ), the signal processing unit  61  detects that a voltage value generated from the sensors  153  and  156  exceeds the threshold. 
     At and after the first time (T 1 ), the signal processing unit  61  determines that the order of detecting the peaks of the positive voltage values is the order from the sensors  151  and  154  to the sensors  152  and  155 . In other words, the order of detecting the peaks of the positive voltage values is the order from the sensor  151  to the sensor  152  adjacent to the sensor  151 , and from the sensor  154  to the sensor  155  adjacent to the sensor  154 . The order of detecting the peaks of the positive voltage values is clockwise when the operation unit  12  is viewed from the front. 
     Further, the signal processing unit  61  detects a peak from the sensor  151 , the sensor  152 , the sensor  154 , and the sensor  155  during the period from the first time (T 1 ) to the third time (T 3 ), and detects that the voltage values generated from the sensor  153  and the sensor  156  exceed the threshold. In other words, the signal processing unit  61  determines that the voltage values generated from all the sensors  151  to  156  exceed the threshold during the period from the first time (T 1 ) to the third time (T 3 ). Therefore, the signal processing unit  61  determines that the user rotates the operation unit  12  to the right. 
     When the user rotates the operation unit  12  counterclockwise to the left, the signal processing unit  61  first detects peaks of positive voltage values from the sensors  152  and  155  as shown in  FIG. 22 . A time at which a voltage value detected from the sensor  152  or the sensor  155  first returns to 0 V, which is a reference value, is defined as a first time (T 1 ). In this case, a time at which a voltage value detected from the sensor  155  returns to 0 V is the first time (T 1 ). 
     At and after the first time (T 1 ), the signal processing unit  61  detects a peak of a first positive voltage value from the sensor  153  and the sensor  156 , and then detects a peak of a second positive voltage value from the sensor  152  and the sensor  155 . The signal processing unit  61  stores a time at which the peak of the first positive voltage value is detected from the sensors  153  and  156  as the second time (T 2 ). The signal processing unit  61  stores a time at which the peak of the second positive voltage value is detected from the sensors  152  and  155  as a third time (T 3 ). During the period (T 4  shown in  FIG. 22 ) from the first time (T 1 ) to the third time (T 3 ), the signal processing unit  61  detects that a voltage value generated from the sensors  151  and  154  exceeds the threshold. 
     At and after the first time (T 1 ), the signal processing unit  61  determines that the order of detecting the peaks of the positive voltage values is the order from the sensors  153  and  156  to the sensors  152  and  155 . In other words, the order of detecting the peaks of the positive voltage values is the order from the sensor  153  to the sensor  152  adjacent to the sensor  153 , and from the sensor  156  to the sensor  155  adjacent to the sensor  156 . The order of detecting the peaks of the positive voltage values is counterclockwise when the operation unit  12  is viewed from the front. 
     Further, the signal processing unit  61  detects a peak from the sensor  152 , the sensor  153 , the sensor  155 , and the sensor  156  during the period from the first time (T 1 ) to the third time (T 3 ), and detects that the voltage values generated from the sensor  151  and the sensor  154  exceed the threshold. In other words, the signal processing unit  61  determines that the voltage values generated from all the sensors  151  to  156  exceed the threshold during the period from the first time (T 1 ) to the third time (T 3 ). Therefore, the signal processing unit  61  determines that the user rotates the operation unit  12  to the left. 
     When the user only grips the operation unit  12 , the signal processing unit  61  first detects peaks of positive voltage values from the sensors  155  and  156  as shown in  FIG. 23 . A time at which a voltage value detected from the sensor  155  or the sensor  156  first returns to 0 V, which is a reference value, is defined as the first time (T 1 ). In this case, a time at which a voltage value detected from the sensor  156  returns to 0 V is the first time (T 1 ). 
     At and after the first time (T 1 ), the signal processing unit  61  detects a peak of a first positive voltage value from the sensor  152 , and then detects a peak of a second positive voltage value from the sensor  151 . The signal processing unit  61  stores a time at which the peak of the first positive voltage value is detected from the sensor  152  as the second time (T 2 ). The signal processing unit  61  stores a time at which the peak of the second positive voltage value is detected from the sensor  151  as the third time (T 3 ). During the period (T 4  shown in  FIG. 23 ) from the first time (T 1 ) to the third time (T 3 ), the signal processing unit  61  detects that a voltage value generated from the sensor  152  does not exceed the threshold. 
     In this manner, the signal processing unit  61  determines that all the voltage values generated from the sensors  151  to  156  do not exceed the threshold during the period from the first time (T 1 ) to the third time (T 3 ). Therefore, the signal processing unit  61  determines that the user only grips the operation unit  12  and there is no rotation operation. 
     As described above, the rotation operation detection mechanism  114  can determine that the user rotates or only grips the operation unit  12 . Further, when determining that the user rotates the operation unit  12 , the rotation operation detection mechanism  114  can determine whether a direction of the rotation is to the right or to the left. 
     Hereinafter, a rotation operation detection method in the rotation operation detection mechanism  114  will be described.  FIG. 24  is a flowchart showing the rotation operation detection method. 
     As shown in  FIG. 24 , when the user grips the operation unit  12  to rotate the unit  12 , the signal processing unit  61  first detects a first peak of a positive voltage value from any one of the sensors  151  to  156  (S 11 ). The signal processing unit  61  determines whether or not a voltage value from the sensor that detects the first peak has first reached 0 V, which is the reference value (S 12 ). When the signal processing unit  61  determines that the voltage value from the sensor that detects the first peak has first reached 0 V, which is the reference value (S 12 : Yes), a time at which the voltage values becomes 0 V is stored as the first time (T 1 ) (S 13 ). When the signal processing unit  61  determines that the voltage value from the sensor that detects the first peak has not reached 0 V, which is the reference value, first (S 12 : No), the signal processing unit  61  continues the detection until the voltage value from the sensor that detects the first peak first reaches 0 V, which is the reference value. 
     At and after the first time (T 1 ), the signal processing unit  61  detects a second peak of a second positive voltage value (S 14 ). The signal processing unit  61  stores a time at which the second peak is detected as the second time (T 2 ) (S 15 ). At and after the second time (T 2 ), the signal processing unit  61  detects a third peak of a third positive voltage value (S 16 ). 
     The signal processing unit  61  stores a time at which the third peak is detected as the third time (T 3 ) (S 17 ). 
     The signal processing unit  61  determines whether or not voltage values from all the sensors exceed the threshold during the period from the first time (T 1 ) to the third time (T 3 ) (S 18 ). When the signal processing unit  61  determines that the voltage values from all the sensors do not exceed the threshold during the period from the first time (T 1 ) to the third time (T 3 ) (S 18 : No), it is determined that the user only grips the operation unit  12  and that there is no rotation operation (S 19 ). 
     When the signal processing unit  61  determines that the voltage values from all the sensors exceed the threshold during the period from the first time (T 1 ) and the third time (T 3 ) (S 18 : Yes), whether or not the detection order of the sensors that detect the second peak and the third peak is clockwise in the operation unit  12  (S 20 ). When determining that the detection order of the sensors that detect the second peak and the third peak is clockwise in the operation unit  12  (S 20 : Yes), the signal processing unit  61  determines that the user rotates the operation unit  12  to the right (S 21 ). When determining that the detection order of the sensors that detect the second peak and the third peak is not clockwise in the operation unit  12  (S 20 : No), the signal processing unit  61  determines that the user rotates the operation unit  12  to the left (S 22 ). 
     As described above, the rotation operation detection method can determine that the user rotates or only grips the operation unit  12 . Further, when determining that the user rotates the operation unit  12 , the rotation operation detection method can determine whether a direction of the rotation is to the right or to the left. 
     It is also noted that, in each of the exemplary embodiments, the housings  10  and  50  are formed in a rectangular parallelepiped. However, the configuration is not limited to the above, and the housings  10  and  50  may be formed in a disc shape, a spherical shape, a polygonal column shape, or the like, in alternative embodiments. 
     It is further noted that the rotation operation detection mechanism in each of the embodiments can be applied to various ones. For example, the mechanism can be applied to an operation panel of electric appliances, such as a washing machine, a microwave oven, a fan, a refrigerator, an air conditioner, a telephone, a personal computer, a mouse, and a clock, household appliances, such as a plug of a faucet of a sink, a door knob, a window sash, and an environment setting panel of a bathroom, evaluation facilities, such as an oscilloscope, a tester, and a stabilized power supply, a power button installed outdoors, and the like. 
     DESCRIPTION OF REFERENCE SYMBOLS 
     
         
         
           
               1 : Main surface (first main surface) 
               10 ,  50 : Housing 
               11 : Operation surface 
               12 ,  13 ,  14 ,  17 ,  18 ,  19 : Operation unit 
               15 ,  81 ,  82 ,  83 ,  84 ,  90 : Sensor 
               16 : Back side 
               20 : Piezoelectric film 
               21 : First electrode 
               22 : Second electrode 
               31 ,  41 ,  42 ,  44 : Holding portion 
               32 ,  38 ,  43 : Support portion 
               51 : Short side 
               52 : Long side 
               61 : Signal processing unit 
               62 : Signal detection unit 
               71 : Boundary 
               101 ,  102 ,  103 ,  104 ,  105 ,  106 ,  107 ,  108 ,  109 ,  110 ,  111 ,  112 ,  113 ,  114 : Rotation operation detection mechanism 
               121 : End portion 
               151 ,  152 ,  153 ,  154 ,  155 ,  156 : Sensor 
               191 : Boundary