Acceleration sensor and method for producing the same

An acceleration sensor formed by the following processing steps:

• providing a piezoelectric vibrator including a piezoelectric element having a first principal surface and a second principal surface opposed to each other;
• forming a first and a second electrode formed on the first and the second principal surface;
• and
• depositing melted particles on the piezoelectric element via a thermal spraying process to form a thick film of large conductive protrusions, wherein the conductive protrusions comprise thermally sprayed melted particles and the thermally sprayed melted particles comprise a heated starting material having a particle size in a range of 5 .mu.m to 300 .mu.m, where the starting material is a metal material or a ceramic material, and wherein the thick film has a minute roughness surface where the minute roughness is in a range of 2 .mu.m to 10 .mu.m.

An acceleration sensor comprising a piezoelectric vibrator and a package enclosing the piezoelectric vibrator,

• the piezoelectric vibrator including:
• a piezoelectric element having two piezoelectric plates attached to each other, defining a plane and having a first face and a second face,
• a first electrode formed on the first face and a second electrode formed on the second face, and
• conductive protrusions, wherein the conductive protrusions comprise thermally sprayed melted particles and the thermally sprayed melted particles comprise a heated starting material having a particle size in a range of 5 .mu.m to 300 .mu.m, where the starting material is a metal material or a ceramic material, and wherein the conductive protrusions form a thick film having a minute roughness surface, wherein the minute roughness is in a range of 2 .mu.m to 10 .mu.m;
• and
• the package having a holder protruding from an internal surface of the package, the holder holding the piezoelectric vibrator at the central portion thereof,
• wherein a distortion in the piezoelectric element is generated by a movement of end portions of the piezoelectric vibrator in a direction perpendicular to the plane in response to a load applied to the piezoelectric vibrator, the distortion generates detectable charges inside the piezoelectric element, and
• wherein the holder cooperates to prevent the end portions of the piezoelectric vibrator from contacting the internal surface of the package when the end portions of the piezoelectric vibrator move in the direction perpendicular to the plane.

An acceleration sensor comprising a piezoelectric vibrator and a package enclosing the piezoelectric vibrator,

• the piezoelectric vibrator including:
• a piezoelectric element having a piezoelectric plate and a metal plate attached to each other, defining a plane and having a first face and a second face,
• a first electrode formed on the first face and a second electrode formed on the second face, and
• conductive protrusions, wherein the conductive protrusions comprise thermally sprayed melted particles and the thermally sprayed melted particles comprise a heated starting material having a particle size in a range of 5 .mu.m to 300 .mu.m, where the starting material is a metal material or a ceramic material, and wherein the conductive protrusions form a thick film having a minute roughness surface, wherein the minute roughness is in a range of 2 .mu.m to 10 .mu.m;
• and
• the package having a holder protruding from an internal surface of the package, the holder holding the piezoelectric vibrator at the central portion thereof,
• wherein a distortion in the piezoelectric element is generated by a movement of end portions of the piezoelectric vibrator in a direction perpendicular to the plane in response to a load applied to the piezoelectric vibrator, the distortion generates detectable charges inside the piezoelectric element, and
• wherein the holder cooperates to prevent the end portions of the piezoelectric vibrator from contacting the internal surface of the package when the end portions of the piezoelectric vibrator move in the direction perpendicular to the plane.

An acceleration sensor comprising:

• a piezoelectric vibrator and a package enclosing the piezoelectric vibrator, the piezoelectric vibrator including:
• a piezoelectric element having two piezoelectric plates attached to each other, defining a plane and having a first face and a second face,
• a first electrode formed on the first face and a second electrode formed on the second face, and
• conductive protrusions, wherein the conductive protrusions comprise thermally sprayed melted particles and the thermally sprayed melted particles comprise a heated starting material having a particle size in a range of 5 .mu.m to 300 .mu.m, where the starting material is a metal material or a ceramic material, and wherein the conductive protrusions form a thick film having a minute roughness surface, wherein the minute roughness is in a range of 2 .mu.m to 10 .mu.m;
• and
• the package having a holder protruding from an internal surface of the package, the holder holding the piezoelectric vibrator at the central portion thereof,
• wherein a distortion in the piezoelectric element is generated by a movement of end portions of the piezoelectric vibrator in a direction perpendicular to the plane in response to a load applied to the piezoelectric vibrator, the distortion generates detectable charges inside the piezoelectric element,
• wherein the holder cooperates to prevent the end portions of the piezoelectric vibrator from contacting the internal surface of the package when the end portions of the piezoelectric vibrator move in the direction perpendicular to the plane, and
• wherein a polarization direction of one of the two piezoelectric plates is contrary to a polarization direction of the other piezoelectric plate of the two piezoelectric plates when the load is provided.

An acceleration sensor comprising:

• a piezoelectric vibrator including a piezoelectric element having two plates attached to each other, wherein the piezoelectric element includes:
• a first principal surface and a second principal surface opposed to each other, and
• a first electrode formed on the first principal surface and a second electrode formed on the second principal surface;
• and
• conductive protrusions, wherein the conductive protrusions are formed directly on the piezoelectric vibrator at longitudinal central portions thereof;
• and
• a holder for holding the piezoelectric vibrator via the conductive protrusions,
• wherein the acceleration sensor transduces a distortion in the piezoelectric element generated by a load in the central portions of the piezoelectric vibrator into charges inside the piezoelectric element.

An acceleration sensor comprising:

• a piezoelectric vibrator including a piezoelectric element having a piezoelectric plate and a metal plate attached to the piezoelectric plate, wherein the piezoelectric element includes:
• a first principal surface and a second principal surface opposed to each other, and
• a first electrode formed on the first principal surface and a second electrode formed on the second principal surface;
• and
• conductive protrusions, wherein the conductive protrusions are formed directly on the piezoelectric vibrator at longitudinal central portions thereof;
• and
• a holder for holding the piezoelectric vibrator via the conductive protrusions,
• wherein the acceleration sensor transduces a distortion in the piezoelectric element generated by a load in the central portions of the piezoelectric vibrator into charges inside the piezoelectric element.

An acceleration sensor comprising:

• a piezoelectric vibrator including a piezoelectric element having
• a first principal surface and a second principal surface opposed each other,
• a first and second electrode formed on the first and second principal surface, and
• conductive protrusions, wherein the conductive protrusions comprise thermally sprayed melted particles and the thermally sprayed melted particles comprise a heated starting material having a particle size in a range of 5 .mu.m to 300 .mu.m, where the starting material is a metal material or a ceramic material, and wherein the conductive protrusions have a height in the range 50 .mu.m to 150 .mu.m and the conductive protrusions form a thick film having a minute roughness surface, wherein the minute roughness is in a range of 2 .mu.m to 10 .mu.m;
• and
• a holding body for the piezoelectric vibrator via the conductive protrusions, wherein a length in a longitudinal direction of the piezoelectric element is longer than 3.5 time of that in a width direction .