JP5164882B2 - Piezoelectric element for pressure sensor and pressure sensor using the same - Google Patents

Description

  The present invention relates to a piezoelectric element for a pressure sensor and a pressure sensor using the same.

  Conventionally, piezoelectric elements have been used as means for measuring various physical quantities such as pressure, force, and acceleration, and their application fields are diverse such as industrial, automotive, medical, and household appliances.

  In general, a piezoelectric element functions by integrating a piezoelectric body and an electrode, and has a very simple structure. Therefore, it can be miniaturized and has high productivity. Also, the sensitivity can be improved.

  In recent years, piezoelectric elements are incorporated in parts such as automobile engines and suspensions, and the pressure applied to the piezoelectric elements is sensed using the positive piezoelectric effect and used for engine combustion control and vehicle body attitude control. In particular, as a piezoelectric element used for engine control, there is an anti-knock sensor in a lean burn type engine which is widely used for the purpose of cleaning exhaust gas and improving fuel consumption. Piezoelectric elements are also being used to measure combustion pressure for the purpose of stable combustion of lean gases among HCCI (Homogenous Charge Compression Ignition) engines that do not use combustion plugs, which are being considered as next-generation engines. Has been.

  Since these piezoelectric elements are mounted in an engine room, element materials having high heat resistance are required. Furthermore, in order to improve fuel efficiency, it is necessary to precisely measure the pressure in the engine cylinder and perform fine lean burn control, so output signal characteristics (pressure characteristics of generated charge) with respect to pressure changes in the cylinder It is important that there is little change in.

  As such a pressure sensor for measuring the pressure in the engine, for example, a sensor that measures the pressure via a glow plug of a diesel engine is known (for example, Patent Document 1).

JP 2005-90954 A

  However, since the piezoelectric element for a pressure sensor of the invention described in the cited document 1 is a disc-shaped element, when a force that is not completely perpendicular to the pressure-applied surface of the piezoelectric element is applied, There is a problem that the S / N ratio of the output signal is lowered due to the generated noise.

  That is, an object of the present invention is to provide a pressure sensor piezoelectric element and a pressure sensor that can reduce output noise when used in a pressure sensor.

  The piezoelectric element for a pressure sensor of the present invention comprises electrodes on opposing main surfaces of a piezoelectric substrate, one of the main surfaces is an outwardly convex spherical surface, and the other main surface is a plane, A charge generated by a load applied between the main surfaces is measured.

  The piezoelectric element for a pressure sensor of the present invention includes electrodes on opposing main surfaces of a piezoelectric substrate, both of the main surfaces are outwardly convex spherical surfaces, and a load applied between the main surfaces. It is characterized in that the charge generated by is measured.

  Furthermore, the shape of the cross section between the opposing main surfaces of the piezoelectric substrate is a circle having a radius r (m), and the radius of curvature of the spherical surface is R (m), 1 ≦ R / r ≦ 10. It is preferable.

  Further, the main component of the piezoelectric substrate is preferably a bismuth layered compound.

  The pressure sensor according to the present invention is a pressure sensor for measuring a load applied between the pedestals by contacting a pedestal for transmitting a load to both of the main surfaces of the piezoelectric element for the pressure sensor, The pedestal that comes into contact with the main surface formed of a spherical surface convex outward of the main surface has a concave surface whose contact with the main surface is a substantially annular surface.

  The pressure sensor piezoelectric element according to the present invention is a pressure sensor for measuring a load applied between the pedestals by contacting a pedestal for transmitting a load to both of the main surfaces of the piezoelectric element for pressure sensor according to the present invention. Of these, the surface of the pedestal that comes into contact with the main surface made of a spherical surface convex outward is a spherical surface having the same curvature as the main surface and concave inward.

  According to the piezoelectric element for pressure sensor of the present invention, electrodes are provided on opposing main surfaces of the piezoelectric substrate, one of the main surfaces is an outwardly convex spherical surface, and the other main surface is a flat surface. At the same time, by measuring the electric charge generated by the load applied between the main surfaces, pressure is applied to one of the main surfaces through a pedestal whose shape is recessed inward. Accordingly, it is possible to reduce noise generated when a force other than the direction orthogonal to the main surface of the piezoelectric element is applied to the main surface of the piezoelectric element.

  The piezoelectric element for a pressure sensor of the present invention includes electrodes on opposing main surfaces of a piezoelectric substrate, both of the main surfaces are outwardly convex spherical surfaces, and a load applied between the main surfaces. By measuring the electric charge generated by the above, noise generated when a force other than the direction orthogonal to the main surface of the piezoelectric element is applied to the main surface of the piezoelectric element can be reduced.

  Furthermore, the shape of the cross section between the opposing main surfaces of the piezoelectric substrate is a circle having a radius r (m), and the radius of curvature of the spherical surface is R (m), 1 ≦ R / r ≦ 10. In this case, noise can be reduced.

Further, when the main component of the piezoelectric substrate is a bismuth layered compound, the piezoelectric constant d ₃₃ is low, and the S / N ratio of the output can be increased even if the original signal is low.

  According to the pressure sensor of the present invention, there is provided a pressure sensor for measuring a load applied between the pedestals by contacting a pedestal for transmitting a load to both of the main surfaces of the piezoelectric element for the pressure sensor. The pedestal that comes into contact with the main surface comprising a spherical surface that protrudes outward from the main surface has a concave surface whose contact with the main surface is a substantially annular surface, so that the piezoelectric element is interposed between the pedestals. Noise generated when a force other than the direction orthogonal to the principal surface of the element is applied can be reduced.

  The pressure sensor piezoelectric element according to the present invention is a pressure sensor for measuring a load applied between the pedestals by contacting a pedestal for transmitting a load to both of the main surfaces of the piezoelectric element for pressure sensor according to the present invention. The surface of the pedestal that comes into contact with the main surface consisting of a spherical surface convex outward is a spherical surface that has the same curvature as the main surface and is concave on the inner side, so that the main surface of the piezoelectric element is between the pedestals. It is possible to reduce noise generated when a force other than the orthogonal direction is applied.

(A) It is a longitudinal cross-sectional view of the piezoelectric element for pressure sensors which is one Embodiment of this invention, (b) is the top view. (A) It is a longitudinal cross-sectional view of the piezoelectric element for pressure sensors which is other embodiment of this invention, (b) is the top view. (A)-(d) is a longitudinal cross-sectional view of the principal part of the pressure sensor using the piezoelectric element for pressure sensors of FIG. (A), (b) is a longitudinal cross-sectional view of the principal part of the pressure sensor using the piezoelectric element for pressure sensors of FIG. (A)-(d) is a longitudinal cross-sectional view of the principal part of the pressure sensor using the piezoelectric element for pressure sensors which is a reference example other than this invention.

  FIG. 1A is a longitudinal sectional view of a piezoelectric element 10 for pressure sensor (hereinafter sometimes simply referred to as a piezoelectric element) according to an embodiment of the present invention, and FIG. 1B is a plan view thereof.

  The pressure sensor piezoelectric element 10 includes electrodes 13 a and 13 b on the opposing main surfaces 11 a and 11 b of the piezoelectric substrate 11, respectively. One main surface 11a of the piezoelectric substrate 11 is an outwardly convex spherical surface, and its radius of curvature is R (m). The other main surface 11b is a plane, and the load applied to the piezoelectric element 10 is measured by collecting and measuring charges generated by the load applied between the main surface 11a and the main surface 11b at the electrodes 13a and 13b. Can do.

The composition of the piezoelectric substrate 11 is not particularly limited, and piezoelectric ceramics such as bismuth layered compound, aluminum nitride, zinc oxide, lead zirconate titanate (PZT) and lead titanate can be exemplified. Since the suppression of noise described later is required as the output generated by the piezoelectric element 10 is lower, it is suitable for a piezoelectric ceramic having a composition having a low piezoelectric constant, and a piezoelectric ceramic having a piezoelectric d ₃₃ constant of 30 pC / N or less. It is especially effective when used for.

  As a piezoelectric ceramic for a pressure sensor, a complex oxide ferroelectric material containing lead, such as PZT, is often used. In particular, PZT piezoelectric ceramics are excellent in piezoelectric characteristics, so that output such as charge or potential difference can be increased with respect to input such as pressure. However, a ferroelectric material typified by PZT is difficult to use at high temperatures because the piezoelectricity disappears above the Curie temperature. In addition, ferroelectric materials are not suitable for precise measurement because they exhibit hysteresis in strain-electric field characteristics. For this reason, as a combustion pressure sensor for an internal combustion engine, aluminum nitride that is not a ferroelectric material or a bismuth layered compound that has a high Curie temperature even if it is a ferroelectric material in consideration of high temperature characteristics and linearity of response. Piezoelectric ceramics such as are preferred.

  However, since these piezoelectric ceramics have a piezoelectric characteristic of about 1/20 or less than that of the PZT system, the output is small and the sensitivity is low, so it is particularly necessary to reduce noise. The piezoelectric ceramic to be used is easy to manufacture because it can be manufactured by a normal ceramic manufacturing process, and since it is an oxide, it is highly reliable at high temperatures, and has a high Curie temperature and high heat resistance. It is preferable to use a main piezoelectric ceramic.

The piezoelectric substrate 11 is polarized in a direction in which the main surfaces 11a and 11b face each other by applying a voltage between the electrodes 13a and 13b. That is, in the piezoelectric element 10, electric charges are generated by the piezoelectric d ₃₃ constant by the pressure applied to the main surfaces 11a and 11b. The shape of the cross section between the opposing principal surfaces 11a, 11b of the piezoelectric element 10 is circular, and the overall shape excluding the spherical principal surface 11a is preferably cylindrical, but the opposing principal surfaces 11a, The shape of the cross section between 11b may be a polygon such as a rectangle, and the entire shape excluding the spherical main surface 11a may be a prismatic shape. If it is a cylindrical shape, it is not necessary to consider the influence of the positional deviation caused by the rotation of the piezoelectric element 10 when it is incorporated in the pressure sensor. In the case of a cylindrical shape, the radius r (m) of the cross section between the opposing principal surfaces 11a and 11b of the piezoelectric substrate 11 and the radius of curvature R (m) of the principal surface 11a are 1 ≦ R / r ≦ 10. Preferably there is. When R / r is less than 1, a portion where no stress is directly applied to the piezoelectric substrate is formed, resulting in poor efficiency. When R / r is larger than 10, the difference from the case where the main surface 11a is a flat surface is reduced, and the effect is lowered.

  Further, when the surface roughness Ra of the main surfaces 11a and 11b is 2 μm or less, particularly 1 μm or less, noise described later can be reduced. The radius r of the piezoelectric substrate 11 is preferably 0.25 to 2.5 mm for improving the S / N ratio, and damage to the piezoelectric element 10 can be reduced.

  Furthermore, since the shapes of the main surface 11a and the main surface 11b are different, it is easy to align the direction when incorporated in the pressure sensor, and it is easy to find an error in the direction after incorporation.

  The electrodes 13a and 13b are formed on substantially the entire main surfaces 11a and 11b. The electrodes 13a and 13b can be made of a metal such as Ag, Au, Pt, Cu, or Ni. However, the electrodes 13a and 13b are mainly composed of Ag for cost, the ability to be fired in the atmosphere, and excellent reliability. Is preferred. The thickness of the electrodes 13a and 13b is preferably 2 to 20 μm. If the electrodes 13a and 13b are metal, the electrodes 13a and 13b exhibit a slight difference in shape between the main surfaces 11a and 11b and a pedestal to be described later, and the surface of the main surfaces 11a and 11b or the surface of the pedestal. Can be deformed and absorbed by the sex. When the thickness is 2 μm or more, absorption is sufficient, and when the thickness is 20 μm or less, the possibility that the deformed electrodes 13a and 13b protrude outside the piezoelectric element 10 is reduced.

  FIG. 3A is a longitudinal sectional view of a pressure sensor according to an embodiment of the present invention incorporating the piezoelectric element 110a. Although details of the structure of the piezoelectric element 110a are omitted, they are the same as those shown in FIG. The pressure transmitted from the pressure transmission members 140a and 150a is transmitted to the piezoelectric element 110a via the pedestals 120a and 130a. The electric charges collected on the electrodes (not shown) of the piezoelectric element 110a can be transmitted with the pedestals 120a and 130a made conductive, or a conductive member is inserted between the pedestals 120a and 130a and the piezoelectric element 110a. It ’s fine. The piezoelectric element 110a side of the pedestal 120a has a spherical shape recessed with the same radius of curvature as the main surface of the piezoelectric element 110a. Note that slight differences in the radius of curvature between the piezoelectric element 110a and the pedestal 120a caused by processing variations and the difference in shape due to surface irregularities are caused by the electrodes formed on the piezoelectric element 110a and the pedestals 120a and 130a and the piezoelectric element 110a. It can be absorbed by deformation of the conductive member interposed therebetween. The difference in shape is preferably 1/3 or less of the thickness of the electrode. The pedestal 130a has a planar shape on the piezoelectric element 110a side.

  In the case of such a structure, the contact surface of the piezoelectric element 110a that is in contact with the pedestal 120a has a spherical main surface, so that even when the pedestal 120a or the pedestal 130a is slightly tilted, the piezoelectric element is surely provided. It becomes possible to transmit pressure to 110a. In particular, when the pressure sensor is fixed on the pressure transmission member 150a side and the pressure change on the pressure transmission member 140a side is measured, the force applied from the pressure transmission member 140a side is in the direction in which the main surface of the piezoelectric element 110a faces. A noise component due to non-uniformity of the contact portion that occurs when the contact between the piezoelectric element 110a and the pedestal 120a is a flat surface when not only a parallel force but also a force deviated from that direction is applied. Can be reduced. In other words, when the contact surface is a flat surface, if a force with a deviation from the vertical direction is applied, the piezoelectric element 110a and the pedestal 120a are displaced at a fine level, or the way of contact is changed. It becomes noise. That is, when the side on which the force fluctuates is the pedestal 120a side, it is important whether the surface on which the piezoelectric element 110a and the pedestal 120a contact is a flat surface.

  FIG. 3B is a longitudinal sectional view of a pressure sensor according to an embodiment of the present invention incorporating the piezoelectric element 110b. Although details of the structure of the piezoelectric element 110b are omitted, they are the same as those shown in FIG. The pressure transmitted from the pressure transmission members 140b and 150b is transmitted to the piezoelectric element 110b via the pedestals 120b and 130b. The piezoelectric element 110b side of the pedestal 120b is a concave surface having a conical surface shape. Due to deformation of the electrodes formed on the piezoelectric element 110b, the contact surface between the piezoelectric element 110b and the pedestal 120b becomes substantially annular. Thereby, it has the effect which suppresses generation | occurrence | production of the noise at the time of the direction to which force is added shifting | deviated like the above-mentioned case. Since the contact surface is not a single plane, noise due to non-uniformity of the contact portion can be reduced, but the pressure sensor shown in FIG.

  In addition, the substantially annular shape includes a state in which the contact surface is not in one plane but has a three-dimensional shape like a part of a conical slope. The substantially annular shape includes a shape in which the shape of the piezoelectric element 120b or the pedestal 120b is slightly deformed due to manufacturing variations.

  FIG. 2A is a longitudinal sectional view of a piezoelectric element 20 for pressure sensor according to an embodiment of the present invention, and FIG. 2B is a plan view thereof.

  The piezoelectric element 20 for pressure sensor is provided with electrodes 23 a and 23 b on the main surfaces 21 a and 21 b facing the piezoelectric substrate 21, respectively. The shapes of the main surfaces 21a and 21b are outwardly convex spherical surfaces, and the radius of curvature is R (m). By collecting and measuring the charges generated by the load applied between the main surface 21a and the main surface 21b by the electrodes 23a and 23b, the load applied to the piezoelectric element 20 can be measured.

  In such a shape, if the curvature is changed between the main surface 21a and the main surface 21b, the shape will be different. Therefore, when incorporating into the pressure sensor, it is easy to align the direction. Cheap.

  FIGS. 3C and 3D are longitudinal sectional views of a pressure sensor according to an embodiment of the present invention in which the piezoelectric elements 110c and 110d are incorporated. Although details of the structure of the piezoelectric elements 110c and 110d are omitted, they are the same as those shown in FIG. The pedestals 130c and 130d are fixed to an external structure or the like, and the piezoelectric elements 110c and 110d are preloaded by the pressurizing members 170c and 170d via the pedestals 130c and 130d. The pressurizing members 170c and 170d are, for example, springs. When a force is applied from the pressure transmission members 160c and 160d, the pressure applied to the piezoelectric elements 110c and 110d is reduced by the amount of the force, and the load applied to the pressure transmission member 160c can be measured by measuring the change.

  The piezoelectric element 110c side of the pedestal 130c has a spherical shape recessed with the same radius of curvature as the main surface of the piezoelectric element 110c. The pedestal 130d has a conical surface shape on the piezoelectric element 110d side.

  In the pressure sensor having such a structure, if the pressure transmission members 160c and 160d are insulated from the pedestals 130c and 130d and voltage is supplied, the pressure transmission members 160c and 160d can be used as glow plugs. Becomes a body pressure sensor.

  There is a fine space between the piezoelectric elements 110c and 110d and the pedestals 130c and 130d, and this space cannot be filled even if the preload is increased. Further, if the preload is excessively increased, the piezoelectric elements 110c and 110d may be damaged. The preloading is performed by a spring or the like, but a minute rattling of the pressure applying jig caused by the above-described minute space occurs, and noise is superimposed on the signal. Further, when a larger pressure signal such as abnormal combustion of the internal combustion engine such as knocking is applied, noise is more significantly superimposed. In such a case, by making the principal surfaces of the piezoelectric elements 110c and 110d spherical, the piezoelectric elements 110c and 110d can be stably provided even if a minute space exists between the piezoelectric elements 110c and 110d and the pedestals 130c and 130d. Since a load can be applied to 110d, noise superposition can be reduced.

  FIG. 4A is a longitudinal sectional view of a pressure sensor according to an embodiment of the present invention in which the piezoelectric element 110e is incorporated. Although details of the structure of the piezoelectric element 110e are omitted, they are the same as those shown in FIG. The pressure transmitted from the pressure transmission members 140e and 150e is transmitted to the piezoelectric element 110e via the pedestals 120e and 130e. The sides of the pedestals 120e and 130e on the piezoelectric element 110e side have a spherical shape recessed with the same radius of curvature as the main surface of the piezoelectric element 110e. Note that slight differences in the radius of curvature between the piezoelectric element 110e and the pedestals 120e and 130e, which are caused by processing variations, and the difference in shape due to surface irregularities are the electrodes formed on the piezoelectric element 110e and the pedestals 120e and 130e and the piezoelectric elements 110e. Can be absorbed by deformation of the conductive member placed between the two. The difference in shape is preferably 1/3 or less of the thickness of the electrode.

  When such a structure is used, a pressure signal can be reliably applied to the piezoelectric element 110e even when the pedestal 120e or the pedestal 130e is slightly inclined, as in the case described above. In this case, even if the force applied from both of the pressure transmission members 140e and 150e fluctuates, noise due to non-uniformity of the contact portion can be reduced.

  FIG. 4A is a longitudinal sectional view of a pressure sensor according to an embodiment of the present invention in which the piezoelectric element 110f is incorporated. Details of the structure of the piezoelectric element 110f are omitted, but are the same as those shown in FIG. The pedestal 120f is fixed to an external structure or the like, and the piezoelectric element 110f is preliminarily applied with a load (preliminary load) via the pedestal 130f by the pressurizing member 170f. The pressurizing member 170f is, for example, a spring. When a force is applied from the pressure transmission member 160f, the pressure applied to the piezoelectric element 110f is reduced by the amount of the force, and the load applied to the pressure transmission member 160f can be measured by measuring the change.

  The sides of the pedestals 120f and 130f on the piezoelectric element 110f side have a spherical shape recessed with the same radius of curvature as the main surface of the piezoelectric element 110f.

  The pressure sensor having such a structure can be used as a glow plug if the pressure transmission member 160f is insulated from the pedestals 130f and 130f and voltage supply is performed. Become.

  There is a fine space between the piezoelectric element 110f and the pedestal 120f and between the piezoelectric element 110f and the pedestal 130f, and even if the preload is increased, this space cannot be filled. Further, if the preload is excessively increased, the piezoelectric element 110f may be damaged. The preloading is performed by a spring or the like, but a minute rattling of the pressure applying jig caused by the above-described minute space occurs, and noise is superimposed on the signal. Further, when a larger pressure signal such as abnormal combustion of the internal combustion engine such as knocking is applied, noise is more significantly superimposed. In such a case, by applying a spherical surface to the main surface of the piezoelectric element 110f, a load is stably applied to the piezoelectric element 110f even if a minute space exists between the piezoelectric element 110f and the pedestals 120f and 130f. Therefore, noise superposition can be reduced.

  In addition, high heat resistance is calculated | required for the pressure sensor taken as the structure directly integrated in the components in an engine as a combustion pressure sensor of an internal combustion engine. Piezoelectric materials such as bismuth layered compound, aluminum nitride, and zinc oxide are preferably used in such an environment. However, since they are brittle materials, too large preload may damage the piezoelectric elements 110d to 110f. The piezoelectric elements 110d to 110f of the present invention are preferable because noise can be reduced even if the preliminary load is reduced.

SrCO ₃ powder purity of 99.9% or more as a starting material, BaCO ₃ powder, the _Bi 2 _{O 3} powder and TiO ₂ powder, the composition formula _{Bi 4 Ti 3 O 12 · 0.47} (Sr 0.5 Ba 0.5 Weighed so as to have a ratio of TiO ₃ ).

0.5 parts by mass of MnO ₂ powder is weighed and mixed with 100 parts by weight of this main component, and the mixture is put into a 500 ml resin pot together with zirconia balls having a purity of 99.9% and water or isopropyl alcohol (IPA). The resin pot was placed on a turntable and mixed for 16 hours.

The mixed slurry is dried in the air, passed through a # 40 mesh, and then calcined by holding at 950 ° C. for 3 hours in the air, and this synthetic powder is mixed with ZrO ₂ balls having a purity of 99.9% and water or isopropyl. The mixture was poured into a 500 ml resin pot together with alcohol (IPA), and the resin pot was placed on a rotating table and ground for 20 hours.

  An appropriate amount of an organic binder was added to the pulverized powder, granulated, and molded to prepare a cylindrical molded body. The molded body was subjected to a binder removal treatment and then fired in an air atmosphere at about 1150 ° C. for 3 hours to obtain a cylindrical piezoelectric ceramic having a diameter of 2 mm and a thickness of 3 mm.

  The piezoelectric ceramic was polished to create a piezoelectric ceramic in which at least one of the upper and lower surfaces of the cylinder is a convex spherical surface. The thickness excluding the upper and lower convex portions of the piezoelectric ceramic was 1 mm. The surface roughness Ra of the upper and lower surfaces serving as the main surface was processed to 1.0 μm or less.

  On the upper and lower surfaces of the piezoelectric ceramic, Ag electrodes were printed and baked by a printing machine having a silicone rubber printing surface. The thickness of the Ag electrode after firing was 6 μm. Note that printing can be performed by screen printing or the like when the radius of curvature of the spherical surface is large. Thereafter, polarization treatment was performed in silicon oil at 200 ° C.

  A stainless steel base having a diameter of 2 mm and a contact surface with a piezoelectric element having a concave spherical surface with R being the same curvature as the piezoelectric element was prepared. Further, other pedestals and pressure transmission jigs are made of the same material, and FIG. 3 (a), FIG. 3 (c), FIG. 4 (a), FIG. 4 (b) and FIG. 5 (a) to FIG. A pressure sensor was prepared.

  A preload of 300 MPa was applied to the manufactured pressure sensor, a pressure signal was applied with a triangular wave at a frequency of 100 Hz, and a pressure of 300 to 250 MPa, and the charge generated from the piezoelectric element was detected by a charge amplifier. The pressure application waveform was measured by attaching a pressure sensor manufactured by Kistler on a pressure transmission jig. The S / N ratio was calculated by quantifying noise generated in the piezoelectric element output using a pressure application waveform (a waveform detected by a pressure sensor manufactured by Kistler) as a reference. The results are shown in Table 1.

  As is apparent from Table 1, the sample No. using the piezoelectric element of the present invention. In 1-10 and 13-22, S / N ratio became low with 8.1% or less. In particular, Sample No. 1 in which 1 ≦ radius of curvature R of main surface / radius of piezoelectric element r ≦ 10 In 1 to 4, 6 to 9, 13 to 16, and 18 to 22, the S / N ratio was as low as 2.6% or less.

10, 20 ... Piezoelectric element for pressure sensor 11, 21 ... Piezoelectric substrate 11a, 11b, 21a, 21b ... Main surface of piezoelectric substrate 13a, 13b, 23a, 23b ... Electrode P ... Polarization Direction 110a-110f ... Piezoelectric element 120a-120f, 130a-130f ... Base 140a, 140b, 140e ... Pressure transmission member 150a, 150b, 150e ... Pressure transmission member 160c, 160d, 160f ... Pressure transmitting members 170c, 170d, 170f ... Pressurizing members

Claims (6)

  Electrodes are provided on opposing main surfaces of the piezoelectric substrate, and one of the main surfaces is an outwardly convex spherical surface, the other main surface is a flat surface, and is generated by a load applied between the main surfaces. A piezoelectric element for pressure sensor, characterized by measuring electric charge.   A pressure characterized by comprising electrodes on opposing main surfaces of a piezoelectric substrate, wherein both of the main surfaces are convex spherical surfaces, and the electric charge generated by a load applied between the main surfaces is measured. Piezoelectric element for sensors.   The shape of the cross section between the opposing principal surfaces of the piezoelectric substrate is a circular shape with a radius r (m), and the radius of curvature of the spherical surface is R (m), 1 ≦ R / r ≦ 10. The piezoelectric element for a pressure sensor according to claim 1 or 2,   4. The piezoelectric element for a pressure sensor according to claim 1, wherein a main component of the piezoelectric substrate is a bismuth layered compound.   5. A pressure sensor for measuring a load applied between the pedestals, wherein a pedestal for transmitting a load is brought into contact with both of the main surfaces of the piezoelectric element for a pressure sensor according to claim 1. The pressure sensor is characterized in that the pedestal that abuts on the main surface formed of a spherical surface convex outward of the main surface has a concave surface whose contact with the main surface is a substantially annular surface.   5. A pressure sensor for measuring a load applied between the pedestals, wherein a pedestal for transmitting a load is brought into contact with both of the main surfaces of the piezoelectric element for a pressure sensor according to claim 1. The pressure sensor is characterized in that the surface of the pedestal that comes into contact with the main surface composed of an outwardly convex spherical surface among the main surfaces is a spherical surface that has the same curvature as the main surface and is concave on the inside.

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