JPH0777474A - Pressure sensor - Google Patents

Abstract

(57) [Abstract] [Purpose] To provide a pressure sensor capable of outputting a stable detection signal having no temperature dependence even when the ambient temperature changes. [Structure] In the casing 11, a piezoelectric element 20 that displaces the displacement of the diaphragm 13 via a pressure receiving rod 15 and outputs a voltage signal according to the pressure is provided. This piezoelectric element 20 has a laminated structure of a piezoelectric layer 23 whose capacitance increases with a positive temperature characteristic due to temperature rise and dielectric layers 24 and 24 whose capacitance decreases with a negative temperature characteristic due to temperature rise. A pair of electrodes 22A and 22B is provided on both end surfaces of the element body 21 formed integrally. Even if the capacitance of the piezoelectric layer 23 changes due to a temperature change, the capacitance of the piezoelectric layer 23 changes with the characteristic opposite to the capacitance of the piezoelectric powder. Offset in minutes.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pressure sensor suitable for use as a combustion pressure sensor for detecting combustion pressure in, for example, an automobile engine.

[0002]

2. Description of the Related Art Generally, a casing, and a diaphragm which is provided on the tip side of the casing and is axially displaced in response to pressure applied from the outside to the tip side of the casing,
A pressure sensor comprising a pressure receiving rod provided in the casing so as to come into contact with the diaphragm, and a piezoelectric element that outputs displacement of the diaphragm transmitted through the pressure receiving rod as a voltage signal according to pressure. The combustion pressure sensor is known, for example, from Japanese Utility Model Laid-Open No. 60-535.

The piezoelectric element 1 used in this type of combustion pressure sensor will be described with reference to FIGS.

In the figure, reference numeral 1 denotes a piezoelectric element according to the prior art. The piezoelectric element 1 is an element body 2 made of a piezoelectric material such as lead zirconate titanate, and a conductive paste or the like on the upper and lower surfaces of the element body 2. It is composed of a pair of electrodes 3 and 3 formed. The piezoelectric element 1 receives displacement of the diaphragm due to combustion pressure via a pressure-receiving rod, and outputs a voltage signal corresponding to the combustion pressure to a control unit (neither is shown). There is. In addition, when the piezoelectric element 1 is manufactured, a high electric field is applied through the respective electrodes 3 so that the directions of spontaneous polarization are aligned to some extent, and the polarization axis P is formed in the vertical direction (axial direction). When pressure (stress) is applied from the stress axis F parallel to the polarization axis P during use, distortion occurs inside the element body 2, and a charge (voltage signal) corresponding to this pressure is applied to each electrode 3. Is output in the direction of the signal axis V via.

The piezoelectric element 1 of this type according to the prior art is used as, for example, a combustion pressure sensor mounted in a combustion chamber of an engine, and the piezoelectric element 1 is incorporated in a casing with a diaphragm of the combustion pressure sensor. Then, the combustion pressure sensor receives a high pressure (combustion pressure) when the fuel burns in the combustion chamber by the diaphragm, and transmits the axial displacement of the diaphragm to the piezoelectric element 1 via the pressure receiving rod.
The piezoelectric element 1 outputs a voltage signal according to the combustion pressure to a control unit or the like, and the control unit determines the magnitude of the combustion pressure based on this voltage signal and controls the fuel injection timing to the engine, the ignition timing, etc. It is like this.

[0006]

By the way, the above-mentioned conventional piezoelectric element 1 can be represented by an equivalent circuit as shown in FIG. That is, since each of the fine particles (not shown) forming the element body 2 is three-dimensionally arranged, the internal capacitances C0, C1 and the internal resistance R1,
It has a component of self-inductance L1.

Here, the piezoelectric d33 constant and the piezoelectric g indicating the relationship between the pressure acting on the piezoelectric element 1 and the detection (voltage) signal.
Considering the 33 constant, the internal capacitances C0, C1, and
The following relationship is established between the internal resistance R1 and the self-inductance L1.

[0008]

[Equation 1]

[0009]

[Equation 2]

However, since the values of the internal capacitances C0 and C1 and the self-inductance L1 change greatly with the temperature change of the piezoelectric element 1, when the high temperature in the combustion chamber is transmitted to the piezoelectric element 1 through the casing, the piezoelectric d33 The constant and the piezoelectric g33 constant fluctuate greatly as indicated by the characteristic lines 4 and 5 shown in FIGS. 12 and 13, and the combustion pressure acting on the diaphragm can be accurately detected unless the temperature change is corrected from the output of the pressure sensor. There is a problem that you can not.

Therefore, in the prior art, a temperature sensor such as a thermocouple or thermistor is provided near the piezoelectric element 1, the ambient temperature of the piezoelectric element 1 is detected by the temperature sensor, and the control unit is based on this detected temperature. The piezoelectric element 1
The detection signal of is corrected. However, since it is necessary to process different signals from the temperature sensor and the piezoelectric element 1, not only the electronic circuit of the control unit and the correction program become complicated and the cost increases significantly, but also the combustion pressure sensor as a whole is attached only by the temperature sensor. Has a problem in that it cannot be accurately corrected when the temperature sensor deteriorates over time, in addition to the large size, which reduces the mounting flexibility.

The present invention has been made in view of the above-mentioned problems of the prior art. The present invention provides a pressure sensor capable of outputting a stable voltage signal having a small temperature dependence even when the temperature of the piezoelectric element changes. It is intended to be provided.

[0013]

In order to solve the above-mentioned problems, a pressure sensor according to the present invention is provided on a casing and a tip side of the casing, and the pressure sensor is provided in response to an external pressure applied to the tip side of the casing. A diaphragm that is displaced in the axial direction, a pressure-receiving rod that is provided inside the casing so as to abut the diaphragm, and a piezoelectric that outputs the displacement of the diaphragm transmitted through the pressure-receiving rod as a voltage signal according to the pressure. And an element.

The features of the configuration adopted by the present invention are as follows:
The piezoelectric element is integrally formed by alternately stacking at least two piezoelectric layers and at least two dielectric layers, the capacitance of the dielectric layer is larger than that of the piezoelectric layer, and the temperature coefficient of the dielectric layer is large. Is composed of a material having characteristics opposite to the temperature coefficient of the piezoelectric layer.

[0015]

With the above structure, the diaphragm receives the external pressure, and the displacement of the diaphragm in the axial direction is transmitted to the piezoelectric element via the pressure receiving rod, so that the voltage signal corresponding to the external pressure detected by the piezoelectric element is transmitted. Output.

At this time, even if the capacitance of the piezoelectric material forming the piezoelectric layer changes due to temperature change with one of the positive and negative temperature characteristics, the electrostatic capacity of the dielectric layer laminated on the piezoelectric layer is changed. Since the capacitance changes with the characteristic opposite to the capacitance of the piezoelectric layer, the change in capacitance of the piezoelectric layer can be offset by the change in capacitance of the dielectric layer, and a pressure sensor can be used to detect external pressure. The output of is not affected by temperature changes.

[0017]

EXAMPLE A pressure sensor according to an example of the present invention will be described below.
A case where the combustion pressure sensor is used will be described as an example with reference to FIGS. 1 to 9.

In the figure, 11 is a casing, 12 is a casing 13 together with a diaphragm 13 and an upper cover 14 which will be described later.
1 shows a casing main body which constitutes 1, and the casing main body 12 is covered at its upper end side by an upper cover 14,
A large-diameter cylindrical portion 12A that houses a contact plate 17, a piezoelectric element 20 and the like, which will be described later, and a tapered shoulder portion 12B that decreases downward from the lower end side of the large-diameter cylindrical portion 12A. A small-diameter cylindrical diaphragm 13 that extends downward and accommodates a pressure receiving rod 15 described later is integrally provided on the lower end side of the. And the casing body 1
No. 2 is attached so that the diaphragm 13 faces the combustion chamber of the engine body, with shoulders 12B abutting on the stepped portions (not shown) of the stepped holes provided in the cylinder head of the engine body.

Reference numeral 13 denotes a diaphragm integrally formed on the lower end side of the shoulder portion 12B of the casing body 12, and the diaphragm 13 is a small-diameter portion 13A formed in a thin cylindrical shape.
And a thick disk-shaped pressure receiving portion 13B formed at the tip of the small diameter portion 13A and facing the combustion chamber. When the pressure in the combustion chamber (combustion pressure) is received, the small diameter portion 1 is generated according to this pressure.
3A bends in the axial direction (upward and downward) to displace the pressure receiving rod 15 in the axial direction.

Reference numeral 14 denotes a large-diameter cylindrical portion 12 of the casing body 12.
A stepped cylindrical upper cover fixed to the upper end side of A by means such as laser welding is shown, and a reduced diameter portion 14A protruding upward to the outside of the cylinder head is formed on the upper side of the upper cover 14. A lead wire 19 described later is provided in the upper cover 14 so as to extend upward.

Reference numeral 15 denotes a pressure receiving rod made of stainless steel or the like which is located inside the diaphragm 13 of the casing body 12 and is displaceable in the axial direction.
Is a small-diameter portion 15A, a hemispherical spherical portion 15B formed on the tip side of the small-diameter portion 15A and contacting the upper surface side of the diaphragm 13, and a taper portion 1 on the proximal end side of the small-diameter portion 15A.
It is composed of a large-diameter pressing portion 15D formed through 5C. When the diaphragm 13 is bent in the axial direction by the combustion pressure, the pressure receiving rod 15 is displaced in the casing body 12 in the axial direction, and the displacement of the diaphragm 13 is transferred to a piezoelectric element described later via a lower plate 16 described later. Twenty.

Reference numeral 16 denotes the pressure receiving rod 15 and the piezoelectric element 20.
A lower plate provided between the lower plate 16 and the lower plate 16 is formed of a hard ceramic material or the like into a thick disk shape, and is disposed on the pressing portion 15D of the pressure receiving rod 15. The lower plate 16 is the pressure receiving rod 1
5, the combustion pressure is transmitted to the piezoelectric element 20 and the casing 11, the pressure receiving rod 15 and the contact plate 17 described later are electrically insulated from each other so as not to be short-circuited. It is arranged so as not to be directly transmitted to the piezoelectric element 20 via the pressure receiving rod 15.

Reference numeral 17 denotes a large-diameter cylindrical portion 12 of the casing body 12.
A contact plate made of a conductive material provided in A is shown. The contact plate 17 is a disk-shaped contact portion 17A that comes into contact with the lower electrode 22B of the piezoelectric element 20 during assembly, and an upper side surface of the contact portion 17A. It is configured by a shaft portion 17B extending upward from the center.
Here, the outer periphery of the shaft portion 17B is covered with an insulating tube 18, and the insulating tube 18 insulates between the contact plate 17 and a set screw 26, an upper cover 14, which will be described later. The upper end side of the shaft portion 17B extends into the reduced diameter portion 14A of the upper cover 14 and is caulked and fixed to a lead wire 19 connected to the control unit side (not shown).

Reference numeral 20 denotes a large-diameter cylindrical portion 12 of the casing body 12.
The piezoelectric element according to the present embodiment provided on the contact portion 17A of the contact plate 17 positioned in A is shown. The piezoelectric element 20 is substantially the same as the piezoelectric element 1 described in the prior art. The pressure sensor according to the present embodiment includes an element body 21 formed of lead or the like in an annular shape, and an upper electrode 22A and a lower electrode 22B formed on the upper and lower end surfaces of the element body 21, respectively. The element body 21 of the piezoelectric element 20 includes a piezoelectric layer 23 and the piezoelectric layer 2
3 has a laminated structure composed of dielectric layers 24, 24 integrally formed on the upper and lower surfaces thereof.

Here, the piezoelectric element 20 is inserted into the outer side of the shaft portion 17B of the contact plate 17 via the insulating tube 18, and a set screw 26 is provided between the contact portion 17A and an upper plate 25 described later. The upper electrode 22A of the piezoelectric element 20 that is sandwiched is grounded to the casing body 12 side via the upper plate 25 and the set screw 26. The lower electrode 22B is in contact with the upper surface of the contact portion 17A of the contact plate 17 and is connected to the lead wire 19 via the shaft portion 17B.

The piezoelectric element 20 is the pressure receiving rod 1.
5. When pressure is transmitted in the vertical direction via the lower plate 16, polarization occurs due to compressive strain, and a voltage corresponding to the pressure is generated from each electrode 22A, 22B.

Reference numeral 25 denotes an upper plate that comes into contact with the upper electrode 22A of the piezoelectric element 20, and the upper plate 2
Reference numeral 5 denotes an annular shape made of a thin metal, and presses and fixes the piezoelectric element 20 with a set screw 26 to prevent the set element 26 from damaging the piezoelectric element 20 and the like. Set screw 26 for casing body 12
Is electrically connected via.

Reference numeral 26 denotes the large-diameter cylindrical portion 12 of the casing body 12.
A set screw screwed into A and having a tip end abutting on the upper surface side of the upper plate 25 is shown. The set screw 26 applies a predetermined load to the piezoelectric element 20 from above and below via the upper plate 25 and the contact plate 17. The initial load is applied by pressing with, and the piezoelectric element 20, the pressure receiving rod 15 and the like are sandwiched and fixed between the piezoelectric element 20 and the diaphragm 13.

The pressure sensor according to this embodiment has the above-mentioned structure. Next, a method for manufacturing the piezoelectric element 20 will be described with reference to FIG.

Here, the element body 21 of the piezoelectric element 20 is composed of a piezoelectric layer 23 made of a piezoelectric material and a dielectric layer 24 made of a dielectric material. Dielectric powder manufacturing process, molding process,
It is manufactured by a manufacturing method including a sintering step, an electrode forming step, and a polarization step.

First, in the piezoelectric powder manufacturing process, 41.5 mol% of PbZrO ₃ and 48.5 mol% were obtained by calcination.
% PbTiO ₃ , 10 mol% Pb (Mn _1/3 , Sb _2/3 ) O 3 so that the components have PbO, ZrO ₂ , TiO ₂ , MnCO ₃ , Sb ₂ O ₃
The basic raw material 101 is weighed, 0.1 wt% of NiO is added to the entire basic raw material, acetone is added, and wet mixing is performed for 20 hours in a ball mill. The piezoelectric material is obtained by firing for 2 to 5 hours.

Then, the calcined piezoelectric material is crushed by an alumina automatic mortar 103 and a ball mill to obtain piezoelectric powder. Here, the piezoelectric powder composed of the above-mentioned components has a characteristic that its capacitance increases as the temperature rises.

In the next step of producing the dielectric powder, calcination is performed to obtain 82 to 87 mol% of Pb (Mg _1/3 , Nb _2/3 )
O ₃ , 9-12 mol% BaTiO ₃ , 4-6 mol% Pb (Co _1/3 , N
b _2/3 ) O ₃ so that PbO, TiO ₂ , MgO
, Nb ₂ O ₅ , BaCO ₃ , CoO, and SrCO ₃ are weighed, and 2 wt% of SrTi is added to the whole of the basic raw material 104.
O ₃ is added, acetone is added, wet mixing is performed in a ball mill for 20 hours, and firing is performed in an air atmosphere in a superheating furnace 105 at 850 ° C. for 2 to 5 hours to obtain a dielectric material.

Then, this dielectric material is used as an automatic mortar 106.
And pulverize with a ball mill to obtain a dielectric powder. Here, the dielectric powder composed of the above components has a characteristic that its capacitance decreases with an increase in temperature.

Next, in the molding step, the dielectric powder is first added to the die 107 for pellet molding, and the press molding machine 10 is used.
8 to lightly press to form the lower dielectric layer 24, then add piezoelectric powder and press lightly to form the piezoelectric layer 23, and finally add dielectric powder again and press at final pressure to form 3 layers. A pellet-shaped body 109 having a structure is formed. At this time, polyvinyl alcohol (PVA) is added as a binder, and the whole is integrally pressure-molded into a pellet having a thickness of 1 to 5 mm. In the embodiment, the dielectric layer 24 has a thickness of 0.2 to 1.0 mm and is formed on the upper and lower surfaces of the piezoelectric layer 23.

Next, in the sintering step, the molded pellet-shaped body 109 is hermetically sealed in a MgO crucible and fired in an overheating furnace 110 at 1200 to 1250 ° C. for 4 hours to form a sintered body 111. To do.

Next, in the electrode forming step (not shown), the end surfaces of the sintered body 111 obtained in the sintering step are numbered 800.
After polishing with a SiC abrasive and polishing the circumferential side surface with No. 1200 sandpaper, electrodes made of a gold thin film or the like are formed on both end surfaces of the sintered body 111.

Further, in the polarization step (not shown), while maintaining the sintered body 111 in silicon oil at 110 ° C., a polarization electric field is applied to each of the electrodes 22A and 22B by applying a DC electric field of 20 KV / cm. As shown in 3, the polarization axis P is formed in the vertical direction.

The pressure sensor according to this embodiment has the above-mentioned structure. When used as a combustion pressure sensor for detecting the combustion pressure of the engine, the air-fuel mixture in the combustion chamber of the engine is ignited to generate combustion pressure. When the diaphragm 13 is bent in the axial direction by this combustion pressure, the pressure receiving rod 15 is displaced in the axial direction, and this displacement is caused by the contact portion 1 of the contact plate 17 via the pressing portion 15D and the lower plate 16.
7A is transmitted upward.

As a result, the piezoelectric element 20 is compressed between the contact portion 17A and the set screw 26, and the piezoelectric element 20 is compressed.
When a pressure in the direction of the stress axis F shown in FIG. 3 is applied to the element main body 21 of FIG. 3, a strain is generated inside the element main body 21 and an electric charge corresponding to the pressure is generated.
The electrodes 22A and 22B at both ends in the direction are led out to the outside via the contact plate 17 and the lead wire 19 and output to a control unit (not shown).

Thus, in the present embodiment, the element body 21 of the piezoelectric element 20 is formed on the piezoelectric layer 23 whose capacitance increases with the temperature rise, and on the upper and lower surfaces of the piezoelectric layer 23.
Dielectric layer 2 whose capacitance decreases with increasing temperature
Since 4, 4 and 24 are integrally formed in the laminated structure, it is possible to provide the same action as that of connecting a capacitor having a temperature characteristic opposite to that of the piezoelectric layer 23 in series to the piezoelectric layer 23.

That is, the ambient temperature rises and the element body 21
When the electrostatic capacity of the piezoelectric layer 23 constituting the
The capacitance of the dielectric layer 24 constituting the element body 21 is reduced, and the piezoelectric d33 constant can be kept constant in the element body 21 as a whole. On the other hand, when the temperature of the piezoelectric element 20 decreases and the electrostatic capacity of the piezoelectric layer 23 forming the element main body 21 decreases, the dielectric layer 24 forming the element main body 21.
The capacitance of the element body 21 increases, and
The constant can be kept constant.

Therefore, the piezoelectric element 20 has the characteristic line 2 in FIG.
As shown by characteristic lines 28 in FIG. 7 and FIG. 6, respectively, stable piezoelectric d33 constants and piezoelectric g33 constants having small temperature dependence are exhibited as compared with the characteristic lines 4 and 5 of the conventional piezoelectric element 1. As a result, the piezoelectric element 20 can output a detection signal having a small temperature dependency, and the pressure can be accurately detected even in an environment where the temperature changes drastically.

Further, in order to obtain the same effect as that of the present embodiment, for example, a piezoelectric element similar to that of the conventional art is provided between the contact plate 17 and the upper plate 25, and the piezoelectric element is manufactured separately from the piezoelectric element. It is also conceivable to provide a dielectric element whose capacitance decreases as the temperature rises so as to overlap in the axial direction.

However, in this case, a gap is apt to be formed between the electrode surface of the dielectric element or the piezoelectric element and the contact surface of the contact plate 17 or the upper plate 25, and this gap impairs pressure transmission and causes an electrical failure. This may cause poor contact, and the floating capacity due to this gap poses a problem. Therefore, the piezoelectric element, the dielectric element, the contact plate 1
7. The upper plate 25 and the like need to be formed such that the surfaces of the respective members contacting each other are parallel and planar, which requires a great deal of time and labor for surface processing.

According to this embodiment, however, the piezoelectric layer 23 and the dielectric layer 24 are integrally laminated to form a single element body 21, so that the number of parts can be reduced and the pressure sensor assembling work can be greatly performed. Can be simplified to

Thus, according to the present embodiment, the combustion pressure in the combustion chamber can be detected with high accuracy for a long period of time, and the combustion pressure sensor having the temperature correction function can be constructed compactly. The electronic circuit for correction and the like can be eliminated, and the circuit configuration of the control unit can be greatly simplified.

In the above embodiment, the casing body 12
It is described that the diaphragm 13 integrally provided with the thin wall cylindrical small diameter portion 13A and the thick pressure receiving portion 13B formed on the tip end side of the small diameter portion 13A are formed. As described above, the diaphragm 13 'is composed of a small diameter portion 13A' extending downward from the lower end side of the shoulder portion 12B of the casing body 12 and a thin disk-shaped pressure receiving portion 13B 'closing the lower end side of the small diameter portion 13A'. However, the spherical surface portion 15B of the pressure receiving rod 15 may be disposed so as to abut on the center of the pressure receiving portion 13B '.

In the above embodiment, the case where the pressure sensor is used as the combustion pressure sensor has been described as an example, but the present invention is not limited to this, and for example, gas such as air, industrial gas, fuel, water, etc. It can also be applied to a pressure sensor that detects the pressure of a liquid such as. On the other hand, it may be used for a knocking sensor that detects knocking of a vehicle.

Further, in the above embodiment, the element body 21 is composed of the piezoelectric layer 23 of one layer and the dielectric layers 24, 24 of two layers, but the present invention is not limited to this, and as shown in FIG. 1
The piezoelectric layers 23 ′ and the dielectric layers 24 ′ may be integrally formed, or two layers of the piezoelectric layers 23 ′ and 23 ′ and the dielectric layers 24 ′ may be formed as shown in FIG. 9. 24 'may be laminated and integrally formed. Further, it may be formed of three or more piezoelectric layers and a dielectric layer.

[0051]

As described in detail above, the pressure sensor of the present invention is provided with a piezoelectric element for displacing the displacement of the diaphragm through the pressure receiving rod in the casing and outputting a voltage signal according to the pressure. Is formed by alternately stacking at least two or more piezoelectric layers and dielectric layers, the capacitance of the dielectric layers is larger than that of the piezoelectric layers, and the temperature coefficient of the dielectric layers is the piezoelectric layers. Since it is composed of a material that has characteristics opposite to the temperature coefficient of, even if the capacitance of the piezoelectric layer changes due to temperature changes, the capacitance of the dielectric layer laminated on the piezoelectric layer is the same as that of the piezoelectric layer. Changes with the opposite characteristics, the change in the electrostatic capacity of the piezoelectric layer can be canceled by the change in the electrostatic capacity of the dielectric layer, and the electrostatic capacity of the entire piezoelectric element can be made almost constant over a wide temperature range. be able to.

Therefore, it is possible to obtain a pressure sensor having a temperature correction function without complicating the structure without using a temperature sensor or an electronic circuit for correction.

[Brief description of drawings]

FIG. 1 is a vertical sectional view showing a pressure sensor according to an embodiment of the present invention.

FIG. 2 is an enlarged perspective view showing a piezoelectric element in FIG.

FIG. 3 is an enlarged vertical sectional view taken along the line III-III in FIG.

FIG. 4 is an explanatory diagram showing a method of manufacturing a piezoelectric element.

FIG. 5 is a characteristic diagram showing the relationship between the temperature of the piezoelectric element and the piezoelectric d33 constant in comparison with the piezoelectric element according to the conventional technique.

FIG. 6 is a characteristic diagram showing a relationship between a temperature of a piezoelectric element and a piezoelectric g33 constant in comparison with a piezoelectric element according to a conventional technique.

FIG. 7 is an enlarged view of essential parts showing a diaphragm and a pressure receiving rod according to a modification.

FIG. 8 is a vertical sectional view showing a modified example of the piezoelectric element.

FIG. 9 is a vertical sectional view showing another modification of the piezoelectric element.

FIG. 10 is a vertical sectional view showing a piezoelectric element according to a conventional technique.

FIG. 11 is an electrical equivalent circuit diagram of the piezoelectric element.

FIG. 12 is a characteristic diagram showing a relationship between a temperature of a piezoelectric element and a piezoelectric d33 constant according to a conventional technique.

FIG. 13 is a characteristic diagram showing a relationship between a temperature of a piezoelectric element and a piezoelectric g33 constant according to a conventional technique.

[Explanation of symbols]

 11 Casing 12 Casing body 13 Diaphragm 15 Pressure receiving rod 20 Piezoelectric element 21 Element body 22A Upper electrode (electrode) 22B Lower electrode (electrode) 23 Piezoelectric layer 24 Dielectric layer

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shoichi Sakai 1370, Onna, Atsugi City, Kanagawa Prefecture

Claims (1)

[Claims] 1. A casing, a diaphragm provided on the front end side of the casing and axially displaced in response to a pressure applied from the outside to the front end side of the casing, and the inside of the casing so as to come into contact with the diaphragm. In a pressure sensor comprising a pressure receiving rod provided and a piezoelectric element that outputs displacement of the diaphragm transmitted through the pressure receiving rod as a voltage signal corresponding to the pressure, the piezoelectric element includes a piezoelectric layer and a dielectric layer. And at least two layers are alternately laminated so as to be integrally formed, the capacitance of the dielectric layer is larger than that of the piezoelectric layer, and the temperature coefficient of the dielectric layer is opposite to the temperature coefficient of the piezoelectric layer. A pressure sensor comprising a material having