JP2558556B2 - Pressure sensor - Google Patents

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 the combustion pressure of, for example, an automobile engine.

[0002]

2. Description of the Related Art Generally, a casing main body, a flat plate-shaped diaphragm provided on the front end side of the casing main body and axially displaced in accordance with an external pressure, and provided on the front end side of the casing main body. And a pressure receiving rod that is displaced in the axial direction according to the displacement of the diaphragm, and the axial displacement of the diaphragm transmitted through the pressure receiving rod, which is transmitted through the pressure receiving rod. A combustion pressure sensor as a pressure sensor including a piezoelectric body that outputs a voltage signal corresponding to the above is known from, for example, Japanese Utility Model Laid-Open No. 60-535.

Therefore, a piezoelectric body used for this type of combustion pressure sensor will be described with reference to FIGS. 9 and 10.

In the figure, reference numeral 1 is a piezoelectric body made of a piezoelectric material such as lead titanate, and electrodes 1A and 1B made of a conductive paste or the like are formed on the upper and lower surfaces of the piezoelectric body 1. The piezoelectric body 1 receives the displacement of the diaphragm due to the 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. Further, as shown in FIG. 9, when a high electric field is applied to the piezoelectric body through the electrodes 1A and 1B during manufacturing, the directions of spontaneous polarization are aligned to some extent, and the polarization axis P is in the vertical direction (axial direction). When a pressure (stress) acts on a stress axis F parallel to the polarization axis P, the piezoelectric body 1 is distorted, and a charge (voltage signal) corresponding to this pressure is applied to each electrode 1A, It is configured as a so-called d33 type element that outputs in the direction of the signal axis V via 1B.

A conventional combustion pressure sensor of this type is mounted in a combustion chamber of an engine, receives a high pressure (combustion pressure) at the time of combustion by a diaphragm, and a displacement of the diaphragm in the axial direction is detected by a pressure receiving rod. When applied to the piezoelectric body 1 via the piezoelectric body 1, the piezoelectric body 1 outputs a voltage signal corresponding to the combustion pressure to a control unit or the like, and the control unit judges the magnitude of the combustion pressure based on this voltage signal, and sends it to the engine. The fuel supply timing and ignition timing are controlled.

[0006]

By the way, in the above-mentioned conventional combustion pressure sensor, in the piezoelectric body 1, the polarization axis P and the signal axis V are formed in the same direction d33 as shown in FIG.
Since it is configured as a mold element, pyroelectricity caused by temperature change is easily superimposed on the detection signal (voltage signal),
When the high temperature in the combustion chamber is transmitted to the piezoelectric body 1 via the casing body, the pressure receiving rod, etc., and the temperature of the piezoelectric body 1 rises, the temperature rise of the piezoelectric body 1 as indicated by the characteristic line 2 shown by the solid line in FIG. Therefore, there is a problem that the detection signal increases and the combustion pressure cannot be output accurately.

Therefore, in the above-mentioned conventional technique, a temperature sensor such as a thermocouple or thermistor is provided near the piezoelectric body 1, the temperature of the piezoelectric body 1 is detected by the temperature sensor, and the control unit detects the temperature. Based on this, the temperature of the detection signal from the piezoelectric body 1 is corrected. However, there is a problem in that the entire combustion pressure sensor becomes large in size by the amount of mounting these temperature sensors, and not only the degree of freedom of mounting decreases but also the electronic circuit of the control unit, the correction program, etc. become complicated and the cost greatly increases. is there.

The present invention has been made in view of the above-mentioned problems of the prior art. The present invention has made it possible to output a stable detection signal having low temperature dependence even when the temperature of the piezoelectric body changes. A pressure sensor is provided.

[0009]

In order to solve the above-mentioned problems, a structure adopted by the present invention is a casing and a pressure which is provided on one end side of the casing and which acts on the one end side of the casing from the outside. A diaphragm that is displaced in the axial direction according to the above, a pressure receiving rod that is provided in the casing so that the tip end side abuts against the diaphragm, and that is displaced in the axial direction according to the displacement of the diaphragm, and that faces the pressure receiving rod. It is composed of a contact plate provided in the casing and a plurality of fan-shaped divided bodies provided between the contact plate and the pressure receiving rod, and the axial displacement of the diaphragm transmitted through the pressure receiving rod is measured. A radial displacement transmitted from the split piece, which is composed of a split piece that is converted into a displacement in the direction and a cylindrical body provided on the outer peripheral side of the split piece. A piezoelectric body that outputs a voltage signal corresponding to the pressure to the outside through the contact plate, and a support plate provided in the casing and having a cylindrical shape with a bottom to accommodate and support the piezoelectric body and the split piece. Consists of.

Further, it is preferable to provide a spring on the inner peripheral side of the split piece to bias the split piece radially outward.

Further, the piezoelectric body has an axial signal axis,
It is preferably formed from a d15 type element having a radial polarization axis and a stress axis.

[0012]

With the above structure, when the diaphragm is displaced in the axial direction by the pressure from the outside, the displacement of the diaphragm is transmitted to the split piece through the pressure-receiving rod, and the split piece makes the axial displacement of each fan-shaped divided body. The piezoelectric body can receive the displacement in the radial direction and output a voltage signal according to the pressure acting on the diaphragm to the outside through the contact plate.

Further, if a spring is provided on the inner peripheral side of the split piece, the split piece can be urged radially outward by the spring, and the split piece is pressed against the inner circumferential side of the piezoelectric body to move the split piece. It can be positioned in the support plate.

Further, if the piezoelectric body is formed of a d15 type element having a signal axis in the axial direction, a polarization axis in the radial direction and a stress axis, the piezoelectric body can apply the radial stress from the split piece in the stress axis. It is possible to receive and generate electric charges in the direction of the polarization axis, and output a voltage signal from the signal axis orthogonal to the polarization axis.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS.

In the figure, 11 is a casing, 12 is a casing body which constitutes the casing 11 together with a diaphragm 13 and an upper cover 14 which will be described later, and the casing body 12 is located at the base end side and has a large-diameter cylindrical shape. Formed,
A large-diameter cylindrical portion 12A that houses a split top 18, a piezoelectric body 19 and the like, which will be described later, and a small-diameter cylindrical portion 12B that is integrally formed on the lower end side of the large-diameter cylindrical portion 12A and that houses a pressure receiving rod 15 that will be described later. A diaphragm 13 is integrally formed on the lower end side of the small-diameter cylindrical portion 12B. The casing body 12 is attached to the cylinder head of the engine body (neither is shown) such that the diaphragm 13 faces the combustion chamber of the engine.

Reference numeral 13 denotes a small-diameter cylindrical portion 12 of the casing body 12.
A thin disk-shaped diaphragm integrally formed at the lower end side of B is shown. When the diaphragm 13 receives the pressure (combustion pressure) in the combustion chamber, it flexes in the axial direction (vertical direction) according to this pressure, The pressure receiving rod 15 is displaced in the axial direction.

Reference numeral 14 denotes a stepped cylindrical upper cover fixed to the upper end side of the casing body 12 by means of laser welding or the like, and an upper side of the upper cover 14 projects upward to the outside of the cylinder head. A reduced diameter portion 14A is formed, and a lead wire 17 described later is provided in the reduced diameter portion 14A.

Reference numeral 15 denotes a small-diameter cylindrical portion 12 of the casing body 12.
A pressure receiving rod provided in B is shown.
Is a rod portion 15A provided in the small-diameter cylindrical portion 12B so as to be displaceable in the axial direction, and a spherical portion 15B formed on the lower end side of the rod portion 15A and abutting on the upper surface side of the diaphragm 13.
And a hemispherical projection 15C that is formed on the upper end side of the rod portion 15A and contacts the lower side of a through hole 18B of the split piece 18 described later.
It consists of and. When the diaphragm 13 is bent by the combustion pressure, the pressure receiving rod 15 is displaced in the axial direction to transmit the displacement of the diaphragm 13 to the split piece 18 and prevent the high temperature in the combustion chamber from being directly transmitted to the piezoelectric body 19. .

Reference numeral 16 denotes a contact plate which is provided inside the large-diameter cylindrical portion 12A of the casing body 12 so as to face the pressure receiving rod 15. The contact plate 16 is provided so as to extend in the large-diameter cylindrical portion 12A in the axial direction. A rod portion 16A formed of a conductive material in a cylindrical shape having a small diameter, a disc-shaped contact portion 16B integrally formed on the lower end side of the rod portion 16A, and an end surface side of the contact portion 16B. It is composed of a hemispherical projection 16C formed, and the hemispherical projection 16C is in contact with the upper side of the through hole 18B of the split piece 18. Then, the rod portion 16 of the contact plate 16
A is expanded into the reduced diameter portion 14A of the upper cover 14 and is caulked and fixed to the lead wire 17, and a voltage signal from the piezoelectric body 19 is passed through the lead wire 17 to a control unit (not shown).
It is designed to be transmitted to.

Reference numeral 18 denotes a hemispherical projection 15C of the pressure receiving rod 15.
And a hemispherical protrusion 16C of the contact plate 16, a split piece provided in a lower plate 21 described later is shown. The split piece 18 is made of an insulating material such as zirconia as shown in FIG. Four fan-shaped divided members 18A, 18A, ... Formed from the material in a four-divided cylindrical shape, and each fan-shaped divided member 18A.
Of the through hole 18B, which is formed on the inner peripheral side and has both upper and lower ends tapered. Also, the through hole 1
The hemispherical projection 16C of the contact plate 16 and the tip end of the hemispherical projection 15C of the pressure receiving rod 15 are inserted into the tapered surface of 8B from above and below, respectively. And
When the pressure receiving rod 15 is displaced in the axial direction, the split piece 18 has a through hole 18 at the tip end side of each hemispherical projection 15C, 16C.
Each of the fan-shaped divided bodies 18A moves radially outward by entering into B, thereby converting the axial displacement of the pressure receiving rod 15 into a radial displacement, and applying a stress to the piezoelectric body 19 from the radial direction. It is supposed to be added.

Reference numeral 19 denotes a piezoelectric body which is located on the outer peripheral side of the split piece 18 and is housed in the lower plate 21 and formed into a cylindrical body from a piezoelectric material such as lead titanate. As shown in FIG. 3, when a predetermined high electric field is applied from the inner peripheral side to the outer peripheral side during manufacturing, the directions of spontaneous polarization are aligned and the polarization axis P and the stress axis F are formed in the radial direction. It is configured as a so-called d15 type element in which the axis V is in the axial direction. Further, a sheet-like upper electrode 19A and a lower electrode 19B made of a conductive paste or the like are formed on the upper and lower surfaces of the piezoelectric body 19, respectively, and the upper electrode 19A of the piezoelectric body 19 is contacted via a disc spring 20. Plate 16
, And the lower electrode 19B is grounded to the casing body 12 via the lower plate 21. Then, in the piezoelectric body 19, the diaphragm 13 receives the combustion pressure in the combustion chamber, the axial displacement of the pressure receiving rod 15 is converted into the radial displacement through the split piece 18, and the split axis 18 causes the stress axis F to move. When it is pressed in the radial direction along with, compression strain occurs and it is polarized in the direction of the polarization axis P, and an electric charge (voltage signal) corresponding to this compression strain is generated as a detection signal corresponding to the combustion pressure, and this combustion A pressure detection signal is output from each of the electrodes 19A and 19B along the signal axis V to the control unit via the disc spring 20, the contact plate 16, the lead wire 17 and the like.

Reference numeral 21 denotes a large-diameter cylindrical portion 12 of the casing body 12.
A bottom plate as a support plate attached to the bottom side is shown, and the bottom plate 21 is formed by a bottom plate portion 21A formed in an annular shape from a conductive material, and protruding upward from the outer peripheral side of the bottom plate portion 21A. The bottom plate 21 is formed into a short bottomed cylindrical shape from the peripheral wall portion 21B formed therein, and the split plate 18 and the piezoelectric body 19 are housed in the lower plate 21. The lower plate 21 supports the split piece 18 and the piezoelectric body 19 from below with the bottom plate portion 21A, and positions the piezoelectric body 19 with the peripheral wall portion 21B.

Reference numeral 22 denotes a C-shaped spring provided by being inserted into the through hole 18B of the split piece 18, and the spring 22 is, as shown in FIGS. 2 and 4, each fan-shaped divided body 18A of the split piece 18. Is constantly urged outward in the radial direction, and the respective fan-shaped divided bodies 18A are pressed against the inner peripheral side of the piezoelectric body 19 for positioning.

Reference numeral 23 denotes the large-diameter cylindrical portion 12 of the casing body 12.
A set screw screwed in A is shown, and the set screw 23 presses a contact portion 16B of the contact plate 16 with a predetermined load via an upper plate 24 formed in an annular shape from an insulating material, and the contact plate 16 The diameter of the split piece 18 is expanded by the hemispherical protrusion 16C of the spring 22
At the same time, a predetermined initial load is applied to the piezoelectric body 19.

The combustion pressure sensor according to the present embodiment has the above-described structure. As shown in FIGS. 4 and 5, the piezoelectric body 19 and the split piece 18 are fitted in the lower plate 21 and the spring 22 is split. It is inserted into the through hole 18B of the top 18, and each fan-shaped divided body 18A of the split top 18 is pressed against the inner peripheral side of the piezoelectric body 19 by the spring force of the spring 22 to move the split top 18 to the piezoelectric body 19 and the lower side. It is integrated with the plate 21. And
After these integrated split piece 18, piezoelectric body 19, and lower plate 21 are mounted in the large-diameter cylindrical portion 12A of the casing body 12, the contact plate 16, the set screw 23, the upper cover 14, etc. are attached to the casing body 12. It is mounted and assembled, and then mounted on the cylinder head of the engine body.

Then, the air-fuel mixture in the combustion chamber of the engine is ignited to generate combustion pressure, and the combustion pressure causes the diaphragm 13 to bend and the pressure receiving rod 15 to be displaced in the axial direction. 15C enters into the through hole 18B of the split piece 18, and pushes and displaces each fan-shaped divided body 18A of the split piece 18 outward in the radial direction, so that the piezoelectric body 19
A stress outward in the radial direction is applied to the stress axis F of. As a result,
An electric charge is generated in the piezoelectric body 19 in the direction of the polarization axis P, and the electric charge is generated from each of the electrodes 19A and 19B along the signal axis V in the axial direction orthogonal to the polarization axis P by a detection signal (voltage) corresponding to the combustion pressure signal. Signal), contact plate 16, lead wire 1
Output to the control unit via 7 etc.

Thus, according to this embodiment, the axial displacement of the pressure receiving rod 15 can be converted into the radial stress through the split piece 18, and the signal axis V orthogonal to the polarization axis P corresponds to the combustion pressure. Since the detection signal can be output, the piezoelectric body 1
Even when the temperature of 9 changes according to the temperature in the combustion chamber, it is possible to effectively prevent the pyroelectricity generated in the direction of the polarization axis P from being superposed on the signal axis V, and as shown by a characteristic line 25 shown by a solid line in FIG. A stable detection signal can be output for a long time with respect to the temperature change of the piezoelectric body 19, and the combustion pressure in the combustion chamber can be accurately detected. As a result, the temperature sensor, the electronic circuit for correction, etc. can be eliminated as described in the prior art, so that the combustion pressure sensor as a whole can be miniaturized, the degree of freedom in mounting can be greatly improved, and the cost can be reduced.

As shown in FIGS. 4 and 5, the piezoelectric body 19 and the split piece 18 are housed in the support plate 21, and the split piece 18 is provided.
Insert the spring 22 into the through hole 18B of the
Since 8 is integrated with the piezoelectric body 19 and the support plate 21, each fan-shaped divided body 18A of the split piece 18 can be effectively positioned in the support plate 21, and the workability of assembly is significantly improved. it can.

Further, the split piece 18 is composed of four fan-shaped divided bodies 18.
Since it is composed of A, when the pressure receiving rod 15 enters into the through hole 18B, each fan-shaped divided body 18A is displaced radially outward and can uniformly press the inner peripheral side of the piezoelectric body 19,
Radial stress can be effectively applied to the stress axis F of the piezoelectric body 19.

In the above embodiment, the split piece 18 is composed of four fan-shaped split bodies 18A, 18 formed in a four-split cylindrical shape.
Although the present invention is not limited to this, the present invention is not limited to this, and for example, as in the modification shown in FIG. 7, two fan-shaped divided bodies 18A ′, 18A ′ are used to form a split piece 18 ′. However, depending on the case, three or five
You may make it comprise from the fan-shaped division body of one piece or more.

Further, in the above-mentioned embodiment, the spring 22 is described as being provided by being inserted into the through hole 18B of the split piece 18, but instead of this, as in another modification shown in FIG. An annular fitting groove 26 may be formed on the inner peripheral side of the fan-shaped divided body 18A, and the spring 22 may be fitted in the fitting groove 26.

Further, in the above-described embodiment, the case where a combustion pressure sensor is used as a pressure sensor has been described as an example.
The present invention is not limited to this, and can be applied to a pressure sensor that detects the pressure of a gas such as air or industrial gas, or a liquid such as fuel or water.

[0034]

As described above in detail, according to the present invention, a plurality of fan-shaped divided bodies provided between the contact plate and the pressure receiving rod, and the axial direction of the diaphragm transmitted through the pressure receiving rod. Composed of a split piece for converting the displacement of the split piece into a radial displacement and a cylindrical body provided on the outer peripheral side of the split piece. The radial displacement transmitted from the split piece is converted into a voltage corresponding to the pressure. The diaphragm is composed of a piezoelectric body that outputs as a signal to the outside through the contact plate, and a bottomed cylindrical support plate that is provided in the casing and accommodates and supports the piezoelectric body and the split piece. When the pressure receiving rod displaces in the axial direction due to bending, each fan-shaped divided body of the split piece can be displaced radially outward and uniformly press the inner peripheral side of the piezoelectric body, and the displacement of the diaphragm in the axial direction can be reduced. Is effective for the displacement of Transformed and can be added to the piezoelectric body, the piezoelectric body can output a voltage signal corresponding to the pressure acting on the diaphragm to the outside via the contact plate.

Since the spring for biasing the split piece radially outward is provided on the inner peripheral side of the split piece, the split piece can be biased radially outward by the spring. Can be pressed against the inner peripheral side of the piezoelectric body to reliably position the split piece within the support plate.

Further, since the piezoelectric body is formed of a d15 type element having an axial signal axis, a radial polarization axis and a stress axis, a pyroelectric substance generated in the polarization axis direction as the temperature of the piezoelectric body rises. Electricity can be effectively prevented from being superimposed on the voltage signal output from the signal shaft, and a stable voltage signal with low temperature dependence can be output to accurately detect the external pressure.

[Brief description of drawings]

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

FIG. 2 is an enlarged sectional view taken in the direction of arrows II-II in FIG.

FIG. 3 is a longitudinal sectional view showing a part of the piezoelectric body in FIG. 1 in an enlarged manner.

FIG. 4 is an enlarged vertical cross-sectional view showing a state in which a split piece, a spring and the like are attached to a support plate.

FIG. 5 is an exploded perspective view showing a split top, a spring, and the like in an enlarged manner.

FIG. 6 is a characteristic diagram showing a relationship between a detection signal of a piezoelectric body and a temperature change according to an example of the present invention.

FIG. 7 is a sectional view similar to FIG. 2, showing an enlarged split frame according to a modification of the present invention.

FIG. 8 is a cross-sectional view similar to FIG. 4 showing an enlarged split piece, spring, etc. according to another modification of the present invention.

FIG. 9 is an enlarged vertical sectional view showing a part of a piezoelectric body used in a combustion pressure sensor according to a conventional technique.

10 is a characteristic diagram showing a relationship between a detection signal of the piezoelectric body in FIG. 9 and a temperature change.

[Explanation of symbols]

 Reference Signs List 11 casing 13 diaphragm 15 pressure receiving rod 16 contact plate 18, 18 'split piece 18A, 18A' fan-shaped divided body 19 piezoelectric body 21 lower plate (support plate) 22 spring

Claims (3)

(57) [Claims] 1. A casing, a diaphragm provided on one end side of the casing and axially displaced in response to a pressure applied to the one end side of the casing from the outside, and the casing so that its tip end side abuts on the diaphragm. A pressure receiving rod that is provided inside and that is displaced in the axial direction according to the displacement of the diaphragm; a contact plate that is provided inside the casing facing the pressure receiving rod; and between the contact plate and the pressure receiving rod. A split piece that is formed of a plurality of fan-shaped divided bodies and that converts the axial displacement of the diaphragm transmitted through the pressure receiving rod into a radial displacement, and a split piece that is located on the outer peripheral side of the split piece. The radial displacement transmitted from the split piece is output to the outside through the contact plate as a voltage signal corresponding to the pressure. A pressure sensor comprising a piezoelectric body that applies force and a bottomed cylindrical support plate that is provided in the casing and that houses and supports the piezoelectric body and the split piece. 2. The pressure sensor according to claim 1, wherein a spring for urging the split piece radially outward is provided on the inner peripheral side of the split piece. 3. The pressure sensor according to claim 1, wherein the piezoelectric body is formed of a d15 type element having an axial signal axis, a radial polarization axis and a stress axis. .