JP2520029Y2 - Pressure sensor - Google Patents

Description

[Detailed description of the device]

[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 The present applicant has previously filed Japanese Patent Application No. 3-11404.
No. 5 (hereinafter referred to as "prior art")
We proposed a combustion pressure sensor as the pressure sensor shown in.

That is, 1 is a casing, 2 is a casing body which constitutes the casing 1 together with a diaphragm 3 and an upper cover 4 which will be described later, and the casing body 2 is located at the base end side and is formed in a cylindrical shape having a large diameter. The large-diameter cylindrical portion 2A, the shoulder portion 2B provided on the lower end side of the large-diameter cylindrical portion 2A, which is formed in a tapered shape to reduce the diameter downward, and the diaphragm 3 are formed into a bottomed stepped cylindrical shape. Has been formed. Further, the casing body 2 is inserted into the stepped hole such that the shoulder portion 2B abuts on the stepped portion (not shown) of the stepped hole provided in the cylinder head of the engine body. . Further, in the casing body 2, a gap of about 100 to 200 μm is interposed between the outer peripheral surface excluding the shoulder portion 2B and the peripheral surface of the stepped hole, and vibration of the engine body will be described later via the casing body 2. The transmission to the piezoelectric body 9 is prevented as much as possible.

Reference numeral 3 denotes a diaphragm which is located on the tip side of the casing main body 2 and is integrally formed so as to project downward from a shoulder portion 2B of the casing main body 2. The diaphragm 3 is formed in a thin cylindrical shape. The small diameter portion 3A,
It is formed at the tip of the small diameter portion 3A, and is formed into a bottomed cylindrical shape having a small diameter from a thick disk-shaped pressure receiving portion 3B facing the combustion chamber. When the pressure (combustion pressure) in the combustion chamber of the diaphragm 3 is received by the pressure receiving portion 3B, the small diameter portion 3A flexes in the axial direction according to the pressure, and the pressure receiving rod 6 described later is displaced in the axial direction. Has become.

Reference numeral 4 denotes a stepped cylindrical upper cover which is fixed to the upper end side of the casing main body 2 by means such as laser welding, and the upper side of the upper cover 4 projects upward to the outside of the cylinder head. A reduced diameter portion 4A is formed, and the upper cover 4 is attached to the engine body through the reduced diameter portion 4A loosely fitted in the attachment stay 5.

Reference numeral 6 denotes a pressure receiving rod made of a conductive material, which is provided in the diaphragm 3 so as to be displaceable in the axial direction. The pressure receiving rod 6 is provided in the small diameter portion 3A of the diaphragm 3 as shown in FIG. A cylindrical rod portion 6A elongated in the axial direction, a spherical portion 6B located on the lower end side of the rod portion 6A and formed in a hemispherical shape, and in contact with the pressure receiving portion 3B of the diaphragm 3, and an upper end of the rod portion 6A. Is formed in a conical shape that is located on the inner side and increases in diameter in the axially upward direction, and is substantially configured from a conical cylindrical portion 6D having a conical space 6C on the inner peripheral side, and the upper end side of the conical cylindrical portion 6D. Is a piezoelectric body 9 described later.
An annular pressing surface 6E that abuts and presses the lower electrode 9B is formed. When the diaphragm 3 is axially bent by the combustion pressure of the pressure receiving rod 6 and the rod portion 6A is axially displaced and the conical cylindrical portion 6D is pressed against the piezoelectric body 9, the conical cylindrical portion 6D is The piezoelectric body 9 is pushed outward in the radial direction and displaced, and the piezoelectric body 9 is moved by the pressing surface 6E as shown in FIG.
The pressure is applied in the directions A and A (oblique direction) indicated by arrows in FIG. 6, and the high temperature in the combustion chamber is prevented from being transmitted to the piezoelectric body 9.

Reference numeral 7 denotes a contact plate made of a conductive material, which is provided inside the large-diameter cylindrical portion 2A of the casing main body 2 so as to face the pressure receiving rod 6, and a disk-shaped contact is provided on the lower end side of the contact plate 7. 7A is formed, the tip surface side of the contact portion 7A abuts on the upper electrode 9A of the piezoelectric body 9 described later, and the upper end side of the contact plate 7 extends into the reduced diameter portion 4A of the upper cover 4 to lead. The wire 8 is fixed by crimping. The contact plate 7 transmits the voltage signal from the piezoelectric body 9 to a control unit (not shown) via the lead wire 8.

Reference numeral 9 is provided in the large-diameter cylindrical portion 2A of the casing main body 2 and is provided on the conical cylindrical portion 6D of the pressure receiving rod 6,
A piezoelectric body formed of a piezoelectric material such as lead titanate in a cylindrical shape is shown. As shown in FIG. 7, the piezoelectric body 9 is applied with a predetermined high electric field from the inner peripheral side toward the outer peripheral side during manufacturing. Thus, the polarization axis P and the stress axis F are formed in the radial direction by aligning the directions of the spontaneous polarization, and the so-called d15 type element is formed in which the signal axis V is in the axial direction. Sheet-shaped upper and lower electrodes 9A and 9B made of a conductive paste or the like are formed on the upper and lower surfaces of the piezoelectric body 9, and the upper electrode 9A of the piezoelectric body 9 is attached to the contact portion 7A of the contact plate 7. In contact with each other, the lower electrode 9B is grounded to the casing body 2 via the pressure receiving rod 6. Then, in the piezoelectric body 9, the diaphragm 3 receives the combustion pressure in the combustion chamber, the diaphragm 3 bends in the axial direction, and the conical cylindrical portion 6D of the pressure receiving rod 6 is pressed against the lower electrode 9B, as shown in FIG. As described above, the horizontal component force A of the force A in the oblique direction is transmitted via the pressing surface 6E of the pressure receiving rod 6.
When h acts along the stress axis F, a compressive strain is generated thereby, and it is polarized in the direction of the polarization axis P, and an electric charge (voltage signal) corresponding to this compressive strain is generated as a detection signal corresponding to the combustion pressure, This combustion pressure detection signal is output from the electrodes 9A and 9B along the signal axis V to the external control unit via the contact plate 7, the lead wire 8 and the like.

Reference numeral 10 denotes a set screw screwed into the large-diameter cylindrical portion 2A of the casing body 2, and the set screw 10 is a contact of the contact plate 7 via an upper plate 11 formed of an insulating material in an annular shape. The piezoelectric body 9 is fixed by pressing the portion 7A with a predetermined load.

Reference numeral 12 is an outer peripheral side of the contact plate 7, and a small-diameter cylindrical upper heat-shrink tube for insulating between the contact plate 7 and the set screw 10. Reference numeral 13 is provided on an outer peripheral side of the contact portion 7A of the contact plate 7. The
The lower heat-shrinkable tube having a large-diameter tubular shape that insulates between the contact portion 7A and the casing body 2 is shown, and the lower heat-shrinkable tube 13 surrounds the piezoelectric body 9 together with the contact portion 7A, Positioned and fixed.

Reference numeral 14 denotes a sealing member fitted and fixed to the upper end side of the reduced diameter portion 4A of the upper cover 4 by means of caulking or the like. The sealing member 14 prevents the lead wire 8 from coming off and prevents external rainwater and the like. Intrusion into the upper cover 4 is prevented.

Reference numerals 15 and 15 denote disc springs disposed between the free end side of the mounting stay 5 and the upper end side of the reduced diameter portion 4A of the upper cover 4, and each disc spring 15 is a shoulder of the casing body 2. Part 2
B is constantly pressed against the stepped portion of the stepped hole formed in the cylinder head to close the stepped hole and prevent the combustion pressure in the combustion chamber from leaking to the outside of the engine body through the stepped hole. The vibration of the engine body transmitted via the mounting stay 5 is buffered by a spring force to prevent the vibration from being transmitted to the piezoelectric body 9.

The combustion pressure sensor according to the prior art has the above-mentioned structure, and its operation will be described below.

First, the air-fuel mixture in the combustion chamber of the engine is ignited to generate a combustion pressure, and the combustion pressure causes the diaphragm 3 to move.
Is bent in the axial direction, the rod portion 6A of the pressure receiving rod 6 is displaced in the axial direction, and the conical tubular portion 6D of the pressure receiving rod 6 is pressed against the piezoelectric body 9 in the direction of arrow A in FIG. As shown in FIG. 5, this diagonal force A is decomposed into a horizontal component force Ah and a vertical component force Av, and acts on the piezoelectric body 9. When this horizontal component force Ah is applied from the pressing surface 6E of the pressure receiving rod 6 along the stress axis F of the piezoelectric body 9, the radially outward stress (horizontal component force Ah) causes the force inside the piezoelectric body 9. Generates a charge in the direction of the polarization axis P, and contacts the charge as a detection signal (voltage signal) corresponding to the combustion pressure signal from each electrode 9A, 9B along the signal axis V in the axial direction orthogonal to the polarization axis P. It is adapted to output to an external control unit via the plate 7, the lead wire 8 and the like.

[0015]

By the way, according to the above-mentioned prior art, the axial displacement acting on the pressure receiving rod 6 is converted into the radial displacement by the conical cylindrical portion 6D, and the displacement is converted into the radial displacement. The piezoelectric body 9 is made to act via the pressing surface 6E of 6. Therefore, the piezoelectric body 9 is sandwiched between the pressure receiving rod 6 and the set screw 10 from above and below, and the pressure receiving rod is pressed by the set screw 10 in the axial downward direction and in the axial upward direction generated by the displacement of the pressure receiving rod 6. A frictional force is generated between the pressing surface 6 and the pressing surface 6E, and the frictional force is utilized to transmit the stress in the radial direction.

However, in the stress transmission by this frictional force,
When the displacement generated by the pressure in the combustion chamber is transmitted to the piezoelectric body 9, slip occurs between the pressing surface 6E of the pressure receiving rod 6 and the piezoelectric body 9 to reduce the efficiency of stress transmission, and the pressure detection sensitivity is low. There is an unsolved problem of becoming.

Further, the piezoelectric body 9 is the pressing surface 6 of the pressure receiving rod 6.
Since it is mounted on E, not only is it time-consuming to position it, but also the piezoelectric body 9 is pressed by the contact plate 7 or the like in the radial direction during assembly and the position shifts, and the displacement of the pressure-receiving rod 6 is accurately received. However, there are unsolved problems such as a decrease in pressure detection accuracy and damage to the piezoelectric body 9 due to local stress concentration that occurs during assembly.

The present invention has been made in view of the above-mentioned problems of the prior art. The present invention prevents slippage between the conical cylindrical portion of the pressure-receiving rod and the piezoelectric body, and stresses the piezoelectric body in the radial direction. An object of the present invention is to provide a pressure sensor capable of improving the transmission efficiency and accurately positioning the piezoelectric body between the contact plate and the pressure receiving rod.

[0019]

In order to solve the above-mentioned problems, the feature of the structure adopted by the present invention is that the pressure receiving rod is directed from the inner circumference at the other end side of the conical cylindrical part toward the other end side in the axial direction. An inner support portion that supports the piezoelectric body from the inner side by being inserted into the inner peripheral side of the piezoelectric body, and the contact plate extends from the outer periphery on one end side of the contact portion toward the one end side in the axial direction. An outer support portion is provided that is formed in a protruding manner and externally fits on the outer peripheral side of the piezoelectric body to support the piezoelectric body from the outside.

[0020]

With the above structure, the piezoelectric body can be supported and positioned between the conical cylindrical portion of the pressure receiving rod and the contact portion of the contact plate by the inner supporting portion and the outer supporting portion. Further, when the conical cylinder portion of the pressure receiving rod is displaced in the radial direction, the piezoelectric body can be pressed radially outward while being supported from the inside by the inside support portion.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment of the present invention will be described below with reference to FIGS. In the embodiments, the same components as those of the prior art shown in FIGS. 5 to 7 described above are designated by the same reference numerals, and the description thereof will be omitted.

In the figure, 21 is a conical cylindrical portion 6 of the pressure receiving rod 6.
D shows the cylindrical inner side support portion that is integrally formed to project upward from the inner circumference of the pressing surface 6E of the pressure receiving rod 6 toward the upper side in the axial direction. The inner side support portion 21 is also shown in FIG. As shown, the outer peripheral surface is slidably contacted with the inner periphery of the lower end side of the piezoelectric body 9 so that the piezoelectric body 9 is positioned and supported by the pressure receiving rod 6, and the conical tubular portion 6D of the pressure receiving rod 6 is radially supported. When it is displaced to, the piezoelectric body 9 is pressed outward in the radial direction.

Reference numeral 22 denotes a cylindrical outer side support portion which is located on the lower surface side of the contact portion 7A of the contact plate 7 and integrally formed so as to protrude axially downward from the outer periphery of the contact portion 7A. The support portion 22 has an inner peripheral surface slidably contacting the outer periphery of the upper end side of the piezoelectric body 9 to be externally fitted to the piezoelectric body 9.
Is positioned and supported on the contact plate 7.

The combustion pressure sensor according to this embodiment has the above-mentioned structure, and its basic operation is not different from that of the prior art.

However, in the present embodiment, the inner support portion 21 and the outer support portion 22 are erected on the pressing surface 6E of the pressure receiving rod 6 and the contact portion 7A of the contact plate 7, respectively, and the inner support portion 21 is piezoelectric. Since the outer support portion 22 is fitted on the inner circumference of the lower end side of the body 9 and is fitted on the outer circumference of the upper end side of the piezoelectric body 9, the piezoelectric body 9 is supported from the inside and the outside, and the pressure receiving rod 6 and the contact plate are supported. 7, and when the conical cylindrical portion 6D of the pressure receiving rod 6 is displaced in the radial direction, the inner support portion 21 causes the piezoelectric body 9 to move.
Can be pressed radially outward.

Therefore, according to this embodiment, when the pressure change in the combustion chamber is transmitted to the piezoelectric body 9 via the pressure receiving rod 6, a slippage occurs between the pressing surface 6E of the pressure receiving rod 6 and the piezoelectric body 9. It can be effectively prevented from occurring, and the radial displacement of the conical cylindrical portion 6D can be effectively transmitted to the piezoelectric body 9,
The detection sensitivity can be significantly improved.

Further, the piezoelectric body 9 can be surely positioned in the radial direction with respect to the pressure receiving rod 6 and the contact plate 7, and the piezoelectric body 9, the pressure receiving rod 6 and the contact plate 7 are integrated to improve the working efficiency of the assembling work. In addition to being able to greatly improve, the displacement of the pressure receiving rod 6 can be accurately received to improve the pressure detection accuracy, the piezoelectric body 9 can be prevented from being damaged due to localized stress concentration, and the reliability and life can be greatly improved. can do.

In the above embodiment, the inner support portion 21,
Although the outer side support portion 22 is formed in a tubular shape and is integrally provided on the pressure receiving rod 6 and the contact plate 7, the present invention is not limited to this, and for example, a plurality of the support portions may be spaced apart in the circumferential direction. It may be formed of an arcuate protrusion, or each support may be formed as a separate member and fixed to the pressure receiving rod 6 and the contact plate 7 by using a fixing means such as laser welding.

Further, in the above-mentioned embodiment, a conical tube is formed on the upper end side of the rod portion 6A of the pressure receiving rod 6 in a conical shape whose diameter gradually increases upward in the axial direction, and has a conical space 6C on the inner peripheral side. Although it has been described that the portion 6D is provided and the annular pressing surface 6E is provided on the upper end side of the conical tubular portion 6D, the present invention is not limited to this and, for example, as in a modification shown in FIG. 3, the conical tubular portion is provided. The slits 23, 23 as so-called "slits" are provided at predetermined intervals in the circumferential direction of the portion 6D to form the conical cylindrical portion 6
Four pieces are formed from the inner peripheral side to the outer peripheral side of D, and four-divided pressing surfaces 6E ′, 6E ′, ... And inner supporting portions 21 ′, 21 ′ ,. Of course, in this case, the conical cylindrical portion 6D can be effectively deformed, and the axial displacement of the diaphragm 3 can be effectively converted into the radial displacement. Also, in some cases, the slits 23 are separated by a predetermined distance in the circumferential direction,
You may form less than 5 pieces or more than 5 pieces.

Further, in the above-described embodiment, the diaphragm 3 is formed into a small-diameter bottomed cylindrical shape from the thin-walled cylindrical small-diameter portion 3A and the thick-walled disc-shaped pressure receiving portion 3B formed at the tip of the small-diameter portion 3A. Although it has been described that the small diameter portion 3A flexes in the axial direction according to this pressure when formed and received by the pressure receiving portion 3B, the present invention is not limited to this and, for example, as in another modification shown in FIG. 4, a diaphragm. A thin disk-shaped pressure receiving portion 3B 'is formed on the tip side of the small diameter portion 3A' of 3 ', and the pressure receiving portion 3B is formed by external pressure.
′ May be displaced in the axial direction, and in this case, the displacement by the pressure receiving portion 3B ′ can be made large,
The stress applied to the piezoelectric body 9 can be increased.

Further, in the above embodiment, the case where the combustion pressure sensor is used as the 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.

[0032]

As described in detail above, according to the present invention, the piezoelectric body is supported between the conical cylindrical portion of the pressure receiving rod and the contact portion of the contact plate by the inner supporting portion and the outer supporting portion. Positioning is possible, and when the conical cylinder portion of the pressure receiving rod is displaced in the radial direction, the inner support portion can press the piezoelectric body in the radial direction. As a result, it is possible to prevent the occurrence of slippage between the conical cylinder of the pressure receiving rod and the piezoelectric body, improve the efficiency of stress transmission from the conical cylinder to the piezoelectric body, and improve the pressure detection sensitivity. it can. Further, the work efficiency of the assembling work can be improved, the piezoelectric body can be effectively prevented from being damaged by stress concentration at the time of assembling, and the detection capability and reliability of the pressure sensor can be improved.

[Brief description of drawings]

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

FIG. 2 is an external perspective view showing a pressure receiving rod, a contact plate and the like in an enlarged manner.

FIG. 3 is an enlarged plan view showing a pressure receiving rod according to a modified example of the present invention.

FIG. 4 is an enlarged vertical sectional view of a diaphragm according to another modification of the present invention.

FIG. 5 is a vertical sectional view showing a combustion pressure sensor according to the prior art.

FIG. 6 is an external perspective view showing a pressure receiving rod in FIG. 5 in an enlarged manner.

7 is a longitudinal sectional view showing a part of the piezoelectric body in FIG. 5 in an enlarged manner.

[Explanation of symbols]

 2 casing 3 diaphragm 6 pressure receiving rod 6A rod portion 6C conical space 6D conical cylindrical portion 6E pressing surface 7 contact plate 7A contact portion 9 piezoelectric body 9A upper electrode 9B lower electrode 21 inner support portion 22 outer support portion

Claims (1)

(57) [Scope of utility model registration request] 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 the one end side abuts on the diaphragm. A pressure-receiving rod which is provided in the casing and has a conical cylindrical portion having a conical space so that the other end side is displaced in the radial direction according to the displacement of the diaphragm in the axial direction; A cylindrical piezoelectric body that is provided on the other end side of the pressure receiving rod and outputs the displacement of the diaphragm transmitted through the conical cylindrical portion of the pressure receiving rod as a voltage signal according to the pressure, and the contact portion are In a pressure sensor comprising a contact plate that contacts the other end of the piezoelectric body and outputs a voltage signal from the piezoelectric body to the outside, the pressure receiving rod has an inner circumference on the other end side of the conical cylindrical portion. An inner side support portion that is formed to project from the other end in the axial direction toward the other end in the axial direction and that is inserted into the inner peripheral side of the piezoelectric body to support the piezoelectric body from the inside. One end of the contact portion is provided on the contact plate. A pressure sensor, characterized in that it is provided with an outer support portion that is formed so as to project from the side outer periphery toward one end side in the axial direction and that is fitted on the outer peripheral side of the piezoelectric body to support the piezoelectric body from the outside.