JPH04130052U - pressure sensor - Google Patents

Abstract

(57) [Summary] [Purpose] The present invention accurately positions a piezoelectric body with respect to a casing. [Structure] An upper plate 21 made of a conductive material is provided between the set screw 12 and the piezoelectric body 10, and the upper plate 2
1 was formed into a stepped cylindrical shape from an upper cylindrical part 23 projecting from the inner periphery of the upper surface of the flat plate part 22 and a lower cylindrical part 24 protruding from the outer periphery of the lower surface of the flat plate part 22. The upper plate 21 has the piezoelectric body 10 inserted into the lower cylindrical part 24, and the outer electrode 10B of the piezoelectric body 10 on the lower sliding surface of the lower cylindrical part 24.
After sliding contact, the flat plate part 22 is pressed from above by the set screw 12 and fixed in the casing main body 2, and the upper sliding surface of the upper cylinder part 23 contacts the inner peripheral surface of the insertion hole 12A of the set screw 12. Can be assembled by sliding contact. As a result, the upper plate 21 fixes and positions the piezoelectric body 10 within the lower cylindrical portion 24, and the outer electrode 10B of the piezoelectric body 10 is grounded to the casing body 2 via the set screw 12.

Description

[Detailed explanation of the idea]

0001

[Industrial application field]

This invention can be used, for example, in combustion pressure sensors that detect combustion pressure in automobile engines, etc. The present invention relates to a suitable pressure sensor.

0002

[Conventional technology]

The present applicant previously disclosed in Japanese Patent Application No. 3-11405 (hereinafter referred to as prior art) , proposed pressure sensors shown in FIGS. 4 and 5.

0003 That is, 1 is a casing, 2 is a diaphragm 3 and an upper cover 4, which will be described later. - shows a casing body constituting casing 1, with casing body 2 located on the proximal side. A large-diameter cylindrical portion 2A formed in a large-diameter cylindrical shape with a A shoulder portion 2B formed in a tapered shape whose diameter decreases downward, and a diaphragm 3. The casing body 2 has a stepped cylindrical shape with a bottom and a shoulder portion 2B that is connected to the engine body. so that it comes into contact with the step part (none of which is shown) of the stepped hole provided in the cylinder head of the cylinder head. It is inserted into the stepped hole in this manner. Moreover, the casing body 2 has a shoulder portion 2B. A gap of approximately 100 to 200 μm is provided between the outer circumferential surface excluding the outer circumferential surface and the circumferential surface of the stepped hole. The vibration of the engine body is transmitted to the piezoelectric body 10 (described later) through the casing body 2. We are trying to prevent this from happening as much as possible.

0004 3 is located on the tip side of the casing body 2, and is attached to the shoulder portion 2B of the casing body 2. shows a diaphragm integrally formed so as to protrude downward from the diaphragm; The beam 3 includes a small diameter portion 3A formed in a thin cylindrical shape and a tip portion of the small diameter portion 3A. The pressure receiving part 3B is formed into a small diameter cylinder with a bottom and is separated from the pressure receiving part 3B in the form of a thick disk facing into the combustion chamber. There is. The diaphragm 3 receives the pressure inside the combustion chamber (combustion pressure) at the pressure receiving part 3B. When the pressure is applied, the small diameter portion 3A is bent in the axial direction according to this pressure, and the pressure receiving rod 6 described later is It is designed to displace in the axial direction.

[0005] 4 is a step fixed to the upper end side of the casing body 2 using means such as laser welding. A cylindrical upper cover is shown, and the upper side of the upper cover 4 has a cylindrical upper cover facing upward to the outside of the cylinder head. A reduced diameter portion 4A protruding from the upper cover 4 is formed with a reduced diameter portion 4A protruding from the upper cover 4. It is attached to the engine body via the diameter portion 4A.

[0006] 6 indicates a pressure receiving rod disposed inside the diaphragm 3 so as to be displaceable in the axial direction; The pressure-receiving rod 6 has a lower end spherical portion 6A in contact with the pressure-receiving portion 3B of the diaphragm 3, and an upper The conical portion 6B on the end side is formed from an insulating material through a lower plate 7 formed into a disk shape. It is in contact with the piezoelectric body 10. Then, the pressure receiving rod 6 is caused to diaphragm by the combustion pressure. When the ram 3 is bent in the axial direction, it is displaced in the axial direction and presses the piezoelectric body 10 from below. In addition, the high temperature inside the combustion chamber is prevented from being transmitted to the piezoelectric body 10.

[0007] 8 is a coil-shaped contact made of conductive material provided on the lower plate 7 The contact spring 8 has a piezoelectric body 10 on the outer peripheral surface side, which will be described later. The contact spring 8 is in contact with the inner electrode 10A, and the upper end side of the contact spring 8 is connected to the lead wire 9. It is connected. The contact spring 8 receives a voltage signal from the piezoelectric body 10. The signal is transmitted to the control unit (not shown) via lead wire 9. ing.

[0008] 10 is provided on the conical portion 6B of the pressure receiving rod 6 via the lower plate 7, and FIG. 5 shows a piezoelectric body formed into a cylinder shape from a piezoelectric material such as lead oxide. As shown in Figure 2, a predetermined high electric field is applied in the axial direction during manufacturing, resulting in spontaneous polarization. The polarization axis P and stress axis F are formed in the axial direction by aligning the directions, and the polarization axis P and stress axis F are formed in the axial direction. The inner electrode 10A and the outer electrode 10B are formed by means such as vapor deposition, and the signal axis V is It is configured as a so-called d15 type element in the radial direction. Moreover, the inside of the piezoelectric body 10 The side electrode 10A contacts the contact spring 8, and the outer electrode 10B contacts the piezoelectric body 10. The casing is connected to the casing through a grounding cylinder part 11 made of a conductive material fitted to the outer circumference of the casing. Grounded to main body 2. The piezoelectric body 10 has a diaphragm 3 inside the combustion chamber. The pressure receiving rod 6 bends in the axial direction in response to the combustion pressure of This stress (axial displacement of the pressure receiving rod 6) acts along the stress axis F. This causes compressive strain and polarization in the direction of the polarization axis P, and in response to this compressive strain, This combustion pressure detection signal is generated as a detection signal (voltage signal) corresponding to the combustion pressure. The signal is transmitted from each electrode 10A, 10B along the signal axis V to the contact spring 8, It is now possible to output to an external control unit via the cable 9 etc. ing.

[0009] 12 indicates a set screw screwed into the large diameter cylindrical portion 2A of the casing body 2; The female thread 12 has an insertion hole 12A formed in the axial direction through which the lead wire 9 is inserted. , the set screw 12 is inserted through an annular upper plate 13 made of an insulating material. The piezoelectric body 10 is fixed.

0010 14 is fitted and fixed to the upper end side of the reduced diameter portion 4A of the upper cover 4 by means such as caulking. The seal member 14 prevents the lead wire 9 from coming off, and also prevents the lead wire 9 from coming off. This prevents rainwater, etc. from entering into the upper cover 4.

[0011] 15, 15 are between the free end side of the mounting stay 5 and the upper end side of the reduced diameter part 4A of the upper cover 4. A disc spring disposed between each disc spring 15 is shown, and each disc spring 15 touches the shoulder 2B of the casing body 2. By constantly pressing against the stepped part of the stepped hole formed in the cylinder head, the stepped hole is blocked. , Prevents the combustion pressure in the combustion chamber from leaking to the outside of the engine body through the stepped hole. At the same time, the vibration of the engine body transmitted via the mounting stay 5 is relaxed by the spring force. This prevents this vibration from being transmitted to the piezoelectric body 10.

0012 The combustion pressure sensor according to the prior art has the above-mentioned configuration, and the operation thereof is as follows. I will explain about it.

[0013] First, the air-fuel mixture in the combustion chamber of the engine is ignited to generate combustion pressure. As a result, the diaphragm 3 is bent in the axial direction, and the pressure receiving rod 6 is displaced in the axial direction. The stress due to the displacement in the direction is transferred from the conical portion 6B of the pressure receiving rod 6 to the stress axis F of the piezoelectric body 10. When applied along the polarization axis P, this axial stress causes the piezoelectric body 10 to have a polarization axis P. A charge is generated in the direction, and this charge is distributed along the signal axis V in the radial direction perpendicular to the polarization axis P. A controller is output as a detection signal (voltage signal) according to the combustion pressure signal from the electrodes 10A and 10B. Output to external control unit via tact spring 8, lead wire 9, etc. It is supposed to be done.

[0014]

[Problem that the idea aims to solve]

By the way, in the prior art described above, the piezoelectric body 10 has a signal axis V in the radial direction. Since it is composed of a d15 type element having a polarization axis P and a stress axis F in the axial direction, the pressure To prevent pyroelectricity generated due to temperature changes of the electric body 10 from being applied to the signal axis V. However, the inner electrode 10A of the piezoelectric body 10 is connected to the contact spring 8. Since it is in contact with the piezoelectric When the body 10 is pressed in the axial direction and is displaced, the piezoelectric body 10 is displaced from its normal position. It may be fixed to the casing body 2 in a state.

[0015] Therefore, in the prior art described above, the piezoelectric body 10 is orientated with respect to the casing body 2. Not only is it difficult to position to the correct value and requires a lot of effort to assemble, but also the pressure The piezoelectric body 10 cannot accurately accept the displacement of the rod 6, resulting in poor pressure detection accuracy. or the piezoelectric body 10 may be damaged due to localized stress concentration that occurs during assembly. There is an unresolved problem that.

[0016] The present invention was devised in view of the problems of the prior art described above. It is possible to accurately position the piezoelectric body with respect to the The purpose of the present invention is to provide a pressure sensor that can

[0017]

[Means to solve the problem]

The features of the configuration adopted by this invention to solve the above problems are the casing and A stepped cylindrical positioning member is provided between the piezoelectric body and the piezoelectric body is inserted into the positioning member. The structure is such that positioning in the radial direction is determined by fitting.

[0018]

[Effect]

By inserting the piezoelectric body into the positioning member, the piezoelectric body can be moved radially within the casing. It can be positioned in the direction.

[0019]

【Example】

Embodiments of the present invention will be described below with reference to FIGS. 1 to 3. In addition, in the example The same reference numerals are given to the same components as in the prior art shown in FIGS. 4 and 5 described above. , the explanation thereof will be omitted.

[0020] In the figure, 21 is provided between the piezoelectric body 10 and the set screw 12, and is made of a conductive material such as a metal material. an upper plate as a positioning member formed from a flexible material; As shown in FIG. 2, the toe 21 includes a flat plate portion 22 having an insertion hole 22A in the center thereof, and An upper side that projects upward from the periphery of the insertion hole 22A of the flat plate portion 22 and is integrally formed. The cylindrical portion 23 and the flat plate portion 22 are integrally protruded downward from the outer peripheral side of the lower surface 22B. The lower cylindrical portion 24 is formed, and the lower surface 22B of the flat plate portion 22 is completely Insulation treatment such as edge paste painting is applied. Moreover, on the outer periphery of the upper cylinder part 23, An upper sliding contact surface 23A is formed to come into sliding contact with the inner peripheral surface of the insertion hole 12A of the set screw 12, A lower sliding contact surface 24 is provided on the inner periphery of the lower cylindrical portion 24 and is in sliding contact with the outer electrode 10B of the piezoelectric body 10. A is formed.

[0021] Then, the upper plate 21 inserts the piezoelectric body 10 into the lower cylindrical part 24, and After the outer electrode 10B of the piezoelectric body 10 is brought into sliding contact with the lower sliding contact surface 24A of the lower cylindrical portion 24 , the flat plate part 22 is pressed and fixed from above by the setscrew 12, and the upper cylinder part 2 The upper sliding surface 23A of 3 slides on the inner peripheral surface of the insertion hole 12A of the set screw 12 and is assembled. As a result, the outer electrode 10B of the piezoelectric body 10 is attached to the casing via the set screw 12. This is to ground the ring body 2.

[0022] As a result, the piezoelectric body 10 is fixed at a fixed position relative to the casing body 2, and In addition to preventing the deterioration of detection ability caused by being fixed in position, The assembly work during assembly can be simplified.

[0023] The pressure sensor according to this embodiment has the above-mentioned configuration, and its basic operation is Regarding the production, there is no particular difference from that based on the prior art.

[0024] However, in this embodiment, a stepped cylindrical upper plate is provided between the set screw 12 and the piezoelectric body 10. A groove 21 is provided, and the piezoelectric body 10 is inserted into and attached to the lower cylindrical part 24. The piezoelectric body 10 is reliably positioned in the radial direction with respect to the casing body 2. This not only greatly improves the efficiency of assembly work, but also reduces the displacement of the pressure receiving rod 6. Accurate pressure detection can improve pressure detection accuracy and prevent local stress from concentrating on the piezoelectric body 10. It is possible to effectively prevent damage to the piezoelectric body 10 by effectively preventing can significantly improve reliability and service life.

[0025] Also, is the piezoelectric body 10 fixed to the casing body 2 via the set screw 12? However, it is not affected by the finishing accuracy of the inner surface of the large diameter cylindrical portion 2A of the casing body 2. , the piezoelectric body 10 can be positioned at a fixed position, and thereby the inner surface of the large diameter cylindrical portion 2A can be adjusted. In addition to simplifying the lifting process and increasing manufacturing efficiency, the upper plate 2 1 is formed from a conductive material such as metal, the earthing cylinder 11 described in the prior art Connect the outer electrode 10B of the piezoelectric body 10 to the upper plate 21 without using 12 to the casing body 2, which can significantly reduce costs. Wear.

[0026] In the embodiment described above, the upper plate 21 includes a flat plate portion 22 and a portion that is connected to the flat plate portion 22. It is composed of an upper cylindrical part 23 and a lower cylindrical part 24, which are made of a conductive material such as metal. However, instead of this, the upper cylindrical portion 23 and the lower cylindrical portion 24 may be Each is formed as a separate member, and each of the cylindrical parts 23 and 24 is fixed using a fixing means such as welding. Alternatively, the upper plate 21 may be made of a conductive heat-resistant resin material. may be formed.

[0027] Further, in the embodiment, the diaphragm 3 includes a thin cylindrical small diameter portion 3A and a thin cylindrical small diameter portion 3A. Formed into a small diameter cylinder with a bottom from the thick disc-shaped pressure receiving part 3B formed at the tip of the part 3A. However, when the pressure receiving part 3B receives pressure, the small diameter part 3A bends in the axial direction in response to this pressure. However, the present invention is not limited to this. For example, as shown in the modification shown in FIG. A thin disc-shaped pressure receiving part 3B' is formed on the tip side of the small diameter part 3A' of the yaphragm 3', and The pressure receiving part 3B' may be displaced in the axial direction by the pressure of can take a large displacement by the pressure receiving part 3B' and reduce the stress applied to the piezoelectric body 10. can be made larger.

[0028] Furthermore, in the embodiment, the inner electrode 10A of the piezoelectric body 10 is a coil-shaped contact. Although it has been described that it is connected to the lead wire 9 via the spring 8, it is possible to Alternatively, a C-clip type contact spring may be used.

[0029] On the other hand, in the above embodiment, an example is given where the pressure sensor is used as a combustion pressure sensor. However, the present invention is not limited to this, and can be applied to gases such as air, industrial gases, and fuels. The present invention can also be applied to pressure sensors that detect the pressure of liquids such as liquids and water.

[0030]

[Effect of the idea]

As detailed above, according to the present invention, there is a stepped tube between the casing and the piezoelectric body. By providing a positioning member with a shape and inserting a piezoelectric body into the positioning member, Since the piezoelectric body is configured to position the pressure rod, the piezoelectric body can accurately receive the displacement of the pressure receiving rod. , External pressure can be detected with high accuracy, making it easy to assemble the piezoelectric body into the casing. In addition to improving work efficiency during assembly, the piezoelectric body will not be damaged due to stress concentration during assembly. This can effectively prevent Ru.

[Brief explanation 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 enlarged cross-sectional perspective view of the upper plate in FIG. 1;

FIG. 3 is an enlarged vertical cross-sectional view of a diaphragm according to a modified example of the present invention.

FIG. 4 is a longitudinal cross-sectional view of a combustion pressure sensor according to the prior art;

FIG. 5 is an enlarged vertical cross-sectional view of a part of the piezoelectric body in FIG. 4;

[Explanation of symbols]

1 Casing 3 Diaphragm 6 Pressure receiving rod 10 Piezoelectric body 21 Upper plate (positioning member)

Claims (1)

[Scope of utility model registration request] 1. A casing, a diaphragm disposed on one end of the casing and displaceable in the axial direction in response to pressure applied from the outside to the one end of the casing, and a diaphragm disposed in the casing such that a distal end thereof abuts the diaphragm. a pressure receiving rod disposed within the casing and displaces in the axial direction according to displacement of the diaphragm; and a radial signal axis and an axial polarization axis disposed within the casing and provided on the base end side of the pressure receiving rod. and a piezoelectric body formed in a cylindrical shape from a d15 type element having a stress axis and a piezoelectric body that outputs the axial displacement of the diaphragm transmitted through the pressure receiving rod as a voltage signal corresponding to the pressure. , wherein a stepped cylindrical positioning member is provided between the casing and the piezoelectric body, and the piezoelectric body is positioned in the radial direction by being inserted into the positioning member. sensor.