JP6381506B2 - Pressure sensor and method of manufacturing pressure sensor - Google Patents

Description

  The present invention relates to a pressure sensor for detecting a pressure in a combustion chamber in an internal combustion engine or the like, and a method for manufacturing the same.

  A pressure sensor having a diaphragm, a piezoelectric element, and a transmission member (for example, a rod) has been proposed. When the diaphragm is deformed according to the pressure in the combustion chamber, the transmission member is displaced in a predetermined direction and applies a force to the piezoelectric element. The piezoelectric element outputs an electric charge (voltage) corresponding to the applied force. As a result, the pressure in the combustion chamber can be detected by measuring the electric charge output from the piezoelectric element.

  In order to stabilize the electric charge output from the piezoelectric element, the pressure sensor is assembled in a state where a load is applied to the piezoelectric element in advance. Patent Document 1 discloses a pressure sensor that includes a fixing member that is positioned on the opposite side of a transmission member with respect to a piezoelectric element and is fixed to a housing. When the pressure sensor is assembled, the fixing member and the housing are welded while the fixing member is pressurized. This makes it possible to stabilize a load (hereinafter also referred to as a preload) applied in advance to the piezoelectric element during assembly.

Japanese Patent Laid-Open No. 7-49283

  However, in the above-described technique, variation in preload on the piezoelectric element may be increased without suppressing variation in pressure applied to the fixed member during assembly. As a result, electric charges output from the piezoelectric element may vary. Variations in the output charge can cause variations in the performance of the pressure sensor.

  The present specification discloses a technique for reducing variation in preload on the piezoelectric element and reducing variation in charge output from the piezoelectric element.

  The technology disclosed in this specification can be implemented as the following application examples.

Application Example 1 A cylindrical casing having a bottom portion extending along the axis and extending radially inward on the rear end side of the axis, a piezoelectric unit disposed in the casing and including a piezoelectric element, A diaphragm fixed to the front end side of the piezoelectric unit in the housing and deformed according to the received pressure, a transmission member fixed to the diaphragm, and a rear end contacting the front end side of the piezoelectric unit, A pressure sensor comprising:
A support member fixed to the housing and having a tip abutting on a rear end side of the piezoelectric unit;
An elastic member having a larger amount of deformation with respect to the force in the direction of the axis than the transmission member and the support member;
The elastic member is between the piezoelectric unit and the bottom of the housing and between the piezoelectric unit and the diaphragm at a first position that is radially outside the support member. And it is arrange | positioned in one of the 2nd positions which are the outer sides of the radial direction of the said transmission member, The pressure sensor characterized by the above-mentioned.

  According to the above configuration, when the elastic member is in the first position, the front end side to the rear end side with respect to the transmission member before the support member is fixed to the housing during assembly. If the transmission member is fixed to the diaphragm in a pressurized state, the preload variation on the piezoelectric element can be reduced by the elastic member at the first position. In addition, when the elastic member is in the second position, during assembly, the support member is pressed from the rear end side to the front end side before being fixed to the diaphragm. If the support member is fixed to the housing, the preload variation on the piezoelectric element can be reduced by the elastic member at the second position. As a result, variation in electric charges output from the piezoelectric element can be reduced.

[Application Example 2] The pressure sensor according to Application Example 1,
The elastic member is a cylindrical member extending along the axis,
The support member is a rod-shaped member extending along the axis,
The pressure sensor, wherein the support member is inserted into the elastic member at the first position.

  In this way, the elastic member can be disposed in the housing in a compact manner, and variations in preload on the piezoelectric element can be appropriately reduced.

[Application Example 3] The pressure sensor according to Application Example 1,
The elastic member is a cylindrical member extending along the axis,
The transmission member is a rod-shaped member extending along the axis,
The pressure sensor, wherein the transmission member is inserted into the elastic member at the second position.

  In this way, the elastic member can be disposed in the housing in a compact manner, and variations in preload on the piezoelectric element can be appropriately reduced.

[Application Example 4] The pressure sensor according to Application Example 2 or 3,
The inner diameter of the cylindrical elastic member is R1,
When the outer diameter of the rod-shaped support member or the transmission member is R2,
A pressure sensor satisfying (R2 / R1) ≧ 0.5.

  If it carries out like this, the dispersion | variation in the position of the radial direction of the elastic member with respect to a supporting member or a transmission member can be reduced. As a result, it is possible to further reduce the variation in preload on the piezoelectric element.

[Application Example 5] The pressure sensor according to any one of Application Examples 1 to 4,
In the cross section including the axis, the minimum value of the angle formed by the surface of the member that contacts the end of the elastic member and the end of the elastic member among the casing, the piezoelectric unit, and the diaphragm is θ And when
The pressure sensor is characterized in that the angle θ is 30 degrees or less.

  If it carries out like this, the dispersion | variation in the position of the radial direction of the elastic member with respect to a supporting member or a transmission member can be reduced. As a result, it is possible to further reduce the variation in preload on the piezoelectric element.

  If it carries out like this, the contact of the edge part of an elastic member and the surface of the member which contacts the said edge part will be stabilized. As a result, it is possible to further reduce the variation in preload on the piezoelectric element.

[Application Example 6] The pressure sensor according to any one of Application Examples 1 to 5,
The pressure sensor according to claim 1, wherein the elastic member is in the first position.

Application Example 7 A cylindrical casing having a bottom portion extending along the axis and extending radially inward on the rear end side of the axis, a piezoelectric unit including a piezoelectric element disposed in the casing, A diaphragm fixed to the front end side of the piezoelectric unit in the housing and deformed according to the received pressure, a transmission member fixed to the diaphragm, and a rear end contacting the front end side of the piezoelectric unit, A method of manufacturing a pressure sensor comprising:
(A) The casing, the diaphragm, the piezoelectric unit, the transmission member, a support member for supporting the rear end side of the piezoelectric unit, and an axial force from the transmission member and the support member A step of preparing an elastic member having a large deformation amount with respect to
(B) Disposing the piezoelectric unit in the housing and disposing the elastic member between the piezoelectric unit in the housing and the bottom of the housing;
(C) With the piezoelectric unit and the elastic member disposed in the housing, the transmission member is brought into contact with the front end side of the piezoelectric unit, and the front end side to the rear end side with respect to the transmission member Fixing the transmission member to the diaphragm while applying pressure toward the diaphragm;
(D) bringing the support member into contact with the rear end side of the piezoelectric unit and fixing the support member to the housing;
A manufacturing method comprising:

  According to the above configuration, with the elastic member disposed between the piezoelectric unit in the housing and the bottom of the housing, the front end side to the rear end side with respect to the transmission member that contacts the front end side of the piezoelectric unit. While applying pressure, the transmission member is fixed to the diaphragm. Then, after that, the support member is brought into contact with the rear end side of the piezoelectric unit, and the support member is fixed to the housing. As a result, variations in preload on the piezoelectric element can be reduced.

Application Example 8 A cylindrical housing having a bottom portion extending along the axis and extending radially inward on the rear end side of the axis, a piezoelectric unit including a piezoelectric element disposed in the housing, A diaphragm fixed to the front end side of the piezoelectric unit of the housing and deformed according to the pressure received, and a transmission member fixed to the diaphragm and having a rear end abutting the front end side of the piezoelectric unit. A pressure sensor manufacturing method comprising:
(A) The casing, the diaphragm, the piezoelectric unit, the transmission member, a support member for supporting the rear end side of the piezoelectric unit, and an axial force from the transmission member and the support member A step of preparing an elastic member having a large deformation amount with respect to
(B) disposing the piezoelectric unit in the housing and disposing the elastic member between the piezoelectric unit in the housing and the diaphragm fixed to the housing;
(C) In a state where the piezoelectric unit and the elastic member are arranged in the housing, the support member is brought into contact with the rear end side of the piezoelectric unit, and the rear end side to the front end side with respect to the support member Fixing the support member to the housing while pressurizing toward the housing;
(D) bringing the transmission member into contact with the distal end side of the piezoelectric unit and fixing the transmission member to the diaphragm;
A manufacturing method comprising:

  According to the above configuration, in a state where the elastic member is disposed between the piezoelectric unit and the diaphragm in the housing, the supporting member that contacts the rear end side of the piezoelectric unit is pressurized from the rear end side toward the front end side. However, the support member is fixed to the casing. As a result, it is possible to reduce variations in preload on the piezoelectric elements and reduce variations in charges output from the piezoelectric elements.

  The technology disclosed in the present specification can be realized in various modes, for example, in a mode of a pressure sensor, an internal combustion engine equipped with the pressure sensor, or the like.

It is explanatory drawing which shows the pressure sensor as 1st Embodiment. It is an enlarged view of the front end unit vicinity of the pressure sensor of 1st Embodiment. It is a disassembled perspective view of a piezoelectric unit. It is explanatory drawing of a cylindrical spring. It is a flowchart of the manufacturing method of the pressure sensor of 1st Embodiment. It is explanatory drawing of the manufacturing method of the pressure sensor of 1st Embodiment. It is a figure explaining the effect of this application. It is an enlarged view of the front end unit vicinity of the pressure sensor of 2nd Embodiment. It is a flowchart of the manufacturing method of the pressure sensor of 2nd Embodiment. It is explanatory drawing of the manufacturing method of the pressure sensor of 1st Embodiment. It is a 1st figure which shows the modification of an elastic member. It is a 2nd figure which shows the modification of an elastic member.

A. First embodiment:
A-1. Configuration of Pressure Sensor 10 FIG. 1 is an explanatory diagram showing a pressure sensor 10 as a first embodiment. The axis line CL is the central axis of the pressure sensor 10. Hereinafter, the direction parallel to the axis CL is also referred to as “axis direction”. The radial direction of a circle centered on the axis CL on a plane perpendicular to the axis CL is also simply referred to as “radial direction”, and the circumferential direction of the circle is also simply referred to as “circumferential direction”. Further, among the directions along the axis CL, the direction toward the lower side of FIG. 1 is referred to as “front end direction Df”, and the direction opposite to the front end direction Df is referred to as “rear end direction Dr”. The front end direction Df side is referred to as “front end side”, and the rear end direction Dr side is also referred to as “rear end side”. FIG. 1 shows a cross-sectional configuration on the left side of the axis line CL of the tip side portion of the pressure sensor 10. This cross section is a flat cross section (cross section cut along a plane) including the axis CL. FIG. 1 shows an external configuration of another part of the pressure sensor 10.

  The pressure sensor 10 of this embodiment is attached to an internal combustion engine and used to detect the pressure in the combustion chamber of the internal combustion engine. As shown in FIG. 1, the pressure sensor 10 includes a cylindrical metal fitting 20, a tip unit 100, and a cable 60 as main components.

  The cylindrical metal fitting 20 has a substantially cylindrical shape extending along the axis line CL, and an axial hole 21 extending along the axis line CL is formed inside. The cylindrical metal fitting 20 is made of, for example, a conductive metal such as stainless steel.

  The cylindrical fitting 20 is provided with a screw portion 22 and a tool engagement portion 24 on the outer peripheral surface of the cylindrical fitting 20 on the rear end side. The screw portion 22 includes a screw groove for fixing the pressure sensor 10 to the cylinder head of the internal combustion engine. The tool engaging portion 24 has an outer peripheral shape (for example, a hexagonal cross section) with which a tool (not shown) used for attaching and detaching the pressure sensor 10 is engaged.

  FIG. 2 is an enlarged view of the vicinity of the tip unit 100 of the pressure sensor 10 of the first embodiment. Specifically, FIG. 2 is an enlarged cross-sectional view showing a portion indicated as a region X in FIG. This cross section is a cross section including the axis CL. The tip unit 100 includes a housing 30, a diaphragm 40, a piezoelectric unit 50, a support rod 70, a cylindrical spring 80, and a transmission rod 90. As shown in FIG. 2, the axis CL of the pressure sensor 10 includes a cylindrical metal fitting 20, a housing 30, a diaphragm 40, a piezoelectric unit 50, a support rod 70, a cylindrical spring 80, and a transmission rod 90 that constitute the pressure sensor 10. It is also the central axis of each.

  The casing 30 is joined to the tip end of the cylindrical metal fitting 20 via the fusion part MT1 by laser welding. The housing 30 has a substantially cylindrical shape extending along the axis line CL, and an axial hole 31 extending along the axis line CL is formed therein. The housing 30 has a bottom portion 32 and an enlarged diameter portion 34. The bottom 32 is located on the rear end side of the housing 30 and extends radially inward from the inner peripheral surface forming the shaft hole 31. The bottom 32 has a through hole 321 that communicates with the shaft hole 31 at a portion that intersects the axis CL. Further, the bottom portion 32 has a cylindrical fixing portion 322 extending toward the rear end side at a portion close to the axis CL, that is, an inner edge portion where the through hole 321 is formed. The enlarged diameter portion 34 is a portion that is located on the front end side of the housing 30 and whose outer diameter increases from the front end side toward the rear end side. When the pressure sensor 10 is attached to the internal combustion engine, the enlarged diameter portion 34 is in close contact with the cylinder head of the internal combustion engine. The housing 30 is formed of a conductive metal such as stainless steel, for example, like the cylindrical metal fitting 20.

  The diaphragm 40 is an annular film centered on the axis CL. The edge on the outer peripheral side of the diaphragm 40 is joined to the tip of the housing 30 through the melting part MT2 over the entire circumference by laser welding. That is, the diaphragm 40 is fixed to the distal end side of the piezoelectric unit 50 in the casing 30 in the casing 30.

  The diaphragm 40 includes a through hole 41 and a fixing portion 42. The through hole 41 is formed at a portion that intersects the axis CL, and communicates with the shaft hole 31. The fixing portion 42 is a cylindrical portion that is positioned near the axis CL of the diaphragm 40, that is, an inner edge portion where the through hole 41 is formed, and extends toward the distal end side. The diaphragm 40 is formed of a conductive metal such as stainless steel, for example.

  The piezoelectric unit 50 is disposed in the shaft hole 31 of the housing 30. The piezoelectric unit 50 includes a piezoelectric element 51, two electrodes 52 sandwiching the piezoelectric element 51, a holding plate 54 disposed on the front end side of the front end electrode 52, and a rear end direction Dr from the rear end side electrode 52. A lead portion 53, a pressing plate 54, and an insulating plate 55 that are arranged in order toward the head (FIG. 2).

  FIG. 3 is an exploded perspective view of the piezoelectric unit 50. As shown in the drawing, the piezoelectric element 51 and the electrode 52 are disk-shaped plate members centered on the axis CL. The holding plate 54 and the insulating plate 55 are annular plate-like members centered on the axis line CL. The electrode 52 and the pressing plate 54 are formed using a conductive metal such as stainless steel. The insulating plate 55 is a member for insulating between the lead portion 53 and the housing 30 (FIG. 2), and is formed of an insulating material such as alumina, for example.

  The lead part 53 includes a disk part 57 that is a substantially disk-shaped plate member, and a terminal part 56 that extends from the center part of the disk part 57 toward the rear end direction Dr. The terminal portion 56 passes through the through hole 54h of the pressing plate 54 and the through hole 55h of the insulating plate 55 and protrudes toward the rear end direction Dr (FIG. 2). The lead portion 53 is formed using a conductive metal such as stainless steel.

  The transmission rod 90 is a rod-like member extending along the axis CL, more specifically, a substantially cylindrical member, and is disposed in the shaft hole 31 of the housing 30 on the distal end side from the piezoelectric unit 50. The transmission rod 90 is made of a conductive metal such as stainless steel, for example.

  The rear end of the transmission rod 90 is in contact with the front end side of the piezoelectric unit 50. Specifically, the transmission rod 90 has a protruding portion 92 that protrudes toward the rear end side at a portion that intersects the axis CL of the surface 91 on the rear end side. The rear end surface 91 of the transmission rod 90 is in contact with the front end surface of the pressing plate 54 on the front end side of the piezoelectric unit 50. Further, the protruding portion 92 of the transmission rod 90 is disposed in the through hole 54 h of the holding plate 54 on the distal end side, and the rear end surface of the protruding portion 92 is on the distal end side of the electrode 52 on the distal end side of the piezoelectric unit 50. Touching the surface. As a result, the force applied to the transmission rod 90 from the front end side to the rear end side is transmitted to the piezoelectric unit 50 and then to the piezoelectric element 51 of the piezoelectric unit 50.

  A portion on the distal end side of the transmission rod 90 is fixed to the diaphragm 40. Specifically, the distal end portion of the transmission rod 90 is inserted into the through hole 41 of the diaphragm 40, that is, into the cylindrical fixing portion 42 of the diaphragm 40. And the outer peripheral surface of the part of the front end side of the transmission rod 90 is joined with the inner peripheral surface of the fixing | fixed part 42 via the fusion | melting part MT3 by laser welding.

  The support rod 70 is a substantially cylindrical member extending along the axis CL, and an axial hole 71 extending along the axis CL is formed therein. The support rod 70 is disposed in the shaft hole 31 of the housing 30 on the rear end side from the piezoelectric unit 50. The support rod 70 is made of, for example, a conductive metal such as stainless steel.

  The tip of the support rod 70 is in contact with the rear end side of the piezoelectric unit 50, specifically, the surface of the piezoelectric plate 50 on the rear end side of the insulating plate 55. The terminal hole 56 of the lead portion 53 of the piezoelectric unit 50 is disposed in the shaft hole 71 of the support rod 70 in a state of being separated from the inner peripheral surface of the support rod 70 so as not to contact the inner peripheral surface of the support rod 70. Has been.

  A portion on the rear end side of the support rod 70 is fixed to the housing 30. Specifically, the rear end portion of the support rod 70 is inserted and disposed in the through hole 321 of the bottom 32 of the housing 30, that is, in the cylindrical fixing portion 322 of the bottom 32. And the outer peripheral surface of the part of the rear end side of the support rod 70 is joined with the inner peripheral surface of the fixing | fixed part 322 through the fusion | melting part MT4 by laser welding.

  The cylindrical spring 80 is a substantially cylindrical member extending along the axis CL, and an axial hole 81 extending along the axis CL is formed therein. The cylindrical spring 80 is formed of, for example, a conductive metal such as stainless steel.

  FIG. 4 is an explanatory diagram of the cylindrical spring 80. 4A shows a perspective view of the cylindrical spring 80, and FIG. 4B shows an enlarged view of a sectional view of the cylindrical spring 80 of FIG. The side wall of the cylindrical spring 80 is a thin plate having a bellows structure. For this reason, as shown in FIG. 4B, the cross section of the side wall has a wavy shape. As a result, the cylindrical spring 80 has a greater amount of axial deformation than the transmission rod 90 and the support rod 70 with respect to the axial force. In other words, the spring constant in the axial direction of the cylindrical spring 80 is smaller than the spring constant in the axial direction of the transmission rod 90 and the support rod 70. Specifically, the spring constant in the axial direction of the cylindrical spring 80 is preferably 1000 N / mm or less, more preferably 500 N / mm or less, and particularly preferably 200 N / mm or less.

  The cylindrical spring 80 is located between the piezoelectric unit 50 and the bottom portion 32 of the housing 30 and is located on the outer side in the radial direction of the support rod 70. Specifically, the rear end of the cylindrical spring 80 is in contact with the surface on the front end side of the bottom portion 32 of the housing 30, and the front end of the cylindrical spring 80 is in contact with the surface on the rear end side of the insulating plate 55. Yes. The cylindrical spring 80 is compressed by a small amount in the axial direction by the bottom 32 and the insulating plate 55. A support rod 70 and a terminal portion 56 disposed in the shaft hole 71 of the support rod 70 are inserted and disposed in the shaft hole 81 of the cylindrical spring 80.

  Here, the inner diameter of the cylindrical spring 80 is R11. As shown in FIG. 4B, the inner peripheral surface of the cylindrical spring 80 is not parallel to the axis CL. In such a case, as shown in FIG. 4, among the virtual cylinders that can be inserted into the shaft hole 81, the outer cylinder is the cylinder with the largest outer diameter and the outer peripheral surface is parallel to the axis CL. The diameter is the inner diameter R11 of the cylindrical spring 80. In other words, in the cross section obtained by cutting the cylindrical spring 80 along the plane including the axis CL, the cylinder spring 80 is located on both sides of the axis CL (the right side and the left side in FIG. 4B), and is parallel to the axis CL. The two tangent lines L1 and L2 that are in contact with the inner peripheral surface of the cylindrical spring 80 are specified. The interval between the two tangents L1 and L2 is defined as the inner diameter R11 of the cylindrical spring 80. At this time, when the outer diameter of the support rod 70 is R12 (FIG. 2), (R12 / R11) ≧ 0.5 is satisfied. That is, the outer diameter R12 of the support rod 70 is more than half of the inner diameter R11 of the cylindrical spring 80.

  Furthermore, in the cross section including the axis line CL shown in FIG. 4B, the contact portions between the surface S1 of the bottom 32 of the housing 30 and the rear end of the cylindrical spring 80 are P1 and P2. As shown in FIG. 4B, four angles θ11 to θ14 can be specified as the angle formed between the surface S1 of the bottom 32 and the rear end of the cylindrical spring 80 in the contact portions P1 and P2. The minimum of these angles is 30 degrees or less. In the example of FIG. 4B, θ11 = θ14 <θ12 = θ13, and thus the minimum angles are θ11 and θ14. Therefore, θ11 <30 degrees and θ14 <30 degrees.

  Similarly, in the cross section including the axis line CL shown in FIG. 4B, the surface on the rear end side of the piezoelectric unit 50 (that is, the surface on the rear end side of the insulating plate 55) S2, the tip of the cylindrical spring 80, These contact portions are P3 and P4. As shown in FIG. 4B, four angles θ21 to θ24 can be specified as the angle formed between the surface S2 of the insulating plate 55 and the tip of the cylindrical spring 80 in the contact portions P3 and P4. The minimum of these angles is 30 degrees or less. In the example of FIG. 4B, θ22 = θ23 <θ21 = θ24, so the minimum angles are θ22 and θ23. Therefore, θ22 <30 degrees and θ23 <30 degrees.

  The cable 60 is disposed on the rear end side of the tip unit 100 in the shaft hole 21 of the cylindrical metal fitting 20. The cable 60 is a member for transmitting the electric charge of the piezoelectric element 51 to an electric circuit (not shown) for detecting the combustion pressure of the internal combustion engine based on the electric charge of the piezoelectric element 51. The cable 60 is a so-called shielded cable coaxial cable having a multilayer structure for reducing noise. Specifically, the cable 60 includes an inner conductor 65, an insulator 64, a conductive coating 63, an outer conductor 62, and a jacket 61 arranged from the center toward the outer peripheral side.

  The internal conductor 65 exposed at the distal end portion of the cable 60 is connected to the terminal portion 56 of the piezoelectric unit 50 via the flat conductor CW1 and the thin conductor CW2. Specifically, the flat conductor CW1 is welded to the front end of the inner conductor 65, and the rear end of the small-diameter conductive wire CW2 wound in a coil shape is welded to the front end of the flat conductor CW1. The distal end of the small-diameter conductive wire CW2 is welded to the rear end portion of the terminal portion 56. In addition, the above-mentioned structure for connecting the internal conductor 65 and the terminal part 56 is an example, and other arbitrary structures are employable.

  The entire terminal portion 56 and the range including the distal end portion of the small-diameter conductive wire CW2 are covered with an insulating heat-shrinkable tube. Thereby, the reliability of the electrical insulation between the terminal part 56 and the surrounding conductor (especially support rod 70) is improved.

  A grounding conductor CW3 extending from the distal end of the external conductor 62 to the distal end side is connected to the distal end portion of the external conductor 62. In the grounding conductor CW3, the tip of the grounding conductor CW3 is joined to the bottom 32 of the housing 30 via the melting part MT5. Thereby, the outer conductor 62 is grounded through the grounding conductor CW3, the housing 30, and the cylinder head of the internal combustion engine.

A-2. Operation of Pressure Sensor 10 The pressure sensor 10 is provided in a cylinder head of an internal combustion engine, and is attached to an attachment hole communicating with the combustion chamber. A female screw is formed in the mounting hole, and the screw portion 22 of the cylindrical metal fitting 20 is fixed to the female screw. In this state, the tip of the tip unit 100 is exposed in the combustion chamber of the internal combustion engine, and the surface on the tip side of the diaphragm 40 receives the pressure of gas (for example, fuel gas) in the combustion chamber.

  The diaphragm 40 deforms (bends) according to the pressure in the combustion chamber. The transmission rod 90 is displaced along the axis CL according to the deformation of the diaphragm 40, thereby transmitting a load corresponding to the pressure received by the diaphragm 40 to the piezoelectric unit 50 on the rear end side. On the piezoelectric element 51 of the piezoelectric unit 50, an electric charge is generated according to the load transmitted from the diaphragm 40 (FIG. 2) through the transmission rod 90. The piezoelectric element 51 outputs an electric charge (for example, an electric signal) corresponding to the load through the two electrodes 52. Based on the output electrical signal, the pressure in the combustion chamber is specified.

A-3. Manufacturing Method of Pressure Sensor 10 Next, a manufacturing method of the pressure sensor 10 will be described. FIG. 5 is a flowchart of the manufacturing method of the pressure sensor 10 of the first embodiment. Drawing 6 is an explanatory view of the manufacturing method of pressure sensor 10 of a 1st embodiment.

  In S110 of FIG. 5, members 20 to 90 constituting the pressure sensor 10 described above are prepared.

  In S <b> 120, the cylindrical spring 80, the piezoelectric unit 50, the transmission rod 90, and the diaphragm 40 are disposed in the housing 30. Specifically, as shown in FIG. 6A, the housing 30 is held by the housing holding member 210 in a state where the front end side is vertically upward and the rear end side is vertically downward. In this state, the cylindrical spring 80 is first disposed in the shaft hole 31 of the housing 30 from the opening on the front end side of the housing 30, and then the terminal portion 56 is inserted into the shaft hole 81 of the cylindrical spring 80. The piezoelectric unit 50 is arranged so as to be inserted. As a result, the piezoelectric unit 50 is disposed in the housing 30, and the cylindrical spring 80 is disposed between the piezoelectric unit 50 in the housing 30 and the bottom 32 of the housing 30. Note that, as shown in FIG. 6A, a thin wire CW <b> 2 is welded to the terminal portion 56 of the piezoelectric unit 50 in advance.

  Further, the transmission rod 90 is disposed in the shaft hole 31 of the housing 30 so that the rear end of the transmission rod 90 abuts on the holding plate 54 on the front end side of the piezoelectric unit 50. And the front-end | tip part of the transmission rod 90 is inserted in the through-hole 41 of the diaphragm 40, and the diaphragm 40 is arrange | positioned so that the diaphragm 40 may cover the opening of the front end side of the axial hole 31 of the housing | casing 30 (FIG. 6). (A)).

  In S <b> 130, the diaphragm 40 is welded to the housing 30. Specifically, as indicated by an arrow Lz in FIG. 6A, a melted portion MT2 (FIG. 2) is formed by laser welding, and the outer edge portion of the diaphragm 40 is joined and fixed to the distal end portion of the housing 30. Is done.

  In S140, as indicated by an arrow Pr in FIG. 6B, the transmission rod 90 abutted on the front end side of the piezoelectric unit 50 is moved from the front end side to the rear end side using a press machine (not shown). When the pressure is applied, the transmission rod 90 is pressed by a specific stroke amount ST (hereinafter, also simply referred to as a press amount ST, for example, 5 mm). The press amount ST is, for example, a predetermined value such that the charge output from the piezoelectric element 51 becomes a target value, or a value determined while monitoring the charge output from the piezoelectric element 51. Accordingly, the piezoelectric unit 50 moves in the rear end direction Dr by the press amount ST. Therefore, the cylindrical spring 80 between the piezoelectric unit 50 and the bottom 32 of the housing 30 is compressed in the axial direction by the press amount ST. As a result, a predetermined preload is applied to the piezoelectric element 51 of the piezoelectric unit 50 sandwiched between the cylindrical spring 80 and the transmission rod 90.

  In S150, the diaphragm 40 and the transmission rod 90 are welded with the transmission rod 90 being pressed by the press amount ST. Specifically, in a state where the transmission rod 90 is pressed by the press amount ST, in other words, while pressing the transmission rod 90 from the front end side toward the rear end side, the arrow Lz in FIG. As shown in FIG. 2, a melted portion MT3 (FIG. 2) is formed by laser welding. As a result, the outer peripheral surface of the transmission rod 90 is joined and fixed to the fixed portion 42 of the diaphragm 40.

  In S160, the housing 30 is inverted. Specifically, as shown in FIG. 6C, the casing 30 and the members 80, 90, 50, and 40 arranged in the casing 30 are arranged such that the front end side is vertically downward and the rear end side is vertical. It is held by the housing holding member 220 in the upward state.

  In S <b> 170, the support rod 70 is disposed on the rear end side of the piezoelectric unit 50. Specifically, as shown in FIG. 6 (C), it is inserted into the through hole 321 of the bottom 32 of the housing 30 from the rear end side toward the front end side. The tip of the support rod 70 contacts the insulating plate 55 of the piezoelectric unit 50 by gravity. The support rod 70 is disposed in the shaft hole 81 of the cylindrical spring 80 and on the outer side in the radial direction of the terminal portion 56 of the piezoelectric unit 50.

  In S180, the housing 30 and the support rod 70 are welded. Specifically, in a state where the tip of the support rod 70 is in contact with the insulating plate 55 of the piezoelectric unit 50 due to gravity, as shown by an arrow Lz in FIG. The outer peripheral surface of the support rod 70 is joined and fixed to the fixing portion 322 of the bottom portion 32. Thereby, the tip unit 100 is completed.

  In S190, the pressure sensor 10 is completed by assembling other members and the tip unit 100. Specifically, the rear end of the thin conductor CW2 drawn from the rear end side of the tip unit 100 and the inner conductor 65 of the cable 60 are connected via the flat plate conductor CW1. Further, the tip end portion of the ground conductor CW3 of the cable 60 and the bottom portion 32 of the housing 30 are welded. Furthermore, after the cable 60 is passed through the shaft hole 21 of the cylindrical metal fitting 20, the casing 30 of the tip unit 100 is welded to the tip of the cylindrical metal fitting 20. Thereafter, molten rubber is injected into the shaft hole 21 of the cylindrical metal fitting 20 to fill the shaft hole 21 with a rubber layer (not shown), and the pressure sensor 10 is completed.

  In the pressure sensor 10 according to the first embodiment described above, the cylindrical spring 80 is between the piezoelectric unit 50 and the bottom portion 32 of the housing 30 and at a position outside the radial direction of the support rod 70. Have been placed. As a result, according to this pressure sensor 10, before the support rod 70 is fixed to the housing 30 at the time of manufacture (S180 in FIG. 5), the transmission rod 90 moves from the front end side to the rear end side. When the transmission member is fixed to the diaphragm in a pressed (pressed) state (S140, S150 in FIG. 5, FIG. 6B), the cylindrical spring 80 causes variations in preload on the piezoelectric element 51. And the variation in the electric charge output from the piezoelectric element 51 can be reduced.

  Further, according to the manufacturing method of the pressure sensor 10 described above (FIG. 5), the piezoelectric unit 50 with the cylindrical spring 80 disposed between the piezoelectric unit 50 in the housing 30 and the bottom 32 of the housing 30. The transmission rod 90 is fixed to the diaphragm 40 while being pressed (pressed) from the front end side to the rear end side with respect to the transmission rod 90 abutting on the front end side (S140 and S150 in FIG. 5). 6 (B)). Thereafter, the support rod 70 is brought into contact with the rear end side of the piezoelectric unit 50, and the support rod 70 is fixed to the housing 30 (S180 in FIG. 5). As a result, it is possible to reduce the variation in preload on the piezoelectric element 51 and to reduce the variation in charge output from the piezoelectric element 51.

  This will be described more specifically. FIG. 7 is a diagram for explaining the effect of the present application. FIG. 7A is a graph showing the relationship between the press amount ST in the present embodiment of FIG. 6B and the preload applied to the piezoelectric element 51. FIG. 7A also shows the relationship between the press amount ST in the comparative embodiment and the preload applied to the piezoelectric element 51. As shown in FIG. 7B, in the comparative embodiment, the cylindrical spring 80 and the support rod 70 are not present. In the comparative embodiment, the insulating plate 55 on the rear end side of the piezoelectric unit 50 is in direct contact with the bottom 32X of the housing 30X.

  In the present embodiment, when the press amount ST increases, the cylindrical spring 80 is compressed and deformed by the press amount ST. Therefore, a load applied to the piezoelectric element 51 in accordance with the compression amount (= press amount ST) of the cylindrical spring 80 becomes a preload to the piezoelectric element 51. Therefore, in the present embodiment, as the press amount increases, the preload of the piezoelectric element 51 increases with a gentle inclination based on the spring constant of the cylindrical spring 80 (FIG. 7A). Therefore, even if there is a certain amount of error ΔST in the press amount ST, the preload of the piezoelectric element 51 becomes a stable value without greatly fluctuating.

  In the comparative embodiment, the piezoelectric unit 50 is sandwiched between the transmission rod 90 that is a substantially rigid body and the bottom 32X of the housing 30X. For this reason, in the comparative embodiment, when the press amount ST increases, the load applied to the piezoelectric element 51 increases abruptly as compared with the present embodiment (FIG. 7A). Therefore, it can be seen that the preload of the piezoelectric element 51 varies greatly with a slight error ΔST of the press amount ST. As can be understood from the above description, according to the present embodiment, it is possible to apply the appropriate preload to the piezoelectric element 51 by reducing variations in the preload on the piezoelectric element 51 as compared with the comparative embodiment. As a result, variation in electric charges output from the piezoelectric element 51 can be reduced.

  Further, the cylindrical spring 80 is a cylindrical member extending along the axis, and has a shaft hole 81 inside. A rod-like (in this embodiment, hollow rod-like (= cylindrical)) support rod 70 is inserted into the cylindrical spring 80. Thereby, the cylindrical spring 80 can be disposed in the housing 30 in a compact manner. In addition, since pressure can be applied to the entire pressing plate 54 of the piezoelectric unit 50 in a balanced manner, variation in preload on the piezoelectric element 51 can be appropriately reduced.

  Furthermore, as described above, when the inner diameter of the cylindrical spring 80 is R11 and the outer diameter of the support rod 70 is R12, (R12 / R11) ≧ 0.5 is satisfied. Thereby, the variation in the radial position of the cylindrical spring 80 with respect to the support rod 70, that is, the variation in the radial position of the cylindrical spring 80 with respect to the axis CL can be reduced. As a result, the variation in preload on the piezoelectric element 51 can be further reduced.

  Further, as described above, in the cross section including the axis CL, the minimum values θ11 and θ14 of the angle formed by the surface of the bottom 32 of the housing 30 and the end of the cylindrical spring 80, and the surface of the piezoelectric unit 50 The minimum values θ22 and θ23 of the angle formed by the end of the cylindrical spring 80 are 30 degrees or less. When the minimum values θ11, θ14, θ22, and θ23 are excessively large, specifically, when they exceed 30 degrees, the radial force is applied when the cylindrical spring 80 is compressed by the press. Is easily applied to the contact portion, and the cylindrical spring 80 is easily displaced in the radial direction. In this embodiment, since the minimum values θ11, θ14, θ22, and θ23 are 30 degrees or less, the contact between the end portion of the cylindrical spring 80 and the surface that contacts the end portion is stable, and such a position is obtained. The occurrence of deviation can be suppressed. As a result, it is possible to further reduce the variation in preload on the piezoelectric element.

  Furthermore, in this embodiment, the cylindrical spring 80 is located between the piezoelectric unit 50 and the bottom part 32 of the housing 30 as described above. That is, it is not located between the piezoelectric unit 50 and the diaphragm 40 as in the second embodiment described later. Therefore, the cylindrical spring 80 does not affect the diaphragm 40.

B. Second embodiment:
B-1. Configuration of Pressure Sensor FIG. 8 is an enlarged view of the vicinity of the tip unit 100B of the pressure sensor of the second embodiment. The cylindrical spring 80 </ b> B of the second embodiment is disposed between the piezoelectric unit 50 and the diaphragm 40 and on the outer side in the radial direction of the transmission rod 90. Specifically, the tip of the cylindrical spring 80B is in contact with the surface on the rear end side of the diaphragm 40, and the rear end of the cylindrical spring 80B is in contact with the surface on the front end side of the pressing plate 54. The cylindrical spring 80 </ b> B is compressed by a small amount in the axial direction by the diaphragm 40 and the insulating plate 55. A transmission rod 90 is inserted and disposed in the shaft hole 81B of the cylindrical spring 80B.

  The general shape of the cylindrical spring 80B is the same as the cylindrical spring 80 of the first embodiment, and the side wall has a substantially cylindrical shape having a bellows shape.

  Further, assuming that the inner diameter of the cylindrical spring 80B is R21 and the outer diameter of the transmission rod 90 is R22, (R22 / R21) ≧ 0.5 is satisfied. That is, the outer diameter R22 of the transmission rod 90 is more than half of the inner diameter R21 of the cylindrical spring 80B.

  Furthermore, although illustration is omitted, in the cross section including the axis CL, the surface of the diaphragm 40 and the cylindrical spring 80B at the contact portion between the surface S1 on the rear end side of the diaphragm 40 and the tip of the cylindrical spring 80B. The minimum angle among the angles formed by the tip is 30 degrees or less, as in FIG. 4B of the first embodiment. Further, in the cross section including the axis line CL, the surface of the pressing plate 54 at the contact portion between the front surface of the piezoelectric unit 50 (that is, the front surface of the pressing plate 54) and the rear end of the cylindrical spring 80B. And the minimum angle among the angles formed by the rear end of the cylindrical spring 80B is 30 degrees or less.

B-2. Manufacturing Method of Pressure Sensor FIG. 9 is a flowchart of the manufacturing method of the pressure sensor according to the second embodiment. 10 of 2nd Embodiment is explanatory drawing of the manufacturing method of the pressure sensor of 2nd Embodiment.

  In S200 of FIG. 9, members 20 to 90 constituting the pressure sensor 10 described above are prepared.

  In S210, the piezoelectric unit 50, the cylindrical spring 80B, and the diaphragm 40 are arranged in the housing 30. Specifically, as shown in FIG. 10A, the housing 30 is held by the housing holding member 230 in a state where the front end side is vertically upward and the rear end side is vertically downward. In this state, the piezoelectric unit 50 is first disposed in the shaft hole 31 of the housing 30 from the opening on the front end side of the housing 30, and then the cylindrical spring is placed on the pressing plate 54 of the piezoelectric unit 50. 80B is arranged. The diaphragm 40 is disposed so that the diaphragm 40 covers the opening on the tip end side of the shaft hole 31 of the housing 30 (FIG. 10A).

  In S <b> 220, the diaphragm 40 is welded to the housing 30. Specifically, as indicated by an arrow Lz in FIG. 10A, a melted portion MT2 (FIG. 8) is formed by laser welding, and the outer edge portion of the diaphragm 40 is joined and fixed to the distal end portion of the housing 30. Is done. As a result, the piezoelectric unit 50 is disposed in the housing 30, and the cylindrical spring 80 </ b> B is disposed between the piezoelectric unit 50 in the housing 30 and the diaphragm 40 fixed to the housing 30. .

  In S230, the housing 30 is inverted. Specifically, as shown in FIG. 10 (B), the housing 30 and the members 80B, 50, 40 disposed in the housing 30 have the front end side vertically downward and the rear end side vertically upward. In this state, it is held by the housing holding member 240.

  In S240, the support rod 70 is disposed on the rear end side of the piezoelectric unit 50. Specifically, as shown in FIG. 10B, the support rod 70 is inserted into the through hole 321 of the bottom 32 of the housing 30 from the rear end side toward the front end side. The front end of the support rod 70 is in contact with the surface on the rear end side of the insulating plate 55 of the piezoelectric unit 50 in the shaft hole 31 of the housing 30.

  In S250, as shown in FIG. 10B, the support rod 70 in contact with the rear end side of the piezoelectric unit 50 is applied from the rear end side to the front end side using a press machine (not shown). By pressing, the support rod 70 is pressed by the press amount ST. The press amount ST is, for example, a predetermined value such that the charge output from the piezoelectric element 51 becomes a target value, or a value determined while monitoring the charge output from the piezoelectric element 51. As a result, the piezoelectric unit 50 moves in the tip direction Df by the press amount ST. Therefore, the cylindrical spring 80B between the piezoelectric unit 50 and the diaphragm 40 is compressed by the press amount ST in the axial direction. As a result, a predetermined preload is applied to the piezoelectric element 51 of the piezoelectric unit 50 sandwiched between the cylindrical spring 80 </ b> B and the diaphragm 40.

  In S260, the housing 30 and the support rod 70 are welded with the support rod 70 being pressed by the press amount ST. That is, as indicated by an arrow Lz in FIG. 10B, a melted portion MT4 (FIG. 8) is formed by laser welding, and the outer peripheral surface of the support rod 70 is joined and fixed to the fixing portion 322 of the bottom portion 32. Is done.

  In S270, the housing 30 is inverted again. Specifically, as shown in FIG. 10C, the casing 30 and the members 80B, 70, 50, and 40 arranged in the casing 30 are arranged such that the front end side is vertically upward and the rear end side is vertical. In the state of being faced down, it is held by the housing holding member 230.

  In S280, the transmission rod 90 is disposed on the tip side of the piezoelectric unit 50. Specifically, as shown in FIG. 10C, the transmission rod 90 is inserted into the through hole 41 of the diaphragm 40 from the front end side toward the rear end side. Due to gravity, the rear end of the transmission rod 90 comes into contact with the front end surface of the pressing plate 54 of the piezoelectric unit 50. The transmission rod 90 is disposed in the shaft hole 81B of the cylindrical spring 80B.

  In S290, the diaphragm 40 and the transmission rod 90 are welded. Specifically, in a state where the rear end of the transmission rod 90 is in contact with the pressing plate 54 of the piezoelectric unit 50 by gravity, as shown by an arrow Lz in FIG. ) Is formed, and the outer peripheral surface of the transmission rod 90 is joined and fixed to the fixing portion 42 of the diaphragm 40. Thereby, the tip unit 100B is completed.

  In S300, as in S190 of FIG. 5, the other members and the tip unit 100B are assembled to complete the pressure sensor.

  In the pressure sensor 10 according to the second embodiment described above, the cylindrical spring 80B is disposed between the piezoelectric unit 50 and the diaphragm 40, and at a position outside the transmission rod 90 in the radial direction. Yes. According to this pressure sensor, before the transmission rod 90 is fixed to the diaphragm 40 (S290 in FIG. 9), pressure is applied to the support rod 70 from the rear end side to the front end side (press). ), The transmission member is fixed to the diaphragm (S250 and S260 in FIG. 9 and FIG. 10B). As a result, similar to the first embodiment, the cylindrical spring 80 </ b> B can reduce the variation in preload on the piezoelectric element 51 and reduce the variation in charge output from the piezoelectric element 51.

  Further, according to the manufacturing method of the pressure sensor 10 described above (FIG. 9), the support rod 70 is attached to the piezoelectric unit 50 in a state where the piezoelectric unit 50 and the cylindrical spring 80 </ b> B are disposed in the housing 30. The support rod 70 is fixed to the housing 30 while being brought into contact with the rear end side and pressing (pressing) the support rod 70 from the rear end side toward the front end side (S250 in FIG. 9). S260, FIG. 10 (B)). Thereafter, the transmission rod 90 is brought into contact with the distal end side of the piezoelectric unit 50, and the transmission rod 90 is fixed to the diaphragm 40 (S290 in FIG. 9). As a result, similarly to the first embodiment, it is possible to reduce the variation in the preload on the piezoelectric element 51 and to reduce the variation in the charge output from the piezoelectric element 51.

  Furthermore, similarly to the first embodiment, the cylindrical spring 80B is a cylindrical member extending along the axis, and has a shaft hole 81B inside. A rod-shaped (in this embodiment, columnar) transmission rod 90 is inserted into the cylindrical spring 80B. In this way, the cylindrical spring 80B can be arranged in the housing 30 in a compact manner. In addition, since pressure can be applied to the entire pressing plate 54 of the piezoelectric unit 50 in a balanced manner, variation in preload on the piezoelectric element 51 can be appropriately reduced.

  Furthermore, as described above, when the inner diameter of the cylindrical spring 80B is R21 and the outer diameter of the transmission rod 90 is R22, (R22 / R21) ≧ 0.5 is satisfied. In this way, variation in the radial position of the cylindrical spring 80B relative to the transmission rod 90, that is, variation in the radial position of the cylindrical spring 80B relative to the axis CL can be reduced. As a result, the variation in preload on the piezoelectric element 51 can be further reduced.

  Further, as described above, in the cross section including the axis CL, the minimum angle formed by the surface of the diaphragm 40 and the end of the cylindrical spring 80B, the surface of the piezoelectric unit 50, and the end of the cylindrical spring 80B. The minimum value of the angle formed by the part is 30 degrees or less. As a result, similarly to the first embodiment, it is possible to further reduce the variation in preload on the piezoelectric element.

C. Variations:
(1) In each of the above embodiments, the cylindrical springs 80 and 80B are used as the elastic member, but this is an example, and the present invention is not limited to this. Instead of the cylindrical springs 80 and 80B, another type of elastic member may be used. 11 and 12 are diagrams showing a modification of the elastic member. For example, as shown in FIG. 11A, a helical spring 80C may be used as the elastic member. Moreover, as shown in FIG. 11B, a cylindrical body 80D in which the cross-sectional shape of the side wall is curved in an S shape in the cross section including the axis line CL may be used. Further, as shown in FIG. 12, a plurality of elastic members may be used. In the example of FIG. 12, a plurality of helical springs 80 </ b> E <b> 1 and 80 </ b> E <b> 2 are disposed between the bottom portion 32 of the housing 30 and the insulating plate 55 of the piezoelectric unit 50 and outside the radial direction of the support rod 70. Has been.

  Further, the elastic member is not limited to a metal spring, and for example, a cylindrical member formed using a material having an elastic coefficient smaller than that of the support rod 70 or the transmission rod 90, for example, heat-resistant rubber. May be.

  Thus, generally speaking, various members having a larger deformation amount with respect to the axial force than the transmission rod 90 and the support rod 70 can be used as the elastic member.

(2) The specific configurations of the members of the above-described embodiments, for example, the shapes of the members 50 to 70 and 90, are examples, and various other configurations may be employed. Moreover, the material such as stainless steel exemplified for each member is an example, and other various materials can be adopted. For example, the transmission rod 90 may be a part or all of a hollow cylindrical member, or may have a prismatic shape or a rectangular tube shape.

  Further, as the configuration of the piezoelectric unit 50, other various configurations can be adopted instead of the configurations of FIGS. For example, at least one of the front end side pressing plate 54 and the rear end side pressing plate 54 may be omitted. Further, the terminal portion 56 may be directly connected to the electrode 52. Further, the electrode 52 and the piezoelectric element 51 may be an annular plate member surrounding the axis line CL, instead of a disk-shaped plate member disposed on the axis line CL. In general, the piezoelectric unit 50 preferably includes a piezoelectric element and is configured to output a signal from the piezoelectric element to the outside of the pressure sensor.

(3) As a configuration for connecting the diaphragm 40 and the piezoelectric element 51, other various configurations can be adopted instead of the configuration described in FIG. For example, the holding plate 54 on the distal end side may be omitted, and the transmission rod 90 may be in contact with only the electrode 52 on the distal end side among the elements of the piezoelectric unit 50. Further, the pressing plate 54 and the electrode 52 on the distal end side may be omitted, and the piezoelectric element 51 may be directly connected to the transmission rod 90. In this case, the transmission rod 90 functions as an electrode.

(4) As a configuration for guiding the signal from the piezoelectric unit 50 to the outside of the pressure sensor 10, various other configurations can be adopted instead of the configuration using the cable 60. For example, a terminal metal fitting may be disposed on the rear end side of the pressure sensor 10, and the terminal metal fitting and the terminal portion 56 of the piezoelectric unit 50 may be connected by a central shaft. In this case, a signal from the piezoelectric unit 50 can be acquired through the terminal fitting and the cylindrical fitting 20.

  As mentioned above, although this invention was demonstrated based on embodiment and a modification, embodiment mentioned above is for making an understanding of this invention easy, and does not limit this invention. The present invention can be changed and improved without departing from the spirit and scope of the claims, and equivalents thereof are included in the present invention.

  DESCRIPTION OF SYMBOLS 10 ... Pressure sensor, 20 ... Cylindrical metal fitting, 21 ... Shaft hole, 22 ... Screw part, 22 ... Minimum value (theta), 24 ... Tool engaging part, 30 ... Case, 30X ... Case, 31 ... Shaft hole, 32 ... Bottom, 34 ... Diameter enlarged portion, 40 ... Diaphragm, 41 ... Through hole, 42 ... Fixed 50 ... Piezoelectric unit, 51 ... Piezoelectric element, 52 ... Electrode, 53 ... Lead part, 54 ... Presser plate, 55 ... Insulating plate, 56 ... Terminal part, 57 ... disk part, 60 ... cable, 61 ... jacket, 62 ... outer conductor, 63 ... conductive coating, 64 ... insulator, 65 ... inner conductor, 70 ... Support rod, 71 ... shaft hole, 80, 80B ... cylindrical spring, 80C ... helical spring, 80D ... cylindrical body, 81, 81B ... shaft hole, 90 ... transmission Rod, 92 ... Projection, 100, 100B ... Tip unit, 100B ... Tip unit, 210-240 ... Housing holding member, 32 ... through hole, 322 ... fixed part, 80E1, 80E2 ... helical spring, MT1-MT5 ... melting part, CW1 ... flat conductor, CW2 ... small conductor, CW3 ... .Grounding conductor

Claims (8)

A cylindrical casing having a bottom portion extending along the axis and extending radially inward on the rear end side of the axis; a piezoelectric unit disposed in the casing and including a piezoelectric element; and A pressure sensor comprising: a diaphragm fixed to the front end side of the piezoelectric unit and deformed according to the received pressure; and a transmission member fixed to the diaphragm and having a rear end contacting the front end side of the piezoelectric unit. There,
A support member fixed to the housing and having a tip abutting on a rear end side of the piezoelectric unit;
An elastic member having a larger amount of deformation with respect to the force in the direction of the axis than the transmission member and the support member;
The elastic member is between the piezoelectric unit and the bottom of the housing and between the piezoelectric unit and the diaphragm at a first position that is radially outside the support member. And it is arrange | positioned in one of the 2nd positions which are the outer sides of the radial direction of the said transmission member, The pressure sensor characterized by the above-mentioned. The pressure sensor according to claim 1,
The elastic member is a cylindrical member extending along the axis,
The support member is a rod-shaped member extending along the axis,
The pressure sensor, wherein the support member is inserted into the elastic member at the first position. The pressure sensor according to claim 1,
The elastic member is a cylindrical member extending along the axis,
The transmission member is a rod-shaped member extending along the axis,
The pressure sensor, wherein the transmission member is inserted into the elastic member at the second position. The pressure sensor according to claim 2 or 3,
The inner diameter of the cylindrical elastic member is R1,
When the outer diameter of the rod-shaped support member or the transmission member is R2,
A pressure sensor satisfying (R2 / R1) ≧ 0.5. The pressure sensor according to any one of claims 1 to 4,
In the cross section including the axis, the minimum value of the angle formed by the surface of the member that contacts the end of the elastic member and the end of the elastic member among the casing, the piezoelectric unit, and the diaphragm is θ And when
The pressure sensor is characterized in that the angle θ is 30 degrees or less. The pressure sensor according to any one of claims 1 to 5,
The pressure sensor according to claim 1, wherein the elastic member is in the first position. A cylindrical casing having a bottom portion extending along the axis and extending radially inward on the rear end side of the axis; a piezoelectric unit disposed in the casing and including a piezoelectric element; and A pressure sensor comprising: a diaphragm fixed to the front end side of the piezoelectric unit and deformed according to the received pressure; and a transmission member fixed to the diaphragm and having a rear end in contact with the front end side of the piezoelectric unit. A manufacturing method comprising:
(A) The casing, the diaphragm, the piezoelectric unit, the transmission member, a support member for supporting the rear end side of the piezoelectric unit, and an axial force from the transmission member and the support member A step of preparing an elastic member having a large deformation amount with respect to
(B) Disposing the piezoelectric unit in the housing and disposing the elastic member between the piezoelectric unit in the housing and the bottom of the housing;
(C) With the piezoelectric unit and the elastic member disposed in the housing, the transmission member is brought into contact with the front end side of the piezoelectric unit, and the front end side to the rear end side with respect to the transmission member Fixing the transmission member to the diaphragm while applying pressure toward the diaphragm;
(D) bringing the support member into contact with the rear end side of the piezoelectric unit and fixing the support member to the housing;
A manufacturing method comprising: A cylindrical housing having a bottom portion extending along the axis and extending radially inward on the rear end side of the axis, a piezoelectric unit disposed in the housing and including a piezoelectric element, and the housing Manufacture of a pressure sensor comprising: a diaphragm fixed to the front end side of the piezoelectric unit and deformed according to the received pressure; and a transmission member fixed to the diaphragm and having a rear end abutting on the front end side of the piezoelectric unit A method,
(A) The casing, the diaphragm, the piezoelectric unit, the transmission member, a support member for supporting the rear end side of the piezoelectric unit, and an axial force from the transmission member and the support member A step of preparing an elastic member having a large deformation amount with respect to
(B) disposing the piezoelectric unit in the housing and disposing the elastic member between the piezoelectric unit in the housing and the diaphragm fixed to the housing;
(C) In a state where the piezoelectric unit and the elastic member are arranged in the housing, the support member is brought into contact with the rear end side of the piezoelectric unit, and the rear end side to the front end side with respect to the support member Fixing the support member to the housing while pressurizing toward the housing;
(D) bringing the transmission member into contact with the distal end side of the piezoelectric unit and fixing the transmission member to the diaphragm;
A manufacturing method comprising:

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