JP2017020894A - Pressure sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pressure sensor that can suppress an error due to a thermal expansion of a diaphragm.SOLUTION: A pressure sensor comprises: a cylindrical housing 30; a diaphragm 42 that is bonded on a tip end side of the housing 30, and bends in accordance with a pressure receiving the pressure; a sensor unit 50 that is arrange in the housing 30, and has an electric characteristic varying by the pressure; and a connection part that connects the diaphragm 42 to the sensor unit 50. The connection unit includes a hollow rod 90 that has an end part on a tip end side opened, has an end part on a rear end side closed, and extends in an axial line direction. The diaphragm 42 is connected to a hollow first part 91 of the hollow rod 90. The sensor unit 50 is connected to a second part 92 on the rear end side further than the first part 91 of the hollow rod.SELECTED DRAWING: Figure 2

Description

  The present disclosure relates to a pressure sensor that measures a pressure in a combustion chamber of an internal combustion engine.

  A pressure sensor that includes a housing, a diaphragm, a sensor element, and a transmission member has been proposed. The transmission member is attached to the diaphragm. When pressure is applied to the diaphragm, the transmission member is displaced in a predetermined direction and applies force to the sensor element. The surface portion on the combustion chamber side of the diaphragm can be thermally expanded by contact with the combustion gas. The contact surface between the diaphragm and the transmission member can be displaced by such thermal expansion of the surface portion. Such displacement may increase the output error of the sensor. In order to suppress such an output error, a technique for providing a diaphragm with a specific shape portion (folded shape portion or depression) has been proposed.

JP 2004-347387 A JP-A-7-19981 Japanese Utility Model Publication No. 6-43538 Japanese Utility Model Publication No. 6-43539 JP-A-6-207875

  However, there has been room for contrivance regarding the suppression of errors.

  The present disclosure provides a new technique for suppressing an error due to thermal expansion of a diaphragm.

  For example, the present disclosure discloses the following application examples.

[Application Example 1]
A cylindrical housing, a diaphragm that is bonded to the front end side of the housing and bends according to the pressure received, a sensor unit that is disposed in the housing and has an electrical characteristic that varies depending on the pressure, and the diaphragm A pressure sensor comprising: a connecting portion that connects the sensor portion;
The connecting portion includes a hollow rod that extends in the direction of the axis, with the end on the front end side opened and the end on the rear end side closed.
The diaphragm is connected to a hollow first portion of the hollow rod,
The sensor unit is connected to the second part of the hollow rod on the rear end side of the first part,
Pressure sensor.

  According to this configuration, when the surface portion on the distal end side of the diaphragm is thermally expanded, the hollow first portion of the hollow rod is deformed, so that the displacement of the hollow rod due to the thermal expansion can be suppressed. As a result, errors due to thermal expansion of the diaphragm can be suppressed.

[Application Example 2]
The pressure sensor according to Application Example 1,
The thickness of the hollow portion of the hollow rod is thinner toward the tip side,
Pressure sensor.

  According to this configuration, the rigidity of the first portion of the hollow rod connected to the diaphragm can be reduced, so that the displacement of the hollow rod due to thermal expansion is caused by the deformation of the first portion of the hollow rod. Can be suppressed appropriately.

[Application Example 3]
The pressure sensor according to Application Example 2,
The inner diameter of the hollow rod increases stepwise toward the tip side.
Pressure sensor.

  According to this configuration, the rigidity of the first portion of the hollow rod connected to the diaphragm can be reduced, so that the displacement of the hollow rod due to thermal expansion is caused by the deformation of the first portion of the hollow rod. Can be suppressed appropriately.

[Application Example 4]
The pressure sensor according to any one of Application Examples 1 to 3,
A distance parallel to the axis from the bottom surface on the rear end side inside the hollow rod to the diaphragm is equal to or greater than a thickness in a direction parallel to the axis of the diaphragm.
Pressure sensor.

  The first portion of the hollow rod can be reinforced by a closed end on the rear end side of the hollow rod. According to the above configuration, since the reinforcement by the closed end on the rear end side of the hollow rod is weak compared to the case where the distance parallel to the axis line from the bottom surface inside the hollow rod to the diaphragm is short, One part is easily deformed. As a result, the deformation of the first portion of the hollow rod can appropriately suppress the displacement of the hollow rod due to thermal expansion.

  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 10 as 1st Embodiment. 3 is an enlarged cross-sectional view of a tip portion of the pressure sensor 10. FIG. 3 is an exploded perspective view of an element unit 50. FIG. It is explanatory drawing of operation | movement of the pressure sensor. It is explanatory drawing of operation | movement of the pressure sensor 10x of a reference example. FIG. 6 is a cross-sectional view of another embodiment of a rod.

A. First embodiment:
FIG. 1 is an explanatory diagram showing a pressure sensor 10 as the first embodiment. 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, as main components, a cylindrical first metal fitting 20 and a second metal fitting 30, a pressure receiving portion 40, a rod 90, an element portion 50, a cable 60, It has. The central axis CL is the central axis of the pressure sensor 10. Hereinafter, the central axis CL is also referred to as an axis line CL, and a direction parallel to the axis line CL is also referred to as an “axis direction”. The radial direction of the circle centered on the axis CL is also simply referred to as “radial direction”, and the circumferential direction of the circle centered on the axis CL is also simply referred to as “circumferential direction”. A direction from the first metal fitting 20 to the second metal fitting 30 along the axis CL is referred to as a “front end direction Df”, and a direction opposite to the front end direction Df is referred to as a “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. In the present embodiment, the central axis CL of the pressure sensor 10 is also the central axis of each of the first metal fitting 20, the second metal fitting 30, the pressure receiving part 40, the rod 90, and the element part 50.

  The first metal fitting 20 and the second metal fitting 30 have a cylindrical shape in which a cross section perpendicular to the central axis CL (hereinafter also referred to as a transverse cross section) is annular and extends in the axial direction. In the present embodiment, the first metal fitting 20 and the second metal fitting 30 are made of stainless steel. However, other materials (for example, steel such as low carbon steel, various metal materials) may be adopted.

  The first metal fitting 20 is formed with a shaft hole 21 that is a through-hole centered on the central axis CL. In addition, a screw portion 22 and a tool engagement portion 24 are provided on the outer peripheral surface of the first metal 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) that engages with a tool (not shown) used for attaching and detaching the pressure sensor 10.

  FIG. 2 is an enlarged cross-sectional view of the distal end portion of the pressure sensor 10, specifically, the portion indicated as the region X in FIG. This cross section is a flat cross section including the axis CL. The second metal fitting 30 is disposed on the front end side of the first metal fitting 20, and is joined to the front end of the first metal fitting 20 via the melting portion 26. A diameter-expanded portion 34 that increases in diameter from the front end side toward the rear end side is formed at the front end portion of the second metal fitting 30. 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. Further, the second metal fitting 30 is formed with a shaft hole 31 which is a through hole centered on the central axis CL. The shaft hole 31 includes a large inner diameter portion 35 and a small inner diameter portion 36 connected to the rear end side of the large inner diameter portion 35 and having an inner diameter smaller than the inner diameter of the large inner diameter portion 35. A step portion 39 is provided between the large inner diameter portion 35 and the small inner diameter portion 36. The step portion 39 forms a surface facing the tip direction Df side. In the shaft hole 31, a pressure receiving part 40, a rod 90, and an element part 50 are arranged in order from the front end side to the rear end side.

  The pressure receiving part 40 includes a diaphragm 42 and a fixing part 41. The diaphragm 42 is an annular film centered on the axis CL. The outer edge 42o of the diaphragm 42 is welded to the tip of the second metal fitting 30 over the entire circumference (for example, laser welding). A fixed portion 41 is connected to an edge 42 i on the inner peripheral side of the diaphragm 42. The fixed portion 41 is a cylindrical portion centered on the axis CL, and extends from the edge 42i of the diaphragm 42 toward the distal direction Df. The fixed portion 41 and the diaphragm 42 are integrally formed using stainless steel (for example, forging or shaving). However, after the fixing portion 41 and the diaphragm 42 are separately formed, the fixing portion 41 and the diaphragm 42 may be integrated by welding or the like. Moreover, you may employ | adopt other materials (For example, steel, such as low carbon steel, various metal materials).

  A rod 90 is disposed on the inner peripheral side of the pressure receiving unit 40. The rod 90 includes a hollow cylindrical portion 96 and a lid portion 97 that closes an end portion on the rear end side of the cylindrical portion 96. The rod 90 is a member extending along the axis CL, and is a hollow rod having a hollow cylindrical portion 96. The inner diameter Di and the outer diameter Do of the cylindrical portion 96 are constant regardless of the position in the distal direction Df. The end of the rod 90 on the tip side is open. The cylinder portion 96 and the lid portion 97 are integrally formed using stainless steel (for example, forging or shaving). In addition, after forming the cylinder part 96 and the cover part 97 separately, you may integrate the cylinder part 96 and the cover part 97 by welding etc. FIG. Moreover, you may employ | adopt other materials (For example, steel, such as low carbon steel, various metal materials).

  The fixing portion 41 of the pressure receiving portion 40 and the cylindrical portion 96 of the rod 90 are welded over the entire circumference (for example, laser welding). Thus, the diaphragm 42 is joined to the rod 90 through the fixing portion 41. Hereinafter, the portion 91 of the rod 90 where the pressure receiving portion 40 is joined is also referred to as a first portion 91. The element unit 50 is connected to the rear end side of the rod 90. Hereinafter, the portion 92 of the rod 90 to which the element unit 50 is connected is also referred to as a second portion 92. In the present embodiment, the second portion 92 is the rear end portion of the rod 90.

  The pressure receiving portion 40 and the rod 90 close the shaft hole 31 at the tip of the second metal fitting 30. The diaphragm 42 is exposed in the combustion chamber of the internal combustion engine, and the surface 42f on the tip end direction Df side of the diaphragm 42 forms a pressure receiving surface. And the diaphragm 42 deform | transforms according to the pressure in a combustion chamber. The rod 90 is displaced along the axis CL according to the deformation of the diaphragm 42, thereby transmitting a load corresponding to the pressure received by the diaphragm 42 to the element portion 50 on the rear end side. As the diaphragm 42 is made thinner, the diaphragm 42 is more easily deformed, so that the sensitivity of the pressure sensor 10 can be increased. Note that the pressure receiving portion 40 and the rod 90 may be integrally formed (for example, forging or shaving).

  The element unit 50 includes two electrodes 52, a piezoelectric element 51 sandwiched between the two electrodes 52, a pressing plate 54 disposed on the front end side of the front end electrode 52, and an electrode 52 on the rear end side. A lead portion 53, a pressing plate 54, and an insulating plate 55 are arranged in order in the rear end direction Dr. As shown in FIG. 2, the pressing plate 54, the electrode 52, the piezoelectric element 51, the electrode 52, the lead portion 53, the pressing plate 54, and the insulating plate 55 are laminated in this order from the front end side to the rear end side. Yes. The rear end surface of the insulating plate 55 is supported by the step 39 of the second metal fitting 30. The rear end portion 92 of the rod 90 is in contact with the front end surface of the front end holding plate 54. As will be described later, the pressing plate 54 has a through-hole 54h centered on the axis CL. The rear end portion 92 of the rod 90 has a protruding portion that is inserted into the through hole 54h. The rear end surface of the projecting portion is in contact with the front surface of the front electrode 52. The piezoelectric element 51 is connected to the rod 90 via the tip-side electrode 52 and the pressing plate 54. The fixed portion 41 of the pressure receiving portion 40, the rod 90, the holding plate 54 on the distal end side, and the electrode 52 form a connection portion 100 that connects the diaphragm 42 and the piezoelectric element 51.

  FIG. 3 is an exploded perspective view of the element 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 piezoelectric element 51 is formed using quartz in the present embodiment, but a piezoelectric element formed of another material may be adopted. On the piezoelectric element 51, an electric charge is generated according to the load transmitted through the rod 90 from the pressure receiving portion 40 (FIG. 2). 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 electric signal, the deformation amount of the diaphragm 42, that is, the pressure in the combustion chamber can be specified. Thus, the piezoelectric element 51 has an electrical characteristic that varies depending on the pressure received by the pressure receiving unit 40. The electrode 52 and the pressing plate 54 are formed using stainless steel in the present embodiment, but may be formed using other metals. The insulating plate 55 is a member for insulating between the lead portion 53 and the second metal fitting 30 (FIG. 2). In this embodiment, the insulating plate 55 is formed of alumina, but may be formed of other types of insulating materials.

  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 stainless steel in the present embodiment, but may be formed using other metals. The lead part 53 can be produced by punching out the shape of the disk part 57 and the terminal part 56 from a stainless steel flat plate, and then bending the part to be the terminal part 56.

  In the shaft hole 31 of the second metal fitting 30 (FIG. 2), the lead portion 53 is disposed such that the disk portion 57 is in surface contact with the electrode 52 and the terminal portion 56 extends to the rear end side. The terminal portion 56 passes through the through hole 54 h at the center of the pressing plate 54 and the through hole 55 h at the center of the insulating plate 55. The rear end portion of the terminal portion 56 is disposed in the small inner diameter portion 36 in a state of being separated from the inner wall surface of the small inner diameter portion 36 of the second metal fitting 30.

  Each member (excluding the insulating plate 55) constituting the element unit 50 is disposed in the shaft hole 31 of the second metal fitting 30 so as to be separated from the inner wall surface of the second metal fitting 30. The electrode 52 on the rear end side of the piezoelectric element 51 is electrically connected to a lead portion 53 (in this embodiment, further, a holding plate 54), and is electrically connected from the first metal fitting 20 and the second metal fitting 30. Away. The electrode 52 on the distal end side of the piezoelectric element 51 is electrically connected to the second metal fitting 30 through the pressing plate 54 on the distal end side, the rod 90 and the pressure receiving portion 40. In the present embodiment, in order to make the distribution of the load applied to the piezoelectric element 51 uniform, the pressing plate 54 is disposed not only on the rear end side but also on the front end side of the piezoelectric element 51.

  A cable 60 is disposed in the shaft hole 21 of the first 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. In this embodiment, noise is reduced by using a so-called shielded wire having a multilayer structure as the cable 60. 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 inner conductor 65 is composed of a plurality of conductive wires. The outer side of the inner conductor 65 in the radial direction is surrounded by an insulator 64. A conductive coating 63 is provided on the outer peripheral surface of the insulator 64. An outer conductor 62 that is a mesh shield is provided on the outer side in the radial direction of the conductive coating 63. The outer peripheral surface of the outer conductor 62 is covered with a jacket 61. A cable including a plurality of members arranged coaxially in this way is also called a coaxial cable.

  As shown in FIG. 2, the outer conductor 62 that is not covered by the jacket 61 is exposed from the portion covered by the jacket 61 toward the distal end side at the distal end portion of the cable 60. Further, the insulator 64 that is not covered by the external conductor 62 is exposed from the portion where the external conductor 62 is exposed toward the tip side. Further, the inner conductor 65 that is not covered by the insulator 64 is exposed from the portion where the insulator 64 is exposed toward the tip side.

  The internal conductor 65 exposed at the distal end portion of the cable 60 is connected to the terminal portion 56 of the element portion 50 through the flat plate conductive wire 75 and the small diameter conductive wire 74. Specifically, the flat conductor 75 is welded to the tip of the inner conductor 65, and the rear end of the thin conductor 74 wound in a coil shape is welded to the tip of the flat conductor 75, The distal end of the small diameter conductive wire 74 is welded to the rear end portion of the terminal portion 56. The flat conductive wire 75 and the thin conductive wire 74 can transmit the electric charge of the piezoelectric element 51 from the terminal portion 56 to the internal conductor 65. In addition, as a structure for connecting the internal conductor 65 and the terminal part 56, it replaces with the structure using the flat conducting wire 75 and the thin diameter conducting wire 74, and can employ | adopt other arbitrary structures.

  From the tip of the terminal portion 56 to the position on the rear end side of the welded portion connecting the terminal portion 56 and the thin wire 74, the range including the entire terminal portion 56 and the tip of the thin wire 74 is Covered by a heat-shrinkable tube 72. Thereby, the reliability of the electrical insulation between the terminal part 56 and the 2nd metal fitting 30 (especially small inner diameter part 36) is improved. When manufacturing the pressure sensor 10, the integration of the lead portion 53 having the terminal portion 56 and the thin lead wire 74 by welding and the covering with the heat shrinkable tube 72 may be performed prior to the entire assembly.

  A grounding conductor 76 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. The grounding conductor 76 is composed of a stranded wire formed continuously from the outer conductor 62. The front end portion of the grounding conductor 76 is welded to the rear end portion of the second metal fitting 30. Thereby, the outer conductor 62 is grounded through the grounding conductor 76, the second metal fitting 30, and the cylinder head of the internal combustion engine.

  When manufacturing the pressure sensor 10, the element portion 50 is inserted into the shaft hole 31 (specifically, the large inner diameter portion 35) from the distal end side of the second metal fitting 30. The terminal portion 56 of the lead portion 53 of the element portion 50 is integrated with the small-diameter conductive wire 74 and the heat shrinkable tube 72 in advance. And the thin diameter conducting wire 74 is inserted from the front end side of the small inner diameter portion 36 of the second metal fitting 30, and the small diameter conducting wire 74 is drawn out from the rear end side of the small inner diameter portion 36. Further, the pressure receiving portion 40 and the rod 90 are disposed on the distal end side of the element portion 50 in a state where the rod 90 is inserted into the through hole of the pressure receiving portion 40. And the edge 42o of the diaphragm 42 and the 2nd metal fitting 30 are welded, and the fusion | melting part 45 is formed. Thereafter, in a state where a load in the rear end direction Dr is applied to the rod 90, the fixing portion 41 of the pressure receiving portion 40 and the cylindrical portion 96 of the rod 90 are welded to form the melting portion 46. As a result, a preload is applied to the element unit 50. Here, the preload can be adjusted by adjusting the load applied to the rod 90. Thus, an appropriate preload can be easily realized. Therefore, the accuracy of pressure measurement can be improved.

  Then, the rear end of the small-diameter conductive wire 74 drawn from the rear end side of the second metal fitting 30 (specifically, the small inner diameter portion 36) and the front end of the internal conductor 65 are welded to the flat plate conductive wire 75. Further, the front end portion of the grounding conductor 76 and the rear end portion of the second metal fitting 30 are welded. Further, the cable 60 is passed through the shaft hole 21 of the first metal fitting 20, and the front end of the first metal fitting 20 and the rear end of the second metal fitting 30 are welded to form the melting portion 26. Thereafter, molten rubber is injected into the shaft hole 21 of the first metal fitting 20 to fill the shaft hole 21 with a rubber layer (not shown), and the pressure sensor 10 is completed. By forming the rubber layer, the waterproof property in the pressure sensor 10 is improved and the vibration proof property is also improved. Note that molten resin may be injected into the shaft hole 21 instead of the molten rubber.

B. About thermal expansion of diaphragm 42:
FIG. 4 is an explanatory diagram of the operation of the pressure sensor 10. FIG. 4A shows a case where a relatively low temperature combustion gas touches the diaphragm 42, and FIG. 4B shows a case where a relatively high temperature combustion gas touches the diaphragm 42. In the drawing, a cross section cut along a plane including an axis CL of a part of the tip side of the pressure sensor 10 is shown. As shown in FIG. 4A, the diaphragm 42 bends (deforms) according to the pressure Pc in the combustion chamber. In the embodiment of FIG. 4A, the diaphragm 42 bends in a direction parallel to the axis line CL. The rod 90 is displaced approximately parallel to the axis CL in accordance with the bending (deformation) of the diaphragm 42. Thereby, the rod 90 transmits a load corresponding to the pressure Pc to the element unit 50.

  When the temperature of the combustion gas is relatively high, the temperature of the pressure receiving surface 42f of the diaphragm 42 can be locally high. Thereby, the part by the side of the front-end | tip direction Df among the diaphragms 42 can be thermally expanded locally. In the present embodiment, the outer edge 42 o of the diaphragm 42 is joined to the second metal fitting 30. Therefore, the diaphragm 42 tends to extend toward the inner peripheral side by thermal expansion. In the present embodiment, the diaphragm 42 is joined to the cylindrical portion 96 of the rod 90. Since the inner peripheral side of the cylindrical part 96 is hollow, the cylindrical part 96 can be easily deformed toward the inner peripheral side. Therefore, as shown in FIG. 4B, when the diaphragm 42 is thermally expanded, the cylindrical portion 96 is deformed to the inner peripheral side to receive a force that is bent in a direction parallel to the axis CL. Thereby, it can suppress that the diaphragm 42 bends in the direction parallel to the axis line CL by the thermal expansion of the diaphragm 42. FIG. In this state, the diaphragm 42 bends (deforms) according to the pressure Pc in the combustion chamber, as in FIG. The rod 90 is displaced approximately parallel to the axis CL in accordance with the bending (deformation) of the diaphragm 42. As a result, errors in the signal from the element unit 50 due to the temperature of the combustion gas can be suppressed.

  FIG. 5 is an explanatory diagram of the operation of the pressure sensor 10x of the reference example. The only difference from the pressure sensor 10 of the embodiment of FIG. 4 is that the rod 90x is not a member having a hollow cylindrical portion 96 but a rod having no cavity from the front end to the rear end. The shape of the outer peripheral surface of the rod 90x is the same as the shape of the outer peripheral surface of the rod 90 of the embodiment. The structure of the other part of the pressure sensor 10x of the reference example is the same as the structure of the corresponding part of the pressure sensor 10 of the embodiment.

  FIG. 5A shows a case where combustion gas having a relatively low temperature touches the diaphragm 42, as in FIG. 4A, and FIG. The case where the high-temperature combustion gas touches the diaphragm 42 is shown. In the drawing, a cross section cut by a plane including a part of the axis CL on the tip side of the pressure sensor 10x is shown. As shown in FIG. 5A, also in the pressure sensor 10x of the reference example, the diaphragm 42 bends (deforms) according to the pressure Pc in the combustion chamber, and the rod 90x responds to the bend (deformation) of the diaphragm 42. Thus, it can be displaced approximately parallel to the axis CL.

  When the temperature of the combustion gas is relatively high, as described with reference to FIG. 4B, a portion of the diaphragm 42 on the tip end direction Df side can locally thermally expand. Due to this thermal expansion, the diaphragm 42 tends to extend toward the inner peripheral side. However, since the rod 90x of the reference example cannot be deformed toward the inner peripheral side, unlike the rod 90 of the embodiment of FIG. 4B, the thermal expansion of the diaphragm 42 cannot be received. In this case, the thermal expansion of the diaphragm 42 can apply a force parallel to the axis CL to the rod 90x. For example, in the example of FIG. 5B, the thermal expansion of the pressure receiving surface 42f of the diaphragm 42 applies a force F in the distal direction Df to the rod 90x. Thereby, the load applied to the element part 50 becomes small. As described above, in the pressure sensor 10x of the reference example, the load applied to the element unit 50 can fluctuate greatly depending on the temperature of the combustion gas, so that the error of the signal from the element unit 50 increases.

  Thus, in this embodiment, the diaphragm 42 is joined to the hollow first portion 91 of the rod 90. Therefore, when the pressure receiving surface 42f, which is the surface portion on the distal end direction Df side of the diaphragm 42, is thermally expanded, as described in FIG. 4B, the hollow cylindrical portion 96 (particularly, the first portion of the rod 90). The deformation of 91) can suppress the displacement of the rod 90 due to thermal expansion. As a result, pressure measurement errors due to thermal expansion of the diaphragm 42 can be suppressed.

  The element unit 50 is disposed in the second metal fitting 30. The piezoelectric element 51 of the element unit 50 is connected to the second portion 92 of the rod 90 via the electrode 52 and the pressing plate 54. The second portion 92 is a portion closer to the rear end direction Dr than the first portion 91. Accordingly, the rod 90 can appropriately transmit a load corresponding to the pressure received by the diaphragm 42 to the piezoelectric element 51 disposed in the second metal fitting 30 when the diaphragm 42 is bent.

  FIG. 2 shows the distance L and the wall thickness T of the diaphragm 42. The distance L is a distance parallel to the axis CL from the bottom surface 99 on the rear end side inside the rod 90 to the diaphragm 42. The wall thickness T is the wall thickness in a direction parallel to the axis CL of the diaphragm 42. The cylindrical portion 96 of the rod 90 can be reinforced by a lid portion 97 that closes the rear end side of the rod 90. The reinforcement by the lid portion 97 is weaker as it is farther from the lid portion 97. When the distance L is long, the first portion 91 that is a joint portion between the cylindrical portion 96 and the diaphragm 42 is far from the lid portion 97. Therefore, when the distance L is long, the first portion 91 is easily deformed because the reinforcement at the first portion 91 is weak. In order for the rod 90 to receive thermal expansion of the diaphragm 42 due to deformation of the cylindrical portion 96 (particularly, the first portion 91), it is preferable that the distance L is long.

  When the rod 90 receives thermal expansion of the diaphragm 42 due to deformation of the cylindrical portion 96, a portion 98 (FIG. 2) corresponding to the distance L in the cylindrical portion 96, that is, the lid portion 97 of the cylindrical portion 96 and the first portion 97. The portion 98 between the first portion 91 is deformed. If the length L of the portion 98 is approximately the same as the thickness T of the diaphragm 42, the rod 90 is heated by the deformation of the portion including the portion 98 and the first portion 91 of the cylindrical portion 96. The expansion can be sufficiently received. Thus, the distance L is preferably equal to or greater than the wall thickness T. In the embodiment of FIG. 2, the distance L is sufficiently larger than the wall thickness T.

C. Another embodiment:
FIG. 6 is a cross-sectional view of another embodiment of a rod. The illustrated cross section is a flat cross section including the axis CL. The rod 90a in FIG. 6A includes a cylindrical portion 96a and a lid portion 97 that closes an end portion on the rear end side of the cylindrical portion 96a. The lid portion 97 is the same as the lid portion 97 in the embodiment of FIG. The only difference from the rod 90 in FIG. 2 is that the thickness T9a of the cylindrical portion 96a is gradually reduced toward the distal direction Df. Specifically, in the embodiment of FIG. 6A, the outer diameter Do of the cylindrical portion 96a is constant regardless of the position in the distal direction Df. The inner diameter Dia of the cylindrical portion 96a gradually increases toward the distal direction Df. The wall thickness T9a is the wall thickness in the radial direction of a circle centered on the axis CL. The structure of the other part of the rod 90a is the same as the structure of the corresponding part of the rod 90 of the first embodiment. The rod 90a can be used instead of the rod 90 of FIG. The distance La in FIG. 6A is a distance parallel to the axis CL from the bottom surface 99a on the rear end side inside the rod 90a to the diaphragm 42. This distance La is larger than the wall thickness T of the diaphragm 42.

  As described above, the thickness T9a of the cylindrical portion 96a in FIG. Since the thickness T9a of the portion close to the lid portion 97 is relatively thick, a significant decrease in the overall rigidity of the rod 90a can be suppressed. Moreover, since the thickness T9a of the portion near the joint portion 91a with the pressure receiving portion 40 (and hence the diaphragm 42) in the cylindrical portion 96a is relatively thin, the rigidity of the portion near the joint portion 91a can be reduced. Therefore, when the diaphragm 42 is thermally expanded, the cylindrical portion 96a (particularly, the joining portion 91a) of the rod 90a can be easily deformed. As described above, it is possible to suppress the displacement of the rod 90a due to the thermal expansion of the diaphragm 42 while suppressing the strength reduction of the rod 90a. And the measurement error of the pressure by the thermal expansion of the diaphragm 42 can be suppressed.

  The rod 90b in FIG. 6B includes a cylindrical portion 96b and a lid portion 97 that closes an end portion on the rear end side of the cylindrical portion 96b. The lid portion 97 is the same as the lid portion 97 in the embodiment of FIG. The only difference from the rod 90 in FIG. 2 is that the thickness T9b of the cylindrical portion 96b is reduced stepwise toward the distal direction Df. Specifically, in the embodiment of FIG. 6B, the outer diameter Do of the cylindrical portion 96b is constant regardless of the position in the distal direction Df. The inner diameter Dib of the cylindrical portion 96b increases stepwise toward the distal direction Df. The structure of the other part of the rod 90b is the same as the structure of the corresponding part of the rod 90 of the first embodiment. The rod 90b can be used instead of the rod 90 of FIG. The distance Lb in FIG. 6B is a distance parallel to the axis CL from the bottom surface 99b on the rear end side inside the rod 90b to the diaphragm 42. This distance Lb is larger than the wall thickness T of the diaphragm 42.

  Thus, the thickness T9b of the cylindrical portion 96b in FIG. 6B is thinner toward the tip side. Since the thickness T9b of the portion close to the lid portion 97 is relatively thick, it is possible to suppress a significant decrease in the overall rigidity of the rod 90b. Further, since the thickness T9b of the portion near the joint portion 91b with the pressure receiving portion 40 (and hence the diaphragm 42) in the cylindrical portion 96b is relatively thin, the rigidity of the portion near the joint portion 91b can be reduced. Therefore, when the diaphragm 42 is thermally expanded, the cylindrical portion 96b (particularly, the joint portion 91b) of the rod 90b can be easily deformed. As described above, it is possible to suppress the displacement of the rod 90b due to the thermal expansion of the diaphragm 42 while suppressing the strength reduction of the rod 90b. And the measurement error of the pressure by the thermal expansion of the diaphragm 42 can be suppressed.

D. Variations:
(1) In the embodiments of FIGS. 2, 6A, and 6B, the bottom surfaces 99, 99a, 99b on the rear end sides inside the rods 90, 90a, 90b are planes perpendicular to the axis CL. is there. However, the bottom surface of the rod may be a curved surface or a surface inclined obliquely with respect to the axis CL. In the embodiment shown in FIGS. 2, 6A, and 6B, the diaphragm 42 is configured to expand in a direction perpendicular to the axis CL. However, the diaphragm 42 may extend in a direction inclined obliquely with respect to the axis CL. For example, the shape of the diaphragm 42 may be the same as the shape of the outer peripheral surface of the truncated cone centering on the axis CL.

  In either case, distances parallel to the axis from the bottom surface on the rear end side inside the rod to the diaphragm (for example, distances L, La, and Lb in FIGS. 2, 6A, and 6B) The distance between the most rear end portion of the bottom surface and the most rear end portion of the diaphragm may be employed. If such a distance is equal to or greater than the diaphragm thickness T, the rod can easily receive the thermal expansion of the diaphragm by deformation of the hollow cylindrical portion.

(2) As a configuration in which the thickness of the hollow cylindrical portion of the rod becomes thinner toward the tip side, various other configurations can be adopted instead of the configurations shown in FIGS. 6 (A) and 6 (B). It is. For example, the inner diameter of the cylindrical portion may change so as to draw a curve with respect to the change in the position in the distal direction Df. Moreover, you may employ | adopt the structure where the outer diameter of a cylinder part becomes small toward the front end side. In either case, the wall thickness may change continuously or the wall thickness may change stepwise with respect to the change in the position in the distal direction Df. And it is preferable that the thickness of the junction part of a cylinder part and a diaphragm is thinner than the thickness in the vicinity of the bottom face of the rear-end side inside a rod. Thereby, the rod can easily receive the thermal expansion of the diaphragm due to the deformation of the cylindrical portion. However, as in the embodiment shown in FIG. 2, the thickness of the cylindrical portion 96 may be constant regardless of the position in the distal direction Df. Further, the cylindrical portion of the rod may include a portion where the thickness increases toward the tip side.

(3) As a portion (for example, the second portion 92 in FIG. 2) connected to the element portion 50 (that is, the piezoelectric element 51) in the rod, an arbitrary portion of the rod is used instead of the rear end portion of the rod. It can be adopted. For example, the element part 50 (for example, electrode 52) may be connected to the outer peripheral surface of the rod. In this case, the electrode 52 and the piezoelectric element 51 may be formed in an annular shape, and a rod may be inserted into the through hole between the electrode 52 and the piezoelectric element 51. Generally, the element part 50 is arrange | positioned rather than the diaphragm 42 which receives the pressure in a combustion chamber. Therefore, the 2nd part connected to the element part 50 among rods is arrange | positioned in the back end side rather than the 1st part to which a diaphragm is joined among rods.

  Here, as in the embodiment of FIG. 2, the second portion is not the hollow cylindrical portion of the rod, but the non-hollow portion of the rod, that is, the bottom surface (for example, FIG. It is preferable that the portion is on the rear end side with respect to the bottom surface 99). According to this structure, it is suppressed that the load applied to the piezoelectric element 51 fluctuates due to the deformation of the hollow cylindrical portion. Therefore, pressure measurement errors can be suppressed.

(4) As a configuration of the rod having a hollow portion, various other configurations can be adopted instead of the configurations of the rods 90, 90a, and 90b in FIGS. 2, 6A, and 6B. is there. For example, a portion of the rod that protrudes to the tip side from the pressure receiving portion 40 may be omitted. Further, the distances L, La, and Lb may be less than the wall thickness T.

(5) As the configuration of the connection portion for connecting the diaphragm 42 and the piezoelectric element 51, other various configurations can be adopted instead of the configuration of the connection portion 100 described in FIG. For example, the holding plate 54 on the distal end side may be omitted, and the rod 90 may be in contact with only the electrode 52 on the distal end side among the elements of the element 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 rod 90. In this case, the rod 90 functions as an electrode. Further, the fixing part 41 of the pressure receiving part 40 may be omitted, and the diaphragm 42 may be directly joined to the rod 90. Further, the diaphragm and the hollow rod may be integrally formed as one member (for example, forging or shaving). Also in this case, it can be said that the diaphragm is connected to the hollow rod. In any case, the connecting portion includes a hollow rod including a hollow portion, and the diaphragm 42 is directly or indirectly connected to the hollow first portion of the hollow rod, and is more than the first portion of the hollow rod. The piezoelectric element 51 is preferably connected directly or indirectly to the second portion on the rear end side.

(6) As the configuration of the element 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. In addition, the electrode 52 and the piezoelectric element 51 may be an annular plate member surrounding the axis CL, instead of a disk-shaped plate member disposed on the axis CL, and a specific circumferential axis CL. The member arrange | positioned in the position away from may be sufficient. In general, the element 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. In addition, as an apparatus having an electrical characteristic that changes depending on the pressure received by the diaphragm, an electrical characteristic that changes according to the load received through the diaphragm and the connecting portion instead of the piezoelectric element (for example, voltage, resistance value, etc.) Various devices having the above can be employed. For example, a strain gauge may be employed.

(7) As a configuration for guiding the signal from the element 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 element unit 50 may be connected by a middle shaft. In this case, a signal from the element unit 50 can be acquired through the terminal fitting and the first fitting 20.

(8) As a configuration of the housing that accommodates the piezoelectric element 51, various cylindrical configurations can be employed instead of the configuration of the second metal fitting 30 described in FIG. For example, the large inner diameter portion 35 and the small inner diameter portion 36 may be separate members separated from each other. In this case, for example, a female screw is formed on the inner peripheral surface of the large inner diameter portion 35, a male screw is formed on the outer peripheral surface of the small inner diameter portion 36, and the small inner diameter portion 36 is connected to the large inner diameter portion 35 from the rear end side of the large inner diameter portion 35. It may be screwed in. In this case, the preload can be adjusted by adjusting the rotational speed of the small inner diameter portion 36 when the small inner diameter portion 36 is screwed.

  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.

10, 10x ... pressure sensor, 20 ... first metal fitting, 21 ... shaft hole, 22 ... screw part, 24 ... tool engaging part, 26 ... melting part, 30 ... Second metal fitting, 31 ... shaft hole, 34 ... expanded diameter part, 35 ... large inner diameter part, 36 ... small inner diameter part, 39 ... step part, 40 ... pressure receiving part, 41 ... fixing part, 42 ... diaphragm, 42f ... pressure-receiving surface, 42i, 42o ... edge, 45, 46 ... melting part, 50 ... element part, 51 ... piezoelectric element , 52 ... Electrode, 53 ... Lead part, 54 ... Holding plate, 54h ... Through hole, 55 ... Insulating plate, 55h ... Through hole, 56 ... Terminal part, 57 ... disk part, 60 ... cable, 61 ... jacket, 62 ... outer conductor, 63 ... conductive coating, 64 ... insulator, 65 ... inner conductor, 72 ... Heat-shrinkable tube, 74 ... thin wire, 75 ... flat wire, 76 ... ground wire, 90, 90a, 90b, 90x ... rod, 91 ... first part, 1a ... joining part, 91b ... joining part, 92 ... second part, 96, 96a, 96b ... cylinder part, 97 ... lid part, 98 ... part, 99, 99a, 99b ... bottom surface, 100 ... connector, X ... region, L, La, Lb ... distance, T ... thickness, CL ... center axis (axis), Pc ... Pressure, Df ... Front end direction, Dr ... Rear end direction, Di ... Inner diameter, Do ... Outer diameter, T, T9a, T9b ... Thickness, Dia ... Inner diameter, Div .. .Inner diameter

Claims (4)

A cylindrical housing, a diaphragm that is bonded to the front end side of the housing and bends according to the pressure received, a sensor unit that is disposed in the housing and has an electrical characteristic that varies depending on the pressure, and the diaphragm A pressure sensor comprising: a connecting portion that connects the sensor portion;
The connecting portion includes a hollow rod that extends in the direction of the axis, with the end on the front end side opened and the end on the rear end side closed.
The diaphragm is connected to a hollow first portion of the hollow rod,
The sensor unit is connected to the second part of the hollow rod on the rear end side of the first part,
Pressure sensor. The pressure sensor according to claim 1,
The thickness of the hollow portion of the hollow rod is thinner toward the tip side,
Pressure sensor. The pressure sensor according to claim 2,
The inner diameter of the hollow rod increases stepwise toward the tip side.
Pressure sensor. The pressure sensor according to any one of claims 1 to 3,
A distance parallel to the axis from the bottom surface on the rear end side inside the hollow rod to the diaphragm is equal to or greater than a thickness in a direction parallel to the axis of the diaphragm.
Pressure sensor.

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