JP6673777B2 - Pressure sensor - Google Patents

Description

  The present invention relates to a pressure sensor for detecting a pressure such as a combustion pressure in a combustion chamber of an engine.

  2. Description of the Related Art A pressure sensor for detecting a combustion pressure in a combustion chamber of an internal combustion engine of a diesel engine has been known. In this pressure sensor, a housing is attached to an engine head in a state where a displacement member is exposed in a combustion chamber, and a combustion pressure (combustion gas pressure) in the combustion chamber is received by the displacement member. And a sensor unit having a strain gauge (gauge) or the like. Furthermore, a glow plug with a pressure sensor is also known in which the function of the above-described pressure sensor is added to a glow plug used to assist the start of a diesel engine (see Patent Document 1).

  As shown in FIGS. 8 and 9, the glow plug with a pressure sensor of Patent Document 1 includes a cylindrical metal shell 10A, a cylindrical metal outer cylinder 30A held at the tip end of the metal shell 10A, It has a rod-shaped ceramic heater 20A held by the outer cylinder 30A and a sensor section 50A. Among them, the ceramic heater 20A and the outer cylinder 30A are arranged so as to be displaceable in the axial direction HJ (direction along the axis AX) according to the combustion pressure.

  As shown in FIG. 9, the sensor unit 50A mainly includes a displacement transmitting member 51A, a sensor supporting member 53A, a diaphragm member 55A, and a sensor element 57A. 8 and 9, one end of the displacement transmitting member 51A is welded to the outer cylinder 30A to form a welded portion W3A, and the other end is connected to the diaphragm member 55A. By doing so, the outer cylinder 30A and the diaphragm member 55A are connected. Thereby, the displacement transmitting member 51A can transmit the displacement of the ceramic heater 20A and the outer cylinder 30A to the diaphragm member 55A. On the other hand, as shown in FIGS. 8 and 9, one end of the sensor support member 53A is fixed (and further welded) to the metal shell 10A, and the other end is connected to the diaphragm member 55A. The metal shell 10A is connected to the diaphragm member 55A.

  Further, in the glow plug with a pressure sensor of Patent Document 1, as shown in FIG. 8, the inner peripheral surface of the metal shell 10A and the outer peripheral surface of the outer cylinder 20A are located closer to the distal end GS in the axial direction HJ than the sensor unit 50. The elastic member 40A which holds the ceramic heater 20A and the outer cylinder 30A while permitting the ceramic heater 20A and the outer cylinder 30A to be displaced in the axial direction HJ is disposed in the annular space KAA. The elastic member 40A has one end welded to the outer cylinder 30A to form a welded portion W2A, and the other end welded to the sensor support member 53A to form a welded portion W1A. The member 40A connects the ceramic heater 20A and the outer cylinder 30A with the metal shell 10A and the sensor support member 53A.

  In the glow plug with the pressure sensor having such a configuration, as shown in FIG. 10, the ceramic heater 20A and the outer cylinder 30A receive the combustion pressure F (arrow in FIG. 10) and move toward the rear end side GK in the axial direction HJ. When displaced, the displacement transmitting member 51A welded to the outer cylinder 30A moves toward the rear end side GK in the same manner as the outer cylinder 30A. On the other hand, since the sensor support member 53A is fixed to the metal shell 10A, it does not move toward the rear end side GK in the axial direction HJ, and the elastic member 40A itself that connects the sensor support member 53A and the outer cylinder 30A. Will be elastically deformed. As a result, the diaphragm member 55A bends, and the sensor element 57A mounted on the diaphragm member 55A detects the bending of the diaphragm member 55A.

JP-A-2015-148386

  The glow plug with a pressure sensor disclosed in Patent Document 1 has a structure in which a combustion gas is exposed to an elastic member 40A. As shown in FIG. GS (arrow T in FIG. 11). This is because the other end of the elastic member 40A is welded to the sensor support member 53A fixed to the metal shell 10A, thereby restricting the elastic member 40A from extending to the rear end side GK. On the other hand, since one end of the elastic member 40A is welded to the displaceable outer cylinder 30A (and the ceramic heater 20A), it does not restrict the elastic member 40A from extending to the distal end GS. is there.

  When the elastic member 40 extends to the distal end GS, the outer cylinder 30A and the ceramic heater 20A welded to one end of the elastic member 40A also move to the distal end GS. Then, the displacement transmitting member 51A with one end welded to the outer cylinder 30A moves toward the distal end GS similarly to the outer cylinder 30A. On the other hand, the sensor support member 53A does not move toward the distal end GS. Therefore, as shown in FIG. 11, the diaphragm member 55A bends in a direction opposite to the case where the combustion pressure F is received, and the sensor element 57A mounted on the diaphragm member 55A detects the bending of the diaphragm member 55A. Become. As a result, there is a possibility that the detection accuracy of the combustion pressure of the glow plug with the pressure sensor is reduced.

  Note that this problem is not limited to the glow plug with a pressure sensor disclosed in Patent Document 1, but a similar problem also occurs, for example, with a displacement member having no heater function if it has the same configuration.

  The present invention has been made to solve the above-described conventional problems, and reduces the pressure detection accuracy even when an elastic member that elastically connects a displacement member and a housing is exposed to combustion gas. It is an object of the present invention to provide a pressure sensor capable of suppressing such a situation.

The pressure sensor according to the present invention includes a cylindrical housing extending in the axial direction, a rod-shaped displacement member that is inserted into the housing, and is displaceable in the axial direction by receiving pressure at a tip end in the axial direction; A sensor unit connected to the member and the housing for detecting pressure, a sensor element for detecting the displacement of the displacement member in the axial direction, a placement unit for placing the sensor element, and the displacement member And a transmission section for transmitting the axial displacement of the displacement member to the sensor element, and a main body fixing section for connecting the mounting section and the housing, wherein the main body fixing section is A sensor section fixed to the housing, disposed at a position closer to the distal end in the axial direction than the sensor section, and connected to at least one of the housing and the body fixing section and the displacement member; A pressure sensor comprising an elastic member,
When the distal end portion of the transmission portion and the rearward end portion of the displacement member are axially engaged with each other, and when the displacement member moves toward the distal end in the axial direction, the distal end portion of the transmission portion And the rearward-facing portion of the displacement member is separated.

  According to the pressure sensor of the present invention, the forward-facing portion of the transmission portion and the rear-facing portion of the displacement member are engaged in the axial direction, and when the displacement member moves to the distal end in the axial direction, the transmission is performed. The front-facing portion of the portion and the rear-facing portion of the displacement member are separated from each other. For this reason, even if the elastic member extends to the front end side due to thermal expansion, and even the displacement member moves to the front end side, the distal end portion of the transmission portion is separated from the rear end portion of the displacement member, and the transmission is performed. It is possible to suppress the member from moving to the distal end side. As a result, deformation of the mounting portion can be suppressed. On the other hand, when the distal end side of the displacement member receives pressure, when the displacement member is displaced toward the rear end side, the rear end facing portion of the displacement member presses the distal end portion of the transmitting portion, so that the transmitting portion is also displaced. As a result, the stage moves to the rear end side, and the mounting portion is deformed. As described above, the mounting portion can be deformed only when the displacement member receives the pressure, and a decrease in the accuracy of detecting the combustion pressure of the pressure sensor can be suppressed.

  Further, in the pressure sensor according to the aspect of the invention, it is preferable that the transmission unit and the displacement member are not joined. As described above, since the transmission portion and the displacement member are not joined, when the displacement member moves to the front end side in the axial direction, the front-facing portion of the transmission portion and the rear-facing portion of the displacement member can be easily formed. The structure of the pressure sensor which can be separated from the pressure sensor can be obtained.

  Furthermore, the pressure sensor of the present invention has a configuration in which the displacement member has a protrusion protruding from an outer surface of the displacement member in a direction intersecting with the axial direction. It is preferable that the tip-facing portion comes into contact. As described above, by providing the convex portion on the displacement member and making the distal end portion of the transmitting portion abut on the rearward facing surface of the convex portion, it is possible to suppress a decrease in the combustion pressure detection accuracy of the pressure sensor. The structure of the pressure sensor can be obtained.

  Further, in the pressure sensor according to the aspect of the invention, the protrusion may include an extension that extends toward the rear end side in the axial direction while being separated from the outer surface of the displacement member. Is preferably inserted between the inner surface of the extending portion and the outer surface of the displacement member. Thereby, even if the transmission portion is not joined to the displacement member, the forward-facing portion of the transmission member can be reliably brought into contact with the rear-facing portion of the displacement member.

FIG. 3 is a partially broken longitudinal sectional view of the pressure sensor 1 according to the first embodiment. FIG. 2 is an enlarged vertical cross-sectional view of a portion of the pressure sensor 1 according to the first embodiment in the vicinity of a heater distal end portion 21 and an outer cylinder protrusion 31. FIG. 2 is an enlarged vertical cross-sectional view of a portion near an elastic member 40 and a sensor unit 50 in the pressure sensor 1 according to the first embodiment. FIG. 3 is an enlarged vertical sectional view of the vicinity of a heater rear end portion 23, a connection ring 81, and a center shaft front end portion 83 in the pressure sensor 1 according to the first embodiment. FIG. 5 is an explanatory diagram illustrating movements of the ceramic heater 20, the outer cylinder 30, the elastic member 40, and the sensor unit 50 when the pressure sensor 1 of the first embodiment receives a combustion pressure F. FIG. 4 is an explanatory diagram illustrating movements of the ceramic heater 20, the outer cylinder 30, the elastic member 40, and the sensor unit 50 when the elastic member 40 of the pressure sensor 1 according to the first embodiment is exposed to a combustion gas. FIG. 10 is an enlarged vertical cross-sectional view of a pressure sensor 200 according to a second embodiment, in which a portion near an elastic member 40 and a sensor unit 50 is enlarged. It is the expansion longitudinal section which expanded the part near the elastic member 40A and the sensor part 50A among the glow plugs with the conventional pressure sensor. FIG. 9 is an enlarged vertical cross-sectional view in which the vicinity of a diaphragm member 55A and a sensor element 57A among conventional glow plugs with pressure sensors are enlarged. It is explanatory drawing explaining movement of ceramics heater 20A, outer cylinder 30A, elastic member 40A, and sensor part 50A when the glow plug with a conventional pressure sensor receives a pressure. It is explanatory drawing explaining the movement of the ceramic heater 20A, the outer cylinder 30A, the elastic member 40A, and the sensor part 50A when the elastic member 40A of the conventional glow plug with a pressure sensor is exposed to combustion gas.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. 1 to 4 show a pressure sensor 1 according to the present embodiment. 1 to 4, the direction along the axis AX of the pressure sensor 1 and the metal shell 10 thereof is defined as an axial direction HJ, and the side of the axial direction HJ on which the ceramic heater 20 is disposed (the lower side in the drawings). The front end GS and the opposite side (upper side in the figure) are referred to as rear end GK.

  The pressure sensor 1 is attached to an engine head in a state where the ceramic heater 20 and the outer cylinder 30 are exposed in a combustion chamber of a diesel engine (not shown). It is used to detect pressure (combustion gas pressure). The pressure sensor 1 includes a metal shell 10, a ceramic heater 20, an outer cylinder 30, an elastic member 40, a sensor unit 50, and the like.

  The metal shell 10 is a cylindrical metal member (specifically, carbon steel or stainless steel) having a shaft hole 10h penetrating in the axial direction HJ. The metal shell 10 has a cylindrical front end cap member 11 located on the front end side GS, a cylindrical rear end cap member 15 located on the rear end side GK, and extends in the axial direction HJ between them. It consists of a cylindrical metal fitting body member 13 (see FIG. 1). The rear end portion 11k of the front end cap member 11 and the front end portion 13s of the metal fitting body member 13 are joined (specifically, welded) via a flange portion 53c of a sensor support member 53 described later (see FIG. 3). . The rear end portion 13k of the metal fitting body member 13 and the front end portion 15s of the rear end cap member 15 are directly joined (specifically, welded) (see FIG. 1).

  The distal end portion 11s (see FIG. 3) of the distal end cap member 11 has a tapered shape whose diameter decreases toward the distal end GS. When the pressure sensor 1 is mounted on an engine head (not shown), the tapered outer peripheral surface 11sm of the distal end portion 11s is pressed against the seat surface of the plug hole to secure airtightness in the combustion chamber. Further, a mounting portion 13d having a male screw for mounting the pressure sensor 1 to the engine head is provided at a portion on the rear end side GK (see FIG. 1) of the metal fitting body member 13. Further, a portion of the rear end cap member 15 on the rear end side GK is provided with a tool engaging portion 15e which has a hexagonal cross section and engages a tool when attaching the pressure sensor 1 to the engine head. I have. The rear end cap member 15 is loaded with a cylindrical sealing resin (connector) member 17 so as to protrude more toward the rear end side GK than the rear end 15 b of the rear end cap member 15. I have.

  Next, the ceramic heater 20 will be described. The ceramic heater 20 is a ceramic heater having a round bar shape extending in the axial direction HJ and having a shape in which the tip is curved into a hemispherical shape. Specifically, the ceramic heater 20 includes a ceramic base 26 made of an insulating ceramic (specifically, a silicon nitride ceramic) and a conductive ceramic (specifically, a nitride containing tungsten carbide as a conductive component). A heating resistor 27 made of silicon ceramic) is embedded.

  The heating resistor 27 includes a heating section 27c, a pair of lead sections 27d and 27e, and a pair of electrode extraction sections 27f and 27g. The heat generating portion 27c (see FIG. 2) is arranged on the distal end side GS, has a U-shaped bent shape, and generates heat at a high temperature when energized. A pair of lead portions 27d and 27e (see FIGS. 2 to 4) are connected to both ends of the heat generating portion 27c and extend parallel to the rear end side GK. The pair of electrode extraction portions 27f and 27g (see FIGS. 3 and 4) are connected to the pair of lead portions 27d and 27e at the rear end side GK, while being exposed to the outer peripheral surface 26m of the ceramic base 26. One electrode extraction portion 27g is located on the rear end side GK with respect to the other electrode extraction portion 27f.

  This ceramic heater 20 is held by an outer cylinder 30. Specifically, of the ceramic heater 20, the heater front end portion 21 (see FIG. 2) projects beyond the front end 31a of the outer cylinder 30 toward the front end GS, and the heater rear end portion 23 (see FIG. 3 and FIG. A heater intermediate portion 22 (see FIGS. 2 to 4) that projects to the rear end side GK from the rear end 33 b of the tube 30 and is located between the heater front end portion 21 and the heater rear end portion 23 is inside the outer tube 30. It is held by the outer cylinder 30 in a form to be arranged. The ceramic heater 20 is held by the metal shell 10 so as to be displaceable in the axial direction HJ together with the outer cylinder 30 as described later.

  The heater rear end 23 of the ceramic heater 20 is connected to a center shaft member 83 (see FIG. 4) via a connection ring 81 (see FIGS. 3 and 4). The connection ring 81 is a cylindrical metal member (specifically, stainless steel) extending in the axial direction HJ. The connection ring 81 is disposed inside the shaft hole 10h of the metal shell 10 and radially inside the displacement transmission member 51 and the sensor support member 53 described later. The heater rear end 23 of the ceramic heater 20 is press-fitted into a portion of the connection ring 81 on the front end side GS. On the other hand, a fitting portion 83sa of the center end portion 83s of the center member 83 is press-fitted into a portion of the connection ring 81 on the rear end side GK. Thereby, one electrode extraction portion 27 g of the ceramic heater 20 is electrically connected to the center shaft member 83 via the connection ring 81.

  The center shaft member 83 is a metal (specifically, carbon steel or stainless steel) member having a round bar shape extending in the axial direction HJ. The center shaft member 83 is inserted into the shaft hole 10h of the metal shell 10 in a state where it is separated from the metal shell 10. In addition, a portion of the center shaft member 83 on the distal end side GS is disposed radially inward of a displacement transmitting member 51 and a sensor supporting member 53 described below and separated from them. The central shaft member 83 includes a large-diameter central shaft end portion 83s located on the distal side GS, and a central shaft body portion 83c smaller in diameter than the central shaft front end portion 83s and extending from the central shaft front end portion 83s to the rear end side GK. . As described above, the connection ring 81 is press-fitted into the fitting portion 83sa of the tip GS of the center shaft tip 83s.

  Next, the outer cylinder 30 will be described. The outer cylinder 30 (see FIGS. 2 to 4) is a cylindrical metal member extending in the axial direction HJ. The outer cylinder 30 has a stepped shape in which the outer diameter is equal in the axial direction HJ, while the inner diameter is large at the front end GS and reduced at the rear end GK.

  The outer cylinder 30 is held by the metal shell 10 together with the ceramic heater 20 so as to be displaceable in the axial direction HJ. Specifically, the outer cylinder projecting portion 31 (see FIG. 2) protrudes toward the distal end GS from the distal end 11sa of the metal shell 10, and the inside 33 of the outer cylindrical hole (see FIGS. 3 and 4) has a shaft hole of the metal shell 10. While being disposed within 10h, the metal shell 10 is held so as to be displaceable in the axial direction HJ via an elastic member 40, a displacement transmitting member 51, a sensor support member 53, and the like, which will be described later.

  On the other hand, the outer cylinder 30 holds the heater intermediate portion 22 of the ceramic heater 20 by press fitting (tight fit). Specifically, the outer cylinder protruding portion 31 of the outer cylinder 30 surrounds the ceramic heater 20 therein while being spaced apart therefrom. Therefore, a gap SA is formed over the entire circumference between the inner peripheral surface 31n of the outer cylinder projecting portion 31 and the outer peripheral surface 20m of the ceramic heater 20.

  On the other hand, the inside 33 of the outer cylinder hole of the outer cylinder 30 is located at the front end side GS and is connected to the heater separation part 34 connected to the above-described outer cylinder protrusion 31, and the heater holding part 35 located at the rear end side GK therefrom. It is composed of Among them, the heater separating portion 34 surrounds the ceramic heater 20 inside the heater separating portion 34 while separating the heater separating portion 34 from itself. Therefore, the gap SB is also formed over the entire circumference between the inner peripheral surface 34n of the heater separation portion 34 and the outer peripheral surface 20m of the ceramic heater 20.

An elastic member 40 to be described later is welded to the heater separating portion 34. A portion of the heater separation portion 34 where the elastic member 40 is welded is referred to as a welded portion 34c. In addition, a portion of the heater separation portion 34 that is located on the distal end side GS from the welded portion 34c and continues to the outer cylinder projecting portion 31 is referred to as a distal end portion 34s, and is located on the rear end side GK than the welded portion 34c. A portion connected to the heater holding portion 35 is referred to as a rear end side portion 34k.
On the other hand, the heater holding section 35 holds the ceramic heater 20 therein by press fitting (tight fit). In the heater holding portion 35, one electrode extraction portion 27f of the ceramic heater 20 is electrically connected to the outer cylinder 30.

  A convex portion 36 is provided on the rear end side portion 34k, and a front-facing surface 51m of a displacement transmitting member 51 described later contacts the rear-facing surface 36m of the convex portion 36. The protrusion 36 protrudes in the circumferential direction in a direction intersecting with the axial direction HJ. The relationship between the protrusion 36 and the displacement transmitting member 51 will be described later.

  Next, the elastic member 40 will be described. The elastic member 40 (see FIG. 3) is a cylindrical member made of metal (specifically, stainless steel). The elastic member 40 is disposed in the annular space KA between the inner peripheral surface of the metal shell 10 (specifically, the inner peripheral surface 11n of the distal end cap member 11) and the outer peripheral surface 30m of the outer cylinder 30.

  Specifically, the elastic member 40 includes an outer cylinder side portion 41, a metal fitting side portion 45, and an intermediate deformation portion 43 located therebetween. The outer cylinder side portion 41 of the elastic member 40 is a cylindrical portion located on the tip side GS, and holds the outer cylinder 30 inside itself. Specifically, the outer tube side portion 41 is welded to the welded portion 34c of the heater separation portion 34 of the outer tube 30 over the entire circumference in the circumferential direction to form a fused portion W2. Further, the metal fitting side portion 45 is a cylindrical portion having a diameter larger than that of the outer cylinder side portion 41 and located at the rear end side GK, and is held by the metal shell 10 via a sensor support member 53 described later. Specifically, the metal fitting side portion 45 is externally fitted to the support distal end portion 53s of the sensor support member 53 and is welded over the entire circumference in the circumferential direction to form a fused portion W1. Further, as described later, the sensor support member 53 is welded to the metal shell 10 over the entire circumferential direction, so that the metal side portion 45 of the elastic member 40 is indirectly fixed to the metal shell 10 by welding. .

  In such a form, the elastic member 40 allows the outer cylinder 30 and the ceramic heater 20 to be held by the metal shell 10, and causes the inner peripheral surface 11 n of the tip cap member 11 of the metal shell 10 and the outer peripheral surface 30 m of the outer cylinder 30 to move. It functions as a seal member that divides the annular space KA therebetween in the axial direction HJ in an airtight manner. Therefore, it is possible to prevent the combustion gas that has entered the annular space KA from the distal end GS of the pressure sensor 1 from entering the rear end GK of the outer cylinder 30 through the annular space KA.

Further, the intermediate deformed portion 43 of the elastic member 40 is a portion that is deformed as the ceramic heater 20 and the outer cylinder 30 are displaced in the axial direction HJ. Specifically, the intermediate deforming portion 43 is formed of an annular plate-shaped membrane (thin film), and the intermediate deforming portion 43 is deformed to allow displacement of the ceramic heater 20 and the outer cylinder 30 in the axial direction HJ. I do.
Since the elastic member 40 also electrically connects the outer cylinder 30 and the metal shell 10, one electrode extraction portion 27f of the ceramic heater 20 is connected to the outer cylinder 30 and the elastic member 40 via the outer cylinder 30 and the elastic member 40. It is electrically connected to the metal shell 10. The elastic member 40 also functions as a heat transfer member that allows the heat of the ceramic heater 20 to escape to the engine head via the metal shell 10.

  Next, the sensor unit 50 will be described. The sensor unit 50 includes a displacement transmitting member 51, a sensor support member 53, a diaphragm member 55, a sensor element 57, a pair of wires 58, and an integrated circuit 59. The displacement transmitting member 51 (see FIGS. 3 and 4) is a tubular metal member (specifically, stainless steel) extending in the axial direction HJ. The displacement transmission member 51 is disposed inside the shaft hole 10 h of the metal shell 10, radially inside the sensor support member 53, and on the rear end side GK of the elastic member 40. The displacement transmitting member 51 surrounds the outer cylinder 30 in a loose fit manner and is not joined to the outer cylinder 30. In addition, it is preferable that the diameter difference (φ2−φ1) between the outer diameter φ1 of the outer cylinder 30 and the inner diameter φ2 of the displacement transmitting member 51 satisfies 0 mm <(φ2−φ1) ≦ 4 mm. Further, the front-facing surface 51m of the displacement transmitting member 51 is in contact with the rear-facing surface 36m of the projection 36 as described above. On the other hand, a diaphragm member 55 is connected to the rear end side GK of the displacement transmitting member 51.

  The sensor support member 53 (see FIGS. 3 and 4) is a cylindrical metal (specifically, stainless steel) member extending in the axial direction HJ. The sensor support member 53 is disposed inside the shaft hole 10h of the metal shell 10 and radially outside the displacement transmitting member 51. The sensor support member 53 includes a cylindrical support tip 53s, a large-diameter flange 53c located at the rear end GK, a cylindrical support main body 53k extending from the flange 53c to the rear end GK. Consists of As described above, the fitting side portion 45 of the elastic member 40 is externally fitted and welded to the support distal end portion 53s. The flange 53c is welded to the metal shell 10 while being sandwiched between the rear end 11k of the front end cap member 11 of the metal shell 10 and the front end 13s of the metal shell body 13. A diaphragm member 55 is connected to the rear end side GK of the support main body 53k.

  The diaphragm member 55 (see FIG. 4) is a member made of metal (specifically, stainless steel), and the sensor element 57 is joined to the main surface of the rear end side GK. The sensor element 57 is a semiconductor strain gauge having a piezoresistor, and its resistance value changes with the flexural deformation of the diaphragm member 55. The integrated circuit 59 is disposed inside the rear end cap member 15 of the metal shell 10, as shown by a broken line in FIG. 1, and has a pair of wirings 58 drawn from the sensor element 57 to the rear end side GK. Is connected to the sensor element 57 via the. The integrated circuit 59 outputs an electric signal to the outside using the resistance value of the sensor element 57.

  Next, movements of the ceramic heater 20, the outer cylinder 30, the elastic member 40, and the sensor unit 50 when the ceramic heater 20 of the pressure sensor 1 according to the first embodiment receives the combustion pressure will be described. FIG. 5 is an explanatory diagram illustrating movements of the ceramic heater 20, the outer cylinder 30, the elastic member 40, and the sensor unit 50 when the pressure sensor 1 receives the combustion pressure F. As shown in FIG. 5, when the ceramic heater 20 (particularly, the heater tip 21) receives the combustion pressure F, the ceramic heater 20 and the outer cylinder 30 are displaced toward the rear end GK in the axial direction HJ. Further, since the rearward facing surface 36 m of the convex portion 36 provided on the outer cylinder 30 is in contact with the forward facing surface 51 of the displacement transmitting member 51, the displacement transmitting member 51 is similar to the ceramic heater 20 and the outer cylinder 30. Moves toward the rear end side GK.

  On the other hand, since the sensor support member 53 is fixed to the metal shell 10 (see FIGS. 3 and 4), it does not move toward the rear end side GK in the axial direction HJ, and the sensor support member 53 and the outer cylinder 30 are not moved. Is elastically deformed by itself. As a result, the diaphragm member 55 bends, and the sensor element 57 mounted on the diaphragm member 55 detects the bending of the diaphragm member 55.

  Next, movements of the ceramic heater 20, the outer cylinder 30, the elastic member 40, and the sensor unit 50 when the elastic member 40 of the pressure sensor 1 according to the first embodiment is exposed to the combustion gas will be described. FIG. 6 is an explanatory diagram illustrating movements of the ceramic heater 20, the outer cylinder 30, the elastic member 40, and the sensor unit 50 when the elastic member 40 of the pressure sensor 1 is exposed to the combustion gas. As shown in FIG. 6, when the elastic member 40 is exposed to the combustion gas, the elastic member 40 thermally expands and extends toward the distal end (arrow T in FIG. 6). This is because, as described above, the metal fitting side portion 45 of the elastic member 40 is welded to the support tip 53 s of the sensor support member 53, and the sensor support member 53 is welded to the metal shell 10. The elastic member 40 restricts extension to the rear end side GK. On the other hand, since the outer cylinder side 41 of the elastic member 40 is welded to the displaceable outer cylinder 30, it does not restrict the elastic member 40 from extending to the distal end GS.

  Then, as the elastic member 40 extends toward the distal end, the outer cylinder 30 and the ceramic heater 20 also move toward the distal end. However, unlike the related art, in the pressure sensor 1 of the first embodiment, the outer cylinder 30 and the displacement transmitting member 51 are not joined while the displacement transmitting member 51 is loosely fitted around the outer cylinder 30. Even if the cylinder 30 and the ceramic heater 20 move to the distal end GS, the distal end surface 51m of the displacement transmitting member 51 is separated from the rear end facing surface 36m of the convex portion 36, and the displacement transmitting member 51 moves to the distal end side. Can be suppressed. As a result, the diaphragm member 55 does not deform.

  As described above, in the pressure sensor 1 according to the first embodiment, the front-facing surface 51m of the displacement transmitting member 51 and the rear-facing surface 36m of the convex portion 36 of the outer cylinder 30 are engaged in the axial direction HJ. When the heater 20 and the outer cylinder 30 move to the distal end GS in the axial direction HJ, the distal end surface 51m of the displacement transmitting member 51 and the rear end surface 36m of the outer cylinder 30 are separated from each other. For this reason, even if the elastic member 40 is exposed to the combustion pressure, as shown in FIG. 6, the displacement transmitting member 51 does not move to the distal end GS, and as a result, the diaphragm member 55 is deformed (deflects). ) Never. On the other hand, when the ceramic heater 20 receives the combustion pressure F, the displacement transmitting member 51 also moves to the rear end side GK along with the outer cylinder 30, and the diaphragm member 55 is deformed (bent). As described above, the diaphragm member 55 can be deformed (bent) only when the ceramic heater 20 receives the combustion pressure F, and a decrease in the detection accuracy of the combustion pressure of the pressure sensor 1 can be suppressed.

  Further, in the pressure sensor 1 of the first embodiment, the displacement transmitting member 51 and the outer cylinder 30 are not joined. Thereby, when the ceramic heater 20 and the outer cylinder 30 move to the front end side GS in the axial direction HJ, the front-facing surface 51m of the displacement transmitting member 51 and the rear-facing surface 36m of the outer cylinder 30 are easily separated from each other. Thus, a structure of the pressure sensor 1 that can perform the above operation can be obtained.

  Further, the pressure sensor 1 of the first embodiment has the convex portion 36 on the outer cylinder 30, and the distal end surface 51 m of the displacement transmitting member 51 is in contact with the rear end surface 36 m of the convex portion 36. Accordingly, it is possible to obtain a structure of the pressure sensor 1 that can suppress a decrease in the detection accuracy of the combustion pressure of the pressure sensor 1.

  The housing 10 of the first embodiment corresponds to a “housing” in the claims, and the ceramic heater 20, the outer cylinder 30, the connection ring 81, and the center shaft 83 correspond to a “displacement member” in the claims. The heater tip 21 corresponds to the “tip (of the displacement member)” in the claims, the sensor unit 50 corresponds to the “sensor” in the claims, and the displacement transmitting member 51 corresponds to the claims. The sensor support member 53 corresponds to the “main body fixing portion” in the claims, the diaphragm 55 corresponds to the “mounting portion” in the claims, and the elastic member 40 corresponds to the claim. And the convex portion 36 corresponds to a “convex portion” in the claims.

  Next, a pressure sensor 200 according to the second embodiment will be described. The pressure sensor 200 according to the second embodiment differs from the pressure sensor 1 according to the first embodiment only in the shape of the convex portion 36 provided on the outer cylinder 30, and the other portions are different from the pressure sensor 1 according to the first embodiment. The same is true. Therefore, in the following description, the convex portion 36 of the pressure sensor 200 according to the second embodiment will be mainly described, and the description of the other portions will be simplified or omitted.

  In the outer cylinder 30B of the pressure sensor 200 according to the second embodiment, a convex portion 36B is provided on the rear end side portion 34kB, and the rear end-facing surface 36mB of the convex portion 36B has a distal end of the displacement transmitting member 51. The facing surface 51m is in contact. The convex portion 36B protrudes in the circumferential direction in a direction intersecting with the axial direction HJ. Specifically, the protrusion 36B includes a protrusion 36nB protruding from the outer surface 30mB of the outer cylinder 30B in a direction intersecting the axial direction HJ, and an extension sB extending from the protrusion nB toward the rear end side GK. Is formed from. The extended portion 36sB is separated from the outer side surface 30mB of the outer cylinder 30B.

  As in the first embodiment, the displacement transmitting member 51 is loosely fitted around the outer cylinder 30B and is not joined to the outer cylinder 30B. The displacement transmitting member 51 is inserted between the inner surface 36rB of the extending portion 36sB and the outer surface 30mB of the outer cylinder 30B, and faces the rear end of the convex portion 36B (specifically, the protruding portion 36nB). The front-facing surface 51m of the displacement transmitting member 51 is in contact with the surface 36mB.

  As described above, in the pressure sensor 200 of the second embodiment, the protruding portion 36B is provided with the extending portion 36sB extending toward the rear end side GK in the axial direction HJ while being separated from the outer side surface 30mB of the outer cylinder 30B. The displacement transmitting member 51 is inserted between the inner surface 36rB of the extending portion 36sB and the outer surface 30mB of the outer cylinder 30B. Accordingly, even when the displacement transmitting member 51 surrounds the outer cylinder 30B in a loosely fitting manner and is not joined to the outer cylinder 30B, the distal end-facing surface 51m of the displacement transmitting member 51 may have the outer cylinder 30B (projecting portion 36nB). ) It can be reliably contacted without falling off from the rear end facing surface 36 mB.

  Note that the housing 10 of the second embodiment corresponds to a “housing” in the claims, and the ceramic heater 20, the outer cylinder 30B, the connection ring 81, and the center shaft 83 correspond to a “displacement member” in the claims. The convex portion 36B corresponds to a “protruded portion” in the claims, and the extended portion 36sB corresponds to a “extended portion” in the claims.

  Although the embodiments of the present invention have been described above, the present invention is not limited to the embodiments, and can be implemented in various modes without departing from the gist of the present invention.

  For example, in the first and second embodiments, the convex portions 36 and 36B are provided on the outer cylinders 30 and 30B, but the present invention is not limited to this. For example, the protrusion may be provided on the ceramic heater, the connection ring, and further on the center shaft. Further, without providing the convex portion on the ceramic heater, the outer cylinder, the connection ring and the center shaft, the front end surface of the displacement transmitting member is provided on the rear end face of the ceramic heater, the outer tube, the connection ring, and the center shaft itself. You may make contact.

  Further, in the first and second embodiments, the rear-facing surface 36m of the convex portion 36 and the front-facing surface 51m of the displacement transmitting member 51 are in contact with each other, but the present invention is not limited to this. For example, the distal end of the displacement transmitting member 51 may have a pointed shape narrowing toward the distal end side. In this case as well, the distal end of the displacement transmitting member 51 is in contact with the rear-facing surface 36m of the convex portion 36. Just do it. Further, the rearward facing surface 36m of the convex portion 36 is a tapered surface whose diameter is reduced or enlarged along the axial direction, and the frontward facing surface 51m of the displacement transmitting member 51 is a taper of the rearward facing surface 36m of the convex portion 36. It may be a tapered surface following the surface.

  In the first and second embodiments, the rearward-facing surface 36m of the convex portion 36 and the front-facing surface 51m of the displacement transmitting member 51 are in contact with each other in an annular shape. However, the present invention is not limited to this. For example, the front-facing surface 51m of the displacement transmitting member 51 and the rear-facing surface 36m of the projection 36 may partially contact each other.

  In the first and second embodiments, the displacement transmitting member 51, the sensor supporting member 53, and the diaphragm member 55 are formed as separate members as the sensor unit 50, but the invention is not limited to this. For example, the displacement transmitting member, the sensor supporting member, and the diaphragm member may be formed by one member.

  In the first and second embodiments, the ceramic heater 20 is used as a member that receives the combustion pressure F. However, the present invention is not limited to this. For example, a glow plug having a tube structure in which a coil material is disposed in a sheath tube may be used instead of the ceramic heater. Further, when the function of the heating element is not required, a solid rod-shaped displacement member may be used.

1, 200 pressure sensor 10 metal shell 20 ceramic heater 30, 30B outer cylinder 36, 36B convex part 40 elastic member 50 sensor part 51 ..Displacement transmitting member 53 ... Sensor support member 55 ... Diaphragm 57 ... Sensor element

Claims (4)

A cylindrical housing extending in the axial direction;
A rod-shaped displacement member that is inserted into the housing and that can be displaced in the axial direction by receiving pressure at the tip end in the axial direction,
A sensor unit connected to the displacement member and the housing to detect pressure;
A sensor element for detecting the displacement of the displacement member in the axial direction,
A mounting part for mounting a sensor element, a transmitting part for connecting the displacement member and the mounting part, and transmitting the axial displacement of the displacement member to the sensor element, and a mounting part and the housing And a main body fixing portion connecting the
Including, a sensor unit wherein the main body fixing unit is fixed to the housing,
An elastic member that is disposed closer to the distal end side in the axial direction than the sensor unit and is joined to at least one of the housing and the main body fixing unit and the displacement member.
A pressure sensor comprising:
When the forward-facing portion of the transmission portion and the rear-facing portion of the displacement member are axially engaged with each other, and when the displacement member moves toward the distal end in the axial direction, the forward-facing portion of the transmission portion And the rearward facing portion of the displacement member is separated,
Pressure sensor characterized by the above-mentioned. The pressure sensor according to claim 1, wherein
The pressure sensor, wherein the transmission unit and the displacement member are not joined. The pressure sensor according to claim 1 or claim 2,
The displacement member has a protrusion protruding from its outer surface in a direction intersecting with the axial direction,
The forward-facing portion of the transmitting portion is in contact with the rear-facing portion of the convex portion,
Pressure sensor characterized by the above-mentioned. The pressure sensor according to claim 3, wherein
The convex portion is provided with an extending portion extending toward the rear end side in the axial direction while being separated from the outer side surface of the displacement member,
The pressure sensor according to claim 1, wherein the transmission portion is inserted between an inner surface of the extension portion and the outer surface of the displacement member.