JP2016145704A - Combustion pressure sensor and glow plug - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the detection accuracy of combustion pressure by a sensor element.SOLUTION: An elastic member of a combustion pressure sensor has: a first cylindrical part joined to a rod-shaped member; a first curved part which extends to the outside of a radial direction from a region at a rear end side of the first cylindrical part; a second curved part which extends to the outside of the radial direction from a region at an external peripheral side of the first curved part; and a second cylindrical part connected to a housing. The housing constitutes an opening part, entirely accommodates at least a part of the first cylindrical part of the elastic member up to at least a part of the second cylindrical part, and has a tip which forms a clearance between at least a part of an outside face of the second cylindrical part and itself. The combustion pressure sensor further comprises a wall part which is arranged at a tip side rather than the second curved part at the inside of the tip, and overlapped with at least a part of the second curved part when viewed from an axial line direction.SELECTED DRAWING: Figure 5

Description

  The present invention relates to a combustion pressure sensor and a glow plug.

  As a glow plug, there is known a glow plug with a sensor that also functions as a combustion pressure sensor by including a sensor element that detects a combustion pressure in a combustion chamber in addition to a rod-shaped heater portion that generates heat when energized (Patent Literature). 1). The glow plug with a sensor includes a cylindrical housing having an opening on the tip end side in the axial direction, and a heater portion and an elastic member connected to the housing inside the housing. The housing of the glow plug with sensor accommodates at least a part of the heater portion. A gap is formed between the opening of the housing and the heater. In the glow plug with sensor, the elastic member is elastically deformed so that the heater portion is movable in the axial direction, and the sensor element detects the combustion pressure received by the heater portion in accordance with the displacement of the heater portion.

Japanese Patent No. 5411363

  In the glow plug of Patent Document 1, since the outer surface of the elastic member is in contact with the inner surface of the housing over the axial direction, the compressive stress in the axial direction applied to the housing when the glow plug is attached to the internal combustion engine is There is a problem that the displacement characteristics of the elastic member may change. The change in the displacement characteristic of the elastic member causes an error in the value of the combustion pressure detected by the sensor element. Further, when a gap is formed between the outer side surface of the elastic member and the inner side surface of the housing, the influence on the elastic member due to the compressive stress of the housing is reduced. However, in this case, since heat absorption from the elastic member through the housing is reduced, the elastic member is heated in a very short time (hereinafter also referred to as thermal shock) by the combustion gas entering the inside of the housing from the opening. This causes another problem that the displacement characteristics of the elastic member may be easily changed.

  The present invention has been made to solve the above-described problems, and can be realized as the following forms.

(1) According to one aspect of the present invention, a rod-like member extending in the axial direction from the rear end side to the tip end side; and a cylindrical shape having an opening on the tip end side, wherein at least a part of the rod-like member is formed A housing for housing; an elastic member for connecting the rod-shaped member and the housing inside the housing and elastically deforming the rod-shaped member so as to be movable in the axial direction; housed in the housing; There is provided a combustion pressure sensor comprising: a sensor element that detects a combustion pressure received by the rod-shaped member according to displacement. In this combustion pressure sensor, the elastic member has a cylindrical shape surrounding a side surface of the rod-shaped member, and is curved in a convex shape toward the rear end side; a first cylindrical portion joined to the rod-shaped member; And a first curved portion extending radially outward from the rear end portion of the first cylindrical portion; and curved in a convex shape toward the distal end side, and the first curved portion A second curved portion extending radially outward from a portion on the outer peripheral side of the portion; a second shape connected to the housing, the second curved portion being connected to the outer peripheral portion of the second curved portion A cylindrical part; and the housing constitutes the opening and extends from at least a part of the first cylindrical part to at least a part of the second cylindrical part in the elastic member. At least part of the outer surface of the second cylindrical part A distal end portion that forms a gap between the second curved portion and the second curved portion on the inner side of the distal end portion. The second curved portion is disposed on the distal end side when viewed from the axial direction. The wall part which overlaps at least one part is provided. According to this aspect, the gap formed between the front end portion of the housing and the outer surface of the second cylindrical portion can suppress the influence of the axial compressive stress applied to the housing on the elastic member, and the opening. The wall portion can prevent the second curved portion from being directly exposed to the combustion gas entering the interior of the housing from the portion. Thereby, the change of the displacement characteristic of the elastic member with respect to the thermal shock by combustion gas can be suppressed. As a result, the detection accuracy of the combustion pressure by the sensor element can be improved.

(2) In the combustion pressure sensor according to the above aspect, the wall portion has a shape that protrudes radially outward of the rod-shaped member from a portion on the tip side from the elastic member on a side surface of the rod-shaped member, and the axial direction When viewed from above, the elastic member may overlap with at least a part of the second curved portion from the first tubular portion. According to this aspect, the wall portion that the first tubular portion and the first curved portion in addition to the second curved portion are directly exposed to the combustion gas entering the inside of the housing from the opening. Can prevent. Thereby, the change of the displacement characteristic of the elastic member with respect to the thermal shock by combustion gas can be suppressed further. As a result, the detection accuracy of the combustion pressure by the sensor element can be further improved.

(3) In the combustion pressure sensor of the above aspect, the wall portion has a shape protruding from the first cylindrical portion to the outside in the radial direction of the rod-like member, and the elastic member when viewed from the axial direction. The first bending portion may overlap with at least a part of the second bending portion. According to this aspect, at least the portion of the first cylindrical portion on the rear end side of the first cylindrical portion and the first curve with respect to the combustion gas entering the inside of the housing from the opening portion. The wall portion can prevent the portion from being directly exposed. Thereby, the change of the displacement characteristic of the elastic member with respect to the thermal shock by combustion gas can be suppressed further. As a result, the detection accuracy of the combustion pressure by the sensor element can be further improved.

(4) In the combustion pressure sensor of the above aspect, the tip portion is formed on the rear end side in the axial direction with respect to the first portion including the opening and the first portion, and has an inner diameter larger than the opening. The second curved portion and the second cylindrical portion of the elastic member, and the second portion when viewed from the axial direction of the wall portion. The outermost diameter portion that overlaps at least a part of the curved portion is disposed in the second portion, and the outermost diameter of the outermost diameter portion may be larger than the inner diameter of the opening. According to this aspect, it is possible to extend the path through which the combustion gas that enters the inside of the housing from the opening reaches the second curved portion. Thereby, the change of the displacement characteristic of the elastic member with respect to the thermal shock by combustion gas can be suppressed further.

(5) In the combustion pressure sensor according to the above aspect, the tip has a tip surface around the opening when viewed from the axial direction, and the tip surface when viewed from the axial direction. May overlap at least a part of the second curved portion. According to this configuration, the tip surface can further prevent the second curved portion from being directly exposed to the combustion gas entering the inside of the housing from the opening.

(6) In the combustion pressure sensor of the above aspect, the wall portion may overlap the entire second curved portion when viewed from the axial direction. According to this aspect, the wall portion can further prevent the second curved portion from being directly exposed to the combustion gas entering the inside of the housing from the opening.

(7) In the combustion pressure sensor of the above aspect, the shortest distance between the wall portion and the second curved portion may be greater than 0.0 mm and 0.5 mm or less. According to this aspect, the wall portion can further prevent the second curved portion from being directly exposed to the combustion gas entering the inside of the housing from the opening.

(8) In the combustion pressure sensor of the above aspect, the wall portion may be a member different from the elastic member. According to this form, the material suitable for each member of a wall part and an elastic member is employable.

  The present invention can be realized in various forms different from the combustion pressure sensor. For example, the present invention can be realized in the form of a glow plug with a sensor, a component of a glow plug, a manufacturing method for manufacturing a glow plug, and the like.

It is an external view which shows a glow plug. It is sectional drawing which shows a glow plug. It is an expanded sectional view showing the tip side of a glow plug. It is an expanded sectional view which expands and shows a part of glow plug centering on the front end side of a housing. It is an expanded sectional view which expands and shows a part of glow plug centering on an elastic member. It is a graph which shows the result of having evaluated the influence which a thermal shock gives to an elastic member. It is a graph which shows the result of having evaluated the relationship between distance and thermal shock. It is an expanded sectional view showing a part of glow plug in a 2nd embodiment. It is an expanded sectional view showing a part of glow plug in a 3rd embodiment. It is an expanded sectional view showing a part of glow plug in a 4th embodiment. It is an expanded sectional view showing a part of glow plug in a 5th embodiment. It is an expanded sectional view showing a part of glow plug in a 6th embodiment. It is an expanded sectional view showing a part of glow plug in a 7th embodiment. It is an expanded sectional view showing a part of glow plug in an 8th embodiment. It is an expanded sectional view showing a part of glow plug in a 9th embodiment. It is an expanded sectional view showing a part of glow plug in a 10th embodiment. It is an external view which shows the combustion pressure sensor in 11th Embodiment.

A. First Embodiment FIG. 1 is an external view showing a glow plug 10. The glow plug 10 is configured as a heat source that assists ignition in starting an internal combustion engine (not shown) such as a diesel engine, and is configured to be able to detect the pressure in the combustion chamber.

  In the description of the present embodiment, the lower side of the paper in the glow plug 10 of FIG. 1 is referred to as “front end side”, and the upper side of the paper in the glow plug 10 of FIG. The XYZ axes in FIG. 1 have an X axis, a Y axis, and a Z axis as three spatial axes orthogonal to each other. In the present embodiment, the Z axis is an axis along the axis AL of the glow plug 10. Among the X-axis directions along the X-axis, the + X-axis direction is a direction from the front of the paper to the back of the paper, and the −X-axis direction is a direction opposite to the + X-axis direction. Among the Y-axis directions along the Y-axis, the + Y-axis direction is a direction from the right side of the drawing to the left side of the drawing, and the −Y-axis direction is a direction opposite to the + Y-axis direction. Among the Z-axis directions (axial directions) along the Z-axis, the + Z-axis direction is a direction from the front end side to the rear end side, and the −Z-axis direction is a direction opposite to the + Z-axis direction. The XYZ axes in FIG. 1 correspond to the XYZ axes in the other drawings.

  FIG. 2 is a cross-sectional view showing the glow plug 10. FIG. 2 shows a cross-sectional shape of the glow plug 10 cut along a plane passing through the axis AL. FIG. 3 is an enlarged cross-sectional view showing the tip side of the glow plug 10. The glow plug 10 includes a heater unit 100, middle shafts 210 and 260, a wall member 310, an elastic member 330, a sleeve 360, a diaphragm 370, a sensor element 375, a support member 380, a housing 500, and a protective cylinder. 610, a polygonal portion 614 for screwing, a connector member 620, a terminal spring 630, and a terminal member 640.

  The heater unit 100 of the glow plug 10 is a heat generating device that generates heat by converting electric energy into heat energy. In the present embodiment, the heater unit 100 is a sheath heater. The heater unit 100 is a bar-shaped member that has a bar shape extending in the axial direction from the rear end side to the front end side. The heater unit 100 includes a sheath tube 110 and a coil 120.

  The sheath tube 110 of the heater unit 100 is a metal conductor and has a cylindrical shape that extends from the rear end side to the front end side about the axis AL. The distal end side of the sheath tube 110 is closed and protrudes from the distal end side of the housing 500. The rear end side of the sheath tube 110 is open and is disposed inside the housing 500. On the rear end side of the sheath tube 110, the middle shaft 210 is inserted together with the sealing material 180. The sealing material 180 is a cylindrical member made of insulating rubber and seals between the sheath tube 110 and the central shaft 210.

  The coil 120 of the heater unit 100 is provided inside the sheath tube 110 and generates heat when energized. The distal end side of the coil 120 is joined to the inside of the sheath tube 110 by welding. The rear end side of the coil 120 is connected to the middle shaft 210.

  An insulating powder 150 is filled inside the sheath tube 110. The insulating powder 150 is a powder having electrical insulating properties, and is mainly composed of magnesium oxide (MgO) in the present embodiment. The insulating powder 150 filled in the sheath tube 110 electrically insulates the gaps between the sheath tube 110, the coil 120, and the central shaft 210.

  The middle shafts 210 and 260 of the glow plug 10 are metal conductors. The middle shafts 210 and 260 relay power supplied from the outside of the glow plug 10 to the coil 120. In the present embodiment, the material of the middle shafts 210 and 260 is stainless steel (for example, SUS430). The middle shafts 210 and 260 have a rod shape extending from the rear end side to the front end side about the axis line AL. The distal end side of the middle shaft 210 is connected to the coil 120 inside the sheath tube 110. The rear end side of the middle shaft 210 protrudes from the sheath tube 110 and is connected to the front end side of the middle shaft 260. The rear end side of the middle shaft 260 is connected to the terminal spring 630.

  The protective cylinder 610 of the glow plug 10 is a metal conductor. In this embodiment, the material of the protection cylinder 610 is stainless steel (for example, SUS410, SUS630, etc.). The protective cylinder 610 has a cylindrical shape extending about the axis AL. The protective cylinder 610 is joined to the rear end portion of the housing 500. A terminal member 640 is held inside the protective cylinder 610 via a connector member 620.

  The connector member 620 of the glow plug 10 is a member having electrical insulation. In the present embodiment, the material of the connector member 620 is an insulating resin. The connector member 620 has a cylindrical shape. A terminal member 640 is fixed inside the connector member 620.

  The terminal spring 630 of the glow plug 10 is a metal conductor. In the present embodiment, the terminal spring 630 is stainless steel (for example, SUS304). The terminal spring 630 mechanically and electrically connects the middle shaft 260 and the terminal member 640 and absorbs the displacement of the middle shaft 260 accompanying the displacement of the heater unit 100. In the present embodiment, the terminal spring 630 is a curved leaf spring.

  The terminal member 640 of the glow plug 10 is a metal conductor. In the present embodiment, the material of the terminal member 640 is stainless steel (for example, SUS410, SUS630, etc.). The terminal member 640 receives power supplied from the outside of the glow plug 10. The electric power supplied to the terminal member 640 is supplied from the middle shaft 260 to the coil 120 via the middle shaft 210.

  FIG. 4 is an enlarged cross-sectional view showing a part of the glow plug 10 further enlarged with the front end side of the housing 500 as the center. The sleeve 360 of the glow plug 10 is a metal conductor. In this embodiment, the material of the sleeve 360 is stainless steel (for example, SUS410, SUS630, etc.). The sleeve 360 has a cylindrical shape extending about the axis AL. The sleeve 360 has a joint portion 362 joined to the side surface of the sheath tube 110. In the present embodiment, a welding portion W11 formed by welding with the sheath tube 110 is formed in the joint portion 362. In other embodiments, the joint 362 may be joined to the side surface of the sheath tube 110 by press-fitting. The rear end side of the sleeve 360 extends from the sheath tube 110 to the rear end side, and is joined to the diaphragm 370. The sleeve 360 transmits the displacement of the heater unit 100 to the diaphragm 370.

  The diaphragm 370 of the glow plug 10 is a metal conductor. In this embodiment, the material of the diaphragm 370 is stainless steel (for example, SUS410, SUS630, etc.). Diaphragm 370 has an annular shape centering on axis AL. A sleeve 360 is joined to the inner peripheral side of the diaphragm 370. A support member 380 is joined to the outer peripheral side of the diaphragm 370. The diaphragm 370 is deformed according to the displacement of the heater unit 100 transmitted through the sleeve 360.

  The sensor element 375 of the glow plug 10 detects the combustion pressure received by the heater unit 100 according to the displacement of the heater unit 100. In the present embodiment, the sensor element 375 is joined to the diaphragm 370 and converts the displacement of the heater unit 100 transmitted to the diaphragm 370 by the sleeve 360 into an electrical signal. The electrical signal output from the sensor element 375 indicates the combustion pressure received by the heater unit 100. In the present embodiment, the sensor element 375 is a piezoresistive element.

  The support member 380 of the glow plug 10 is a metal conductor. In the present embodiment, the material of the support member 380 is stainless steel (for example, SUS410, SUS630, etc.). The support member 380 has a cylindrical shape extending about the axis AL. The rear end side of the support member 380 is joined to the diaphragm 370. The support member 380 has a tip portion 382 and a joint portion 384. The distal end portion 382 of the support member 380 constitutes a portion on the distal end side of the support member 380 and is joined to the elastic member 330. In the present embodiment, a welded portion W14 formed by welding with the elastic member 330 is formed at the distal end portion 382. The joint portion 384 of the support member 380 is located on the rear end side from the front end portion 382 and is joined to the housing 500. In the present embodiment, welded portions W15 and W16 formed by welding with the housing 500 are formed in the joint portion 384.

  The housing 500 of the glow plug 10 is a metal conductor and has a cylindrical shape having an opening 512 on the tip side. The housing 500 accommodates a part of the heater unit 100 in a state where the heater unit 100 protrudes from the opening 512 toward the tip side. In this embodiment, the housing 500 includes the inner shafts 210 and 260, the wall member 310, the elastic member 330, the sleeve 360, the diaphragm 370, the sensor element 375, and the support member 380 in addition to the heater unit 100. To house. In the present embodiment, the housing 500 includes a distal end portion 510 and a main body portion 550.

  The front end portion 510 of the housing 500 is a cylindrical member that is positioned on the front end side of the housing 500 and that forms the opening 512. In the present embodiment, the material of the tip portion 510 is stainless steel (for example, SUS630). In the present embodiment, the rear end side of the front end portion 510 is connected to the front end side of the main body portion 550 via the joint portion 384 of the support member 380. In the present embodiment, the tip portion 510 accommodates the wall member 310 and the elastic member 330 inside.

  The main body 550 of the housing 500 is a cylindrical member located on the rear end side from the front end portion 510. In the present embodiment, the main body 550 is made of carbon steel. In another embodiment, the material of the main body 550 may be stainless steel (for example, SUS630). In the present embodiment, the main body portion 550 has a screw portion 554 configured to be fitted to a female screw formed in an internal combustion engine (not shown).

  FIG. 5 is an enlarged cross-sectional view showing a part of the glow plug 10 further enlarged with the elastic member 330 as the center. The elastic member 330 of the glow plug 10 is a cylindrical member formed by molding a thin metal plate. In the present embodiment, the material of the elastic member 330 is stainless steel (for example, SUS316). In another embodiment, the material of the elastic member 330 may be a nickel alloy (for example, Inconel 718 (“INCONEL” is a registered trademark)).

  The elastic member 330 connects the heater unit 100 and the housing 500 inside the housing 500, and is elastically deformed so that the heater unit 100 can move in the axial direction along the axis AL. In the present embodiment, the elastic member 330 connects the heater unit 100 and the housing 500 via the support member 380 inside the front end portion 510 of the housing 500. The elastic member 330 includes a first tubular portion 332, a first curved portion 334, a second curved portion 336, and a second tubular portion 338.

  The first tubular portion 332 in the elastic member 330 has a tubular shape surrounding the side surface of the heater unit 100 and is joined to the heater unit 100. In the present embodiment, the first cylindrical portion 332 is joined to the side surface of the sheath tube 110 on the distal end side from the sleeve 360. In the present embodiment, a welded portion W13 formed by welding with the sheath tube 110 is formed in the first tubular portion 332. In the present embodiment, the welded portion W13 is formed over the entire circumference of the first cylindrical portion 332.

  The first curved portion 334 of the elastic member 330 is curved in a convex shape toward the rear end side, and extends radially outward from the rear end side portion of the first cylindrical portion 332. A base point P12 illustrated in FIG. 5 indicates a position where the first tubular portion 332 and the first bending portion 334 are connected.

  The second curved portion 336 of the elastic member 330 is curved in a convex shape toward the distal end side, and extends radially outward from the outer peripheral side portion of the first curved portion 334. A base point P14 illustrated in FIG. 5 indicates a position where the first bending portion 334 and the second bending portion 336 are connected.

  The second cylindrical portion 338 of the elastic member 330 has a cylindrical shape connected to the outer peripheral side portion of the second curved portion 336 and is connected to the housing 500. A base point P16 illustrated in FIG. 5 indicates a position where the second bending portion 336 and the second tubular portion 338 are connected. In the present embodiment, the second cylindrical portion 338 is joined to the distal end portion 382 of the support member 380 and connected to the housing 500 via the support member 380. In the present embodiment, the second cylindrical portion 338 is joined to the outer surface of the distal end portion 382 of the support member 380. In the present embodiment, a welded portion W14 formed by welding with the support member 380 is formed on the second cylindrical portion 338. In the present embodiment, the welded portion W14 is formed over the entire circumference of the second cylindrical portion 338. The front end portion 510 of the housing 500 forms a gap GP between at least a part of the outer surface of the second cylindrical portion 338. In the present embodiment, the tip portion 510 forms a gap GP over the entire area on the outer surface of the second cylindrical portion 338.

  The wall member 310 of the glow plug 10 is a cylindrical member formed by molding a thin metal plate. In the present embodiment, the material of the wall member 310 is stainless steel (for example, SUS316). In another embodiment, the material of the wall member 310 may be a nickel alloy (for example, Inconel 718 (“INCONEL” is a registered trademark)). The wall member 310 is a member different from the elastic member 330. In the present embodiment, the wall member 310 includes a cylindrical portion 312 and a wall portion 314.

  The tubular portion 312 of the wall member 310 has a tubular shape surrounding the side surface of the heater portion 100 and is joined to the heater portion 100. In the present embodiment, the cylindrical portion 312 is joined to the side surface of the sheath tube 110 on the distal end side from the elastic member 330. In the present embodiment, the cylindrical portion 312 is formed with a welded portion W12 formed by welding with the sheath tube 110. In the present embodiment, the welded portion W12 is formed over the entire circumference of the cylindrical portion 312.

  The wall portion 314 of the wall member 310 is disposed on the distal end side of the second curved portion 336 inside the distal end portion 510, and is at least a part of the second curved portion 336 when viewed from the axial direction (Z-axis direction). And overlap. In the present embodiment, the wall portion 314 has a shape that protrudes radially outward of the sheath tube 110 from the distal end side portion of the elastic member 330 on the side surface of the sheath tube 110 on the inner side of the distal portion 510, and the axial direction (Z When viewed from the axial direction, the elastic member 330 overlaps at least part of the second curved portion 336 from the first tubular portion 332. In the present embodiment, the wall portion 314 has a shape extending radially outward from a portion on the rear end side of the tubular portion 312 and the entire elastic member 330 when viewed from the axial direction (Z-axis direction). And overlap. In the present embodiment, the wall 314 constitutes a surface along the XY plane. In other embodiments, the wall portion 314 may be an inclined surface inclined toward the front end side or an inclined surface inclined toward the rear end side.

  The distance Dw that is the shortest distance between the wall portion 314 and the second curved portion 336 is greater than 0.0 mm and less than or equal to 0.5 mm. The distance Dw is more preferably greater than 0.0 mm and less than or equal to 0.3 mm.

  The front end portion 510 of the housing 500 includes a first portion 521 including an opening 512 and a second portion 522 formed on the rear end side in the axial direction with respect to the first portion 521. The second portion 522 has an inner diameter larger than that of the opening 512, and the second portion 522 includes at least the second curved portion 336 and the second tubular portion 338 of the elastic member 330 and the wall portion 314. An outermost diameter portion that overlaps at least a part of the second bending portion 336 when viewed from the axial direction (Z-axis direction) is disposed. In the example of FIG. 5, the entire wall portion 314 is disposed in the second portion 522. However, when the position of the tubular portion 312 is changed to a lower side than that of FIG. Only a part of the second part 522 is disposed in the second part 522, and the other part is disposed in the first part 521. In this case, a portion of the wall portion 314 disposed in the second portion 522 corresponds to the “outermost diameter portion”. The outermost diameter of the wall portion 314 (outermost diameter portion) is preferably larger than the inner diameter of the opening 512. Here, the “outermost diameter of the wall portion 314 (outermost diameter portion)” means the outer diameter in a state where the wall portion 314 (outermost diameter portion) is projected in the direction of the axis AL. These configurations are also the same in second to eighth embodiments described later. By adopting such a shape, it is possible to extend the path through which the combustion gas entering the inside of the housing 500 from the opening 512 reaches the second curved portion 336. Moreover, the change of the displacement characteristic of the elastic member 330 with respect to the thermal shock by combustion gas can be suppressed further.

  When viewed from the axial direction (Z-axis direction) (when viewed from the bottom to the top in FIG. 5), the distal end portion 510 of the housing 500 has an opening 512 and a substantially conical distal end around the opening 512. A surface 530. In the example of FIG. 5, the front end surface 530 is divided into a flat surface 531 that surrounds the opening 512 and a tapered surface 532 that follows the rear end side of the flat surface 531, but a continuous curved surface without such a division. It is good. The tip surface 530 preferably overlaps at least a part of the second curved portion 336 when viewed from the axial direction. By adopting such a shape, the tip surface 530 can further prevent the second curved portion 336 from being directly exposed to the combustion gas entering the inside of the housing 500 from the opening 512.

  FIG. 6 is a graph showing the results of evaluating the influence of thermal shock on the elastic member 330. In the evaluation test of FIG. 6, the tester prepared a plurality of glow plugs having different modes for protecting the elastic member 330 as samples E0, E1, E2, E3, E4, and E5.

  The sample E0 is the same as the glow plug 10 described above except that the wall member 310 is not provided.

  The sample E1 is the same as the sample E0 except that the resin is applied only to the outer surface of the first cylindrical portion 332 in the surface of the elastic member 330.

  The sample E2 is the same as the sample E0 except that the resin is applied only to the outer surface of the first curved portion 334 in the surface of the elastic member 330.

  The sample E3 is the same as the sample E0 except that the resin is applied only to the outer surface of the second curved portion 336 in the surface of the elastic member 330.

  The sample E4 is the same as the sample E0 except that the resin is applied only to the outer surface of the second cylindrical portion 338 in the surface of the elastic member 330.

  The sample E5 is the same as the sample E0 except that a resin is applied to the entire outer surface of the elastic member 330.

  The tester attaches each sample to a test internal combustion engine equipped with a reference sensor and then operates the internal combustion engine at no load and 1000 rpm, while detecting the combustion pressure detected by the reference sensor and the combustion pressure detected by each sample. And measured. Thereafter, the tester obtained the result of FIG. 6 by calculating the error of each sample with respect to the reference sensor for each crank angle. The horizontal axis of FIG. 6 shows the crank angle of the internal combustion engine, and the vertical axis of FIG. 6 shows the error of each sample.

  According to the evaluation test of FIG. 6, it can be seen from the comparison between the sample E0 and the sample E5 that the error relative to the reference sensor can be suppressed by protecting the elastic member 330 from thermal shock. In addition, with respect to the portion that protects the elastic member 330, the first bending portion 334 (sample E2) and the second cylindrical portion 338 (sample E4) are more first than the first bending portion 334 (sample E4) from the viewpoint of suppressing an error with respect to the reference sensor. Next to the cylindrical portion 332 (sample E1), the second curved portion 336 (sample E3) is preferable.

  The result of the evaluation test in FIG. 6 is considered to be due to the following reason. The thermal shock is generated by adding the amount of thermal expansion in the axial direction of each part of the elastic member 330, so that the portions extending along the axial direction, such as the first cylindrical portion 332 and the second cylindrical portion 338. The effect of thermal shock tends to appear greatly in The second cylindrical portion 338 is joined to the housing 500 via the distal end portion 382 of the support member 380, and when the second cylindrical portion 338 is heated, the heat of the second cylindrical portion 338 is transferred to the housing. Heat is easily drawn to the 500 side. For this reason, even if the 2nd cylindrical part 338 is heated, the temperature rise of the 2nd cylindrical part 338 is small, and the influence of the thermal shock in the 2nd cylindrical part 338 is small. Therefore, when the sample E4 and the sample E1 are compared in the evaluation test of FIG. 6, it is considered that the sample E1 has a higher error suppression effect. On the other hand, in the first bending portion 334 and the second bending portion 336 that are portions extending along the direction intersecting the axial direction of the elastic member 330, the magnitude of the thermal shock is as viewed from the axial direction. It is influenced by each area. In the present embodiment, since the area of the second bending portion 336 when viewed from the axial direction is larger than the area of the first bending portion 334, the second bending portion 336 is more than the first bending portion 334. The impact of thermal shock is also great. Therefore, when the sample E2 and the sample E3 are compared in the evaluation test of FIG. 6, it is considered that the sample E3 has a higher error suppression effect.

  FIG. 7 is a graph showing the results of evaluating the relationship between the distance Dw and the thermal shock. The tester prepared a plurality of glow plugs having different distances Dw as samples, and obtained the result of FIG. 7 by measuring the pressure change due to the thermal shock in the second bending portion 336. The horizontal axis in FIG. 7 indicates the distance Dw, and the vertical axis in FIG. 7 indicates the pressure change due to the thermal shock in the second bending portion 336. According to the evaluation test of FIG. 7, the distance Dw is preferably 0.5 mm or less and more preferably 0.3 mm or less from the viewpoint of suppressing the pressure change due to the thermal shock in the second bending portion 336. preferable.

  According to the first embodiment described above, the axial direction (Z-axis direction) applied to the housing 500 by the gap GP formed between the front end portion 510 of the housing 500 and the outer surface of the second cylindrical portion 338. The wall portion 314 can prevent the second curved portion 336 from being directly exposed to the combustion gas that enters the inside of the housing 500 from the opening portion 512. Thereby, the change of the displacement characteristic of the elastic member 330 with respect to the thermal shock by combustion gas can be suppressed. As a result, the detection accuracy of the combustion pressure by the sensor element 375 can be improved.

  Further, the wall portion 314 has a shape that protrudes radially outward of the sheath tube 110 from a portion of the side surface of the sheath tube 110 on the side surface of the sheath tube 110 on the side of the distal end side of the distal end portion 510, and is axially (Z-axis direction). When viewed from above, the first cylindrical portion 332 and the second curved portion 336 of the elastic member 330 overlap with the whole. Therefore, in addition to the second curved portion 336, the first cylindrical portion 332 and the first curved portion 334 are directly exposed to the combustion gas that enters the inside of the housing 500 from the opening 512. This can be prevented by the part 314. Thereby, the change of the displacement characteristic of the elastic member 330 with respect to the thermal shock by combustion gas can be suppressed further. As a result, the detection accuracy of the combustion pressure by the sensor element 375 can be further improved.

  In addition, since the distance Dw between the wall portion 314 and the second curved portion 336 is greater than 0.0 mm and equal to or less than 0.5 mm, the second curve is applied to the combustion gas that enters the housing 500 from the opening 512. The wall 314 can further prevent the part 336 from being directly exposed. Moreover, since the wall part 314 is a member different from the elastic member 330, the material suitable for each member of the wall part 314 and the elastic member 330 is employable.

B. Second Embodiment FIG. 8 is an enlarged cross-sectional view showing a part of a glow plug 10B according to a second embodiment. The glow plug 10B of the second embodiment is the same as the glow plug 10 of the first embodiment except that the wall member 310B and the elastic member 330B are provided instead of the wall member 310 and the elastic member 330.

  The elastic member 330B of the glow plug 10B is the first embodiment except that the first tubular portion 332B configured to be welded to the sheath tube 110 together with the wall member 310B is replaced with the first tubular portion 332. It is the same as the elastic member 330 of the form. In the present embodiment, the first tubular portion 332B of the elastic member 330B is the same as the first tubular portion 332 except that the first tubular portion 332B is longer in the axial direction than the first tubular portion 332. In the present embodiment, a welded portion W22 formed by welding with the sheath tube 110 is formed in the first tubular portion 332B. In the present embodiment, the welded portion W22 is formed over the entire circumference of the first cylindrical portion 332B.

  The wall member 310B of the glow plug 10B is the same as the wall member 310 of the first embodiment except that the wall member 310B of the glow plug 10B is welded to the sheath tube 110 via the elastic member 330B. In the present embodiment, a welded portion W22 formed by welding with the sheath tube 110 via the elastic member 330B is formed in the tubular portion 312 of the wall member 310B. In the present embodiment, the welded portion W22 is formed over the entire circumference of the cylindrical portion 312.

  According to the second embodiment described above, the detection accuracy of the combustion pressure by the sensor element 375 can be improved as in the first embodiment. The wall portion 314 has a shape protruding from the first tubular portion 332B to the outside in the radial direction of the sheath tube 110, and the second curved portion 336 as a whole when viewed from the axial direction (Z-axis direction). And overlap. Therefore, in addition to the second curved portion 336, a part of the first tubular portion 332B and the first curved portion 334 are directly exposed to the combustion gas entering the inside of the housing 500 from the opening 512. This can be prevented by the wall portion 314. Thereby, the change of the displacement characteristic of the elastic member 330B with respect to the thermal shock by combustion gas can be suppressed further. As a result, the detection accuracy of the combustion pressure by the sensor element 375 can be further improved.

C. Third Embodiment FIG. 9 is an enlarged cross-sectional view showing a part of a glow plug 10C according to a third embodiment. The glow plug 10C of the third embodiment is the same as the glow plug 10 of the first embodiment, except that the wall member 310C is provided instead of the wall member 310.

  The wall member 310C of the glow plug 10C is the same as the wall member 310 of the first embodiment except that the wall part 314C is provided instead of the wall part 314. The wall portion 314C of the wall member 310C extends from the tubular portion 312 in the + Z-axis direction to the first tubular portion 332 of the elastic member 330 and has a shape that protrudes outward in the radial direction of the sheath tube 110. This is the same as the wall portion 314 of the first embodiment.

  According to the third embodiment described above, the wall portion 314 </ b> C can prevent the second curved portion 336 from being directly exposed to the combustion gas that enters the inside of the housing 500 from the opening portion 512. As a result, as with the first embodiment, the detection accuracy of the combustion pressure by the sensor element 375 can be improved.

D. Fourth Embodiment FIG. 10 is an enlarged cross-sectional view showing a part of a glow plug 10D according to a fourth embodiment. The glow plug 10D of the fourth embodiment is the same as the glow plug 10 of the first embodiment, except that the wall member 310D is provided instead of the wall member 310.

  The wall member 310D of the glow plug 10D is the same as the wall member 310 of the first embodiment except that the wall part 314D is provided instead of the wall part 314. The wall portion 314D of the wall member 310D is the same as the wall portion 314 of the first embodiment except that the wall portion 314D is an inclined surface facing the side surface and the rear end side of the sheath tube 110. In the present embodiment, the wall portion 314D overlaps the entire elastic member 330 when viewed from the axial direction (Z-axis direction).

  According to the fourth embodiment described above, the wall portion 314D can prevent the second curved portion 336 from being directly exposed to the combustion gas entering the interior of the housing 500 from the opening portion 512. As a result, as with the first embodiment, the detection accuracy of the combustion pressure by the sensor element 375 can be improved.

  Further, since the surface area of the wall portion 314D having the inclined surface is increased as compared with the case where the wall portion 314D is perpendicular to the side surface of the sheath tube 110, the wall portion 314D is removed from the combustion gas entering the inside of the housing 500 from the opening portion 512. The amount of heat taken away can be increased. As a result, the thermal shock received by the elastic member 330 can be suppressed.

E. Fifth Embodiment FIG. 11 is an enlarged cross-sectional view showing a part of a glow plug 10E according to a fifth embodiment. The glow plug 10E of the fifth embodiment is the same as the glow plug 10 of the first embodiment, except that the wall member 310 and the elastic member 330 are replaced with an elastic member 330E.

  The elastic member 330E of the glow plug 10E is the same as the elastic member 330 of the first embodiment except that it has a wall portion 314E. The wall portion 314E of the elastic member 330E has a shape extending radially outward from the distal end side portion of the first tubular portion 332. A base point P51 illustrated in FIG. 11 indicates a position where the first cylindrical portion 332 and the wall portion 314E are connected. The wall portion 314E overlaps at least a part of the second bending portion 336 when viewed from the axial direction (Z-axis direction). In the present embodiment, the wall portion 314E overlaps the entire second bending portion 336 when viewed from the axial direction (Z-axis direction). In the present embodiment, the wall portion 314E constitutes a surface along the XY plane. In another embodiment, the wall portion 314E may be an inclined surface inclined toward the front end side, or may be an inclined surface inclined toward the rear end side.

  According to the fifth embodiment described above, the wall portion 314E can prevent the second curved portion 336 from being directly exposed to the combustion gas entering the inside of the housing 500 from the opening portion 512. As a result, as with the first embodiment, the detection accuracy of the combustion pressure by the sensor element 375 can be improved.

F. 6th Embodiment FIG. 12: is an expanded sectional view which shows a part of glow plug 10F in 6th Embodiment. The glow plug 10F according to the sixth embodiment is the same as the glow plug 10 according to the first embodiment except that an elastic member 330F is provided instead of the elastic member 330.

  The elastic member 330F of the glow plug 10F is the same as the elastic member 330 of the first embodiment except that a linear portion 335F is provided between the first curved portion 334 and the second curved portion 336. The straight portion 335F of the elastic member 330F has a cylindrical shape that connects the first bending portion 334 and the second bending portion 336. The cross section of the straight line portion 335F along the axial direction forms a straight line. A base point P64 illustrated in FIG. 12 indicates a position where the first bending portion 334 and the linear portion 335F are connected. A base point P65 illustrated in FIG. 12 indicates a position where the straight portion 335F and the second curved portion 336 are connected.

  According to the sixth embodiment described above, the detection accuracy of the combustion pressure by the sensor element 375 can be improved as in the first embodiment.

G. 7th Embodiment FIG. 13: is an expanded sectional view which shows a part of glow plug 10G in 7th Embodiment. The glow plug 10G of the seventh embodiment is the same as the glow plug 10 of the first embodiment except that an elastic member 330G is provided instead of the elastic member 330.

  The elastic member 330G of the glow plug 10G has the first bending portion 334G and the second bending portion 336G in place of the first bending portion 334 and the second bending portion 336, except for the point of the first embodiment. Similar to the elastic member 330. The first bending portion 334G in the elastic member 330G is the same as the first bending portion 334 in the first embodiment, except that the first bending portion 334G has a shape protruding to the rear end side from the base point P74 connected to the second bending portion 336G. It is. The second bending portion 336G in the elastic member 330G is the same as the second bending portion 336 in the first embodiment, except that the second bending portion 336G has a shape protruding to the distal end side from the base point P74 connected to the first bending portion 334G. is there.

  According to the seventh embodiment described above, the detection accuracy of the combustion pressure by the sensor element 375 can be improved as in the first embodiment.

H. Eighth Embodiment FIG. 14 is an enlarged cross-sectional view showing a part of a glow plug 10H in an eighth embodiment. The glow plug 10H of the eighth embodiment is the same as the glow plug 10G of the seventh embodiment except that an elastic member 330H is provided instead of the elastic member 330G.

  The elastic member 330H of the glow plug 10H is the same as the elastic member 330G of the seventh embodiment, except that the second tubular portion 338 is provided instead of the second tubular portion 338. The second cylindrical portion 338H in the elastic member 330H is the second cylindrical portion 338 in the seventh embodiment, except that the portion joined to the distal end portion 382 of the support member 380 is thicker than other portions. It is the same.

  According to the eighth embodiment described above, the combustion pressure detection accuracy by the sensor element 375 can be improved as in the seventh embodiment.

I. Ninth Embodiment FIG. 15 is an enlarged cross-sectional view showing a part of a glow plug 10I according to a ninth embodiment. The glow plug 10I according to the ninth embodiment is the same as the glow plug 10 according to the first embodiment except that a wall portion 314I is provided instead of the wall member 310.

  The wall portion 314I of the glow plug 10I has a shape protruding toward the sheath tube 110 from the distal end side portion of the second curved portion 336 on the inner surface of the distal end portion 510, and is second when viewed from the axial direction. This overlaps at least a part of the curved portion 336. In the present embodiment, the wall portion 314I overlaps with the entire second curved portion 336 when viewed from the axial direction. In the present embodiment, the wall portion 314 </ b> I is configured as a part of the distal end portion 510. In other embodiments, the wall portion 314 </ b> I may be configured by joining a member different from the tip portion 510 to the tip portion 510. In this embodiment, the distance Dw between the wall part 314I and the 2nd curved part 336 is larger than 0.0 mm and 0.5 mm or less.

  According to the ninth embodiment described above, the wall configured as a part of the housing 500 that the second curved portion 336 is directly exposed to the combustion gas entering the interior of the housing 500 from the opening 512. This can be prevented by the part 314I. As a result, as with the first embodiment, the detection accuracy of the combustion pressure by the sensor element 375 can be improved.

J. et al. Tenth Embodiment FIG. 16 is an enlarged cross-sectional view showing a part of a glow plug 10J in a tenth embodiment. The glow plug 10J of the tenth embodiment is the same as the glow plug 10I of the ninth embodiment, except that a wall portion 316J is provided.

  The wall portion 316J of the glow plug 10J protrudes radially outward of the sheath tube 110 from the distal end portion of the side surface of the sheath tube 110 on the inner side of the distal portion 510 and is at least first when viewed from the axial direction. This is another wall portion overlapping the cylindrical portion 332. Similar to the wall portion 314 of the first embodiment described in FIG. 5, the outermost diameter of the wall portion 316 </ b> J is preferably larger than the inner diameter of the opening portion 512.

  In the present embodiment, the wall portion 316J is a cylindrical member formed by molding a thin metal plate, similar to the wall member 310 of the first embodiment. In the present embodiment, the wall portion 316J is joined to the side surface of the sheath tube 110 by welding.

  In the present embodiment, the wall portion 316J is disposed on the tip side from the wall portion 314I. In other embodiments, the wall portion 316J may be disposed on the rear end side of the wall portion 314I.

  According to the tenth embodiment described above, the detection accuracy of the combustion pressure by the sensor element 375 can be improved as in the ninth embodiment. Further, the wall portion 316J can prevent the first cylindrical portion 332 from being directly exposed to the combustion gas entering the inside of the housing 500 from the opening portion 512. Thereby, the change of the displacement characteristic of the elastic member 330 with respect to the thermal shock by combustion gas can be suppressed further. As a result, the detection accuracy of the combustion pressure by the sensor element 375 can be further improved.

  Further, since the wall portion 316J is arranged on the front end side from the wall portion 314I, compared with the case where the wall portion 316J is arranged on the rear end side from the wall portion 314I, the inside of the housing 500 is formed from the opening portion 512. It is possible to extend the path of the combustion gas that enters into the second curved portion 336. Thereby, the change of the displacement characteristic of the elastic member 330 with respect to the thermal shock by combustion gas can be suppressed further.

K. Other Embodiments The present invention is not limited to the above-described embodiments, examples, and modifications, and can be realized with various configurations without departing from the spirit thereof. For example, among the technical features in the embodiments, examples, and modifications, those corresponding to the technical features in each embodiment described in the summary section of the invention are for solving some or all of the above-described problems. Alternatively, in order to achieve part or all of the above-described effects, replacement and combination can be performed as appropriate. Further, technical features that are not described as essential in the present specification can be appropriately deleted.

  For example, the heater unit 100 is not limited to a sheath heater, and may be a ceramic heater. Further, the present invention can be applied to a combustion pressure sensor in which the heater unit 100 is replaced with another rod-like member different from the heat generating device. Moreover, the wall part should just overlap with at least one part of the 2nd curved part in an elastic member instead of the whole elastic member, when it sees from an axial direction.

  FIG. 17 is an external view showing a combustion pressure sensor 10K in the eleventh embodiment. The difference from the first embodiment shown in FIG. 1 is that a rod-like member (not shown) that does not have a heat generation function is used instead of the heater portion 100, and this rod-like member protrudes from the tip portion 510 of the housing 500 to the outside. There are only points that are not present, and other configurations are the same as those of the first embodiment. In addition, it is preferable that the front-end | tip of a rod-shaped member is extended to the position where the periphery is enclosed by the opening part 512 (FIG. 4) of the housing 500. This combustion pressure sensor 10K can also exhibit substantially the same effect as in the first embodiment.

10, 10B to 10J ... Glow plug 10K ... Combustion pressure sensor 100 ... Heater (bar-shaped member)
DESCRIPTION OF SYMBOLS 110 ... Sheath tube 120 ... Coil 150 ... Insulating powder 180 ... Sealing material 210, 260 ... Middle shaft 310, 310B, 310C, 310D ... Wall member 312 ... Cylindrical part 314, 314C, 314D, 314E, 314I, 316J ... Wall part 330 , 330B, 330E, 330F, 330G, 330H ... elastic members 332, 332B ... first cylindrical portion 334, 334G ... first curved portion 335F ... linear portion 336, 336G ... second curved portion 338, 338H ... first 2 cylindrical part 360 ... sleeve 362 ... joint part 370 ... diaphragm 375 ... sensor element 380 ... support member 382 ... tip part 384 ... joint part 500 ... housing 510 ... tip part 512 ... opening 521 ... first part 522 ... first part 2 parts 530 ... tip surface 531 ... flat surface 532 ... taper surface 50 ... main body 554 ... the screw 610 ... protecting cylinder 614 ... polygonal portion 620 ... connector member 630 ... terminal spring 640 ... terminal member

Claims (9)

A rod-like member extending in the axial direction from the rear end side to the front end side;
A cylindrical housing having an opening on the tip side, and housing at least a part of the rod-shaped member;
An elastic member that connects the rod-shaped member and the housing inside the housing, and the rod-shaped member is elastically deformed so as to be movable in the axial direction;
A combustion pressure sensor comprising: a sensor element that is housed in the housing and detects a combustion pressure received by the rod-shaped member in response to displacement of the rod-shaped member;
The elastic member is
A cylindrical shape surrounding a side surface of the rod-shaped member, a first cylindrical portion joined to the rod-shaped member;
A first curved portion that curves in a convex shape toward the rear end side and extends radially outward from a portion on the rear end side in the first cylindrical portion;
A second curved portion that curves in a convex shape toward the distal end side and extends radially outward from a portion on the outer peripheral side of the first curved portion;
A cylindrical shape connected to an outer peripheral portion of the second curved portion, and a second cylindrical portion connected to the housing;
The housing constitutes the opening, accommodates at least a part of the first cylindrical part to at least a part of the second cylindrical part in the elastic member, and the second cylindrical shape A tip portion that forms a gap with at least a portion of the outer surface of the portion;
And a wall portion that is disposed closer to the distal end side than the second curved portion inside the distal end portion and overlaps at least a part of the second curved portion when viewed from the axial direction. Combustion pressure sensor.   The wall portion has a shape protruding radially outward of the rod-shaped member from a portion on the tip side from the elastic member on the side surface of the rod-shaped member, and the wall portion of the elastic member when viewed from the axial direction. 2. The combustion pressure sensor according to claim 1, wherein the combustion pressure sensor overlaps from one cylindrical portion to at least a part of the second curved portion.   The wall portion has a shape protruding from the first tubular portion to the outside in the radial direction of the rod-shaped member, and when viewed from the axial direction, the wall portion extends from the first curved portion in the elastic member. The combustion pressure sensor according to claim 1, wherein the combustion pressure sensor overlaps with at least a part of the curved portion. The tip has a first part including the opening, and a second part formed on the rear end side in the axial direction than the first part and having a larger inner diameter than the opening,
Outermost diameter that overlaps at least a part of the second curved portion when viewed from the axial direction among the wall portions, and at least the second curved portion and the second cylindrical portion of the elastic member. Part is arranged in the second part,
The combustion pressure sensor according to any one of claims 1 to 3, wherein an outermost diameter of the outermost diameter portion is larger than an inner diameter of the opening. The tip has a tip surface around the opening when viewed from the axial direction;
The combustion pressure sensor according to any one of claims 1 to 4, wherein the tip surface overlaps at least a part of the second curved portion when viewed from the axial direction.   The combustion pressure sensor according to any one of claims 1 to 5, wherein the wall portion overlaps the entire second curved portion when viewed from the axial direction.   The combustion pressure sensor according to any one of claims 1 to 6, wherein a shortest distance between the wall portion and the second curved portion is greater than 0.0 mm and equal to or less than 0.5 mm.   The combustion pressure sensor according to any one of claims 1 to 7, wherein the wall portion is a member different from the elastic member. A heater portion that forms a rod shape extending in the axial direction from the rear end side to the front end side, and generates heat by energization;
A housing having an opening on the tip side, and housing at least a part of the heater;
An elastic member that connects the heater part and the housing inside the housing and elastically deforms the heater part so as to be movable in the axial direction;
A glow plug including a sensor element housed in the housing and detecting a combustion pressure received by the heater unit in accordance with a displacement of the heater unit,
The elastic member is
A cylindrical shape surrounding a side surface of the heater portion, a first cylindrical portion joined to the heater portion;
A first curved portion that curves in a convex shape toward the rear end side and extends radially outward from a portion on the rear end side in the first cylindrical portion;
A second curved portion that curves in a convex shape toward the distal end side and extends radially outward from a portion on the outer peripheral side of the first curved portion;
A cylindrical shape connected to an outer peripheral portion of the second curved portion, and a second cylindrical portion connected to the housing;
The housing constitutes the opening, accommodates at least a part of the first cylindrical part to at least a part of the second cylindrical part in the elastic member, and the second cylindrical shape A tip portion that forms a gap with at least a portion of the outer surface of the portion;
And a wall portion that is disposed closer to the distal end side than the second curved portion inside the distal end portion and overlaps at least a part of the second curved portion when viewed from the axial direction. Glow plug.

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