JP5047770B2 - Glow plug with combustion pressure sensor - Google Patents

Description

  The present invention relates to a glow plug with a combustion pressure sensor used for an internal combustion engine such as an automobile engine.

2. Description of the Related Art Conventionally, a glow plug with a combustion pressure sensor provided with a combustion pressure sensor for detecting the combustion pressure of the internal combustion engine is known as a glow plug used in an internal combustion engine such as a diesel engine for automobiles. As such a glow plug with a combustion pressure sensor, for example, a heater is supported on the housing in a state in which the heater can be displaced in the axial direction by a support tube or the like provided in the housing and having axial extensibility. A glow plug with a combustion pressure sensor is known in which a heater is displaced toward the rear end side in the axial direction by a combustion pressure applied to the pressure sensor and presses the pressure sensor (see, for example, Patent Document 1).
JP 2007-120939 A

  In the above-described conventional glow plug with a combustion pressure sensor, the soot generated in the combustion chamber is clogged between the support tube having axial extensibility that supports the heater and the housing, and the displacement of the heater is hindered or the combustion is prevented. When used over a long period of time, for example, the axial extensibility of the support tube changes due to the influence of heat, there has been a problem that it becomes increasingly difficult to detect the combustion pressure with high accuracy.

  The present invention has been made to solve the above problems. An object of this invention is to provide the glow plug with a combustion pressure sensor which can detect a combustion pressure with high precision over a long period of time.

The glow plug with a combustion pressure sensor of the present invention is formed in a cylindrical shape, has a seat surface in close contact with the engine on the axial front end side, and an engine mounting screw on the outer peripheral surface on the axial rear end side from the seat surface A housing having a portion, a pressure detection element, and a heater provided such that a front end side protrudes from a front end portion of the housing and a rear end side is accommodated in the housing, and a front end surface is a pressure receiving surface, A heater that transmits a combustion pressure to a pressure detection element; and a heater support member that supports the heater with respect to the housing, and is provided so as to be positioned on the front end side of the seat surface and applied to the pressure receiving surface. A cylindrical movable part that displaces the heater in the axial direction by being elastically deformed in accordance with the combustion pressure, and a heater connection part that is provided on the distal end side of the movable part and connected to the heater The at the rear end side of the sheet surface; and a heater support member; and a housing connection portion connected to the housing, wherein the outer diameter R1 of the heater connection portion to the outer diameter R2 of the movable portion R1> It is characterized by R2 .

  In the glow plug with a combustion pressure sensor according to the present invention, the heater supporting member that supports the heater with respect to the housing is provided so as to be positioned on the front end side from the seat surface, and is elastic according to the combustion pressure applied to the pressure receiving surface. A cylindrical movable part that displaces the heater in the axial direction by being deformed in a mechanical manner is provided. That is, this movable part is provided outside the housing. Therefore, a flaw is clogged between the movable part and the housing, the axial displacement of the heater is not hindered and the combustion pressure detection accuracy is not lowered, and high-precision combustion pressure detection can be performed over a long period of time. .

  In the glow plug with a combustion pressure sensor having the above configuration, it is preferable that the pressure detection element is provided on the rear end side of the housing connecting portion of the heater support member. With such a configuration, it is possible to suppress the pressure detection element from being deteriorated due to the thermal influence of the combustion gas. That is, in general, in a glow plug with a combustion pressure sensor, combustion gas enters the housing up to the housing connecting portion of the heater support member, and is greatly affected by the thermal influence. For this reason, if a pressure detection element is provided in the rear end side from the housing connection part of a heater support member, the thermal influence of combustion gas can be reduced.

  In the glow plug with the combustion pressure sensor having the above-described configuration, the movable portion is provided at a position where the movable portion is hidden from view by a member provided on the distal end side of the movable portion when viewed from the distal end side in the axial direction. It is preferable. With such a configuration, it is possible to suppress the heat in the combustion chamber from being directly applied to the movable part and degrading the movable part due to thermal influence.

  In the glow plug with the combustion pressure sensor configured as described above, the movable portion of the heater support member can be formed of a thin portion that is thinner than the portion of the heater support member other than the movable portion. Moreover, the movable part of the heater support member can also be constituted by a bellows. Furthermore, it is preferable that the movable part of the heater support member is composed of a member having a Young's modulus lower than that of the heater support member other than the movable part. By adopting such a configuration, it is possible to promote the displaceability in the axial direction of the heater and perform good pressure transmission of the combustion pressure to the pressure sensor.

  According to the glow plug with a combustion pressure sensor of the present invention, it is possible to provide a glow plug with a combustion pressure sensor that can detect combustion pressure with high accuracy over a long period of time.

  Embodiments of the present invention will be described below with reference to the drawings. 1 and 2 show a configuration of a glow plug 100 with a combustion pressure sensor according to an embodiment of the present invention. FIG. 1 is an enlarged cross-sectional view showing a tip portion of the glow plug 100 with a combustion pressure sensor. FIG. 2 is a partially cutaway side view showing the overall configuration of a glow plug 100 with a combustion pressure sensor.

  As shown in FIGS. 1 and 2, the glow plug 100 with a combustion pressure sensor is made of a high-strength metal such as carbon steel (S45C, etc.), stainless steel (eg, SUS430, SUS630, etc.), and has a substantially cylindrical shape. A formed housing 1 is provided. The housing 1 is configured by connecting a front end side housing 2 and a rear end side housing 3.

  As shown in FIG. 2, a screw portion 4 for attaching the glow plug 100 with a combustion pressure sensor to an engine (engine) (not shown) is formed on the outer peripheral surface of the rear end side housing 3. A tool engaging portion 5 for engaging a tool such as a spanner or a wrench when the housing 1 is attached to the engine is provided on the outer peripheral portion on the rear end side of the screw portion 4.

  As shown in FIG. 1, the front end side housing 2 has an opening 6 for causing the heater 20 to protrude from the front end of the housing 1, and the end surface on the front end side in the axial direction is an automobile diesel engine. A sheet surface (tapered surface) 7 that is in close contact with the engine is formed. A heater support member 10 made of a metal such as stainless steel (for example, SUS430, SUS630, etc.) and formed in a substantially cylindrical shape is provided in the opening 6, and the heater 20 is provided inside the heater support member 10. Is provided. The heater 20 is composed of, for example, a ceramic heater (made of silicon nitride, alumina, or the like) in which a conductive ceramic 22 is provided inside an insulating ceramic 21, or a metal glow heater (made of a coil, a stainless tube, insulating powder, or the like). Has been. The tip surface 23 of the heater 20 shown in FIG. 2 is a pressure receiving surface that receives the combustion pressure in the combustion chamber.

  As shown in FIG. 1, the heater support member 10 includes a housing connection portion 11 formed of a flange protruding in a bowl shape on the outer side of the intermediate portion. The heater support member 10 is connected to the housing 1 by fixing the housing connection portion 11 by welding or the like in a state of being interposed between the front end side housing 2 and the rear end side housing 3.

  Further, the heater support member 10 is provided with a movable portion 12 so that the entire heater support member 10 is located on the front end side of the seat surface 6, that is, the entire state is exposed on the front end side of the housing 1. The movable portion 12 has a function of displacing the heater 20 in the axial direction by elastically deforming according to the combustion pressure applied to the pressure receiving surface of the heater 20. In the present embodiment, the movable portion 12 is configured by a thin portion whose thickness is thinner than that of the other heater support member 10. Thus, when the movable part 12 is comprised by a thin part, thickness is about 0.2 +/- 0.1mm (it is about 0.4 mm for another site | part (for example, heater connection part 13 mentioned later)), and an axial direction The length is preferably about 5 mm, for example. As the material constituting the movable part, it is preferable to use a material having repeated yield strength and a low Young's modulus. For example, stainless steel (for example, SUS430, SUS630, etc.), maraging steel, pure titanium, titanium alloy (Ti -6Al-4V or the like). As another embodiment of this movable part 12, you may comprise the movable part 12 with a bellows-like bellows. Further, only the movable portion 12 is configured by a member whose Young's modulus is lower than the Young's modulus of the other heater support member 10 portion, without reducing the wall thickness or the bellows-like shape, but with the same shape as other portions. May be.

  A heater connecting portion 13 is provided on the distal end side of the movable portion 12 of the heater support member 10. The heater connecting portion 13 is in a state in which its inner peripheral portion is connected to the heater 20 by press-fitting or brazing, and its thickness is made thicker (for example, about 0.4 mm) than the movable portion 12. Yes.

In the present embodiment, as shown in FIG. 1, the outer diameter R1 of the heater connecting portion 13 is larger than the outer diameter R2 of the movable portion 12, and R1> R2, and as a result, from the axial front end side. When the front end portion of the heater connecting portion 13 is viewed, the movable portion 12 is hidden by the heater connecting portion 13 and cannot be seen. By setting it as such a structure, it can prevent that the heat in a combustion chamber is directly transmitted to the movable part 12, and can suppress that the movable part 12 deteriorates with a heat | fever. In order to obtain such an action, it is sufficient that R1 ≧ R2. Further, as described above, since the heater connecting portion 13 is thick and has a large volume, the heat capacity of the heater connecting portion 13 is increased and the heat shielding effect on the movable portion 12 is increased.

  A rear end side of the heater support member 10 from the housing connection portion 11 extends in a cylindrical shape toward the rear end side, and an element presser 31 is fixed to the rear end side end portion. A pressure detection element 30 is provided via an insulating member 40 in the rear end side portion of the heater support member 10 on the front end side of the element presser 31. As this pressure detection element 30, a piezoelectric element etc. can be used, for example. The element holder 31 is made of, for example, a high-strength metal such as carbon steel (such as S45C) or stainless steel (such as SUS430 or SUS630).

  A through hole 32 is formed in the center of the element presser 31, and a conductive central shaft 33 formed in a rod shape is provided so as to penetrate the through hole 32. A flange portion 34 having a large diameter is formed at the front end portion of the middle shaft 33, and the flange portion 34 is disposed so as to be interposed between the pressure detection element 30 and the rear end portion of the heater 20. The combustion pressure transmitted from 20 is transmitted to the pressure detection element 30 via the flange portion 34 and the insulating member 41 provided between the flange portion 34 and the pressure detection element 30. The middle shaft 33 is electrically connected to the conductive ceramic 22 of the heater 20 through a conductive ring member 35, and power is supplied to the heater 20 through the middle shaft 33. The middle shaft 33 is electrically connected to the heater energization line 8 shown in FIG. 2, and the pressure detection element 30 is electrically connected to the signal output line 9 and is electrically led out of the housing 1. Yes.

  As described above, in the present embodiment, the pressure detecting element 30 is provided on the rear end side of the housing connecting portion 11 of the heater support member 10. Thereby, it can suppress that the pressure detection element 30 deteriorates by the thermal influence of combustion gas. That is, in the glow plug 100 with the combustion pressure sensor, the combustion gas from the combustion chamber enters from the gap between the heater support member 10 and the housing 1 to the distal end side of the housing connection portion 11. For this reason, the thermal influence of the combustion gas is greatly received on the front end side from the housing connection portion 11, but the thermal influence of the combustion gas is reduced on the rear end side from the housing connection portion 11. By providing the pressure detection element 30 on the rear end side from the housing connection portion 11 where the thermal influence of the combustion gas is small, the thermal influence of the combustion gas on the pressure detection element 30 can be reduced.

  In FIG. 1, a portion 14 adjacent to the rear end side from the housing connection portion 11 is a press-fit portion that is thicker and larger in diameter than the other portions of the rear end side portion of the heater support member 10. When the press-fit portion 14 is press-fitted into the rear end side housing 3, the rear end side housing 3 and the heater support member 10 are aligned with the rear end side housing 3 (housing 1). The heater support member 10 is fixed.

  In the glow plug 100 with the combustion pressure sensor configured as described above, as shown in FIG. 2, the leading end of the heater 20 is in a state of protruding from the leading end of the housing 1. The glow plug 100 is inserted into a plug mounting hole of an engine (not shown), and the screw portion 4 is fastened to the mounting screw of the engine to bring the seat surface 7 into contact with the engine, thereby ensuring airtightness. In this state, the heater 20 is attached to the internal combustion engine so that the front end side is located in the combustion chamber, and the heater 20 is energized to generate heat, thereby assisting in starting the internal combustion engine.

  When combustion pressure is applied to the front end surface (pressure receiving surface) 23 of the heater 20, the movable portion 12 is elastically deformed (bends), whereby the heater 20 is displaced in the axial direction toward the rear, and the pressure detection element. When 30 is pressed, a pressure detection signal is detected. An electronic circuit (not shown) for processing an output signal from the pressure detection element 30 is mounted in the housing 1 on the rear end side of the pressure detection element 30, and the signal of this electronic circuit is a signal. A change in combustion pressure in the engine (engine) is detected by being input to a control device such as an ECU via the output line 9.

  When the glow plug 100 with the combustion pressure sensor is used for a long time in such a state, the soot generated in the combustion chamber may be clogged in the gap between the inside of the housing 1 and the outside of the heater support member 10. is there. However, in the glow plug 100 with the combustion pressure sensor, since the entire movable part 12 that is elastically deformed is provided outside the housing 1, the mobility of the movable part 12 is impaired due to clogging of soot. There is no. This makes it possible to detect combustion pressure with high accuracy over a long period of time.

  Further, since the distal end side housing 2 constituting the seat surface 7 that is brought into contact with the engine to ensure airtightness and the movable portion 12 are made of different members, the screw portion 4 is fastened to the mounting screw of the engine. Even when the seat surface 7 is brought into close contact with the engine and the front end side housing 2 is deformed to be bent, the influence of the bending on the pressure detection result can be reduced. Furthermore, the influence of the distortion of the engine head portion due to combustion on the pressure detection result can be reduced. Therefore, highly accurate combustion pressure detection can be performed.

  The pressure detection element 30 may be composed of, for example, a Si element or an SOI element in addition to the piezoelectric element, and may be configured to output an electrical signal corresponding to a strain when pressure is applied. When the pressure detection element 30 is configured, a structure in which an element such as an Si element or an SOI element is bonded to a substrate made of glass, metal, or the like can be used. A piezoresistor is formed on the surface of the element, and the pressure is detected from a change in resistance value when the element is pressed.

  In the above, the present invention has been described with reference to the embodiment. However, the present invention is not limited to the above-described embodiment and the like, and it is needless to say that the present invention can be appropriately modified and applied without departing from the gist thereof.

The figure which shows the principal part structure of the glow plug with a combustion pressure sensor which concerns on embodiment of this invention. The figure which shows the whole structure of the glow plug with a combustion pressure sensor which concerns on embodiment of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Housing, 2 ... Front end side housing, 3 ... Rear end side housing, 4 ... Screw part, 5 ... Tool engaging part, 6 ... Opening part, 7 ... Seat surface, 8 ... Heater Current-carrying wire, 9 ... signal output wire, 10 ... heater support member, 11 ... housing connection portion, 12 ... movable portion, 13 ... heater connection portion, 14 ... press-fit portion, 20 ... heater, 21 ... Insulating ceramic, 22 ... Conductive ceramic, 23 ... Tip surface (pressure-receiving surface), 30 ... Pressure sensing element, 31 ... Element presser, 32 ... Through hole, 33 ... Middle shaft, 34 ... Flange 35, ring member, 40, 41 ... insulating member, 100 ... glow plug with combustion pressure sensor.

Claims (6)

A housing that is formed in a cylindrical shape, has a seat surface in close contact with the engine on the axial front end side, and has a screw portion for engine attachment on the outer peripheral surface on the axial rear end side from the seat surface;
A pressure sensing element;
A heater provided such that a front end side protrudes from a front end portion of the housing and a rear end side is accommodated in the housing, the front end surface being a pressure receiving surface, and a heater for transmitting combustion pressure to the pressure detecting element; ,
A heater support member for supporting the heater with respect to the housing, and the elastic support member is elastically deformed in accordance with a combustion pressure applied to the pressure receiving surface provided so as to be positioned on the front end side of the seat surface. A cylindrical movable portion that displaces the heater in the axial direction, a heater connecting portion that is provided on the front end side of the movable portion and connected to the heater, and is connected to the housing on the rear end side of the seat surface. A heater support member provided with a housing connection part ,
A glow plug with a combustion pressure sensor , wherein an outer diameter R1 of the heater connecting portion and an outer diameter R2 of the movable portion satisfy R1> R2 . The glow plug with a combustion pressure sensor according to claim 1,
A glow plug with a combustion pressure sensor, wherein the pressure detection element is provided on a rear end side of the housing connecting portion of the heater support member. The glow plug with a combustion pressure sensor according to claim 1 or 2,
The glow plug with a combustion pressure sensor, wherein the movable part is provided at a position hidden from view by a member provided on the tip side of the movable part when viewed from the tip side in the axial direction. In the glow plug with a combustion pressure sensor according to any one of claims 1 to 3,
The glow plug with a combustion pressure sensor, wherein the movable portion of the heater support member is formed of a thin portion that is thinner than a portion of the heater support member other than the movable portion. In the glow plug with a combustion pressure sensor according to any one of claims 1 to 3,
The glow plug with a combustion pressure sensor, wherein the movable part of the heater support member is constituted by a bellows. In the glow plug with a combustion pressure sensor according to any one of claims 1 to 5,
The glow plug with a combustion pressure sensor, wherein the movable portion of the heater support member is composed of a member having a Young's modulus lower than that of the heater support member other than the movable portion.

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