JP5797486B2 - Glow plug with combustion pressure detection sensor - Google Patents

Description

  The present invention relates to a glow plug with a combustion pressure detection sensor having a function of accelerating ignition in a combustion chamber of an engine and detecting (detecting) pressure (combustion pressure) in the combustion chamber.

  This type of glow plug with a combustion pressure detection sensor (hereinafter also simply referred to as a glow plug) is attached to the engine head so that the tip of a rod-shaped heater is exposed in the combustion chamber, and the heater accelerates the ignition of fuel. Is planned. On the other hand, as a means for detecting the combustion pressure (combustion gas pressure), forward / reverse movement (relative displacement of the heater in the axial direction with respect to the fixed position of the combustion pressure sensor) generated when the heater is pushed backward from the tip by the combustion pressure. For example, there is a sensor using a sensor that deforms a strain member having a diaphragm or the like provided on a glow plug and detects a combustion pressure from the deformation of the strain member (Patent Document 1). In such a glow plug, a rod-shaped heater with its tip exposed from its tip is disposed in a cylindrical metal shell (housing) so as to be movable back and forth in the axial direction. The strain member is deformed by first moving back and forth, and the combustion pressure is detected by a sensor such as a strain sensor (gauge) from the deformation of the strain member. In this glow plug, as shown in FIG. 8 (FIG. 3 of the same document), a metal shaft member (medium shaft) for applying a voltage to a heater (not shown) is provided near the rear end of the metal shell 40. 30) is arranged behind the heater so as to be movable back and forth in the axial direction together with the heater. On the other hand, a strain member (also referred to as a diaphragm) 210 having an annular (or cylindrical) metal diaphragm portion is provided on the shaft member (medium shaft) 30 via an inner peripheral side portion (cylindrical small diameter portion 211). The outer peripheral side portion (large diameter portion 212) is fixed to the rear end of the metal shell 40. In this device, the pressure received by the heater is transmitted to the shaft member 30, and the pressure is transmitted to the strain member 210 provided at the rear end or the rear end portion by the displacement of the shaft member (front-rear movement). By deforming the annular diaphragm 215 of the strain member, for example, a change in resistance value is measured by the strain detection element 220 attached thereto, and the combustion pressure is detected.

  By the way, in such a glow plug with a combustion pressure detection sensor, in order to fix the inner peripheral portion 211 of the metallic strain member 210 constituting the diaphragm to the shaft member 30, the shaft member 30 and the strain member 210 are mutually connected. It is necessary to maintain electrical insulation between them. This is because, in such a glow plug, the ground side electrode of the heater electrodes is connected to the metal shell 40 which is a cylindrical metal housing, and the strain member 210 is welded to the metal shell. It is because it is fixed by. For this reason, in the structure in which the inner peripheral side portion 211 of the strain member 210 is fixed to the shaft member 30, as shown in the enlarged view of FIG. 9, the outer peripheral surface of the shaft member 30 and the inner peripheral side of the strain member 210 An insulating member (insulating ring, cylindrical member) 260 is interposed between the inner peripheral surface of the portion (cylindrical small diameter portion 211), and the respective portions are fixed by adhesion or the like (paragraph 0025 of Patent Document 1). Etc.).

  More specifically, between the outer peripheral surface of the shaft member 30 and the inner peripheral surface of the insulating member 260 fitted and externally fitted thereto, the outer peripheral surface of the insulating member 260, and the small diameter portion 211 of the strain member 210. Adhesives 310 and 320 were poured into and adhered to each of the inner peripheral surfaces. That is, through the cylindrical insulating member (ring) 260, the shaft member 30 and the strain member 210 positioned inside and outside are poured adhesives (glass or cement) 310, 320 having insulating properties between them. , And fixed between each.

JP 2007-57140 A

  In the structure in which the strain member 210 is fixed to the shaft member 30 via the insulating member (ring) 260 as in the conventional glow plug described above, between the shaft member 30 and the strain member 210 located inside and outside the shaft member 30, Adhesives (glass and cement) 310 and 320 having insulating properties are poured and bonded. For this reason, in the bonding process, positioning between the members is required and a pouring process of the adhesives 310 and 320 is required. In addition, since it takes a considerable amount of time to solidify after pouring, there is a problem that the efficiency of manufacturing and assembling the glow plug is poor.

  Further, even if a hard material such as ceramic is used for the insulating member (ring) 260, since the adhesive (layer) 310, 320 exists between the components sandwiching the insulating member (ring) 260, the displacement of the shaft member 30 due to the previous / rearward movement. Is applied to the diaphragm 215 of the distorting member 210, the adhesive 310, 320 itself is deformed or distorted by the amount of the adhesive 310, 320 (see FIG. 9). . That is, in the case of such adhesion, it is preferable that the forward / rearward movement displacement of the shaft member 30 is transmitted to the strain member 210 as it is, but actually the adhesives 310 and 320 themselves inside and outside the insulating member 260 are also deformed or distorted. Will occur. As a result, the displacement is reduced and transmitted to the strain member 210. For this reason, in the glow plug with a combustion pressure detection sensor having such a fixed structure between the shaft member 30 and the strain member 210, the detection accuracy (or sensitivity) of the combustion pressure may be lowered.

  The present invention has been made to solve such problems. In the glow plug as described above, an adhesive is used to fix the strain member to the shaft member via an insulating member (insulating ring). It is an object of the present invention to improve the accuracy of detection of combustion pressure by making it possible to carry out the process easily and without transmitting an adhesive layer so that the forward / rearward movement displacement of the shaft member is directly transmitted to the strain member.

According to a first aspect of the present invention for solving the above-mentioned problem, a rod-shaped heater having its tip exposed from its tip is disposed in a metal-made cylindrical housing so that it can be moved back and forth in the axial direction. Combustion pressure detection provided with a sensor capable of deforming the strain member by a forward / backward movement generated when the heater is pushed rearward from the tip by the combustion pressure, and detecting the combustion pressure from the deformation of the strain member Glow plug with sensor,
A metal shaft member can be moved back and forth in the axial direction together with the heater, and is disposed behind the heater in a state where electrical insulation is maintained between the inner peripheral surface of the housing. Moreover, an insulating ring made of an insulating material is fixed to the shaft member so as to surround the axis,
In the glow plug with a combustion pressure detection sensor, the strain member has a structure in which an outer peripheral side portion of the strain member is fixed to the housing and an inner peripheral side portion of the strain member is fixed to the insulating ring.
The shaft member is provided with a small-diameter shaft portion and a shaft portion for fitting the insulating ring that is thicker than this and fixed in a tight-fitting state from the rear end toward the front at a portion near the rear end,
The insulating ring has a portion close to the tip of the inner peripheral surface thereof fixed to the outer peripheral surface of the shaft portion for fitting the insulating ring in a tightly fitted state, and a portion closer to the rear end of the inner peripheral surface of the insulating ring. And an annular gap between the small diameter shaft portion and
In the insulating ring, an inner peripheral side portion of the strain member is fixed to an outer peripheral surface of a front and rear portion corresponding to the annular gap in an interference fit state.

In a second aspect of the present invention, a rod-shaped heater having its tip exposed from its tip is disposed in a cylindrical housing made of metal so as to be movable back and forth in the axial direction. A glow plug with a combustion pressure detection sensor that includes a sensor capable of detecting the combustion pressure from the deformation of the strain member by deforming the strain member by forward and backward movement generated by being pushed backward from the tip by the combustion pressure. And
A metal shaft member can be moved back and forth in the axial direction together with the heater, and is disposed behind the heater in a state where electrical insulation is maintained between the inner peripheral surface of the housing. Moreover, an insulating ring made of an insulating material is fixed to the shaft member so as to surround the axis,
In the glow plug with a combustion pressure detection sensor, the strain member has a structure in which an outer peripheral side portion of the strain member is fixed to the housing and an inner peripheral side portion of the strain member is fixed to the insulating ring.
A flange projecting outward is formed near the rear end of the shaft member, and the flange includes an annular convex portion projecting rearward so as to have an annular gap on the inner peripheral side. And
On the inner peripheral surface of the annular convex portion, the outer peripheral surface of the portion near the tip of the insulating ring is fixed in an interference fit state,
The inner peripheral surface of the inner peripheral side portion of the strain member is fixed to the outer peripheral surface near the rear end portion of the insulating ring in an interference fit state .

According to a third aspect of the present invention, a rod-shaped heater having its tip exposed from its tip is disposed in a cylindrical housing made of metal so that it can be moved back and forth in the axial direction. A glow plug with a combustion pressure detection sensor that includes a sensor capable of detecting the combustion pressure from the deformation of the strain member by deforming the strain member by forward and backward movement generated by being pushed backward from the tip by the combustion pressure. And
A metal shaft member can be moved back and forth in the axial direction together with the heater, and is disposed behind the heater in a state where electrical insulation is maintained between the inner peripheral surface of the housing. Moreover, an insulating ring made of an insulating material is fixed to the shaft member so as to surround the axis,
In the glow plug with a combustion pressure detection sensor, the strain member has a structure in which an outer peripheral side portion of the strain member is fixed to the housing and an inner peripheral side portion of the strain member is fixed to the insulating ring.
A flange projecting outward is formed near the rear end of the shaft member, and the flange includes an annular convex portion projecting rearward so as to have an annular gap on the inner peripheral side. And
The outer peripheral surface or inner peripheral surface of the portion near the tip of the insulating ring is fixed to the inner peripheral surface or outer peripheral surface of the annular convex portion in an interference fit state,
The outer peripheral surface or the inner peripheral surface of the inner peripheral side portion of the strain member is fixed to the inner peripheral surface or the outer peripheral surface near the rear end of the insulating ring in an interference fit state .

The invention according to claim 4 is the glow plug with a combustion pressure detection sensor according to any one of claims 1 to 3 , wherein the insulating ring is a cylindrical body that forms a straight pipe.
The invention according to claim 5 is the glow plug with a combustion pressure detection sensor according to any one of claims 1 to 4 , wherein the interference fit is an interference fit by press fitting.

A sixth aspect of the present invention is the glow plug with a combustion pressure detecting sensor according to any one of the first to fifth aspects, wherein the insulating ring is made of ceramic.

  In the present invention, the fixing of the insulating ring to the shaft member and the fixing of the strain member to the insulating ring are fixed in an interference fit state without using conventional bonding. It can be carried out. Accordingly, since the fixing can be performed in a short time compared to the fixing by bonding, the glow plug can be manufactured and assembled more efficiently. In addition, in the propagation of displacement (transmission of pressure in the axial direction) to the distorted member such as a diaphragm in the forward / backward movement (displacement) of the shaft member, there is no adhesive, and therefore no cushioning action occurs. Accordingly, since the transmission of the displacement of the forward / rearward movement of the shaft member is improved, the detection accuracy of the combustion pressure is increased accordingly. In the present invention, both the fixing of the strain member to the housing and the fixing of the strain member to the insulating ring are both directly fixed and indirectly fixed via another member. Good. Of course, when a separate member is used, it is preferable to use a rigid body that does not generate a cushioning action.

  In the present invention, both of the insulating rings are provided so that electrical insulation between the strain member and the shaft member is ensured and the forward / backward movement (displacement) of the shaft member can be transmitted to the strain member with high sensitivity. As long as they can be coupled together. Therefore, a hard insulating ceramic with a large elastic coefficient is preferable, but it can be made of plastic such as engineering plastic containing reinforcing fibers, or it is made of metal and an oxide film (insulating film) is formed on the surface thereof. It is good also as what you did. However, in the case of using a ceramic, the deformation (strain) of the insulating ring itself is small, and therefore, the axial displacement of the shaft member can be directly applied to the strain member, which is particularly preferable. In the case of ceramic, alumina, zirconia, or silicon nitride is exemplified. The insulating ring is preferably a cylindrical body that forms a straight pipe. In the present invention, the means for interference fitting of the insulating ring with respect to the shaft member and the means of interference fitting of the strain member with respect to the insulating ring are not particularly limited. When it becomes, you may use together the shrink fitting performed by heating it.

As in the first aspect of the invention, when the insulating ring is tightly fitted to the shaft member in an externally fitted state, the inner peripheral surface of the inner peripheral side portion of the strain member is tightly fitted to the outer peripheral surface of the insulating ring in an externally fitted state. , across the wall of the insulating ring, since it is possible to fix the strain member and the shaft member, arbitrary preferred over ease of insulating securing or fixing step. That is, as in the first aspect of the present invention, it is preferable that the interference fitting portions of the shaft member and the strain member do not overlap each other through the insulating ring. In this case, the insulating ring is in an interference fit state in which the portion near the tip thereof is expanded, and is in an interference fit state in which the portion near the rear end is reduced in diameter. Therefore, in such an insulating ring, since the outer peripheral surface thereof is an interference fit in the radial direction at a position where the outer peripheral surfaces overlap in the front-rear direction, the insulating ring is sandwiched between two walls and compressed and crushed. Since it does not become a stress state, even if it is made of ceramic, it is difficult to cause damage such as crack.

In addition, for example, when the inner peripheral surfaces of the shaft member and the strain member are externally fitted so as to reduce the diameter of the insulating ring at the front and rear of the outer peripheral surface of the insulating ring, the insulation margin is large. If the radial tightening margins at the front and rear of the ring are different, the fixing force with the smaller tightening margin is reduced, so that the fixing reliability may be lowered. On the other hand, according to the invention of claim 1, such a risk can be reduced.

Further, in the invention according to claim 2 , the insulating ring is provided with a strain member and an annular ring provided on the shaft member from the outside in the radial direction to the inside (center of the shaft member). Due to both inner peripheral surfaces of the convex portion, the diameter is reduced. When ceramic is used for the insulating ring, it is possible to greatly resist such stress. In addition, since it is preferable that the insulating ring is a cylindrical body (cylindrical shape) that forms a straight pipe having the same diameter later, the inner peripheral surface of the strain member that is externally fitted to the cylindrical ring and the annular protrusion provided on the shaft member. It is preferable to set the thickness and the like of the parts of the opposite members to be externally fitted so that the inner peripheral surface of the part has the same diameter and is given a tightening so that the fixing force at the front and rear of the insulating ring is the same. . In addition, in invention of Claim 2, it is suitable for press-fitting (shrink fitting) under high temperature. This is because the insulating ring has a structure that is internally fitted to both counterparts (metal), and therefore, when heated, the counterpart (metal) has a large thermal expansion, so that it is easy to fit. In addition, each structure of the interference fit of the insulating ring with respect to the shaft member and the interference fit of the strain member with respect to the insulation ring is not limited to the above-described structure, and may be an appropriate combination as described in claim 3. It can be embodied. The “shaft member” in the present invention is not limited to a solid shaft, and a hollow shaft (pipe) can also be used. The weight can be reduced by using a pipe. The shaft member can also serve as a voltage application to the heater. For example, by using a hollow shaft (pipe), an electric wire is separately passed through the inside (in the pipe). The voltage may be applied to the heater at.

BRIEF DESCRIPTION OF THE DRAWINGS The longitudinal cross-sectional view of the glow plug with a combustion pressure detection sensor (1st Embodiment) which actualized this invention, and the enlarged view of the site | part near the front-end | tip and the rear end side (principal part). The further enlarged view of the principal part (B section) of FIG. The enlarged view of the C section of FIG. The elements on larger scale explaining the process of press-fitting an insulating ring in a shaft member, and press-fitting a distortion member into the insulating ring. The enlarged view of the principal part of 2nd Embodiment. The enlarged view of the principal part of a modification. The enlarged view of the principal part of a modification. The enlarged view of the principal part of the conventional glow plug with a combustion pressure detection sensor. FIG. 9 is a further enlarged view of the enlarged view of FIG. 8.

  A glow plug with a combustion pressure detection sensor according to an embodiment of the present invention (first embodiment) will be described with reference to FIGS. The glow plug 101 of this example is a ceramic heater 10 in which a metal-made housing 40 having a substantially cylindrical shape and a tip (lower end in the figure) 10a inside the housing 40 are projected from a tip 53 of a tip-side cylindrical housing 50. Further, a shaft member (solid shaft member) 30 for applying voltage, which is disposed so as to extend rearward from the rear end of the heater 10 in the housing 40, and the rear end of the shaft member 30. It is composed of a strain member 210 and the like constituting a combustion pressure detection sensor provided between the outer peripheral surface of the part and the inner peripheral surface of the housing 40. The present invention has a feature in a structure in which the insulating ring 260 is fixed to the shaft member 30 in an interference fit state, and the strain member 210 is fixed and attached to the insulating ring 260 in an interference fit state. The overall configuration of the glow plug 101 will be described sequentially.

  In this example, the housing 40 is made of, for example, SUS303, and includes a substantially cylindrical housing main body 41 and a front end side cylindrical housing 50 or the like that is coaxially fitted to the front end side and welded. Yes. The ceramic heater 10 has a cylindrical shape, and is arranged coaxially with the axis G of the housing 50 so that the tip 10 a protrudes from the tip 53 of the tip-side cylindrical housing 50. The heater 10 has a resistance heating element (conductive ceramic) 12 arranged in a folded shape (U-shape) at the tip 10 a inside the ceramic base, and is located on the side surface near the rear end of the heater 10. The electrode terminals 16 and 17 for energization are exposed. However, the heater 10 has a metal pipe 15 externally fitted by press-fitting to an intermediate portion thereof, and is electrically connected to the grounding electrode terminal 16 positioned relatively on the front end side on the inner peripheral surface of the rear end portion. Connected. A metal bellows 18 is loosely inserted into the metal pipe 15 in an outer fitting manner. The bellows 18 has a rear end portion welded in a seal shape on the inner peripheral surface of the distal end side cylindrical housing 50 and a tip end side thereof is welded in a seal shape to the outer peripheral surface of the metal pipe 15. That is, the bellows 18 allows forward and backward movement (displacement) of the heater 10 with respect to the housing 40, forms a relay conduction portion between the electrode terminal 16 for grounding the heater 10 and the housing 40, and places the heater 10 in the housing 40. And holds the inside of the distal end side.

  In addition, a shaft member 30 for applying voltage is coaxially disposed at the rear end of the heater 10 and is directed toward the rear end so as to maintain insulation (air insulation in this embodiment) in the housing 40. The housing 40 is arranged coaxially. However, a metal connection pipe 19 is fitted on the rear end of the heater 10 and the front end of the shaft member 30 by press-fitting or the like, and an electrode terminal (positive potential side terminal) positioned relatively rearward of the heater 10. 17 is electrically connected to the shaft member 30 while maintaining its electrical connection on the inner peripheral surface of the connecting pipe 19. In other words, the connection pipe 19 is responsible for ensuring the conduction as well as the integration of the heater 10 and the shaft member 30.

  In this example, the housing 40 includes a housing main body 41, a distal end side cylindrical housing 50, etc., and a glow plug is fixed to the outer peripheral surface of the main body 41 by screwing into a plug hole of an engine head (not shown). The screw 43 is formed with a predetermined length. Further, the rear end portion of the housing main body 41 has a diameter-expanded cylindrical portion 45 that is expanded so that a predetermined range from the rear end to the front end has a relatively large diameter. At the rear end of the cylindrical portion 45, a sealing protective cylinder (cap) which is a rear end side cylindrical housing 60 having a relatively small diameter and a different diameter cylindrical shape on the rear end side is a sensor distortion member 210 described below. It is attached on both sides of the outer periphery side. The strain member 210 has an annular shape (or a cylindrical shape) as a whole, and will be described in detail later. However, the strain member 210 is closer to the rear end of the shaft member 30 via the insulating ring 260 at the inner peripheral portion. It is fixed to the site.

  In this example, the shaft member 30 is formed such that the front end portion and the rear end portion are partially thick in the entire length. The rear end protrudes rearward from the rear end of the housing main body 41 and is located at a position near the front end of the large-diameter cylindrical portion 63 of the sealing cylinder (rear end side cylindrical housing) 60 at the rear end. Further, in the portion near the rear end of the shaft member 30, a tapered diameter-reduced portion that is tapered and coaxially reduced from the position corresponding to the distal end portion of the diameter-expanded cylindrical portion 45 of the housing body 41 toward the rear end. 33 and a parallel reduced diameter shaft portion 34 that forms an insulating ring fitting shaft portion that is coaxially further reduced in diameter at the rear end of the tapered diameter reduced portion 33. Further, behind the parallel reduced diameter shaft portion (insulating ring fitting shaft portion) 34, there is a small diameter shaft portion 35 that is concentric and thinner. At the rear end of the small-diameter shaft portion 35 that is the rear end of the shaft member 30, a plug that protrudes outward from the rear end via a terminal spring 71 that allows displacement in the front-rear direction within the seal protection cylinder 60 at the rear end. A terminal fitting 75 having a terminal 73 is welded and connected. A seal member 69 made of, for example, rubber is loaded in the small-diameter portion 65 on the rear end side of the seal cylinder 60 for the rear end.

  Next, a structure and the like in which the strain member 210 and the shaft member 30 constituting the pressure detection sensor constituting the main part of the present invention are fixed via the insulating ring 260 will be described (FIG. 2). FIG. 3). The strain member 210 is disposed so as to close the annular space between the inner side of the housing main body 41 and the outer periphery of the portion near the rear end of the shaft member 30, and is annular (cylindrical) as a whole. ). The shaft member 30 is provided so that the strain member 210 itself is deformed at the same time when the shaft member 30 is subjected to the front-rear movement displacement. That is, the strain member 210 has an annular thick portion 212a on the outer periphery, and the annular thick portion 212a is connected to the rear end of the diameter-expanded tubular portion 45 and the sealing protective cylinder (rear end side) The cylindrical housings 60 are fitted to each other so as to be sandwiched between the front ends of the cylindrical housing 60, and are fixed by laser welding in the circumferential direction from the outer peripheral surface side at each of the butted portions, for example.

  On the other hand, the strain member 210 has an outer cylindrical portion 212 that extends rearward (upward in FIG. 2) inside the outer annular thick portion 212a. (Annular diaphragm part) 215 is provided. And inside this annular film part 215 (inner peripheral side part), it has the inner side cylinder part 211 extended ahead. The inner cylindrical portion 211 extends so as to be positioned closer to the distal end side than the outer peripheral annular thick portion 212a, and the outer diameter of the distal end portion 211a of the outer peripheral surface of the inner cylindrical portion 211 is relatively small, The tip end portion 211a is relatively thin.

  On the other hand, in this example, the insulating ring 260 that forms a cylindrical body is fixed to the parallel reduced-diameter shaft portion 34 in the portion near the rear end of the shaft member 30 in an interference fit state. That is, the insulating ring 260 is fixed so that the inner peripheral surface near the tip thereof is tightly fitted to the parallel reduced diameter shaft portion 34. The inner peripheral surface of the distal end portion 211a of the inner cylindrical portion 211 of the strain member 210 is fixed to the outer peripheral surface of the insulating ring 260 at the rear end portion. In this example, these interference fits are made by press-fitting, and therefore, the dimensions before press-fitting of each part are set as follows (see FIG. 3) so as to obtain an appropriate interference fit. That is, the inner diameter D2 of the insulating ring 260 is set to be appropriately smaller than the outer diameter D1 of the parallel reduced diameter shaft portion 34. In addition, the inner diameter D4 of the portion 211a near the tip of the inner cylindrical portion 211 in the strain member 210 is set to be appropriately smaller than the outer diameter D3 of the insulating ring 260.

  As shown in FIG. 4, this press-fitting is performed by press-fitting the insulating ring 260 in a coaxial arrangement from the rear end side of the shaft member 30, and the inner cylindrical portion 211 of the strain member 210 is inserted into the insulating ring 260 after the press-fitting. What is necessary is just to press-fit the part 211a near the front end in a coaxial arrangement. Then, the heater 10 may be connected to the tip of the shaft member 30 in the shaft member 30 side subassembly after such press-fitting by the connecting pipe 19 and incorporated into the housing 40. Note that the press-fitting may be performed by pressing the three parts in a coaxial arrangement at the same time. In this example, after the terminal spring 71 in the terminal fitting 75 with the terminal spring 71 is welded to the small-diameter shaft portion 35 of the shaft member 30, the insulating ring 260 and the strain member 210 are externally fitted from the rear of the terminal fitting 75. Then, the inner and outer diameter dimensions of each of these parts are set so that the press-fitting is performed. In this example, the insulating ring 260 is made of silicon nitride ceramic.

In such a glow plug 101 of this example, the inner peripheral surface of the insulating ring 260 behind the portion that is fitted on the parallel reduced diameter shaft portion 34 near the tip is a small diameter shaft portion that forms the shaft member 30. 35 has an air gap (annular air gap) K1. In addition, the inner peripheral surface of the distal end portion 211 a of the inner cylindrical portion 211 of the strain member 210 is in an interference fit state with the outer peripheral surface of the insulating ring 260 at the front and rear position corresponding to the parallel reduced diameter shaft portion 34 of the shaft member 30 . Instead, the inner peripheral surface of the tip end portion 211a is in an interference fit state with the outer peripheral surface of the inner peripheral surface of the insulating ring 260 that has the annular gap K1 between the small-diameter shaft portion 35. It is fixed in this way. That is, the depth of press-fitting between the components is such that the dimension L1 is maintained between the rear end of the parallel reduced diameter shaft portion 34 of the shaft member 30 and the front end of the inner cylindrical portion 211 of the strain member 210. (La, Lb) is set (see FIGS. 2 and 3).

  For example, an appropriate number of strain sensors (sensor elements) 220 are attached to the surface of the strain member 210 facing the rear end of the annular film portion (annular diaphragm portion) 215, and through a device including a circuit (not shown). The strain amount based on the deformation of the strain member 210 that is deformed in response to the front-rear movement displacement of the shaft member 30 is detected, and an electric signal based on the detected amount is output via an output output wire (not shown). As a result, the glow plug 101 of this example deforms the strain member 210 by moving the heater 10 and the shaft member 30 together in the direction of the axis G of the heater 10 and the shaft member 30 by combustion pressure. Combustion pressure is detected by using a strain sensor (strain gauge) 220.

  According to the glow plug 101 of this example, the fixing of the insulating ring 260 to the shaft member 30 and the fixing of the strain member 210 to the insulating ring 260 are not bonded as in the prior art, but are fixed in an interference fit state. Therefore, the fixing can be performed by press-fitting or shrink fitting. Therefore, since the time required for fixing can be shortened as compared with fixing by bonding, the efficiency of manufacturing and assembling the glow plug can be improved. In addition, since there is no adhesive in the propagation of displacement to the strain member 210 such as a diaphragm during the forward / backward movement (displacement) of the shaft member 30 (the transmission of pressure in the axial direction), the cushioning action caused thereby is eliminated. Therefore, since the transmission property or transmission sensitivity of the displacement of the forward / rearward movement of the shaft member 30 is increased, the detection accuracy of the combustion pressure is increased accordingly.

  In addition, in this example, the insulating ring 260 is tightly fitted to the shaft member 30 in an externally fitted state, and the inner peripheral surface of the inner cylindrical portion 211 of the strain member 210 is tightly fitted to the outer peripheral surface of the insulating ring 260 in an externally fitted state. . For this reason, since the distortion member 210 and the shaft member 30 can be fixed with the wall of the insulating ring 260 (the wall of the cylindrical body) interposed therebetween, it is excellent in ensuring insulation, and the fixing process is facilitated. Furthermore, in the present example, the interference fit portion between the shaft member 30 and the strain member 210 is configured so as not to overlap with each other through the insulating ring 260. Therefore, the insulating ring 260 is in an interference fit state in which the portion near the tip thereof is expanded, and the portion near the rear end is in an interference fit state in which the diameter is reduced, and the shaft member 30 and the strain member 210 are In this case, the stress does not occur in such a manner that the wall of the insulating ring 260 is sandwiched and compressed and crushed, so that it is difficult to cause damage such as cracks.

  In the above example, the press-fitting is exemplified to obtain the interference fit. However, in order to facilitate this, the press-fitting start side corners (C1 to C4 in FIG. 3) of the press-fitting shaft side and the hole side are provided. In this case, a guide such as a taper or chamfering having an appropriate angle and size may be provided and formed along the circumferential direction. In addition, when the strain member 210 is press-fitted into the insulating ring 260 in this example, the press-fit resistance can be reduced by performing shrink fitting under heating. A lubricant is preferably used for press-fitting, and sodium stearate and sodium oleate may be used as the lubricant (press-fit lubricant). Incidentally, the insulating ring 260 forming a cylindrical body has an outer diameter of 5 mm, an inner diameter of about 2 mm, a thickness of about 1.5 mm, and a length of about 10 to 20 mm due to the overall dimensions of the glow plug 101. . When such an insulating ring 260 is made of ceramic, it is preferable to set the dimensions (D1 to D4) of each press-fitting part so that the press-fitting allowance is 20 to 40 μm in diameter (both sides). The press-fit depth (La, Lb) is preferably set in the range of 1 to 5 mm.

  Next, a second embodiment that embodies the glow plug of the present invention will be described with reference to FIG. However, the thing of this example is different only in the structure of the part from which the said form differs from the rear end part of the shaft member 30, and the part to which the insulating ring 260 is fixed, and the fixing structure. Therefore, in the figure, the same parts as those in the above embodiment are given the same reference numerals, and only the differences will be described. The same applies to the following examples.

  That is, the shaft member 30 in this example does not include the tapered diameter-reduced portion 33 or the parallel diameter-reduced shaft portion 34 that is reduced in diameter at the rear end, unlike the portion near the rear end in the above example. A flange 36 described below is provided at a position corresponding to the front-rear position where 33 is provided, and the rear side of the flange 36 is a small-diameter shaft portion 35 that is thinner than the diameter of the shaft member (main body portion) 30 on the front side. Is coaxial. Note that the shaft member 30 in this example is thinner than that in the above example. That is, in this example, an annular flange (annular flange) 36 that protrudes outward in the circumferential direction is provided at a portion near the rear end of the shaft member 30. An annular convex portion 37 is formed on the outer peripheral portion of the annular flange 36 so as to protrude rearward so as to form an annular gap K2 between the annular flange 36 and the small-diameter shaft portion 35 on the inner peripheral side. Note that a gap (insulating retention dimension) is provided between the rear end of the annular convex portion 37 and the front end of the inner cylindrical portion 211 in the strain member 210. The diameter (inner diameter) of the inner peripheral surface of the annular convex portion 37 is the same as the diameter (inner diameter) of the inner peripheral surface of the inner cylindrical portion 211 in the strain member 210. In this example, the thickness (wall thickness) in the radial direction of the annular convex portion 37 of the shaft member 30 is set to be the same as the thickness of the portion 211 a near the tip of the inner cylindrical portion 211 in the strain member 210. ing.

  Thus, in this example, the insulating ring 260 is press-fitted into the inner peripheral surface of the annular convex portion 37 of the shaft member 30 and fixed in an interference fit state on the outer peripheral surface near the tip. The insulating ring 260 has an annular gap K2 between its inner peripheral surface and the small-diameter shaft portion 35, and its front end is abutted against the rear end facing surface of the annular flange 36. Is positioned. On the outer peripheral surface of the insulating ring 260 near the rear end of the insulating ring 260 fixed to the shaft member 30 in an interference fit state, a portion (a thin portion) 211a near the tip of the inner cylindrical portion 211 of the strain member 210 is externally fitted. It is press-fitted in and fixed with an interference fit. In addition, between the front-end | tip of the inner side cylinder part 211 and the rear end of the cyclic | annular convex part 37 of the shaft member 30, a space | gap is hold | maintained and insulation is ensured as mentioned above.

  In such a glow plug of this example, the same effect as the above example can be obtained. That is, the insulating ring 260 is fitted and fixed in an interference fit state instead of being bonded between each of the inner cylindrical portion 211 which is the inner peripheral side portion of the strain member 210 and the annular convex portion 37 of the shaft member 30. Therefore, the fixing can be performed by press-fitting or the like. Therefore, since the fixing can be simplified as compared with the fixing with the adhesive, the glow plug can be manufactured and assembled more efficiently. In addition, in the propagation of the displacement to the strain member 210 (the transmission of pressure in the axial direction) in the forward / rearward movement displacement of the shaft member 30, since no adhesive is used, it is directly performed as in the above example. It is the same. Therefore, since the pressure transferability and sensitivity are improved, the detection accuracy of the combustion pressure is increased accordingly.

  Further, in this example, due to the fixing structure of the insulating ring 260, stress that is reduced in diameter toward the axis G from the outer peripheral surface side acts on the insulating ring 260 after that. For this reason, it is considered that the insulating ring 260 is mainly subjected to compressive stress. For this reason, an insulating material made of a material that is weak against tensile stress and bending force such as ceramic is expected to improve or stabilize its own durability. Furthermore, in this example, the thickness of the portion 211a near the tip of the inner cylindrical portion 211 in the strain member 210 is relatively thin, and the thickness in the radial direction of the thin portion and the annular convex portion 37 of the shaft member 30 is Since they are set to be the same, the shaft member 30 and the strain member 210 are formed of the same material (or a material having the same degree of strength and rigidity) and press-fitted with the same tightening allowance (press fit allowance). Since the same stress can be applied to the insulating ring 260 later, a stable fixation without relaxation can be obtained.

  As can be understood from the above embodiments, in the present invention, the strain member has a structure in which the outer peripheral portion thereof is fixed to the housing and the inner peripheral portion of the strain member is fixed to the insulating ring. In the attached glow plug, the insulating ring may be fixed to the shaft member in an interference-fitted state, and the inner peripheral side portion of the strain member may be fixed to the insulating ring in an interference-fitted state. Therefore, the interference fit of the insulating ring to the shaft member may be an external fit or an internal fit. Further, in each of the above examples, the case in which the insulating ring 260 is embodied as the inner peripheral side portion of the strain member 210 is illustrated as an example, but conversely, the insulating ring is used as the inner peripheral side portion of the strain member. It is good also as fitting outside. In other words, in the present invention, the strain member may be fixed to the shaft member by holding the insulation with an interference fit through the insulating rings fixed with each other without using an adhesive. It is.

  Therefore, as in the modification shown in FIG. 6, in the above example, the insulating ring 260 is connected to both the annular convex portion 37 of the shaft member 30 and the distal end portion 211a of the inner cylindrical portion 211 of the strain member 210. You may fix in the interference fit state of an external fit. Further, as in the modified example shown in FIG. 7, in the above example, the insulating ring 260 is fitted into the annular convex portion 37 of the shaft member 30, and the outer end portion 211 a of the inner cylindrical portion 211 of the strain member 210 is externally attached. As the fitting, each may be fixed in an interference fit state. In each of the above examples, the outer peripheral side portion of the strain member 210 has been described as being fixed by welding on the outer peripheral surface of the housing, but may be fixed by welding on the inner peripheral surface of the housing. It may be fixed by caulking or the like.

  The glow plug of the present invention is not limited to the above examples, and can be embodied with appropriate modifications. For example, in the above example, each of the insulating rings is a cylindrical body that forms a straight pipe, but it may be a cylindrical body having a different diameter or may not be a cylindrical body. That is, the insulating ring is fixed to the shaft member so as to surround the axis, and is electrically insulated from the shaft member, and the inner peripheral side portion of the strain member is fixed to the insulating ring. Any material can be used as long as electrical insulation between the strain member and the shaft member can be maintained. Therefore, it is not always necessary to be composed of one member, and a form in which a plurality of members are intermittently arranged around the shaft member may be employed. In the above example, the shaft member is a solid shaft (bar material) for applying a voltage to the heater, but it may be a hollow shaft (a pipe such as a circular tube). When such a pipe is used, a lead wire (electric wire) may be separately passed through the inside (inside the pipe), and voltage application (power feeding) to the heater may be performed using this lead wire.

  In the above example, the strain member has a shape and a structure in which one side in the radial direction is folded back in the longitudinal section in the longitudinal section, but the strain member is generated when the heater is pushed rearward from the tip by the combustion pressure. It is only necessary to be able to be deformed by the forward / backward movement and to be able to detect the combustion pressure from the deformation by the sensor. Therefore, it should be of an appropriate shape and structure, such as a simple ring-shaped diaphragm (thin film). Can do. Moreover, although the strain gauge was used as the sensor in the above example, various sensors (sensor elements) such as a semiconductor strain gauge such as a semiconductor element provided with a piezoresistor can be used. Further, in each of the above examples, the case where the straining member is disposed at the rear end of the housing body and the portion located near the rear end of the shaft member is illustrated, but the strain member is arranged in the front-rear direction of the housing or the shaft member. It can also be provided at an intermediate site. In the glow plug of the above example, the bellows that is not directly related to the main part of the present invention is welded in a sealing manner to the inner peripheral surface of the distal end side portion of the distal end side cylindrical housing. However, the rear end of this bellows is modified and embodied, for example, by being sandwiched and welded to the joint (butting portion) between the rear end of the front cylindrical housing and the front end of the housing body. it can. That is, in the glow plug of the present invention, portions that are not the main part of the invention can be appropriately changed.

  The glow plug in the above example is embodied by using a ceramic heater as the heater. However, in the glow plug with a combustion pressure detection sensor of the present invention, a resistance heating coil is incorporated in a metal tube whose tip is closed. It can be applied to those using metal glow plugs.

DESCRIPTION OF SYMBOLS 10 Heater 30 Shaft member 34 Shaft part 35 for insulation ring fitting Small diameter shaft part 36 near the rear end part of the shaft member Flange 37 near the rear end part of the shaft member Annular convex part 40 Housing 53 Front end 101 of the housing With combustion pressure detection sensor Glow plug 210 Strain member 220 Sensor 260 Insulating ring G Axis K1 Annular gap K2 between the inner peripheral surface of the insulating ring and the small diameter shaft part An annular gap on the inner peripheral side of the flange

Claims (6)

In a cylindrical housing made of metal, a rod-shaped heater with its tip exposed from its tip is disposed so as to be movable back and forth in the axial direction, and the heater is pushed backward from the tip by combustion pressure. A glow plug with a combustion pressure detection sensor comprising a sensor that is capable of detecting the combustion pressure from the deformation of the strain member by deforming the strain member by forward and backward movement generated by
A metal shaft member can be moved back and forth in the axial direction together with the heater, and is disposed behind the heater in a state where electrical insulation is maintained between the inner peripheral surface of the housing. Moreover, an insulating ring made of an insulating material is fixed to the shaft member so as to surround the axis,
In the glow plug with a combustion pressure detection sensor, the strain member has a structure in which an outer peripheral side portion of the strain member is fixed to the housing and an inner peripheral side portion of the strain member is fixed to the insulating ring.
The shaft member is provided with a small-diameter shaft portion and a shaft portion for fitting the insulating ring that is thicker than this and fixed in a tight-fitting state from the rear end toward the front at a portion near the rear end,
The insulating ring has a portion close to the tip of the inner peripheral surface thereof fixed to the outer peripheral surface of the shaft portion for fitting the insulating ring in a tightly fitted state, and a portion closer to the rear end of the inner peripheral surface of the insulating ring. And an annular gap between the small diameter shaft portion and
A glow plug with a combustion pressure detection sensor , wherein an inner peripheral side portion of the strain member is fixed in an interference fit state on an outer peripheral surface of a front and rear portion corresponding to the annular gap in the insulating ring . In a cylindrical housing made of metal, a rod-shaped heater with its tip exposed from its tip is disposed so as to be movable back and forth in the axial direction, and the heater is pushed backward from the tip by combustion pressure. A glow plug with a combustion pressure detection sensor comprising a sensor that is capable of detecting the combustion pressure from the deformation of the strain member by deforming the strain member by forward and backward movement generated by
A metal shaft member can be moved back and forth in the axial direction together with the heater, and is disposed behind the heater in a state where electrical insulation is maintained between the inner peripheral surface of the housing. Moreover, an insulating ring made of an insulating material is fixed to the shaft member so as to surround the axis,
In the glow plug with a combustion pressure detection sensor, the strain member has a structure in which an outer peripheral side portion of the strain member is fixed to the housing and an inner peripheral side portion of the strain member is fixed to the insulating ring.
A flange projecting outward is formed near the rear end of the shaft member, and the flange includes an annular convex portion projecting rearward so as to have an annular gap on the inner peripheral side. And
On the inner peripheral surface of the annular convex portion, the outer peripheral surface of the portion near the tip of the insulating ring is fixed in an interference fit state,
A glow plug with a combustion pressure detection sensor, wherein an inner peripheral surface of an inner peripheral portion of the strain member is fixed to an outer peripheral surface of a portion near the rear end of the insulating ring with an interference fit. In a cylindrical housing made of metal, a rod-shaped heater with its tip exposed from its tip is disposed so as to be movable back and forth in the axial direction, and the heater is pushed backward from the tip by combustion pressure. A glow plug with a combustion pressure detection sensor comprising a sensor that is capable of detecting the combustion pressure from the deformation of the strain member by deforming the strain member by forward and backward movement generated by
A metal shaft member can be moved back and forth in the axial direction together with the heater, and is disposed behind the heater in a state where electrical insulation is maintained between the inner peripheral surface of the housing. Moreover, an insulating ring made of an insulating material is fixed to the shaft member so as to surround the axis,
In the glow plug with a combustion pressure detection sensor, the strain member has a structure in which an outer peripheral side portion of the strain member is fixed to the housing and an inner peripheral side portion of the strain member is fixed to the insulating ring.
A flange projecting outward is formed near the rear end of the shaft member, and the flange includes an annular convex portion projecting rearward so as to have an annular gap on the inner peripheral side. And
The outer peripheral surface or inner peripheral surface of the portion near the tip of the insulating ring is fixed to the inner peripheral surface or outer peripheral surface of the annular convex portion in an interference fit state,
A combustion pressure detection sensor characterized in that an outer peripheral surface or an inner peripheral surface of an inner peripheral side portion of the strain member is fixed to an inner peripheral surface or an outer peripheral surface near a rear end portion of the insulating ring in an interference fit state. With glow plug. The glow plug with a combustion pressure detection sensor according to any one of claims 1 to 3, wherein the insulating ring is a cylindrical body forming a straight pipe. The glow plug with a combustion pressure detection sensor according to any one of claims 1 to 4, wherein the interference fit is an interference fit by press-fitting. The glow plug with a combustion pressure detecting sensor according to any one of claims 1 to 5, wherein the insulating ring is made of ceramic.

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