JP2006308252A - Glow plug with combustion pressure detecting sensor and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent rotation of a shaft member for power distribution in a main body in fastening a glow plug with a combustion pressure sensor having a constitution to generate compression stress on an internal piezoelectric element by fastening the combustion pressure detecting sensor by screwing a fastening screw member to a screw 45 of the shaft member 41 for power distribution. <P>SOLUTION: In this glow plug with the combustion pressure detecting sensor, a retainable tool engagement portion (polygonal portion ) 44 is formed on the shaft member 41 for power distribution to prevent the shaft member 41 for power distribution from rotating with the fastening screw member 66 when the combustion pressure detecting sensor 50 is fastened by screwing the fastening screw member 66 to the screw 45 of the shaft member 41 for power distribution. As the main body 31 and the tool engagement portion 44 are retained and fastened by screwing the fastening screw member 66, the shaft member 41 for power distribution is not rotated, and a problem such as breaking of a wire can be prevented. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a glow plug with a combustion pressure detection sensor having a function of detecting combustion pressure in a combustion chamber in addition to promoting ignition of fuel of an engine.

  As this type of glow plug with a combustion pressure detection sensor (hereinafter also simply referred to as a glow plug), there is one having the cross-sectional structure shown in FIG. 12 (for example, Patent Document 1). This is a cylindrical metal fitting body having a shaft-like heater (for example, a ceramic heater) 11 that generates heat when energized, and a screw 32 for attaching to an engine head (hereinafter also simply referred to as an engine) on the outer peripheral surface. (Glow plug body) 31 has a structure in which a tip (lower end in the drawing) 10 is protruded and fixed. However, in the same figure, the heater 11 is fixed in the metal cylindrical member 21 by press-fitting, and this cylindrical member 21 is press-fitted into the tip of the main body 31 and further fixed by welding. . An energizing shaft member 41 is disposed inside the main body 31 such that the front end thereof is connected to the rear end of the heater 11 and partially protrudes from the rear end of the main body 31. In the figure, the heater 11 and the energizing shaft member 41 are fixed by press-fitting or press-fitting and welding via a cylindrical terminal fitting (ring) 18. Also. At the rear end (the upper end in the figure) of the main body 31, when the glow plug is screwed into the mounting hole of the engine, it is rotated, for example, a polygonal part for screwing (hereinafter simply referred to as a “polygonal part” which forms the head shape of a hexagon bolt) 33 (also called a square portion) is provided in a bulging shape.

  On the other hand, the combustion pressure detection sensor 50 incorporating the piezoelectric element is formed in a ring shape, and is disposed and fixed on the rear end facing surface 34 of the polygonal portion 33 of the main body 31. For this fixing, a screw 45 formed on the rear end portion (outer peripheral surface) of the energizing shaft member 41 is used, and for example, an energizing terminal 71 is used as a tightening screw member on the screw 45 as indicated by an arrow in FIG. The combustion pressure detection sensor 50 is pressed against the distal end side through an insulating ring 61 made of an insulating member by screwing into the tip. That is, by screwing and tightening the screwing tightening member 71, the combustion pressure detection sensor 50 is sandwiched between the rear end facing surface 34 of the main body 31 via the insulating ring 61, and a predetermined pre-load is applied to the internal piezoelectric element. A load (compressive stress) is applied. Incidentally, 39 in the figure is for ensuring insulation between the main body 31 and the shaft member 41. In the figure, the combustion pressure detection sensor 50 is arranged so as to be in contact with the insulation ring 61 in a tightened state. Yes. Further, the seal is secured by the ring packing 40 at the tip. Thus, in such a glow plug with a combustion pressure detection sensor, the combustion pressure in the combustion chamber, which changes as the engine starts, is applied from the heater 11 to the current-carrying shaft member 41, thereby tightening and fixing the piezoelectric element. Since the compressive stress (preload) in the piezoelectric element changes based on the axial displacement of the current-carrying terminal 71 that is a tightening screw member, the combustion is performed based on a signal that is output along with the change in the load. A change in pressure is detected.

In the glow plug with the combustion pressure detection sensor as described above, since the combustion pressure detection sensor is compressed using the screw 45 of the shaft member 41 for energization, a special component is used to apply a preload to the piezoelectric element. Does not lead to the need for or the complexity of the structure. For this reason, there is an advantage that a load can be applied to the piezoelectric element at a low cost. On the other hand, in the combustion pressure detection sensor 50, in order to improve output sensitivity and responsiveness, it is necessary to apply a preload as large as possible to the piezoelectric element. On the other hand, for this purpose, it is necessary to tighten the energizing terminal 71 forming the tightening screw member with as much torque as possible. With a glow plug having such a tightening structure, when the energizing terminal 71 is tightened with a large tightening torque, Such a serious problem sometimes occurred.
JP 2004-124910 A

  In the above glow plug, in order to apply a large preload to the piezoelectric element in the assembly process, for example, the polygonal portion 33 is held with a jig or a tool K so that the main body 31 does not rotate, and finally Therefore, the energization terminal 71 is screwed and tightened by a desired large screwing torque. However, in the tightening, the energizing shaft member 41 rotates together with the energizing terminal 71 around its axis due to the torque at the time of screwing, and due to its torsional stress, the joint part with other parts or other parts mutually Among the joints, problems such as separation (disconnection) or relaxation of joints may occur at low strength sites. Specifically, in the glow plug described above, the energizing shaft member 41 and the heater 11 are connected via a cylindrical terminal fitting 18 that is attached to the rear end of the heater 11 by press-fitting. And this cylindrical terminal metal fitting 18 and the front-end | tip of the shaft member 41 for electricity supply are attached by press injection and welding, for example. Moreover, such a cylindrical terminal metal fitting 18 is formed from a thin metal, and its own strength is not high. For this reason, when the rotational force (torsional stress) of the current-carrying shaft member 41 accompanying the screwing of the current-carrying terminal 71 is applied, problems such as separation may occur in such a connection portion. Furthermore, the heater 11 is fixed in the cylindrical member 21 by press-fitting, and the cylindrical member 21 is press-fitted at the rear end portion inside the front end of the main body 31 and is fixed by welding. A high fixing force cannot always be obtained due to the short press-fitting depth. Therefore, in some cases, even such a connection portion may have a problem such as separation. The conventional glow plug with the combustion pressure detection sensor uses the current-carrying terminal 71 as a tightening screw member. However, a nut other than this is used as a tightening screw member to preload the piezoelectric element. Even in the case of providing the same problem.

  Further, when the combustion pressure detection sensor 50 is tightened by fixing the main body 31 and screwing a tightening screw member such as the energization terminal 71, a tensile force acts on the energization shaft member 41 in addition to the torsional stress. Therefore, there is also a risk that the cylindrical terminal fitting 18 is separated in such a manner that it is detached from the heater 11, or particularly the screw 45 of the energizing shaft member 41 is broken. Such a problem is not limited to the glow plug shown in FIG. 12, but the heater has a heating coil in a metal tube with a bottom, and a current-carrying shaft member connected to the end of the heating coil in the open end of the tube. Is inserted, an insulating material (for example, rubber tube) is interposed on the inner peripheral surface of the tube, a coaxial member is fixed by swaging, and the open end side of the tube is press-fitted into the tip of the main body. However, if the structure is such that the piezoelectric element is compressed in the same manner as described above by using the screw at the rear end of the energizing shaft member, there is a risk that the same problem will occur. That is, in this case, there is a risk that the energizing shaft member rotates in the tube and is separated (disconnected) from the heat generating coil.

  The present invention has been made in view of these problems, and an object thereof is to generate a compressive stress in an internal piezoelectric element by screwing a tightening screw member into a combustion pressure detection sensor. The glow plug with the combustion pressure detection sensor is configured to prevent the energizing shaft member from rotating in the main body during tightening.

In the invention according to claim 1 of the present invention, a heater that generates heat when energized is fixed in a cylindrical metal fitting body, and an energizing shaft member for energizing the heater has a rear end attached to the metal fitting body. Protruding from the rear end and holding the insulation inside the metal fitting body, and the combustion pressure detection with a built-in piezoelectric element on the rear end surface of the metal fitting main body at the rear end or near the rear end. A sensor is arranged, and the combustion pressure detection sensor is configured to generate a compressive stress in the piezoelectric element by screwing a tightening screw member into a screw formed on an outer peripheral surface of the energizing shaft member. In a glow plug with a combustion pressure detection sensor,
When tightening the combustion pressure detection sensor by screwing the tightening screw member into the screw of the energizing shaft member, the energizing shaft member can be held to prevent rotation with the tightening screw member. The tool engaging portion is formed on the energizing shaft member.

  The invention according to claim 2 is characterized in that the tool engaging portion is formed at a rear end portion of the energizing shaft member or a portion near the rear end, and the glow with a combustion pressure detection sensor according to claim 1 It is a plug. The invention according to claim 3 is characterized in that the tool engaging portion is formed on the outer peripheral surface of the rear end portion or the rear end portion of the energizing shaft member. Glow plug with pressure detection sensor. Here, a typical example of the tool engaging portion formed on the outer peripheral surface is a polygonal portion that forms a polygon when viewed from the axial direction of the screw. The invention according to claim 4 is characterized in that the tool engaging portion is a polygonal hole or a slit formed in a rear end surface of the energizing shaft member. Glow plug with detection sensor.

In the invention according to claim 5, a heater that generates heat when energized is fixed in a cylindrical metal fitting body, and an energizing shaft member for energizing the heater has a rear end extending from the rear end of the metal fitting main body. A combustion pressure detection sensor with a built-in piezoelectric element is arranged on the rear end face of the rear end of the metal fitting body or a portion near the rear edge. The combustion pressure detection sensor is configured to generate a compressive stress in the piezoelectric element by screwing a tightening screw member into a screw formed on the outer peripheral surface of the energizing shaft member. In a method of manufacturing a glow plug with a detection sensor,
For the energizing shaft member, a long one provided with a discarding margin part to be cut off after tightening the combustion pressure detection sensor on the rear end side,
In tightening the combustion pressure detection sensor by screwing the tightening screw member,
The tightening screw member is screwed into the screw and advanced so that at least the rear end of the energizing shaft member is exposed, and in this state, the energizing screw located behind the tightening screw member. In the discarding portion of the shaft member,
A tool engaging member provided so as to be able to hold the energizing shaft member to prevent the energizing shaft member from rotating together with the tightening screw member when the tightening screw member is screwed into the screw and the combustion pressure detection sensor is tightened. Is fixed,
With the metal fitting main body and the tool engaging member held, the tightening screw member is screwed to tighten the combustion pressure detection sensor, and after the tightening, the throw-off shaft member including the tool engaging member is discarded. This is a method for manufacturing a glow plug with a combustion pressure detection sensor, characterized in that a prosthesis is cut off.

  The invention according to claim 6 is the method of manufacturing a glow plug with a combustion pressure detection sensor according to claim 5, wherein the tool engaging member is fixed by welding. In the present invention, the tool engaging portion refers to a portion where a tool mouth such as a spanner can be engaged or fitted, and the tool engaging member refers to a member provided with this portion.

  In the glow plug according to claims 1 to 4 of the present invention, with the above-described configuration, when the combustion pressure detection sensor is tightened by screwing the tightening screw member, the body is fixed (or held) for tightening. This is performed by rotating the screw member with a screwing tool. In this case, the tool engaging portion formed on the energizing shaft member can be held by a tool. That is, since the combustion pressure detection sensor can be tightened by screwing the tightening screw member with the tool engaging portion held by the tool in this way, the shaft member for energization is connected to the main body in the tightening. It can be prevented from rotating.

  As described above, in the glow plug of the present invention, when compressive stress (preload) is generated in the piezoelectric element by screwing the tightening screw member into the screw, the body is rotated around the screw axis. The fastening screw member can be tightened in a state where the tool engaging portion formed on the energizing shaft member is held by a tool while being fixed (or held) so as not to Can be tightened without rotating around the axis of the screw. Therefore, it is desirable for the piezoelectric element without incurring problems such as separation (disconnection) or relaxation at a joint with another part connected (joined) to the current-carrying shaft member or between each part. A sufficiently large preload can be applied. In the method for producing a glow plug according to claims 5 and 6 of the present invention, the tightening screw member is used to tighten the combustion pressure detection sensor without rotating the energizing shaft member around the screw axis in a simple process. Tightening can be performed.

  A first embodiment of a glow plug according to the present invention will be described in detail with reference to FIGS. The glow plug 1 of this embodiment includes a ceramic heater 11 having an axial shape, a metallic cylindrical member 21 formed by fixing the heater 11 to the inside with a tip 10 protruding, and a rear of the cylindrical member 21. A cylindrical metal fitting body 31 or the like that is press-fitted and welded to the outer side of the end portion and joined coaxially is configured as follows. In this specification, “first” means the bottom of the glow plug or its component parts in the figure, and “rear” means the opposite.

  The ceramic heater 11 is formed in a columnar shape or a round bar shape having substantially the same diameter in the direction of the axis G. The ceramic heater 11 is formed in a U-shaped cross section at a position near the tip in an insulating base (for example, silicon nitride ceramic). Thus, a resistance heater 12 that generates heat is embedded. The relay wire 14 is connected to both ends of the internal resistance heater 12, and both ends of the relay heater 14 are exposed on the outer peripheral surface of the heater 11 at the rear end and the rear end portion. 2 and 16) and 17). Of these, a cylindrical terminal fitting 18 is fitted into the outer peripheral surface of the heater 11 in the vicinity including the first electrode 16 at the rear end by press-fitting, and the cylindrical shape is fitted to the first electrode 16. The inner peripheral surface of the terminal fitting 18 is pressed and brought into conduction. Then, on the inner side of the rear end side (the upper side in the drawing) of the cylindrical terminal fitting 18, the tip end (the lower end in the drawing) of the energizing shaft member 41 disposed coaxially in the fitting main body 31 via a ring-shaped gap. The small-diameter portion 42 is fixed by welding after being press-fitted. A portion near the rear end of the energizing shaft member 41 protrudes from the rear end (upper end in the figure) of the main body 31 by a predetermined length, and is screwed to the outer peripheral surface over a predetermined length from the rear end 43 of the shaft member toward the front end. 45 is formed. In the present specification, the axis G of the screw 45 is the same as the axis G of the ceramic heater 11 and the axis G of other components.

  The heater 11 is fixed by press-fitting inside the metallic cylindrical member 21 so as to cover the outer peripheral surface of the intermediate portion, and the second electrode 17 is attached to the inner surface of the metallic cylindrical member 21. Electrical connection is established by pressure contact, and the glow plug 1 is configured to be grounded by being attached to the engine. In addition, the metallic cylindrical member 21 of the present embodiment integrally has an annular convex portion 22 that protrudes in the shape of a flange outward in the radial direction on the outer peripheral surface of the portion near the rear end in the axis G direction and is annular in the circumferential direction. It has a cylindrical shape with different outer diameters. Such a metallic cylindrical member 21 is press-fitted and welded at the rear end thereof inside the front end of the main body 31 until the rear end-facing surface of the annular convex portion 22 abuts.

  The metal fitting body 31 in the present embodiment has a substantially straight cylindrical shape except for a portion near the rear end, and the glow plug 1 is attached to the engine mounting hole on the outer peripheral surface of the intermediate portion in the axis G direction. A mounting screw 32 is formed over a predetermined length range. On the other hand, a screw-in polygon part 33 for screwing the glow plug 1 with the mounting screw 32 is formed in a bulging shape on the outer peripheral surface near the rear end. In the present embodiment, the polygonal portion 33 has, for example, a hexagonal shape (hex head shape) as viewed from the direction of the axis G. In addition, the metal fitting body 31 in this embodiment is a cylindrical shape that protrudes rearward concentrically with the axis of the main body 31 at a portion near the inner peripheral edge of the flat (planar) rear end facing surface 34 of the polygonal portion 33. A cylindrical wall portion 35 is formed. Note that the height (projection amount) of the cylindrical wall portion 35 at the rear end facing surface 34 is smaller than the thickness of an annular combustion pressure detection sensor (hereinafter also simply referred to as a sensor) 50, The outer diameter of the cylindrical wall portion 35 is set slightly smaller than the inner diameter of the sensor 50.

  Further, the inner diameter of the main body 31 includes a large-diameter portion 38 having a relatively large-diameter circular cross-section within a predetermined range from the rear end, including the inside of the cylindrical wall portion 35 located near the rear end. Are concentric and straight holes having a relatively small circular cross section. In this embodiment, a cylindrical insulating member 39 is inserted into a cylindrical space (gap) formed by the inner peripheral surface of the large-diameter portion 38 and the outer peripheral surface of the energizing shaft member 41, and the energizing shaft. The member 41 is positioned in the center of the main body 31 while maintaining insulation. This insulating member 39 has a flange 39b protruding from the outer periphery of its rear end (upper end in the figure), and the front-facing surface (lower face in the figure) of the flange 39b is located inside the rear end (end of the cylindrical wall portion 35) of the main body 31. It is locked to the periphery. In order to tighten the sensor 50, the dimension obtained by adding the thickness of the flange 39 b to the height of the cylindrical wall portion 35 is set to be smaller than the thickness of the sensor 50. Further, an O-ring-shaped rubber packing 40 is loaded between the tip of the large-diameter portion 38 on the inner peripheral surface of the main body 31 and the tip of the insulating member 39. The seal between the inner peripheral surface of 31 and the energizing shaft member 41 is held. In this embodiment, as described above, after the heater 11 is press-fitted into the cylindrical member 21, the heater 11 and the energizing shaft member 41 are joined by the cylindrical terminal fitting 18 to form an assembly. The cylindrical member 21 is joined to the main body, the energizing shaft member 41 is disposed in the main body 31, and the rubber packing 40 and the insulating member 39 are inserted thereafter.

  On the other hand, among the portions of the shaft member 41 for energization that protrude from the rear end of the metal fitting body 31 and the flange 39b of the insulating member 39, in the present embodiment, within a predetermined range L1 from the rear end 43 to the front end of the present invention. A tool engaging portion 44 that forms a gist is formed. In this embodiment, the tool engaging portion 44 is formed by partially cutting a screw 45 so that the outer peripheral surface forms a substantially square polygonal portion when viewed from the axis G direction. A wrench is formed to engage (fit). The screw 45 of the energizing shaft member 41 is formed from the rear end 43 to the vicinity of the rear end of the sensor 50. As will be described later, the screw 45 is energized regardless of the presence of the tool engaging portion 44. A tightening screw member 66 having a nut shape from the rear end 43 of the shaft member 41 can be screwed.

  Further, the rear end-facing surface 34 of the polygonal portion 33 at the rear end of the main body 31 has an annular shape, and a combustion pressure detection sensor 50 having a piezoelectric element therein is concentric with the axis G of the screw 45. Is arranged. In this embodiment, the combustion pressure detection sensor 50 has a structure as shown in an enlarged view in FIG. That is, a lower electrode plate (metal annular base plate) 52, a piezoelectric element 53, an upper electrode plate 54, and an insulating plate each having an annular shape from the tip (lower side) side in a metal case 51. 55 is arranged. An insulating plate (for example, a rubber plate) 56 is disposed on the inner peripheral surface side of the piezoelectric element 53, and a resin (insulating material) 57 is filled on the outer peripheral side. 3 is a lead wire case in which the lead wire 59 connected to the upper electrode plate 54 is taken out to the rear end side through the resin 57, and the lower electrode plate 52 has the case 51 attached thereto. It is configured to be connected to the main body 31 and grounded to the engine.

  In this embodiment, the combustion pressure detection sensor 50 is disposed on the rear end facing surface 34 of the polygonal portion 33 of the main body 1 so as to surround the cylindrical wall portion 35, and the combustion pressure detection sensor 50 has a rear end side. An insulating ring 61 having an annular shape with an angular cross section made of an insulating material (for example, ceramic) is disposed on the outer periphery of which a tightening screw member 66 having a hexagonal nut shape is provided on the outer peripheral surface of the energizing shaft member 41. 45 is screwed in from the rear end 43 side. Then, by rotating and tightening the tightening screw member 66, the combustion pressure detection sensor 50 is tightened through the insulating ring 61, a preload is applied to the internal piezoelectric element 53, and a predetermined compressive stress is generated. ing. Thus, in this embodiment, after the tightening screw member 66 is tightened, the energization terminal 71 having a nut portion 71b as illustrated is screwed into the rear end (the upper end in the figure) of the energization shaft member 41, Thereafter, for example, the body portion 72 is crimped and fixed in a reduced diameter to form the glow plug 1 with a combustion pressure detection sensor.

  It should be noted that the front end surface (lower surface in the drawing) 63 of the insulating ring 61 has an outer diameter outside the rear end surface of the combustion pressure detection sensor 50 so that substantially the entire rear end surface (upper surface in the drawing) of the combustion pressure detection sensor 50 can be pressed. The inner diameter is slightly larger than the outer diameter (shaft diameter) of the energizing shaft member 41, and is arranged concentrically with the axis G. Further, the tightening screw member 66 has a tip surface formed so that it can be pressed except for a portion near the outer periphery of the rear end surface 65 of the insulating ring 61. The tightening screw member 66 has a thickness (dimension) that does not hinder the exposure of the polygonal portion forming the tool engaging portion 44 of the energizing shaft member 41 when screwed. ). The tightening screw member 66 may be a square nut or other polygonal nut. In this embodiment, the protruding length of the screw 45 from the rear end of the main body 31 is set so that the energizing terminal 71 can be screwed and joined to the rear end portion of the energizing shaft member 41.

  In the glow plug 1 of the present embodiment, in order to generate a compressive stress in the piezoelectric element 53 by tightening the combustion pressure detection sensor 50 by screwing the tightening screw member 66 from the structure, each component as described above. And the combustion pressure detection sensor 50 and the insulating ring 61 are disposed on the rear end facing surface 34 of the main body 31 (see FIG. 4). Next, the tightening screw member 66 is screwed from the rear end 43 of the energizing shaft member 41 and tightened. In this case, first, the tightening screw member 66 is screwed into the screw 45 of the rear end 43 of the energizing shaft member 41. However, in the temporary screwing before the sensor 50 is tightened (clamped up), it is substantially. Since no torque is required, the tightening screw member 66 is simply rotated and screwed until it abuts against the rear end surface 65 of the insulating ring 61. On the other hand, when the tightening screw member 66 performs tightening to apply a preload to the combustion pressure detection sensor 50, a large tightening torque is required. For this reason, the main body 31 is held (fixed) by an appropriate tool K, for example, at the polygonal portion 33, and the tool engaging portion 44 formed at the rear end portion or the rear end portion of the energizing shaft member 41 is provided. What is necessary is just to clamp | tighten by hold | maintaining (fixing) with a tool (for example, box wrench), and rotating the screw member 66 for a tightening with the appropriate screwing tool in the state. When the tool engaging portion 44 of the energizing shaft member 41 is held together with the main body 31 with a tool and the tightening screw member 66 is screwed in this way, the energizing shaft member 41 is attached to the main body 31. There is no rotation. That is, according to the glow plug 1 of the present embodiment, when the tightening screw member 66 is tightened when compressive stress is generated in the piezoelectric element 53 in the sensor 50, the current-carrying shaft member 41 and There is no occurrence of problems such as separation (disconnection) or relaxation at the joint with other parts that are connected (joined) or at the joint between the parts.

  That is, in the glow plug 1 of this embodiment, when the tightening screw member 66 is screwed, the main body 31 is fixed, and the tool engaging portion 44 of the energizing shaft member 41 is held by a tool, thereby energizing. Since the shaft member 41 does not rotate in the main body 31, the tightening screw member 66 can be tightened with a sufficiently large torque. As a result, it is possible to obtain a very remarkable effect that a desired and sufficiently large preload can be applied to the piezoelectric element 53 incorporated in the combustion pressure detection sensor 50 without causing problems such as disconnection. . Moreover, this embodiment does not increase the number of parts or complicate the structure even when compared with a conventional glow plug.

  In the glow plug 1 of this embodiment, the sensor 50 is tightened via the insulating ring 61. However, the tightening screw member 66 is formed of an insulating material such as ceramic or resin, and the sensor 50 is When electrical insulation from the main body 31 is ensured at the end face (upper end face in the figure), an intermediate member such as a metal washer can be used instead of the insulating ring 61. Further, without providing the insulating ring 61, it is also possible to apply a preload by directly tightening with a tightening screw member made of such an insulating material.

  In the said form, although the tool engaging part 44 of the shaft member 41 for electricity supply was formed in the rear-end part or the part near a rear end, the tool engaging part 44 in this invention is the screw 45 of the shaft member 41 for electricity supply. In addition, any member that can be held to prevent the energizing shaft member 41 from rotating together with the tightening screw member 66 when the combustion screw detection sensor 50 is tightened by screwing the tightening screw member 66 may be used. Therefore, as shown in FIG. 5, the tool engaging portion 44 can be provided at a position with a distance S from the rear end 43 depending on the length of the rear end side of the energizing shaft member 41. That is, like the glow plug shown in FIG. 5, the tool engaging portion 44 has two parallel surfaces 44b and 44b corresponding to the two surface widths of the mouth of a tool such as a spanner used for holding the same. As shown in the figure, both sides of the circular cross section may be cut. Since the glow plug of FIG. 5 is not different from that described above except for the tool engaging portion 44, the same reference numeral is assigned to the same part. The same applies to the following embodiments.

  In other words, in the present invention, the tool engaging portion has no trouble in screwing the screw member 66 for tightening to the screw 45 of the shaft member 41 for energization and screwing and tightening the combustion pressure detection sensor 50 by screwing method. The shaft member 41 may be provided so as to be held in order to prevent the shaft member 41 from rotating together with the tightening screw member 66. Therefore, it is not limited to a polygonal portion such as a square or the parallel two surfaces 44b and 44b when viewed from the direction of the axis G, and although not shown, it hinders the screwing of the tightening screw member 66 on the opposite side surface of the screw 45. As long as there is no, a several recessed part (recess) can be provided and this recessed part can also be made into a tool engaging part. Furthermore, when using a tool that can hold a circular pipe (cylindrical body), such as a pipe wrench, the shape of the tool engaging portion 44 is not a polygon, and the outer diameter is the screw 45. It may be formed in a circular shape (cylindrical shaft portion) as long as it is not more than the diameter of the valley and does not interfere with screwing of the tightening screw member 66. The same applies to the tightening screw member 66.

  And the tool engaging part 44 of the shaft member 41 for electricity supply in this invention is not restricted to what is formed in the outer peripheral surface, For example, as shown in FIG. It is also possible to use a tool engaging portion 44 in which a through hole penetrating in the direction is inserted and a rod-shaped tool is inserted therein. Further, as shown in FIG. 7, the tool engaging portion 44 of the energizing shaft member 41 in the present invention is a square formed on the rear end (rear end surface) 43 of the energizing shaft member 41 when viewed from the axis G direction. It can also be embodied as a polygonal hole or slot, such as a hexagonal or cross-shaped hole.

  Next, an embodiment of a method for manufacturing a glow plug similar to the above-described glow plug 1 with a combustion pressure detection sensor (the invention according to claim 5), which should be called an application example of the present invention, will be described. A description will be given based on FIGS. In this device, when the tightening screw member 66 is screwed into the screw 45 of the energizing shaft member 41 and the combustion pressure detection sensor 50 is tightened, the energizing shaft member 41 rotates together with the tightening screw member 66 in the main body 31. In order to prevent this, the holding tool engaging portion is formed on the energizing shaft member 41, which is the same as the above-described technical content. However, when this is viewed as a finished product of the glow plug, in the above-described glow plug, the tool engaging portion of the shaft member for energization remains as it is, but it does not exist. It is different in point.

  That is, in this manufacturing method, as shown in FIG. 8, the glow plug described above is provided in the energizing shaft member 41 provided with the disposal margin N to be removed after tightening of the combustion pressure detection sensor 50 on the rear end side. Use a longer one. In tightening the combustion pressure detection sensor 50 by screwing the tightening screw member 66, first, the tightening screw member 66 is screwed from the rear end of the energizing shaft member 41, and at least the rear end of the energizing shaft member 41. Screw until 43 is exposed. In this case, it is preferable that the screw is screwed until it contacts the insulating ring 61. The current-carrying shaft member 41 is long as the predetermined length from the rear end 43 has a disposal margin N, but the tightening screw member 66 is screwed from the rear end 43 of the current-carrying shaft member 41, and There is no difference from the conventional shaft member for energization in that a screw 45 is formed on the outer peripheral surface so that the sensor 50 can be tightened.

  Next, as shown in FIG. 9, the tool engaging member 68 is fixed to the disposal margin portion N on the rear end 43 side of the energizing shaft member 41. The tool engaging member 68 prevents the energizing shaft member 41 from rotating together with the tightening screw member 66 when the tightening screw member 66 in the above-described screwed state is screwed to tighten the combustion pressure detection sensor 50. In order to do so, it may be anything that can be held. Specifically, a hexagon nut and a square nut are preferable. In these cases, the energizing shaft member 41 is screwed or screwed in an appropriate amount to the screw of the disposal margin portion N near the rear end portion of the energizing shaft member 41, and the inner peripheral edge P of the rear end of the nut is used as the energizing shaft member 41. This is because it can be easily fixed by welding, but as is apparent from the above, it may be of any shape and structure. Further, fixing may not be performed by welding, but can be easily performed by welding. As a fixing means other than welding in the case of using a nut for the tool engaging member 68, for example, in a screw at a portion of the disposal margin N, a screw thread is tightened so that the nut does not rotate around the screw 45. Although not shown, the tool engaging member 68 may be crushed or a lock pin may be driven in the radial direction of the energizing shaft member 41 perpendicular to the axis G.

  After fixing the tool engaging member 68 to the disposal margin N of the energizing shaft member 41 in this manner, the metal fitting body 31 and the tool engaging member 68 are held by the tool K in the above-described embodiment. Similarly, the tightening screw member 66 is screwed to tighten the combustion pressure detection sensor 50, but the energizing shaft member 41 does not rotate with respect to the main body 31 in this tightening. That is, according to such a method for manufacturing a glow plug, the tightening screw member 66 required for generating a compressive stress in the piezoelectric element 53 built in the sensor 50 is energized regardless of the tightening torque. There is no occurrence of problems such as separation (disconnection) or relaxation at a joint portion with another component connected (joined) to the shaft member 41 or a joint portion between the components. Therefore, after the tightening, as shown in FIG. 10, the scraping margin N of the energizing shaft member 41 including the tool engaging member 68 is cut and removed, and then the energization is performed as shown in FIG. A desired glow plug with a combustion pressure detection sensor is obtained by screwing the terminal 71 from the rear end 43 of the energizing shaft member 41 after the cutting.

  The glow plug and the manufacturing method thereof according to the present invention are not limited to those described above, and can be embodied with appropriate modifications without departing from the spirit of the present invention. For example, in the above description, the present invention is embodied in a glow plug with a combustion pressure detection sensor provided with a ceramic heater. However, the present invention can also be embodied in a glow plug with a combustion pressure detection sensor provided with a so-called metal heater. Furthermore, although the rear end facing surface of the main body on which the combustion pressure detection sensor is disposed is the rear end facing surface in the screw-in polygonal portion, a rear end facing surface provided separately from this can also be used.

BRIEF DESCRIPTION OF THE DRAWINGS The half sectional view which shows 1st Embodiment of the glow plug with a combustion pressure detection sensor which concerns on this invention, and its principal part enlarged view. The figure which looked at the principal part enlarged view of FIG. 1 from the rear end (illustrated upper end) side. The expanded sectional view explaining a combustion pressure detection sensor. The exploded view which shows the principal part of the glow plug of FIG. The partially broken principal part enlarged view of the glow plug explaining another example of a tool engaging part. The partially broken principal part enlarged view of the glow plug explaining another example of a tool engaging part. A is a partially broken main part enlarged view of a glow plug for explaining another example of the tool engaging portion, and B is a view of A from the rear end (upper end in the drawing) side. The partially broken principal part enlarged view of the principal part explaining the manufacturing method of this invention. The figure after fixing a tool engagement member to the shaft member for electricity supply in FIG. The figure which cut away the discard margin part of the axial member for electricity supply containing a tool engaging member in FIG. The figure of the glow plug finished product which screwed and installed the energization terminal in FIG. The half sectional view of the conventional glow plug with a combustion pressure detection sensor, and its principal part enlarged view.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Glow plug with a combustion pressure detection sensor 11 Heater 31 Metal fitting body 34 Rear end facing surface 41 of the metal fitting body Energizing shaft member 43 Energizing shaft member rear ends 44, 44b Tool engaging portion 45 Energizing shaft member screw 50 Combustion Pressure detection sensor 53 Piezoelectric element 66 Tightening screw member 68 Tool engaging member G Screw axis N Discarding allowance

Claims (6)

A heater that generates heat when energized is fixed inside the cylindrical metal fitting body, and an energizing shaft member for energizing the heater projects the rear end from the rear end of the metal fitting body to insulate the metal fitting body. In addition, a combustion pressure detection sensor with a built-in piezoelectric element is disposed on the rear end surface of the metal fitting body at the rear end or the rear end portion, and this combustion pressure detection sensor is In the glow plug with a combustion pressure detection sensor having a configuration in which compressive stress is generated in the piezoelectric element by screwing a tightening screw member into a screw formed on the outer peripheral surface of the energizing shaft member.
When tightening the combustion pressure detection sensor by screwing the tightening screw member into the screw of the energizing shaft member, the energizing shaft member can be held to prevent rotation with the tightening screw member. A glow plug with a combustion pressure detecting sensor, wherein the tool engaging portion is formed on the energizing shaft member.   The glow plug with a combustion pressure detection sensor according to claim 1, wherein the tool engaging portion is formed at a rear end portion or a rear end portion of the energizing shaft member.   The glow plug with a combustion pressure detection sensor according to claim 1, wherein the tool engaging portion is formed on an outer peripheral surface of a rear end portion of the energizing shaft member or a portion near the rear end.   The glow plug with a combustion pressure detection sensor according to claim 1, wherein the tool engaging portion is a polygonal hole or a slit formed in a rear end surface of the energizing shaft member. A heater that generates heat when energized is fixed inside the cylindrical metal fitting body, and an energizing shaft member for energizing the heater projects the rear end from the rear end of the metal fitting body to insulate the metal fitting body. In addition, a combustion pressure detection sensor with a built-in piezoelectric element is disposed on the rear end surface of the metal fitting body at the rear end or the rear end portion, and this combustion pressure detection sensor is A method of manufacturing a glow plug with a combustion pressure detection sensor having a configuration in which compressive stress is generated in the piezoelectric element by screwing a tightening screw member into a screw formed on an outer peripheral surface of the energizing shaft member. In
For the energizing shaft member, a long one provided with a discarding margin part to be cut off after tightening the combustion pressure detection sensor on the rear end side,
In tightening the combustion pressure detection sensor by screwing the tightening screw member,
The tightening screw member is screwed into the screw and advanced so that at least the rear end of the energizing shaft member is exposed, and in this state, the energizing screw located behind the tightening screw member. In the discarding portion of the shaft member,
A tool engaging member provided so as to be able to hold the energizing shaft member to prevent the energizing shaft member from rotating together with the tightening screw member when the tightening screw member is screwed into the screw and the combustion pressure detection sensor is tightened. Is fixed,
With the metal fitting main body and the tool engaging member held, the tightening screw member is screwed to tighten the combustion pressure detection sensor, and after the tightening, the throw-off shaft member including the tool engaging member is discarded. A method for manufacturing a glow plug with a combustion pressure detection sensor, wherein a proximate portion is cut off.   6. The method for manufacturing a glow plug with a combustion pressure detection sensor according to claim 5, wherein the tool engaging member is fixed by welding.

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