WO2003052323A1

WO2003052323A1 - Glow plug for diesel engine and method of manufacturing the glow plug

Info

Publication number: WO2003052323A1
Application number: PCT/JP2002/011146
Authority: WO
Inventors: Arihito Tanaka; Takashi Aota; Jian Zhao; Toshitsugu Miura
Original assignee: Bosch Automotive Systems Corporation
Priority date: 2001-12-18
Filing date: 2002-10-28
Publication date: 2003-06-26
Also published as: CN1606678A; EP1457736A1; CN1292196C; JP2003185137A

Abstract

A glow plug for diesel engine, wherein one end of a ceramic heater (2) is fixed to one end of a metallic outer tube (4) and the negative pole of the heater (2) is electrically connected to the metallic outer tube (4), the positive pole thereof is connected to an outer connection terminal (8) through an electrode extractor (6), the metallic outer tube (4) having the heater (2) and the outer connection terminal (8) therein are inserted into the internal hole (16) of a housing (10) and, after the tip of the heater (2) is positioned relative to the seat face (10a) of the housing (10), swading is performed from the outer peripheral side of the housing (10), an annular projected part (10d) is formed on the inner peripheral surface of the housing (10) and an annular recessed part (4c) fitted to the annular projected part (10d) is concurrently formed in the outer peripheral surface of the metallic outer tube (4), whereby the metallic outer tube (4) holding the heater (2) can be firmly fixed to the housing (10), and a cost can be reduced since a high accuracy is not requested for the inner diameter of the housing (10).

Description

TECHNICAL FIELD The present invention relates to a glow plug used for assisting starting of a diesel engine, and in particular, relates to a sheath holding a heater and a cylinder head of the engine. The present invention relates to a glow plug for a diesel engine, which is characterized in that it is fixed to a housing, which is a mounting bracket for the diesel engine, and a method for manufacturing the glove lug for a diesel engine. BACKGROUND ART Generally, a glow plug for a diesel engine holds a heater in a metal sheath, and inserts one end of the sheath into a front end of a mounting bracket (a cylindrical housing) to an engine cylinder head. While electrically connecting one electrode of the heater to the sheath and extracting the other electrode to the outside through an electrode extraction metal fitting, and fixing the other electrode to the other end of the housing via an insulator. It is configured to be electrically connected to the external connection terminal.

In the above-mentioned glow plug for diesel engines, silver brazing or press fitting has been conventionally performed as a method for fixing the sheath holding the heater and the housing. When fixing by brazing, a slight gap is formed between the inner peripheral surface of the housing and the outer peripheral surface of the sheath, and the molten brazing material is poured into this gap to separate the housing and the sheath. Join. In the case of press-fitting, a portion slightly smaller than the outer diameter of the sheath is formed in the inner hole of the housing as a press-fitting allowance, and the sheath is fixed by pressing and pushing the sheath into the small-diameter portion. ing.

When fixing the sheath holding the heater inside the housing by brazing Requires a gap between the inner peripheral surface of the housing and the outer peripheral surface of the sheath, so that misalignment is likely to occur, and concentricity between the housing and heat sink can be ensured. There was a problem that it was difficult. Moreover, due to the repeated action of high heat, there was a possibility that the sheath holding the heater would enter the eight housings, and that the sheath could escape from the housing.

When the sheath is fixed to the housing by press-fitting, it is necessary to process the inner diameter of the portion of the inner surface of the housing into which the sheath is press-fitted and the length of the press-fitted portion with high precision. Since the internal holes are processed, there is a problem that the processing cost of the housing is extremely high. Further, in order to change the distance from the front end of the heater to the seat surface to the cylinder head formed at the front end of the housing according to the required performance, the press-fitted portion of the housing internal hole should be removed. Since they must be formed at different positions, it is necessary to manufacture various kinds of housings according to each specification, which is costly. In addition, when the sheath holding the sheath is press-fitted into the housing, if the press-fit portion is galled, the press-fitting load increases, resulting in a problem that the heater and the housing may be damaged. . The present invention has been made in order to solve the above-mentioned problem, and there is no danger of misalignment between a sheath holding a heater and a housing as when the sheath is fixed by brazing. An object of the present invention is to provide a glow plug for a diesel engine having a strong holding force and a method for manufacturing the same.

It is another object of the present invention to provide a low-cost housing and a method for manufacturing a glow plug for diesel engines and a method for manufacturing the same, which do not damage the heater during press-fitting.

DISCLOSURE OF THE INVENTION The glow plug for a diesel engine according to the invention described in claim 1 is one in which one end of a sheath holding a heater is inserted and fixed into an inner hole of a cylindrical housing. Plastic working from the outer surface of the inner surface An annular projection formed on the outer surface of the sheath and an annular recess formed on the outer surface of the sheath via the housing by the plastic working are fitted to each other, and the housing and the sheath are fixed. Is what you do.

In the glow plug for a diesel engine according to the present invention, since the annular convex portion of the housing formed by plastic working and the annular concave portion of the sheath are firmly engaged, the sheath may move in the axial direction of the housing. There is no danger of getting inside the housing or getting out of the housing. In addition, there is no risk of misalignment between the housing and the sheath. In addition, since there is no need to perform high-precision machining of the internal hole of the housing, machining of the housing is inexpensive.

Further, the invention according to claim 2 is characterized in that the annular convex portion and the annular concave portion formed by the plastic working are formed of a surface parallel to the axis of the housing.

Further, the invention according to claim 3 is characterized in that the annular convex portion and the annular concave portion formed by the plastic working are constituted by surfaces inclined with respect to the axis of the housing.

In the configuration of the present invention, the diameter of the annular convex portion and the annular concave portion is continuously changed from the large diameter portion to the small diameter portion, so that the annular convex portion and the annular concave portion have the same diameter over the entire length in the axial direction. Also, it is easy to maintain the airtightness between the housing and the sheath.

The invention according to claim 4 is characterized in that a plurality of annular convex portions and annular concave portions formed by the plastic working are provided in an axial direction. The invention according to claim 5 is a method for manufacturing a glow plug for diesel engine in which one end of a sheath holding a heater is inserted and fixed into an internal hole of a cylindrical housing, and After inserting one end of the sheath into the inner hole and positioning the distal end of the heater held by the sheath and the seat surface to the cylinder head provided in the housing, the sheath is positioned on the outer peripheral surface of the housing. An annular convex portion is formed on the inner surface of the housing by performing plastic working, and an annular concave portion is formed on the outer surface of the sheath so that the annular convex portion is fitted to fix the sheath to the housing. It is.

In the method of the present invention, plastic working of the manufactured diesel engine glow plug is performed. The annular convex portion of the housing and the annular concave portion of the sheath are firmly engaged with each other, so that the sheath does not move in the axial direction of the housing, and there is no risk of misalignment. In addition, since high-precision machining is not required for the housing, machining of the housing is low in cost. In addition, when the heater is joined to the housing, the distance between the tip of the heater and the seat surface of the housing can be set arbitrarily. Can be

A method of manufacturing a glow plug for a diesel engine according to claim 6, wherein one end of the sheath is inserted into an inner hole of the housing, and plastic processing is performed on an outer peripheral surface of the housing, so that an annular convex surface is formed on an inner surface of the housing. Forming an annular concave portion on the outer surface of the sheath, into which the annular convex portion fits, and fixing the sheath to the housing, and at the same time, attaching the seat surface to the cylinder head to the distal end surface of the housing. It is characterized by forming.

In the method of the present invention, when the housing and the heater are joined by the plastic working, the seat surface of the housing is formed at the same time, so that the dimensional accuracy from the front end of the heater to the seat surface of the housing can be further improved.

A method for manufacturing a glow plug for a diesel engine according to claim 7, wherein one end of the sheath is inserted into an inner hole of the housing, and an insulator is interposed between an inner surface of the housing and an outer surface of the sheath. After positioning the tip of the heater held by the sheath and the seat surface to the cylinder head provided in the housing, plastic processing is performed from the outer surface side of the housing to form an annular shape on the inner surface of the housing. A projection is formed, and the sheath is fixed to the housing via the insulator.

The glow plug for a diesel engine manufactured by the method of the present invention has an insulator interposed between the inner surface of the housing and the outer surface of the sheath, and these are fixed in an insulated state. Can be used.

BRIEF DESCRIPTION OF THE FIGURES 【Figure 1】

It is a longitudinal section of a glow plug for diesel engine concerning one embodiment of the present invention.

【Figure 2】

FIG. 3 is an enlarged view of a main part (A in FIG. 1) of the diesel engine glow plug.

FIG. 2 is a longitudinal sectional view for explaining an assembling process of the diesel engine glow plug.

[Figure 4]

FIG. 4 is a longitudinal sectional view showing a step subsequent to FIG.

[Figure 5]

FIG. 5 is a longitudinal sectional view showing a step subsequent to FIG. 4.

[Fig. 6]

FIG. 7 is a longitudinal sectional view of a glow plug for a diesel engine according to a second embodiment.

FIG. 9 is a longitudinal sectional view for explaining a process of assembling a global plug for diesel engine according to a second embodiment.

[Fig. 8]

FIG. 8 is a longitudinal sectional view illustrating a step subsequent to FIG. 7.

[Fig. 9]

FIG. 8 is a circuit diagram showing an operation electric circuit of a glow plug for a diesel engine according to a second embodiment.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described with reference to the embodiments shown in the drawings. FIG. 1 is a vertical cross-sectional view of a glow plug for a diesel engine (indicated by reference numeral 1) according to an embodiment of the present invention, and FIG. 2 is an enlarged view of a main part (A part in FIG. 1). The green plug 1 of this embodiment is a ceramic green plug using a ceramic glass 2 as a heating element.

The ceramic heater 2 has a well-known structure and its details are not shown. However, a heating wire made of a refractory metal such as tungsten (W) in a coil shape is formed inside a ceramic insulator constituting a main body. The heating wire has one end connected to the negative lead wire and the other end connected to the positive lead wire. The lead wire on the negative electrode side is taken out from the outer peripheral surface of the ceramic insulator, and is joined to the inner surface of a sheath (metal outer cylinder) 4 described later by brazing to be electrically connected. On the other hand, the positive lead wire extends to the end opposite to the position where the heating wire is buried (the left end in Fig. 1), and within the mounting hole 2b formed on this end surface, the tip of the electrode extraction metal fitting 6 It is electrically connected to the section by brazing. Further, the rear end of the electrode extraction fitting 6 is fixed to the front end of the external connection terminal 8.

A ceramic housing 2 having the above-described configuration is joined to a sheath (metal outer cylinder) 4 by brazing, and is a mounting bracket to a cylinder head via the metal outer cylinder 4. Fixed to 10 In this embodiment, the metal outer cylinder 4 has a slightly smaller diameter at the distal end portion 4a and a larger diameter at the rear portion 4b side, and a rear portion of the ceramic heater 2 inside the small diameter portion 4a. Are inserted and joined by brazing or the like. The housing 10 has a seat surface 10a at the front end (the left end in FIG. 1) to the cylinder head of the engine, and a screw portion 10b to the cylinder head at the rear side. Further, a nut portion 10c for fastening is formed at the rear end.

One end of an external connection terminal 8 electrically connected to a positive lead wire of the ceramics heater 2 via an electrode extraction fitting 6 is fixed in a metal outer cylinder 4 by swaging. . A process of fixing the external connection terminal 8 by this swaging will be briefly described. First, the electrode take-out fitting 6 is inserted into the mounting hole 2b of the ceramic heat sink 2, and the electrode take-out fitting 6 and the ceramic heat sink 2 are inserted. And the ceramics heater 2 is fixed by brazing to the end of the metal outer cylinder 4 closer to the ceramic heater fixing side (the end on the small diameter portion 4a side). At this time, it is a matter of course that the heating portion 2 a in which the heating wire near the tip of the ceramic heater 2 is embedded is exposed outside the metal outer cylinder 4.

After fixing the ceramic heater 2 in the small-diameter portion 4 a of the metal outer cylinder 4, insert the tip of the external connection terminal 8 from the opening 4 c on the large-diameter portion 4 b side of the metal outer cylinder 4. Connect to the other end of the electrode take-out bracket 6. Thereafter, the heat-resistant insulating powder (for example, magnesia (MgO)) is introduced from the opening 4 c of the metal outer cylinder 4 into the space in which the connection between the electrode extraction fitting 6 and the external connection terminal 8 is accommodated. Etc.) Fill 1 and 2. Next, a rubber sealing member (silicon rubber, fluorine rubber, etc.) 14 is attached to the opening 4 c of the metal outer cylinder 4. By mounting the sealing member 14 in the opening 4c of the metal outer cylinder 4, it is possible to prevent the heat-resistant insulating powder 12 from spilling when swaging is performed in a later step. In addition, it is possible to prevent the electrode extraction fitting 6 from contacting the metal outer cylinder 4.

Then, the outer diameter of the metal outer cylinder 4 is reduced by swaging the large-diameter portion 4 b of the metal outer cylinder 4 that houses the connection between the electrode extraction fitting 6 and the external connection terminal 8. The external connection terminal 8 is fixed in the metal outer cylinder 4 by increasing the density of the heat-resistant insulating powder 1 2

The metal outer cylinder 4 to which the ceramic heater 2, the electrode extraction metal fitting 6, and the external connection terminal 8 are fixed has a large-diameter portion 4 b on the rear side inserted and fixed in a cylindrical housing 10. I have. In this embodiment, the portion slightly before the distal end of the housing 10 is located on the outer periphery of the large-diameter portion 4b of the metal outer cylinder 4 near the small-diameter portion 4a. Is swaged from the outside of the housing 10 (the swaged portion is indicated by the symbol S), and an annular convex portion 10d is formed on the inner peripheral side (part A in FIG. 1). This swaging process also forms an annular concave portion 4c on the outer peripheral surface of the metal outer cylinder 4 at the same time, and these annular convex portions 10d of the housing 10 and The annular concave portion 4c of the metal outer cylinder 4 is fitted with each other. The annular projection 10 d formed by swaging and the annular The fitting and close contact of the recesses 4 c secure the housing 10 and the metal outer cylinder 4 and maintain airtightness.

As described above, the housing 10 and the metal outer cylinder 4 are fixed by swaging from the outer peripheral side of the housing 10 so that the housing 10 and the metal outer cylinder 4 are completely adhered to each other. Therefore, there is no possibility that both of them are misaligned. Further, airtightness between the housing 10 and the metal outer cylinder 4 is reliably maintained. In addition, since the annular convex portion 10d and the annular concave portion 4c are engaged with each other, the holding force in the axial direction is strong, and the ceramic heater 2 held by the metal outer cylinder 4 has the housing 10 Without getting out of the housing or getting inside the housing 10. Next, a process of assembling the glow plug 1 for a diesel engine having the above structure will be described with reference to FIGS. 1, 2, and 3 to 5. First, the assembly consisting of the ceramic heater 2, the electrode extraction metal fitting 6, and the external connection terminal 8 fixed in the metal outer cylinder 4 is attached to the tip of the housing 10 with the screw 8a side of the external connection terminal 8 first. (Seat surface 10a side to cylinder head) and insert into internal hole 16 (see Fig. 3). Before the housing 10 is assembled, the entire inner hole 16 has an inner diameter large enough to allow the large-diameter portion 4b of the metal outer cylinder 4 to pass therethrough.

As described above, the external connection terminal 8 is inserted from the screw portion 8 a side into the internal hole 16 of the housing 10, and the large-diameter portion 4 b side of the metal outer cylinder 4 is also inside the internal hole 16 of the housing 10. Insert At the end of the housing 10, a seat surface 10a to the cylinder head of the engine is formed, and a distance L1 between the seat surface 10a and the end of the ceramic heater 2 has a predetermined size. (See Figure 4). In this state, swaging is performed from the outer peripheral side to a portion slightly before the front end portion of the housing 10 (see reference numeral S in FIG. 5). By performing swaging, as shown in the enlarged view of FIG. 2, the outer peripheral surface of the housing 10 is recessed, and an annular convex portion 10d is formed on the inner surface side. Further, through the plastic deformation of the housing 10, an annular concave portion 4c is also formed on the outer surface side of the metal outer cylinder 4. By this swaging, the housing 10 and the metal outer cylinder 4 are firmly adhered and joined.

In this embodiment, the internal hole 16 of the housing 10 may have an inner diameter slightly larger than the outer diameter of the metal outer cylinder 4 so that the large-diameter portion 4b of the outer cylinder 4 can pass through. Since high precision is not required, processing can be performed at extremely low cost as compared with the case of fixing by press fitting. Further, the distance L 1 between the seat surface 10 a of the housing 10 and the tip of the ceramic heater 2 can be set arbitrarily at the time of joining, so that the housing 10 having one type of dimension and the ceramic heater 2 provide Glow plugs 1 of various performances can be manufactured, and the cost is extremely low. Furthermore, unlike the case of fixing by press-fitting, there is no risk of damaging the ceramic heater 2. In the above embodiment, the housing 10 and the metal outer cylinder 4 are simultaneously deformed by swaging from the outer peripheral surface of the housing 10 to fix both of them. Not limited to this, the annular convex portion 10d and the annular concave portion 4c to be fitted to each other may be formed in the housing 10 and the metal outer cylinder 4 by other plastic working such as rolling. Conventionally, a housing having an internal hole was manufactured by cutting a solid steel material, but in this embodiment, the internal hole 16 of the housing 10 is not required to be processed with high precision. By using inexpensive pipe material and forming the screw 10b for mounting to the engine, the nut 10c at the rear end, and the seat 10a at the top by rolling, etc., the cost can be further reduced. You can also plan.

In the glow plug 1 according to the embodiment, the portion deformed by the plastic working is constituted by a surface parallel to the axis of the housing 10, that is, the swaged portion S is the housing 10. Have the same diameter over the longitudinal direction. The annular convex portion 10a and the annular concave portion 4c are not limited to those having the same diameter over the longitudinal direction as described above. Alternatively, it may be constituted by an inclined surface.

Further, a seat surface 10a for mounting to the cylinder head of the engine is formed at the end of the housing 10, but only when the housing 10 is formed in advance in the housing 10 as in the above embodiment. Instead, when the housing 10 and the metal outer cylinder 4 are fixed by plastic processing such as swaging or rolling, the sheet surface 10a can be formed at the same time. By simultaneously forming the seat surface 10a of the housing 10 in this manner, the dimensional accuracy between the tip of the ceramic heater 2 and the seat surface 10a of the housing 10 can be improved. Furthermore, by connecting the plastically processed part of the outer periphery of the housing 10 and the adjacent part with a smooth R shape, the protection for the housing 10 is prevented from peeling off when performing swaging. can do.

Also, in the above description, the metal outer cylinder 4 is filled with the heat-resistant insulating powder 12, and the external connection terminal 8 connected to the electrode extraction bracket 6 is swaged to form the metal outer cylinder 4. Although it is fixed, it is also possible to omit this swaging step and also to perform swaging processing for fixing the housing 10 and the metal outer cylinder 4. In this case, airtightness is not required, and it is only necessary to securely fix the positive electrode, so that the swaging step can be omitted and the cost can be further reduced.

FIG. 6 is a longitudinal sectional view showing a diesel engine glow plug 101 according to the second embodiment. The glow plug 101 is similar to the diesel engine glow plug 1 having the above-described configuration. It integrates an ion sensor that detects the ion current and detects the combustion state of the engine.

In the ceramic heater 102 of the glow plug 101, a heating element 102b is embedded in a ceramic insulator 102a, a negative lead wire 102c at one end thereof, Positive lead wires 102d are connected to the other ends, respectively. This heating element 102b has a tip 102ba exposed to the outside of the ceramic insulator 102a in order to be used also as an electrode for ion detection.

The lead wire 102 c on the negative electrode side is taken out from the side surface of the ceramic insulator 102 a and is electrically connected to the inner surface of the sheath (metal outer cylinder) 104. The reference numeral 02 d is electrically connected to one end of the electrode extraction metal fitting 106 inside the ceramic insulator 102 a. Further, the other end of the electrode extraction metal fitting 106 is connected to an external connection terminal 108.

Unlike the configuration of the first embodiment, the metal outer cylinder 104 to which the ceramic heater 102 is fixed has a longer overall length than the housing 110, and In a state where the ceramic heater 102 is fixed to 0, the end 104 e opposite to the tip 104 d to which the ceramic heater 102 is fixed has reached the rear end of the housing 110. The inside of the metal outer cylinder 104 is filled with heat-resistant insulating powder 112, Density is increased by aging to fix the external connection terminal 108 and insulate the external connection terminal 108 on the positive electrode side from the metal outer cylinder 104 on the negative electrode side. A metal outer cylinder 104 having a ceramic heater 102 fixed to one end 104 d and an external connection terminal 108 extending to the other end 104 e is a cylindrical housing. It is inserted into the internal hole 1 16 of 110 and fixed. An insulator 118 is inserted between the inner surface of the housing 110 near the tip and the outer surface of the metal outer cylinder 104, and the housing 110 and the metal outer cylinder 1 are inserted. 04 is electrically insulated. In this embodiment, the portion filled with the insulator 118 is swaged from the outer peripheral side of the housing 110 (see reference symbol S in FIG. 6), and an annular convex is formed on the inner peripheral side. A part 110d is formed, and the metal outer cylinder 104 is fixed to the housing 110 at the swaged part S.

The process of assembling the ion sensor body type plug 101 will be described with reference to FIGS. 6, 7 and 8 described above. The assembly including the ceramic ceramic holder 102 held in the metal outer cylinder 104, the electrode extraction metal fitting 106 and the external connection terminal 108 was connected to the external connection terminal 108. Insert the threaded part from the end of the housing 110 (the end on the side where the ceramics is mounted 102) with the threaded part 108a first (see Fig. 7).

After the distance L 2 between the seat surface 1 1 0 _a to the ceramic heater 1 0 2 tip and the housing 1 1 0 Siri cylinder head formed on the tip and positioned so as to have a predetermined size, the housing A seal member 120 is attached between the tip of 110 and the outer peripheral surface of the metal outer cylinder 104, and heat-resistant insulating powder 118 is further applied from the rear opening side of the housing 110. After filling, seal members 122 are fitted (see FIG. 8). Thereafter, the outer peripheral side of the portion filled with the heat-resistant insulating powder 118 is swaged to plastically deform the housing 110, and an annular convex portion 110d is formed on the inner peripheral surface thereof. Densify the heat-resistant powder 1 18 and fix the metal outer cylinder 104

(State in Fig. 6).

The ion sensor body type plug 101 is provided with a metal outer cylinder 104 electrically connected to a negative electrode lead wire 102 c of a ceramic heater 102, and a rear end portion of a housing 110. Side is connected to the negative terminal 1 2 4 and is connected to the positive lead 10 2 d. The external connection terminal 108 electrically connected via the pole extraction bracket 106 is connected to the positive electrode side terminal 126. An insulating ring 128 is interposed between the negative electrode terminal 124 electrically connected to the metal outer cylinder 104 and the housing 110. An insulator 130 is interposed between the positive electrode terminal 126 and the positive electrode terminal 126 to be electrically insulated.

As shown in FIG. 9, the positive terminal 1 26 is connected to the positive side of the battery 13 2 via a first relay 13 A, and the negative terminal 12 4 is connected to the battery 13. 2 is connected to the minus side via a second relay 134B. Therefore, the positive pole of the battery 13, the first relay 13 A, the positive terminal 12 6, the external connection terminal 10 8, the electrode extraction fitting 10 6, and the positive lead wire of the ceramic heater 10 2 102 d, heating element 102 b, negative lead wire 102 c, metal outer cylinder 104, negative terminal 1 24, second relay 1 3 4 B and battery 1 3 2 The negative pole forms a globe-lag electrical circuit.

The housing 110 is fixed to a cylinder head 1336 of the engine. The negative pole of the battery 1332 is grounded to the cylinder head 1336, and the battery 13 The positive electrode 2 and the positive terminal 1 26 of the green plug 101 are connected via current detecting means 1 38 and a sensor relay 140. Therefore, the positive pole of the battery 13 2, the current detection means 1 38 and the sensor relay 140, the positive terminal 1 26, the external connection terminal 108, the electrode extraction bracket 106 and the ion The electric circuit of the ion sensor is formed by the heating element 102 b as the detection electrode and the earth of the cylinder head 1 36.

If the glow plug 101 of the ion sensor type is to function as a glow plug, the first and second relays 1334 A and 1348 for the glow plug are set to 0 N and Turn off the sensor relay 140. Then, an electric current flows through the electric circuit for the glow plug, and the heating element 102b generates heat, thereby preheating the engine.

When the glow plug 101 of the above configuration functions as an ion sensor, turn off the glow plug relays 134 A and 134 B and turn on the ion sensor relay 140. I do. Then, the ceramic electrode as an electrode for ion detection A voltage is applied between the heating element 102 b of the night 102 and the cylinder head 136, and a current flows through the sensor electric circuit due to ions in the combustion chamber generated when the engine is burning. This current is detected by the current detecting means 138, and feedback control of the engine is performed.

Also with the glow plug 101 for a diesel engine according to this embodiment, as in the first embodiment, the structure of the housing 110 is simplified, so that the housing 110 can be manufactured at low cost. Can be. Also, without changing the shape of the housing 110, the distance L2 between the seat surface 110a to the cylinder head 13 6 of the housing 110 and the tip of the ceramic heater 102 Can be set arbitrarily, and cost can be significantly reduced.

The insulator interposed between the housing 110 and the metal outer cylinder 104 is limited to the above-described heat-insulated insulating powder 118 densified by swaging. Instead, for example, other insulators such as resin can be used.

Further, in each of the above-described embodiments, the ceramic heater-type glow plugs 1 and 101 using the ceramic heaters 2 and 102 as heating elements have been described. However, the present invention is not limited to the ceramic heaters. It is also possible to apply the present invention to a glow plug using a heater made of.

Claims

The scope of the claims

1. In a glow plug for diesel engine fixed by inserting one end of sheath holding

An annular convex portion formed on the inner surface of the housing by performing plastic working from the outer peripheral surface of the housing and an annular concave portion formed on the outer surface of the sheath via the housing by the plastic working are fitted to each other. And a sheath fixed to the glow plug for a diesel engine.

2. The glow plug for a diesel engine according to claim 1, wherein the annular convex portion and the annular concave portion formed by the plastic working are constituted by surfaces parallel to an axis of the housing.

3. The glow plug for diesel engine according to claim 1, wherein the annular convex portion and the annular concave portion formed by the plastic working are formed of surfaces inclined with respect to the axis of the housing.

4. The glow plug for a diesel engine according to claim 1, wherein a plurality of annular convex portions and annular concave portions formed by the plastic working are provided in an axial direction.

5. In the method of manufacturing a globe lug for diesel engine, in which one end of a sheath holding a heater is inserted into an inner hole of a cylindrical housing and fixed.

After inserting one end of the sheath into the internal hole of the housing and positioning the tip of the heater held by the sheath and the seat surface to the cylinder head provided in the housing, the outer periphery of the housing By performing plastic working on the surface, an annular convex portion is formed on the inner surface of the housing, and an annular concave portion on which the annular convex portion is fitted is formed on the outer surface of the sheath, thereby fixing the sheath to the housing. Features Manufacturing method for glow plugs for diesel engines.

6. A method for manufacturing a glow plug for a diesel engine in which one end of a sheath holding a heater is inserted into an inner hole of a cylindrical housing and fixed.

Inserting one end of the sheath into the internal hole of the housing, and performing plastic working on the outer peripheral surface of the housing, thereby forming an annular convex portion on the inner surface of the housing and fitting the annular convex portion on the outer surface of the sheath. A method of manufacturing a glow plug for a diesel engine, comprising: forming an annular concave portion; fixing the sheath to the housing; and forming a seat surface to a cylinder head at a distal end surface of the housing. .

7. A method for manufacturing a glow plug for a diesel engine in which one end of a sheath holding a heater is inserted into an inner hole of a cylindrical housing and fixed.

One end of the sheath is inserted into an internal hole of the housing, an insulator is interposed between an inner surface of the housing and an outer surface of the sheath, and a distal end of a heater held by the sheath and the housing are provided. After positioning with respect to the seat surface to the cylinder head, plastic processing is performed on the outer peripheral surface of the housing to form an annular convex portion on the inner surface of the housing, and the sheath is connected to the housing via the insulator. A method for manufacturing a glow plug for a diesel engine, comprising: