JP2003185137A - Glow plug for diesel engine and method of manufacturing the glow plug - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To firmly fix a metal outer tube 4 holding a heater 2 to a housing 10, and simplify the structure and reduce the cost of the housing 10. <P>SOLUTION: One end of the ceramic heater 2 is fixed to one end of a metal outer tube 4, and the negative pole of the heating element thereof is electrically connected to the metal outer tube 4. On the other hand, a positive pole is connected to an outer connection terminal 8 through an electrode extraction metal bar 6. The metal outer tube 4 having the heater 2 and the outer connection terminal 8 is inserted into the inner hole 16 of the housing 10 and, after the tip of the heater 2 is positioned relative to the seat face 10a of the housing 10, a swaging 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 for fitting the annular projected part 10d thereinto is simultaneously formed in the outer peripheral surface of the metal outer tube 4. Since a high accuracy is not requested for the inner diameter of the housing 10, the housing can be provided at a low cost. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a glow plug used as a starting aid for a diesel engine,
In particular, the present invention relates to a glow plug for a diesel engine and a method for manufacturing the glow plug for a diesel engine, which is characterized by fixing a sheath holding a heater to a housing that is a fitting for attaching to a cylinder head of an engine.

[0002]

2. Description of the Related Art Glow plugs for diesel engines are
Generally, the heater is held in a metal sheath, and one end of the sheath is inserted into and fixed to the front end of a fitting (cylindrical housing) to the cylinder head of the engine, and one electrode of the heater is fixed. In addition to being electrically connected to the sheath, the other electrode is taken out to the outside via an electrode take-out fitting and electrically connected to an external connection terminal fixed to the other end of the housing via an insulator. is doing.

In the glow plug for a diesel engine, 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 join the housing and the sheath. . In the case of press-fitting, a portion with a diameter slightly smaller than the outer diameter of the sheath is formed in the inner hole of the housing as a press-fitting margin, and the sheath is fixed by pressurizing and pushing it into this small-diameter portion. There is.

[0004]

When the sheath holding the heater is fixed in the housing by brazing, it is necessary to fix the sheath between the inner peripheral surface of the housing and the outer peripheral surface of the sheath.
Since a gap into which the wax is inserted is required, there is a problem in that misalignment is likely to occur and it is difficult to secure the concentricity between the housing and the heater. Moreover, due to the repeated application of high heat, there is a possibility that the sheath holding the heater may enter the housing or come out of the housing.

When the sheath is fixed to the housing by press fitting, the inner diameter of the portion on the inner surface of the housing where the sheath is press fitted and the length of this press fitting portion must be processed with high accuracy, and therefore, usually, cutting is performed. Since the internal hole is processed by the above method, there is a problem that the processing cost of the housing is very high. Further, in order to change the distance from the tip of the heater to the seat surface of the cylinder head formed at the tip of the housing according to the required performance, the press-fitted portions of the housing internal holes are formed at different positions. Therefore, various types of housings have to be manufactured according to each specification, which is expensive. Further, when the sheath holding the heater is press-fitted into the housing, if the press-fitting portion is galled or the like, the press-fitting load is increased, and as a result, the heater or the housing is damaged.

The present invention has been made to solve the above-mentioned problems, and there is no risk of misalignment between the sheath holding the heater and the housing, which would occur if they were fixed by brazing. An object of the present invention is to provide a glow plug for a diesel engine having a strong directional holding force and a method for manufacturing the same.

It is another object of the present invention to provide a glow plug for a diesel engine and a method for manufacturing the same, which makes the housing inexpensive and does not damage the heater during press fitting.

[0008]

In the glow plug for a diesel engine according to the invention described in claim 1, one end of a sheath holding a heater is inserted and fixed in an inner hole of a cylindrical housing. In particular, the annular convex portion formed on the inner surface of the outer peripheral surface of the housing by the plastic working and the annular concave portion formed on the outer surface of the sheath through the housing by the plastic working are fitted to each other. It is characterized in that the housing and the sheath are fixed.

In the glow plug for a diesel engine according to the present invention, since the annular convex portion of the housing formed by swaging and the annular concave portion of the metal outer cylinder are firmly meshed with each other, the metal outer cylinder is the shaft of the housing. There is no possibility of moving in the direction, and there is no risk of misalignment. In addition, since it is not necessary to process the inner hole of the housing with high accuracy, the cost of processing the housing is low.

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 by planes 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 structure of the present invention, since the annular convex portion and the annular concave portion are continuously changed in diameter from the large diameter portion to the small diameter portion, they have the same diameter over the entire axial length. It is easier to maintain airtightness between the housing and the metal outer cylinder than in the case.

The invention as set forth in claim 4 is characterized in that a plurality of annular convex portions and annular concave portions formed by the plastic working are provided.

According to a fifth aspect of the present invention, there is provided a method for producing a glow plug for a diesel engine, wherein one end of a sheath holding a heater is inserted and fixed in an inner hole of a cylindrical housing. After inserting one end of the sheath into the inner hole of the housing and positioning the tip of the heater held by the sheath and the seat surface on the cylinder head provided in the housing, the outer peripheral surface of the housing is plastically worked. By doing so, an annular convex portion is formed on the inner surface of the housing, and an annular concave portion into which the annular convex portion fits is formed on the outer surface of the sheath to fix the sheath to the housing.

In the method of the present invention, since the annular convex portion of the housing formed by swaging and the annular concave portion of the metal outer cylinder of the manufactured glow plug for a diesel engine are firmly meshed with each other, the metal outer cylinder is There is no risk of moving in the axial direction of the housing, and there is no risk of misalignment. Moreover, since the housing does not need to be processed with high precision, the housing can be processed at low cost. Furthermore, since the distance between the tip of the heater and the seat surface of the housing can be set arbitrarily when the heater and the housing are joined together, glow plugs of various performances can be manufactured with a single-sized housing and heater. .

According to a sixth aspect of the present invention, there is provided a method for manufacturing a glow plug for a diesel engine, wherein one end of the sheath is inserted into an inner hole of the housing and the outer peripheral surface of the housing is plastically worked to form an annular shape on the inner surface of the housing. A convex portion is formed, and an annular concave portion to which the annular convex portion fits is formed on the outer surface of the sheath to fix the sheath to the housing, and at the same time, a seat surface to the cylinder head is formed on the tip end surface of the housing. It is characterized by doing.

According to the method of the present invention, since the seat surface of the housing is formed at the same time when the housing and the heater are joined by the plastic working, the dimensional accuracy from the tip of the heater to the seat surface of the housing can be further improved. .

In the method for manufacturing a glow plug for a diesel engine according to a seventh aspect, one end of the sheath is inserted into the inner hole of the housing, and an insulator is interposed between the inner surface of the housing and the outer surface of the sheath. After positioning the tip of the heater held by the sheath and the seat surface on the cylinder head provided in the housing,
By performing plastic working from the outer surface side of the housing, an annular convex portion is formed on the inner surface of the housing, and the sheath is fixed to the housing via the insulator.

In the glow plug for a diesel engine manufactured by the method of the present invention, an insulator is interposed between the inner surface of the housing and the outer surface of the sheath to fix the two in an insulated state. Can be used as

[0020]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described below with reference to embodiments shown in the drawings. FIG. 1 is a vertical cross-sectional view of a glow plug for a diesel engine (the whole is shown 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 of FIG. 1). The glow plug 1 of this embodiment is a ceramic heater type glow plug using a ceramic heater 2 as a heating element.

The ceramic heater 2 has a conventionally well-known structure, and although its details are not shown, a heating element is embedded in a ceramic insulator forming the main body, and one end of the heating element has a negative lead wire. And a lead wire on the positive electrode side is connected to the other end. The lead wire on the negative electrode side is taken out to the outer peripheral surface of the ceramic insulator and is electrically connected to the inner surface of a sheath (metal outer cylinder) 4 described later by brazing. on the other hand,
The positive electrode side lead wire is at the position where the heating element is embedded (see FIG. 1).
The left end) of the electrode lead-out metal fitting 6 and is electrically connected to the tip end of the electrode lead-out metal fitting 6 by brazing in a mounting hole formed in this end face. Further, the rear end of the electrode take-out fitting 6 is fixed to the tip of the external connection terminal 8.

The ceramic heater 2 having the above-mentioned structure is joined by brazing in a sheath (metal outer cylinder) 4 and is connected to a cylindrical housing 10 which is a metal fitting for a cylinder head through the metal outer cylinder 4. It is fixed. In this embodiment, the metal outer cylinder 4 has a slightly smaller diameter on the tip side portion 4a and a larger diameter on the rear portion 4b side, and the rear portion of the ceramic heater 2 is inserted into the small diameter portion 4a. It is joined by brazing or the like. A seat surface 10a for the cylinder head of the engine is formed at the front end (the left end in FIG. 1) of the housing 10, a mounting screw portion 10b for mounting on the cylinder head is provided near the rear portion, and a tightening portion is provided at the rear end portion. The nut portion 10c and the like are formed.

The external connection terminal 8 electrically connected to the positive electrode side lead wire of the ceramics heater 2 through the electrode lead-out metal fitting 6 has a metal outer cylinder 4 by swaging.
It is fixed inside. The process of fixing the external connection terminal 8 by this swaging will be briefly described. First,
The electrode lead-out metal fitting 6 is inserted into the mounting hole of the ceramics heater 2, the electrode lead-out metal fitting 6 and the positive electrode lead wire of the ceramics heater 2 are joined by brazing, and the ceramics heater 2 is attached to the metal outer tube 4. The ceramic heater is fixed by brazing to the end on the fixed side (the end on the small diameter portion 4a side). At this time, it goes without saying that the heat generating portion 2a in which the heat generating element is embedded near the tip of the ceramic heater 2 is exposed to the outside of the metal outer cylinder 4.

After fixing the ceramics heater 2 in the small-diameter portion 4a of the metallic outer cylinder 4, the tip of the external connection terminal 8 is inserted through the opening 4c on the large-diameter portion 4b side of the metallic outer cylinder 4. It is joined to the other end of the electrode take-out fitting 6. After that, heat-resistant insulating powder (for example, magnesia (MgO)) 12 is introduced from the opening 4c of the metal outer cylinder 4 into the space where the connection between the electrode take-out fitting 6 and the external connection terminal 8 is accommodated. Fill. Next, a rubber seal member (silicon rubber, fluororubber, etc.) 14 is attached to the opening 4c of the metallic outer cylinder 4. The seal member 14 is attached to the opening 4 of the metal outer cylinder 4.
By mounting it in c, it is possible to prevent the heat-resistant insulating powder 12 from spilling during swaging in a later step. Further, it is possible to prevent the electrode take-out fitting 6 from coming into contact with the metal outer cylinder 4.

Thereafter, the large-diameter portion 4b of the metal outer cylinder 4 in which the connection portion between the electrode take-out fitting 6 and the external connection terminal 8 is housed is swaged to form the metal outer cylinder 4 therein.
The outer diameter of is reduced and the heat resistant insulating powder 12 is densified to fix the external connection terminals 8 in the metal outer cylinder 4.

A metal outer cylinder 4 to which the ceramic heater 2, the electrode lead-out metal fitting 6 and the external connection terminal 8 are fixed.
Has a cylindrical housing 10 having a large diameter portion 4b on the rear side thereof.
It is inserted and fixed inside. In this embodiment,
A portion of the front end portion of the housing 10 slightly near the front is located on the outer periphery of a portion of the large diameter portion 4b of the metal outer cylinder 4 near the small diameter portion 4a. This portion is swaged from the outer peripheral side of the housing 10 ( The swaged portion is indicated by symbol S), and an annular convex portion 10d is formed on the inner peripheral side (see FIG. 2 showing an enlarged portion A of FIG. 1). Due to the processing, an annular recess 4c is also formed on the outer peripheral surface of the metal outer cylinder 4 at the same time.
The annular convex portion 10d and the annular concave portion 4c of the metal outer cylinder 4 are fitted to each other. By fitting and closely contacting the annular convex portion 10d and the annular concave portion 4c formed by swaging as described above, the housing 10 and the metallic outer cylinder 4 are fixed and the airtightness is maintained. ing.

Since the housing 10 and the metal outer cylinder 4 are fixed by swaging from the outer peripheral side of the housing 10 as described above, the housing 10 and the metal outer cylinder 4 are completely adhered to each other. Therefore, there is no risk of misalignment between them. Further, the airtightness between the housing 10 and the metallic outer cylinder 4 is reliably maintained. Moreover, since the annular convex portion 10d and the annular concave portion 4c are meshed with each other, the holding force in the axial direction is strong, and the ceramic heater 2 held by the metal outer cylinder 4 comes out of the housing 10 or the housing 10. It doesn't get inside.

Next, the assembly process of the glow plug 1 for a diesel engine having the above structure will be described with reference to FIGS.
And FIG. 3 to FIG. First, an assembly composed of the ceramics heater 2, the electrode lead-out metal fitting 6, and the external connection terminal 8 fixed in the metal outer cylinder 4 is installed in the housing 10 with the screw portion 8a side of the external connection terminal 8 first.
Is inserted into the internal hole 16 from the tip end side (the seat surface 10a side toward the cylinder head) (see FIG. 3). In the housing 10 before assembly, 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 connected to the screw portion 8a.
Side is inserted into the internal hole 16 of the housing 10, and the large diameter portion 4b side of the metal outer cylinder 4 is also inserted into the internal hole 1 of the housing 10.
Insert into 6 A seat surface 10a for the cylinder head of the engine is formed at the tip of the housing 10, and the seat surface 10a and the tip of the ceramics heater 2 are positioned so as to have a predetermined distance (FIG. 4). reference).

In this state, swaging is performed from the outer peripheral side to a portion slightly in front of the tip of the housing 10 (see symbol S in FIG. 5). By performing swaging, as shown in an enlarged view in FIG. 2, the outer peripheral surface of the housing 10 is recessed to form an annular convex portion 10d on the inner surface side. Further, an annular recess 4c is also formed on the outer surface side of the metal outer cylinder 4 through the plastic deformation of the housing 10. By this swaging process, the housing 10 and the metal outer cylinder 4 are firmly adhered and joined.

In this embodiment, the inner hole 16 of the housing 10 may have an inner diameter slightly larger than the outer diameter thereof so that the large diameter portion 4b of the metal outer cylinder 4 can pass therethrough. Since high precision is not required, it is possible to process at an extremely low cost as compared with the case of fixing by press fitting. Further, the distance between the seat surface 10a of the housing 10 and the tip of the ceramic heater 2 can be set arbitrarily at the time of joining, so that the glow plug 1 having various performances can be obtained by the housing 10 and the ceramic heater 2 having one kind of dimensions. Can be manufactured at an extremely low cost. Further, unlike the case where the ceramic heater 2 is fixed by press fitting, there is no possibility of damaging the ceramic heater 2.

In the above embodiment, the housing 1
Although the housing 10 and the metal outer cylinder 4 are deformed at the same time by performing swaging from the outer peripheral surface of No. 0 to fix both of them, other plastic working such as rolling is not limited to swaging. Thus, the housing 10 and the metal outer cylinder 4 may be formed with an annular convex portion 10d and an annular concave portion 4c which are fitted to each other. Further, conventionally, a housing having an internal hole was manufactured by cutting using a solid steel material, but in this embodiment, the internal hole 16 of the housing 10 is not required to be machined with high precision, so that it is inexpensive. Further cost reduction can be achieved by using a pipe material and forming the mounting screw portion 10b to the engine, the nut portion 10c at the rear end, the seat surface 10a at the front end, etc. by rolling.

The glow plug 1 according to the above embodiment is
The portion deformed by plastic working is constituted by a surface parallel to the axis of the housing 10, that is, the swaged portion S has the same diameter in the longitudinal direction of the housing 10. The annular convex portion 10a and the annular concave portion 4c are not limited to those having the same diameter in the lengthwise direction as described above, and the diameters thereof are continuously changed to change from a surface inclined with respect to the axis of the housing 10. It may be configured.

A seat surface 10a for attaching to a cylinder head of an engine is provided at the tip of the housing 10.
However, the housing 10 and the metal outer cylinder 4 are fixed by plastic working such as swaging or rolling, not only when the housing 10 is formed in advance as in the above embodiment. At the same time, this seat surface 1
It is also possible to form 0a. By simultaneously forming the seat surface 10a of the housing 10 in this way,
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 worked portion of the outer periphery of the housing 10 and its adjacent portion with a smooth R shape, the rustproof plating of the housing 10 is peeled off when swaging is performed. Can be prevented.

In the above description, the metal outer cylinder 4 is filled with the heat-resistant insulating powder 12 and swaged so that the external connection terminals 8 connected to the electrode take-out fittings 6 are connected to the metal outer cylinder. However, it is also possible to omit this swaging step and use it as a swaging process for fixing the housing 10 and the metal outer cylinder 4 together. In this case, airtightness is not required, and the electrode on the positive electrode side can be fixed securely, so that the swaging process can be omitted and the cost can be further reduced.

FIG. 6 is a vertical cross-sectional view showing a glow plug 101 for a diesel engine according to a second embodiment. The glow plug 101 detects an ion current in the glow plug 1 for a diesel engine having the above-mentioned structure. Then, an ion sensor that detects the combustion state of the engine is integrated.

In the ceramic heater 102 of the glow plug 101, a heating element 102b is embedded inside a ceramic insulator 102a, one end of which is connected to a negative electrode lead wire 102c, and the other end of which is connected to a positive electrode lead wire 102d. Has been done. The heating element 102b has a tip exposed to the outside of the ceramic insulator 102a in order to be used also as an ion detection electrode.

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

The metal outer cylinder 104 to which the ceramics heater 102 is fixed has a total length longer than that of the housing 110 unlike the configuration of the first embodiment, and is fixed to the housing 110. The end portion 104e opposite to the end portion 104d to which the ceramic heater 102 is fixed reaches the rear end portion of the housing 110. Inside the metal outer cylinder 104, the heat resistant insulating powder 1
12 is filled and densified by swaging,
The external connection terminal 108 is fixed, and the external connection terminal 108 on the positive electrode side and the metallic outer cylinder 104 on the negative electrode side are insulated.

The ceramic heater 10 is provided at one end 104d.
The metal outer cylinder 104 in which the external connection terminal 108 extends to the side of the other end 104e is fixed in the inner hole 116 of the cylindrical housing 110. An insulator 118 is inserted between the inner surface of the portion 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 104 are inserted.
And are electrically insulated. In this embodiment, the portion filled with the insulator 118 is swaged from the outer peripheral side of the housing 110 (see symbol S in FIG. 6) to form an annular convex portion 110d on the inner peripheral side. The metal outer cylinder 104 is fixed to the housing 110 at the swaged portion S.

Glow plug 1 integrated with the ion sensor
The process of assembling 01 is shown in FIGS.
This will be described with reference to FIG. The ceramic heater 102 and the electrode lead-out metal fitting 10 held in the metal outer cylinder 104.
6 and the external connection terminal 108 are integrated, and the tip portion of the housing 110 (ceramic heater 1
(02 end on the mounting side) side (see FIG. 7).

After positioning the tip of the ceramic heater 102 and the seat surface 110a for the cylinder head formed at the tip of the housing 110 at a predetermined distance, the tip of the housing 110 and the outer surface of the metal outer cylinder 104 are separated. A seal member 120 is mounted in between, a heat-resistant insulating powder 118 is filled from the rear opening side of the housing 110, and then a seal member 122 is 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 to form an annular convex portion 110d on the inner peripheral surface thereof, and the heat resistant insulating powder 118 is removed. The outer casing 104 made of metal is densified and fixed (state of FIG. 6).

The ion sensor integrated glow plug 10
1 is a lead wire 10 on the negative electrode side of the ceramic heater 102.
The metal outer cylinder 104 electrically connected to 2c is connected to the negative terminal 124 on the rear end side of the housing 110,
The external connection terminal 108 electrically connected to the positive electrode side lead wire 102d via the electrode lead-out metal fitting 106 is connected to the positive electrode side terminal 126. The metal outer cylinder 104
Negative side terminal 124 and housing 1 electrically connected to
An insulating ring 128 is provided between the negative electrode side terminal 10 and the positive electrode side terminal 10, and an insulator 130 is interposed between the negative electrode side terminal 124 and the positive electrode side terminal 126 to be electrically insulated.

As shown in FIG. 9, the positive electrode side terminal 126 is connected to the positive side of the battery 132 via the first relay 134A, and the negative electrode side terminal 124 is connected to the battery 132.
Is connected to the negative side via the second relay 134B. Therefore, the positive electrode of the battery 132, the first relay 134A, the positive electrode side terminal 126, the external connection terminal 10
8, electrode take-out fitting 106, ceramic heater 10
2 positive electrode side lead wire 102d, heating element 102b, negative electrode side lead wire 102c, metallic outer cylinder 104, negative electrode side terminal 12
4, an electric circuit of the glow plug is formed by the negative pole of the second relay 134B and the battery 132.

The housing 110 is fixed to the cylinder head 136 of the engine, the negative pole of the battery 132 is grounded to the cylinder head 136, and the positive pole of the battery 132 and the positive pole of the glow plug 101 are connected. The side terminal 126 is connected via the current detection means 138 and the sensor relay 140. Therefore, the positive electrode of the battery 132, the current detection means 138, the sensor relay 140, the positive electrode side terminal 126, the external connection terminal 108, the electrode lead-out fitting 1
06, the heating element 102b as an electrode for ion detection, and the cylinder head 136 are grounded to form an electric circuit of the ion sensor.

Glow plug 1 integrated with the ion sensor
When 01 is made to function as a glow plug, the first and second relays 134A and 134B for the glow plug are used.
Is turned on and the sensor relay 140 is turned off
To Then, a current flows through the electric circuit for the glow plug, and the heating element 102b generates heat to preheat the engine.

When the glow plug 101 having the above-mentioned structure is to function as an ion sensor, the glow plug relays 134A and 134B are turned off and the ion sensor relay 140 is turned on. Then, the heating element 102 of the ceramic heater 102 as the ion detection electrode
A voltage is applied between b and the cylinder head 136, and a current flows through the sensor electric circuit due to the ions in the combustion chamber generated during combustion of the engine. This current is detected by the current detection means 138 to perform feedback control of the engine.

Also in the glow plug 101 for a diesel engine according to this embodiment, the housing 110 can be manufactured at a low cost because the structure of the housing 110 is simple as in the first embodiment. Also,
Even if the shape of the housing 110 is not changed, the distance between the seat surface 110a to the cylinder head 136 of the housing 110 and the tip of the ceramic heater 102 can be arbitrarily set, and the cost can be significantly reduced. .

The insulator interposed between the housing 110 and the metal outer cylinder 104 is not limited to the above-described insulating insulating powder 118 densified by swaging, and for example, Other insulators such as resin can also be used.

In each of the above embodiments, the ceramic heater type glow plugs 1 and 101 using the ceramic heaters 2 and 102 as the heating elements have been described, but the present invention is not limited to the ceramic heaters, and metal heaters may be used. The present invention can also be applied to the glow plug used.

[0052]

As described above, according to the first aspect of the present invention, since the housing and the sheath are fixed by plastic working, misalignment occurs as in the case of fixing by brazing. , There is no risk of axial displacement. Moreover, since the structure of the housing can be simplified as compared with the case where the housing is fixed by press fitting, the housing can be manufactured at low cost.

According to the fifth aspect of the present invention, the glow plug for a diesel engine can be manufactured in a simple process, and the housing and the sheath can be securely fixed to each other. Furthermore, since the distance between the tip of the heater and the seat surface on the cylinder head may be positioned during assembly, glow plugs of various performances can be manufactured with the same size housing and heater, which is low cost.

Further, according to the method of the invention described in claim 6, since the housing and the sheath are fixed by plastic working, and at the same time, the seat surface for the cylinder head is formed on the tip end surface of the housing, the manufacturing process is simplified. The cost can be reduced, and the dimensional accuracy from the tip of the heater to the seat surface of the housing can be improved.

According to the seventh aspect of the present invention, since the insulator is interposed between the inner surface of the housing and the outer surface of the sheath, a glow plug also serving as an ion sensor can be easily realized. You can

[Brief description of drawings]

FIG. 1 is a vertical sectional view of a glow plug for a diesel engine according to an embodiment of the present invention.

FIG. 2 is an enlarged view of a main part of the glow plug for a diesel engine.

FIG. 3 is a vertical cross-sectional view illustrating an assembling process of the glow plug for a diesel engine.

FIG. 4 is a vertical cross-sectional view showing the next step of FIG.

5 is a vertical cross-sectional view showing the next step of FIG.

FIG. 6 is a vertical sectional view of a glow plug for a diesel engine according to a second embodiment.

FIG. 7 is a vertical cross-sectional view illustrating an assembling process of a glow plug for a diesel engine according to a second embodiment.

FIG. 8 is a vertical sectional view for explaining the next step in FIG.

FIG. 9 is a circuit diagram showing an operating electric circuit of a glow plug for a diesel engine according to a second embodiment.

[Explanation of symbols]

1 Glow plug for diesel engine 2 heater 4 sheath (metal outer cylinder) 4c Sheath annular recess 10a Seat surface of housing 10d annular projection of housing

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Takashi Aota             3-13-26, Yumichocho, Higashimatsuyama City, Saitama Prefecture             Expression company Bosch Automotive System             Higashi Matsuyama Factory (72) Inventor Zhao             3-13-26, Yumichocho, Higashimatsuyama City, Saitama Prefecture             Expression company Bosch Automotive System             Higashi Matsuyama Factory (72) Inventor Shunji Miura             3-13-26, Yumichocho, Higashimatsuyama City, Saitama Prefecture             Expression company Bosch Automotive System             Higashi Matsuyama Factory

Claims (7)

[Claims] 1. A glow plug for a diesel engine, wherein one end of a sheath holding a heater is inserted and fixed in an inner hole of a cylindrical housing, wherein an annular projection formed on the inner surface of the outer peripheral surface of the housing by plastic working. A glow plug for a diesel engine, wherein the portion and an annular recess formed on the outer surface of the sheath through the housing by the plastic working are fitted to each other to fix the housing and the sheath. 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 formed by a surface parallel to the axis of the housing. 3. 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 formed by a surface 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 protrusions and annular recesses formed by the plastic working are provided. 5. A method of manufacturing a glow plug for a diesel engine, wherein one end of a sheath holding a heater is inserted into and fixed to an inner hole of a cylindrical housing, wherein one end of the sheath is inserted into the inner hole of the housing.
After positioning the tip of the heater held by the sheath and the seat surface on the cylinder head provided in the housing, the outer peripheral surface of the housing is subjected to plastic working to form an annular convex portion on the inner surface of the housing. And forming an annular recess on the outer surface of the sheath into which the annular projection fits, and fixing the sheath to the housing. 6. A method for manufacturing a glow plug for a diesel engine, wherein one end of a sheath holding a heater is inserted into and fixed to an inner hole of a cylindrical housing, wherein one end of the sheath is inserted into the inner hole of the housing.
When the annular convex portion is formed on the inner surface of the housing and the annular concave portion to which the annular convex portion fits is formed on the outer surface of the sheath by performing plastic working on the outer peripheral surface of the housing, and the sheath is fixed to the housing. At the same time, a seat surface for the cylinder head is formed on the front end surface of the housing, the method for manufacturing a glow plug for a diesel engine. 7. A method for manufacturing a glow plug for a diesel engine, wherein one end of a sheath holding a heater is inserted into and fixed to an inner hole of a cylindrical housing, wherein one end of the sheath is inserted into the inner hole of the housing,
An insulator is interposed between the inner surface of the housing and the outer surface of the sheath, and the tip of the heater held by the sheath,
After positioning with the seat surface on the cylinder head provided in the housing, the outer peripheral surface of the housing is subjected to plastic working to form an annular convex portion on the inner surface of the housing, and through the insulator, A method for manufacturing a glow plug for a diesel engine, which comprises fixing a sheath to a housing.