GB2024942A

GB2024942A - Spark plug for an internal combustion engine

Info

Publication number: GB2024942A
Application number: GB7923761A
Authority: GB
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 1978-07-07
Filing date: 1979-07-06
Publication date: 1980-01-16
Also published as: FR2430677B1; GB2024942B; DE2829918A1; DE2829918C2; FR2430677A1

Abstract

The plug is of the screened type with the screen 25 being joined to a housing 10 of the plug by a shoulder 30 and a turned over edge portion 13 of the housing; the housing being "heat shrunk" onto the sleeve. Relative rotation is prevented by, e.g. flats 28, 29 formed respectively on the housing and the screen. <IMAGE>

Description

SPECIFICATION Spark plug for an internal combustion engine The present invention relates to a spark plug for an internal combustion engine, the connection end of which is surrounded by a screening sleeve. A screened spark plug is already known (German Patent Specification No. 1,003,508) whose screening sleeve is screwed into a housing of the plug, the known hot-shrinking method being used to fix the housing and the screening sleeve. The material entering the interior of the housing as a result of the hot-shrinking operation then presses against a milled portion on the screening sleeve.

Furthermore, in screened spark plugs, it is known to secure the screening sleeve to the housing by soldering or welding (U.S. Patent Specification No. 2,469,211, U.S. Patent Specification No. 2,409,795).

However, these known joints are very expensive to manufacture or are not satisfactory with respect to securing the parts against turning.

It is an object of the present invention to provide an improved screened sparking plug.

There is provided by the present invention a spark plug for an internal combustion engine comprising a housing and a screening sleeve which extends out of the housing of the spark plug in the direction of the connection end of the plug to surround the insulator and contact pin, and which is fixed in the housing by means of hotshrinking, wherein the end portion of the housing nearer the connection end of the plug is in the form of a flanged edge which abuts rigidly against a head formed on that portion of the screening sleeve which extends into the housing, and there is located in the region of the screening sleeve surrounded by the housing, at least one locking element which abuts against a locking element in the housing in order to prevent the housing and the screening sleeve from turning relative to one another.

In contrast to prior art plug, the spark plug in accordance with the invention has the advantage that the connection between the spark plug housing and the screening sleeve is fully secured against turning and that a joint of this kind is inexpensive to manufacture.

An embodiment of the invention is illustrated in the accompanying drawings in which: Figure 1 is a longitudinal section through a screened spark plug, drawn to an enlarged scale, Figure 2 is a cross section, taken on the line I-I, through the spark plug shown in Figure 1.

The spark plug comprises a metal housing 10 whose outside is provided with a hexagonal nut 11 and a screw-in thread 12 for screwing the spark plug into the internal combustion engine.

The portion at the connection end of the housing 10 is of very thin-walled construction and forms a flanged edge 1 3 when the spark plug is assembled. The central region of the housing 10 also incorporates a thin-walled region 14 which is bellied in a known manner during the hotshrinking operation. The end of the housing 1 0 presented to the combustion chamber carries an earth electrode 1 5.

The longitudinal bore 1 6 leading through the housing 10 has a shoulder 1 7 against which a sealing ring 18 abuts, and a shoulder 20 of the insulator 19 in turn abuts against the sealing ring.

The insulator 19 has a shoulder 23, and the end of the insulator presented to the combustion chamber carries the central electrode 21 while the connection end of the insulator carries the contact pin 22. A sealing ring 24 abuts against the shoulder 23, and the end face oi a metal screening sleeve 25, extending into the housing 1 C), presses against the sealing ring 24. The screening sleeve 25 extends beyond the insulator 1 9 at the connection end, and the outside of its end portion at the connection end carries a connection thread 26.

The end portion of the screening sleeve 25 extending into the housing 10 is in the form of a head 27 which abuts closely against the wall of this region of the longitudinal bore 1 6 in the housing. A locking flat 28 is formed laterally on the head 27 of the screening sleeve and abuts closely against a locking flat 29 formed in the longitudinal bore 16 of the housing.

Advantageously, the flat 29 formed in the housing can be formed by extrusion moulding during manufacture of the housing 16. The locking flat 28 formed on the screening sleeve and the locking flat 29 formed in the housing constitute an excellent means for preventing the two parts from turning relative to one another.

A shoulder 30 at the connection end of the head 27 of the screening sleeve acts as an abutment for the flanged edge 1 3 of the housing.

It may be mentioned that an electrically conductive glass melt (not illustrated) is disposed in a conventional manner between the contact pin 22 and the central electrode 21, and, if required, resistance elements can also be provided between the central electrode 21 and the contact pin 22.

Alternatively, several pairs of locking flats can be used instead of a single pair as shown by flats 28,29.

Although locking flats 28, 29 constitute the preferred embodiment as described in the present example, it is also possible to use locking elements in the form of a recess and complementary male part such as a groove and complementary projection or a hole and complementary lug.

1. A spark plug for an internal combustion engine comprising a housing and a screening sleeve which extends out of the housing of the spark plug in the direction of the connection end of the plug to surround the insulator and contact pin, and which is fixed in the housing by means of hot-shrinking, wherein the end portion of the housing nearer the connection end of the plug is in the form of a flanged edge which abuts rigidly

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Spark plug for an internal combustion engine The present invention relates to a spark plug for an internal combustion engine, the connection end of which is surrounded by a screening sleeve. A screened spark plug is already known (German Patent Specification No. 1,003,508) whose screening sleeve is screwed into a housing of the plug, the known hot-shrinking method being used to fix the housing and the screening sleeve. The material entering the interior of the housing as a result of the hot-shrinking operation then presses against a milled portion on the screening sleeve. Furthermore, in screened spark plugs, it is known to secure the screening sleeve to the housing by soldering or welding (U.S. Patent Specification No. 2,469,211, U.S. Patent Specification No. 2,409,795). However, these known joints are very expensive to manufacture or are not satisfactory with respect to securing the parts against turning. It is an object of the present invention to provide an improved screened sparking plug. There is provided by the present invention a spark plug for an internal combustion engine comprising a housing and a screening sleeve which extends out of the housing of the spark plug in the direction of the connection end of the plug to surround the insulator and contact pin, and which is fixed in the housing by means of hotshrinking, wherein the end portion of the housing nearer the connection end of the plug is in the form of a flanged edge which abuts rigidly against a head formed on that portion of the screening sleeve which extends into the housing, and there is located in the region of the screening sleeve surrounded by the housing, at least one locking element which abuts against a locking element in the housing in order to prevent the housing and the screening sleeve from turning relative to one another. In contrast to prior art plug, the spark plug in accordance with the invention has the advantage that the connection between the spark plug housing and the screening sleeve is fully secured against turning and that a joint of this kind is inexpensive to manufacture. An embodiment of the invention is illustrated in the accompanying drawings in which: Figure 1 is a longitudinal section through a screened spark plug, drawn to an enlarged scale, Figure 2 is a cross section, taken on the line I-I, through the spark plug shown in Figure 1. The spark plug comprises a metal housing 10 whose outside is provided with a hexagonal nut 11 and a screw-in thread 12 for screwing the spark plug into the internal combustion engine. The portion at the connection end of the housing 10 is of very thin-walled construction and forms a flanged edge 1 3 when the spark plug is assembled. The central region of the housing 10 also incorporates a thin-walled region 14 which is bellied in a known manner during the hotshrinking operation. The end of the housing 1 0 presented to the combustion chamber carries an earth electrode 1 5. The longitudinal bore 1 6 leading through the housing 10 has a shoulder 1 7 against which a sealing ring 18 abuts, and a shoulder 20 of the insulator 19 in turn abuts against the sealing ring. The insulator 19 has a shoulder 23, and the end of the insulator presented to the combustion chamber carries the central electrode 21 while the connection end of the insulator carries the contact pin 22. A sealing ring 24 abuts against the shoulder 23, and the end face oi a metal screening sleeve 25, extending into the housing 1 C), presses against the sealing ring 24. The screening sleeve 25 extends beyond the insulator 1 9 at the connection end, and the outside of its end portion at the connection end carries a connection thread 26. The end portion of the screening sleeve 25 extending into the housing 10 is in the form of a head 27 which abuts closely against the wall of this region of the longitudinal bore 1 6 in the housing. A locking flat 28 is formed laterally on the head 27 of the screening sleeve and abuts closely against a locking flat 29 formed in the longitudinal bore 16 of the housing. Advantageously, the flat 29 formed in the housing can be formed by extrusion moulding during manufacture of the housing 16. The locking flat 28 formed on the screening sleeve and the locking flat 29 formed in the housing constitute an excellent means for preventing the two parts from turning relative to one another. A shoulder 30 at the connection end of the head 27 of the screening sleeve acts as an abutment for the flanged edge 1 3 of the housing. It may be mentioned that an electrically conductive glass melt (not illustrated) is disposed in a conventional manner between the contact pin 22 and the central electrode 21, and, if required, resistance elements can also be provided between the central electrode 21 and the contact pin 22. Alternatively, several pairs of locking flats can be used instead of a single pair as shown by flats 28,29. Although locking flats 28, 29 constitute the preferred embodiment as described in the present example, it is also possible to use locking elements in the form of a recess and complementary male part such as a groove and complementary projection or a hole and complementary lug. CLAIMS

1. A spark plug for an internal combustion engine comprising a housing and a screening sleeve which extends out of the housing of the spark plug in the direction of the connection end of the plug to surround the insulator and contact pin, and which is fixed in the housing by means of hot-shrinking, wherein the end portion of the housing nearer the connection end of the plug is in the form of a flanged edge which abuts rigidly against a head formed on that portion of the screening sleeve which extends into the housing, and there is located in the region of the screening sleeve surrounded by the housing, at least one locking element which abuts against a locking element in the housing in order to prevent the housing and the screening sleeve from turning relative to one another.

2. A spark plug as claimed in claim 1, wherein the or each locking element of the screening sleeve is a lateral surface of the head, and the or each locking element of the housing is a surface formed in the longitudinal bore in the housing.

3. A spark plug as claimed in claim 2, wherein each of the said surfaces is in the form of a flat.

4. A spark plug as claimed in claim 2, wherein one of said surfaces is a recess and the other is a complementary male part to engage therein.

5. A spark plug as claimed in claim 4, wherein the one of said surfaces is a groove and the other of them is a complementary projection to engage therein.

6. A spark plug as claimed in claim 4, wherein the one of the said surfaces is a hole and the other of them is a lug to engage therein.

7. A spark plug substantially as hereinbefore described with reference to the accompanying drawing.