Glow plug

Abstract

A glow-plug ignitor for diesel engines and the like, comprising a tubular body having external screw threads and an adjoining hexagonal formation by which a tool such as a wrench can be applied to the body to screw it into the a threaded cavity of a cylinder. Next to the hexagonal formation is a spade lug connector for bringing current to the plug, the connector being so arranged as to permit the application of either a socket-type wrench or else a box-end wrench. The inner end of the body has an elongate projecting pin on which there is a tightly wound resistance coil that becomes incandescent when excited with the proper electric current. The valleys of the coil show higher temperatures, for a given heating current, due to the radiation and reception of radiated heat involving the opposed surfaces; therefore, starts at lower engine temperatures are improved.

Description

BACKGROUND

This invention relates to theignitor plug as provided by the invention comprises a tubular metal body or tubular metal support structure 20 having intermediate its inner rightmost and outer leftmost ends external screw threads 22 and at its outer end adjacent said threads having an hexagonal configuration 24 adapted for engagement by a wrench. The screw threads 22 are acceptable, for example, in the threaded ignitor plug openings of the cylinders of diese engines, as will be understood.

As seen in FIGS. 2, 12 and 13, the bore of the body 20 is stepped, that is, it has a large-diameter bore 26 and a smaller-diameter bore 28 which are separated by an internal annular or conical shoulder 30.

The body 20 nominally can be constituted of steel, with suitable surface treatment such as plating.

Disposed within and insulated from the body 20 is an elongate electrically conductive member, or electrically conductive core pin 32, see FIGS. 1, 2, 12 and 13, which is preferably made from stainless steel. The core pin 32 comprises an elongate straight shank having intermediate its ends an integral annular shoulder 34 with one flat circular face 36 and an opposite conical face 38.

As provided by the invention, the core pin 32 has areas or projecting portions of it insulated by a plasma-sprayed ceramic coating, as seen in FIG. 7. This coating is designated "C", and is applied especially to the projecting shank portion or inner end or coil support portion 40 and the shoulder 34; optionally it can be omitted from the flat circular surface 36 of the shoulder 34.

The core pin 32 has a smooth support shank portion 42 which is provided with a roughened area 44 that can be advantageously in the form of a series of annular grooves.

The positioning of the core pin 32 in the body 20 is effected by engagement between the coated shoulder 34 of the pin and the internal annular shoulder 30 of the body 20, and as thus located the pin 32 will be insulated from the body 20 by the plasma-sprayed ceramic coating "C".

According to the invention, prior to the positioning of the pin 32 in the body 20, a quantity of slurry of ceramic cement "CC" is injected in the space within the walls of the large body bore 26. Then the pin 32 is pushed into the body until the shoulder 34 of the pin engages the shoulder 30 of the body. Now additional ceramic cement slurry is injected in the space between the walls of the bore 26 and the smooth shank portion 42 (also referred to as a second projecting portion) of the core pin 32, and thereafter a ceramic sleeve 46 is pushed into the injected cement "CC", and propelled to an intervening position (FIG. 13) by a plunger 48. This assembly is illustrated in FIGS. 12 and 13, wherein the sleeve 46 is seen to act as a ram, forcing the cement "CC" into all spaces, crevices or interstices, so that it completely eliminates air pockets and also permeates and forms an interlock with the roughened area 44 of the pin, when it has hardened and such that the cement is forcibly engaged with the sleeve. The ceramic cement "CC" by its engagement with the shoulder 34 of the core pin securely and rigidly positions the pin in the body 20, in insulated relation therewith, such that the pin and body are physically structurally united. As shown in FIGS. 2 and 10, one end of the sleeve 46, the right-hand end in FIG. 10, has a reduced wall thickness with respect to its remainder, to provide a lead-in which facilitates its insertion, as in FIGS. 12 and 13.

As provided by the invention, referring to FIGS. 9 and 14-16, the inner or end face 48 of the body 20 is formed with a plurality of ribs or ridges 50, and one the outer end 52 of a resistance wire or heater wire 54 is welded to the end face, as by the use of a suitable welding electrode 56. This is preferably done prior to the attachment of the core pin 32 to the body in the manner set forth above, and also the heating coil of the ignitor plug is preferably wound before placement of the core pin. In accomplishing this, the heating coil wire 54 which is attached to the body 20 is tight-wound about a mandrel 57 as seen in FIG. 15. It is seen in FIG. 1 that the wire 54 is tightly and closely coiled to form a helical heater or igniting coil 58. The wire 54 is bare, and the convolutions are made to touch each other during the winding. It can be noted here that during the later initial energization of the coil 58 an oxide coating forms on the surfaces and insulates adjoining convolutions from each other to prevent adjacent turns from short-circuiting each other.

After winding is completed, the mandrel 57 and coil 58 with the body 20 are separated, whereupon the core pin 32 is assembled to the body in the manner explained above. Then the free end or inner end convolution of the coil is cross-welded to the free (inner tip or end of the core pin by the use of opposed electrodes 60, 62 as seen in FG. 16 . , the weld and ribs 50 constituting a conductor means, or a means for making electrical connection to the outer end of the coil 58.

The provision of the parallel ridges 50 on the inner end face 48 of the body 20 can be easily done; it results in a secure and effective weld of the outer end of the coil to the inner end of the body, and one which will withstand considerable use and vibration without failure. Likewise, the cross welding of the last, inner end of end convolution of the coil 58 to the free end of the core pin 32 results in a very secure, failure-resistant connection. Accordingly, one the outer end of the coil 58 is obviously at substantially the same electrical potential as the body 20, and the other inner end of the coil 58 is at substantially the same electrical potential as the core free end of the pin 32.

The tight-wind of the coil 58 is of great advantage in producing a high heat density in a very small space, according to the invention, and this gives very quick heating, and improved, more rapid starts where the plug is used in the cylinder of the a diesel engine. Surface temperatures in the valleys of the coil are much hotter than at the coil crests, due to the heat radiation striking the opposite surfaces in the valleys. Thus, higher temperatures are attained for a given, maximum specified value of heating current. This results in faster starts at lower engine temperatures. At the same time, the coil construction is mutually supportive and especially resistant to vibration and failure. The convolutions of the coil do not short-circuit to the projecting portion of the core pin 32 due to the plasma sprayed insulating coating thereon.

The invention further provides an advantageous connector structure by which current can be brought to the core pin 32 while at the same time there is avoided interference with socket or box end wrenches that are to be applied to the hexagonal portion 24 of the body 20.

As seen in FIGS. 1, 2 and 6, a spade terminal 64 is welded to the outer end 66 of the core pin 32, such terminal being located within the confines of the theoretical hexagonal shell which would be obtained if the six sides of the hexagonal portion 24 were to be extended to the left as viewed in FIGS. 1 and 2. Thus a socket or box end wrench for the portion 24 can be easily applied over the terminal 64 to screw in, or unscrew the body 20.

It will now be seen from the foregoing that we have provided a novel and improved diesel engine plug ignitor glow-plug which is especially efficient in the use of the heating current, quick-acting, simple and economical to fabricate, convenient in its use, and capable of reliable operation over an extended period of time.

Variations and modifications are possible without departing from the spirit of the claims.

Claims

1. A diesel glow-plug ignitor comprising, in combination:

(a) a tubular metal body having an inner end securely carried in a cylinder opening of an engine,

(b) an electrically conductive core pin insulatedly carried in the bore of the body, physically structurally united therewith, and having a portion projecting from said inner end thereof, said projecting portion of said core pin being coated with insulating material, and

(c) a tight-wound helical igniting coil of resistance wire on said projecting portion of the core pin, having its ends respectively welded to the body and welded substantially to the end of said projecting portion of the pin,

(d) the convolutions of said coil having an insulating oxide coating thereon to prevent them from short-circuiting each other,

(e) said insulating material on the core pin having ceramic-containing insulation and being plasma sprayed thereon to further prevent the convolutions of the coil from electrically contacting the projecting portion of the core pin.

2. The invention as defined in claim 1, wherein:

(a) the inner end of the metal body has a plurality of ridges to which the one end of the coil is welded.

3. The invention as defined in claim 1, wherein:

(a) an end convolution of the coil is welded at diametrically opposite spots to the core pin.

4. A diesel glow-plug ignitor as defined in claim 1, wherein:

(a) said tubular metal body has an hexagonal configuration at one end, to enable it to have a wrench applied to it for installing it in said cylinder,

(b) said core pin having an additional portion projecting from the hexagonal configuration of the body and being externally exposed, and

(c) a spade terminal carried by and welded to the side of the additional portion of the core pin,

(d) said spade terminal being so located and having a small enough dimension so as to facilitate installation of a cup-type socket wrench of similar hexagonal configuration which is intended to be applied to said hexagonal configuration of the body past the spade terminal.

5. A diesel glow-plug ignitor comprising, in combination:

(a) a tubular metal body having an inner end securely carried in a cylinder opening of an engine,

(b) an electrically conductive core pin insulatedly carried in the bore of the body and extending through the bore of the body, physically structurally united therewith and having a portion projecting from the inner end thereof,

(c) an insulating sleeve disposed within and in spaced relation to the metal body and surrounding said core pin and spaced therefrom,

(d) a helical igniting coil of resistance wire on the projecting portion of the core pin and being electrically insulated therefrom, said coil having its ends respectively electrically connected to the body and electrically connected substantially to the end of said projecting portion of the pin, and

(e) ceramic cement disposed in the spaces between the body, core pin and sleeve.

6. The invention as defined in claim 5, wherein:

(a) the core pin has a shoulder intermediate its ends,

(b) said body having an internal cooperable annular shoulder engaged with the shoulder of the core pin to position the latter.

7. The invention as defined in claim 6, wherein:

(a) the shoulder of the core pin has a plasma-sprayed coating of insulation.

8. A heater plug for use with an internal combustion engine, comprising, in combination:

(a) a tubular metal support structure having an outer end and an inner end,

(b) an electrically conductive core pin insulatedly carried in the bore of the support structure, physically structurally united therewith, and having a coil-supporting projecting portion terminating in a free end, said projecting portion being coated with insulating material, and

(c) a helical heater coil of resistance wire on said projecting portion of the core pin, said coil having an outer end welded to the inner end of the support structure and having an inner end welded to the free end of the projecting portion of the core pin,

(d) the convolutions of said heater coil being closely spaced and having an insulating oxide coating thereon to prevent them from short-circuiting each other,

(e) said insulating material on the core pin comprising ceramic-containing insulation which is plasma sprayed thereon to further prevent the convolutions of the coil from electrically contacting the said projecting portion of the core pin. 9. The invention as defined in claim 8, wherein:

(a) the inner end of the support structure has a plurality of ridges to which the outer end of the heater coil is welded. 10. The invention as defined in claim 8, wherein:

(a) the innermost convolution of the heater coil is welded at diametrically opposite spots to the free end of the core pin. 11. A heater plug for use with an internal combustion engine, comprising, in combination:

(a) a tubular metal body having an inner end adapted to be carried in a supporting opening,

(b) an elongate electrically conductive member having a plasma-sprayed insulating coating thereon and insulatedly carried in the bore of the body and extending through said bore, said member being physically structurally united therewith and having a coil-supporting projecting portion terminating in a free end,

(c) an insulating sleeve disposed within and in spaced relation to the metal body and surrounding said elongate conductive member in spaced relation thereto,

(d) a helical coil of resistance wire mounted on said projecting portion of the elongate member and insulated therefrom by said plasma-sprayed coating, said coil having its outer end electrically connected to the inner end of the tubular metal body and having its inner end welded to said free end of the projecting portion, and

(e) ceramic cement disposed in the space between the tubular body and the insulating sleeve and in the space between the insulating sleeve and the elongate conductive member, said cement being forcibly engaged with the inner and outer surfaces of the insulating sleeve under pressure. 12. A heater plug for use with an internal combustion engine, comprising, in combination:

(a) a tubular metal body having an inner end adapted to be carried in a supporting opening,

(b) an electrically conductive core pin having a plasma-sprayed insulating coating thereon and insulatedly mounted in the bore of the body and extending therethrough, said core pin being physically structurally united with the tubular metal body and having a coil-supporting projecting portion terminating in a free end,

(c) an insulating ceramic sleeve of generally tubular configuration, disposed within and in spaced relation to the tubular metal body and surrounding said core pin and being spaced therefrom,

(d) a helical coil of resistance wire on the projecting portion of the core pin and having its intermediate convolutions insulated therefrom by said plasma-sprayed insulating coating, said coil having its inner end electrically connected to said free end of the core pin and having its outer end welded to the inner end of the tubular metal body, and

(e) ceramic cement disposed in the space between the tubular metal body and the ceramic sleeve, and in the space between the ceramic sleeve and the core pin, said cement being forcibly engaged with the inner and outer surfaces of the sleeve under pressure.