WO2011069732A1 - Housing‑free spark plug for an internal combustion engine - Google Patents

Abstract

A housing‑free spark plug (1) for an internal combustion engine, comprising a clamping nut (3) in order to clamp the spark plug (1) in the internal combustion engine, a seat support (4) via which the spark plug (1) is supported in the internal combustion engine, a central electrode (5), at least one earth electrode (6) which is arranged on the seat support (4), and an insulator (7) in order to separate the central electrode (5) from the earth electrode (6), wherein, in the clamped state, the clamping nut (3) clamps the spark plug (1) via a clamping nut shoulder (11) on the insulator (7) and, in the process, the clamping nut (3) is in direct contact with the insulator (7).

Description

 Description title

 Housing-free spark plug for an internal combustion engine prior art

The present invention relates to a caseless spark plug for a

Internal combustion engine with a clamping nut to clamp the spark plug in the internal combustion engine.

From the prior art spark plugs are known, which have a thread on the housing and are screwed into the cylinder head. The modern multi-valve technology with enlarged inlet and outlet ports as well as the close installation position at the injection valve required for direct injection require a constant reduction of the installation space for spark plugs. In particular, here refers to the space reduction to a reduced diameter of the spark plug. However, the isolation of the high voltage between the two requires

Electrodes a minimum wall thickness. This minimum wall thickness of the insulation precludes the desired diameter reduction. The absence of a thread on the housing of the spark plug opens up possibilities for

Diameter reduction and consequently for space reduction.

Disclosure of the invention

The spark plug according to the invention with the features of claim 1 allows a spark plug without a housing. The omission of a housing allows a reduction in the outer diameter of the spark plug and the cylinder head bore diameter. The wall thicknesses of the insulator can be kept the same or increased if necessary. As a result, the spark plug according to the invention, especially in engines with multi-valve technology, enlarged inlet and outlet ports and / or direct injection very close to Injector be installed. The minimum wall thickness for insulation of the high voltage can still be met, since according to the invention no space is consumed by a candle housing. All this will happen

achieved by a caseless spark plug for a

An internal combustion engine comprising a clamp nut for clamping the spark plug in the internal combustion engine, a seat support over which the spark plug is supported in the internal combustion engine, a center electrode, at least one ground electrode disposed on the seat support, and an insulator around the center electrode from the ground electrode to separate. It clamps in the assembled state of the spark plug, the clamping nut on a

 Lock nut shoulder on the insulator the spark plug in the

Internal combustion engine or in the cylinder head. The nut is in direct contact with the insulator and in particular with the

Lock nut shoulder on insulator. There is no further housing or no further sheathing of the insulator provided, so that the inventive

Spark plug has the smallest possible outer diameter.

The dependent claims show preferred developments of the invention. In a preferred embodiment it is provided that the clamping nut and the

Seat support are formed as two separate, non-contacting parts. The outer circumference of the entire spark plug according to the invention is characterized defined only in the area between the clamping nut and seat support by the insulator.

Furthermore, it is preferred that the seat support is designed as a sleeve on the insulator. The seat support is thus a hollow cylindrical metallic component which is plugged as close to the combustion chamber as possible on the insulator. At least one ground electrode is attached to this seat carrier, wherein the

Ground electrode on the seat support with the internal combustion engine or with the cylinder head is in electrical contact.

In a preferred embodiment, the seat support comprises an inner shoulder and an outer shoulder, wherein the insulator rests on the inner shoulder and wherein the

Outer paragraph is designed to support in the internal combustion engine. The hollow cylindrical seat carrier has a tapered inner diameter, whereby the inner paragraph arises. In a corresponding manner, the insulator tapers toward the tip of the center electrode. By this taper of the insulator creates a bearing surface, with which the insulator rests on the inner shoulder of the seat support. Preferably, the inner shoulder on the seat support and the support surface on the insulator tapered, so that the insulator on

Seat carrier centered. The outer shoulder on the insulator is preferably formed closer to the combustion chamber than the inner shoulder. By a preferred conical configuration of the outer paragraph, the seat carrier and thus the entire housing-less spark plug in the internal combustion engine centered.

In an advantageous embodiment of the housing-less spark plug according to the invention, the seat support has an inner sealing surface towards the insulator and an outer sealing surface toward the internal combustion engine. The inner sealing surface is preferably formed on the inner shoulder of the seat support. The outer sealing surface is preferably formed on the outer shoulder of the seat support. The clamping of the spark plug according to the invention by means of the clamping screw ensures the inner tightness between insulator and seat support and the outer tightness between seat support and cylinder head and the internal combustion engine. In a preferred embodiment of these sealing surfaces is provided that the inner

Sealing surface is directly in contact with the insulator and / or the outer

Sealing surface is designed for direct contact with the internal combustion engine. That is, the insulator is supported on the seat support without

From sealing element. For this purpose, the support area between insulator and seat support is preferably provided with a glaze. The beneficial lack of a

 Sealing element which is formed in prior art spark plugs usually as a metallic disc, reduces the probability of occurrence

Funkdurchschläge on the insulator, which preferably arise at edges and ridges. The seal between seat support and internal combustion engine is preferably designed as a conical seat or flat sealing seat. Preferably, this seal can be sealed with a sufficiently accurate production of the flat surfaces on a flat sealing seat without sealing element. Advantage of

Flat sealing seat opposite the conical seat is a simpler manufacturing. Consequently, with sufficiently accurate production both seals, both the inner seal between seat support and insulator and the outer seal between seat support and internal combustion engine, without further sealing element be executed. However, in order to simplify the production, it is likewise preferably provided to provide a further sealing element on the inner sealing surface and / or on the outer sealing surface. Furthermore, it is preferred that the insulator has a glaze on its bearing surface in the seat carrier and / or on the clamping nut shoulder. As already described, the glaze on the insulator optimizes the inner sealing surface between seat support and insulator. Advantageously, the clamping nut by means of a first crimp collar is captively secured to the insulator. The clamping nut is this at the

Bottom, so the brennraumnäheren side, provided with a collar which is folded over by flanging and thus represents a captive. For this purpose, the insulator preferably comprises an insulator shoulder. This isolator shoulder with enlarged outer diameter forms on its upper side, so the brennraumferneren side, the Spannmutternabsatz over which the

Clamping nut transmits the tensioning force to the insulator. The clamping nut sits cuff-like over the entire insulator shoulder, whereby the lower collar of the clamping nut can be crimped towards the insulator and thus creates a flared collar for captive protection. In a preferred embodiment, the

Insulator shoulder shorter than the distance between the support surface of the

Clamping nut on the clamping nut shoulder and the flared collar. Thereby, in the unmounted state of the spark plug, i. before the spark plug is clamped in the internal combustion engine, the clamping nut to be displaced axially to a limited extent on the insulator. The sizing of

Spark plug and in particular the height of the collar is structurally designed so that the clamping nut before screwing into the cylinder head on the

Cylinder head thread rests, while the seat support rests in the cylinder head. Preferably, therefore, the caseless spark plug together with its clamping nut a coherent, easy to assemble and disassemble

Component.

Furthermore, it is preferable that the ground electrode is aligned with a mark on the spark plug to detect the position of the ground electrode in the spark plug

Determine internal combustion engine. The seat carrier becomes one

Marking on the insulator or on the electrical connection pin oriented attached. An alignment of the electrode in the combustion chamber is thus possible by simply turning the spark plug. The position of the ground electrode in turn in the combustion chamber can be seen after installation at the position of the marker.

It is further preferred that the seat support is fastened by means of a further bead collar on the insulator. In particular, in this flanging

takes into account that the ground electrode on the seat support coincides with a mark on the insulator or on the connecting bolt.

A first preferred variant provides that the crimp collar of the seat support surrounds a small shoulder on the insulator and thus the seat support is firmly connected to the insulator. A second preferred variant provides that a small depression is provided in the insulator, the crimping collar of the seat carrier engaging in this depression. Preferably, this recess is formed completely circumferentially as a groove in the insulator. The seat support thus has a crimp collar, which is formed in a recess of the insulator to ensure a positive connection of the components. The recess of the ceramic of the insulator is advantageously in a range of thicker

Wall thickness so as not to reduce the electrical breakdown strength of the candle.

In a preferred embodiment, therefore, the depression between a seat of a central electrode head of the center electrode in the insulator and the support of the insulator on the inner shoulder. As a result, the outer diameter of the spark plug according to the invention need not be increased unnecessarily.

Furthermore, it is preferably provided that the surface of the recess is electrically conductive. To increase the electrical

Dielectric strength in the region of the depression, this is advantageously carried out electrically conductive and connected to the electrical potential of the seat support. The electric field in the area of the depression becomes uniform and sliding sparks are suppressed. The electrical line can preferably by applying electrically conductive layers on the

Isolator ceramic and / or be achieved by placing an electrically conductive film under the flared collar. Advantageously, the spark plug according to the invention is mounted in the cylinder head or in the internal combustion engine as follows: The spark plug is inserted into the cylinder head and preferably influences the position of the ground electrode by rotating the entire spark plug. For detecting the position of the ground electrode is advantageously a mark on the

Connection nut or on the connecting bolt, wherein here preferably an axial or radial slot is attached. Over the insulator or the connecting bolt an axial force is applied to the spark plug, which is greater than that of the

Gas tightness is required preload force. While the spark plug

is biased, the clamping nut is tightened to the concern on the insulator. After tightening the clamping nut, the axial force is removed. The thread friction has no influence on the preload force of the spark plug. In an alternative, preferred and simplified mounting option, the spark plug can be mounted and biased without applying the axial force only by tightening the clamping nut.

In a preferred embodiment, the caseless spark plug according to the invention replaces existing spark plugs of conventional design with M12 thread or smaller.

Short description of the drawing

Hereinafter, two embodiments of the invention below

Reference to the accompanying drawings described in detail. In the drawing show:

1 shows a housing-less spark plug according to the invention according to a first embodiment, and

Figure 2 is a detail view of a housing-less invention

 Spark plug according to a second embodiment.

Embodiments of the invention 1 shows a housing-less spark plug 1 according to the invention according to a first embodiment before tightening a clamping nut 3 in a cylinder head 2. The cylinder head 2 is here a part of a

Internal combustion engine dar.

The spark plug 1 comprises an insulator 7 with clamping nut 3 seated thereon and a seat carrier 4 mounted on it. In the insulator 7, a center electrode 5, a resistor chip 9 and a connecting bolt 8 are inserted. On the

Terminal bolt 8 is a connection nut 10 is screwed. On the seat support 4, a ground electrode 6 is attached.

The insulator 7 comprises three areas of constant diameter. In its upper region, between the connecting nut 10 and clamping screw 3, the insulator 7 has a first diameter D1. This first diameter D1 widens on an insulator shoulder 12 to a second diameter D2.

 Between the insulator shoulder 12 and the seat support 4, the insulator 7 has a constant third diameter D3. This third diameter D3 is smaller than the first diameter D1 and smaller than the second diameter D2. In the seat support 4, the insulator 7 tapers as far as a tip of the center electrode 5.

The region with the second diameter D2 extends over one

Shoulder length 22. The transition from the first diameter D1 to the second diameter D2 forms a Spannmutternabsatz 1 1. In the clamped state of the spark plug 1, the clamping nut 3 sits on this Spannmutternabsatz 1 1.

The clamping nut 3 sits like a sleeve over this insulator shoulder 12. The lower collar of the clamping nut 3 is crimped inwardly at the transition from the second diameter D2 to the third diameter D3, whereby the first flared collar 13 is formed. Between a nut head 25 of the clamping nut 3 and this first flared collar 13, a clearance 23 is formed, wherein this clearance 23 has an inner diameter greater than the second diameter D2. Furthermore, the axial free space length 24 of this free space 23 is greater than the shoulder length 22. As a result, the clamping nut 3 is axially displaceable in a certain area on the insulator 7. For mounting the spark plug 1 in the cylinder head 2, an external thread 14 is provided on the clamping nut 3. The cylinder head 2 has a corresponding internal thread 34. The

Dimensioning of the spark plug 1, in particular the free space length 23 and the shoulder length 23, is selected so that in the state shown in Figure 1, ie before tightening the clamping nut 3, the clamping nut 3 rests with its first flared collar 13 on the insulator shoulder 12, at the same time the thread 14 of the clamping nut 3 rests on the cylinder head 2, but not yet screwed in and at the same time the insulator 7 is seated in the seat support 4 and the seat support 4 rests in the cylinder head 2.

As the figure 1 shows, the insulator 7 comprises at the height of a head of

Center electrode 6 has a small, outwardly projecting shoulder 26. The seat support 4 is crimped around this small shoulder 26, whereby the second flared collar 18 is formed. The exact configuration of the seat support 4 will be explained in more detail with reference to Figure 2 and the second embodiment. The geometric configuration of the seat support 4 is approximately equal to that in the second embodiment in the first embodiment. The two

Embodiments differ only in the crimping of the seat support 4 with the insulator. 7

On the basis of the first embodiment has been shown how the

housing-less spark plug 1 according to the invention can be structurally designed. The abandonment of a housing allows a reduction of

Outside diameter of the spark plug 1 and the cylinder head bore diameter. The wall thickness of the insulator, in particular in the region close to the combustion chamber, for example at the third diameter D3, could be kept the same or increased. The seat support 4 and the clamping nut 3 are, in contrast to a flow-molded housing, manufacturing technology relatively simple components.

In the following, a second exemplary embodiment of the housing-less spark plug 1 according to the invention will be explained with reference to FIG. Identical or functionally identical components are designated in the two embodiments with the same reference numerals. The spark plugs 1 of the two embodiments are identical except for the crimping of the seat support 4 with the insulator 7. Figure 2 shows how the insulator 7 rests with a support surface 15 on an inner shoulder 16 of the seat support 4. The seat support 4 in turn comprises a

Outside paragraph 17, which is designed for support in the cylinder head 2. The support surface 15, the inner shoulder 16 and the outer shoulder 17 are conical and taper in each case in the direction of the combustion chamber. This conical design of the contact surfaces a simple centering of the spark plug 1 in the cylinder head 2 is possible. This embodiment of

Support surface 15, the inner shoulder 16 and the outer shoulder 17 is identical in the first and second embodiments.

The insulator 7 of the second embodiment, as shown in Figure 2, has a recess 19 formed as a circumferential groove on. In these

Recess 19 engages the second flared collar 18 of the seat support 4 a. By this recess 19 according to the second embodiment of the small paragraph 26 is avoided from the first embodiment. This will be the

Outer diameter of the entire spark plug 1 reduced. In particular, no enlargement of the third diameter D3 to form the small paragraph 26 is necessary and the insulator 7 can directly on the support surface 15 from the third

Pass diameter D3 into the taper towards the center electrode tip. The surface of the recess 19 is formed with an electrically conductive layer. As an alternative to this electrically conductive layer on the surface, embedding of an electrically conductive foil between the second flanging collar 18 and the depression 19 is also preferred. The recess 19 is located in the axial direction of the spark plug 1 between the seat of the central electrode head 20 in the insulator 7 and the support surface 15 of the insulator 7 in the seat support 4th

To increase the electrical breakdown strength in the region of the recess 19, the surface thereof is made electrically conductive and connected to the electrical potential of the seat support 4. In this case, the electric field in the recess 19 is more uniform and sliding sparks are suppressed.

Claims

claims 1 . Housing-free spark plug (1) for an internal combustion engine,  full  a clamping nut (3) to the spark plug (1) in the  Clamp internal combustion engine,  a seat support (4), over which the spark plug (1) is supported in the internal combustion engine,  a center electrode (5),  at least one ground electrode (6), which is arranged on the seat support (4), and  isolating an insulator (7) around the center electrode (5) from the ground electrode (6),  in the clamped state, the clamping nut (3) via a  Clamping nut shoulder (1 1) on the insulator (7) Clamps the spark plug (1) while the clamping nut (3) is in direct contact with the insulator (7). 2. Housing loose spark plug according to claim 1, characterized in that the clamping nut (3) and the seat support (4) are formed as two separate, non-contacting components. 3. Housing loose spark plug according to one of the preceding claims,  characterized in that the seat support (4) is designed as a sleeve on the insulator (7). 4. Housing loose spark plug according to one of the preceding claims,  characterized in that the seat support (4) comprises an inner shoulder (16) and an outer shoulder (17), wherein the insulator (7) rests on the inner shoulder (16), and wherein the outer shoulder (17) abuts against the Internal combustion engine is formed. 5. Housing loose spark plug according to one of the preceding claims, characterized in that the seat support (4) has an inner sealing surface to the insulator (7) and an outer sealing surface to the internal combustion engine (2) out. 6. Housing loose spark plug according to claim 5, characterized in that the inner sealing surface is directly in contact with the insulator (7) and / or the outer sealing surface for direct contact with the  Internal combustion engine (2) is formed. 7. Housing loose spark plug according to one of the preceding claims,  characterized in that the insulator (7) is provided on its support surface (15) in the seat support (4) and / or on the clamping nut shoulder (1 1) with a glaze. 8. Housing loose spark plug according to one of the preceding claims,  characterized in that the clamping nut (3) by means of a first crimp collar (13) captive on the insulator (7) is attached. 9. Housing loose spark plug according to one of the preceding claims,  characterized in that the ground electrode (6) is aligned with a mark on the spark plug (1) to determine the position of the ground electrode (6) in the internal combustion engine (2). 10. Housing loose spark plug according to one of the preceding claims,  characterized in that the seat support (4) by means of a second crimp collar (18) on the insulator (7) is attached. 1 1. Caseless spark plug according to claim 10, characterized in that the second flared collar (18) engages in a recess (19) in the insulator (7). 12. Housing loose spark plug according to claim 1 1, characterized in that the recess (19) between a seat (21) of a central electrode head (20) of the center electrode (5) in the insulator (7) and the support (15) of the insulator (7) is formed on the inner shoulder (16). 13. Housing loose spark plug according to one of claims 1 1 or 12, characterized in that the surface of the recess (19) is electrically conductive.