Spark plug including a multi-step insulator seat

Abstract

A spark plug is provided, including a housing, an insulator situated within a housing, the insulator having a longitudinal axis, an insulator foot, body, head, and seat. Inside the housing is a housing seat which is in contact with the insulator seat of the insulator. An inner seal is situated between the housing seat and the insulator seat, so that the inner seal, the housing seat, and the insulator seat form a sealing system. The insulator seat includes a step that has a first section and a second section having an angle γ to one another that is greater than 0° and the first section being parallel to the insulator longitudinal axis. The inner seal is in contact with this first section, so that a radial sealing surface is formed at the insulator.

Claims

1. A spark plug, comprising: a housing; an insulator situated within the housing, the insulator having a longitudinal axis, and including an insulator foot, an insulator body, and an insulator head, and an insulator seat which forms a transition from the insulator foot to the insulator body; a center electrode situated within the insulator; and a ground electrode situated at a front side of the housing facing a combustion chamber, the ground electrode and the center electrode being situated in such a way that the two electrodes form an ignition gap at a bottom of the spark plug; wherein: the housing has on its inside a housing seat which is in contact with the insulator seat of the insulator, an inner seal being situated between the housing seat and the insulator seat, so that the inner seal, the housing seat, and the insulator seat, form a sealing system; the insulator seat includes at least one step that has a first section and at least one second section, the first section and the second sections having an angle γ to one another that is greater than 0° and the first section being parallel to the insulator longitudinal axis, the inner seal being in contact with the first section, so that a radial sealing surface is formed at the insulator; and at least one of the following four features (I)-(IV): (I) (a) the at least one step includes at least two steps, the at least one second section including two second sections between which the first section extends, (b) the housing seat is a step formed by a transition, in a first axial region of the spark plug, from a single first inner housing surface to a single second inner housing surface that is arranged at a non-zero and non-straight angle relative to the first inner housing surface, (c) the inner seal, within the first axial region of the spark plug, contacts the at least two second sections and is arranged between (i) the first section and the at least two second sections of the insulator seat and (ii) the single first inner housing surface and the single second inner housing surface of the housing seat, and (d) the housing does not include, within the first axial region, any step other than the step formed by the transition from the single first inner housing surface to the single second inner housing surface; (II) the spark plug further comprises a resistor and the inner seal is arranged entirely below the resistor; (III) the spark plug further comprises an outer sealing element and the inner seal is arranged entirely below the outer sealing element; and (IV) the spark plug further comprises a thread by which the spark plug can be screwed into an internal combustion engine, and the inner seal is arranged entirely within an axial region of the spark plug that the thread occupies.

2. The spark plug as recited in claim 1, wherein the at least two steps at the insulator seat, beside the radial sealing surface, additionally has at least two axial sealing surfaces formed at the at least two second sections of the step.

3. The spark plug as recited in claim 2, wherein the radial sealing surface is situated between two axial sealing surfaces.

4. The spark plug as recited in claim 1, wherein the at least two steps forms multiple radial sealing surfaces together with the inner seal.

5. The spark plug as recited in claim 4, wherein the multiple radial sealing surfaces are each connected by axial sealing surfaces.

6. The spark plug as recited in claim 5, wherein there is one radial main sealing surface including at least one radial ancillary sealing surface and/or there is one axial main sealing surface including at least one axial ancillary sealing surface at the insulator seat.

7. The spark plug as recited in claim 1, wherein the second sections of the steps at the insulator seat include an angle of 90° to 175° with regard to the insulator longitudinal axis.

8. The spark plug as recited in claim 7, wherein all second sections of the steps include the same angle with regard to the insulator longitudinal axis.

9. The spark plug as recited in claim 1, wherein the housing seat spans an angle with regard to the insulator longitudinal axis having a value of at least 80° and maximally 170°.

10. The spark plug as recited in claim 9, wherein the value is between 90° and 160°.

11. The spark plug as recited in claim 1, wherein prior to installation, the inner seal on average has a height h, measured in parallel to the insulator longitudinal axis, and a width d, measured perpendicular to the insulator longitudinal axis, and the inner seal has a ratio of width d to height h of at least 0.5, prior to the installation.

12. The spark plug as recited in claim 11, wherein the ratio is at least 0.75, prior to the installation.

13. The spark plug as recited in claim 1, wherein prior to installation, the inner seal on average has a height h, measured in parallel to the insulator longitudinal axis, and a width d, measured perpendicular to the insulator longitudinal axis, and the radial sealing surface at the insulator seat has a height, measured in parallel to the insulator longitudinal axis of at least 30% of the height h of the inner seal.

14. The spark plug as recited in claim 13, wherein the radial sealing surface at the insulator seat has the height, measured in parallel to the insulator longitudinal axis of at least 36% of the height h of the inner seal.

15. The spark plug as recited in claim 6, wherein prior to installation, the inner seal on average has a height h, measured in parallel to the insulator longitudinal axis, and a width d, measured perpendicular to the insulator longitudinal axis, and the radial main sealing surface at the insulator seat has a height, measured in parallel to the insulator longitudinal axis, of at least 30% of the height h of the inner seal.

16. The spark plug as recited in claim 15, wherein the radial main sealing surface at the insulator seat has the height, measured in parallel to the insulator longitudinal axis, or at least 36% of the height h of the inner seal.

17. The spark plug as recited in claim 4, wherein prior to installation, the inner seal on average has a height h, measured in parallel to the insulator longitudinal axis, and a width d, measured perpendicular to the insulator longitudinal axis, and the radial ancillary sealing surfaces at the insulator seat have a height, measured in parallel to the insulator longitudinal axis, of at least 1% of the height h of the inner seal.

18. The spark plug as recited in claim 4, wherein prior to installation, the inner seal on average has a height h, measured in parallel to the insulator longitudinal axis, and a width d, measured perpendicular to the insulator longitudinal axis, and the radial ancillary sealing surfaces at the insulator seat have a height, measured in parallel to the insulator longitudinal axis, of at least 5% of the height h of the inner seal.

19. The spark plug as recited in claim 1, wherein prior to installation, the inner seal on average has a height h, measured in parallel to the insulator longitudinal axis, and a width d, measured perpendicular to the insulator longitudinal axis, and the inner seal and the housing form an axial sealing surface at the housing seat and a radial sealing surface on the inside of the housing, the radial sealing surface at the housing having a height, measured in parallel to the insulator longitudinal axis, of at least 30% of the height h of the inner seal.

20. The spark plug as recited in claim 1, wherein prior to installation, the inner seal on average has a height h, measured in parallel to the insulator longitudinal axis, and a width d, measured perpendicular to the insulator longitudinal axis, and the inner seal and the housing form an axial sealing surface at the housing seat and a radial sealing surface on the inside of the housing, the radial sealing surface at the housing having a height, measured in parallel to the insulator longitudinal axis, of at least 36% of the height h of the inner seal.

21. The spark plug as recited in claim 1, wherein prior to installation, the inner seal on average has a height h, measured in parallel to the insulator longitudinal axis, and a width d, measured perpendicular to the insulator longitudinal axis, and the axial sealing surface at the insulator seat has a width, measured perpendicular to the insulator longitudinal axis, of at least 15% of the width d of the inner seal.

22. The spark plug as recited in claim 1, wherein prior to installation, the inner seal on average has a height h, measured in parallel to the insulator longitudinal axis, and a width d, measured perpendicular to the insulator longitudinal axis, and the axial sealing surface at the insulator seat has a width, measured perpendicular to the insulator longitudinal axis, of at least 20% of the width d of the inner seal.

23. The spark plug as recited in claim 6, wherein prior to installation, the inner seal on average has a height h, measured in parallel to the insulator longitudinal axis, and a width d, measured perpendicular to the insulator longitudinal axis, and the axial main sealing surface at the insulator seat has a width, measured perpendicular to the insulator longitudinal axis, of at least 15% of the width d of the inner seal.

24. The spark plug as recited in claim 6, wherein prior to installation, the inner seal on average has a height h, measured in parallel to the insulator longitudinal axis, and a width d, measured perpendicular to the insulator longitudinal axis, and the axial main sealing surface at the insulator seat has a width, measured perpendicular to the insulator longitudinal axis, of at least 20% of the width d of the inner seal.

25. The spark plug as recited in claim 4, wherein prior to installation, the inner seal on average has a height h, measured in parallel to the insulator longitudinal axis, and a width d, measured perpendicular to the insulator longitudinal axis, and the axial ancillary sealing surfaces at the insulator seat have a width, measured perpendicularly to the insulator longitudinal axis, of at least 1% of the width d of the inner seal.

26. The spark plug as recited in claim 4, wherein prior to installation, the inner seal on average has a height h, measured in parallel to the insulator longitudinal axis, and a width d, measured perpendicular to the insulator longitudinal axis, and the axial ancillary sealing surfaces at the insulator seat have a width, measured perpendicularly to the insulator longitudinal axis, of at least 5% of the width d of the inner seal.

27. The spark plug as recited in claim 2, wherein the axial sealing surface at the insulator seat, which directly adjoins the insulator foot, has at least a width that corresponds to a narrowest gap width between the insulator foot and the inside of the housing opposite the insulator foot.

28. The spark plug as recited in claim 1, wherein: (a) the at least one step includes at least two steps, the at least one second section including the two second sections between which the first section extends; (b) the housing seat is the step formed by the transition, in the first axial region of the spark plug, from the single first inner housing surface to the single second inner housing surface that is arranged at the non-zero and non-straight angle relative to the first inner housing surface; (c) the inner seal, within the first axial region of the spark plug, contacts the at least two second sections and is arranged between: (i) the first section and the at least two second sections of the insulator seat; and (ii) the single first inner housing surface and the single second inner housing surface of the housing seat; and (d) the housing does not include, within the first axial region, any step other than the step formed by the transition from the single first inner housing surface to the single second inner housing surface.

29. The spark plug as recited in claim 1, wherein the spark plug further comprises the resistor and the inner seal is arranged entirely below the resistor.

30. The spark plug as recited in claim 1, wherein the spark plug further comprises the outer sealing element and the inner seal is arranged entirely below the outer sealing element.

31. The spark plug as recited in claim 1, wherein the spark plug further comprises the thread by which the spark plug can be screwed into the internal combustion engine, and the inner seal is arranged entirely within the axial region of the spark plug that the thread occupies.

32. A spark plug, comprising: a housing; an insulator situated within the housing, the insulator having a longitudinal axis, and including an insulator foot, an insulator body above the insulator foot, and an insulator head above the insulator body, and an insulator seat which forms a transition from the insulator foot to the insulator body; a center electrode situated within the insulator; and a ground electrode situated at a front side of the housing facing a combustion chamber, the ground electrode and the center electrode being situated in such a way that the two electrodes form an ignition gap at a bottom of the spark plug; wherein: the housing has on its inside a housing seat corresponding and facing opposite to the insulator seat of the insulator, an inner seal being situated between the housing seat and the insulator seat, so that the inner seal, the housing seat, and the insulator seat, form a sealing system; the insulator seat includes a step that has a first section and a second section above the first section; the first section and the second section have an angle γ to each other that is greater than 0°; the first section is approximately parallel to the insulator longitudinal axis; the inner seal protrudes from on the second section to on the first section so that the inner seal is in contact with the second section and also the first section, forming a radial sealing surface at the insulator foot; and at least one of the following two features (I) and (II): (I) the spark plug further comprises a resistor, and the first and second sections are both entirely below the resistor; and (II) the second section is a bottom-most radial widening section of the insulator that forms the step to connect a pair of adjacent sections of the insulator, including the first section, a diameter of the insulator differing between the pair of adjacent sections.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 shows one example of a spark plug.

(2) FIG. 2 shows in detail the arrangement of the housing seat, the insulator seat, and the inner seal of a spark plug according to the related art.

(3) FIG. 3 shows in detail the insulator seat including a step, the inner seal, and the housing seat of the spark plug according to an example embodiment of the present invention prior to the installation.

(4) FIG. 4 shows in detail the insulator seat including a step, the inner seal, and the housing seat of the spark plug according to the present invention following the installation.

(5) FIG. 5 shows the insulator seat including a step for a spark plug according to the present invention.

(6) FIG. 6 shows one example of a housing seat for a spark plug according to the present invention.

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS

(7) FIG. 1 shows a spark plug 1 in a half-sectional view. Spark plug 1 includes a housing 2. An insulator 3 is inserted into housing 2. Housing 2 and insulator 3 each have a bore along their longitudinal axes. The longitudinal axis of housing 2, longitudinal axis X of insulator 3, and the longitudinal axis of spark plug 1 coincide. A center electrode 4 is inserted into insulator 3. A connecting bolt 8 furthermore extends into insulator 3. A connecting nut 9, via which spark plug 1 is electrically contactable to a voltage source, is situated at connecting bolt 8. Connecting nut 9 forms the end of spark plug 1 facing away from the combustion chamber.

(8) A resistor element 7, also referred to as a Panat, is located in insulator 3 between center electrode 4 and connecting bolt 8. Resistor element 7 electrically conductively connects center electrode 4 to connecting bolt 8. Resistor element 7 is built as a layer system from a first contact Panat, a resistor Panat, and a second contact Panat, for example. The layers of the resistor element differ in their material composition and the electrical resistance resulting therefrom. The first contact Panat and the second contact Panat may have a different or an identical electrical resistance.

(9) On the front side of housing 2 facing the combustion chamber, a ground electrode 5 is electrically conductively situated. An ignition spark is generated between ground electrode 5 and center electrode 4.

(10) Housing 2 has a shaft. A polygon 21, a shrinkage groove, and a thread 22 are designed at this shaft. Thread 22 is used to screw spark plug 1 into an internal combustion engine. An outer sealing element 6 is situated between thread 22 and polygon 21. Outer sealing element 6 is designed as a folding seal in this exemplary embodiment.

(11) Insulator 3 is typically divided into three areas: insulator foot 31, insulator body 32, and insulator head 33. The three areas are differentiated, for example, by different diameters. Insulator foot 31 is the end of insulator 3 facing the combustion chamber. Center electrode 4 is situated within insulator foot 31. In general, insulator foot 31 is situated completely or at least over the large part of its length, measured in parallel to the spark plug longitudinal axis or insulator longitudinal axis X, within housing 2. Insulator foot 31 generally has the smallest outer diameter at insulator 3.

(12) Insulator body 32, which is generally completely encompassed by housing 2, is situated in an adjoining manner at insulator foot 31. Insulator body 32 has a larger outer diameter than insulator foot 31. The transition between insulator foot 31 and insulator body 32 is designed as a shoulder or a fillet. This transition is also referred to as a foot fillet or an insulator seat 35.

(13) Insulator head 33 adjoins the end of insulator body 32 facing away from the combustion chamber and forms the end of insulator 3 facing away from the combustion chamber. Insulator head 33 protrudes from housing 2. The outer diameter of insulator head 33 is between the outer diameter of insulator foot 31 and insulator body 32, the areas typically not having constant outer diameters over their lengths, but potentially varying outer diameters.

(14) Housing 2 has a seat 25 at its inside. The shoulder or insulator seat 35 of the insulator is in contact with housing seat 25. An inner seal 10 is situated between insulator seat 35 and housing seat 25. Area 30 of housing seat 25 and of insulator seat 35 is indicated by a circle in FIG. 1 and described in greater detail in subsequent FIGS. 2 through 6.

(15) FIG. 2 shows in detail area 30 including housing seat 25, insulator seat 35, and inner seal 10 according to the related art. Housing seat 25 has an inclination of α=55°-65° with regard to the spark plug longitudinal axis. The area of insulator seat 35 results from the transition of insulator foot 31 to insulator body 32, in which the outer diameter continuously increases. This arrangement results in an axial sealing surface between housing seat 25, insulator seat 35, and inner seal of approximately 10 mm.sup.2, the pretensioning force, with the aid of which housing 2 and insulator 3 are pressed into each other, being at 1.5 kN up to 10 kN.

(16) FIG. 3 shows in detail area 30 including housing seat 25, insulator seat 35, and inner seal 10 prior to the installation of insulator 3 into housing 2 according to the present invention. Inner seal 10 is in contact with housing seat 25. Prior to the installation of insulator 3, the inner seal has a height h, measured in parallel to the longitudinal axis of the spark plugs or insulator longitudinal axis X, and a width d, measured perpendicular to the longitudinal axis of the spark plugs or insulator longitudinal axis X.

(17) Insulator seat 35, which forms the transition between insulator foot 31 and insulator body 32, has one step in this example. The step may be divided into three sections. A first section 3510 has a surface that is parallel to insulator longitudinal axis X and thus this first section 3510 is also parallel to insulator longitudinal axis X. The two other sections 3520, also referred to as the second section, are inclined by an angle γ with regard to first section 3510. Here, every second section 3520 has a different angle γ with regard to first section 3510 or to insulator longitudinal axis X, for example. Alternatively, different second sections 3520 may have same angle γ with regard to first section 3510 or to insulator longitudinal axis X.

(18) FIG. 4 shows in detail area 30 including housing seat 25, insulator seat 35, and inner seal 10 after the installation of insulator 3 into housing 2 according to the present invention. As a result of the installation of insulator 3 into housing 2, a force acts on inner seal 10, whereby inner seal 10 is deformed and radial sealing surfaces 251, 351a, 351b, 351c and axial sealing surfaces 252, 352a, 352b, 352c are formed on insulator 3 and on insulator seat 35 as well as on housing 2 and on housing seat 25. Radial sealing surfaces 351a, 351b are always formed between inner seal 10 and the surfaces of insulator 3 or housing 2 that are parallel to insulator longitudinal axis X. In the sense of this application, surfaces are also contemplated as being parallel that have a minor inclination, i.e., an angle smaller than 10°, with regard to the longitudinal axis of the spark plugs or to insulator longitudinal axis X.

(19) A radial sealing surface 251 is formed on housing 2 and an axial sealing surface 252 is formed on housing seat 25.

(20) In this exemplary embodiment, insulator seat 35 includes two steps and thus two first sections 3510a, 3510b and multiple second sections 3520a, 3520b, 3520c. Radial sealing surfaces 351a, 351b are formed at first sections 3510a, 3510b. In this case, a radial main sealing surface 351a is formed at first section 3510a and a radial ancillary sealing surface 351b is formed at other first section 3510b. Typically, one main sealing surface and multiple ancillary sealing surfaces are formed, the main sealing surface being enclosed by adjacent ancillary sealing surfaces. The main sealing surface is typically the largest area. In addition to the radial sealing surfaces, axial sealing surfaces 352a, 352b are also formed on the insulator seat at second sections 3520a, 3520b. In the case of axial sealing surfaces 352a, 352b, it may be differentiated again between the main sealing surface and the ancillary sealing surfaces.

(21) As a result of the step-like shape of the insulator seat, radial and axial sealing surfaces alternate.

(22) It is not excluded that radial sealing surfaces are also formed on insulator foot 31 or insulator body 32, such as radial sealing surface 351c on insulator foot 31.

(23) It is not necessary that a sealing surface is formed at all sections of a step on insulator seat 35. As is shown in this example, it is not a problem if no sealing surface is formed at a section 3520c situated at the edge of insulator seat 35.

(24) Axial ancillary sealing surface 352b, which abuts insulator foot 31, should be wider than gap width e between insulator foot 31 and housing 2, i.e., below insulator seat 35, and/or wider than gap width f between insulator body 32 and housing 2, i.e., above insulator seat 35.

(25) FIG. 5 shows once again in detail insulator seat 35 including two steps. Insulator longitudinal axis X is visible. The two steps at insulator seat 35 have a different angle γ between their first and second sections 3510, 3520a, 3520b. Angle γ has a value of 90° to 175°. Depth a.sub.i of insulator seat 35 results from the half difference of diameter b.sub.i at insulator foot 31 and diameter c.sub.i at insulator body 32.

(26) In FIG. 6, housing seat 25 is shown in detail. Depth a.sub.g of housing seat 25 results from the half difference of the inner diameter of the housing at the height of the insulator foot and of the housing inner diameter c.sub.g above housing seat 25. The diameters are measured perpendicular to the housing longitudinal axis. Housing seat 25 is inclined at an angle ß with regard to the housing longitudinal axis. ß has a value of 90° to 160°. In principle, ß may also have values smaller than 90°, however this makes the manufacturing process more difficult and the manufacturing costs higher.