WO2016026597A1

WO2016026597A1 - Spark plug with a multiple ground electrode

Info

Publication number: WO2016026597A1
Application number: PCT/EP2015/063703
Authority: WO
Inventors: Detlef Hartmann; Andreas Benz
Original assignee: Robert Bosch Gmbh
Priority date: 2014-08-21
Filing date: 2015-06-18
Publication date: 2016-02-25
Also published as: DE102014216582A1

Abstract

Spark plug, in particular for an internal combustion engine, having a housing, an insulator which is arranged in the housing and has an axial hole, a centre electrode which is arranged in the axial hole in the insulator, wherein the spark plug has a longitudinal axis, and wherein at least one spark gap is formed between the centre electrode and the housing, wherein the spark gap is formed substantially parallel to the longitudinal axis of the spark plug and at a distance from the longitudinal axis of the spark plug.

Description

description

Spark plug with multi-mass electrode

State of the art

The invention relates to a spark plug according to the preamble of the independent

Claim.

In the spark plug development is constantly working to increase the life of the spark plug. In today's spark plugs, both for use in the automotive sector as well as for use in stationary gas engines, the term could be increased by the use of precious metal wear surfaces. In the recent past, further increases in spark plug life have been achieved by increasing the precious metal content in the spark plug. In this case, for the automotive applications primarily spark plugs are used with multi-ground electrodes, compared to spark plugs with a

Ground electrode provide a larger electrode wear volume. In the case of spark plugs for use in stationary gas engines, the noble metal overlays in the

Ground electrode and if necessary. the center electrode increases to increase the amount of the noble metal. Due to the high or increasing proportion of precious metal in the spark plug and the cost of materials in the production of the spark plug increase.

Disclosure of the invention

The spark plug according to the invention with the characterizing feature of the independent claim has the advantage that an increase in the efficiency and the duration of the spark plug according to the invention is achieved.

The invention provides that the spark gap is formed substantially parallel to the longitudinal axis of the spark plug and spaced from the longitudinal axis of the spark plug, there is the advantage that the spark gap for the mixture to be ignited, such as a fuel mixture, is more accessible and thus the Inflammation of the mixture is favored. This improves the

Overall performance of the spark plug. The spark plug according to the invention can be operated under the spark plug less abrasive conditions and thereby achieved nevertheless comparable results in the operational reliability as a spark plug of the state of the art, which is operated under more extreme conditions and thus wears faster. The spark plug comprises a housing, an insulator arranged in the housing with an axial bore and a center electrode arranged in the axial bore of the insulator. The spark plug has a longitudinal axis. The longitudinal axis of the spark plug extends from the combustion chamber end of the spark plug to the combustion chamber end remote from the spark plug. The longitudinal axis of the spark plug corresponds to the axis about which the spark plug would rotate when screwed into, for example, an engine block.

The spark plug has at least one spark gap, which is in the range of

Ignition gap forms, wherein the ignition gap between the center electrode and the housing is arranged. The spark gap is the shortest distance between the center electrode and the housing in the region of the ignition gap. In essence, the spark gap is formed parallel to the longitudinal axis of the spark plug. In addition, the spark gap is formed spaced from the longitudinal axis, i. the spark gap has a radial distance to the longitudinal axis of the spark plug. By substantially parallel, it is meant that the spark gap can have some deviation from the parallel orientation to the longitudinal axis due to production or operational reasons. For the purposes of this invention, a spark gap which has an angle of up to 10 °, in particular up to 5 ° or up to 2 °, to the longitudinal axis of the spark plug, considered as substantially parallel to the longitudinal axis.

The term center electrode refers to the electrode, which is arranged at least in some areas within the insulator and whose electrical contacting takes place via the connection bolt arranged at the end remote from the combustion chamber. Further advantageous embodiments are the subject of the dependent claims.

In a further development of the invention, it is provided that the distance of the

Spark gap to the longitudinal axis of the spark plug greater than or equal to half

Inner diameter D | of the housing is. Additionally or alternatively, the distance of the spark gap to the longitudinal axis is less than or equal to half the outer diameter D _{A of} the housing. The inner diameter D | of the housing and the

Outer diameter D _{A of} the housing at the combustion chamber end of the housing measured, which is assumed by rectangular edges in the measurement, ie possible chamfers or fillets at the edges of the housing are in the

Determination of diameter neglected. Advantageously, it can be provided that the center electrode at its

The end portion of the combustion chamber has a portion extending radially outwards from the longitudinal axis of the spark plug toward the housing, also abbreviated to "radial portion." The radial portion may be substantially perpendicular to the longitudinal axis of the spark plug, with the radial portion of FIG The radial section can have a deviation of up to 35 °, in particular up to 20 °, or in particular up to 10 °, from the vertical arrangement of the section The radial section can be straight in itself.

Alternatively, the radial section can also have a curvature, as a result of which the radial section can be arranged maximally in regions perpendicular to the longitudinal axis of the spark plug.

Between the housing and the region of the radial section or the center electrode which is closest to the housing, a spark gap is formed. In the area of the ignition gap, the spark gap is formed.

The center electrode has the radial portion and a base to which the radial portion is fixed.

The radial section is cohesively and / or non-positively connected to the base of the

Center electrode connected. For example, the radial portion and the base of the center electrode may be formed by conventional welding techniques, such as

Resistance welding, laser welding and / or electron beam welding, are joined together. The radial section consists of a nickel alloy. For example, the radial portion may be made of the same nickel alloy as the base of the center electrode.

In an advantageous development, at least one wear surface may be arranged on a combustion chamber-side end face of the housing, in particular, the

Wear surface arranged directly on the front side of the housing. It is also conceivable that the wear surface is arranged partially or completely, for example in a recess provided for this purpose in the end face of the housing. By the renunciation On a ground electrode base body there is the advantage that the thermal contact and the heat flow between the wear surface and the housing can be improved. This reduces the temperature and the associated wear of the wearing surface. The life of the spark plug is extended.

The wear surface or the front side of the housing take over the function of the ground electrode of a conventional spark plug.

Additionally or alternatively, at least one wear surface may be arranged on the center electrode. Preferably, the at least one wear surface is disposed on the radial portion of the center electrode. Preferably, the radial section at its end remote from the longitudinal axis, in particular on the housing-facing side of the end of the radial section, the wear surface. The spark gap or the spark gap is formed between the center electrode or its radial section and the housing or the front side of the housing, wherein the center electrode or its radial section and / or the housing or its end face have at least one wear surface. The wear surfaces are, for example, by means of laser welding to the housing or its front side and / or the

Center electrode or its radial portion connected. Typically, the surfaces defining the spark gap have a pitch in the range of 0.2 mm to 2.5 mm. By providing the radial portion of the center electrode, by bending the radial portion, the ideal spacing of the surfaces for the intended use can be adjusted. If necessary, the distance can be readjusted during the runtime of the spark plug, or during routine maintenance work on the stationary gas engine.

Ideally, the wear surface arranged on the center electrode or on its radial section is arranged opposite the wear surfaces arranged on the housing or on the front side of the housing. That In a projection of a wear surface along the longitudinal axis of the spark plug to the other wear surface, the projection of a wear surface would cover the other wear surface at least partially, preferably completely cover. For example, one wearing surface has a larger end face than the other

Wear surface, for example, the end face of a wear surface at least by a factor of 1.2, in particular by a factor of 1.5, greater than the end face of the opposite arranged wear surface. This will be the one

manufacturing inaccuracies in the opposite and congruent arrangement of two spark gaps forming wear surfaces corrected to a certain extent. On the other hand, by the arrangement of a wear surface edge opposite the end face or part of the end face of the other, oppositely disposed wear surface necessary for the triggering of a spark

Tension can be reduced. At one edge, a larger gradient of the electric field is formed than at one surface, and therefore even at a lower voltage, the electrons can be released from the surface of the wear surface and generate a spark. As a result, the material and the spark plug is less stressed and extends the life of the spark plug.

Preferably, the at the center electrode or at the radial portion of the

Center electrode arranged wearing surface of an equal or larger diameter than that arranged on the housing or on the housing end face

Wear surface on. By way of example, the diameter of the wear surface arranged on the center electrode or on the radial section of the center electrode is greater than the diameter of the wear surface arranged on the housing or on the housing end side by at least a factor of 1.2, in particular by a factor of 1.5.

The wear surfaces typically comprise a noble metal or a noble metal alloy, wherein the wear surfaces may consist of the same or different metals or alloys. Preferably, the main constituent of the alloy is platinum (Pt), iridium (Ir), rhodium (Rh) and / or an alloy of the elements.

The wear surfaces may be round, oval or polygonal, e.g. square,

Have cross-sectional area and / or end face. The width of the wear surfaces is smaller than the width of the housing edge or the width of the front side of the housing. For example, the width of the wear surfaces or the diameter in a round cross-sectional area of the wear surfaces in the range of 1 mm to 4 mm. Typically, the wear surface is wider and / or longer than high. The height of the wear surfaces is measured along a direction parallel to the spark plug longitudinal axis direction.

Typically, the height of the wear surfaces is in the range of 0.4 mm to 1.5 mm. The length of the wear surfaces is measured along the circumference of the housing. The width of the wear surfaces is correspondingly along a radial direction perpendicular to the longitudinal axis of the spark plug. In principle, the wear surfaces arranged on the center electrode or on its radial section can have the same or at least similar geometries and / or materials as those on the housing or on its front side

Wear surfaces have.

In a further development of the spark plug according to the invention, at least two, in particular three or four or five, on the housing or on its front side,

Wear surfaces be arranged. Preferably, the wear surfaces are distributed uniformly over the circumference of the housing or the combustion chamber-side end face of the housing. Advantageously, the wear surfaces each between each other a arc distance of approximately n * (D _A -D |) / n, where n is the number of

Wear surfaces and D _A and Di are the outer diameter and the inner diameter of the housing. The distance may be subject to certain fluctuations due to production, which are included by the use of the term approx.

In an advantageous development of the radial portion of the center electrode is formed with one arm or more arm, wherein the or the arms extend from the longitudinal axis of the spark plug radially outward in the direction of the housing edge. In particular, the multi-arm radial section has m arms. Ideally, m is equal to n, where n is the number of wear surfaces arranged on the housing or its front side.

For example, the radial section is two-armed or three-armed or five-armed

educated. Typically, two, in particular adjacent, arms of the radial section enclose an angle of approximately 360 ° / m. The angle may be subject to certain fluctuations due to production, which are included by the use of the term approx.

The multi-arm radial section preferably has a wear surface at each of its ends facing away from the longitudinal axis of each arm, in particular on the sides of the arms facing the housing.

The radial portion with its arms may be formed in one piece or several pieces. In an even number of arms, the arms may be formed in pairs in one piece, for example. In a multi-piece embodiment of the radial portion with its arms, the individual components of the radial portion are connected to each other, for example by welding. The arms are typically longer than half the inside diameter D | of the housing and / or shorter than the sum of half the outer diameter D _{A of} the housing and half the diameter d of the center electrode at its combustion chamber end. In principle, it is also conceivable that the radial section of the center electrode is formed as a disk or as a wheel. The wheel may have, for example, I spokes, wherein ideally I corresponds to the number of wear surfaces arranged on the housing or its front side. The spark plug according to the invention and its developments can be stationary

Gas engines, such as generators or compressor, are used. An embodiment of the spark plugs according to the invention with correspondingly reduced

Dimensions and geometries can also be used in the automotive sector. Other features, applications and advantages of the invention will become apparent from the following description of embodiments of the invention, which are illustrated in the figures of the drawing.

drawing

Figure 1 shows an example of a spark plug according to the invention with a single-arm center electrode in a half-cut side view. Figure 2 shows a second example of a spark plug according to the invention with a two-armed center electrode in a half-cut side view

Figure 3 shows the example according to Figure 2 in a plan view Figure 4 shows a third example of a spark plug according to the invention with a three-arm center electrode in a plan view

Description of the embodiment

Figure 1 shows a schematic representation of the combustion chamber end of the

The spark plug according to the invention has a housing 2 with a therein arranged insulator 3 and arranged in the insulator 3 center electrode 4. The spark plug 1 has a longitudinal axis XX which extends from the combustion chamber end of the spark plug 1 to the combustion chamber facing away from the end of the spark plug 1. The combustion chamber-side end of the center electrode 4 protrudes from the combustion chamber end of the insulator 3 out. The combustion chamber-side end of the insulator 3 can be flush with the

combustion chamber end of the housing 2 or within the housing 2 ends. Alternatively, the combustion chamber end of the insulator can also protrude from the housing 2. The housing 2 has at its combustion-chamber-side end an inner diameter D | and an outer diameter D _A. Half the difference between the outer diameter D _A and the inner diameter Di corresponds to the width of the combustion chamber side

Gehäuserands or the width of the combustion chamber-side end face 10 of the housing 2. At the edge of the housing or on the end face 10 of the housing, a wear surface 8 may be arranged. For example, the wear surface 8 consists of a noble metal or a noble metal-containing alloy. Preferably, as a precious metal for the

Wear surface 8 platinum (Pt), iridium (Ir) and / or rhodium (Rh) or an alloy with at least two of these elements used. The wear surface 8 may be a round, oval or polygonal, z. B. quadrangular, cross-sectional area. The width of the

Wear surface 8 is smaller than the width of the housing edge or the end face 10 of the housing 2. For example, the width of the wear surface 8 or the

Diameter at a circular cross-sectional area of the wear surface 8 in the range of 1 mm to 4 mm. Typically, the wear surface 8 is wider and / or longer than high. The height of the wear surface 8 is thereby along a parallel direction of the

Spark plug longitudinal axis X-X measured. Typically, the height of the

Wear surface in the range of 0.4 mm to 1.5 mm. The length of wear surface 8 is measured along the circumference of the housing. The width of the wear surface 8 is given correspondingly along a radial direction perpendicular to the longitudinal axis X-X. As shown in FIG. 1, a radial section 6 is arranged at the combustion chamber end of the center electrode 4. The radial portion 6 extends from the

Longitudinal axis XX radially outward in the direction of the housing 2. The radially outwardly extending portion of the radial portion 6 is also referred to as arm 9. As shown here, the radial portion 6 is arranged substantially perpendicular to the longitudinal axis XX, with "essentially" manufacturing-related uncertainties and resulting deviations and / or aging-related deviations and / or operational deviations from the radial arrangement are included It is also conceivable that the radial portion 6 has a curvature, whereby the portion 6 is arranged at most partially perpendicular to the longitudinal axis XX.

The radial section 6 is connected in a material-locking and / or non-positively connected manner to a base 11 of the center electrode 4. For example, the radial portion 6 and the base 11 of the center electrode 4 may be formed by the usual welding techniques, such as

Resistance welding, laser welding and / or electron beam welding to be interconnected. The radial section 6 is made of a nickel alloy. For example, the radial portion 6 may be made of the same nickel alloy as the base 11 of the center electrode 4.

At its side facing away from the longitudinal axis, the radial section 6 has a

Wear surface 7 on. Preferably, the wear surface 7 of the arranged on the end face 10 of the housing wear surface 8 is arranged opposite, so that the spark between the wear surfaces 7, 8 must travel as short a path as possible. The gap located between the wear surfaces 7, 8 is called spark gap 5. In principle, the wear surface 7 arranged on the section 6 can have the same or at least similar geometries and / or materials as the wear surface 8 arranged on the end face 10 of the housing 2, see also those described above

Materials and geometries. The two wear surfaces 7, 8 can be the same

Have geometry or different geometries. The wear surfaces 7, 8 consist of the same material or different materials.

Figure 2 shows a second embodiment of the spark plug according to the invention. The embodiment of Figure 2 differs from the embodiment of Figure 1 in that the spark plug two Zündspalte 5 and thus two

Has spark gaps. On the front side 10 of the housing 2, two wear surfaces 8 are arranged. The radial portion 6 has a length of at least the

Inner diameter D | of the housing 2 and at most the outer diameter D _{A of} the housing 2. The radial section 6 has two arms 9. As can be seen in FIG. 3, the arms 9 enclose an angle of approximately 180 °, whereby the "approx."

manufacturing-related uncertainties and resulting deviations from the declared value are included. In this embodiment, the radial portion 6 is formed integrally with its two arms. Alternatively, it is also conceivable that the radial portion is formed in several pieces. For example, each arm 9 may be formed in one piece and the radial portion 6 results from a frictional and / or

cohesive connection of the arms.

FIG. 4 shows a third exemplary embodiment of the spark plug according to the invention. This embodiment differs from the first two

Embodiments in that the spark plug has three Zündspalte and thus also three spark gaps. The radial section 6 has three arms 9. At each end of the arms 9, a wear surface 7 is arranged on the combustion chamber side facing away from the arms 9. In Figures 3 and 4, the wear surfaces 7 are indicated by circles.

The arms 9 each enclose an angle of approximately 120 °, whereby the "approx." Manufacturing-related uncertainties and resulting deviations from the stated value are included.

Claims

claims

1. spark plug (1), in particular for an internal combustion engine, comprising a housing (2), one in the housing (2) arranged insulator (3) having an axial bore, one in the axial bore of the insulator (3) arranged center electrode (4) , wherein the spark plug (1) has a longitudinal axis (XX), and wherein at least one spark gap between the central electrode (4) and housing (2) is formed, characterized in that the spark gap substantially parallel to the longitudinal axis (XX) of the spark plug (1 ) and spaced from the longitudinal axis (XX) of the spark plug (1) is formed.

2. Spark plug (1) according to claim 1, characterized in that the distance of the spark gap to the longitudinal axis (XX) of the spark plug (1) is greater than or equal to half an inner diameter (D |) of the housing (2) and / or less than or equal half the outer diameter (D _A ) of the housing (2).

3. Spark plug (1) according to claim 1 or 2, characterized in that the

Center electrode (4) at its combustion chamber end has a portion (6) extending from the longitudinal axis (X-X) of the spark plug (1) in the direction of the housing (2).

4. Spark plug (1) according to one of the preceding claims, characterized in that on a combustion chamber side end face (10) of the housing (2), in particular directly, at least one wear surface (8) is arranged and / or that at the center electrode (4) , In particular on the portion (6), at least one wear surface (7) is arranged.

5. Spark plug (1) according to claim 4, characterized in that at the

Center electrode (4) arranged wear surfaces (7) arranged on the housing (2) wear surfaces (8) are arranged opposite one another.

6. Spark plug (1) according to claim 4 or 5, characterized in that at least one of the wear surfaces (7, 8) comprise a noble metal or a noble metal alloy, in particular an alloy with Pt, Ir and / or Rh as the main component.

7. Spark plug (1) according to one of claims 4 to 6, characterized in that the wear surfaces (7, 8) have a diameter of 1 mm to 4 mm and / or a thickness of 0.4 mm to 1.5 mm.

8. Spark plug (1) according to one of claims 4 to 7, characterized in that an end face of the at the center electrode (4) arranged wear surfaces (7) of

Center electrode (4) greater than or equal to an end face of the oppositely disposed wear surface (8) of the housing (2).

9. Spark plug according to one of claims 4 to 8, characterized in that the housing (2) at least two, in particular three or four or five, wear surfaces (8) are arranged.

10. Spark plug (1) according to claim 9, characterized in that the wear surfaces (8) over the circumference of the combustion chamber side end face (10) of the housing (2) are distributed, and that in particular the wear surfaces (8) between each other

Arc distance of about 7t * (D _A -D |) / n, where n is the number of

Wear surfaces (8) and D _A or D | the outer diameter or the inner diameter of the housing are.

11. Spark plug (1) according to one of claims 3 to 10, characterized in that the radial portion (6) of the center electrode (4) is one-armed or multi-armed, in particular two-armed or three-armed or four-armed or fünfarmig, wherein

in particular, the section (6) is formed in one piece or in several pieces.

12. spark plug (1) according to claim 11, characterized in that in multi-arm section (6) of the center electrode (4) between two arms (9) an angle of about 360 ° / nn is included, where m is the number of arms ( 9).

13. Spark plug (1) according to claim 11 or 12, characterized in that the portion (6) at its end or at each of the longitudinal axis (XX) facing away from the end of each arm (9), in particular on the housing (2) facing Side of the arm (9) and the arms (9), a wear surface (7).

14. Spark plug (1) according to one of the preceding claims, characterized in that a base (5) of the center electrode (4) and / or the portion (6) of the center electrode (4) have a nickel alloy.