Classifications

• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01T—SPARK GAPS; OVERVOLTAGE ARRESTERS USING SPARK GAPS; SPARKING PLUGS; CORONA DEVICES; GENERATING IONS TO BE INTRODUCED INTO NON-ENCLOSED GASES
  • H01T13/00—Sparking plugs
  • H01T13/54—Sparking plugs having electrodes arranged in a partly-enclosed ignition chamber
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01T—SPARK GAPS; OVERVOLTAGE ARRESTERS USING SPARK GAPS; SPARKING PLUGS; CORONA DEVICES; GENERATING IONS TO BE INTRODUCED INTO NON-ENCLOSED GASES
  • H01T13/00—Sparking plugs
  • H01T13/20—Sparking plugs characterised by features of the electrodes or insulation
  • H01T13/39—Selection of materials for electrodes
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01T—SPARK GAPS; OVERVOLTAGE ARRESTERS USING SPARK GAPS; SPARKING PLUGS; CORONA DEVICES; GENERATING IONS TO BE INTRODUCED INTO NON-ENCLOSED GASES
  • H01T13/00—Sparking plugs
  • H01T13/46—Sparking plugs having two or more spark gaps
  • H01T13/467—Sparking plugs having two or more spark gaps in parallel connection
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01T—SPARK GAPS; OVERVOLTAGE ARRESTERS USING SPARK GAPS; SPARKING PLUGS; CORONA DEVICES; GENERATING IONS TO BE INTRODUCED INTO NON-ENCLOSED GASES
  • H01T21/00—Apparatus or processes specially adapted for the manufacture or maintenance of spark gaps or sparking plugs
  • H01T21/02—Apparatus or processes specially adapted for the manufacture or maintenance of spark gaps or sparking plugs of sparking plugs

Definitions

• the present disclosure generally relates to a method for manufacturing an ignition electrode of a spark plug configured to be used in an internal combustion engine, particularly in a gaseous fuel internal combustion engine.
• a spark plug including a prechamber in the following referred to as "pre-combustion chamber" in some internal combustion engine applications, such as gaseous fuel applications.
• a pre- combustion chamber is a relatively small gas accumulating chamber located in the spark plug cap or in the engine cylinder head.
• the pre-combustion chamber is in fluid communication with the main combustion chamber of the internal combustion engine via a number of small flow channels.
• a spark plug ignites a mixture of gaseous fuel and air within the pre-combustion chamber (as opposed to igniting the gaseous fuel in the main combustion chamber). Ignition of the gaseous fuel in the pre-combustion chamber generates a front of burning fuel which is jetted or otherwise advanced through the flow channels into the main combustion chamber thereby igniting the mixture of gaseous fuel and air therein.
• the ignition electrode may be provided in a crucial shape.
• the ignition electrode may include a plurality of electrode arms extending upright from a connecting section into the interior of the pre-combustion chamber.
• the manufacturing process of the ignition electrode may include some mechanical manufacturing steps including, for example, cutting a crucial piece out of a metal sheet, bending each electrode arms into the desired position, and applying a metal coat, such as, for instance, an iridium coat to the bended ignition electrode.
• the mechanical bending process may be limited due to, for example, the material's yield strength and, during operation of the ignition electrode, the electrode arms may break as the bending radius were to small for the used material and used material thickness.
• the ignition electrode comprising an ignition electrode with several electrode arms.
• the ignition electrode is made of a cross-shaped blank that is cut out of sheet metal and then the electrode arms are set upright by bending.
• US 5 554 908 A discloses a pre-combustion chamber device
• an electrode carrier extending into the pre-combustion chamber and on it at least one ignition electrode is attached, which has at least one ignition portion, which cooperates with an internal wall surface of the pre-combustion chamber in defining at least one spark gap extending substantially athwart the longitudinal axis of the pre-combustion chamber.
• the present disclosure is directed, at least in part, to improving or overcoming one or more aspects of prior systems.
• a method for manufacturing an ignition electrode of a spark plug configured to be used in an internal combustion engine and including a pre-combustion chamber.
• the ignition electrode may be configured to at least partially protrude into the pre-combustion chamber.
• the disclosed method may comprise providing a mixture of powdered metal and binder material, forming the mixture of powdered metal and binder material into a desired shape, debinding the formed mixture of powdered metal and binder material for driving off the binder material, thereby forming a blank, and sintering the blank.
• a spark plug of an internal combustion engine may comprise a spark plug main body forming at least a portion of a pre-combustion chamber, a spark plug cap attached to the spark plug body and forming at least a portion of the pre-combustion chamber, a middle electrode configured to extend through the spark plug main body and to at least partially extend into the pre-combustion chamber, and an ignition electrode according to the present disclosure, wherein the ignition electrode may be attached to the middle electrode.
• the disclosed method may be performed by the so-called metal injection molding process.
• the disclosed ignition electrode may be manufactured by the disclosed method for manufacturing an ignition electrode.
• FIG. 1 is a diagrammatic cross-sectional view of an internal
• Fig. 2 is a diagrammatic cross-sectional view of the spark plug of Fig. 1 shown in greater detail;
• Fig. 3 is a perspective view of an exemplary ignition electrode of the present disclosure.
• the present disclosure may be based in part on the realization that manufacturing an ignition electrode by a molding process may increase the degree of freedom in designing and constructing ignition electrodes.
• the shape of the electrode arms may be provided in a desired shape with desired diameters or thickness at the different positions.
• the diameter of the electrode arms may be increased at locations of high thermal and mechanical stress for preventing the electrode arms from braking off from the connecting section configured to receive the respective ends of each electrode arm.
• negative impact of, for example, the bending process of the ignition electrode which may limit the degree of freedom in providing the ignition electrode in a desired shape with respect to the bending radius, may be prevented. Therefore, the ignition electrode may be provided in a desired shape without any influence of the specific material properties.
• manufacturing an ignition electrode by a metal injection process may support in shaping and forming the ignition electrode with a desired shape. Additionally, the material composition of the ignition electrode may be adjusted as desired such that any postprocessing of the molded ignition electrode, especially any mechanical postprocessing process, may be omitted resulting in lowering the manufacturing costs and increasing the efficiency in manufacturing.
• the internal combustion engine 10 may include features not shown, such as fuel systems, air systems, cooling systems, peripheries, drivetrain components, turbochargers, etc.
• the internal combustion engine 10 is considered a four-stroke gaseous fuel internal combustion engine.
• the gaseous fuel internal combustion engine 10 may be any type of engine (turbine, gas, diesel, natural gas, propane, two- stroke, etc.) that would utilize a spark plug having an integrated pre-combustion chamber.
• the internal combustion engine 10 may be of any size, with any number of cylinders, and in any configuration ("V,” in-line, radial, etc.).
• the internal combustion engine 10 may be used to power any machine or other device, including locomotive applications, on-highway trucks or vehicles, off- highway trucks or machines, earth moving equipment, generators, aerospace applications, marine applications, pumps, stationary equipment, or other engine powered applications.
• the internal combustion engine 10 includes an engine block 12 having a plurality of cylinders 14 (one of which is illustrated in Fig. 1).
• a piston 16 is slidably disposed within the cylinder 14 to reciprocate between a top-dead- center position and a bottom-dead-center position.
• a connecting rod 18 connects the piston 16 to an eccentric crankpin 20 of a crankshaft 22 such that
• the internal combustion engine 10 also includes a cylinder head
• the cylinder head 24 engages with the engine block 12 to cover the cylinder 14, thereby defining a main combustion chamber 26.
• the cylinder head 24 defines intake and exhaust openings 28 that allow intake gases into the main combustion chamber 26 and exhaust gases out of the main combustion chamber 26, respectively.
• the engine valves 30 are positioned to selectively open and close the openings 28.
• Each cylinder 14 includes multiple intake and exhaust openings 28.
• the internal combustion engine 10 includes a series of valve
• valve actuation assemblies 40 (one of which is illustrated in Fig. 1).
• the multiple valve actuation assemblies 40 are provided per cylinder 14.
• one valve actuation assembly may be used to open and close the intake valves and another valve actuation assembly may be provided to open and close the exhaust valves.
• the valve actuation assembly 40 includes a rocker arm 46.
• the rocker arm 46 is pivotally mounted in the cylinder head 24 and attaches to the engine valves 30 at one end and attaches to a push rod 48 at the other end.
• valve actuation assembly 40 also includes valve springs 52 that bias the valves 30 toward the closed position (i.e. closing the intake and exhaust openings 28).
• crankshaft 56 The other end of the push rod 48 engages a lifter 54 which may engage a camshaft 56.
• the camshaft 56 operatively engages the crankshaft 22.
• the camshaft 56 is connected with crankshaft 22 in any manner readily apparent to one skilled in the art where rotation of the crankshaft 22 results in rotation of the camshaft 56.
• camshaft 56 may be connected to crankshaft 22 through a gear train (not shown).
• a first cam lobe 58 is disposed on the camshaft
• camshaft 56 may include additional cam lobes to engage with other lifters in order to actuate additional engine valves.
• the internal combustion engine 10 also includes a spark plug 60 having a pre-combustion chamber 66 (see Fig. 2).
• the spark plug 60 is not explicitly shown, but an ignition plug sleeve denoted with reference sign 60 is shown, which accommodates the ignition plug.
• the spark plug 60 is positioned within the cylinder head 24 between the valves 30.
• the spark plug 60 may be configured in a variety of ways. Any assembly capable of being positioned in the cylinder head 24 to support a combustion event outside of the main combustion chamber 26, and direct the combustion into the main combustion chamber 26 may be used.
• the spark plug 60 of Fig. 1 includes a spark plug main body 62 and a spark plug cap 70 attached to the spark plug main body 62.
• the spark plug main body 62 includes a threaded portion 64 configured to engage with a threaded portion of the cylinder head 24 (see Fig. 1).
• Both the spark plug main body 62 and the spark plug cap 70 may be formed by casting.
• the spark plug cap 70 may be formed by metal sintering and may consist of a material having a high thermal and mechanical stress resistance, such as, for example, a chrome-nickel alloy.
• spark plug main body 62 and the spark plug cap 70 are identical to each other.
• the spark plug main body 62 defines a first portion 68 of a pre- combustion chamber 66.
• the spark plug cap 70 defines a second portion 69 of the pre-combustion chamber 66.
• the first portion 68 and the second portion 69 are in fluid communication with each other.
• a sealing mechanism 98 may be provided at the first portion 68 of the pre-combustion chamber 66 for sealing the pre- combustion chamber 66 with respect to the upper portion of the pre-combustion chamber 66.
• At least one middle electrode 85 extends along the center axis 90 and is attached to an ignition electrode 80 including at least one electrode arm 82 at least partially extending into the first and second portions 68, 69 of the pre- combustion chamber 66.
• At least one ignition electrode 80 may be electrically connected to an engine control unit (not shown) and may be configured to generate a spark at the at least one electrode arm 82 upon an electric signal provided by the engine control unit via the middle electrode 85.
• the at least one ignition electrode 80 is connected via, for instance, a weld 83 to the middle electrode 85 supported by an insulator 84, such as, for example, a ceramic insulator.
• the weld 83 may be a laser beam weld, a friction weld, an electronic beam weld, or any other weld suitable for attaching the at least one ignition electrode 80 to the middle electrode 85.
• the spark plug cap 70 comprises a connecting portion 72 and a nozzle portion 74.
• the connecting portion 72 is configured to be inserted into a receiving portion 65 of the spark plug main body 62.
• the connecting portion 72 and the receiving portion 65 have a cylindrical shape substantially corresponding to each other, such that the connecting portion 72 of the spark plug cap 70 at least partially form-fits into the receiving portion 65 of the spark plug main body 62.
• the spark plug cap 70 is fixedly attached to the spark plug main body 62 by means of welding, such as, for example, laser beam welding. It is understood that the beam weld circumferentially extends around the entire flange formed between the bottom end of the spark plug main body 62 and a shoulder 71 of the nozzle portion 74 of the spark plug cap 70.
• the spark plug cap 70 may be fixedly attached to the spark plug main body 62 by means of, for instance, soldering or any other suitable means.
• the spark plug cap 70 may be removably attached to the spark plug main body 62 by means of, for instance, snap fit, pressure fit, or any other suitable means.
• the spark plug cap 70 comprises an inner surface 75 forming the second portion 69 of the pre-combustion chamber 66.
• the inner surface 75 includes a bottom portion 76 having a generally convex funnel-like shape. It is preferred that the bottom portion 76 is cup-like shaped having a convex form.
• the spark plug cap 70 includes an outer surface 73 configured to at least partially extend into the main combustion chamber 26 of the internal combustion engine 10.
• the spark plug cap 70 includes at least one flow channel 1 10 disposed at the nozzle portion 74.
• the at least one flow channel 1 10 is configured to fluidly connect the pre-combustion chamber 66 with the main combustion chamber 26 (see Fig. 1). It is further preferred that the at least one flow channel 110 fluidly connects the pre-combustion chamber 66 at the bottom portion 76 with the main combustion chamber 26.
• the ignition electrode 80 may include four electrode arms 82. However, in some embodiments, the ignition electrode may include, for example, five or six electrode arms 82, or any other suitable quantity of electrode arms. Each electrode arm 82 is configured to generate a spark at the portion between the inner wall of the pre-combustion chamber 66 and the electrode arm 82..
• the at least one electrode arm 82 may generally extend along the inner wall of the pre-combustion chamber 66 in direction of the spark plug cap 70.
• the at least one electrode arm 82 may include a distal end 86 and a proximal end 87 configured to be attached to a connecting section 88 of the ignition electrode 80. Therefore, the at least one electrode arm 82 may extend upright from the connecting section 88 configured to be directly attached to the middle electrode 85 via the weld 83.
• the at least one electrode arm 82 may include a longitudinal axis 92.
• the electrode arms 82 may extend upright from the connecting section 88, for example, the electrode arms 82 may perpendicular extend from the connecting section 88.
• the longitudinal axis 92 may form an angle a with the center axis 90. The angle a may range from about 0° to about 20°, such that the distal end 86 of the electrode arm 82 is closer to the inner wall of the pre-combustion chamber 66 than the proximal end 87 of the electrode arm 82.
• the spark may be generated at the gap between the distal end 86 and the inner wall of the pre-combustion chamber 66, which results in that the electrode arm 82 is worn in a direction from the distal end 86 to the proximal end 87, such that falling off of the electrode arm 82 from the connecting section 88 may be prevented. Further, due to the inclined electrode arms 82, demolding of the casted ignition electrode 80 may be facilitated.
• the ignition electrode 80 may also comprise, for example, two, three, five or six electrode arms 82 or any other suitable quantity of electrode arms 82.
• the ignition electrode 80 is provided in a cross like shape having symmetrically arranged electrode arms 82.
• the ignition electrode 80 may include six symmetrically arranged electrode arms 82 having, for instance, an angle of 60° to each other.
• the electrode arms 82 may include alternating angles of 40° and 80° to each other.
• the ignition electrode 80 may have a flat shape having a predetermined quantity of flat electrode arms 82.
• the ignition electrode 80 may comprise a cup-like shaped plate or a semispherical shape.
• the electrode arms 82 may include a
• the at least one electrode arm 82 may include a circular cross-section, an oval cross-section, or any other suitable cross-section. As further illustrated, the electrode arms 82 may include a substantially constant cross-section from the proximal end 87 to the distal end 86. However, in some embodiments, the electrode arms 82 may include a variable cross-section. For example, the cross-section of the electrode arms 82 may gradually decrease from the distal end 86 to the proximal end 87.
• the electrode arms 82 may include a diameter or thickness
• the connecting section 88 may include a thickness being substantially higher than the diameter of the electrode arms 82, as the thermal and mechanical stress at the connecting section 88 may be higher than the stress at the electrode arms. Thus, the thickness of the connecting section 88 may range from about 0.4 mm to 2.0 mm.
• the ignition electrode 80 may further include a receiving section
• the receiving section 89 for accommodating an end of the middle electrode 85.
• the receiving section 89 may be, for instance, a recess configured to accommodate an end of the middle electrode 85. Therefore, the shape of the receiving section 89 may correspond to the shape of the end of the middle electrode 85.
• the proximal ends 87 of the electrode arms 82 may have a variable cross-section. As indicated, the cross-section of the connecting section 88 may decrease from the proximal ends 87 to the receiving section 89 configured to be centered at the center axis 90 of the spark plug 60. In other words, the thickness of the connecting section 88 may be substantially larger than the thickness of the electrode arms 82. This may provide more thermal and mechanical stress resistance at the connecting section 88, as at this position, the ignition electrode 80 may be exposed to high thermal and mechanical stress.
• ignition electrode 80 may be described in greater detail with respect to Figs. 1 to 3.
• the ignition electrode 80 may be manufactured by metal sintering.
• a metal sintering process is a process in which a mixture of powdered metal and binder material is applied with heat for debinding the binder material and melting the powdered metal together for generating, for instance, a work piece with a desired shape.
• a mixture of powdered metal and binder material may be provided.
• the mixture of powdered metal and binder material may include a predetermined mixing ratio.
• the powdered metal may include transition metals selected from the group consisting of, for example, platinum, titanium, cobalt, palladium, hafnium, iridium, etc.
• the binder material may include wax materials or synthetics selected from the group consisting of, for instance, polyamide, polyethylene, polypropylene, etc..
• the binder material may be mixed with the powdered metal such that the binder material microscopically envelops the powdered metal.
• the mixture of powdered metal and binder material is formed into a desired shape. Specifically, the mixture of powdered metal and binder material is inserted into a casting mold provided in the negative shape of the desired shape. In some embodiments, the mixture of powdered metal and binder material may be injected via a so-called injection molding process. Due to subsequent heating processes, the shaped parts of the mixture of powdered metal and binder may be exposed to shrinking. Therefore, the shaped parts may be typically 10 % to 20 % larger than the finished products. The shaped parts may be referred to as "green parts".
• the depending process may start, which means that the binder is driven off from the green parts formed by the shaped powdered metal/binder material mixture.
• This may be achieved by, for example, applying heat to the casting mold.
• the applied heat may range from about 400° C to about 600° C.
• the debinding process may include applying solvents for removing most of the binder material.
• the above-mentioned debinding process may also be performed after having the casting mold evacuated, in other words in an evacuated environment.
• the parts after the debinding process may be referred to as blank or "brown parts".
• the blank obtained by the debinding process may be removed from the casting mold.
• the blank may be porous and brittle. Therefore, for increasing the strength of the blank, the blank may be sintered, which means that heat may be applied to the blank for heat-treating the same.
• the sinter heat may be higher than the applied heat during the debinding process. In some cases, the sinter heat may be in a range from about 1500° C to about 2200° C.
• the sinter heat may be configured to melt the powdered metal with each other for providing a strong composition.
• the blanks may be sintered in vacuum-type furnaces. Further, the intense heat applied to the blanks or brown parts may shrink the parts in range from about 10 % to 20 % to almost complete density. However, the shrinkage has already been taken into consideration when the green parts were shaped. Subsequently, if necessary, some secondary machining or surface treatment may be available.

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• Spark Plugs (AREA)

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• 2013
  • 2013-05-02 EP EP13720796.5A patent/EP2992579A1/de not_active Withdrawn
  • 2013-05-02 WO PCT/EP2013/001308 patent/WO2014177169A1/en active Application Filing
  • 2013-05-02 CN CN201380076092.5A patent/CN105247748A/zh active Pending

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