Spark plug resistor element assembly, method of manufacture thereof, and spark plug for an internal combustion engine

Abstract

The present invention relates to a spark plug resistor element assembly (20) comprising, in the following order: a combustion chamber-side conductive end portion (22), a resistor element (8) including a resistive material, and a connection-side conductive end portion (21), wherein the resistor element (8) has a porosity of less than 0.3%.

Description

[Technical field]

[0001] The present invention relates to a spark plug resistor element assembly having a uniform current density distribution and reduced electrical load, resulting in a long product durability. Furthermore, the present invention also relates to a method for producing the spark plug resistor element assembly, and to a spark plug for an internal combustion engine that is characterized in terms of an improved service life by using the spark plug resistor element assembly. [Background technology]

[0002] From the patent DE 10 200 03 133 A1 a spark plug for an internal combustion engine is known, which comprises an insulator with a hole, in which a panette is inserted, which includes a first contact panette, a second contact panette and a resistance panette located between them, the second contact panette being connected to the central electrode of the spark plug and the first contact panette being connected to an electrical terminal. The compounds and / or chemical elements used for the resistance panette are characterized by a specially adjusted electrical resistance and are formed into the resistance panette without special processing by mixing and compaction of the holes provided in the insulator of the spark plug. Typical porosities achieved in this case are in the range of more than 5%, in particular more than 10%, resulting in a relatively short useful life of the spark plug. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] DE 1020090470055 Summary of the Invention

[0004] In contrast, the spark plug resistor element assembly according to the invention as defined in claim 1 is characterised by a very good durability and long-term high performance due to a uniform current density distribution and the absence or a small number of areas of high electrical load. Furthermore, the spark plug resistor element assembly according to the invention has a low tendency to electrical malfunctions, which secondarily prevents a complete failure of the spark plug in which it is integrated.

[0005] To this end, the spark plug resistor element assembly according to the invention comprises, in the following order, an electrically conductive end portion on the combustion chamber side, an electrically resistive element comprising a resistive material, and an electrically conductive end portion on the connection side, each of which in specified use provides a good connection of the resistor element with surrounding spark plug components, such as, for example, a central electrode in the combustion chamber end portion and an electrical connection area in the connection end portion. Other components may also be provided.

[0006] The resistor element comprises a resistor material and has a porosity of less than 0.3%. This means that the resistor element may be formed from one or more resistor materials that together form the resistor element, but the porosity of the entire resistor element in the spark plug resistor element assembly is less than 0.3%. The porosity of the resistor element is then measured after its manufacture by analyzing the microstructure of a ground cross section with a scanning electron microscope (REM) (the volume fraction of the phases is determined by evaluating the microstructural images, in which case the porosity is determined as well as the second phase of the structure, see EN ISO 13383-2:2016).

[0007] Without being bound by theory, it is believed that a porosity of less than 0.3% results in a high and uniform density of the resistive material with only a small number of small cavities between the material particles. This allows the material particles in the resistive material to be in good contact with each other, so that the formation of areas of high local electrical load can be prevented or at least significantly reduced, so that electrical malfunctions are impossible. This also improves the service life of the spark plug resistor element assembly. The proper use of the spark plug resistor element assembly according to the invention therefore also improves the service life of the product into which it is incorporated.

[0008] Preferably, the spark plug resistor element assembly has an electrical resistance of 1 to 14 kΩ, in particular 3 to 10 kΩ. According to the present invention, the electrical resistance is determined at a measurement temperature of T=20° C. according to JIS B8031 (2006 edition), Ch.7.13.

[0009] The dependent claims indicate preferred developments of the invention.

[0010] According to an advantageous development, the resistor element has a porosity of at least 0.05%, whereby a lower limit of 0.05% is advantageous with respect to the simplification of the manufacture of the resistor element, as high compression would mean higher technical efforts which are directly reflected in the manufacturing costs of the spark plug resistor element assembly.

[0011] The resistor element has a porosity of 0.05 to 0.30%, particularly 0.10 to 0.25%, from the viewpoint of balancing the high manufacturing costs of the spark plug resistor element assembly with the improvement of the power density distribution.

[0012] In the case of the use of the spark plug resistor element assembly in a spark plug for an internal combustion engine, the conductive end part of the spark plug resistor element assembly facing the combustion chamber preferably comprises a contact pannette and / or the conductive end part facing the connection preferably comprises a contact pannette in order to improve the electrical connection of the resistor element with the combustion chamber or the electrical connection. A contact pannette in the sense of the present invention is in particular an element formed from electrically conductive particles, which in the specified use can be connected to the respective component to be connected in a geometrically correct manner while providing a good electrical contact with the resistor element. In particular, a composite material consisting of at least electrically insulating glass particles and an electrically conductive material, such as, for example, a metal (iron, copper, etc.) and / or a carbon-containing compound (graphite, carbon black, SiC, etc.) is conceivable.

[0013] In order to further improve the coupling of the spark plug resistor element assembly to the electrical connection, the conductive end portion facing the connection preferably comprises a contact pin, which can be formed as a bolt and can also be used for the manufacture of the spark plug resistor element assembly by contributing at the same time to the compression of the resistor material. The contact pin is most often a more or less cylindrical element of metal base, the length of which is adapted to the internal bore of the spark plug insulator, into which the spark plug resistor element assembly can be inserted.

[0014] According to another advantageous development, the contact pin adjoins, on the connection side, the contact plate on the connection side, which also serves to improve the connection to the electrical connection and to simplify the production of the preferably highly compressed resistor element.

[0015] In order to achieve a porosity of less than 0.3% in the resistor element, it is advantageously intended to use a resistor material with a maximum primary particle size of less than 10 μm. In this case, primary particle size is understood to mean the particle size of the respective starting materials before mixing and forming the resistor element. If two or more resistor materials are used, each of the resistor materials used has a primary particle size of less than 10 μm. Resistance materials with a primary particle size of less than 10 μm are made particularly easy to process into compactable and highly compacted resistor elements. According to the invention, the primary particle size is determined by analyzing the microstructure of the ground cross section with a scanning electron microscope (REM), i.e. by determining the grain size and grain size distribution according to method B of Ch. 9.3 of EN ISO 13383-1:2012.

[0016] In view of good processability while avoiding dust generation, in particular resistive materials are used which have a minimum primary particle size of 5 nm, in particular 10 nm.

[0017] Taking into account the above effects of the minimum and maximum primary particle size of the resistor material, the resistor material has a primary particle size of 5 nm to less than 10 μm, particularly 10 nm to less than 10 μm, and especially 100 nm to 5 μm. These materials are easy to manufacture, easy to handle, and have little tendency to generate dust. In that case, all the above size statements apply to all resistor materials used in spark plug resistor element assemblies.

[0018] Resistive materials include borosilicate glass and ZrO2 due to their very good tunability of the pre-determined resistance value. Other compounds and elements may be included, for example carbon-based substances such as carbon or titanium dioxide.

[0019] The invention further discloses a method for manufacturing the above-mentioned spark plug resistor element assembly. According to the invention, the method comprises a step of grinding the resistor material to a primary particle size of less than 10 μm, in particular 5 nm to 10 μm, in particular 10 nm to 10 μm, in particular 100 nm to 5 μm. The grinding, which can be carried out with any device, for example a bead mill or an agitated ball mill, results in a very high degree of compression of the resistor material for forming the resistor element. Only a small number of voids can be formed between the individual particles during the molding or forming of the resistor element, which mainly results in a porosity of the resistor element of less than 0.3%, which results in a particularly uniform current density distribution when the spark plug resistor element assembly is assembled in a spark plug of an internal combustion engine. By incorporating the resistor material ground according to the invention into the resistor element, the formation of areas of high local electrical loads can be effectively prevented. The method is highly efficient and technically easy to realize.

[0020] In addition to the above steps, further method steps can follow, such as, for example, arranging the conductive end part on the combustion chamber side and the conductive end part on the connection side in the resistor element. It is also possible to carry out compression molding of the resistor material to form the resistor element, for example by means of contact pins which are inserted from each side of the conductive end part on the connection side.

[0021] The present invention further discloses a spark plug for an internal combustion engine comprising a spark plug resistor element assembly as described above. By incorporating the spark plug resistor element assembly of the present invention into the spark plug of the present invention, electrical malfunctions are avoided and a uniform current density distribution is achieved, thereby increasing the useful life or service life of the spark plug.

[0022] Besides the spark plug resistor assembly according to the invention, the spark plug may comprise further components, such as a housing comprising a center electrode, a ground electrode, an insulator, the spark plug resistor assembly being arranged in a bore of the insulator and connected to the center electrode on the combustion chamber side and to an electrical connection of the spark plug on the connection side. [Brief description of the drawings]

[0023] [Figure 1] 1 is a partial cross-sectional view of a spark plug according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0024] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

[0025] 1 shows a spark plug 1 according to one embodiment. The spark plug 1 has an insulator 2, a housing 3, a contact pin 7 formed as a terminal, a spark plug resistor element assembly 20, a center electrode 9, a ground electrode 10, and a connecting nut 18. The insulator 2 has a cavity 6 which is continuous throughout its entire length. The center electrode 9, the spark plug resistor element assembly 20, and the contact pin 7 are inserted in this cavity 6 in that order. Reference numeral 5 denotes an insulator head.

[0026] A connection nut 18 is screwed onto the outer terminal of the insulator 2. The spark plug resistor element assembly 20 includes a conductive end portion 21 on the connection side formed as a first contact panart, a conductive end portion 22 on the combustion chamber side formed as a second contact panart, and a resistor element 8 disposed between the first and second contact panarts.

[0027] The cavity 6 in the insulator is cylindrical and extends from the starting end (farther from the combustion chamber) on the connection side of the insulator 2 to a tapered section 12 formed in multiple steps. In the multiple tapered section 12, the cavity 6 of the insulator 2 provides a seat for the center electrode head 13 of the center electrode 9.

[0028] The spark plug resistor element assembly 20 extends from approximately the center of the insulator shoulder 4 to a multi-step transition 12. In the region of the transition 12, preferably only the second contact plate and no resistor element 8 is provided, so that the dispersion of the resistance values ​​is as large as possible.

[0029] On the side closer to the combustion chamber, the central electrode head 13 is inserted into the second contact pannel, and on the side further from the combustion chamber, the terminal is inserted into the first contact pannel.

[0030] The spark plug resistor element assembly 20 comprises a resistor material which is preferably poured into the cavity 6 and formed into the resistor element 8 after solidification.

[0031] The terminal is embedded in the first contact pannel and fixedly connected to the completed spark plug resistor element assembly 20.

[0032] A housing 3 is seated on the outside of the insulator 2. This housing 3 extends from the connection side (away from the combustion chamber) of the insulator shoulder 4 to the combustion chamber end of the insulator 2. At this combustion chamber end of the insulator 2, a ground electrode 10 is attached to the housing 3. The housing 3 further comprises an external hexagonal bolt 14, an external thread 15 and peripheral collars 16. The external hexagonal bolt 14 and the thread 15 are used to screw the spark plug 1 into an internal combustion engine, in particular into a cylinder head.

[0033] At the connection end, the terminal projects from the insulator 2 by a projection 17 which is provided with a thread onto which a connection nut 18 is screwed. The length of the projection 17 is selected so that it forms a flush end 11 with the connection nut 18.

[0034] The resistive element 8 comprises a resistive material, in particular borosilicate glass and ZrO2, ZrO2 being a ceramic material. In addition thereto, the resistive material may comprise further components, such as, for example, carbon black or other conductive carbon materials. The resistive material, or all resistive materials used for the resistive element 8, have a maximum primary particle size of less than 10 μm before being processed into the resistive element 8, in particular a minimum primary particle size of 0.5 nm, in particular 5 nm, in particular 10 nm. The desired particle size can be achieved by grinding the respective resistive material.

[0035] The resistor element 8 is formed from a crushed resistor material or crushed resistor materials, in particular by pouring and / or compacting into the cavity 6, the porosity of the resistor element 8 being less than 0.3%, in particular between 0.05 and 0.28%, resulting in a highly compacted resistor element 8, in which the particles of the resistor material are very close to one another and few inter-particle voids are present, thereby resulting in a very uniform current density distribution, which is characterized by a low number of electrical malfunctions and which thereby gives the spark plug resistor element assembly 20, and thus the spark plug 1, a long useful life and a long service life. [Explanation of symbols]

[0036] 1 Spark plug 2. Insulator 3. Housing 4 Insulating shoulder 5 Insulator Head 6 cavities 7 Contact pin 8 Resistance elements 9 Center electrode 10 Ground electrode 11 Terminal 12 Tapered section, transition section 13 Center electrode head 14 Outer hex bolt 15 External Thread 16 Periphery Color 17 Protrusion 18 Connecting nut 20 Spark plug resistor element assembly 21 Conductive end portion on the connection side 22 Conductive end portion on the combustion chamber side

Claims

1. A spark plug resistor element assembly comprising: an electrically conductive end part (22) facing the combustion chamber; - a resistive element (8) comprising a resistive material, - a conductive end portion (21) on the connection side, A spark plug resistor element assembly, wherein the resistor element (8) has a porosity of less than 0.3%.

2. 2. The spark plug resistor element assembly of claim 1, wherein the resistor element (8) has a porosity of at least 0.05%.

3. Spark plug resistor element assembly according to claim 1 or 2, wherein the resistor element (8) has a porosity of 0.05 to 0.30%, in particular 0.10 to 0.25%.

4. 4. A spark plug resistor element assembly according to claim 1, wherein the conductive end portion (22) on the combustion chamber side comprises a contact pannel and / or the conductive end portion (21) on the connection side comprises a contact pannel.

5. 5. A spark plug resistor element assembly according to claim 1, wherein the connection-side conductive end portion (21) comprises a contact pin (7).

6. 5. A spark plug resistor element assembly according to claim 4, wherein the contact pin (7) adjoins, on the connection side, the contact pant (21) on the connection side.

7. 7. A spark plug resistor element assembly as claimed in claim 1, wherein the resistor material has a maximum primary particle size of less than 10 microns.

8. 8. Spark plug resistor element assembly according to claim 7, wherein the resistor material has a minimum primary particle size of 0.5 nm, in particular 5 nm, or in particular 10 nm.

9. 9. Spark plug resistor element assembly according to claim 7 or 8, wherein the resistor material has a primary particle size of ≥ 5 nm and < 10 μm, in particular ≥ 10 nm and < 10 μm, in particular ≥ 100 nm and < 5 μm.

10. The resistive material is borosilicate glass and ZrO ２ 10. A spark plug resistor element assembly as claimed in any preceding claim, comprising:

11. 11. A method for manufacturing a spark plug resistor element assembly (20) according to any one of claims 1 to 10, comprising the step of grinding the resistor material to a primary particle size of less than 10 μm, in particular ≥ 5 nm and < 10 μm, in particular ≥ 10 nm and < 10 μm, in particular ≥ 100 nm and < 5 μm.

12. A spark plug for an internal combustion engine comprising a spark plug resistor assembly (20) according to any one of claims 1 to 10.

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