Patent Application
20140009058
The present disclosure relates generally to spark plugs for use in internal construction engines and, more particularly, to a spark plug having a partial shroud for improved ground electrode heat dispersion.
This section provides background information related to the present disclosure which is not necessarily prior art.
Conventional spark plugs for use in internal combustion engines generally include metal shell housing, a ceramic insulator, a center electrode, and a ground electrode. The shell housing has a threaded portion for locating an end portion of the spark plug in a combustion chamber of the engine. The insulator is fixed in the shell housing such that an end of the insulator protrudes from an end of the shell housing. The center electrode is secured in a center bore of the insulator such that a tip end of the center electrode protrudes from the end of the insulator. The ground electrode is fixed to the shell housing and has a side surface that is opposed to and spaced from the tip end of the center electrode so as to form a spark gap therebetween. By applying a high voltage across the center electrode and the ground electrode, a spark discharge takes place within the spark gap, thereby igniting the air-fuel mixture within the combustion chamber.
Spark plug technology for gasoline engines continues to develop in an effort to promote higher performance and longer service life. Following this trend, gasoline engines have also continued to develop as fuel economy and emission standards have advanced. As a result, lean burn engines now create higher combustion chamber temperatures which can directly influence spark plug performance, specifically ignitability and heat dispersion away from the ground electrode. To avoid engine damage from pre-ignition events and alleviate durability concerns, it is known that combustion chamber temperatures exceeding the ground electrode threshold must be kept to a minimum.
In an effort to address these concerns, “shrouded” spark plugs have been used in some severe engine environments to assist in dissipating heat away from the ground electrode. The concept of a shroud-type spark plug is based upon joining a shortened ground electrode to a cylindrical collar that is fixed to the shell housing and configured to completely surround the center electrode as well as some or all of the ground electrode. This shrouded shell housing configuration creates higher heat conductivity which promotes quicker heat mass transfer to the shell housing and away from the ground electrode. While shroud-type spark plugs assist in promoting improved cooling of the ground electrode, they have a negative effect on the optimal tumble pattern for the air-fuel mixture around and within the sparking area which can result in lower ignitability and less complete combustion.
Accordingly, as engine technology continues to advance, a need exists to continue development of advanced spark plug technologies directed to improved heat dissipation from the ground electrode while maintaining high ignitability for a complete burn and ensuring a long service life.
This section provides a general summary of the disclosure, and is not a comprehensive disclosure of its full scope or all of its features and advantages.
It is an aspect of the present disclosure to provide a partially-shrouded spark plug which addresses and overcomes the shortcomings of prior art spark plugs. In particular, the partially-shrouded spark plug of the present disclosure addresses ground electrode temperature reduction requirements while promoting a better air-fuel mixture tumble pattern around and within the sparking area for higher ignitability and more complete combustion.
In accordance with this and other aspects of the present disclosure, a spark plug is provided with a semi-cylindrical shroud extending from the shell housing and which is arranged and configured to allow fuel flow to reach the sparking area with an improved tumble pattern. The shroud will incorporate advanced edge profiles such as, for example, chamfers and/or fillets, to prevent localized hot spots and aid in heat transfer.
Further areas of applicability will become apparent from the description provided herein. The description and specific examples in this summary are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure.
The drawings described herein are for illustrative purposes only of selected exemplary embodiments and not all possible implementations, and are not intended to limit the scope of the present disclosure.
Example embodiments will now be described more fully with reference to the accompanying drawings. It should be understood that throughout the drawings, corresponding reference numerals indicate like or corresponding parts and features. Example embodiments are provided so that this disclosure will be thorough, and will fully convey the scope to those who are skilled in the art. Numerous specific details are set forth such as examples of specific components, devices, and methods, to provide a thorough understanding of the exemplary embodiments of the present disclosure. It will be apparent to those skilled in the art that specific details need not be employed, that example embodiments may be embodied in many different forms and that neither should be construed to limit the scope of the disclosure. In some example embodiments, well-known processes, well-known device structures, and well-known technologies may not be described in detail.
The spark plug 10 generally includes a metallic shell housing 20, an insulator 30, a center electrode 40, a ground electrode 50, a first noble metal chip 45, and a second noble metal chip 55. The metal shell housing 20 can be made of an electrically conductive material, such as, for example, a low-carbon steel. The metal shell housing 20 can be a tubular or hollow structure having a threaded portion 22 on its outer periphery for fitting the spark plug 10 into the threaded bore of the engine block. The shell housing 20 is configured to withstand the torque of tightening the spark plug 10 into the engine block, remove excess heat from the spark plug 10, and transfer the excess heat to the engine block.
The insulator 30 can be installed in the hollow shell housing 20 and is fixedly and coaxially supported therein along a central axis Y. The insulator 30 can be made of a porcelain material such as, for example, alumina ceramic. The insulator 30 may include a first or distal end 32 that protrudes outwardly from an upper end portion 24 of the shell housing 20 and second or proximal end 34 that protrudes outwardly from a cylindrical lower end portion 26 of the shell housing 20. The length of the insulator 30 can be selected to provide an appropriate length for the spark plug 10. Furthermore, an annular air pocket is formed between an inner peripheral surface 28 of the shell housing 20 and an outer peripheral surface 36 of the insulator 30.
The insulator 30 can have an axial bore 38 for fixedly retaining and encircling the center electrode 40 in an electrically insulated state and which also extends along the central axis Y. A proximal end portion 42 of the center electrode 40 may protrude from the proximal end 34 of the insulator 30 such that the center electrode 40 protrudes a predetermined distance from a terminal end surface 29 of the shell housing 20. The first noble metal chip 45 is secured (i.e., welded) to the proximal end portion 42 of the center electrode 40. The cylindrically-shaped center electrode 40 can be made to include a highly heat conductive core material and a highly heat resistant and corrosion-resistant cladding material.
As will be detailed hereinafter in greater detail, the ground electrode 50 may be joined to and extend from a shroud member 100 which extends downward from the terminal end surface 29 of the shell housing 20. The ground electrode 50 may take the form of a rectangular columnar configuration having a first portion 52 secured to the shroud member 100 extending from the shell housing 20, a second portion 54 bent in a substantially orthogonal configuration, and a third portion 56 laterally extending from the second portion 54. It is contemplated that the first portion 52 can be welded to a terminal end surface 102 of the shroud member 100 for securing the ground electrode 50 to the shell housing 20. As seen, the second noble metal chip 55 can be secured (i.e., welded) to a face surface 58 on the third portion 56 of the ground electrode 50 and is aligned relative to the first noble metal chip 45. A predetermined spark gap 60 is established between the first noble chip 45 and the second noble metal chip 55.
It is contemplated that the first and second noble metal chips 45 and 55 can be joined to the center and ground electrodes 40 and 50, respectively, using any suitable joining methodology such as laser welding, plasma welding, resistance welding and suitable adhesives. Likewise, the first portion 52 of the ground electrode 50 can be joined to the terminal end surface 102 of the shroud member 100 using any suitable joining methodology.
Referring particularly to
The semi-cylindrical shroud member 100 extends an arcuate length having an angular dimension (Ø°) which can be selected to meet specific operating and durability characteristics for the spark plug 10A. In the first exemplary embodiment shown in
Referring now specifically to
Referring now to
As noted, the arcuate length (Ø°) of the shroud member 100 extending from the shell housing 20 can be selected to inhibit undesirable pre-ignition events while promoting a more complete burn. The shroud members 100 associated with spark plugs 10A, 10B, and 10C have been illustrated for exemplary purposes only, to extend less than 180° and more specifically about 90°. Referring now to
Referring to
As noted, the angular length (Ø°) of the shroud portions 100 and 100′ can be selected to promote the delivery of the air-fuel mixture into the spark area in and around the spark gap 60 while promoting improved mass heat transfer characteristics. Specifically, the tumble and/or swirl pattern of the air-fuel mixture is not detrimentally affected by the integration of the partial shrouds 100 and 100′ into the spark plugs. It is contemplated that the partial shrouds 100 and 100′ can be formed integrally with the shell housing 20 and 20′ or, in the alternative, the partial shrouds 100 and 100′ can be formed as an independent semi-cylindrical component that is joined to the terminal end surface 29 of a non-shrouded shell housing. In such a scenario, the separate shroud component can be made of a different material than the non-shrouded shell housing if desired to modify the heat transfer characteristics.
The foregoing description of the embodiments has been provided for purposes of illustration and description. It is not intended to be exhaustive or to limit the disclosure. Individual elements or features of a particular embodiment are generally not limited to that particular embodiment, but, where applicable, are interchangeable and can be used in a selected embodiment, even if not specifically shown or described. The same may also be varied in many ways. Such variations are not to be regarded as a departure from the invention, and all such modifications are intended to be included within the scope of the invention.
