Source: http://patents.com/us-10439367.html
Timestamp: 2019-10-17 10:53:33
Document Index: 319593078

Matched Legal Cases: ['art.\n2', 'Application No. 2016', 'art 32', 'art 31', 'art 31', 'art 31', 'art 32', 'art 32', 'art 32', 'art 31', 'art 32', 'art 31', 'art 32', 'art 31', 'art 32', 'art 32', 'art 31', 'art 31', 'art 32', 'art 31', 'art 31', 'art 31', 'art 32', 'art 31', 'art 31', 'art 32', 'art 32', 'art 31', 'art 31', 'art 31', 'art 31', 'art 32', 'art 31', 'art 31']

US Patent # 1,043,9367. Ignition plug for an internal combustion engine and method for manufacturing the same - Patents.com
United States Patent 10,439,367
Tamura , et al. October 8, 2019
Tamura; Masayuki (Kariya, JP), Abe; Nobuo (Kariya, JP), Shibata; Masamichi (Kariya, JP)
Family ID: 1000004329416
16/088,971
PCT/JP2017/012156
WO2017/170273
US 20190214795 A1 Jul 11, 2019
Mar 29, 2016 [JP] 2016-066269
Current CPC Class: H01T 13/39 (20130101); H01T 13/08 (20130101); H01T 13/32 (20130101); H01T 21/02 (20130101)
Current International Class: H01T 13/34 (20060101); H01T 13/52 (20060101); H01T 13/08 (20060101); H01T 13/39 (20060101); H01T 21/02 (20060101); H01T 13/32 (20060101)
8760045 June 2014 Kawashima
9929542 March 2018 Araya
2010/0213812 August 2010 Kawashima et al.
2010/0289397 November 2010 Hanashi et al.
2011/0210659 September 2011 Suzuki et al.
2011/0316408 December 2011 Suzuki
2012/0190266 July 2012 Hanashi et al.
5545166 Jul 2014 JP
1. An ignition plug for an internal combustion engine comprising: a center electrode; a ground electrode that is disposed opposing the center electrode to form a discharge gap between the center electrode and the ground electrode; and an electrode protrusion that protrudes from an electrode base material of the ground electrode toward the discharge gap, wherein the electrode protrusion has a base part that is integrated with the electrode base material and a cover part that is joined to the base part and faces the discharge gap, the base part has an end surface facing a protrusion direction of the base part and a side peripheral surface that leads from an outer edge of the end surface to the electrode base material, the outer edge of the end surface forming a curved surface, the cover part is formed from a precious metal or a precious metal alloy having a lower linear expansion coefficient than that of a material for forming the base part and covers at least a part of the side peripheral surface and the end surface, and when the ignition plug is attached to an internal combustion engine and the electrode protrusion is heated and then cooled in a cylinder, a projection is formed on an outer surface of a portion of the cover part covering the side peripheral surface of the base part.
2. The ignition plug for an internal combustion engine according to claim 1, wherein a difference .alpha. in linear expansion coefficient between the material for forming the cover part and the material for forming the base part satisfies 3.3.times.10.sup.-6/K.ltoreq..alpha..ltoreq.4.5.times.10.sup.-6/K.
3. The ignition plug for an internal combustion engine according to claim 1, wherein a curvature radius R of the outer edge of the end surface satisfies 0.1 mm.ltoreq.R.
4. The ignition plug for an internal combustion engine according to claim 1, wherein the curvature radius R of the outer edge of the end surface satisfies 0.1 mm.ltoreq.R.ltoreq.0.45 mm.
5. The ignition plug for an internal combustion engine according to claim 1, wherein a height H of the projection and the curvature radius R of the outer edge of the end surface satisfy 0.05 mm.ltoreq.H.ltoreq.-0.067R+0.227 mm.
6. The ignition plug for an internal combustion engine according to claim 1, wherein the material for forming the base part is nickel or a nickel alloy, and the material for forming the cover part is platinum, a platinum alloy, iridium, an iridium alloy, or a platinum-iridium alloy.
7. A method for manufacturing the ignition plug for the internal combustion engine according to claim 1, wherein the method comprises: a joint step of joining a cover part raw material formed from a precious metal or a precious metal alloy lower in linear expansion coefficient than a material for forming the electrode base material to the electrode base material by resistance welding; a preparation step of setting a first jig with a concave portion along the cover part raw material joined to the electrode base material to form a space between the cover part raw material and the concave portion; and an extrusion step of pressing a second jig with a convex portion larger than an opening in the concave portion against the concave portion at a portion of the electrode base material on the side opposite to a raw material joint part joined to the cover part raw material to extrude the raw material joint part into the space and form a convex base part and forming a cover part in which the cover part raw material covers at least a part of a side peripheral surface and an end surface facing the protrusion direction of the base part, thereby forming the electrode protrusion.
8. The method for manufacturing the ignition plug for the internal combustion engine according to claim 7, wherein the first jig is set along the cover part raw material such that the cover part raw material covers the opening in the preparation step.
This application is the U.S. national phase of International Application No. PCT/JP2017/012156 filed on Mar. 24, 2017 which designated the U.S. and claims priority to Japanese Patent Application No. 2016-66269 filed on Mar. 29, 2016, the entire contents of each of which are incorporated herein by reference.
Another aspect of the present disclosure is a method for manufacturing the ignition plug for the internal combustion engine. The method includes: a joint step of joining a cover part raw material formed from a precious metal or a precious metal alloy having a lower linear expansion coefficient than that of a material for forming the electrode base material to the electrode base material by resistance welding; a preparation step of setting a first jig with a concave portion along the cover part raw material joined to the electrode base material to form a space between the cover part raw material and the concave portion; and an extrusion step of pressing a second jig with a convex portion larger than an opening in the concave portion against the concave portion at a portion of the electrode base material on the side opposite to a raw material joint part joined to the cover part raw material to extrude the raw material joint part into the space and form a convex base part and forming a cover part in which the cover part raw material covers at least a part of a side peripheral surface and an end surface facing the protrusion direction of the base part, thereby forming the electrode protrusion.
An ignition plug 1 for an internal combustion engine in the embodiment (hereinafter, also called "ignition plug 1") includes a center electrode 2 and a ground electrode 3 as illustrated in FIG. 1. The ground electrode 3 is opposed to the center electrode 2 to form a discharge gap G between the ground electrode 3 and the center electrode 2. The ground electrode 3 has an electrode protrusion 30 that protrudes from an electrode base material 3a toward the discharge gap G.
As illustrated in FIG. 2, the outer edge 34 of the end surface 33 has a curved surface that leads to the side peripheral surface 35 substantially parallel to the protrusion direction Y2. A cross section of the outer edge 34 including the plug central axis 1a preferably has a curvature radius R of 0.1 mm.ltoreq.R, more preferably 0.1 mm.ltoreq.R.ltoreq.0.45 mm.
The cover part 32 is formed from a precious metal or a precious metal alloy having the lower linear expansion coefficient than that of the material for forming the base part 31. In the present embodiment, the material for forming the base part 31 may be, for example, nickel (Ni) with a linear expansion coefficient (10.sup.-6/K) of 13.3, copper (Cu) with a linear expansion coefficient (10.sup.-6/K) of 16.5, iron (Fe) with a linear expansion coefficient (10.sup.-6/K) of 11.8, or a nickel alloy, a copper alloy, or an iron alloy with a linear expansion coefficient (10.sup.-6/K) of about 10 to 18. In the present embodiment, Inconel 600 ("Inconel" is a registered trademark) of Special Metals Corporation, which is a nickel alloy with a linear expansion coefficient (10.sup.-6/K) of 12.8, is used as the material for forming the base part 31.
The material for forming the cover part 32 may be a precious metal or a precious metal alloy such as platinum (Pt) with a linear expansion coefficient (10.sup.-6/K) of 8.9, iridium (Ir) with a linear expansion coefficient (10.sup.-6/K) of 6.5, or a platinum alloy, an iridium alloy, or a platinum-iridium alloy with a linear expansion coefficient (10.sup.-6/K) of less than 10. In the present embodiment, platinum is used as material for forming the cover part 32. A difference .alpha. in linear expansion coefficient between the material for forming the cover part 32 and the material for forming the base part 31 preferably satisfies 3.3.times.10.sup.-6/K.ltoreq..alpha..ltoreq.4.5.times.10.sup.-6- /K, and is 3.9.times.10.sup.-6/K in the present embodiment.
The process of formation of the projection 36 is as described below. First, as illustrated in FIGS. 4(a), 5(a), and 5(b), the outer surface 37 of the cover part 32 does not have yet the projection 36 in the initial state. Then, the ignition plug 1 is attached to the internal combustion engine not illustrated, the electrode protrusion 30 is heated at a high temperature in the cylinder to expand the base part 31 and the cover part 32. The expansion takes place by heating at about 800.quadrature., for example.
As illustrated in FIG. 3, in the present embodiment, the height H (mm) of the projection 36, that is, an amount of protrusion in a direction orthogonal to the plug axial direction Y preferably satisfies H.ltoreq.-0.067R+0.227 where the curvature radius of the outer edge 34 is designated as R (mm). In the present embodiment, H is 0.2 mm.
In the joint step S1, as illustrated in FIG. 8(a), a cover part raw material 32a is joined to the electrode base material 3a of the ground electrode 3 by resistance welding. In the present embodiment, the cover part raw material 32a is formed from platinum as a precious metal having a lower linear expansion coefficient than that of Inconel 600 ("Inconel" is a registered trademark) of Special Metals Corporation, which is the material for forming the electrode base material 3a.
Test examples 1 to 3 for the evaluation test 1 were configured as described below. That is, the test example 1 was the ignition plug 1 in the embodiment with a difference .alpha. in linear expansion coefficient of 3.3.times.10.sup.-6/K between the base part 31 and the cover part 32, the test example 2 was the ignition plug 1 in the embodiment with a difference .alpha. of 3.8.times.10.sup.-6/K, and the test example 3 was the ignition plug 1 in the embodiment with a difference .alpha. of 4.5.times.10.sup.-6/K.
As test conditions, in one cycle, the ignition plugs of the test examples 1 to 3 were set in a temperature-controllable cooling/heating bench, heated with a temperature increase from ambient temperature to 900.degree. C., and then cooled to the ambient temperature again. The test examples 1 to 3 were subjected to 200 cycles. During the execution of 200 cycles, the test example without cracks was evaluated as good (.smallcircle.) and the test example with cracks in the projection 36 was evaluated as poor (x). Table 1 below indicates the test results and FIG. 9 illustrates the test results in graph form.
TABLE-US-00001 TABLE 1 Difference in linear Curvature radius Evaluation result expansion coefficient of outer edge Height of projection (with cracks: x) .alpha. (10-6/K) R (mm) H (mm) (without cracks: .smallcircle.) Test example 1 3.3 0.05 0.054 x 0.10 0.050 .smallcircle. 0.20 0.043 .smallcircle. 0.30 0.036 .smallcircle. 0.40 0.030 .smallcircle. 0.45 0.026 .smallcircle. Test example 2 3.8 0.05 0.054 x 0.10 0.050 .smallcircle. 0.20 0.043 .smallcircle. 0.30 0.036 .smallcircle. 0.40 0.030 .smallcircle. 0.45 0.026 .smallcircle. Test example 3 4.5 0.05 0.054 x 0.10 0.050 .smallcircle. 0.20 0.043 .smallcircle. 0.30 0.036 .smallcircle. 0.40 0.030 .smallcircle. 0.45 0.026 .smallcircle.
At the evaluation test 1, all the test examples 1 to 3 had cracks in the projection 36 and were rated as poor (x) when the curvature radius R of the outer edge 34 was 0.05 mm, whereas all the test examples 1 to 3 had no cracks in the projection 36 and were rated as good (.smallcircle.) when the curvature radius R of the outer edge 34 fallen within a range of 0.1 to 0.45 mm.
Referring to FIG. 9, the test example 3 with the expansion coefficient difference .alpha. of 4.5.times.10.sup.-6/K had an approximate straight line L expressed as H=-0.067R+0.227. According to the evaluation result 1, it has been revealed that the good ignition plug 1 can be obtained with no cracks in the projection 36 when 0.1.ltoreq.R and H.ltoreq.-0.067R+0.227.
Accordingly, the evaluation tests 1 and 2 have revealed that satisfying 3.3.times.10.sup.-6/K.ltoreq..alpha..ltoreq.4.5.times.10.sup.-6/K would ensure the difference .alpha. in linear expansion coefficient between the material for forming the cover part 32 and the material for forming the base part 31 to form the projection 36 in a reliable manner by heating and cooling.
Further, the test results have shown that ignition performance would be further improved by the curvature radius R of the outer edge 34 of the end surface 33 of the base part 31 satisfying 0.1 mm.ltoreq.R. Moreover, the test results have revealed that ignition performance would be reliably improved by the curvature radius R of the outer edge 34 satisfying 0.1 mm.ltoreq.R.ltoreq.0.45 mm.
In addition, the test results have demonstrated that the projection 36 would have no cracks but ignition performance would be improved by the height H of the projection 36 and the curvature radius R of the outer edge 34 of the end surface 33 satisfying 0.05 mm.ltoreq.H.ltoreq.-0.067R+0.227 mm.
In addition, the precious metal or the precious metal alloy for forming the cover part 32 has lower linear expansion coefficient than that of the material for forming the base part 31, and thus there occurs the difference .alpha. in linear expansion coefficient between the two parts. However, the outer edge 34 of the end surface 33 of the base part 31 has a curved surface in the protrusion direction that makes it less likely to form corners in the joint portion between the base part 31 and the cover part 32 covering the base part 31. This suppresses excessive concentration of thermal stress from occurring resulting from the difference .alpha. in linear expansion coefficient. As a result, the occurrence of cracks due to thermal stress is suppressed from occurring in the joint portion between the base part 31 and the cover part 32 to achieve a longer lifetime of the ignition plug 1 from this viewpoint as well.
Further, when the ignition plug 1 is attached to an internal combustion engine and the electrode protrusion 30 is heated and cooled in a cylinder, the portion 37 of the cover part 32 covering the side peripheral surface 35 of the base part 31 is formed with the projection 36. Accordingly, in a lean-combustion engine with a fast airflow in a cylinder, even when the spark discharge P generated in the discharge gap G starts to move to the base part 31 side due to the high-velocity airflow, the spark discharge P is likely to concentrate on the projection 36 of the portion 37 covering the side peripheral surface 35 of the base part 31, which prevents the discharge path from becoming lengthen excessively. This suppresses the spark discharge P from being blown-off. As a result, the ignition performance is improved. The projection 36 is formed resulting from the difference .alpha. in linear expansion coefficient between the materials for forming the base part 31 and the cover part 32.
In addition, in the ignition plug 1 of the present embodiment, the material for forming the base part 31 is a nickel alloy, and the material for forming the base part 31 is platinum. Accordingly, the difference .alpha. in expansion coefficient between the two parts satisfies 3.3.times.10.sup.-6/K.ltoreq..alpha..ltoreq.4.5.times.10.sup.-6/K described above. As a result, the difference .alpha. in linear expansion coefficient is ensured to form the projection 36 in a reliable manner by heating and cooling.
According to the method for manufacturing the ignition plug 1 for the internal combustion engine of the present embodiment, the cover part raw material 32a is joined to the electrode base material 3a by resistance welding in the joint step S1. Accordingly, the cover part raw material 32a and the electrode base material 3a do not have an intermediate layer therebetween that would be formed by melt-mixing the two materials in a case of using laser welding or electronic beam welding, but has an interface therebetween. Therefore, when the ignition plug 1 is attached to the internal combustion engine and the electrode protrusion 30 is heated and cooled in the cylinder, the ignition plug 1 has the projection 36 formed in a reliable manner in the presence of the difference .alpha. in linear expansion coefficient between the materials for forming the two parts. This facilitates the manufacture of the ignition plug 1 in the embodiment.
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