What is claimed is:
1. A gas charging device which reversely supplies fresh gas from a gas outlet (7b) of a pressure reducing valve (7) to a gas inlet (7a) thereof, a pressure reducing member (17) of the pressure reducing valve (7) having a communication passage (30) which communicates the gas outlet (7b) with an actuation chamber (29), the communication passage (30) having a peripheral wall (30a) provided in its end surface with a portion (43) to be sealed, which faces the gas outlet (7b), the pressure reducing member (17) separating from a pressure reducing valve seat (18) with a pressure of the gas inlet (7a) and coming close to the pressure reducing valve seat (18) by a pressure of the actuation chamber (29), the gas charging device comprising:
a charging nozzle (34) which has a nozzle leading end portion (45);
a charging passage (35) provided within the charging nozzle (34) and communicating with the gas outlet (7b),
a push member (37) attached to the charging nozzle (34) and having a projection (40) which sticks out toward the pressure reducing member (17) ahead of the nozzle leading end portion (45); and
a sealing means (41) provided in the projection (40) and directed from the gas outlet (7b) to the actuation chamber (29) so that it comes into sealing contact with the portion (43) to be sealed, thereby inhibiting the fresh gas supplied to the gas outlet (7b) from flowing into the actuation chamber (29).
2. The gas charging device as set forth in claim 1, wherein the push member (37) is supported by the charging nozzle (34) so that it advances and retreats with respect to the pressure reducing member (17) and is urged toward the pressure reducing member (17) by an urging means (38).
3. The gas charging device as set forth in claim 1, wherein the charging nozzle (34) has the nozzle leading end portion (45) provided with a gas discharge port (46) which communicates the charging passage (35) within the charging nozzle (34), with the gas outlet (7b).
4. The gas charging device as set forth in claim 1, wherein the projection (40) of the push member (37) is formed cylindrical and has a cylindrical wall provided with a gas discharge port (47) which communicates the charging passage (35) within the charging nozzle (34), with the gas outlet (7b).
5. The gas charging device as set forth in claim 2, wherein the charging nozzle (34) has the nozzle leading end portion (45) provided with a gas discharge port (46) which communicates the charging passage (35) within the charging nozzle (34), with the gas outlet (7b).
6. The gas charging device as set forth in claim 2, wherein the projection (40) of the push member (37) is formed cylindrical and has a cylindrical wall provided with a gas discharge port (47) which communicates the charging passage (35) within the charging nozzle (34), with the gas outlet (7b).
The claims below are in addition to those above.
All refrences to claim(s) which appear below refer to the numbering after this setence.
What is claimed is:
1. A spark plug comprising:
a metal housing;
a porcelain insulator installed in said metal housing;
a center electrode retained within said porcelain insulator, said center electrode having a length and a tip portion projecting from a tip of said porcelain insulator;
a shoulder formed on a side wall of said center electrode to define a large-diameter portion and a small-diameter portion of said center electrode, said shoulder tapering off to the tip portion of said center electrode and having a boundary leading to the large-diameter portion located inside said porcelain insulator;
a first ground electrode installed on said metal housing which has an end portion opposed to the tip portion of said center electrode to define a first spark gap therebetween;
a second ground electrode installed on said metal housing which has an end arranged outside the tip of said porcelain insulator and opposed over the tip of said porcelain insulator to a portion of the side wall of said center electrode to define a second spark gap in which sparks are to be generated to burn away carbon adhered to a surface of the tip of said porcelain insulator, resulting in a decrease in insulation resistance offered by said porcelain insulator; and
a wear resisting member provided on said portion of the side wall of said center electrode for offering resistance to wear caused by the sparks generated in the second spark gap.
2. A spark plug as set forth in claim 1, wherein if an interval between an inner wall of said porcelain insulator and the side wall of said center electrode is defined as d, and a circle is defined which has a center on an inside corner of the tip of said porcelain insulator facing said center electrode and a radius R defined on a plane including a longitudinal center line of the spark plug, the interval d is the radius R plus 1 mm, and said wear resisting member is located at least inside the circle.
3. A spark plug as set forth in claim 1, wherein said wear resisting member has a width which is opposed to said center electrode and greater than or equal to 0.5 mm.
4. A spark plug as set forth in claim 3, wherein said wear resisting member is provided over an entire periphery of the side wall of said center electrode.
5. A spark plug as set forth in claim 1, wherein said wear resisting member has a surface substantially lying flush with a surface of the side wall of said center electrode.
6. A spark plug as set forth in claim 1, wherein said wear resisting member is made of a metallic material which is higher in melting point than an Ni alloy.
7. A spark plug as set forth in claim 6, wherein said metallic material is one of a Pt alloy and an Ir alloy.
8. A method of producing a spark plug including: (a) a metal housing; (b) a porcelain insulator installed in said metal housing; (c) a center electrode which is retained within the porcelain insulator and has a tip portion projecting from a tip of said porcelain insulator; (d) a first ground electrode installed on the metal housing which has an end portion opposed to the tip portion of the center electrode; and (e) a second ground electrode installed on the metal housing which has an end arranged outside the tip of the porcelain insulator and opposed over the tip of the porcelain insulator to a portion of a side wall of the center electrode, the method comprising the steps of:
preparing a center electrode material for making the center electrode;
machining said center electrode material to form a large-diameter portion, a small-diameter portion closer than the large-diameter portion to a tip of said center electrode material, and a shoulder between the large-diameter and the small-diameter portions; and
welding a wear resisting member to the shoulder of said center electrode material:
9. A method as set forth in claim 8, further comprising the step of machining said center electrode material and said wear resisting member welded to the shoulder of said center electrode material to establish a desired shape of the center electrode.
10. A method as set forth in claim 8, further comprising the step of welding a noble metal chip to a tip of the center electrode.
11. A method of producing a spark plug including: (a) a metal housing; (b) a porcelain insulator installed in said metal housing; (c) a center electrode which is retained within the porcelain insulator and has a tip portion projecting from a tip of said porcelain insulator; (d) a first ground electrode installed on the metal housing which has an end portion opposed to the tip portion of the center electrode; and (e) a second ground electrode installed on the metal housing which has an end arranged outside the tip of the porcelain insulator and opposed over the tip of the porcelain insulator to a portion of a side wall of the center electrode, the method comprising the steps of:
preparing a ring-shaped wear resisting member working to provide resistance to spark-caused wear;
preparing a center electrode material for making the center electrode;
machining said center electrode material to form a large-diameter portion, a small-diameter portion closer than the large-diameter portion to a tip of said center electrode material, and a shoulder between the large-diameter and the small-diameter portions; and
welding said ring-shaped wear resisting member to the shoulder of said center electrode material:
12. A method as set forth in claim 11, further comprising the step of machining said center electrode material and said ring-shaped wear resisting member welded to the shoulder of said center electrode material to establish a desired shape of the center electrode.
13. A method as set forth in claim 11, further comprising the step of welding a noble metal chip to a tip of the center electrode.