Source: http://www.google.com/patents/US4317267
Timestamp: 2018-01-23 12:21:22
Document Index: 307779424

Matched Legal Cases: ['art 3', 'art 3', 'arts 6', 'art 5', 'art 5', 'art 3']

Patent US4317267 - Method for making valve moving push rod for internal combustion engines - Google Patents
This invention is made with a view to increasing the fusing strength of an end piece in a valve moving push rod for internal combustion engines. The fusing part of the push rod according to the present invention consists of an α-martensite structure and a primary truestite structure in a cotransition...http://www.google.com/patents/US4317267?utm_source=gb-gplus-sharePatent US4317267 - Method for making valve moving push rod for internal combustion engines
Publication number US4317267 A
Application number US 06/136,357
Publication number 06136357, 136357, US 4317267 A, US 4317267A, US-A-4317267, US4317267 A, US4317267A
Original Assignee Usui Kokusai Sangyo, K.K.
Patent Citations (11), Non-Patent Citations (2), Referenced by (5), Classifications (11)
US 4317267 A
This invention is made with a view to increasing the fusing strength of an end piece in a valve moving push rod for internal combustion engines. The fusing part of the push rod according to the present invention consists of an α-martensite structure and a primary truestite structure in a cotransition boundary range of a segmental section formed into the hardened layer of the end piece from the fused boundary surface of the end piece with a tube end part and is provided with a tough mixed layer arcuated from the inside end part of the above mentioned fused boundary surface to the outside end part thereof. This mixed layer is obtained by reducing by a heat feeding means a quick temperature drop caused by the fusing part simultaneously with cutting off the fusing current in welding by electric resistance the end piece on the fixed side surface to the peripheral edge of the end port of a tube material. Such crack as is recognized in the fusing part of a conventional product is not recognized in a product obtained by reducing the quick cooling by this method.
1. A method of manufacturing an improved valve moving push rod for an internal combustion engine wherein each push rod consists of a steel tube material welded by electric resistance to an end piece, said steel tube material having at one end an annular port, while the end piece has an end surface made of one of a concave or convex arcuate surface and a fixed side surface made of a flat surface, said end piece having a peripheral wall surface formed with a carbon-hardened layer, said annular port being welded to said fixed side surface of said end piece so that a cotransition boundary range including a fusing boundary surface is formed annularly about the periphery of said port at the end of said steel tube material and extends in a segmental section into said carbon-hardened layer, said method comprising the steps of:
providing a steel tube and an end piece having a carbon hardened layer on the peripheral wall surface of said fixed side surface;
bringing the carbon hardened layer of the fixed side surface of said end piece into contact with the periphery of the annular port of said steel tube material;
welding said contacted members by instantaneously passing a welding current therethrough in such manner as to confine the expansion of the cotransition boundary range for both inside and outside of the tube so as to be limited within the fusing boundary layer; and
high frequency electrically heating the contacted members simultaneously with cutting off of the welding current, thereby reducing the quick temperature drop which would otherwise be effected in the fused parts so as to inhibit the generation of cracks therein.
The present invention is made to solve such problem. Its subject matter shall be explained with reference to the drawings in the following.
FIG. 1 is an elevation showing an embodiment of the push rod according to the present invention.
In FIGS. 1 and 2, reference numeral 1 indicates a steel tube material and 2 indicates an end piece having the end surface 2' formed to be a concave arcuate surface 2a or a convex arcuate surface 2b and having the fixing side surface 2" made flat 2c. Said piece 2 is welded by electric resistance to the peripheral edge 1a' of the port at the end of the steel tube material 1. The one illustrated in FIG. 1 has at one end an end piece having the end surface 2' formed to be a concave arcuate surface 2a and is provided at the other end with an end piece of a convex arcuate surface 2b.
In both cases of the product of the present invention and the conventional product, the valve moving push rod is made by bringing the peripheral edge 1a' of the port at the end of the steel tube material into contact with the fixed side surface 2" of the end piece as illustrated in FIG. 4 and resistance-welding them by instantaneously passing a high current as a fusing current through them but the cooling method after cutting off the current is different. The conventional product is obtained by natural air-cooling but such fusing part 3 on the end piece side as is obtained by air-cooling consists of an α-martensite layer as illustrated in FIG. 3, is hard and brittle and can not have the presence of fine cracks 6" prevented. When a high current is instantaneously passed at the room temperature at the time of welding, the temperature of the welding part 3 will instantaneously reach about 1400° C. but will instantaneously drop to be below 1000° C. and will further continue to drop so quickly that the generation of the cracks will be unavoidable at the time of such quick cooling. The cracks will be generated between 900° and 100° C. at the time of quick cooling and will be likely to be generated by quick cooling particularly near 700° and 250° C.
In the valve moving push rod welding step, the velocity near 250° C. is reduced by the residual heat of the chuck which is also an electrode and of the push rod bur no means of reducing the quick cooling of the high temperature produced in the fusing part by instantaneously passing a high current is known.
A steel tube material 1 of ASTM A512-66 MT1010, a tube diameter of 8.0 mm, thickness of 1.2 mm and length of 186.0 mm was borne in the end part with a chuck, an end piece 2 of ASTM A-575-73 G10120, a carbon-hardened depth of 0.6 mm (full cementation), surface hardness Hv of 700, outside diameter R of 10.5 mm, thickness t of 10 mm and bottom thickness t' of 5 mm having the end surface 2" made a flat surface was mounted on the peripheral edge 1a' of the port at the tube end of the above mentioned steel tube material 1, then a welding current of a voltage of 8 volts, 50 cycles and an intensity of 16,000 A/cm2 was passed through them under a pressing force of 1,100 kg for 2/100 second, then a current of the same voltage and cycles and 4,500 A/cm2 was synchronously passed as a gradually cooling means under the same pressure for 6/100 second simultaneous with cutting off the current to reduce the quick cooling and then they were naturally air-cooled to obtain an expected product.
The above mentioned manner was repeated to obtain 50 expected products. 13 samples were indiscriminately taken out of them. 3 of the samples were subjected to the section test of the fusing part and the remaining 10 were subjected to the test of the fusing strength.
In the section of the obtained sample, as illustrated in FIG. 2, said expansion W of the cotransition boundary range 6 being within the fusing boundary surface 5, and a taugh mixed layer 6b having notch-shaped recess parts 6', accuated over outside end part 5b from inside end part 5a of the fusing boundary surface 5 were observed within said cotransition boundary range 6. The results of the strength test of the fusing part 3 were as mentioned in Table 1.
By the way, in the table, the sample of the conventional product was obtained in exactly the same manner except that no heat feeding means was applied to reduce the cooling in the above mentioned manner of making the product of the present invention. This heat feeding means is a means of synchronously passing an electric current of 4,500 A/cm2 for 6/100 second as mentioned in the above mentioned manufacturing manner.
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US3857013 * Jun 25, 1973 Dec 24, 1974 Western Electric Co Methods of and apparatus for joining materials
1 * Gillette, R. T., "Resistance-Welding Laboratory Facilities," from General Electric Review, Jul. 1945, pp. 26-29.
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U.S. Classification 29/888.2, 219/78.13, 219/67, 219/117.1
International Classification F01L1/14, B23P15/00
Cooperative Classification B23P15/00, F01L1/146, Y10T29/49295
European Classification F01L1/14D, B23P15/00