JP2005002861A - Piston structure - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide piston structure high in strength and durable for high heat load, for providing a small-sized and thin-walled piston to enable the weight reduction. <P>SOLUTION: A whole piston 1 is integrated structure with no joint by steel casting. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a piston structure in which a piston is made of cast steel and has an integral structure with no joints.
[0002]
[Prior art]
Generally, the pistons of engines used in automobiles and the like are mainly made of aluminum alloys. However, combustion pressure tends to increase due to recent improvements in engine horsepower and torque, or exhaust gas reduction, and aluminum alloy pistons cannot withstand high heat loads.
[0003]
Therefore, in order to cope with an increase in combustion pressure due to an improvement in engine horsepower and torque or a reduction in exhaust gas, recently, a piston made of cast iron or spheroidal graphite cast iron, a piston made of forged steel, as shown in FIG. The piston upper member a made of forged steel and the piston lower member b made of spheroidal graphite cast iron including the skirt portion and the pin boss portion are joined by welding c (see Patent Document 1), as shown in FIG. A piston upper member d made of steel, a pin boss member e made of cast steel, and a skirt member f made of cast iron are provided, the piston upper member d and the pin boss member e are diffusion-bonded, and the pin boss member e and the skirt member f are connected to an electron beam. A piston joined by welding (see Patent Document 2), as shown in FIG. 4, a steel piston upper member g and a steel piston lower member h including a skirt portion and a pin boss portion are ground. Such welding the piston (see Patent Document 3) have been used or proposed.
[0004]
[Patent Document 1]
Japanese Patent Laid-Open No. 55-1553838 [Patent Document 2]
JP-A-7-293326 [Patent Document 3]
US Pat. No. 6,526,871
[Problems to be solved by the invention]
Cast iron or spheroidal graphite cast iron pistons are stronger than aluminum alloy pistons, but are still insufficient to withstand high heat loads. Forged steel pistons have improved strength and can withstand high heat loads, but the thickness of each part increases, resulting in increased size, increased weight, and increased man-hours for machining, leading to increased costs. To do.
[0006]
The piston shown in FIG. 2 has improved strength and can withstand a high heat load. However, the piston is increased in size and weight, and the number of processing steps increases, resulting in an increase in cost. Further, although the piston shown in FIG. 3 has improved strength and can withstand high heat load, since the three parts are joined by diffusion joining and electron beam welding, the number of steps is increased and the cost is increased. Further, the piston shown in FIG. 4 has improved strength and can withstand a high heat load, but it increases in size and weight, and further increases the number of processing steps, leading to an increase in cost, and the piston upper member g and Since a flash i is generated at the joint with the piston lower member h, and the flash i may drop into the cooling oil passage j during operation, the operation may be hindered. Therefore, the reliability as a product is low.
[0007]
SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has an object to provide a piston structure that is high in strength and can withstand a high heat load, and that is small and can be reduced in weight and thickness.
[0008]
[Means for Solving the Problems]
In the piston structure of the present invention, since the piston is made of cast steel and has an integrated structure without a joint, the piston structure is high in strength and can withstand a high heat load, and can be small and thin, and can be reduced in weight. . In addition, since the joining process is unnecessary, a product with low cost and high reliability can be obtained.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the accompanying drawings.
FIG. 1 is an example of an embodiment for carrying out the present invention. The feature of this illustrated example is that the entire piston is integrally formed of cast steel formed by casting molten steel into a mold without having a joint. In the figure, 1 is a piston, 2 is a recess formed at the top of the piston 1 to form a part of the combustion chamber, 3 is a groove for a piston ring formed on the outer periphery of the upper part of the piston 1, and 4 is a lower part of the piston 1 The formed skirt portion 5 is a pin boss through which a piston pin is inserted, and 6 is a cooling oil passage.
[0010]
Since the piston 1 in the piston structure of the illustrated example is made of cast steel without a joint portion, the piston 1 has high strength and can withstand a high heat load, and can be reduced in size and thickness, and thus can be reduced in weight. In addition, since the joining process is unnecessary, a product with low cost and high reliability can be obtained.
[0011]
It should be noted that the piston structure of the present invention is not limited to the above-described embodiment, and it goes without saying that various changes can be made without departing from the scope of the present invention.
[0012]
【The invention's effect】
As described above, since the piston structure of the present invention is made of cast steel and has an integral structure without a joint portion as described above, it has high strength and can withstand high heat loads, and can be made small and thin. Thus, it is possible to reduce the weight, and it is possible to obtain an excellent effect that a joining process is not required and a highly reliable product can be obtained at low cost.
[Brief description of the drawings]
FIG. 1 is a longitudinal sectional view of an example of an embodiment of a piston structure of the present invention.
FIG. 2 is a longitudinal sectional view of an example of a conventional piston.
FIG. 3 is a longitudinal sectional view of another example of a conventional piston.
FIG. 4 is a longitudinal sectional view of still another example of a conventional piston.
[Explanation of symbols]
1 piston

Claims (1)

A piston structure characterized in that the piston is made of cast steel and has an integrated structure with no joints.

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