JP2004028025A - Piston for internal combustion engine - Google Patents

Abstract

A piston for an internal combustion engine is provided to prevent a local increase in surface pressure inside a piston pin insertion hole and to prevent occurrence of scuffing.
A piston for an internal combustion engine in which conical processing is performed from the inside of a pin boss portion with respect to each piston pin insertion hole formed through a pair of pin boss portions formed below a piston top surface portion. In the above, the starting point 18 of the conical processing on the piston pin insertion hole 14 of the pin boss portion 13 is set outside the end face 20a of the piston pin 20 inserted into the piston pin insertion hole 14.
[Selection diagram] FIG.

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a piston for an internal combustion engine that performs conical processing on each piston pin insertion hole penetrating a pair of pin bosses formed below a piston top surface.
[0002]
[Prior art]
As a conventional piston for an internal combustion engine, there is a technique disclosed in JP-A-11-303993. This technique is used in a piston for an internal combustion engine in which conical processing is performed from the inside of the pin boss portion to each piston pin insertion hole penetrated through a pair of pin boss portions formed below the top surface portion of the piston. The conical processing of the piston pin insertion hole of the portion is performed asymmetrically in the vertical direction so that the inclination angle with respect to the cylindrical inner surface of the piston pin insertion hole becomes larger below the upper side of the piston pin insertion hole. This alleviates the tensile stress acting on the pin boss portion when an explosive load acts on the piston for an internal combustion engine and the tensile stress acting on the pin boss portion when a piston inertia force acts.
[0003]
[Problems to be solved by the invention]
However, according to the above-mentioned conventional technology, since the conical processing start point of the piston pin insertion hole surface and the outer peripheral surface of the piston pin come into contact with each other, the surface pressure is locally increased and a scuff is generated in the piston pin insertion hole portion.
[0004]
Accordingly, it is a technical object of the present invention to provide a piston for an internal combustion engine, in which a local increase in surface pressure inside a piston pin insertion hole is prevented to prevent scuffing.
[0005]
[Means for Solving the Problems]
Means taken in the invention of claim 1 in order to solve the above technical problem is that the piston pin insertion holes respectively penetrated by a pair of pin bosses formed below the top surface of the piston, In a piston for an internal combustion engine in which conical processing is performed from the inside of a pin boss portion, a start point of the conical processing with respect to the piston pin insertion hole of the pin boss portion is located outside an end face of a piston pin inserted into the piston pin insertion hole. It is to be.
[0006]
According to this means, the outer peripheral surface of the piston pin and the inside of the piston pin insertion hole are in contact with each other, so that a local increase in surface pressure due to contact with a point can be prevented, and scuffing can be prevented.
[0007]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described.
[0008]
1 and 2 are sectional views of a piston showing an embodiment of the present invention.
[0009]
The piston 10 is made of an aluminum alloy or the like, and is disposed in a cylinder (not shown) provided in an engine (not shown). The rotation is converted into a rotational motion and transmitted to a crankshaft (not shown) via the connecting rod 20 and the connecting rod 30.
[0010]
A pair of pin bosses 13 is formed below a piston land portion 12 where the piston top surface portion 11 of the piston 10 is formed above, and a piston pin insertion hole 14 is formed in the pin boss portion 13, respectively. I have. The piston pin 20 to which the connecting rod 30 is assembled is inserted into the piston pin insertion hole 14. A pin ring fixing groove 16 for inserting a pin ring (not shown) for positioning the piston pin 20 in the axial direction of the piston pin 20 or a pin ring fixing groove 16 is inserted into the piston pin insertion hole 14 of each pin boss portion 13. On the other hand, a pin ring attaching / detaching groove 17 for attaching / detaching the pin ring is formed.
[0011]
In such a piston pin insertion hole 14, a tapered hole 15 is formed from the inside of the piston pin insertion hole 14 by performing a conical process on the piston pin insertion hole 14. The conical processing start point 18 of the tapered hole 15 is provided outside the end face 20 a of the piston pin 20. The conical processing start point 18 is a portion where the inner peripheral surface of the piston pin insertion hole 14 and the inner peripheral surface of the tapered hole 15 intersect. Further, the conical processing start point 18 in the present embodiment is provided at substantially the center of the axial width of the piston pin 20 of the pin ring fixing groove 16 as shown in FIG.
[0012]
The operation of the piston for an internal combustion engine according to the present embodiment configured as described above will be described.
[0013]
During operation of the engine, the piston 10 receives a load caused by an explosion of an air-fuel mixture in a cylinder (not shown) provided in the engine (not shown) at the piston top surface portion 11, and passes through the piston land portion 12 and the pin boss portion 13. To the piston pin 20. Further, the piston pin 20 to which the connecting rod 30 is assembled transmits a load due to the explosion to the crankshaft via the connecting rod 30. At this time, as shown in FIG. 3, the piston land portion 12 is elastically deformed into a concave shape due to the load due to the explosion, but since the starting point 18 of the conical processing is located outside the end face 20a of the piston pin 20, the piston land 20 And the piston pin insertion hole 14 comes into contact with each other to prevent a local increase in surface pressure. Therefore, scuffing between the outer peripheral surface of the piston pin 20 and the piston pin insertion hole 14 can be prevented.
[0014]
In the above-described embodiment, the full flow type piston 10 in which the piston pin 20 and the connecting rod 30 are rotatably assembled has been described. However, a semi-flow type piston in which the piston pin 20 and the connecting rod 30 are fixed as shown in FIG. It may be applied to the piston 10.
[0015]
【The invention's effect】
As described above, according to the present invention, the outer peripheral surface of the piston pin and the inside of the piston pin insertion hole are in contact with each other, so that a local increase in surface pressure due to contact with a point can be prevented, and scuffing can be prevented.
[Brief description of the drawings]
FIG. 1 is a sectional view of a piston according to an embodiment of the present invention.
FIG. 2 is an assembly diagram in which a piston pin and a connecting rod in FIG. 1 are assembled.
FIG. 3 is an operation explanatory view in the embodiment of the present invention.
FIG. 4 is a sectional view of a piston showing another embodiment of the present invention.
FIG. 5 is an enlarged view of a portion A in FIG.
[Explanation of symbols]
11 Piston top surface 13 Pin boss 14 Piston pin insertion hole 18 Starting point 20 Piston pin 20a End surface

Claims (1)

For a piston for an internal combustion engine in which conical processing is performed from the inside of the pin boss portion, for each piston pin insertion hole penetrated through a pair of pin boss portions formed below the piston top surface portion, the pin boss portion A piston for an internal combustion engine, wherein a starting point of the conical processing with respect to a piston pin insertion hole is located outside an end face of a piston pin inserted into the piston pin insertion hole.

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