JP2529243Y2 - piston - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a piston of an internal combustion engine, and relates to a structure of a piston having a strength suitable for an internal combustion engine operating at a high gas pressure.

(Prior Art) In recent years, the output of an internal combustion engine has been remarkably improved, and accordingly, particularly in a diesel engine, the gas pressure in a cylinder has increased.

On the other hand, with the aim of improving the acceleration performance and reducing the friction horsepower with the speeding-up of the engine, it is becoming difficult to achieve structural strength because the piston is lightened by a thin structure.

On the other hand, the conventional piston has a structure in which the material strength is increased and the radius of the corner of the connection between the piston pin boss and the inner periphery of the piston is increased.

In order to prevent the stress around the piston pin hole from becoming excessive due to the increasing gas pressure in the cylinder, stress relief processing, taper processing of the piston pin hole, and the like are performed.

(Problems to be Solved by the Invention) In the prior art, if the connection portion beside the piston pin boss is reinforced to withstand high gas pressure in the cylinder, the weight of the piston increases, which hinders speeding up of the engine. Therefore, satisfying both the gas pressure and the high speed is a difficult problem in design.

The structure of the piston pin hole by stress relief or taper processing of the pin hole allows deformation of the entire piston to some extent, and has a disadvantage that the stress of the combustion chamber forming portion on the upper part of the piston increases.

It is an object of the present invention to solve the above-mentioned disadvantages.

(Means and Actions for Solving the Problems) The present invention has been made in view of the above points, and has been described in connection with the piston inner periphery of the piston pin boss on the thrust side of the piston as viewed on a plane perpendicular to the central axis of the piston. The radius of the connection corner is 30 to 50% of the radius of the connection corner on the anti-thrust side
Due to the large formed shape, the weight increase can be suppressed by selectively strengthening the radius of the connection corner at the side of the piston pin boss on the thrust side of the piston supporting the side thrust due to the gas pressure.

Regarding the strengthening of the periphery of the piston pin hole, an electron beam remelting process is performed over a half circumference or the entire circumference on the center line of the piston pin hole, and the crystal of the metal structure inside the piston pin hole is refined. The hole can be strengthened without any other reaction.

Thus, a piston that solves the above-mentioned problem is provided.

(Example) Next, an example of this invention is described based on a drawing.

FIG. 1 is a sectional view of the device according to claim 1 of the present invention, FIG. 2 is a sectional view taken along line AA of FIG. 1, FIG. 3 is a sectional view taken along line BB of FIG. The figure is a cross-sectional view taken along the line CC of FIG.
FIG. 6 is a cross-sectional view of the second embodiment.

1 to 4, reference numeral 1 denotes a piston, 2 denotes a piston pin hole, 3 denotes a piston pin boss, 4a denotes a radius of a connection portion corner beside the thrust side piston pin boss, and 5a denotes a connection portion corner on the anti-thrust side. Shows the radius of

As shown by 4a, 4b, and 4c in FIGS. 2, 3, and 4, respectively, the radius of the corner of the connection portion varies depending on the position in the height direction. 4b is a radius approximately 1 mm larger than 4a. 4c is about 1 mm larger than 4b, that is, the cross section in FIG. 1 is larger as it is closer to the bottom of the piston 1.

Similarly, the radius of the connection corner on the anti-thrust side is 5a, 5b, and 5c.
The radius is 1mm larger.

The radius 5a of the connection corner is about 7 mm in this embodiment, and the radius 4a of the connection corner is about 3 mm larger than 5a, that is, about 10 mm.

Therefore, the radius of the connection corner is 3 mm larger on the thrust side than the anti-thrust side, that is, 30 to 50% larger than the radius of the connection corner on the anti-thrust side.

Since the thrust side of the piston 1 supports the side thrust due to the explosion pressure at the time of combustion of the engine, the radius of the connection corner beside the piston pin boss, that is, 4a, 4b, 4a, 4b,
A large stress is generated around 4c.

Increasing the radius of the corner of the connection portion only on the thrust side is an effective means for reducing the stress generated in this portion.

On the anti-thrust side, the stress generated at the radius of the corner of the connecting portion is not high, so that the radius can be small.

Thus, it is possible to prevent unnecessary portions from being thickened in order to reduce the stress in the vicinity of 5a, 5b, and 5c in FIGS.

FIG. 5 shows the stress generated at the connection portion corner on the thrust side, and shows the stress state and the stress variation range when the radius of the connection portion corner is increased.

As shown in the figure, the larger the radius of the corner, the smaller the average stress and stress amplitude, and the smaller the stress fluctuation range.

The generated stress on the anti-thrust side is extremely small and almost zero.

Although the shape of the side of the piston pin boss can be improved in this way, a measure for preventing cracks in the piston pin boss which often poses a problem in mechanical strength of the piston will be described below with reference to embodiments.

In FIG. 6, 2 is a piston pin hole, 32 is a critical portion of a piston pin boss portion, and 33 is a cast-in portion of a copper alloy.

For convenience of explanation, only the cast-in portion 33 is shown on one side of the piston pin hole, but is applied on both sides.

As shown in FIG. 7, an electron beam remelting process is performed on the semicircular area of the piston pin hole 2 including the critical portion 32.

The electron beam remelting process is performed after casting of the piston.Then, it is heated to a depth of 5 mm from the surface by the electron beam, and after heating, the heat is transferred to the aluminum base material. This reduces the fatigue strength
30% improvement.

By casting a copper alloy or the like during the electron beam remelting process, higher strength can be obtained.

Although the electron beam remelting process is performed in the range of a semicircle including the critical portion 32, the process may be performed over the entire circumference. (See FIG. 7) The processing range E in the pin direction of the piston pin hole 2 may be about 0.3 to 1 times the piston pin diameter F.

As described above, in the embodiment of the present invention, the radius of the connection portion corner beside the piston pin boss on the thrust side is increased,
The stress can be reduced, the fatigue strength can be improved by electron beam remelting around the critical portion of the piston pin hole, and the strength of the piston can be improved.

(Effects of the Invention) This invention is made as described above. The radius of the connecting portion corner of the piston pin boss is made larger on the thrust side than on the anti-thrust side to reduce the stress on the side of the piston pin boss. The inner surface of the hole was subjected to an electron beam melting process to make the metal structure into fine crystals, thereby increasing the fatigue strength of the piston pin hole and improving the reliability of the piston.

[Brief description of the drawings]

FIG. 1 is a sectional view of the device according to claim (1) of the present invention;
FIG. 2 is a sectional view taken along line AA of FIG. 1, and FIG.
FIG. 4 is a sectional view taken along line CC of FIG. 1, FIG.
The figure is a stress diagram at the corner of the connection, and FIG. 6 is the claim (2).
FIG. 7 is a cross-sectional view of the above-described one, and FIG. 7 is an explanatory view of an electron beam remelting processing range. 1 ... Piston, 2 ... Piston pin hole 3 ... Piston pin boss, 4a ... Radius of thrust side connection part corner 4b ... Radius of thrust side connection part corner, 4c ... Thrust side connection part corner radius 5a ... Anti-thrust side connection part corner 5b: Radius of the corner on the anti-thrust side, 5c: Radius of the corner on the anti-thrust side, 32: Critical part 33: Cast-in

Claims (2)

(57) [Scope of request for utility model registration] In a piston of an internal combustion engine, a radius of a corner of a connection portion between a piston pin boss on a thrust side of the piston and an inner periphery of the piston as viewed on a plane perpendicular to a central axis of the piston is a radius of a corner of a connection portion on an anti-thrust side. A piston characterized by being formed 30 to 50% larger than the piston. 2. An aluminum alloy piston for an internal combustion engine, wherein an electron beam remelting process is performed over a half circumference on the center line of the piston pin hole or over the entire circumference. piston.