JPH04203462A - Piston - Google Patents

Abstract

PURPOSE:To reduce the hitting sound of a piston while preventing a seizure of the piston by making the outer formation of a piston skirt in a form to contract the diameter toward the lower end edge, and providing a metallic strut with a smaller thermal expansion coefficient than the piston main body and with a high rigidity, integrally at the part near the lower end edge. CONSTITUTION:At a high thickness part formed near the lower end edge 7 of a skirt 6, a material with a high rigidity and a low thermal expansion coefficient lower than the light alloy of the piston material, a strut 10 made of a steel, for example, is fixed integrally by the method of a casting, for example, and the upper part (a) of the skirt is contracted in the diameter gradually as coming to the upper side, making the clearance 17 between a cylinder wall 16 a little larger, and at the center (b) which is the largest diameter part of the strut 6, the clearance 17 is made to have almost a constant value from the upper side to the lower side, a little narrower than the conventional one, to make the outer diameter almost constant, while the lower part (c) of the skirt is contracted in the diameter relatively sharply toward the lower end edge, making the clearance 17 with the cylinder wall 16 larger.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a piston used in a reciprocating internal combustion engine or the like.

[Conventional technology]

During operation of a reciprocating internal combustion engine, the piston receives the explosion pressure in the combustion chamber and transmits force to the connecting rod, but since the connecting loft is tilted at positions other than top dead center and bottom dead center, the component of the force is The piston is intermittently pressed against the cylinder wall by the thrust force.

-a, between the internal combustion engine piston and the cylinder wall,
In order to prevent an increase in sliding resistance, a fairly large gap is provided when the piston is cold, taking into account the thermal expansion of the piston at high temperatures, so the thrust force is applied intermittently through this large gap. As a result, a striking sound is generated between the piston and the cylinder wall, which is one of the causes of noise in the internal combustion engine.

As one means to deal with this problem,
Publication No. 5-54545 discloses that the gap between the piston and the cylinder wall is made smaller than before over the entire length of the piston to reduce hitting noise, and at the lower end of the skirt of the piston,
A technique has been disclosed in which the thermal expansion of the lower end of the skirt is suppressed and this part is reinforced by casting a ring made of a material such as iron, which has a lower coefficient of thermal expansion and greater strength than the material of the piston.

[Problem to be solved by the invention]

In one of the conventional techniques described in the above-mentioned Japanese Utility Model Publication No. 55-54545, the lower end of the skirt is reinforced with an iron ring, which increases the rigidity of that part and makes it difficult to deform elastically. In this case, the gap between the piston and the cylinder wall is made small over the entire length of the piston, so the piston skirt and cylinder wall come into strong contact, and the skirt scrapes off the oil film on the cylinder wall, causing oil film breakage. The possibility of seizure and abnormal wear increased, and in some cases, the hitting sound became louder.

The present invention solves the problems of the conventional technology and seeks a means for reducing hitting noise while preventing piston seizure.

[Means to solve the problem]

In order to solve the above-mentioned problems, the present invention molds the outer shape of the piston skirt into a shape that decreases in diameter toward the lower edge, and the material of the piston skirt has a lower coefficient of thermal expansion and rigidity than the material of the piston body in a portion close to the lower edge. The present invention provides a piston characterized in that a high metal strut is integrally provided along the lower edge.

[Function] In the piston according to the present invention, the outer diameter of the skirt is reduced toward the lower edge, and a high-strength metal strut is integrated as a reinforcing material at the small outer diameter part near the lower edge. Because of this, there is a large gap between the bottom edge of the skirt where the struts are located and the cylinder wall, and the oil film is not scraped off by the skirt. Moreover, the struts make it difficult for the skirt to change shape, which reduces hitting noise.

〔Example〕

In FIG. 1, reference numeral 1 shows a cross section of a piston for an internal combustion engine, which is an embodiment of the present invention.

Like conventional pistons, this piston 1 has a generally cylindrical shape as a whole and is manufactured from a light alloy mainly made of aluminum.The top wall surface 2 has a large wall thickness to withstand the explosion pressure, and has a is provided with a depression 3 forming part of the combustion chamber. Three circumferential grooves 5 into which piston rings (not shown) are fitted are provided in the upper part 4 of the cylindrical side surface, and the wall thickness is relatively thick in that part. The walls are relatively thin except for some parts. Further, reference numeral 8 denotes a bottle post into which a piston pin is fitted, and a thick wall portion 9 is formed from the vicinity of the bottle post 8 to below the top wall surface 2 for reinforcement.

Corresponding to one of the features of the present invention, in the embodiment shown in FIG. A ring (generally a strut) 10 made of a material with a low hardness, such as steel, and having a planar shape as shown in FIG. 2 is integrally fixed by a method such as casting.

The reason why the ring 10 is not circular but has a straight portion 11 is because
This is because this portion 11 is provided in a portion where a portion 12 of the skirt 6 has a nearly flat shape corresponding to the position of the bin post 8. In the example of Fig. 2, the circular part 1
3 is provided with a large number of small protrusions 14 facing outward to strengthen the bond between the material of the piston 1 and the ring IO depending on the casting number. Furthermore, although a plate-shaped ring 10 is used in the illustrated case, it may also have a circular or elliptical cross section.

Corresponding to the most important feature of the invention, the outer surface of the piston skirt 6 of the embodiment, in the vicinity of the cylinder wall 16, has a curve 15 shown in an exaggerated manner in FIG. It has a shape. That is, the outer surface of the piston skirt 6 is formed into a so-called drum shape during casting or by subsequent machining.

To explain in more detail, the area from the upper part of the skirt 6 to the lower edge 7 is divided into three areas: an upper part a, a middle part, and a lower part C, and the ring (strut) 10 is placed in the lower part C. Cast along the edges. The skirt upper part a gradually reduces in diameter as it goes upward, so that the gap 17 between it and the cylinder wall 16 becomes slightly larger.
The outer diameter is made substantially constant so that the gap 17 with the cylinder wall from top to bottom is a substantially constant value, which is slightly smaller than before, and the lower part of the skirt C is made to contract relatively suddenly toward the lower edge 7. The gap 17 between the cylinder wall 16 and the cylinder wall 16 is made larger. The gap 17 between the lower edge 7 and the cylinder wall 16 is, for example, 3 mm larger than that at the center.
The number of particles should be increased by 0 microns or more. The external shape of the side surface upper part 4 of the piston 1 connected to the upper part a of the skirt 6 may be approximately cylindrical, or may be formed into a shape that gradually contracts upward as an extension of the outer shape of the skirt upper part a. It may also have a round shape.

As a matter of course, the amount of deformation of the piston skirt caused by thrust force etc. during operation of the internal combustion engine is
The closer it gets, the bigger it gets. When the piston skirt 6 deforms, the lateral vibration of the piston increases, and the hitting sound generated by the collision between the piston 1 and the cylinder wall 16 increases. The gap 17 between the skirt and the cylinder wall increases towards the end of the skirt, and since a ring (strut) 10 is embedded in the lower part C near the lower edge 7, the rigidity of the lower edge 7 of the skirt is increased and the overall This makes it difficult for the skirt 6 to deform.

Moreover, since the ring 10 is made of a material with a lower coefficient of thermal expansion than the material of the piston, the lower part of the skirt 6 does not undergo large thermal expansion even in high-temperature conditions during operation of the internal combustion engine. There is no possibility that the oil film will be scraped off to cause an oil film breakage, or that the oil film will collide with the cylinder wall 16 and generate a hammering sound, and that seizure or scuffing will not occur.

〔Effect of the invention〕

Although the piston of the present invention makes less hitting noise against the cylinder wall and can realize a low-noise internal combustion engine, it also has excellent lubricity and does not cause seizure or abnormal wear between the piston and the cylinder wall. There is no fear.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional front view showing a piston according to an embodiment of the present invention;
FIG. 2 is a plan view of the ring (strand), and FIG. 3 is an explanatory diagram of the main parts. 1-piston, 6-skirt, 7-lower edge,
10- ring (strut) 15- curve;
16 - cylinder wall, 17 - gap.

Claims (1)

[Claims] 1. The outer shape of the piston skirt is formed so that its diameter decreases toward the lower edge, and a metal strut with a higher coefficient of thermal expansion and higher rigidity than the material of the piston body is installed near the lower edge. A piston characterized by being integrally provided along.