JPH03117656A - Piston for internal combustion engine - Google Patents

Abstract

PURPOSE:To prevent the occurrence of seizure to a piston and to improve an output and fuel consumption by a method wherein two coupling wall parts positioned facing each other with a piston therebetween are extended approximately at right angles with a piston pin or inclined from the one end of a skirt part toward the outside and from the other end thereof toward the inside. CONSTITUTION:Two coupling wall parts 7 and 9 positioned facing each other with a piston central line 0 therebetween are curved from ends 5b and 6b on the one side of left and right skirt parts 5 and 6 and extended approximately at right angles with a piston pin 2. Meanwhile, two coupling wall parts 8 and 10 positioned facing each other with the piston central line 0 therebetween are inclined at a given angle from ends 5b and 6b on the other side of the left and right skirt parts 5 and 6 toward the inner side of a piston. This constitution suppresses deformation of pin boss parts 3 and 4 due to a gas pressure in a combustion chamber, reliably prevents the occurrence of seizure to the piston pin 2, reduces the occurrence of engine friction through suppression of the increase of the widths of the skirt parts 5 and 6, and improves an output and fuel consumption.

Description

[Detailed description of the invention] (Industrial application field) The present invention relates to improvements in pistons for internal combustion engines.

(Prior Art and Problems) In a reciprocating internal combustion engine, it is necessary to ensure sufficient rigidity of the piston against the gas pressure in the combustion chamber.

As shown in FIG. 5, for example, a conventional internal combustion engine piston has left and right skirt portions 5, 6 located on the sides of the piston pin 2 and slidingly in contact with the cylinder, and skirt portions 5, 6 that are spaced apart from the cylinder. Some devices have four connecting walls 7, 8°9.10 that connect both ends of the engine to the pin bosses 3, 4, thereby reducing the area of the piston in contact with the cylinder and reducing the liquefaction of the engine 7. .

However, as shown in FIG. 3, the piston 1 has a crown surface 11.
When the gas pressure in the combustion chamber acts as shown by the arrow in the figure, the left and right ends of the crown surface 11 bend downward using the pin boss parts 3 and 4 as fulcrums, so that the left and right skirt parts 5 and 6 are bent inward to the inside of the piston. The stress that tries to reduce the amount of stress acts as shown by the white arrow in the figure. Along with this deformation of the skirt parts 5 and 6,! #4
As shown in the figure, the front and rear pin boss portions 3, 4 expand outward from the piston, and the bearing area for the piston pin 2 becomes significantly smaller, which may cause seizure or the like to occur in the pin boss portion 3.4.

As a countermeasure against this problem, conventionally, as shown in FIG. 6, the connecting walls 7, 8, 9.10 are formed so as to be inclined from both ends of the skirt parts 5.6 to the inside of the piston. , 6 is deformed to fall inside the piston,
In some cases, the pin bosses 3 and 4 are made to fall inwards of the piston to secure a bearing area for the piston pin 2 (IFZ750 Service Manual, Yamaha Motor Co., Ltd.) However, in this case, each connecting wall 7.8.9.

10 is inclined toward the inside of the piston, so the scar)
A problem arose in that the width of 1i5 and 6 increased, leading to an increase in the length of engine 7.

The present invention aims to solve these conventional problems.

(Means for solving the problem) In order to achieve the above object, the present invention includes two pin boss parts into which both ends of the piston pin are fitted, and an arcuate cross section located on the side of the piston pin and slidingly in contact with the sill. In a piston for an internal combustion engine, the piston has two skirt portions having two skirt portions, and four connecting wall portions that curve from both ends of each skirt portion and connect to each pin boss. Either the skirts are approximately perpendicular to the pin, or they are inclined at a predetermined angle toward the outside of the piston from one end of each skirt, while the two connecting walls, which also face each other with the piston center line in between, are connected from the other end of each skirt. The piston was tilted inward at a predetermined angle.

(Function) Due to the gas pressure in the combustion chamber acting on the crown surface of the piston, the two connecting walls that are perpendicular to the piston pin or inclined toward the outside of the piston from the left and right skirt portions try to expand each pin boss portion to the outside of the piston. While the stress of
Stress that tends to cause each pin boss part to collapse into the inside of the piston is exerted from the two connecting walls that slope from the left and right skirt parts toward the inside of the piston. Therefore, in each pin boss part, the stress from each connecting wall part on both sides opposes each other, and the gas pressure in the combustion chamber prevents the front and rear pin boss parts from expanding to the outside of the piston, and the bearing area for the piston pin is significantly reduced. 6. While the skirt portion is in contact with the silling, the connecting wall that slopes inward from the line that bisects the piston and is perpendicular to the piston pin, prevents seizure, etc. from occurring on the bearing surface of the pin boss. Although the width to the piston increases, the distance from the line bisecting the skirt perpendicular to the piston pin to the connecting wall that slopes outward from the piston does not increase, and the distance between the piston and the silling increases. By suppressing the contact area, it is possible to reduce the engine's cost.

(Example) Embodiments of the present invention will be described below with reference to the accompanying drawings.

Note that the same reference numerals are given to parts that are substantially the same as those of the conventional example.

As shown in Fig. 1, the piston 1 has front and rear pin boss parts 3.4 into which both ends of the piston pin 2 are fitted, and left and right pin boss parts 3.4 that are located on the sides of the piston pin 2 and have an arcuate cross section that slides into contact with the sill. It has a skirt portion 5.6 and four connecting wall portions 7t8, 9, 10 that are continuous from both ends of each skirt portion 5, 6 and are connected to the front and rear pin boss portions 3, 4.

In FIG. 2, 11 is a crown surface defining a combustion chamber;
12, 13, and 14 are ring grooves into which piston rings are fitted, respectively.

two connecting walls 7 facing each other with the piston center line 0 in between;
9 is curved from one end 5b, 6b of the left and right skirt portions 5, 6, and is made substantially orthogonal to the piston pin 2.

On the other hand, in addition to the left and right skirt parts 5, 6, the two connecting walls 8, 10 facing each other across the piston center line 0 are connected to the left and right skirt parts 5, 6 and 15b.
6b toward the inside of the piston at a predetermined angle.

Explain the effects to your dog.

As shown in FIG. 3, when the gas pressure in the combustion chamber acts on the crown surface 11 of the piston 1 in the direction shown by the arrow in the figure, the left and right ends of the crown surface 11 bend downward using the pin boss portion 3.4 as a fulcrum. , stress acts on the left and right skirt portions 5 and 6 to cause the piston to collapse inward, as shown by the white arrows in the figure.

Along with the deformation of the skirt parts 5, 6, among the four joint walls 7, 8, 9.10, the joint walls 7, 9 formed perpendicular to the piston pin 2 have front and rear pin boss parts ,4
On the other hand, the front and rear pin bosses 3, 4 are released from the connecting walls 10, 8 which are inclined towards the inside of the piston from the ends 5b, 6b of the left and right skirt parts 5.6. There is a stress that causes the piston to fall down inside the piston. Therefore, in the front pin boss 3, the stress from the left connecting wall 7 that tries to expand it outward and the stress from the right connecting wall 9 that tries to make it collapse inward oppose each other. Similarly, in the rear pin boss portion 4, the stresses from the left and right connecting walls 8 and 9 oppose each other, and the front and rear pin boss portions 3 and 4 are prevented from expanding to the outside of the piston due to the large pressure in the combustion chamber. As a result, as shown in FIG. 4, the front and rear pin bosses 3, 4 are prevented from expanding outward and the bearing area for the piston pin 2 is significantly reduced, and seizure, etc. on the bearing surfaces of the pin bosses 3, 4 is prevented. This can be prevented from occurring.

In addition, as the stress from each of these joint walls 7, 8, 9, 10 tilts and opposes the pin boss parts 3, 4, a slight torsional deformation occurs in the pin boss parts 3, 4, but each joint By appropriately setting the inclination angles of the walls 7, 8, 9, and 10 with respect to the piston pin 2 within a predetermined range, the amount of torsional deformation can be sufficiently suppressed, and the contact area with the piston pin 2 can be significantly reduced. This prevents this and ensures smooth bearing performance.

During contact of the right side skirt portion 6 with the cylinder, i0L
2 is one connecting wall portion 10 that is inclined inward from a line P that is perpendicular to the piston pin 2 and bisects the piston 1;
While the width increases, it bisects #j! The width L2 from P to the other connecting wall 9 perpendicular to the piston pin 2 does not increase, and L1+L2 can be kept relatively small while the skirt 6 is in contact with the cylinder.

Similarly, in the left side skirt portion 5, the contact area between the piston 1 and the cylinder can be reduced, and the engine's displacement can be suppressed.

In addition, the connecting wall portions 7 and 9 are connected to the left and right skirt portions 5 and 6, respectively.
-j95a, 6a may be inclined at a predetermined angle toward the outside of the piston, and in that case, L2 during contact can be made smaller and lighter.

In this way, each skirt portion 5.6 is formed asymmetrically with respect to the line P that is perpendicular to the piston pin 2 and bisects the piston 1, but the bisector P where the surface pressure against the Schilling is the largest is formed. Since a sufficient area is secured for each skirt portion 5, 6 in the vicinity region, the function of controlling the attitude of the piston 1 is sufficiently performed, and the sealing performance of the piston ring is maintained.

(Effects of the Invention) As described above, according to the present invention, in a piston of an internal combustion engine, two connecting walls facing each other across the piston center line are made substantially perpendicular to the piston pin, or one end of each skirt portion is made substantially perpendicular to the piston pin. While tilting the piston at a predetermined angle toward the outside of the piston, two
Since the two connecting walls are inclined at a predetermined angle from the other end of each skirt section toward the inside of the piston, deformation of the pin boss section due to gas pressure in the combustion chamber can be suppressed, and seizing on the piston pin can be reliably prevented. By suppressing an increase in the width of the skirt portion, the engine 7 lux a is reduced, and output and fuel efficiency are improved.

[Brief explanation of drawings]

FIG. 1 is a plan view of a piston showing an embodiment of the present invention, and FIG.
The figure is also a side view. Figure 3 is a cross-sectional view of the piston showing its action. Figure #4 is also a longitudinal sectional view of the piston. 5 and 6 are vertical sectional views of pistons showing conventional examples, respectively. 1... Piston, 2... Piston pin, 3, 4...
・Pin boss section, 5, 6...skirt section,? , 8, 9.
10...Joining wall part.

Claims (1)

[Claims] two pin boss parts into which both ends of the piston pin are inserted;
A piston for an internal combustion engine having two skirt parts having an arcuate cross section located on the sides of a piston pin and slidingly in contact with a cylinder, and four connecting wall parts separated from the cylinder and connecting both ends of each skirt part to each pin boss. In this case, the two connecting walls facing each other with the piston center line in between are made substantially perpendicular to the piston pin, or are inclined at a predetermined angle from one end of each skirt part toward the outside of the piston, while the piston center line is also A piston for an internal combustion engine, characterized in that two connecting walls sandwiching and opposing each other are inclined at a predetermined angle from the other end of each skirt portion toward the inside of the piston.