JPH04244677A - Piston for internal combustion engine - Google Patents

Abstract

PURPOSE:To make it lighter in weight and compact in size in addition to the promotion of high rigidity, in a piston for an internal combustion engine. CONSTITUTION:A skirt part 10 is made up of a pair of skirt upside parts 5 extending along a cylinder from a ring groove part 3, and tow pairs of skirt downside parts 6 extending along the cylinder at relatively small circumferential width from these skirt upside parts 5, while such a reinforcing rib part 11 as protuberating in a rib form from a head part back 2b and connecting the skirt upside part 5 and a pin boss 4, is formed there, and a pair of reinforced beam part 12 connecting these skirt downside parts 6 being opposed to each other in holding a piston pin between, is formed as well.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to improvements in pistons for internal combustion engines.

0002

[Prior art and its problems] In automobile engines, etc., there is a strong demand for lighter and smaller pistons in order to improve fuel efficiency, but on the other hand, there is a demand for higher strength as the load increases in order to achieve higher output. It is being

[0003] Conventional pistons include a skirt section that extends cylindrically from the head section that defines the combustion chamber along the cylinder, and this skirt section has a notch formed in the direction of the end of the piston pin where side pressure is not applied. , the mass is reduced and the sliding contact area with the cylinder is reduced (for example, Japanese Patent Laid-Open No. 61-8
1558, see).

However, in such conventional devices, since the skirt portion is formed into a cylindrical shape over a wide area, the skirt portion is pressed against the cylinder by the combustion pressure or inertia force applied to the piston, such as on the thrust side or on the opposite side. On the thrust side, the surface pressure on the cylinder may become excessive in the lateral region of the pin where this load is greatest.
Alternatively, the area of sliding contact with the cylinder is unnecessarily increased in other areas.

[0005] Furthermore, as a countermeasure to this problem, if a large notch is made in the region of the cylindrical skirt portion to which no lateral pressure is applied, the rigidity of the skirt portion is insufficient, causing scuffing and the like.

The present invention aims to solve these conventional problems.

[0007]

[Means for Solving the Problems] The present invention includes a head portion defining a combustion chamber, a skirt portion extending from the head portion along the cylinder via a ring groove portion, and a pin boss portion into which a piston pin is inserted. In each piston of an internal combustion engine, a pair of skirt upper sides that extend in the circumferential direction in the lateral area of the piston pin including the piston pin axis surface perpendicular to the piston central axis, and a relatively small circumferential side extending from the upper side of each skirt. a skirt portion is formed by two pairs of skirt lower side portions extending along the cylinder and having a width of In addition, a pair of reinforcing beams were formed across the connecting rod to connect the lower sides of each skirt facing each other with the piston pin in between.

[0008]

[Operation] On the thrust side or anti-thrust side where the skirt is pressed against the cylinder due to the combustion pressure or inertia applied to the piston, in the side region of the piston pin where this load is greatest, the upper side of the skirt extends over a wide area in the circumferential direction. Since the skirt is widened, the contact pressure of the upper side of the skirt against the cylinder is effectively dispersed, and wear of the piston and cylinder is suppressed.

[0010] Since the two pairs of skirt lower sides extend along the cylinder on the thrust side or the anti-thrust side, the skirt portions ensure a sufficient contact length in the axial direction of the cylinder to adjust the posture of the piston relative to the cylinder. control and reduce slap sound.

[0011] In this way, by forming the skirt portion from the upper side of each skirt to the lower side of each skirt extending along the cylinder with a relatively small width in the circumferential direction,
In addition to reducing the weight of the piston, unnecessary contact area in the skirt portion can be reduced, and friction loss of the piston can be reduced.

The load that the skirt part is pressed against the cylinder due to the combustion gas pressure or inertia force that the piston receives is absorbed by the reinforcing rib part that connects the upper side of each skirt and the pin boss part in a rib shape, and by each skirt facing each other with the piston pin in between. The piston is mutually supported by a pair of reinforcing beams that connect the lower side in a beam-like manner, and this load reduces the amount of deflection of the skirt section inward in the radial direction of the piston, ensuring sufficient rigidity to prevent scuffing, etc. can.

0012

DESCRIPTION OF THE PREFERRED EMBODIMENTS Examples of the present invention will be described below with reference to the accompanying drawings.

As shown in FIGS. 1, 2, and 3,
The disk-shaped head portion 2 of the piston 1 defines a combustion chamber on its top surface 2a, and has a ring groove portion 3 on its outer periphery.

A pressure ring and an oil ring are interposed between each ring groove 3 and the cylinder to prevent high-pressure combustion gas from leaking from the combustion chamber to the crankcase and to adjust the lubricating oil film on the cylinder wall. It has become.

In the figure, S1 is a piston axis surface that is perpendicular to the piston pin's central axis O4 and includes the piston central axis O1;
4 is a piston pin axial center surface that is orthogonal to the piston center axis O1 and includes the center axis O4 of the piston pin.

The skirt portion 10 extends symmetrically about the piston axis S1, and includes a pair of skirt upper sides 5 extending along the cylinder from the land portion 3a of the ring groove 3, and a relatively small circumference extending from each skirt upper side 5. It is constituted by two pairs of skirt lower side parts 6 extending along the cylinder with a width in the direction.

Each skirt upper side portion 5 is provided in a lateral region of the piston pin including the piston pin axial center surface S4, and the area located above the pin axial center surface S4 is larger than the area located below it by a predetermined ratio. formed to become larger. This ratio is set so as to equalize the distribution of contact surface pressure on the cylinder in response to the fact that the load applied to the area above the piston pin is greater than the load applied to the area below the piston pin.

Each skirt upper side 5 has a predetermined length X1 in the piston axial direction, and the area of each skirt upper side 5 is:
The contact surface pressure with respect to the cylinder is set to be suppressed to a permissible value or less in accordance with the maximum load on the thrust side or anti-thrust side that the piston 1 receives.

As shown in FIGS. 4 and 5, the cross sections of the skirt upper side 5 and the skirt lower side 6 are formed in an elliptical shape with a focal point on the piston axis plane S1 perpendicular to the piston pin. This ellipse has longer diameters in the thrust and anti-thrust directions, and during engine operation, the ellipse approaches a perfect circle due to thermal expansion, increasing the area in contact with the cylinder. In the figure, the broken line indicates a perfect circle.

As shown in FIGS. 6 and 7, the longitudinal cross-sectional shape from the skirt upper side 5 to the skirt lower side 6 basically changes the long axis of the former ellipse along the piston axial direction, and It is formed into a barrel shape that is squeezed by. As a result, a gap with a wedge-shaped cross section is created between the edges of the skirt upper side 5 and the skirt lower side 6 and the cylinder, and lubricating oil is sent between the surface of the skirt and the cylinder through this wedge-shaped gap, thereby providing lubrication. This prevents oil film from running out and maintains good lubricity.

Although the dimensions of each part shown in FIGS. 4 to 7 are exaggerated to be larger than the actual size for convenience, they are actually quite small, on the order of several tens of μm.

Two pairs of reinforcing rib portions 11 are integrally formed which protrude from the back surface 2b of the head portion 2 in a rib shape and connect each skirt upper side portion 5 and each pin boss portion 4.

Each reinforcing rib portion 11 has one end connected to the outer periphery of the front and rear pin boss portions 4 in a substantially orthogonal manner, and the other end connected to the peripheral end portion of the back surface 5a of each skirt upper side portion 5. The upper end is coupled to the back surface 2b of the head portion 2 substantially orthogonally. The reinforcing rib portion 11 has a cross-sectional thickness that gradually becomes thinner from each pin boss portion 4 to each skirt upper side portion 5, and is curved and connected to the arcuate cross section of each skirt upper side portion 5 in a tangential direction. Each reinforcing rib part 11 has a lightening hole 1
3 is formed

The two pairs of skirt lower sides 6 extend in the piston axial direction from the circumferential end of each skirt upper side 5, and the length X2 in the piston axial direction is the distance between the piston 1 and the cylinder.
It is set to sufficiently suppress the tilt (oscillation) of the

[0025] In order to ensure the rigidity of each skirt portion 10,
A pair of reinforcing beam portions 12 are integrally formed on the inside thereof, which connect the skirt lower side portions 6 facing each other across the piston pin in a beam shape. Each reinforcing beam part 12 extends in a straight line parallel to each other, and a connecting rod (not shown) passes between them and is connected to the crankshaft side. Each reinforcing beam part 12 is connected to the end part of each of the skirt parts 6 by being curved in a tangential direction to the arcuate cross section of each skirt lower side part 6 and becoming tapered.

In this embodiment, the reinforcing beam portion 12 has a substantially rectangular cross-sectional shape as shown in FIG. The cross-sectional shape and cross-sectional area of the reinforcing beam portion 12 are determined to ensure sufficient rigidity and strength in accordance with the maximum input to the skirt lower side portion 6 due to engine load. As other embodiments, it may be formed into a U-shaped cross section as shown in FIG. 9, with the right side of the U-shaped being placed on the outside in the radial direction of the piston, or it may be formed into a T-shaped cross section as shown in FIG. Hey, this T
It is also conceivable to arrange the upper side of the shape on the outside in the piston radial direction to reduce the weight of this part.

In this manner, the skirt portion 10 is composed of a pair of skirt upper side portions 5 and two pairs of skirt lower side portions 6 extending from the skirt upper side portions 6 with a relatively small width in the circumferential direction, thereby reducing combustion gas pressure and Large notches 9 are formed in the direction of the end of the piston pin, where the load pressed against the cylinder due to inertial force is almost not applied, thereby reducing the mass of the piston 1 and unnecessary contact area of the skirt portion 10 with the cylinder. , the friction loss of the piston 1 can be reduced.

By providing the skirt upper side portions 5 in the side areas of the piston pin, the contact surface pressure of each skirt upper side portion 5 pressed against the cylinder by the combustion gas pressure or inertia force applied to the piston 1 is effectively dispersed. Piston and cylinder wear is suppressed.

Since the two pairs of skirt lower sides 6 extend along the cylinder on either the thrust side or the anti-thrust side, a sufficient contact length is ensured in the axial direction of the cylinder, and the skirt portion 10 extends between the piston 1 and the cylinder. By controlling the posture and reducing the slap sound, the pin boss part 4
This effectively reduces wear on pin holes and piston pins.

The load that each skirt upper side 5 is pressed against the cylinder due to the combustion gas pressure or inertia force applied to the piston 1 is supported by each reinforcing rib portion 11 that connects each skirt upper side 5 and each pin boss portion 4 in a rib shape. Thus, the rigidity of the skirt upper side portion 5 is sufficiently ensured. On the other hand, in a structure in which the reinforcing rib part 11 is not provided and the skirt upper side part 5 is connected to the ring groove part 3 only through its upper end,
Due to the load that is pressed against the cylinder, the skirt upper side portion 5 is deflected by a large amount such that its circumferential end portion collapses inward in the radial direction of the piston 1, leaving a highly rigid circumferential center portion, resulting in the risk of scuffing. There is.

In addition, the reinforcing rib portion 11 of the head portion 2 is raised in a rib shape from the back surface 2b and is connected to the head portion 2 together with the pin boss portion 4, so that the head portion 2 has sufficient resistance to the combustion pressure applied to the top surface 2a. Strength can be ensured.

The load that the skirt portion 10 is pressed against the cylinder due to the combustion gas pressure or inertia force that the piston 1 receives is applied to each reinforcing beam portion 1 that connects each skirt lower side portion 6 in a beam shape.
It is also supported by 2. Thereby, the amount of deflection of each skirt lower side portion 6 to fall inward in the radial direction of the piston 1 can be reduced, sufficient rigidity can be ensured, and scuffing etc. can be prevented. Furthermore, by providing the reinforcing beam portions 12, it is possible to reduce the width of each skirt lower side portion 6 in the circumferential direction and form a lightening hole 13 in each reinforcing rib portion 11.

Next, in other embodiments shown in FIGS. 11, 12, and 13, a pair of reinforcing beams 22 connecting the lower sides 6 of each skirt in a beam-like manner are connected from both ends to the center in a side view. It is formed by curving upwards towards the end. In this case, by arbitrarily setting the degree of curvature of each reinforcing beam part 22, the rigidity of the skirt part 10 can be made appropriate and the contact with the cylinder can be adjusted favorably.

[0034]

As explained above, the present invention provides a piston for an internal combustion engine, in which a pair of skirt upper sides extend along the cylinder from a ring groove, and a cylinder with a relatively small circumferential width from each skirt upper side. A skirt part is formed by two pairs of skirt lower sides extending along the piston pin, and a reinforcing rib part is formed by protruding in a rib shape from the back of the head part to connect the skirt upper part and the pin boss part. Since a pair of reinforcing beams are formed to connect the lower sides of each opposing skirt in a beam-like manner, the skirt has sufficient rigidity and effectively disperses the contact surface pressure against the cylinder, making the piston lighter and smaller. It is possible to achieve both operability and durability.

[Brief explanation of the drawing]

FIG. 1 is a front view of a piston showing an embodiment of the present invention.

FIG. 2 is a side view of the piston.

FIG. 3 is a plan view of the piston seen from below.

4 is a contour view taken along line DD in FIG. 2; FIG.

FIG. 5 is a contour view taken along line BB in FIG. 2;

6 is a contour view taken along line AA in FIG. 2; FIG.

7 is a contour view taken along line CC in FIG. 2; FIG.

8 is a longitudinal cross-sectional view taken along the line EE in FIG. 1; FIG.

FIG. 9 is a sectional view of a reinforcing beam portion showing another embodiment.

FIG. 10 is a sectional view of a reinforcing beam portion showing still another embodiment.

FIG. 11 is a front view of a piston showing still another embodiment.

FIG. 12 is a side view of the piston.

FIG. 13 is a plan view of the piston seen from below.

[Explanation of symbols]

1 Piston 2 Head part 3 Ring groove 4 Pin boss part 5 Upper part of skirt 6 Lower part of skirt 10 Skirt part 11 Reinforcement rib part 11 Reinforcement beam part

Claims (1)

[Claims] 1. A piston for an internal combustion engine, each comprising: a head portion defining a combustion chamber; a skirt portion extending from the head portion along the cylinder through a ring groove; and a pin boss portion into which a piston pin is inserted. a pair of skirt upper sides extending in the circumferential direction in a lateral region of the piston pin including a piston pin axis surface perpendicular to the piston central axis;
A skirt portion is formed by two pairs of skirt bottom portions that extend along the cylinder with a relatively small circumferential width from the top portion of each skirt, and a rib-like protuberance from the back surface of the head portion that extends from the top portion of each skirt. An internal combustion engine characterized in that a reinforcing rib portion is formed to connect the pin boss portion, and a pair of reinforcing beam portions are formed to sandwich the connecting rod and connect the lower side portions of each skirt facing each other across the piston pin in a beam shape. piston.