JPH04244676A - Piston for internal combustion engine - Google Patents

Abstract

PURPOSE:To make it lighter in weight and compacting size in addition to the promotion of high rigidity, in a piston for an internal combustion engine. CONSTITUTION:A T-shaped skirt part 10 is made up of a pair of skirt upside parts 5 extending along a cylinder from a piston ring groove part 3, and each skirt downside part 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 and a pin boss part 4, is formed there, and a reinforced beam part 12, connecting each skirt downside part 6 into a ring-form beam, 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 piston ring groove, and a pin boss portion into which a piston pin is inserted. In the piston of an internal combustion engine, the upper side of the skirt expands in the circumferential direction in the lateral area of the piston pin including the piston pin axis surface perpendicular to the piston center axis, and the width in the circumferential direction is relatively small from the upper side of the skirt. and a lower side of the skirt extending along the cylinder to form a pair of T-shaped skirt parts, and a reinforcing rib part that is raised in a rib shape from the back surface of the head part and connects each skirt upper side and the pin boss part. death,
In addition, a reinforcing beam connecting the lower sides of both skirts into a ring-shaped beam was formed with a connecting rod sandwiched therebetween.

[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.

[0009] Since the lower side of the skirt extends along the cylinder on the thrust side or the anti-thrust side, the skirt part secures a sufficient contact length in the axial direction of the cylinder to control the attitude of the piston with respect to the cylinder. Reduces slap sound.

[0010] In this way, by forming the skirt portion from the upper side of each skirt to the lower side of the skirt extending along the cylinder with a relatively small circumferential width, the weight of the piston is reduced, and the skirt Friction loss of the piston can be reduced by reducing unnecessary contact area at the piston.

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 a reinforcing rib part that connects the upper part of each skirt and the pin boss part in a rib shape, and a ring-shaped beam that connects the lower part of both skirts. They are mutually supported by the reinforcing beams connected in a shape, and the amount of deflection of the skirt portion to fall inward in the radial direction of the piston due to this load is reduced, sufficient rigidity is ensured, and scuffing etc. can be prevented.

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 piston ring groove portion 3 on its outer periphery.

A pressure ring and an oil ring are interposed between each piston 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 surface. 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 in a T-shape with respect to the piston axial center surface S1, and has a pair of skirt upper sides 5 extending along the cylinder from the land portion 3a of the piston ring groove 3. and a pair of skirt lower sides 6 extending along the cylinder with a relatively small circumferential width.

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.

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 length X2 of each skirt lower side portion 6 in the piston axial direction is set so as to sufficiently suppress the inclination of the piston 1 with respect to the cylinder.

[0025] In order to ensure the rigidity of each skirt portion 10,
On the inside thereof, a reinforcing beam portion 12 is integrally formed which connects the lower side portions 6 of both skirts together in a ring-shaped beam shape. Reinforcement beam part 12
is curved in a ring shape of an elliptical arc in a plan view, and its ends are curved and connected in the tangential direction to the arc cross section of each skirt lower side 6, and a connecting rod (not shown) passes between them and connects to the crankshaft side. Join.

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, since the skirt portion 10 is composed of the skirt upper side portion 5 and the skirt lower side portion 6 extending from the skirt upper side portion 5 with a relatively small circumferential width, the combustion gas pressure and inertia force are applied to the cylinder. A large notch 9 is formed in the direction of the end of the piston pin where almost no pressing load is applied, reducing the mass of the piston 1 and unnecessary contact area of the skirt portion 10 with the cylinder. Friction loss 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 skirt lower side portion 6 extends along the cylinder on 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 controls the attitude of the piston 1 with respect to the cylinder. do,
Reduces slap sound.

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 portion 11 is not provided and the skirt upper side portion 5 is coupled to the piston ring groove portion 3 only through its upper end, the skirt upper side portion 5 is moved in the circumferential direction due to the load pressed against the cylinder. The amount of deflection in which the end portion falls inward in the radial direction of the piston 1 increases, leaving a highly rigid circumferential center portion, which may cause scuffing.

The load that the skirt portion 10 is pressed against the cylinder due to the combustion gas pressure or inertia force applied to the piston 1 is also supported by the reinforcing beam portion 12 that connects the lower side portions 6 of both skirts in a ring-shaped beam shape. 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. Further, 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.

Further, 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 received on the top surface 2a. Strength can be ensured.

Next, in other embodiments shown in FIGS. 11, 12, and 13, in order to make the rigidity of each T-shaped skirt part 10 appropriate, a beam is provided between the lower sides 6 of both skirts on the inside thereof. The reinforcing beam portions 22 connected in a shape are formed by dividing, and the ends of each reinforcing beam portion 22 are tapered and joined to both ends in the circumferential direction of each skirt lower side portion 6, and a part of the skirt lower side portion 6 is formed. and the reinforcing beam portion 22 form a ring shape.

As a result, each skirt lower side portion 6 having a width of X3 in the circumferential direction has a wall thickness that gradually increases toward the circumferential end portion at the joint portion of the reinforcing beam portion 22, and has a wall thickness gradually increasing at the circumferential center portion. The rigidity of the skirt portion 10 can be made appropriate and the contact with the cylinder can be improved without increasing the wall thickness.

Next, in other embodiments shown in FIGS. 14, 15, and 16, in order to make the rigidity of each T-shaped skirt part 10 appropriate, a ring is provided between the lower sides 6 of both skirts on the inside thereof. A reinforcing beam portion 32 is provided which is connected in a beam-like shape, and the reinforcing beam portion 32 is curved upward from both ends to the center portion in a side view.

In this case, the reinforcing beam portion 32 is inclined upward from the lower side portion 6 of each skirt at an angle θ in the front view, but by setting this inclination angle θ arbitrarily, the skirt portion 1
By setting the rigidity of 0 to an appropriate value, it is possible to satisfactorily adjust the contact with the cylinder.

[0037]

As explained above, the present invention provides a piston for an internal combustion engine that includes a pair of skirt upper sides extending from the piston ring groove along the cylinder, and a relatively small circumferential width extending from the upper side of each skirt. A T-shaped skirt part is formed by the lower side of each skirt extending along the cylinder, and a reinforcing rib part is formed in a rib shape from the back of the head part to connect the upper side of the skirt and the pin boss part, and the lower side of each skirt By forming a reinforcing beam that connects the parts into a ring-shaped beam, the skirt part has sufficient rigidity and effectively disperses the contact pressure against the cylinder, making the piston lighter and smaller, and improving the operability and durability of the piston. It is possible to balance securing sex.

[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 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.

FIG. 14 is a front view of a piston showing still another embodiment.

FIG. 15 is a side view of the piston.

FIG. 16 is a plan view of the piston seen from below.

[Explanation of symbols]

1 Piston 2 Head part 3 Piston 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, which includes a head portion defining a combustion chamber, a skirt portion extending from the head portion along the cylinder through a piston ring groove portion, and a pin boss portion into which a piston pin is inserted. , an upper side of the skirt that expands in the circumferential direction in a lateral region of the piston pin including the piston pin axial center plane perpendicular to the piston center axis, and a lower side of the skirt that extends along the cylinder with a relatively small width in the circumferential direction from the upper side of the skirt. A pair of T-shaped skirt parts are formed by the parts, and a reinforcing rib part is formed in a rib-like manner and protrudes from the back surface of the head part to connect the upper part of each skirt and the pin boss part, and the lower part of both skirts is A piston for an internal combustion engine, characterized in that a reinforcing beam part connected in a ring-shaped beam shape is formed with a connecting rod sandwiched therebetween.