JPH04244673A - 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 composed of a skirt upside part 5 extending along a cylinder from a ring groove part 3 and a skirt downside part 6 extending along the cylinder at relatively small circumferential width from the skirt upside part 5, and this skirt upside part 5 is installed in the side range of a piston pin, while such a reinforced beam part 11 as connecting the skirt downside part 6 and a pin boss part 4 in beam form is formed there.

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] A conventional piston has a skirt portion that extends in a cylindrical shape from a head portion that defines a combustion chamber along the cylinder, and this skirt portion 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. 61-81
558, 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 the region of the cylindrical skirt portion to which no lateral pressure is applied is largely cut out, the stiffness distribution of the skirt portion becomes uneven, 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, the skirt portion is formed by a pair of skirt upper side portions extending along the cylinder from the ring groove portion and a skirt lower side portion extending along the cylinder from the skirt upper side portion with a relatively small circumferential width. The upper side of the skirt is provided in a lateral region of the piston pin including the piston pin axial surface perpendicular to the piston central axis, and a reinforcing beam part is formed to connect the lower side of the skirt and the pin boss part in a beam shape. .

[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 in the axial direction on the thrust side or the anti-thrust side, a sufficient contact length is ensured in the axial direction of the cylinder, the attitude of the piston relative to the cylinder is controlled, and slap noise 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 supported by each reinforcing beam part that connects the skirt lower part and each pin boss part in a beam shape, and this load causes the skirt part to It is possible to reduce the amount of deflection of the piston radially inward and ensure sufficient rigidity.

[0011] 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.

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, respectively, 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. .

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 side portions 5 extending along the cylinder from the land portion 3a of the ring groove portion 3, and a pair of skirt upper side portions 5 extending relatively from each skirt upper side portion 5. and a pair of skirt lower sides 6 extending along the cylinder with a 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 width X1 in the piston axial direction, and the area of each skirt upper side 5 corresponds to the maximum load on the thrust side or anti-thrust side that the piston 1 receives. It is set to suppress the contact surface pressure to below the allowable value.

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 upper side of the skirt 5 to the lower side of the skirt 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 the 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.

The distance 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.

[0022] In order to ensure the rigidity of each skirt portion 10,
Two pairs of reinforcing beam portions 11 are integrally formed on the inside thereof to connect each skirt lower side portion 6 and each pin boss portion 4 in a beam shape.

Each reinforcing beam portion 11 has one end connected to the outer periphery of the front and rear pin boss portions 4 substantially orthogonally, and the other end connected to the back surface 6a of each skirt lower side portion 6. The cross-sectional thickness of the reinforcing beam portion 11 gradually becomes thinner from each pin boss portion 4 to each skirt lower side portion 6, and is curved in the tangential direction of the arc cross section of each skirt lower side portion 6.

In this embodiment, the reinforcing beam portion 11 has a substantially rectangular cross-sectional shape as shown in FIG. The cross-sectional shape and cross-sectional area of the reinforcing beam portion 11 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. It is also conceivable to form the upper side of this T-shape on the outside in the radial direction of the piston to reduce the weight of this portion.

In this manner, 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, so that 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 pressure 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 6 extends in the axial direction on the thrust side or the anti-thrust side, a sufficient contact length is ensured in the axial direction of the cylinder, the attitude of the piston 1 with respect to the cylinder is controlled, and the slap noise is suppressed. Can be reduced.

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 supported by each reinforcing beam portion 11 that connects the skirt lower side portion 6 and each pin boss portion 4 in a beam shape. That is, the upper end of the skirt upper side portion 5 is connected to the ring groove portion 3 and the head portion 2.
The skirt portion 10 is supported by the piston pin via the pin boss portion 4, and its lower end is supported by the piston pin via the skirt lower side portion 6 and the pin boss portion 4, so that the skirt portion 10 is moved from the piston by the load applied from the cylinder to the skirt portion 10. It is possible to reduce the amount of deflection that causes radial inward bending, ensure sufficient rigidity, and prevent scuffing.

Next, other embodiments shown in FIGS. 11 and 12 will be described.

The skirt portion 20 includes a pair of skirt upper side portions 25 extending along the cylinder from the head portion 2 via the ring groove portion 3, and a pair of skirt upper side portions 25 extending along the cylinder from each skirt upper side portion 25 with a relatively small circumferential width. It is constituted by two pairs of extending skirt lower side portions 26. Four reinforcing beam parts 21 are integrally formed to connect the four skirt lower side parts 26 and the front and rear pin boss parts 4 in a beam shape.

Each skirt upper side 25 has a predetermined width 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.

The distance X2 of each skirt lower side portion 26 in the piston axial direction is set so as to sufficiently suppress the inclination of the piston 1 with respect to the cylinder. Two pairs of skirt lower sides 26
The total contact area is set to be equal to the total contact area of the pair of skirt lower sides 6 in the above embodiment.

The load that each skirt portion 20 is pressed against the cylinder due to the combustion pressure or inertia force received by the piston 1 is supported by the reinforcing beam portion 21 that connects each skirt lower side portion 26 and each pin boss portion 4 in a beam shape. Part 20
Sufficient rigidity is ensured.

In this case, the four skirt lower sides 26 extend along the cylinder, thereby suppressing the horizontal inclination of the piston 1, as well as effectively suppressing the longitudinal inclination. Alternatively, wear of the piston pin can be suppressed, and the piston 1 can be prevented from slamming against the cylinder wall surface and generating noise.

[0035]

As explained above, the present invention provides a piston for an internal combustion engine with a skirt extending along the cylinder from the ring groove, and a skirt extending along the cylinder with a relatively small circumferential width from the skirt upper side. The skirt part is formed by the extending lower part of the skirt, the upper part of the skirt is provided in the side area of the piston pin, and a reinforcing beam part is formed to connect the upper part of each skirt and the pin boss part in a beam shape, so that the skirt part is sufficient. This rigidity effectively disperses the contact surface pressure on the cylinder, making it possible to reduce the weight and size of the piston while ensuring operability and durability of the piston.

[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 sectional view taken along the line EE in FIG. 2; 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 another embodiment.

FIG. 11 is a front view of a piston showing 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 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. The skirt portion is constituted by a pair of skirt upper side portions extending from the ring groove portion along the cylinder, and a skirt lower side portion extending from the skirt upper side portion along the cylinder with a relatively small circumferential width, and the skirt upper side portion is An internal combustion engine characterized in that a reinforcing beam part is formed in a side region of the piston pin including the piston pin axis surface perpendicular to the piston central axis, and connects the skirt lower side part and the pin boss part in a beam shape. piston.