JP2549460Y2 - Piston for internal combustion engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to the structure of a piston of an internal combustion engine, and more particularly to the structure of a piston that optimizes the rigidity distribution of a skirt.

[Conventional technology]

A clearance is provided between the piston and the cylinder bore in consideration of thermal expansion. The clearance is set so as to become larger toward the upper part in consideration of the temperature of each part of the piston.

If a large clearance is provided between the piston and the cylinder bore, the maximum impact force at which the piston hits the cylinder bore increases, which causes a problem that the oil film becomes short and the slap noise increases. Therefore, various proposals have been made as measures to solve the conflicting conditions.

Japanese Patent Application Laid-Open No. 62-85152 is known as a prior art related to the invention of the piston. The piston disclosed in this publication is provided with a notch in the skirt portion adjacent to the pin boss portion in order to reduce the weight and reduce the sliding area, and the angle of the sidewall portion with respect to the pin boss portion is reduced. It is constant from the top to the bottom of the piston.

In addition, as shown in FIGS. 11 to 14, in the conventional piston 1, the cross-sectional shape of the sidewall portion 4 connecting the pin boss portion 2 and the skirt portion 3 is usually the same at the lower portion and the upper portion of the skirt. .

[Problems to be solved by the invention]

However, as described above, when the angle of the sidewall portion with respect to the pin boss portion is constant, the rigidity of the upper portion and the lower portion of the skirt is substantially the same. As a result, there is a problem that scuffing at the shoulder of the skirt, deformation at the lower part of the skirt, and the like are caused. As described above, the sidewall portion has a great influence on the rigidity of the skirt portion.

An object of the present invention is to provide a piston that optimizes the rigidity distribution of the skirt portion, reduces slap noise, and prevents deformation of the lower portion of the skirt portion.

[Means for solving the problem]

The internal combustion engine piston according to the present invention that achieves this object is as follows.

A piston having a sidewall portion that connects a skirt portion and a pin boss portion and is arranged in plane symmetry with respect to a plane including both a piston pin axis and a piston axis, wherein the piston in at least a part of the sidewall portion The angle with respect to the pin axis is changed so as to increase as going from the upper part to the lower part of the skirt part in the piston axis direction, and the rigidity of the skirt part in the direction orthogonal to the piston pin axis becomes lower from the upper part to the lower part. Therefore, a piston for an internal combustion engine characterized by being large.

[Action]

In the piston for an internal combustion engine configured as described above, since the angle of the sidewall portion with respect to the piston pin axis changes, the rigidity can be made different between the upper portion and the lower portion of the skirt portion, and the rigidity distribution of the skirt portion is reduced. It becomes possible to make it appropriate. That is, by placing a part of the sidewall portion in a direction parallel to the piston pin axis in the upper portion of the sidewall portion, a bending load mainly acts on the upper portion of the sidewall portion. The rigidity of the skirt portion connected to the skirt portion in the direction orthogonal to the piston pin axis decreases. Therefore, the impact at the time of contact between the upper part of the skirt and the cylinder bore is reduced, and the slap noise is reduced. In addition, since the contact of the upper portion of the skirt portion is reduced, the surface pressure at the collision portion is also reduced, and the oil film breakage at that portion is also eliminated.

Conversely, in the lower part of the side wall part, by placing a part of the side wall part in a direction orthogonal to the axis of the piston pin, the load acting on this part is mainly a compressive load, and is connected to this part. The rigidity of the skirt portion in the direction orthogonal to the axis of the piston pin is increased. Therefore, deformation of the lower part of the piston when the piston hits the cylinder bore is prevented.

〔Example〕

Hereinafter, preferred embodiments of the piston for an internal combustion engine according to the present invention will be described with reference to the drawings.

First Embodiment FIGS. 1 to 3 show a first embodiment of the present invention. In the figure, reference numeral 11 denotes a piston, and the piston 11 is made of an aluminum alloy. The top surface 12 of the piston 11 is formed flat. A ring groove for mounting a piston ring (not shown) on the upper outer peripheral surface of the piston 11
13 and a ring groove 14 for mounting an oil ring (not shown)
Are formed. Below the ring groove 14, there is formed a pair of pin bosses 15 located on the piston pin axis (axis Y) with the piston axis (axis X) interposed therebetween. Immediately below the ring groove 14, there is formed a skirt portion 16 that is integrally connected in the circumferential direction. Each pin boss 15 is provided with a piston pin hole 17 through which a piston pin is inserted.

The upper width of the skirt portion 16 is smaller than the lower width, and the width end face 16a is inclined inward with respect to the axis X.

The side wall portion 18 connecting the skirt portion 16 and the pin boss portion 15 has a substantially rectangular cross-sectional shape, and the top is directed outward in the radial direction. The angle of the wall portion 18a connected to the skirt portion 16 of the sidewall portion 18 with respect to the piston pin axis (axis Y) is shown in FIGS.
As shown in the figure, the width is gradually reduced toward the lower portion along the piston axis (axis X). That is, as shown in FIG. 3, the lower angle θ ₁ ′ of the wall 18a is large with respect to the axis Y, and the angle θ ₁ of the portion of the skirt portion 16 higher than this is As shown in the figure, it is smaller than the axis Y. In this embodiment, the angle theta ₁ is the angle of the central portion near the pin boss portion 15, the upper (shoulder) of the wall portion 18a is further a smaller than the angle theta ₁ '.

In the present embodiment, the angle α of the wall portion 18b connected to the pin boss portion 15 of the sidewall portion 18 is the same in the axis X direction, but the angle α of the wall portion 18b with respect to the axis Y is the angle. if to change the axis X direction in the same manner as theta _1, it is possible to change the rigidity of the axis Z direction of the upper and lower skirt portion 16.

 Next, the operation of the first embodiment will be described.

When the piston 11 reciprocates in the cylinder bore, the piston 11 swings around the piston pin through which the piston pin hole 17 is inserted.
Direction load acts. Here, since the angle θ ₁ of the upper portion of the wall portion 18a of the sidewall portion 18 is small with respect to the axis Y, the rigidity of this portion in the direction of the axis Z is small. In other words, the angle theta ₁ by the small, the wall portion 18a acts as a load a load mainly bending axis Z direction, the strength of the wall portion 18a of the upper skirt portion 16, the load in the axial direction Z On the contrary.

Therefore, the upper portion of the skirt portion 16 is easily elastically deformed in the direction of the axis Z, so that the impact at the time of contact between the upper portion of the skirt portion 16 and the cylinder bore is reduced, and the slap noise is reduced. In addition, since the rigidity of the upper portion of the skirt portion 16 is reduced, even if the clearance between the piston 11 and the cylinder bore is reduced, there is no problem such as seizure due to thermal expansion. The effect can be enhanced.

On the other hand, since the lower angle θ ₁ ′ of the wall portion 18a of the sidewall portion 18 is larger than the angle θ _{1 with} respect to the axis Y, the rigidity of the wall portion 18a in the direction of the axis Z is large. Becomes That is, by making the angle θ ₁ ′ larger than the angle θ ₁ , the load in the axis Z direction acts mainly as a compressive load on the lower part of the wall 18a, and the strength of the wall 18a is reduced by the load in the axis Z direction. On the other hand, it becomes big. Therefore, deformation of the lower portion of the skirt portion 16 when the lower portion of the skirt portion 16 hits the cylinder bore is prevented.

In this way, by changing the angle of the wall portion 18a of the sidewall portion 18, the rigidity of the wall portion 18a in the direction of the axis Z can be made small at the upper portion and large at the lower portion.

In this embodiment, since the cross-sectional shape of the side wall portion 18 is substantially rectangular, as shown in FIG. 4, when the side wall portion 18 thermally expands, the skirt portion 16 The skirt portion 16 is pulled toward the portion 18 (in the direction of arrow F), so that the shoulder portion of the skirt portion 16 can be restrained from expanding in the radial direction.

Second Embodiment FIGS. 5 to 7 show a second embodiment of the present invention. The second embodiment is different from the first embodiment only in the skirt portion and the side wall portion, and the other portions are the same as those in the first embodiment. The description of the corresponding portions will be omitted, and only different portions will be described. The same applies to other embodiments described later.

5 to 7, reference numeral 21 denotes a side wall portion. The side wall portion 21 includes a first wall portion 21a.
And a second wall 21b. First wall 21a
Is a connecting portion with the pin boss portion 15, and the second wall portion 21b is a connecting portion with the skirt portion 16. FIG. 6 shows a cross section of the upper portion of the sidewall portion 21, and the cross-sectional shape of the sidewall portion 21 at this portion is substantially in a V shape. The first in the upper part of the side wall part 21
The wall portion 21a extends radially outward from the pin boss portion 15. Similarly, the second wall portion 21b in this portion extends toward the skirt portion 16 while protruding inward in the radial direction. The angle between the second wall 21b and the axis Y is θ _2, and the second wall 21b is inclined inward with respect to the axis Y by the angle θ ₂ .

FIG. 7 shows a cross section at the lower portion of the sidewall portion 21, and the cross-sectional shape of the sidewall portion 21 in this portion is substantially straight. The first wall portion 21a below the sidewall portion 21 extends substantially along the axis Z, and the second wall portion 21b similarly extends substantially along the axis Z. First wall portion 21a and second wall portion 21b
Are tilted inward by an angle θ ₂ ′ with respect to the axis Z.

In the second embodiment configured as described above, the angle of the second wall portion 21b of the sidewall portion 21 with respect to the axis Y decreases from the lower portion to the upper portion.
As in the embodiment, the rigidity of the sidewall portion 21 in the direction of the axis Z is small at the upper portion and becomes larger toward the lower portion. In addition, since the upper part of the sidewall part 21 is directed to the skirt part 16 from a position close to the outer peripheral surface of the pin boss part 15 having a relatively low temperature, the amount of thermal expansion is suppressed to a small extent. The first wall portion 21a and the second wall portion 2 in the lower portion of the side wall portion 21
Since 1b is substantially parallel to the direction of the axis Z, the length of the side wall portion 21 can be made shorter than in the first embodiment, and the rigidity can be increased accordingly.

Third Embodiment FIGS. 8 to 10 show a third embodiment of the present invention.

In the figure, reference numeral 31 denotes a sidewall portion. In the first embodiment and the second embodiment, the cross-sectional shape of the upper portion of the sidewall portion has a substantially rectangular shape, but in the present embodiment, the cross-sectional shape is straight. FIG. 9 shows the side wall section.
A cross section of the upper part of 31 is shown, and the side wall part 31 in this part is inclined at an angle θ ₃ inward with respect to the axis Y. FIG. 10 shows a cross section of a lower portion of the sidewall portion 31, in which the sidewall portion 31 is inclined inwardly with respect to the axis Y by an angle θ ₃ ′. The angle θ ₃ ′ is slightly smaller than a right angle, and the lower sidewall portion 31 is parallel to the tenon axis Z.

In the third embodiment configured as described above, since the angle with respect to the axis Y becomes smaller as the sidewall portion 31 goes from the lower portion to the upper portion, the rigidity in the direction of the axis Z also changes. Soft and rigid at the bottom.

As described above, in each embodiment, the side wall portion 1
Since the angles of the upper part, the lower part, and the lower part of the lower part with respect to the axis Y are different, the rigidity distribution of the skirt part 16 is optimized.

[Effect of the invention]

According to the piston for an internal combustion engine according to the present invention, the following effects can be obtained.

(A) The angle of at least a part of the sidewall portion with respect to the piston pin axis is changed so as to increase from the upper portion to the lower portion of the skirt portion in the piston axis direction, and the angle in the direction orthogonal to the piston pin axis is changed. Since the stiffness of the skirt is increased from the upper part to the lower part, the stiffness of the skirt can be optimally set in the axial direction of the piston. Therefore, while preventing seizure due to thermal expansion, the clearance with the cylinder bore can be made smaller than before, and slap noise can be reduced.

(B) Since the rigidity of the lower portion of the skirt portion is increased, the deformation of the lower portion of the skirt portion due to impact can be suppressed.

(C) Since the rigidity distribution of the skirt portion is optimized, the load does not concentrate on a specific portion, and the oil film between the piston and the cylinder bore can be made uniform. Therefore, the impact force at the time of contact between the piston and the cylinder bore can be reduced, the effect of reducing the slap noise can be enhanced, and the effect of preventing seizure can be enhanced.

(D) The reliability of the piston can be improved by suppressing the deformation of the skirt and reducing the impact force.

[Brief description of the drawings]

1 is a front view of a piston for an internal combustion engine according to a first embodiment of the present invention, FIG. 2 is a sectional view taken along the line II-II of FIG. 1, FIG. 3 is a bottom view of FIG. 4 is an enlarged cross-sectional view of the vicinity of the side wall portion in FIG. 2, FIG. 5 is a front view of an internal combustion engine piston according to a second embodiment of the present invention, and FIG. 6 is a line VI-VI in FIG. 7 is a sectional view taken along the line VII-VII of FIG. 5, FIG. 8 is a front view of a piston for an internal combustion engine according to a third embodiment of the present invention, FIG. 9 is a view of FIG. FIG. 10 is a sectional view taken along the line XX of FIG. 8, FIG. 11 is a front view showing an example of a conventional piston, FIG. 12 is a sectional view taken along the line XII- of FIG. 13 is a cross-sectional view taken along line XII, FIG. 13 is a front view showing another example of the conventional piston, and FIG. 14 is a cross-sectional view taken along line XIV-XIV in FIG. 11 ...... piston 15 ...... pin boss portion 16 ...... skirt 18,21,31 ...... sidewall portion _{θ 1, θ 1 ', θ} 2, θ 2', θ 3, θ 3 '...... sidewall portion Angle X: axis of piston Y: axis of piston pin Z: axis perpendicular to axis Y

 ──────────────────────────────────────────────────続 き Continuation of the front page (56) References Practical application Microfilm (JP, U) photographing the contents of the specification and drawings attached to the application form of Japanese Patent Application No. 62-120682 (Japanese Utility Model Application No. 64-25446) Microfilm (JP, U) of the contents of the specification and drawings attached to the application form of Japanese Patent Application No. 55-86833 (Japanese Utility Model Application No. 57-10441)

Claims (1)

(57) [Scope of request for utility model registration] 1. A piston having a sidewall portion that connects a skirt portion and a pin boss portion and is disposed in plane symmetry with respect to a plane including both a piston pin axis and a piston axis, The angle of at least a part of the skirt in the direction perpendicular to the piston pin axis is increased by increasing the angle of the skirt in the direction perpendicular to the piston pin axis. A piston for an internal combustion engine characterized by increasing in size from the bottom to the bottom.