JPH078544U - Piston for internal combustion engine - Google Patents

Abstract

(57) [Abstract] [Purpose] Even when a moment around the compression top dead center is generated when the internal combustion engine is input at medium speed and high load before warming up,
(EN) A piston for an internal combustion engine in which the inclination of the piston body is made as small as possible to prevent the topland striking sound of the crown portion and to effectively prevent seizure of the thrust side skirt portion with the inner wall of the cylinder. [Structure] Center O of piston pin hole 7 of piston body A
Is offset to the thrust side with respect to the axial centerline C of the piston body A, and the oil ring groove 1
3, a slit 10 is provided at the thrust-side bottom portion of the oil ring groove 13, and the length a of the slit 10 is longer than the basic outer wall width b of both apron portions 4 and 5. Furthermore,
The piston body A has an elliptical shape in which both skirt portions 2 and 3 have a long diameter and both apron portions 4 and 5 have a short diameter, and the oval amount of the anti-thrust skirt portion 3 is larger than that of the thrust side skirt portion 2. I made it smaller.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to improvement of a piston for an internal combustion engine of an automobile or the like.

[0002]

[Prior art]

 Conventionally, in this type of piston, in order to suppress slap noise and improve seizure resistance, the center of the piston pin hole of the piston body is offset toward the thrust side with respect to the center line of the piston body, and It is known that the thickness of the skirt portion is made larger than the thickness of the skirt portion on the thrust side and a slit is provided on the anti-thrust side of the oil ring groove (for example, Japanese Utility Model Publication No. 2-90342). ). In such a piston, the weight balance is intentionally changed by increasing the wall thickness of the skirt part on the anti-thrust side to suppress swinging of the piston body due to inertia and reduce the slap noise. The slits on the anti-thrust side make it easier to deform the anti-thrust side by the slits in order to prevent the thickened skirt from sticking to the cylinder wall due to local high surface pressure on the cylinder wall. is there.

[0003]

[Problems to be solved by the device]

 However, in such a conventional piston for an internal combustion engine, when the operating speed of the internal combustion engine, in particular, the influence of the combustion pressure load is far greater than the influence of the inertial force, at the time of inputting the medium-speed rotation and high load before warming up the engine, When a load due to combustion pressure is applied to the crown surface of the crown around compression top dead center, a moment is generated that causes the piston body to rotate from the anti-thrust side to the thrust side due to the offset of the piston pin hole center. . Due to this moment, the thrust side skirt portion comes in contact with the cylinder inner wall at the lower side from the center of the piston pin, and the anti-thrust side skirt portion comes in contact with the cylinder inner wall at the upper side from the center of the piston pin hole and stops. At this time, both skirts are deformed and tilted by receiving a reaction force from the cylinder inner wall, and the anti-thrust side top land of the crown portion collides with the cylinder inner wall, and a top land striking sound is generated. Since the oil ring groove of the crown part has a slit, the skirt part on the anti-thrust side becomes the fixed end, and the crown part becomes a whipping state, which warps the top land striking sound. It

Further, paying attention to the thrust side skirt portion, when the above-mentioned moment is generated, this moment is the fixed end at the upper side of the skirt connected to the apron portion and the apron portion is connected at the lower side of the skirt portion. As a result, it becomes an open end and the lower side of this skirt is deformed. The amount of this deformation increases as it goes downward, resulting in large surface contact with the inner wall of the cylinder. This surface contact inevitably causes the piston body to tilt with respect to its axial center, and warps against the skirt. There was a risk that the parts would be easily worn.

In view of the above points, the present invention has an advantage that even when a moment around the compression top dead center is generated at the time of inputting a medium-speed rotation high load before engine warming, in which the influence of the combustion pressure load is particularly large, the piston (EN) It is possible to provide a piston for an internal combustion engine in which the inclination of the main body is made as small as possible to prevent the topland striking sound in the crown portion, and also to effectively prevent strong wear contact of the thrust side skirt portion with the cylinder inner wall. To aim.

[0006]

[Means for Solving the Problems]

 The piston for an internal combustion engine of the present invention is such that the center of the piston pin hole of the piston body is offset to the thrust side with respect to the axis center line of the piston body, and the oil ring groove is formed in the crown portion, and the thrust ring side of the oil ring groove is formed. It is characterized in that a slit is provided at the bottom, and the slit reaches at least the vicinity of the apron portion.

[0007]

[Action]

 Based on this configuration, when the internal combustion engine operating condition, especially the influence of the combustion pressure load, is much greater, when the engine is warming up to medium speed rotation and high load input, combustion occurs on the crown surface of the crown portion around the compression top dead center. A load due to pressure is applied, and a moment that rotates the piston body from the anti-thrust side to the thrust side is generated.This moment causes the thrust-side skirt portion to fall from the center of the piston pin hole to the anti-thrust side. When the side skirt comes into contact with the inner wall of the cylinder from the center of the piston pin hole to the upper side and stops, there is no slit in the oil ring groove on the anti-thrust side. It does not cause topland tapping sound that is generated when the anti-thrust side of the topland collides with the cylinder inner wall.

Further, paying attention to the thrust side skirt portion, when the above moment is generated, this moment has a reaction force received from the cylinder inner wall because the upper side of the skirt portion is an open end together with the lower side of the skirt portion. The lower side of the skirt and the upper side are also deformed and absorbed, reducing the inclination of the piston body.

[0009]

【Example】

 Next, an embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a front view seen from the direction of a piston pin hole of a piston for an internal combustion engine adopting an embodiment of the present invention, and FIG. 2 is a view taken in the direction of arrow X in FIG.

Reference numeral A denotes a piston body, which is manufactured by using a lightweight alloy such as an aluminum alloy as a base material, and a crown portion 1 which constitutes a combustion chamber of an engine, and a thrust side and an anti-thrust side of the crown portion 1. The skirt portions 2 and 3 are formed continuously, and the apron portions 4 and 5 that connect the skirt portions 2 and 3 and are continuous with the crown portion 1 are formed.

A pin boss portion 6 is provided on each of the apron portions 4 and 5, and a piston pin hole 7 into which a piston pin (not shown) is inserted is formed in the pin boss portion 6. The center O of the piston pin hole 7 is formed in the pin boss portion 6 with a predetermined width offset S on the thrust side with respect to the axial center line C of the piston body A.

On the outer peripheral portion of the crown portion 1, two compression rings 21, 12 and one compression ring grooves 12 and 22 in which the two compression rings 21 and 22 are inserted in order from the combustion chamber 9 side of the cylinder 8 are formed. An oil ring groove 13 into which the oil ring 23 is inserted is engraved, and the top land 14, the second land 15, and the third land 16 are formed by these grooves.

A slit 10 is provided at the thrust-side bottom of the oil ring groove 13, and the length a of the slit 10 is longer than the width b between the basic outer walls of the apron parts 4 and 5. There is.

Further, the piston body A has an elliptical shape in which both skirts 2 and 3 have a long diameter and both aprons 4 and 5 have a short diameter, and the anti-thrust side skirt 3 has an oval amount. As compared with the thrust side skirt portion 2 side, the size is smaller by a predetermined amount, so that the shape of the anti-thrust side skirt portion 3 is closer to a circle.

Next, the operation of the above embodiment will be described with reference to FIG. FIG. 3 is an explanatory diagram for explaining the swinging motion of the piston body during operation of the internal combustion engine. In the operating state of the internal combustion engine, the crankshaft (not shown) rotates in the K direction (clockwise direction in the figure), which causes the piston body A to move up and down via the connecting rod 17. When a load due to combustion pressure is applied to the crown surface of the crown portion 1 around the top dead center of the piston, especially around the top dead center at the time of input of medium-speed rotation high load before engine warm-up, the piston pin A will receive Due to the offset S of the hole 7, a moment M that causes rotation from the anti-thrust side to the thrust side is generated. Due to this moment M, the piston main body A tilts clockwise in the drawing, and a force F is generated at the center of the piston pin hole 7. In the thrust side skirt portion 2, this force F stops from the center of the piston pin hole 7 by contacting the cylinder inner wall 8a of the cylinder 8, and in the anti-thrust side skirt portion 3 from the center of the piston pin hole 7 to the upper side. On the side, the cylinder wall 8a of the cylinder 8 comes into contact with the cylinder wall 8a to stop and receive a reaction force.

In this state, first, focusing on the inclination of the piston body A on the anti-thrust side, the reaction force from the cylinder inner wall 8a on the anti-thrust side is smaller than the reaction force on the thrust side. However, the upper contact portion 19 is formed above the center O of the piston pin hole 7 in the anti-thrust side skirt portion 3 with the cylinder inner wall 8a. When a slit is provided on the anti-thrust side skirt portion 3 above the center O of the piston pin hole 7 on the anti-thrust side of the oil ring groove as in the conventional case, the deformation due to the reaction force becomes large, Although the inclination of the axial centerline C of the piston body A is increased, in this embodiment, since no slit is formed on the anti-thrust side of the oil ring groove 13, the anti-thrust side skirt portion 3 is formed. The amount of deformation above the center O of the piston pin hole 7 can be minimized, and even if the contact portion 20 with the cylinder inner wall 8a is formed on the top land 14 of the crown portion 1, the whipping phenomenon of the crown portion 1 is prevented. Therefore, the top land 14 does not generate a top land hammering sound generated when the anti-thrust side of the top land 14 collides with the inner wall of the cylinder.

However, since the deformation amount in the anti-thrust side skirt portion 3 is suppressed, there is a possibility that the center portion of the anti-thrust side skirt portion 3 may locally hit the cylinder inner wall 8a, but this problem is solved. Therefore, in this embodiment, as described above, the piston main body A has an elliptical shape in which the skirt portions 2 and 3 sides have a long diameter and the aprons 4 and 5 sides have a short diameter. As a result of making the amount of oval of the thrust side skirt portion 3 smaller than that of the thrust side skirt portion 2 side by a predetermined amount, the anti thrust side skirt portion 3 becomes closer to a circular shape and has a larger circumferential area. The upper contact portion 19 with the cylinder inner wall 8a is formed to support the load in a wide range, and local contact with the cylinder inner wall 8a of the anti-thrust side skirt portion 3 is avoided. It

Also, paying attention to the thrust side skirt portion 2, when the moment M is generated, a slit 10 is provided at the thrust side bottom portion of the oil ring groove 13, and the length a of the slit 10 is set to be equal to both aprons. Since it is longer than the width b between the basic outer walls of the parts 4 and 5, the upper side of the piston pin hole center O in the thrust side skirt part becomes the open end together with the lower side, so that from the cylinder inner wall 8a. The reaction force received will be reduced, and the inclination of the piston body A on the thrust side will be greatly reduced.

In the above embodiment, the length a of the slit 10 is longer than the width b between the basic outer walls of the apron portions 4 and 5, but the invention is not limited to this. Even if the length of the apron parts 4 and 5 is equal to the width b between the basic outer walls, that is, at least the vicinity of the apron parts 4 and 5 is reached, the same effect is exhibited.

[0021]

[Effect of device]

 The piston for an internal combustion engine according to the present invention having the above-described structure includes a crown portion forming a combustion chamber of the engine, a skirt portion continuously formed on a thrust side and an anti-thrust side of the crown portion, and both skirt portions. In a piston for an internal combustion engine having a piston main body that is connected and has an apron portion that is continuous with the crown portion, the piston pin hole center of the piston main body is thrust toward the axial center line of the piston main body. In addition to fusing, an oil ring groove is formed in the crown part, and a slit is provided in the thrust side bottom part of the oil ring groove, and the slit reaches at least the vicinity of the elongate part. Operating condition Especially, when the engine is warmed up, the influence of combustion pressure load is much larger. A load due to combustion pressure is applied to the crown surface of the piston, and a moment is generated that causes the piston body to rotate from the anti-thrust side to the thrust side.This moment causes the thrust-side skirt to move downward from the center of the piston pin hole. Side and the anti-thrust side skirt from the center of the piston pin hole to the upper side contact with the inner wall of the cylinder and stop, there is no slit in the oil ring groove on the anti-thrust side. It does not cause the whipping phenomenon of the crown part, and does not generate the topland striking sound generated when the anti-thrust side of the top land collides with the cylinder inner wall.

Further, paying attention to the thrust side skirt portion, when the above-mentioned moment is generated, this moment has the upper side of the skirt and the lower side of the skirt which are open ends, and therefore the reaction force received from the inner wall of the cylinder is generated by the skirt. The upper side as well as the lower side is deformed and absorbed, and the inclination of the piston body is reduced, so that seizure and the like due to strong wear contact of the skirt portion with the cylinder inner wall can be prevented.

Further, in the present invention, the piston body is configured to have an elliptical shape with a long diameter on the skirt side and a short diameter on the apron side, and the oval amount of the anti-thrust skirt portion is smaller than that of the thrust side skirt portion. As a result, the anti-thrust side skirt part becomes more circular and forms a contact part with the cylinder inner wall in a large area in the circumferential direction, supporting the load in a wide range, and the anti-thrust side skirt part It is possible to prevent local contact with the inner wall of the cylinder by suppressing the amount of deformation at. Further, since the local contact with the inner wall of the cylinder is not prevented by increasing the wall thickness of the skirt as in the conventional case, the weight of the entire piston body is reduced.

[Brief description of drawings]

FIG. 1 is a front view of a piston for an internal combustion engine according to a first embodiment of the present invention as viewed from a piston hole direction.

FIG. 2 is a view on arrow X in FIG.

FIG. 3 is an explanatory diagram for explaining a swinging motion of the piston body shown in FIG. 1 during operation of the internal combustion engine.

[Explanation of symbols]

 A Piston main body C Piston main body axis center line O Piston pin hole center 1 Crown part 2 Thrust side skirt part 3 Anti thrust side skirt part 4 Apron part 5 Apron part 7 Piston pin hole 8 Cylinder 8a Cylinder inner wall 9 Combustion chamber 10 Slit

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI technical display area F16J 9/00 A

Claims (2)

[Scope of utility model registration request] 1. An apron which connects a crown portion forming a combustion chamber of an engine, a skirt portion continuously formed on a thrust side and an anti-thrust side of the crown portion, and both skirt portions and which is continuous with the crown portion. For a piston for an internal combustion engine having a piston body and a piston pin hole center of the piston body is offset to the thrust side with respect to the axial center line of the piston body, and an oil ring groove is formed in the crown portion. A piston for an internal combustion engine, characterized in that a slit is provided in a bottom portion on the thrust side of the oil ring groove, and the slit reaches at least the vicinity of the apron portion. 2. The piston body is formed in an elliptical shape having a long diameter on the skirt side and a short diameter on the apron side, and the amount of oval in the anti-thrust skirt is smaller than that in the thrust skirt. Claim 1 characterized by
The internal combustion engine piston described.