JP5292486B2 - Piston of internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a piston for an internal combustion engine, which is enabled to suppress permanent deformation of skirts, to achieve wear reduction and improvement in the seizure resistance of a sliding part, and to achieve reduction in weight, friction, noise, oil consumption, blow-by gas and the like. <P>SOLUTION: In the piston 1D of the internal combustion engine, the skirts 7A extending downwardly from the peripheral edge of a head 2 are partially provided on portions corresponding to end parts of first and second sidewalls 5A, 6A on the peripheral edge lower side of the head 2. The sidewalls are a pair of sidewalls. Connection parts 8A which connect the portions near the lower part including the lower part of the skirt on the same side of the pin boss side are further provided in the pair of sidewalls. <P>COPYRIGHT: (C)2012,JPO&amp;INPIT

Description

  The present invention relates to a piston for an internal combustion engine.

FIG. 16 is a diagram schematically showing an example of a conventional general piston. 2. Description of the Related Art Conventionally, a piston of an internal combustion engine is generally provided with a partially cylindrical skirt below the peripheral edge of the head. The skirt is slidably in contact with the bore of the internal combustion engine during engine operation, so that the posture of the piston that reciprocates in the cylinder is prevented from tilting (falling).
As a technique considered to be related to the present invention for a piston of an internal combustion engine, techniques related to this skirt are proposed in Patent Documents 1 to 4, for example.

JP 2001-82246 A Japanese Utility Model Publication No. 6-53743 JP 2000-337212 A JP-A-9-317554

  As shown in FIG. 16, in the conventional general piston, the skirt is connected to the side wall provided on the side (usually both sides) of the pin boss. For this reason, the rigidity of the skirt is greatly different between the central portion and both end portions in the circumferential direction. That is, both ends of the skirt are directly supported by the sidewalls, so that the rigidity is very high, whereas the central part is low in rigidity. FIG. 17 is a diagram showing an example of the stiffness distribution of the skirt, and it can be seen from FIG. 17 that the stiffness value is higher at both ends of the skirt than at the center. And since the largest thrust force acts on the center part of a skirt, it is easy to produce a permanent deformation.

On the other hand, in order to increase the rigidity of the central part of the skirt so as to suppress the occurrence of such permanent deformation, it is conceivable to increase the thickness of the skirt, for example. However, in this case, the piston weight is increased, so that the reciprocating performance of the piston is lowered, the output performance of the internal combustion engine may be adversely affected, and the rigidity of both ends of the skirt will be increased. Therefore, there is a possibility that both ends are seized by contact with the bore.
In order to increase the rigidity of the central part of the skirt, it may be possible to reduce the width of the skirt, for example. In this case, the surface pressure increases as the sliding area of the skirt decreases. In particular, there is a risk of increased wear of the skirt, bore, piston ring, etc.), seizure, increased noise, and the like.

  Therefore, the present invention has been made in view of the above problems, and can suppress permanent deformation of the skirt, reduce the wear of the sliding portion and improve seizure resistance, reduce the weight and reduce friction. It is an object of the present invention to provide a piston for an internal combustion engine that can reduce noise and reduce oil consumption and blow-by gas.

The present invention for solving the above problems is a piston of an internal combustion engine comprising a head, a pin boss provided at a lower portion of the head, and a sidewall provided on a side of the pin boss, A skirt extending downward from the peripheral edge portion is partially provided in a portion corresponding to the end of the sidewall below the peripheral edge portion of the head, and the sidewall is a pair of sidewalls, and the pair of side walls The wall further includes a connecting portion for connecting portions near the lower portion including the lower portion of the skirt on the same side of the pin boss, and the connecting portion is provided so as to extend straight. .

  According to the present invention, permanent deformation of the skirt can be suppressed, and in addition to reducing wear of the sliding portion and improving seizure resistance, it is possible to reduce weight, reduce friction, and reduce noise. Oil consumption and blow-by gas can be reduced.

It is a perspective view of piston 1A. It is a figure which shows typically piston 1A at the time of seeing along the axial direction of a pin hole. It is a figure which shows typically piston 1A at the time of seeing along a thrust and an anti-thrust direction. It is a perspective view of piston 1B. It is a figure which shows typically piston 1B at the time of seeing along a thrust and an anti- thrust direction. It is a perspective view of piston 1C. It is a figure which shows typically piston 1C at the time of seeing along the axial direction of a pin hole. It is a perspective view of piston 1D. It is a figure which shows typically piston 1D at the time of seeing along a thrust and anti- thrust direction. It is a figure which shows piston 1D typically by bottom view. FIG. 6 is a diagram schematically showing how a skirt 7A is deformed by a thrust force generated immediately after an explosion of combustion during engine operation in a piston 1A and a modified example of the piston 1A. It is a figure which shows typically piston 1E which concerns on a present Example at the time of seeing along a thrust and an anti- thrust direction. It is a figure which shows piston 1E typically by a bottom view. It is a figure which shows piston 1F typically by bottom view. It is a figure which shows piston 1G typically by bottom view. It is a figure which shows typically an example of the conventional general piston. It is a figure which shows an example of the rigidity distribution of a skirt.

  DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments for carrying out the present invention will be described in detail with reference to the drawings.

FIG. 1 is a perspective view of a piston (hereinafter simply referred to as a piston) 1A of an internal combustion engine according to the present embodiment. 2 is a diagram schematically showing the piston 1A when viewed along the axial direction of the pin hole, and FIG. 3 schematically shows the piston 1A when viewed along the thrust / anti-thrust direction. FIG.
The piston 1A includes a head 2, a pair of first and second pin bosses 3 and 4 provided at the lower portion of the head 2, a first sidewall 5A provided on both sides of the first pin boss, and a second It has a second side wall 6A provided on both sides of the pin boss and a skirt 7A.
The head 2 is a disk-shaped portion, and a ring groove 21 for mounting a piston ring and an oil ring (not shown) is formed on the outer periphery of the head 2. Note that the number of the ring grooves 21 is not limited to the two shown in the figure, and may be three, for example, which are generally employed.

First and second pin bosses 3 and 4 are provided below the head 2A. Piston pins (not shown) are attached to the first and second pin bosses 3 and 4.
The first sidewalls 5A provided on both sides of the first pin boss 3 are connected to the side of the first pin boss 3 and the lower part of the head 2, respectively.
The second side walls 6 </ b> A provided on both sides of the second pin boss 4 are respectively connected to the side portion of the second pin boss 4 and the lower portion of the head 2.

  The first and second sidewalls 5A, 6A include the central axis of the piston 1A and sandwich a plane that is substantially orthogonal to the central axis of the pin hole of the first pin boss 3 (or the second pin boss 4). A pair of side walls are formed, and the first and second side walls 5A and 6A are formed so as to have a symmetrical shape in the plane. The first and second sidewalls 5A, 6A are set so that the distance gradually increases from the first or second pin boss 3, 4 side toward the peripheral side. Each of the first and second sidewalls 5A and 6A is formed with a through hole H penetrating the wall surface.

  The skirt 7 </ b> A is provided extending downward from the peripheral edge of the head 2. Further, in this piston 1A, the skirt 7A is partially provided only at the portion corresponding to the end portions of the first and second sidewalls 5A, 6A below the peripheral edge of the head 2. The surface of the skirt 7A is a cylindrical surface formed with a diameter substantially the same as the outer diameter of the head 2, and is in sliding contact with a bore (not shown) of the internal combustion engine during engine operation.

Since the piston 1A having such a skirt 7A has a structure that facilitates uniform rigidity distribution in design, it is possible to optimize the surface pressure distribution so that the contact surface pressure distribution with the bore is uniform. it can. For this reason, in the piston 1A, permanent deformation of the skirt 7A is suppressed, wear of the sliding portion is reduced, and seizure resistance is improved.
The piston 1A having such a skirt 7A does not have a portion corresponding to the central portion of the skirt of the conventional general piston described above, so that the weight of the piston 1A can be reduced and the sliding area of the skirt can be reduced. A significant reduction in friction due to the reduction can also be realized. Further, in the piston 1A, the weight can be reduced also by the lightening by the through hole H.
Furthermore, in the piston 1A, since there is no portion corresponding to the center portion of the skirt, the oil scraped off by the piston ring is returned to the lower side as it is, and the oil consumption is thereby reduced.

In addition, since the bore is greatly deformed in the thrust / anti-thrust direction during engine operation, the clearance between the center of the skirt and the bore increases with the conventional general piston described above, resulting in increased noise (slap noise). In the piston 1A, the skirt portion 7A is formed at a position deviated from the center and slides where the deformation of the bore is relatively small. Therefore, such an increase in noise can be avoided. .
In addition, in the piston 1A, the engine startability at the time of cold start is particularly improved with the weight reduction of the piston, and the harmful exhaust gas and the cost can be reduced by reducing the auxiliary machine capacity.

FIG. 4 is a perspective view of the piston 1B according to the present embodiment. FIG. 5 is a diagram schematically showing the piston 1B when viewed along the thrust / anti-thrust direction.
The piston 1B according to the present embodiment is provided with a skirt 7B instead of the skirt 7A, and in accordance with this, the sidewall provided with the skirt 7B at a portion corresponding to the end instead of the sidewalls 5A and 6A. Except for having 5B and 6B, it is substantially the same as piston 1A.
The skirt 7B is configured by separating the skirt 7A into an upper part and a lower part. Specifically, the skirt 7B is separated into an upper part and a lower part by the dividing part B. The dividing portion B is formed so as to cut out the first and second sidewalls 5B and 6B along the thrust / anti-thrust direction from the central portion in the vertical direction of the skirt 7B, and further communicates with the through hole H. ing.

In the piston 1B provided with such a skirt 7B, the heat transfer to the lower part of the skirt 7B is interrupted, so that the temperature decreases (approaches the temperature on the bore side). The heat transfer is suitably interrupted by providing the through hole H and communicating the divided portion B to the through hole H. Thereby, since the clearance between the bore and the lower part of the skirt 7B can be reduced to the minimum, the piston posture can be further improved in the piston 1B.
For this reason, in addition to further reducing noise, the piston 1B can further reduce oil consumption and blow-by gas, and can also reduce weight by reducing the height of the compressor.
In the piston 1B, the stress received by the skirt 7B can be separated from the stress received from the head 2 and the stress received from the first and second sidewalls 5B and 6B, so that an appropriate profile is set for each of the upper and lower portions of the skirt 7B. Since this makes it possible to further optimize the surface pressure distribution, it is possible to reduce the friction due to the minimum skirt sliding area.

FIG. 6 is a perspective view of the piston 1C according to the present embodiment. FIG. 7 is a view schematically showing the piston 1C when viewed along the axial direction of the pin hole.
The piston 1C according to the present embodiment, except that the through hole H is not provided and the side walls 5C and 6C in which the through hole H is not provided instead of the side walls 5A and 6A. It is substantially the same as the piston 1A.

According to this piston 1C, it is possible to make the rigidity distribution in the vertical direction of the skirt 7A uniform with an extremely small skirt sliding area, thereby optimizing the surface pressure distribution so that the surface pressure distribution becomes uniform. Can be suitably achieved.
Further, since the piston 1C is not provided with the through hole H, the rigidity of the first and second sidewalls 5C and 6C is improved, thereby reducing the stress amplitude with respect to the combustion load. It is also possible to reduce the weight by making it easier.
Furthermore, since it is not necessary to form the through hole H in the piston 1C, it is possible to reduce mold costs, processing costs, and the like, thereby reducing costs.

  FIG. 8 is a perspective view of the piston 1D according to the present embodiment. 9 is a diagram schematically showing the piston 1D when viewed along the thrust / anti-thrust direction, and FIG. 10 is a diagram schematically showing the piston 1D in a bottom view. In the piston 1D according to the present embodiment, the lower portions of the skirt 7A related to the first and second sidewalls 5A and 6A, which are a pair of sidewalls, are arranged on the same side of the first and second pin bosses 3 and 4. It is substantially the same as the piston 1A except that it further includes a connecting portion 8A to be connected.

Here, in the above-described piston 1A, as shown in FIG. 11A, the skirt 7A is deformed by the thrust force generated immediately after the combustion explosion during engine operation, and is tilted in the axial direction of the pin hole (pin axial direction). We are concerned about the problem of Alternatively, as shown in FIG. 11B, the distance between the pair of first and second sidewalls 5A and 6A is set so as to gradually narrow from the first and second pin bosses 3 and 4 toward the peripheral side. In that case, there is a concern that the piston may be tilted in the axial direction (thrust direction) of the piston along the thrust / anti-thrust direction.
In this case, the clearance between the bore and the skirt 7A according to the set profile changes, and cracks and the like may easily occur in the first and second sidewalls 5A and 6A due to uneven wear and stress concentration due to local contact. There is.

In contrast, in the piston 1D, a connecting portion 8A formed integrally with the piston 1A is provided so as to be in sliding contact with the bore. Specifically, as shown in FIG. 10, the connecting portion 8A has a cylindrical surface whose surface is formed with a diameter substantially the same as the outer diameter of the piston 1D, and this cylindrical surface is in sliding contact with the bore during engine operation. It has become. For this reason, the connecting portion 8A also has a function as a skirt.
According to the piston 1D, the skirt 7A can be prevented from being deformed and tilted as shown in FIG. 11 by the connection of the connecting portion 8A.
Further, in the piston 1D, since the connecting portion 8A also has a function as a skirt, the swinging (swinging) of the piston 1D can be suppressed, and the connecting portion 8A is provided at the lower portion of the skirt 7A. The suppression effect can be enhanced.

For this reason, the piston 1D can further reduce the wear of the sliding portion, improve the seizure resistance, and reduce the noise as compared with the piston 1A, and also can reduce the blow-by gas, and includes the connecting portion 8A. It is possible to establish a minimal skirt sliding area with a decrease in the surface pressure of the entire skirt.
Further, in the piston 1D, since no skirt exists between the connecting portion 8A and the peripheral portion of the head 2, it is possible to reduce the weight and reduce the friction as compared with the above-described conventional general piston.
Further, in the piston 1D, oil stays in the upper portion of the connecting portion 8A during engine operation, and the staying oil scatters upward due to inertial force, resulting in improved lubrication of the sliding portion. The wear of the moving part can be reduced, and the cooling effect of the entire piston 1D can be obtained.

  FIG. 12 is a diagram schematically showing the piston 1E according to this embodiment when viewed along the thrust / anti-thrust direction, and FIG. 13 is a diagram schematically showing the piston 1E in a bottom view. The piston 1E according to the present embodiment is substantially the same as the piston 1D except that the connecting portion 8B is provided instead of the connecting portion 8A. Further, the connecting portion 8B is substantially the same as the connecting portion 8A except that the portion C near the center in the circumferential direction is formed so as not to be in sliding contact with the bore by performing the lightening. It has become.

According to the piston 1E, the friction can be reduced by reducing the skirt sliding area as compared with the piston 1D, and the clearance with the bore is obtained in the portion C near the center in the circumferential direction. It is possible to drop the scraped oil downward without retaining it, thereby suppressing an increase in oil consumption.
Further, by forming the portion C in the vicinity of the center in the circumferential direction so as not to be in sliding contact with the bore, and leaving the remaining portion so as to be in sliding contact with the bore, it becomes possible to disperse the surface pressure accordingly. Thereby, wear of the skirt 7A can be suppressed low.

As a modified example of the piston 1E, a connecting portion formed so that the portion C in the vicinity of the center in the circumferential direction of the connecting portion 8A remains in sliding contact with the bore and the remaining portion does not slide in contact with the bore. You may prepare instead of.
In this case, since the contact with the bore is supported at three points by the skirt 7A on both sides of the connecting portion and the connecting portion, the piston swing can be greatly reduced, and a very large noise reduction effect can be obtained. .
Further, in this case, the seizure can be avoided since the contact with the bore is eliminated in the connecting portion with the lower portion of the skirt 7A having the highest rigidity among the connecting portions.

FIG. 14 is a diagram schematically illustrating the piston 1F according to the present embodiment in a bottom view. In the piston 1F according to the present embodiment, the first and second side walls 5A and 6A, which are a pair of side walls, of the first and second pin bosses 3 and 4 are arranged in the vicinity of the lower part of the skirt 7A. The piston 1A is substantially the same as that of the piston 1A except that the connecting portion 8C is further connected on the same side.
The connecting portion 8C is provided so as to extend straight, so that the connecting portion 8C does not slide in contact with the bore. The connecting portion 8C is integrally formed with the first and second sidewalls 5A and 6A.

  According to the piston 1F, since the connecting portion 8C is provided so as to extend straight, it is preferable to structurally prevent the skirt 7A from being tilted by deformation as shown in FIG. 11 described above. Therefore, for example, it is possible to reduce the cross-sectional area as compared with the above-described connecting portion 8A. Therefore, the piston 1F can be further reduced in weight as compared with the piston 1D including the connecting portion 8A and the piston 1E including the connecting portion 8B.

FIG. 15 is a diagram schematically illustrating the piston 1G according to the present embodiment in a bottom view. In the piston 1G according to the present embodiment, the first and second portions of the first and second sidewalls 5A and 6A, which are a pair of sidewalls, in the same manner as the connecting portion 8C described above, are located near the lower portion of the skirt 7A. The piston 1A is substantially the same as the piston 1A except that it further includes a connecting portion 8D that is connected on the same side of the two pin bosses 3 and 4. The connecting portion 8D is provided so as to extend straight like the connecting portion 8C. For this reason, the connecting portion 8D is not slidably contacted with the bore.
On the other hand, the connecting portion 8D is made of an elastic member (for example, resin or hard rubber) that is lighter than the material (for example, aluminum alloy) of the piston 1G, and is formed separately from the piston body. The connecting portion 8D is assembled to the first and second sidewalls 5A and 6A by a method such as press fitting, adhesion, or diffusion bonding.

  According to the piston 1G, by providing the connecting portion 8D made of a lightweight elastic member, it is possible to further reduce the weight as compared with the piston 1F including the connecting portion 8C. Further, since the connecting portion 8D is made of an elastic member, the stress acting on the first and second sidewalls 5A and 6A and the skirt 7A can be absorbed and thereby the generation of cracks can be further suppressed. You can also

  The embodiment described above is a preferred embodiment of the present invention. However, the present invention is not limited to this, and various modifications can be made without departing from the scope of the present invention. For example, in the above-described embodiment, the case of a piston having a pair of pin bosses at the lower portion of the head has been described. However, the piston may be a so-called single pin boss type piston integrally having a pin boss at the lower center of the head.

DESCRIPTION OF SYMBOLS 1 Piston 2 Head 3 1st pin boss 4 2nd pin boss 5 1st side wall 6 2nd side wall 7 Skirt 8 Connection part

Claims (1)

A piston of an internal combustion engine comprising a head, a pin boss provided at a lower portion of the head, and a sidewall provided on a side of the pin boss,
A skirt extending downward from the peripheral edge portion of the head is partially provided in a portion corresponding to an end portion of the sidewall, below the peripheral edge portion of the head,
The sidewalls are a pair of sidewalls;
Of the pair of sidewalls, further comprising a connecting portion for connecting portions near the lower portion including the lower portion of the skirt on the same side of the pin boss ,
A piston for an internal combustion engine, wherein the connecting portion is provided so as to extend straight .

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