JP2008038748A - Piston of reciprocating internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce a hitting sound and a friction loss caused between a piston and a cylinder inner wall surface, while reducing weight of the piston of a reciprocating internal combustion engine. <P>SOLUTION: Two pairs of rollers R, R, etc. are installed in a piston skirt part 22. The two pairs of rollers R, R, etc. are arranged in a lower position of a piston pin 31 in a side view, and are distributively arranged by pair in a symmetrical position sandwiching the piston pin 31 in a plan view. The respective pairs of rollers R and R are distributively arranged in a symmetrical position for sandwiching a motion reference surface P1 of a connecting rod 32 orthogonal to the piston pin 31. These two pairs of rollers R, R, etc. rollingly contact with the cylinder inner wall surface instead of a piston skirt of a conventional piston, and stabilize a reciprocating motion attitude of a piston 20A. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a piston for a reciprocating internal combustion engine in which a reciprocating motion of a piston is converted into a rotational motion using a crank and output.

  The reciprocating internal combustion engine is an internal combustion engine that is most frequently used as a prime mover for automobiles, and has a long history of improvement. Today, from the viewpoint of environmental issues, etc., a hybrid with an electric motor or a transition to a fully electric vehicle is being sought.However, in terms of the magnitude of the output relative to the weight of the engine in an operable state and the sharpness of the output rise, It is not easy to follow cars. Therefore, it is expected that the reciprocating internal combustion engine will maintain its leading role as a prime mover for automobiles for a considerable period of time, subject to further improvements in line with the demands of the times such as diversification of fuel used. .

  The reciprocating internal combustion engine is composed of a large number of mechanical elements and functional parts, and the improvements are wide-ranging. The present invention relates to a piston among them. The piston is slidably loaded into the cylinder bore so as to face the cylinder head to form a combustion chamber of the engine. A crankshaft is disposed below the piston, and the piston and the crankshaft are connected via a connecting rod. One end of the connecting rod is called a connecting rod small end, and a pin hole for inserting a piston pin is formed. On the other hand, the other end of the connecting rod is referred to as a connecting rod large end, and a shaft hole having a divided structure for holding the crank portion of the crankshaft is formed.

  The piston is formed with a pair of boss portions for supporting both ends of the piston pin. The piston and the connecting rod small end position the connecting rod small end between the pair of boss portions. It is connected by inserting a piston pin from the part to the other boss part side. That is, the piston has a structure in which the head is swung with the piston pin as the rotation axis.

  In a reciprocating internal combustion engine, a reciprocating motion and a rotational motion are mechanically linked by a combination of a piston, a connecting rod, and a crankshaft. In the reciprocating four-stroke engine, the piston drives the crankshaft via the connecting rod in the explosion stroke, and the crankshaft drives the piston in the intake stroke, the compression stroke, and the exhaust stroke. Thus, even if the transmission direction of power varies depending on the stroke, the piston reciprocates and the crankshaft rotates. At this time, the connecting rod performs a combined motion of a swing motion around the piston pin, a reciprocating motion associated with the crankshaft, and a turning motion. This combined motion is a motion that belongs to one plane that is orthogonal to the piston pin and the crankshaft and passes through the center of the piston, and is expressed as a “motion reference plane” of the connecting rod in the present application.

Among the moving members of the engine, the rotational inertial mass of the rotating member contributes to smooth rotation of the engine and is not necessarily a negative factor. On the other hand, the reciprocating inertial mass of the reciprocating member consumes energy generated by the explosion stroke, which is a negative factor in the operation of the engine. Therefore, the piston skirt portion tends to be gradually shortened in order to reduce the weight of the piston, which is a reciprocating member. For example,
JP-A-8-338529

  The idea to reduce the weight of the piston by shortening the piston skirt cannot be realized without sacrificing the inherent function of the piston skirt that stabilizes the reciprocating posture of the piston in the cylinder. It is an idea. The instantaneous uneven distribution of pressure in the combustion chamber during the explosion stroke and the reaction force of the swinging motion component of the connecting rod act as a force for tilting the piston. And the force which inclines a piston is received by the piston ring and piston skirt which were fitted by the side part of the piston crown surface part.

At this time, if the piston skirt portion is short, there is a problem that unpleasant hammering noise and a large frictional force are generated between the piston skirt portion and the cylinder inner wall surface. This is because a predetermined gap is set between the piston diameter and the cylinder bore in consideration of the thermal deformation of the cylinder. And generation | occurrence | production of such an unpleasant noise and unstable frictional force between a piston and a cylinder becomes a factor which consumes explosive energy wastefully, and impairs sensory engine performance, what is called engine feeling. Engine feeling is a big evaluation point on the consumer side for a vehicle equipped with the engine.

  In the present invention, the hitting sound and friction generated between the piston and the cylinder are caused by the piston trying to incline around the piston pin. Therefore, a specific portion of the piston skirt, specifically, the lower end of the piston skirt Note that this occurs in a limited part including the reference plane of motion of the connecting rod of the part, and a member for reducing friction is interposed in this part, more preferably, a member for reducing friction is interposed between the cylinder bore and It is an object of the present invention to provide a piston for a reciprocating internal combustion engine having a comfortable engine feeling as well as achieving both a reduction in weight and a smooth reciprocating motion without hitting sound by interposing it without setting a gap.

  The present invention employs the following means in order to solve the above problems.

  The piston of the reciprocating internal combustion engine according to claim 1 of the present invention includes a piston crown surface portion that receives explosion pressure, a piston skirt portion that stabilizes the reciprocating motion posture of the piston by sliding contact with the cylinder inner wall surface, and a small connecting rod. In a piston of a reciprocating internal combustion engine in which a pair of bosses that receive both ends of a piston pin inserted through the end are integrally formed of a light metal alloy, two pairs of rollers are assembled to the piston skirt portion. When the piston pin is attached to the boss, the piston pin is used as a reference, and the piston is disposed at a position below the piston pin in a side view as seen from the side, and in a plan view as seen from the piston crown side. A pair of rollers is arranged at symmetrical positions with the piston pin in between, and each pair of rollers is orthogonal to the piston pin. The two pairs of rollers are arranged at symmetrical positions across the motion reference plane of the connecting rod, and the two pairs of rollers stabilize the reciprocating motion posture of the piston by rolling contact with the inner wall surface of the cylinder instead of the piston skirt. To do.

  The piston according to the above configuration has two pairs of rollers in rolling contact with the inner wall surface of the cylinder in place of the piston skirt at the piston skirt portion. That is, the piston loaded in the cylinder bore comes into contact with the cylinder inner wall surface by the piston ring and the two pairs of rollers that are fitted into the side surface portion of the piston crown surface portion. Here, the positional relationship between the two pairs of rollers and the piston is such that the two rollers are in a position below the piston pin in a side view and a symmetrical position sandwiching the piston pin in a plan view with respect to the piston pin. Each pair of rollers is arranged at a symmetrical position across the motion reference plane of the connecting rod orthogonal to the piston pin. On the other hand, the motion that the piston tries to tilt is the motion that belongs to the plane orthogonal to the piston pin, that is, the motion that belongs to the motion reference plane of the connecting rod. Therefore, the stress for tilting the piston is distributed and distributed substantially evenly to each pair of rollers that are arranged with the motion reference surface of the connecting rod interposed therebetween. Here, the first difference is seen in comparison with a conventional piston in which stress is concentrated at one location of the piston skirt. Further, friction is generated between the roller and the inner wall surface of the cylinder due to the stress distributed to each pair of rollers. The friction loss at this time is extremely small as the rollers roll. Can be suppressed. Here, there is a second difference from the conventional piston in which the friction between the piston skirt and the cylinder inner wall surface is sliding friction.

  The piston of the reciprocating internal combustion engine according to claim 2 of the present invention is such that each pair of rollers in the piston of the reciprocating internal combustion engine according to claim 1 is attached in a direction in which the distance between the rollers is increased via the resilient member. It is characterized by being energized.

  In each pair of rollers according to the above configuration, the distance between each pair of rollers in the state inscribed in the cylinder inner wall surface having a constant bore diameter at a position other than the diameter portion is increased. That is, the roller is pressed against the inner wall surface of the cylinder. That is, as a result of energizing the pair of rollers in the direction of enlarging the distance between the rollers via the elastic member, the pair of rollers can be elastically pressed against the inner wall surface of the cylinder. In this case, it is not necessary to set a gap between the two pairs of rollers and the inner wall surface of the cylinder, so that it is possible to prevent the hitting sound caused by the gap.

  The piston of the reciprocating internal combustion engine according to claim 3 of the present invention is characterized in that each pair of rollers in the piston of the reciprocating internal combustion engine according to claim 1 is integrally formed or connected.

  Each pair of rollers according to the above configuration can adopt a complementary structure that is impossible with an independent structure by being integrally formed or connected, and realizes a roller having high strength per weight and high durability. In addition, the mounting man-hour for the piston can be reduced.

  The piston of the reciprocating internal combustion engine according to claim 4 of the present invention is such that two pairs of rollers in the piston of the reciprocating internal combustion engine according to any one of claims 1 to 3 are arranged via a resilient member. It is assembled to the skirt part.

  It is preferable that the total number of the two pairs of rollers in the piston of the reciprocating internal combustion engine of the present invention always be in contact with the inner wall surface of the cylinder with an appropriate contact pressure. To realize such a state, However, unrealistic mechanical accuracy is required, and it becomes difficult to adapt to thermal deformation of the cylinder. Therefore, when two pairs of rollers are fixedly attached, it is required to set an appropriate gap between the diameter of the circumscribed circle of the two pairs of rollers and the cylinder inner diameter. In this case, only one of the two pairs of rollers contacts the inner wall surface of the cylinder during the reciprocating motion of the piston, and the other pair of rollers operates in a state of floating from the inner wall surface of the cylinder. The occurrence of hitting sound is inevitable. Therefore, by attaching the two pairs of rollers to the piston skirt portion via the resilient member, the two pairs of rollers can be brought into contact with the inner wall surface of the cylinder simultaneously and stably. Since the elastic member functions as a suspension of the roller, an extremely smooth reciprocating motion of the piston can be realized.

  Since the piston of the reciprocating internal combustion engine of the present invention can stabilize the reciprocating posture of the piston smoothly by the two pairs of rollers that are in rolling contact with the inner wall surface of the cylinder instead of the piston skirt, the piston and the inner wall surface of the cylinder The friction loss between the two can be reduced, the engine feeling can be improved, and the piston skirt part other than the part where the two pairs of rollers are attached can be largely omitted, so the weight of the piston can also be reduced. Can do.

  In addition, when the two pairs of rollers are assembled to the piston via the resilient member, it is not necessary to provide a gap between the two pairs of rollers and the cylinder inner wall surface. The occurrence of hitting sound is effectively suppressed, and at the same time, the engine feeling is improved. Further, since the elastic member functions as a roller suspension and absorbs a transient external force during an explosion stroke or the like, the service life of the roller can be extended.

  The piston of the reciprocating internal combustion engine of the present invention (hereinafter simply referred to as “piston”) can take various forms, and two typical embodiments will be described below.

  The piston 20A of the present invention includes a piston crown surface portion 21, a piston skirt portion 22, a pair of boss portions 23, 23 for receiving both ends of the piston pin 31, two pairs of rollers R, R. It consists of two pairs of flanges 24, 24 ... for attaching R ... (FIGS. 1 to 3). These members have no special material requirements and are integrally formed from a light metal alloy mainly composed of aluminum except for the rollers R, R. 1 is a perspective view of the piston 20A, FIG. 2 is a side view of the piston 20A, and FIG. 3 is a bottom view of the piston 20A.

  The piston crown surface portion 21 is provided with a sufficient thickness to receive the explosion pressure, and ring grooves 2G, 2G... For mounting the compression ring and oil ring are cut into the side surface portion of the piston crown surface portion 21. It is rare. The piston skirt portion 22 is set to be extremely short, and a pair of boss portions 23, 23 are formed on the inner surface thereof. In addition, the part corresponding to the boss | hub parts 23 and 23 of the piston skirt 22 is partially chamfered, and it is set as the hollow surfaces 2B and 2B.

  The small end portion 3S of the connecting rod 32 is supported by the boss portions 23, 23 via the piston pin 31, and the large end portion 3B of the connecting rod 32 is connected so as to grip the crank portion C2 of the crankshaft CS. (Fig. 1). When the crankshaft CS rotates, the large end portion 3B of the connecting rod 32 performs a turning motion, and the connecting rod 32 moves up and down while swinging around the piston pin 31. Such movement of the connecting rod 32 is performed so as to belong to one plane orthogonal to the piston pin 31, and this one plane is referred to as a movement reference plane P1 of the connecting rod 32 in the present application. The motion reference plane P1 is a conceptual plane that does not actually exist, and FIG. 1 shows a part thereof.

  In the piston 20 </ b> A, two pairs of flanges 24, 24... For attaching the rollers R, R. At this time, the base portions of the pair of flanges 24 and 24 are connected to the inner side surface of the piston skirt portion 22 and the boss portions 23 and 23. The two pairs of flanges 24, 24... Are formed in a direction orthogonal to the direction of the axis P2 of the piston pin 31 inserted through the boss portions 23, 23 as a whole. The rollers R, R in a form in which the pair of rollers R, R are integrally formed are assembled in parallel with the direction of the axis P2 of the piston pin 31 (FIG. 3).

  Here, the two pairs of rollers R, R... Are disposed at a position below the piston pin 31 in a side view when the piston 20A is viewed from the side with reference to the piston pin 31 (FIG. 2), and the piston 20A is disposed on the piston 20A. In a plan view viewed from the piston crown 21 side, a pair of pairs of rollers R, R are arranged at symmetrical positions sandwiching the piston pin 31 (FIG. 3), and each pair of rollers R, R is a connecting rod 32 orthogonal to the piston pin 31. Are arranged at symmetrical positions with respect to the motion reference plane P1. FIG. 3 is a bottom view, but the arrangement relationship between the piston pin 31 and the two pairs of rollers R, R... Is the same even in the plan view, and is quoted instead of the plan view.

The two pairs of rollers R, R,... Are arranged close to the motion reference plane P1 of the connecting rod 32 after satisfying such an arrangement condition. In relation to the cylinder bore, Is inscribed through a predetermined gap.

  Each pair of rollers R and R is integrally formed with a body portion R1 interposed therebetween, and has a drum shape as a whole (FIG. 4). The pair of integrally formed rollers R and R is rotatably supported by a mounting shaft 25 provided horizontally between the pair of flanges 24 and 24. Two pairs of ball bearings B1 and B1 are loaded in parallel inside the pair of rollers R and R, respectively, and can rotate with low friction while increasing the load bearing capacity.

  In the piston 20A according to the above-described embodiment, in use, only the compression ring and the oil ring fitted in the ring grooves 2G, 2G... And the two pairs of rollers R, R. Therefore, a smooth operating state can be realized with extremely low loss. Therefore, the piston skirt portion 22 is not necessary for the operation of the piston 20A, and the piston skirt portion 22 is further reduced within a range in which the strength of the flanges 24, 24. It is possible to reduce the weight.

  The gap between the cylinder bore LB and the two pairs of rollers R, R... Set in the above embodiment is preferably not set in order to ensure a smoother reciprocating motion of the piston 20A. For this purpose, some measures against thermal expansion and thermal deformation of each part of the cylinder bore and the piston are required. As this measure, two pairs of rollers R, R... Can be attached via the elastic member 26 (FIG. 5).

  In FIG. 5, sleeve-like elastic members 26, 26 are interposed between the mounting shafts 25 of the rollers R, R and the flanges 24, 24. As the resilient member 26, a Teflon (registered trademark) sleeve, a fluororubber tube, a metal tube with a wave process, or the like can be used, but here, a material in which roll pins are simply doubled is used. The roll pin itself is not originally a member having a resilient property, but it cannot be a perfect cylindrical shape. This is because the elastic displacement range of the elastic member 26 may be 0.2 mm. The two pairs of rollers R, R... Are maintained in a stable contact state with the cylinder inner wall surface LB even when the engine is cold or when the engine is warm. can do.

  When each of the two pairs of rollers R, R... Is provided independently, a resilient member 27 is interposed between each pair of rollers R, R facing each other across the motion reference plane P1 of the connecting rod 32. The roller can be biased in the direction in which the distance between the rollers increases (FIG. 6). As the resilient member 27 used in the present embodiment, a member in which a displacement is imparted in the axial direction by engraving a number of independent slits in the circumferential direction in a metal tube is used. This is, for example, a configuration used for flexible coupling of a rotation transmission shaft.

The elastic member 27 having such a configuration is incorporated between the rollers R and R using the mounting shaft 25 of the rollers R and R. At this time, predetermined clearances G1, G1 may be set between the rollers R, R and the adjacent flanges 24, 24 in a state where the pair of rollers R, R are in contact with the cylinder inner wall surface LB. is necessary. Since each roller R is always subjected to a thrust load by the elastic member 27, the ball bearings B1 and B1 are of an angular contact type. By adjusting the elastic force of the elastic member 27, the contact pressure of each roller R against the cylinder inner wall surface LB can be easily optimized.

  A piston 20B according to another embodiment of the present invention is attached in such a manner that two pairs of rollers R, R... Are embedded in the piston skirt portion 22 (FIGS. 7 to 9). The arrangement relationship between the two pairs of rollers R, R... With respect to the movement reference plane P1 of the piston pin 31 and the connecting rod 32 is the same as that of the piston 20A in the previous embodiment.

  The piston skirt portion 22 of the piston 20B is formed with a total of four plane portions 22S, 22S... At two symmetrical positions sandwiching the piston pin 31, and a square hole is formed in each plane portion 22S. Yes. At this time, each planar portion 22S is set in a posture orthogonal to the radial direction of the piston 20B at that position. Each roller R is housed in a case 28 having a pair of left and right flanges 28F, 28F, and is rotatably supported by a shaft 25S provided horizontally in the case 28 (FIG. 9). A needle roller bearing B2 is interposed between the shaft 25S and the roller R. A part of the roller R protrudes outside the case 28.

  Each roller R is embedded in a square hole provided in the flat surface portion 22S of the piston skirt portion 22 together with the case 28, and is positioned by flanges 28F and 28F of the case 28. Each roller R is restrained so that it cannot escape when the piston 20B is loaded into the cylinder bore and the portion protruding from the case 28 abuts against the cylinder inner wall surface LB. At this time, the elastic members 29 are interposed between the back surfaces of the flanges 28 </ b> F and 28 </ b> F of the case 28 and the flat portion 22 </ b> S of the piston skirt portion 22, so that each roller R can be elastically supported together with the case 28. . The elastic member 29 in this case is suitably a concave or convex surface or a leaf spring processed into a W shape. The piston 20B of the type shown in this embodiment has an advantage that each roller R can abut on the cylinder inner wall surface LB in an ideal posture.

  In the pistons 20A and 20B of any of the above-described embodiments, the arrangement angle A of the pair of rollers R and R arranged with the motion reference plane P1 of the connecting rod 32 in the range of 30 degrees to 50 degrees. It is preferable to do. This is because the stress to incline the piston concentrates in the vicinity of the motion reference plane P1. As for the material of the roller R, at present, steel for bearings is used. From the viewpoint of further weight reduction, pursuit of quietness, and smooth operation, a resin material or a resin material that can withstand the in-cylinder environment. The possibility of using composite materials of ceramics and metal materials, ceramics, foamed metals, etc. is for further study.

It is a perspective view which shows embodiment of the piston of this invention. It is a side view which shows embodiment of the piston of this invention. It is a bottom view which shows embodiment of the piston of this invention. FIG. 3 is an enlarged sectional view taken along line XX in FIG. 2. FIG. 5 is a view corresponding to FIG. 4 showing another embodiment of the piston of the present invention. FIG. 5 is a view corresponding to FIG. 4 showing another embodiment of the piston of the present invention. It is a perspective view which shows other embodiment of the piston of this invention. It is a bottom view which shows other embodiment of the piston of this invention. It is an expanded sectional view of the principal part of FIG.

Explanation of symbols

20A Piston 20B Piston P1 Motion reference surface LB Cylinder inner wall surface R Roller 21 Piston crown surface portion 22 Piston skirt portion 23 Boss portion 24 Flange 26 Bulleting member 27 Bulleting member 29 Bulleting member 32 Connecting rod 3S Connecting rod small end 3B Connecting rod Big end

Claims (4)

A piston crown surface portion that receives the explosion pressure, a piston skirt portion that stabilizes the reciprocating motion posture of the piston by sliding contact with the cylinder inner wall surface, and a pair of boss portions that receive both ends of the piston pin inserted through the small end of the connecting rod; In a piston of a reciprocating internal combustion engine formed integrally from a light metal alloy,
Two pairs of rollers are assembled to the piston skirt portion, and the two pairs of rollers are piston pins in a side view when the piston is viewed from the side with respect to the piston pin when the piston pin is attached to the boss portion. And a pair of rollers arranged at symmetrical positions sandwiching the piston pin in a plan view when the piston is viewed from the piston crown surface side, and each pair of rollers is a connecting rod orthogonal to the piston pin. Are arranged at symmetrical positions across the motion reference plane,
The piston of the reciprocating internal combustion engine, wherein the two pairs of rollers stabilize a reciprocating motion posture of the piston by rolling contact with a cylinder inner wall surface instead of the piston skirt.   2. The piston of the reciprocating internal combustion engine according to claim 1, wherein each of the pair of rollers in the two pairs of rollers is urged in a direction in which a distance between the rollers increases via a resilient member.   2. The piston of the reciprocating internal combustion engine according to claim 1, wherein each pair of rollers in the two pairs of rollers is integrally formed or connected. The piston of the reciprocating internal combustion engine according to any one of claims 1 to 3, wherein the two pairs of rollers are assembled to the piston skirt portion via a resilient member.

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