JP2008111405A - Structure for piston - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a structure for a piston capable of providing ring tension of an oil ring required according to an engine operation condition. <P>SOLUTION: The oil ring 23 is provided with a ring body 233 including a pair of an upper and a lower side rail 231, 232 projecting to an outer circumference side at an upper and a lower part in a piston axial direction, and a coil expander 243 combined in an inner circumference side of the ring body 233 and applying tension by pressing the ring body 233 from the inner circumference side. A piston axial direction upper surface 13a of an oil ring groove 13 is inclined piston axial direction upward as it goes to the outer circumference side from the inner circumference side with respect to an upper surface 231a of the upper side rail 231. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a structure of a piston, and more particularly, to a countermeasure for obtaining a ring tension of an oil ring required according to an operating state of an internal combustion engine.

  Conventionally, pistons of an internal combustion engine have been provided with an oil ring groove for inserting an oil ring that uniformly applies the lubricant to the cylinder bore and collects excess lubricant. And as an oil ring, it is combined with the substantially annular ring main body which has a pair of side rail which protrudes on the outer peripheral side in the up-and-down direction of the piston axis, and the inner peripheral side of the ring main body. A two-piece type comprising an expander that is pressed to give tension is used (see, for example, Patent Document 1).

In this case, if the amount of lubricating oil applied to the cylinder bore is large or is not recovered, the lubricating oil will be carried to the combustion chamber and burned, resulting in an increase in the amount of lubricating oil consumed. Therefore, in order to reduce the consumption of lubricating oil, it is important to keep the amount of lubricating oil applied to the cylinder bore thin as long as the cylinder, piston and compression ring do not seize, and to efficiently recover excess lubricating oil Therefore, it is necessary to increase the ring tension that is the basis of the force with which the side rail of the ring body presses the cylinder bore as compared with the compression ring.
JP 2004-162634 A

  By the way, the lubricating oil applied to the cylinder bore by the oil ring is scraped off and recovered from the cylinder bore by the compression ring located on the upper side in the piston axial direction from the oil ring.

  In that case, in the above-mentioned conventional one, the upper surface of the oil ring groove in the piston axial direction is formed in parallel with the surface orthogonal to the piston shaft (cross section of the piston). The upper surface of the piston ring axial direction and the upper surface of the side rail on the piston ring upper side of the ring body of the oil ring are in close contact with each other, and the lubricating oil scraped off from the cylinder bore by the compression ring is between the upper side rail of the piston axial direction. It accumulates and becomes very difficult to collect.

  Therefore, the ring tension of the oil ring is optimized, and the lubricating oil scraped off from the cylinder bore by the compression ring is passed between the side rails on the piston axial direction upper side of the ring body of the oil ring and the cylinder bore, and the upper and lower sides in the piston axial direction. Lubricating oil is introduced into the piston through oil drain holes that open to the inner peripheral surface of the oil ring groove from a plurality of through holes that are guided between the rails and penetrate from the inner peripheral side to the outer peripheral side at predetermined intervals in the circumferential direction of the link body. It is conceivable to drop it and collect it.

  However, the ring tension of the oil ring is required at the time of high rotation and high load of the internal combustion engine, but not so high at low rotation and low load, and is necessary according to the operating condition of the internal combustion engine. A difference will occur in the ring tension.

  In other words, if the ring tension of the oil ring is too small during high speed or high load of the internal combustion engine, excess lubricating oil adhering to the cylinder bore cannot be recovered efficiently, and the scraping performance of the lubricating oil deteriorates. Therefore, the amount of consumption of lubricating oil will increase.

  On the other hand, if the ring tension of the oil ring is too large at the time of low rotation or low load of the internal combustion engine, the frictional force against the cylinder bore becomes too large and the piston friction increases, which may adversely affect the fuel efficiency.

  The present invention has been made in view of the above points, and an object of the present invention is to provide a piston structure capable of obtaining a ring tension of an oil ring required according to an operating state of an internal combustion engine. There is.

  In order to achieve the above object, the present invention is based on the premise of a piston structure in which an oil ring for recovering excess lubricating oil while being uniformly applied to the cylinder bore is inserted into the oil ring groove. In addition, a ring main body having a pair of side rails projecting to the outer peripheral side in the upper and lower directions in the piston axial direction, and an expander that is combined with the inner peripheral side of the ring main body and applies tension by pressing the ring main body from the inner peripheral side With. And the piston axial direction upper surface of the oil ring groove is inclined upward in the piston axial direction from the inner peripheral side to the outer peripheral side with respect to the upper surface of the side rail on the upper side in the piston axial direction.

  Due to this special feature, the upper surface of the side rail on the upper side of the piston axis of the oil ring to which tension is applied by the expander, and the upper surface of the side rail are inclined upward in the direction of the piston axis from the inner side to the outer side. A wedge-shaped space is formed between the oil ring groove and the upper surface in the axial direction of the piston, and the lubricating oil scraped off from the cylinder bore by the compression ring is guided to the upper surface of the side rail and is wedge-shaped. Is discharged to the back surface (inward side) of the oil ring through the space between the inner end of the upper surface of the side rail and the upper surface of the oil ring groove in the axial direction of the piston. The oil is dropped into the piston through the oil drain hole and collected.

  Accordingly, when the lubricating oil is discharged from the wedge-shaped space between the inner end of the upper surface of the side rail and the upper surface in the piston axial direction of the oil ring groove to the rear surface of the oil ring, the upper surface of the side rail The side rail on the upper side in the piston axial direction is pressed toward the cylinder bore by the lubricating oil passing between the inner end of the oil ring groove and the upper surface in the piston axial direction of the oil ring groove, and the ring tension of the oil ring increases. The increase in the ring tension of the oil ring due to the passage of the lubricating oil appears remarkably when the internal combustion engine is at a high speed or a high load. For this reason, it is not necessary to set the ring tension of the oil ring large, it is possible to reduce the friction of the piston by reducing the frictional force against the cylinder bore when the internal combustion engine is running at a low speed or a low load, and therefore It becomes possible to keep fuel consumption favorable. In addition, it is not necessary to set the ring tension of the oil ring small, and excess lubricating oil adhering to the cylinder bore is efficiently recovered when the internal combustion engine is at high speed or high load, and the lubricating oil is scraped off. It becomes possible to improve, and it becomes possible to suppress consumption of lubricating oil.

  In addition, the upper surface of the side rail on the upper side in the piston axial direction is inclined upward in the direction of the piston axis as it goes from the inner peripheral side to the outer peripheral side with respect to the surface orthogonal to the piston axis. Is set to an angle smaller than the inclination angle of the upper surface in the piston axial direction of the oil ring groove, the lubricating oil scraped off from the cylinder bore by the compression ring is Together, the oil ring is smoothly guided to the upper surface of the side rail and smoothly guided to the wedge-shaped space, and passes between the inner end of the upper surface of the side rail and the upper surface in the piston axial direction of the oil ring groove. Efficiently discharged to the back surface of the oil ring and dropped into the piston through the oil drain hole on the inner peripheral surface of the oil ring groove. That.

  As a result, the lubricating oil is easily discharged from the wedge-shaped space between the inner end of the upper surface of the side rail and the upper surface in the piston axial direction of the oil ring groove to the back surface of the oil ring. The side rail on the upper side in the piston axial direction is pressed toward the cylinder bore by the lubricating oil passing between the inner end of the oil ring groove and the upper surface in the piston axial direction of the oil ring groove, and the ring tension of the oil ring is further increased. . At this time, the increase in the ring tension of the oil ring due to the passage of the lubricating oil appears remarkably at the time of high rotation and high load of the internal combustion engine, so it is not necessary to set the ring tension of the oil ring large, Since the frictional force against the cylinder bore can be reduced to reduce the friction of the piston when the engine is running at a low speed or at a low load, the fuel consumption can be kept good. In addition, it is no longer necessary to set the ring tension of the oil ring small, and excess lubricating oil adhering to the cylinder bore is recovered more efficiently when the internal combustion engine is at high speed or high load, and the lubricating oil is scraped off. Can be further improved, and consumption of the lubricating oil can be effectively suppressed.

  In short, the upper surface of the side rail and the piston shaft of the oil ring groove are inclined by tilting the upper surface of the oil ring groove in the piston axial direction upward from the inner peripheral side to the outer peripheral side with respect to the upper surface of the side rail. A wedge-shaped space is formed between the upper surface in the direction and the lubricating oil scraped off from the cylinder bore by the compression ring is formed between the inner end of the upper surface of the side rail and the upper surface in the piston axial direction of the oil ring groove from the wedge-shaped space. When passing between the cylinders, the passage of the lubricating oil pushes the side rail on the upper side in the piston axial direction toward the cylinder bore to increase the ring tension of the oil ring. Piston friction is reduced by reducing the frictional force against the cylinder bore when the engine is running at low speed or under low load. Therefore, it is possible to maintain good fuel efficiency, and on the other hand, even if the ring tension of the oil ring is not set small, the excess lubricating oil adhering to the cylinder bore at the time of high rotation and high load of the internal combustion engine is efficiently obtained. It can collect | recover and it can improve the scraping performance of lubricating oil, and also can suppress the consumption of lubricating oil.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a cross-sectional view of the vicinity of a piston having a piston structure according to Embodiment 1 of the present invention. A top ring groove 11, a second ring groove 12, and an oil ring groove 13 are formed on the upper outer peripheral surface of the piston 1, respectively. The compression rings 21 and 22 and the oil ring 23 are respectively attached to the ring grooves 11 to 13.

  Here, the compression rings 21 and 22 block the gap between the piston 1 and the cylinder bore 31 of the cylinder 3, and prevent the compressed gas and the high-pressure combustion gas from leaking from the combustion chamber 10 to the crankcase (not shown) as blow-by gas. The heat received by the piston 1 is transmitted to the cylinder bore 31 to perform a heat dissipation function.

  On the other hand, the oil ring 23 includes a ring body 233 having a substantially E-shaped cross section having a pair of upper and lower side rails 231 and 232 projecting toward the outer periphery in the upper and lower directions of the piston 1 axial direction, and the inner periphery of the ring body 233. And a so-called two-piece type comprising a coil expander 234 that applies tension by pressing the ring body 233 from the inner peripheral side. The ring main body 233 has a plurality of through holes that penetrate from the inner peripheral side to the outer peripheral side at predetermined intervals in the circumferential direction. The coil expander 234 is formed in a substantially annular shape so as to apply a tension to the ring body 233 by pressing the ring body 233 combined with the coil expander 234 from the inner peripheral side. The oil ring 23 is responsible for controlling the formation of the lubricating oil film in the cylinder bore 31. That is, in the oil ring 23, the coil expander 234 is combined from the inner peripheral side so that the oil (lubricating oil) can be easily scraped off by the upper and lower side rails 231 and 232 of the ring body 233, and scraped from the cylinder bore 31. The dropped oil is guided from each through hole of the ring body 233 to the inner peripheral surface of the ring groove (oil ring groove) 13, and through the oil drain hole 131 formed on the inner peripheral surface of the oil ring groove 13. It is dropped into the piston 1 and collected.

  As a characteristic part of the present invention, as shown in FIG. 2, the upper surface 231a of the upper side rail 231 is formed in parallel with the surface A (transverse section of the piston 1) orthogonal to the piston 1 axis. On the other hand, the piston ring axial upper surface 13a of the oil ring groove 13 is directed upward in the piston one axial direction as it goes from the inner peripheral side to the outer peripheral side with respect to the upper surface 231a (surface A orthogonal to the piston one axis) of the upper side rail 231. It is inclined to. In this case, the inclination angle α of the upper surface 13a of the oil ring groove 13 is set to, for example, 2 to 3 ° with respect to the upper surface 231a of the upper side rail 231.

  Therefore, in the first embodiment, the upper surface 231a of the upper side rail 231 of the oil ring 23 to which the tension is applied by the coil expander 234 and the upper surface 231a of the upper side rail 231 are moved from the inner peripheral side to the outer peripheral side. A wedge-shaped space Z is formed between the upper surface 13a of the oil ring groove 13 inclined upward in the axial direction of the piston, and the oil scraped off from the cylinder bore 31 by the compression rings 21 and 22 The rear surface of the oil ring 23 is guided by the upper surface 231a of the side rail 231 and guided to the wedge-shaped space Z and passes between the inner end of the upper surface 231a of the upper side rail 231 and the upper surface 13a of the oil ring groove 13. The oil ring groove 13 is discharged through the oil drain hole 131 on the inner peripheral surface. It will be recovered plunge into tons 1 inside.

  Thus, when oil is discharged from the wedge-shaped space Z to the back surface of the oil ring 23 through the space between the inner end of the upper surface 231 a of the upper side rail 231 and the upper surface 13 a of the oil ring groove 13, The oil passing between the inner end of the upper surface 231a of the side rail 231 and the upper surface 13a of the oil ring groove 13 presses the upper side rail 231 toward the cylinder bore 31, and the ring tension of the oil ring 23 increases. . The increase in the ring tension of the oil ring 23 due to the passage of the oil appears remarkably at the time of high engine speed and high load. For this reason, it is not necessary to set the ring tension of the oil ring 23 large, and the frictional force on the cylinder bore 31 can be suppressed to be small and the friction of the piston 1 can be reduced at the time of low engine speed or low load. , Fuel economy can be kept good. In addition, it is not necessary to set the ring tension of the oil ring 23 small, and excess oil adhering to the cylinder bore 31 is efficiently recovered at the time of high engine speed and high load, thereby improving the oil scraping performance. In addition, oil consumption can be suppressed.

  Next, a second embodiment of the present invention will be described with reference to FIGS.

  In this embodiment, the configuration of the upper side rail of the ring body is changed. In addition, the structure other than an upper side rail is the same as that of the case of the said Example 1, The same code | symbol is attached | subjected about the same part and the detailed description is abbreviate | omitted.

  That is, in this embodiment, as shown in FIG. 3, the upper surface 231a of the upper side rail 231 of the ring body 233 is in the direction of the piston shaft 1 as it goes from the inner periphery side to the outer periphery side with respect to the surface A orthogonal to the piston 1 axis. It is inclined upward. The inclination angle β of the upper surface of the upper side rail 231 is set to be smaller than the inclination angle α of the upper surface 13 a of the oil ring groove 13. In this case, the difference (α−β) between the inclination angle α of the upper surface 13a of the oil ring groove 13 and the inclination angle β of the upper surface 231a of the upper side rail 231 is set to 2 to 3 °.

  Therefore, in the second embodiment, the oil scraped off from the cylinder bore 31 by the compression rings 21 and 22 is smoothly guided to the upper surface 231a of the upper side rail 231 together with the inclination of the upper surface 231a of the upper side rail 231. Smoothly guided to the wedge-shaped space Z, passes between the inner end of the upper surface 231a of the upper side rail 231 and the upper surface 13a of the oil ring groove 13, and is efficiently discharged to the back surface of the oil ring 23. The oil is dropped into the piston 1 through the oil drain hole 131 on the inner peripheral surface of the groove 13 and is effectively recovered.

  Accordingly, oil is easily discharged from the wedge-shaped space Z to the back surface of the oil ring 23 through the inner end of the upper surface 231a of the upper side rail 231 and the upper surface 13a of the oil ring groove 13, The upper side rail 231 is pressed toward the cylinder bore 31 by the oil passing between the inner end of the upper surface 231a of the side rail 231 and the upper surface 13a of the oil ring groove 13, and the ring tension of the oil ring 23 is further increased. It will be. At this time, the increase in the ring tension of the oil ring 23 due to the passage of the oil appears remarkably at the time of high engine speed and high load, so that it is not necessary to set the ring tension of the oil ring 23 large. Since the frictional force on the cylinder bore 31 can be suppressed to a low level when the engine is rotating at low speed or at a low load, the friction of the piston 1 can be reduced, so that the fuel efficiency can be kept good. In addition, it is not necessary to set the ring tension of the oil ring 23 small, and excess oil adhering to the cylinder bore 31 is recovered more efficiently at the time of high engine speed and high load, and the oil scraping performance is improved. It can be further improved and the oil consumption can be effectively suppressed.

  In addition, this invention is not limited to said each Example, Other various modifications are included. For example, in the first embodiment, the upper surface 13a of the oil ring groove 13 is inclined by 2 to 3 ° with respect to the upper surface 231a of the upper side rail 231. However, the inclination angle of the upper surface of the oil ring groove is limited to this. Instead, it may be any number of times as long as it is easy to guide oil into the wedge-shaped space.

  In the second embodiment, the difference (α−β) between the inclination angle α of the upper surface 13a of the oil ring groove 13 and the inclination angle β of the upper surface of the upper side rail 231 is set to 2 to 3 °. The difference between the inclination angle of the upper surface of the groove and the inclination angle of the upper surface of the upper side rail is not limited to this, and may be any number as long as it is an angle at which oil can be easily guided into the wedge-shaped space.

It is sectional drawing of the oil ring vicinity of the piston which concerns on Example 1 of this invention. It is an enlarged sectional view near the oil ring. It is sectional drawing of the oil ring vicinity of the piston which concerns on Example 2 of this invention. It is an enlarged sectional view near the oil ring.

Explanation of symbols

1 piston 13 oil ring groove 13a top surface (top surface in the piston axial direction)
23 Oil ring 231 Upper side rail 231a Upper surface 233 Ring body 234 Coil expander (expander)
3 Cylinder block 31 Cylinder bore A Surface orthogonal to the piston axis α Inclination angle of the upper surface of the oil ring groove β Inclination angle of the upper surface of the side rail

Claims (2)

A piston structure in which an oil ring that uniformly collects lubricating oil on the cylinder bore and collects excess lubricating oil is inserted into the oil ring groove,
The oil ring is combined with a ring body having a pair of side rails projecting to the outer peripheral side in the upper and lower direction of the piston axis, and an inner peripheral side of the ring main body, and applies tension by pressing the ring main body from the inner peripheral side. And an expander that
A piston structure, wherein an upper surface in the piston axial direction of the oil ring groove is inclined upward in the piston axial direction from the inner peripheral side to the outer peripheral side with respect to the upper surface of the side rail on the upper side in the piston axial direction. The structure of the piston according to claim 1,
The upper surface of the side rail on the upper side in the piston axis direction is inclined upward in the piston axis direction as it goes from the inner circumference side to the outer circumference side with respect to the plane orthogonal to the piston axis,
A piston structure characterized in that an inclination angle of an upper surface of the side rail on the upper side in the piston axial direction is set to be smaller than an inclination angle of an upper surface in the piston axial direction of the oil ring groove.

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