JP2009243357A - Structure of piston - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a structure of a piston by which "oil rising" is prevented without deteriorating functions of posture-holding for an oil ring and a compression ring, a uniform oil film is stably formed on the surface of a cylinder bore, and slide resistance between the compression ring and the cylinder bore is reduced. <P>SOLUTION: In the structure of a piston reciprocating in a cylinder bore, a land 12 is provided with one or more compression rings 14a, 14b, and an oil ring 18 under the compression ring. The structure of the piston includes further a lubricating-oil recovering/supplying means which is provided with a lubricating-oil reservoir 20 formed in the land 12, an opening formed at the peripheral face of the land 12 between the compression ring 14b and the oil ring 18, an oil path 22 allowed to communicate with the lower part of the lubricating-oil reservoir 20, and an air path 24 allowing the upper part of the lubricating-oil reservoir 20 to communicate with the inside space of the piston 10. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a piston structure that reciprocates in a cylinder bore of an engine, and belongs to the technical field of engine production.

  The piston that reciprocates in the cylinder bore of the engine has a compression ring attached to its land (outer peripheral surface part on the combustion chamber side) that prevents leakage of combustion gas from the combustion chamber to the crank chamber. In order to reduce friction between the outer peripheral surface of the piston and the surface of the cylinder bore, a uniform lubricating oil film is formed on the surface of the cylinder bore, and when the piston is lowered, excess lubricating oil is scraped off to the combustion chamber. An oil ring is installed to prevent intrusion (so-called oil rise).

  As such a piston structure, there exists a thing of patent document 1, for example. As shown in FIG. 4, a circumferential groove 106 is formed in a portion of the land portion of the piston 100 between the compression ring 102 and the oil ring 104. The groove 106 is a space for temporarily storing the lubricating oil left by the oil ring 104 when the piston 100 descends in the cylinder bore 108.

  The lubricating oil stored in the groove 106 flows out in the first half of the ascending stroke (the piston is accelerating toward the combustion chamber) after the piston 100 changes from descending to ascending, and is uniformly distributed by the oil ring 104. An oil film is formed. At this time, the depth of the groove 106 is set so as to become shallower as it is closer to the oil ring 104 so that the lubricating oil easily flows out of the groove 106.

  Accordingly, excessive accumulation of lubricating oil in the vicinity of the compression ring 102 is suppressed, and oil rising to the combustion chamber is prevented. Further, it is possible to reduce the sliding resistance between the oil ring 104 and the surface of the cylinder bore 108 by reducing the tension of the oil ring 104 while preventing the oil from rising, and the improvement of the fuel consumption performance of the engine can be expected. .

JP 2001-214804 A

  However, the depth of the groove 106 for temporarily storing the lubricating oil formed in the land portion between the compression ring 102 and the oil ring 104 described in Patent Document 1 is the amount of lubricating oil that can be stored. Has its limits. For example, if the storage limit of the groove 106 is exceeded because the scraping ability of the lubricating oil of the oil ring 104 decreases due to deterioration of the oil ring 104 or the like, the oil cannot be stored in the groove 106 when the piston 100 is lowered. There is a possibility that the lubricating oil that has passed through the compression ring 102 leaks into the combustion chamber and the oil rises.

  As a countermeasure, it is conceivable that the groove 106 for temporarily storing the lubricating oil is deeply formed. In this case, the groove 106 for storing the lubricating oil, and the ring into which the compression ring 102 or the oil ring 104 is fitted. The partition wall portion 110 between the grooves is increased, the rigidity of the portion 110 is lowered, and the posture holding function of the compression ring 102, the oil ring 104, and the like is lowered. Further, when the groove 106 is deepened, the lubricating oil stored in the deep portion becomes difficult to flow out during the first half of the upward stroke of the piston 100, and there is a possibility that a uniform oil film cannot be formed on the surface of the cylinder bore 108.

  Therefore, the present invention can reduce the sliding resistance of the oil ring and can stably form a uniform oil film of the lubricating oil on the surface of the cylinder bore while maintaining the posture maintaining function for each ring, and further to the combustion chamber. It is an object of the present invention to provide a piston structure that can prevent oil from rising.

In order to solve the above-mentioned problem, the invention described in claim 1 is a piston structure that reciprocates in a cylinder bore and includes at least one compression ring at a land portion and an oil ring below the land.
A lubricating oil storage chamber formed inside the land portion;
An oil passage provided with an opening in a peripheral surface of a land portion between the compression ring and the oil ring, and communicated with a lower portion of the lubricating oil storage chamber;
Lubricating oil recovery and supply means having an air passage connecting the upper portion of the lubricating oil storage chamber and the internal space of the piston is provided.

The invention according to claim 2 is the piston structure according to claim 1,
At least two of the lubricating oil collection and supply means are provided in the circumferential direction of the land portion.

Furthermore, the invention according to claim 3 is the piston structure according to claim 1 or 2,
The lubricating oil storage chamber is formed by closing an opening of a non-through hole formed by a drill from below the piston.

  According to the first aspect of the present invention, the lubricating oil that has passed between the oil ring and the surface of the cylinder bore during the lowering of the piston partly accumulates in the vicinity of the compression ring, but the excess amount remains in the compression ring and the oil. The oil flows into the lubricating oil storage chamber formed inside the land portion through an oil passage having an opening on the peripheral surface of the land portion between the ring and stored. At this time, the lubricating oil smoothly flows into the lubricating oil storage chamber because the air in the storage chamber escapes from the upper portion of the lubricating oil storage chamber to the internal space (crank chamber) of the piston via the air passage. As a result, excessive lubricating oil accumulates in the vicinity of the compression ring while the piston is descending, and the lubricating oil enters the combustion chamber, that is, prevents the oil from rising.

  In addition, during the first half of the upward stroke of the piston, the lubricating oil stored in the lubricating oil storage chamber flows out between the compression ring and the oil ring through the oil passage. At this time, the lubricating oil flows out smoothly from the lower portion of the lubricating oil reservoir chamber due to the fact that the upper portion of the lubricating oil reservoir chamber is in communication with the internal space of the piston through the air passage and the inertial force acting on the lubricating oil. Thus, during the first half of the upward stroke of the piston, the lubricating oil is stably supplied to the oil ring, and a uniform oil film is stably formed on the surface of the cylinder bore.

  In addition, a compression ring or an oil ring as described in Patent Document 1 is fitted in a space for temporarily storing lubricating oil that has passed between the oil ring and the surface of the cylinder bore while the piston is descending. Since it is not a deep groove disposed between the ring grooves but a lubricating oil storage chamber that is a space formed inside the land portion, the posture holding function of each piston ring is not impaired. Also, by forming a large lubricating oil reservoir, it is possible to increase the amount of lubricating oil that passes between the oil ring and the cylinder bore surface while the piston is descending, that is, to reduce the tension of the oil ring. The sliding resistance between the oil ring and the surface of the cylinder bore can be reduced.

  According to the second aspect of the present invention, at least two lubricating oil collection and supply means including a lubricating oil storage chamber, an oil passage, and an air passage are provided in the circumferential direction of the land portion. At least two lubricating oil recovery and supply means share and store an appropriate amount of lubricating oil in the respective lubricating oil storage chambers, so that excessive lubricating oil is present in the vicinity of the compression ring while the piston is descending over the entire circumference. Accumulation can be prevented more reliably, and the lubricating oil can be supplied to the oil ring more reliably and stably during the first half of the piston lifting stroke.

  According to the third aspect of the present invention, the lubricating oil storage chamber is formed by closing the opening of the non-through hole machined by a drill from below the piston. A lubricating oil storage chamber, which is a space, can be easily formed inside the land portion of the piston.

  Hereinafter, embodiments of the present invention will be described.

  FIG. 1 shows a cross section of a piston structure according to an embodiment of the present invention. The piston denoted by reference numeral 10 in the figure reciprocates in the cylinder bore of the engine and has a bottomed cylindrical shape whose outer peripheral surface is in sliding contact with the surface of the cylinder bore.

  The piston 10 has two compression rings 14 a and 14 b attached to a land portion (an outer peripheral portion on the combustion chamber side) 12. Specifically, the piston 10 in a state in which the compression rings 14a and 14b having a substantially “C” shape are forcibly deformed and fitted into the ring grooves formed at the positions of the corresponding land portions 12 are fitted into the cylinder bores. Thus, the compression rings 14a and 14b are held in the ring groove of the piston 10 while being in contact with the surface of the cylinder bore with a constant pressure by the restoring force. The compression rings 14 a and 14 b prevent combustion gas generated in the combustion chamber from leaking into the crank chamber through the space between the cylinder bore and the piston 10.

  The piston 10 has an oil ring 18 attached to a portion of the land portion 12 below (on the skirt portion 16 side) the compression rings 14a and 14b. The oil ring 18 is also attached to the land portion 12 of the piston 10 in the same manner as the compression rings 14a and 14b. The oil ring 18 scrapes most of the lubricating oil on the surface of the cylinder bore while the piston 10 is descending to prevent the lubricating oil from entering the combustion chamber (oil rising). In order to reduce the friction between the outer peripheral surface of the cylinder and the surface of the cylinder bore, a uniform oil film of lubricating oil is formed on the surface of the cylinder bore. In the drawing, a compression ring and an oil ring and a groove therefor are simply shown.

  Inside the land portion 12 is formed a lubricating oil storage chamber 20 for temporarily storing the lubricating oil that has passed between the oil ring 18 and the surface of the cylinder bore while the piston 10 is being lowered. In order to collect the lubricating oil in the lubricating oil storage chamber 20, an opening is provided in the peripheral surface of the land portion 12 between the compression ring 14 b and the oil ring 18 and communicates with the lower portion of the lubricating oil storage chamber 20. An oil passage 22 is formed in the piston 10. Further, in order to facilitate the inflow and outflow of the lubricating oil to and from the lubricating oil storage chamber 20, an air passage 24 that connects the upper portion of the lubricating oil storage chamber 20 and the internal space (crank chamber) of the piston 10 is formed in the piston 10. Has been. The lubricating oil storage chamber 20, the oil passage 22, and the air passage 24 constitute the lubricating oil collection and supply means described in the claims. In the piston 10 shown in FIG. There are two in the direction.

  The lubricating oil storage chamber 20 is formed by fitting a plug 26 into an opening of a non-through hole that is machined from below the piston 10 and extends in the reciprocating direction of the piston 10.

  The oil passage 22 has an opening at the bottom of a shallow groove 28 formed around the land portion 12 between the compression ring 14 b and the oil ring 18, and communicates with the lower portion of the lubricating oil storage chamber 20. The oil passage 22 is formed by, for example, a drill.

  The groove 28 is used to facilitate the flow of the lubricating oil that has passed between the oil ring 18 and the surface of the cylinder bore into the oil passage 22 while the piston 10 is descending, and is formed for the purpose of storing the lubricating oil. It is not necessarily done. If the lubricating oil flows smoothly into the oil passage 22 without the groove 28, the groove 28 may be omitted.

  The air passage 24 is arranged so that the lubricating oil flows smoothly into the lubricating oil storage chamber 20 through the oil passage 22 while the piston 10 is descending, and in the first half of the upward stroke of the piston 10 (the piston 10 moves toward the combustion chamber). The upper portion of the lubricant reservoir 20 and the internal space (crank chamber) of the piston 10 so that the lubricant in the lubricant reservoir 20 flows smoothly toward the oil ring 18 through the oil passage 22 during acceleration. And contact. The air passage 24 is formed by, for example, a drill.

  From here, the operation of the lubricating oil recovery and supply means, that is, the roles of the lubricating oil storage chamber 20, the oil passage 22, and the air passage 24 will be described.

  FIG. 2 shows the state of the piston 10 in the first half of the upward stroke of the piston 10. The piston 10 moves in the cylinder bore 50 toward the combustion chamber 60.

  During the first half of the upward stroke of the piston 10, the lubricating oil L stored in the lubricating oil storage chamber 20 flows out between the compression ring 14 b and the oil ring 18 through the oil passage 22 due to inertial force. Then, the lubricating oil L that has flowed out is supplied to the oil ring 18 and formed into a uniform oil film Lf on the surface of the cylinder bore 50. The upper part of the lubricating oil storage chamber 20 is connected to the internal space (crank chamber 70) of the piston 10 via the air passage 24, and the oil passage 22 is connected to the lower part of the lubricating oil storage chamber 20. This is because the lubricating oil L flows out of the lubricating oil reservoir 20 smoothly.

  The recovery of the lubricating oil to the lubricating oil storage chamber 20 is performed while the piston 10 is being lowered, as shown in FIG. When the piston 10 is lowered, the lubricating oil L that has passed between the oil ring 18 and the surface of the cylinder bore 50 fills the space between the compression ring 14b and the oil ring 18, and then the oil L It flows into the lubricating oil storage chamber 20 via the passage 22 (in other words, a part of the compression ring 14b is accumulated in the vicinity of the compression ring 14b, but an excess amount flows into the storage chamber 20). At this time, the lubricating oil L smoothly flows into the lubricating oil reservoir 20 because the upper part of the lubricating oil reservoir 20 is connected to the internal space (crank chamber 70) of the piston 10 via the air passage 24. This is because the air in the lubricating oil storage chamber 20 escapes into the internal space of the piston 10 (the crank chamber 70). As a result, excessive lubricating oil L accumulates in the vicinity of the compression ring 14b while the piston 10 is descending, and the lubricating oil L enters the combustion chamber 60, that is, oil rise is prevented.

  According to this embodiment, as described above, oil rise is prevented, and a uniform oil film is stably formed on the surface of the cylinder bore. Further, a space for temporarily storing the lubricating oil L that has passed between the oil ring 18 and the surface of the cylinder bore 50 during the lowering of the piston 10, that is, the lubricating oil storage chamber 20 is formed inside the land portion 12. Therefore, the posture holding function with respect to the compression rings 14a and 14b and the oil ring 18 is impaired as compared with the case where the space is configured by a groove formed in the land portion between the compression ring and the oil ring (Patent Document 1). There is nothing.

  Further, by forming the lubricating oil storage chamber 20 large, it is possible to increase the amount of the lubricating oil L that passes between the oil ring 18 and the surface of the cylinder bore 50 while the piston 10 is lowered. By reducing the tension of the ring 18, the sliding resistance between the oil ring 18 and the surface of the cylinder bore 50 can be reduced.

  Although the present invention has been described with reference to one embodiment, the present invention is not limited to this.

  For example, in the case of the above-described embodiment, as shown in FIG. 1, only two lubricating oil recovery and supply means composed of a lubricating oil storage chamber, an oil passage, and an air passage are provided in the circumferential direction of the land portion. However, the present invention does not limit the number to two. However, it is preferable to provide at least two lubricating oil collecting / supplying means on the piston rather than one, and since it distributes and stores an appropriate amount of lubricating oil in each lubricating oil storage chamber, It is possible to more reliably prevent excessive accumulation of lubricating oil in the vicinity of the compression ring while the piston is descending, and to supply the lubricating oil to the oil ring more reliably and stably during the first half of the piston lifting stroke. is there.

  Moreover, in the case of the above-mentioned embodiment, although the lubricating oil storage chamber is formed by closing the non-through hole processed with the drill, this invention is not limited to this. However, the method of forming the lubricating oil storage chamber, which is a space inside the land, is simple and easy as the method of forming the lubricating oil storage chamber by closing the non-through hole processed with a drill.

  Furthermore, in the case of the above-described embodiment, two compression rings are attached to the piston, but the present invention is not limited to two as long as the leakage of combustion gas to the crank chamber can be prevented. Of course, one is necessary.

  As described above, the piston structure according to the present invention can reduce the sliding resistance of the oil ring and maintain a posture maintaining function with respect to each ring while stably providing a uniform oil film on the surface of the cylinder bore. In addition, oil can be prevented from rising into the combustion chamber. Therefore, it may be suitably used in the field of engine manufacturing industry.

It is a figure which shows the cross section of the piston structure which concerns on embodiment of this invention. It is a figure which shows the cross section of the land part periphery of the piston in the raising. It is a figure which shows the cross section of the land part periphery of the piston in descending. It is a figure which shows the cross section around the land part of the conventional piston.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Piston 12 Land part 14a Compression ring 14b Compression ring 18 Oil ring 20 Lubricating oil storage chamber 22 Oil path 24 Air path

Claims (3)

A piston structure that reciprocates in a cylinder bore and includes at least one compression ring at a land portion and an oil ring below the compression ring,
A lubricating oil storage chamber formed inside the land portion;
An oil passage provided with an opening in a peripheral surface of a land portion between the compression ring and the oil ring, and communicated with a lower portion of the lubricating oil storage chamber;
A piston structure comprising a lubricating oil recovery and supply means having an air passage connecting the upper portion of the lubricating oil storage chamber and the internal space of the piston. The piston structure according to claim 1,
The piston structure according to claim 1, wherein at least two of the lubricating oil recovery and supply means are provided in the circumferential direction of the land portion. The piston structure according to claim 1 or 2,
The said lubricating oil storage chamber is formed by closing the opening part of the non-through-hole processed with the drill from the downward direction of the piston.

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