JP2014055550A - Piston for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To efficiently discharge oil scraped off from an inner wall surface of a cylinder bore 4a to an inner side of a piston 3 for an internal combustion engine by an oil ring 8, in the piston 3 in which the oil ring 8 is mounted on a peripheral groove 3c formed on its outer periphery.SOLUTION: An oil return hole 3d for discharging oil to an inner side of a piston 3, is formed on at least one of a thrust-side region 100 and an anti-thrust-side region 200 of a peripheral groove 3c of the piston 3. An oil ring 8 is provided with an oil passage 8c in the radial direction, in the regions (100, 200) corresponding to an installation region of the oil return hole 3d, and further provided with an oil passage 8c in the radial direction in an engine front-side region 300 and an engine rear-side region 400, and an oil passage similar to the oil passages 8c is not formed in a region between the regions.

Description

  The present invention relates to a piston for an internal combustion engine in which an oil ring is mounted in a circumferential groove provided on the outer periphery.

  Generally, three circumferential grooves are provided on the outer periphery of a piston used in an internal combustion engine. A compression ring is attached to each of the first circumferential groove and the second circumferential groove from the top, and an oil ring is attached to the third circumferential groove from the top.

  The oil ring is provided mainly for scraping off oil adhering to the inner wall surface of the cylinder bore.

  For example, in Patent Document 1, a part of the oil scraped off from the inner wall surface of the cylinder by the oil ring is discharged from the drain path provided in the circumferential groove for mounting the oil ring of the piston to the inside of the piston and dropped to the oil pan. I have to.

  Further, for example, in Patent Documents 1 and 2, oil holes that penetrate radially inward and outward are provided at circumferentially equidistant positions on the entire circumference of the oil ring. In such a configuration, oil scraped off from the cylinder inner wall surface by the oil ring flows through the oil hole of the oil ring into the inner diameter side annular gap between the oil ring and the circumferential groove of the piston. It is made to discharge | emit to the piston inner side from the drain path of the circumferential groove | channel of a piston from a side annular clearance.

JP 2007-32777 A JP 2008-232312 A

  In the above conventional example, since oil holes are provided at equal circumferential circumferential positions on the entire circumference of the oil ring, the oil flow to the inside of the piston becomes worse, for example, the oil flow tends to stay. It can be said that. As a result, there are concerns about piston friction loss and oil consumption increase associated with the operation of the internal combustion engine.

  In view of such circumstances, the present invention provides a piston for an internal combustion engine in which an oil ring is mounted in a circumferential groove provided on the outer periphery, and the oil scraped off from the inner wall surface of the cylinder bore by the oil ring is efficiently injected into the piston. The purpose is to make it possible to discharge well.

  The present invention relates to a piston for an internal combustion engine in which an oil ring is mounted in a circumferential groove provided on an outer periphery, and oil is supplied to at least one of a thrust side region and an anti-thrust side region in the circumferential groove. An oil return hole is provided in the oil ring, and an oil passage along the radial direction is provided in a region corresponding to the installation region of the oil return hole in the oil ring, and an engine front side region and an engine rear side region are provided. An oil passage along a radial direction is provided, and an oil passage similar to the oil passage is not provided in a region between the regions in the oil ring.

  Generally, when the piston moves up in the cylinder bore, the oil ring is lowered in the circumferential groove, and the oil adhering to the inner wall surface of the cylinder bore is scraped off. On the other hand, when the piston descends in the cylinder bore, the oil ring rises in the circumferential groove and scrapes off the oil adhering to the inner wall surface of the cylinder bore.

  In any case, most of the oil scraped off by the oil ring flows into the opposing gap (inner diameter side annular gap) between the oil ring and the circumferential groove.

  These oils are dropped into the oil pan by being discharged to the inside of the piston through an oil return hole provided in the circumferential groove. For example, the oil collected in the oil pan is again sprayed to the inner wall surface of the cylinder bore, the inside of the piston, or the like.

  More specifically, the oil that has flowed into the inner ring-side annular gap passes through the oil passages installed in the engine front side region and the engine rear side region in the oil ring outward in the radial direction, so that the inside of the oil ring and the cylinder bore In addition to flowing into the facing gap (outer diameter side annular gap) with the wall surface, it passes through the oil return hole installed in at least one of the thrust side region or the anti-thrust side region inward in the radial direction, and inside the piston Will be discharged.

  By the way, the oil that has flowed into the outer diameter side annular gap is divided into the outer diameter side annular gap in one direction and the other in the circumferential direction, and at least one of the thrust side area and the anti-thrust side area in the oil ring. The oil passes through the oil passage installed in the radially inward direction and flows into the inner annular clearance, but this oil quickly passes through the oil return hole in the vicinity of the oil passage inward in the radial direction. To be discharged inside the piston.

  Thus, if the structure of this invention is employ | adopted, it will become difficult to retain oil in the surrounding groove of a piston like a prior art example, and will come to flow smoothly. That is, since the oil collected in the circumferential groove of the piston can be efficiently discharged to the inside of the piston, it is possible to reduce piston friction loss and oil consumption accompanying the operation of the internal combustion engine.

  Preferably, the oil return hole may be provided in both the thrust side region and the anti-thrust side region in the circumferential groove.

  In this case, the oil in the outer diameter side annular gap passes through the oil passage provided corresponding to the two azimuth areas of the thrust side area and the anti-thrust side area in the radial direction and flows into the inner diameter side annular gap. Be able to. As a result, the amount of oil passing from the outer diameter side annular gap to the inner diameter side annular gap increases, so that the amount of oil discharged to the inside of the piston increases.

  Preferably, the oil ring includes a ring main body and an expander that is fitted on the inner diameter side of the ring main body and applies a radially outward tension, and the oil passage has a diameter on the ring main body. It can be set as the structure made into the hole provided so that it may penetrate in and out of a direction.

  According to the present invention, oil scraped off from the inner wall surface of the cylinder bore by the oil ring can be efficiently discharged to the inside of the piston. Thereby, it is possible to reduce the friction loss of the piston and the oil consumption accompanying the operation of the internal combustion engine.

It is a figure which shows schematic structure of the piston support structure of the engine used as the application object of one Embodiment of the piston which concerns on this invention. It is a figure which shows the piston of FIG. 1 in cross section. FIG. 3 is an exploded perspective view of the oil ring of FIG. 2. It is a top view which fractures | ruptures and shows the half of the ring main body of the oil ring of FIG. FIG. 3 is a cross-sectional view taken along line (5)-(5) in FIG. 2. FIG. 3 is an enlarged view of a part of the oil ring in FIG. 2 and is a view for explaining the flow of oil when the piston is raised. FIG. 3 is an enlarged view of a part of the oil ring in FIG. 2 and is a view for explaining the flow of oil when the piston is lowered. It is the graph which investigated the oil circulation property of the engine. It is a disassembled perspective view which shows other embodiment of an oil ring. It is a perspective view which shows the state which combined the oil ring of FIG. It is the figure which expanded a part of oil ring of FIG. FIG. 10 is a plan view showing a half of the oil ring of FIG.

  BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the best mode for carrying out the present invention will be described in detail with reference to the accompanying drawings.

  1 to 8 show an embodiment of the present invention. A piston 3 is supported on a crankshaft 1 of an engine (not shown) via a connecting rod (hereinafter simply referred to as a connecting rod) 2. The piston 3 is slidably accommodated in the cylinder bore 4a of the cylinder block 4.

  The crankshaft 1 includes a crank journal 1a that is rotatably supported by the cylinder block 4 and a crank pin 1b that is rotatably supported by the large end 2a of the connecting rod 2. The small end 2 b of the connecting rod 2 is connected to the piston 3 via a piston pin 5.

  On the outer periphery of the piston 3, three circumferential grooves 3a, 3b, 3c are provided at predetermined intervals in the central axis direction (reciprocating stroke direction of the piston 3).

  Compression rings 6 and 7 called top rings and second rings are respectively provided in the first circumferential groove 3a and the second second circumferential groove 3b from the crown side of the piston 3 with gaps in the axial and radial directions, respectively. It is installed in the state of holding.

  An oil ring 8 called a third ring is mounted in the third circumferential groove 3c third from the crown surface side of the piston 3, in other words, first from the skirt side of the piston 3 with gaps in the axial direction and the radial direction, respectively. Has been.

  The compression rings 6 and 7 seal the gap between the piston 3 and the cylinder bore 4a so as to suppress or prevent leakage of compressed gas and combustion gas in a combustion chamber (not shown) to a crankcase (not shown). Is provided. The compression rings 6 and 7 are flat plate members or the like having a substantially C-shape in plan view with a single circumference separated.

  The oil ring 8 is provided to scrape off oil adhering to the inner wall surface of the cylinder bore 4a. As shown in FIG. 3, the oil ring 8 has a two-piece structure in which a ring body 8a and an expander 8b are combined.

  The ring main body 8a is formed of a substantially C-shaped member in plan view with one circumference separated, and the cross-sectional shape is substantially U-shaped, and the open side is located on the outer diameter side. The expander 8b is fitted to the inner diameter side of the ring main body 8a and applies a radially outward tension, and is made of a member in which a cylindrical coil is formed into a ring shape.

  These two compression rings 6, 7 and one oil ring 8 are incorporated into the circumferential grooves 3 a, 3 b, 3 c of the piston 3 once elastically expanded in diameter, but are reduced in diameter by the elastic restoring force. Therefore, it fits in each peripheral groove 3a-3c. In this state, the outer peripheral part of each ring 6-8 will be in the state which protruded from each circumferential groove 3a-3c.

  When the piston 3 fitted with each of the rings 6 to 8 is inserted into the cylinder bore 4a, each ring 6 to 8 is elastically contracted so that it does not protrude into the circumferential grooves 3a to 3c. To. Therefore, in a state where the piston 3 is inserted into the cylinder bore 4a, the respective rings 6 to 8 are pressed against the inner wall surface of the cylinder bore 4a with its elastic restoring force.

  Incidentally, a plurality of oil return holes 3 d are provided in the thrust side region 100 and the anti-thrust side region 200 in the third circumferential groove 3 c of the piston 3.

  The oil return hole 3 d is a hole provided so as to penetrate the third circumferential groove 3 c of the piston 3 inward and outward in the radial direction, and is provided for discharging oil to the inside of the piston 3.

  The cross-sectional shape of the oil return hole 3d can be set to an appropriate shape such as a circle, an oval hole, an elliptical hole, or a rectangular hole, and the number and size of the oil return holes 3d are also set as appropriate. Is possible.

  Incidentally, when the piston 3 is pushed to the crankshaft 1 side with the combustion of the engine and the connecting rod 2 is tilted to the maximum as shown in FIG. 1, a predetermined region in the circumferential direction of the skirt 3e of the piston 3 (the left region in FIG. 1). It is known that the cylinder bore 4a is pressed in the direction indicated by the arrow in FIG. In general, the pressed side is referred to as the “thrust side”, and the opposite side is referred to as the “anti-thrust side”.

  When the connecting rod 2 is tilted to the maximum, the straight line X along the longitudinal direction of the connecting rod 2 and the straight line Y passing through the center of the crank journal 1a of the crankshaft 1 and the center of the crank pin 1b are orthogonal to each other. .

  As shown in FIG. 5, the thrust side region 100 and the anti-thrust side region 200 include, for example, a straight line 10 extending in the thrust direction and the anti-thrust direction from the center of the piston 3 (or a central axis and a crankshaft along the stroke direction of the piston 3). 1 is set so as to open by a predetermined angle θ in each of the left and right directions.

  The cylindrical inner bottom wall portion of the oil ring 8 along the axial direction of the ring body 8a is provided with an oil passage 8c for allowing oil to flow in and out of the radial direction.

  The oil passage 8c is, for example, a hole that penetrates inward and outward in the radial direction, and allows oil to move from the inner diameter side of the oil ring 8 to the outer diameter side or from the outer diameter side to the inner diameter side. Is provided.

  The cross-sectional shape of the oil passage 8c can be set to an appropriate shape such as a circular shape, an oval hole, an elliptical hole, or a rectangular hole, and the number and size of the oil passages 8c can be set as appropriate. Is possible.

  Next, with reference to FIGS. 4 and 5, the installation place of the oil return hole 3d and the installation place of the oil passage 8c will be described in detail.

  First, a plurality of (for example, four) oil return holes 3d are provided at equal intervals in the circumferential direction in the thrust side region 100 and the anti-thrust side region 200 in the third circumferential groove 3c of the piston 3.

  In addition, the oil passage 8c has a plurality (for example, six) of oil passages 8c at equal intervals in the circumferential direction in an installation region of the oil return hole 3d in the oil ring 8, that is, a region corresponding to the thrust side region 100 and the anti-thrust side region 200. is set up. Further, a plurality of (for example, six) oil passages 8c are provided in the engine front side region 300 and the engine rear side region 400 at equal intervals in the circumferential direction.

  And the oil path similar to the above-mentioned oil path 8c is not intentionally provided in the area | region between each area | region 100,200,300,400 of the said 4 directions.

  The engine front side region 300 and the engine rear side region 400 are, for example, left and right with a straight line (or a straight line 11 along the rotation center axis of the crankshaft 1) extending from the center of the piston 3 to the engine front side and the engine rear side. Each is set to open by a predetermined angle θ.

  In general, the engine rear side is a side where a flywheel (not shown) is attached to the crankshaft 1, and the opposite side of the crankshaft 1 from the engine rear side is an engine front side.

  In order to prevent the oil ring 8 from moving in the circumferential direction within the third circumferential groove 3 c of the piston 3, a positioning pin 9 is attached to the piston 3. The positioning pin 9 is disposed at one separation portion in the circumferential direction of the ring body 8a of the oil ring 8. That is, both ends in the circumferential direction of the ring main body 8 a of the oil ring 8 come into contact with the positioning pins 9.

  Next, the operation of the oil ring 8 when the piston 3 reciprocates with the operation of the internal combustion engine will be described with reference to FIGS.

  For example, when the piston 3 moves up in the cylinder bore 4a, as shown in FIG. 6, the oil ring 8 is lowered in the third circumferential groove 3c, and the oil adhering to the inner wall surface of the cylinder bore 4a is scraped off. Become.

  On the other hand, when the piston 3 descends in the cylinder bore 4a, as shown in FIG. 7, the oil ring 8 rises in the third circumferential groove 3c and scrapes off the oil adhering to the inner wall surface of the cylinder bore 4a. become.

  In any case, most of the oil scraped off by the oil ring 8 is a gap between the ring body 8a of the oil ring 8 and the third circumferential groove 3c (inner diameter side annular ring) as shown by arrows in FIGS. It will flow into the gap 20). A part of the oil may flow into the facing gap (outer diameter side annular gap 30) between the inside of the ring body 8a, that is, between the ring body 8a and the inner wall surface of the cylinder bore 4a.

  These oils are dropped into the oil pan by being discharged to the inside of the piston 3 through the oil return hole 3d provided in the third circumferential groove 3c. The oil collected in the oil pan is again sprayed to the inner wall surface of the cylinder bore 4a and the inside of the piston 3.

  More specifically, as shown in FIG. 5, the oil scraped off by the oil ring 8 and flowing into the inner diameter side annular gap 20 is mainly installed in the engine front side region 300 and the engine rear side region 400 in the ring body 8a. The oil returns to the third circumferential groove 3c of the piston 3 installed in the thrust side region 100 and the anti-thrust side region 200 in addition to passing through a certain oil passage 8c radially outward and flowing into the outer diameter side annular gap 30. It passes through the hole 3d inward in the radial direction and is discharged to the inside of the piston 3.

  Then, the oil that has flowed into the outer diameter side annular gap 30 divides the gap 30 into one side and the other side in the circumferential direction, and is installed in the thrust side region 100 and the anti-thrust side region 200 in the ring body 8a. The oil passes through a certain oil passage 8c inward in the radial direction and flows into the inner diameter side annular gap 20, but this oil quickly passes through the oil return hole 3d existing in the vicinity of the oil passage 8c inward in the radial direction to form a piston. 3 can be discharged inside.

  Thus, the oil is less likely to stay in the third circumferential groove 3c of the piston 3 as in the conventional example, and flows smoothly.

  Here, referring to the graph of FIG. 8, the oil circulation in the third circumferential groove 3 c of the piston 3 is examined, which will be described.

  In addition, as an object to be investigated, this embodiment, a conventional example (not shown, a configuration in which oil passages are provided at equal circumferential positions on the entire circumference of the oil ring), and a reference example (not shown) The configuration in which no oil passage is provided in the oil ring) is taken as an example.

Further, the dimension of the inner diameter side annular gap 20 between the ring main body 8a of the oil ring 8 and the groove bottom of the third circumferential groove 3c of the piston 3 is, for example, about 2 mm. The kinematic viscosity is 32 mm ² / sec.

  As the piston 3 reciprocates, the oil in the third circumferential groove 3 c of the piston 3 is dropped onto an oil pan (not shown), then sprayed onto the inner wall surface of the cylinder bore 4 a and scraped off by the oil ring 8. As a result, it flows into the third circumferential groove 3c. Here, the ratio (%) at which the oil in the third circumferential groove 3c is replaced while the piston 3 reciprocates once is defined as the oil circulation property.

  As shown in FIG. 8, the oil circulation is about 3% in the reference example, about 4.2% in the conventional example, and about 10% in the present embodiment. That is, in the present embodiment, the oil circulation property is improved more than twice as compared with the conventional example and the reference example.

  From this result, it is understood that if the configuration of the present embodiment is adopted, the oil in the third circumferential groove 3c can be efficiently discharged to the inside of the piston 3, and the oil circulation property is improved.

  As described above, in the embodiment to which the present invention is applied, the oil scraped off from the inner wall surface of the cylinder bore 4a by the oil ring 8 can be efficiently discharged to the inside of the piston 3.

  As a result, the oil circulation in the third circumferential groove 3c of the piston 3 can be improved, so that the friction loss and oil consumption of the piston 3 associated with the operation of the internal combustion engine can be reduced. Can contribute to the improvement of the service life and reliability.

  In addition, this invention is not limited only to the said embodiment, It can change suitably in the range equivalent to the claim and the said range.

  (1) In the above embodiment, an example in which two compression rings 6 and 7 and one oil ring 8 are attached to the piston 3 is given, but the present invention is not limited to this and is illustrated. However, the present invention can also be applied to a configuration in which one compression ring and one oil ring are attached to the piston 3.

  (2) In the above-described embodiment, an example in which the oil ring 8 having a two-piece structure is used is described. However, the present invention is not limited to this, and for example, a three-piece structure as shown in FIGS. An oil ring 80 can be used.

  The oil ring 80 has a three-piece structure in which a spacer expander 83 is interposed between an upper rail 81 and a lower rail 82 as shown in FIG.

  Each of the upper rail 81 and the lower rail 82 is a flat plate-like member having a substantially C-shape in plan view, with one circumference separated. The spacer expander 83 is a corrugated member having a substantially C-shape in plan view with one circumference separated.

  In the oil ring 80, as shown in FIGS. 10 to 12, a large number of spaces 84 are created in the circumferential direction between the wave-like portion of the spacer expander 83 and the upper rail 81 and the lower rail 82. The space 84 is opened inward and outward in the radial direction, and becomes an oil passage (corresponding to the oil passage 8c in the above embodiment) for allowing oil to flow inward and outward in the radial direction.

  Then, as shown in FIG. 12, each region between the four regions in the circumferential direction (thrust side region 100, anti-thrust side region 200, engine front side region 300, engine rear side region 400) in the spacer expander 83. The filling member 85 is attached so as to fill the space 84 existing in the space.

  As a result, the space 84 is eliminated in each region between the four regions 100, 200, 300, and 400 in the spacer expander 83, and the 4 in the circumferential direction in the spacer expander 83 is eliminated. In the two regions 100, 200, 300, and 400, the space 84 described above is left.

  When the spacer expander 83 is made of an iron-based metal, the filling member 85 can be the same type of metal or an appropriate synthetic resin (for example, an engineering plastic having excellent heat resistance).

  In the case of such an oil ring 80, it is possible to obtain substantially the same operations and effects as in the above embodiment.

  The present invention can be suitably used for a piston for an internal combustion engine in which an oil ring is mounted in a circumferential groove provided on the outer periphery.

DESCRIPTION OF SYMBOLS 1 Crankshaft 2 Connecting rod 3 Piston 3a 1st circumferential groove 3b 2nd circumferential groove 3c 3rd circumferential groove 3d Oil return hole 4a Cylinder bore 6,7 Compression ring 8 Oil ring 8a Ring main body 8b Expander 8c Oil path 20 Inner diameter side annular clearance 30 Outer diameter side annular clearance 100 Thrust side region 200 Anti-thrust side region 300 Engine front side region 400 Engine rear side region

Claims (3)

A piston for an internal combustion engine in which an oil ring is mounted in a circumferential groove provided on the outer periphery,
In the circumferential groove, at least one of the thrust side region and the anti-thrust side region is provided with an oil return hole for discharging oil to the inside of the piston,
In the oil ring, an oil passage along the radial direction is provided in a region corresponding to the installation region of the oil return hole, and an oil passage along the radial direction is provided in the engine front side region and the engine rear side region,
The piston for an internal combustion engine, wherein an oil passage similar to the oil passage is not provided in a region between the regions in the oil ring. The piston for an internal combustion engine according to claim 1,
The piston for an internal combustion engine, wherein the oil return hole is provided in both the thrust side region and the anti-thrust side region in the circumferential groove. The piston for an internal combustion engine according to claim 1 or 2,
The oil ring is configured to include a ring main body and an expander that is fitted on the inner diameter side of the ring main body and applies a radially outward tension.
The piston for an internal combustion engine, wherein the oil passage is a hole provided in the ring main body so as to penetrate inside and outside in the radial direction.

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