JP7259710B2 - piston top ring - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a top ring, among piston rings mounted on the outer peripheral surface of a piston of a reciprocating engine, mounted at a position close to the top surface of the piston.

As the piston of the engine reciprocates in the axial direction inside the cylinder, the piston ring attached to the outer peripheral surface of the piston slides on the inner peripheral surface of the cylinder, so that an appropriate oil film is formed on the inner peripheral surface of the cylinder. adjusted to form.

As such a piston ring, an oil ring 100 exemplified in Patent Document 1 has been proposed (see FIG. 8 of the present application).
FIG. 8 is an explanatory diagram of the configuration and problems of the oil ring of Patent Document 1. As shown in FIG. However, FIG. 8 schematically shows the thickness and the like of the oil film formed on the inner peripheral surface of the cylinder.

In the oil ring 100 of Patent Document 1, the central portion 102c in the vertical direction of the outer peripheral surface 102 presses radially outward against the upper and lower sides 102a and 102b so as to slide against the inner peripheral surface 1a of the cylinder 1. A barrel-shaped outer peripheral sliding surface 102 protruded, and chamfers that are inclined radially inwardly so as to separate from the upper and lower ends of the outer peripheral sliding surface 102 to the upper and lower sides of the outer peripheral sliding surface 102. Parts 103a and 103b are formed.
In the outer peripheral surface 101 of the oil ring 100 of Patent Document 1, the upper portion 102a of the outer peripheral sliding surface 102 and the upper portion of the outer peripheral surface corresponding to the chamfered portion 103a located above are separated from the inner peripheral surface 1a of the cylinder 1. s (hereinafter referred to as "upper gap s") is formed. The upper gap s is formed so that the gap gradually widens upward (that is, toward the combustion chamber 3 side) (see FIG. 8).

Therefore, the oil 7 (lubricating oil) scraped off by the oil ring 100 as the piston 2 moves toward the combustion chamber 3 is required so that the oil film formed on the inner peripheral surface 1a of the cylinder has an appropriate thickness. ) accumulates in the upper gap s.

Here, when the piston 2 reaches the top dead center (TDL) and momentarily stops, the oil 7 accumulated in the upper gap s has an inertial force in the moving direction of the piston 2 toward the combustion chamber 3 side. works.

Therefore, when the oil ring 100 of Patent Document 1 is the piston ring closest to the combustion chamber 3 side among the piston rings assembled to the outer peripheral surface of the piston 2 (that is, when it is the top ring), the upper clearance There is a concern that the oil 7 accumulated in s may be scattered toward the center of the combustion chamber 3 due to the inertial force in the moving direction of the piston 2 toward the combustion chamber 3 side.

The oil 7 scattered toward the center of the combustion chamber 3 mixes with the air-fuel mixture in the combustion chamber 3 and burns together with the air-fuel mixture, resulting in accelerated oil consumption.

JP 2012-107710 A

The present invention has been made in view of this problem. To provide a piston top ring capable of reducing oil consumption by suppressing scattering toward the center of a combustion chamber due to inertial force.

INDUSTRIAL APPLICABILITY The present invention is used in an engine provided with a cylinder and a piston reciprocating between a combustion chamber side and a crank chamber side inside the cylinder, and is mounted on the outer peripheral surface of the piston. A top ring of the piston, which is arranged closest to the combustion chamber, among piston rings having an outer peripheral surface having a sliding surface that slides on the inner peripheral surface of the cylinder with the reciprocating motion of the and
In a cross section along the axis of the piston, a concave portion is formed on the outer peripheral surface of the ring on the combustion chamber side of the sliding surface, the concave portion being concave inward in the ring radial direction,
The inner surface of the recess in the ring radial direction is at least partially formed with a curved surface that extends toward the crank chamber while curving inward in the ring radial direction from the end of the recess on the combustion chamber side, An end portion of the recess on the side of the combustion chamber is formed so as to face the inner peripheral surface of the cylinder.

According to the above configuration, part of the film-like oil formed on the inner peripheral surface of the cylinder (cylinder liner) is scraped off by the top ring when moving toward the combustion chamber, and the piston moves to the top dead center ( TDC), it uses inertia to move along the curved surface. Then, the oil is blown from the combustion chamber side end of the curved surface toward the inner peripheral surface of the cylinder. As a result, the top ring of the present invention can suppress oil from being blown toward the center of the combustion chamber, thereby reducing oil consumption.

As an aspect of the present invention, the curved surface on the ring radial direction inner surface is inclined outward in the ring radial direction from the curved surface, from the crank chamber side end portion of the curved surface toward the crank chamber side and the ring radial direction outer side. An inclined surface extending along the

According to the above configuration, when the piston moves toward the combustion chamber, the oil scraped from the inner peripheral surface of the cylinder and introduced into the recess smoothly moves toward the curved surface by utilizing the inclined surface of the recess. Therefore, the effect of scattering the oil toward the inner peripheral surface of the cylinder can be more preferably obtained.

As an aspect of the present invention, the inclined surface is subjected to a surface treatment for enhancing oil repellency as compared to the periphery thereof.

According to the above configuration, by increasing the oil repellency of the inclined surface, the oil scraped from the inner peripheral surface of the cylinder and introduced into the recess can be more smoothly guided from the inclined surface to the curved surface.

As an aspect of the present invention, the ring outer peripheral surface includes a combustion chamber side outer peripheral surface formed on the combustion chamber side having at least a part of the combustion chamber side end of the recess, and the crank of the recess. a crank-chamber-side outer peripheral surface extending from the chamber-side end toward the crank-chamber side and having the sliding surface formed at least partially thereon, wherein the maximum-diameter portion of the combustion-chamber-side outer peripheral surface is the sliding surface. It is formed so that the distance from the inner peripheral surface of the cylinder is wider than the surface.

According to the above configuration, since the outer peripheral surface on the combustion chamber side can be formed to be spaced further inward in the ring radial direction from the inner peripheral surface of the cylinder than the outer peripheral surface on the crank chamber side, the piston moves toward the combustion chamber side. In addition, oil can be scraped off from the inner peripheral surface of the cylinder by the sliding surface of the crank chamber side outer peripheral surface of the ring outer peripheral surface of the top ring.

Therefore, the oil scraped by the sliding surface of the top ring when the piston moves toward the combustion chamber can be smoothly guided to the recess located closer to the combustion chamber than the sliding surface.

As an aspect of the present invention, the distance between the combustion chamber side end portion and the deepest portion (inner end portion in the ring radial direction) of the recess in the ring radial direction is the distance between the recess in the piston axial direction of the combustion chamber. It is set shorter than the distance between the side end and the end opposite to the combustion chamber side end.

According to the above configuration, the distance (depth) of the recess in the ring radial direction is shorter (shallower) than the opening width in the cylinder axial direction of the recess that opens outward in the ring radial direction. When the oil moves along the curved surface due to inertia, it is possible to prevent the oil from stagnation in the concave portion, and the oil can be smoothly scattered toward the inner peripheral surface of the cylinder.

As an aspect of the present invention, the curved surface is formed over the entire circumference of the outer peripheral surface of the ring.

According to the above configuration, it is possible to obtain the effect of scattering the oil toward the inner peripheral surface of the cylinder using the curved surface over the entire circumference of the outer peripheral surface of the ring.

According to this invention, oil scraped from the inner peripheral surface of the cylinder as the piston moves toward the combustion chamber moves toward the center of the combustion chamber due to inertial force when the piston reaches top dead center. By suppressing the scattering, oil consumption can be reduced.

FIG. 2 is a front view showing a partial cross section of a piston having a top ring according to the present embodiment and a cylinder into which the piston is inserted; The perspective view which looked the top ring of this embodiment from the upper direction. FIG. 2 is an enlarged view of a region Z1 in FIG. 1; FIG. 4 is an enlarged view of a region Z2 in FIG. 3; FIG. 2 is a cross-sectional view showing, in a plan view, a part of a piston fitted with a top ring of the present embodiment and a cylinder into which the piston is inserted; FIG. 5 is a cross-sectional view showing only a part of top rings of modifications A and B corresponding to FIG. 4; FIG. 3 is an external view showing only a part of the top ring of Modification C corresponding to FIG. 2; FIG. 4 is a vertical cross-sectional view showing the main parts of a piston fitted with a conventional top ring and a cylinder into which the piston is inserted.

First, the background leading to the creation of the present invention will be described.

Engine oil is consumed by various factors.
Among these various factors, the consumption caused by oil entering the combustion chamber and being burned by the combustion gas is caused by oil entering the combustion chamber through the gap between the outer peripheral surface of the piston and the inner peripheral surface of the cylinder ( (also called "slow-off"), and vaporized oil in the crank chamber passing through the blow-by gas passage and the intake passage and entering the combustion chamber are factors of oil consumption.
Therefore, the inventors paid particular attention to the fact that the slow-off factor occupies a large proportion of the oil consumption, and made earnest studies to solve the problem of suppressing the oil consumption due to the slow-off. Specifically, the inventors found that part of the oil adhering to the inner peripheral surface of the cylinder was scraped up by the top ring attached to the piston, and the inertia force when the piston reached top dead center (TDC) The inventors diligently studied to solve the problem of consuming by being burned by the combustion gas inside the combustion chamber by scattering to the side of the combustion chamber. As a result, the inventors have created the piston top ring according to the present invention.

An embodiment of the present invention will be described below with reference to the drawings.
FIG. 1 is a partial cross-sectional view showing the left side of the paper as a front view of the piston and the right side of the paper as a cross section from the arrow A in the figure, showing the positional relationship between the piston and the cylinder into which the piston is inserted. 2 is a top ring of this embodiment, and is a perspective view of the top ring with a reduced diameter when attached to the piston, as viewed from above; FIG. 3 is an enlarged view of region Z1 in FIG. 1; FIG. 5 is a part of the piston fitted with the top ring of this embodiment and the cylinder into which the piston is inserted, viewed from above. 1 shows a cross-sectional view showing only the .

In FIG. 5, for the sake of convenience, the structure of the piston top 21, which will be described later, such as a protuberant portion 21a (see FIG. 1), is omitted, and the piston top 21 is shown flat. In the figure, arrows X, Xu, and Xd indicate the axial direction (vertical direction), upward direction (combustion chamber side), and downward direction (opposite to the combustion chamber side, ie, crank chamber side) of the piston, respectively. Di and Do indicate radial direction, radial inner side and radial outer side, respectively.

FIG. 1 is a partial cross-sectional view showing a cylinder 1 and a piston 2 inserted through the cylinder 1, which are main parts of a reciprocating piston engine (reciprocating engine). The piston 2 is inserted so as to be able to move up and down (reciprocate) while sliding on the peripheral surface 1a (cylinder liner).

A combustion chamber 3 surrounded by the piston 2, the inner peripheral surface 1a of the cylinder 1, and a cylinder head (not shown) is provided above the piston 2, and a crank chamber (not shown) is provided below the piston 2. is provided.

The piston 2 is made of aluminum or an aluminum alloy, and includes a piston upper portion 22 (head portion), and a piston skirt 23 and a piston boss portion 24 provided below the piston upper portion 22 .

The piston skirts 23 are provided so as to extend downward from the periphery of the piston upper portion 22 and face each other in the radial direction of the piston 2 . The piston boss portion 24 is provided between the pair of piston skirts 23 .

As shown in FIG. 1, the piston top 21 forms the bottom surface of the combustion chamber 3 and has a raised portion 21a for adjusting the volume of the combustion chamber 3 and setting the geometric compression ratio of the cylinder 1 high. It is

The piston upper part 22 is formed in a columnar or cylindrical shape, and a plurality of pistons for mounting the piston rings 4 on an outer peripheral surface 25 (hereinafter referred to as "upper outer peripheral surface 25") of the piston upper part 22. A ring groove 251 is recessed in an annular shape over the entire circumference.

In this embodiment, three piston ring grooves 251 corresponding to the three piston rings 4 are formed in the upper outer peripheral surface 25 so as to be separated from each other in the vertical direction (piston axial direction). Between the piston ring grooves 251 in the vertical direction of the upper outer peripheral surface 25 and between the piston top 21 and the piston ring groove 251 located most upward (that is, on the side of the combustion chamber 3 or the side of the piston top 21), lands are provided. A portion 261 is formed.

Specifically, the land portion 261 is composed of a top land 261a, a second land 261b and a third land 261c, which are arranged from top to bottom of the upper outer peripheral surface 25 in this order. The top land 261a is formed between a top ring groove 251a and the piston top 21, which will be described later.

Between the top land 261a and the second land 261b, among the three piston ring grooves 251, the top ring groove 251a positioned most upward (on the side of the combustion chamber 3) is recessed. Between the second land 261b and the third land 261c, among the three piston ring grooves 251, a second ring groove 251b located in the middle in the vertical direction is recessed. Directly below the third land 261c, among the three piston ring grooves 251, an oil ring groove 251c located at the lowest position (on the side opposite to the combustion chamber) is recessed.

Of the three piston rings 4, the top ring 4a as a first compression ring is mounted in the top ring groove 251a. Of the three piston rings 4, the second ring 4b as a second compression ring is mounted in the second ring groove 251b.

Furthermore, the oil ring 4c of the three piston rings 4 is mounted in the oil ring groove 251c.
It is assumed that the radial direction of the piston rings 4 coincides with the radial direction of the piston 2 when the three piston rings 4 are mounted in the corresponding piston ring grooves 251 of the piston upper portion 22 .

These three piston rings 4 slide together on the inner peripheral surface 1a of the cylinder 1 when the piston 2 is moved, so that an oil film 7a (lubricating oil film) having an appropriate thickness on the inner peripheral surface 1a of the cylinder 1 (Fig. 4) is formed. , see FIG. 5).

Specifically, when the piston 2 moves downward, the oil ring 4c scrapes off excess oil 7 (lubricating oil) adhering to the inner peripheral surface 1a of the cylinder 1, thereby forming an oil film 7a having an appropriate thickness. It has the function to

Both the top ring 4 a and the second ring 4 b have the function of sealing combustion gas and oil 7 between the piston 2 and the inner peripheral surface 1 a of the cylinder 1 . Further, the top ring 4a also has a function of forming an oil film 7a having an appropriate thickness by scraping up the oil 7 adhering to the inner peripheral surface 1a of the cylinder 1 when the piston 2 moves upward.

As shown in FIG. 2, the top ring 4a will be described as an example. The abutment portion 49 is a portion obtained by dividing a part of an annular shape, and has a pair of abutment end portions 49t, 49t (free ends) facing each other.

The piston ring 4 is mounted in the piston ring groove 251 while being compressed radially inward with a slight gap 49s (abutment gap 49s) left in the abutment portion 49 . As a result, the piston ring 4 is urged toward the inner peripheral surface 1 a of the cylinder 1 (outward in the radial direction) to improve the sealing performance with the inner peripheral surface 1 a of the cylinder 1 .

Next, of the three piston rings 4, the top ring 4a will be further explained.
As shown in FIGS. 2 to 5, the top ring 4a is made of steel such as stainless steel. and an outer peripheral surface lower portion 35 protruding toward the side of the peripheral surface 1a (that is, radially outward).

In particular, as shown in FIG. 3, the outer peripheral surface lower portion 35 extends vertically in parallel with the inner peripheral surface 1a of the cylinder 1 and slides on the inner peripheral surface 1a of the cylinder 1 as the piston 2 moves up and down. The surface 36 is located on each side above and below the sliding surface 36, and is separated from the inner peripheral surface 1a of the cylinder 1 (that is, positioned radially inward) as it is separated from the sliding surface 36 on each side above and below. and chamfered portions 38a and 38b formed at the upper and lower ends of the outer peripheral surface lower portion 35. As shown in FIG.

As shown in FIGS. 3 and 4, the outer peripheral surface upper portion 31 corresponds to the upper end portion of the outer peripheral surface 30 of the top ring 4a, and forms a concave portion 32 recessed radially inward and the upper end peripheral edge of the top ring 4a. An outer peripheral surface upper end portion 33 is formed.

As shown in FIG. 4, the radial inner surface 40 of the recess 32 includes a curved surface 41 that descends from the upper end (41a) of the recess 32 in the radial direction while curving in an arched shape (arc shape) as a whole, and a curved surface. 41 and an inclined surface 42 that descends linearly outward in the radial direction from the lower end 41b of the lower end 41b.

The upper end 41a of the curved surface 41 is positioned at the upper end (41a) of the recess 32 (the radial inner surface 40), and in this example, the curved surface 41 extends from the upper end (41a) of the radial inner surface 40 of the recess 32 to the upper end (41a). It is formed continuously until it is positioned at a position (41b) immediately below 41a). That is, the curved surface 41 is formed in a portion of the radial inner surface 40 of the recess 32 corresponding to the radially inner side of the upper end (41a) of the recess 32 and the position (41b) immediately below the upper end 41a. .

The radially deepest portion 41c of the recess 32 (the radially inner end (41c) of the curved surface 41) is positioned at the same height as the vertically intermediate position between the upper end 41a and the lower end 41b of the curved surface 41. there is In a cross section along the axis of the piston 2 (that is, a cross section perpendicular to the circumferential direction of the top ring 4a), the curved surface 41 has a tangential gradient that approaches the deepest portion 41c from the lower end 41b. It is formed with a curved surface that gradually becomes steeper, and with the deepest portion 41c as an inflection point, the portion above the deepest portion 41c is curved outward in the radial direction.

That is, the curved surface 41 is formed in a semi-elliptical arc shape that is line-symmetrical on each side above and below the deepest portion 41c.

Furthermore, the curved surface 41 is formed in a semi-elliptical arc shape in which the vertical direction is longer than the radial direction in a cross section along the axis of the piston 2 (see FIG. 4).

Specifically, the radial distance (b) from the upper end (41a) of the recess 32 to the radially inner end (41c) is from the upper end (41a) of the recess 32 to the position (41b) directly below the upper end (41a). ) is shorter than the distance (a) (see FIG. 4).

In other words, the radial depth (b) of the recess 32 is formed shorter than the vertical opening length (a) of the recess 32 that opens radially outward in a cross section along the axis of the piston 2 . (a>b (see FIG. 4)).

Further, as shown in FIG. 4, the upper end 41a of the curved surface 41 is located at the upper end (41a) of the recess 32 as described above, and the upper end 33 of the outer peripheral surface extends from the upper end 41a of the curved surface 41 to the top ring 4a. extends linearly continuously upward to the upper surface 4au of the .

An upper end 41a of the curved surface 41 faces the inner peripheral surface 1a of the cylinder 1 in a cross section along the axis of the piston 2 (see straight line L indicated by a phantom line in FIG. 4). That is, the tangent line (L) at the upper end 41a of the curved surface 41 extends obliquely so as to be located radially outward as it goes upward, and points toward the inner peripheral surface 1a of the cylinder 1 at a position above the upper end 41a of the curved surface 41. That is, it extends in a direction intersecting with the inner peripheral surface 1a.

However, in this embodiment, the upper end 41a of the curved surface 41 is not oriented above the height h (see FIG. 3) of the piston top 21 (the top surface of the piston 2), that is, toward the combustion chamber 3 where the temperature is high. , the inner peripheral surface 1a of the cylinder 1 is oriented below the height h of the piston top 21 as much as possible.

As shown in FIG. 4 , the inclined surface 42 corresponds to substantially the lower surface of the recess 32 and forms part of the radial inner surface 40 . The inclined surface 42 linearly descends radially outward from the lower end 41b of the curved surface 41 to the lower end 42a of the recess 32 (the radial inner surface 40) in a cross section along the axis of the piston 2. A lower end 42a (outer end in the radial direction) of the inclined surface 42 is positioned at the lower end (42a) of the recess 32 and continuously extends downward from the lower end 42a, that is, to the side of the lower outer peripheral surface 35 (chamfered portion 38a).

The slanted surface 42 is surface-treated to have higher oil repellency than its surroundings.

The surface treatment for enhancing the oil repellency is a treatment to make the inclined surface 42 a fine structure (oil repellent texture) in which a large number of recesses are formed so as to have a lotus effect, and a treatment to make the inclined surface 42 a Teflon (registered trademark). It has at least one treatment among the treatments provided with an oil-repellent material such as fluorocarbon resin (PTFE).
Here, the treatment with the material having oil repellency described above is, for example, coating the surface of the inclined surface 42 with a material having oil repellency, or arranging a member having oil repellency on a portion corresponding to the inclined surface 42. forming the surface of the ramp 42 by squeezing. In addition, it is preferable to employ a crosslinked fluororesin as the fluororesin, since high water and oil repellency can be obtained over a long period of time.

As shown in FIG. 4 , both the outer peripheral surface upper end portion 33 and the outer peripheral surface lower portion 35 protrude radially outward from the radially deepest portion 41 c of the concave portion 32 .
However, the entire outer peripheral surface upper end portion 33, including the upper end (41a) of the recessed portion 32 corresponding to the lower end of the outer peripheral surface upper end portion 33, is radially outward of the sliding surface 36 of the outer peripheral surface lower portion 35. It is formed so as to be spaced (retracted) from the inner peripheral surface 1a of the cylinder 1 so as not to protrude inward.
Specifically, when the piston 2 ascends, the sliding surface 36 slides against the inner peripheral surface 1a of the cylinder 1, thereby scraping off part of the oil 7 adhering to the inner peripheral surface 1a of the cylinder 1. It corresponds to the part to raise. That is, the sliding surface 36 corresponds to the maximum diameter portion in the vertical direction of the outer peripheral surface lower portion 35 and is the portion closest to the inner peripheral surface 1 a of the cylinder 1 .

On the other hand, the maximum diameter portion in the vertical direction of the upper end portion 33 of the outer peripheral surface is formed so as not to protrude radially outward from the sliding surface 36 of the lower portion 35 of the outer peripheral surface.

In other words, the upper end portion 33 of the outer peripheral surface is formed so that the entire vertical interval thereof with the inner peripheral surface 1a of the cylinder 1 is wider than the sliding surface 36 (e>f (FIG. 4). reference)). In other words, at least a portion of the inclined surface 42 corresponding to the radially outer portion of the recess 32 in the cross section along the axis of the piston 2 faces upward (toward the combustion chamber 3 ) without being blocked by the upper end portion 33 of the outer peripheral surface. (See FIGS. 4 and 5).

Furthermore, in the present embodiment, the outer peripheral surface upper end portion 33 is located closer to the inner peripheral surface 1a of the cylinder 1 than the lower end (42a) of the recessed portion 32, in other words, the upper end (42a) of the outer peripheral surface lower portion 35. It is formed so that the radial interval is wide (e>g (see FIG. 4)).

By forming the upper end portion 33 of the outer peripheral surface to protrude radially outward in this manner, the radially inner surface 40 of the recessed portion 32 has the above-described arcuate curved surface 41 that scoops out the piston 2 radially inward. can be reliably formed, and by separating the sliding surface 36 radially inward from the inner peripheral surface 1a of the cylinder 1, when the piston 2 rises, it adheres to the inner peripheral surface 1a of the cylinder 1 It is possible to prevent the oil 7 from being carelessly scraped up by the outer peripheral surface upper end portion 33 of the outer peripheral surface 30 of the top ring 4a.

As a result, when the piston 2 ascends, the oil 7 adhering to the inner peripheral surface 1 a of the cylinder 1 can be scraped up by the sliding surface 36 and introduced into the recess 32 .

In this example, the outer peripheral surface upper end portion 33 extends vertically in parallel with the inner peripheral surface 1a of the cylinder 1 between the upper surface 4au of the top ring 4a and the upper end (41a) portion of the recessed portion 32. The entire vertical direction is separated radially inward from the inner peripheral surface 1a of the cylinder 1 from the sliding surface 36 .

The cross-sectional shape of the above-described top ring 4a along the axis of the piston 2 is formed uniformly over the entire circumference of the top ring 4a. That is, the recessed portion 32 (the curved surface 41 and the inclined surface 42) is formed over the entire circumferential direction of the outer peripheral surface 30 of the top ring 4a.

As shown in FIG. 1, the top ring 4a of the piston 2 of the present embodiment includes a cylinder 1 and a piston 2 that reciprocates inside the cylinder 1, and the cylinder 1 and the piston 2 move the combustion chamber. 3 is defined, and the uppermost of the plurality of piston rings 4 mounted separately in the axial direction (vertical direction) of the upper outer peripheral surface 25 (outer peripheral surface) of the piston 2 It is located at a position (near the combustion chamber 3).

As shown in FIGS. 2 to 4, the top ring 4a of the present embodiment has an outer peripheral surface 30 (ring outer peripheral A concave portion 32 is formed on the outer peripheral surface 30 above the sliding surface 36 , that is, on the upper end portion, and is recessed radially inward.

Further, as shown in FIG. 4, the top ring 4a of the present embodiment descends from the upper end (41a) of the recess 32 to the radial inner surface 40 of the recess 32 while curving in a bow shape as a whole. A curved surface 41 is formed. In addition, the top ring 4 a of this embodiment is formed so that the upper end 41 a of the curved surface 41 faces the inner peripheral surface 1 a of the cylinder 1 in a cross section along the axis of the piston 2 .

According to the above configuration, part of the oil 7 formed in a film on the inner peripheral surface 1a of the cylinder 1 is scraped by the sliding surface 36 of the top ring 4a when the piston 2 ascends inside the cylinder 1. It is raised and introduced into the recess 32 of the top ring 4a.

Since the top ring 4a has a curved surface 41 formed on the radial inner surface 40 of the recess 32, the oil 7 introduced into the recess 32 is caused to flow by the inertia when the piston 2 reaches the top dead center (TDC). It can be moved upward along the curved surface 41 in the concave portion 32 using force (see arrow d2 in FIG. 4).

Furthermore, the top ring 4a pushes the oil 7 reaching the upper end 41a of the curved surface 41 (that is, the upper end (41a) of the recessed portion 32) radially outward from the upper end 41a of the curved surface 41, that is, the inner peripheral surface 1a of the cylinder 1. (see arrow d3 in FIG. 4).

As a result, the oil 7 can be circulated to the inner peripheral surface 1a side of the cylinder, and as a result, the oil 7 is prevented from being blown to the center side of the high-temperature combustion chamber 3 and burned. Oil consumption can be reduced.

As shown in FIG. 4 as an embodiment of the present invention, the top ring 4a of the piston 2 is radially outward of the curved surface 41 on the radial inner surface 40 of the recess 32 and continues to the lower end 41b of the curved surface 41. An inclined surface 42 descending outward is formed.

In this way, by forming the inclined surface 42 radially outside and below the curved surface 41 of the recess 32, the sliding surface 36 of the top ring 4a moves the cylinder 1 as the piston 2 rises. When the ascending piston 2 reaches the top dead center, the oil 7 raked up from the inner peripheral surface 1a and introduced into the recess 32 is pushed in the direction of the curved surface 41 in the recess 32 by utilizing the inertial force of the oil 7. can be moved smoothly (see arrow d1 in FIG. 4).

Therefore, the effect of scattering to the inner peripheral surface 1a of the cylinder 1 can be obtained more suitably than in the case where, for example, a horizontal surface is formed radially outside the curved surface 41 on the radial inner surface 40 of the recess 32 . can.

As an aspect of the present invention, the top ring 4a of the piston 2 is such that the inclined surface 42 is subjected to a surface treatment for enhancing the oil repellency as compared to the periphery thereof.

According to the above configuration, by increasing the oil repellency of the inclined surface 42 , the oil 7 that has been raked up from the inner peripheral surface 1 a of the cylinder 1 and introduced into the inclined surface 42 of the recess 32 flows from the inclined surface 42 to the curved surface 41 . and can be guided more smoothly.

As shown in FIG. 4 as an embodiment of the present invention, the top ring 4a of the piston 2 has an outer peripheral surface 30 (ring outer peripheral surface), an outer peripheral surface upper end portion 33 corresponding to a position above the upper end (41a) of the recess 32, an outer peripheral surface lower portion 35 corresponding to a position below the lower end (42a) of the recessed portion 32 and having the sliding surface 36 formed on at least a part thereof in the vertical direction; portion is formed so that the distance from the inner peripheral surface 1a of the cylinder 1 is wider than the sliding surface 36, which is the maximum diameter portion in the vertical direction of the outer peripheral lower portion 35 (e>f (see FIG. 4). )).

That is, both the outer peripheral surface upper end portion 33 on the upper side and the outer peripheral surface lower portion 35 on the lower side protrude radially outward from the radial inner end ( 41 c ) of the recess 32 . However, as described above, the upper end portion 33 of the outer peripheral surface is formed radially more distant from the inner peripheral surface 1a of the cylinder 1 than the lower portion 35 of the outer peripheral surface.

As a result, when the piston 2 ascends, the oil 7 adhering to the inner peripheral surface 1a of the cylinder 1 is not inadvertently scraped up by the outer peripheral surface upper end portion 33 of the outer peripheral surface 30 of the top ring 4a. The surface lower part 35 can surely rake up.

Therefore, the oil 7 that has been raked up by the sliding surface 36 of the top ring 4a can be smoothly guided to the recessed portion 32 positioned above the lower portion 35 of the outer peripheral surface.

As shown in FIG. 4 as an aspect of the present invention, the top ring 4a of the piston 2 is such that the radial distance (b) from the upper end (41a) to the radially inner end (41c) in the recess 32 is , the vertical distance (a) from the upper end (41a) to the vertically lower position (41b) of the upper end (41a) (in other words, the vertical opening width (a) of the recess 32 that opens radially outward. ) is set shorter than

First, as the piston 2 ascends, the oil 7 that is raked up from the inner peripheral surface 1a of the cylinder 1 by the sliding surface 36 and introduced into the recess 32 is released when the ascending piston 2 reaches the top dead center. , the oil 7 tends to move upward along the curved surface 41 due to inertia.

At that time, as described above, the radial length (a) (depth) of the recess 32 should be shorter (b) (shallower) than the length in the vertical direction (cylinder axial direction) of the opening. (see FIG. 4), it is possible to prevent the oil 7 from staying in the concave portion 32, and to smoothly scatter the oil 7 toward the inner peripheral surface 1a of the cylinder 1. As shown in FIG.

As shown in FIGS. 2 to 5 as an aspect of the present invention, the top ring 4a of the piston 2 has the curved surfaces 41 opposed to each other in the entire circumference of the outer peripheral surface 30, that is, in the circumferential direction of the outer peripheral surface 30 of the top ring 4a. It is formed over the entire area between the abutment ends 49t, 49t (see FIG. 2).

According to the above configuration, the effect of scattering the oil 7 toward the inner peripheral surface 1 a of the cylinder 1 using the curved surface 41 can be obtained over the entire circumference of the outer peripheral surface 30 .

The present invention is not limited to only the configurations of the examples described above, but can be formed in various embodiments.

For example, the top ring of the present invention, like the top ring 4a of the above-described embodiment, has an inclined surface 42 (see FIG. 4) on the radial inner surface 40 of the concave portion 32 radially outward and downward with respect to the curved surface 41. , the entire vertical direction of the radial inner surface 40A from the upper end (41a) to the lower end (42a) of the recessed portion 32A is formed by the curved surface 41A, like the top ring 4aA shown in Modification A. (See FIG. 6(a)).
FIG. 6(a) is a cross-sectional view showing the top ring of Modification A corresponding to FIG. In addition, among modifications A and modifications described below, the same configurations as in the above-described embodiment are denoted by the same reference numerals, and descriptions thereof are omitted.

The curved surface 41A is a curved surface that descends from the upper end (41a) of the recess 32A radially inward while curving in an arched shape (arc shape) as a whole. is formed with a constant curvature in its entirety in the vertical direction.

According to the curved surface 41A, when the rising piston 2 reaches the top dead center, the oil 7 guided to the recessed portion 32 is caused to flow along the curved surface 41A of the recessed portion 32A using inertia. It can be smoothly moved to the upper end (41a), and can be vigorously scattered toward the inner peripheral surface 1a of the cylinder 1 from the upper end (41a).

In addition, the top ring of the present invention is not limited to the top ring 4a of the above-described embodiment or the top ring 4aA of Modification A, but also the top ring 4aB of Modification B, for example, the inclined surface 42 of the above-described embodiment. A horizontal surface 42B may be formed instead of (see FIG. 6(b)).
FIG. 6(b) is a cross-sectional view showing the top ring of Modification B corresponding to FIG.

According to the above configuration, a wider space can be secured in the lower portion of the recessed portion 32B as compared with the case where the lower portion of the recessed portion 32B is formed by the inclined surface 42 or the curved surface 41A. The oil 7 can be positively introduced into the recess 32B.

Further, the top ring of the present invention is not limited to forming the concave portion 32 over the entire circumference of the outer peripheral surface 30 like the top ring 4a of the above-described embodiment. A configuration in which the recesses 32C are arranged at regular intervals in the circumferential direction of the outer peripheral surface 30C may be employed (see FIG. 7).
7 is an external view showing only a part of the top ring of Modification C in the circumferential direction corresponding to FIG.

The recessed portion 32C of the top ring 4aC of Modified Example C can be formed in the same cross-sectional shape as the recessed portion 32 in the above-described embodiment in a cross section along the axis of the piston 2, but is not limited thereto. or the recessed portion 32B of Modified Example B may have the same cross-sectional shape.

That is, the recessed portion 32C of the top ring 4aC of Modified Example C has a radially inner surface 40C that descends from the upper end (41a) of the recessed portion 32C in the cross section along the axis of the piston 2 while curving radially inward in an arched shape. There is no particular limitation as long as the cross-sectional shape is such that the upper end (41a) of the recess 32C is directed toward the inner peripheral surface 1a of the cylinder 1 while having a curved surface.

Needless to say, although not shown, the top ring of the present invention is not limited to a configuration in which a plurality of recesses 32C are arranged at equal intervals in the circumferential direction of the ring outer peripheral surface 30. A configuration in which the portions are discontinuously provided may be adopted.

Further, in the top ring of the present invention, the crank chamber-side outer peripheral surface extends continuously downward from the lower end of the recess and has a sliding surface on at least part of the vertical direction. Like the surface lower portion 35, it may be formed without the inclined surfaces 37a, 37b and the chamfered portions 38a, 38b (see FIGS. 3 and 4).

In addition, the curved surface of the recess of the top ring of the present invention is formed so that, in a cross section along the axis of the piston 2, the curve descends from the upper end of the recess inward in the radial direction while curving in a bow shape as a whole. As long as it has a curved shape in which the upper part is warped with respect to the lower part when viewed from the direction outside, the curved surface may not be formed with a constant curvature from the upper end to the lower end, but may be formed by combining curved surfaces with different curvatures. .

In the top ring 4a of the above-described embodiment, the outer peripheral surface upper end portion 33 (combustion chamber side outer peripheral surface) extends vertically from the upper end (41a) of the recessed portion 32 (combustion chamber side end portion of the recessed portion) to the upper surface 4au of the top ring 4a. It is formed so as to extend to However, the top ring of the present invention is not limited to the above embodiment, and although not shown, the upper end (41a) of the recessed portion 32 is positioned on the upper surface 4au of the top ring 4a, that is, the outer peripheral surface upper end portion 33 (combustion chamber side). A configuration in which the outer peripheral surface) protrudes radially outward in a dot shape may be adopted.

DESCRIPTION OF SYMBOLS 1... Cylinder 1a... Inner peripheral surface of cylinder 2... Piston 3... Combustion chamber 4... Piston ring 4a... Top ring 25... Upper peripheral surface (outer peripheral surface of piston)
30... Outer peripheral surface (ring outer peripheral surface)
32... Recess 33... Upper end of outer peripheral surface (combustion chamber side outer peripheral surface)
35: Lower outer peripheral surface (crank chamber side outer peripheral surface)
36 Sliding surface 40 Radial inner surface of recess 41 Curved surface 41a Upper end of recess (combustion chamber side end of recess)
41c... Deepest part in the radial direction of the recess 42a... Lower end of the recess (end part of the recess on the crank chamber side)
42... Inclined surface Xu... Upward (combustion chamber side)
Xd...Downward (crank chamber side)
D...Radial direction (ring radial direction)

Claims (6)

Used in an engine comprising a cylinder and a piston that reciprocates between the combustion chamber side and the crank chamber side inside the cylinder, and is mounted on the outer peripheral surface of the piston to support the reciprocating motion of the piston. A top ring of the piston arranged closest to the combustion chamber among the piston rings formed with the ring outer peripheral surface having the sliding surface that slides on the inner peripheral surface of the cylinder,
In a cross section along the axis of the piston, a concave portion is formed on the outer peripheral surface of the ring on the combustion chamber side of the sliding surface, the concave portion being concave inward in the ring radial direction,
The inner surface of the recess in the ring radial direction is at least partially formed with a curved surface that extends toward the crank chamber while curving inward in the ring radial direction from the end of the recess on the combustion chamber side, A piston top ring formed so that an end portion of the recess on the side of the combustion chamber faces the inner peripheral surface of the cylinder. An inclined surface is formed on the radially inner surface of the ring outside the curved surface in the ring radial direction and extends from the end of the curved surface on the crank chamber side toward the crank chamber and radially outward of the ring. 2. A top ring for a piston according to claim 1. 3. The top ring for a piston according to claim 2, wherein the inclined surface is surface-treated to enhance oil repellency compared to the periphery thereof. The ring outer peripheral surface includes a combustion chamber side outer peripheral surface formed on the combustion chamber side and having at least a portion of the combustion chamber side end of the recess, and a crank-chamber-side outer peripheral surface that extends toward the crank-chamber side and at least a part of which is formed with the sliding surface; 4. The piston top ring according to any one of claims 1 to 3, wherein the top ring is formed so as to widen the distance from the inner peripheral surface. The distance between the end portion on the combustion chamber side and the deepest portion in the radial direction of the ring of the recess is
5. The piston according to any one of claims 1 to 4, wherein the distance in the axial direction of the piston of the recess is shorter than the distance between the end on the side of the combustion chamber and the end opposite to the end on the side of the combustion chamber. top ring. The top ring for a piston according to any one of claims 1 to 5, wherein the curved surface is formed along the entire circumference of the outer peripheral surface of the ring.

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