JPH04136463A - Piston for internal combustion engine - Google Patents

Abstract

PURPOSE:To eliminate oil rising, reduce the lubricating oil consumption, suppress friction, and secure the airtightness holding performance by forming an annular groove on the second rand and installing an oil ring which has a specific shape and has the passages for gas and lubricating oil at a convergence part. CONSTITUTION:On a piston 1 which moves in reciprocation in a cylinder 20, the first and the second annular ring grooves 2 and 3 are formed on the outer periphery. Further, the second rand 7 is formed between the first and the second annular ring grooves 2 and 3. In this case, on the surface of the second rand 7, the second rand annular groove 10 which does not communicate to both of the first and second annular ring grooves 2 and 3 is formed. Pressure is easily transmitted in the circumferential direction by increasing the capacity of the space formed from the cylinder inner wall surface and the second rand 7 by the second rand annular groove 10. While, at least a central annular projecting strip 51 having the contact surface with the cylinder inner wall is formed on an oil ring 5 installed in the second annular ring groove 3. Accordingly, at least friction is reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a piston for an internal combustion engine having a pressure ring and an oil ring.

[Conventional technology]

Pistons used in internal combustion engines such as gasoline engines and diesel engines are usually equipped with three rings: two pressure rings located on the combustion chamber side and one oil ring located on the crankcase side. ing. As is well known, the piston ring has the function of maintaining airtightness between the piston and the cylinder wall and minimizing the leakage of combustion gases (blow pie) in the combustion chamber (mainly due to the pressure ring), and the function of maintaining airtightness between the piston and the cylinder wall (mainly due to the pressure ring) It must have a function (mainly by the oil ring) to properly scrape off the lubricant that has adhered to the crankcase and keep the lubricant consumption at an appropriate level.

The ring configuration required at least three rings.

On the other hand, with the increase in engine output and rotation speed in recent years,
Since there is a demand for lighter weight and smaller pistons, it is necessary to shorten the axial length of the piston itself.

By the way, a plurality of annular ring grooves are formed on the piston for mounting rings, and considering the mechanical strength around the ring grooves, the portion between the ring grooves (land portion) also has a predetermined axial length. Must be. therefore,
In order to make the piston itself smaller and lighter, it is essential to reduce the number of rings itself. Reducing the number of rings is also effective in reducing piston system friction in internal combustion engines and improving fuel efficiency.

[Problem to be solved by the invention]

However, reducing the number of rings prevents the combustion gas from leaking toward the crankcase, which is the original role of the rings.
Alternatively, various functions such as prevention of lubricant consumption due to lubricating oil rising toward the combustion chamber may be deteriorated.

For example, during high vacuum boost with the throttle closed, or more specifically when engine braking is applied, high negative pressure builds up in the intake manifold and cylinders, causing a tendency for lubricating oil to be sucked up toward the combustion chamber. It is known. That is, by creating a negative pressure inside the cylinder, lubricating oil from the crankcase side is sucked toward the combustion chamber through the vicinity of the piston ring.

Therefore, if the number of rings is reduced, it becomes difficult to prevent such a lubricating oil suction phenomenon, and the amount of lubricating oil consumed increases.

Japanese Utility Model Application Publication No. 61-51455 discloses a combination of a pressure ring whose inner circumferential upper edge is cut off and a piston ring which contacts the cylinder inner circumferential surface with a thin contact surface. Its configuration is shown in FIG. In FIG. 6, piston ring grooves 102 and 103 are formed in a piston 101, a top land 104 is formed above the piston ring groove 102 (in the direction of the combustion chamber), and piston ring grooves 102 and 103 are formed.
A second land portion 105 is formed between. A pressure ring 106 is attached to the upper ring groove 102, and an oil ring 107 is attached to the lower ring groove 103. This oil ring 107 has a so-called N5OR (Na r
This is called ``rowSingle Oil Rtng''. In a piston for an internal combustion engine using this N5OR, lubricating oil flows out to the oil relief hole 108 in the upward stroke through the flow path shown by the arrow in FIG. 6(a) due to a so-called check valve action.

Further, in the downward stroke, as shown in FIG. 6(b), the upper side (combustion chamber side) of the oil ring is in close contact to prevent the lubricating oil from rising.

That is, in a piston for an internal combustion engine using this N5OR, the amount of lubricating oil consumed can be reduced by actively utilizing a so-called check valve action.

However, even in conventional pistons for internal combustion engines using N5OR, the reduction in lubricating oil consumption is not necessarily sufficient in engines that rotate at high speeds and have large bore deformations.

Therefore, as a result of intensive study, the inventor of the present application found that the above-mentioned N.
For internal combustion engine pistons using 5OR, N5OR
Since the sloped surface of the abutment forms a passage for the lubricating oil at the abutment, the gas and lubricating oil will disappear, and in the downward stroke, the oil ring will normally not move as shown in Figure 6(b). The upper side should be in close contact to prevent the lubricating oil from rising, but in some cases, the pressure in the space formed by the pressure ring, the edge of the second land, and the inner peripheral surface of the cylinder may be unavoidably released from the pressure ring. It was found that the oil ring was not only pushed downward by this pressure, but also deformed and showed a tendency for oil to rise because the pressure was increased by the gas that leaked out and the pressure distribution became uneven in the circumferential direction. did.

Based on this knowledge, the inventor of the present application further investigated and found that 2.
In the internal combustion engine piston with this ring configuration, by aligning the abutment part of the pressure ring and the abutment part of N5OR in the same direction and installing it, the space formed by the edge of the second land and the inner peripheral surface of the cylinder can be reduced. It is possible to reduce the pressure and make the pressure uniform in the circumferential direction, and the oil ring is pushed down by the pressure in the space formed by the edge of the second land and the inner peripheral surface of the cylinder. We have found that it is possible to prevent this phenomenon and further reduce lubricant consumption, but the conventional so-called N5OR
The problem of gas and lubricating oil passages being formed at the joints due to the shape of the joints has not yet been resolved.

The present invention has been made based on the above circumstances.

That is, an object of the present invention is to provide a piston for an internal combustion engine that has low friction, further reduces lubricating oil consumption, and ensures sufficient airtightness.

[Means to solve the problem]

The gist of the present invention to achieve the above object is to provide a top land on the engine combustion chamber side, a first annular ring groove adjacent to the top land for mounting a pressure ring, and a first annular ring groove for mounting an oil ring. a second annular ring groove;
In a piston for an internal combustion engine that has an annular ring groove and a second land formed between the second annular ring groove and reciprocates within a cylinder, the first annular ring groove and the The oil ring has a second land annular groove that does not communicate with any of the second annular ring grooves, and has a central annular convex band in the middle portion of the outer circumferential surface facing the inner wall of the cylinder of the oil ring installed in the second annular ring groove. A piston for an internal combustion engine, which is characterized by a top land on the engine combustion chamber side, a first annular ring groove adjacent to the top land for mounting a pressure ring, and a first ring groove for mounting an oil ring. In an internal combustion engine piston having two annular ring grooves and a second land formed between the first annular ring groove and the second annular ring groove and reciprocating within a cylinder, a surface intermediate portion of the second land. has a second land annular groove that does not communicate with either the first annular ring groove or the second annular ring groove, and the pressure on the outer peripheral surface facing the cylinder inner wall of the oil ring installed in the second annular ring groove. This piston for an internal combustion engine is characterized in that it has an end annular convex band on the ring side edge and an inner circumferential annular notch cut out on the cylinder bottom side of the oil ring inner circumferential surface.

[Effect]

During the downward stroke, gas inevitably leaks from the pressure ring into the space formed by the second land and the cylinder wall, but the volume of this space is increased by the second land annular groove formed on the surface of the second land. Therefore, the rate of pressure increase in the space is small, and the pressure distribution is uniform in the circumferential direction. Therefore, the pressure of the space formed by the second land and the cylinder wall surface eliminates the pushing down of the oil ring due to partial deformation toward the bottom surface of the cylinder, and no oil leakage occurs.

Moreover, the oil ring attached to the second annular ring groove is
Since it has a central annular convex band with a contact surface with the cylinder inner wall, frixitane is reduced, and compared to conventional N5O
Compared to R, the gas and lubricant passages formed at the abutment are narrower, and the amount of gas and lubricant lost per unit time is reduced.

Similarly, in the piston for an internal combustion engine according to claim 2, the oil ring installed in the second annular ring groove has an end annular convex band at the end of the outer peripheral surface, and an inner peripheral surface of the oil ring has an inner peripheral surface. Because it has an annular notch on the circumference, the gas and lubricant passage formed at the abutment is narrower compared to the conventional so-called N5OR, and the amount of gas and lubricant lost per unit time is reduced. do. Moreover, since an annular notch is formed on the inner circumferential surface of the oil ring on the cylinder bottom side, twisting of the ring due to the annular convex band at the end is corrected by this annular notch, and the second annular ring groove is formed. It does not twist even when installed.

〔Example〕

Next, examples of the present invention will be described.

In FIG. 1, a piston 1 reciprocating within a cylinder 20 has a first annular ring groove 2 and a second east annular ring groove 3 formed on its outer periphery, and a pressure ring 4 is formed in the first annular ring groove 2. Oil rings 5 are installed in the second annular ring grooves 3, respectively.

A top land 6 facing the combustion chamber is formed at the upper part of the first annular ring groove 2 , and a second land 7 is formed between the first annular ring groove 2 and the second annular ring groove 3 . Also,
A piston skirt 8 facing the crankcase is formed below the second annular ring groove 3. Furthermore, a passage 9 is formed in the piston 1 to communicate the first annular ring groove 2, the second annular ring groove 3, and the crankcase.

A second land annular groove 10 that does not communicate with either the first annular ring groove 2 or the second annular ring groove 3 is formed on the surface of the second land 7 .

This second land annular groove 10 connects the cylinder inner wall surface with the second land annular groove 10.
The volume of the space formed by the land 7 increases, making it easier for pressure to be transmitted in the circumferential direction. Therefore, even if gas inevitably leaks from the pressure ring into the space formed by the second land 7 and the cylinder wall, the rate of pressure increase in this space will be small, and the pressure distribution will be uniform in the circumferential direction. . Therefore, since the oil ring 5 is not pushed down due to partial deformation toward the bottom surface of the cylinder due to the pressure in this space, no oil leakage occurs.

Furthermore, as shown in FIG. 3, the oil ring 5 installed in the second annular ring groove 3 has a central annular convex band 51 having a contact surface with the cylinder inner wall, and an annular notch 52 at the end on the combustion chamber side.
and an annular notch 53 at the bottom end of the cylinder. This central annular convex band 51 is formed at the center of the oil ring, has a contact surface with the cylinder inner wall, and is sandwiched between an annular notch 52 at the end on the combustion chamber side and an annular notch 53 at the end on the bottom side of the cylinder. ing. And the combustion chamber side end annular notch 5
2 and the annular notch 5 at the bottom end of the cylinder.
The longitudinal cross-sectional shapes of No. 3 are equal rectangles. If the vertical cross-sectional shape of the combustion chamber side end annular notch 52 and the vertical cross-sectional shape of the cylinder bottom side end annular notch 53 are not equal to each other,
When installed in the second annular ring groove 3, the oil ring 5 is more likely to be twisted. In addition, if the vertical cross-sectional shape of the combustion chamber side end annular notch 52 and the vertical cross-sectional shape of the cylinder bottom side end annular notch 53 are not rectangular, increase the volume of the gas and lubricating oil passage at the abutment. invite

Figure 5 is a graph showing the relationship between the oil ring shape (abutment gaps of 0.1 mm and 0.3 mm, compression ring abutment and oil ring abutment installed in the same direction) and lubricating oil consumption at 500° rpm. be.

As is clear from the figure, in the internal combustion engine piston of this embodiment, the lubricating oil consumption per hour when the abutment gap Q is 1 mm is 22 g, and the amount of lubricating oil consumed per hour is 1 when the abutment gap is 0.3 mm.
Lubricant oil consumption per hour is 20g. This value corresponds to the lubricating oil consumption per hour of 30g (0.1mm gap) and 39g measured under the same conditions for the internal combustion engine piston equipped with the conventional so-called N5OR shown in Figure 6.
Both are reduced compared to g (abutment gap 0.3 mm).

The oil ring 5 installed in the second annular ring groove 3 of the piston for an internal combustion engine shown in FIG. It has an annular band 54, an annular notch 55 at the end of the cylinder bottom surface that is in contact with the annular convex band 54, and an annular notch 56 on the inner peripheral surface.

The cylinder bottom side end annular notch 55 and the inner peripheral surface annular notch 56 are formed in a balanced manner so that the oil ring 5 is not twisted when the oil ring 5 is installed in the second annular ring groove 3. ing.

Further, the vertical cross-sectional shape of the annular notch 55 at the end of the cylinder bottom surface is rectangular. If this cross-sectional shape is not rectangular, the volume of the gas and lubricating oil passages at the abutment will increase.

In other words, as shown in Fig. 5, the lubricating oil consumption per hour of a piston for an internal combustion engine equipped with this oil ring is 24g per hour when the gap is 0.1 mm.
lubricating oil consumption per hour measured under the same conditions for an internal combustion engine piston equipped with a conventional so-called N5OR shown in Fig. 6 (with a gap of 0.2 mm).
3mm) is reduced compared to 39g.

〔Effect of the invention〕

According to the present invention, the annular groove is provided in the second land, and an oil ring of a specific shape with a narrow passage for gas and lubricating oil at the abutment part is attached, so that the oil ring is formed by the second land and the inner wall surface of the cylinder. Not only does the rate of pressure increase in the space become smaller, but the pressure distribution becomes uniform in the circumferential direction, so the oil ring is not partially pushed down toward the crankcase during the downward stroke, so there is no oil leakage. It is possible to provide a piston for an internal combustion engine that reduces lubricant consumption, has low friction, and has sufficient airtightness.

[Brief explanation of the drawing]

1 and 2 are cross-sectional views showing an example of a piston for an internal combustion engine according to the present invention, FIG. 3 and FIG. 4 are cross-sectional views showing an oil ring in a piston for an internal combustion engine according to the present invention, and FIG. 6 is a graph showing the relationship between oil ring shape and lubricating oil consumption, FIG. 6(a) is a sectional view showing the upward stroke state of a conventional two-ring piston for an internal combustion engine, and FIG. It is a sectional view showing a state of a descending stroke similarly. 1... Piston, 2... First annular ring groove, 3...
- Second annular ring groove, 4... Pressure ring, 5... Oil ring, 6... Top land, 7... Second land, 10... Second land annular groove, 51... Central annular convex band, 54... End annular convex band,... End annular convex band, 55... Cylinder bottom side end annular notch, 56
...An annular notch on the inner peripheral surface. Applicant's representative Yasushi Ishikawa 2'

Claims (1)

[Claims] 1. A top land on the engine combustion chamber side, a first annular ring groove adjacent to the top land for mounting a pressure ring, and a second annular ring groove for mounting an oil ring. and a piston for an internal combustion engine that has a second land formed between the first annular ring groove and the second annular ring groove and reciprocates within the cylinder. It has a second land annular groove that does not communicate with either the annular ring groove or the second annular ring groove, and a central annular groove in the middle part of the outer peripheral surface facing the cylinder inner wall of the oil ring installed in the second annular ring groove. A piston for an internal combustion engine characterized by having a convex band. 2. A top land on the engine combustion chamber side, a first annular ring groove adjacent to the top land for mounting a pressure ring, a second annular ring groove for mounting an oil ring, and the first annular ring groove. In a piston for an internal combustion engine that reciprocates within a cylinder and has a second land formed between a ring groove and a second annular ring groove, the first annular ring groove and the first annular ring groove are formed in a middle portion of a surface of the second land. It has a second land annular groove that does not communicate with either of the two annular ring grooves, and an end annular convex shape on the pressure ring side edge of the outer peripheral surface facing the cylinder inner wall of the oil ring installed in the second annular ring groove. 1. A piston for an internal combustion engine, characterized in that the piston has an annular inner circumferential notch formed on the cylinder bottom side of the inner circumferential surface of an oil ring.