JPH02540B2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to an airtight piston ring in a reciprocating machine, and specifically relates to a piston ring for an internal combustion engine, a gas seal ring for a Stirling engine, and a piston ring for a high compression ratio compressor. It is.

First, piston rings for internal combustion engines, which have the most severe operating conditions, will be explained. The first requirement for piston rings in reciprocating internal combustion engines is airtightness of combustion gas and control of lubricating oil. In recent years, there has been a strong desire to reduce the number of piston rings in order to improve engine efficiency. This not only reduces the number of piston rings (usually 3 to 4 are required) and reduces friction loss between the piston rings and the inner peripheral surface of the cylinder liner, but also reduces the axial length of the piston. The aim is to reduce the height of the entire engine and also to achieve the effect of making the engine itself smaller and lighter.

In order to reduce the number of piston rings in this manner, it is essential that the piston rings have excellent gas sealing properties and lubricant control properties, which are the basic functions of piston rings.

When considering the airtightness of the combustion gas, the combustion gas leaks from the abutment 15 on the outer peripheral side of the piston ring 1 as shown in Fig. 1, so there is a step in the axial direction called a step cut as shown in Fig. 2. It is said that the piston ring 1 provided with 15 is effective. However, simply providing the step 15 does not provide much effect because gas leaks from the inner circumferential surface 13 side to the lower abutment 152 via the piston ring upper surface 12 and inner circumferential surface 13. Therefore, the third
A special gap piston ring with steps in the axial and radial directions of the gap as shown in the figure has been devised, but it is not possible to make the piston ring sufficiently gas-tight by simply improving the gap shape. cannot be retained.

The reason for this is that, as shown in FIG. 4, the piston ring 1 is not constantly pressed against the piston ring groove 4, but there is a period in which it floats within the piston ring groove, and in this state, the piston ring 1 Combustion gas leaks through the inner peripheral surface 13 side. The amount of gas leaking is significantly larger than the amount leaking from the outer peripheral surface side. In consideration of this point, a piston ring in which a piston ring with a U-shaped or H-shaped cross section is combined on the inner peripheral surface side (for example, U.S. Pat. No. 2,745,704,
Special Publication No. 47-21164) has also been proposed. These piston rings almost completely shut off gas by making the piston ring that forms the outer circumferential surface a gap with a step in the axial direction. The piston ring arranged on the circumferential side blocks the piston ring, and the piston ring has poor followability with respect to the cylinder liner, which tends to cause gas leakage from the outer circumferential surface.

Normally, two piston rings for gas sealing are arranged in the axial direction as shown in Figure 5, so gas leaking from the first piston ring 1 expands in the land portion 8. , the gas leaks downward from the second piston ring 1', but the gas is throttled by the first and second piston rings and expands during its path to reduce the pressure, so the gas leak becomes small.

Therefore, in order to obtain a piston ring with extremely excellent gas sealing properties, it is necessary to prevent leakage from the inner peripheral surface of the piston ring, and to have one piston ring perform the same sealing function as the conventional two piston rings. have to have it.

As a method of blocking leakage from the inner peripheral surface of the piston ring, as shown in Fig. 6, a piston ring that combines a first ring 1 and a second ring 2 (for example, Utility Model Publication No. 36-10004, Japanese Patent Publication No. 54-30451) is used. No.) has been proposed. In this piston ring, a groove 19 is provided in the piston ring inner peripheral surface 13, a groove 41 is also provided in the piston ring groove 4, and the second ring 2 is fitted into these grooves 19,41. The main purpose of this piston ring is to
The second ring 2 blocks lubricating oil from entering from the fourth side, and prevents the lubricating oil from leaking through the first ring inner peripheral surface 13 to the combustion chamber side. Even in the conventional configuration, the second ring has the upper surface 1 of the first ring.
Although it has the effect of blocking gas leaking from the second side through the first ring inner circumferential surface 13 to some extent, gas leaks much more easily than lubricating oil under conditions such as viscosity and pressure, so no significant prevention effect can be obtained. . The reason for this is that, as shown in FIG. 6, conventional piston rings are basically designed to block lubricating oil, and no consideration is given to gas-tightness. For example, no measures have been taken to prevent the piston rings from lifting, and no path has been set for gas leakage.

An object of the present invention is to provide a piston ring that has gas-tightness equivalent to that of two conventional piston rings and can also reduce lubricant consumption. The piston ring of the present invention can be used not only in the above-mentioned internal combustion engine, but also in reciprocating machines that particularly require airtightness, such as gas seal rings for Stirling engines, compressors with high compression ratios, and the like.

In order to achieve the above object, the gist of the present invention is as follows: A first ring 1 having a sliding surface on its outer periphery and a groove 19 on its inner periphery is disposed, and the piston ring groove bottom 43 is provided with a groove 41 or Recess 4
0, and a second ring 2 fitted in the groove 19 of the first ring 1 and the groove 41 or recess 40 of the piston ring groove bottom 43, the second ring 2 has an external tension, and The first ring 1 is in contact with the inner peripheral part 113 of the groove 19 of the ring 1, and the abutment shape of the first ring 1 has an upper abutment 151 and a lower abutment 152 with a step at least in the axial direction. The step 150 position of the abutment 152 is below the second ring upper surface 22 and above the second ring bottom surface 24, and the abutment position of the first ring 1 and the second ring 2 is shifted in the circumferential direction, and the groove 19 of the first ring 1 is One axial surface of the piston ring 2 contacts one axial surface of the second ring 2, and at the same time one axial surface of the groove 41 or recess 40 at the bottom of the piston ring groove contacts one axial surface of the second ring 2. It is in.

The piston ring of the present invention will be explained based on the embodiments shown in FIGS. 7, 8, 11, and 13 to 20.

The piston ring of the embodiment shown in FIG. 7 can almost completely block gas leakage from the outer circumferential side and the inner circumferential side. Gas leaking from the outer circumferential surface side is completely blocked by the abutment shape of the first ring 1 having a step in the axial direction, similar to a conventional piston ring. Gas leakage from the inner peripheral side is prevented as follows. First, gas entering from the upper abutment 151 of the first ring enters the first ring 1 above the second ring.
Although it flows out into the inner peripheral space 101, no leakage occurs because the second ring 2 is in contact with the first ring groove inner peripheral surface 113 side. If the second ring 2 does not have self-tension and the second ring 2 and the groove inner circumferential surface 113 are apart, gas will leak from the upper abutment 151 along the groove inner circumferential surface 113 to the lower abutment 152. Self-tensioning of the second ring 2 is essential. When the step 150 is located above the upper surface 22 of the second ring 2, the lower abutment 152 of the first ring communicates with the space 101 on the upper surface side of the second ring 2, as shown in FIG. The sticker has no meaning, and on the contrary, there is a step difference of 15
When the 0 position is below the bottom surface 24 of the second ring 2, as shown in FIG. It has no effect. The upper aperture 151 of the present invention is the space 1 on the upper surface side of the second ring.
01, and the lower abutment 152 communicates with the space 102 on the lower surface side of the second ring, but the upper abutment and the lower abutment communicate via the second ring 2, so
The gas infiltration passage leading to the space 102 on the lower surface side of the second ring is narrowed to the passage from the second ring abutment. This not only has the effect of simply narrowing down the gas infiltration route, but also brings about the following significant gas sealing effect.
That is, as shown in FIG.
abutment 25 and a lower abutment 152 of the first ring 1
By shifting the two rings, the gas leaking from the second ring abutment 25 is transferred to a space on the second ring lower surface side surrounded by the second ring lower surface 24, the first ring inner circumferential surface 13, and the piston ring groove bottom 43. 102, expands and decompresses there, passes through the first ring lower joint 152, and leaks out from the gap between the cylinder liner 3 and the piston 5. Such a gas path is shown in FIG. This is substantially the same as the gas outflow path of two piston rings arranged in the axial direction with a narrow land portion, and one piston ring can improve the gas sealing effect of two piston rings. . More specifically, the gap G ¹ between the second ring abutment 25 and the first ring inner peripheral surface 13
The gas leakage area of the second ring joint 25 multiplied by the gap C ¹ between the piston ring groove bottom surface 43 is G ¹ ×
C ¹ , which almost matches the leakage area at the joint of a normal piston ring, and the second ring joint 25
space 10 from to the first ring lower abutment 152
2 corresponds to the volume of the land portion between the ordinary piston rings, and the first ring lower abutment 152
The abutment leakage area of G ² ×C ² , which is the product of the gap G ² and the gap C ² between the cylinder liner 3 and the piston 5, is equal to the abutment leakage area of the second piston ring of a normal piston ring. As shown in FIG. 7, when the gas leaks from the second ring inner peripheral surface 23 side,
One axial surface 22 or 24 of the second ring 2 must abut one axial surface 420 or 421 of the piston ring groove bottom 43, since the effect thereof is significantly reduced.

The above effect is based on the assumption that the piston ring does not lift up, but the piston ring of the present invention effectively prevents lifting. That is, since the second ring 2 and the first ring 1 of the conventional piston ring as shown in FIG. A distributed pressure of up to the pressure p ₂ in the space 102 is applied to the upper surface 12 of the second ring, and a pressure p ₇ approximately equal to the trapland pressure is applied to the upper surface 12 of the second ring. Since this p ₂ is almost equal to p ₇ , the condition for the first ring 1 to be lifted by the inertial force I of the first ring 1 is that the radial width of the first ring is T, the force applied to the upper surface is P ₂ , the lower surface is The force applied to P ₄
Then, it is expressed by the following formula. ( _P8 indicates the land pressure directly below the first ring.) I> _P2 - _P4 = _p7・T-( _p2 + _p8 )/2・T= _p7 − _p8 /2・T Invention Since the piston ring blocks gas leakage into the space 102, as shown in _{FIG .} Therefore, the conditions for lifting the first ring are expressed by the following equation.

I ₁ > P ₂ - P ₄ = p ₇ · T - p ₂ + p ₈ /2 · T = (p ₇ - p ₈ ) T Here, since the inertial force is proportional to the square of the rotational speed, the piston ring of the present invention Compared to conventional piston rings, it can be said that the piston ring does not lift up until it rotates at about 4 times the high speed.

In this way, the piston ring of the present invention can almost completely block not only gas leakage from the outer circumferential surface but also gas leakage from the inner circumferential surface, and moreover, one piston ring can replace two conventional pistons. Performs the same function as the ring's gas seal function. Furthermore, since the piston ring of the present invention does not lift up even when rotated at a considerably high speed, it is excellent as a piston ring for gas sealing.

The features of the piston ring of the present invention that provide a gas sealing effect are that the inner peripheral surface of the piston ring has a high airtightness and is difficult to lift up. This prevents lubricating oil from entering and leaking from the inner peripheral surface to the upper surface of the piston ring, thereby reducing lubricating oil consumption.

A more preferred embodiment of the present invention is to increase the volume of the space 102 surrounded by the second ring lower surface 24, the first ring inner peripheral surface 13, and the piston ring groove bottom 43, as shown in FIGS. 14 to 16. It is. The piston ring with such a configuration is the 11th
By increasing the volume of the space 102, which has the effect of expanding the gas in the gas passage and reducing the pressure, as explained in the figure, the pressure reduction effect can be further enhanced and the airtightness can be improved. As a concrete example, the 14th
The embodiment shown in the figure has a notch 130 in the lower part 13 of the inner peripheral surface of the first ring 1, the embodiment shown in FIG. 15 has a notch 430 in the bottom 43 of the piston ring groove, and the embodiment shown in FIG. 44 has a notch 440. A combination of the embodiments shown in FIGS. 14 to 16 is also a preferred embodiment. or,
As shown in FIG. 17, the piston ring groove bottom 43
Instead of providing a groove, a recess 40 may be provided.

Furthermore, it is most desirable that the lower surface 24 of the second ring 2 contacts the upper surface 420 of the groove 41 at the bottom of the piston ring groove and the upper surface 194 of the groove 19 of the first ring, as shown in FIG. As shown in FIG. 19, the effect of the piston ring of the present invention is improved by stopping the second ring 2 from rotating at a position approximately 180 degrees rotated from the lower abutment 152 of the first ring 1 via the detent 8. Become more certain.

The piston ring of the present invention also has effects other than those described above. That is, as shown in Fig. 20, when looking at the force in the radial direction of the piston ring of the present invention, the difference between the force P ₁ from the outer peripheral surface side and the force P ₃ from the inner peripheral surface side is expressed by the following equation. .

P ₁ − P ₃ = (p ₇ + p ₈ )/2h ₁ − (p ₇・h ₂ +p ₂・h ₃ ) where p ₇ is the top land pressure, p ₈ is the piston ring lower land pressure, and p ₂ is Space 102 pressure is approximately equal to p ₈ . h ₁ is the height of the piston ring, h ₂ is the height to the bottom surface of the second ring, and h ₃ is the height below the bottom surface of the second ring. Therefore, by rearranging the above equation, the following equation is obtained.

P ₁ - P ₃ = 1/2 (p ₇ - p ₈ ) (h ₃ - h ₂ ) In this case, if h ₃ = h ₂ , theoretically the piston ring of the present invention has no force other than the self-tension of the piston ring. No force is applied, and no high pressure or pushing force is applied. Furthermore, considering that the first ring is pushed into the bottom of the piston ring groove, h ₃ < h ₂
is desirable. Furthermore, the piston ring of the present invention has nothing that impedes the radial movement of the first ring and the second ring, and has very good followability to the cylinder liner.

In this way, the piston ring of the present invention does not come into contact with the cylinder liner under high pressure and has excellent followability, so it is possible to use lubricating oil with less wear and low viscosity, reducing wear loss. It has the effect of significantly reducing

As mentioned above, the piston ring of the present invention blocks gas leakage on both the inner and outer peripheral surfaces of the piston ring, has the same gas-tight path as two piston rings as a basic function, and does not lift up the piston ring. It also has a remarkable gas sealing effect.

Furthermore, the path through which lubricating oil passes from the lower surface of the piston ring to the upper surface via the inner circumferential surface is completely blocked, and the amount of lubricating oil consumed is significantly reduced. In addition, since radial movement cannot be prevented and the piston ring is not pressed against the cylinder liner under high pressure, it is possible to use lubricating oil with less wear and low viscosity, which has the effect of reducing wear loss. Have both.

The piston ring of the present invention has excellent heat conductivity because heat is transmitted to the piston ring not only from the upper and lower surfaces of the piston ring groove but also from the bottom side of the piston ring groove via the second ring. It is possible to transmit more to the cylinder liner side.

The piston ring of the present invention allows the piston ring to be assembled into the piston ring groove after the second ring is installed into the groove on the inner circumferential surface of the first ring, making it easy to install the piston ring.

In addition, in the piston ring of the present invention, the sliding portions of the outer and inner circumferential surfaces of the first ring and the second ring are subjected to surface coating such as plating or thermal spraying, or are subjected to heat treatment such as nitriding or quenching. Needless to say, this improves wear resistance, and furthermore,
It is also possible to provide tapers on each surface of the first ring and the second ring. It goes without saying that the position of the groove on the inner circumferential surface of the first ring 1 is appropriately selected in consideration of the balance of forces in the radial direction, as explained in FIG. 20.

[Brief explanation of drawings]

Figures 1 to 6 and 12 are drawings showing conventional piston rings, and Figures 1 to 3 are drawings showing conventional piston rings.
The figure is a perspective view of the joint, Figure 4 is a partial sectional view, and Figure 5 is a partial sectional view.
The figure is an elevational view of the piston with the piston ring fitted.
Fig. 6 is a partial sectional view of a conventional piston ring consisting of a first ring and a second ring, Fig. 12 is an axial pressure distribution diagram thereof, and Figs. 7, 8, and 11 are one embodiment of the present invention. FIG. 7 is a partial cross-sectional view of a piston ring according to an embodiment of the present invention, FIG. 8 is a perspective view of the abutment of the piston ring in FIG. 7, and FIG. FIGS. 9 and 10 are perspective views showing the gas path at the joint, and FIGS. 9 and 10 are partial sectional views of the joint different from the present invention. FIG. 13 is an axial pressure distribution diagram of the piston ring of the present invention, and FIGS. FIG. 18 is a partial sectional view of another embodiment, and FIG.
20 is a plan view of the piston ring of the present invention, and FIG. 20 is a pressure distribution diagram in the radial direction of the piston ring of the present invention. 1: First ring, 2: Second ring, 4: Piston ring groove, 13: First ring inner peripheral surface, 15: First ring joint, 19: First ring groove, 24:
Second ring bottom surface, 25: Second ring joint, 4
0: recess, 41: groove, 151: upper abutment, 15
2: Lower joint.

Claims (1)

[Scope of Claims] 1. A first ring having a sliding surface on its outer periphery and a groove on its inner periphery, a groove provided on the inner periphery of the first ring, and a groove or recess provided in the piston ring groove. In a piston ring in which a second ring is disposed in a space surrounded by
The first ring 1 has an upper abutment 151 and a lower abutment 1 which are stepped at least in the axial direction.
52, and the stepped position of these joints is between the upper surface and the lower surface of the second ring, and the position of the joint between the first ring 1 and the second ring 2 is shifted in the circumferential direction, and One axial surface of the groove 19 and one axial surface of the second ring 2 come into contact, and at the same time, one axial surface of the groove 41 or recess 40 at the bottom of the piston ring groove and one axial surface of the second ring 2 contact each other. A piston ring characterized by abutment. 2. The piston ring according to claim 1, wherein the first ring 1 and the second ring 2 are provided with rotation preventing means 8. 3 A notch 130 provided in the lower inner circumferential surface 13 of the first ring 1 and a notch 43 provided in the portion of the piston ring groove 4 facing the first ring lower inner circumferential surface 13
0 and the second ring lower surface 24 of the piston ring groove 4
The piston ring according to claim 1, further comprising at least one notch 440 provided in a portion facing the piston ring. 4 Inner circumference of first ring 1 and piston ring groove 4
2. The piston ring according to claim 1, wherein grooves 19 and 41 are provided at the same position in the axial direction of the piston ring, and the second ring 2 is fitted into the grooves 19 and 41. 5 Upper surface 1 of the groove 19 provided on the inner peripheral side of the first ring
20. The piston ring according to claim 1, wherein the second ring lower surface 24 and the groove 41 provided in the piston ring groove or the upper surface 420 of the recess 40 and the lower surface 24 of the second ring are in simultaneous contact with each other.