Field of the Invention

The present invention relates to the field of automotive components, and in particular to an elliptical ring groove piston and an engine.

Description of Related Art

The existing engine piston is provided with three ring grooves in a circumferential direction, which are named as a first ring groove, a second ring groove and a third ring groove respectively along the direction away from a top ring. The walls on both sides of the first ring groove are a first ring land and a second ring land respectively, the walls on both sides of the second ring groove are the second ring land and a third ring land respectively, and the walls on both sides of the third ring groove are the third ring land and a fourth ring land respectively.

In the existing design, due to uneven temperature distribution over a bottom diameter of the first ring groove in the circumferential direction, engine oil distribution over the bottom diameter of the first ring groove in the circumferential direction is uneven, which is prone to cause uneven accumulation and distribution of carbon deposits, the risk of clamping stagnation of the top ring of the piston ring, and serious problems in gas leakage and engine oil consumption.

The design of the second ring land of the piston generally is an elliptical design. Because airflow passing through the second ring land is uneven in the circumferential direction of the piston, the bottom diameter of the second ring groove with a full-circle design may cause uneven pressure distribution of the gas pressure over the second ring land and the second ring groove in the circumferential direction, uneven acting force and movement of the top ring and the second ring land in a circle, and unstable movement of the top ring and the second ring land, affecting the gas leakage and engine oil consumption.

Due to the full-circle design of the third ring groove in the circumferential direction, the layout of oil return holes in the direction of the pin hole is relatively limited, affecting the movement and accumulation of engine oil and affecting the engine oil consumption. Summary of the Invention

The present invention provides an elliptical ring groove piston and an engine, in order to alleviate the following problems existing in the prior art:

1. Problems in clamping stagnation, gas leakage and engine oil consumption caused by carbon deposits in the first ring groove;

2. The acting force and movement of the top ring and the second ring land in a circle is uneven, affecting the gas leakage and engine oil consumption; and

3. The layout of the oil return holes corresponding to the third ring groove in the direction of the pin hole is relatively limited, affecting the movement and accumulation of engine oil and affecting the engine oil consumption.

To alleviate the above-mentioned technical problems, the technical solutions provided in the present invention are in that:

An elliptical ring groove piston, wherein the piston comprises a piston head and a skirt portion, an inner cooling gallery for cooling the piston is provided inside the piston head, and the inner cooling gallery is provided with an oil inlet for a cooling medium to enter and an oil outlet for the cooling medium to flow out after heat exchange; and ring lands and ring grooves are provided on the outer side of the piston head, and the piston is provided with a first ring groove adjacent to the top of the piston; on a section of the first ring groove, the profile of a bottom diameter of the first ring groove is elliptical, and the direction of the major axis of the ellipse generally coincides with a connecting line which connects a center line of the oil outlet of the inner cooling gallery and an axis of the piston.

Further, a second ring land is provided as a sectional elliptical structure, and with a cross-section passing through the bottom diameter of the first ring groove as a first cross-section, the major axis and the minor axis of a projection of the second ring land on the first cross-section do not overlap with the major axis and the minor axis of the bottom diameter of the first ring groove.

Further, the direction of the major axis of the elliptical section of the second ring land is perpendicular to the direction of an axis of a piston pin. Further, the piston is provided with a second ring groove along a circumferential direction, and the walls of the second ring groove proximate to the second ring groove are a second ring land and a third ring land; and the bottom of the second ring groove is a bottom diameter of the second ring groove, the cross- sectional profile of the bottom diameter of the second ring groove is elliptical, and the major axis of the bottom diameter of the second ring groove is along the direction of main and auxiliary thrusts.

Further, a projection of the second ring land along an axial direction covers the bottom diameter of the second ring groove.

Further, with a cross-section passing through the bottom diameter of the second ring groove as a second cross-section, the major axis and the minor axis of a projection of the second ring land on the second crosssection overlap with the major axis and the minor axis of the bottom diameter of the second ring groove respectively.

Further, the piston is provided with a third ring groove along a circumferential direction, the walls on both sides of the third ring groove are a third ring land and a fourth ring land respectively, the bottom of the third ring groove is a bottom diameter of the third ring groove, the cross-sectional profile of the bottom diameter of the third ring groove is elliptical, and the major axis of the bottom diameter of the third ring groove is along the direction of main and auxiliary thrusts.

Further, the profile of the fourth ring land in a cross-section is circular, and a projection of the fourth ring land along an axial direction covers the bottom diameter of the third ring groove.

Further, oil return holes are provided on the bottom diameter of the third ring groove in the direction of the pin axis.

An engine comprising the above-mentioned elliptical ring groove piston.

Technical effects:

The present solution provides a piston provided with the first ring groove along a circumferential direction. The bottom of the first ring groove is a bottom diameter of the first ring groove, and the walls proximate to the first ring groove are the first ring land and the second ring land. The cross- sectional profile of the bottom diameter of the first ring groove is elliptical, the elliptical bottom diameter of the first ring groove has a major axis, and an end of the major axis of the bottom diameter of the first ring groove is pointed to the position of the oil outlet of the inner cooling gallery and passes through the center of the piston.

The fact that an end of the major axis of the bottom diameter of the first ring groove is pointed to the position of the oil outlet of the inner cooling gallery and passes through the center of the piston can achieve the following advantages:

1. The temperature at the position of the first ring groove corresponding to the oil outlet of the inner cooling gallery is high, and at the major axis of the ellipse, because the volume of the piston ring at the bottom diameter of the first ring groove is relatively small, so that engine oil accumulation and thus carbon deposits are unlikely to occur.

2. When the piston ring in a closed state operates to the major axis of the first ring groove where the temperature is relatively high, due to the existence of the major axis, the airflow velocity is relatively large, and engine oil is less likely to stay at the major axis for a long time. In this case, carbon deposits are unlikely to occur at the high temperature.

Brief Description of the Drawings

To illustrate the technical solutions in the specific implementations of the present invention or in the related art more clearly, the accompanying drawings required for describing the specific implementations or the related art are briefly introduced below. It is obvious that the accompanying drawings in the following description show some implementations of the present invention, and for those of ordinary skill in the art, other drawings can also be obtained from these drawings without any creative efforts.

FIG. 1 is a schematic diagram of an axial section of a piston ring provided in an embodiment of the present invention;

FIG. 2 is a schematic diagram of an axial section of a piston ring provided in an embodiment of the present invention (shown with A- A);

FIG. 3 is a schematic diagram of an A-A section of a bottom diameter of a first ring groove of a piston ring provided in an embodiment of the present invention;

FIG. 4 is a schematic diagram of an axial section of a piston ring provided in an embodiment of the present invention (shown with B-B and C-C);

FIG. 5 is a schematic diagram of a B-B section of a second ring land of a piston ring provided in an embodiment of the present invention;

FIG. 6 is a schematic diagram of a C-C section of a bottom diameter of a second ring groove of a piston ring provided in an embodiment of the present invention;

FIG. 7 is a schematic diagram of an axial section of a piston ring provided in an embodiment of the present invention (shown with D-D);

FIG. 8 is a schematic diagram of a D-D section of a bottom diameter of a third ring groove of a piston ring provided in an embodiment of the present invention;

FIG. 9 is a picture of carbon deposits of a bottom diameter of a first ring groove in the prior art;

FIG. 10 is a picture of carbon deposits of a bottom diameter of a first ring groove provided in an embodiment of the present invention;

FIG. 11 is a gas pressure condition of a second ring groove at the corresponding position of the major axis of an ellipse of a second ring land in the prior art;

FIG. 12 is a gas pressure condition of a second ring groove at the corresponding position of the minor axis of an ellipse of a second ring land in the prior art;

FIG. 13 is a gas pressure condition at the major axis of an ellipse of a second ring groove at the corresponding position of the major axis of an ellipse of a second ring land in the present solution;

FIG. 14 is a gas pressure condition at the minor axis of an ellipse of a second ring groove at the corresponding position of the minor axis of an ellipse of a second ring land in the present solution;

FIG. 15 is a schematic diagram of an arrangement of oil return holes in the prior art; and

FIG. 16 is a schematic diagram of an arrangement of oil return holes corresponding to an elliptical design of a bottom diameter of a third ring groove in the present solution.

Detailed Description of the Embodiments

Embodiment 1

This embodiment provides an elliptical ring groove piston. Please refer to FIG. 1 to FIG. 16 together. It is well known that, in the side structure of the piston as shown in FIG. 1, there are a first ring land, a first ring groove, a second ring land, a second ring groove, a third ring land, a third ring groove (or referred to as an oil ring groove), a fourth ring land and a skirt portion (not shown) in sequence from a combustion chamber side to a skirt portion side.

The piston is provided with the first ring groove along a circumferential direction. The bottom of the first ring groove is a bottom diameter of the first ring groove, and the walls proximate to the first ring groove are the first ring land and the second ring land.

On a section of the first ring groove, the profile of a bottom diameter of the first ring groove is elliptical, and the direction of the major axis of the ellipse generally coincides with a connecting line which connects a center line of the oil outlet of the inner cooling gallery and an axis of the piston.

The reasons why the present solution adopts the above-mentioned arrangement are in that:

The temperature of the first ring groove is not evenly distributed in an axial direction. Near the position of an oil outlet of an inner cooling gallery, the temperature of the bottom diameter of the first ring groove is higher relative to other positions, which results in the uneven distribution of carbon deposits over the first ring groove in the circumferential direction. Referring to FIG. 9, more carbon deposits are produced at a corresponding bottom diameter of the first ring groove.

By use of the design of the present solution, i.e., the technical solution where on a section of the first ring groove, the profile of a bottom diameter of the first ring groove is elliptical, and the direction of the major axis of the ellipse generally coincides with a connecting line which connects a center line of the oil outlet of the inner cooling gallery and an axis of the piston, the following advantages can be achieved:

1. The temperature at the position of the first ring groove corresponding to the oil outlet of the inner cooling gallery is high, and at the major axis of the ellipse, because the volume of the piston ring at the bottom diameter of the first ring groove is relatively small, so that engine oil accumulation and thus carbon deposits are unlikely to occur. Specifically, referring to FIG. 10, less carbon deposits exist at the corresponding bottom diameter of the first ring groove.

2. When the piston ring in a closed state runs to the major axis of the first ring groove where the temperature is relatively high, due to the existence of the major axis, the airflow velocity is relatively large, and engine oil is less likely to stay at the major axis for a long time. In this case, carbon deposits are unlikely to occur at the high temperature.

More specifically, the second ring land is provided as an elliptical structure. A projection of the second ring land along an axial direction covers the bottom diameter of the first ring groove, that is, the elliptical bottom diameter of the first ring groove is completely located in the first ring groove. With a cross-section passing through the bottom diameter of the first ring groove as a first crosssection, the major axis and the minor axis of a projection of the second ring land on the first crosssection do not overlap with the major axis and the minor axis of the bottom diameter of the first ring groove.

Embodiment 2

This embodiment is on the basis of embodiment 1, and further, the piston is provided with a second ring groove along a circumferential direction, and the walls of the second ring groove proximate to the second ring groove are a second ring land and a third ring land; the bottom of the second ring groove is a bottom diameter of the second ring groove, the cross- sectional profile of the bottom diameter of the second ring groove is elliptical, the major axis of the bottom diameter of the second ring groove is along the direction of main and auxiliary thrusts, and the bottom diameter of the second ring groove is directed in the direction of a pin hole.

Further, the second ring land is provided as an elliptical structure. A projection of the second ring land along an axial direction covers the bottom diameter of the second ring groove.

Further, with a cross-section passing through the bottom diameter of the second ring groove as a second cross-section, the major axis and the minor axis of a projection of the second ring land on the second cross-section overlap with the major axis and the minor axis of the bottom diameter of the second ring groove respectively.

The reasons why the present embodiment adopts the above-mentioned technical solutions are in that:

The design of the second ring land of the piston generally is an ellipse design. The ellipse design of the second ring land has a minor axis in the direction of the pin hole, and a major axis in the direction of main and auxiliary thrusts. With this design feature, the pressure of gas leaked from the second ring land is unevenly distributed in the circumferential direction of the second ring groove.

Therefore, this embodiment adopts the design that the bottom diameter of the second ring groove is consistent in directions with the ellipse of the second ring land to adapt to the influence from the ellipse of the second ring land, namely, an arrangement in which the bottom diameter of the second ring groove has a major axis in the direction of main and auxiliary thrusts, and has a minor axis in the direction of the pin hole.

The technical solutions provided in this embodiment can achieve the following technical effects:

1. Because the layout is consistent with the direction of the ellipse of the second ring land, the pressure of gas leaked from the second ring land can be evenly released, that is, the gas pressure is evenly distributed in terms of the pressure over the second ring groove and the second ring land in a circle, such that the pressure distribution over the lower side of a top ring/upper side of the second ring in a circle is even, and the movement stability of the ring in a circle is guaranteed. As a result, the risk of instable gas leakage and high engine oil consumption is reduced.

2. During operation, the piston has transverse movement along the direction of main and auxiliary thrusts and rotation and swing movement with the central axis in the direction of the pin hole. The major axis design of the bottom diameter of the second ring groove in the direction of main and auxiliary thrusts can reduce the accumulation of engine oil on the major axis of the bottom diameter of the second ring groove and facilitate engine oil to move in the direction of the pin hole of the bottom diameter of the second ring groove. Because of the minor axis design in the direction of the pin hole, engine oil accumulated in the minor axis of the bottom diameter can be partially stored in the bottom diameter of the second ring groove, and can partially flow through the third ring groove from the bottom diameter of the second ring groove via a gap of the third ring land and be released. As a result, engine oil consumption is reduced.

Please refer to FIG. 11, FIG. 12, FIG. 13 and FIG. 14 for specific experimental data:

FIG. 11 is a gas pressure condition of a second ring groove at the corresponding position of the major axis of an ellipse of a second ring land in the prior art, and the peak value of the gas pressure corresponding to the major axis of the second ring land in the prior art solution is about 5bar; FIG. 12 is a gas pressure condition of a second ring groove at the corresponding position of the minor axis of an ellipse of a second ring land in the prior art, and the peak value of the gas pressure corresponding to the minor axis of the second ring land in the prior art solution is about 6bar; FIG. 13 is a gas pressure condition at the major axis of an ellipse of a second ring groove at the corresponding position of the major axis of an ellipse of a second ring land in the present solution, and the peak value of the gas pressure corresponding to the major axis of the second ring land in the present solution is about 6bar; FIG. 14 is a gas pressure condition at the minor axis of an ellipse of a second ring groove at the corresponding position of the minor axis of an ellipse of a second ring land in the present solution, and the peak value of the gas pressure corresponding to the minor axis of the second ring land in the present solution is about 6bar.

From the above-mentioned values, it can be seen that where the second ring groove does not have an elliptical feature, the gas pressure is unevenly distributed in terms of the pressure over the second ring groove in a circle (with a large difference between the values of the major axis and the minor axis).

Once the second ring groove has an elliptical design feature, because the elliptical design feature of the second ring groove and the elliptical design feature of the second ring land are synchronized, the gas pressure distribution over the second ring groove in a circle can be kept in an even distribution. Embodiment 3

This embodiment is on the basis of embodiment 2, and further, the piston is provided with a third ring groove along a circumferential direction, the walls on both sides of the third ring groove are a third ring land and a fourth ring land respectively, the bottom of the third ring groove is a bottom diameter of the third ring groove, the cross-sectional profile of the bottom diameter of the third ring groove is elliptical, the major axis of the bottom diameter of the third ring groove is along the direction of main and auxiliary thrusts, and the bottom diameter of the third ring groove is directed in the direction of the pin hole.

Further, the profile of the fourth ring land in a cross section is circular, and a projection of the fourth ring land along an axial direction covers the bottom diameter of the third ring groove.

The reasons why the present embodiment adopts the above-mentioned technical solutions are in that:

Below the third ring groove is a design of the fourth ring land. Below the fourth ring land is a hollow design in the direction of the pin hole, and engine oil can be well released into the crankcase in this direction. Below the fourth ring land is a skirt portion design of the piston in the direction of main and auxiliary thrusts, and the skirt portion design participates in supporting the main movement of the piston, but to a certain extent also hinders the release of engine oil in this direction. Therefore, the minor axis design of the third ring groove in the direction of the pin hole can increase the release of engine oil in the direction of the pin hole, reducing engine oil consumption.

The technical solutions of this embodiment can achieve the following technical effects:

1. With the minor axis design of the third ring groove in the direction of the pin hole, it is possible to accumulate engine oil in this direction and quickly release engine oil into the crankcase through the fourth ring land. As a result, engine oil consumption is reduced.

2. Because of the short axis design of the bottom diameter of the third ring groove in the direction of the pin hole, more radial or axial oil return holes can be arranged on the lower side of the third ring groove in the direction of the pin hole, such that engine oil accumulated in the bottom diameter of the third ring groove (in the direction of the pin hole) is quickly released into the crankcase.

3. During operation, the piston has transverse movement along the direction of main and auxiliary thrusts and rotation and swing movement with the central axis in the direction of the pin hole. The major axis design of the bottom diameter of the third ring groove in the direction of main and auxiliary thrusts can reduce the accumulation of engine oil on the major axis of the bottom diameter of the third ring groove and facilitate engine oil to move in the direction of the pin hole of the bottom diameter of the third ring groove. Because of the minor axis design in the direction of the pin hole, engine oil accumulated in the minor axis of the bottom diameter can be partially stored in the bottom diameter of the third ring groove, and can partially flow through the third ring groove from the bottom diameter of the third ring groove via a gap of the third ring land and be released. As a result, engine oil consumption is reduced.

The technical solutions provided in this embodiment can also effectively improve the arrangement of the oil return holes, increase the oil return area, and improve the control of engine oil consumption.

For the comparison of radially distributed oil return holes, see FIG. 15 and FIG. 16. FIG. 15 is a schematic diagram of an arrangement of oil return holes in the prior art. FIG. 16 is a schematic diagram of an arrangement of oil return holes corresponding to an elliptical design of the bottom diameter of the third ring groove in the present solution.

In the present solution, the oil return area (dotted line area) of the oil return holes is much larger than the oil return area without the ellipse design, with the oil return area being at least 50% larger (depending on the size of the ellipse design). The larger the oil return area, the better the oil return effect and control of engine oil consumption.

Additionally, in the technical solutions provided in the present solution, at least four oil return holes can be arranged between the bottom diameter of the third ring groove and the fourth ring land. The way of arranging the oil return holes is more flexible and a large number of oil return holes can be arranged. Finally, it should be noted that the foregoing implementations are merely intended for describing the technical solutions of the present invention rather than limiting the present invention. Although the present invention has been described in detail with reference to the foregoing implementations, those of ordinary skill in the art should understand that modifications may be made to the technical solutions described in the foregoing implementations or equivalent substitutions are made to some technical features therein, and these modifications or substitutions do not cause the essence of respective technical solutions to depart from the scope of the technical solutions of the implementations of the present invention.