Oil scraper ring for piston of internal combustion engine

Abstract

The present disclosure relates to an oil scraper ring for a piston (2) of an internal combustion engine, in which an oil scraper ring groove (4) of the piston (2) is arranged without at least one oil drain hole. The oil scraper ring includes a ring body (6) having an upper ring side surface (8), a lower ring side surface (10), an inner ring surface (12), an outer ring surface (14), and two abutment surfaces (16, 18). An upper oil scraper rail (20) and a lower oil scraper rail (22) are arranged on the outer ring surface (14), extending circumferentially and spaced apart from each other in the axial direction and extending radially outward from the outer ring surface (14). A radially extending oil passage is arranged in the region between the upper scraper rail (20) and the lower scraper rail (22). At least one radially extending groove (26) is formed on the lower ring side surface (10).

Description

Technical Field

[0001] The present invention relates to a piston of an internal combustion engine, particularly an oil scraper ring for a piston without an oil drain hole.

Background Art

[0002] An oil scraper ring is designed to distribute the oil on the cylinder wall in the circumferential direction and scrape off the excess oil from the cylinder wall. In order to enhance the sealing function and scraping function, two scraper rails are usually provided on the oil scraper ring. Each of these rails scrapes off the excess oil from the cylinder wall. Therefore, a certain amount of oil that must be discharged from the ring region accumulates not only at the lower end of the oil scraper ring but also between the rails. In particular, during the working stroke of a two-stroke engine or during the intake stroke and working stroke of a four-stroke engine, the oil originating from the crankcase and scraped by the upper rail and accumulating between the rails must be discharged from that region. This is because in some cases, the oil may exceed the oil scraper ring and needs to be scraped by the second seal ring. Oil scraper rings of one-piece and two-piece structures usually have longitudinal slits or holes extending radially between the ring rails, whereby the excess oil located between the scraper rails can be discharged inward. The oil scraped by the upper rail during the downward movement of the piston is guided through these openings provided in the ring body to the back side of the ring and into the ring base. The scraped oil is discharged from there in different ways. The oil is usually guided inside the piston through the holes in the oil scraper groove, whereby it can drip back into the oil pan from there. Also, it is possible to return the scraped oil through the recess in the piston bolt region on the outside of the piston by means of a so-called cover slot. However, combinations of both embodiments are also applicable.

[0003] Pistons for reciprocating piston engines are mainly made of aluminum alloy, but there are also those made of cast iron and steel. In this case, the aluminum blanks are cast or forged in a mold. Thereafter, the jacket surface, valve pockets, piston ring grooves, and piston bolt holes are machined mechanically.

[0004] On the other hand, there are steel pistons. These steel pistons expand only about half as much as aluminum pistons, so the clearance in the aluminum housing becomes smaller, and thus the friction is reduced by about 40 to 50 percent. Furthermore, the thermodynamic efficiency is improved. This is because the thermal conductivity of steel is smaller, so the component temperature rises, leading to an improvement in ignition performance and a shortening of the combustion time.

[0005] However, steel pistons have a major drawback. This is because it is very costly to manufacture the ducts for discharging the oil in the oil scraper grooves. Therefore, in steel pistons, there is a tendency to no longer provide the discharge ducts, often resulting in problems with oil consumption.

[0006] From Patent Document 1, an oil scraper ring for a reciprocating piston is known. This oil scraper ring has a pair of rails, which are held at a distance and extend radially outward, thereby contacting the cylinder wall as the only part that receives spring pressure. An oil collecting groove is formed between the rails. In this case, the ring has intermediate pieces that are circumferentially distributed and held at a distance on the lower side opposite the piston head. These intermediate pieces are dimensioned radially such that an oil collecting chamber communicating with the internal space of the piston is formed below the rails via passages and openings, and the oil collecting groove has no connection to the internal space of the piston between the rails forming the oil collecting groove.

Prior Art Documents

Patent Documents

[0007] [Patent Document 1] German Patent No. 1242957 Specification [Summary of the Invention] [Problems to be Solved by the Invention]

[0008] The problem of the present invention is to form an oil scraper ring for a piston without an oil drain hole so as to have an optimized oil scraping effect, and thus avoid weakening or tearing of the oil film. [Means for Solving the Problems]

[0009] According to a first aspect, the present invention relates to an oil scraper ring for a piston of an internal combustion engine. The oil scraper ring groove of the piston is arranged without at least one oil drain hole. The oil scraper ring includes a ring body having an upper ring side surface, a lower ring side surface, an inner side of the ring, an outer side of the ring, and two contact surfaces. An upper oil scraper rail and a lower oil scraper rail that extend in the circumferential direction while being spaced apart from each other in the axial direction and extend radially outward from the outer side of the ring are arranged on the outer side of the ring. Further, an oil passage extending in the radial direction is arranged in a region between the upper scraper rail and the lower scraper rail. In addition, at least one groove extending in the radial direction is formed on the lower ring side surface.

[0010] The advantage of the oil scraper ring according to the present invention is that the scraped oil flows out through the oil passage behind the ring from the oil collection groove and then flows out from there through at least one groove on the lower side ring surface into the gap between the piston and the cylinder. In this case, there is no need to provide any oil drain holes in the oil scraper ring groove in the piston. In this embodiment, since the oil is only carried below the piston ring, it is ensured that the oil film between the piston and the cylinder is not weakened or torn. Since there is more oil below the piston ring, insufficient lubrication can be eliminated.

[0011] In an exemplary embodiment of the oil scraper ring, at least one groove has a constant depth and / or a constant width. The manufacture of such a shape is cost-effective. This type of groove shape enables a constant discharge of the scraped oil.

[0012] In another exemplary embodiment of the oil scraper ring, at least one groove has a depth or width that decreases from the inside to the outside in the radial direction. The advantage of such a groove shape is that the outflow of oil can be more easily controlled. This is because only the minimum cross-sectional area of the groove determines the outflow rate. Furthermore, this groove shape reduces the oil flow from the outside to the inside in the radial direction, thus avoiding insufficient lubrication.

[0013] In a further embodiment of the oil scraper ring, at least one groove has a semi-circular cross-section. The semi-circular cross-section can be advantageously drilled technically and provides an outflow shape that is not affected by interference.

[0014] In a further embodiment of the oil scraper ring, the groove bottom of at least one groove is formed in a semi-circular shape, and the groove side surfaces are aligned parallel to the opposing groove side surfaces. The semi-circular cross-section at the groove bottom can be advantageously drilled technically and provides an oil outflow surface that is not affected by interference, whereby the subsequent parallel groove side surfaces increase the oil outflow rate.

[0015] In a further exemplary embodiment of the oil scraper ring, several grooves are provided, which are arranged at equal angular intervals on the lower ring side surface in the circumferential direction. Thereby, a constant oil outflow is ensured to avoid insufficient lubrication over the entire sliding surface. In this case, the equal angular intervals refer to two adjacent grooves in the circumferential direction. Further, it is preferable to regard the ring gap as one of each groove.

[0016] In one embodiment of the piston ring, when the number of grooves is n > 1, each groove is arranged at an angular distance of 360 / (n + 1)° with respect to the other grooves of at least one groove, and the groove located closest to the oil scraper ring gap also has an angular distance of 360 / (n + 1)° from the oil scraper ring gap in the oil scraper ring plane or the oil scraper ring projection plane with respect to the center point of the oil scraper ring. These specifications can have a deviation of up to ±3°. This arrangement of the grooves ensures a constant oil outflow to avoid insufficient lubrication over the entire circumference of the entire sliding surface. The manufacture of symmetrically arranged grooves can be advantageously realized.

[0017] In another exemplary embodiment of the oil scraper ring, six grooves are arranged on the oil scraper ring. These six grooves are arranged within the oil scraper ring plane or the oil scraper ring projection plane with respect to the center point, and are respectively at an angular distance of 14.5° - 30.5°, 104.5° - 120.5°, 149.5° - 165.5°, 194.5° - 210.5°, 239.5° - 255.5°, 329.5° - 345.5° from the contact surface or from the contact surface. Preferably, they are at an angular distance of 17.5° - 27.5°, 107.5° - 117.5°, 152.5° - 162.5°, 197.5° - 207.5°, 242.5° - 252.5°, 332.5° - 342.5°. Particularly preferably, they are at an angular distance of 20.5° - 24.5°, 110.5° - 114.5°, 155.5° - 159.5°, 200.5° - 204.5°, 245.5° - 249.5°, 335.5° - 339.5°. It is advantageous that the number of grooves is six, because the six grooves ensure optimal oil outflow, thus avoiding lubrication deficiency across the entire sliding surface. The symmetry of the groove positions is technically optimal in terms of cost.

[0018] In a further embodiment of the oil scraper ring, a groove is provided inside the oil scraper ring, the groove extending in the circumferential direction and having an expander spring, preferably a tubular spring, inserted therein. Compared with the one-piece oil scraper ring, the two-piece oil scraper ring has a significantly smaller cross-sectional area. Therefore, the ring body is relatively flexible and has extremely good mold filling ability. The groove inside the ring forms the spring bed of the tubular spring, and its cross-section is formed in a semi-circular or V-shaped. The force with which the scraper rail of the oil scraper ring is pressed against the inside of the cylinder is derived from an expander spring, preferably a tubular spring, made of heat-resistant spring steel. During operation, the spring abuts firmly against the back side of the ring body and forms a unit together with the ring body. The spring does not rotate relative to the ring, but the entire oil scraper ring rotates circumferentially in the piston ring groove during operation, like other rings. In the case of the two-piece oil scraper ring, since the contact pressure is uniformly large over the entire circumference of the coil spring, the radial pressure distribution is always symmetrical.

[0019] According to a further aspect of the present invention, the present invention relates to a piston comprising at least one oil scraper piston ring groove, the piston not having an oil drain opening in the direction of the crankcase from the scraper piston ring groove, the oil scraper ring being arranged in the oil scraper ring groove, and the piston being made of steel or aluminum.

[0020] It is envisaged to provide an aluminum or steel piston without an oil drain opening. In the case of a steel piston, providing an oil drain opening is particularly costly. However, the advantage of a steel piston is that it expands only half as much as an aluminum piston, and thus the play of the steel piston in the aluminum housing can be made smaller. This increases the effective play of the piston in the cylinder and reduces friction.

[0021] Since the steel piston has greater strength, the advantages of friction during operation are further realized, the thermodynamic efficiency is improved, and thus the internal combustion engine can operate at a higher temperature. The overall height of the steel piston can be made smaller than that of the aluminum piston, and thus the entire engine can be designed to be smaller. In this case, the smaller overall height, and thus the flatter engine block, can achieve weight reduction and / or a large ignition pressure compared to the conventional design. By using the above-described oil scraper ring, an oil scraper ring groove without an oil drain hole in the crankcase direction can be used from the oil scraper ring groove.

[0022] According to a further aspect, the present invention relates to an internal combustion engine comprising at least one piston provided with one of the above-described oil scraper rings.

[0023] According to a further aspect, the present invention relates to an internal combustion engine, the piston of which is made of steel or aluminum.

[0024] The possibility of using a scraper ring in a piston ring groove without an oil drain hole is distinctive from the prior art. The oil scraper ring includes grooves extending in the radial direction in addition to the oil passage, and the combined shape of these grooves ensures optimal oil scraping behavior. The systematic flow of oil from the inside of the ring in the crankcase direction and the opposite direction avoids the breakage or excessive thinning of the oil film. The ratio of the support surface of the lower ring side surface to the opening surface of the groove is more advantageous for a piston without an oil drain opening, particularly a steel piston without an oil drain opening, due to greater mechanical forces and temperatures. This is because if the support surface is relatively small, seizure of the piston is promoted.

[0025] Hereinafter, exemplary embodiments of the present invention will be described in more detail below with reference to schematic drawings.

Brief Description of the Drawings

[0026]

Figure 1

Figure 2

Embodiments for Carrying Out the Invention

[0027] FIG. 1 shows a cross-sectional view of an oil scraper ring mounted in an oil scraper piston ring groove 4 in a piston 2 not provided with an oil draining means. The oil scraper ring includes an upper ring side surface 8, a lower ring side surface 10, an inner ring 12, and an outer ring 14. The upper ring side surface 8 is disposed on the combustion chamber side, and the lower ring side surface is disposed on the crankcase side. Two oil scraper rings are spaced apart on the outer ring 14. The upper oil scraper rail 20 is disposed on the combustion chamber side, and the lower oil scraper rail 22 is disposed on the crankcase side. The two oil scraper rails 20, 22 scrape oil from a cylinder inner wall (not shown) forming a sliding surface (running surface) of the piston.

[0028] Two types of oil passages are arranged in the ring body 6. One oil passage 24 is disposed between the two oil scraper rails 20, 22 and extends radially inward toward the inner ring. Oil accumulated between the two oil scraper rails can be discharged to the inner ring 12 through the oil passage 24. In the other groove 26, it is disposed on the lower ring side surface 10, and oil can flow not only from the inner ring 12 toward the outer ring 14 but also from the outer ring 14 toward the inner ring 12. Both the oil passage 24 and the groove 26 extend in the radial direction of the ring body 6. The axial direction corresponds to the longitudinal axis of the piston 2 or the moving direction of the piston and is orthogonal to the radial direction.

[0029] Figure 1 further shows a circumferential groove 32 in which an expander spring, preferably a tubular spring, extends internally. The expander spring is shown as a circle. Compared with an oil scraper ring of one-piece structure, an oil scraper ring of two-piece structure with an expander spring has a significantly smaller cross-sectional area. Therefore, the ring body 6 is relatively flexible and shows extremely good mold filling ability in combination with the expander spring. The oil scraper ring is mainly pressed against the cylinder wall by the expander spring. The expander spring is made of heat-resistant spring steel. In the case of an oil scraper ring of two-piece structure, since the contact pressure is uniformly large over the entire circumference of the coil spring, the radial pressure distribution is always almost symmetric. To extend the life, the outer diameter of the expander spring is polished, wound more strongly on the contact surfaces 16, 18, or covered with a Teflon tube. These measures expand the support surface, reduce the surface load, and further reduce the friction and wear between the ring body 6 and the expander spring. The ring body 6 is made of aluminum, gray cast iron, or steel.

[0030] Figure 2 shows an axial plan view of the ring body 6. In this case, the contact surfaces 16, 18, the oil scraper gap 28, and the center point 30 of the oil scraper ring are shown.

Explanation of Signs

[0031] 2 pistons 4 oil scraper piston ring grooves 6 ring body 8 upper ring side surface 10 lower ring side surface 12 ring inner side 14 ring outer side 16, 18 contact surfaces 20 upper oil scraper rail 22 lower oil scraper rail 24 oil passage 26 groove 28 oil scraper ring gap Center point of the 30 oil scraper ring Groove extending in the circumferential direction of 32

Claims

1. An oil scraper ring for a piston (2) of an internal combustion engine, wherein the oil scraper ring groove (4) of the piston (2) is arranged without at least one oil drain hole, and the oil scraper ring has - an upper ring side surface (8), - a lower ring side surface (10), - a ring inner side (12), - a ring outer side (14), - two contact surfaces (16, 18), and comprises a ring body (6) having them, an upper oil scraper rail (20) and a lower oil scraper rail (22) which extend in the circumferential direction while being spaced apart from each other in the axial direction and extend radially outward from the ring outer side (14) are arranged on the ring outer side (14), an oil passage (24) extending in the radial direction is arranged in a region between the upper oil scraper rail (20) and the lower oil scraper rail (22), in an oil scraper ring in which one or more grooves (26) extending in the radial direction are formed on the lower ring side surface (10), the at least one groove (26) has a depth or width that decreases from the inner side to the outer side in the radial direction, and a groove (32) is provided on the ring inner side (12) of the oil scraper ring, and the groove (32) extends in the circumferential direction and an expander spring, preferably a tubular spring, is inserted therein. An oil scraper ring characterized by this.

2. The oil scraper ring according to claim 1, wherein the plurality of grooves (26) have a semi-circular cross-section. An oil scraper ring.

3. The oil scraper ring according to claim 1 or 2, wherein some of the grooves (26) are arranged at equal angular intervals on the lower ring side surface (10) in the circumferential direction. An oil scraper ring.

4. The oil scraper ring according to any one of claims 1 to 3, when the number of grooves (26) is n>1, each groove (26) is arranged at an angular distance of 360 / (n + 1)° with respect to the other grooves of the at least one groove (26), and the groove (26) closest to the oil scraper ring gap (28) also has an angular distance of 360 / (n + 1)° from the oil scraper ring gap in the oil scraper ring plane or the oil scraper ring projection plane with respect to the center point (30) of the oil scraper ring. An oil scraper ring. **Claim 5** The oil scraper ring according to any one of claims 1 to 3, wherein six grooves (26) are arranged on the oil scraper ring, and the six grooves (26) are in the oil scraper ring plane or the oil scraper ring projection plane with respect to the center point (30) of the oil scraper ring, and are respectively at an angular distance of 14.5° to 30.5°, 104.5° to 120.5°, 149.5° to 165.5°, 194.5° to 210.5°, 239.5° to 255.5°, 329.5° to 345.5° from the contact surface (16) or from the contact surface (18), preferably at an angular distance of 17.5° to 27.5°, 107.5° to 117.5°, 152.5° to 162.5°, 197.5° to 207.5°, 242.5° to 252.5°, 332.5° to 342.5°, and particularly preferably at an angular distance of 20.5° to 24.5°, 110.5° to 114.5°, 155.5° to 159.5°, 200.5° to 204.5°, 245.5° to 249.5°, 335.5° to 339.5°. **Claim 6** The oil scraper ring according to claim 4, wherein six grooves (26) are arranged on the oil scraper ring, and the six grooves (26) are in the oil scraper ring plane or the oil scraper ring projection plane with respect to the center point (30) of the oil scraper ring, and are respectively at an angular distance of 14.5° to 30.5°, 104.5° to 120.5°, 149.5° to 165.5°, 194.5° to 210.5°, 239.5° to 255.5°, 329.5° to 345.5° from the contact surface (16) or from the contact surface (18), preferably at an angular distance of 17.5° to 27.5°, 107.5° to 117.5°, 152.5° to 162.5°, 197.5° to 207.5°, 242.5° to 252.5°, 332.5° to 342.5°, and particularly preferably at an angular distance of 20.5° to 24.5°, 110.5° to 114.5°, 155.5° to 159.5°, 200.5° to 204.5°, 245.5° to 249.5°, 335.5° to 339.5°.

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