ECCENTRIC MEMBER AND A V-TYPE INTERNAL COMBUSTION ENGINE

Abstract

An eccentric member for a system for varying compression ratio of an internal combustion engine comprises two circumferential bearing portions for bearing respective big ends of connecting rods of a V-type internal combustion engine. The bearing portions are eccentric with respect to an inner surface of the eccentric member and located at a distance from each other in axial direction of the eccentric member. The eccentric member also comprises two external gears between which the bearing portions are located. The eccentric member is made of two half-sleeves which are fixed to each other at least between the bearing portions.

Claims

1. An eccentric member for a system for varying compression ratio of an internal combustion engine, comprising: two circumferential bearing portions for bearing respective big ends of connecting rods of a V-type internal combustion engine, which bearing portions are eccentric with respect to an inner surface of the eccentric member and located at a distance from each other in an axial direction of the eccentric member, wherein the eccentric member comprises two half-sleeves which are fixed to each other at least between the bearing portions; and two external gears between which the bearing portions are located.

2. The eccentric member according to claim 1, wherein the half-sleeves are fixed to each other between the bearing portions through bolts.

3. The eccentric member according to claim 2, wherein the bolts extend in a direction parallel to a tangential direction of a cylindrical surface of the eccentric member.

4. The eccentric member according to claim 1, wherein the eccentric member comprises a flange between the bearing portions.

5. The eccentric member according to claim 1, wherein positions of maximum eccentricity of the respective bearing portions are shifted with respect to each other in a rotational direction about a centerline of the inner surface of the eccentric member.

6. The eccentric member according to claim 1, wherein said two half-sleeves are also fixed to each other at the external gears.

7. The eccentric member according to claim 6, wherein the external gears are located at opposite ends of the eccentric member and the two half-sleeves are fixed by I-shaped locking elements which are inserted in an axial direction of the external gears in respective cavities, wherein each cavity is partially realized in each half-sleeve.

8. The eccentric member according to claim 1, wherein each of the bearing portions is provided with a first aperture and the inner surface is provided with two second apertures at an angular distance from each other about a centerline of the inner surface at a location between the bearing portions, wherein the first apertures communicate with the respective second apertures via respective oil channels.

9. The eccentric member according to claim 1, wherein the two half-sleeves are separated at a plane which substantially forms a mirror plane of positions of maximum eccentricity or a plane perpendicular thereto.

10. A V-type internal combustion engine including variable compression ratio, comprising: a crankshaft including a crankpin; two connecting rods including respective big ends and small ends; two pistons being rotatably connected to the respective small ends; an eccentric member rotatably mounted on the crankpin, the eccentric member comprising: two circumferential bearing portions for bearing respective big ends of the connecting rods, which bearing portions are eccentric with respect to an inner surface of the eccentric member and located at a distance from each other in an axial direction of the eccentric member, wherein the eccentric member comprises two half-sleeves which are fixed to each other at least between the bearing portions; and two external gears between which the bearing portions are located: and an auxiliary shaft having a gear mating with one of the external gears.

11. The V-type internal combustion engine according to claim 10 wherein the crankshaft includes a second crankpin, and further comprising a second eccentric member rotatably mounted on the second crankpin, the second eccentric member having a third external gear, the shaft having a second gear mating with the third external gear.

12. The V-type internal combustion engine according to claim 11, wherein the half-sleeves are fixed to each other between the bearing portions through bolts.

13. The V-type internal combustion engine according to claim 12, wherein the bolts extend in a direction parallel to a tangential direction of a cylindrical surface of the eccentric member.

14. The V-type internal combustion engine according to claim 11, wherein the eccentric member comprises a flange between the bearing portions.

15. The V-type internal combustion engine according to claim 11, wherein positions of maximum eccentricity of the respective bearing portions are shifted with respect to each other in a rotational direction about a centerline of the inner surface of the eccentric member.

16. V-type internal combustion engine according to claim 11, wherein said two half-sleeves are also fixed to each other at the external gears.

17. The eccentric member according to claim 16, wherein the external gears are located at opposite ends of the eccentric member and the two half-sleeves are fixed by I-shaped locking elements which are inserted in an axial direction of the external gears in respective cavities, wherein each cavity is partially realized in each half-sleeve.

18. The V-type internal combustion engine according to claim 11, wherein each of the bearing portions is provided with a first aperture and the inner surface is provided with two second apertures at an angular distance from each other about a centerline of the inner surface at a location between the bearing portions, wherein the first apertures communicate with the respective second apertures via respective oil channels.

19. The V-type internal combustion engine according to claim 11, wherein the two half-sleeves are separated at a plane which substantially forms a mirror plane of positions of maximum eccentricity or a plane perpendicular thereto.

20. The V-type internal combustion engine according to claim 11 and further comprising an auxiliary shaft having a gear mating with the external gear not mating with the gear of the shaft.

Description

BRIEF DESCRIPTION OF THE DRAWING

[0015] Aspects of the invention will hereafter be elucidated with reference to very schematic drawings showing an embodiment of the invention by way of example.

[0016] FIG. 1 is a perspective view of an embodiment of a V-type internal combustion.

[0017] FIG. 2 is an enlarged perspective sectional view of a part of the engine of FIG. 1.

[0018] FIG. 3 is a perspective view of an embodiment of an eccentric member.

[0019] FIG. 4 is a similar view as FIG. 3, but showing a cross-sectional view of the eccentric member.

[0020] FIG. 5 is a similar view as FIG. 3, but showing a sectional view of the eccentric member at an oil channel

[0021] FIG. 6 is a diagram, illustrating the eccentricity of the eccentric member of FIGS. 3-5.

[0022] FIG. 7 is a similar diagram as FIG. 6, but showing a different embodiment of the eccentric member.

DETAILED DESCRIPTION OF AN ILLUSTRATIVE EMBODIMENT

[0023] FIG. 1 shows an embodiment of a V-type internal combustion engine 1. The engine has a variable compression ratio in order to achieve a high efficiency under part-load conditions. In the embodiment as shown in FIG. 1 the engine 1 comprises eight cylinders, but a different number of cylinders is conceivable. FIG. 1 shows that the engine 1 has eight pistons 2 and eight connecting rods 3, each including a big end 4 and a small end 5. Each piston 2 is rotatably connected to the small end 5 of one connecting rod 3.

[0024] The engine 1 is also provided with a crankshaft 6 which is shown in greater detail in FIG. 2. The crankshaft 6 has four crankpins 7. Each crankpin 7 supports two connecting rods 3 through an eccentric member 8. FIGS. 3 and 4 show an embodiment of the eccentric member 8, which embodiment is also applied in the internal combustion engine 1 as shown in FIGS. 1 and 2.

[0025] The eccentric member 8 is made from two half-sleeves 9a, 9b that are assembled together. In assembled condition the eccentric member 8 comprises two circumferential bearing portions 10, 11 for bearing the respective big ends 4 of two corresponding connecting rods 3 of the engine 1. The bearing portions 10, 11 are eccentric with respect to an inner surface 12 of the eccentric member 8 and they are located at a distance from each other in axial direction of the eccentric member 8. The positions of maximum eccentricity of the respective bearing portions 10, 11 are shifted with respect to each other in rotational direction about a centerline CL of the inner surface 12 of the eccentric member 8. The eccentric members 8 fit on the respective crankpins 7 of the crankshaft 6.

[0026] Each of the eccentric members 8 also comprises two external gears 13, 14 which are located at opposite ends of the eccentric member 8. The bearing portions 10, 11 are located between the gears 13, 14.

[0027] In the embodiment as shown in FIGS. 3 and 4 the two half-sleeves 9a, 9b are fixed to each other at three different locations as seen along the centerline CL. The two half-sleeves 9a, 9b are fixed to each other by two I-shaped locking elements 15 at each of the gears 13, 14. The I-shaped locking elements 15 are inserted in axial direction of the eccentric member 8 in respective cavities 16 at the gears 13, 14. Each cavity 16 is partially realized in each half-sleeve 9a, 9b at a contact surface between the half-sleeves 9a, 9b.

[0028] The eccentric member 8 comprises a flange 17 between the bearing portions 10, 11, which provide sufficient material to apply holes in tangential direction of the eccentric member 8 for receiving cooperating bolts 18, see FIG. 4.

[0029] FIG. 2 shows that one of the external gears 13 of the eccentric member 8 which is located at a front side of the engine 1 is drivably coupled to an auxiliary shaft 19 via a gear transmission 20. The auxiliary shaft 19 extends concentrically through the crankshaft 6 and has a fixed position with respect to a crankcase (not shown) when the engine 1 runs at a fixed compression ratio. The compression ratio can be varied by changing the rotational position of the auxiliary shaft 19. The eccentric member 8 at the front side of the engine drives the other three eccentric members 8 through driving shafts 21 which extend concentrically through the crankshaft 6 between two neighbouring crankpins 7.

[0030] FIG. 5 shows a sectional view of the eccentric member 8 at an oil channel 22 which extends in axial direction of the eccentric member 8 between a front side of one of the external gears 14 and a location between the bearing portions 10, 11. The oil channel 22 is closed at the front side by a closure 23. The bearing portion 11 has a first aperture 24 and the inner surface 12 has a second aperture 25. The first and second apertures 24 communicate with each other through the oil channel 22 so as to allow oil to flow from the crankpin 7 to the bearing portion 11. Similarly, the other bearing portion 10 is also provided with another first aperture which communicates with another second aperture at another location between the bearing portions 10, 11 via another oil channel

[0031] The eccentric member 8 can be manufactured as one piece and subsequently put into a machine that splits it in half by a split fracture. The mating surfaces of the two halves are jagged and sharp. When put back together, these jagged edges interlock perfectly causing an extremely strong connection. The eccentric member 8 as shown in FIGS. 1-5 has an ideal location of the split fracture, which is illustrated in FIG. 6. FIG. 6 shows cross-sections of the two bearing portions 10, 11 of the eccentric member 8 in a single diagram. Two small circles in the diagram indicate the positions of the respective maximum eccentricities with respect to the inner surface 12 of the eccentric member 8. The shortest angular distance 2 between the positions of maximum eccentricities is 135. In the embodiment as illustrated in FIG. 6 the location of the split fracture, indicated by vertical line 26, lies in a plane in which the centerline CL of the inner surface 12 lies and which forms a mirror plane of the positions of maximum eccentricity. FIG. 6 shows that the angles between the plane of the split fracture and each of the positions of maximum eccentricity of the respective bearing portions 10, 11 are equal.

[0032] FIG. 7 shows an alternative embodiment of the eccentric member 8 which has a different location of the split fracture; in this case the shortest angular distance between the positions of maximum eccentricities 2 is 45. Line 26 that indicates the plane of the split fracture extends horizontally. In the embodiment as shown in FIG. 7 the shortest angular distance between the positions of maximum eccentricity is smaller than in the embodiment as shown in FIG. 6. In the embodiment of FIG. 7 the plane of the split fracture is formed by a plane in which the centerline CL of the inner surface 12 lies and which extends perpendicular to the mirror plane of the positions of maximum eccentricity. In this case both bearing portions 10, 11 are divided at a location at greatest angular distance from their minimum radial thicknesses at the respective bearing portions 10, 11 such that the minimum radial thickness of the eccentric member 8 at the location of separation is as large as possible.

[0033] The invention is not limited to the embodiments shown in the drawings and described hereinbefore, which may be varied in different manners within the scope of the claims and their technical equivalents.