Internal combustion engine piston crank mechanism

Abstract

A piston crank mechanism has an upper link coupled to a piston by a piston pin, a lower link having a crankpin journal, wherein the crankpin journal is coupled to a crankpin of a crankshaft and is coupled to the upper link by an upper pin, and a control link is coupled to an eccentric cam of a control shaft that is supported by an engine block and coupled to a control pin boss by a control pin. The crankpin journal of the lower link is arranged and dimensioned relative to the upper pin such that a projection area defined by projecting the width of the upper pin along a direction line passing through a center of the piston pin and a center of the upper pin does not obscure an area defined by the crankpin during operation of the crankshaft as viewed in an axial direction of the crankpin.

Description

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a cross-sectional diagram showing a piston crank mechanism in which a lower link according to one or more embodiments of the present invention is used.

FIG. 2 is a perspective view of a lower link according to an embodiment of the present invention.

FIG. 3 shows the relative positions of the lower link and upper link according to one or more embodiments of the present invention.

FIG. 4( a)-(c) show load transmission paths according to different embodiments of the present invention.

FIG. 5 is a perspective view of a lower link according to an embodiment of the present invention.

FIG. 6 is a cut away perspective view of a lower link according to one or more embodiments of the present invention, the cut away taken along the center of one of the bolts.

FIG. 7 is a partial cross-sectional view showing meshing with the internal thread portion.

FIG. 8 is a perspective view showing a lower link according to an embodiment of the present invention.

FIG. 9 is a cross section, in the axial direction of the crankshaft, of the piston crank mechanism shown in FIG. 1.

Claims

1. A piston crank mechanism for an engine having a piston in a cylinder, the piston crank mechanism comprising: an upper link having a first end operably coupled to a piston by a piston pin;a lower link having a first end, a second end, and a crankpin journal arranged therebetween, wherein the crankpin journal is rotatably coupled to a crankpin of a crankshaft, and the first end is arranged with an upper pin boss to be operably coupled to a second end of the upper link by an upper pin; anda control link having a first end operably coupled to an eccentric cam of a control shaft that is supported by an engine block and a second end operably coupled to a control pin boss arranged at the second end of the lower link by a control pin, wherein the crankpin journal of the lower link is arranged and dimensioned relative to the upper pin such that a projection area defined by projecting the width of the upper pin along a direction defined by a line passing through a center of the piston pin and a center of the upper pin does not obscure an area defined by the crankpin during operation of the crankshaft as viewed in an axial direction of the crankpin.

2. The piston crank mechanism of claim 1, wherein the crankshaft is offset from am axial centerline of a cylinder in a direction toward the control pin boss such that locations of the upper pin boss, the crankpin boss, and the control pin boss result in the projection area not being obscured by the crankpin of the crankshaft during operation of the crankshaft.

3. The piston crank mechanism of claim 1, wherein the lower link comprises: an upper portion having the upper pin boss formed therein; anda lower portion having the control pin boss formed therein; wherein the upper and lower portions are separate parts defined by a surface passing through a center of the crankpin journal, andthe upper and lower portions are fastened with at least two bolts on opposing sides of the crankpin journal.

4. The piston crank mechanism of claim 3, wherein the upper pin boss is formed in a bifurcated shape that supports each end of the upper pin.

5. The piston crank mechanism of claim 4, wherein an internal thread portion configured to couple one of the at least two bolts that passes through the lower portion of the lower link is formed in a recessed portion of the bifurcated shape of the upper pin boss.

6. The piston crank mechanism of claim 5, wherein an end of the internal thread portion is open in the recessed portion, and substantially the all of the plurality of threads of the internal thread portion engage the bolt.

7. The piston crank mechanism of claim 5, wherein the lower link comprises a portion that is formed thinner than the crankpin journal in an axial direction of the crankpin.

8. The internal combustion engine piston crank mechanism of claim 3, wherein the lower link comprises a part, between the crankpin journal and the upper pin boss, that is formed thinner than the crankpin journal in an axial direction of the crankpin of the crankshaft.

9. The internal combustion engine piston crank mechanism of claim 3, wherein the lower link comprises a part, between the crankpin journal and the control pin boss, that is formed thinner than the crankpin journal in an axial direction of the crankpin of the crankshaft.