NL1043295B1 - Internal combustion engine provided with a variable compression ratio mechanism - Google Patents

Abstract

The invention pertains to an internal combustion engine provided with a variable compression ratio mechanism, the engine comprising a crankshaft and a piston which are connected via a connecting rod, wherein the connecting rod is connected to the crankshaft at its big end enclosing the crankshaft, and connected to the piston at its small end enclosing a bearing surface of a gudgeon pin which rotatably extends through the smal! end of the connecting rod and which gudgeon pin has at least one end with a circular circumference to support the piston, wherein the said end of the gudgeon pin is positioned eccentric with respect to the bearing surface of the gudgeon pin.

Description

INTERNAL COMBUSTION ENGINE PROVIDED WITH A VARIABLE COMPRESSION RATIO MECHANISM

FIELD OF THE INVENTION The present invention in general pertains to the area of internal combustion engines. In particular it pertains to internal combustion engines having a variable compression ratio mechanism.

BACKGROUND OF THE INVENTION Known from the prior art is the concept of an internal combustion engine provided with a variable compression ratio mechanism which can change a mechanical compression ratio of the internal combustion engine. For such a variable compression ratio mechanism, various mechanisms have been proposed. For example, it has been proposed to change the effective length of a connecting rod used in the internal combustion engine. In this regard, the “effective length of a connecting rod” means the distance between a center of a crank pin receiving opening which receives a crank pin and a center of a piston pin receiving opening which receives a piston pin. Therefore, if the effective length of a connecting rod becomes longer, a combustion chamber volume when the piston is at top dead center of the compression stroke becomes smaller, and therefore the mechanical compression ratio increases. On the other hand, if the effective length of a connecting rod becomes shorter, the combustion chamber volume when the piston is at top dead center of the compression stroke becomes larger, and therefore the mechanical compression ratio falls. As a variable length connecting rod which can be changed in effective length, known is one which is provided with a connecting rod body with a small end on which an eccentric member (eccentric arm or eccentric sleeve), which can swivel with respect to the connecting rod body, is provided, e.g. WO 2014/019683 (assigned to FEV). The eccentric member has a piston pin receiving opening which receives the piston pin. This piston pin receiving opening is provided so as to offset with respect to a swivel axis of the eccentric member.

In such a variable length connecting rod, if changing the swivel position of the eccentric member, the effective length of the connecting rod can be changed accordingly.

In this known engine two piston mechanisms are used in order to make the eccentric member rotate.

The cylinders of the two piston mechanisms are connected through a fluid path.

Part of the hydraulic fluid flowing out from one cylinder flows into the other cylinder.

However in this engine, along with operation of the piston mechanism, hydraulic fluid is fed to the piston mechanism and the fluid path between the piston mechanisms from the outside hydraulic fluid feed source.

If hydraulic fluid is fed from the outside in this way, the greater the amount of feed or the faster the rate of feed, the more bubbles enters into the hydraulic fluid.

If bubbles enter into the hydraulic fluid in this way, the piston mechanism unintentionally fluctuates.

From US 2017/0342897 (assigned to Toyota) an alternative system is known to change the effective length of the connecting rod.

This system comprises a connecting rod body having at its big end a crank receiving opening which receives a crank pin; an eccentric member which is attached at a small end in the opposite side to the big end to be able to swivel with respect to the connecting rod body in the circumferential direction of the small end and change an effective length of the variable length connecting rod if swiveled; a first piston mechanism which has a first cylinder provided in the connecting rod body and a first piston sliding in the first cylinder, and which is configured so that if hydraulic fluid is fed into the first cylinder, the eccentric member is swiveled in one direction to make the effective length longer; a second piston mechanism which has a second cylinder provided in the connecting rod body and a second piston sliding in the second cylinder, and which is configured so that if hydraulic fluid is fed into the second cylinder, the eccentric member is swiveled in an opposite direction to the one direction to make the effective length shorter; and a flow direction changing mechanism which can be switched between a first state where it prohibits flow of hydraulic fluid from the first cylinder to the second cylinder, but permits flow of hydraulic fluid from the second cylinder to the first cylinder and a second state where it permits flow of hydraulic fluid from the first cylinder to the second cylinder, but prohibits flow of hydraulic fluid from the second cylinder to the first cylinder, wherein the first piston mechanism and the second piston mechanism are formed so that a first cylinder volume defined by a stroke length of the first piston and a cross-sectional area of the first cylinder is equal to a second cylinder volume defined by a stroke length of the second piston and a cross-sectional area of the second cylinder.

This system has the disadvantage of being very complicated and again depends on the feeding of hydraulic fluid. US 2014/0096748 (assigned to BMW) discloses an internal combustion engine that has a crank drive with a crankshaft with at least one crank pin, mounted in a rotationally movable fashion, connected to a connecting rod and a piston arranged in a cylinder of the internal combustion engine. In order to convert rotational movement of the crankshaft into a bidirectional movement of the piston with a defined stroke height, a rotationally movable, externally toothed eccentric for changing the piston stroke height is arranged between the crank pin and an eyelet on the connecting rod. In order to rotate the eccentric, an externally toothed first gearwheel is axially connected in a rotationally fixed fashion to a second gearwheel via a shaft arranged parallel to the crankshaft which is arranged in a meshing fashion on a third gearwheel which can be rotated by an actuating element. This system is very complicated, has many moving parts and therefore is prone to excessive engine failure.

16 US 2019/0017434 (assigned to General Motors) discloses an engine wherein an eccentric shaft is coupled to the crankshaft and to the piston in such a manner that through the action of this shaft the strokes of the piston are adjustable. The engine includes a phase adjuster for adjusting the phase of the coupling of the eccentric shaft to the crankshaft and/or a stroke adjuster for adjusting strokes of the piston. This system is very complicated, has many moving parts and therefore is prone to excessive engine failure. WO 2014/183460 (assigned to Shen Dazi) discloses an internal combustion engine wherein the variable compression ratio mechanism is highly complicated comprising an execution motor, a worm, a worm gear, a central gear, a first transmission shaft, a plurality of transmission shafts, a first eccentric bushing, a plurality of eccentric bushings, a first eccentric bushing front gear, a plurality of eccentric bushing front gears, a first eccentric bushing rear gear, a plurality of eccentric bushing rear gears, a planetary gear, a first transmission shaft rear gear, a plurality of transmission shaft front gears, and a plurality of transmission shaft rear gears. A first supporting cylindrical hole is disposed on a neck of a first main shaft, and an axis of the first main shaft and an axis of the crank shaft form an included angle. A supporting cylindrical hole is disposed on a neck of each of a plurality of first main shafts, and axes of the main shafts and the axis of the crank shaft are overlapped, or parallel but not overlapped, or form in a non-zero included angle.

OBJECT OF THE INVENTION It is an object of the invention to provide an internal combustion engine with an alternative mechanism for varying the compression ratio.

SUMMARY OF THE INVENTION In order to meet the object of the invention, an internal combustion engine has been devised comprising a crankshaft and a piston which are connected via a connecting rod, wherein the connecting rod is connected to the crankshaft at its big end enclosing the crankshaft, and connected to the piston at its small end enclosing a bearing surface of a gudgeon pin which rotatably extends through the small end of the connecting rod and which gudgeon pin has at least one end with a circular circumference to support the piston, the improvement being that the said end of the gudgeon pin is positioned eccentric with respect to the bearing surface of the gudgeon pin.

As opposed to the systems known for example from WO 2014/019683 and US 2017/0342897, in this system the effective length of the connecting rod is not variable, and still a change in compression ration can be effected, namely by positing the piston movable with respect to the small end via an eccentric supporting surface of the gudgeon pin. This system may be used to arrive at the same effect as that obtainable with any of the existing systems, but is significantly more simple, and thus less expensive to actually apply in an internal combustion engine, less prone to wear and less prone to inducing engine failure.

FURTHER EMBODIMENTS OF THE INVENTION In a further embodiment of the internal combustion engine in which embodiment the gudgeon pin extends through the small end at both sides of the connecting rod, and wherein the gudgeon pin has two opposing ends with a circular circumference to support the piston, both said ends are positioned eccentric with respect to the bearing surface of the gudgeon pin and both ends are positioned in line. In yet a further embodiment of the internal combustion engine the gudgeon pin comprises three separate pieces that are mechanically connected, wherein the center piece comprises the bearing surface and the two outer pieces comprise the eccentric ends.

5 In another embodiment of the internal combustion engine the gudgeon pin is toothed in order to drive the at least one end so as to swivel this end with respect to the small end of the connecting rod.

In a further embodiment of the toothed gudgeon pin, the toothing is provided by providing the gudgeon pin with a sprocket wheel, wherein the sprocket wheel is positioned coaxially with respect to the small end. In yet a further embodiment the sprocket wheel is rotatably driven by a chain. In still a further embodiment the chain is driven by a second sprocket wheel that is part of the crankshaft.

In an alternative further embodiment of the toothed gudgeon pin, the toothing is provided by providing at least part of the circumference of the gudgeon pin at a location between the small end and the eccentric end with gear teeth. In yet a further embodiment the gear teeth are rotatably driven by a toothed bar. In still a further embodiment the toothed bar at its end opposing the gudgeon pin is connected to the crankshaft.

The invention will now be further illustrated using the following specific examples.

EXAMPLES Figure 1 is a prior art mechanism for varying the compression ratio of an internal combustion engine.

Figure 2 schematically depicts a mechanism for varying the compression ratio of an internal combustion engine according to a first embodiment of the invention.

Figure 3 schematically depicts a mechanism for varying the compression ratio of an internal combustion engine according to a second embodiment of the invention.

Figure 1 Figure 1 is a prior art mechanism for varying the compression ratio of an internal combustion engine as known from US 2017/0342987 (Figure 3 of this publication, which publication is incorporated in its entirety). The first piston mechanism 33 has a first cylinder 33a formed in the connecting rod body 31 and a first piston 33b sliding in the first cylinder 33a. The first cylinder 33a is almost entirely or entirely arranged at the first arm 32b side from the axis X of the connecting rod 6. Further, the first cylinder 33a is arranged slanted by a certain extent of angle with respect to the axis X so that it sticks out in the width direction of the connecting rod body 31 the more to the small end 31b. Further, the first cylinder 33a is connected to the flow direction switching mechanism 35 through a first piston communicating fluid path 51 and a second piston communication fluid path 52. The first piston 33b is connected with the first arm 32b of the eccentric member 32 through a first connecting member 45. The first piston 33b is connected by a pin 45a to the first connecting member 45 to be able to rotate. The first arm 32b is connected to the first connecting member 45 by a pin 45b to be able to rotate, at the end part opposite to the side connected to the sleeve 32a.

The second piston mechanism 34 has a second cylinder 34a formed in the connecting rod body 31 and a second piston 34b sliding in the second cylinder 34a. The second cylinder 34a is almost entirely or entirely arranged at the second arm 32c side with respect to the axis X of the connecting rod 6. Further, the second cylinder 34a is arranged inclined from the axis X by a certain extent of angle so that it sticks out further in the width direction of the connecting rod body 31 the closer to the small end 31b. Further, the second cylinder 34a is communicated through a third piston communicating fluid path 53 and a fourth piston communicating fluid path 54 with the flow direction changing mechanism 35. In addition, in the present embodiment, the second cylinder 34a is provided at the small end 31b side compared with the first cylinder 33a.

The second piston 34b is connected through a second connecting member 46 to the second arm 32c of the eccentric member 32. The second piston 34b is connected by a pin 46a to the second connecting member 46 to be able to rotate. The second arm 32c is connected by a pin 46b to the second connecting member 46 to be able to rotate at the end part of the opposite side to the side connected to the sleeve 32a.

In this regard, the volume defined by the stroke length S of the first piston 33b and the bore diameter d: of the first cylinder 33a (that is, the cross-sectional area of the first cylinder 33a) is referred to as the first cylinder volume V (V1=S: = TT = d 2/4). Similarly, the volume defined by the stroke length S2 of the second piston 34b and the bore diameter d2 of the second cylinder 34a (that is, the cross-sectional area of the second cylinder 34a) is referred to as the second cylinder volume V: (V2=S:2 - TT + dz 2/4). In the shown embodiment, the first piston mechanism 33 and second piston mechanism 34 are formed so that the thus defined first cylinder volume V1 and second cylinder volume V, are equal.

In addition, in the shown embodiment, the bore diameter d: of the first cylinder 33a is larger than the bore diameter d2 of the second cylinder 34a. That is, the cross-sectional area of the first cylinder 33a is larger than the cross-sectional area of the second cylinder 34a. Therefore, the stroke length S of the first piston 33b is shorter than the stroke length S2 of the second piston 34b so that the first cylinder volume V and the second cylinder volume V; are equal.

In the shown embodiment, the length of the first arm 32b of the eccentric member 32 and the length of the second arm 32c are different so that the stroke length S of the first piston 33b is shorter than the stroke length S2 of the second piston 34b. Specifically, these arms 32b, 32c are formed so that the length of the first arm 32b is shorter than the length of the second arm 32c. As a result, the distance R: between the connecting point of the first connecting member 45 with the first arm 32b (that is, the axis of the pin 45b) and the center axis Y2 of the sleeve receiving opening 42 is shorter than the distance R2 between the connecting point of the second connecting member 46 with the second arm 32c (that is, the axis of the pin 46b) and the center axis Y2 of the sleeve receiving opening 42. Accordingly, the stroke length Si can be shorter than the stroke length S.. Figure 2 Figure 2, composed of subfigures 2A and 2B, schematically depicts a mechanism for varying the compression ratio of an internal combustion engine according to a first embodiment of the invention. In figure 2A the crankshaft 41, connecting rod 31, gudgeon pin 21 and piston 5 are depicted as actually present in the combustion engine.

In figure 2B the parts are shown separately to make the constitution more clear. As can be seen, the gudgeon pin comprise three separate parts 21a, 21b and 21c that are mechanically connected to form the actual gudgeon pin 21. Part 21b is the part that mates with the small end 31b of the connecting rod and holds the bearing surface which rotatably extends through this small end of the connecting rod. The gudgeon pin has two end section 21a and 21b, each end section having a circular circumference to support the piston. The said ends of the gudgeon pin are positioned eccentric with respect to the bearing surface of section 21b the gudgeon pin, and are positioned in line to be able and stably support the piston. The big end 31a of the connecting rod is connected to the crankshaft 41. The gudgeon pin is toothed in order to provide a means for driving the two eccentric ends so as to swivel these ends, and therewith the piston 5, with respect to the small end of the connecting rod. For this, the gudgeon pin is provided with a sprocket wheel 21d, wherein the sprocket wheel is positioned coaxially with respect to the small end 31b. This sprocket wheel is rotatably driven by a chain (not depicted in figure 2) which is driven by a second sprocket wheel 210d that is part of the crankshaft, i.e. that is mechanically connected thereto. By rotating of the crankshaft, the position of the piston with respect to the connecting rod varies, without changing the effective length of the connecting rod.

Figure 3 Figure 3, composed of subfigures 3A and 3B, schematically depicts a mechanism for varying the compression ratio of an internal combustion engine according to a second embodiment of the invention. In figure 3A the crankshaft 41, connecting rod 31, gudgeon pin 21 and piston 5 are depicted as actually present in the combustion engine.

In figure 3B the parts are shown separately to make the constitution more clear. As can be seen, the gudgeon pin comprise three separate parts 21a, 21b and 21c that are mechanically connected to form the actual gudgeon pin 21. Part 21b is the part that mates with the small end 31b of the connecting rod and holds the bearing surface which rotatably extends through this small end of the connecting rod. The gudgeon pin has two end section 21a and 21b, each end section having a circular circumference to support the piston. The said ends of the gudgeon pin are positioned eccentric with respect to the bearing surface of section 21b the gudgeon pin, and are positioned in line to be able and stably support the piston. The big end 31a of the connecting rod is connected to the crankshaft 41.

The gudgeon pin is toothed in order to provide a means for driving the two eccentric ends so as to swivel these ends, and therewith the piston 5, with respect to the small end of the connecting rod.

For this, part of the circumference of the gudgeon pin is provided with gear teeth 21e at a location between the small end 31b and the eccentric end 21a.

These gear teeth are rotatably driven by a toothed bar 80, which is provided with a toothed extension 80b which mates with the teeth 21e.The toothed bar 80 at its end 80a opposing the gudgeon pin is connected to the crankshaft 41. By rotating of the crankshaft, the position of the piston with respect to the connecting rod varies, without changing the effective length of the connecting rod.

Claims (10)

CONCLUSIONS 1. Internal combustion engine provided with a mechanism for a variable compression ratio, the engine comprising a crankshaft and a piston connected by a connecting rod, the connecting rod being connected to the crankshaft at its large end while engaging the crankshaft, and connected to the piston at its small end while engaging a bearing surface of a piston pin, which piston pin protrudes rotatably through the small end of the connecting rod and which piston pin has at least one end with a circular circumference to support the piston, characterized in that said end of the gudgeon pin is eccentrically positioned with respect to the bearing surface of the gudgeon pin. Internal combustion engine according to claim 1, wherein the piston pin protrudes through the small end on both sides of the connecting rod, and wherein the piston pin has two opposite ends with a circular circumference to support the piston, characterized in that both said ends Be eccentrically positioned with respect to the bearing surface of the gudgeon pin and that both ends are aligned. Internal combustion engine according to claim 2, characterized in that the piston pin comprises three distinct parts which are mechanically connected, the central part comprising the bearing surface and the two outer parts the eccentric ends. Internal combustion engine according to any one of the preceding claims, characterized in that the piston pin is toothed to drive the at least one end to rotate this end relative to the small end of the connecting rod. Internal combustion engine according to claim 4, characterized in that the teeth are provided by providing the piston pin with a sprocket, said sprocket being positioned coaxially with respect to the small end. Internal combustion engine according to claim 5, characterized in that the sprocket wheel is rotatably driven by a chain. Internal combustion engine according to claim 6, characterized in that the chain is driven by a second sprocket wheel that forms part of the crankshaft. Internal combustion engine according to claim 4, characterized in that the gearing is provided by providing gear teeth at least part of the circumference of the piston pin at a location between the small end and the eccentric end. Internal combustion engine according to claim 8, characterized in that the gear teeth are driven by a gear rack. Internal combustion engine according to claim 9, characterized in that the gear rack is connected to the crankshaft at its end opposite the piston pin.