GB2161580A

GB2161580A - Variable length connecting rod

Info

Publication number: GB2161580A
Application number: GB08417381A
Authority: GB
Inventors: Peter Robert Davis; Bernard Frank Davis
Original assignee: Individual
Current assignee: Individual
Priority date: 1984-07-07
Filing date: 1984-07-07
Publication date: 1986-01-15
Also published as: GB2161580B; GB8417381D0

Abstract

A variable length connecting rod allows extension and retraction during each or any stroke of the four or two stroke cycles of an internal combustion engine. This is carried out with cams, eccentric gears, sun and planet gears or by hydraulics. In the drawing, oil, supplied under pressure through a conduit in the crankshaft, is lead through conduit 4 or 5 to activate piston 3 within the shank of the rod. <IMAGE>

Description

SPECIFICATION Variable length connecting rod This invention relates to variable length connecting rods in an internal combustion engine.

The rod connecting the crankshaft to the piston of an internal combustion engine is of fixed length and provides a fixed relationship between the rotary action of the crankshaft and the reciprocating action of the piston.

This fixed relationship is not always the most efficient. When the piston is at 'top dead centre' and maximum compression is suitable for combustion, the crankshaft is at an inefficient angle to convert the force applied into torque. The position of the cylinder bore and the time allowed for inlet and exhaust can also be improved.

According to the present invention there is provided a variable length connecting rod allowing extension and retraction during each or any stroke of the four or two stroke cycles of the internal combustion engine. This is carried out with cams, eccentric gears, sun and planet gears or as in the following example, by hydraulics.

An example of the invention will now be described with reference to the accompanying drawing in which: Figure 1 shows in cross section, a hydraulically operated connecting rod.

Referring to the drawing, the connecting rod comprises of two parts, the small end 1 which connects to the piston of the engine and the big end 2 which connects to the crankshaft. The two parts are connected by a double sided hydraulic piston 3.

The oil pressure required to operate the hydraulic piston 3 comes from a suitable pump along the centre of the shaft to the crank, where a 'pressure port' allows the oil to the big end 2. The shape and position of this port controls the action of the hydraulic piston 3.

During operation of the engine the crank rotates inside the big end 2 and when the pressure port of the crank is in line with the extension port 4, oil is fed to the area on one side of the hydraulic piston 3, causing it to extend. Oil from the other side of the hydraulic piston 3 travels through port 5 to an exhaust cut out on the crank providing lubrication to the big end 2 and is then returned to the sump.

During further rotation of the crank the pressure port is out of line with the extension port 4, a hydraulic lock is formed fixing the length of the connecting rod which can now transmit the external loads applied to it.

After the power stroke a position will be reached when the pressure port of the crank will be in line with the retraction port 5 of the hydraulic piston 3 and port 4 will be open to exhaust causing the connecting rod to retract ready for the next stroke. Efficiency of the engine is also increased by placing the cylinder bore so that the piston is more inline with the big end during combustion and the extended time that the piston is stationary or near stationary being used to improve heat transfer and the aspiration of the engine.

1. A variable length connecting rod to allow combustion to take place at an improved position of the crankshaft, thereby obtaining improved mechanical advantage.

2. A variable length connecting rod as claimed in Claim 1 wherein it's use allows improved valve timing giving greater fuel efficiency and heat transfer.

3. A variable length connecting rod as claimed in Claim 1 wherein it's use allows the engine to be constructed with the cylinder bore in an offset position relative to the crankshaft.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Variable length connecting rod This invention relates to variable length connecting rods in an internal combustion engine. The rod connecting the crankshaft to the piston of an internal combustion engine is of fixed length and provides a fixed relationship between the rotary action of the crankshaft and the reciprocating action of the piston. This fixed relationship is not always the most efficient. When the piston is at 'top dead centre' and maximum compression is suitable for combustion, the crankshaft is at an inefficient angle to convert the force applied into torque. The position of the cylinder bore and the time allowed for inlet and exhaust can also be improved. According to the present invention there is provided a variable length connecting rod allowing extension and retraction during each or any stroke of the four or two stroke cycles of the internal combustion engine. This is carried out with cams, eccentric gears, sun and planet gears or as in the following example, by hydraulics. An example of the invention will now be described with reference to the accompanying drawing in which: Figure 1 shows in cross section, a hydraulically operated connecting rod. Referring to the drawing, the connecting rod comprises of two parts, the small end 1 which connects to the piston of the engine and the big end 2 which connects to the crankshaft. The two parts are connected by a double sided hydraulic piston 3. The oil pressure required to operate the hydraulic piston 3 comes from a suitable pump along the centre of the shaft to the crank, where a 'pressure port' allows the oil to the big end 2. The shape and position of this port controls the action of the hydraulic piston 3. During operation of the engine the crank rotates inside the big end 2 and when the pressure port of the crank is in line with the extension port 4, oil is fed to the area on one side of the hydraulic piston 3, causing it to extend. Oil from the other side of the hydraulic piston 3 travels through port 5 to an exhaust cut out on the crank providing lubrication to the big end 2 and is then returned to the sump. During further rotation of the crank the pressure port is out of line with the extension port 4, a hydraulic lock is formed fixing the length of the connecting rod which can now transmit the external loads applied to it. After the power stroke a position will be reached when the pressure port of the crank will be in line with the retraction port 5 of the hydraulic piston 3 and port 4 will be open to exhaust causing the connecting rod to retract ready for the next stroke. Efficiency of the engine is also increased by placing the cylinder bore so that the piston is more inline with the big end during combustion and the extended time that the piston is stationary or near stationary being used to improve heat transfer and the aspiration of the engine. CLAIMS