Internal-combustion engines – Four-cycle – Variable clearance
Reexamination Certificate
2000-02-23
2001-09-18
Argenbright, Tony M. (Department: 3747)
Internal-combustion engines
Four-cycle
Variable clearance
C123S0480AA
Reexamination Certificate
active
06289857
ABSTRACT:
TECHNICAL FIELD
The invention relates to reciprocating engines and a mechanism for converting reciprocating motion of a piston to rotary motion of a torque output shaft.
BACKGROUND ART
The invention comprises an improvement in the reciprocating machine disclosed in U.S. Pat. No. 5,762,480, issued to Carmeli Adahan.
A reciprocating piston engine capable of embodying the improvements of the present invention, like the reciprocating machine of the '480 patent, converts linear reciprocating motion of the piston in the cylinder to rotary motion of a power output shaft wherein the piston is drivably connected to the power output shaft through a connecting rod that moves in a substantially linear fashion. Side loading of the piston is avoided since there are minimal transverse force components associated with the force exerted on the piston by the piston rod. The absence of transverse loading on the piston avoids piston and cylinder wear due to frictional contact between the piston and the surrounding wall of the cylinder.
The reciprocating machine of the '480 patent is characterized also by a reduction in the speed of travel of the piston as the piston reaches its top dead center position. This increases the mechanical efficiency of the reciprocating engine.
In the case of a conventional engine with a crankshaft and a connecting rod between the piston and the crankshaft, it is possible to adjust the compression ratio by changing the effective length of the connecting rod. An example of a hydraulic piston and cylinder mechanism for adjusting the piston rod length is described, for example, in SAE Technical Paper No. 920453, by Kajiwara. The effective connecting rod length can be changed also by a cam and eccentric mechanism, as described in U.S. Pat. No. 4,319,498.
A double connecting rod assembly for a reciprocating piston engine is disclosed in U.S. Pat. No. 4,437,438, which includes a swinging lever that is connected to both elements of a two-piece connecting rod assembly, resulting in higher friction compared to the engine of the '498 patent.
A guide rod in a double connecting rod assembly is disclosed in prior art U.S. Pat. No. 4,131,094, wherein the pivot axis for the guide rod can be changed to alter the effective compression ratio of the reciprocating piston engine.
None of the teachings of these prior art devices is adaptable for use with an engine of the Adahan type to vary compression ratio. Each of the prior art devices for achieving a variable compression ratio increases the effective overall length, weight and friction of the piston and cylinder assembly.
DISCLOSURE OF INVENTION
The variable displacement engine of the invention has a piston and cylinder assembly that define a combustion chamber. A rotary torque output shaft is journalled on a torque output shaft axis that is perpendicular to the piston and cylinder assembly axis.
A crank pin is connected to the torque output shaft. An L-shaped connecting rod has a first portion pivotally connected at one end to the piston. A crank link is pivoted to the crank pin at one of its ends and to the first connecting rod portion at its other end. A second portion of the connecting rod is fixed to the other end of the first connecting rod portion and extends generally transversely relative to the piston and cylinder assembly axis.
An alignment member is pivoted to the transversely extending second connecting rod portion on one side of the piston and cylinder assembly axis and to a pivot member carried by the engine housing at the opposite side of the piston and cylinder assembly axis.
The compression ratio is changed as the distance of the pivot member from the piston and cylinder assembly axis is changed.
It is an objective of the present invention to provide a reciprocating engine of the type disclosed in the '480 patent wherein provision is made for adjusting the displacement of the engine to effect a variable compression ratio. It is possible to vary the compression ratio to achieve improved efficiency with high compression ratio during light load operation and to change the compression ratio so that the engine can operate during high load with a lower compression ratio. The motion transmitting mechanism of the reciprocating engine of the invention will allow for movement of the piston, as it approaches the top dead center position, to be closer to the cylinder head, thereby reducing the effective volume of the combustion chamber defined by the cylinder, the piston and the cylinder head.
The torque transmitting crank link is connected at one end to a drive pin that is offset with respect to the axis of rotation of the torque output shaft. At the other end, the link is connected to the other end of the first connecting rod portion. The generally transversely disposed end of the second connecting rod portion is connected to the alignment member, the opposite end of the alignment member being pivotally mounted on the transmission housing. Reciprocating motion of the piston is transferred through the connecting rod to the torque transmitting link, which in turn drives the torque output shaft, the axis of the output shaft being located intermediate the ends of the first connecting rod portion. The generally transversely disposed end of the second connecting rod portion, which is connected to the alignment member, has a reciprocating motion as the alignment link pivots about its fixed axis. In this way, the first connecting rod portion travels in a substantially linear fashion, thus avoiding development of side loads on the piston.
Provision is made for adjusting the pivot point for the alignment member toward and away from the axis of rotation of the torque output shaft. The pivotal axis of the alignment member is transversely situated relative to the direction of reciprocating linear motion of the piston.
Movement of the pivot axis for the alignment member effects a change in compression ratio since the end points of the piston travel are changed when the pivot axis is adjusted. Movement of the pivot axis can be accomplished manually or, for example, by means of an electronically controlled motor or a fluid pressure servo.
The geometry of the combustion chamber is not substantially affected by the motion translation mechanism. Conventional combustion chamber geometry may be used.
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“A Variable-Radius/Length Engine”, by Kenichi Kajiwara, SAE Technical Paper No. 920453, pp. 1-8.
“The Otto-Atkinson Cycle Engine-Fuel Economy And Emissions Results And Hardware Design”, by D.L. Boggs et al, SAE Technical Paper No. 950089, Feb. 27-Mar. 2, 1995, pp. 1-13.
Argenbright Tony M.
Drouillard Jerome R.
Ford Global Technologies Inc.
Harris Katrina B.
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