Internal-combustion engines – Four-cycle – Variable clearance
Reexamination Certificate
1999-11-05
2002-03-12
Yuen, Henry C. (Department: 3747)
Internal-combustion engines
Four-cycle
Variable clearance
C123S0480AA, C123S197300
Reexamination Certificate
active
06354252
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The subject of the present invention is a device allowing the effective volumetric displacement and/or the effective volumetric ratio of a piston engine to be varied while it is running.
2. Background of the Invention and Related Art
The volumetric displacement of an engine usually denotes the geometric characteristics of said engine defined by the bore and the stroke. Here, we shall adopt the idea of effective volumetric displacement represented by the volume of gas at atmospheric pressure actually retained by the engine in order to perform each cycle.
In conventional parlance the volumetric ratio is also a geometric relationship between the volume of the chamber and the volume defined by the stroke multiplied by the bore. Here we shall adopt the effective volumetric ratio determined by the effective compression ratio of the fresh gases.
Maximum performance in internal combustion piston engines is generally recorded at full load, that is to say at wide-open throttle at the speed or range of speeds at which the mean effective pressure of the engine cycle is at its maximum value.
For each engine, these operating conditions correspond to a defined power and a defined speed. What this amounts to is that as soon as the work demanded of an engine no longer corresponds to these power and speed conditions, its performance drops.
The main characteristic of engines which defines the power and speed at which maximum performance is found is their volumetric displacement.
In everyday use, particularly in the field of motor vehicles, the engine operating conditions which give rise to optimal performance are rarely united. This is because the volumetric displacement of engines is constant and the power demanded of them by the driver varies considerably.
In general practice, the further the working conditions imposed on the engine by the driver are from its maximum-performance conditions, the poorer its performance.
In low-power use, for example when travelling through town, for the same amount of work, engines with a large volumetric displacement consume more energy than engines with a large volumetric displacement [sic], because they are operating further from their maximum-performance operating conditions. The drawbacks of engines with a large volumetric displacement may become an advantage when the conditions of use require high power, for example on high-speed freeways.
In any event, engine power is altered mainly by changing their speed using a gearbox and changing their load using the throttle which controls the inlet pressure by throttling and modifies the degree of filling of the cylinder(s) and the mean effective pressure for the engine cycle.
Another characteristic of engines determines their overall performance and this is their volumetric ratio. The latter is defined by the relationship between the volume of the cylinder and the volume of the combustion chamber. This ratio is fixed and is calculated to take account of the maximum load conditions of the engine and of the fuel used although at part load, or when the cylinder is insufficiently filled at high speeds, this ratio could be significantly increased in order to improve engine performance.
While the advantage of adapting the volumetric displacements of engines to suit the work demanded of them is clear, their is currently practically no effective device which allows engines, particularly motor vehicle engines, to achieve this result.
Experiments have, however, been performed on devices which, in particular, envisage disengaging or passivating a number of cylinders on multicylinder engines.
None of these devices, on account of the impracticalities of implementing them and of their relative effectiveness, has been considered worthy of being produced in any number.
While it is advantageous, in order to maintain optimum performance, for the volumetric ratio of engines to be adapted to suit the filling of their cylinder(s), particularly at high speeds, no device yet provides a relevant solution for obtaining such a result.
It is to significantly improve the overall performance of internal combustion piston engines, given the varying context in which they are used, that the device according to the invention envisages that any engine equipped therewith should exhibit specific features which distinguish it from an engine as defined according to the rules of the prior art.
SUMMARY OF THE INVENTION
The invention therefore provides for a device for varying an effective volumetric displacement and/or an effective volumetric ratio of an engine which comprises a piston and a cylinder, the device comprising a first device for controlling the effective volumetric ratio of the engine by modifying a starting point of a stroke of the piston with respect to the cylinder, and a second device for controlling the effective volumetric displacement of the engine by discharging into an inlet pipe excess gases let into the cylinder of the engine. The first device may be adapted for controlling the effective volumetric ratio of the engine without modifying a length of the stroke. The first device may be adapted to adjusting the length of a piston upstroke. The first device may comprise a system of gears. The system of gears may comprises a first rack arranged on a lower part of the piston, the rack being held in a guide system which allows the rack to move longitudinally, and a second rack disposed in an engine block of the engine, the second rack being movably longitudinally. The system of gears may further comprise a device for controlling the position of the second rack, and a gear mounted on a connecting rod which is coupled to a crankshaft. The gear may be positioned between the first and second racks.
The second device may further comprise an additional inlet valve, and a device for controlling the opening and closing of the inlet valve. The device for controlling the opening and closing of the additional inlet valve may be adapted to modify an angular offset of a point at which the inlet valve opens and closes. The second device may comprise a device for controlling the opening and closing of an intake valve. The device for controlling the opening and closing of the intake valve may be adapted to modify an angular offset of a point at which the intake valve opens and closes. The device which controls the opening and closing of the additional inlet valve may comprise a camshaft which is coupled to a device which controls an angular offset with respect to a crankshaft. The device which controls the opening and closing of the intake valve may comprise an additional camshaft coupled to a device which controls an angular offset with respect to a crankshaft. The additional camshaft may be coupled to the intake valve via a mechanical linkage. The device for controlling the opening and closing of the inlet valve may further comprise a movable intermediate pulley. The device for controlling the opening and closing of the inlet valve may comprise an intermediate pulley and one of a timing belt or a timing chain, and wherein the intermediate pulley which adjusts a length of one of the timing belt or the timing chain.
The device may further comprise a device which controls a position of the second rack. The device which controls a position of the second rack may comprise an actuator. The actuator may comprise a hydraulic actuator which is coupled to the second rack via a mechanical linkage. The device for controlling the opening and closing of the inlet valve may comprise an actuator which controls the position of the intermediate pulley. The actuator may comprise a hydraulic actuator. The gear may have a truncated profile. The gear may have teeth which transmit movement between the piston and the connecting rod. The gear may be constantly centered between the first and second racks. The piston may comprise a shortened piston having piston rings and no piston skirt.
The first device may comprise a hydraulic actuator comprising a rod and an actuator piston, the hydraulic actuator being adapte
Huynh Hai
Yuen Henry C.
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