Variable force valve spring

Abstract

Devices and related methods are disclosed that generally involve variable force valve springs for controlling the motion of an engine valve. The force exerted by the valve spring can be adjusted by altering the pressure at which a fluid is supplied to a fluid chamber thereof, by altering the volume of the fluid chamber, and / or by changing the aggregate surface area over which fluid pressure is coupled to the engine valve. Associated fluid control systems are also disclosed herein, as are various methods for adjusting the force of a valve spring based on a variety of engine parameters, such as engine speed, engine load, and / or a combination thereof.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS[0001]This application claims the benefit of priority of U.S. Provisional Patent Application No. 61 / 436,739, filed on Jan. 27, 2011, the entire contents of which are incorporated herein by reference.FIELD[0002]The present invention relates to methods and devices for actuating an engine valve. More particularly, the invention relates to variable force valve springs and methods related thereto.BACKGROUND[0003]Internal combustion engines generally include one or more valves for controlling the flow of air and fuel through the engine. These valves are usually actuated by a mechanical cam. For example, a rotating shaft having a teardrop-shaped cam lobe can be configured to impart motion to the valve, either directly or via one or more intermediate elements. As the shaft rotates, the eccentric portion of the cam lobe imparts a linear motion to the valve over a range of the shaft's rotation.[0004]It is often necessary to bias the valve towards a parti...

AI Technical Summary

Benefits of technology

[0047]In another aspect of at least one embodiment of the invention, a valve spring system is provided that includes a cap defining a first bore therein and a piston coupled to an engine valve, the piston being slidably disposed within the first bore such that the piston and the cap define a first fluid chamber. The system also includes an outer housing defining a second bore therein, the cap being slidably disposed within the second bore such that the cap and the outer housing define a second fluid chamber, and a fluid port configured to selectively release pressurized fluid from the second fluid chamber, thereby allowing the cap to slide relative to the outer housing such that a volume of the first fluid chamber is increased.

[0049]In another aspect of at least one embodiment of the invention, a method of actuating a valve of an engine is provided that includes increasing a spring force of a valve spring associated with the valve based on an increase in an engine parameter, and decreasing the spring force of the valve spring based on a decrease in the engine parameter.

Problems solved by technology

One problem with this system is that there is no way to alter or control the amount of force required to compress the valve spring.

In conventional internal combustion engines, a stronger valve spring produces higher rocker shaft and cam shaft bearing friction, contributing to the parasitic losses of the engine and reducing overall engine efficiency.

Traditional mechanical valve springs are also poorly suited for “lost-motion” valve train systems.

Since none of the energy is returned to the cam, the energy spent to compress the valve spring in the first place is essentially wasted.

Images