Lost motion full authority valve actuation system

Details Lost motion full authority valve actuation system Lost motion full authority valve actuation system

1998-11-04

2001-07-10

Kamen, Noah P. (Department: 3747)

Internal-combustion engines

Poppet valve operating mechanism

Hydraulic system

C123S090150

Reexamination Certificate

active

06257183

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to engine valve actuation systems for internal combustion engines. More particularly, the invention is directed to a lost motion valve actuation system.
BACKGROUND OF THE INVENTION
Engine cylinder chamber valves are typically poppet type valves. These poppet type engine valves are normally biased closed by a valve spring. The valves open when sufficient force is applied to overcome the spring force. There are many different methods of generating valve opening force. Many valve actuation systems utilize hydraulic pressure. These systems typically include a master and slave piston arrangement The slave piston contacts the valve stem of the engine valve. Motion of the master piston generates an increase in hydraulic pressure on the slave piston. In response to the increased hydraulic pressure, the slave piston moves forcing the engine valve open.
The master and slave pistons are hydraulically linked. In such systems, a rotating cam typically causes the displacement of the master piston. The motion of the master piston is transferred to the slave piston by means of the hydraulic link between the two pistons. The motion of the slave piston, relative to the cam profile, may be modified by draining and filling the hydraulic link between the master and slave pistons. This process provides for transferring selected portions of the master piston's motion, i.e. the cam profile, to the slave piston. A system capable of transferring only a portion of the motion is commonly called a “lost motion” system. An example of such a system is described in Hu, U.S. Pat. No. 5,537,976, assigned to the assignee of the present application and incorporated herein by reference.
Lost motion systems may be used to vary engine valve timing. In order to achieve enhanced internal combustion engine performance and fuel economy, it may be necessary to vary the timing of the engines intake and exhaust events. It may be desirable in engines having multiple intake and/or exhaust valves per cylinder to effect staggered opening among the valves in a cylinder. It also may be desired to operate a four valve cylinder in either a two valve or four valve mode. Additionally, it may be necessary to “cut-out” the cylinder. Cylinder cut-out can be achieved by failing to actuate all of one cylinders, intake, and exhaust valves. A valve actuation system which is capable of varying the cylinder operation from all valve operation to cylinder cut-out is termed a fully variable system. Fully variable valve actuation systems are also known as “full authority” systems.
As discussed above, the typical valve actuation system utilizes a cam to impart motion to a master piston. However, recent efforts to achieve variable control over intake and exhaust valve events have focused on camless engine designs. An example of a camless engine is disclosed in U.S. Pat. No. 5,619,965, which is incorporated herein by reference. Camless engine designs have proved to be difficult and expensive to implement. A further disadvantage of many camless designs is the lack of any mechanical backup. The failure of electric power or loss of hydraulic pressure may result in no valve motion at all. In fact, even some cam-driven designs cannot produce valve motion in the event of a loss of hydraulic pressure. These systems lack a fail-safe operating mode.
There is a need for a lost motion variable valve actuation system which provides control of an engine cylinder's intake and an exhaust valve using a common trigger valve. Current valve actuation systems typically rely on a single trigger valve for each engine valve. The few systems which utilize a single solenoid to control multiple engine valves, do not have the capability to independently control the positions of the valves. There is also a need for a valve actuation system which has the practical benefits of a fully variable system with the security and reliability of a mechanical, cam-driven valve train, and with the advanced system features commonly available in camless engine designs.
The present invention provides a means for controlling the engine valves in an internal combustion engine cylinder having multiple intake and/or exhaust valves utilizing a novel electro-hydraulic valve actuation system. By pairing an intake and exhaust valve under the control of a single hydraulic solenoid, or trigger, valve, independent control of each valve may be obtained, allowing for such features as enhanced intake air swirl, two-valve operation over a certain speed range, and staggered valve opening. This is possible since in most cases, relevant intake and exhaust events occur at different times in a four-cycle engine. Thus, at any given time, only one of the two valves in a set (either the intake or the exhaust) is active, with the other at base circle. Opening the trigger valve at such time would only affect the valve driven by the cam lobe off base circle at that instant. Events which overlap significantly, but which need independent control, can be placed on different cams (i.e., on one of two exhaust cams in a dual-overhead cam system with discrete lobes for each valve).
OBJECTS OF THE INVENTION
It is therefore an object of the present invention to provide innovative and economical variable timing valve actuation design.
It is a further object of the present invention to provide a fail-safe operating mode for a valve actuation system.
It is also an object of the present invention to provide common control of both intake and exhaust valve actuation circuits in a cylinder with one high-speed trigger valve.
It is also an object of the present invention to provide enhanced reliability through an innovative yet simple design of a variable timing engine valve actuation system.
It is another object of the present invention to provide independent control of each pair of intake and exhaust valves.
It is also an object of the present invention to provide a valve actuation system capable of cylinder cut-out.
It is another object of the present invention to provide selectable valve operation for each cylinder.
It is another object of the present invention to provide staggered opening of either intake or exhaust valves.
It is also an object of the present invention to provide a full-authority valve actuation system for an internal combustion engine.
Additional objects and advantages of the invention are set forth, in part, in the description which follows and, in part, will be apparent to one of ordinary skill in the art from the description and/or from the practice of the invention.
SUMMARY OF THE INVENTION
In response to the foregoing challenges, applicants have developed an innovative, economical method and apparatus for controlling engine valve operation in an internal combustion engine. The present invention is directed to a valve actuation system for a cylinder of an internal combustion engine having an intake and an exhaust valve comprising: an intake valve train; an exhaust valve train; an intake valve hydraulic actuator that selectively responds to motion of the intake valve train and causes the intake valve to open; an exhaust valve hydraulic actuator that selectively responds to motion of the exhaust valve train and causes the exhaust valve to open; a control valve for controlling the supply of hydraulic fluid to the intake valve actuator and the exhaust valve actuator to control the response of the actuators to the motion of the valve trains. The hydraulic actuators may include a master piston; a slave piston; and a variable volume fluid chamber formed between the master and slave piston. The control valve may be a solenoid actuated valve or a spool valve. The actuators may be oriented so that the slave piston contacts the engine valve and the master piston contacts the valve train. However, the master piston may contact the engine valve and the slave piston may contact the valve train.
The control valve controls the amount of fluid in the variable volume fluid chamber in order to selectively modify the openings of the exhaust valve in response to th

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