Internal-combustion engines – Poppet valve operating mechanism – Hydraulic system
Patent
1982-09-17
1985-03-05
Lazarus, Ira S.
Internal-combustion engines
Poppet valve operating mechanism
Hydraulic system
123 9016, 123198F, 123345, 123347, F01L 124, F02D 1302
Patent
active
045024251
DESCRIPTION:
BRIEF SUMMARY
This invention relates to hydraulic valves or hydraulic cam followers for internal combustion engines and more particularly relates to a cam follower in which a variable lift is provided to vary the opening of the valves of the internal combustion engine.
In internal combustion engines the cam shafts are usually connected in operation to the tappets of the valves, or directly to the valve stems through means which compensate for wear, temperature and other differences which would increase the amount of slack between the tappet and the cam follower.
According to a known method the tappets are operated by direct contact or through a push rod and rocker gear to a cam follower which is guided axially and positioned adjacent the cam so that it moves under the influence of the cam, spring loading being provided to return the cam follower after displacement to ensure that at all times it maintains contact with the cam.
Hydraulic cam followers are of two types, each however using a fluid such as oil to take up any slack in the action, the one type being actuated by engine oil and the other being self contained by having a sealed oil supply which takes up the necessary slack should it occur.
The principle of operation is to have between the cam follower member and the push rod or valve stem, a member which is kept extended from the cam follower by oil pressure plus spring pressure between the cam follower and this member, the arrangement however being such that over a time oil is drawn into the space between the cam follower and the inner end of the member which operates a tappet to fill this space so that when the cam pushes on the cam follower, because of the presence of oil which is sealed in this position, the cam follower and tappet member moves simultaneously. However during such motion some oil is expressed from the oil reservoir within the cam follower and the loss is replaced when the cam follower is stationary, either from engine supply or from a sealed reservoir forming a part of the cam follower assembly.
Then with these devices as used hereinbefore, motion of the cam follower is simply transmitted to the valve which it operates so that the cam follower moves the required distance such that proper opening and closing of the valve occurs. It is known also to provide a hydraulic cam follower to provide a fast lift or a high lift and in which the movement of the cam lobe itself is amplified hydraulically to give a greater movement of the valve or push rod, this movement being greater than the actual lift of the cam itself.
One form of such cam follower for actuating the valves of internal combustion engines and the like comprises a hollow cylindrical body closed at one end and slidably mounted on a sleeve fixed relative to the body, the hollow cylindrical body being formed as the cam follower to be in contact with the cam body itself. A piston is slidably mounted within the sleeve, the outer end of the piston being in engagement with the push rod, a chamber being defined between the inner end of the piston and the closed end of the body and containing hydraulic fluid. Displacement of the body by the cam displaces the hydraulic fluid which moves the piston within the fixed sleeve to give the push rod a longer and quicker stroke than the stroke of the cam or body.
However with internal combustion engines the valve timing is critical for the performance of the engine and thus if the valves are timed to give maximum performance then due to the large period of overlap of the valves and the timing of the opening of the valves and closing of the valves in relation to the piston movement these engines are difficult to run at lower speeds and poor performance is achieved at lower speeds and light loads of the engine.
Conversely if the engine is timed to have a satisfactory performance at lower speeds and to be able to idle satisfactorily then the performance suffers at higher speeds and under higher loadings.
Thus it is an object of this invention to provide a means whereby the valve timing can be varied as desired
REFERENCES:
patent: 1688164 (1928-10-01), Tarrant
patent: 3439661 (1969-04-01), Weiler
patent: 3612015 (1971-10-01), Hausknecht
patent: 3817228 (1974-06-01), Bywater
patent: 3865088 (1975-02-01), Links
patent: 4161166 (1979-07-01), Roznovsky
patent: 4261307 (1981-04-01), Oldberg
patent: 4357917 (1982-11-01), Aoyama
Bailey R. S.
Lazarus Ira S.
Wride Marlene A.
LandOfFree
Variable lift cam follower does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Variable lift cam follower, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Variable lift cam follower will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-1728985