Internal-combustion engines – Poppet valve operating mechanism – Hydraulic system
Reexamination Certificate
2000-03-02
2001-07-24
Walberg, Teresa (Department: 3742)
Internal-combustion engines
Poppet valve operating mechanism
Hydraulic system
C123S090110, C251S030010
Reexamination Certificate
active
06263842
ABSTRACT:
TECHNICAL FIELD
The present invention relates to internal combustion engines. More particularly, the present invention relates to engine valve actuation.
BACKGROUND OF THE INVENTION
It is desirable that a hydraulically-assisted engine valve actuator provide for flexible engine valve operation under a wide band of engine operating conditions. The hydraulically-assisted engine valve actuator should provide for variable valve timing of closing and opening and variable lift as desired in order to achieve the greatest engine efficiencies. Presently, hydraulic fluid is supplied to hydraulically actuated valves through tubes commonly called rails. Valve motion profiles in current hydraulic actuation designs depend on a pre-established constant value of oil pressure at the supply rails because rail pressures cannot be adjusted fast enough to modulate valve profiles. The constant rail pressure values result in constant valve profiles regardless of engine rpm.
Present hydraulic actuation schemes add complexity to the engine design. Some hydraulic actuation designs rely on additional hydraulic supply rails at constant pressure levels. Further, hydraulic actuation that relies on on/off solenoid (spool or poppet) valve operations require engine valve position sensors for reliable timing of the solenoids and for safe operation. The plurality of sensors required, further adds to the engine complexity.
There is a need in providing such valve actuation to do so in as economical a manner as possible. A linear motor provides an excellent source of control actuation for the valve actuator. However, a linear motor is considerably more expensive than a solenoid. A solenoid should be used if its limitations can be accommodated.
The valve actuator should demonstrate simplicity of module. There should be no double dependencies in order to minimize the criticality of certain machining tolerances. The concentricity requirements of the device should be as lenient as possible.
The valve actuator should readily accommodate the extremes of valve lash that occur in a diesel cycle engine. Within several minutes after starting a cold engine, it is not uncommon for a valve to grow 0.020 inch due to increased valve temperature. It is helpful if the valve control module be not directly coupled to the engine valve so that no complexities need be designed into the control module to account for valve lash.
SUMMARY OF THE INVENTION
The hydraulically-assisted engine valve actuator of the present invention allows for flexible engine valve operation: variable valve timing of the closing and the opening and variable valve lift. Further, the mechanical components needed to effect the hydraulic actuation are relatively simple, thereby minimizing the additional engine components required. No sensors or mechanical damping mechanisms are needed. Additionally, the hydraulic actuation of the present invention is designed to provide for uniform actuation over a wide range of hydraulic fluid temperatures and viscosities.
The foregoing advantages of the present invention are effected by the use of fine needle control. The fine needle control provides for modulation of engine valve profiles: varying engine profiles at varying engine speeds, varying the shape of the profiles at a given rpm. The present invention further allows aggressive valve openings and closings which translates into better volumetric efficiency of the engine.
The hydraulically-assisted engine valve actuator of the present invention is not sensitive to pressure variation in the high-pressure rail, that is, the modulation of engine valve motion is capable of tolerating a substantial variation of pressure (above a predetermined threshold pressure) in the high-pressure rail.
The device of the present invention only requires one high-pressure supply line. The low-pressure line in an embodiment of the present invention is shared with the existing lubricating oil supply already available. In the case of engines with a fuel injection system incorporating a high-pressure rail for fuel injector actuation, the same high-pressure fluid supply is used for valve actuation in order to further minimize the added components to the engine.
In the case of the present invention, the output, i.e. the engine valve position, very closely follows the input to the hydraulic actuator. Therefore, the device of the present invention does not require the added complexity of requiring a sensor to measure engine valve position for feedback control. Accurate control of valve seating is attained by accurate control of the needle at the end of the stroke.
The present invention further provides very good cold temperature operating performance despite the hydraulic actuating fluid preferably being lubricating oil. The proportional flow areas of the hydraulic fluid passages are not so small as to compromise performance under variable operating temperatures. This is especially important in cold temperature operation since the viscosity of hydraulic fluid, particularly lubricating oil, is significantly higher when the engine is cold than after the engine has warmed up.
In an embodiment, the present invention incorporates a needle and main piston that are decoupled from the engine valve. A secondary piston is coupled to the engine valve for providing actuation of the engine valve. The hydraulic coupling between the secondary piston and the main piston is automatically adjusted to accommodate engine lash. Additionally, the stroke of the main piston acts as a stroke length magnifier, permitting the use of a solenoid controller. The linear stroke of a solenoid is limited to about 4 mm. A typical engine valve requires an opening stroke of about 12 mm. In an embodiment, a 3:1 ratio between the main piston and the secondary piston provides for an effective three times increase in the stroke of the solenoid to effect the full opening stroke of the engine valve.
Further, the mechanical components that are required for valve actuation by the present invention do not significantly increase the engine complexity, i.e., very few modifications to an existing cylinder head are needed in order to incorporate the valve actuator module of the present invention.
REFERENCES:
patent: Re. 35303 (1996-07-01), Miller et al.
patent: 4200067 (1980-04-01), Trenne
patent: 4206728 (1980-06-01), Trenne
patent: 4476823 (1984-10-01), Williams
patent: 5012778 (1991-05-01), Pitzi
patent: 5191867 (1993-03-01), Glassey
patent: 5224683 (1993-07-01), Richeson
patent: 5231959 (1993-08-01), Smietana
patent: 5248123 (1993-09-01), Richeson et al.
patent: 5287829 (1994-02-01), Rose
patent: 5335633 (1994-08-01), Thien
patent: 5339777 (1994-08-01), Cannon
patent: 5392749 (1995-02-01), Stockner
patent: 5410994 (1995-05-01), Schechter
patent: 5419301 (1995-05-01), Schecheter
patent: 5421359 (1995-06-01), Meister et al.
patent: 5448973 (1995-09-01), Meyer
patent: 5456221 (1995-10-01), Schechter
patent: 5456222 (1995-10-01), Schechter
patent: 5456223 (1995-10-01), Miller et al.
patent: 5509637 (1996-04-01), Leonard
patent: 5529030 (1996-06-01), Rose
patent: 5542382 (1996-08-01), Clarke
patent: 5582141 (1996-12-01), Meyer
patent: 5595148 (1997-01-01), Letsche et al.
patent: 5619965 (1997-04-01), Cosma et al.
patent: 5636602 (1997-06-01), Meister
patent: 5683781 (1997-11-01), Sturman
patent: 5713916 (1998-02-01), Sturman
patent: 5960753 (1999-10-01), Sturman
patent: 5970956 (1999-10-01), Sturman
patent: 6135073 (2000-10-01), Feucht et al.
Das Pranab K.
de Ojeda William
Calfa Jeffrey P.
Dahbour Fadi H.
Hernadez Gilberto
International Truck and Engine Corporation
Sullivan Dennis Kelly
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