Internal-combustion engines – Lubricators – Crankcase – pressure control
Reexamination Certificate
2000-05-09
2001-09-25
Kamen, Noah P. (Department: 3747)
Internal-combustion engines
Lubricators
Crankcase, pressure control
C123S1960CP
Reexamination Certificate
active
06293244
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates internal combustion engines which include variable cam timing systems, wherein a flow of valvetrain-lubricating oil to the cylinder head is controllably diverted to thereby provide pressurized fluid to a cam phaser unit, for example, mounted on an end of a cam shaft.
2. Background Art
The prior art teaches internal combustion engines wherein a fixed relationship between camshaft rotation and crankshaft rotation is maintained to thereby preserve the relationship between intake and exhaust vale events and piston motion. Alternatively, the prior art teaches so-called variable cam timing engines which seek to adjust this relationship to thereby achieve various advantages including increased fuel economy and reduced regulated emissions. Under one prior art approach, as disclosed in U.S. Pat. No. 5,363,817, actual cam timing is measured using a toothed wheel on the camshaft and a toothed wheel on the crankshaft. The time, or angle, between receiving pulses from the wheel on the crankshaft and the wheel on the camshaft represents the actual cam timing. A desired cam timing is determined as a function of engine operating conditions, and an error signal is created from the difference of the desired cam timing and the actual cam timing. Control signals based upon the error signal are then generated and supplied to actuators capable of adjusting the cam timing, typically by supplying pressurized oil to a solenoid valve for controllably directing pressurized oil to a selected passage in the camshaft which, in turn, directs the pressurized oil to an oil-pressure-responsive cam phaser unit.
Significantly, in such a system, the cylinder heads are specifically designed for variable cam timing, i.e., the heads include oil-porting passages to communicate pressurized oil to the passages defined in the camshaft. Such systems thus require extensive design considerations and machining of the heads and camshaft to accommodate the oil passages, as well as consideration to the mounting of the solenoid valves.
Alternatively, the prior art teaches use of ported camshaft bearings to define the paths by which pressurized oil is supplied to the cam phaser unit. Such ported camshaft bearings either require similar oil-porting passages in the cylinder head, or external oil routing tubes and flow control structures which, in turn, present additional packaging and mechanical attachment issues, each serving to increase the cost of providing variable cam timing to an existing engine that has fixed cam timing.
SUMMARY OF THE INVENTION
It is an object of the invention to provide simplified oil supply and control system for a variable cam timing system of an internal combustion engine and, particularly, a system and method for controlling such oil flow by which given engine architectures are selectively provided with either fixed cam timing or variable cam timing.
Under the invention, a system for controlling oil flow to the cylinder head of an internal combustion engine includes an oil flow control module having a generally-flat mating surface that is secured against a generally-flat external surface of the cylinder head. The oil flow control module includes at least a first passage that places a pressurized oil outlet defined in the external surface of the cylinder head in fluid communication with an oil inlet, also defined in the external surface of the cylinder head.
In accordance with a feature of the invention, the first passage of the module includes an oil restrictor, such as a first section having a relatively-reduced hydraulic diameter. Preferably, the first passage further defines a reservoir disposed between the restrictor and the inlet of the cylinder head and, preferably, arranged to be positioned on the engine below the inlet of the cylinder head, whereby oil is contained in the reservoir during engine shut-off. In this manner, the module advantageously insurers a supply of valvetrain-lubricating oil to the cylinder head inlet upon a subsequent engine start-up.
In accordance with another feature of the invention, the system and method advantageously allow for the use of a single finished cylinder pad assembly to be used in an engine equipped with either variable cam timing or conventional fixed cam timing. Thus, for an engine to be equipped with variable cam timing, the module also includes a first bore or cavity adapted to receive a spool valve that is operative to direct a second portion of the unrestricted oil flow into a selected one of a plurality of additional passages leading to a hydraulically-responsive cam phaser unit. While the invention contemplates use of any suitable configuration for the oil feeds to the cam phaser unit, by way of example only, in an exemplary system, the additional passages leading to the cam phaser unit are routed back through additional ports defined in the external surface of the cylinder head. In the exemplary system, the module further provides a high-precision mount for the phase angle sensor to be used with the variable cam timing system.
In accordance with another feature of the invention, the module preferably further includes a second bore or cavity adapted to receive a filter, with the first passage intersecting the second cavity such that at least a portion of the unrestricted oil flow passes through the filter before being diverted by the spool valve to the variable cam timing system.
In this manner, the invention advantageously provides certain necessary components of a variable cam timing system in a single package while further eliminating the extra machining operations on the cylinder head that are typical of prior art systems, e.g., to accommodate the spool valve, phase angle sensor and associated pressurized oil circuits. Indeed, it will be appreciated that a variable-cost savings is readily achieved under the invention because component assembly operations are minimized, and because machined surfaces that are typically in the cylinder head are instead obtained on the much smaller oil flow control module, with faster manufacturing cycle times.
Other objects, features and advantages of the present invention are readily apparent from the following detailed description when taken in connection with the accompanying drawings.
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Diggs Matthew Byrne
Mullins Jeffrey Allen
Schrader Michael Joseph
Drouillard Jerome R.
Ford Global Technologies Inc.
Huynh Hai
Kamen Noah P.
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