US 4,856,465 AGranted

Multidependent valve timing overlap control for the cylinders of an internal combustion engine

AssigneeRobert Bosch GmbH

InventorsHelmut Denz, Martin Person

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Abstract

The oil pressure applied to a hydraulic device for controlling within a limited angular range of a cam shaft and its drive gear is controlled by a magnetic valve (35) which is switched between its open and closed position under control of the same microcomputer which controls engine ignition and/or fuel injection with reference to a predetermined function of some of the same engine operation parameters, namely engine speed and engine load, which are used to control ignition and/or fuel injection. The control function can advantageously also take account of rate of change of engine load or engine speed. A transducer (43) for reporting back the sleeve (22) which controls the mechanical rotary shift in response to oil pressure can be used to provide an actual value signal to the computer for generation of an error signal for controlling the magnetic valve so as to provide a continuous control of the overlap of the open periods of the intake and exhaust valves of the engine. The control function for the operation of the magnetic valve provides for hysteresis to prevent excessive switching back and forth.

Claims4

Dependent claims

Apparatus for controlling valves of an internal combustion engine through a camshaft having a drive gear which is hydraulically rotatably on said camshaft over a predetermined angle, the rotation of said camshaft drive gear relative to said camshaft being controllable in a manner dependent upon engine speed by a hydraulic device in turn controlled by a valve affecting flow of a hydraulic fluid, said engine having an engine block and having at least one of the functions of engine ignition and fuel injection controlled by a computer associated with said engine, said apparatus having the improvement which comprises:

an electromagnetic valve serving as said valve and located outside said engine block in a hydraulic line for control of said hydraulic medium;
rotary feed-through bearing means for connecting said line to said hydraulic device;
means for operating said electromagnetic valve for rotating said camshaft relative to said drive gear under control through electrical circuits by said computer which also controls at least one of the functions of engine ignition and fuel injection for said engine, said electromagnetic valve having two switching positions between which it is moved under control of said computer in accordance with a predetermined function that depends upon engine speed (n) and engine load (t.sub.1) of said engine, said predetermined function providing for hysteresis in the switch over of said magnetic valve between its switching positions and being stored in said computer as a field of function values addressable by corresponding combinations of values of engine speed and engine load as detected for and furnished to said computer.

Apparatus for controlling valves of an internal combustion engine, having an engine block through a camshaft having a drive gear which is hydraulically rotable on said camshaft over a predetermined angle, the rotation of said camshaft drive gear relative to said camshaft being controllable in a manner dependent upon engine speed by a hydraulic device within said engine block, which device is in turn controlled by a valve affecting flow of a hydraulic fluid, said engine having at least one of its functions of engine ignition and fuel injection controlled by a computer associated with said engine, said apparatus having the improvement which comprises:

an electromagnetic valve serving as said valve and located outside said engine block in a hydraulic line for control of said hydraulic medium;
rotary feed-through bearing means (31, 32) for connecting said line to said hydraulic device;
means for indicating the position of said hydraulic device and thereby the actual relative angular position of said camshaft and said drive gear, and for producing an electrical signal representative thereof;
means for pulsing said electromagnetic valve at a controllable variable duty cycle for rotating said camshaft relative to said drive gear under control through electrical circuits by said computer, in response to a computation by said computer of a desired position of said hydraulic device in accordance with a predetermined function of engine speed (n) and engine load (t.sub.1) made available to said computer for its control of at least one of said engine functions, comparison of said desired position with a signal produced by said position indicating means, and provision by said computer of a succession of outputs for variation of said duty cycle of pulsing sense appropriate for causing said actual position to approach said desired position, said predetermined function being stored in said computer as a field of function values addressable by corresponding combinations of values of engine speed and engine load.

1 more element

Dependencies are inferred from the claim text.