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AssigneeBorgWarner Inc.
InventorsRoger Simpson, Braman Wing
Estimating the term…
The present invention controls the position of a center mounted spool valve (192) with an externally mounted vacuum controlled actuator (301). The actuator position is preferably controlled by a pulse width modulated or variable force solenoid (302), which modulates the amount of vacuum going to the actuator (301). A microprocessor (208) reads the phase angle and adjusts the duty cycle or current based on the error signal of the control loop (450). In a preferred embodiment, a position sensor (304) further controls the position of the spool valve (192). The position sensor (304) creates an inner loop (400) with position feedback on the position of the actuator (301) and spool valve (192), while the outer loop controls the phase angle. Added to the spool valve position is an offset to move the spool valve (192) to its steady state or null position (410).
A variable cam timing system for an internal combustion engine having a crankshaft, at least one camshaft, a cam drive connected to the crankshaft, and a variable cam phaser having an inner portion mounted to at least one camshaft and a concentric outer portion connected to the cam drive, the relative angular positions of the inner portion and the outer portion being controllable in response to a fluid control input, such that the relative phase of the crankshaft and at least one camshaft can be shifted by varying the fluid at the fluid control input of the variable cam phaser, the variable cam timing system comprising:
An internal combustion engine, comprising:
In an internal combustion engine having a variable camshaft timing system for varying the phase angle of a camshaft relative to a crankshaft, a method of regulating the flow of fluid from a source to a means for transmitting rotary movement from the crankshaft to a housing, comprising the steps of:
Dependencies are inferred from the claim text.
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From the US filing history. Foreign family members aren’t listed.
Backward citations are indexed for grants only.
Valve drive: chain drive
Valve drive: belt drive
Details relating to the hydraulic feeding circuit: oil control valves
Cyclically operating valves for machines or engines: using particular materials
Term end not estimated
1. Field of the Invention
The invention relates to a hydraulic control system for controlling the operation of a variable camshaft timing (VCT) system. More particularly, the invention pertains to the use of an externally mounted vacuum controlled actuator to control the position of a center mounted spool valve.
2. Description of Related Art
FIG. 1 is a sectional view of a cam phaser with an externally mounted vacuum controlled actuator of the invention.
FIG. 2 is a sectional view of a cam phaser with an externally mounted vacuum controlled actuator and position sensor of the invention.
FIG. 3 is a block diagram of a cam torque actuated variable cam timing device with a vacuum controlled spool valve in an embodiment of the present invention.
The present invention controls the position of a center mounted spool valve, which controls the oil flow to and from the chambers of a vane or piston-style cam phaser, using an externally mounted vacuum controlled actuator. The “phaser” is all of the parts of the engine which allow the camshaft to run independently of the crankshaft. The actuator position is preferably controlled by a pulse width modulated or variable force solenoid to control the amount of vacuum going to the actuator. The solenoid is preferably located in a vacuum control valve. However, the solenoid or other vacuum control may also be located within the actuator itself. A microprocessor reads the phase angle and adjusts the duty cycle or current based on the error signal of the control loop. The microprocessor is preferably an engine control unit (“ECU”) which monitors various engine parameters. The ECU receives signals from sensors corresponding to camshaft and crankshaft positions and utilizes this information to calculate a relative phase angle. A closed-loop feedback system which corrects for any phase angle error is preferably employed. This method controls the position of the actuator and maps the position of the actuator versus command signal (duty cycle or current).
These types of actuators have certain manufacturing tolerances which often result in the position of the actuator being off as much as 10% of full travel. Although the integrator in the control loop compensates for this error, a more robust control system of the present invention has an inner loop that includes position feedback on the position of the actuator and spool valve. The present invention reduces the error created by the prior art by having a position sensor mounted to an actuator rod, or spool valve position, of the vacuum controlled actuator. A feedback control loop controls the position of the spool valve. This method reduces any frictional or magnetic hysteresis in the spool and actuator control system. There is also preferably a second, outer feedback loop to control the phaser angle. An offset is preferably added to the spool valve position to move the spool valve to its steady state or null position. The null position is required so that the spool can move in to move the phaser in one direction and move out to move the phaser in the other direction.
FIG. 1 shows a cam phaser of the present invention in which a housing in the form of a sprocket (132) is oscillatingly journalled on a camshaft (126). The camshaft (126) may be considered to be the only camshaft of a single camshaft engine, either of the overhead camshaft type or the in block camshaft type. Alternatively, the camshaft (126) may be considered to be either the intake valve operating camshaft or the exhaust valve operating camshaft of a dual camshaft engine. In any case, the sprocket (132) and the camshaft (126) are rotatable together, and are caused to rotate by the application of torque to the sprocket (132) by an endless roller chain (138), shown fragmentarily, which is trained around the sprocket 132 and also around a crankshaft (100) with its own sprocket (101). The sprocket (132) is oscillatingly journalled on the camshaft (126) so that it is oscillatable at least through a limited arc with respect to the camshaft (126) during the rotation of the camshaft, an action which will adjust the phase of the camshaft (126) relative to the crankshaft (100).