Dual PWM control of a center mounted spool value to control a cam phaser
Patent No. 6,622,675
Issued: September 23, 2003
Inventors: Simpson; Roger (Ithaca, NY)
A remotely mounted 4-way valve (2) or two solenoid valves (12) (13) control a center mounted spool valve (28). In the 4-way valve embodiment, one control port (3) provides oil pressure to one end (26) of the spool valve (28) and the other control port (4) provides oil pressure to the other end (27) of the spool (25). In the embodiment with two solenoid valves, one solenoid valve control port (16) feeds oil to one end (26) of the spool (25) and another solenoid valve control port (17) feeds oil to the other end (27). For both of these control systems, the relationship of percent of control signal to percent of control pressure is mapped into the controller, and varies as the engine oil pressure and temperature changes. In a preferred embodiment, a position sensor (34) mounted to the spool valve position reduces this error by having a control loop controlling the position of the spool valve. There is also another loop to control the phaser angle.
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