Patent ID: 8463525
Filing Date: 2013-06-11
Classification: F01L,F02D,Y02T

Abstract:
1. A variable valve timing control apparatus for a variable valve timing device for an internal combustion engine, the variable valve timing device driven by a hydraulic pressure and configured to change a VCT phase of a camshaft relative to a crankshaft to control a valve timing, the variable valve timing device including i) a lock pin configured to lock the VCT phase in an intermediate lock phase between a most retarded phase and a most advanced phase of a controllable range and ii) a hydraulic pressure control device configured to control a hydraulic pressure to drive the variable valve timing device and the lock pin, the variable valve timing control apparatus configured to control the hydraulic pressure control device to project the lock pin to lock the VCT phase in the intermediate lock phase when a lock request occurs, the variable valve timing control apparatus comprising: a VCT phase calculating unit configured to calculate the VCT phase based on a phase difference between a time point, in which a crank angle sensor generates a crank angle signal at a predetermined crank angle with an operation of the internal combustion engine, and a time point, in which a cam angle sensor generates a cam angle signal at a predetermined cam angle with the operation of the internal combustion engine; a reference phase learning unit configured to learn one of the most retarded phase, the most advanced phase, and the intermediate lock phase, as a reference phase; a VCT phase control unit configured to set a target phase according to a learning value of the reference phase and configured to control the hydraulic pressure control device such that the VCT phase coincides with the target phase; and a lock abnormality monitor unit configured to monitor a change in the VCT phase and determine that the VCT phase has passed through the intermediate lock phase when i) the lock request occurs in a period before the reference phase learning unit completes learning of the reference phase, and ii) the monitored change in the VCT phase becomes greater than a threshold, wherein the threshold is set to be greater than a sum of i) a design value of a phase difference between the intermediate lock phase and one of the most retarded phase and the most advanced phase and ii) a range of a product variation of the phase difference, when the change in the VCT phase after the lock request occurs becomes greater than the threshold, i) the lock abnormality monitor unit determines that the VCT phase has passed through the intermediate lock phase, and ii) the lock abnormality monitor unit determines that it is an abnormal condition, in which the lock pin is not normally projected.