Variable Valve Timing Control Unit Startup Phase Calculation
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Solution Overview
Problem
Conventional control apparatuses for variable valve timing mechanisms fail to achieve quick calculation of the absolute position at startup, affecting vehicle startup performance.
Innovation Solution
A control apparatus comprising a crank angle sensor, a cam sensor, and an actuator that computes the actual rotational phase angle of the intake camshaft based on a first cam signal pulse and a reference position of the crank angle signal, allowing for the calculation of the absolute position of the variable valve timing mechanism.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional control apparatus calculates valve timing based on crank angle signal and cam signal difference, then valve timing control is achieved, but absolute position calculation at startup is delayed
Solution Approach 1:
The control unit performs preliminary identification of the intake camshaft's rotational phase angle at startup by detecting the first cam signal pulse and calculating the phase angle before full operation begins. This preliminary action enables the system to have the absolute position ready before normal valve timing control starts, eliminating startup delays.
Solution Approach 2:
The system uses the existing cam signal pulses generated during normal operation to simultaneously determine the absolute position of the intake camshaft. The cam signal pulses that indicate the opening/closing timing of engine valves are also utilized to identify the rotational phase angle, making the system self-sufficient without requiring additional sensors or complex startup procedures.
2Ease of operation
If conventional control apparatus uses motor rotational speed difference to calculate valve timing variation, then valve timing adjustment is achieved, but quick absolute position determination at startup is not achieved
Solution Approach 1:
The invention replaces the mechanical approach of using motor rotational speed differences to infer camshaft position with an electrical/signal-based approach. By detecting the phase relationship between crank angle signals and cam signal pulses, the system directly calculates the intake camshaft's rotational phase angle, providing faster and more accurate startup response.
Data Source
AI summary
The present invention has: a crank angle sensor 4 that outputs a crank angle signal in response to rotation of a crankshaft 2, the crank angle signal being preset to indicate reference positions; a cam sensor 5 that outputs cam signal pulses in response to rotation of an intake camshaft 3 for opening and closing an engine valve; an electric motor 6 that relatively rotates intake camshaft 3 with respect to crankshaft 2, so that electric motor 6 can change a rotational phase angle of intake camshaft 3 with respect to crankshaft 2; and an electronic control unit 7 that computes an actual rotational phase angle of intake camshaft 3 based on a first cam signal pulse detected after start of cranking and a first reference position of the crank signal detected thereafter, to calculate an absolute position of a variable valve timing mechanism 14.