Variable Valve Timing Actuator Torque Control
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Solution Overview
Problem
Variable Valve Timing (VVT) systems using electric motors face challenges with torque generation, leading to restricted phase shift and increased power consumption and heat generation, which can result in mechanical damage.
Innovation Solution
A variable valve timing apparatus with an actuator that adjusts torque based on a command value, utilizing an operation unit to control the command value's upper limit according to the operating state, and selecting between different control modes (feedback and feed-forward) to manage torque, power consumption, and heat generation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If an electric motor is used to rotate the camshaft, then the phase can be changed, but the torque for rotating the camshaft is difficult to obtain and the rotational speed is reduced by a speed reducer mechanism, restricting the degree of phase shift
Solution Approach 1:
The patent applies dynamics by making the upper limit of the command value changeable according to operating state. The operation unit dynamically adjusts the command value upper limit based on real-time operating conditions (engine speed, load, temperature), allowing the system to optimize torque generation and phase shift capability under different conditions, resolving the contradiction between limited torque and required phase shift range.
Solution Approach 2:
The patent changes the parameter of command value upper limit based on operating state. By varying this parameter according to engine conditions (such as engine speed, load, and temperature), the system can generate appropriate torque levels to achieve the desired phase shift without being constrained by fixed torque limitations of the electric motor.
2Adaptability or versatility
If the electric motor is controlled to generate higher torque for greater phase shift, then the degree of freedom of phase shift increases, but power consumption and heat generation increase, which can result in mechanical damage
Solution Approach 1:
The operation unit implements feedback control by monitoring the operating state and adjusting the command value upper limit accordingly. This feedback mechanism ensures that the electric motor operates within optimal power consumption ranges while achieving the necessary phase shift, preventing excessive power consumption and heat generation that could lead to mechanical damage.
3Adaptability or versatility
If the electric motor is controlled to generate higher torque for greater phase shift, then the degree of freedom of phase shift increases, but heat generation increases, which can result in mechanical damage
Solution Approach 1:
The operation unit monitors operating state parameters including temperature and adjusts the command value upper limit in response. This feedback control prevents excessive heat generation by limiting the torque and phase shift commands when thermal conditions indicate potential damage risks, thus protecting the mechanical components while maintaining adaptability.
Data Source
AI summary
An ECU executes a program including the steps of: controlling, when the phase of an intake valve is a phase advanced relative to a threshold value CA (FF) (NO in S106), an electric motor operating an intake VVT mechanism by feedback control (S202); and controlling, when the phase of the intake valve is a phase retarded relative to the threshold value CA (FF) (YES in S106), the electric motor by feed-forward control (S200). Under the feed-forward control, a duty command value is output that is smaller than an upper limit of a duty command value under the feedback control.