Motor Control Apparatus Heat Management via Periodic Switching
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Solution Overview
Problem
Conventional motor control systems for internal combustion engines face issues with excessive heat generation in switching elements and incorrect determination of rotation direction, leading to inadequate motor torque generation during restart, especially when the motor stops at specific rotation angles.
Innovation Solution
A motor control apparatus with an inverter, rotation angle detection, and a motor control part that operates in normal and power generation control modes, ensuring continuous current supply to the stator coil in normal mode and intermittent supply in power generation mode to manage rotation torque and prevent excessive heat, while using a rotation angle sensor to determine the correct operation mode based on rotation direction changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the motor shaft rotates opposite to the target rotation direction, then the induced voltage is generated in the same direction as the supplied voltage, but large current flows in the switching elements causing excessive heat generation
Solution Approach 1:
The control apparatus divides the rotation angle range into on-state range and off-state range, periodically switching the switching elements on and off based on the motor shaft's rotation angle. This periodic action prevents continuous current flow during reverse rotation, reducing heat generation while maintaining necessary motor control functionality.
Solution Approach 2:
The rotation angle range is segmented into distinct on-state range and off-state range. By dividing the continuous rotation cycle into discrete control zones, the system can apply different switching element control strategies in different angular regions, preventing excessive current during reverse rotation while maintaining normal operation in appropriate zones.
2Measurement precision
If the braking torque reverses the rotation direction of the motor shaft momentarily before stopping, then the rotation direction detection becomes incorrect, but the power supply driving part stops operation erroneously
Solution Approach 1:
The control apparatus determines the rotation angle at which the motor shaft stops in advance, before restart operation begins. Based on this pre-determined stop angle information, the system proactively sets the on-state range and off-state range to ensure proper motor restart functionality, preventing erroneous operation stoppage.
Solution Approach 2:
The control apparatus continuously monitors the rotation angle and rotation direction of the motor shaft, using this feedback information to dynamically adjust the on-state and off-state ranges. This feedback mechanism allows the system to distinguish between momentary reverse rotation due to braking torque and actual intended reverse rotation, maintaining reliable operation.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution effectively suppresses excessive heat generation and ensures the motor can generate rotation torque at any stop angle, enabling proper camshaft phase adjustment for engine restart, thereby improving engine reliability and efficiency.
Implementation Method 1
When the motor shaft rotates under a state that a current flows in the stator coil and the stator coil generates a magnetic field
Implementation Method 2
a current flows in the stator coil to generate magnetic fluxes, which exert on the permanent magnets to generate a rotation torque
Implementation Method 3
an induced voltage is generated in the stator coil
Implementation Method 4
magnetic force is generated between the metallic parts and the permanent magnets. This magnetic force exerts on the motor shaft as a braking torque
Data Source
AI summary
A motor control apparatus for adjusting a cam phase includes a motor control part, which controls a current supplied to a stator coil by controlling plural switching elements forming an inverter to turn on and off. The motor control part stops the current supplied to the stator coil each time a motor rotates a predetermined rotation angle interval in a power generation control mode, in which a rotation torque is generated in a direction to impede the motor rotation. The motor control part maintains the power generation control mode when a rotation signal is determined as varying in a predetermined time period. The motor control part switches over an operation mode to a normal control mode to generate a rotation torque in a direction to promote the motor rotation when the rotation signal is determined as not varying in the predetermined time period.