Motor Driving Device Cryogenic Control for Electric Oil Pump
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Solution Overview
Problem
Conventional motor driving devices for electric oil pumps in hybrid vehicles face issues with high viscosity oil at low temperatures, leading to increased load torque and output current, which can trigger a fail-safe function and prevent motor operation when the viscosity of the oil becomes extremely high, such as at −10° C. or less.
Innovation Solution
A motor driving device with a controller that adjusts the duty ratio of the drive signal based on three control parameters, including an initial duty ratio, duty ratio increasing speed, and target duty ratio, with a cryogenic control mode that reduces these parameters to manage high viscosity conditions, preventing excessive load torque and output current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If duty control is performed to bring the rotation speed of the electric oil pump to the target rotation speed when the oil temperature is in the cryogenic state, then the rotation speed reaches the target, but the load torque of the motor increases and the output current value rises, which may trigger the fail-safe function and stop current supply
Solution Approach 1:
The controller performs preliminary warming-up control before normal operation by controlling the rotation speed of the electric oil pump to be lower than the target rotation speed when the oil temperature is below the reference temperature. This preliminary action prevents excessive current increase before the fail-safe function can be triggered, ensuring reliable motor operation during cold starts.
Solution Approach 2:
The controller dynamically adjusts the rotation speed of the electric oil pump based on the detected oil temperature. When the oil temperature is below the reference temperature, the controller lowers the rotation speed to reduce load torque and current consumption. This dynamic adjustment allows the system to adapt to changing thermal conditions and maintain reliable operation across different temperature ranges.
2Power
If the rotation speed of the electric oil pump is increased to supply required hydraulic pressure, then the hydraulic pressure requirement is met, but the output current value increases and may exceed the upper limit value, triggering the fail-safe function
Solution Approach 1:
The controller performs preliminary warming-up control by limiting the rotation speed to below the target rotation speed when oil temperature is low. This preliminary action prevents current from exceeding the upper limit before the fail-safe function activates, ensuring continuous operation while gradually warming the oil to improve its flow characteristics.
Solution Approach 2:
The controller changes the operating parameters (rotation speed) of the electric oil pump based on oil temperature conditions. By adjusting the rotation speed parameter dynamically, the system optimizes the balance between hydraulic pressure supply capability and current consumption, preventing fail-safe activation while meeting pressure requirements.
3Speed
If conventional duty control is used in high viscosity oil conditions, then the rotation speed reaches the target, but the load torque increases excessively, causing the output current to rise and potentially triggering the fail-safe function
Solution Approach 1:
The controller performs preliminary warming-up control by controlling the rotation speed to be lower than the target rotation speed when oil temperature is below the reference temperature. This preliminary action reduces the load torque demand on the motor during high viscosity conditions, preventing excessive current draw while gradually warming the oil to reduce its viscosity.
Solution Approach 2:
The controller changes the rotation speed parameter based on oil temperature detection. When the oil is cold and highly viscous, the controller reduces the rotation speed parameter to lower the load torque requirement. As the oil warms and viscosity decreases, the controller can increase the rotation speed to reach the target, dynamically optimizing the force-speed relationship.
Data Source
AI summary
A motor driving device for driving a motor is provided. The motor driving device includes: a driver outputting a drive signal for driving the motor to the motor; and a controller controlling a duty ratio of the drive signal based on three control parameters which are an initial duty ratio, a duty ratio increasing speed, and a target duty ratio. The controller has a normal control mode in which each of the three control parameters is a predetermined value, and a cryogenic control mode in which at least one of the three control parameters is a smaller value than in the normal control mode.