Vehicular Drive Differential Mechanism Torque Control
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Solution Overview
Problem
Existing vehicular drive systems with differential mechanisms suffer from large size due to large electric motors and poor fuel economy, especially during high-speed running, as they rely on both mechanical and electric energy transmission paths.
Innovation Solution
A control device that switches the differential mechanism between differential and locked states to prioritize mechanical power transmission during high-output engine states, reducing the size of electric motors and minimizing energy conversion losses, while using a switching control system to manage torque changes and reduce operating shocks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the differential mechanism functions as an electrically controlled continuously variable transmission with both mechanical and electric energy transmission paths, then the fuel economy can be improved by keeping the engine in an optimum operating state, but the system size increases due to large-sized electric motors and the fuel economy deteriorates during high-speed running due to energy conversion losses
Solution Approach 1:
The patent dynamically switches the differential mechanism between differential state and locked state based on vehicle operating conditions. During high-speed running, the system locks the differential mechanism to eliminate the electric energy transmission path, thereby avoiding energy conversion losses while maintaining the ability to use electric path during low-speed or high-efficiency operating conditions
2Use of energy by moving object
If the differential mechanism functions as an electrically controlled continuously variable transmission, then the fuel economy can be improved, but the system becomes large-sized due to large electric motors required for high-output engine states
Solution Approach 1:
The system dynamically adjusts its configuration by locking the differential mechanism during high-output engine states, eliminating the need for large-sized electric motors to handle peak power requirements. This allows the use of smaller electric motors while maintaining both fuel economy benefits during efficient operation and adequate power transmission capability during high-output conditions
3Volume of moving object
If the differential mechanism is switched between differential and locked states, then the operating shock increases, but the system can reduce size and improve fuel economy
Solution Approach 1:
The control device performs preliminary actions by gradually changing the output torque of the drive power source before and during the switching process. This preliminary torque management smooths the transition between differential and locked states, reducing operating shocks while enabling the system to achieve compact size and improved fuel economy through state switching
Data Source
AI summary
A control device for a vehicular drive system including (a) a differential mechanism operable to distribute an output of an engine to a first electric motor and a power transmitting member, and (b) a second electric motor disposed between the power transmitting member and a drive wheel of a vehicle, and a differential-state switching device operable to place the differential mechanism selectively in one of a differential state and a locked or non-differential state. The control device may include a switching control portion operable to control the differential-state switching device to place the differential mechanism selectively in one of the differential and locked states, and a power-source torque-change restriction control portion operable to restrict a change of an output torque of the engine upon switching of the differential mechanism between the differential and locked states.