Vehicle Drive Control Device Engine Operating Point
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Solution Overview
Problem
Existing vehicle drive devices with hydraulic power transmission and electric motors struggle to improve fuel efficiency due to constrained engine operating points, especially when using a lockup clutch, as the engine rotation speed is determined by the hydraulic power transmission device, limiting the control of the engine operating point by the electric motor.
Innovation Solution
A control device that adjusts the torque of the first electric motor to control the engine operating point, selecting between electric and hydraulic transmission paths to optimize power transmission efficiency, including the use of a lockup clutch for engagement or slip operations to enhance fuel efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the lockup clutch is engaged to transmit power mechanically without fluid, then power transmission efficiency is improved, but the engine operating point is uniquely constrained and cannot be arbitrarily controlled
Solution Approach 1:
The system dynamically switches between two transmission modes: hydraulic transmission (torque converter) and mechanical transmission (lockup clutch). The control device selectively engages or disengages the lockup clutch based on operating conditions, allowing the engine operating point to be adjusted via the first electric motor when the clutch is disengaged, while maintaining high transmission efficiency when the clutch is engaged.
Solution Approach 2:
The transmission system is designed to perform multiple functions through a single integrated mechanism. The lockup clutch serves dual purposes: when engaged, it provides high-efficiency mechanical power transmission; when disengaged, it enables hydraulic transmission that allows engine operating point control. This multi-functionality resolves the contradiction between efficiency and controllability.
2Loss of energy
If the first electric motor arbitrarily controls the engine operating point, then fuel efficiency is improved, but power transmission efficiency in the mechanical path changes and combined efficiency must be optimized
Solution Approach 1:
The control device continuously monitors transmission efficiency in both the electric path (first electric motor to second electric motor) and the mechanical path (through the hydraulic power transmission device). Based on this feedback, the system dynamically adjusts the engine operating point and selects the optimal transmission path to maximize overall fuel efficiency while accounting for changes in combined power transmission efficiency.
Solution Approach 2:
The system changes operational parameters by adjusting the torque of the first electric motor to control the engine operating point. The control device optimizes parameters such as engine rotation speed and torque output, selecting between different transmission paths based on which provides better overall efficiency under current operating conditions.
3Ease of operation
If the engine rotation speed is passively determined by the hydraulic power transmission device, then the system is simpler to control, but fuel efficiency cannot be optimized by controlling the engine operating point
Solution Approach 1:
The power transmission system is segmented into two independent paths: a mechanical path through the hydraulic power transmission device and an electric path through the first and second electric motors. This segmentation allows the first electric motor to independently control the engine operating point without being constrained by the passive rotation speed determination of the hydraulic device, thereby optimizing fuel efficiency while maintaining control simplicity through modular architecture.
Data Source
AI summary
The control device of a vehicle drive device is configured to have an electric path and a mechanical path, to control an operating point of the engine by adjusting a torque of the first electric motor, to select a transmission path with better power transmission efficiency between a power transmission efficiency in a first transmission path transmitting the power of the engine toward the drive wheels by using both the power transmission via the electric path and the power transmission only via fluid in the hydraulic power transmission device in the mechanical path and a power transmission efficiency in a second transmission path transmitting the power of the engine toward the drive wheels through power transmission when the lockup clutch of the hydraulic power transmission device is driven to perform an engagement or slip operation in the mechanical path.