Differential Drive Control for Smooth 2WD-4WD Mode Switching
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Solution Overview
Problem
The issue with existing vehicle drive devices is that when switching from a two-wheel drive state to a four-wheel drive state, the rotational speed difference between the output shaft and the rotating element prevents appropriate connection, leading to inefficiencies in power transfer.
Innovation Solution
A vehicle drive device with a differential mechanism that includes a disconnection-connection mechanism and engaging elements, controlled by an electronic control device, synchronizes rotational speeds and selectively connects output shafts to ensure seamless transitions between drive modes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the disconnection-connection mechanism is used to connect the output shaft and the third rotating element, then the four-wheel drive state can be realized, but the connection cannot be appropriately made when switching from two-wheel drive to four-wheel drive due to rotational speed difference
Solution Approach 1:
The control device performs preliminary synchronous control before connection. When switching from two-wheel drive to four-wheel drive, the control device first controls the rotational speed of the third rotating element to match the rotational speed of the output shaft before engaging the disconnection-connection mechanism, thereby eliminating rotational speed difference and enabling reliable connection.
Solution Approach 2:
The control device uses feedback control to monitor and adjust rotational speeds. By continuously monitoring the rotational speeds of the output shaft and the third rotating element, the control device adjusts the third rotating element's speed to match the output shaft's speed before connection, ensuring reliable engagement of the disconnection-connection mechanism.
2Adaptability or versatility
If the third rotating element is fixed to the fixing member during two-wheel drive, then the two-wheel drive state can be maintained, but the connection to the output shaft cannot be established when switching to four-wheel drive
Solution Approach 1:
The control device performs preliminary synchronous control before connection. When switching from two-wheel drive to four-wheel drive, the control device first controls the rotational speed of the third rotating element to match the rotational speed of the output shaft before engaging the disconnection-connection mechanism, thereby eliminating rotational speed difference and enabling reliable connection.
Solution Approach 2:
The control device uses feedback control to monitor and adjust rotational speeds. By continuously monitoring the rotational speeds of the output shaft and the third rotating element, the control device adjusts the third rotating element's speed to match the output shaft's speed before connection, ensuring reliable engagement of the disconnection-connection mechanism.
Data Source
AI summary
In a vehicle drive device, a second power source is connected to a first rotating element of a differential mechanism. The other output shaft of a first output shaft and a second output shaft is connected to a third rotating element so as to be disconnectable and connectable by a disconnection-connection mechanism. A control device places the disconnection-connection mechanism in a disconnected state. When a second traveling mode in which the third rotating element is fixed to a fixing member through engagement of a first engaging element is switched to a first traveling mode in which the disconnection-connection mechanism is placed in a connected state, the control device disengages the first engaging element, executes synchronous control in which rotational speeds of the other output shaft and the third rotating element are synchronized by a second engaging element, and switches the disconnection-connection mechanism from the disconnected state to the connected state.