Self-Energizing Differential Locking Mechanism
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Solution Overview
Problem
Conventional differential systems, such as open and fully locked differentials, face challenges in efficiently distributing torque between wheels during cornering, leading to inside wheel spin and yaw resisting moments, while limited slip differentials compromise between differentiation and torque biasing, resulting in inefficiencies and potential understeer.
Innovation Solution
A differential gear with a self-energizing locking device that automatically adjusts between four working modes, locking or unlocking based on the crossover point, ensuring optimal torque distribution and minimizing inside wheel spin without excessive yaw resisting moments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If an open differential is used to divide engine torque equally between wheels, then torque distribution is simplified and mechanical complexity is reduced, but inside wheel spin occurs during cornering and yaw resisting moments compromise vehicle stability
Solution Approach 1:
The differential mechanism dynamically adjusts between open and locked states based on real-time driving conditions. The control system monitors wheel speeds and torque distribution, automatically transitioning the differential from an open state (during straight-line driving) to a locked state (during cornering or low-traction conditions), thereby optimizing both simplicity and stability across varying operational contexts
Solution Approach 2:
The system changes the torque distribution parameter dynamically by controlling the differential lock engagement. When the lock is disengaged, torque is distributed equally (open differential mode); when engaged, torque distribution is restricted to prevent wheel spin (locked differential mode). This parameter switching resolves the contradiction by adapting torque distribution to specific driving scenarios
2Reliability
If a fully locked differential is used to prevent wheel spin, then traction is improved, but the vehicle cannot corner properly due to forced equal rotational speed of both wheels
Solution Approach 1:
The differential mechanism dynamically adjusts between open and locked states based on real-time driving conditions. The control system monitors wheel speeds and torque distribution, automatically transitioning the differential from a locked state (during straight-line driving or low-traction conditions) to an open state (during cornering), thereby optimizing both traction and cornering ability across varying operational contexts
Solution Approach 2:
The system changes the torque distribution parameter dynamically by controlling the differential lock engagement. When the lock is engaged, torque is restricted to prevent wheel spin (improving traction); when disengaged, torque is distributed equally allowing free differentiation (enabling proper cornering). This parameter switching resolves the contradiction by adapting torque distribution to specific driving scenarios
3Reliability
If differential brakes are used to limit wheel spin, then traction control is improved, but efficiency is lowered due to friction losses and mechanical complexity increases
Solution Approach 1:
The patent replaces the traditional mechanical differential brake system with an electronically controlled differential lock mechanism. Instead of using friction-based brakes to limit wheel spin, the system uses a controllable mechanical lock that can be engaged or disengaged electronically. This substitution eliminates continuous friction losses while maintaining traction control capability, as the lock only engages when necessary and does so through a more efficient mechanical locking action rather than friction braking
Solution Approach 2:
The control system automatically monitors driving conditions and activates the differential lock only when wheel spin is detected, without requiring continuous driver intervention or complex brake modulation. The system serves itself by detecting traction loss and applying the appropriate correction, minimizing energy loss through precise, condition-based activation rather than continuous operation
Data Source
AI summary
A differential gear is equipped with a selectively controllable locking device which is self energizing, i.e. it utilizes the differentiation energy to self-lock on its own accord. The control signal is therefore not needed to lock the locking device but rather to selectively, separately for each of the two possible differentiation directions, control it to not lock itself. This gives the differential gear four different working modes. These are: open regardless of differentiation direction; open in one differentiation direction but self-locking in the other direction; open in the other direction but self-locking in the first one; self locking regardless of differentiation direction. A control unit is supplied with sensor data of the present “driving situation”. The control unit has a steering strategy. With the right steering strategy it can regulate the control signal so as to permit the differential gear to equalize the torque at each output shaft for as long as possible but still to practically eliminate the risk of one wheel spin.