Driving Force Transmission Control Apparatus for Four-Wheel Drive Stability
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Solution Overview
Problem
Four-wheel drive vehicles face instability due to insufficient distribution of driving force to auxiliary wheels, as existing systems set upper limits on driving force to prevent damage, limiting the effectiveness of driving force distribution and potentially causing overshoot, which can lead to component damage.
Innovation Solution
A driving force transmission control apparatus that adjusts the upper limit value of driving force transmitted to auxiliary wheels based on rotation speed differences, using a command value calculator, limiter, and current controller to ensure stable transmission while preventing damage, by dynamically setting the upper limit value smaller as the rotation speed difference increases.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the upper limit value of driving force is set smaller to prevent damage to transmission components, then reliability is improved, but the driving stability cannot be increased sufficiently due to limited driving force distribution to auxiliary wheels
Solution Approach 1:
The upper limit value of the command value is made dynamic by adjusting it based on the rotation speed difference between main and auxiliary driving wheels. When rotation speed difference increases, the upper limit value is increased, allowing greater driving force distribution to auxiliary wheels and improving driving stability while maintaining component safety through conditional adjustment rather than fixed limitation
Solution Approach 2:
The system changes the parameter of upper limit value based on operating conditions (rotation speed difference). By monitoring the rotation speed difference and adjusting the upper limit value accordingly, the system optimizes driving force distribution to auxiliary wheels, enabling sufficient driving stability while preventing component damage through condition-based parameter adjustment
2Stability of the object's composition
If the engagement force of the clutch is increased to transmit more driving force to auxiliary wheels, then driving stability is improved, but the driving force may temporarily overshoot its target value causing component damage
Solution Approach 1:
The system uses feedback from the rotation speed difference between main and auxiliary driving wheels to dynamically adjust the upper limit value. This feedback mechanism allows the system to respond to actual operating conditions, increasing the upper limit value when rotation speed difference indicates a need for greater driving force distribution, thereby improving driving stability while preventing overshoot through condition-based control
Solution Approach 2:
The upper limit value is made dynamic rather than fixed, adjusting in response to rotation speed difference. This dynamic adjustment allows the system to transmit sufficient driving force to auxiliary wheels for improved driving stability while preventing overshoot by adapting the limit to actual operating conditions rather than using a conservative fixed value
Data Source
AI summary
A control apparatus configured to control a driving force transmission apparatus. The control apparatus includes a torque command value calculator configured to calculate a torque command value for the right and left rear wheels based on a front-rear wheel rotation speed difference, a command value limiter configured to limit the torque command value to a value equal to or smaller than an upper limit value, and a current controller configured to control a current to be supplied to the driving force transmission apparatus so that a driving force determined based on the torque command value is transmitted to the right and left rear wheels. When the front-rear wheel rotation speed difference increases, the command value limiter sets the upper limit value smaller as a change amount of the front-rear wheel rotation speed difference per unit time increases.