4WD Transmission Control With Variable Front Axle Lead
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Solution Overview
Problem
Agricultural vehicles with four-wheel drive (4WD) systems face issues such as increased turning radius and discomfort during steering, as well as sudden torsional energy release when the front drive shaft is activated or deactivated, leading to poor drivability and tire wear.
Innovation Solution
Implementing a method where the front axle has a positive lead greater than zero when engaged and service brakes are released, proportional to the steering angle, and a negative lead when brakes are activated, to maintain vehicle drivability and comfort, using dynamic control of the front axle connection through epicyclic gearing, power split gearing, or controlled slip clutches.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the front drive is activated while steering, then the vehicle can maintain four-wheel drive, but the turning radius increases causing steering discomfort
Solution Approach 1:
The patent applies dynamics by making the front axle speed variable relative to the rear axle. Instead of a fixed connection, the front axle speed is dynamically adjusted to have a positive lead (higher speed) during 4WD engagement, which compensates for the increased turning radius and improves steering comfort while maintaining 4WD functionality.
Solution Approach 2:
The patent changes the speed parameter of the front axle relative to the rear axle. By introducing a positive speed lead (front axle rotating faster than rear axle), the system modifies the operational parameters to reduce the adverse effects of 4WD engagement on steering performance.
2Speed
If the front drive shaft is suddenly activated or deactivated, then the 4WD system responds quickly, but torsional energy is suddenly released causing a bang
Solution Approach 1:
The patent applies beforehand cushioning by maintaining a positive speed lead in the front axle before deactivation. This pre-positioning of the front axle at a higher speed creates a buffer that absorbs the torsional energy that would otherwise be suddenly released, preventing the bang when the clutch opens.
Solution Approach 2:
The patent applies preliminary anti-action by creating a speed differential (positive lead) that counteracts the tendency for sudden torsional energy release. The front axle is deliberately kept rotating faster than the rear axle, which prevents the buildup and sudden discharge of torsional energy in the drive shaft.
3Ease of operation
If the front axle speed is increased proportionally to steering angle, then steering performance improves, but soil surface is destroyed and front tires wear significantly
Solution Approach 1:
The patent changes the speed parameter of the front axle by introducing a positive lead that is proportional to the steering angle. This dynamic parameter adjustment improves steering performance by compensating for the increased turning radius, while being more moderate than simply increasing front axle speed, thereby reducing tire wear and soil destruction.
Data Source
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AI summary
Method for controlling a 4WD transmission of an agricultural vehicle wherein the front axle drive can be selectively activated or deactivated, wherein when the front axle is engaged and the service brakes are released the front axle has a positive lead strictly greater than zero and preferably function of a vehicle steering angle, and, instead, service brakes activation causes the lead becoming zero or slightly negative, wherein the positive lead consists of a proportionally higher rotation speed of the front axle in respect of the rear axle