Differential Tank Steer Using a Grounded Case and Single Drive Unit
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Solution Overview
Problem
Existing vehicles are limited by the turning circle of their steering systems, especially in off-road conditions, and current electric tank steer systems are expensive due to the need for multiple electric machines and components.
Innovation Solution
A vehicle system that enables tank steer operation by using a differential case grounded to an axle case and a gearbox assembly, with a single drive unit rotating half shafts in opposite directions through a planetary gear set and selective engagement of dog clutches, allowing tight turns without the need for multiple electric motors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If a tank steer system uses four electric machines, four power inverters, and associated high voltage cables to achieve tight turns, then the turning radius is improved, but the system cost and complexity increase significantly
Solution Approach 1:
The patent combines multiple drive functions into a single electric machine by using a differential mechanism. Instead of requiring four separate electric machines (one per wheel), the system uses one electric machine connected to a differential that distributes power to multiple wheels, some in opposite directions, achieving tank steer capability with reduced complexity
Solution Approach 2:
The differential mechanism serves multiple functions: it acts as a power distribution device, a direction control mechanism, and a tank steer actuator. By grounding the differential case and selectively connecting half shafts, the same differential structure enables both normal differential operation and tank steer mode, eliminating the need for separate steering motors
2Length of moving object
If a tank steer system uses four electric machines, four power inverters, and associated high voltage cables to achieve tight turns, then the turning radius is improved, but the system cost increases
Solution Approach 1:
The patent merges the functions of multiple expensive components (four electric machines, four power inverters, high voltage cables) into a single electric machine setup with a modified differential. This consolidation dramatically reduces component count, material costs, and manufacturing complexity while maintaining tank steer functionality
Solution Approach 2:
Instead of using separate electric machines for each wheel, the system uses a single electric machine that copies its output through the differential mechanism to multiple wheels. The differential acts as a mechanical copier, distributing the single motor's output to multiple drive points with different rotation directions when needed
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enables tight turns by rotating wheels in opposite directions, reducing the need for multiple electric motors and associated components, thus lowering costs and improving packaging efficiency.
Implementation Method 1
a differential having a differential case, first and second half shafts operably coupled to the differential... such that the drive unit rotates the first half shaft in the first direction and, via the differential, rotates the second half shaft in the opposite second direction
Implementation Method 2
a low ratio unit, wherein in the tank steer mode, the differential case is grounded by connecting the differential case to the low ratio unit; wherein the low ratio unit is a planetary gear set
Data Source
AI summary
A vehicle configured to perform a tank steer operation includes a differential having a differential case, first and second half shafts operably coupled to the differential, a drive unit configured to drive the vehicle, and a gearbox assembly coupled to the drive unit. The vehicle is selectively operable in a tank steer mode that rotates one or more wheels on a first side of the vehicle in a first direction, and rotates one or more wheels on an opposite second side of the vehicle in a second direction opposite the first direction to rotate the vehicle. The vehicle operates in the tank steer mode by selectively grounding the differential case and connecting an output of the gearbox assembly to the first half shaft, such that the drive unit rotates the first half shaft in the first direction and, via the differential, rotates the second half shaft in the second direction.