Work Vehicle Drivetrain Variator Assembly
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Solution Overview
Problem
Conventional dual output work vehicle drivetrains rely on large hydrostatic drives, which are inefficient, costly, and bulky, and provide only stepped speed selection, limiting efficiency and flexibility in powering shaft-powered implements and ground wheels.
Innovation Solution
A dual output work vehicle drivetrain incorporating a variator assembly with a variator motor and gearbox, including a planetary gear system, that allows for independent speed control of shaft-powered implements and ground wheels, enabling non-stepped or infinitely variable power output by summing power from the variator motor and prime mover, and compensating for stepped gear ratio settings.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If large hydrostatic drives are used to power shaft-powered implements and ground wheels, then power delivery capability is improved, but device size and weight increase, and energy efficiency deteriorates
Solution Approach 1:
The drivetrain is segmented into two independent power paths: a primary power path for ground wheel propulsion and an auxiliary power path for shaft-powered implements. This segmentation allows each path to be optimized independently, eliminating the need for a large hydrostatic drive that must accommodate both power demands simultaneously, thereby improving energy efficiency while maintaining adequate power delivery capability.
Solution Approach 2:
The primary power path serves dual functions by providing power to both the ground wheels for vehicle propulsion and to the auxiliary PTO shaft for powering implements. This multi-functionality eliminates the need for separate large hydrostatic drives for each function, reducing overall system size and improving energy efficiency.
2Power
If large hydrostatic drives are used to provide power delivery, then power capability is improved, but device complexity and cost increase
Solution Approach 1:
The drivetrain is divided into a simple primary power path using conventional mechanical components and an auxiliary power path using a compact variator assembly. This segmentation replaces the complex large hydrostatic drive with simpler, more cost-effective components while maintaining the required power capability.
Solution Approach 2:
The auxiliary power path uses a variator assembly with a planetary gear system to provide infinitely variable speed control, replacing the need for complex hydrostatic control systems. This substitution reduces device complexity and cost while maintaining power capability.
3Power
If conventional hydrostatic drives are used, then power delivery is achieved, but speed selection is limited to stepped values, reducing adaptability
Solution Approach 1:
The variator assembly incorporates a planetary gear system with a variable ratio mechanism that allows continuous adjustment of the gear ratio, enabling infinitely variable speed selection rather than fixed stepped values. This dynamic adjustment capability significantly improves adaptability while maintaining power delivery capability.
Solution Approach 2:
The drivetrain system allows continuous variation of the gear ratio parameter in the auxiliary power path, enabling smooth speed transitions and infinite speed selection. This parameter change capability provides superior adaptability compared to fixed stepped speed selection in conventional hydrostatic drives.
4Volume of moving object
If the planetary gear system uses an offset planetary axis, then compact gearbox design is achieved, but mechanical complexity increases
Solution Approach 1:
The planetary gear system uses an offset planetary axis that is parallel to but offset from the primary power path axis, creating a three-dimensional power flow path. This dimensional arrangement allows for a more compact gearbox design by utilizing spatial relationships rather than simple linear arrangements, while the modular design keeps mechanical complexity manageable.
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
This configuration reduces the size and power requirements of the variator motor, improves overall drivetrain efficiency, and allows for constant engine speed over a wide range of ground speeds, providing efficient and flexible power delivery to both implements and ground wheels.
Implementation Method 1
The planetary gear system includes a ring gear, a sun gear, a set of planet gears, and a carrier
Data Source
AI summary
High efficiency work vehicle drivetrains containing variator assemblies are provided. In one embodiment, the work vehicle drivetrain includes an engine, a variator assembly, and an auxiliary power takeoff (PTO) shaft, which is coupled to the engine and rotatable about a primary power path axis when driven by the engine. The variator assembly includes, in turn, a variator motor and a variator gearbox. The variator gearbox contains a planetary gear system, which is coupled to the variator motor and to the auxiliary PTO shaft. The planetary gear system is rotatable about a planetary axis substantially parallel and offset from the primary power path axis.