Planetary CVT Torque Boost With Power Absorption Control
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Solution Overview
Problem
Existing speed-changing devices for vehicles like wheel loaders face challenges in providing sufficient torque output while maintaining a compact and inexpensive design, particularly when operating at low vehicle speeds, due to limitations in the maximum output torque of the second stepless adjustment unit.
Innovation Solution
The speed-changing device incorporates a planetary mechanism with a first and second variator, a power absorption device, and a controller to manage rotation speeds, allowing the second variator to absorb excess power and increase torque output, even when compact and inexpensive.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If the second stepless adjustment unit is sized to have large maximum output torque, then sufficient output torque can be secured, but the device becomes expensive and large in size
Solution Approach 1:
The power transmission path is segmented into two separate variators (first and second variators) with different torque capacities. The first variator handles high torque during low-speed operations, while the second variator handles normal torque during high-speed operations. This segmentation allows each variator to be optimized for its specific torque range, enabling the use of a smaller, more economical second variator while maintaining sufficient overall output torque through the planetary mechanism's torque multiplication.
2Device complexity
If a compact and inexpensive second variator is used, then cost and size are reduced, but sufficient output torque cannot be secured
Solution Approach 1:
The planetary mechanism performs preliminary torque multiplication before power reaches the second variator. By positioning the planetary mechanism between the engine and the second variator, the system pre-amplifies the torque so that a smaller second variator can still deliver sufficient output torque during low-speed high-torque operations. The controller manages the engagement of the first and second variators to ensure optimal torque delivery across different operating conditions.
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 enables the device to deliver sufficient torque for excavating operations while maintaining a compact and cost-effective design, enhancing traction force and operational efficiency.
Implementation Method 1
a planetary mechanism configured to include a carrier, a first sun member rotating about a rotation center axis of the carrier, and a second sun member rotating about the rotating center axis of the carrier
Implementation Method 2
a power absorption device disposed between the second variator and the first variator to absorb power
Data Source
AI summary
A speed-changing device (21) is provided with an input shaft (22), an output shaft (23), a planetary gear mechanism (29), a first variator (33), a second variator (34), and a controller (25). The second variator (34) transmits power, which is transmitted from the first variator (33), to the output shaft (23). A power absorption device (38) is disposed between the second variator (34) and the first variator (33). When the controller (25) changes the absorption torque of the first variator (33) to generate an amount of power equal to or greater than that which can be absorbed in the second variator (34), the power is absorbed by the power absorption device (38) to increase the torque of the output shaft (23).