Hydro-Mechanical Transmission Capacity Switching for Wider Speed Range
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Solution Overview
Problem
Conventional hydro-mechanical transmission (HMT) systems with hydrostatic transmission (HST) and planetary gear mechanisms struggle to cover the range of required maximum towing force and vehicle traveling speed effectively, necessitating multiple speed-change stages which increases complexity and cost.
Innovation Solution
A transmission structure with an HST and planetary gear mechanism that includes a pump shaft, pump body, motor shaft, and motor body with adjustable capacities, along with sensors and a control device to optimize the speed of the HMT output by varying the capacities of the pump and motor bodies, allowing for expanded speed-changeable ranges without rapid speed changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the capacity of only the pump body is varied to change HST output rotation speed, then the HST can be simplified in structure, but the speed-changeable range of the HMT output is insufficient to cover the required maximum towing force and vehicle traveling speed
Solution Approach 1:
The patent applies parameter changes by varying the capacity of the motor body in addition to the pump body. Specifically, the motor body capacity is changed between a first capacity (when vehicle traveling speed is low) and a second capacity (when vehicle traveling speed is high), while the pump body capacity is simultaneously adjusted. This dual parameter change expands the speed-changeable range of the HMT output to cover both the required maximum towing force and vehicle traveling speed, resolving the contradiction between simplified structure and adequate speed range.
2Adaptability or versatility
If multiple speed-change stages are added to cover the required maximum towing force and vehicle traveling speed, then the speed-changeable range is expanded, but the device complexity and cost increase
Solution Approach 1:
The patent applies universality by making the HST itself multi-functional. The HST is configured to perform both capacity variation of the pump body and capacity variation of the motor body, allowing it to cover a wide speed-changeable range without requiring a separate auxiliary speed-change mechanism. This integrates the speed-changing function into the existing HST structure, expanding the adaptability while avoiding additional complexity from separate mechanisms.
3Adaptability or versatility
If the motor body capacity is varied between low-speed and high-speed capacities, then the speed-changeable range is expanded, but the control system complexity increases
Solution Approach 1:
The patent applies feedback by using a vehicle traveling speed sensor to detect the current traveling speed and a control device to compare it with a switching speed. Based on this feedback, the control device automatically determines whether to switch the motor body capacity between the first and second capacities, and simultaneously adjusts the pump body capacity. This feedback-based automatic control expands the speed-changeable range while managing control system complexity through intelligent decision-making rather than complex mechanical linkages.
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
The solution enables the transmission structure to cover the required maximum towing force and vehicle traveling speed with fewer speed-change stages, reducing complexity and cost while maintaining efficient operation.
Implementation Method 1
a hydrostatic transmission (HST) and a planetary gear mechanism (30) that form a hydro-mechanical transmission (HMT)
Data Source
AI summary
A transmission structure of the present invention changes capacity of pump body so that vehicle speed detected by vehicle speed sensor increases and reduces according to speed-increasing and speed-reducing operations of speed-change operating member while fixing capacity of motor body at a low-speed motor capacity when the vehicle speed is equal to or lower than a switching speed that is realized by setting motor body to the low-speed motor capacity and setting the pump body to a predetermined pump switching capacity, and changes capacity of motor body so that vehicle speed increases and reduces in accordance with speed-increasing and speed-reducing operations of speed-change operating member while fixing capacity of the pump body at the pump switching capacity when vehicle speed is higher than the switching speed.