Hydrostatic Transmission for Continuous Ratio Control
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Solution Overview
Problem
Existing hydromechanical transmissions have limited gearing ratios, lack full control, cannot provide a reverse function, and require hydraulic boosting to start.
Innovation Solution
A variable ratio drive assembly with a brake gear, brake pump, and restriction means to selectively apply braking torque, along with motor/pump devices that drive ring gears, allowing for continuous variation of gear ratios and reverse operation by controlling hydraulic fluid flow and pressure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a standard planetary automatic transmission is used, then the structure is simple and easy to manufacture, but the gear ratios are limited and fuel efficiency is reduced
Solution Approach 1:
The patent replaces the traditional mechanical planetary gear system with a hydrostatic transmission system using variable displacement pumps and motors. This substitution enables continuous variable ratio control through hydraulic fluid flow management, eliminating the fixed gear ratio limitations of planetary transmissions while improving fuel efficiency through optimized power delivery across the entire operating range.
Solution Approach 2:
The patent employs variable displacement pumps and motors that can continuously adjust their displacement parameters. By varying the pump displacement and motor displacement ratios, the system achieves continuous variable transmission ratios without requiring multiple fixed gear sets, thereby improving fuel efficiency while maintaining a relatively simple overall structure.
2Productivity
If a continuously variable transmission with belt and pulley is used, then fuel efficiency improves, but the transmission lacks reverse function and full control capability
Solution Approach 1:
The patent designs the hydrostatic transmission system with bidirectional capability by configuring the variable displacement pump and motor to operate in both forward and reverse directions. The same hydraulic components that provide continuous variable ratio control for fuel efficiency also enable reverse function through controlled reversal of hydraulic fluid flow direction, eliminating the need for separate reverse gear mechanisms.
Solution Approach 2:
The patent uses hydraulic fluid flow direction control to achieve bidirectional operation. By reversing the flow direction of hydraulic fluid through the variable displacement pump and motor, the system can switch between forward and reverse motion while maintaining continuous variable ratio control, thus providing both fuel efficiency and reverse functionality through hydraulic means.
3Force
If hydraulic boosting is used to start the transmission, then the transmission can overcome initial resistance, but the system complexity increases and efficiency is reduced
Solution Approach 1:
The patent employs a variable displacement pump that can dynamically adjust its displacement based on operating conditions. At startup, the pump displacement is maximized to generate high starting torque without requiring hydraulic boosting components. As the system accelerates, the displacement is reduced to maintain optimal efficiency, providing dynamic adaptability that eliminates the need for separate boosting mechanisms while maintaining low system complexity.
Solution Approach 2:
The patent uses variable displacement technology to change the pump's operational parameters in real-time. By adjusting the pump displacement from maximum at startup to lower values during operation, the system generates sufficient starting torque without hydraulic boosting while maintaining efficiency across the operating range, thereby avoiding the added complexity of boosting systems.
4Power
If a hydromechanical transmission with planetary gear set and clutches is used, then power transmission capability improves, but the number of components increases and control becomes less full
Solution Approach 1:
The patent replaces the complex mechanical combination of planetary gear sets and clutches with a pure hydrostatic transmission system using variable displacement pumps and motors. This substitution maintains high power transmission capability through hydraulic fluid power while significantly reducing the number of mechanical components and enabling more complete electronic control without the constraints of mechanical gear engagement and disengagement.
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 continuous variation of gear ratios and reverse functionality without hydraulic boosting, improving control and efficiency by using motor/pump devices to manage hydraulic fluid flow and pressure.
Implementation Method 1
a brake pump driven by said brake gear so that the brake pump produces hydraulic fluid under pressure
Implementation Method 2
each said pump device is a motor/pump device that upon receiving hydraulic fluid under pressure acts as a motor to drive a respective one of the ring gears
Implementation Method 3
second restriction means operatively associated with the brake pump to receive hydraulic fluid under pressure therefrom, the second restriction means being operable to restrict the flow of hydraulic fluid produced by said brake pump to thereby selectively apply a braking torque
Data Source
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AI summary
A variable ratio drive assembly (10) including: a planetary gear device (13) having an input shaft (15), an output shaft (17), with the shafts having a common rotational axis (21 ), an input gear (16) attached to the input shaft, an output gear (18) attached to the output shaft, a carriage (20) mounted for rotation about said axis, at least one planetary gear (19) meshed with the input gear and output gear, the planetary gear being rotatably mounted in the carriage, a ring gear (23) fixed to the carriage so as to be rotated about said axis, a pump gear (24) meshingly engaged with the ring gear, a pump device (51) drivingly connected to the pump gear and restriction means to control the flow so that said pump device (51 ) applies a torque to said pump gear to control rotation of said ring gear and therefore rotation of said output shaft.