Integrated Hydrostatic Transmission for Valve-Free Flow Control
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Solution Overview
Problem
Conventional hydrostatic transmission systems are complex, prone to damage, and unreliable due to the use of multiple components that are susceptible to degradation in harsh environments, leading to increased machine downtime and reduced reliability.
Innovation Solution
A compact and reliable hydrostatic transmission design featuring a closed-loop system with a hydraulic motor, storage device, and pump assembly integrated within a transmission casing, using a variable-speed and/or variable-torque pump to control fluid flow and pressure without additional flow control devices, ensuring precise control and reduced risk of cavitation and high fluid temperatures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If multiple components (connecting shafts, hoses, pipes, fittings) are used to interconnect the prime mover, pump, motor, and reservoir, then the system can be assembled with spaced-apart components, but the system becomes complex and susceptible to damage or degradation in harsh environments
Solution Approach 1:
The patent integrates the prime mover, pump, motor, and reservoir into a single integrated assembly, eliminating the need for multiple external connecting components such as shafts, hoses, pipes, and fittings. This merging of previously separate components into one unified structure directly reduces the number of potential failure points while maintaining all necessary functional connections, thereby resolving the contradiction between assembly flexibility and system reliability.
2Productivity
If the electric motor and hydraulic pump are run at high speed to control fluid flow, then the flow control is effective, but temperature builds up in the hydraulic fluid
Solution Approach 1:
The patent introduces a heat exchanger as an intermediary component within the integrated assembly to manage thermal energy. This heat exchanger actively removes excess heat from the hydraulic fluid during high-speed operation, allowing the system to maintain effective flow control at high speeds while preventing dangerous temperature buildup that would otherwise occur.
3Temperature
If a reservoir acts to keep the average fluid temperature down by increasing the fluid volume, then thermal management is improved, but the system becomes larger and more complex
Solution Approach 1:
The patent combines the reservoir function with the existing hydraulic circuit components within the integrated assembly, eliminating the need for a separate, large-volume reservoir. The integrated design uses the fluid volume already present in the pump and motor housings and circulation system to provide thermal mass, thereby achieving temperature management without increasing overall system size or complexity.
4Ease of operation
If conventional hydraulic systems use directional flow control valves to control motor speed and direction, then flow control is achieved, but the system becomes more complex and components are more susceptible to damage
Solution Approach 1:
The patent removes directional flow control valves from the system entirely, extracting this control function and replacing it with a variable displacement pump that can directly control fluid flow direction and magnitude. This elimination of separate control valves simplifies the system architecture, reduces the number of components susceptible to damage, while maintaining full flow control capability through the pump's variable displacement mechanism.
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 integrated design enhances reliability and reduces downtime by providing precise control of fluid flow and pressure, while minimizing the risk of component damage and improving thermal stability, resulting in a more efficient and durable hydrostatic transmission system.
Implementation Method 1
Hydrostatic transmissions use a fluid such as hydraulic fluid to transmit power from a power source, e.g. an engine or an electric motor, to a driven mechanism
Implementation Method 2
The storage device stores or releases pressurized fluid into the system as required
Data Source
AI summary
A hydrostatic transmission system includes a fluid-driven motor and an integrated pump assembly connected to the fluid-driven motor to provide fluid to operate the fluid-driven motor. The integrated pump assembly includes a pump with at least one fluid driver comprising a prime mover and a fluid displacement assembly to be driven by the prime mover such that fluid is transferred from a first port of the pump to a second port of the pump. The pump assembly also includes two valve assembles to isolate the pump from the system. The hydrostatic transmission system also includes a controller that establishes at least one of a speed and a torque of the at least one prime mover to exclusively adjust at least one of a flow and a pressure in the hydrostatic transmission system to an operational set point.