Hydrostatic Transmission Cooling Passages for Lower Parasitic Loss
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Solution Overview
Problem
Hydrostatic transmission systems in work machines face high parasitic losses due to the need for high flushing flow to cool components, which increases power consumption and requires external hoses and lines, leading to inefficiencies and potential leakage.
Innovation Solution
A closed case hydrostatic transmission system with integrated fluid passageways within the gearbox and variator case, utilizing a separate low-pressure fluid source for lubrication and cooling of shaft bearings, reducing the need for external hoses and lowering the pressure requirement for flushing fluid.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a high flushing flow is used to cool transmission components, then cooling effectiveness is improved, but parasitic losses and power consumption increase
Solution Approach 1:
The patent divides the fluid supply system into two separate circuits: a high-pressure charge pump circuit for lubrication and a low-pressure feed pump circuit for cooling. This segmentation allows each circuit to operate at its optimal pressure level, reducing the energy required for cooling while maintaining effective heat removal from transmission components.
Solution Approach 2:
The patent changes the pressure parameter for the cooling circuit by introducing a separate low-pressure feed pump (e.g., 10-50 bar) distinct from the high-pressure charge pump (e.g., 200-500 bar). This parameter change enables cooling flow to be supplied at lower pressure, significantly reducing parasitic losses while maintaining adequate cooling effectiveness through integrated fluid passages.
2Ease of manufacture
If external hoses and lines are used for lubrication, then ease of assembly is improved, but system complexity and leakage risk increase
Solution Approach 1:
The patent merges the lubrication and cooling fluid passages into a single integrated housing structure. The housing contains both high-pressure charge passages and low-pressure feed passages as integral features, eliminating the need for external hoses and connections. This integration reduces the number of components and potential leakage points while maintaining manufacturing feasibility through modular housing design.
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 solution reduces parasitic losses by minimizing the volume of pressurized charge fluid required, maintaining effective cooling and lubrication of components without external hoses, thus enhancing efficiency and reducing manufacturing complexity and costs.
Implementation Method 1
The feed passage may be configured to conduct fluid at a first pressure from a first source to the set of rotating elements
Implementation Method 2
The charge passage may be configured to conduct fluid at a second pressure from a second source to the set of rotating elements
Implementation Method 3
when a hydrostatic transmission is operated under heavy loads for an extended period of time, for example, the circulating fluid may become heated to an extent that may be undesirable
Data Source
AI summary
A system including a gearbox and a hydraulic machine connected by a working fluid circuit. The gearbox including a gearbox housing having first and second gearbox fluid passages integrated into the gearbox housing. The hydraulic machine including a case having first and second hydraulic machine fluid passages, the first and second hydraulic machine fluid passages being integrated into the case. A set of rotating elements enclosed within the case. The first gearbox fluid passage and the first hydraulic machine fluid passage align to form a feed passage to conduct fluid at a first pressure from a first source to the set of rotating elements. The second gearbox fluid passage and the second hydraulic machine fluid passage align to form a charge passage to conduct fluid at a second pressure from a second source to the set of rotating elements. The first pressure being less than the second pressure.