External Gear Pump Bushing Lubrication Using Outlet Pressure
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Solution Overview
Problem
Existing external gear pumps face challenges in stably supplying high-pressure lubricating oil to the sliding surfaces of bushings, which affects the tolerance against loads acting on the rotational shafts and bushings.
Innovation Solution
The external gear pump design includes a pair of gears, a pump body with segmented pressure ranges, bushings with recesses for lubricating oil supply, and supply passages connecting high-pressure outlets to the bushings, ensuring stable high-pressure lubrication.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If lubricating oil is supplied from the inlet chamber side, then the structure is simple, but the lubricating oil pressure is insufficient to support heavy loads on the rotational shafts and bushings
Solution Approach 1:
The invention applies different pressure conditions to different locations of the bushing. The rear surface of the bushing (facing the outlet chamber) receives high-pressure lubricating oil, while the front surface (facing the inlet chamber) receives lower pressure oil. This local differentiation of pressure quality enables the bushing to withstand higher loads without requiring a complete redesign of the lubrication system.
2Strength
If high-pressure lubricating oil is supplied to the bushing rear surface, then the load tolerance increases, but additional supply passages and pressure control mechanisms are required
Solution Approach 1:
The outlet chamber serves multiple functions: it acts as the high-pressure fluid discharge chamber for the pump and simultaneously serves as the pressure source for lubricating the bushing rear surface. The lubricating oil is taken from the outlet chamber and supplied through the bushing passage, eliminating the need for a separate high-pressure lubrication system.
Solution Approach 2:
The system uses its own outlet chamber pressure to provide lubrication for the bushing, rather than requiring an external lubrication system. The high-pressure lubricating oil is directly tapped from the outlet chamber and delivered to where it is needed, making the system self-sufficient.
3Manufacturing precision
If the bushing is fixed rigidly, then the positioning is precise, but the lubricating oil film cannot distribute pressure evenly under varying load conditions
Solution Approach 1:
The bushing is designed to be movable in the axial direction rather than rigidly fixed. This allows the bushing to dynamically adjust its position in response to varying load conditions, enabling the lubricating oil film to distribute pressure evenly. The rotational shaft can press the bushing against the pump body to maintain precise positioning while allowing axial movement for pressure distribution.
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 design enhances the tolerance against loads on the rotational shafts and bushings by maintaining stable high-pressure lubrication, preventing oil shortage, and ensuring efficient pressure distribution within the lubricating oil film.
Implementation Method 1
Lubricating oil is supplied between the outer circumferential surfaces of the rotational shafts and the inner circumferential surfaces of the bushings (sliding surfaces) to reduce a load acting on the rotational shafts
Implementation Method 2
The pressure of the fluid in the outlet chamber is higher than the pressure of the fluid in the inlet chamber due to flow resistance on a side of the outlet chamber and so on. Thus, the external gear pump raises the pressure of the fluid
Data Source
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AI summary
In an external gear pump, a first bushing (F11) that holds a rotational shaft of a first gear has a second surface (P2) that faces to a first surface of a pump body and is perpendicular to the rotational shaft. A recess (105) for supplying high pressure lubricating oil between an inner circumferential surface (100) of the first bushing (F11) and an outer circumferential surface of the rotational shaft is opened on the inner circumferential surface (100) within a low pressure range associating with an inlet chamber of fluid (a low pressure depressed portion 101). A bushing-side supply passage (106) for supplying the high pressure lubricating oil to the recess (105) is formed within the first bushing (F11). A bushing-side inlet port (106a) of the bushing-side supply passage (106) is opened on the second surface (P2) within a high pressure range associating with an outlet chamber of the fluid (a high pressure depressed portion 102a). A body-side supply passage for supplying the high pressure lubricating oil to a body-side supply port opened on the first surface is formed within the pump body.