External Gear Pump Pressure-Zone Lubrication for Bushing Loads
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Solution Overview
Problem
External gear pumps face challenges in maintaining a high tolerance against loads acting on rotational shafts and bushings due to insufficient lubrication, leading to potential galling and reduced performance.
Innovation Solution
The design incorporates a pair of gears with a pump body featuring a gear accommodation chamber, hollow cylindrical bushings, and a segmented pressure range along the inner circumference to efficiently supply high-pressure lubricating oil to the sliding surfaces, utilizing recesses, bushing-side and body-side supply passages, and coil springs to maintain a stable lubricating oil film.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If high pressure lubricating oil is supplied to the sliding surfaces, then the tolerance against load acting on the rotational shafts and bushings can be made large, but the structure becomes more complex due to the need for supply passages and pressure control mechanisms
Solution Approach 1:
The gear accommodation chamber is divided into a low pressure range and a high pressure range along the inner circumference. The recess is positioned in the low pressure range while the supply passage inlet is in the high pressure range, creating segmented pressure zones that enable targeted lubrication without complex external control systems
Solution Approach 2:
The system uses the pump's own discharged high pressure fluid to supply lubrication to the bushings, eliminating the need for separate lubrication pumps or external high pressure sources. The fluid serves dual purposes: pumping function and lubrication function
2Reliability
If the recess is opened on the inner circumferential surface within the low pressure range, then lubricating oil can be supplied to the sliding surfaces, but the pressure distribution becomes more complex to control
Solution Approach 1:
Different pressure ranges are assigned to different circumferential positions of the gear accommodation chamber. The recess is specifically positioned in the low pressure range to receive lubrication, while the supply passage inlet is in the high pressure range, creating localized quality differences that enable reliable lubrication
Solution Approach 2:
The pressure control is achieved by utilizing the circumferential dimension of the gear accommodation chamber rather than adding complex axial or radial control mechanisms. The low pressure range and high pressure range are segmented along the inner circumference, transforming a potential 3D pressure control problem into a 1D circumferential segmentation solution
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 configuration enhances the tolerance against loads on the rotational shafts and bushings, ensuring stable lubrication and preventing galling, even under high loads, by maintaining a consistent high-pressure lubricating oil supply and optimizing pressure distribution within the gear pump.
Implementation Method 1
Lubricating fluid 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
Data Source
AI summary
In an external gear pump, a first bushing of a rotational shaft of a first gear has a second surface facing to a first surface of a pump body. A recess for supplying high-pressure lubricating oil between an inner circumferential surface of the first bushing and an outer circumferential surface of the rotational shaft is opened on the inner circumferential surface within a low pressure range associating with an inlet chamber of fluid. A bushing-side supply passage for supplying the high-pressure lubricating oil to the recess is formed within the first bushing. A bushing-side inlet port of the bushing-side supply passage is opened on the second surface within a high pressure range associating with an outlet chamber of the fluid. 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.