Internal Gear Pump Groove Design for Oil Film Stability
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Internal gear pumps face instability in the outer rotor due to oil whirl caused by thin oil films and suffer from discharge performance deterioration due to fluid leakage into grooves designed to increase film thickness and stabilize the rotor.
Innovation Solution
The internal gear pump design includes a housing with a pump chamber, inner and outer rotors, suction and discharge ports, and a unique inner wall configuration with a groove in the suction region to enlarge clearance between the outer rotor and inner wall, preventing fluid leakage in the discharge region and maintaining a stable oil film thickness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If a groove is formed at the inner wall at a location close to the discharge port to negate the force applied to the outer rotor, then the force on the outer rotor is reduced, but the rotational axis of the outer rotor becomes unstable and oil whirl occurs
Solution Approach 1:
The inner wall is divided into multiple regions: discharge region, first suction region, and second suction region. The groove is selectively formed only in the first suction region, while the discharge region and second suction region maintain direct contact between the outer rotor and inner wall. This segmentation allows the groove to reduce force in the suction region while preserving stability in the discharge region.
Solution Approach 2:
Different regions of the inner wall are given different properties: the first suction region has a groove to reduce pressing force and allow rotor movement, while the discharge region and second suction region have no groove to maintain stable contact and prevent oil whirl. This local differentiation resolves the contradiction by applying the groove only where force reduction is needed without compromising overall stability.
2Reliability
If a groove is widely formed on the inner wall at the location extending along the suction port to increase oil film thickness, then the outer rotor is protected from seizure, but discharge fluid leaks into the groove and discharge performance deteriorates
Solution Approach 1:
The suction region is divided into two parts: the first suction region where the groove is formed to protect from seizure, and the second suction region where no groove exists to prevent discharge fluid leakage. This segmentation allows the groove to be limited to a specific area, maintaining both protection from seizure and discharge performance.
Solution Approach 2:
The groove is formed locally only in the first suction region rather than widely across the entire suction port area. This localized groove provides sufficient oil film thickness for protection while limiting the groove's extent to prevent discharge fluid from leaking into it, thus maintaining discharge performance.
3Shape
If the groove is formed to enlarge clearance between outer rotor and inner wall, then oil film thickness is increased, but fluid leakage into the groove deteriorates discharge performance
Solution Approach 1:
The inner wall is segmented into regions with and without grooves. The groove is formed only in the first suction region to enlarge clearance and increase oil film thickness where needed, while the discharge region and second suction region maintain smaller clearance to prevent fluid leakage and preserve discharge performance.
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 stabilizes the outer rotor's behavior, prevents oil whirl, and maintains discharge performance by ensuring a consistent oil film thickness and preventing fluid leakage, thus enhancing the pump's operational stability and efficiency.
Implementation Method 1
the groove that enlarges a clearance between the outer rotor and the inner wall is provided at least at a portion of the first suction region
Implementation Method 2
a suction port that is in communication with the pump chamber and supplies a fluid thereto, a discharge port that is in communication with the pump chamber and discharges the fluid therefrom
Data Source
AI summary
An internal gear pump includes a housing having a pump chamber in which an inner rotor and an outer rotor are arranged. A suction port in communication with a suction path and a discharge port in communication with a discharge path are formed at the housing. The pump chamber includes an inner wall having a suction region at a suction port-side and a discharge region at a discharge port-side. The suction region includes a first suction region extending towards the suction path from a pressing point, where the outer rotor is pressed when the internal gear pump is in operation, and a second suction region between the first suction region and the discharge region. A groove that enlarges a clearance between the outer rotor and the inner wall is formed in the first suction region, but the groove is not formed in the second suction region.