Gear Pump Suction Passage Asymmetry for Efficiency
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Solution Overview
Problem
Hydraulic gear pumps face challenges in increasing capacity without compromising pump volumetric efficiency due to interference between large suction passage openings and sealing areas, leading to either inadequate sealing or cavitation issues.
Innovation Solution
The design of the suction passage with a larger opening dimension along the tooth width and a smaller opening dimension perpendicular to the tooth width, maintaining a constant cross-sectional area, ensures adequate sealing while increasing the suction passage area, preventing volumetric efficiency deterioration and cavitation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the suction passage is enlarged to increase pump capacity, then the flow rate of hydraulic oil is increased, but the opening of the suction passage interferes with the sealing area, causing volumetric efficiency to deteriorate
Solution Approach 1:
The suction passage opening is designed with an asymmetric rectangular cross-section where the dimension in the tooth width direction (a1) is larger than the dimension perpendicular to it (a2). This asymmetric configuration allows the opening area to be increased for higher pump capacity while the smaller dimension perpendicular to the tooth width ensures the opening does not interfere with the sealing area, thus maintaining volumetric efficiency.
Solution Approach 2:
Instead of increasing the suction passage opening area by uniformly enlarging a circular opening, the invention transitions to a rectangular opening with different dimensions in two perpendicular directions. By making the opening dimension in the tooth width direction larger while keeping the perpendicular dimension smaller, the passage area increases for higher capacity without encroaching on the sealing area, resolving the contradiction between productivity and reliability.
2Productivity
If the suction passage opening area is increased to increase pump capacity, then the flow rate is improved, but the sealing area is reduced, leading to hydraulic oil leakage
Solution Approach 1:
The rectangular opening of the suction passage has asymmetric dimensions where a1 (dimension along tooth width) > a2 (dimension perpendicular to tooth width). This asymmetry enables the opening area (a1 × a2) to be sufficiently large for high flow rate while the smaller a2 dimension ensures the opening remains distant from the sealing area, preventing hydraulic oil leakage and maintaining effective sealing.
Solution Approach 2:
The invention changes from a circular opening to a rectangular opening with differentiated dimensions in two perpendicular directions. By allocating more dimension along the tooth width direction and less dimension perpendicular to it, the passage achieves large area for high flow rate while preserving the sealing area, thus resolving the contradiction between productivity and the area of stationary object.
3Reliability
If the suction passage opening is kept small to maintain sealing area, then volumetric efficiency is maintained, but the flow velocity increases causing cavitation
Solution Approach 1:
The asymmetric rectangular opening with a1 > a2 allows the passage area to be increased without proportionally increasing the velocity in a way that causes cavitation. The larger dimension a1 along the tooth width provides sufficient flow area to maintain acceptable flow velocity, while the smaller dimension a2 keeps the opening away from the sealing area, thus maintaining volumetric efficiency and preventing cavitation simultaneously.
Solution Approach 2:
By transitioning to a rectangular opening with differentiated dimensions, the invention increases the flow area along the tooth width direction (a1) to reduce flow velocity and prevent cavitation, while keeping the perpendicular dimension (a2) small to maintain sealing effectiveness and volumetric efficiency. This dimensional differentiation resolves the contradiction between reliability and harmful factors.
Data Source
AI summary
A gear pump is capable of maintaining the pump volumetric efficiency for preferably supplying a hydraulic liquid while adequately securing a sealing area, even if a cross sectional area of a flow-in passage is increased. The cross section of a suction passage has a rectangular shape in a side close to a hollow space in a body, and has a circular shape in the outside of the body. The rectangular shape of the suction passage in the hollow space side in the body has a long side extending in a direction along the tooth width of the spur gears, and a short side extending along a direction perpendicular to the tooth width direction. The suction passage has a shape that smoothly connects the rectangular shape in the hollow space side in the body with the circular shape in the outside of the body.