Gerotor Pump Inclined Lubricating Surface
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Solution Overview
Problem
Gerotor pumps used in the automotive sector for delivering low-viscosity motor oils face issues with high drive torque and efficiency loss due to wear and friction, especially when operating with low-viscosity media at high pressures, leading to reduced reliability and service life.
Innovation Solution
The design incorporates a sleeve-guided rotor with inclined lubricating surfaces on the end wall of the rotor, which helps in building a hydrodynamically load-bearing lubricating film even at low sliding speeds, and a ceramic bearing sleeve with low peak-to-valley height to reduce friction and wear, along with a pump housing made of cast aluminum for enhanced rigidity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a sleeve-guided rotor is used to reduce friction and wear, then reliability and service life are improved, but at low sliding speeds with low-viscosity media, a lubricating film cannot build up, leading to mixed friction state and increased drive torque
Solution Approach 1:
The invention changes the geometric parameters of the rotor end wall by introducing an inclined lubricating surface instead of a flat surface. This inclination angle parameter enables the low-viscosity medium to generate sufficient pressure to build a lubricating film even at low sliding speeds, transitioning the friction state from mixed friction to hydrodynamic lubrication, thereby reducing drive torque while maintaining reliability
Solution Approach 2:
The invention applies local quality by creating a specific inclined lubricating surface only on the rotor end wall where contact with the side wall occurs. This localized modification with different geometric properties (inclination angle) enables hydrodynamic film formation at the critical contact zone without affecting other parts of the rotor, solving the low-speed lubrication problem while maintaining overall rotor functionality
2Reliability
If hard and corrosion-resistant materials like ceramic or hard metal are used for functional components, then wear resistance is improved, but manufacturing cost increases significantly
Solution Approach 1:
The invention changes the operational parameters by introducing an inclined surface geometry that enables hydrodynamic lubrication. This parameter change reduces the sliding velocity and contact pressure at the rotor-end wall interface, creating favorable tribological conditions that allow the use of cost-effective materials like cast aluminum housing and standard rotor materials while achieving wear resistance comparable to or better than ceramic or hard metal solutions
3Reliability
If the rotor is pressed against the end wall to reduce leakage gap, then sealing performance is improved, but frictional forces and drive torque increase excessively
Solution Approach 1:
The invention changes the geometric parameter of the rotor end wall by introducing an inclination angle to create a lubricating surface. This parameter change enables the formation of a hydrodynamic pressure film that simultaneously achieves two functions: maintaining adequate sealing to prevent leakage and reducing contact pressure to minimize frictional forces, thereby resolving the contradiction between sealing performance and drive torque
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 significantly reduces drive torque and maintains high efficiency and reliability, with no detectable wear even after extended testing, ensuring a long service life and cost-effective production.
Implementation Method 1
on/in the end wall (5) of the rotor (1) adjacent to the pressure chamber (8) and the end wall (5) adjacent to the suction chamber (9) via each tooth (10) of the rotor (1) a lubricating surface (11) that is inclined relative to the surface plane of the end wall (5) of the rotor (1) in the direction of rotation (R) of the rotor (1)
Implementation Method 2
a ceramic bearing sleeve (4) with low peak-to-valley height
Data Source
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AI summary
The invention relates to a gerotor pump for rotors with tooth tip diameters of from approximately 20 to approximately 40 mm which operate at delivery pressures in the range from 3 to 20 bar and are used to deliver barely lubricating media, such as, for example, an oil pump in the automotive sector for delivering engine oils of low viscosity. The invention is based on the problem of developing a gerotor pump with a sleeve-guided rotor, which gerotor pump, if low-viscosity delivery media are used, such as "thin low-viscosity oil", in conjunction with the use in relatively small pump systems, the rotors of which have tooth tip diameters of from approximately 20 to approximately 40 mm and the delivery pressures of which lie in the range from 3 to 20 bar, and which considerably reduce the disproportionate rise in the drive torque with a simultaneous loss of the degree of efficiency at low rotational speeds in the range from 500 to 1000 rpm and high delivery pressures. The gerotor pump according to the invention, with side walls (6) which are arranged on both sides of the end walls (5) of the gear wheels which mesh with one another, wherein in each case one circularly arcuate pressure kidney (8) and, lying opposite, a circularly arcuate suction kidney (9) are arranged in at least one of said side walls (6), is characterized in that in each case one lubricating surface (11) which either begins in the tooth centre plane (M) or begins "offset" in the rotational direction (R) of the rotor (1) in front of the tooth centre plane (M) and is inclined in the rotational direction (R) of the rotor (1) with respect to the surface plane of the end wall (5) of the rotor (1) is arranged at each tooth (10) over the tooth height (H) thereof on that end wall (5) of the rotor (1) which is adjacent to the pressure kidney (8) and the suction kidney (9), which lubricating surface (11) is formed from a planar surface or a plurality of planar part surfaces which adjoin one another and in each case enclose an angle of inclination (α, β, γ…) which lies in each case in the range from 0.2° to 7° with respect to the surface plane of the end wall (5) of the rotor (1).