Internal Gear Pump Rotor Design for Reduced Pulsation
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Solution Overview
Problem
Internal gear pumps face challenges in increasing the number of teeth while maintaining a constant outer diameter and theoretical discharge amount, leading to increased discharge pulsation and larger rotor diameters, which are undesirable in vehicle applications.
Innovation Solution
A pump rotor configuration with an inner rotor having N teeth and an outer rotor with N+1 teeth, arranged eccentrically, where the working position of the rotors is always rearward of the eccentric axis, with a maximum working pitch diameter satisfying the expression φD max < 1.7e ⋅ sin(π/180) / sin(N ⋅ π/180), allowing for increased teeth without increasing the outer diameter or reducing discharge.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the number of teeth in the rotor is increased to reduce discharge pulsation, then the discharge pulsation decreases, but the working pitch diameter becomes larger, resulting in an increased outer diameter of the rotor
Solution Approach 1:
The patent changes the working position parameter from forward of the eccentric axis to rearward of the eccentric axis. This parameter change allows the working pitch diameter to be controlled within a specific range, enabling increased tooth count for reduced discharge pulsation while maintaining a compact outer diameter suitable for vehicle applications
Solution Approach 2:
The patent establishes a dynamic relationship between the number of teeth N and the maximum working pitch diameter through the inequality φDmax < 1.7e·sin(π/180)/sin(N·π/180). This dynamic constraint allows optimization of tooth count while controlling the outer diameter, resolving the contradiction between reducing discharge pulsation and maintaining compact dimensions
2Productivity
If the number of teeth in the rotor is increased while ensuring a required discharge amount, then the discharge amount is maintained, but the working pitch diameter becomes larger, resulting in an increased outer diameter of the rotor
Solution Approach 1:
By changing the working position to rearward of the eccentric axis and establishing the inequality constraint on the maximum working pitch diameter, the patent enables increased tooth count for improved discharge performance while preventing the outer diameter from increasing, thus resolving the contradiction between productivity and compactness
Data Source
Figure 1
Figure 2(a)~2(b)
Figure 3~4
AI summary
An object is to meet the demands for increasing the number of teeth of a rotor in an internal gear pump while maintaining a theoretical discharge amount by using an equivalent body configuration so as to enhance the pump performance relating to discharge pulsation due to the increased number of teeth. In a pump rotor 1 formed by combining of an inner rotor (2) having N teeth and an outer rotor (3) having (N+1) teeth and disposing the rotors eccentrically relative to each other, the relational expression φDmax < 1.7e·sin(π/180)/sin{π/(180·N)} is satisfied, φDmax being a maximum value of a working pitch diameter of the inner rotor (2) and the outer rotor (3), and a working position (G) of the inner rotor (2) and the outer rotor (3) is always located rearward of an eccentric axis (CL) in a rotating direction of the rotor.