Oil Pump Rotor Tooth Profile Modification for Ripple Reduction
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Solution Overview
Problem
Conventional oil pumps face challenges in increasing discharge capacity without enlarging the outer diameter or axial thickness of the rotor, leading to increased ripple and noise due to reduced tooth count, which is mitigated by increasing the number of teeth but results in weight and friction issues.
Innovation Solution
The oil pump rotor features a modified tooth profile with a cycloid curve design, where the inner rotor's external teeth are modified radially on the outer and inner sides of specific circles, and the outer rotor's internal teeth are modified on their root and addendum profiles, allowing for increased discharge without altering the rotor's dimensions, using specific mathematical formulas to define the radii and angles of these modifications.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the number of teeth is reduced to increase discharge amount, then the discharge capacity increases, but the ripple and noise increase
Solution Approach 1:
The patent modifies the tooth profile parameters by introducing specific mathematical curve modifications (epicycloid and hypocycloid curves) to the addendum and root portions. This changes the geometry of the teeth while maintaining the same number of teeth, thereby increasing discharge capacity without increasing ripple and noise
2Object-generated harmful factors
If the number of teeth is increased to reduce ripple and noise, then the ripple and noise decrease, but the discharge amount decreases
Solution Approach 1:
Instead of changing the number of teeth, the patent changes the tooth profile parameters through mathematical curve modifications. This allows maintaining a lower tooth count for higher discharge capacity while the modified profiles control the ripple and noise generation
3Productivity
If the outer diameter or axial thickness is increased to ensure required discharge amount, then the discharge amount increases, but the weight and friction increase
Solution Approach 1:
The patent applies local modifications to specific portions of the tooth profile (addendum and root portions) rather than changing the overall rotor dimensions. This localized approach increases discharge capacity through optimized fluid displacement in the cell volumes without increasing the rotor's outer diameter or axial thickness, thereby avoiding increased weight
4Productivity
If the outer diameter or axial thickness is increased to ensure required discharge amount, then the discharge amount increases, but the friction increases
Solution Approach 1:
The patent achieves increased discharge capacity through local modifications of the tooth profiles, maintaining the same rotor dimensions. This avoids increasing the contact area between rotating components, thereby preventing increased friction and energy loss
Data Source
Figure 1~2
Figure 3(a)~3(b)
Figure 4
AI summary
An oil pump rotor for use in an oil pump includes an inner rotor having (n: "n" is a natural number) external teeth, an outer rotor having (n+1) internal teeth meshing with the external teeth, and a casing forming a suction port for drawing a fluid and a discharge port for discharging the fluid, such that in association with meshing and co-rotation of the inner and outer rotors, the fluid is drawn/discharged to be conveyed according to volume changes of cells formed between teeth faces of the two rotors. For a tooth profile formed of a mathematical curve and having a tooth addendum circle A1 with a radius RA1 and a tooth root curve A2 with a radius RA2, a circle D1 has a radius RD1 which satisfies Formula (1) and a circle D2 has a radius RD2 which satisfies both Formula (2) and Formula (3), RA1>RD1>RA2 RA1>RD2>RA2 RD1≧RD2 a tooth profile of the external teeth of the inner rotor includes at least either one of a modification, in a radially outer direction, of the tooth profile, on the outer side of the circle D1 and a modification, in a radially inner direction, of the tooth profile, on the inner side of the circle D2.