Variable Displacement Vane Pump Thermal Expansion Control
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Solution Overview
Problem
Mechanical lubricant vane pumps face hydraulic inefficiency and high production costs due to thermal expansion differences between materials used in the pump housing and control ring, leading to increased axial clearances and leakage at elevated temperatures.
Innovation Solution
The control ring is made of plastic material with a thermal expansion coefficient matched to the metal pump housing, reducing axial clearance and using fiber-reinforced plastic for the rotor body and vanes to minimize thermal expansion differences, along with a separate sliding ring for improved mechanical and frictional properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If steel or sintered steel is used for the control ring, the vanes and the rotor body, then mechanical strength is improved, but the axial clearance increases significantly at elevated temperatures due to thermal expansion differences with the aluminium housing
Solution Approach 1:
The patent applies composite materials by combining plastic control ring bodies with metal sliding rings. The plastic material provides thermal expansion compatibility with the aluminium housing, while the metal sliding ring maintains mechanical strength and wear resistance. This composite approach resolves the contradiction between strength and thermal expansion compatibility.
Solution Approach 2:
The patent changes the material parameter (thermal expansion coefficient) by selecting plastic materials whose thermal expansion coefficients are matched to the aluminium housing (between 65% and 150% of the housing material's coefficient). This parameter matching significantly reduces thermal expansion differences and maintains axial clearance at elevated temperatures.
2Weight of moving object
If aluminium is used for the pump housing, then weight is reduced, but the axial clearance increases at elevated temperatures due to large thermal expansion differences with steel control ring materials
Solution Approach 1:
The patent changes the material parameter by selecting plastic materials with thermal expansion coefficients matched to aluminium (between 65% and 150% of the housing material's coefficient). This resolves the contradiction by maintaining axial clearance precision while keeping the housing lightweight.
Solution Approach 2:
The patent converts the harmful effect of thermal expansion into a beneficial one by selecting plastic materials that expand at rates compatible with aluminium. The thermal expansion that would normally cause clearance issues in steel-aluminium combinations becomes an advantage, as the plastic control ring expands in harmony with the aluminium housing at elevated temperatures.
3Loss of energy
If very tight and precise mechanical clearances are realized in production, then hydraulic efficiency is improved, but production cost increases significantly
Solution Approach 1:
The patent changes the material parameter (thermal expansion coefficient) to match the housing material, which inherently maintains tighter clearances at operating temperatures. This eliminates the need for extremely tight manufacturing tolerances, thereby improving hydraulic efficiency without significantly increasing production cost.
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
Significantly reduced axial clearance and improved hydraulic efficiency at elevated temperatures, along with lower production costs and enhanced pressure control quality.
Implementation Method 1
The thermal expansion coefficient aP of the control ring plastic material is between 65% and 150% of the thermal expansion coefficient aM of the housing metal
Implementation Method 2
The sliding ring material is chosen to provide good mechanical properties to provide good lubricational and frictional conditions. The sliding ring material is plastic with a low friction coefficient with respect to the material of the vane head.
Data Source
Figure 1~2
Figure 3~4
Figure 5
AI summary
A variable displacement lubricant vane pump (10) is provided with a pump rotor (20) rotating around a rotor axis (21) and with a rotor body (24) provided with vane slits (25) wherein shiftable rotor vanes (26) are arranged. A shiftable control ring (30) is provided wherein the slidable vanes (26) are rotating, the control ring (30) being actuated to control the eccentricity of the control ring (30) with respect to the rotor axis (21). A metal pump housing (12) including two parallel sidewalls (16, 17) is provided which axially cover the rotor body (24), the rotor vanes (26) and the control ring (30). The control ring (30; 30') is provided with a control ring body (31; 31') made out of the same plastic material with a thermal expansion coefficient ap of 65% to 150% of the thermal expansion coefficient aM of the housing metal.