Motor Vehicle Fluid Pump Bearing Layout for Thermal Expansion Damping
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Solution Overview
Problem
High-speed rotor shaft rotation in motor vehicle fluid pumps causes unbalanced loads and stress in shaft bearing systems due to material differences and temperature-induced expansion, leading to potential damage and reduced pump efficiency.
Innovation Solution
A fluid pump design featuring a static bearing receptacle with two floating ball bearings and elastic support rings, allowing axial and radial movement to minimize vibration and temperature-induced stress, with preload springs and positioning grooves for stable support and vibration damping.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a floating bearing receptacle is used to avoid vibration transfer, then vibration damping is improved, but device complexity increases due to complex attachment requirements
Solution Approach 1:
The harmful vibration transfer function is extracted from the bearing receptacle attachment system. Instead of making the receptacle itself float with complex attachments, the vibration damping function is transferred to separate damping elements (elastomeric elements) that are simply inserted into the receptacle, separating the support function from the vibration isolation function.
Solution Approach 2:
Elastomeric damping elements are introduced as intermediary components between the bearing receptacle and the rotor shaft/bearing assembly. These elastomeric elements serve as mediators that absorb and dampen vibrations while simplifying the attachment mechanism, replacing complex floating receptacle attachments with simple insertable damping elements.
2Productivity
If high-speed rotor shaft rotation is used to achieve high flow rate, then productivity is improved, but reliability deteriorates due to unbalanced bearing loads and thermal expansion
Solution Approach 1:
Elastomeric damping elements are pre-installed in the bearing receptacle to provide beforehand cushioning against thermal expansion and vibration-induced stresses. These elements are positioned in advance to compensate for anticipated thermal growth and mechanical shocks during high-speed operation, preventing bearing damage before it occurs.
Solution Approach 2:
The bearing receptacle design incorporates parameters that accommodate thermal expansion, such as clearance gaps and elastomeric elements with appropriate durometer ratings. These parameter changes allow the bearing system to maintain reliability at high speeds by compensating for thermal effects and dynamic loads through material selection and geometric design.
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
The design minimizes mechanical load and wear, ensuring high pump performance and extended lifetime by effectively damping vibrations and accommodating thermal expansions without generating unbalanced loads.
Implementation Method 1
The elastic support rings minimize mechanical loads and wear of the ball bearings by damping vibrations and accommodating axial and radial movements of the rotor shaft
Implementation Method 2
both ball bearings are radially supported within the bearing receptacle only by elastic support rings
Implementation Method 3
The outer race of the second ball bearing is axially preloaded away from the support flange by a preload spring
Implementation Method 4
Since, typically, the bearing receptacle, the rotor shaft and the ball bearings are made of different materials with different thermal expansion coefficients, and since the pump has to withstand ambient temperatures between -40 °C and 150 °C for automotive applications, temperature-induced expansion of the rotor shaft and/or of the bearings relative to the bearing receptacle can also cause an unbalanced bearing load
Data Source
Figure 1
Figure 2~3
Figure 4
AI summary
Fluid pump (10; 10') for a motor vehicle, with a driving means (18), a pump wheel (12) being co-rotatably connected with the driving means (18) by a rotor shaft (16) and a shaft bearing system (22; 22') for the rotor shaft (16), comprising a static bearing receptacle (24; 24') with a radially inwardly directed axial support flange (32) and two floating ball bearings (28, 30; 28', 30') both fixed to the radial outside of the rotor shaft (16) and provided axially shiftable within the bearing receptacle (24; 24'), wherein a first ball bearing (28; 28') is positioned at a first axial side of the support flange (32) and a second ball bearing (30; 30') is positioned at a second opposite side of the support flange (32), wherein an outer race (28c; 28c') of the first ball bearing (28; 28') is in touching axial contact with the support flange (32) and an outer race (30c; 30c') of the second ball bearing (30; 30') is axially preloaded away from the support flange (32) by a preload spring (36), wherein each ball bearing (28, 30; 28', 30') is provided with at least one elastic support ring (34) radially surrounding the outer race (28c, 30c; 28c', 30c') of the ball bearing (28, 30; 28', 30'), and wherein both ball bearings (28, 30; 28', 30') are radially supported within the bearing receptacle (24; 24') only by the support rings (34).