Electric Vacuum Pump Bearing Ventilation Design
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Solution Overview
Problem
The existing motor vehicle vacuum pumps face a challenge in maintaining the lubrication of roller bearings due to suction of lubricant into the pump module, leading to reduced service life.
Innovation Solution
An electric motor vehicle vacuum pump design featuring a motor module with a fixed and floating roller bearing, where the fixed roller bearing is axially arranged between the motor rotor and pump module, and an annular channel connected to atmosphere via a radial ventilation line, ensuring static atmospheric pressure and preventing lubricant suction, combined with a dry-running rotary vane pump module with an overhung pump rotor shaft.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If the roller bearing is cooled with intake air flowing into the pump module, then the bearing temperature is reduced, but the lubricant is sucked into the pump module and lubrication deteriorates
Solution Approach 1:
The patent divides the bearing cooling function from the pump intake function by providing a separate ventilation line that connects the annular channel directly to the atmosphere, independent of the pump inlet. This segmentation allows the bearing to be cooled without introducing pump intake air that would carry lubricant away.
Solution Approach 2:
The annular channel acts as an intermediary between the roller bearing and the atmosphere, providing a dedicated pathway for cooling air. This intermediary structure ensures that bearing ventilation is decoupled from the pump's suction side, preventing lubricant suction while maintaining cooling effectiveness.
2Manufacturing precision
If the fixed roller bearing is positioned axially between the motor rotor and pump module, then heat-related axial changes are minimized and leakage gaps are reduced, but the bearing requires effective lubrication protection from suction
Solution Approach 1:
The ventilation system is segmented into a separate pathway for the fixed bearing via the annular channel and ventilation line, distinct from the pump intake pathway. This ensures the bearing receives cooling air from the atmosphere without exposure to suction conditions that would compromise lubrication.
Solution Approach 2:
The fixed bearing is provided with localized atmospheric pressure through the annular channel and ventilation line, creating a protected zone with static atmospheric pressure that prevents lubricant suction while maintaining the bearing's precise axial positioning for minimal leakage gaps.
3Device complexity
If a single bearing supports the motor shaft, then the structure is simpler, but the axial bearing precision and service life are reduced
Solution Approach 1:
The bearing support system is segmented into two distinct bearings: a floating bearing that accommodates thermal expansion and a fixed bearing that provides precise axial positioning. This segmentation of functions allows each bearing to optimize its specific role, achieving high axial precision without excessive overall complexity.
Solution Approach 2:
The fixed bearing acts as an intermediary element between the motor rotor and pump module, providing the necessary axial positioning precision. Its dedicated atmospheric ventilation through the annular channel protects its lubrication, ensuring long-term maintenance of axial bearing precision.
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 design significantly extends the service life of the vacuum pump by maintaining effective lubrication and reducing leakage gaps, enhancing pump efficiency and axial bearing precision.
Implementation Method 1
An annular channel is provided between the fixed bearing and the pump module, which is directly adjacent to the fixed bearing axially and proximally, so that the fixed bearing is directly aerated via the annular channel. Furthermore, at least one aeration line, which runs radially for example, is provided, which connects the ring channel to the atmosphere surrounding the vacuum pump.
Implementation Method 2
the annular gap between the motor shaft or pump rotor shaft and the shaft opening in the partition wall between the motor module and the pump module is sealed by a gap seal
Implementation Method 3
The motor shaft is mounted on the housing of the motor module by a fixed roller bearing and a floating roller bearing.
Implementation Method 4
The fixed roller bearing of the motor module is arranged axially between the motor rotor and the pump module, so that the floating roller bearing is arranged at the distal end of the motor shaft
Implementation Method 5
The pump module is a dry-running rotary vane pump module with an overhung pump rotor shaft. The pump rotor shaft therefore does not have its own bearing, but protrudes into the pump module as a rigid extension of the motor shaft.
Data Source
AI summary
The pump (10) has a motor module (12) comprising a stator sided motor coil (20) and a motor rotor (18) carrying a motor shaft (16). A fixed roller bearing (24) i.e. ball bearing, is axially arranged between the motor rotor and a pump module (14). An annular passage (32) is provided between the fixed roller bearing and the pump module. A ventilation duct (34) connects the annular passage with atmosphere surrounding the vacuum pump. The annular passage is fluidically separated from the pump module.