Two-Stage Piston Pump Direct Drive for Low Noise and Vibration
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Solution Overview
Problem
Piston type vacuum pumps in vehicles suffer from noise, vibration, and power consumption issues, particularly in two-stage designs with high out-of-balance inertia loading, and often require complex and large components.
Innovation Solution
A piston type pump design featuring a direct drive mechanism with phase-shifted eccentrics to convert rotary motion into linear motion, eliminating intermediate sliding mechanisms and allowing for a compact, robust, and balanced design with larger rolling element bearings.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a two-stage piston pump design is used to improve vacuum generation capability, then the vacuum level is improved, but noise and vibration increase due to high out-of-balance inertia loading
Solution Approach 1:
The patent applies counterbalancing weights integrated into the piston assembly to offset the out-of-balance inertia forces generated during reciprocating motion. The counterweights are positioned and dimensioned to create opposing forces that neutralize the vibratory forces, thereby reducing noise and vibration while maintaining the two-stage vacuum generation capability
2Ease of operation
If sliding block guides with Scotch yoke mechanism are used to convert rotary motion to linear motion, then motion conversion is achieved, but wear and noise issues arise along with high power consumption
Solution Approach 1:
The patent replaces the sliding block guide and Scotch yoke mechanism with a direct-acting piston design where the piston is directly connected to the crankshaft via a connecting rod. This substitution eliminates the intermediate sliding contacts that cause wear and high friction losses, resulting in lower power consumption and reduced noise while maintaining effective motion conversion
3Volume of moving object
If compact piston design is implemented to reduce size, then space efficiency is improved, but bearing size is constrained preventing adequate support
Solution Approach 1:
The patent employs an articulated connecting rod mechanism that transforms the spatial arrangement of components. The connecting rod allows the piston to be positioned offset from the crankshaft centerline, creating additional dimensional space for adequate bearing installation and support while maintaining a compact overall pump envelope. This dimensional reconfiguration enables larger bearings without increasing the pump's external dimensions
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 achieves reduced noise and vibration, lower power consumption, improved durability, and a more compact form factor while enabling easier assembly and manufacturing.
Implementation Method 1
The driving shaft comprises a first eccentric and a second eccentric, which are phase shifted by 180°; the first primary stage piston and the second secondary stage piston rod are mounted on, and directly driven by, the second eccentric and the first secondary stage piston rod and the second primary stage piston are mounted on, and directly driven by, the first eccentric
Data Source
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AI summary
A double acting two stage piston type pump, comprising a pump housing having a piston arrangement connected to a driving shaft which, when driven, sets the piston arrangement into movement, wherein the piston arrangement comprises at least two first primary stage pistons, the first primary stage pistons being slidably seated in respective first primary stage cylinders formed in the pump housing. The piston arrangement also comprises at least two secondary stage pistons slidably seated in respective secondary stage cylinders formed in the primary stage pistons. The primary stage pistons and the second secondary stage pistons are mounted on, and directly driven by, eccentrics mounted on the driving shaft.