Motor-Pump Eccentric Positive Interlock Design
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Solution Overview
Problem
The manufacture and assembly of eccentrics in electric motor-pump assemblies for motor vehicle brake systems are expensive due to the complex and costly process of achieving a rotationally locked connection using frictional grips and position coding.
Innovation Solution
A positive interlock is used between the bearing journal and eccentrics, featuring non-circular cross sections with flats or knurled surfaces, and a clamping sleeve with a spring steel design to ensure a durable and easy-to-produce rotational locking mechanism.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a frictional grip press-fit connection is used between the bearing journal and eccentrics, then a rotationally locked connection is achieved, but the manufacture and assembly process becomes expensive and complex
Solution Approach 1:
The bearing journal and opening are given non-circular cross-sections with flats or knurled surfaces that create a positive interlock. This asymmetric geometry prevents relative rotation between the bearing journal and eccentrics, replacing the need for expensive frictional grip press-fit connections while simplifying manufacture and assembly.
2Manufacturing precision
If position coding pins and holes are added to eccentrics to ensure angular position, then the desired angular position is achieved, but the manufacture and assembly process becomes expensive
Solution Approach 1:
The positive interlock geometry serves dual functions: it provides the rotationally locked connection and simultaneously defines the angular position through its asymmetric flat or knurled surface configuration. This eliminates the need for separate position coding pins and holes, reducing manufacturing complexity and 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
This solution simplifies the assembly process, reduces costs, and provides a reliable rotational locking system that maintains angular position and torque transmission, enhancing the operational efficiency of the vacuum pump.
Implementation Method 1
The clamping sleeve is radially pre-stressed, so that it tends to expand, producing a frictional grip between the clamping sleeve and the circumferential surface of the holes which is durable, since the pre-stressing of the clamping sleeve is also retained over time.
Implementation Method 2
producing a frictional grip between the clamping sleeve and the circumferential surface of the holes
Data Source
AI summary
In an electric motor-pump assembly, two working diaphragms, each delimiting a working chamber, are cyclically driven by a crank drive via connecting rods. The crank drive includes eccentrics for each connecting rod, which are placed on an axial bearing journal in the extension of an output shaft of an electric motor. In order to ensure a rotationally fixed connection between the eccentrics and the bearing journal to be produced and in order to ensure an angularly precise position of the two eccentrics, each of the eccentrics is connected to the bearing journal by a positively locking engagement.