Eccentric Bearing for Electrohydraulic Brake Pump
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Solution Overview
Problem
Existing eccentric bearings in electrohydraulic piston pump units for motor vehicle brake systems face inefficiencies in converting rotary motion to stroke motion, leading to friction losses and requiring larger, heavier electric motors due to unsuitable speed ratios.
Innovation Solution
The eccentric bearing features a rotationally driven shaft with a bearing ring and rolling elements of varying diameters, where the bearing ring is eccentric to the shaft, allowing for a changing gap width and halving the rotational speed of the bearing ring, enabling a higher speed drive with a smaller, lighter motor, and utilizing a spring clip for low-noise and durable operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the shaft is driven at high rotational speed, then productivity is improved, but friction losses increase and the bearing ring cannot properly convert rotary motion to stroke motion
Solution Approach 1:
The bearing ring is designed with an asymmetric cross-sectional shape that is wider at the front side (facing the direction of motion) and narrower at the rear side. This asymmetric geometry allows the bearing ring to be pushed forward by the shaft during rotation while reducing contact pressure and friction at the rear, enabling efficient motion conversion even at high rotational speeds
Solution Approach 2:
The bearing ring is designed to be movable rather than fixed, allowing it to dynamically respond to the rotating shaft. The bearing ring can shift position along the shaft axis and rotate to some extent, adapting its orientation to minimize friction during high-speed operation while maintaining effective motion conversion
2Speed
If the bearing ring is made non-rotatable relative to the shaft, then speed reduction is achieved, but device complexity increases
Solution Approach 1:
The bearing ring utilizes curved and rounded geometric features, including a circumferentially extending groove with rounded cross-section and spheroidal contact surfaces. These curved geometries naturally guide the bearing ring's motion and reduce the need for complex mechanical constraints, achieving speed reduction through geometry rather than additional components
3Productivity
If rolling elements with different diameters are used, then motion conversion efficiency is improved, but manufacturing precision requirements increase
Solution Approach 1:
The bearing ring incorporates a circumferentially extending groove with varying cross-sectional dimensions around its circumference. This creates local variations in the gap between the shaft and bearing ring, allowing different regions to accommodate rolling elements of different diameters. Each local region is optimized for its specific function, reducing overall manufacturing precision requirements while maintaining conversion efficiency
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 configuration results in a low-noise, durable, and cost-effective eccentric bearing that efficiently converts rotary motion to stroke motion, allowing for a smaller and lighter electric motor while minimizing friction losses.
Implementation Method 1
the spring clip elastically pushing the connected rolling bodies apart in the circumferential direction of the eccentric bearing
Implementation Method 2
the rolling bodies roll on the shaft and in the bearing ring and run around the shaft
Data Source
Figure 1
AI summary
The invention relates to an eccentric bearing (1) for an electrohydraulic piston pump assembly of a vehicle brake system. The invention proposes the provision of a shaft (2) which can be driven in rotation about its axis (6), a bearing ring (3) which is eccentric with respect to the shaft (2), and rolling bodies (5) between the bearing ring (3) and the shaft (2), which rolling bodies have different diameters corresponding to a varying width of a gap (4) between the bearing ring (3) and the shaft (2). When the shaft (2) is driven in rotation, an eccentricity of the bearing ring (3) circulates around the shaft (2) at half of the rotational speed of the latter and drives pump pistons (9), which bear at the outside against the bearing ring (3), such that these perform a reciprocating movement.