Pump Eccentric Bearing Undercut for Brake Fluid Leakage

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Solution Overview

Problem

In electronically controllable vehicle brake systems, brake fluid can escape into the eccentric bearing and electric drive motor due to capillary effects, leading to increased current values, brush run-off, potential short circuits, and bearing wear, as existing pumps lack effective compensation for preventing fluid ingress.

Innovation Solution

The introduction of an undercut on the wall of the motor bore between the drive bearing and eccentric bearing, which enlarges the eccentric space and interrupts the transmission path for leakage liquid, allowing it to drain into a leakage reservoir, thus preventing fluid ingress into the electric drive motor.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the eccentric space is enlarged to prevent capillary action, then the risk of brake fluid penetration is reduced, but additional compensating means are required which increase device complexity

Engineering Contradiction:
Improveprevention of brake fluid penetrationVSAvoidstructure of compensating means
Core Design Contradiction:
ReliabilityVSDevice complexity

Solution Approach 1:

The motor bore wall is segmented into different regions: a first region forming the eccentric space, a second region forming the drive bearing, and a third region forming the undercut. This segmentation allows the undercut to be positioned strategically to interrupt the transmission path of brake fluid while maintaining the functional integrity of the eccentric bearing and drive bearing, thus preventing fluid penetration without requiring complete redesign of the entire motor bore structure

Inventive Principle:
Principle #1Segmentation

Solution Approach 2:

The undercut acts as an intermediary structure between the eccentric space and the drive bearing region. It creates a geometric discontinuity that serves as a barrier to brake fluid flow, interrupting the transmission path without directly modifying the eccentric bearing or drive bearing themselves. This intermediary approach prevents fluid penetration while minimizing changes to the overall device structure

Inventive Principle:
Principle #24Intermediary (Mediator)

2Reliability

If the motor bore is lowered to enlarge the eccentric space, then capillary action is reduced, but the position of the drive shaft bearing must be changed which increases manufacturing complexity

Engineering Contradiction:
Improveprevention of capillary actionVSAvoidpositioning of drive shaft bearing
Core Design Contradiction:
ReliabilityVSEase of manufacture

Solution Approach 1:

Instead of lowering the entire motor bore, the invention applies a localized modification in the form of an undercut only in the specific region of the motor bore wall that forms the transmission path for brake fluid. This local quality approach creates the necessary geometric discontinuity to prevent capillary action and fluid penetration while maintaining the original overall position of the motor bore and the standard positioning of the drive shaft bearing, thus avoiding increased manufacturing complexity

Inventive Principle:
Principle #3Local quality

3Reliability

If brake fluid penetrates into the electric drive motor, then current values increase and brush run-off increases, but the pump structure lacks effective compensation to prevent this

Engineering Contradiction:
Improveelectric drive motor performanceVSAvoidcompensation structure
Core Design Contradiction:
ReliabilityVSDevice complexity

Solution Approach 1:

The invention extracts or removes the transmission path for brake fluid from the system by creating an undercut that interrupts the continuous path between the eccentric space and the drive bearing region. This extraction approach prevents brake fluid from reaching the electric drive motor, thereby maintaining normal current values and brush run-off without requiring complex active compensation mechanisms or additional components

Inventive Principle:
Principle #2Taking out (Extraction)

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 significantly reduces the risk of capillary action, prevents fluid ingress into the electric drive motor, and increases the robustness and service life of the system by ensuring leakage fluid is directed away from critical components.

Implementation Method 1

small amounts of brake fluid can escape from the pump elements and penetrate directly into the eccentric bearing during pump operation due to a capillary effect caused by narrow gaps in an eccentric space

Methodology Applied
Scientific EffectCapillary effect: Capillary Action

Data Source

PatentEP2205868B1Pump, particularly for a hydraulic unit of an electronically controlled vehicle brake unit
Publication Date: 2012.09.12 ROBERT BOSCH GMBH
  • EP2205868B1 patent drawingFigure 1
  • EP2205868B1 patent drawingFigure 2

AI summary

The invention relates to a pump (1') comprising an eccentric bearing (2), a drive bearing (3), a drive shaft (4), an electric drive motor (5), and a pump housing (6'). The pump housing (6') is provided with an eccentric chamber (2.1), which is formed on the pump housing (6') by an engine bore (6.1) in the form of a blind hole. The pump (1') comprises compensating means (9, 11) that enlarge the eccentric chamber (2.1) of the eccentric bearing (2). According to the invention, said compensating means (9, 11) comprise at least one recess (11) arranged on the wall of the engine bore (6.1).