Conical Spring Washer Stator Mounting Thermal Expansion

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Solution Overview

Problem

Conventional methods for fastening a stator in an electrical machine, such as screw connections, are inefficient in terms of space and temperature stability, leading to mechanical stress and vibration issues due to thermal expansion and varying material tolerances.

Innovation Solution

A clamping disk with axial spring structures and a spreading device is used to securely fix the stator, compensating for thermal expansion and production tolerances while providing vibration damping over a wide temperature range, and allowing for easy assembly and adjustment.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If screw connections are used to fasten the stator, then the stator can be securely fixed, but the space requirement and cost increase, and the prestressing force becomes temperature-dependent and decreases sharply

Engineering Contradiction:
Improvefixation strengthVSAvoidtemperature stability
Core Design Contradiction:
StrengthVSTemperature

Solution Approach 1:

The patent uses spring elements with adjustable spring constants to provide temperature-compensated prestressing force. The spring elements are designed with different geometries (curved, spiral, zigzag) to achieve specific force-displacement characteristics that maintain stable fixation across temperature variations, replacing the temperature-sensitive screw connection prestressing force.

Inventive Principle:
Principle #35Parameter changes

Solution Approach 2:

The patent replaces the rigid mechanical screw connection system with an elastic spring-based system. This substitution allows the fixation mechanism to adapt to thermal expansion and contraction dynamically, maintaining stable contact force without the sharp decrease seen in conventional screw connections under temperature changes.

Inventive Principle:
Principle #28Mechanics substitution (Replace mechanical system)

2Strength

If rigid fastening methods are used, then the stator is securely fixed, but vibration transmission to other components increases

Engineering Contradiction:
Improvefixation strengthVSAvoidvibration transmission
Core Design Contradiction:
StrengthVSObject-generated harmful factors

Solution Approach 1:

The patent introduces spring elements as intermediary components between the stator and housing. These elastic intermediaries absorb and dampen vibration energy, preventing direct transmission of mechanical shocks and vibrations to the housing and other components, while still maintaining secure fixation of the stator.

Inventive Principle:
Principle #24Intermediary (Mediator)

Solution Approach 2:

The spring elements are designed with specific geometric parameters (curvature, spiral patterns, zigzag configurations) that optimize their damping characteristics. By adjusting these parameters, the system can control the level of vibration absorption while maintaining adequate fixation strength.

Inventive Principle:
Principle #35Parameter changes

3Ease of manufacture

If conventional tension washers are used, then the stator can be fastened, but they do not adequately compensate for thermal expansion and production tolerances

Engineering Contradiction:
Improveassembly simplicityVSAvoidtolerance compensation
Core Design Contradiction:
Ease of manufactureVSAdaptability or versatility

Solution Approach 1:

The spring elements are designed with variable geometric parameters along their length, including curved sections, spiral patterns, and zigzag configurations. These parameter variations allow the springs to provide both compliance for tolerance compensation and sufficient stiffness for stable fixation, overcoming the limitations of conventional rigid tension washers.

Inventive Principle:
Principle #35Parameter changes

4Object-generated harmful factors

If damping elements are used to reduce vibration transmission, then vibration damage is reduced, but the tolerance compensation capability is limited and the operating temperature range is restricted

Engineering Contradiction:
Improvevibration transmissionVSAvoidoperating temperature range
Core Design Contradiction:
Object-generated harmful factorsVSAdaptability or versatility

Solution Approach 1:

The spring elements are designed with geometric configurations (curved, spiral, zigzag) that provide both damping capability and wide temperature adaptability. The elastic properties of the spring materials and their geometric design allow them to function effectively across a broad temperature range while maintaining vibration damping performance, unlike conventional damping elements with limited temperature ranges.

Inventive Principle:
Principle #35Parameter changes

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 clamping disk ensures a constant prestressing force, reduces vibration transmission, and effectively compensates for thermal and mechanical stresses, enhancing the stability and reliability of the stator fixation.

Implementation Method 1

a number of spring structures extending from the annular base body in the direction of the stator and supporting the stator axially by means of a predetermined spring force

Methodology Applied
Scientific EffectSpring force: Spring

Implementation Method 2

The axial support of the stator by means of spring structures allows movements of the stator, such as thermally induced expansion processes, as well as production-related tolerances to be compensated

Methodology Applied
Scientific EffectElasticity: Elasticity

Implementation Method 3

The spring structures also have a dampening effect on high vibration accelerations of the stator

Methodology Applied
Scientific EffectVibration damping: Damping

Implementation Method 4

The spreading device is arranged radially compressed inside the housing and is fixed in the housing by means of its radial expansion

Methodology Applied
Scientific EffectRadial expansion:

Data Source

PatentEP2625769B1Conical spring washer for mounting a stator in the housing of an electrical machine
Publication Date: 2015.06.10 ROBERT BOSCH GMBH
  • EP2625769B1 patent drawingFigure 1
  • EP2625769B1 patent drawingFigure 2
  • EP2625769B1 patent drawingFigure 3~4

AI summary

An electrical machine (100) comprises a housing (110), a stator (200) arranged in the housing and a conical spring washer (300), which holds the stator (200) in its installed position by means of a predetermined axial spring force (FA). In this case, the conical spring washer (300) comprises an annular base body (310), which is attached to a housing inner wall (110) by means of an attachment device (330), as well as a number of spring structures (320) which extend from the annular base body (310) in the direction of the stator (200) and support the stator (200) axially.