Motor Plate Protrusion Design for Throttle Body Assembly

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Solution Overview

Problem

Traditional motor plate configurations with large surface area interference fits face challenges such as difficult assembly, stress concentration, deformation, and misalignment due to thermal expansion, while configurations with more clearance lead to shaft and gear alignment issues.

Innovation Solution

A motor end plate design featuring protrusions on its outer edge that provide line contact with the housing, reducing stress and deformation, and facilitating easier assembly by minimizing surface contact to approximately 1% of the outer edge, thus maintaining gear alignment and reducing stress on the bearing portion.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Stability of the object's composition

If large surface area interference fit is used between end plate and housing, then stability of motor within housing is improved, but assembly difficulty increases and stress concentration occurs causing deformation

Engineering Contradiction:

Improvestability of motor within housingVSAvoidassembly ease

Core Design Contradiction:

Stability of the object's compositionVSEase of operation

Solution Approach 1:

The continuous outer edge of the end plate is segmented into discrete protrusions (e.g., three equally spaced protrusions around the circumference). This segmentation transforms the contact interface from a continuous large-surface interference fit to discrete point contacts, reducing assembly difficulty and stress concentration while maintaining motor stability through the distributed arrangement of protrusions.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The end plate design concentrates the interference fit function locally at specific protrusions rather than distributing it across the entire outer edge. Each protrusion is locally optimized with specific dimensional tolerances and geometric features to provide sufficient holding force and stability, while the majority of the end plate surface remains free from stress concentrations.

Inventive Principle:

Principle #3Local quality

2Stability of the object's composition

If large surface area interference fit is used between end plate and housing, then motor stability is improved, but stress concentration causes deformation and potential motor seizure

Engineering Contradiction:

Improvemotor stabilityVSAvoidrisk of motor seizure

Core Design Contradiction:

Stability of the object's compositionVSReliability

Solution Approach 1:

Segmenting the contact interface into discrete protrusions distributes the thermal expansion and stress forces across multiple isolated contact points rather than concentrating them across a large continuous surface. This reduces the risk of deformation propagating through the end plate and causing motor seizure, while maintaining adequate motor stability through the distributed geometric constraints.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The protrusion design inherently cushions against thermal expansion stresses by providing discrete contact points that can accommodate dimensional changes without generating excessive concentrated forces. The gaps between protrusions allow for stress relief and prevent the buildup of deformative forces that would occur in a continuous large-surface interference fit.

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

3Stress or pressure

If clearance is increased between plate and housing to reduce stress, then stress concentration is reduced, but shaft and gear alignment problems occur

Engineering Contradiction:

Improvestress in end plateVSAvoidgear alignment precision

Core Design Contradiction:

Stress or pressureVSManufacturing precision

Solution Approach 1:

The protrusions are precisely positioned and dimensioned to provide local geometric constraints that ensure accurate motor alignment and gear meshing. The specific radii, angles, and spacing of the protrusions are optimized to maintain proper shaft and gear alignment while keeping the overall interference fit minimal, thus reducing stress without compromising alignment precision.

Inventive Principle:

Principle #3Local quality

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 stabilizes the motor within the housing, reduces stress concentrations, and maintains proper gear alignment, even under thermal expansion, by localizing stress through minimal contact points, enhancing assembly ease and preventing deformation.

Implementation Method 1

The contact between the end plate and the housing is substantially only between the at least one protrusion on the outer edge of the end plate and the inner wall of the housing. The line contact reduces and localizes the amount of stress observed in the end plate.

Methodology Applied

Scientific EffectLine contact stress distribution:

Implementation Method 2

Stress and deformation at the end plate can be further increased due to the thermal expansion characteristics of the interference fitted end plate and housing.

Methodology Applied

Scientific EffectThermal expansion: Thermal Expansion

Data Source

PatentUS7385326B2Motor plate

Publication Date: 2008.06.10 ROBERT BOSCH CORP

AI summary

A throttle body assembly including an end plate. The throttle body assembly includes a housing having an inner wall, and a motor located within the housing. The motor end plate is coupled to the motor and is in contact with the inner wall of the housing. The end plate includes an outer edge having at least one protrusion extending therefrom. The contact between the end plate and the housing is substantially only between the at least one protrusion on the outer edge of the end plate and the inner wall of the housing.