Motor-Reducer Housing Centering With a Common Support Piece

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Solution Overview

Problem

The existing electric motor architectures for motor vehicles face challenges in ensuring precise centering of casings without incurring noise, premature bearing failure, or excessive bulkiness, particularly due to the direct and permanent coupling of shafts which lacks flexibility and precision in machining processes.

Innovation Solution

The solution involves machining a female cylindrical centering surface on one casing that engages with a cylindrical bearing seat of greater diameter, allowing for precise alignment without the need to turn the casing, using a common intermediate part and lip rings for sealing, which enables simultaneous machining of the centering and bearing surfaces with a stepped cutter.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If cylindrical pins are inserted into the housings to center the shafts, then the centering is easier to implement, but the positioning precision relative to the shaft axes deteriorates because the housings must be reversed between machining the pin recesses and machining the bearing housings

Engineering Contradiction:

Improveease of centering implementationVSAvoidpositioning precision of centering elements

Core Design Contradiction:

Ease of manufactureVSManufacturing precision

Solution Approach 1:

The invention merges the centering function and bearing support function into a single integrated structure. The common intermediate piece with cylindrical outer surface serves as both the centering element and the bearing mounting surface, eliminating the need for separate centering pins and bearing housings. This integration allows both functions to be achieved in a single machining operation without reversing the housing, thus maintaining high positioning precision while simplifying manufacturing.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The female centering bearing and the common intermediate piece serve multiple functions simultaneously. The female centering bearing provides both centering and sealing functions, while the common intermediate piece with its cylindrical outer surface provides both centering and bearing support functions. This multi-functionality reduces the number of separate components and machining operations required, eliminating the need to reverse the housing for different machining operations.

Inventive Principle:

Principle #6Universality (Multi-functionality)

2Manufacturing precision

If centering spans are created on the shafts to improve alignment, then the alignment precision is considerably improved, but hyperstaticity is introduced into the connection generating problems of premature wear of the bearings

Engineering Contradiction:

Improvealignment precision of shaftsVSAvoidbearing durability

Core Design Contradiction:

Manufacturing precisionVSReliability

Solution Approach 1:

The invention applies local quality by creating a specific geometric relationship between the centering surfaces and bearing surfaces. The cylindrical outer surface of the common intermediate piece is positioned at a controlled distance from the bearing seats, and the lip seal is positioned to contact the shaft at a specific location. This localized geometric control achieves precise alignment without creating hyperstatic constraints that would cause premature bearing wear.

Inventive Principle:

Principle #3Local quality

3Manufacturing precision

If the housing is inverted on the machining center to machine the centering surface, then the centering can be achieved, but the positioning of the surfaces produced in the second stage loses accuracy compared to the surfaces machined in the first stage

Engineering Contradiction:

Improvecentering surface accuracyVSAvoidmachining accuracy loss due to repositioning

Core Design Contradiction:

Manufacturing precisionVSLoss of time

Solution Approach 1:

The invention merges the machining of the centering surface and bearing surface into a single machining operation. The stepped cutter machines both surfaces in one setup without requiring the housing to be inverted or repositioned. This eliminates the accuracy loss that would occur from repositioning the housing between machining operations, while also reducing manufacturing time.

Inventive Principle:

Principle #5Merging (Combining)

4Reliability

If an intermediate coupling piece is introduced between the two shafts to dampen radial movements and eliminate angular coupling defects, then the coupling flexibility is improved, but the device becomes expensive and too bulky for electric motor couplings

Engineering Contradiction:

Improvecoupling stabilityVSAvoidcoupling piece bulkiness

Core Design Contradiction:

ReliabilityVSVolume of moving object

Solution Approach 1:

The invention extracts the centering and coupling functions from a separate intermediate coupling piece and integrates them directly into the housing structure. The female centering bearing and common intermediate piece are built into the housing itself, eliminating the need for an additional bulky coupling component between the shafts. This achieves the same coupling stability without the extra volume and cost.

Inventive Principle:

Principle #2Taking out (Extraction)

Data Source

PatentEP3764521B1Electric motorization for motor vehicle and housing machining process

Publication Date: 2023.11.22 RENAULT SA

Figure 1~4A
Figure 4B~5A
Figure 4C

AI summary

Electric motorization for motor vehicle, comprising an electric traction machine housed in a first casing (2), the output shaft (4) of which is coupled by a splined link with an input shaft (5) of a reducer housed in a second casing requiring the mutual centering of the two casings (3), characterized in that each of the casings has a female centering bearing (2c, 3c) engaged around a common support piece (10).