Electric Drive Assembly Intermediate Shaft Speed Sensor Placement

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Solution Overview

Problem

Existing drive arrangements for vehicles with electric axles face challenges in accommodating standardized speed sensors due to the larger diameter required for coaxial designs, limiting the use of conventional speed sensors and increasing installation space needs.

Innovation Solution

A drive arrangement with an electric machine featuring a rotor shaft coupled to an intermediate shaft via a transmission, where the speed sensor is positioned on the intermediate shaft, allowing the rotor shaft's speed to be determined through the transmission ratio, enabling a compact design and reuse of standardized speed sensors.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If the rotor shaft is designed as a hollow shaft with larger diameter for coaxial construction, then the structural integrity and load-bearing capacity are improved, but standardized speed sensors cannot be used and extensive conversion work is required

Engineering Contradiction:
Improvestructural integrityVSAvoidsensor compatibility
Core Design Contradiction:
StrengthVSEase of manufacture

Solution Approach 1:

The patent introduces an intermediate shaft as a mediator between the hollow rotor shaft and the speed sensor. The intermediate shaft has a smaller diameter that accommodates standardized speed sensors, while being driven by the hollow rotor shaft through a transmission mechanism. This intermediary component resolves the contradiction by allowing the use of standard sensors without compromising the structural integrity of the hollow rotor shaft design.

Inventive Principle:
Principle #24Intermediary (Mediator)

2Measurement precision

If the speed sensor is arranged on the rotor shaft, then the speed measurement is direct and accurate, but additional installation space is required which increases device complexity

Engineering Contradiction:
Improvespeed measurement accuracyVSAvoidinstallation space
Core Design Contradiction:
Measurement precisionVSDevice complexity

Solution Approach 1:

The intermediate shaft serves as a mediator that carries the speed sensor while being driven by the rotor shaft through a transmission. This allows the sensor to be positioned in a space-efficient location while still providing accurate speed measurement through the transmission ratio relationship.

Inventive Principle:
Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent replaces direct mechanical coupling between the rotor shaft and speed sensor with a transmission mechanism. This substitution allows indirect speed measurement while reducing space requirements and device complexity, as the intermediate shaft can be positioned more flexibly within the available space.

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

Data Source

PatentEP3940391B1Drive assembly with speed detector and vehicle with such a drive assembly
Publication Date: 2023.05.03 ROBERT BOSCH GMBH
  • EP3940391B1 patent drawingFigure 1
  • EP3940391B1 patent drawingFigure 2
  • EP3940391B1 patent drawingFigure 3

AI summary

The invention relates to a drive arrangement (10), in particular for a vehicle, and a vehicle, in particular a motor vehicle, with an electric machine (12) comprising a rotor shaft (14), an intermediate shaft (16), and a speed sensor (18) for determining the rotational speed of the rotor shaft (14), wherein the rotor shaft (14) and the intermediate shaft (16) are coupled to each other by means of a fixed gear ratio (19), and the intermediate shaft (16) can be driven or is driven by the rotor shaft (14), wherein the speed sensor (18) is arranged on the intermediate shaft (16) and detects the rotational speed of the intermediate shaft (16). The rotational speed of the intermediate shaft is converted into the rotational speed of the motor using the known gear ratio.