Rotary Actuator Speed Reducer Inversion for Compact Mountability

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Solution Overview

Problem

Rotary actuators for shift-by-wire systems in vehicles face challenges in achieving downsized mountability without compromising responsiveness and torque performance, due to spatial restrictions and the need for a speed-reducing mechanism that requires a curved driven gear to bypass the ring gear.

Innovation Solution

The rotary actuator rearranges the speed-reducing mechanism to eliminate the curved driven gear by positioning the second speed-reducing portion ahead of the first, allowing the driven gear to be straight and reducing the distance between the motor and output shafts, while maintaining the required gear ratio and performance.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Power

If the first speed-reducing portion (ring gear and sun gear) is positioned between the motor and the second speed-reducing portion (drive gear and driven gear) in the axial direction, then the speed reduction is achieved, but the driven gear must be curved to bypass the ring gear, increasing the distance between motor and output shafts and compromising mountability

Engineering Contradiction:

Improvetorque performanceVSAvoiddistance between motor and output shafts

Core Design Contradiction:

PowerVSLength of moving object

Solution Approach 1:

The patent inverts the conventional arrangement by positioning the second speed-reducing portion (drive gear and driven gear) ahead of the first speed-reducing portion (ring gear and sun gear) in the axial direction. This reversal eliminates the need for the driven gear to be curved, allowing it to be straight and reducing the distance between motor and output shafts while maintaining the required speed reduction and torque performance

Inventive Principle:

Principle #13The other way round (Inversion)

Solution Approach 2:

The patent changes the spatial arrangement from a configuration where gears are stacked in a way that requires radial bypassing to one where the second speed-reducing portion is positioned axially ahead, utilizing the axial dimension more effectively to eliminate the curved gear design and reduce overall length

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

2Power

If the driven gear is curved to bypass the ring gear, then the speed-reducing mechanism can be implemented, but the actuator size increases and mountability is compromised

Engineering Contradiction:

Improvegear ratioVSAvoidactuator size

Core Design Contradiction:

PowerVSVolume of moving object

Solution Approach 1:

By inverting the axial arrangement to place the second speed-reducing portion ahead of the first, the patent eliminates the need for curved driven gear, thereby reducing the actuator's volume and improving mountability while preserving the required gear ratio and power transmission capability

Inventive Principle:

Principle #13The other way round (Inversion)

3Power

If the drive gear and driven gear are positioned to serve as parallel shafts type gears, then the speed reduction is achieved, but the curved driven gear increases complexity and reduces ease of manufacture

Engineering Contradiction:

Improvespeed reductionVSAvoidgear geometry

Core Design Contradiction:

PowerVSEase of manufacture

Solution Approach 1:

The inverted axial arrangement allows the driven gear to be straight rather than curved, significantly simplifying manufacturing processes and reducing complexity while maintaining the parallel shafts type gear configuration and speed reduction functionality

Inventive Principle:

Principle #13The other way round (Inversion)

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 configuration improves mountability and reduces the actuator's size without sacrificing responsiveness, torque performance, and weight, enhancing vibration proofing and controllability.

Implementation Method 1

a motor (30) having a motor shaft (33)

Methodology Applied

Scientific EffectElectromagnetic conversion: Electromagnetic Induction

Implementation Method 2

The speed-reducing mechanism includes a first speed-reducing portion including a ring gear (51) and a sun gear (52), and a second speed-reducing portion including a drive gear (53) and a driven gear (54)

Methodology Applied

Scientific EffectGear mechanism: Gear

Data Source

PatentUS11545873B2Rotary actuator

Publication Date: 2023.01.03 DENSO CORP

AI summary

A rotary actuator for a shift-by-wire system of a vehicle includes a motor with a motor shaft, an output shaft disposed in parallel with the motor shaft, a speed-reducing mechanism configured to reduce a rotational speed of the motor and transmit the rotation of the motor to the output shaft, and a case housing the motor and the speed-reducing mechanism. The speed-reducing mechanism includes a first speed-reducing portion including a ring gear and a sun gear, and a second speed reducing portion including a drive gear and a driven gear. The drive gear and the driven gear are coaxially disposed with the motor shaft and the output shaft, respectively, to serve as parallel shafts type gears. The drive gear is disposed between the motor and the first speed-reducing portion in an axial direction of the motor.