Shift-by-wire Transmission Backup Drive Mechanism

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Solution Overview

Problem

In vehicles with 'shift-by-wire' systems, the loss of electrical power disrupts the operator's ability to control transmission shifting, as there is no mechanical backup to shift the transmission into a safe gear like park, potentially leading to unintended vehicle movement.

Innovation Solution

A gear shift control system that includes a drivetrain with a first drive member, a return spring, a retainer, and a power storage device, allowing the system to shift gears electrically when power is available and mechanically shift to park when power is lost, using a planetary gear set and a second drive member laterally offset from the drivetrain to ensure safe gear engagement.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of operation

If a shift-by-wire system is used to eliminate mechanical coupling, then ease of operation and control precision are improved, but reliability deteriorates due to loss of mechanical backup during power failure

Engineering Contradiction:

Improveshift controlVSAvoidgear shifting capability during power loss

Core Design Contradiction:

Ease of operationVSReliability

Solution Approach 1:

The system segments the drive train into two independent drive members: a first drive member for normal electrical operation and a second drive member for mechanical backup operation. This segmentation allows each drive member to be optimized for its specific function while maintaining overall system reliability.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The system changes the operational parameter from electrical power-dependent to mechanical power-dependent by switching between the first drive member (electrical) and the second drive member (mechanical). This parameter change enables the system to adapt to power loss conditions while maintaining gear shifting capability.

Inventive Principle:

Principle #35Parameter changes

2Reliability

If a second drive member is added for mechanical backup, then reliability during power loss is improved, but device complexity increases

Engineering Contradiction:

Improvegear shifting capability during power lossVSAvoiddrive train configuration

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The second drive member is designed with multi-functionality: it serves as a backup drive during power loss, provides return spring biasing force, and can be integrated with the planetary gear set. This universal design reduces the need for separate dedicated components for each function.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Solution Approach 2:

The second drive member is laterally offset from and axially positioned within the axial height of the drivetrain, nesting it within the existing drive train structure. This nesting approach minimizes additional space requirements and reduces overall system complexity.

Inventive Principle:

Principle #7Nested doll (Nesting)

3Volume of moving object

If the second drive member is positioned within the axial height of the drivetrain, then compactness is improved, but manufacturing precision requirements increase

Engineering Contradiction:

Improvedrive train footprintVSAvoidaxial positioning accuracy

Core Design Contradiction:

Volume of moving objectVSManufacturing precision

Solution Approach 1:

The second drive member is positioned laterally offset from the drivetrain axis rather than symmetrically aligned. This asymmetric positioning allows for more flexible manufacturing tolerances while achieving the compact axial footprint, as it avoids the need for precise concentric alignment.

Inventive Principle:

Principle #4Asymmetry

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

Ensures the transmission can be safely shifted into park even without electrical power, preventing unintended vehicle movement and maintaining operational control during power outages.

Implementation Method 1

The return spring provides a force on the second input tending to drive the second input in a direction that would shift the vehicle transmission to its park gear

Methodology Applied

Scientific EffectSpring: Spring

Implementation Method 2

The power storage device may include a capacitor that stores a charge that may be provided to the release mechanism

Methodology Applied

Scientific EffectCapacitor: Capacitance

Data Source

PatentUS10234028B2Shift by wire transmission shift control system

Publication Date: 2019.03.19 DUS OPERATING INC

AI summary

A gear shift control system may include an output mechanism, first and second drive members and a drivetrain. The first drive member may be coupled to the output mechanism to drive the output mechanism and cause a transmission shift. The drivetrain includes a first input driven by the drive member during a first mode of operation and an output coupled to both the first input and the output mechanism to drive the output mechanism as commanded by the drive member. During a second mode of operation a second input is coupled to the output and a second drive member is coupled to the second input to drive the output mechanism through the second input and the output to cause a transmission gear shift. The second drive member may be laterally offset from the drivetrain and axially positioned within an axial height of the drivetrain.