Electric Drive Axle Claw Shift Layout for Independent Parking Lock

Solution Overview

Problem

The existing electric drive axles with parking locks face challenges in decoupling the electric drive and ensuring the parking lock functionality independently, as the parking lock cannot effectively block the output when the clutch mechanism is open, leading to issues with drag losses and engagement shocks during vehicle braking.

Innovation Solution

An electric drive axle design that incorporates a claw shift element upstream of the parking lock in the power flow direction, allowing for decoupling of the drive shaft from the intermediate shaft and independent operation of the parking lock, minimizing drag losses and ensuring effective engagement when stationary.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Loss of energy

If a clutch mechanism is associated with the intermediate shaft to decouple the electric motor from the differential subassembly, then the electric drive can be decoupled in high-speed operating states, but the parking lock cannot block the output when the clutch mechanism is open

Engineering Contradiction:

Improvedrag lossesVSAvoidparking lock functionality

Core Design Contradiction:

Loss of energyVSReliability

Solution Approach 1:

The power transmission path is segmented into two independent controllable sections: the clutch mechanism on the intermediate shaft for decoupling the electric motor, and the parking lock on the output shaft for blocking the final output. This segmentation allows independent operation of decoupling and parking lock functions, resolving the contradiction where one function would otherwise depend on the other.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The differential subassembly acts as an intermediary element between the clutch mechanism and the parking lock. By placing the parking lock downstream of the differential subassembly on the output shaft, the system ensures that the parking lock can engage and block the output independently of the clutch mechanism's state, as the differential subassembly transmits power regardless of clutch position.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Ease of operation

If the parking lock engages to brake the vehicle to a standstill, then the vehicle can be held stationary, but kinetic energy and rotational energy must be decreased within a very short amount of time causing engagement shocks

Engineering Contradiction:

Improvevehicle stationary holdingVSAvoidengagement shocks

Core Design Contradiction:

Ease of operationVSObject-affected harmful factors

Solution Approach 1:

The clutch mechanism is activated in advance to decouple the electric motor from the powertrain before the parking lock engages. This preliminary decoupling removes the rotating mass of the electric motor and drive train components from the braking process, significantly reducing the kinetic energy that must be dissipated and thereby minimizing engagement shocks when the parking lock engages.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

By decoupling the electric drive beforehand, the system cushions the impact that would otherwise occur during parking lock engagement. The separation of the electric motor's rotational energy from the vehicle's kinetic energy creates a buffer that prevents the full force of the rotating masses from transmitting shock loads to the parking lock mechanism and vehicle structure.

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

3Reliability

If the claw shift element is arranged downstream of the parking lock, then the parking lock can block the output, but the claw shift element generates additional drag losses in the open state

Engineering Contradiction:

Improveoutput blockingVSAvoiddrag losses

Core Design Contradiction:

ReliabilityVSLoss of energy

Solution Approach 1:

The power transmission path is segmented into two independent controllable sections: the clutch mechanism on the intermediate shaft for decoupling the electric motor, and the parking lock on the output shaft for blocking the final output. This segmentation allows independent operation of decoupling and parking lock functions, resolving the contradiction where one function would otherwise depend on the other.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The differential subassembly acts as an intermediary element between the clutch mechanism and the parking lock. By placing the parking lock downstream of the differential subassembly on the output shaft, the system ensures that the parking lock can engage and block the output independently of the clutch mechanism's state, as the differential subassembly transmits power regardless of clutch position.

Inventive Principle:

Principle #24Intermediary (Mediator)

Data Source

PatentUS11945292B2Electric drive axle of a vehicle

Publication Date: 2024.04.02 ZF FRIEDRICHSHAFEN AG

AI summary

An electric drive axle of a vehicle with a parking lock and with at least one electric drive with a drive gear of a drive shaft. The drive gear is coupled via at least one intermediate gear of an intermediate shaft to an output gear of a differential gear unit for driving at least one output shaft. For decoupling the electric drive, at least one claw shift element is associated with the drive shaft and/or with the intermediate shaft in such a way that the claw shift element is arranged upstream of the parking lock in power flow direction from electric drive to differential gear unit.