Four-wheel-drive mesh clutch synchronization mechanism

Solution Overview

Problem

Four-wheel-drive vehicles lack efficient synchronization mechanisms for mesh clutches, leading to prolonged switching times and low reliability when transitioning between two-wheel-drive and four-wheel-drive modes.

Innovation Solution

Incorporating a synchronizing mechanism with one-sided chamfers on the meshing teeth of the first and second mesh clutches, allowing for parallel surface abutment and preventing rotational axis separation forces, and using flat and alternating long/short teeth in the second mesh clutch to prevent tooth jumping.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If a synchronizing mechanism is provided in the first mesh clutch to enable 4WD state when vehicle is moving, then the adaptability of the four-wheel-drive vehicle is improved, but the switching time of the first mesh clutch becomes relatively long and switching reliability becomes comparatively low

Engineering Contradiction:

Improveability to engage 4WD state when vehicle is movingVSAvoidswitching reliability of the first mesh clutch

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

The synchronizing mechanism performs preliminary synchronization of rotation speeds between the first clutch drum and first clutch hub before engagement. The synchronizing friction surfaces engage first to equalize rotational speeds, and only after synchronization is achieved do the meshing teeth engage, preventing tooth jumping and ensuring reliable switching even during vehicle motion.

Inventive Principle:

Principle #10Preliminary action

2Loss of time

If the meshing teeth are engaged without synchronization, then the switching time is short, but the teeth will jump and the reliability is low

Engineering Contradiction:

Improveswitching time of the first mesh clutchVSAvoidswitching reliability of the first mesh clutch

Core Design Contradiction:

Loss of timeVSReliability

Solution Approach 1:

The synchronizing mechanism performs preliminary synchronization of rotation speeds between the first clutch drum and first clutch hub before engagement. The synchronizing friction surfaces engage first to equalize rotational speeds, and only after synchronization is achieved do the meshing teeth engage, preventing tooth jumping and ensuring reliable switching even during vehicle motion.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The synchronizing friction surfaces act as an intermediary between the first clutch drum and first clutch hub. These friction surfaces temporarily engage to transfer torque and synchronize rotation speeds before the final meshing tooth engagement, serving as a mediator that prevents direct tooth impact and jumping.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Reliability

If a synchronizing mechanism is provided, then the meshing teeth can be synchronized and engaged, but the meshing teeth may jump during engagement due to resistance torque differences

Engineering Contradiction:

Improveengagement reliability of the first mesh clutchVSAvoidstability of meshing teeth engagement

Core Design Contradiction:

ReliabilityVSStability of the object's composition

Solution Approach 1:

The synchronizing friction surfaces act as an intermediary between the first clutch drum and first clutch hub. These friction surfaces temporarily engage to transfer torque and synchronize rotation speeds before the final meshing tooth engagement, serving as a mediator that prevents direct tooth impact and jumping.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The resistance torque generation mechanism changes the resistance torque parameter dynamically during engagement. When the rotation speed difference exceeds a threshold, resistance torque is generated to slow down the faster component and accelerate the slower one, ensuring synchronized engagement and preventing tooth jumping.

Inventive Principle:

Principle #35Parameter changes

Data Source

PatentUS9925870B2Four-wheel-drive vehicle

Publication Date: 2018.03.27 TOYOTA JIDOSHA KK

AI summary

A four-wheel-drive vehicle includes a driving source, main driving wheels, auxiliary driving wheels, a power transmitting member, a first mesh clutch, and a second mesh clutch. Meshing teeth on the driving source side of the first mesh clutch each have, along an entire tooth width thereof, an inclined surface in which a length in a rotational axis direction increases in a direction in which the meshing teeth on the driving source side rotate when the four-wheel-drive vehicle is traveling forward. The meshing teeth on the power transmitting member side of the first mesh clutch each have, along an entire tooth width thereof, an inclined surface in which a length in a rotational axis direction decreases in a direction in which the meshing teeth on the driving source side rotate when the four-wheel-drive vehicle is traveling forward.