Heavy-Vehicle Differential With Selectable Ratios and Locking
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Solution Overview
Problem
Existing vehicle differentials lack versatility and efficiency in handling varying torque transmission ratios and grip conditions, particularly in heavy vehicles, leading to suboptimal performance in different driving scenarios.
Innovation Solution
A differential group with a transmission system comprising bevel gears and a carrier with selectively engageable pinions and crowns, allowing for two distinct torque transmission ratios through a pneumatic actuator system, and a locking mechanism to integrate the carrier with the casing for enhanced grip.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a differential provides a locking function to constrain axle shafts for improved grip, then traction on low-grip surfaces is improved, but the differential loses the ability to allow different velocities between wheels during normal operation
Solution Approach 1:
The differential system dynamically switches between two operational states: a locked state where the carrier is constrained to provide equal torque to both wheels for improved traction, and an unlocked state where the carrier rotates freely to allow differential velocities. This dynamic reconfiguration resolves the contradiction by making the system adaptable to different driving conditions.
Solution Approach 2:
The differential mechanism serves multiple functions: it acts as a standard open differential during normal operation to allow velocity differentiation, and transforms into a locked differential when the carrier is constrained to provide enhanced traction. This multi-functionality resolves the contradiction by combining both velocity differentiation and traction improvement capabilities in a single system.
2Strength
If a differential is designed for heavy vehicle applications with high torque capacity, then strength and durability are improved, but the device size and complexity increase
Solution Approach 1:
The patent combines the open differential and locked differential functions into a single integrated mechanism sharing common components such as the carrier, planets, and ring gear. This merging approach allows the system to achieve high torque capacity and multiple operational modes without proportionally increasing complexity, as the same structural elements serve multiple purposes.
Solution Approach 2:
The differential components are designed to perform multiple functions: the carrier both transmits torque and provides the locking interface, the planets both reduce torque and enable differential rotation, and the ring gear both supports the planets and provides the locked state constraint. This multi-functionality allows heavy-duty performance without excessive complexity.
3Ease of operation
If a differential allows different velocities to be delivered to wheels, then ability to follow trajectories during bends is improved, but torque is dispersed to the wheel with reduced grip
Solution Approach 1:
The system dynamically adapts its torque distribution characteristics based on operating conditions. During normal operation including bends, the differential allows velocity differentiation for easy trajectory following. When grip conditions deteriorate, the system transitions to a locked state that constrains the carrier, thereby preventing torque dispersion to the slipping wheel and improving torque transmission efficiency.
Solution Approach 2:
The differential mechanism provides both velocity differentiation and torque locking functions within the same system. This multi-functionality resolves the contradiction by allowing the system to exhibit appropriate behavior for each condition: velocity differentiation for trajectory following and torque equalization for grip maintenance, eliminating the need to choose between the two opposing requirements.
Data Source
Figure 1
Figure 2~3
Figure 4a~4b
AI summary
Differential group (1) for a heavy vehicle comprising a casing (2) defining a space (3), a differential (8) and a transmission (9) housed inside the space (3), the transmission (9) is interposed between a drive source (7) and the differential (8) and comprise two pairs of bevel gears (17, 18), one of the crowns (17a, 18a) and the pinions (17b, 18b) being able to be selectively engaged, alternatively relative to one another, between the drive source (7) and the differential (8).