Axle Disconnect Spring Preload for Rapid Engagement
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Solution Overview
Problem
Existing axle disconnect systems for four-wheel drive vehicles face challenges in rapid and frequent engagements and disengagements under high driveline drag conditions without increasing system mass, weight, and cost.
Innovation Solution
An improved axle disconnect system featuring an engagement spring, a power source, a stationary axle housing with threaded surfaces, a slidable gear, and side gears that allow for preload and alignment of teeth for efficient engagement and disengagement, even under high driveline drag conditions, using a combination of gears and springs to manage torque and alignment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If conventional axle disconnect systems are used, then system mass and cost are controlled, but the system cannot achieve rapid and frequent engagements and disengagements under high driveline drag conditions
Solution Approach 1:
The slidable gear pre-loads the engagement spring before teeth alignment is achieved, storing elastic potential energy that is released to rapidly drive the engagement process. This preliminary action eliminates the need for high-power actuators during actual engagement, enabling fast operation without proportionally increasing system complexity
Solution Approach 2:
The system transitions from static gear alignment to dynamic engagement by using a slidable gear that moves axially under spring force. The engagement spring provides dynamic force multiplication, allowing the system to overcome high driveline drag during engagement while maintaining controlled disengagement, achieving rapid operation without excessive complexity
2Reliability
If high driveline drag conditions are overcome, then engagement reliability is improved, but system mass and weight increase
Solution Approach 1:
The engagement spring provides periodic force pulses during the engagement process, delivering high force only when needed to overcome tooth misalignment and driveline drag. This periodic action achieves reliable engagement under high drag conditions without requiring continuously high force transmission components, thereby avoiding proportional weight increases
Solution Approach 2:
The system changes the force parameter dynamically through spring pre-loading, converting stored elastic energy into high engagement force only when required. This parameter change enables reliable operation under high drag without permanently increasing the force transmission capacity of all components, maintaining system weight efficiency
3Productivity
If frequent engagements and disengagements are enabled, then fuel economy is improved, but system durability deteriorates
Solution Approach 1:
The engagement spring is pre-loaded before each engagement cycle, storing energy that is released to complete the engagement quickly. This preliminary action reduces the duration of high-stress conditions during each engagement, allowing frequent cycles without proportionally reducing system service life
Solution Approach 2:
The system rushes through the engagement process by using spring force to quickly overcome the misalignment and drag conditions, minimizing the time spent in high-stress states. This rapid transition through the critical engagement phase enables frequent operations while maintaining component durability
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
Enables rapid and frequent engagements and disengagements of axles under high driveline drag conditions without increasing system mass or cost, ensuring efficient power transfer and fuel economy.
Implementation Method 1
an engagement spring positioned on the radially outer surface of the first side gear
Implementation Method 2
a slidable gear drivingly connected to the power source having a radially inner surface and a radially outer surface with a set of threads thereon, a first side gear drivingly connected to a first axle half shaft and the slidable gear having two axial ends and a radially outer surface
Data Source
AI summary
An axle disconnect system for drive axles that utilizes an engagement spring, an electric motor and a slidable gear. The motor is connected to the slidable gear which moves along threads thereby engaging or disengaging clutch teeth on a first side gear which selectively engages a second side gear. The engagement spring is located between a bearing and the first side gear wherein when engagement is desired, but blocked by misalignment of the teeth, the engagement spring can apply a load to allow for engagement once alignment of the teeth is achieved. The use of a second engagement spring allows for the disengagement of the system when disengagement is typically blocked due to high driveline torques without having to reapply current to the motor.