Variable-Engagement Clutch for Vehicle Differential Pump Control
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Solution Overview
Problem
Conventional electronically-controlled, limited-slip differentials with hydraulically-actuated clutches suffer from parasitic energy losses and reduced fuel economy due to continuous operation of the hydraulic pump, even when traction is not needed, leading to shortened hydraulic fluid life.
Innovation Solution
A vehicle differential assembly with a variable-engagement clutch that selectively drives a hydraulic pump only when needed, using a magnetic particle clutch to transmit torque between the input and pump, allowing for variable engagement and minimizing energy loss by eliminating unnecessary pump operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the hydraulic pump operates continuously to power the hydraulically-actuated clutch, then the differential can provide traction control when needed, but parasitic energy losses increase and fuel economy deteriorates
Solution Approach 1:
The patent applies a variable-engagement clutch that dynamically adjusts the connection between the hydraulic pump and the hydraulically-actuated clutch based on system needs. When traction control is required, the variable-engagement clutch engages to drive the pump; when not needed, it disengages to eliminate parasitic losses. This dynamic engagement mechanism resolves the contradiction by making the energy-consuming component operational only when necessary.
2Reliability
If the hydraulic pump operates continuously, then hydraulic fluid pressure is always available for clutch engagement, but the useful life of the hydraulic fluid shortens due to continuous circulation and heat generation
Solution Approach 1:
The patent implements periodic operation of the hydraulic pump through the variable-engagement clutch mechanism. Instead of continuous operation, the pump operates only during periods when traction control is needed. This periodic activation reduces cumulative thermal exposure and mechanical stress on the hydraulic fluid, thereby extending its service life while maintaining pressure availability when required.
3Loss of energy
If the variable-engagement clutch is used to selectively drive the hydraulic pump, then energy losses are reduced, but the device complexity increases
Solution Approach 1:
The variable-engagement clutch serves multiple functions: it acts as a torque transmission device, an engagement control mechanism, and an energy management component. By making this single component multi-functional, the patent reduces the need for additional separate systems that would further increase complexity, thereby achieving energy savings with minimal added complexity.
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
This solution reduces parasitic energy losses, enhances fuel economy, and extends the life of hydraulic fluid by ensuring the hydraulic pump operates only when required, while providing improved traction control and vehicle stability through controlled torque distribution.
Implementation Method 1
using a magnetic particle clutch to transmit torque between the input and pump
Data Source
AI summary
A vehicle differential assembly is provided that includes a differential adapted to allow differing rotational speed between a pair of outputs. The differential includes a gear assembly connected to the outputs and one or more hydraulically-actuated clutches for selectively and variably coupling the outputs. A hydraulic pump is adapted to generate hydraulic fluid pressure for engagement of the hydraulically-actuated clutches. A variable-engagement clutch is operatively connected to the input and the hydraulic pump such that the input selectively drives the hydraulic pump during engagement of the clutch to provide hydraulic fluid pressure to the hydraulically-actuated clutches. A valve operatively connected to the hydraulic pump and the hydraulically-actuated clutches to selectively and variably provides fluid pressure from the hydraulic pump to the hydraulically-actuated clutches. A method of controlling vehicle stability is also provided.