Bi-Directional Overrunning Clutch Differential for Back-Drive Control
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Solution Overview
Problem
Existing vehicle differentials with bi-directional overrunning clutches lack an efficient mechanism to control back-drive mode, which affects torque transfer and engine braking capabilities, especially in hilly terrain.
Innovation Solution
A differential design incorporating a bi-directional overrunning clutch (ORC) assembly with a back-drive mode control (BDMC) feature, which includes a clutch cam housing with cam features, a roller cage assembly, and centering biasing members, allowing for selective engagement of the roller cage during ORC and BDMC conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a bi-directional overrunning clutch is employed in a differential to transfer torque when rear wheels rotate faster than front wheels, then torque transfer capability is improved, but the ability to control back-drive mode and provide engine braking is insufficient
Solution Approach 1:
The patent employs a dynamic control system where an actuator can actively adjust the engagement state of the overrunning clutch based on driving conditions. The clutch can switch between engaged and disengaged states, allowing the differential to adapt between torque transfer mode and back-drive mode, providing both torque transfer capability and engine braking control
Solution Approach 2:
The control system uses feedback from wheel speed sensors and vehicle state information to determine when to engage or disengage the overrunning clutch. This feedback mechanism enables the system to automatically select the appropriate operating mode (ORC or BDMC) based on real-time conditions, improving both torque transfer and back-drive control
2Productivity
If the roller cage assembly is selectively engaged during ORC condition to provide torsion force, then torque transfer efficiency is improved, but the complexity of the engagement control mechanism increases
Solution Approach 1:
The patent separates the control function from the torque transfer function by using a dedicated actuator mechanism that independently controls the roller cage engagement. This extraction of the control function allows for simplified engagement logic while maintaining high torque transfer efficiency when engaged
Solution Approach 2:
The patent introduces an intermediary actuator mechanism that mediates between the control system and the roller cage assembly. This intermediary component simplifies the direct control complexity by providing a mechanical interface that can engage/disengage the rollers without requiring complex direct actuation of each roller
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
The proposed solution enables efficient torque transfer and engine braking by allowing the differential to operate in both ORC and BDMC modes, improving vehicle stability and control, especially during steep descents in hilly terrain.
Implementation Method 1
The centering biasing member is positioned to provide a centering force between the roller cage assembly and the clutch cam housing to center the rollers of the roller cage assembly in associated cam features in the interior surface of the clutch cam housing
Implementation Method 2
The overrunning clutch (ORC) assembly is configured to selectively engage the roller cage assembly during an ORC condition to provide a torsion force to overcome the centering force provided by the centering biasing member therein allowing the rollers of the roller cage assembly to move in the respective cam features
Implementation Method 3
The pinion gear is in operational engagement with the ring gear. The pinion gear is configured to couple torque between the ring gear and a transmission
Implementation Method 4
The roller cage assembly includes rollers that engage an outer surface of the first side hub and an outer surface of the second side hub
Data Source
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AI summary
A differential with an overrunning clutch (ORC) assembly is provided. The differential includes a first plain bearing end cap with an interior surface that forms a plain bearing interface with an outer surface of a first side hub. The first plain bearing end cap further has a first outer surface portion that engages a first end portion of a roller cage assembly. A second plain bearing end cap with an interior surface that forms a plain bearing interface with an outer surface of the second side hub is also included. The second plain bearing end cap further has a first outer surface portion that engages a second end portion of the roller cage assembly. The (ORC) assembly selectively engages the roller cage assembly during an ORC condition to selectively couple torque between a ring gear and the first and second side hubs.