Transfer Case Clutch Actuator Torque Management
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Solution Overview
Problem
Conventional transfer cases for four-wheel drive vehicles often malfunction in releasing from four-wheel drive engagement, especially under torque load, leading to potential driveline damage due to friction in spline teeth, which can result in destructive torque and part failure.
Innovation Solution
A transfer case system utilizing an electric actuator with a rotary cam and pivoting lever mechanism to effectively actuate a clutch, allowing reliable engagement and disengagement of four-wheel drive mode, using a low-cost electric motor and control systems to manage torque transmission and prevent malfunctions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a synchronizer with splined teeth is used to engage four-wheel drive mode, then the system can be made with relatively low cost, but friction on the spline teeth will prevent disengagement when transmitting high torque
Solution Approach 1:
The patent replaces the conventional synchronizer mechanism with a clutch assembly that uses friction plates and a pressure plate to transmit torque. This substitution eliminates the splined teeth engagement problem while maintaining cost-effectiveness through the use of an electric actuator similar to those used in conventional synchronizers.
Solution Approach 2:
The patent extracts the problematic splined teeth engagement mechanism from the system and replaces it with a clutch-based torque transmission system. The synchronizer is completely removed and replaced with a clutch assembly that includes friction plates, a pressure plate, and an actuator shaft, thereby eliminating the friction-induced disengagement failure mode.
2Force
If a hydraulic actuator is used to actuate the clutch, then the actuation force can be sufficient, but the control system becomes more complicated and expensive
Solution Approach 1:
The patent substitutes the hydraulic actuator system with an electric actuator system. The electric motor-driven actuator shaft with cam mechanism provides sufficient actuation force to engage and disengage the clutch while eliminating the complexity of hydraulic fluid systems, pumps, and control valves.
Solution Approach 2:
The patent introduces a cam mechanism as an intermediary between the electric actuator and the clutch pressure plate. The cam converts the rotational motion of the electric actuator shaft into the linear pressing force needed to engage the clutch, providing mechanical advantage while maintaining system simplicity.
3Ease of manufacture
If a conventional electric motor is used to actuate the synchronizer, then the system cost is low, but the torque multiplication is insufficient for reliable clutch actuation
Solution Approach 1:
The patent introduces a cam mechanism as a mechanical intermediary that multiplies the torque from the electric motor. The cam's geometric design provides mechanical advantage, converting the limited torque from a conventional electric motor into sufficient pressing force to engage and disengage the clutch reliably.
Solution Approach 2:
The cam mechanism uses curved surfaces to achieve torque multiplication. The cam's curved profile converts rotational motion into linear motion while providing mechanical advantage, enabling a low-torque electric motor to generate the high forces needed for clutch actuation.
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 system ensures reliable engagement and disengagement of four-wheel drive mode without malfunctions, reducing the risk of driveline damage by effectively managing torque and using cost-effective electric actuators, suitable for both manual and automatic on-demand systems.
Implementation Method 1
an electric actuator for applying forces to a clutch mechanism
Implementation Method 2
a plurality of frictional clutch plates, the frictional clutch plates formed of at least one frictional clutch plate coupled with the inner drum member and at least one frictional clutch plate coupled with the outer drum member
Data Source
AI summary
A transfer case for vehicles comprises: a first output shaft; a second output shaft; a clutch assembly disposed at the second output shaft, the clutch assembly including inner and outer drum members, one of the inner and outer drum members rotatable in association with rotation of the first output shaft and the other one of the inner and outer drum members coupled with the second output shaft, the clutch assembly further including a plurality of frictional clutch plates, the frictional clutch plates formed of at least one frictional clutch plate coupled with the inner drum member and at least one frictional clutch plate coupled with the outer drum member; an actuator shaft rotatably coupled with an actuator; and a clutch actuator means coupled with the actuator for applying axial force to the frictional clutch plates to transmit a drive torque of the first output shaft to the second output shaft.