Hydraulic Multi-Piston Actuator for Transfer Case Clutch
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Solution Overview
Problem
Modern four-wheel drive vehicle transfer cases with electromechanical actuation systems are complex and costly, placing additional load on the vehicle's electrical system and requiring advancements for reliable and cost-effective actuation.
Innovation Solution
A hydraulically actuated drive torque transfer case using a multi-piston actuator and hydraulic chambers to selectively translate a dog clutch for engaging and disengaging gear components, allowing for efficient torque distribution between the front and rear drivelines, with a mode clutch assembly for two-wheel and four-wheel drive modes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If electromechanical power-operated clutch actuators and electronic control modules are used for transfer case actuation, then the transfer case can achieve reliable and automated clutch engagement and disengagement, but the vehicle wiring requirements become complex and create additional load on the vehicle electrical system
Solution Approach 1:
The patent replaces the electromechanical actuation system with a purely mechanical hydraulic actuation system. The multi-piston actuator uses hydraulic pressure from the transmission fluid to directly engage and disengage the range clutch and mode clutch, eliminating the need for electric motors, sensors, and complex electronic control modules while maintaining reliable clutch actuation
Solution Approach 2:
The patent utilizes the vehicle's existing hydraulic system (transmission fluid under pressure) to actuate the clutch assemblies. The multi-piston actuator converts hydraulic pressure into mechanical motion to engage/disengage clutches, leveraging an existing fluid power source rather than requiring separate electrical actuation systems
2Extent of automation
If electromechanical actuation systems are implemented in transfer cases, then automated clutch control is achieved, but the cost becomes prohibitive for some four-wheel drive vehicles
Solution Approach 1:
The hydraulic actuation system is self-actuating through the natural operation of the transmission. When the transmission operates, it generates hydraulic pressure that automatically flows to the multi-piston actuator, which then automatically engages or disengages the clutches based on the selected gear range, without requiring external electrical power or complex control electronics
Solution Approach 2:
The patent makes the transmission hydraulic system serve dual purposes: both power transmission and clutch actuation. The same hydraulic fluid that lubricates and cools the transmission is also used to power the clutch actuation system, eliminating the need for separate actuation systems and reducing overall cost
3Productivity
If a multi-piston actuator is used to selectively translate the clutch member, then efficient torque distribution and seamless mode switching are achieved, but the actuator structure becomes more complex
Solution Approach 1:
The actuator is divided into multiple independent pistons (first piston and second piston) that can operate independently to control different clutch members. Each piston has its own hydraulic control circuit, allowing simultaneous or independent actuation of range clutch and mode clutch, enabling efficient torque distribution across different drive modes
Solution Approach 2:
The multi-piston actuator design nests multiple pistons within a single hydraulic housing, with pistons arranged in series or parallel configurations within the same actuator body. This compact nesting allows multiple clutch actuation functions to be integrated into a single actuator assembly, managing structural complexity while maintaining actuation efficiency
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 solution provides a reliable, cost-effective, and efficient method for torque transfer, reducing electrical system load and improving the actuation of transfer cases by using pressurized transmission fluid to axially translate clutch members, enabling seamless mode switching and torque distribution.
Implementation Method 1
a multi-piston actuator configured to receive a pressurized transmission fluid from a transmission for selectively axially translating the clutch member
Data Source
AI summary
A drive torque transfer case is provided. The transfer case includes an input shaft, an output shaft, a gear assembly coupled to the input shaft, and a range clutch assembly coupled to the output shaft. The range clutch assembly includes a clutch member and a multi-piston actuator configured to receive a pressurized transmission fluid for selectively axially translating the clutch member to engage a component of the gear assembly for transmitting a drive torque from the input shaft to the output shaft. The multi-piston actuator includes an internal piston having a first annular surface area A1 and a third annular surface area A3, and an external piston having a second annular surface area A2 and a fourth annular surface area A4. The A1 and A2 are in hydraulic communication with a first hydraulic chamber, and A3 and A4 are in hydraulic communication with a second hydraulic chamber.