Hydraulic Transfer Case Lock Mechanism for Mode Stability
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Solution Overview
Problem
Conventional automotive powertrain systems face challenges in maintaining mode stability, particularly in four-wheel-drive configurations, due to hydraulic clutch assemblies that lose holding force over time due to bleed down, leading to unintended mode changes and reduced efficiency.
Innovation Solution
A hydraulic mode-stable powertrain transfer case with a lock mechanism that prevents movement of the clutch assembly between positions, ensuring mode stability despite hydraulic bleed down, comprising a housing, primary and secondary shafts, a clutch assembly, and an actuator with a piston and cylinder, along with a lock mechanism that can be selectively locked or unlocked to maintain desired torque distribution between drivelines.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If hydraulic clutch assemblies are used to selectively translate rotational torque between drivelines, then adaptability to different driving conditions is improved, but mode stability deteriorates due to bleed down causing unintended mode changes
Solution Approach 1:
A lock mechanism is introduced as an intermediary component between the hydraulic clutch assembly and the torque transmission path. This lock mechanism includes a lock member that can engage with a ramp surface to physically prevent the clutch pack from moving out of engagement, thereby stabilizing the selected mode despite hydraulic pressure loss over time
Solution Approach 2:
The lock mechanism proactively counteracts the anticipated harmful effect of hydraulic bleed down before it can cause mode switching. By pre-positioning the lock member to engage with the ramp surface, the system prevents the clutch assembly from moving to a different position, thereby maintaining mode stability against the predicted deterioration
2Reliability
If lock mechanism is added to maintain mode stability, then reliability is improved, but device complexity increases
Solution Approach 1:
The lock mechanism is merged with the existing actuator assembly rather than being a completely separate system. The lock member is positioned within the actuator housing and utilizes the existing ramp surface geometry, combining the locking function with the existing structural elements to minimize additional complexity
Solution Approach 2:
The lock mechanism is designed to be automatically actuated by the existing hydraulic pressure changes that already control the clutch assembly. When hydraulic pressure moves the clutch pack along the ramp surface, the lock member passively engages or disengages based on the position, allowing the system to self-lock without requiring additional control mechanisms
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 enhances powertrain system performance by maintaining mode stability, reducing manufacturing complexity and cost, and improving efficiency, drivability, and component life while allowing for flexible operation in various driving conditions.
Implementation Method 1
an actuator having a cylinder and a piston movably supported in the cylinder. The piston is disposed in force translating relationship with the clutch assembly such that movement of the piston along the cylinder causes corresponding movement of the clutch assembly
Data Source
AI summary
A transfer case (26) for translating rotational torque from an engine (22) to first and second differentials (34, 36). A primary shaft (50) is supported in a housing (48) and has an input in communication with the engine (22) and an output in communication with the first differential (34). A secondary shaft (52) is disposed in communication with the second differential (36). A clutch (54) selectively translates torque between the shafts (50, 52) and moves between a first position (54A) wherein torque is translated to the secondary shaft (52), and a second position (54B) wherein torque is interrupted. An actuator (64) with a piston (68) movably supported in a cylinder (66) moves the clutch (54). A lock (70) moves between a locked configuration (70A) engaging the piston (68) to prevent the clutch (54) from moving, and an unlocked configuration (70B) releasing the piston (68) allowing the clutch (54) to move.