Transfer Case Plunger Brake for Neutral Mode Locking
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Solution Overview
Problem
Existing vehicle powertrain systems lack a reliable mechanism to prevent inadvertent range shifts that could cause a vehicle to roll away when the driver is not in control, particularly in modes like neutral.
Innovation Solution
A transfer case design incorporating a dual drive gear with a radial cam surface that actuates a plunger to engage with the output shaft's radial flange, preventing rotation and thus immobilizing the vehicle during unintended range shifts, utilizing a combination of cam follower and blocking springs for secure engagement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a range shifter is added to enable neutral mode shifting, then vehicle mode versatility is improved, but the risk of inadvertent range shifts causing vehicle rolling increases
Solution Approach 1:
The plunger is pre-positioned and spring-loaded to engage with the output shaft before any inadvertent rotation can occur. The cam surface is designed so that during normal operation the plunger maintains continuous contact with the output shaft, preventing rotation before it can cause harm. This preliminary engagement eliminates the harmful effect of inadvertent range shifts while preserving neutral mode functionality.
2Reliability
If a plunger engagement mechanism is added to prevent output shaft rotation, then safety against inadvertent range shifts is improved, but device complexity increases
Solution Approach 1:
The plunger serves multiple functions: it prevents inadvertent range shifts by grounding the output shaft, it engages/disengages based on cam surface geometry during normal operation, and it works passively with spring force without requiring additional actuators. The cam surface itself becomes the control mechanism, eliminating the need for separate valves, sensors, or actuators that would increase complexity.
Solution Approach 2:
The spring-loaded plunger automatically engages and disengages based on the cam surface geometry during normal transfer case operation. The system uses its own operational movements to control the plunger position, requiring no external control system. The cam surface converts the rotational motion of the output shaft into the appropriate plunger engagement/disengagement sequence, making the safety mechanism self-regulating.
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
Effectively prevents vehicles from rolling away due to inadvertent range shifts by ensuring the output shaft is grounded and locked during mode changes, enhancing safety by maintaining vehicle control.
Implementation Method 1
A failsafe transfer case may include a mechanical brake, which may be constructed and arranged to prevent rotation of an output shaft during a range shift
Implementation Method 2
The plunger may be spring-loaded so that the plunger is actuated by the cam surface
Data Source
AI summary
A number of variations may include a product comprising an output shaft having a radial flange comprising a plurality of teeth; a range shifter operatively connected to the output shaft constructed and arranged to selectively shift a vehicle between a low range, high range, and neutral mode; a mode shifter operatively connected to the output shaft constructed and arranged to shift the vehicle between a four-wheel and two-wheel drive mode; a dual drive gear operatively attached to the output shaft between the range shifter and the mode shifter constructed and arranged so that rotation of the dual drive gear drives the range shifter and the mode shifter; and at least one plunger radially displaced around the output shaft which is actuated by the dual drive gear to engage a slot between the plurality of teeth on the output shaft to prevent rotation of the shaft during a range shift.