Transfer Case Hub and Hall Sensor Neutral Detection
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Solution Overview
Problem
Existing transfer cases in rear wheel drive vehicles with four wheel drive capabilities face challenges in distinguishing between high gear, low gear, and neutral positions due to dimensional tolerances and spring compliance, leading to difficulties in sensor accuracy for determining the neutral position, and a need for immediate shift from low to high gear without a neutral intermediate step.
Innovation Solution
A transfer case design featuring a first hub with exclusive torsional engagement in extreme neutral, intermediate, and low gear positions, along with a second hub torsionally connected to the output shaft, and a planetary gear set that disengages in high gear mode, allowing for clear neutral position determination and immediate gear shifts through a shift fork and sensor confirmation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a sensor is used to detect the neutral position in existing transfer cases, then the neutral position can be detected, but the detection accuracy is poor due to dimensional tolerances and spring compliance causing ambiguous sensor readings between high gear, low gear, and neutral positions
Solution Approach 1:
The patent uses magnetic field changes (analogous to color changes in optical detection) detected by a Hall effect sensor to identify gear positions. The magnetic field strength varies distinctly between neutral, high gear, and low gear positions, providing clear differentiation despite mechanical tolerances and spring compliance variations.
Solution Approach 2:
The patent replaces mechanical position detection methods with a magnetic field-based detection system using a Hall effect sensor. This substitution eliminates the problems of mechanical wear and tolerance accumulation, providing more reliable and accurate position detection.
2Power
If a planetary gear set is engaged in high gear mode, then gear reduction is provided, but parasitic losses occur due to continuous engagement of the planetary gear set
Solution Approach 1:
The patent makes the planetary gear set dynamically engageable and disengageable rather than continuously engaged. A hub assembly with splined connections allows the planetary gear set to be selectively engaged for low gear operation and disengaged for high gear operation, eliminating parasitic losses when gear reduction is not needed.
Solution Approach 2:
The patent segments the power transmission path into two separate routes: one through the planetary gear set for low gear and another direct route for high gear. The hub assembly acts as a selector that divides the power flow, allowing the system to choose the appropriate transmission path based on operating conditions.
3Ease of manufacture
If dimensional tolerances and spring compliance are present in the transfer case components, then manufacturing is feasible, but the neutral position cannot be clearly distinguished from other gear positions
Solution Approach 1:
The patent introduces a magnetic field as an intermediary between the mechanical components and the position detection system. The Hall effect sensor detects magnetic field changes caused by the relative positions of magnetized components, providing accurate position information without being affected by mechanical tolerances or spring compliance variations.
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 design ensures clear identification of the neutral position and enables immediate gear shifts from low to high gear, preventing parasitic losses and ensuring accurate operational status, thus enhancing the reliability and efficiency of four wheel drive operations.
Implementation Method 1
A Hall effect sensor is provided to detect a strength of a magnetic field
Implementation Method 2
The housing 52 has annular cup 53 formed about an annular shape electromagnet 56. When actuated the electromagnet 56 attracts a clutch plate 58 to make contact therewith.
Data Source
AI summary
A vehicle transfer case is provided including input and output shafts mounted within a housing, a secondary shaft selectively driven by the output shaft, a first hub having an inner diameter splined section having a first extreme neutral position with exclusive torsional engagement with the output shaft, and in a second intermediate high position having torsional engagement with the output shaft and input shafts, and in a third extreme low position having exclusive torsional engagement with the input shaft. A second hub is provided, rotatably mounted on the first hub and axially fixed therewith. The second hub is torsionally fixed to the output shaft, and a shift fork is provided to translate the second hub. A planetary gear set is provided, having a ring gear, a plurality of planet gears connected to each other by a carrier and a sun gear; and wherein in the extreme neutral position the output shaft is disengaged from the input shaft, and in the second intermediate position the input shaft is directly connected to the output shaft without rotating the planetary gear set, and in the extreme third position the first hub torsionally connects the input shaft to the sun gear, and the second hub is connected with the carrier.