Transfer Case Clutch Hub Direct Engagement
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Solution Overview
Problem
The existing transfer cases for two-wheel rear drive vehicles with selective four-wheel drive capabilities suffer from issues such as noise, rattle, and lubrication leakage due to the use of a flat thrust washer between the clutch housing and the hub, which also increases fabrication costs and reduces the torsional engagement capacity.
Innovation Solution
Eliminating the flat thrust washer between the clutch housing and the hub allows for full torsional engagement of the clutch housing with the main sprocket extension, enhancing the torsional capacity and eliminating noise and leakage, while simplifying the fabrication process by removing the need for locking tabs and staking the washer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a flat thrust washer is used between the clutch housing and hub, then the cost of fabrication is reduced and assembly is simplified, but noise and rattle occur and lubrication leakage increases
Solution Approach 1:
The patent eliminates the flat thrust washer component from the clutch housing assembly. By removing this intermediate element, the hub can directly engage with the clutch housing, which eliminates the noise and rattle generated by the washer while also preventing lubrication leakage that occurred through the washer's interface.
Solution Approach 2:
The patent merges the hub and clutch housing into a direct engagement relationship, eliminating the separate thrust washer component. This consolidation allows the hub's outer diameter surface to directly contact the clutch housing's inner diameter surface, creating a more integrated and efficient torque transmission path.
2Ease of manufacture
If a flat thrust washer is used between the clutch housing and hub, then assembly is simplified, but torsional engagement capacity is reduced
Solution Approach 1:
By removing the flat thrust washer, the patent eliminates the gap and interference that prevented full torsional engagement. The hub's outer diameter can now fully engage with the clutch housing's inner diameter along the entire axial length, maximizing the torque transmission capacity without the constraint of a separate washer component.
3Reliability
If locking tabs and staking are used to retain the thrust washer, then the washer is securely positioned, but fabrication complexity and cost increase
Solution Approach 1:
The patent removes the thrust washer component entirely, which eliminates the need for locking tabs, staking operations, and associated fabrication processes. The direct engagement between the hub and clutch housing provides inherent retention without requiring additional fastening features or complex assembly steps.
4Strength
If the thrust washer is eliminated, then torsional capacity is enhanced and noise is reduced, but the clutch housing must be directly heat treated
Solution Approach 1:
The patent changes the material properties of the clutch housing by applying heat treatment to achieve the necessary hardness and wear resistance for direct engagement with the hub. This parameter change in the clutch housing's physical properties compensates for the elimination of the thrust washer, enabling the clutch housing to withstand the increased torsional loads and wear without the protective washer.
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
This solution enhances the torsional capacity of the transfer case, reduces noise and leakage, and lowers production costs by eliminating the flat thrust washer, resulting in a more efficient and cost-effective transfer case design.
Implementation Method 1
A first thrust bearing 26 is provided. The first thrust bearing 26 has a race 28 on its front end that is adjacent the radial shoulder 24 on the main input shaft 22.
Implementation Method 2
The friction members 85 and 89 are typically provided by metal plates coated with friction material intertwined with uncoated metal plates.
Implementation Method 3
A chain 72 is provided which torsionally connects the main sprocket 30 with the front axle output sprocket 21.
Data Source
AI summary
A transfer case for a vehicle having a selective four wheel drive mode of operation is provided. The transfer case includes a front shell boltably connected with a rear shell, a front axle output shaft and sprocket, and a main input shaft torsionally connected with a transmission and rear axle of the vehicle. A main sprocket is provided, rotatably mounted on the main input shaft. The sprocket has an axial extension. A chain torsionally connects the main sprocket with the front axle output sprocket. A clutch housing having a splined opening is torsionally connected with the main sprocket extension. A hub is spline connected on the main input shaft. A clutch pack is selectively torsionally connected with the clutch housing and with the hub. A pressure plate is provided to actuate the clutch pack. An electrically powered ball ramp mechanism is provided for axially displacing the pressure plate to torsionally join the main input shaft to the front axle input shaft causing the main sprocket extension to contact the hub.