Transfer Case Variable Ratio Planetary Gear Clutch
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Solution Overview
Problem
Existing transfer cases for four-wheel drive vehicles cannot achieve a transmission ratio between 1 and 2 in off-road gear, leading to inefficient power distribution and increased wear due to fixed design constraints.
Innovation Solution
The transfer case design includes an input shaft connected to a first ring gear with radial connecting webs, allowing for a clutch to selectively couple the sun gear to the housing, enabling a variable transmission ratio by driving the ring gear and decoupling in road gear, thus distributing torque through both the sun gear and ring gear, reducing friction and wear.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the input shaft is decoupled from the planet carrier and coupled to the sun gear in off-road gear, then the transmission ratio is greater than 2, but this does not meet practical requirements for optimal power distribution
Solution Approach 1:
The patent introduces a clutch mechanism that allows dynamic switching between coupling the input shaft to the planet carrier (road gear) and coupling it to the sun gear (off-road gear). This dynamic reconfiguration enables the transmission ratio to be adjusted based on driving conditions, optimizing power distribution efficiency while providing adaptability between different gear modes.
Solution Approach 2:
The patent modifies the planetary gear system by introducing a clutch that can change the effective gear ratio parameter. By selectively engaging the clutch to couple the input shaft to either the planet carrier or sun gear, the transmission ratio parameter is changed from a fixed value to a variable parameter, enabling ratios between 1 and 2 in off-road gear which were previously unachievable.
2Power
If the sun gear is firmly connected to the housing to provide off-road gear, then torque is transmitted through the planetary gears, but friction and wear increase due to the fixed design constraints
Solution Approach 1:
The clutch mechanism enables dynamic engagement and disengagement of the sun gear with the housing. In off-road gear, the clutch engages to firmly connect the sun gear to the housing for torque transmission. In road gear, the clutch disengages, allowing the sun gear to rotate freely and reducing friction and wear. This dynamic operation extends the service life of the planetary gear components.
3Ease of manufacture
If the transmission ratio is fixed at greater than 2 in off-road gear, then the gear design is simplified, but the power distribution becomes inefficient for practical requirements
Solution Approach 1:
The patent segments the power transmission path by introducing a clutch that can selectively engage different gear paths. The planetary gear system is divided into two operational paths: one through the planet carrier (road gear) and another through the sun gear (off-road gear). This segmentation allows the system to achieve variable transmission ratios while maintaining relatively simple gear design.
4Ease of operation
If the input shaft is coupled to the planet carrier in road gear, then the transmission ratio is 1:1, but the system cannot provide variable transmission ratios for different driving conditions
Solution Approach 1:
The clutch mechanism provides multi-functionality by enabling the same planetary gear system to operate in multiple modes: road gear with 1:1 ratio when the clutch is disengaged, and off-road gear with variable ratios between 1 and 2 when the clutch is engaged. This universal design allows the system to adapt to different driving conditions while maintaining ease of operation in both modes.
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 design allows for a transmission ratio between 1 and 2 in off-road gear, improving power distribution and reducing wear by ensuring the rotational speeds of the sun gear, ring gear, and planetary carrier are identical, enhancing the service life and reducing friction.
Implementation Method 1
The planetary gear part consists of a sun gear, a planetary carrier, several planetary gears and a ring gear which forms the internal teeth of the housing
Data Source
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AI summary
The gearbox has a housing (2), an input shaft (32), and a planetary gear part (10) having a sun gear (12), a ring gear (14) and a planetary gear carrier (16) arranged in driving connection with the input shaft. The ring gear is rotatably mounted in the housing, where the ring gear is driven from the input shaft such that the sun gear is rotatably coupled to the housing through a switching element (60). Another planetary gear part (20) is arranged with the former planetary gear part.