Off-Axis Transfer Case Pump Layout for Low-Power Lubrication
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Solution Overview
Problem
Existing transfer case pumps, particularly those in two-speed transfer cases, consume high power due to their large size and are not suitable for both single-speed and two-speed transfer cases, leading to inefficiencies in lubrication.
Innovation Solution
The development of an off-axis transfer case pump system that includes an oil pump, a cover assembly, and a torque transfer mechanism, where the pump shaft rotates parallel and offset from the rear shaft, allowing for efficient lubricant pressurization and distribution using gear or chain-driven torque transfer mechanisms, enabling smaller, more efficient pump designs for both single-speed and two-speed transfer cases.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If large on-axis transfer case pumps are implemented to maintain minimum lubrication rates in two-speed transfer cases during low gear, then lubrication is maintained, but power consumption increases to approximately 250 watts at 2,000 revolutions per minute
Solution Approach 1:
The patent moves the pump from the traditional on-axis position (sharing the same axis as the rear shaft) to an off-axis position (parallel but offset axis). This dimensional change allows the pump to be driven through a torque transfer mechanism (gears or chains) rather than direct shaft connection, enabling smaller pump size and reduced power consumption while maintaining adequate lubrication delivery to all transfer case components.
Solution Approach 2:
The patent separates the pump function from the main rear shaft by introducing a dedicated torque transfer mechanism with driving gears (on rear shaft) and driven gears (on pump shaft). This segmentation allows independent optimization of the pump size and speed, enabling the use of a smaller, more efficient pump that consumes significantly less power while still delivering required lubrication flow rates.
2Adaptability or versatility
If on-axis transfer case pumps are used in both single-speed and two-speed transfer cases, then the same pump design can be used, but the pump size must be large enough to handle the lowest operating speeds, resulting in inefficiency at higher speeds
Solution Approach 1:
The off-axis pump configuration with torque transfer mechanism allows the pump speed to be dynamically adjusted relative to the rear shaft speed through gear ratios. This enables the pump to operate at optimal speeds across different transfer case operating modes (single-speed, two-speed low range, two-speed high range), maintaining high efficiency while accommodating all application requirements through a single standardized design.
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 reduces power consumption by up to 90% compared to traditional on-axis pumps, achieving efficient lubrication while maintaining proper lubrication levels across various operational modes, thereby enhancing fuel efficiency and reducing emissions.
Implementation Method 1
The torque transfer mechanism includes a rear gear couplable to the rear shaft, and a pump gear coupled to the pump shaft and configured to engage with the rear gear
Implementation Method 2
The torque transfer mechanism includes a rear sprocket coupled to the rear shaft, a pump sprocket couple to the pump shaft, and a pump chain disposed around the rear sprocket and the pump sprocket
Implementation Method 3
The oil pump has a pump shaft, and is configured to pressurize a lubricant in response to a rotation of the pump shaft
Data Source
AI summary
A transfer case pump includes an oil pump, a cover assembly, and a torque transfer mechanism. The oil pump has a pump shaft, and is configured to pressurize a lubricant in response to a rotation of the pump shaft. The pump shaft rotates around a pump axis. The pump axis is parallel to a rear axis of a rear shaft. The pump axis is offset from the rear axis. The cover assembly has a channel configured to transfer the lubricant from the oil pump to the rear shaft. The cover assembly extends around the rear shaft and around the pump shaft. The torque transfer mechanism is configured to transfer a torque from the rear shaft to the pump shaft.