Integrated Transfer Case Hydraulic Control and Lubrication
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Solution Overview
Problem
Existing vehicle powertrain systems lack an integrated hydraulic control system that efficiently manages power distribution between all four wheels, particularly in low-range and high-range modes, and fails to ensure proper lubrication during towing, leading to potential wear and inefficiency.
Innovation Solution
A vehicle powertrain with an automatic transmission and transfer case sharing a common hydraulic control system, including high and low range circuits, a torque on demand clutch, and a lubrication circuit with a drainback passageway, where fluid pressure controls the operation of the transfer case and ensures lubrication through a supplemental electric pump for towing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a common hydraulic control system is used for both transmission and transfer case, then system complexity is reduced and control is integrated, but the reliability of independent control for each component may be compromised
Solution Approach 1:
The hydraulic control system is segmented into separate circuits: a transmission control circuit and a transfer case control circuit. Each circuit has its own control valves and pathways, allowing independent operation. The transmission circuit controls clutch engagement for gear shifts, while the transfer case circuit controls the TOD clutch and range selection, eliminating interference between systems while maintaining overall system integration.
Solution Approach 2:
A priority control valve acts as an intermediary component that mediates between the transmission and transfer case control circuits. This valve ensures that transmission control takes precedence when both systems require simultaneous operation, preventing conflicts and ensuring reliable control by arbitrating resource allocation between the two circuits.
2Use of energy by moving object
If the vehicle is towed with the engine off, then fuel consumption is reduced, but the transmission and transfer case components fail to receive proper lubrication
Solution Approach 1:
The system uses a drainback mechanism where lubricating fluid automatically drains from the transmission and transfer case components back to the sump through gravity when the vehicle is towed. This self-service mechanism ensures continuous lubrication of rotating components during towing without requiring engine operation or external power sources.
Solution Approach 2:
The lubrication system operates periodically through the drainback cycle: during normal operation, the pump circulates fluid through the system; during towing, gravity causes fluid to drain back to the sump, creating periodic lubrication cycles that maintain component protection without continuous energy input.
3Productivity
If the TOD clutch is controlled independently of transmission clutches, then front wheel power delivery is optimized, but the overall powertrain control efficiency decreases
Solution Approach 1:
The control systems for the TOD clutch and transmission clutches are merged into a single integrated hydraulic control architecture. The same hydraulic pump, fluid reservoir, and control valve body serve both functions, with dedicated control valves for each clutch. This merging reduces overall system complexity while maintaining the ability to independently control power distribution to front and rear wheels.
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
Enables efficient power distribution to all four wheels in various modes and ensures proper lubrication during towing, reducing wear and fuel consumption by using a supplemental electric pump to maintain lubrication without engine operation.
Implementation Method 1
The transfer case operates in high range in response to fluid pressure in the high range circuit and operates in low range in response to fluid pressure in the low range circuit
Implementation Method 2
a drainback passageway from a transfer case front sump to the transmission sump
Data Source
AI summary
A transfer case and transmission are designed to permit the transmission hydraulic control system to control a range selection coupler and a torque on demand clutch in the transfer case. Two pressure circuits are transmitted from the transmission to the transfer case: a high range circuit and a low range circuit. The low range circuit is pressurized to engage low range while the range circuit is pressurized to engage high range. The torque on demand clutch is controlled by whichever of these circuits has the higher pressure. Lubrication is provided to a front section of the transfer case via the transmission output shaft, with the fluid returning to the transmission sump through a drainback passageway. The rear portion of the transfer case has a segregated sump. A control strategy is employed to partially fill front section of the transfer case with fluid in preparation for vehicle towing.