Hydraulic System Shifting Piston Valve Control
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Solution Overview
Problem
Existing hydraulic systems for AWD coupling and transfer case gear shifting are complex, heavy, and inefficient, with high cost, weight, and packaging issues, as well as poor torque accuracy and controllability, due to the use of multiple actuators and complex control strategies.
Innovation Solution
A hydraulic system that utilizes the movement of a shifting piston to achieve a valve function, allowing pressure to be applied to the AWD clutch piston only when the shifting piston reaches its end positions, thereby avoiding unintentional torque transfer during shifting, using a reversible pump assembly and mechanically actuated piston valves or pilot-controlled ball valves.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If multiple actuators are used for shift actuation and AWD clutch actuation, then the system can achieve independent control of shifting and clutch functions, but the system complexity, weight, and cost increase
Solution Approach 1:
The patent combines the shift actuation function and AWD clutch actuation function into a single integrated actuator. The actuator includes a piston that can move in different directions to control both the shifting mechanism and the AWD clutch, eliminating the need for separate actuators while maintaining independent control capability through hydraulic circuit design
Solution Approach 2:
The single actuator is designed to perform multiple functions: it can actuate the shifting mechanism in both directions and also actuate the AWD clutch. This multi-functional design reduces the total number of actuators while preserving the ability to independently control shifting and clutch operations
2Ease of operation
If a slide valve is used in the hydraulic system, then pressure distribution can be controlled, but the system requires high cleanliness and an oil filter
Solution Approach 1:
The patent removes the slide valve component from the hydraulic system and replaces it with a piston-based pressure control mechanism. This extraction eliminates the need for high cleanliness requirements and oil filters associated with slide valves, while maintaining the ability to control pressure distribution to different hydraulic circuits
3Device complexity
If electromechanical systems with one actuator are used for both shifting and clutch actuation, then the number of actuators is reduced, but torque accuracy and controllability worsen
Solution Approach 1:
The patent employs a hydraulic system with a single actuator that uses hydraulic pressure and circuit design to achieve precise torque control. The hydraulic medium transmits force accurately to both the shifting mechanism and AWD clutch, maintaining torque accuracy and controllability despite using fewer actuators
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 system complexity, weight, and cost, while improving torque accuracy and controllability by using the shifting piston's movement to control pressure application to the AWD clutch, allowing seamless gear shifting without engaging the clutch during maneuvers.
Implementation Method 1
a first port 118 of the pump assembly 100 is in fluid connection with a shifting piston 202 arranged in the transfer case 20, wherein movement of the shifting piston 202 between two end positions actuates a shifting mechanism to change between low and high range gear
Implementation Method 2
a reversible pump assembly 100 for actuating the shifting piston 202
Data Source
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AI summary
A hydraulic system is provided, comprising a hydraulically actuated clutch, a hydraulically actuated shifting piston, and a pressure source for actuating the clutch as well as the shifting piston. The movement of the shifting piston also controls a valve function which serves to open a connection from the pressure source to the clutch only when the shifting piston has reached one of its end positions.