Hydraulic Machine Pre-Pressurization for Smooth Cylinder Control
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Solution Overview
Problem
Existing methods for controlling hydraulic cylinders in work machines, such as wheel loaders, often result in rough operations that cause shocks and jerks, which can be uncomfortable for the driver and inefficient in terms of energy use.
Innovation Solution
A control system that includes a hydraulic machine functioning as both a pump and motor, connected to an electric machine, which detects the initiation of implement movement and pre-pressurizes the hydraulic cylinder before the movement begins, allowing for smooth operation by controlling the piston speed and pressure, thereby reducing shocks and optimizing energy recovery.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the hydraulic cylinder is controlled by direct hydraulic connection without pre-pressurization, then the system response is fast, but the operation becomes rough causing shocks and jerks
Solution Approach 1:
The patent applies preliminary action by pre-pressurizing the hydraulic line connected to the piston rod side of the cylinder before the actual lowering movement begins. When the control lever is moved to initiate lowering, the hydraulic machine first pressurizes the line in advance, so that when the cylinder subsequently moves, the pre-established pressure prevents sudden shocks and jerks during the operation.
2Power
If the hydraulic machine operates only as a pump, then lifting function is achieved, but energy recovery during lowering is not possible
Solution Approach 1:
The hydraulic machine is designed to perform multiple functions: it operates as a pump during lifting operations to raise the implement, and as a motor during lowering operations to recover energy from the descending implement. This multi-functionality allows the system to both lift effectively and recover energy during lowering, converting what would be energy loss into useful energy storage.
Solution Approach 2:
The patent converts the potentially harmful energy loss during implement lowering into a beneficial energy recovery opportunity. By enabling the hydraulic machine to function as a motor during lowering, the system captures the gravitational potential energy being lost and stores it, transforming an energy waste scenario into an energy recovery opportunity that can be reused for subsequent lifting operations.
3Device complexity
If the hydraulic line is not pre-pressurized, then the system is simpler, but the driver experiences discomfort from rough operation
Solution Approach 1:
The system implements preliminary pressurization of the hydraulic line as an intermediate step between the simple unpressurized state and the final pressurized state. This preliminary action adds controlled complexity to the system, introducing a pre-pressurization phase that smooths out the transition and eliminates rough operation, thereby improving driver comfort while maintaining reasonable system complexity.
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
The system provides a smoother operation of hydraulic cylinders, reducing shocks and jerks experienced by the driver and enhancing energy efficiency by allowing for controlled pressure and speed adjustments during lifting, lowering, and tilting functions.
Implementation Method 1
The hydraulic machine therefore functions as a pump in a first operating state and supplies pressurized hydraulic fluid to the hydraulic cylinder
Implementation Method 2
The hydraulic machine also functions as a hydraulic motor in a second operating state and is driven by a hydraulic fluid flow from the hydraulic cylinder
Implementation Method 3
The electric machine therefore functions as an electric motor in the first operating state
Implementation Method 4
The electric machine therefore functions as an electric motor in the first operating state and as a generator in the second operating state
Data Source
AI summary
A method is provided for controlling a hydraulic cylinder in a work machine, which hydraulic cylinder is arranged to move an implement in relation to a part of a vehicle, with the hydraulic cylinder being controlled by a hydraulic machine. The method includes the steps of detecting initiation of a movement of the implement that is such that the piston of the hydraulic cylinder is moved in a first direction, of driving the hydraulic machine in a first rotational direction, prior to the movement of the implement taking place, so that a line from the hydraulic machine is pressurized, which line is arranged to connect the hydraulic machine to the side of the cylinder toward which the piston will be moved during the movement of the implement.