Hydraulic Control System for Bucket Shake Operation
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Solution Overview
Problem
In hydraulic power systems of work machines with tilting buckets, the existing methods for dislodging debris using rapid rack-dump movements often result in inadequate pressure maintenance, leading to inefficient debris removal due to hysteresis and lag in the hydraulic control system, causing the bucket to respond slowly to fluctuating commands.
Innovation Solution
A control system that maintains a constant pressure signal in the load sensing line to keep the unloader valve closed during the bucket shake operation, ensuring consistent hydraulic pressure and improved actuator response, utilizing a second actuator to maintain the coupling mechanism in a locked position and apply constant pressure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the unloader valve is used to relieve pressure in the main supply line during idle operations, then the fixed displacement pump can rotate with minimal load, but the pressure maintenance becomes inadequate during rapid bucket shake operations
Solution Approach 1:
The control system is divided into separate functional pathways: a load sensing line for pressure control and a separate bucket control line for actuation. This segmentation allows independent control of pressure maintenance and bucket movement, enabling the unloader valve to remain closed during shake operations while still providing idle relief when needed.
Solution Approach 2:
A pilot valve is introduced as an intermediary component that receives signals from the bucket control valve and modulates the unloader valve operation. This pilot valve acts as a mediator between the bucket control system and the pressure relief system, preventing premature unloading during shake operations while maintaining normal idle relief functionality.
2Productivity
If the joystick is moved rapidly between rack and dump positions to shake the bucket, then debris can be dislodged, but the hydraulic control system exhibits hysteresis and lag causing slow bucket response
Solution Approach 1:
The system establishes normal operating pressure in the main supply line before initiating bucket shake operations by maintaining the unloader valve in the closed position through the load sensing line. This preliminary pressure establishment eliminates hysteresis and lag, enabling immediate and vigorous bucket response when shake commands are given.
Solution Approach 2:
The control system dynamically adjusts the unloader valve position based on operational conditions. During shake operations, the pilot valve keeps the unloader valve closed to maintain high pressure for rapid response. The system transitions smoothly between different pressure states depending on whether idle relief or active operation is required.
3Use of energy by moving object
If a variable displacement pump is used to control pressure based on LS signal, then power consumption is reduced when little power is demanded, but the system becomes complex and expensive
Solution Approach 1:
The pilot valve serves as an intermediary that decouples the simple fixed displacement pump from the need for complex variable displacement mechanisms. By using the pilot valve to modulate the unloader valve based on LS pressure signals, the system achieves variable power consumption characteristics without requiring a complex variable displacement pump.
Solution Approach 2:
The patent replaces the mechanical complexity of a variable displacement pump with a hydraulic control mechanism involving the pilot valve and unloader valve. This substitution maintains the energy efficiency benefits of variable power consumption while using simpler, more reliable fixed displacement pump mechanics.
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 approach enhances the vigor and effectiveness of the bucket's shaking action, ensuring faster and more efficient debris removal by maintaining normal operating pressure and reducing mechanical stress on the system components.
Implementation Method 1
a hydraulic pump for supplying hydraulic pressure to a supply line; an unloader valve openable in use to relieve the hydraulic pressure from the supply line to unload the hydraulic pump
Implementation Method 2
a load sensing line arranged to apply a pressure signal, responsive to demand for hydraulic power, to the unloader valve actuator, to close the unloader valve to maintain the hydraulic pressure in the supply line
Implementation Method 3
at least one bucket actuator operable by the hydraulic pressure to tilt the bucket between an upwardly facing, rack position and a downwardly facing, dump position
Data Source
Figure 1
Figure 2~8
AI summary
An excavator or other work machine (1) includes a tilting bucket (2) operated by a hydraulic actuator (3) controlled by a bucket control valve (26) responsive to control signals (13) including a bucket shake control signal (13'), which causes the bucket to move repeatedly in the rack and dump directions to shake debris from the bucket in a bucket shake operation. The actuator (3) is powered by pressure from a hydraulic pump (14), and a control system (20) includes an unloader valve (21) to relieve pressure from the supply line (15) to unload the pump when there is no demand for power. The control system (20) is arranged to maintain a constant pressure signal in a load sensing line (25), to maintain the unloader valve (21) constantly in a closed condition, for the duration of the bucket shake operation. This may be achieved by pressurising an actuator (8) of a quick coupler (5) to lock the bucket to the machine.