Hydraulic Bleed-Off Valve Control for Smooth Actuator Startup
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Solution Overview
Problem
Existing hydraulic systems in work machines like excavators face issues with abrupt actuation and shock during operation due to the bleed-off function, leading to inefficiencies in energy-saving performance and operability, especially when switching between sole and combined operations of actuators.
Innovation Solution
A work machine equipped with a hydraulic pump of variable displacement type, a pump regulator, directional control valves, and a bleed-off valve controlled by a controller that opens the bleed-off valve before the pump flow rate increases and closes it after the flow rate has started, ensuring smooth operation and reducing unnecessary bleed-off flow rates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the bleed-off function is employed to prevent abrupt actuation and shock, then operability is improved, but energy-saving performance deteriorates due to unnecessary bleed-off flow rate
Solution Approach 1:
The bleed-off valve opening area is dynamically adjusted based on the operational state of the actuator. When the actuator is fully operated, the opening area is reduced or closed to minimize bleed-off flow rate and improve energy efficiency. When the actuator is half-operated, the opening area is maintained to ensure smooth operation and prevent shock. This dynamic adjustment resolves the contradiction between operability and energy-saving performance.
Solution Approach 2:
The control system changes the opening area parameter of the bleed-off valve based on the operation amount of the actuator. By monitoring the actuator position and adjusting the bleed-off valve opening area accordingly, the system optimizes the balance between preventing abrupt actuation and reducing energy loss through unnecessary bleed-off flow rate.
2Loss of energy
If the bleed-off opening area is reduced to improve energy-saving performance, then bleed-off flow rate decreases, but shock absorption capability deteriorates
Solution Approach 1:
The system dynamically changes the bleed-off valve opening area parameter based on the actuator's operational state. When the actuator is in the half-operated position, the opening area is maintained at a level that provides sufficient shock absorption capability. When the actuator reaches full operation, the opening area is reduced to minimize energy loss. This parameter adjustment strategy resolves the contradiction between energy-saving performance and shock absorption capability.
Solution Approach 2:
The bleed-off valve opening area is made dynamic rather than fixed, allowing the system to adapt to different operational conditions. The control system continuously adjusts the opening area based on real-time feedback from the actuator position, ensuring optimal shock absorption when needed and minimal energy loss when the actuator is fully operated.
3Productivity
If the pump flow rate is increased to supply multiple actuators in combined operation, then productivity is improved, but shock due to sudden pressure increase occurs
Solution Approach 1:
The bleed-off valve is opened in advance before the pump flow rate is increased during combined operation of multiple actuators. This preliminary action allows the system to absorb the sudden pressure increase and prevent shock. The control system detects when multiple actuators are being operated simultaneously and opens the bleed-off valve beforehand to accommodate the increased flow demand without causing pressure shocks.
Solution Approach 2:
The bleed-off valve acts as an intermediary element between the hydraulic pump and the actuators during combined operation. By providing an additional flow path through the bleed-off valve, the system can smoothly accommodate the increased flow demand from multiple actuators without causing sudden pressure increases and shock. The bleed-off valve mediates the transition from sole operation to combined operation.
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 configuration prevents abrupt actuation and shock, enhancing operability and improving energy-saving performance by optimizing the bleed-off function during actuator operation.
Implementation Method 1
a hydraulic pump of variable displacement type... that supplies a hydraulic operating fluid to the hydraulic pump
Implementation Method 2
a bleed-off valve disposed on a flow line that connects a pump line of the hydraulic pump to a hydraulic operating fluid tank... open the bleed-off valve at a timing at which the operation device is being operated and before a flow rate of the hydraulic pump starts increasing
Data Source
AI summary
The invention of the present application intends to provide a work machine that can ensure high operability by preventing abrupt actuation of an actuator and a shock to a machine body by use of a bleed-off function at the time of starting of the actuator and that can improve the energy-saving performance by reducing a bleed-off flow rate after the starting of the actuator. For this purpose, a controller opens a bleed-off valve at a timing at which an operation device is being operated and before a flow rate of a hydraulic pump starts increasing, and closes the bleed-off valve at a timing at which the operation device is being operated and after the flow rate of the hydraulic pump has started increasing.