Hydraulic Control Apparatus Managing Driving Force and Energy Efficiency
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Solution Overview
Problem
Existing hydraulic control systems for working machines, such as hydraulic excavators, face issues with driving force shortages due to cutoff control, which also result in inadequate energy efficiency and increased installation costs from additional detection and wiring requirements.
Innovation Solution
A hydraulic control apparatus that adjusts the flow rate command value over time by reducing control gain or increasing set pressure during pressure feedback control, allowing for improved energy efficiency and driving force, without the need for additional sensors or wiring, and enables mode switching between energy-saving and high-power modes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If pressure feedback control is performed to reduce pump pressure below the relief valve set pressure, then relief flow rate is reduced and energy efficiency is improved, but pump pressure cannot reach maximum pressure and driving force becomes insufficient
Solution Approach 1:
The control gain is dynamically reduced over time during pressure feedback control. Initially, a higher control gain maintains pump pressure below the relief valve set pressure to reduce relief flow rate and improve energy efficiency. As time progresses, the control gain is automatically reduced, allowing pump pressure to increase toward maximum pressure and restore driving force when needed for operations like hill-climbing.
Solution Approach 2:
The control gain reduction is performed in advance based on elapsed time before driving force becomes critically insufficient. By proactively reducing the control gain as time passes, the system prevents driving force shortage from occurring, ensuring that when operations requiring maximum driving force are needed, the pump can reach maximum pressure without delay.
2Force
If tilt detection means and wiring equipment are added to switch off pressure feedback control on sloping roads, then hill-climbing ability is maintained, but installation cost increases and application on existing machines becomes difficult
Solution Approach 1:
The control system uses its own existing pressure feedback control mechanism to automatically adapt to different operating conditions. By incorporating time-based control gain reduction, the system self-adjusts to maintain adequate driving force during operations without requiring external tilt sensors or additional wiring equipment, making it compatible with existing machines.
Solution Approach 2:
The control gain parameter is changed over time based on elapsed time during pressure feedback control. This parameter change allows the system to transition from energy-saving mode (higher control gain) to driving force mode (lower control gain) automatically, eliminating the need for additional detection means while maintaining hill-climbing ability.
3Loss of energy
If pressure feedback control is continuously performed to reduce relief flow rate, then energy efficiency is improved, but actuator flow rate becomes insufficient and driving force is reduced
Solution Approach 1:
The pressure feedback control is applied periodically with varying intensity. Initially, strong pressure feedback control reduces relief flow rate to improve energy efficiency. As time progresses, the control intensity is reduced by lowering the control gain, allowing actuator flow rate to increase and restore driving force when productivity becomes insufficient.
Data Source
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AI summary
With respect to a method of controlling a pump flow rate of a hydraulic pump, a method having a small flow rate command value is selected between a pressure feedback control for controlling the pump flow rate based on a set pressure (a cutoff pressure) and a pump pressure, and, an ordinary control for controlling the pump flow rate based on operation information, and in a case that the pressure feedback control is selected, a flow rate increasing control for increasing the flow rate command value after the case with the passage of time is performed.