Two-Pump Hydraulic Control for Excavator Leveling Efficiency
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Solution Overview
Problem
In two-pump type hydraulic drive systems of construction machines like hydraulic excavators, the energy efficiency deteriorates during leveling operations where arm crowding and boom raising are performed simultaneously, due to excessive displacement volume and delivery pressure of the hydraulic pumps.
Innovation Solution
A construction machine with variable displacement hydraulic pumps and regulators, controlled by a controller that adjusts displacement volumes based on operation amounts and delivery pressure, ensuring the displacement volume of the first hydraulic pump supplying the boom cylinder decreases with reduced boom raising operation, preventing excessive delivery pressure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the displacement volume of the first hydraulic pump is controlled according to the maximum value among target displacement volumes based on boom raising operation amount and arm crowding operation amount, then the arm crowding operation speed is maintained, but the delivery pressure rises excessively and energy efficiency deteriorates
Solution Approach 1:
The control method dynamically changes the displacement volume parameter of the first hydraulic pump based on the operational phase. During the first half of leveling operation, the pump operates at maximum displacement volume to maintain arm crowding speed. During the second half, the displacement volume is reduced to match the decreased boom raising operation amount, preventing excessive pressure buildup and improving energy efficiency.
Solution Approach 2:
The system transitions from a static maximum-value-based control approach to a dynamic control approach that adapts to changing operational conditions. The controller continuously monitors operation amounts and adjusts the first hydraulic pump's displacement volume in real-time, switching between different control strategies based on the operational phase detected through pressure sensors and operation amount sensors.
2Ease of operation
If the displacement volume of the first hydraulic pump is increased to supply hydraulic fluid mainly to the boom cylinder, then the boom raising operation is enabled, but the delivery pressure becomes excessively large
Solution Approach 1:
The system employs pressure sensors to monitor the delivery pressure of the first hydraulic pump in real-time. This feedback information is fed back to the controller, which adjusts the displacement volume of the pump accordingly. When the boom raising operation amount decreases, the pressure feedback triggers a reduction in displacement volume, preventing excessive pressure buildup while maintaining sufficient pressure for boom raising operation.
3Reliability
If the displacement volume is controlled based on maximum value selection, then the hydraulic actuators receive sufficient fluid, but the energy efficiency deteriorates due to excessive delivery pressure
Solution Approach 1:
The control strategy is segmented into two distinct phases: the first half of the leveling operation where maximum displacement volume is maintained for reliable hydraulic supply, and the second half where displacement volume is reduced to improve energy efficiency. This segmentation allows the system to prioritize reliability when needed and energy efficiency when operational demands decrease.
Data Source
AI summary
To provide a construction machine that can improve the energy efficiency in a leveling operation in which an arm crowding operation and a boom raising operation are performed simultaneously. A controller (30) controls a first regulator (60a) according to the maximum value among target displacement volume (Qa1) of a first hydraulic pump (1) that is based on a boom raising operation amount (Pi1), and target displacement volume (Qa2) of the first hydraulic pump (1) that is based on an arm crowding operation amount (Pi2) of an arm operation device (18) if the boom raising operation amount (Pi1) of a boom operation device (17) is smaller than a predetermined operation amount, or if a delivery pressure (P2) of a second hydraulic pump (2) is equal to or higher than a predetermined pressure, and controls the first regulator (60a) according only to the target displacement volume (Qa1) of the first hydraulic pump (1) that is based on the boom raising operation amount (Pi1) if the boom raising operation amount (Pi1) is equal to or larger than the predetermined operation amount, and the delivery pressure (P2) of the second hydraulic pump (2) is lower than the predetermined pressure.