Closed-Center Hydraulic Pump Control for Pressure Loss Reduction
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Solution Overview
Problem
The existing hydraulic systems for construction equipment suffer from inefficiencies such as flow rate and pressure loss, wasted engine power, and inability to utilize maximum horsepower due to equally distributed engine horsepower across pumps, leading to suboptimal fuel efficiency and wasted fuel.
Innovation Solution
A hydraulic system incorporating a closed center-type main control valve and pressure control-type hydraulic pumps, along with an electronic proportional pressure reducing (EPPR) valve and a controller that dynamically adjusts the distribution ratio of engine horsepower to pumps based on operation mode and load, ensuring complete utilization of engine power.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an open center flow path is used to bypass working oil when the spool is in neutral state, then the hydraulic system can maintain readiness for operation, but flow rate is lost and pressure is lost according to spool design, degrading efficiency
Solution Approach 1:
The patent inverts the traditional open center configuration by using a closed center main control valve. Instead of bypassing working oil through the valve body in neutral state, the closed center design directs all working oil through the actuators and returns it to the tank, eliminating the bypass flow path that causes energy loss while maintaining system readiness.
Solution Approach 2:
The patent extracts and eliminates the open center bypass flow path from the hydraulic system. By removing the bypass function from the main control valve and using a closed center configuration, the system eliminates the source of flow rate and pressure loss that occurs during standby operations.
2Stability of the object's composition
If engine horsepower is equally distributed to multiple hydraulic pumps, then power balance is maintained, but maximum horsepower cannot be utilized and fuel efficiency deteriorates
Solution Approach 1:
The patent implements dynamic horsepower distribution among multiple hydraulic pumps based on real-time load conditions and operation modes. The control system continuously adjusts the power allocation ratio to match actual demand, allowing the system to transition from static equal distribution to dynamic optimized distribution, thereby maximizing fuel efficiency while maintaining power balance.
Solution Approach 2:
The patent changes the distribution ratio parameter of engine horsepower dynamically based on operation mode and load conditions. By adjusting this parameter according to actual hydraulic demand, the system optimizes energy utilization and prevents wasted fuel consumption that occurs with fixed equal distribution.
3Loss of energy
If flow rate control is applied to hydraulic pumps to match actuator demand, then energy efficiency improves, but the system cannot implement free load feeling and pressure control is limited
Solution Approach 1:
The patent introduces an electronic proportional pressure reducing valve as an intermediary device between the hydraulic pump and the actuator. This valve provides precise pressure control and enables free load feeling by regulating the pressure delivered to the actuator, while the pump itself operates under flow rate control for energy efficiency. The intermediary valve decouples the pump's flow control function from the actuator's pressure control requirement.
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 solution prevents flow rate and pressure loss, implements a free load feeling, and optimizes fuel efficiency by ensuring all engine horsepower is used without waste, particularly by adjusting the distribution ratio to match the load applied to each pump.
Implementation Method 1
the EPPR valve controls the pressure of the hydraulic pump to be proportional to the current command
Implementation Method 2
a hydraulic pump that discharges working oil; an actuator that is driven by the working oil discharged from the hydraulic pump
Implementation Method 3
a closed center-type main control valve that prevents working oil from bypassing
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
Disclosed are a hydraulic system for construction equipment and a method of controlling the same, and the hydraulic system for construction equipment includes: a plurality of pressure control-type hydraulic pumps driven by an engine provided in construction equipment; an actuator driven by working oil discharged from the hydraulic pump; a closed center-type main control valve provided between the hydraulic pump and the actuator, and bypassing a virtual flow rate; and a controller configured to control the hydraulic pump by receiving the bypassed virtual flow rate from the main control valve.