Hydraulic Pump Control With LS Pressure Compensation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing hydraulic systems in working machines face challenges in accurately controlling horsepower due to temperature variations affecting hydraulic fluid viscosity, leading to inconsistent delivery flow rates and inefficiencies in load-sensing differential pressure control.
Innovation Solution
A hydraulic system utilizing a pressure compensator with different throttles and solenoid valves to adjust pilot pressure, combined with an electrical controller, to maintain consistent load-sensing differential pressure and compensate for temperature changes, ensuring precise horsepower control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a throttle is used for horsepower control, then the delivery amount of hydraulic fluid is less affected by temperature, but the differential pressure across the throttle increases in low-temperature periods causing higher LS differential pressure
Solution Approach 1:
A pressure compensator is introduced as an intermediary device between the throttle and the hydraulic pump. The pressure compensator includes a compensating piston that responds to differential pressure across a compensating throttle, automatically adjusting the spool opening area of the main throttle to maintain constant LS differential pressure regardless of temperature variations
Solution Approach 2:
The pressure compensator establishes a feedback mechanism where the differential pressure across the compensating throttle acts on the compensating piston, which in turn adjusts the main throttle opening. This closed-loop feedback ensures that LS differential pressure remains constant even when temperature and viscosity change
2Ease of operation
If a proportional valve is used for horsepower control, then temperature correction of pilot pressure is simplified, but accuracy of horsepower control decreases due to delivery amount variations with temperature
Solution Approach 1:
The invention uses hydraulic principles with a pressure compensator that utilizes pilot fluid pressure and differential pressure mechanisms to automatically compensate for temperature effects. The compensating piston responds to pressure changes and mechanically adjusts the throttle opening, providing passive hydraulic compensation without complex electronic temperature sensing and adjustment systems
3Device complexity
If the spool opening area is kept constant, then the control valve switching is simplified, but the delivery flow rate changes with temperature due to viscosity changes
Solution Approach 1:
The invention makes the spool opening area dynamic rather than fixed. The pressure compensator automatically adjusts the spool opening area in response to temperature-induced viscosity changes, increasing the opening area when viscosity increases (low temperature) and decreasing it when viscosity decreases (high temperature), thereby maintaining consistent delivery flow rate
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
The system achieves accurate horsepower control by compensating for temperature variations, maintaining consistent delivery flow rates and improving efficiency by stabilizing load-sensing differential pressure.
Implementation Method 1
Since a change in the temperature of the hydraulic fluid may cause a change in the viscosity of the hydraulic fluid, the flow rate of the hydraulic fluid passing through the opening of the spool may change even if the opening area of the spool is constant and the LS differential pressure is constant
Implementation Method 2
a solenoid valve in the second pilot fluid passage to change a pilot pressure of the pilot fluid applied to the hydraulic controller
Implementation Method 3
a first hydraulic pump to be driven by power of the prime mover to deliver pilot fluid to switch the control valve
Implementation Method 4
a second hydraulic pump to be driven by power of the prime mover to deliver hydraulic fluid to activate the hydraulic actuator
Data Source
AI summary
A hydraulic system for a working machine includes a prime mover, a boom cylinder, a control valve, a first hydraulic pump to deliver pilot fluid to switch the control valve, a second hydraulic pump to deliver hydraulic fluid to activate the boom cylinder, a hydraulic controller configured or programmed to control the second hydraulic pump to set a load-sensing (LS) differential pressure, a first pilot fluid passage, a second pilot fluid passage branching off from the first pilot fluid passage and connected to the hydraulic controller, a solenoid valve to change a pilot pressure that is a pressure of the pilot fluid applied to the hydraulic controller, and a pressure compensator to increase the LS differential pressure as a temperature of the hydraulic fluid including the pilot fluid decreases.