Electric Displacement Control for Variable Displacement Pump
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Solution Overview
Problem
Existing control systems for open circuit variable displacement pumps face challenges in reducing manufacturing costs and space requirements while maintaining application efficiency, particularly with electric displacement controls (EDCs) that are costly and inefficient in terms of hydraulic losses.
Innovation Solution
An electric displacement control system utilizing a two-way or three-position spool type valve with a solenoid actuator and feedback spring, which vents fluid pressure from the servo bore to the pump case, allowing for adjustable flow rates and reduced space usage, including a two-way two-position spool valve for zero flow and minimum fail-safe design or a two-way three-position spool valve for full flow and maximum pressure fail-safe control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Extent of automation
If a traditional EDC system is used to control variable displacement pump, then the pump displacement can be controlled electrically, but the manufacturing cost and space requirements increase significantly
Solution Approach 1:
The patent combines the spool valve, solenoid actuator, and feedback spring into a single integrated control assembly that fits within the pump housing. This merging of components eliminates the need for separate external EDC hardware, reducing both manufacturing cost and space requirements while maintaining automated displacement control capability
Solution Approach 2:
The control spool serves multiple functions: it acts as a valve to regulate fluid flow to the servo piston, provides a mounting structure for the solenoid and feedback spring, and enables both electric control and mechanical feedback within a single component. This multi-functionality reduces the number of separate parts needed
2Productivity
If a spool type valve with orifice is used to vent fluid from servo bore, then the flow rate can be controlled, but the device complexity increases
Solution Approach 1:
The spool valve features a localized orifice specifically positioned to vent fluid from the servo bore to the pump case. This localized flow control feature is integrated directly into the spool structure, providing precise flow rate control without requiring a complex external valve assembly
Solution Approach 2:
The spool valve acts as an intermediary component that mediates between the solenoid actuator force and the feedback spring force to control fluid flow. By positioning the orifice in the spool, the system achieves flow control through a simple mechanical structure rather than complex valve mechanisms
3Measurement precision
If feedback spring and solenoid actuator forces are balanced to control flow, then precise displacement control is achieved, but the system becomes more sensitive to force balance variations
Solution Approach 1:
The feedback spring provides mechanical feedback force that opposes the solenoid actuator force. This feedback mechanism creates a natural force balance that stabilizes the spool position and compensates for variations in solenoid force, reducing sensitivity while maintaining precision
Solution Approach 2:
The feedback spring acts as a counterbalancing element that provides a force opposing the solenoid actuator force. This counterforce creates a stable equilibrium point for the spool, making the system less sensitive to variations in solenoid force and improving reliability
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 solution effectively reduces manufacturing costs and space requirements while maintaining efficient operation of the variable displacement pump by balancing fluid forces between the solenoid actuator and feedback spring, enabling precise control of pump displacement and providing a fail-safe mechanism in case of solenoid power loss.
Implementation Method 1
a feedback spring at a first side and a solenoid actuator at a second side. Preferably the control spool valve is a two-way, two-position spool type valve or a two-way, three-position spool type valve
Implementation Method 2
a feedback spring on a first side of the control spool valve and a solenoid actuator force on a second side of the control spool valve
Implementation Method 3
The spool type valve meters fluid from system pressure to the servo bore and the flow rate across the valve depends on a force balanced between a feedback spring force on one side of the spool and a solenoid actuator force on another side of the spool
Implementation Method 4
a control spool valve having an orifice that vents fluid pressure from the servo bore to a pump case
Data Source
AI summary
An electric displacement control system has a hydraulic variable displacement pump that operates in an open hydraulic circuit. A servo piston is disposed within a servo bore that is connected to the hydraulic variable displacement pump. Located in the servo bore is a control spool valve having an orifice that vents fluid pressure from the servo bore to a pump case. The flow rate of the system depends upon a fluid force between a feedback spring on a first side of the control spool valve and a solenoid actuator force on a second side of the control spool valve.