Capacity Control Valve Hunting Prevention
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Solution Overview
Problem
Flow control valves in variable displacement compressors experience hunting phenomena due to discharge pressure, leading to insufficient fluid control and unpredictable operations, especially with high-pressure operating fluids like CO2, which complicates precise flow management.
Innovation Solution
The flow control valve design includes a larger pressure-receiving area for discharge pressure at the valve seat interface compared to the shaft portion, ensuring a consistent force for valve operation and preventing hunting by utilizing a solenoid-actuated rod and strategically placed fluid passages to manage suction and discharge pressures effectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the valve body is actuated by discharge pressure alone, then the valve opening action is simple, but hunting phenomenon occurs due to pressure differential changes
Solution Approach 1:
The patent applies the counterweight principle by introducing a suction pressure receiving area that generates a counteracting force to balance the discharge pressure fluctuations. The suction pressure force acts in opposition to the discharge pressure force on the valve body, creating a stabilizing effect that prevents hunting phenomenon while maintaining the simplicity of the valve actuation mechanism.
2Area of stationary object
If the diametral dimension of the valve body is larger than the discharge port, then the pressure-receiving area is increased, but the valve becomes more susceptible to pressure-driven hunting
Solution Approach 1:
The patent resolves this contradiction by adding a suction pressure receiving area that provides a counterbalancing force. The larger pressure-receiving area is compensated by the opposing suction pressure force, ensuring that the increased area does not lead to hunting but rather provides sufficient force for reliable valve actuation while maintaining stability.
Solution Approach 2:
The patent applies local quality by creating distinct pressure-receiving areas with different functions: the discharge pressure receiving area provides the primary actuation force, while the suction pressure receiving area provides stabilizing counterbalance. This differentiation of local functions allows the valve body to have large surface area without suffering from hunting phenomenon.
3Force
If the diameters of the valve orifices are equal, then the forces from control fluids negate each other, but the valve body hunting cannot be prevented under high pressure differential
Solution Approach 1:
The patent extends the counterweight principle by introducing suction pressure as a stabilizing force that acts on the valve body. The suction pressure receiving area generates a force that counterbalances the destabilizing effect of discharge pressure fluctuations, preventing hunting even when control fluid forces are balanced and the pressure differential is high.
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 design prevents hunting of the valve body, enhances flow control precision, and maintains operational stability even under high-pressure conditions, ensuring accurate flow management and improved performance in variable displacement compressors.
Implementation Method 1
a solenoid portion 120... Supplying electric current to the solenoid portion 120 actuates a solenoid rod 122 being guided by a bearing 123 in accordance with the intensity of the current
Implementation Method 2
When the pressure differential between discharge pressure Pd and suction pressure Ps becomes greater than an attraction force determined by the current supplied to the solenoid portion 120, high-pressure valve body 102A opens
Data Source
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AI summary
A capacity control valve,comprising a first valve chamber formed in a valve body, a first fluid passage communicatig with the first valve chamber to flow a fluid with a discharge pressure therein, a valve seat formed around a valve port between the first valve chamber and the first fluid passage, a second fluid passage communicating with the first valve chamber to flow the fluid with the discharge pressure therefrom, a second valve chamber communicating with the first valve chamber through a guide hole, a third fluid passage communicating with the second valve chamber to flow the fluid with a suction pressure therein and therfrom, a valve element disposed in the first valve chamber and having a valve part separated from and brought into contact with the valve seat to flow the fluid with the discharge pressure therein and a stem part movably fitted to the guide hole, and a solenoid having a solenoid rod connected to the connection face of the valve element and moving the solenoid rod with a current, A discharge pressure receiving area in a connection surface between the valve part and the valve seat is set larger than the pressure receiving area of the stem part.