Composite Valve Pilot Control for Precise Low-Flow Switching
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Solution Overview
Problem
Existing composite valves for heat pump systems face challenges in achieving precise flow rate control and reducing pressure loss while minimizing size and electric power consumption, particularly in switching between small and large flow rates, due to suboptimal design and increased motion load.
Innovation Solution
A composite valve design featuring a piston-type first valve body and a needle-type second valve body, with a pilot valve that opens and closes based on the elevating motion of the valve shaft, allowing for independent optimization of the second valve's dimensions and shape for small flow rate control and secure operation of the first valve for large flow rates, avoiding malfunctions by bypassing narrow sliding surface gaps.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single electrically operated valve is used to achieve both cooling bypass function and heating expansion function, then the system size is reduced and electric power consumption is lowered, but the valve must be designed to handle large flow rates which increases the valve size and motion load
Solution Approach 1:
The valve is segmented into two independent control mechanisms: a first control valve for large flow rates and a second control valve for small flow rates. This segmentation allows each control mechanism to be optimized for its specific flow rate range, reducing the motion load required for each individual control while maintaining the ability to handle both large and small flow rates.
Solution Approach 2:
A pilot valve is introduced as an intermediary mechanism that controls the opening and closing of the first control valve. The pilot valve, being small in size, can be easily controlled by the electrically operated valve, and in turn controls the larger first control valve, thereby reducing the direct motion load on the electrically operated valve while still enabling large flow rate control.
2Productivity
If the second control valve is designed with larger bore diameter to switch from small to large flow rate control, then the flow rate control precision for small flow rates deteriorates and the valve size increases
Solution Approach 1:
The flow rate control function is segmented into two independent control valves: the second control valve optimized for small flow rates with precise control capability, and the first control valve optimized for large flow rates. This segmentation allows each valve to maintain optimal control precision for its designated flow rate range without compromising the other.
Solution Approach 2:
The pilot valve acts as an intermediary that enables the second control valve to control the first control valve's opening state. This indirect control mechanism allows the small second control valve to effectively manage the large first control valve without requiring the second valve itself to handle large flow rates, thereby maintaining small flow rate control precision.
3Device complexity
If the refrigerant flows through the narrow sliding surface gap of the first valve body during small flow rate control, then the system is compact, but malfunctions occur due to foreign material accumulation
Solution Approach 1:
The harmful flow path through the narrow sliding surface gap is extracted and eliminated from the small flow rate control path. The second control valve provides an alternative flow path that does not require passing through narrow gaps, thereby removing the source of malfunction while maintaining system compactness through integrated design.
Solution Approach 2:
The pilot valve serves as an intermediary that enables the second control valve to control the first valve body's opening state without requiring refrigerant to flow through the narrow sliding surface gap. This indirect control mechanism eliminates the reliability issue while maintaining the compact structure.
Data Source
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AI summary
The invention provides a composite valve which is provided with a pilot type first control valve for a large flow rate and a second control valve for a small flow rate, can set a dimension and a shape of the second control valve for the small flow rate to optimum ones for the small flow rate control, can securely carry out an opening and closing of the first control valve for the large flow rate at a desired timing, and is hard to generate a malfunction, in order to achieve both an improvement of a flow rate control precision at a time of the small flow rate and an increase of a controllable flow rate (a reduction of a pressure loss). In the case that a lift amount of a second valve body (24) for controlling a small flow rate is equal to or less than a predetermined amount (Tc), a pilot passage (19) is closed by a pilot valve body (27), and a first valve port (13) is closed by a first valve body (15) for controlling a large flow rate, thereby taking a small flow rate control state in which a flow rate is controlled in correspondence to the lift amount of the second valve body (24), and in the case that the lift amount of the second valve body (24) goes beyond the predetermined amount (Tc), the pilot valve body (27) is moved up in conjunction with an upward movement of a valve shaft (25) so as to open the pilot passage (19), thereby taking a large flow rate control state in which the first valve body (15) opens the first valve port (13) on the basis of this.