Composite Valve Pilot Structure for Precise Low-Loss Flow Control
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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, particularly when switching between small and large flow rates, leading to increased size, motion load, and risk of foreign material malfunctions.
Innovation Solution
A composite valve design featuring a piston-type first valve body, a needle-type second valve body, and a pilot valve body, where the second valve body serves as a pilot for the first valve, allowing for optimized dimensions and timing of large flow rate control without passing refrigerant through narrow gaps, thus enhancing precision and reducing pressure loss.
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 with a large bore diameter to minimize pressure loss during bypass operation, which increases the motion load and size of the driving portion
Solution Approach 1:
The valve is segmented into two independent valve bodies: a first valve body with a large bore diameter for bypass operation (cooling mode) and a second valve body with a small bore diameter for expansion operation (heating mode). This segmentation allows each valve body to be optimized for its specific function, eliminating the need for the driving portion to handle the full motion load of a single large-bore valve during bypass operation.
Solution Approach 2:
Different parts of the valve have different bore diameters tailored to their specific functions. The first valve body has a large bore diameter optimized for high-flow bypass operation, while the second valve body has a small bore diameter optimized for precise expansion control. This local quality optimization reduces the motion load on the driving portion during bypass operation while maintaining precise control during expansion operation.
2Device complexity
If the second valve body for small flow rate control is used as the pilot valve for the first valve body, then the dimensional and shape constraints are relaxed, but the flow rate control precision at small flow rates deteriorates and the risk of foreign material malfunction increases
Solution Approach 1:
The pilot valve function is separated from the second valve body and assigned to a dedicated pilot valve body. This segmentation allows the second valve body to be optimized exclusively for small flow rate control with precise dimensional specifications, while the pilot valve body handles the pilot function. This eliminates the compromise that would otherwise be necessary between pilot valve requirements and small flow rate control precision.
Solution Approach 2:
A dedicated pilot valve body acts as an intermediary between the second valve body and the first valve body. The pilot valve body receives control signals from the second valve body and translates them into appropriate actuation of the first valve body, enabling precise small flow rate control without the dimensional and shape constraints that would otherwise limit the second valve body's design.
3Device complexity
If refrigerant passes through the narrow sliding surface gap of the first valve body during small flow rate control, then the valve structure is simplified, but the risk of foreign material biting and malfunction increases
Solution Approach 1:
The refrigerant flow path is extracted from the narrow sliding surface gap of the first valve body and redirected through the second valve body during small flow rate control. This extraction eliminates the risk of foreign material biting in the narrow gap, as the refrigerant no longer passes through that critical area. The valve structure remains relatively simple, as the second valve body is already present for small flow rate control and can now also serve as the flow path conduit.
Data Source
AI summary
In the case that a lift amount of a second valve body for controlling a small flow rate is equal to or less than a predetermined amount, a pilot passage is closed by a pilot valve body, and a first valve port is closed by a first valve body 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, and in the case that the lift amount of the second valve body goes beyond the predetermined amount, the pilot valve body is moved up in conjunction with an upward movement of a valve shaft so as to open the pilot passage, thereby taking a large flow rate control state in which the first valve body opens the first valve port on the basis of this.