JPS5874970A - Expansion valve - Google Patents

Abstract

PURPOSE:To prevent a flow passage from being closed by freezed moisture by making the surface of a part forming a throttle from a hydrophobic material. CONSTITUTION:Respective parts 3 and 4 of needle valve 1 and a valve seat 2 are subjected to hydrophobic surface treatment or lining. A suitable material for the purpose of the lining may be fluorine resin, polyacrylonitrile, copolymer of vinylidene chloride and acrylonitrile or the like. Because of the presence of the hydrophobic material, the freezing may mainly proceeds in the broader area of the flow passage behind the throttle, thereby preventing an expansion valve from being closed by freezed moisture, at the throttled part.

Description

[Detailed description of the invention] The present invention relates to an expansion valve for a refrigeration system.

There are various configurations of expansion valves.

FIG. 1 shows an example of this, in which a constricted portion is formed between a two-conical needle valve 1 and a valve seat 2.

In the refrigeration cycle, the refrigerant becomes a high-temperature, high-pressure liquid in a condenser, and then passes through an expansion valve where it undergoes adiabatic expansion and becomes a low-temperature, low-pressure liquid.

At this time, by adjusting the gap width between the needle valve of the expansion valve and the valve seat, the degree of pressure drop when the liquid passes through this can be adjusted.
l# tension outlet refrigerant liquid temperature is adjusted.

It is known that in a refrigerant refrigerating cycle, various problems occur if moisture is mixed into the refrigerant refrigerant. For this reason, a high-performance dehumidifier such as silica or alumina is usually installed in the refrigerant flow path to dehumidify the refrigerant. If the refrigerant piping is made entirely of metal, the refrigerant flow path is completely sealed, except when filling the installation with refrigerant.

After that, there is no need to worry about moisture intrusion (if the above measures are taken, problems due to moisture will not occur. However, among the products that use the 0-cycle refrigeration cycle, installation is not required for automotive cooling systems. Due to the above constraints, 2.Nylon is used for part of the normal piping.
It is known that refrigerant leaks and moisture infiltrates through these parts.

Furthermore, the amount of moisture that enters tends to increase depending on the frequency of use of the air conditioner, and malfunctions of air conditioners occur due to moisture intrusion, especially in taxis and other vehicles that are frequently used. Intruding moisture is not completely adsorbed by the desiccant,
In particular, this is caused by freezing in the gap of the expansion valve (or an intermediate tube is sometimes used) where the flow path is the narrowest, resulting in the flow path being blocked.

Freezing of moisture occurs when the refrigerant R12 (CCMUF) used in automotive refrigeration systems passes through pressure and temperature conditions of 5ata and 11℃ during the adiabatic expansion process.
A hydrated crystal called 12.17HtO.

It is also known to form deicing that passes through 0°C.

The present invention has been proposed in view of the above-mentioned points, and an object thereof is to provide an expansion valve that can prevent passage blockage due to freezing of water.

The present invention is characterized in that the surface of the portion forming the constriction portion is made of a hydrophobic material.

By configuring the surface of the part that forms the constricted portion with a hydrophobic material, ice due to freezing of water does not adhere to the expansion valve. Therefore, it is possible to prevent the expansion valve from being blocked due to freezing of water. This will be explained based on an example.

In refrigeration and cycles, an expansion valve is used in the refrigerant flow path constriction section that adiabatically expands the refrigerant.

#The main part of the overhang is 1llK shown in Figure 1, and the high temperature and high pressure refrigerant liquid passes through the narrow gap between the needle valve 1 and the valve seat 2, and is mixed with the low temperature and low pressure refrigerant liquid. Become.

In order to prevent channel blockage due to frozen moisture, the needle valve and the valve seat 2 should be subjected to hydrophobic surface treatment or lining on the shaded area 5.4 shown in FIG. The seat itself can also be made of a hydrophobic material.

Note that the material used here is required to have both hydrophobicity and refrigerant resistance. Suitable materials that satisfy these conditions include fluorine resins, polyacrylonitrile, and vinylidene chloride acrylonitrile copolymers.

When freezing water, fine crystal nuclei are generated, and then solids are precipitated one after another on these crystal nuclei (thus, freezing progresses. Whether or not the bulk of the liquid flow is formed is an important point in determining whether freezing will lead to blockage.Generally, when the affinity between the precipitated crystal nuclei and the wall material is large, wall soil nucleation occurs; *
When the partner is small, nucleation is said to occur in the liquid bulk part, but it is in the case of wall nucleation that it leads to the blockage of the flow path constriction part in the expansion valve.

The flow channel constriction parts that have been used so far are made of copper or brass, and the surface state is thought to be an oxide of the constituent metals, so there is a strong effect similar to hydrogen bonding between the water crystals and ice. Power is expected.

As a result, crystal nuclei are generated in the wall soil, and the crystals grow in the wall soil, causing flow channel blockage. However, if the surface of the flow channel constriction is covered with a hydrophobic material as described above, freezing will be prevented from occurring at the constricted section. The expansion mainly occurs in the later wide flow path, and it is possible to prevent the expansion valve from being blocked due to moisture freezing at the constriction part.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing an example of a conventional device, and FIG. 2 is a sectional view showing an embodiment of the present invention. 1: needle valve, 2: valve seat, 5, 4: hydrophobic material part.

Claims (1)

[Claims] An expansion valve characterized in that the surface of the part forming the throttle part is made of a hydrophobic material.