JPH0215789B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a thermostatic expansion valve whose opening degree can always be adjusted at an appropriate degree of superheat.

In a refrigeration system consisting of a cycle in which an evaporator, a compressor, a condenser, and a temperature-sensitive expansion valve are connected in series, the temperature-type expansion valve is located on the evaporator outlet side and changes depending on the evaporation rate of the liquid refrigerant in the evaporator. This is a device that precisely controls and adjusts the proportion of liquid refrigerant that is transmitted to the pressure chamber of the expansion valve as gas pressure and flows into the evaporator by detecting the degree of superheat of the refrigerant gas with a temperature-sensitive cylinder. It is generally difficult to precisely adjust the control of the expansion valve when the refrigeration system is operated under conditions where load conditions and outside air conditions vary widely.

In other words, for example, if the load increases significantly, the degree of superheat will increase and the opening of the expansion valve will increase, but since the degree of opening of the expansion valve is proportional to the degree of superheat, the system will eventually become overheated. As a result, the effective evaporation area of the evaporator decreases. Conversely, if the load decreases significantly, the degree of superheating will decrease, and the refrigerant in the evaporator will not evaporate sufficiently, and the refrigerant will be sucked into the compressor mixed with liquid refrigerant. This may not only reduce the efficiency of the compressor due to liquid compression, but may even cause damage to the compressor.

Therefore, in order to solve the above-mentioned problems, it is necessary to reduce the fluctuation range of the degree of superheating of the refrigerant at the evaporator outlet side as much as possible so as to always maintain an appropriate set degree of superheating (for example, +
It is desirable to operate the expansion valve at a temperature of 5°C), and the variation range of superheat degree can be reduced by changing the valve opening degree largely with a small change in superheat degree. However, in this case, since the valve opening changes greatly, it is difficult to maintain the expansion valve opening at an appropriate value due to the effects of dead time in the refrigeration cycle and suction pressure fluctuations, and the refrigeration cycle It is difficult for a single conventional expansion valve to control the refrigerant superheat degree over the entire range of fluctuations, as this can cause hunting. Alternatively, as described in Japanese Patent Publication No. 57-47380, the static superheating degree of the expansion valve can be set higher than the standard value, and as a means of doing so, an indirect electric heater can be installed in the temperature sensing tube to adjust the superheating degree of the refrigerant gas. Attempts have also been made to adjust the spring pressure of the expansion valve so that the

However, there are various methods for adjusting the static superheating degree of the expansion valve by attaching an electric heater to a temperature-sensitive tube attached to the refrigerant gas pipe on the evaporator outlet side and adjusting the voltage applied to the heater. There are drawbacks. That is,
The difference in degree of superheating between fully closed and fully opened expansion valves is usually 5°C.
Since the temperature is around 1°C, the valve opening will change when the temperature changes by 1°C.
It will change by 20%. Therefore, the valve opening error is reduced to 10%.
In order to keep it within ±0.5℃, the stop superheat degree must be adjusted to within ±0.5℃, but with this method, the gas temperature inside the thermosensor cylinder must be adjusted within ±0.5℃ relative to the set value temperature.
Adjusting the temperature to a precise temperature range within this range is due to heat transfer to the piping due to contact between the thermosensor and the refrigerant piping,
Differences in heat transfer coefficient due to differences in the heat capacity of the refrigerant flowing inside the pipes, heat transfer due to condensation on the thermosensor tube, heat transfer due to frost formation, wind speed around the thermosensor tube, heat transfer due to differences in the method of attaching the thermosensor tube to the refrigerant piping. This is considered impossible considering the mounting conditions of the thermosensor tube, which are susceptible to a wide variety of influences, such as differences in heat capacity and heat capacities of mounting tools.

From this point of view, the present invention solves the above-mentioned problems associated with conventional expansion valves, and can always maintain an appropriate set value of superheat degree even when load conditions and outside air conditions fluctuate significantly, and furthermore, the present invention can maintain an appropriate set value of superheat degree even when the load conditions and outside air conditions change significantly. The purpose is to provide a temperature-type expansion valve with a small width, and two large and small temperature-sensitive cylinders filled with an inert gas and an adsorbent for the gas are connected to the pressure chamber of the expansion valve with a thin tube. , by attaching a large temperature-sensing tube to the refrigerant pipe on the evaporator outlet side and attaching a variable superheat heater to the small temperature-sensing tube, the gas pressure inside the small temperature-sensing tube can be varied;
To provide a temperature-type expansion valve that makes it possible to precisely adjust the opening degree of the expansion valve without significantly changing the superheat setting of a large temperature-sensitive tube.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the accompanying drawings showing embodiments. FIG. 1 is a cross-sectional view including a partial cutout of a thermostatic expansion valve according to the present invention, in which a high-temperature, high-pressure refrigerant liquid flows into the lower end of the valve body 1 from an inflow pipe B from a condenser (not shown). A valve body 3 for adjusting the amount of refrigerant liquid is provided integrally with a spring 4, and the valve body 3 is formed integrally with the lower end of a valve rod 7 fixed to the lower surface of a diaphragm 6. A is an outflow pipe for the refrigerant liquid that flows into the expansion valve 2 in accordance with the opening and closing of the valve body 3 and is lowered in temperature and pressure by adiabatic expansion, and this outflow pipe A is connected to an evaporator (not shown). Reference numeral 8 denotes an external pressure equalizing pipe that communicates with the refrigerant on the evaporator outlet side, and communicates with the pressure equalizing chamber 5b through a passage in the valve body 1. Acts on the lower surface. 5 is the upper lid body and diaphragm 6
A pressure chamber 5a is formed on the upper surface, and the pressure chamber 5a communicates with one end of a large adsorption type temperature sensing tube _T1 via a capillary tube (thin tube) 9, and the other end of the temperature sensing tube _T1 is It is connected via a capillary tube 10 to one end of a small adsorption type temperature sensing tube _T2 whose other end is sealed.
Adsorbent K enclosed in these large and small adsorption type thermosensor cylinders
Activated carbon can be suitably used as the carbon, but it is not particularly limited to activated carbon as long as it can easily desorb or adsorb the enclosed inert gas by heating or cooling. Further, the ratio of the amounts of adsorbents filled in the adsorption type temperature sensing cylinders of different sizes can be adjusted as appropriate, for example, to 10:1. In addition, even smaller adsorption type thermosensor
A heater 11 whose heating temperature can be variably adjusted by means of voltage adjustment or the like is wound around or inserted into the cylindrical body of _T2 .

The thermostatic expansion valve of the present invention has the above configuration,
The valve body 1 is installed in the condenser outlet piping and the evaporation chamber inlet piping, and a large adsorption type temperature sensing tube _T1 is attached to the refrigerant piping on the evaporator outlet side to detect the refrigerant temperature. The adsorption type thermosensor tube T ₂ is installed in an indoor location with a stable ambient temperature that is not affected by the outside air temperature around the evaporator.

Next, the operation of the thermostatic expansion valve of the present invention will be explained with reference to the graph shown in Figure 2 which shows the relationship between the degree of superheating and the valve opening of the expansion valve.For example, the heating temperature of the small thermosensitive tube _T2 is maintained at 80℃ In this case, if the valve opening is 1.0 and the appropriate degree of superheat at the evaporator outlet is maintained at the standard value of +5°C and refrigeration operation is performed, the set value of the static degree of superheat is t ₂ , and the line 2 The valve operation is performed according to the following.

However, if the load on the evaporator increases during operation and it is desired to increase the valve opening degree to 1.5, the conventional expansion valve will increase the superheat degree corresponding to a ₂ to a' ₂ of line 2, that is, about +7
The valve opening cannot be set to 1.5 unless the degree of superheating of the refrigerant at the evaporator outlet increases to ℃. However, increasing the degree of superheat above the standard setting (eg, +5° C.) has undesirable consequences as described above.

However, according to the present invention, the static heating degree of the expansion valve can be easily shifted to line ₁ of t1 by increasing the heating temperature of the small temperature-sensitive tube _T2 above the standard value (for example, 80°C). In this case, the degree of superheating can be adjusted to 1.5 while keeping the degree of superheating at point _a1 , that is, +5°C. Conversely, if the load becomes too small, the static superheat degree can be shifted to line ₃ with t3 by lowering the heating temperature of the small thermosensor tube _T2 from the standard value, and similarly. The valve opening degree can be adjusted to 0.5 while keeping the standard setting value of superheat degree (+5℃).

In this way, according to the present invention, by appropriately adjusting the heating temperature of the small temperature-sensitive tube _T2 according to the magnitude of the load, it is possible to always adjust the valve opening degree at a constant standard setting value of superheat degree. . Therefore, one expansion valve is sufficient to handle refrigeration equipment with different refrigerating capacities, and fluctuations in the degree of superheating can be eliminated by changing the voltage applied to the heater, reducing the need to adjust the valve opening degree depending on the degree of superheating. It is also possible to prevent hunting of the expansion valve and refrigeration cycle.

In addition, in the present invention, the large temperature-sensitive tube _T1 and the small temperature-sensitive tube _T2 are provided to adjust the heating of the small temperature-sensitive tube _T2 . By adjusting the amount ratio of the agent to, for example, 10:1, the effect of heating on the small thermosensor can be reduced to 1/10 on the large thermosensor.
Therefore, even if the change in the heating temperature of the small thermosensor is, for example, ±5°C, the temperature change of the large thermosensor can be adjusted to within a minute range of ±0.5°C. This makes it possible to precisely adjust the valve opening based on increases and decreases in the degree of superheating.

Furthermore, according to the present invention, since the small temperature-sensing cylinder can be installed in a place where the ambient temperature is stable, the superheat degree setting value of the expansion valve can be controlled fairly accurately in response to changes in the ambient temperature, that is, changes in the load. Therefore, by automatically controlling load fluctuations and heating of the small temperature-sensing tube in conjunction with each other, automatic operation or remote operation can be easily carried out.

Furthermore, in the present invention, by installing the small temperature-sensing tube separately from the refrigeration equipment, the heater can be operated safely without the risk of condensation or frost formation, and the amount of adsorbent filled in the small temperature-sensing tube can be reduced. Since only a small amount is required, the pressure of the generated gas does not increase excessively due to heating, and even if abnormal heating occurs, there is no risk of damaging the diaphragm of the expansion valve.

[Brief explanation of drawings]

FIG. 1 is a sectional view including a partially cut-out portion of the thermostatic expansion valve of the present invention, and FIG. 2 is a diagram showing the operating state of the thermostatic expansion valve of the present invention. DESCRIPTION OF SYMBOLS 1... Valve body, 3... Adjustment valve body, 4... Spring, 5... Upper lid body, 5a... Pressure chamber, 5B...
Pressure equalization chamber, 6...Diaphragm, 8...External pressure equalization pipe, 9, 10...Capillary tube, 11...Heater, A...Outflow pipe, B...Inflow pipe, _T1 , _T2 ...
...Adsorption type thermosensor, K...Adsorbent.

Claims (1)

[Claims] 1. A thermosensor tube is attached to the refrigerant pipe on the evaporator outlet side of the refrigeration cycle, and the inert gas Two large and small temperature-sensing cylinders filled with an adsorbent for the gas are connected to the pressure chamber of the expansion valve with a thin tube, and the large temperature-sensing cylinder is attached to the refrigerant pipe on the evaporator outlet side, and the small temperature-sensing cylinder is attached to the refrigerant pipe on the outlet side of the evaporator. A temperature-type expansion valve characterized by being equipped with a variable superheating heater.