JP3594770B2 - Refrigerant circuit of refrigeration and air conditioning system - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a refrigeration / air-conditioning apparatus, and more particularly to a refrigeration / air-conditioning apparatus having a refrigerant circuit for preventing occurrence of a liquid back phenomenon in a compressor at an early stage of startup.
[0002]
[Prior art]
For example, a refrigerant sealed in a refrigerating air conditioner is condensed and liquefied in a condenser, and the refrigerant liquid changed in state is decompressed by an expansion valve and then evaporated in an evaporator. The refrigerant circuit repeats a refrigeration cycle in which the refrigerant is sent to a compressor while depriving it of heat, and is compressed by the compressor and sent to the condenser again as high-temperature and high-pressure refrigerant gas.
[0003]
FIG. 2 shows an example of such a refrigerant circuit, wherein 1 is a main liquid solenoid valve, 2 is an expansion valve for controlling the flow rate of refrigerant, 3 is an evaporator, and 4 is a condenser (not shown) from a main liquid solenoid valve. 1, a pipe for supplying a refrigerant (liquid / gas) to a compressor (not shown) via an expansion valve 2 and an evaporator 3.
[0004]
Near the outside of the pipe 4 on the outlet side of the evaporator 3, a temperature sensing cylinder 5 is provided as a temperature monitoring means for monitoring the temperature of the refrigerant passing through the evaporator 3.
[0005]
The expansion valve 2 operates with the temperature sensing cylinder 5 and the external pressure equalizing pipe 6 as operation inputs, and operates so that the difference between the saturation pressure of the temperature sensing cylinder 5 and the pressure of the external pressure equalizing pipe 6 becomes constant.
[0006]
[Problems to be solved by the invention]
By the way, in the refrigerant circuit of the refrigeration / air-conditioning apparatus in which the dry evaporator configured as described above and the temperature type automatic expansion valve are combined, constant control of superheat (superheat) is performed at the outlet side of the evaporator 3. However, in the early stage of the activation of the refrigeration / air-conditioning apparatus, the temperature of the temperature-sensitive cylinder 6 may not follow the drop of the external pressure, and the opening of the expansion valve 2 may be excessive.
[0007]
That is, immediately after the start of the refrigeration / air-conditioning apparatus, the control is started from a state in which each part of the refrigerant circuit is at an equal temperature. Therefore, the evaporation pressure detected through the external pressure equalizing pipe 6 is lower than the saturation pressure of the temperature-sensitive cylinder 5. Therefore, the opening of the expansion valve 2 becomes excessive.
[0008]
Therefore, in the initial stage of the start-up of the refrigeration / air-conditioning apparatus, the transient refrigerant flow caused by the operation delay of the expansion valve 2 immediately after the start-up and the expansion valve 2 being fully opened cause the liquid refrigerant from the compressor to the evaporator 3. There is a possibility that the compressor may be damaged due to the liquid back phenomenon that the liquid is sucked.
[0009]
Therefore, in order to avoid such a liquid back phenomenon, the main liquid solenoid valve 1 is closed and the pump-down operation is performed before the refrigerating air conditioner is stopped, and the liquid refrigerant remaining in the evaporator 3 is collected in the condenser. In addition, a capacity control operation is performed such that a pump-down operation is performed immediately after the driving of the refrigeration air conditioner to restrict an excessive inflow of refrigerant into the compressor.
[0010]
Further, a gas-liquid separator 7 for separating a gas from a refrigerant liquid that cannot be evaporated by the evaporator 3 is provided on the suction side (the outlet side of the evaporator 3) of the compressor to prevent the refrigerant liquid from flowing into the compressor. The method is adopted.
[0011]
However, if the pump-down operation is performed before the refrigeration / air-conditioner is stopped, there is a problem that the refrigerant capacity remains in the evaporator 3 because the control capacity is limited. If this is done, problems occur such as low pressure abnormalities occurring after the pump-down is released due to the temperature drop of the temperature-sensitive cylinder 5 and the winding temperature of the compressor motor (not shown) increasing due to large suction overheating. Was.
[0012]
Further, when the gas-liquid separator 7 is installed, there is a problem that a necessary volume must be secured according to the amount of the refrigerant.
[0013]
The present invention has been made in view of the above circumstances, and has as its object to provide a refrigerant circuit of a refrigeration / air-conditioning apparatus.
[0014]
[Means for Solving the Problems]
In order to achieve the object, the invention according to claim 1 has a pipe from an expansion valve to a compressor via an evaporator, and monitors the temperature of the refrigerant passing through the evaporator outside the pipe. In a refrigerant circuit of a refrigeration / air-conditioning apparatus that controls opening and closing of the expansion valve based on a detection result of a temperature detection unit, one end is connected to the pipeline before the expansion valve, and the other end is a temperature detection unit for the pipeline. there a bypass conduit connected to sites located, the initial driving of the refrigerating and air-conditioning device a part of the refrigerant from the front of the expansion valve of the conduit to a position where said temperature sensing means monitors the temperature of the refrigerant A detour pipe to be detoured in, and the temperature detection via the detour pipe than the temperature and pressure of the refrigerant at a position provided in the detour pipe and monitored by the temperature detecting means via the pipe. Refrigerant at a position whose temperature is monitored by means Comprising a decompression means for the temperature and pressure into a low-temperature low-pressure, wherein the closed expansion valve when the refrigerant is supplied to the bypass pipe to the initial driving of the refrigerating and air-conditioning apparatus, is a low-temperature and low-pressure by the pressure reducing means The point is that the temperature detecting means is cooled by the cooled refrigerant .
[0015]
The gist of the invention described in claim 2 is that the pressure reducing means is provided in multiple stages so as to attenuate the pressure of the refrigerant stepwise.
[0016]
BEST MODE FOR CARRYING OUT THE INVENTION
Next, an embodiment of a refrigerant circuit of a refrigerating air conditioner of the present invention will be described with reference to the drawings.
[0017]
In FIG. 1, reference numeral 11 denotes a main liquid solenoid valve, 12 denotes an expansion valve for controlling the flow rate of refrigerant, 13 denotes an evaporator, and 14 denotes a main liquid solenoid valve 11, an expansion valve 12, and an evaporator 13 from a condenser (not shown). A pipe (pipe) for supplying a refrigerant (liquid / gas) to a compressor (not shown) via the pipe.
[0018]
In the vicinity of the outside of the pipe 14 on the outlet side of the evaporator 13, a temperature sensing tube 15 is provided as temperature monitoring means for monitoring the temperature of the refrigerant passing through the evaporator 13.
[0019]
Further, a bypass pipe 16 is provided in the pipe 14 at a position where the temperature-sensitive cylinder 15 is located from just before the expansion valve 12 so as to bypass a part of the refrigerant liquid at an early stage of driving the refrigeration / air-conditioning apparatus.
[0020]
The bypass pipe 16 is located between the solenoid valve 17 and the small pipes (capillary tubes) 18, 19 for gradually reducing the temperature of the refrigerant liquid supplied to the bypass pipe 16 to a low temperature and low pressure. A pressure chamber 20 for buffering rapid fluctuations of the external pressure equalization pressure, and an external pressure equalizing pipe 21 connected to the expansion valve 12 from the pressure chamber 20.
[0021]
The bypass conduit 16 is at a position where the temperature is monitored by the thermosensitive cylinder 15 at a lower temperature and a lower pressure by the thin tubes 18 and 19 than the refrigerant liquid at a position where the temperature is monitored by the thermosensitive cylinder 15 via the pipe 14. Refrigerant liquid at low temperature and low pressure.
[0022]
The expansion valve 12 operates with the temperature-sensitive cylinder 15 and the external pressure equalizing pipe 21 as differential inputs, and operates so that the difference between the saturation pressure of the temperature-sensitive cylinder 15 and the pressure of the external pressure equalizing pipe 21 is constant.
[0023]
In the above configuration, when the refrigerating air conditioner starts to operate, the solenoid valve 17 opens to equalize the front and rear pressures of the expansion valve 12, then the compressor starts operating, and the main liquid solenoid valve 11 opens.
[0024]
When the main liquid electromagnetic valve 11 is opened, a high-temperature and high-pressure refrigerant liquid is supplied from the condenser to the pipe 14 and supplied to the expansion valve 12. Further, a part thereof is branched to the bypass pipe 16.
[0025]
A part of the refrigerant liquid branched to the bypass pipe 16 is reduced in temperature and pressure through the narrow pipes 18 and 19 and flows to the outlet side of the evaporator 13, and the temperature is detected by the thermosensitive cylinder 15. You.
[0026]
At this time, the expansion valve 12 is fully closed because the pressure of the refrigerant liquid from the external pressure equalizing pipe 21 (outer pressure equalizing) is higher than the saturation pressure in the temperature-sensitive cylinder 15.
[0027]
Therefore, the refrigerant liquid is sucked into the compressor (not shown) via the small tubes 18 and 19. At this time, the compressor motor is cooled by the refrigerant liquid. Further, when the temperature-sensitive cylinder 15 is cooled by the low-temperature and low-pressure refrigerant liquid via the bypass pipe 16, the electromagnetic valve 17 is closed and the expansion valve 12 is opened to be in a steady operation state.
[0028]
At this time, the electromagnetic valve 17 monitors the cooling by the low-temperature and low-pressure refrigerant liquid supplied to the temperature-sensitive cylinder 15 via the bypass pipe 16 by counting the timer.
[0029]
In addition, the expansion valve 12 is prevented from overheating because the change in the external pressure equalization pressure is integrated by the pressure chamber 20 and the thin tube 19.
[0030]
As described above, according to the refrigerant circuit of the refrigeration / air-conditioning apparatus of the present invention, since the inflow of the refrigerant is suppressed by restricting the operation of the expansion valve 12, the occurrence of the liquid back phenomenon can be prevented with simple control.
[0031]
That is, the expansion valve 12 is forcibly closed by the refrigerant liquid from the external pressure equalizing pipe 21 which is lower in temperature and pressure than the temperature and pressure of the refrigerant in the vicinity of the temperature sensing cylinder 15, and then the low temperature and low pressure only from the bypass line 16. The operation of the expansion valve 12 is eliminated by cooling the temperature sensing cylinder 15 with a part of the refrigerant liquid to promote the opening of the expansion valve 12, and the transient refrigerant generated due to the operation delay of the expansion valve 12 immediately after the startup. An increase in the flow rate can be suppressed, so that the liquid back phenomenon can be prevented, and the protection of the compressor can be ensured and the reliability of the product can be improved.
[0032]
【The invention's effect】
As described above, in the refrigerant circuit of the refrigeration / air-conditioning apparatus of the present invention, a part of the refrigerant is driven from the position before the expansion valve to the position where the temperature detection means monitors the temperature of the refrigerant in the pipeline. In addition to providing a detour pipe for detouring at an initial stage, the temperature is monitored by the temperature detection means via the detour pipe rather than the temperature and pressure of the refrigerant at the position where the temperature is monitored by the temperature detection means via the pipe in the detour pipe. Pressure reducing means for reducing the temperature and pressure of the refrigerant at a low temperature and low pressure at a certain position, and an external near-pressure pipe for applying a part of the refrigerant decompressed by the pressure reducing means to the expansion valve to prevent a liquid back phenomenon. In addition, the reliability of the product can be improved by ensuring the protection of the compressor.
[Brief description of the drawings]
FIG. 1 is a refrigerant circuit of a refrigeration / air-conditioning apparatus according to the present invention.
FIG. 2 is a refrigerant circuit of a conventional refrigeration / air-conditioning apparatus.
[Explanation of symbols]
12 expansion valve, 13 evaporator, 14 pipe (pipe), 15 temperature-sensitive cylinder (temperature detecting means), 16 bypass pipe, 18 thin pipe (decompression means), 19 thin pipe (decompression means), 21 external pressure equalizing pipe.

Claims (2)

It has a conduit from the expansion valve to the compressor via the evaporator, and controls the opening and closing of the expansion valve based on the detection result of the temperature detecting means for monitoring the temperature of the refrigerant passing through the evaporator outside the conduit. In the refrigerant circuit of the refrigerating air conditioner,
One end connected to the front of the expansion valve of the conduit, the other end a bypass conduit temperature sensing means is connected to a site located in the conduit, from the front of the expansion valve of the conduit A bypass pipe that bypasses a part of the refrigerant to a position at which the temperature detection unit monitors the temperature of the refrigerant at an initial stage of driving the refrigeration / air-conditioning apparatus ;
Provided detour line in, at positions temperature monitored by said temperature detecting means through said bypass line than the temperature and pressure of the refrigerant at positions temperature monitored by the temperature detection means via the conduit Pressure reducing means for reducing the temperature and pressure of the refrigerant to a low temperature and a low pressure ;
With
Refrigeration characterized by closing the expansion valve when supplying refrigerant to the bypass pipe at the initial stage of driving the refrigeration air conditioner, and cooling the temperature detection means by the refrigerant whose temperature and pressure are lowered by the pressure reducing means. Refrigerant circuit of air conditioner. The refrigerant circuit of a refrigeration / air-conditioning apparatus according to claim 1, wherein the pressure reducing means is multistage so as to attenuate the pressure of the refrigerant stepwise.

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