JPH09138026A - Refrigerating cycle and air conditioner provided with the refrigerant cycle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the generation of an abnormal high pressure in a refrigerant circuit by a method wherein the refrigerant pressure of the refrigerant circuit having a compressor, a condenser, an evacuator and an evaporator, is detected while the opening degree of an evacuating device is controlled based on the detected pressure. SOLUTION: Refrigerant, obtained by mixing two kinds or more of refrigerants having different characteristics, is circulated through a compressor 1, a muffler 2a, a four-way valve 3, a condenser or a heat source side heat exchanger 4, an evacuator or a motor-driven expansion valve 5, a screen filter 6, an evaporator or a utilizing side heat exchanger 7, another muffler 8, the four-way valve 3, an accumulator 9 and the compressor 1 sequentially. In this case, a pressure sensor 2 is provided at the discharging side of the compressor 1 to detect a refrigerant pressure in a refrigerant circuit while the opening degree of the motor-driven expansion valve 6 is controlled by a control unit 41 based on the detected pressure. According to this method, the generation of an abnormal high pressure in the refrigerant circuit can be prevented.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a compressor, a condenser,
The present invention relates to a refrigeration cycle including a refrigerant circuit having a decompression device, an evaporator and the like, and particularly to a refrigeration cycle using a mixed refrigerant in which two kinds of refrigerants having different characteristics are mixed, and an air conditioner including the refrigeration cycle.

[0002]

2. Description of the Related Art Generally, a refrigerant circuit of an air conditioner is constructed by connecting a compressor, a four-way switching valve, a condenser, a pressure reducing device, and an evaporator with a refrigerant pipe. There is.

Since the refrigerant circuit compresses and discharges the refrigerant and circulates the refrigerant circuit, a predetermined refrigerant pressure is generated in the refrigerant circuit. However, the refrigerant circuit is designed to be sufficiently safe to withstand the predetermined pressure. There is. However, as in the case where the outside air temperature unexpectedly rises, the pressure in the refrigerant circuit may abnormally rise above the assumed pressure due to the influence of the external environment and the like. When the refrigerant pressure in the refrigerant circuit becomes abnormally high, the compressor in the refrigerant circuit may be stopped and the abnormal pressure in the refrigerant circuit may be lost because the refrigerant circuit may be damaged. To prevent the rise of.

On the other hand, as the refrigerant filled in the refrigerant circuit,
Conventionally, R-12 and R-50 having a chlorine group were used, but R-22 (chlorodifluoro) having a low chlorine group content is used for the purpose of environmental protection because of the potential for depleting the ozone layer above the ground. Methane) and R-32 containing no chlorine group
(Difluoromethane), R-125 (pentafluoroethane), R-134a (tetrafluoroethane) or a mixture thereof (hereinafter referred to as "HFC-based refrigerant") is used as an alternative refrigerant.

When such an HFC type refrigerant is used as the refrigerant, the operating pressure is higher than that of a conventional single refrigerant (for example, R-22) due to the nature of the mixed refrigerant, so that the refrigerant circuit is abnormal. It is easy to generate high pressure.

[0006]

When an HFC type refrigerant having a high pressure during operation is used as a refrigerant, if the conventional refrigerant circuit (refrigerant pipe, refrigerant device, etc.) is used as it is, the refrigerant circuit It is necessary to stop the compressor described above to prevent damage.

However, if the compressor is stopped during operation,
The operation capacity as an air conditioner is interrupted, and particularly when a mixed refrigerant having a high pressure during operation is used, the compressor is often stopped, and the operation is frequently interrupted, which is not preferable.

It is also possible to review the pressure resistance of the refrigerant circuit. However, reviewing the pressure resistance requires changing the strength setting of the components such as the refrigerant pipe and the refrigerant equipment, and the thickness of the refrigerant pipe becomes thick. There are problems such as an increase in weight and an increase in size.

The present invention has been made in order to solve the above problems, and a refrigeration cycle capable of preventing an abnormally high pressure from being generated in a refrigerant circuit with a simple structure and preventing a significant decrease in operating capacity, and An air conditioner provided with the refrigeration cycle is provided.

[0010]

According to a first aspect of the present invention, there is provided a refrigerant circuit having a compressor, a condenser, a pressure reducing device, and an evaporator, which is a mixed refrigerant prepared by mixing at least two kinds of refrigerants having different characteristics. In the refrigeration cycle configured to circulate in, based on the pressure detected by the pressure detection means for detecting the refrigerant pressure of the refrigerant circuit, the pressure detection means,
And a control device for controlling the opening degree of the pressure reducing device.

According to the first aspect of the present invention, the opening / closing of the pressure reducing device is controlled based on the refrigerant pressure in the refrigerant circuit. Therefore, for example, the refrigerant pressure in the refrigerant circuit is a predetermined value. If higher than the pressure, the controller opens the pressure reducer of the refrigerant circuit to reduce the pressure of the refrigerant circuit.
This prevents the occurrence of abnormally high pressure in the refrigerant circuit, and in particular, even when a mixed refrigerant is used as the refrigerant, the conventional pressure-resistant designed refrigerant circuit can be used. In addition, since continuous operation can be performed without interruption of operation, it is possible to prevent the air conditioner from significantly deteriorating its performance.

According to a second aspect of the present invention, in the first aspect of the present invention, the control device opens the pressure reducing device when the pressure value detected by the pressure detecting means is equal to or more than a predetermined value. It opens the degree at a fixed rate.

According to the second aspect of the present invention, when the detected pressure value is equal to or higher than the predetermined value, the decompression device is opened at a constant rate. Therefore, decompression at high pressure can be performed easily and effectively. realizable. As a result, it is possible to maintain the inside of the refrigerant circuit at a predetermined pressure while minimizing the decrease in the operating capacity of the air conditioner.

According to a third aspect of the invention, in the invention of the second aspect, the opening ratio of the decompression device is 3 to 10%.

In the invention according to claim 3, the reason why the content is 3% or more is that if the content is less than 3%, the pressure reducing effect is too small to expect a sufficient pressure drop, and the content is 10%.
This is because if the pressure is higher, the decompression is too rapid and the capacity of the refrigeration cycle is significantly reduced at one time, making stable operation difficult.

The invention described in claim 4 is the first to third aspects of the present invention.
In the invention described in (1), the pressure detecting means detects the pressure at every arbitrary fixed time (T1), and when the pressure equal to or more than the predetermined value is detected, the constant time (T1) is detected.
The detection time varying means for detecting the pressure again when a time (T2) shorter than 1) has elapsed is provided.

According to the invention described in claim 4, the pressure of the refrigerant is detected every T1 hours, but when the pressure equal to or higher than a predetermined pressure value is detected, the opening degree of the pressure reducing device is opened at a constant rate. , In that case, a shorter time T2 than T1
After the passage of time, the pressure is detected again, and if it is still equal to or higher than the predetermined pressure value, the decompression device is further opened at a constant rate. By performing such control,
High pressure in the refrigerant circuit can be reliably prevented.

[0018] The invention according to claim 5 is the invention according to claims 1 to 4.
In the invention described in (1), the condenser or the evaporator is an air conditioner that is a heat source side heat exchanger or a utilization side heat exchanger, respectively.

In the invention described in claim 5, the refrigeration cycle described in claims 1 to 4 is used as an air conditioner, and in the air conditioner, the same as the inventions described in claims 1 to 4 above. It works.

[0020]

Embodiments of the present invention will be described with reference to the accompanying drawings.

FIG. 1 is a perspective view showing a general household air conditioner. This type of air conditioner is composed of a use side unit A arranged indoors and a heat source side unit B arranged outdoors, both of which are connected by a refrigerant pipe 300.

FIG. 2 is a refrigerant circuit diagram showing a refrigeration cycle of the air conditioner shown in FIG.

Reference numeral 1 denotes a compressor (compressor) comprising a motor section and a compression section driven by the motor section. The compressor 1 is a so-called rated compressor having a constant discharge amount. Therefore, even when the pressure of the refrigerant circuit becomes high, the discharge amount cannot be changed unlike the case of the inverter compressor.

A pressure detecting sensor (pressure detecting means) 2 for detecting the refrigerant pressure in the refrigerant circuit is provided on the discharge side of the compressor 1.

The pressure sensor 2 is for detecting the pressure in the refrigerant circuit, and is connected to a microcomputer 41 as a control device which will be described later to issue a detection signal. The pressure sensor 2 may be one that constantly detects pressure, or the microcomputer 41.
May issue a detection command every predetermined time and measure the pressure when the command is issued.

Although the pressure sensor 2 is arranged on the discharge side of the compressor 1 in this embodiment, the pressure sensor 2 is not necessarily provided at this position, but may be any one that detects the refrigerant pressure in the refrigerant circuit. Good. However, if it is arranged on the discharge side of the compressor 1, it is possible to measure the location where the pressure is highest in the refrigerant circuit, so this is the most effective position for preventing the occurrence of abnormally high pressure. Further, in controlling the compressor 1 based on the detected pressure, it is better to detect the pressure at the position closest to the discharge port of the compressor for better responsiveness.

Reference numeral 2a is a muffler, and 3 is a four-way switching valve for switching the flow of refrigerant during cooling / heating operation. 4 is a heat source side heat exchanger, 5 is an electric expansion valve as a pressure reducing device, 6
Is a screen filter, 7 is a heat exchanger on the use side, 8 is a muffler, 9 is an accumulator, and 10 is an electromagnetic on-off valve.

With the configuration of the refrigerant circuit as described above, the refrigerant discharged from the compressor 1 is shown by a solid arrow (cooling operation) and a dotted line depending on the switching position of the four-way switching valve 3 and the opening / closing of the electromagnetic opening / closing valve 10. The direction of flow is determined according to the three modes, as indicated by the arrow (heating operation) and the arrow at the midpoint of the solid line (defrosting operation).

That is, the refrigerant discharged from the compressor 1 has a solid arrow (cooling operation), a dotted arrow (heating operation), depending on the switching position of the four-way switching valve 3 and the opening / closing of the electromagnetic opening / closing valve 10. The flow direction is determined according to the three modes, as indicated by the solid-line arrow (defrosting operation). During the cooling operation, the refrigerant discharged from the compressor 1 is the compressor 1, the muffler 2a, the four-way switching valve 3, the heat source side heat exchanger 4, the electric expansion valve 5, the screen filter 6, the use side heat exchanger 7, the muffler. 8, four-way switching valve 3, accumulator 9, compressor 1
, The heat source side heat exchanger 4 functions as a condenser, and the use side heat exchanger 7 functions as an evaporator.
The air conditioning operation by becomes possible. During the heating operation, the refrigerant discharged from the compressor 1 is the compressor 1, the muffler 2a, the four-way switching valve 3, the muffler 8, the use side heat exchanger 7, the screen filter 6, the electric expansion valve 5, the heat source side heat exchanger. 4, the four-way switching valve 3, the accumulator 9, and the compressor 1 are circulated in that order, the heat source side heat exchanger 4 functions as an evaporator, the use side heat exchanger 7 functions as a condenser, and heating by the use side heat exchanger 7 is performed. It becomes possible to drive. During the defrosting operation (when the refrigerant is circulating as in the heating operation), the electromagnetic opening / closing valve 10 is opened, and a part of the high-temperature refrigerant discharged from the compressor 1 is transferred to the heat source side heat exchanger 4. Is directly supplied to the heat source side heat exchanger 4 in order to raise the temperature of the heat source. As a result, the temperature of the heat source side heat exchanger 4 rises, frost is less likely to form, and some defrosting is performed. When the defrosting operation does not function sufficiently (when the outside air temperature is particularly low), reverse cycle defrosting (the refrigerant circulates as in the cooling operation) is forcibly performed.

Next, the refrigerant will be described.

In the present embodiment, it is suitable for a refrigerant having a high pressure during operation, and either a single refrigerant or a mixed refrigerant can be used. For example, R-41
0A and R-410B are used. R-410A is 2
It is a mixed refrigerant of component system, 50 wt% of R-32, R-32
125 is composed of 50 wt% and has a boiling point of -52.2.
C, dew point is -52.2C. R-410B has a composition of 45 wt% for R-32 and 55 wt% for R-125.

In such a two-component mixed refrigerant, R-22
When compared with the conventional single refrigerant of No. 6, the discharge temperature of the compressor is 66.0 ° C. at R-22 under predetermined conditions.
On the other hand, R-410A has a temperature of 73.6 ° C., and R-22 has a condensation pressure of 17.35 bar, whereas
At 410A, it is 27.30 bar, and the evaporation pressure is R-
22 is 6.79 bar, while R-410A
Has a characteristic of 10.86 bar, and the entire refrigerant circuit has a higher temperature and a higher pressure than in the case where the conventional single refrigerant of R-22 is used.

On the other hand, when a mixed refrigerant such as R-410A and R-410B is used, since the boiling points of the refrigerants of the respective components are close to each other, it is difficult for the refrigerant composition to change, and the refrigerant composition changes. There is no need to consider the problems such as temperature glide that occur. Therefore, control during driving becomes easy.

FIG. 3 is a control circuit diagram of the air conditioner.
The left side shows the control circuit of the utilization side unit A, and the right side shows the control circuit of the heat source side unit B with the dashed line in the center of FIG. 3 as the boundary. Both control circuits have power line 10
0 and the control line 200.

The user side unit A includes a rectifying circuit 11 and
A power supply circuit 12 for the motor, a power supply circuit 13 for the control, a motor drive circuit 15, a switch board 17,
The receiving circuit 18a, the display board 18, and the flap motor 1
9 and 9 are provided.

The rectifying circuit 11 rectifies 100V AC power supplied through the plug 10a and supplies DC power to the respective power supply circuits 12 and 13. The motor power supply circuit 12 adjusts the DC voltage supplied to the DC fan motor 16 to a voltage of 10 to 36V. This power supply circuit 1
Reference numeral 2 is a heat exchanger on the use side by a fan driven by the DC fan motor 16 by changing the rotation speed of the DC fan motor 16 by varying the DC voltage in the range of 10 to 36 V according to the signal sent from the microcomputer 14. This is for controlling the amount of conditioned air conditioned in 7 to be blown into the conditioned room.

The control power supply circuit 13 generates a DC voltage of 5V to be supplied to the microcomputer 14. The motor drive circuit 15 responds to a signal from the microcomputer 14 based on the rotational position information of the DC fan motor 16 to control the timing of switching the energization to the stator winding of the DC fan motor 16. Switch board 17
Is fixed to the operation panel of the use side unit A, and the switch board 17 is provided with an on / off switch, a trial run switch, and the like. The state of these switches is captured by the microcomputer 14 by key scanning.
The receiving circuit 18a is the wireless remote controller 6
The remote control signal from 0 (for example, ON / OFF signal, cooling / heating switching signal, room temperature setting signal, etc.) is received, demodulated, and transferred to the microcomputer 14.
The display board 18 dynamically lights an LED based on a signal from the microcomputer 14 to display an operating state of the air conditioner. The flap motor 19 functions to move the flap that is conditioned in the utilization side heat exchanger 7 and changes the blowing direction of the conditioned air blown by the fan.

Further, in this control circuit, a room temperature sensor 20 for measuring the room temperature, a heat exchanger temperature sensor 21 for measuring the temperature of the utilization side heat exchanger 7, and a room humidity are measured. Humidity sensor 22 of The measured values detected by these sensors are A / D converted by the microcomputer 14 and taken in. The microcomputer 14 calculates based on these input information (acquisition information), and sends a signal for determining the operating capacity of the four-way switching valve and the compressor 1 to the heat source side unit B through the serial circuit 23 and the terminal board T3. send. Also, Triac 26
The heater relay 27 and the heater relay 27 are controlled by the microcomputer 14 through the driver 24. Thereby, the electric power supplied to the reheating heater 25 used in the dehumidifying operation (state of the refrigerating cycle used during the cooling operation) is controlled stepwise.

Reference numeral 30 is an external ROM that stores specific data indicating the type and characteristics of the air conditioner. These specific data are taken out from the external ROM immediately after the plug 14a is connected to the outlet and power is supplied to start up the microcomputer 14. The microcomputer 14 does not input a command from the wireless remote controller 60 or detect the state of an ON / OFF switch or a trial run switch (operation will be described later) until the specific data is taken out from the external ROM 30.

Next, the control circuit of the heat source side unit B will be described.

In the heat source side unit B, the terminal board T'1
, T'2, T'3 are respectively connected to terminal plates T1, T2, T3 arranged in the use side unit A. Reference numeral 31 is a varistor connected in parallel to the terminal plates T'1 and T'2, 32 is a noise filter, 34 is a reactor, 35 is a voltage doubler rectifier circuit, and 36 is a noise filter.

Reference numeral 39 is a serial circuit for dispersing the control signal supplied from the utilization side unit A from the power line through the terminal board T'3, and the dispersed signal is transmitted to the microcomputer 41. Reference numeral 40 is a current detector, which detects the current supplied to the heat source side unit B by current transformation (CT) and converts it into a signal for the microcomputer 41. 42 is a constant current circuit for generating electric power for operating the microcomputer 41, 43 is a motor unit for operating the compressor 1 of the refrigeration cycle, 44
Is a discharge-side temperature sensor that detects the temperature of the refrigerant discharged from the compressor 1. Reference numeral 45 is a fan motor, the speed of which is controlled in three stages and is arranged so that air can be sent to the heat source side heat exchanger. Four-way switching valve 3, solenoid valve 10,
As described above, the refrigerant passages of the refrigeration cycle are switched. Further, in the heat source side unit B, an outdoor temperature sensor 48 for detecting the outdoor temperature is provided with a fan motor 45.
A heat exchanger temperature sensor 49 for detecting the temperature of the heat source side heat exchanger is attached to the heat source side heat exchanger. These temperature sensors 48, 49
The detection value obtained by the above is A / D converted by the microcomputer 41 and taken in.

Reference numeral 50 is an external ROM of the user side unit A.
It is an external ROM having the same function as 30. The specific data of the heat source side unit B is the same as that described for the external ROM 30, but is stored in the ROM 50.

The symbol F in each control circuit of the heat source side unit B and the use side unit A is a fuse.

Each of the microcomputers (control devices) 14 and 41 is a ROM that stores a program in advance,
A RAM that stores reference data and a CPU that calculates a program are stored in the same container (87C196MC (MC sold by Intel Corporation).
S-96 series) and the like can be used).

On the other hand, the microcomputer 41 is connected to the pressure sensor 2 in this embodiment, and controls the valve opening of the electric expansion valve 5 in response to the detected pressure. Step motor 5 for driving throttle valve 5
The opening signal is issued to the first position.

That is, the opening degree of the electric expansion valve 5 is usually controlled on the basis of the refrigerant evaporation temperature so that the refrigerant evaporation temperature in the refrigeration cycle becomes constant. In the present embodiment, the pressure is further increased. The control is also performed based on the pressure detected by the sensor 2.

As shown in FIG. 2, the microcomputer 41 as a control device is provided with a detection time varying means 71. As will be described later, the detection time by the pressure sensor 2 is determined and the detection time is determined. It changes according to the detected pressure.

Next, the operation of this embodiment will be described.

During the cooling operation, the refrigerant discharged from the compressor 1 is the muffler 2a, as shown by the solid arrow in FIG.
Four-way switching valve 3, heat source side heat exchanger (outdoor heat exchanger) 4, electric expansion valve 5, screen filter 6, use side heat exchanger (outdoor heat exchanger) 7, muffler 8, four-way switching valve 3, accumulator 9 In this order, the use side heat exchanger 7 functions as an evaporator, and the electric expansion valve 5 reduces the pressure. During heating operation, the compressor 1
The refrigerant discharged from the muffler 2a, the four-way switching valve 3,
The muffler 8, the use side heat exchanger (outdoor heat exchanger) 7, the screen filter 6, the electric expansion valve 5, the heat source side heat exchanger (outdoor heat exchanger) 4, the four-way switching valve 3, and the accumulator 9 in this order in the refrigerant circuit. The heat source side heat exchanger 4 functions as an evaporator, and the pressure is reduced by the electric expansion valve 5.

In the present embodiment, as described above, since R-410A and R-410B, which are two-component mixed refrigerants, are used as refrigerants, compared with the case where a single refrigerant is used,
The refrigerant pressure in the refrigerant pipe during operation is high. For this reason,
Conventionally, when the pressure exceeds a predetermined value, the compressor is stopped and the pressure in the refrigerant circuit is kept below the specified value.However, a rated compressor is used for the compressor, and a constant speed motor is used as the compressor motor. Each time it is used, it takes time to increase the pressure in the circuit to the desired value again. Therefore, in the embodiment of the present invention, the opening of the electric expansion valve 5 as the pressure reducing device is controlled based on the refrigerant pressure in the refrigerant circuit without stopping the compressor as in the conventional case.

The control method will be described below with reference to FIG.

After the start of operation, in step S1, it is determined whether or not a predetermined time has elapsed, and if the predetermined time has elapsed, the process proceeds to step S2. The predetermined time determined in step S1 is a time for stabilizing the refrigerant circulating in the refrigerant circuit, and the predetermined time is preferably 2 to 5 minutes,
In this embodiment, it is 3 minutes, for example. If the predetermined time has not elapsed, the process returns to step S1 again.

In step S2, the pressure sensor 2 detects the discharge pressure P of the compressor 1, and the process proceeds to step S3.

In step S3, it is determined whether the detected pressure P is equal to or higher than a predetermined first pressure value. This predetermined first
The pressure value varies depending on the refrigeration cycle, the refrigerant used, etc., but is 10% to 20% from the pressure resistance safety limit value of the refrigerant circuit.
Any low value. In this embodiment, the withstand pressure safety limit is 4
If it is 0 Kg / cm2 (step S8 described later),
The first pressure value is 34Kg / cm2 and the second pressure value is 35K
g / cm2 (see step S6 described later).

The detection pressure P is the first pressure of 34 Kg / cm.
If it is smaller than 2, the process proceeds to step S4, and the opening degree of the electric expansion valve 5 is maintained as it is. That is, when the pressure in the refrigerant circuit is smaller than the first pressure of 34 Kg / cm @ 2, the electric expansion valve 5 is controlled based on the evaporation temperature of the refrigerant without any limitation based on the refrigerant pressure.

Next, in step S5, it is judged whether or not a fixed time, 30 seconds in the present embodiment, has passed. If the fixed time has passed, the process returns to step S1. Therefore, in the refrigerant circuit, when the refrigerant pressure is not particularly high, the pressure is detected every 30 seconds.

In step S3, the detected pressure is 34 Kg / cm.
If it is 2 or more, the process proceeds to step S6, and it is determined whether or not the refrigerant pressure is 35 Kg / cm2 or more. If it is smaller than 35 kg / cm2, the process proceeds to step S7, and the opening degree of the electric expansion valve 5 is 5% of the current opening degree.
Control the opening. That is, when the detected pressure P is 34 Kg / cm2 or more and less than 35 Kg / cm2 (34≤P <35)
Since the pressure in the refrigerant circuit is relatively high, the electric expansion valve 5 is controlled to be opened in step S7, and the pressure in the refrigerant circuit is lowered so that the pressure in the refrigerant circuit does not rise any further.

In this case, the opening degree of the electric expansion valve is 3
% To 10% is preferable. As a result of the experiment, when the opening degree is less than 3%, the result of the experiment is that the pressure reducing effect is too small to expect a sufficient pressure drop, and when the opening degree is more than 10%, the pressure temporarily drops and becomes stable. Because it was difficult to drive well. Since the best results were obtained in the present embodiment, the electric expansion valve 5 was opened by 5%.

In step S7, the opening degree of the electric expansion valve 5 is set to 5%.
After opening, the process proceeds to step S5 described above, and after 30 seconds have passed, the process returns to step S1 again.

On the other hand, in step S6, the detected pressure P is 35
If it is not less than Kg / cm2, the process proceeds to step S8, and it is judged whether the refrigerant pressure is not less than 40 Kg / cm2.
If it is less than 40 kg / cm2 (35≤P <4
In 0), the process proceeds to step S9, and the opening degree of the electric expansion valve 5 is controlled to be opened by 5% with respect to the current opening degree. After that, the process proceeds to step S10, it is determined whether 10 seconds have elapsed, and 1
After the lapse of 0 seconds, the process returns to step S1 and the pressure sensor 2 starts detecting pressure in the refrigerant circuit again.

That is, the refrigerant pressure P is 35 to 40 kg / cm2.
If it is high (we will call it "second zone"),
In the case of 34 to 35 kg / cm2 (referred to as "first zone")
The electric expansion valve 5 is opened by 5% in the same manner as, but unlike the case of 30 seconds in the first zone, the pressure is still detected after the pressure is detected again in a short time of 10 seconds in the second zone. Is in the second zone, the electric expansion valve 5 is further opened by 5%. Therefore, in the second zone, it is possible to prevent a further increase in pressure quickly and reliably.

On the other hand, in step S8, the detected pressure P
If is greater than 40 kg / cm @ 2, the process proceeds to step S11, and the electric expansion valve 5 is fully opened. As a result, the pressure of the refrigerant in the refrigerant circuit can be immediately reduced, and damage to the refrigeration equipment and the refrigerant circuit can be prevented.

Moreover, even when the refrigerant pressure exceeds the second zone as described above, the compressor 1 is continuously operated without being stopped, so that it is possible to prevent a significant decrease in the capacity of the air conditioner.

After the electric expansion valve 5 is fully opened in step S11, the above control is performed again after waiting 30 seconds in step S12. Therefore, when the pressure in the refrigerant circuit becomes normal, The electric expansion valve 5 quickly returns.
Therefore, it is possible to prevent a significant decrease in the capacity of the air conditioner and to quickly restore the capacity.

According to the above-described embodiment, it is possible to prevent the abnormal high pressure from being generated in the refrigerant circuit with a simple structure. Moreover, since continuous operation can be performed without interrupting the operation of the air conditioner, it is possible to prevent a significant decrease in operating capacity.

In particular, even when a mixed refrigerant is used as the refrigerant, the conventional pressure-resistant designed refrigerant circuit can be used.

Next, a second embodiment will be described with reference to FIG. The second embodiment is different in that a pressure switch P1 which is turned on when the pressure exceeds a predetermined pressure is used as the pressure detecting means. As described above, by using the pressure switch as the pressure detecting means, the device can be manufactured at low cost and the structure can be simplified as compared with the above-described embodiment using the pressure detector.

In the second embodiment, after the operation is started, it is determined in step S101 whether a predetermined time has elapsed, and if the predetermined time has elapsed, the process proceeds to step S102. The predetermined time determined in step S101 is a time for stabilizing the refrigerant circulating in the refrigerant circuit, as in the above-described embodiment, and is 2 to 5 minutes.

In step S102, the pressure switch P1
It is determined whether or not is turned on. The pressure switch P1 is a switch that is turned on when the detected pressure is 34 Kg / cm2 or more, and sends a detection signal to the control device 41 when turned on. If the pressure switch P1 is not turned on, the inside of the refrigerant circuit does not have an abnormally high pressure.
03, the process proceeds to step S104 without correcting the valve opening degree, waits 30 seconds, and then returns to step S101.

On the other hand, in step S102, when the pressure switch P1 is turned on, the pressure in the refrigeration cycle is 34 kg /
Since the pressure is higher than cm2, the routine proceeds to step S105, where it is determined whether or not the pressure switch P2 is ON. This pressure switch P2 has a detection pressure of 40 kg.
It is a switch that is turned on at / cm 2 or more, and when it is turned on, a detection signal is sent to the control device 41.

In step S105, the pressure switch P
When 2 is not ON, the pressure in the refrigerant circuit is 34
Value above 40kg / cm2 in Kg / cm2 (34K
Since g / cm @ 2 .ltoreq.P <40 Kg / cm @ 2), the valve opening degree of the expansion valve is corrected to be opened by 5% as in the above-described embodiment. Then, after 10 seconds have elapsed in step S108, the process returns to step S101 and the control operation is repeated.

In step S105, when the pressure switch P2 is further turned on, the pressure in the refrigerant circuit is 40 kg / cm2 or more, so the flow proceeds to step S106, and the opening degree of the expansion valve is fully opened. . Then, the process proceeds to step S104, and after 30 seconds have passed, step S10 is performed again
Return to 1.

According to the above-described embodiment, it is possible to prevent abnormal high pressure from occurring in the refrigerant circuit with a simple structure. Moreover, since continuous operation can be performed without interrupting the operation of the air conditioner, it is possible to prevent a significant decrease in operating capacity.

The present invention is not limited to the above-mentioned embodiments, and various modifications can be made without departing from the gist of the present invention.

For example, in the first embodiment, the pressure sensor 2 is not limited to being arranged in the vicinity of the discharge port of the compressor 1, but the same effect can be obtained in the refrigerant circuit.

Further, a temperature sensor is used in place of the pressure sensor 2, the pressure is estimated based on the detected temperature, and the electromagnetic expansion valve 5
Even if the opening degree is controlled, the same effect can be obtained. In this case, since the relationship between the pressure and the temperature varies depending on the characteristics of the refrigerant, it is desirable to find the relationship between the temperature and the pressure based on the experimental data conducted in advance. Further, a pressure expansion valve or a thermal expansion valve that opens and closes in response to a direct pressure can be used.

Further, in the above-mentioned embodiment, the air conditioner has been described as an example, but the present invention is not limited to this, and any device having a refrigeration cycle may be used in, for example, a refrigerator or a vending machine. You can

[0079]

According to the first aspect of the present invention, in the refrigerating cycle configured to circulate the mixed refrigerant in the refrigerant circuit, the opening degree of the pressure reducing device is determined based on the refrigerant pressure detected by the pressure detecting means. Therefore, it is possible to prevent abnormal high pressure from being generated in the refrigerant circuit. Especially,
Even when a mixed refrigerant is used as the refrigerant, the conventional pressure-resistant designed refrigerant circuit can be used. In addition, since continuous operation can be performed without interruption of operation, it is possible to prevent the air conditioner from significantly deteriorating its performance.

According to the second aspect of the invention, when the detected pressure value is equal to or higher than the predetermined value, the decompression device is opened at a constant rate, so that the refrigerant circuit can be easily and effectively operated at high pressure. Decompression can be realized.

According to the third aspect of the invention, since the ratio of the opening degree of the pressure reducing device is 3% to 10%, stable operation can be performed.

According to the fourth aspect of the present invention, when a pressure equal to or higher than a predetermined pressure value is detected, the pressure is detected and controlled at shorter time intervals, so that the high pressure of the refrigerant circuit can be reliably ensured. It can be prevented.

According to the invention described in claim 5, particularly in the air conditioner, the same effect as that of the invention described in claims 1 to 4 can be obtained.

[0084]

[Brief description of the drawings]

FIG. 1 is a perspective view of an air conditioner applied to an embodiment of the present invention.

FIG. 2 is a refrigerant circuit diagram of the air conditioner shown in FIG.

FIG. 3 is a control circuit diagram of the air conditioner shown in FIG. 1.

FIG. 4 is a flowchart showing a control operation of the electric expansion valve according to the embodiment of the present invention.

FIG. 5 is another embodiment of the present invention (second embodiment).
6 is a flowchart showing a control operation of the electric expansion valve according to the above.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Compressor 2 Pressure sensor (pressure detection means) 5 Electric expansion valve (decompression device) 41 Control device 47 Detection time varying means

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Susumu Mikiyasu 2-5-5 Keihan Hondori, Moriguchi City, Osaka Prefecture Sanyo Electric Co., Ltd. (72) Inventor Takahiro Suzuki 2-5 Keihan Hondori, Moriguchi City, Osaka Prefecture No. 5 within Sanyo Electric Co., Ltd. (72) Inventor Shigeya Ishigaki 2-5-5 Keihan Hondori, Moriguchi City, Osaka Prefecture Within Sanyo Electric Co., Ltd. (72) Norio Akutagawa, 2 Keihan Hondori, Moriguchi City, Osaka Prefecture 5-5, Sanyo Electric Co., Ltd.

Claims (5)

[Claims] 1. A refrigeration cycle in which a mixed refrigerant in which at least two kinds of refrigerants having different characteristics are mixed is circulated in a refrigerant circuit having a compressor, a condenser, a decompression device, and an evaporator. The refrigeration cycle, comprising: a pressure detection unit that detects the refrigerant pressure of the above; and a control device that controls the opening degree of the decompression device based on the pressure detected by the pressure detection unit. 2. The control device opens the opening degree of the pressure reducing device at a constant rate when the pressure value detected by the pressure detecting means is equal to or more than a predetermined value.
Refrigeration cycle described in. 3. The ratio of the opening degree of the pressure reducing device is 3 to 1.
The refrigerating cycle according to claim 2, wherein the refrigerating cycle is 0%. 4. The pressure detecting means is for a fixed time (T1).
The pressure is detected every time, and when a pressure equal to or higher than the predetermined value is detected, a detection time varying means for detecting the pressure again when a time (T2) shorter than the constant time (T1) has elapsed is provided. The refrigerating cycle according to any one of claims 1 to 3, further comprising: 5. The air provided with the refrigeration cycle according to claim 1, wherein the condenser or the evaporator is a heat source side heat exchanger or a utilization side heat exchanger, respectively. Harmony machine.