JPH11142006A - Refrigerant circulation system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce a current leaking by means of oil attached to a motor even in a state where a high voltage is supplied to the motor by using a refrigerant having no mutual solubility or having a weak solubility with respect to the refrigerant because the refrigerator scarcely contains a refrigerant of high dielectric constant. SOLUTION: A compressor 1 controlling a motor unit by an inverter driving circuit capable of making a supply voltage greater than a voltage smoothed from a main power source and controlling the speed of rotation, an outdoor heat exchanger 3, a throttle mechanism 4, and an indoor heat exchanger 5 are connected by a refrigerant piping. A refrigerant containing mainly a hydrofluorocarbon(HFC) is used as the refrigerant and oil which has no mutual solubility or has weak solubility with respect to the refrigerant is used as a refrigerator oil sealed in the compressor 1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a refrigerant circulation system used for domestic and industrial use.

[0002]

2. Description of the Related Art FIG. 6 is a refrigerant circuit diagram showing a conventional refrigerant circulation system (here, a refrigerating air conditioner) disclosed in Japanese Patent Application Laid-Open No. Hei 5-17789. In the figure, 1 is a compressor whose rotation speed can be controlled by inverter driving, 5 is an indoor heat exchanger which is a use side heat exchanger, 4 is a throttle mechanism, 3
Is an outdoor heat exchanger which is a heat source side heat exchanger, and 2 is a four-way valve having a function of reversing the flow of the refrigerant. These are connected in series by piping to constitute a refrigeration cycle.

In this refrigerating air conditioner, a mixed refrigerant containing, for example, HFC32, which is a flammable refrigerant, is used as a refrigerant, and as a refrigerating machine oil, for example, an ester oil which is mutually soluble in the mixed refrigerant. Is used.

[0004] By the way, the leakage current is generated through the refrigerating machine oil attached to the motor unit in a state where a voltage is applied to the motor unit of the compressor 1. FIG. 7 shows the relationship between the amount of refrigerant dissolved in the refrigerating machine oil and the leakage current. When the amount of refrigerant dissolved in the refrigerating machine oil increases from FIG. Since the amount of penetration increases, the leakage current easily flows through the oil attached to the motor section of the compressor 1. In the case of an inverter drive in which the voltage supplied to the motor section of the compressor to be used is higher than the voltage obtained by smoothing the main power supply, the leakage current is more likely to flow.

In general, the leakage current tends to increase as the relative permittivity of the oil or refrigerant used increases. The liquid refrigerant has a relative dielectric constant that is two to three times that of the refrigerating machine oil. In order to suppress the leakage current, it is necessary to use a refrigerator oil and a refrigerant having a low relative dielectric constant of the refrigerator oil or to reduce the dissolution of a refrigerant having a high relative dielectric constant into the refrigerator oil. With a compatible refrigerating machine oil such as described above, the amount of penetration could not be controlled.

FIG. 8 shows the relationship between the relative permittivity when the refrigerant and the refrigerating machine oil are mixed. R22 and H which are HCFC refrigerants
Comparing the relative dielectric constant of the saturated physical property of R410A, which is an FC-based refrigerant, the relative dielectric constant of R410A, which is an HFC-based refrigerant, is about 1.5 times higher, and the leakage current is easy to flow. The ester oil used conventionally has a high relative permittivity of the oil itself, and the ester oil is a compatible oil, so the amount of refrigerant having a high relative permittivity increases and the leakage current increases. Had become.

[0007]

Since the conventional refrigerant circulation system is configured as described above, an HFC-based refrigerant is used, and the voltage supplied to the motor section of the compressor as in an inverter drive circuit is reduced. A refrigerant circuit equipped with an electric circuit that is higher than the smoothed voltage of the power supply.When a refrigerant with high solubility is used for the refrigerating machine oil enclosed in the compressor, a large amount of refrigerant with a high relative dielectric constant is contained in the oil. Therefore, there is a problem that leakage current increases through oil adhering to the motor.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems, and has as its object to realize a refrigerant circulation system having a small leakage current.

[0009]

[Means for Solving the Problems]

[0010] The refrigerant circulation system according to the present invention provides a compressor, a heat source side heat exchanger, and a throttle, in which a supply voltage can be made higher than a voltage obtained by smoothing an original power supply and a motor section is controlled by an inverter drive circuit capable of controlling a rotation speed. The mechanism and the use-side heat exchanger are connected by a refrigerant pipe, and a refrigerant mainly composed of hydrofluorocarbon (HFC) is used as the refrigerant, and the refrigerating machine oil sealed in the compressor has no mutual solubility with the refrigerant. Alternatively, a poorly soluble one is used.

[0011] Further, an alkylbenzene-based oil or a mineral oil is used as the refrigerating machine oil.

[0012] Further, as the refrigerating machine oil, the saturation weight dissolution rate of the refrigerant dissolved in the refrigerating machine oil in the temperature range of 10 deg or more with respect to the saturation temperature of the refrigerant under the pressure conditions used in the motor section of the compressor. 15% or less. (Here, the saturated weight dissolution rate (α) means α = weight of liquid refrigerant dissolved in oil / (weight of liquid refrigerant dissolved in oil + weight of oil))

Further, R410A is used as a refrigerant, and an alkylbenzene-based oil is used as a refrigerating machine oil.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment 1 Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a refrigerant circuit diagram showing an example of an embodiment of the present invention.
Is a compressor driven by an inverter having a motor unit and capable of controlling the rotation speed, 2 is a four-way valve for switching a flow during cooling and heating, 3 is an outdoor heat exchanger which is a heat source side heat exchanger, and 4 is a throttle mechanism. The electronic expansion valves 5 and 5 are indoor heat exchangers which are use side heat exchangers, and these are sequentially connected by refrigerant pipes. Numeral 11 denotes the compressor 1 by an inverter drive circuit.
Is a compressor drive device for controlling the rotation speed of the compressor. Compressor 1
Of the compressor drive device 11 from an external commercial power supply
Power is supplied via the.

An outdoor unit 31 includes a compressor 1, a four-way valve 2, an outdoor heat exchanger 3, an electronic expansion valve, and the like. An indoor unit 32 includes an indoor heat exchanger 5 and the like. Machine 32
Are connected by a gas side indoor / outdoor connection pipe 21 and a liquid side indoor / outdoor connection pipe 22, and constitute a refrigerant circulation system. 6
Is an outdoor blower fan that blows air with the outdoor heat exchanger, 7 is an indoor blower fan that blows air with the indoor heat exchanger, 12 is an outdoor blower fan driving device that controls the rotation speed of the outdoor blower fan 6, and 13 is an indoor blower fan. 7 is an indoor fan driving device for controlling the rotation speed of the fan 7.

Reference numeral 14 denotes an outdoor microcomputer control unit for totally controlling the compressor drive unit 11, the outdoor blower fan drive unit 12 and the like, and 15 denotes a total connection control of the indoor blower fan drive unit 13 and the like, and a signal connection with the outdoor microcomputer control unit 14. Of the room microcomputer. Further, in this refrigerant circulation system, R410A which is a mixed refrigerant of R32 and R125 is used as a refrigerant, and as a refrigerating machine oil, for example, mutual solubility with R410A is small, and its specific gravity is smaller than that of the liquid refrigerant. Alkylbenzene oils are used.

Next, the operation will be described with reference to the pressure-enthalpy diagram shown in FIG. First, during heating operation,
As shown by a solid line arrow in FIG. 1, the high-temperature and high-pressure refrigerant (point A in the figure) compressed by the compressor 1 is supplied to a gas side indoor / outdoor connection pipe 2.
1 and condensed and liquefied in the indoor heat exchanger 5 operating as a condenser (point B in the figure). The liquid refrigerant passes through the liquid-side indoor / outdoor connection pipe 22 and is decompressed by the electronic expansion valve 4 to become a low-temperature low-pressure gas-liquid two-phase refrigerant and evaporates in the outdoor heat exchanger 3 operating as an evaporator. 2 and return to the compressor 1 to be compressed again.

On the other hand, at the time of cooling, as indicated by a broken line arrow in the figure, a high-temperature and high-pressure refrigerant vapor (A in the figure) compressed by the compressor 1 is used.
(Point) is condensed and liquefied in the outdoor heat exchanger 3 operating as a condenser (point B in the figure). This liquid refrigerant is supplied to the electronic expansion valve 4.
And becomes a low-temperature low-pressure gas-liquid two-phase refrigerant, and flows into the indoor heat exchanger 5 that operates as an evaporator through the liquid side indoor / outdoor connection pipe 22 (point C in the figure). Further, the refrigerant evaporates in the indoor heat exchanger 3, returns to the compressor 1 through the gas side indoor / outdoor connection pipe 21 and the four-way valve 2, and is compressed again.

FIG. 7 shows the relationship between the refrigerant dissolution rate in the refrigerating machine oil and the leakage current. When the compressor motor contains a large amount of refrigerant having a high relative dielectric constant and a high voltage is supplied to the compressor motor, a leakage current easily flows through oil adhering to the motor.

Therefore, in this embodiment, a refrigerating machine oil (weakly compatible oil) having low solubility in the refrigerant is used. FIG.
Refrigeration oil with low solubility in refrigerant (weakly compatible oil) has little refrigerant with a high relative permittivity dissolved in the oil, so even when a high voltage is supplied to the motor, In addition, it is possible to suppress an increase in current leaking through oil attached to the motor.

As means for improving the motor efficiency of the compressor, there is an increase in the core stacking width of the motor part of the compressor. In this case, the space between the compressor shell part and the motor part is reduced, and as a result, the leakage current increases. I do. Until now, there was a limit to the efficiency improvement of the compressor in order to suppress the leakage current, but by using the refrigerating machine oil with low solubility with the refrigerant,
It is possible to improve the efficiency of the compressor.

Further, when the rotational speed of the compressor is varied by an inverter drive circuit, when the carrier frequency is increased, the waveform approaches a sine wave to improve the efficiency. At that time, however, the leakage current also tends to increase. A trade-off with efficiency was needed. Since the leakage current is reduced by using the refrigerating machine oil having low solubility in the refrigerant, it is possible to improve the inverter efficiency.

Embodiment 2 FIG. FIG. 9 shows R22, which is an HCFC-based refrigerant, and Alkylbenzene oil + as a refrigerating machine oil, which have been used for a refrigerant circulation device.
It shows the relationship between the difference between the refrigerating machine oil temperature and the saturated liquid refrigerant temperature of the mineral oil (hereinafter referred to as the refrigerating machine oil temperature superheat), the refrigerating machine oil viscosity, and the refrigerant dissolution rate in the refrigerating machine oil. When the superheat of the refrigerating machine oil temperature is 10 deg or less, the viscosity of the refrigerating machine oil rapidly decreases, and reliability such as abnormal wear and seizure due to poor lubrication of sliding parts of the compressor becomes a problem.

FIG. 5 is a diagram showing superheat and leakage current of refrigerating machine oil when each refrigerant and refrigerating machine oil are mixed. In the conventional refrigeration cycle using R22, which is an HCFC-based refrigerant as the refrigerant, and alkylbenzene oil + mineral oil as the refrigeration oil, the relative permittivity of the refrigerant itself is lower than that of the HFC-based refrigerant. Under the condition where the ratio is small, the relative dielectric constant when the refrigerant and the refrigerating machine oil are mixed is low.

According to FIG. 9, under the operating condition in which the refrigerating machine oil temperature is superheated, the dissolution rate of the refrigerant in the refrigerating machine oil is low. Therefore, as shown in FIG. It is lower than that using a system refrigerant. But,
From FIG. 9, when the superheat of the refrigerating machine oil temperature decreases, the amount of the refrigerant dissolved in the refrigerating machine oil increases.
The relative permittivity at the time of mixing of the refrigerating machine oil increases, and in order to secure the superheat of the refrigerating machine oil temperature of 10 deg which can ensure the safety of the compressor under the pressure conditions used in the motor part of the compressor, FIG. Thus, the weight dissolution rate of the refrigerant dissolved in the refrigerating machine oil is 30%, and the relative dielectric constant when the refrigerant and the refrigerating machine oil are mixed at that time is about 3.5.

When R410A is used as the refrigerant and alkylbenzene oil is used as the refrigerating machine oil, the weight dissolution rate of the refrigerant dissolved in the refrigerating machine oil is set to 15% or less as shown in FIG. , A highly efficient refrigerant circulation system can be obtained without exceeding the relative permittivity that has been proven in the refrigerant circulation device.

[0027]

As described above, according to the present invention, the compressor and the heat source side heat exchanger which control the motor unit by the inverter drive circuit capable of controlling the rotation speed while making the supply voltage higher than the voltage obtained by smoothing the original power supply. The throttle mechanism and the use-side heat exchanger are connected by a refrigerant pipe, and a refrigerant mainly containing hydrofluorocarbon is used as a refrigerant, and as a refrigerating machine oil sealed in the compressor, is there any mutual solubility in the refrigerant? Alternatively, since a refrigerant having a low solubility is used, a refrigerant having a high relative dielectric constant is hardly contained in the refrigerator, and therefore, even when a high voltage is supplied to the motor, the refrigerant adheres to the motor via oil attached thereto. The effect of reducing the leakage current can be obtained.

Further, since an alkylbenzene-based oil or a mineral oil is used as the refrigerating machine oil, a refrigerant having a high relative dielectric constant is hardly contained in the refrigerating machine, so that the effect of reducing the leakage current from the compressor motor can be obtained.

In addition, as the refrigerating machine oil, the saturation weight dissolution rate of the refrigerant dissolved in the refrigerating machine oil in the temperature range of 10 deg or more with respect to the saturation temperature of the refrigerant under the pressure condition in which the motor section of the compressor is used is determined. Since it is 15% or less, the effect of reducing the current leaking through the oil attached to the motor can be obtained even in a region where the superheat of the refrigerator oil temperature is small.

Further, since R410A is used as the refrigerant and an alkylbenzene-based oil is used as the refrigerating machine oil, even in a region where the superheat of the refrigerating machine oil temperature is small, it is possible to reduce the current leaking through the oil adhering to the motor. can get.

[Brief description of the drawings]

FIG. 1 is a refrigerant circuit diagram illustrating a refrigerant circulation system according to Embodiment 1 of the present invention.

FIG. 2 is a pressure diagram showing the operation of the refrigerant circulation system of FIG.
It is an enthalpy diagram.

FIG. 3 is a solubility curve diagram of R22, (alkylbenzene-based oil + mineral oil).

FIG. 4 is a solubility curve of R410A, an alkylbenzene-based oil.

FIG. 5 is a correlation diagram showing a relationship between superheat of refrigerator oil temperature and leakage current.

FIG. 6 is a refrigerant circuit diagram showing a conventional refrigerant circulation system.

FIG. 7 is a correlation diagram showing a relationship between a refrigerant dissolution rate in refrigerating machine oil and a leakage current.

FIG. 8 is a correlation diagram showing a relative dielectric constant when a refrigerant and a refrigerating machine oil are mixed.

FIG. 9 is a correlation diagram (refrigerant: R22, refrigeration oil: alkylbenzene oil + mineral oil) showing the relationship between the superheat of the refrigeration oil temperature and the viscosity of the refrigeration oil.

[Explanation of symbols]

1 compressor, 2 four-way valve, 3 outdoor heat exchanger, 4
Throttling mechanism, 5 indoor heat exchanger, 11 compressor drive.

Claims (4)

[Claims] 1. A compressor, a heat source side heat exchanger, a throttle mechanism, and a use side heat exchanger that control a motor unit by an inverter drive circuit capable of controlling a rotation speed while controlling a supply voltage to be higher than a voltage obtained by smoothing a source power supply. Are connected by a refrigerant pipe, and a refrigerant mainly containing hydrofluorocarbon (HFC) is used as a refrigerant, and as a refrigerating machine oil sealed in the compressor, there is no mutual solubility or weak solubility in the refrigerant. A refrigerant circulation system characterized by using a refrigerant. 2. The refrigerant circulation system according to claim 1, wherein an alkylbenzene-based oil or a mineral oil is used as the refrigerating machine oil. 3. The refrigerating machine oil has a saturation temperature of 10% for a refrigerant under a pressure condition in which a motor portion of a compressor is used.
The refrigerant circulation system according to claim 1, wherein the saturated weight dissolution rate of the refrigerant dissolved in the refrigerating machine oil is set to 15% or less in a temperature range of deg or more. 4. Using R410A as a refrigerant,
The refrigerant circulation system according to claim 3, wherein an alkylbenzene-based oil is used as the refrigerating machine oil.