JP3228172B2 - Refrigeration equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a refrigeration system using lubricating oil which is liable to deteriorate at high temperatures, and more particularly to a refrigeration system for performing operation control for preventing a rise in lubricating oil temperature.

[0002]

2. Description of the Related Art Conventionally, Japanese Patent Application Laid-Open No.
No. 64, a compressor, a condenser,
BACKGROUND ART An air conditioner including a refrigerant circuit including an expansion valve and an evaporator is known. In this air conditioner, the compressor takes in the gas refrigerant evaporated by the evaporator, raises the pressure to a high temperature and a high pressure, and then discharges the gas refrigerant toward the condenser.

However, as in the case of defrost operation,
In an operation in which the refrigerant is not sufficiently evaporated, it is easy to perform a so-called wet operation in which the liquid phase remains in a part of the refrigerant and is sucked into the compressor. In this case, the liquid refrigerant causes adverse effects such as diluting the lubricating oil stored in the compressor. Therefore, in the air conditioner disclosed in the above publication, an oil temperature sensor for detecting the temperature of lubricating oil is provided in the compressor, and when the oil temperature is equal to or lower than a predetermined value, the rotation speed of the compressor is reduced, and the liquid refrigerant is cooled. Was prevented from being sucked into the compressor. In other words,
When the oil temperature is equal to or lower than a predetermined value, an operation for increasing the oil temperature has been performed.

[0004]

In recent years, replacement of HCFC-based refrigerants with HFC-based refrigerants has been promoted in view of global environmental problems. Therefore, it is necessary to change the lubricating oil used for the compressor to one suitable for the HFC-based refrigerant, and ether-based or ester-based synthetic oil is used as such a lubricating oil.

[0005] These synthetic oils are liable to deteriorate when moisture or mineral oil is mixed therein. In particular, when the oil temperature is high, the deterioration speed is accelerated and the synthetic oil is liable to deteriorate rapidly. Therefore, if the compressor is operated in a state where the oil temperature is high, the lubricating oil may be degraded, the viscosity may be reduced, and lubrication failure may be caused.

However, in a conventional refrigeration system using an HCFC-based refrigerant, no meticulous attention has been paid to the increase in oil temperature as required for the synthetic oil.
If the HCFC-based refrigerant and the synthetic oil are used as they are in a conventional refrigeration system, the above-mentioned adverse effects may be caused.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and an object of the present invention is to suppress a rise in lubricating oil temperature, prevent deterioration thereof, and improve the reliability of a refrigeration system. It is in.

[0008]

In order to achieve the above object, the present invention provides an oil temperature detecting means, and when the oil temperature becomes higher than a predetermined value, performs a wet operation to suction the oil into the compressor. The lubricating oil is cooled by the liquid refrigerant and the oil temperature is lowered.

More specifically, a means of the present invention is a compressor having an oil reservoir for storing lubricating oil.
(1), a refrigerant circuit (20) in which a heat source side heat exchanger (3), a pressure reducing means (4), and a use side heat exchanger (7) are connected in order, and an oil sump of the compressor (1). Oil temperature detecting means (17) for detecting the temperature of the lubricating oil stored in the section, the oil temperature detected by the oil temperature detecting means (17) is not less than a predetermined value (Te + T1) Control means (40) for performing a wet operation in which the compressor (1) inhales wet steam when the compressor (1) is provided, and the pressure reducing means comprises an expansion valve (4), and the control means (40) Is the oil temperature
When (To) exceeds a predetermined value (Te + T1), the expansion valve
When the wet operation is performed by increasing the opening of (4) and the oil temperature (To) is equal to or higher than the first predetermined temperature (Te + T1),
The opening degree of the expansion valve (4) is controlled so that the suction superheat (SHS) becomes a negative predetermined value (NSH), while the oil temperature (To) becomes the first value.
When the temperature is lower than the second predetermined temperature (Te + T2) which is lower than the predetermined value (Te + T1), the suction superheat (SHS) is a positive predetermined value.
(PSH) to control the degree of opening of the expansion valve (4).

When the oil temperature reaches a predetermined temperature (Te + T1) at which the lubricating oil easily deteriorates,
Liquid refrigerant is sucked into the compressor (1). The lubricating oil is cooled by the liquid refrigerant, the rise in the oil temperature is suppressed, and the deterioration of the lubricating oil is prevented.

According to the above-mentioned invention specific matter, when the oil temperature (To) becomes equal to or higher than a predetermined value (Te + T1) with a specific configuration,
A wet operation is performed to cool the lubricating oil and prevent the oil temperature from rising.

When the oil temperature (To) is equal to or higher than the first predetermined temperature (Te + T1) at which the lubricating oil easily deteriorates,
By controlling the opening of the expansion valve (4) so that the suction superheat (SHS) becomes a negative predetermined value (NSH), as a result,
A wet operation will be performed. Here, since the control target value of the suction superheat (SHS) is a negative predetermined value (NSH), even if the accuracy of the oil temperature detecting means (17) is poor, the actual suction superheat is Even if it is larger than (SHS), the wet operation is reliably performed. On the other hand, when the oil temperature (To) is lower than the second predetermined temperature (Te + T2), the suction superheat (SHS) becomes a positive predetermined value (PSH).
By controlling the opening of the expansion valve (4) so that
Normal operation in which only the gas refrigerant is sucked into the compressor (1) is performed. Therefore, a large amount of liquid refrigerant is accumulated in the compressor (1)
The adverse effects such as dilution of the lubricating oil due to being sucked into the compressor and breakage of the compressor (1) due to liquid compression are prevented. Furthermore, the second
Since the predetermined temperature (Te + T2) is lower than the first predetermined temperature (Te + T1), control to set the suction superheat (SHS) to a negative predetermined value (NSH) and control to set a positive predetermined value (PSH) Is not frequently switched, and the operation of the refrigeration system does not become unstable.

According to a second aspect of the present invention, in the refrigerating apparatus according to the first aspect, the control means (40) determines that the oil temperature (To) is higher than the evaporation temperature (Te) by a predetermined temperature (T1). ) When the high first predetermined temperature (Te + T1) or more and the discharge superheat (DSH) is the first predetermined value (SH1) or more, the suction superheat (SHS)
While the opening degree of the expansion valve (4) is controlled so that the oil temperature (NSH) becomes a negative predetermined value (NSH), the oil temperature (To) is higher than the evaporation temperature (Te) by a predetermined temperature (T2).
When the temperature is lower than the high second predetermined temperature (Te + T2) or the discharge superheat (DSH) is lower than the second predetermined value (SH2), the suction superheat (SHS) is set to a positive predetermined value (PSH). ), The opening degree of the expansion valve (4) is controlled.

If the discharge superheat (DSH) does not become equal to or more than the first predetermined value (SH1), control is performed such that the suction superheat (SHS) becomes a negative predetermined value (NSH). I can't. Therefore, even if the oil temperature (To) is high, the wet operation is not forcibly performed when the liquid refrigerant is being sucked into the compressor (1). As a result, a large amount of liquid refrigerant is prevented from being sucked into the compressor (1).

According to a third aspect of the present invention, there is provided the refrigeration apparatus according to the first aspect, wherein the compressor comprises a compressor (1) having a variable capacity, and the control means (40) comprises: When (To) becomes equal to or more than a predetermined value (Te + T1), the capacity of the compressor (1) is reduced to perform wet operation.

According to the specific features of the invention, with a specific configuration, when the oil temperature (To) exceeds a predetermined value, a wet operation for cooling the lubricating oil to prevent the oil temperature (To) from rising is performed. Will be

According to a fourth aspect of the present invention, in the refrigeration apparatus according to the first aspect, the refrigerant circuit (20) includes:
The lubricating oil is filled with an HFC-based refrigerant, and the lubricating oil is an ether-based or ester-based synthetic oil.

According to the above-mentioned invention specifying matter, the effect of the present invention for suppressing the deterioration of the lubricating oil due to the temperature rise is more remarkably exhibited.

[0019]

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

-Configuration of Air Conditioner (30)-The air conditioner (30) according to the present invention includes a refrigerant circuit (20) as shown in FIG. This refrigerant circuit (20) is a compressor
(1), four-way switching valve (2), outdoor heat exchanger (3), outdoor electronic expansion valve (4), receiver (5), multiple indoor electronic expansion valves (6,
,) And a plurality of indoor heat exchangers (7, 7,...) And an accumulator (8) are connected by piping.
This refrigerant circuit (20) is filled with R407C, which is an HFC-based refrigerant, and the compressor (1) is filled with ether-based synthetic oil as lubricating oil.

The compressor (1), the four-way switching valve (2), the outdoor heat exchanger (3), the outdoor electronic expansion valve (4), the receiver (5), and the accumulator (8) include an outdoor unit (U1). ).
Each indoor heat exchanger (7) and indoor electronic expansion valve (6) are housed in an indoor unit (U2), and are installed in each room.

The compressor (1) includes a first compressor (1a) whose capacity is adjusted by an inverter (not shown) and a second compressor (1b).
Is connected in parallel, and is a compressor with variable capacity (1)
Is composed. Lower side surfaces of the first compressor (1a) and the second compressor (1b) are connected by an oil equalizing pipe (16). Both compressors (1
An oil sump (not shown) for storing lubricating oil provided at the bottom of a, 1b) is communicated with the oil equalizing pipe (16).
The lubricating oil in (1a, 1b) is equalized.

An oil temperature sensor (17) as oil temperature detecting means for detecting the temperature of the lubricating oil is attached to the oil equalizing pipe (16). The attachment of the oil temperature sensor (17) is performed, for example, by the method described in the above-mentioned Japanese Patent Application Laid-Open No. 8-128764.

Further, a pressure sensor and a temperature sensor described below are attached to the refrigerant circuit (20).

That is, a high pressure sensor (11) is provided on the discharge side pipe of the compressor (1), and a low pressure sensor (12) is provided on the suction side pipe. A discharge temperature sensor for detecting the temperature of the refrigerant discharged from the compressor is provided on the discharge pipe of the compressor (1).
(13) is attached. The suction side pipe of the compressor (1) has a suction temperature sensor (1
5) is installed.

Each pressure sensor (11), (12) and each temperature sensor
(13), (15), and (17) are electrically connected to the control means (40) provided in the outdoor unit (U1). Next, the control means (4
The configuration of (0) will be described.

As shown in FIG. 2, the control means (40) mainly comprises an input section (41), an oil temperature judging section (42), a discharge superheat judging section (43), an operation mode judging section (44), It comprises an intake superheat calculation unit (45) and an operation control unit (46). The input unit (41) includes each of the pressure sensors (11) and (12) and each temperature sensor.
This is a part for inputting information on the pressure and temperature detected in (13), (15), and (17). The oil temperature determination unit (42) is a unit that receives information of the oil temperature sensor (17) from the input unit (41) and compares the detected oil temperature (To) with a predetermined value. The discharge superheat judging section (43) receives the high pressure received from the input section (41).
This is a part for calculating the discharge superheat (DSH) based on the information of (Pc) and the compressor discharge refrigerant temperature (Td) and comparing the discharge superheat (DSH) with a predetermined value. The operation mode determination unit (44) is a unit that receives the result of the magnitude comparison in the oil temperature determination unit (42) and the discharge superheat determination unit (43), and selects an operation mode based on an algorithm described later. Inhalation superheat calculation section (4
5) is based on the low pressure (Pe) and compressor suction refrigerant temperature (Te) information received from the input section (41), and
(SHS). The operation control unit (46) selects a control target value according to the operation mode, and controls the opening of the outdoor electronic expansion valve (4) so that the suction superheat (SHS) becomes the control target value. Part.

-Operation of the air conditioner (30)-Next, the operation of the air conditioner (30) will be described. The air-conditioning apparatus (30) can perform the cooling operation and the heating operation by switching the four-way switching valve (2). Here, only the heating operation will be described. During heating operation, four-way switching valve
(2) is set on the solid line side shown in FIG.

In the air conditioner (30), the following normal operation or wet operation is alternatively performed depending on the oil temperature (To). First, normal operation will be described.

-Normal operation- After the refrigerant discharged from the compressor (1) passes through the four-way switching valve (2), it is divided into the indoor units (U2, U2, ...), and the indoor heat exchanger ( (7,7, ...) exchange heat with indoor air and condense. The condensed refrigerant is decompressed and expanded by the indoor electronic expansion valves (6, 6, ...) and the outdoor electronic expansion valve (4). The refrigerant that has expanded into the two-phase state exchanges heat with the outside air in the outdoor heat exchanger (3) and evaporates. The evaporated and gasified refrigerant is supplied to the four-way switching valve.
After passing through (2) and the accumulator (8), it is sucked into the compressor (1).

In the normal operation, the opening of the outdoor electronic expansion valve (4) is controlled so that the suction superheat (SHS) becomes a predetermined positive value (PSH), for example, +5 degrees. I have. Further, the following oil temperature determination is performed.

As shown in FIG. 3, first, the high pressure sensor (11)
Is high pressure (Pc), low pressure sensor (12) is low pressure (Pe), discharge temperature sensor (13) is discharge refrigerant temperature (Td), suction temperature sensor (15).
Is the suction refrigerant temperature (Ts), and the oil temperature sensor (17) is the lubricating oil temperature.
(To) are detected, and their information is input to the input unit (41) (step S1).

Next, the oil temperature judging section (42) judges the magnitude of the oil temperature (To) (step S2). In the present embodiment, the oil temperature (To) is
It is determined whether or not the temperature is equal to or higher than a first temperature (Te + T1) which is an addition value of the evaporation temperature (Te) and a predetermined value (T1). The evaporation temperature (Te) is a function of the evaporation pressure (Pe) (Te = f (Pe))
It is expressed as

Next, the operation mode judgment section (44) judges the operation mode. When the oil temperature (To) is lower than the first temperature (Te + T1), the operation mode determination unit (44) considers that the oil temperature (To) is not so high as to deteriorate the lubricating oil. Then, the operation mode is maintained as normal operation (step S5). on the other hand,
If the oil temperature (To) is equal to or higher than the first temperature (Te + T1), step S3
Move on to

In step S3, the discharge superheat (DS
Determine the magnitude of H). Specifically, the discharge superheat determination unit (43) determines whether the discharge superheat (DSH) is equal to or greater than a predetermined value (SH1).

The discharge superheat (DSH) is equal to the first predetermined value (SH
1) In the case above, the process proceeds to step S4, and the operation mode is switched from the normal operation to the wet operation (step S4). on the other hand,
When the discharge superheat (DSH) is smaller than the first predetermined value (SH1), the process proceeds to step S5, and the operation mode is maintained in the normal operation (step S5).

For the above determination, not only the determination of the oil temperature (To) but also the determination of the magnitude of the discharge superheat (DSH) when switching the operation mode is performed for the following reason. That is, when the discharge superheat (DSH) is small, there is a high possibility that the liquid refrigerant has already been sucked into the compressor (1). This is because, when the operation is shifted, the amount of the liquid refrigerant sucked into the compressor (1) is considerably increased, and a danger of liquid compression or the like is generated. Therefore, the determination of discharge superheat (DSH) is a step provided for protecting the compressor (1).

-Wet operation-Next, the wet operation will be described. In the wet operation, all the refrigerant is not evaporated in the outdoor heat exchanger (3), and a part of the refrigerant is sucked into the compressor (1) in a liquid state. Therefore, the high-temperature lubricating oil is cooled by the low-temperature liquid refrigerant, and deterioration due to temperature rise is suppressed. The rest of the refrigerant circulation operation is the same as in the normal operation, and a description thereof will be omitted.

In this wet operation, the opening degree of the outdoor electronic expansion valve (4) is controlled so that the suction superheat (SHS) becomes a predetermined negative predetermined value (NSH), for example, -2 degrees. ing. Theoretically, if the suction superheat (SHS) is 0 degrees or less, the wet operation will be performed, but in actuality, the error of the suction temperature sensor (15) is about 2 degrees. Superheat (SHS) inhaling a negative predetermined value (NSH)
Is set as the control target value.

Further, in the wet operation, the following oil temperature judgment is performed.

As shown in FIG. 4, first, the high pressure sensor (11)
Is high pressure (Pc), low pressure sensor (12) is low pressure (Pe), discharge temperature sensor (13) is discharge refrigerant temperature (Td), suction temperature sensor (15).
Is the suction refrigerant temperature (Ts), and the oil temperature sensor (17) is the lubricating oil temperature.
(To) are detected (step S11), and the information is input to the input unit (41).

Next, the oil temperature judging section (42) judges the level of the oil temperature (To) (Step S12). In the present embodiment, the oil temperature (To)
Is lower than a second temperature (Te + T2), which is an addition value of the evaporation temperature (Te) and a predetermined value (T2). The predetermined value (T2) is set to a value smaller than the predetermined value (T1) in order to provide a differential for preventing frequent switching of the operation mode.

When the oil temperature (To) is lower than the second temperature (Te + T2), it is determined that the deterioration of the lubricating oil is unlikely to progress, and the operation mode determining unit (44) changes the operation mode from the wet operation to the wet operation. Switch to normal operation (step S14). On the other hand, when the oil temperature (To) is equal to or higher than the second temperature (Te + T2), the process proceeds to step S13.

In step S13, the discharge superheat determining section (43) determines the magnitude of the discharge superheat (DSH). Specifically, it is determined whether or not the discharge superheat (DSH) is smaller than a second predetermined value (SH2). The second predetermined value (SH2) is set to a value smaller than the first predetermined value (SH1).

The discharge superheat (DSH) is equal to the second predetermined value (SH
If smaller than 2), the process proceeds to step S14, and the operation mode is switched from wet operation to normal operation. On the other hand, when the discharge superheat (DSH) is equal to or smaller than the second predetermined value (SH2), the process proceeds to step S15, and the operation mode is maintained as the wet operation.

The heating operation of the air conditioner (30) is performed as described above. Therefore, based on the determination of the oil temperature (To) and the discharge superheat (DSH), in addition to the normal operation, a wet operation in which the opening of the outdoor electronic expansion valve (4) is slightly opened is performed.

-Effect of air conditioner (30)-As described above, in the air conditioner (30), the temperature (T) of the lubricating oil during operation is determined by the oil temperature sensor (17) provided in the compressor (1).
o) is detected, and when the temperature (To) is so high that the deterioration of the lubricating oil proceeds, a wet operation for cooling the lubricating oil is performed.
Therefore, the deterioration of the lubricating oil due to the temperature rise is suppressed, and the possibility of damage to the compressor (1) due to a decrease in viscosity or the like can be reduced.

After the lubricating oil temperature (To) has dropped,
Since the operation mode is switched to the normal operation, the wet operation is continued for a long time, and a large amount of liquid refrigerant is not sucked into the compressor (1). Therefore, damage to the compressor (1) due to dilution of the lubricating oil or liquid compression is prevented beforehand.

Further, since the discharge superheat (DSH) is not changed from the normal operation to the wet operation unless the discharge superheat (DSH) is equal to or greater than the first predetermined value (SH1), the discharge superheat (DSH) is small, and the liquid refrigerant is discharged from the compressor (1). When the air is being sucked in, the operation does not forcibly shift to the wet operation. Therefore, a large amount of liquid refrigerant is not sucked into the compressor (1) at one time.

Further, since a differential is provided between the first temperature (Te + T1) and the second temperature (Te + T2) which is a reference for comparing the oil temperature (To), the normal operation and the normal operation can be performed. Wet driving is not frequently repeated. Therefore, stable operation can be performed.

Therefore, even in the case of using synthetic oil which is apt to deteriorate with increasing temperature, the reliability of the compressor (1) can be improved, and as a result, the reliability of the air conditioner (30) can be improved. Can be improved.

(Modification) In the above embodiment, the wet operation is performed by slightly opening the outdoor electronic expansion valve (4). However, the method of wet operation is not limited to this,
This may be performed by controlling the capacity of (1). That is, the operation control unit (46) of the control means (40) adjusts the frequency of the inverter (not shown) of the compressor (1a) instead of adjusting the opening of the outdoor electronic expansion valve (4). Such control may be performed. Also, both the outdoor electronic expansion valve (4) and the inverter may be controlled simultaneously.

The refrigerant used for the air conditioner (30) is R41.
Another HFC-based refrigerant such as 0A may be used, and the lubricating oil may be an ester-based synthetic oil.

The present invention has a particularly remarkable effect on the above-mentioned synthetic oil, but also exerts an effect on a conventional refrigeration system using HFC refrigerant such as R22 and mineral oil. Therefore, it is of course possible to use the present invention in a refrigeration system using mineral oil.

The refrigerating device according to the present invention is:
The refrigeration system is not limited to the refrigeration system in a narrow sense, but is a refrigeration system in a broad sense including an air conditioner, a refrigerator, and the like.

[0056]

As described above, according to the present invention, the following effects are exhibited.

According to the first aspect of the present invention, when the oil temperature becomes higher than the temperature at which the lubricating oil easily deteriorates, the liquid refrigerant is sucked into the compressor, and the lubricating oil is cooled by the liquid refrigerant. An increase in oil temperature is suppressed, and deterioration of the lubricating oil is prevented. Therefore, the reliability of the compressor is improved, and as a result,
The reliability of the refrigeration system is improved.

With a specific configuration, it is possible to realize a refrigeration apparatus that performs a wet operation when the oil temperature becomes equal to or higher than a predetermined value to suppress an increase in the oil temperature.

When the oil temperature is equal to or higher than the first predetermined temperature at which the lubricating oil tends to deteriorate, the opening degree of the expansion valve is controlled so that the suction superheat has a negative predetermined value. Driving can be performed. Here, since the control target value of the suction superheat is a negative predetermined value,
Even if the accuracy of the oil temperature detecting means is low, the wet operation can be reliably performed. On the other hand, when the oil temperature is lower than the second predetermined temperature, the normal operation can be specifically performed by controlling the opening of the expansion valve so that the intake superheat has a positive predetermined value. Therefore, a large amount of liquid refrigerant is not cumulatively sucked into the compressor, and it is possible to effectively prevent problems such as dilution of lubricating oil and damage to the compressor due to liquid compression. Further, since a differential is provided between the first predetermined temperature and the second predetermined temperature, it is possible to prevent frequent switching between control for setting the intake superheat to a predetermined negative value and control for setting the suction superheat to a predetermined positive value. As a result, unstable operation of the refrigeration system can be prevented.

According to the second aspect of the present invention, if the discharge superheat does not exceed the first predetermined value, control is not performed so that the suction superheat becomes a negative predetermined value. Even in a high state, when the liquid refrigerant is being sucked into the compressor, the wet operation is not forcibly performed. Therefore, it is possible to effectively prevent the compressor from being damaged due to a large amount of liquid refrigerant being sucked into the compressor.

According to the third aspect of the present invention, with a specific configuration, it is possible to realize a refrigeration apparatus that suppresses a rise in oil temperature by performing a wet operation when the oil temperature exceeds a predetermined value. .

According to the fourth aspect of the present invention, the effect of the present invention of suppressing deterioration of lubricating oil due to a rise in temperature can be more remarkably exhibited.

[Brief description of the drawings]

FIG. 1 is a refrigerant circuit diagram of an air conditioner.

FIG. 2 is a configuration diagram of a control unit.

FIG. 3 is a flowchart illustrating control during normal operation.

FIG. 4 is a flowchart showing control during wet operation.

[Explanation of symbols]

 (1) Compressor (2) Four-way switching valve (3) Outdoor heat exchanger (4) Outdoor electronic expansion valve (5) Receiver (7) Indoor heat exchanger (8) Accumulator (11) High pressure sensor ( 12) Low pressure sensor (13) Discharge temperature sensor (15) Suction temperature sensor (16) Oil equalizing pipe (17) Oil temperature sensor (40) Control means

────────────────────────────────────────────────── (5) References JP-A-8-200234 (JP, A) Patent 2572648 (JP, B2) (58) Fields investigated (Int. Cl. ⁷ , DB name) F25B 1/00

Claims (4)

(57) [Claims] A compression having an oil reservoir for storing lubricating oil.
Machine (1), heat source side heat exchanger (3), decompression means (4), and use side
A refrigerant circuit (20) comprising a heat exchanger (7) connected in order,
Detects the temperature of lubricating oil stored in the oil sump of the compressor (1)
The oil temperature detected by the oil temperature detecting means (17) is a predetermined value (Te + T1).
When this happens, the compressor (1) inhales wet steam
Control means (40) for performing wet operation is provided, the pressure reducing means comprises an expansion valve (4), and the control means (40) controls the oil temperature (To) to a predetermined value (Te + T1) or more. When it becomes
Perform wet operation by increasing the opening of the expansion valve (4)
At the same time, when the oil temperature (To) is equal to or higher than the first predetermined temperature (Te + T1), the opening degree of the expansion valve (4) is controlled so that the suction superheat (SHS) becomes a negative predetermined value (NSH). On the other hand, the oil temperature (To) is
When the temperature is lower than the second predetermined temperature (Te + T2) lower than (Te + T1), the opening of the expansion valve (4) is adjusted so that the suction superheat (SHS) becomes a positive predetermined value (PSH). A refrigeration apparatus characterized by controlling. 2. The refrigeration apparatus according to claim 1 , wherein the control means (40) includes a first predetermined temperature (Te + T1) in which the oil temperature (To) is higher than the evaporation temperature (Te) by a predetermined temperature (T1). When the discharge superheat (DSH) is equal to or greater than the first predetermined value (SH1), the opening of the expansion valve (4) is adjusted so that the suction superheat (SHS) becomes a negative predetermined value (NSH). On the other hand, the oil temperature (To) is lower than the second predetermined temperature (Te + T2), which is higher than the evaporation temperature (Te) by a predetermined temperature (T2), or the discharge superheat (DSH) is a second predetermined value. A refrigerating apparatus characterized in that when the pressure is smaller than (SH2), the opening of the expansion valve (4) is controlled so that the suction superheat (SHS) becomes a positive predetermined value (PSH). 3. The refrigeration apparatus according to claim 1, wherein the compressor comprises a compressor (1) having a variable capacity, and the control means (40) controls the oil temperature (To) to a predetermined value (Te + T1). When the above becomes the case, the refrigeration apparatus is characterized in that the wet operation is performed by reducing the capacity of the compressor (1). 4. The refrigeration apparatus according to claim 1, wherein the refrigerant circuit (20) is filled with an HFC-based refrigerant, and the lubricating oil is an ether-based or ester-based synthetic oil. apparatus.