WO2016117037A1

WO2016117037A1 - Refrigeration device

Info

Publication number: WO2016117037A1
Application number: PCT/JP2015/051428
Authority: WO
Inventors: 伊藤　健; 雅章上川; 和幸塚本
Original assignee: 三菱電機株式会社
Priority date: 2015-01-20
Filing date: 2015-01-20
Publication date: 2016-07-28
Also published as: TW201627620A

Abstract

This refrigeration device comprises: an oil cooler 7 which subjects the oil separated by an oil separator 2 to heat exchange with a heating medium and cools the oil; an oil cooler expansion valve 6 which serves as an oil temperature adjusting means for adjusting the flow rate of the heating medium flowing into the oil cooler 7, and thus adjusting the temperature of oil supplied to a screw compressor 1; and a control device 100. In the high superheat operation in which the degree of superheat of the refrigerant gas sucked into the screw compressor 1 exceeds a preset threshold value, the control device 100 controls the oil cooler expansion valve 6 to supply the screw compressor 1 with the oil at a temperature lower than that in the steady operation in which the degree of superheat is at the threshold value or less.

Description

Refrigeration equipment

The present invention relates to a refrigeration apparatus equipped with a screw compressor.

In the conventional refrigeration apparatus, when the oil separated from the refrigerant discharged from the compressor by the oil separator is returned to the compressor, the oil is cooled by the refrigerant (for example, Patent Document 1 and Patent Document 2). reference). In the refrigeration apparatuses of

Patent Documents

1 and 2, the flow rate of the refrigerant that is a cooling source is controlled so that the temperature of the oil becomes a preset temperature during steady operation.

JP 2002-31420 A Japanese Patent No. 5264874

The suction superheat degree of the refrigerant sucked into the compressor is generally controlled at 10 to 20 ° C. during steady operation, but when the pull-in temperature is high, the suction superheat degree is 50 to 70 ° C. due to the restriction of the low pressure upper limit. There is a case.

In the refrigeration apparatus disclosed in

Patent Documents

1 and 2, the suction superheat degree increases, so that the discharge temperature of the refrigerant discharged from the compression unit also increases. In this case, since the amount of cooling heat necessary for cooling the compression section increases, when the oil having the same temperature as that in the steady operation is supplied to the compressor, the cooling of the compression section is insufficient. As a result, the screw rotor of the compression section is thermally expanded, and there is a problem that inconveniences such as the screw rotor and the casing housing the screw rotor come into contact with each other and are seized.

For this reason, the clearance between the screw rotor and the casing is generally set on the basis of not contacting even when the suction superheat degree is high, and is therefore larger than necessary during steady operation. It has become. If this gap is too large, the refrigerant once compressed leaks from this gap, causing a problem that the performance is reduced. In particular, such a problem is likely to occur when a high-pressure refrigerant such as R410A whose temperature tends to rise during compression is used.

This invention is made in view of such a problem, and it aims at obtaining the refrigerating device which can aim at a performance improvement by suppressing expansion | swelling of the screw rotor in a state with high suction superheat degree. .

In the refrigeration apparatus according to the present invention, a screw compressor, a condenser, a decompression device, and an evaporator are connected by piping, and are arranged between a refrigeration cycle in which refrigerant circulates, and a screw compressor and a condenser in the refrigeration cycle, An oil separator that separates oil contained in refrigerant gas discharged from the screw compressor, an oil cooler that cools the oil separated by the oil separator by heat exchange with a heat medium, and an oil separator. An oil supply circuit that cools the oil to be supplied to the screw compressor after being cooled by an oil cooler, an oil temperature adjusting means that adjusts the temperature of the oil supplied from the oil supply circuit to the screw compressor, and a suction to the screw compressor A superheat degree detecting means for detecting the superheat degree of the refrigerant gas to be mixed and a control device for controlling the oil temperature adjusting means based on the superheat degree, and the control apparatus has a superheat degree exceeding a preset threshold value. High superheat operation , In which low temperature oil than during steady operation superheat is below the threshold to control the oil temperature adjusting unit so as to be supplied to the screw compressor.

According to the present invention, it is possible to obtain a refrigeration apparatus capable of suppressing the expansion of the screw rotor in a state where the suction superheat degree is high and improving the performance.

It is a figure which shows an example of schematic structure of the freezing apparatus which concerns on Embodiment 1 of this invention. It is a flowchart explaining the example of control of the freezing apparatus which concerns on Embodiment 1 of this invention. It is a refrigerant circuit figure of the freezing apparatus which concerns on this Embodiment 2 of this invention. It is a refrigerant circuit figure of the freezing apparatus which concerns on this Embodiment 3 of this invention. It is a refrigerant circuit figure of the freezing apparatus which concerns on Embodiment 4 of this invention. It is a control flowchart in the freezing apparatus which concerns on Embodiment 4 of this invention. It is a refrigerant circuit figure for demonstrating the other oil temperature adjustment means with the oil cooler in the refrigeration apparatus which concerns on Embodiment 4 of this invention. It is a refrigerant circuit figure of the freezing apparatus which concerns on Embodiment 5 of this invention. It is the figure which showed the flow of the refrigerant | coolant, oil, and cooling water at the time of high superheat driving | operation in the refrigeration apparatus which concerns on Embodiment 5 of this invention.

Embodiment 1 FIG.
FIG. 1 is a diagram illustrating an example of a schematic configuration of a refrigeration apparatus according to Embodiment 1 of the present invention. Here, in FIG. 1 and the following drawings, the same reference numerals denote the same or corresponding parts, and are common to the whole text of the embodiments described below. And the form of the component represented by the whole specification is an illustration to the last, Comprising: It does not limit to the form described in the specification.

As shown in FIG. 1, the refrigeration apparatus is a two-stage screw compressor (hereinafter simply referred to as a screw compressor) 1, an oil separator 2, a condenser 3, a main expansion valve 4, an evaporator 5, and a flow rate adjustment valve. An oil cooler expansion valve 6, an oil cooler 7, and a motor cooling expansion valve 8 are provided, and these are connected by a refrigerant pipe to constitute a refrigeration cycle in which the refrigerant circulates. For example, R410A, R32 or the like is used as the refrigerant. The screw compressor 1, the oil separator 2, the condenser 3, the main expansion valve 4, and the evaporator 5 constitute a main circuit 10 of the refrigeration cycle.

The refrigeration apparatus includes an oil cooling circuit 70 that branches from between the condenser 3 and the main expansion valve 4 and is connected to the screw compressor 1 via the oil cooler expansion valve 6 and the oil cooler 7. Yes. The refrigeration apparatus further includes a motor cooling circuit 80 branched from between the condenser 3 and the main expansion valve 4 and connected to the motor chamber 14a of the screw compressor 1 via the motor cooling expansion valve 8. The refrigeration apparatus includes an oil supply circuit 90.

In the screw compressor 1, a low-stage compression unit 11, a high-stage compression unit 13, and a motor 14 that rotationally drives the

compression units

11 and 13 are connected in series to compress and discharge the refrigerant. An intermediate pressure chamber 12 is formed between the low-stage compression unit 11 and the high-stage compression unit 13. Each of the low-stage compression unit 11 and the high-stage compression unit 13 includes a screw rotor (not shown) and a gate rotor (not shown) that meshes with a screw groove provided in the screw rotor, and the screw groove (not shown). 1), a gate rotor, and a casing that accommodates the screw rotor therein, the refrigerant is compressed in a compression chamber. The motor 14 may be a constant speed machine or an inverter machine.

The main expansion valve 4, the oil cooler expansion valve 6, and the motor cooling expansion valve 8 are decompression devices that decompress and expand the refrigerant, and are configured by, for example, an electronic expansion valve that can be variably controlled. The The oil cooler expansion valve 6 constitutes the oil temperature adjusting means of the present invention.

The oil cooling circuit 70 branches a part of the refrigerant from the condenser 3 toward the oil cooler expansion valve 6 in the main circuit 10 and decompresses the refrigerant by the oil cooler expansion valve 6. In this circuit, the oil is supplied to the intermediate pressure chamber 12 after the oil separator 2 is cooled and the oil is exchanged with the oil flowing into the oil flow path side of the oil cooler 7 to cool the oil.

The oil supply circuit 90 allows the oil separated by the oil separator 2 to flow into the oil flow path side of the oil cooler 7 and is cooled and cooled by heat exchange with the refrigerant passing through the refrigerant flow path side of the oil cooler 7. This is a circuit for supplying the oil to the low-stage compression section 11 and the high-stage compression section 13 of the screw compressor 1.

Further, the motor cooling circuit 80 depressurizes a part of the refrigerant from the condenser 3 toward the main expansion valve 4 by the motor cooling expansion valve 8, and cools the motor 14 by supplying the depressurized refrigerant to the motor chamber 14a. Circuit.

The refrigeration apparatus further includes a suction temperature detection device 91, an oil supply temperature detection device 92, a suction pressure detection device 93, a control device 100, and the like. The suction temperature detection device 91 detects the temperature of the refrigerant gas sucked into the screw compressor 1. The oil supply temperature detection device 92 detects the temperature of the oil after being cooled by the oil cooler 7. The suction pressure detection device 93 detects the pressure of the refrigerant gas sucked into the screw compressor 1. Detection values detected by these detection devices are output to the control device 100.

The control device 100 includes the motor 14 of the screw compressor 1, the main expansion valve 4, and the oil cooler expansion valve 6 based on the detection values detected by the suction temperature detection device 91, the oil supply temperature detection device 92, and the suction pressure detection device 93. And the expansion valve 8 for motor cooling is controlled.

The control device 100 appropriately sets the target oil temperature of the oil supplied from the oil supply circuit 90 to the screw compressor 1 based on the degree of superheat of the refrigerant gas sucked into the screw compressor 1, and sets the set target oil temperature and Thus, the opening degree of the expansion valve 6 for the oil cooler is controlled. The degree of superheat is obtained from the suction temperature detected by the suction temperature detection device 91 and the saturation temperature converted from the suction pressure detected by the suction pressure detection device 93. As described above, the suction temperature detection device 91 and the suction pressure detection device 93 constitute superheat degree detection means. The superheat detection means only needs to be able to detect the superheat, and the difference between the suction temperature detected by the suction temperature detection device 91 and the temperature detected by the temperature detection device that detects the refrigerant temperature at the inlet of the evaporator 5 is calculated. It may be used as the degree of superheat. The control of the oil cooler expansion valve 6 based on the target oil temperature will be described in detail again.

The control device 100 can be configured by hardware such as a circuit device that realizes the function, or can be configured by an arithmetic device such as a microcomputer or a CPU, and software executed thereon.

The refrigeration apparatus according to Embodiment 1 is characterized in that different temperatures are set as the target oil temperature during steady operation of the screw compressor 1 and during high superheat operation described later. The target oil temperature during normal operation is set lower than the target oil temperature during steady operation. Specifically, the target oil temperature during steady operation is, for example, 40 ° C. to 50 ° C., and the target oil temperature during high superheat operation is, for example, 20 ° C. to 30 ° C. The high superheat degree operation refers to an operation time during which the suction superheat degree exceeds a preset threshold value, such as immediately after startup of the screw compressor 1 and until steady operation. In this way, during high superheat operation, the target oil temperature is set to a lower temperature than during steady operation, thereby suppressing the thermal expansion of the screw rotor as compared with the conventional control.

In addition, the screw compressor 1 of this Embodiment 1 is a two-stage compressor, and suppresses the raise of the discharge temperature of the discharge refrigerant | coolant especially discharged from the low-stage compression part 11 among the two

compression parts

11 and 13. As a result, thermal expansion of the screw rotor in both the low stage compression unit 11 and the high stage compression unit 13 is suppressed.

Hereinafter, operation | movement of a freezing apparatus is demonstrated in order using a figure.
The refrigerant compressed by the low stage compression unit 11 of the screw compressor 1 is further compressed by the high stage compression unit 13 and then discharged from the high stage compression unit 13. The refrigerant discharged from the high-stage compression unit 13 is separated into refrigerant gas and oil by the oil separator 2, and the refrigerant gas flows into the condenser 3. The refrigerant gas that has flowed into the condenser 3 condenses into a refrigerant liquid, is decompressed by the main expansion valve 4, and then sent to the evaporator 5. The refrigerant sent to the evaporator 5 exchanges heat with air to become refrigerant gas and flows into the screw compressor 1.

In addition, a part of the refrigerant liquid condensed in the condenser 3 flows into the oil cooling circuit 70 and is decompressed by the oil cooler expansion valve 6, and then exchanges heat with oil in the oil cooler 7, and refrigerant gas. And flows into the intermediate pressure chamber 12 of the screw compressor 1. Further, another part of the refrigerant liquid condensed in the condenser 3 flows into the motor cooling circuit 80 and is decompressed by the motor cooling expansion valve 8, and then supplied to the motor chamber 14a to cool the motor 14. .

On the other hand, the high-temperature oil separated from the gas refrigerant in the oil separator 2 is cooled by exchanging heat with the refrigerant in the oil cooling circuit 70 in the oil cooler 7 and then cooled, and then the low-stage compression section of the screw compressor 1. 11 and supplied to the high-stage compression unit 13. In the oil cooling circuit 70, the opening degree of the oil cooler expansion valve 6 is controlled by the control device 100, and the temperature of oil supplied to the screw compressor 1 is adjusted by adjusting the amount of refrigerant flowing into the oil cooler 7. Is controlled.

Next, the control flow of the control device 100 will be described with reference to FIG.

FIG. 2 is a flowchart illustrating a control example of the refrigeration apparatus according to Embodiment 1 of the present invention. The process shown in the flowchart of FIG. 2 is performed at arbitrarily set control time intervals.

(Step S11)
The control device 100 calculates the suction superheat degree based on the suction temperature detected by the suction temperature detection device 91 and the suction pressure detected by the suction pressure detection device 93. When the calculated suction superheat degree is equal to or less than a preset threshold value (for example, 40 ° C.) (S11), the control device 100 determines that the operation is in steady operation, and if it exceeds the threshold value, the operation is in high superheat operation. Judge. Hereinafter, the processing when it is determined that the operation is in steady operation will be described, and then the processing when it is determined that the operation is in high superheat degree will be described.

<During steady operation>
(Step S12)
When determining in step S11 that the operation is steady, the control device 100 sets the target oil temperature of the oil temperature to a steady-state target range (eg, 40 ° C. to 50 ° C.) that is an initial value (S12).

(Step S13 to Step S17)
The control device 100 controls the opening of the oil cooler expansion valve 6 based on the oil temperature detected by the oil supply temperature detection device 92 (S13 to S17). Specifically, the control device 100 controls the opening degree of the oil cooler expansion valve 6 so that the oil temperature detected by the oil supply temperature detection device 92 falls within the steady-state target range.

That is, first, the control device 100 determines whether or not the oil temperature is equal to or higher than the target oil temperature lower limit value (the lower limit value of the steady-state target range) (S13). When it is determined that the oil temperature is lower than the target oil temperature lower limit value, the control device 100 reduces the opening of the oil cooler expansion valve 6 because the oil temperature is too low (S14). Thereby, since the flow rate of the refrigerant flowing through the oil cooler 7 is reduced, the cooling capacity for cooling the oil is lowered and the oil temperature is raised. On the other hand, if the oil temperature is equal to or higher than the target oil temperature lower limit value, then control device 100 determines whether or not the oil temperature is equal to or lower than the target oil temperature upper limit value (the upper limit value of the steady-state target range) (S15). . When it is determined that the oil temperature exceeds the target oil temperature upper limit, the oil temperature is too high, so the control device 100 increases the opening of the oil cooler expansion valve 6 (S16). As a result, the flow rate of the refrigerant flowing through the oil cooler 7 increases, so that the cooling capacity for cooling the oil increases and the oil temperature decreases.

When it is determined in step S15 that the oil temperature is equal to or lower than the target oil temperature upper limit value, the control device 100 maintains the current opening of the oil cooler expansion valve 6 because the oil temperature is within the steady-state target range. (S17). The steady-state target range is set in the control device 100 in advance.

As described above, step S11 to step S17 are performed at every control time interval. As a result, the oil temperature can be kept within the steady-state target range during steady operation, that is, while the suction superheat is equal to or less than the threshold value.

<During high superheat operation>
(Step S21)
When the control device 100 determines that the high superheat operation is being performed in step S11, the target oil temperature of the oil temperature is set to a target range for the high superheat degree that is lower than the steady target range (for example, 40 ° C. to 50 ° C.). (For example, 20 ° C. to 30 ° C.) (S21). The target range for high superheat degree is also set in the control device 100 in advance like the target range for steady state.

(Step S22 to Step S26)
The control device 100 determines whether the oil temperature detected by the oil supply temperature detection device 92 is equal to or lower than the upper limit value of the high superheat degree target range (S22). When the control device 100 determines that the oil temperature exceeds the target oil temperature upper limit value (the upper limit value of the target range for the high superheat degree), the oil is in a state of insufficient cooling, so the oil cooler expansion valve 6 The opening is increased (S23). On the other hand, when determining that the oil temperature is equal to or lower than the target oil temperature upper limit value, the control device 100 subsequently determines whether the oil temperature is equal to or higher than the target oil temperature lower limit value (the lower limit value of the target range for high superheat degree). (S24).

When the control device 100 determines that the oil temperature is lower than the target oil temperature lower limit value, the control device 100 reduces the opening of the oil cooler expansion valve 6 because the oil has been cooled excessively (S25). On the other hand, when it is determined that the temperature of the oil is equal to or higher than the target oil temperature lower limit value, the control apparatus 100 maintains the current opening of the expansion valve 6 for the oil cooler because the oil temperature is within the target range for the high superheat degree. (S26)

As described above, the process from step S21 to the process of step S26 is performed at every control time interval. Thereby, at the time of high superheat operation, that is, when the suction superheat degree exceeds the threshold value, the oil temperature of the oil supplied to the screw compressor 1 falls within the target range for high superheat degree lower than the target range for steady state. be able to. Therefore, even if the suction superheat degree exceeds the threshold and the screw rotor of the low stage compression section 11 (hereinafter referred to as the low stage screw rotor) is likely to expand, the low stage screw rotor can be sufficiently cooled. For this reason, the degree of expansion of the low stage screw rotor during high superheat operation can be suppressed to a low level. Therefore, the gap between the low-stage screw rotor and the casing can be set narrower during high superheat operation than when oil having the same oil temperature as that during steady operation is supplied to the screw compressor 1.

-Effect of Embodiment 1-
As described above, in the first embodiment, oil having a lower temperature than that during steady operation is supplied to the low stage compression unit 11 during high superheat operation. For this reason, the temperature rise of the low stage compression part 11 at the time of high superheat degree driving | operation can be suppressed, and the thermal expansion of the screw rotor of the low stage compression part 11 by insufficient cooling can be suppressed. Thereby, even if it does not ensure the clearance gap between a low stage screw rotor and a casing large, the contact with the low stage screw rotor and casing at the time of a high superheat degree driving | operation can be suppressed. As a result, the gap between the low-stage screw rotor and the casing can be set narrower than in the conventional technique in which the temperature of the oil supplied to the low-stage compression unit 11 is not changed between the steady operation and the high superheat operation. Thus, the performance can be improved. Moreover, since low temperature oil is supplied to the high stage compression part 13 at the time of high superheat driving | operation, the clearance gap between a high stage screw rotor and a casing can be set narrow similarly to low stage, and a performance can be improved.

In addition, although the judgment of steady operation or high superheat degree operation was judged based on the threshold value (40 degreeC) of suction superheat degree, you may give a range to this threshold value.

Moreover, although the screw compressor 1 showed the example of the two-stage screw compressor in FIG. 1, the screw compressor 1 of the refrigerating apparatus of this invention is not restricted to a two-stage screw compressor, Three stages or more are used. A multi-stage screw compressor may be used, and a single-stage screw compressor may be used. In the case of using a multistage screw compressor having three or more stages, the temperature of the oil supplied to the lowermost compression section on the suction side may be set to a lower temperature in the high superheat operation than in the steady operation.

Embodiment 2. FIG.
In the first embodiment, there is one oil cooler 7 in the oil supply circuit 90, and the oil at the same temperature is supplied to each of the low-stage compression unit 11 and the high-stage compression unit 13. In the second embodiment, the oil supply circuit 90 has two oil coolers, controls oil temperature in two stages, and supplies oil at different temperatures to the low-stage compressor 11 and the high-stage compressor 13. This is a possible configuration. Other configurations, operations, and the like of the refrigerant circuit are the same as those in the first embodiment. In the following, the second embodiment will be described focusing on the differences from the first embodiment. Note that the modification applied to the same components as those in the first embodiment is similarly applied to the second embodiment. This also applies to embodiments described later.

FIG. 3 is a refrigerant circuit diagram of the refrigeration apparatus according to Embodiment 2 of the present invention.
The oil supply circuit 90 of the refrigerating apparatus according to the second embodiment includes two oil coolers 71 and an oil cooler 72 instead of the oil cooler 7 according to the first embodiment. In the oil supply circuit 90, the oil cooler 71 and the oil cooler 72 are provided in series with each other. Moreover, the oil cooling circuit 70 of the first embodiment shown in FIG. 1 has a flow path configuration that branches from one place between the condenser 3 and the main expansion valve 4 and connects to the intermediate pressure chamber 12. . On the other hand, the oil cooling circuit 70 according to the second embodiment includes refrigerant passages that are parallel to each other and branch from two locations between the condenser 3 and the main expansion valve 4 and are connected to the intermediate pressure chamber 12. In addition, an oil cooler expansion valve 61 and an oil cooler 71 are provided in one refrigerant flow path, and an oil cooler expansion valve 62 and an oil cooler 72 are provided in the other refrigerant flow path. . The oil cooler expansion valve 61 and the oil cooler expansion valve 62 are flow rate adjusting valves and constitute the oil temperature adjusting means of the present invention.

Further, in each refrigerant flow path in the oil cooling circuit 70, a high-stage oil supply temperature detection device 92 a that detects the temperature of oil supplied to the high-stage compressor 13, and oil supplied to the low-stage compressor 11. A low-stage oil supply temperature detecting device 92b for detecting the temperature is provided. The detection values of the high-stage oil supply temperature detection device 92a and the low-stage oil supply temperature detection device 92b are output to the control device 100.

In the refrigeration apparatus of Embodiment 2 configured as described above, the refrigerant between the condenser 3 and the main expansion valve 4 branches and flows into the two refrigerant flow paths of the oil cooling circuit 70, and each branched refrigerant is oil. After the pressure is reduced by the

cooler expansion valves

61 and 62, heat is exchanged with the oil by the

oil coolers

71 and 72 to cool the oil, and then the oil is joined and supplied to the intermediate pressure chamber 12.

On the other hand, the oil separated by the oil separator 2 is first cooled by the oil cooler 71 in the oil supply circuit 90, and then a part thereof is supplied to the high stage compression unit 13, and the other is supplied to the oil cooler 72. After flowing in and further cooled, it is supplied to the low stage compression section 11. As described above, the low-stage compression unit 11 is supplied with oil having a temperature lower than that of the oil supplied to the high-stage compression unit 13.

And the control apparatus 100 is the target oil temperature of the oil supplied to the low stage compression part 11 side lower than the time of steady operation at the time of high superheat operation where the suction superheat degree exceeded the threshold value similarly to the said Embodiment 1. Change to temperature. And the control apparatus 100 is the expansion valve 61 for oil coolers so that the oil temperature supplied to the low stage compression part 11 side detected by the low stage side oil supply temperature detection apparatus 92b may become the target oil temperature after a change. And the oil cooler expansion valve 62 is controlled.

In addition, the target oil temperature of the oil supplied to the high stage compression unit 13 side is not particularly limited. Since the original refrigeration operation in the refrigeration apparatus is performed by the main circuit 10, there is a situation where it is not desired to reduce the amount of refrigerant flowing through the main circuit 10 too much. Therefore, if the target oil temperature of the oil supplied to the high-stage compression unit 13 is set low, it is necessary to secure a large amount of refrigerant flowing into the oil cooler 71, reducing the amount of refrigerant flowing into the main circuit 10 and reducing performance. It leads to. Therefore, based on this point, the target oil temperature of the oil to be supplied to the high stage compression unit 13 may be determined.

―Effects of Embodiment 2―
In the second embodiment, the same effects as in the first embodiment can be obtained, and the following effects can be further obtained. That is, in the second embodiment, the two

oil coolers

71 and 72 are used so that only the oil supplied to the low-stage compression unit 11 has a target oil temperature lower than that during steady operation. For this reason, compared with Embodiment 1 which lowers oil temperature to target oil temperature using one oil cooler 7, the amount of refrigerant which flows into

oil coolers

71 and 72 can be decreased. As a result, the configuration of the second embodiment can improve the performance of the refrigeration apparatus compared to the first embodiment.

Embodiment 3 FIG.
In the second embodiment, the

oil coolers

71 and 72 are arranged in series in the oil supply circuit 90, but in the third embodiment, the

oil coolers

71 and 72 are arranged in parallel. Other configurations and operations of the refrigerant circuit are the same as those in the second embodiment. In the following, the third embodiment will be described focusing on the differences from the second embodiment.

FIG. 4 is a refrigerant circuit diagram of the refrigeration apparatus according to Embodiment 3 of the present invention.
In the refrigeration apparatus of the third embodiment,

oil coolers

71 and 72 are arranged in parallel in the oil supply circuit 90. In the oil supply circuit 90, the oil branched into two after being separated by the oil separator 2 flows into the

oil coolers

71 and 72, respectively, and is cooled. It is supplied to the stage compression unit 13. Therefore, the oil supplied to the high stage compression unit 13 is cooled by the oil cooler 71, and the oil supplied to the low stage compression unit 11 is cooled by the oil cooler 72. With this configuration, the temperature of the oil supplied to the high stage compression unit 13 and the temperature of the oil supplied to the low stage compression unit 11 are completely independently controlled. The oil cooler expansion valve 62 constitutes the oil temperature adjusting means of the present invention.

Then, similarly to the second embodiment, the control device 100 lowers the target value of the oil temperature supplied to the low-stage compression unit 11 side during the high superheat operation when the suction superheat degree exceeds the threshold value than during the steady operation. Change to temperature. And the control apparatus 100 controls the expansion valve 62 for oil coolers so that the oil temperature detected by the low stage side oil supply temperature detection apparatus 92b becomes the target oil temperature after a change. In addition, the temperature of the oil supplied to the high stage compression unit 13 is not particularly limited as in the second embodiment.

―Effects of Embodiment 3―
The third embodiment can obtain the same effect as the second embodiment. In the third embodiment, since the

oil coolers

71 and 72 are connected in parallel in the oil supply circuit 90, the temperature of the oil supplied to the low-stage compression unit 11 is controlled only by the oil cooler expansion valve 61. it can. Therefore, when controlling the temperature of the oil supplied to the low-stage compression unit 11, the control is performed as compared with the second embodiment in which the opening control of both the oil cooler expansion valve 61 and the oil cooler expansion valve 62 is required. Can be simplified.

In addition, the temperature of the oil supplied to the high stage compression unit 13 is not particularly limited as described above, and strict temperature control is not necessary. For this reason, the oil cooler 71 of the second embodiment and the third embodiment may be configured by an air cooling type oil cooler that cools oil by exchanging heat with the outside air, for example.

Embodiment 4 FIG.
In Embodiment 1-3 above, the oil cooler 7 is a system that cools oil using a refrigerant, but in Embodiment 4, a system that cools oil using water (cooling water) is used. It is. Other configurations, operations, and the like of the refrigerant circuit are the same as those in the first embodiment. Hereinafter, the difference between the fourth embodiment and the first embodiment will be mainly described.

FIG. 5 is a refrigerant circuit diagram of the refrigeration apparatus according to Embodiment 4 of the present invention.
The refrigeration apparatus of the fourth embodiment replaces the oil cooler 7 of the first embodiment shown in FIG. 1 with oil that exchanges heat between the oil separated by the oil separator 2 and the cooling water supplied from the outside. A cooler 73 and a cooling water amount adjusting valve 63 that adjusts the flow rate of the coolant supplied to the oil cooler 73 are provided. In the refrigeration apparatus of the fourth embodiment, the oil cooling circuit 70 is omitted from the refrigeration apparatus of the first embodiment shown in FIG. The cooling water amount adjusting valve 63 constitutes the oil temperature adjusting means of the present invention.

FIG. 6 is a control flowchart in the refrigeration apparatus according to Embodiment 4 of the present invention.
The control flowchart of the fourth embodiment shown in FIG. 6 is different from the control flowchart of the first embodiment shown in FIG. 2 in that the oil cooler expansion valve 6 is replaced with a cooling water amount adjusting valve 65. The rest is the same as the control flowchart of FIG. That is, in both of the steady operation and the high superheat operation, when the oil temperature is desired to be lowered, the opening of the cooling water amount adjusting valve 65 is increased (S16a, S23a) and the oil cooler 73 is passed. Increase the amount of cooling water and increase the cooling capacity.

On the other hand, when it is desired to raise the temperature of the oil, the opening degree of the cooling water amount adjusting valve 65 is reduced (S14a, S25a), the amount of cooling water passing through the oil cooler 73 is reduced, and the cooling capacity is lowered. Further, when it is desired to maintain the current temperature of the oil, the opening degree of the cooling water amount adjusting valve 65 is left as it is (S17a, S26a).

―Effects of Embodiment 4―
According to the fourth embodiment, the same effects as those of the first embodiment can be obtained, and further the following effects can be obtained. That is, since the cooling water is used instead of the refrigerant as the cooling medium for cooling the oil, it is not necessary to use the refrigerant flowing through the main circuit 10 for oil cooling. For this reason, the expansion of the low-stage screw rotor can be suppressed without reducing the original refrigeration capacity of the refrigeration apparatus.

In the fourth embodiment, the temperature of the oil supplied to the screw compressor 1 is controlled by controlling the flow rate of the cooling water flowing into the oil cooler 73. Good.

FIG. 7 is a refrigerant circuit diagram for explaining another oil temperature adjusting means in the oil cooler in the refrigeration apparatus according to Embodiment 4 of the present invention.
In FIG. 7, instead of the cooling water amount adjusting valve 63 of FIG. 5, a water temperature adjusting means 63a for controlling the temperature of the cooling water is provided. The water temperature adjusting means 63a may be constituted by, for example, a heat exchanger and a flow rate adjusting valve for adjusting a flow rate of a heat medium that can exchange heat with cooling water in the heat exchanger, or may be constituted by a heater. In the fourth embodiment, the flow rate of the cooling water flowing into the oil cooler 73 is kept constant, and the temperature of the cooling water is controlled by the water temperature adjusting means 63a to adjust the oil cooling capacity in the oil cooler 73. And control the oil temperature. The water temperature adjusting means 63a corresponds to the oil temperature adjusting means of the present invention.

Embodiment 5 FIG.
In the fifth embodiment, as in the fourth embodiment, the oil is cooled using cooling water. In the fourth embodiment, the oil temperature supplied to the low-stage compression unit 11 is controlled by controlling the flow rate of the cooling water supplied to the oil cooler 7. In Embodiment 5, the flow rate of the cooling water supplied to the oil cooler 7 is not controlled, and the oil temperature supplied to the low-stage compression unit 11 is controlled by switching the oil flow path length in the oil cooler 7. It is what I did. The following description will focus on the differences of the fifth embodiment from the fourth embodiment.

FIG. 8 is a refrigerant circuit diagram of the refrigeration apparatus according to Embodiment 5 of the present invention.
The refrigeration apparatus of the fifth embodiment includes an oil cooler 74 instead of the oil cooler 73 of the fourth embodiment. The oil cooler 74 has two

oil outlets

96b and 96c which are provided at positions where the oil flow path lengths from the oil inlet 96a are different and flow out oils having different temperatures. The oil outlet 96b is provided on the upstream side of the oil outlet 96b, and is connected to the high-stage compression portion 13 by an oil pipe 97a. The oil outlet 96c is provided at the end of the oil flow that passes through the oil cooler 74, and is connected to the low-stage compression unit 11 by an oil pipe 97b. And the solenoid valve 94 is provided in the oil piping 97a. In addition, an electromagnetic valve 95 is provided in an oil pipe 98 that connects the oil pipe 97b and the downstream of the electromagnetic valve 94 of the oil pipe 97a. The oil path is changed by switching the

electromagnetic valves

94 and 95, and the ratio of heat exchange between the oil supplied to the high-stage compressor 13 and the refrigerant of the oil supplied to the low-stage compressor 11 is changed.

The refrigeration apparatus of the fourth embodiment configured as described above can switch the temperature of oil supplied to the low-stage compression unit 11 by switching between the electromagnetic valve 94 and the electromagnetic valve 95. The electromagnetic valve 94 and the electromagnetic valve 95 constitute the oil temperature adjusting means of the present invention.

FIG. 8 shows the flow of refrigerant, oil, and cooling water during steady operation. FIG. 9 is a diagram showing the flow of refrigerant, oil, and cooling water during high superheat operation in the refrigeration apparatus according to Embodiment 5 of the present invention. Hereinafter, the operation of the refrigeration apparatus of the fourth embodiment will be described with reference to FIGS. 8 and 9 and the following Table 1.

Table 1 is a table showing the open / closed state of the

solenoid valves

94 and 95.

During normal operation, as shown in FIG. 8 and Table 1, the control device 100 sets the electromagnetic valve 94 to “closed” and the electromagnetic valve 95 to “open”. As a result, the oil separated by the oil separator 2 is cooled by exchanging heat with the cooling water in the oil cooler 74 and then cooled, and then flows out from the oil outlet 96c. 11 and the high stage compression unit 13 respectively. Here, the oil temperature supplied to the low stage compression unit 11 and the high stage compression unit 13 is the same temperature.

On the other hand, during high superheat operation, as shown in FIG. 9 and Table 1, the control device 100 sets the electromagnetic valve 94 to “open” and the electromagnetic valve 95 to “closed”. As a result, a part of the oil being cooled by the oil cooler 74 flows out from the oil outlet 96b just before reaching the oil outlet 96c, and is supplied to the high-stage compression unit 13. On the other hand, the remaining oil further proceeds through the oil flow path in the oil cooler 74 and is further cooled by the cooling water, and then flows out from the oil outlet 96b and is supplied to the low-stage compression unit 11. That is, at the time of high superheat operation, a part of the oil being cooled is taken out by the oil cooler 74 and supplied to the high stage compression unit 13 while the remaining oil is further cooled, and then the low stage compression unit 11 is supplied.

Here, the temperature of the oil supplied to the low stage compression unit 11 during steady operation and the temperature of the oil supplied to the low stage compression unit 11 during high superheat operation are compared. During high superheat operation, the oil cooler 74 extracts a portion of the oil that is being cooled and the remaining oil whose flow rate has been reduced is further cooled in the oil flow path from the oil outlet 96b to the oil outlet 96c. For this reason, the temperature of the oil flowing out from the oil outlet 96c during the high superheat operation is lower than the temperature of the oil flowing out from the oil outlet 96c during the steady operation. That is, oil having a lower temperature than that during steady operation can be supplied to the low stage compression unit 11 during high superheat operation.

On the other hand, since the oil flowing out from the oil outlet 96b during the high superheat operation is oil taken out during the cooling, the temperature is higher than the oil flowing out from the oil outlet 96b during the steady operation.

-Effect of Embodiment 5-
According to the fifth embodiment, the same effects as in the fourth embodiment can be obtained, and the following effects can be further obtained. That is, in the oil cooler 74, oil having a temperature lower than that during steady operation can be supplied to the low stage compression unit 11 during high superheat operation without changing the cooling water amount and the cooling water inlet temperature.

In

Embodiments

4 and 5, the heat medium that exchanges heat with oil in the oil cooler 74 is water, but water itself may be used, or a mixed solution in which an additive having a high anticorrosion effect is mixed with water. It may be used.

1 Screw compressor, 2 Oil separator, 3 Condenser, 4 Main expansion valve, 5 Evaporator, 6 Oil cooler expansion valve, 7 Oil cooler, 8 Motor cooling expansion valve, 10 Main circuit, 11 Low stage compression Section, 12 intermediate pressure chamber, 13 high-stage compression section, 14 motor, 14a motor chamber, 61 expansion valve for oil cooler, 62 expansion valve for oil cooler, 63 cooling water amount adjusting valve, 63a water temperature adjusting means, 65 cooling water amount adjusting valve 70 oil cooling circuit, 71 oil cooler, 72 oil cooler, 73 oil cooler, 74 oil cooler, 80 motor cooling circuit, 90 oil supply circuit, 91 suction temperature detection device, 92 oil supply temperature detection device, 92a high Stage side oil temperature detector, 92b Low stage oil temperature detector, 93 Suction pressure detector, 94 Solenoid valve, 95 Solenoid valve, 96a oil inlet, 96b oil out (Second oil outlet), 96c oil outlet (first oil outlet), 97a-oil piping, 97b oil pipe, 98 an oil pipe, 100 controller.

Claims

A screw compressor, a condenser, a decompression device and an evaporator are connected by piping, and a refrigeration cycle in which refrigerant circulates;
An oil separator that is disposed between the screw compressor and the condenser of the refrigeration cycle and separates oil contained in refrigerant gas discharged from the screw compressor;
An oil cooler that cools the oil separated by the oil separator by heat exchange with a heat medium; and
An oil supply circuit that cools the oil separated by the oil separator by the oil cooler and supplies the oil to the screw compressor;
Oil temperature adjusting means for adjusting the temperature of the oil supplied from the oil supply circuit to the screw compressor;
A superheat degree detection means for detecting the superheat degree of the refrigerant gas sucked into the screw compressor;
A control device for controlling the oil temperature adjusting means based on the degree of superheat,
The controller is configured to supply the screw compressor with oil having a temperature lower than that in steady operation in which the superheat degree is equal to or less than the threshold value during high superheat degree operation in which the superheat degree exceeds a preset threshold value. A refrigerating apparatus for controlling the oil temperature adjusting means.
The oil temperature adjusting means is a flow rate adjusting valve that adjusts the flow rate of the heat medium flowing into the oil cooler,
An oil cooling circuit branched from between the condenser and the pressure reducing device and connected to the screw compressor via the flow rate adjusting valve and the oil cooler;
The refrigeration apparatus according to claim 1, wherein the heat medium that exchanges heat with the oil in the oil cooler is the refrigerant.
The said control apparatus makes the opening degree of the said flow control valve large so that the flow volume of the said thermal medium which flows in into the said oil cooler may increase rather than the time of the said steady operation at the time of the said high superheat operation. Refrigeration equipment.
The screw compressor is a multi-stage screw compressor including a plurality of compression units,
The oil supply circuit is a circuit that supplies oil to each of the plurality of compression units,
The oil at a temperature lower than that in the steady operation is supplied to the lowest-stage low-stage compression unit among the plurality of compression units during the high superheat operation. The refrigeration apparatus described in 1.
The oil supply circuit includes a plurality of the oil coolers arranged in series with each other, and out of the plurality of oil coolers, the oil flowing out from the oil cooler on the most downstream side of the oil is supplied to the low-stage compression unit. The refrigeration apparatus according to claim 4, wherein the refrigeration apparatus is configured to supply.
The oil supply circuit includes a plurality of the oil coolers arranged in parallel, and each oil branched into a plurality of parts after being separated by the oil separator is caused to flow into the plurality of oil coolers and cooled. The refrigeration apparatus according to claim 4, wherein the refrigeration apparatus is configured to be supplied to the plurality of compression units.
The heat medium is water;
The refrigeration apparatus according to claim 1, wherein the oil temperature adjusting means is a flow rate adjusting valve for adjusting a flow rate of the water flowing into the oil cooler.
The refrigeration apparatus according to claim 7, wherein the control device controls the flow rate adjustment valve during the high superheat operation to increase the flow rate of water flowing into the oil cooler than during the steady operation.
The heat medium is water;
The refrigeration apparatus according to claim 1, wherein the oil temperature adjusting means is water temperature adjusting means for adjusting a temperature of water flowing into the oil cooler.
10. The refrigerating apparatus according to claim 9, wherein the control device controls the water temperature adjusting means during the high superheat operation so that water having a temperature lower than that during the steady operation flows into the oil cooler.
The screw compressor is a multi-stage screw compressor including a plurality of compression units,
The oil having a temperature lower than that in the steady operation is supplied to the lowest stage low-stage compression unit among the plurality of compression units during the high superheat operation. The refrigeration apparatus described in 1.
The heat medium is water;
The screw compressor is a multi-stage screw compressor including a plurality of compression units,
The oil cooler has a first oil outlet from which a part of the oil being cooled is taken out, and a second oil outlet to be taken out after the remaining oil passes to the end of the oil flow path in the oil cooler. And
During the steady operation, the oil taken out from the second oil outlet is supplied to each of the plurality of compression units,
During the high superheat operation, a part of the oil that has flowed into the oil cooler is taken out from the first oil outlet in the middle of cooling, and among the plurality of compression units, other than the lowest low-stage compression unit While supplying to a compression part, after passing the remaining oil to the terminal of the said oil flow path, and performing further heat exchange with the said heat carrier, it takes out from the said 2nd oil outlet, and supplies it to the said low stage compression part The refrigeration apparatus of claim 11 having a configuration.