JP2003214733A - Refrigerating apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suitably control the operating capacity of a compressor 15 even if a low pressure sensor 34 for detecting the low pressure refrigerant pressure of the compressor 15 becomes abnormal. <P>SOLUTION: This refrigerating apparatus includes an injection circuit 25 for supplying liquid refrigerant to the inlet side of the compressor 15, a temperature sensor 33 for detecting the inlet refrigerant temperature of the compressor 15, an estimating part 52 for estimating the low pressure refrigerant pressure of the inlet side of the compressor 15 from the inlet refrigerant temperature detected by the temperature sensor 33 when the liquid refrigerant is supplied by an injector circuit 25, and a capacity control part 54 for controlling the operating capacity of the compressor 15 according to the low pressure refrigerant pressure estimated by the estimating part 52 when a low pressure sensor 34 for detecting low pressure refrigerant pressure of the compressor 15 is abnormal. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a refrigerating apparatus having a compressor whose operating capacity is controlled based on the low pressure refrigerant pressure on the suction side.

[0002]

2. Description of the Related Art Conventionally, a refrigerating apparatus provided with a refrigerant circuit in which a refrigerant circulates to perform a vapor compression refrigeration cycle
It is widely known that the capacity of a compressor is controlled by changing the rotation speed of the compressor in accordance with the fluctuation of the refrigerating load for the purpose of efficient operation.

By the way, when the refrigeration load changes, the pressure of the refrigerant drawn into the compressor also changes accordingly. Therefore, it is generally practiced to provide a low pressure sensor for detecting the low pressure refrigerant pressure on the suction side of the compressor and to control the capacity of the compressor based on the output of the low pressure sensor.

[0004]

However, in the above-mentioned conventional apparatus, when the low-pressure sensor becomes abnormal and the low-pressure refrigerant pressure cannot be accurately detected, the compressor cannot be properly controlled. There is a problem.

In particular, when this type of refrigerating apparatus is applied to, for example, a refrigerating showcase installed in a convenience store or the like, if the low-pressure sensor becomes abnormal, the quality of the product in the refrigerating showcase is deteriorated. It will not be able to be retained and will cause a great deal of damage.

The present invention has been made in view of the above points, and an object thereof is to devise a structure for controlling the operating capacity of a compressor of a refrigerating apparatus.
Even if the low-pressure sensor becomes abnormal, it is intended to appropriately maintain the capacity control of the compressor.

[0007]

In order to achieve the above object, according to the present invention, when the low pressure sensor for detecting the low pressure refrigerant pressure on the suction side of the compressor is abnormal, the temperature at the time of injection of the liquid refrigerant is increased. The capacity of the compressor is controlled based on the temperature of refrigerant sucked into the compressor detected by the sensor.

Specifically, in the first invention, the compressor (15)
(13) Refrigerant circuit with vapor compression refrigeration cycle equipped with
And an injection circuit (25) provided in the refrigerant circuit (13) for supplying liquid refrigerant to the suction side of the compressor (15).
A temperature sensor (33) for detecting the temperature of the refrigerant sucked into the compressor (15), and a compressor (from the temperature of the refrigerant sucked by the temperature sensor (33) detected when the liquid refrigerant is supplied by the injection circuit (25). The prediction means (52) predicts when the prediction means (52) for predicting the low pressure refrigerant pressure on the suction side of 15) and the low pressure sensor (34) for detecting the low pressure refrigerant pressure of the compressor (15) are abnormal. Compressor based on low pressure refrigerant pressure (1
5) The capacity control means (54) for controlling the operating capacity is provided.

According to the above invention, when the refrigerant circulates in the refrigerant circuit (13) to perform the refrigeration cycle and the refrigeration load changes, the low pressure of the refrigerant sucked into the compressor (15) in response to the change. The refrigerant pressure also changes. This change in low-pressure refrigerant pressure is detected by the low-pressure sensor (34). The capacity control means (54) is based on the detected low pressure refrigerant pressure.
This controls the operating capacity of the compressor (15).

On the other hand, the predicting means (52) is provided with a temperature sensor (3) when the liquid refrigerant is supplied by the injection circuit (25).
The low-pressure refrigerant pressure on the suction side of the compressor (15) is predicted from the suction refrigerant temperature detected by 3). When an abnormality occurs in the low pressure sensor (34), the capacity control means (54) causes the compressor (15) to replace the low pressure sensor (34) based on the low pressure refrigerant pressure predicted by the prediction means (52). The operating capacity of is properly controlled.

Therefore, even if the low pressure sensor (34) becomes abnormal during the operation of the refrigeration system, the capacity control of the compressor (15) is maintained regardless of the abnormality. Especially when the refrigerant circuit (13) has, for example, a refrigerated showcase,
Even if an abnormality occurs in the low pressure sensor (34),
The quality of the goods in the refrigerated showcase is kept good.

In the second aspect of the invention, a refrigerant circuit (13) having a compressor (15) for performing a vapor compression refrigeration cycle, and a low pressure sensor (for detecting the low pressure refrigerant pressure on the suction side of the compressor (15) ( 34), a capacity control means (54) for controlling the operating capacity of the compressor (15) based on the low pressure refrigerant pressure detected by the low pressure sensor (34), and a suction refrigerant temperature of the compressor (15). Temperature sensor (33) for detecting the
An injection circuit (25) that operates so as to intermittently supply the liquid refrigerant to the suction side of the compressor (15) when the degree of superheat of the discharged refrigerant of 5) exceeds a predetermined value, and the injection circuit described above. When the operation of (25) is performed, there is provided a prediction means (52) for predicting the low pressure refrigerant pressure by using the suction refrigerant temperature detected by the temperature sensor (33) as a saturation temperature equivalent to the low pressure refrigerant pressure, and the capacity control means (54). Is an abnormality that controls the operating capacity of the compressor (15) based on the low pressure refrigerant pressure predicted by the prediction means (52) instead of the low pressure sensor (34) when the low pressure sensor (34) is abnormal. The controller (55) is provided.

According to the above invention, like the first invention, when the low pressure sensor (34) is operating normally, the capacity control is performed based on the low pressure refrigerant pressure detected by the low pressure sensor (34). The means (54) controls the operating capacity of the compressor (15).

On the other hand, when the degree of superheat of the refrigerant discharged from the compressor (15) exceeds a predetermined value, the injection circuit (25) operates to intermittently transfer the liquid refrigerant to the suction side of the compressor (15). Is supplied to. This allows the compressor (15)
The degree of superheat of the refrigerant inside is reduced and maintained appropriately.

The predicting means (52) is provided with a temperature sensor (3) when the liquid refrigerant is supplied by the injection circuit (25).
The low-pressure refrigerant pressure is predicted by regarding the intake refrigerant temperature detected in 3) as the saturation temperature equivalent to the low-pressure refrigerant pressure.

When an abnormality occurs in the low pressure sensor (34), the predicting means (52) replaces the low pressure sensor (34).
The operating capacity of the compressor (15) is appropriately controlled by the abnormality control section (55) based on the low-pressure refrigerant pressure predicted by. Therefore, similarly to the first aspect of the invention, even when the low pressure sensor (34) becomes abnormal during the operation of the refrigeration system, the capacity control of the compressor (15) is maintained regardless of the abnormality.

In a third aspect based on the first or second aspect, the injection circuit (25) is configured to supply the liquid refrigerant to the compressor (15) without depressurizing the liquid refrigerant during operation.

By the way, the pressure of the liquid refrigerant is reduced to the compressor (15).
When supplied to the side, the liquid refrigerant may become superheated due to the reduced pressure. On the other hand, according to the present invention, the liquid refrigerant flowing through the refrigerant circuit (13) is supplied to the suction side of the compressor (15) without being depressurized during the operation of the injection circuit (25). The occurrence of the degree of superheat due to Therefore, the degree of superheat of the refrigerant sucked into the compressor (15) is effectively reduced.

Further, since the flow velocity is prevented from decreasing due to the pressure reduction, the superheat degree of the refrigerant sucked into the compressor (15) is rapidly lowered during the operation of the injection circuit (25), so that the low pressure refrigerant of the refrigerant is sucked. Pressure is predicted quickly.

[0020]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below in detail with reference to the drawings.

As shown in FIG. 1, the refrigerating apparatus (10) according to the present embodiment is provided in a convenience store and is for cooling a showcase in the refrigerator.

The refrigeration system (10) includes an outdoor unit (1
1) and a refrigeration unit (12), and a refrigerant circuit (13) for performing a vapor compression refrigeration cycle. The refrigerating unit (12) is installed in a refrigerating showcase to cool the air inside the showcase.

<Outdoor unit> The outdoor unit (11) is
It is provided with an inverter compressor (15) and an outdoor heat exchanger (16) which is a heat source side heat exchanger. The compressor (15) is, for example, a hermetic high-pressure dome scroll compressor. Further, the compressor (15) is configured such that the electric motor is inverter-controlled and the operating capacity is variable stepwise or continuously. The compressor (15) is provided with a compressor temperature sensor (35) for detecting the internal temperature of the compressor (15).

The discharge side of the compressor (15) has a high pressure gas pipe (1
7), and the other end of the high pressure gas pipe (17) is connected to the gas side of the outdoor heat exchanger (16). The high pressure gas pipe (17) is provided with a pressure switch (31) that opens when the high pressure refrigerant pressure reaches a predetermined value. Further, the high pressure gas pipe (17) is provided with a discharge side temperature sensor (32) that is a temperature sensor that detects the temperature of the refrigerant discharged from the compressor (15).

The outdoor heat exchanger (16) is, for example, a cross-fin type fin-and-tube heat exchanger, and the outdoor fan (18) which is a heat source fan is arranged close to it.

On the liquid side of the outdoor heat exchanger (16), a liquid pipe (1
One end of the liquid pipe (19) is connected and the other end of the liquid pipe (19) is closed (20).
connected to a). The liquid pipe (19) is provided with an expansion valve (21) which is an expansion mechanism for reducing the pressure of the passing refrigerant. Further, a communication liquid pipe (38) for supplying the refrigerant flowing through the liquid pipe (19) to the refrigeration unit (12) side is connected to the shutoff valve (20a).

On the other hand, the suction side of the compressor (15) is connected to one end of the low pressure gas pipe (22), and the other end of the low pressure gas pipe (22) is connected to the closing valve (20b). Low pressure gas pipe (22)
A low pressure sensor (34) for detecting the low pressure refrigerant pressure on the suction side of the compressor (15) is provided in the. Further, the low pressure gas pipe (22) is provided with a suction side temperature sensor (33) which is a temperature sensor for detecting the temperature of the refrigerant sucked into the compressor (15). And, the shut-off valve (20b) has a refrigeration unit (12).
A connecting gas liquid pipe (39) for supplying the refrigerant from the side to the low pressure gas pipe (22) is connected. The stop valve (20a, 2
0b) is opened after the outdoor unit (11) and the refrigeration unit (12) are connected.

The refrigerant circuit (10) has a compressor (15).
Injection circuit (2 that supplies liquid refrigerant to the suction side of
5) is provided. Injection circuit (25)
Is composed of a liquid injection pipe (26) and a solenoid valve (SV) provided in the liquid injection pipe (26). Liquid injection pipe (2
6) is connected between the liquid pipe (19) and the low pressure gas pipe (22). That is, the injection circuit (25)
It does not have a depressurizing mechanism such as a capillary and is configured to supply the liquid refrigerant to the compressor (15) without depressurizing it during operation. Then, when the degree of superheat of the refrigerant discharged from the compressor (15) exceeds a predetermined value, the liquid refrigerant flowing through the liquid pipe (19) is intermittently supplied to the suction side of the compressor. .

<Refrigeration Unit> The refrigeration unit (12) is
The showcase (not shown) is provided with a refrigerating heat exchanger (41) which is a use side heat exchanger. The refrigerating heat exchanger (41) is, for example, a cross-fin type fin-and-tube heat exchanger, and the refrigerating fan (42) that is a utilization fan is arranged in close proximity. The liquid side of the refrigerating heat exchanger (41) is connected to the communication liquid pipe (38).
On the other hand, the gas side of the refrigerating heat exchanger (41) is connected to the connecting gas pipe (3
9) is connected.

<Controller> The outdoor unit (11) is
It has a controller (50). Controller (50)
Is an injection control unit (51) and a prediction unit (52)
And an abnormality determination section (53) and a capacity control section (54).

The injection control section (51) is configured to control the operation of the injection circuit (25). That is, the superheat degree of the discharge refrigerant is derived based on the discharge refrigerant temperature detected by the discharge side temperature sensor (32), and when the superheat degree exceeds a predetermined value (for example, 30 ° C.), the solenoid valve ( The open / closed state of SV) is switched intermittently.

The abnormality judging section (53) detects an abnormality of the low pressure sensor (34). That is, for example, when the detection value output from the low pressure sensor (34) deviates from the normally assumed predetermined range, it is determined that the low pressure sensor (34) is abnormal.

The predicting section (52) detects that the low pressure sensor (34) is abnormal and the compressor (from the suction refrigerant temperature detected by the heat absorption side temperature sensor (33) when the liquid refrigerant is supplied by the injection circuit (25). It is configured to predict the low pressure refrigerant pressure on the suction side of 15). That is, the low-pressure refrigerant pressure is predicted by setting the intake refrigerant temperature during the operation of the injection circuit (25) as the saturation temperature corresponding to the low-pressure refrigerant pressure.

The capacity control section (54) uses the low pressure refrigerant pressure detected by the low pressure sensor (34) to determine the compressor (15).
Is configured to control the operating capacity of the. On the other hand, the capacity control section (54) includes an abnormality control section (55) that controls the operating capacity of the compressor (15) when the low pressure sensor (34) is abnormal.

That is, when the abnormality determination unit (53) determines that the low pressure sensor (34) is abnormal, the abnormality control unit (55) replaces the low pressure sensor (34) with the prediction unit (52). The capacity of the compressor (15) is controlled based on the low-pressure refrigerant medium pressure predicted by. In this way, the capacity control unit (54) is configured to control the operating capacity of the compressor (15) based on the low pressure refrigerant pressure predicted by the prediction unit (52) when the low pressure sensor (34) is abnormal. ing.

-Driving Operation- Next, the driving operation performed by the refrigeration system (10) will be described.

First, the compressor (15) of the outdoor unit (11)
Sucks the low-pressure gas refrigerant flowing through the low-pressure gas pipe (33), compresses the sucked refrigerant, and discharges the compressed refrigerant. The high-pressure gas refrigerant discharged from the compressor (15) flows through the high-pressure gas pipe (17). At this time, when the pressure of the discharged refrigerant is equal to or higher than the predetermined value, the pressure switch (31) is opened to allow the refrigerant to flow. And, by the discharge side temperature sensor (32),
The temperature of the discharged refrigerant is detected and output to the injection control section (51) of the controller (50).

The refrigerant flowing through the high pressure gas pipe (17) is supplied to the outdoor heat exchanger (16). This outdoor heat exchanger (16)
In, the outdoor fan (18) is operating, and the passing refrigerant is condensed. In this way, heat exchange is performed between the outdoor air and the refrigerant. The condensed high-pressure liquid refrigerant flows into the expansion valve (21).
It flows through the liquid pipe (19) toward.

The refrigerant passing through the expansion valve (21) is depressurized. The low-pressure liquid refrigerant decompressed by the expansion valve (21)
It flows through the communication liquid pipe (38) through the closing valve (20a) and is supplied to the refrigerating heat exchanger (41) of the refrigerating unit (12). In the refrigerating heat exchanger (41), the refrigerating fan (42) is operating, and the passing refrigerant is evaporated. In this way, heat is exchanged between the air inside the showcase and the refrigerant, and the inside air is cooled. The evaporated low-pressure gas refrigerant flows through the communication gas pipe (39) toward the closing valve (20b).

The refrigerant flowing through the connecting gas pipe (39) passes through the stop valve (20b) and then flows through the low pressure gas pipe (22). The refrigerant flowing through the low pressure gas pipe (22) is sucked into the compressor (15). Then, the temperature of the suction refrigerant is detected by the suction side temperature sensor (33), and the prediction unit (5) of the controller (50) is detected.
It is output to 1). Further, the low pressure sensor (34) detects the low pressure refrigerant pressure of the suctioned refrigerant, and the controller (50).
Is output to the capacity control unit (52) and the abnormality determination unit (53).

After that, the refrigerant sucked into the compressor (15) is compressed and discharged again. In this way, by the operation of the compressor (15), the refrigerant circulates in the refrigerant circuit (13) to perform a refrigeration cycle, and the inside of the showcase of the refrigeration unit (12) is cooled.

-Operation of Controller- Next, the control operation performed by the controller (50) will be described with reference to the flowcharts of FIGS.

<Injection control section> First, the injection control section (51) discharges the discharge refrigerant based on the temperature of the discharge refrigerant detected by the discharge side temperature sensor (32) and the internal temperature of the compressor (15). The open / close state of the solenoid valve (SV) is controlled so that the degree of superheat of the refrigerant is appropriately reduced.

Specifically, as shown in FIG. 2, first, in step (S1), the temperature of the discharge refrigerant detected by the discharge side temperature sensor (32) is the injection control unit (5).
It is input to 1) and the superheat degree (DSH) of the discharged refrigerant is derived. Further, the compressor temperature (Tp) detected by the compressor temperature sensor (35) is input to the injection control section (51).

Then, in step (S2), whether the compressor temperature (Tp) is a predetermined value of, for example, 120 ° C. or higher, and the superheat degree (DSH) is a predetermined value of, for example, 30 ° C.
Regarding the above, it is determined whether at least one of the conditions is satisfied. As a result, the compressor temperature (Tp) is 1
When the temperature is lower than 20 ° C. and the degree of superheat (DAH) is lower than 30 ° C. and NO is determined, the process proceeds to step (S3). Then, in step (S3), the solenoid valve (SV) is maintained in the closed state. Then return.

On the other hand, in the step (S2), the compressor temperature (Tp) is 120 ° C. or higher and the degree of superheat (DSH).
If the temperature is above 30 ° C and it is judged as YES,
Go to step (S4). In step (S4), at least one of the conditions is further determined with respect to whether the compressor temperature (Tp) is a predetermined value of, for example, 130 ° C. or higher and the superheat degree (DSH) is a predetermined value of, for example, 40 ° C. or higher. It is determined whether or not it is satisfied. As a result, the compressor temperature (T
If p) is less than 130 ° C and the degree of superheat (DAH) is less than 40 ° C and NO is determined, the step (S
Go to 5). Then, in this step (S5), the solenoid valve (SV) is opened for 10 seconds to inject the liquid refrigerant on the high pressure side to the low pressure side, and then closed for 10 seconds.
Then return.

By the way, in the step (S4),
Compressor temperature (Tp) is over 130 ℃ and superheat (DS
If H) is 40 ° C. or higher and YES is determined, the process proceeds to step (S6). Then, in this step (S6), the solenoid valve (SV) is opened, for example, for 20 seconds to inject the liquid refrigerant on the high pressure side to the low pressure side, and then closed for 10 seconds. Then return.

In this way, when the compressor temperature (Tp) and the degree of superheat (DSH) exceed the predetermined values and the compressor (15) is in the overheated state, the solenoid valve (SV) is intermittently opened. As a result, the liquid refrigerant is supplied to the suction side of the compressor (15). As a result, the degree of superheat of the refrigerant in the compressor (15) is appropriately reduced.

<Prediction Unit, Abnormality Judgment Unit, Capacity Control Unit> Next, referring to the flowchart of FIG. 3, the prediction unit (52),
The control operations of the abnormality determination unit (53) and the capacity control unit (54) will be described.

First, in step (S11), it is determined whether or not the low pressure sensor (34) is abnormal. That is,
The low pressure refrigerant pressure of the suction refrigerant output from the low pressure sensor (34) is input to the abnormality determination unit (53). On the other hand, in the abnormality determination section (53), when the low pressure sensor (34) is normal, a predetermined range of possible values of the low pressure refrigerant pressure is preset. Then, the abnormality determination unit (53) determines that the low-pressure sensor (34) has an abnormality when the input low-pressure refrigerant pressure is a value outside the predetermined range. In this step (S11), if the abnormality determination unit (53) determines that the low pressure sensor (34) is normal and the determination is NO, the process proceeds to step (S12).

In step (S12), when the compressor (15) is operating and the solenoid valve (SV) is closed, the superheat degree (SH1) of the suction refrigerant is detected every 5 seconds five times. In this way, the average value of the detected superheat (SH1) is calculated as
2) After setting the superheat degree (SH2), the process returns.

As described above, when the low pressure sensor (34) is normal, the operating capacity of the compressor (15) is based on the low pressure refrigerant pressure detected by the low pressure sensor (34). 54).

On the other hand, in step (S11), if the low pressure sensor (34) is abnormal and YES is determined, the process proceeds to step (S13). In step (S13), it is determined whether the solenoid valve (SV) is open. When the solenoid valve (SV) is in the closed state and it is determined NO, the process proceeds to step (S14).

In step (S14), it is determined whether or not 5 seconds or more have passed since the solenoid valve (SV) was closed. As a result, if less than 5 seconds have passed and it is determined to be NO, the process proceeds to step (S27). Then, in this step (S27), the low pressure refrigerant pressure (LP) is predicted by the prediction unit (52).

That is, when it is less than 5 seconds after the solenoid valve (SV) is closed, it is considered that the influence of the injection of the liquid refrigerant in the previous open state remains strong. Therefore, in this step (S27), the superheat degree of the suction refrigerant is regarded as zero. As a result, step (S2
In 7), the intake refrigerant temperature (Ti1) is regarded as the saturation temperature (TeG) corresponding to the low pressure refrigerant pressure. That is, the low pressure refrigerant pressure (LP) is predicted based on the suction refrigerant temperature (Ti1). Then return.

By the way, in the step (S14), if 5 seconds or more have passed since the solenoid valve (SV) was closed, and if YES is determined, the step (S1)
Go to 5). In step (S15), the intake refrigerant temperature (Ti1) detected by the intake side temperature sensor (33) is changed to the intake refrigerant temperature (TiX) when the solenoid valve (SV) is closed.
Set as. Then, it progresses to step (S16).

In step (S16), the low pressure refrigerant pressure (LP) is predicted by the prediction section (52). That is, the equivalent saturation temperature (TeG) is set by the difference between the suction refrigerant temperature (TiX) and the superheat degree (SH2), and the low pressure refrigerant pressure (LP) is predicted based on this equivalent saturation temperature (TeG). Then return.

On the other hand, in the step (S13), if the solenoid valve (SV) is in the open state and it is judged YES, the process proceeds to step (S17). In step (S17),
Judges whether the solenoid valve (SV) has just changed from the closed state to the open state. As a result, if the state has just changed to the open state and YES is determined, step (S1
Go to 8).

In step (S18), it is determined whether or not the state in which the solenoid valve (SV) was closed last time was longer than 10 seconds. For example, when the injection circuit (25) is operating, the solenoid valve (SV) is opened for 10 seconds or 20 seconds and then closed for 10 seconds, as described with reference to FIG. Therefore, the injection circuit (2
During the continuous operation of 5), the open state of the solenoid valve (SV) is 10 seconds. In this way, when the previous closed state of the solenoid valve (SV) is 10 seconds or less and it is determined NO in step (S18), the process proceeds to step (S27).

That is, when the previous closed state of the solenoid valve (SV) is relatively short, the degree of superheat of the suction refrigerant is regarded as zero. Then, in this step (S27), as described above, the low pressure refrigerant pressure (LP) is predicted based on the suction refrigerant temperature (Ti1).

On the other hand, for example, when the compressor (15) is not overheated and the injection circuit (25) is not operating (that is, the solenoid valve (SV) is kept closed), The closed state may be longer than 10 seconds. After that, when the operation of the injection circuit (25) is started and the solenoid valve (SV) is opened, it is determined as YES in the above step (S18). In this case, the process proceeds to step (S19).

In step (S19), a 5-second timer for counting 5 seconds and a 2-minute timer for counting 2 minutes start counting. Then step (S2
Move to 0). On the other hand, in the above step (S17),
Even if the solenoid valve (SV) has not only changed from the closed state to the open state but also is determined to be NO, the step (S20)
Move to.

In step (S20), it is determined whether or not the 5-second timer has timed out. As a result, when the time is up and it is determined to be YES, the process proceeds to step (S21).

In step (S21), the suction refrigerant temperature (Ti1) detected by the suction side temperature sensor (33) when the solenoid valve (SV) is in the open state is set to the equivalent saturation temperature (TS) of the low pressure refrigerant pressure. ). Then step (S2
Go to 2).

In step (S22), the above step (S1
The degree of superheat obtained as the difference between the suction refrigerant temperature (TiX) when the solenoid valve (SV) set in 5) is closed and the equivalent saturation temperature (TS) set in step (S21) above ( Ti
X-TS) is determined to be a value within a predetermined range. That is, the degree of superheat (TiX-TS) is equal to the degree of superheat (SH
Greater than (SH2-2) minus 2 ° C from 2) and less than (SH2 + 2) above 2 ° C added to superheat (SH2) ((SH2-2) <(TiX-TS) <(SH2 + 2)) It is determined whether or not the above conditions are satisfied. As a result, if the above predetermined range is satisfied and YES is determined, step (S2
Go to 3).

On the other hand, in the above step (S20), 5
Even if the second timer has not timed out and is determined to be NO, the process proceeds to step (S23). In this step (S23), the average value of five superheat degrees (TiX-TS) including those obtained before (when the low pressure sensor (34) is normal) is set as the superheat degree (SH2). Then step (S2
Go to 5).

By the way, in the step (S22), the degree of superheat (TiX-TS) is within the predetermined range ((SH2-2) <(TiX
If -TS) <(SH2 + 2)) is not satisfied and NO is determined, the process proceeds to step (S24). Step (S
In 24), the superheat degree (TiX-TS) obtained in the step (S22) is set as the superheat degree (SH2). Then, the process proceeds to step (S25).

In step (S25), it is determined whether or not the two-minute timer has timed out. As a result, when the time is up and it is determined to be YES, the process proceeds to step (S27). That is, the solenoid valve (S
If V) is open for a relatively long period of time, it is considered to be zero because the superheat of the suction refrigerant is sufficiently low. Therefore, in this step (S27), the low pressure refrigerant pressure (LP) is predicted based on the suction refrigerant temperature (Ti1) as described above.

On the other hand, in the above step (S25), 2
If the minute timer has not timed out and it is determined to be NO, the process proceeds to step (S26). In this case, since the suction refrigerant has a certain degree of superheat (SH2), the prediction unit (52) predicts the low-pressure refrigerant pressure (LP) in consideration of the degree of superheat (SH2). That is, in this step (S26), the saturation temperature (TeG) corresponding to the low pressure refrigerant pressure
Is derived as the difference (TiX-SH2) between the suction refrigerant temperature (TiX) when the solenoid valve (SV) is closed and the superheat degree (SH2). Then, based on this difference (TiX-SH2),
Predict low pressure refrigerant pressure (LP). Then return.

In this way, when the low pressure sensor (34) is abnormal, the low pressure refrigerant pressure (LP) sucked into the compressor (15) is equal to the suction refrigerant temperature (Ti1) when the solenoid valve (SV) is open. ) As the saturation temperature equivalent to the low pressure refrigerant pressure,
2) Predicted by

As described above, when the low pressure sensor (34) is abnormal, the low pressure refrigerant pressure (LP) predicted by the prediction unit (52) is the abnormal pressure control unit (5) of the capacity control unit (54).
Entered in 5). Then, the abnormality control section (55)
Based on the input low pressure refrigerant pressure (LP), the compressor (1
The operating capacity of 5) is controlled.

As described above, according to this embodiment, not only when the low pressure sensor (34) is normal, but also when the low pressure sensor (34) is abnormal, the low pressure sensor (34) ), The abnormality control section (53) can appropriately control the operating capacity of the compressor (15) based on the low pressure refrigerant pressure (LP) predicted by the prediction section (52).

Therefore, even if the low pressure sensor (34) becomes abnormal during the operation of the refrigeration system (10), the capacity control of the compressor (15) is maintained regardless of the abnormality, so that the refrigeration unit ( It is possible to maintain the inside temperature of the showcase in 12) appropriately. As a result, it is possible to maintain good quality of the products in the showcase.

Furthermore, in this embodiment, since the injection circuit (25) is configured to supply the liquid refrigerant to the compressor (15) without depressurizing it during its operation, the liquid refrigerant to be supplied is accompanied by depressurization. The occurrence of superheat is prevented, and the flow velocity is prevented from decreasing due to the pressure reduction. As a result, the degree of superheat of the refrigerant sucked into the compressor (15) can be rapidly reduced, and the low-pressure refrigerant pressure (LP) of the refrigerant sucked can be predicted quickly.

In the above embodiment, only the refrigerating unit (12) is provided as the use side unit.
In addition, an indoor unit of an air conditioner for cooling and heating the room, a freezing unit for freezing and storing foods, and the like may be provided. Further, the outdoor unit may be provided with a plurality of compressors.

[0076]

As described above, according to the present invention,
An injection circuit that is provided in the refrigerant circuit and supplies the liquid refrigerant to the suction side of the compressor, a temperature sensor that detects the refrigerant refrigerant intake temperature, and an intake refrigerant temperature that the temperature sensor detects when the liquid refrigerant is supplied by the injection circuit. From the prediction means for predicting the low pressure refrigerant pressure on the suction side of the compressor from, and when the low pressure sensor for detecting the low pressure refrigerant pressure of the compressor is abnormal,
By including the capacity control means for controlling the operating capacity of the compressor on the basis of the low-pressure refrigerant pressure predicted by the prediction means, even if the low-pressure sensor becomes abnormal, the capacity control of the compressor is appropriately performed regardless of the abnormality. Can be maintained at.

According to the third aspect of the present invention, the injection circuit is configured to supply the liquid refrigerant to the compressor without depressurizing it during operation, so that the flow rate is prevented from lowering due to depressurization. At the time of the operation of 1, the superheat degree of the refrigerant sucked into the compressor can be rapidly reduced, and the low-pressure refrigerant pressure of the refrigerant sucked can be predicted quickly.

[Brief description of drawings]

FIG. 1 is a refrigerant circuit diagram showing a refrigeration system according to an embodiment of the present invention.

FIG. 2 is a flowchart showing a control operation of an injection control unit.

FIG. 3 is a flowchart showing control operations of a prediction unit, an abnormality determination unit, and a capacity control unit.

[Explanation of symbols]

(10) Refrigeration equipment (11) Outdoor unit (13) Refrigerant circuit (15) Compressor (25) Injection circuit (33) Suction side temperature sensor (temperature sensor) (34) Low pressure sensor (54) Capacity control unit (capacity control means) (55) Abnormal control section

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Satoru Sakie             1304 Kanaoka-cho, Sakai City, Osaka Prefecture Daikin Industries             Sakai Plant Kanaoka Factory

Claims (3)

[Claims] 1. A refrigerant circuit (13) comprising a compressor (15) for performing a vapor compression refrigeration cycle, and a liquid refrigerant supplied to the suction side of the compressor (15) provided in the refrigerant circuit (13). Injection circuit (25), a temperature sensor (33) that detects the temperature of the refrigerant sucked into the compressor (15), and a suction that the temperature sensor (33) detects when the liquid refrigerant is supplied by the injection circuit (25). The predicting means (52) for predicting the low-pressure refrigerant pressure on the suction side of the compressor (15) from the refrigerant temperature and the low-pressure sensor (34) for detecting the low-pressure refrigerant pressure of the compressor (15), the predicting means when there is an abnormality. A refrigeration system comprising: a capacity control means (54) for controlling the operating capacity of the compressor (15) based on the low-pressure refrigerant pressure predicted by (52). 2. A refrigerant circuit (13) including a compressor (15) for performing a vapor compression refrigeration cycle; a low pressure sensor (34) for detecting a low pressure refrigerant pressure on the suction side of the compressor (15); A capacity control means (54) for controlling the operating capacity of the compressor (15) based on the low-pressure refrigerant pressure detected by the low-pressure sensor (34), and a temperature for detecting the suction refrigerant temperature of the compressor (15). The sensor (33) and the compressor (15) operate so as to intermittently supply the liquid refrigerant to the suction side of the compressor (15) when the degree of superheat of the refrigerant discharged from the compressor (15) exceeds a predetermined value. An injection circuit (25), and a prediction means (52) for predicting the low pressure refrigerant pressure when the injection circuit (25) is in operation, using the suction refrigerant temperature detected by the temperature sensor (33) as the low temperature refrigerant pressure equivalent saturation temperature. And the capacity control means (54), Note that when the low pressure sensor (34) is abnormal, an abnormality control unit that controls the operating capacity of the compressor (15) based on the low pressure refrigerant pressure predicted by the prediction means (52) instead of the low pressure sensor (34). A refrigerating apparatus comprising (55). 3. The refrigerating apparatus according to claim 1, wherein the injection circuit (25) is configured to supply the liquid refrigerant to the compressor (15) without depressurizing the liquid refrigerant during operation.