JP2008076017A - Refrigerating device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a constitution for accurately controlling humidity in response to the outlet gas temperature of a compressor even in a low flow rate area, in a refrigerating device having a high pressure domed compressor. <P>SOLUTION: The outlet gas temperature Tp1 is determined from suction side superheat and delivery pressure of the compressors 11a, 11b and 11c (Step S1). The outlet gas temperature Tp2 is determined based on the temperature of a delivery pipe of the compressors 11a, 11b and 11c (Step S2). While injecting liquid into the suction side of the compressors 11a, 11b and 11c with the higher temperature as the outlet gas temperature among the Tp1 and Tp2 when the delivery pipe temperature Td is smaller than a predetermined value (Step S4), a liquid injection quantity is controlled based on a time variation in the delivery pipe temperature Td when the delivery pipe temperature Td is the predetermined value or more and predetermined superheat is not applied to the suction side (Step S6). <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a refrigeration apparatus provided with a high-pressure dome type compressor, and relates to a control technology of discharge gas temperature of the compressor.

  Conventionally, as a refrigerant of a refrigeration apparatus, R404A, which is difficult to raise the discharge gas temperature, as disclosed in Patent Document 1, for example, has been used in the field of refrigeration and refrigeration. However, this R404A has disadvantages such as high GWP (global warming potential), poor theoretical COP, high cost, and large pressure loss compared to other typical HFC refrigerants. It is not a good refrigerant.

In contrast, R410A, a high-pressure refrigerant that has been widely used in the field of air conditioning, has advantages over R404A, such as lower GWP, better theoretical COP, and lower pressure loss than R404A. There are many.
JP 2000-193328 A

  However, since the discharge gas temperature of R410A is higher than that of R404A due to its physical properties, it is necessary to provide means for reliably reducing the discharge gas temperature in order to use it in the refrigeration / refrigeration field.

  As a means for reducing the discharge gas temperature, for example, it may be possible to perform wet control such as injecting liquid refrigerant on the suction side of the compressor, but a low-pressure dome type compressor in which lubricating oil is stored in the low-pressure dome. On the other hand, when the moisture control on the suction side (low pressure side) is performed, the lubricating oil in the compressor is diluted and the lubricating performance of the sliding portion is impaired.

  Therefore, when R410A is used as a refrigerant, it is necessary to use a high-pressure dome type compressor in which lubricating oil is stored in the high-pressure dome and the lubricating oil is not diluted even when the suction side of the compressor is moistened.

  By the way, when performing the wetness control as described above, generally, the refrigeration apparatus is configured to detect the temperature of the discharge pipe of the compressor and perform control based on the temperature. In the case of the high-pressure dome type compressor connected to the dome, the temperature of the discharge pipe is delayed with respect to the temperature change of the high-pressure dome, and at a timing delayed from the actual state due to the response delay. There was a problem of wetness control.

  In particular, in the low circulation amount region where the flow rate is small, the delay in response of the discharge pipe temperature tends to be large, and it is difficult to accurately control the humidity according to the outlet gas temperature.

  The present invention has been made in view of such a point, and in a refrigeration apparatus including a high-pressure dome-type compressor, a configuration capable of accurately performing wetness control according to the outlet gas temperature of the compressor even in a low flow rate region. The purpose is to obtain.

  In order to achieve the above object, in the refrigeration apparatus according to the present invention, the compressor (11a, 11b, 11c, 101a, 101b, 101c) is a compressor ( 11a, 11b, 11c, 101a, 101b, 101c) is controlled to be wet on the suction side.

  Specifically, the first invention includes a high-pressure dome type compressor (11a, 11b, 11c, 101a, 101b, 101c), a heat source side heat exchanger (13), and a use side heat exchanger (16, The refrigeration apparatus including the refrigerant circuit (20, 160, 204) connected to 17) is a target.

  And discharge pipe temperature detecting means (19a, 19b, 19c, 19d, 19e, 19f) for detecting the temperature of the discharge pipe of the compressor (11a, 11b, 11c, 101a, 101b, 101c), and the compression By the discharge pipe temperature detecting means (19a, 19b, 19c, 19d, 19e, 19f) so that the outlet gas temperature (Tp) of the machine (11a, 11b, 11c, 101a, 101b, 101c) is below a predetermined temperature. And outlet gas temperature control means (80, 90, 180, 190, 280, 290) for controlling the outlet gas temperature (Tp) based on the detected time variation of the discharge pipe temperature (Td).

  As described above, in the high-pressure dome type compressor (11a, 11b, 11c, 101a, 101b, 101c) with the discharge pipe provided in the casing, the followability of the change in the discharge pipe temperature (Td) with respect to the temperature change of the outlet gas Therefore, if the outlet gas temperature (Tp) is controlled based on the value of the discharge pipe temperature (Td), it will be controlled at a temperature different from the actual outlet gas temperature (Tp). (Tp) cannot be controlled, but if the control is based on the time variation of the temperature of the discharge pipe as in the above configuration, the degree of increase or decrease in the outlet gas temperature (Tp) Therefore, the outlet gas temperature (Tp) can be controlled more accurately than the conventional method based on the value of the discharge pipe temperature (Td).

  As another conventional method of estimating the outlet gas temperature (Tp), there is a method of estimating the outlet gas temperature (Tp) using the heating degree and the discharge pressure on the suction side. In this case, the outlet gas temperature (Tp) cannot be estimated accurately. On the other hand, by considering the time variation of the discharge pipe temperature (Td) as described above, the outlet gas temperature (Tp) can be estimated with higher accuracy even when the suction side is wet.

  Therefore, by considering the tendency of the temperature change of the discharge pipe as described above, it is possible to control the outlet gas temperature in accordance with the actual state rather than controlling based on the value of the discharge pipe temperature (Td).

  In the above-described configuration, the outlet gas temperature control means (80, 90, 180, 190) includes a liquid injection circuit (80, 180) for injecting liquid refrigerant into the suction side of the compressor (11a, 11b, 11c, 101a, 101b, 101c). And the injection amount of the liquid injection circuit (80, 180) is adjusted based on the amount of time variation of the discharge pipe temperature (Td) (second invention).

  By controlling the liquid injection amount based on the time variation of the discharge pipe temperature (Td) in this way, the suction side of the compressor (11a, 11b, 11c, 101a, 101b, 101c) is moistened without excess or deficiency. The outlet gas temperature (Tp) of the compressor (11a, 11b, 11c, 101a, 101b, 101c) can be reliably reduced to a predetermined temperature or lower.

  The compressor (11a, 11b, 11c, 101a, 101b, 101c) further includes superheat degree detection means (24, 18a, 90, 190) for detecting the superheat degree of the refrigerant sucked into the compressor (11a, 11b, 11c, 101a, 101b, 101c). When the superheat degree detected by the superheat degree detection means (24,18a, 90,190) becomes smaller than a predetermined value, the control means (80,90,180,190) is based on the time variation of the discharge pipe temperature (Td). It is preferable that the injection amount is adjusted (third invention).

  Here, the predetermined value is a degree of superheat at which the refrigerant on the suction side of the compressor (11a, 11b, 11c, 101a, 101b, 101c) becomes dry (for example, a state of superheat less than 5 degrees is continuous). It means the lower limit of 10 seconds or more, or the state of superheat less than 3 degrees is continuous 5 seconds).

  That is, when the degree of superheat is greater than a predetermined value, that is, when the refrigerant on the suction side of the compressor (11a, 11b, 11c, 101a, 101b, 101c) is dry, the compressor (11a, 11b, 11c , 101a, 101b, 101c), it is possible to estimate the outlet gas temperature (Tp) based on the superheat degree on the suction side and control the liquid injection amount, but the superheat degree is smaller than the predetermined value and compression is performed. When the refrigerant on the suction side of the machine (11a, 11b, 11c, 101a, 101b, 101c) is moist, the outlet gas temperature (Tp) cannot be accurately estimated from the degree of superheat on the suction side. As described above, by controlling based on the amount of change in the discharge pipe temperature (Td) over time, it is possible to perform control in accordance with the actual change in the outlet gas temperature (Tp).

  On the other hand, as described above, liquid injection is not performed on the suction side of the compressor, but the outlet gas temperature control means (280, 290) is placed in the intermediate pressure compression chamber of the compressor (11a, 11b, 11c). A liquid injection circuit (280) for injecting the refrigerant is provided, and when the discharge pipe temperature (Td) is equal to or higher than a predetermined value, the liquid injection circuit (280 ) May be adjusted (fourth invention).

  Here, the predetermined value means a discharge pipe temperature at which the outlet gas temperature (Tp) needs to be accurately controlled by adjusting the liquid injection amount.

  That is, when the discharge pipe temperature (Td) is equal to or higher than a predetermined value and the outlet gas temperature (Tp) needs to be accurately controlled, the liquid injection amount is controlled based on the time variation of the discharge pipe temperature (Td). By doing so, the outlet gas temperature (Tp) can be controlled with higher accuracy, and the outlet gas temperature (Tp) can be surely set to a predetermined temperature or lower.

  The outlet gas temperature control means (80, 90, 180, 190, 280, 290) is connected to the compressor (11a, 11b, 11c, 101a, 101b, 101c) when the time variation of the discharge pipe temperature (Td) is zero or more. The liquid injection amount of the compressor is increased while the amount of liquid injection to the compressor (11a, 11b, 11c, 101a, 101b, 101c) is decreased when the time variation is negative. (5th invention). Thereby, since the liquid injection amount can be adjusted according to the tendency of the discharge pipe temperature (Td) to change with time, the outlet gas temperature (Tp) can be controlled easily and accurately.

  In the above configuration, the outlet gas temperature control means (80, 90, 180, 190, 280, 290) is configured such that the discharge pipe temperature (Td) is increased and the time variation of the discharge pipe temperature (Td) is greater than a first predetermined amount. It is preferable that the rate of increase of the liquid injection amount per unit time is increased as compared with the case where the time change amount is equal to or less than the first predetermined amount (sixth invention).

  Here, the first predetermined amount means an upper limit of the temporal change amount of the discharge pipe temperature so that the outlet gas temperature (Tp) does not need to be quickly lowered.

  That is, when the discharge pipe temperature (Td) rises and the time change amount of the discharge pipe temperature (Td) is larger than the first predetermined amount, the outlet gas temperature (Tp) needs to be quickly lowered. Therefore, the increase rate per unit time of the liquid injection amount is made larger than when the amount of change with time is equal to or less than the first predetermined amount, so that the liquid injection amount is increased rapidly. Thereby, the outlet gas temperature (Tp) can be more reliably reduced to a predetermined temperature or lower.

  Further, the outlet gas temperature control means (80, 90, 180, 190, 280, 290) is configured such that when the discharge pipe temperature (Td) is lowered and the time change amount of the discharge pipe temperature (Td) is smaller than a second predetermined amount. It is preferable that the rate of decrease of the liquid injection amount per unit time is increased as compared with the case where the time change amount is equal to or greater than the second predetermined amount (seventh invention).

  Here, the second predetermined amount means the lower limit of the amount of change over time in the discharge pipe temperature so that the outlet gas temperature (Tp) does not need to be raised immediately.

  That is, when the discharge pipe temperature (Td) is decreased and the time change amount of the discharge pipe temperature (Td) is smaller than the second predetermined amount, the suction-side refrigerant is further moistened. Is not preferable, and the rate of decrease of the liquid injection amount per unit time is made larger than when the amount of change with time is equal to or greater than the second predetermined amount, so that the liquid injection amount is rapidly reduced. As a result, it is possible to reliably prevent the refrigerant on the suction side from getting wet in vain.

  Further, the use side heat exchangers (16, 17) are preferably cooling heat exchangers for cooling the interior (eighth invention). As described above, in the case of the refrigeration apparatus (1,150,201) used for refrigeration / freezing, the outlet gas temperature (Tp) of the compressor (11a, 11b, 11c, 101a, 101b, 101c) becomes high. By providing the gas temperature control means (80, 90, 180, 190, 280, 290), the outlet gas temperature (Tp) of the compressor (11a, 11b, 11c, 101a, 101b, 101c) can be reliably lowered.

  The refrigerating apparatus (150) includes a compressor (11a, 11b, 11c, 101a, 101b, 101c), a low stage compressor (101a, 101b, 101c) and a high stage compressor (11a, 11b). 11c), and the outlet gas temperature control means (80, 90, 180, 190) is at least one of the low-stage compressor (101a, 101b, 101c) and the high-stage compressor (11a, 11b, 11c). The outlet gas temperature (Tp) of the one compressor may be controlled based on the amount of change in the discharge pipe temperature (Td) over time (the ninth invention).

  Thus, also in the refrigeration apparatus (150) that performs the two-stage compression operation, the low-stage compressor (101a, 101b, 101c) and the high-stage compressor (11a) are controlled by the outlet gas temperature control means (80, 90, 180, 190). , 11b, 11c) of the high stage compressor (11a, 11b, 11c) by controlling the outlet gas temperature (Tp) of at least one of the discharge pipe temperature (Td) based on the time variation of the discharge pipe temperature (Td). The outlet gas temperature (Tp) can be reliably lowered.

  One of R410A and CO2 is used as the refrigerant (tenth invention). Thus, even when R410A or CO2 is used as the refrigerant, the outlet gas temperature (Tp) of the compressor (11a, 11b, 11c, 101a, 101b, 101c) can be ensured by adopting the configuration as in each of the above-described inventions. Can be reduced.

  As described above, according to the refrigeration apparatus (1,150,201) according to the present invention, the outlet is based on the amount of time variation of the discharge pipe temperature (Td) in the high-pressure dome type compressor (11a, 11b, 11c, 101a, 101b, 101c). Since the outlet gas temperature control means (80, 90, 180, 190, 280, 290) controls the outlet gas temperature (Tp) so that the gas temperature (Tp) is lower than the predetermined temperature, the outlet gas temperature (Tp) is determined from the discharge pipe temperature (Td). ), And the outlet gas temperature (Tp) can be controlled more accurately than when the outlet gas temperature (Tp) is estimated from the superheating degree on the suction side and the discharge pressure. The outlet gas temperature (Tp) can be reliably reduced.

  Further, according to the second invention, the liquid injection amount to the suction side of the compressor (11a, 11b, 11c, 101a, 101b, 101c) is adjusted based on the time change amount of the discharge pipe temperature (Td). As a result, the outlet gas temperature (Tp) of the compressor (11a, 11b, 11c, 101a, 101b, 101c) can be reliably reduced.

  According to the third invention, when the superheat degree of the refrigerant on the suction side of the compressor (11a, 11b, 11c, 101a, 101b, 101c) becomes smaller than a predetermined value, the time of the discharge pipe temperature (Td) is reached. Since the liquid injection amount is adjusted based on the amount of change, the outlet gas temperature (Tp) can be estimated more accurately and the outlet gas temperature (Tp) even when the degree of superheat is small and the refrigerant on the suction side is moist. ) Can be reliably kept below a predetermined temperature.

  Further, according to the fourth invention, when the discharge pipe temperature (Td) is equal to or higher than a predetermined value, the liquid injection amount into the compression chamber of the intermediate pressure of the compressor (11a, 11b, 11c) is calculated as the discharge pipe temperature. (Td) is adjusted based on the amount of change over time, so that the outlet gas temperature (Tp) can be reliably set to the predetermined temperature even in the configuration in which liquid injection is performed into the compression chamber of the intermediate pressure of the compressor (11a, 11b, 11c). It can be:

  According to the fifth aspect of the invention, the liquid injection amount is increased if the time change amount of the discharge pipe temperature (Td) is zero or more, and the liquid injection amount is decreased if the time change amount is negative. The outlet gas temperature (Tp) can be controlled easily and reliably using the time variation of the discharge pipe temperature (Td).

  Further, according to the sixth aspect of the present invention, when the amount of time change in the discharge pipe temperature (Td) is larger than the first predetermined amount, the rate of increase per unit time of the liquid injection amount is increased. Therefore, even when the outlet gas temperature (Tp) is rising rapidly, the liquid injection amount can be increased rapidly accordingly, and the outlet gas temperature (Tp) can be reliably reduced.

  In addition, according to the seventh invention, when the time variation of the discharge pipe temperature (Td) is smaller than the second predetermined amount, the reduction rate per unit time of the liquid injection amount is increased. Therefore, when the outlet gas temperature (Tp) suddenly decreases, the amount of liquid injection can be reduced to reliably prevent the intake-side refrigerant from getting wet wastefully.

  Further, according to the eighth invention, even if the use side heat exchanger (16, 17) is a cooling heat exchanger that cools the inside of the refrigerator, by adopting the configuration of each invention as described above, the compressor The outlet gas temperature (Tp) of (11a, 11b, 11c, 101a, 101b, 101c) can be reliably reduced.

  According to the ninth invention, the compressor (11a, 11b, 11c, 101a, 101b, 101c) is composed of a low-stage compressor (101a, 101b, 101c) and a high-stage compressor (11a, 11b, 11c). In the refrigeration apparatus (150) configured to perform the two-stage compression operation, at least one outlet of the low-stage compressor (101a, 101b, 101c) and the high-stage compressor (11a, 11b, 11c) Since the gas temperature (Tp) is configured to be controlled based on the time variation of the discharge pipe temperature (Td), the outlet gas temperature (Tp) of the high-stage compressor (11a, 11b, 11c) is ensured. Can be lowered.

  Furthermore, according to the tenth invention, even when R410A or CO2 is used as the refrigerant, the outlet gas temperature of the compressor (11a, 11b, 11c, 101a, 101b, 101c) can be obtained by adopting the above-described configuration. (Tp) can be reliably reduced.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. It should be noted that the following description of the preferred embodiment is merely illustrative in nature and is not intended to limit the present invention, its application, or its use.

Embodiment 1
-Configuration of refrigeration equipment-
As shown in FIG. 1, Embodiment 1 of the present invention is a refrigeration apparatus (1) that performs cooling operation of a refrigerator or a cooling room, and includes an outdoor unit (2), a refrigeration unit (3), a controller (90), It has.

  In the refrigeration apparatus (1), the outdoor unit (2) is provided with an outdoor circuit (20), and the refrigeration unit (3) is provided with a refrigerator internal circuit (30, 30). In the refrigeration apparatus (1), the gas end side of the outdoor circuit (20) is connected to the gas end side of the refrigerator internal circuit (30, 30) by a gas side communication pipe (22), and the outdoor circuit ( 20) is connected to the liquid end side of the above refrigerator internal circuit (30, 30) via the liquid side connecting pipe (21), so that the refrigerant circuit (10) of the vapor compression refrigeration cycle is configured. Yes. Note that the refrigerant in the present embodiment is a high-pressure refrigerant R410A.

<Outdoor unit>
The outdoor circuit (20) of the outdoor unit (2) includes three compressors (11a, 11b, 11c), an outdoor heat exchanger (13), a receiver (14), and a refrigerant heat exchanger (50). A first expansion valve (45), a second expansion valve (46), and a third expansion valve (47). The outdoor circuit (20) is provided with a four-way switching valve (12), a liquid side closing valve (53), and a gas side closing valve (54). Here, one end of the liquid side connecting pipe (21) is connected to the liquid side closing valve (53), and one end of the gas side connecting pipe (22) is connected to the gas side closing valve (54). ing.

  The three compressors (11a, 11b, 11c) are connected in parallel to each other in the refrigerant circuit (10). Each of the three compressors (11a, 11b, 11c) is a high-pressure dome type scroll compressor, and the first compressor (11a) and the second compressor (11b) are compressions with fixed operating capacities. On the other hand, the third compressor (11c) is configured to be supplied with electric power through an inverter, and the operating capacity is variable by changing the output frequency of the inverter. . Of the three compressors (11a, 11b, 11c), the variable capacity third compressor (11c) is preferentially driven during the operation of the refrigeration apparatus (1), and the refrigeration apparatus (1) is used. The second compressor (11b) and the first compressor (11a) are sequentially driven in accordance with the operation status on the side.

  A suction main pipe (55) is connected to the suction side of each of the first to third compressors (11a, 11b, 11c) via each suction branch pipe (61a, 61b, 61c). Specifically, the suction main pipe (55) has one end connected to the four-way switching valve (12) and the other end provided with a main branch portion (92). The suction main pipe (55) is connected to the one end of the first suction branch pipe (61a) and one end of the suction connection pipe (56) at the main branch portion (92), and the first suction branch pipe (61a) Is connected to the suction side of the first compressor (11a). On the other hand, the suction connection pipe (56) is provided with a sub-branch portion (94) at the other end, and in the sub-branch portion (94), one end of the second suction branch pipe (61b) and the third suction branch pipe (61c ) Is branched and connected. The other end of the second suction branch pipe (61b) is connected to the suction side of the second compressor (11b), while the other end of the third suction branch pipe (61c) is connected to the third compressor. (11c) connected to the suction side.

  A discharge main pipe (64) is connected to the discharge side of the three compressors (11a, 11b, 11c). Specifically, one end of the discharge main pipe (64) is connected to the four-way switching valve (12), while the other end is connected to the first discharge branch pipe (64a) and the second discharge branch pipe (64b). It branches off to the third discharge branch pipe (64c). The first discharge branch pipe (64a) is connected to the discharge side of the first compressor (11a), and the second discharge branch pipe (64b) is connected to the discharge side of the second compressor (11b), The third discharge branch pipe (64c) is connected to the discharge side of the third compressor (11c). Each discharge branch pipe (64a, 64b, 64c) has a check valve (CV-1, which allows only the refrigerant flow from each compressor (11a, 11b, 11c) to the four-way selector valve (12). CV-2 and CV-3) are provided respectively.

  The outdoor heat exchanger (13) is a cross-fin type fin-and-tube heat exchanger that exchanges heat between the refrigerant and the outdoor air. The outdoor heat exchanger (13) has one end connected to the four-way switching valve (12) and the other end connected to the top of the receiver (14) via the first liquid pipe (81). The first liquid pipe (81) is provided with a check valve (CV-4) and a shut-off valve (57) that allow only the refrigerant to flow from the outdoor heat exchanger (13) to the receiver (14). ing. On the other hand, one end of the second liquid pipe (82) is connected to the bottom of the receiver (14).

  The refrigerant heat exchanger (50) is a plate heat exchanger, and performs heat exchange between the refrigerant and the refrigerant. The first flow path (50a) and the second flow path (50b) It has. One end of the first flow path (50a) of the refrigerant heat exchanger (50) is connected to the other end of the second liquid pipe (82), and the other end is connected to one end of the third liquid pipe (83). ing. The other end of the third liquid pipe (83) is connected to one end of the liquid side connecting pipe (21) via the liquid side closing valve (53). The third liquid pipe (83) is provided with a check valve (CV-5) that allows only the refrigerant to flow from the other end of the first flow path (50a) to the liquid side stop valve (53). It has been. The second liquid pipe (82) is provided with a closing valve (58).

  One end of a fourth liquid pipe (84) is connected to the third liquid pipe (83) between the check valve (CV-5) and the refrigerant heat exchanger (50). The other end of (84) is connected to one end of the second flow path (50b) of the refrigerant heat exchanger (50). The second expansion valve (46) and the closing valve (59) are provided on the fourth liquid pipe (84). The second expansion valve (46) is an electronic expansion valve whose opening degree can be adjusted, and is configured to control supercooling by adjusting the flow rate of the refrigerant flowing through the fourth liquid pipe (84). ing.

  The other end of the second flow path (50b) of the refrigerant heat exchanger (50) is connected to the suction main pipe (55) through a gas injection pipe (85). The gas injection pipe (85) is for injecting a gas refrigerant into the suction side of the compressor (11a, 11b, 11c).

  In the third liquid pipe (83), one end of a fifth liquid pipe (88) is connected between the check valve (CV-5) and the liquid side stop valve (53). The other end of the fifth liquid pipe (88) is connected between the check valve (CV-4) and the receiver (14) in the first liquid pipe (81). The fifth liquid pipe (88) is provided with a check valve (CV-6) that allows only the refrigerant to flow from one end to the other end.

  One end of the sixth liquid pipe (89) is connected between one end of the fourth liquid pipe (84) and the second expansion valve (46), and the other end of the sixth liquid pipe (89) is The first liquid pipe (81) is connected between the other end of the outdoor heat exchanger (13) and the check valve (CV-4). The sixth liquid pipe (89) is provided with a first expansion valve (45) composed of an electronic expansion valve whose opening degree is adjustable.

  One end of a communication pipe (78) is connected between the check valve (CV-4) and the connection part of the fifth liquid pipe (88) in the first liquid pipe (81). The other end of (78) is connected to the discharge main pipe (64). The communication pipe (78) is provided with a check valve (CV-7) that allows only the refrigerant to flow from the receiver (14) to the discharge main pipe (64).

  The four-way switching valve (12) has a first port at the discharge main pipe (64), a second port at the suction main pipe (55), a third port at one end of the outdoor heat exchanger (13), and a fourth port. Are connected to the gas-side closing valve (54), respectively. The four-way switching valve (12) is in a first state in which the first port and the third port communicate with each other and the second port and the fourth port communicate with each other (state indicated by a solid line in FIG. 1). ) And a second state (state indicated by a broken line in FIG. 1) in which the first port and the fourth port communicate with each other and the second port and the third port communicate with each other. ing.

  Further, the outdoor circuit (20) is provided with an oil separator (70), while three oil leveling pipes (72, 73, 74), a liquid injection circuit (80), and three oil recovery pipes (75 , 76, 77).

  The oil separator (70) is provided in the discharge main pipe (64) and separates refrigeration oil from the refrigerant discharged from the compressors (11a, 11b, 11c). The oil separator (70) is connected to the downstream side of the connection portion of the gas injection pipe (85) in the suction main pipe (55) via the oil return pipe (71). The oil return pipe (71) is provided with a solenoid valve (SV-1). When the solenoid valve (SV-1) is opened, the refrigerating machine oil separated by the oil separator (70) is sucked. It is configured to be returned to the main pipe (55).

  The three oil equalizing pipes (72, 73, 74) are composed of a first oil equalizing pipe (72), a second oil equalizing pipe (73), and a third oil equalizing pipe (74). The first oil equalizing pipe (72) has one end connected to a predetermined height position of the dome of the first compressor (11a), the other end connected to the suction connecting pipe (56), and an electromagnetic valve (SV-2). It has. The second oil equalizing pipe (73) has one end connected to a predetermined height position of the dome of the second compressor (11b), the other end connected to the third suction branch pipe (61c), and a solenoid valve ( SV-3). The third oil equalizing pipe (74) has one end connected to a predetermined height position of the dome of the third compressor (11c), the other end connected to the oil return pipe (71), and a solenoid valve ( SV-4). The first oil leveling pipe (72) may be connected to the suction main pipe (55), the second oil leveling pipe (73) may be connected to the second suction branch pipe (61b), and the third oil leveling pipe ( 74) may be directly connected to the third suction branch pipe (61c).

  The liquid injection circuit (80) includes a liquid injection main pipe (86) and first to fourth liquid injection branch pipes (86a, 86b, 86c, 86d). One end of the liquid injection main pipe (86) is connected between one end of the fourth liquid pipe (84) and a connection portion between the sixth liquid pipe (89) and the other end is a first liquid injection branch pipe ( 86a), one end of the second liquid injection branch pipe (86b) and the third liquid injection branch pipe (86c). The liquid injection main pipe (86) is provided with the third expansion valve (47) configured by an electronic expansion valve whose opening degree is adjustable. One end of the fourth liquid injection branch pipe (86d) is connected to the middle of the first liquid injection branch pipe (86a).

  Each of the first to fourth liquid injection branch pipes (86a, 86b, 86c, 86d) includes a capillary tube (87a, 87b, 87c, 87d). The first to third injection branch pipes (86a, 86b, 86c) are respectively connected at the other ends to the suction branch pipes (61a, 61b, 61c) of the first to third compressors (11a, 11b, 11c). 61c). As a result, the liquid refrigerant flowing through the third liquid pipe (83) flows through each liquid injection branch pipe (86a, 86b, 86c) via the fourth liquid pipe (84) and the liquid injection main pipe (86), and is compressed. Is supplied to the suction branch pipe (61a, 61b, 61c) of the machine (11a, 11b, 11c). On the other hand, the fourth liquid injection branch pipe (86d) is connected between the solenoid valve (SV-4) and the connection portion of the oil return pipe (71) in the third oil equalizing pipe (74). If the liquid refrigerant is supplied to the pipe on the suction side before branching in this way, the liquid refrigerant, together with the refrigerating machine oil, the first compressor (11a), the second compressor (11b), and the third compressor (11c) Therefore, even when the third compressor (11c) has a low output, the liquid refrigerant is pulled by the first and second compressors (11a, 11b) and the discharge temperature of the third compressor (11c). It is possible to prevent only the decrease.

  The three oil recovery pipes (75, 76, 77) include a first oil recovery pipe (75), a second oil recovery pipe (76), and a third oil recovery pipe (77). One end of the first oil recovery pipe (75) is between the connection portion and the other end of the first liquid injection branch pipe (86a) in the first suction branch pipe (61a) of the first compressor (11a). It is connected. One end of the second oil recovery pipe (76) is between the connection portion and the other end of the second liquid injection branch pipe (86b) in the second suction branch pipe (61b) of the second compressor (11b). It is connected. One end of the third oil recovery pipe (77) is connected between the connection portion and one end of the third liquid injection branch pipe (86c) in the third suction branch pipe (61c) of the third compressor (11c). Has been. The other ends of the oil recovery pipes (75, 76, 77) are joined together.

  The outdoor circuit (20) is provided with various sensors and pressure switches (95a, 95b, 95c, 95d). Specifically, the suction pressure sensor (25) and the suction temperature sensor (24) are provided in the suction main pipe (55), the discharge pressure sensor (23) is provided in the discharge main pipe (64), and the discharge pipe temperature detection means Each discharge temperature sensor (19a, 19b, 19c) is provided in each discharge branch pipe (64a, 64b, 64c). Moreover, the temperature sensor (51) is provided in the connection part of the 1st flow path (50a) of the refrigerant | coolant heat exchanger (50) in a 3rd liquid pipe (83). In addition, a pressure switch (95a, 95b, 95c, 95d) is provided in the pipe between the gas side shut-off valve (54) and the four-way switching valve (12) and in each discharge branch pipe (64a, 64b, 64c). Is provided.

  Furthermore, the outdoor unit (2) is provided with an outdoor air temperature sensor (13a) and an outdoor fan (13f). Outdoor air is sent to the outdoor heat exchanger (13) by the outdoor fan (13f).

<Refrigerator unit>
As shown in FIG. 1, in the refrigeration unit (3), the refrigerator internal circuits (30, 30) are provided in parallel, and each circuit includes a refrigeration heat exchanger (16, 17) and a drain pan. A heater (26, 27) and a refrigeration expansion valve (15a, 15b) are provided.

  Each of the refrigeration heat exchangers (16, 17) is the same fin-and-tube heat exchanger of the same cross fin type, and performs heat exchange between the refrigerant and the air in the cooling chamber. One end of each refrigeration heat exchanger (16, 17) is connected to one end of each drain pan heater (16, 17) via each refrigeration expansion valve (15a, 15b), and the other end is connected to each gas side branch pipe ( 22a, 22b) is connected to one end. And each gas side branch piping (22a, 22b) mutually joins in the other end, and is connected to the other end of the said gas side connection piping (22).

  Each said refrigeration expansion valve (15a, 15b) is comprised with the electronic expansion valve which can adjust an opening degree. Each of the refrigeration heat exchangers (16, 17) is provided with a first refrigerant temperature sensor (16b, 17b) for measuring the evaporation temperature of the refrigerant, while each of the refrigeration heat exchangers (16, 17) A second refrigerant temperature sensor (18a, 18b) is provided at the other end. In the refrigeration expansion valve (15a, 15b), the measured temperature of the second refrigerant temperature sensor (18a, 18b) is a predetermined temperature (for example, higher than the evaporation temperature of the refrigerant measured by the first refrigerant temperature sensor (16b, 17b)). The opening degree is adjusted to be higher by 5 ° C.).

  The drain pan heaters (26, 27) are arranged in a drain pan of a refrigeration heat exchanger (16, 17) (not shown), and a high-temperature and high-pressure refrigerant flows to heat the drain pan to prevent frost formation and ice formation. Is. The other end of each drain pan heater (26, 27) is connected to one end of each liquid side branch pipe (21a, 21b), and the other end of each liquid side branch pipe (21a, 21b) joins each other. It is connected to the other end of the liquid side connecting pipe (21).

  The refrigeration unit (3) is provided with a cooling chamber temperature sensor (16a, 17a) and a cooling chamber fan (16f, 17f). Air in the cooling chamber is sent to the refrigeration heat exchangers (16, 17) by the cooling chamber fans (16f, 17f).

<Controller>
The controller (90) switches various valves (SV-1, SV-2, SV-3, SV-4, 45, 46, 47, 15a, 15b) provided in the refrigerant circuit (10). While adjusting the opening, the compressors (11a, 11b, 11c) and the fans (13f, 16f, 17f) are driven to control the operation of the refrigeration apparatus (1).

  Specifically, the operation of the refrigeration apparatus (1) as described later is performed, and wetness control is performed on the suction side of the compressor (11a, 11b, 11c) based on the flow shown in FIGS. And configured to control the outlet gas temperature.

-Driving action-
First, the operation of the refrigeration apparatus (1) of this embodiment will be described.

  The refrigeration apparatus (1) is configured to perform a cooling operation in the cooling chamber, for example, at a set temperature of 5 ° C.

<Cooling operation>
In the cooling operation, as shown in FIG. 2, the four-way switching valve (12) of the outdoor circuit (20) is set to the first state and the first expansion valve (45) is fully closed by the control of the controller (90). Is done. In this state, the first to third compressors (11a, 11b, 11c) are driven, and the refrigeration expansion valve (15a, 15b), the second expansion valve (46), and the third expansion valve (47). Is appropriately adjusted so that the refrigerant circulates in the direction of the solid arrow in FIG. 2, while the outdoor fan (13f) and the refrigeration fans (16f, 17f) are driven. In addition, the solenoid valve (SV-1) of the oil return pipe (71) is appropriately opened and closed by the controller (90), and the solenoid valve of each oil leveling pipe (72, 73, 74) is, for example, the first leveling pipe. The solenoid valve (SV-2) of the oil pipe (72), the solenoid valve (SV-3) of the second oil equalizing pipe (73), and the solenoid valve (SV-4) of the third oil equalizing pipe (74) are opened in this order. To be controlled.

  Specifically, the refrigerant discharged from the first to third compressors (11a, 11b, 11c) flows from the discharge branch pipes (64a, 64b, 64c) to the discharge main pipe (64), and the four-way switching valve ( 12) is sent to the outdoor heat exchanger (13). In the outdoor heat exchanger (13), the refrigerant dissipates heat to the outdoor air and is condensed and liquefied. The liquefied refrigerant flows through the first liquid pipe (81), passes through the receiver (14), flows into the second liquid pipe (82), and enters the first flow path (50a) of the refrigerant heat exchanger (50). Inflow. And the liquid refrigerant which flowed through the 1st channel (50a) flows through the 3rd liquid pipe (83), and a part of it is shown in the 4th liquid pipe as shown by the dashed line arrow (a, b) of Drawing 2. Flows into (84).

  A part of the refrigerant flowing into the fourth liquid pipe (84) is depressurized through the second expansion valve (46) as indicated by a broken line arrow (a), and the refrigerant heat exchanger (50) Heat is exchanged with the liquid refrigerant flowing into the two flow paths (50b) and flowing through the first flow path (50a) to evaporate, and the liquid refrigerant flowing through the first flow paths (50a) is cooled to a predetermined low temperature. Then, the liquid refrigerant flowing through the first flow path (50a) exchanges heat with the branched refrigerant flowing through the second flow path (50b), and is cooled to, for example, 15 ° C., and then the third liquid pipe (83) and It flows through the liquid side connecting pipe (21) via the liquid side closing valve (53) and flows into the refrigerator internal circuit (30). The branched liquid refrigerant in the second flow path (50b) evaporates and is injected into the suction main pipe (55) through the gas injection pipe (85).

  Further, the remaining part of the refrigerant that has flowed through the fourth liquid pipe (84) flows through the liquid injection main pipe (86) as indicated by the broken line arrow (b), and the third expansion valve (47) whose opening is adjusted. ) Through the liquid injection branch pipes (86a, 86b, 86c) and supplied to the suction branch pipes (61a, 61b, 61c) of the compressors (11a, 11b, 11c). Thereby, since the temperature of the suction side of each compressor (11a, 11b, 11c) can be lowered, the discharge gas temperature of each compressor (11a, 11b, 11c) can be reduced. Such suction-side wetness control is performed based on the flow shown in FIGS. 3 and 4 as described later.

  In the refrigerator internal circuit (30), the liquid refrigerant at about 15 ° C. is divided into the liquid side branch pipes (21a, 21b) and flows through the drain pan heaters (26, 27), thereby preventing the drain pan from frosting. The frost that has fallen into the drain pan from the refrigerated heat exchanger (16, 17) is surely melted. The liquid refrigerant flowing out of the drain pan heater (26, 27) is decompressed and expanded when passing through the refrigeration expansion valves (15a, 15b), and is introduced into the refrigeration heat exchangers (16, 17). In each of the refrigeration heat exchangers (16, 17), the refrigerant absorbs heat from the air in the cooling chamber and evaporates at an evaporation temperature of about −5 ° C., for example. Thereby, in the refrigeration unit (3), the air cooled by the refrigeration heat exchanger (16, 17) is supplied into the cooling chamber, and the temperature in the cooling chamber is maintained at the set temperature of 5 ° C.

  The gas refrigerant evaporated in each of the refrigeration heat exchangers (16, 17) flows through the gas side branch pipes (22a, 22b) and then joins in the gas side communication pipe (22). Thereafter, the gas refrigerant flows through the gas side communication pipe (22), and then flows through the suction main pipe (55) via the four-way switching valve (12). The refrigerant that has flowed through the suction main pipe (55) is divided into the first suction branch pipe (61a) and the suction connection pipe (56), and the refrigerant that has flowed through the first suction branch pipe (61a) is the first compressor. (11a) is inhaled and compressed. On the other hand, the refrigerant flowing through the suction connection pipe (56) is divided into the second suction branch pipe (61b) and the third suction branch pipe (61c), and the refrigerant flowing through the second suction branch pipe (61b) The refrigerant that has been sucked into the second compressor (11b) and compressed and has flowed through the third suction branch pipe (61c) is sucked into the third compressor (11c) and compressed.

<Outlet gas temperature control>
Next, the outlet side gas temperature control of each compressor (11a, 11b, 11c), which is a characteristic part of the present invention, will be described.

  In this embodiment, as described above, the liquid injection circuit (80) is provided on the suction side of each of the compressors (11a, 11b, 11c), and the refrigerant is wetted by liquid injection on the refrigerant on the suction side. The outlet gas temperature of each compressor (11a, 11b, 11c) is reduced.

  Here, when liquid injection is performed on the suction side of each of the compressors (11a, 11b, 11c), conventionally, the superheat (superheat) on the suction side detected by the suction temperature sensor (24) and the discharge on the high pressure side are conventionally used. A discharge temperature sensor that estimates the outlet gas temperature of each compressor (11a, 11b, 11c) based on the output of the pressure sensor (23) and detects the temperature of the discharge pipe of the compressor (11a, 11b, 11c) The outlet gas temperature is also estimated from the outputs of (19a, 19b, 19c), and the opening degree of the third expansion valve (47) is controlled so that the estimated outlet gas temperature is equal to or lower than a predetermined temperature. I have to.

  However, when the suction side is moistened by liquid injection, it becomes difficult to accurately estimate the outlet gas temperature based on the suction side superheat and the discharge pressure, and the high-pressure dome type compressor (11a, 11b, 11c) In this case, since the discharge pipe is provided in the casing and the temperature of the discharge pipe changes with respect to the outlet gas temperature, it is difficult to accurately estimate the outlet gas temperature based on the discharge pipe temperature. Become.

  Therefore, in the present invention, as in the flow shown in FIG. 3, the liquid injection amount is adjusted based on the time change amount of the discharge pipe temperature to reliably reduce the outlet gas temperature.

  Hereinafter, the flow of the outlet gas temperature control shown in FIG. 3 will be described.

  First, when the flow shown in FIG. 3 starts, in step S1, the superheat on the suction side of the compressor (11a, 11b, 11c) obtained from the output of the suction temperature sensor (24) and the discharge pressure sensor are obtained in the same manner as in the past. Based on the output of (23), the predicted value Tp1 of the outlet gas temperature is obtained.

  Next, in step S2, the predicted temperature difference between the discharge pipe temperature and the outlet gas temperature obtained from a function, a table or the like is added to the discharge pipe temperature detected by the discharge temperature sensor (19a, 19b, 19c). Obtain the predicted value Tp2 of the outlet gas temperature. Here, since the predicted temperature difference is a function of the flow rate through the compressor, it can be obtained based on the output value of the suction pressure sensor (25) and the rotational speed of the compressor.

  In subsequent step S3, it is determined whether or not the discharge pipe temperature Td detected by the discharge temperature sensor (19a, 19b, 19c) is smaller than a predetermined value. This predetermined value is a threshold value for determining whether or not superheat is being performed on the suction side. If the discharge pipe temperature Td is smaller than this predetermined value, superheat control on the suction side is performed. If the discharge pipe temperature Td is higher than the predetermined value, the suction side temperature is sufficiently high, and the refrigerant is gasified, so there is a high possibility that the superheat control on the suction side is not performed. to decide.

  Specifically, the predetermined value is determined by the estimated temperature difference between the discharge pipe temperature and the outlet gas temperature based on the port temperature of the compressor when the superheat is unnecessary on the suction side at about 100 ° C. This is a value obtained by subtracting the correction Td. The correction Td is determined by the function of the predicted temperature difference, and is set so as to increase when the circulation amount becomes low. Thereby, when the amount of circulation is low, the temperature difference between the discharge pipe temperature and the outlet gas temperature is deviated accordingly, and for example, the case where the outlet gas temperature is high even when the discharge pipe temperature is low can be considered.

  When it is determined in step S3 that the discharge pipe temperature Td is equal to or lower than the predetermined value (in the case of YES), the process proceeds to the subsequent step S4, and the predicted value of the outlet gas temperature obtained in steps S1 and S2 above. The liquid injection amount is controlled using the higher temperature of Tp1 and Tp2 as the current outlet gas temperature.

  Specifically, in step S4, the third expansion is performed so that the higher one of the predicted values Tp1 and Tp2 of the outlet gas temperature obtained in steps S1 and S2 becomes the target Tp (= 125 ° C.). Adjust the opening of the valve (47). At this time, the pulse command value (Pls command) to the third expansion valve (47) gradually increases / decreases at a predetermined rate (dPls) per unit time as Pls command value = current Pls + dPls (or -dPls). To do.

  And after adjusting the opening degree of a 3rd expansion valve (47) by said step S4, this flow is complete | finished, it returns to a start, and this flow is started again (return).

  On the other hand, when it is determined in step S3 that the discharge pipe temperature Td is larger than the predetermined value (in the case of NO), the process proceeds to step S5, and based on the output of the suction temperature sensor (24), It is determined whether or not the superheat on the suction side satisfies a predetermined condition (predetermined value). That is, in this step S5, either the state where the superheat is lower than 5 ° C. continues for 10 seconds or the state where the superheat is lower than 3 ° C. continues for 5 seconds is satisfied. If this is the case (YES), there is a possibility that the superheat on the suction side is insufficient and the refrigerant on the suction side of the compressor (11a, 11b, 11c) may be wet. Control based on the time variation of the discharge pipe temperature Td is performed. Thereafter, this flow is terminated, and the flow returns to the start and starts again (return).

  If it is determined in step S5 that the superheat is on the suction side than the above-described conditions (in the case of NO), the refrigerant on the suction side of the compressor (11a, 11b, 11c) is not wet. Since it is dry and the exit gas temperature based on the superheat obtained from the output of the suction temperature sensor (24) and the output of the discharge pressure sensor (23) can be predicted with a certain degree of accuracy, the process proceeds to step S4. The outlet gas temperature is controlled based on the predicted values Tp1 and Tp2 of the outlet gas temperature obtained in steps S1 and S2.

  Next, the control based on the time change of the discharge pipe temperature Td performed in step S6 will be described using the flow of FIG.

  When the control based on the time variation of the discharge pipe temperature Td is started in step S6, first, in step SA1, the current discharge pipe temperature Td, the discharge pipe temperature Td_4 20 seconds ago, the discharge pipe temperature Td_3 15 seconds ago, It is determined whether the difference between the discharge pipe temperature Td_2 10 seconds ago and the discharge pipe temperature Td_1 5 seconds ago is greater than 20 ° C., 15 ° C., 10 ° C., 5 ° C. (first predetermined amount). That is, in step SA1, it is determined whether or not the current discharge pipe temperature Td is higher than a predetermined discharge pipe temperature by a predetermined amount or more.

  If any one of the conditions is satisfied in step SA1 (YES), the process proceeds to step SA2 to determine a pulse command value (Pls command value) that determines the opening of the third expansion valve (47). Pls command value = Pls + dPls × α, and the opening of the third expansion valve (47) is increased as soon as possible so as to be larger than the pulse increment performed in step S4 in FIG. That is, when the above-described conditions are satisfied in Step SA1, the discharge pipe temperature Td is rapidly increased, so the outlet gas temperature is considered to be high, and the third expansion valve ( 47) Increase the amount of liquid injection rapidly by increasing the opening as much as possible. Thereby, the exit gas temperature of a compressor can be reduced effectively. Here, α is a value larger than 0, may be a constant, or may be a variable that changes in accordance with the amount of change over time in the discharge pipe temperature.

  On the other hand, if none of the conditions is satisfied (in the case of NO) in step SA1, the process proceeds to step SA3 to determine whether or not the discharge pipe temperature Td tends to increase. That is, in step SA3, as in step SA1, it is determined whether the temperature difference between the current discharge pipe temperature Td and the past discharge pipe temperatures Td_4, Td_3, Td_2, Td_1 is 0 ° C. or more.

  If it is determined in step SA3 that the temperature increase of the discharge pipe temperature Td is 0 ° C. or more (in the case of YES), the process proceeds to the subsequent step SA4, where the opening of the third expansion valve (47) is increased. The determined pulse command value (Pls command value) is Pls command value = Pls + dPls, and the opening of the third expansion valve (47) is gradually increased.

  When it is determined in step SA3 that the discharge temperature Td tends to decrease (in the case of NO), the process proceeds to step SA5, and the current discharge pipe temperature Td and the past discharge are determined as in steps SA1 and SA3. It is determined whether the temperature differences from the tube temperatures Td_4, Td_3, Td_2, and Td_1 are smaller than −20 ° C., −15 ° C., −10 ° C., and −5 ° C. (second predetermined amount), respectively.

  If it is determined in step SA5 that the above-described conditions are satisfied (in the case of YES), it is determined that the outlet gas temperature of the compressor is low because the discharge pipe temperature Td has greatly decreased. Subsequently, in step SA6, the pulse command value (Pls command value) for determining the opening of the third expansion valve (47) is set to Pls command value = Pls + dPls × (−β), and the opening of the third expansion valve (47). To reduce the amount of liquid injection. As a result, the outlet gas temperature can be controlled more accurately following the decrease in the outlet gas temperature, and the refrigerant on the suction side of the compressor (11a, 11b, 11c) can be prevented from being wetted wastefully. it can. Here, β is a value larger than 0, may be a constant, or may be a variable that changes according to the amount of time change of the discharge pipe temperature Td.

  On the other hand, if it is determined in step SA5 that the above condition is not satisfied (in the case of NO), the process proceeds to step SA7 to determine the pulse command value (Pls) for determining the opening of the third expansion valve (47). (Command value) is set to Pls command value = Pls−dPls, and the opening of the third expansion valve (47) is gradually reduced.

  Then, after setting the pulse command value (Pls command value) as described above, the flow of FIG. 4 is ended, the flow returns to the flow of FIG. 3 (return), and the flow of FIG. 3 is started again.

  The controller (90) and the liquid injection circuit (80) that perform the control as described above constitute the outlet gas temperature control means of the present invention.

-Effect of Embodiment 1-
As described above, according to the first embodiment, the liquid injection circuit (80) is provided on the suction side of the compressor (11a, 11b, 11c), and the third expansion valve (47) provided in the liquid injection main pipe (86). Is controlled according to the wet state on the suction side of the compressor (11a, 11b, 11c), so that the outlet gas temperature of the compressor (11a, 11b, 11c) tends to be high. Even when R410A is used, the outlet gas temperature can be reliably reduced.

  That is, when the superheat on the suction side of the compressor (11a, 11b, 11c) does not satisfy a predetermined condition and the refrigerant on the suction side is in a wet state, the compressor (11a, 11b, The state of the outlet gas temperature is predicted based on the time variation of the discharge pipe temperature Td in 11c), and the opening degree of the third expansion valve (47) is adjusted. On the other hand, when the superheat on the suction side of the compressor (11a, 11b, 11c) satisfies the predetermined condition and the refrigerant on the suction side is in a dry state, the compressor (11a, 11b, 11c), the predicted value Tp1 of the outlet gas temperature determined from the superheat on the suction side determined from the suction temperature of the compressor 11b, 11c) and the discharge pressure of the compressor (11a, 11b, 11c), the predicted value determined from the discharge pipe temperature Tp The opening of the third expansion valve (47) was adjusted using the higher temperature of Tp2.

  Thus, when the refrigerant on the suction side of the compressor (11a, 11b, 11c) is dry and the outlet gas temperature can be accurately predicted from the superheat on the suction side, the predicted value is used while the compressor is used. When the refrigerant on the suction side of (11a, 11b, 11c) is wet and the outlet gas temperature cannot be accurately predicted from the superheat on the suction side, the time of the discharge pipe temperature of the compressor (11a, 11b, 11c) By considering the change in the outlet gas temperature using the amount of change, the outlet gas temperature can be controlled with higher accuracy in accordance with the state of the compressor (11a, 11b, 11c).

  Moreover, as described above, when the refrigerant on the suction side of the compressor (11a, 11b, 11c) is dry, it is obtained based on the superheat on the suction side of the compressor (11a, 11b, 11c). By setting the higher one of the predicted value Tp1 and the predicted value Tp2 obtained from the discharge pipe temperature Td as the outlet gas temperature, the outlet gas temperature can be controlled more safely.

<< Embodiment 2 >>
The refrigeration apparatus (150) of Embodiment 2 is installed in a convenience store or the like, and cools the inside of a refrigerator or a freezer. As shown in FIG. 5, the first embodiment is different from the first embodiment only in that the booster unit (152) is provided and the two-stage compression is possible. Only the part will be described.

-Configuration of refrigeration equipment-
As shown in FIG. 5 above, the refrigeration apparatus (150) of Embodiment 2 controls the outdoor unit (2), the refrigerated showcase (151), the booster unit (152), and various valves and compressors. A controller (190) is provided. The outdoor unit (2) is installed outdoors, while the remaining units (151 and 152) are all installed in a store such as a convenience store.

  The outdoor unit (2) has the same outdoor circuit (20) as in the first embodiment, and the refrigerated showcase (151) has the same refrigerator circuit (30) as the refrigerated unit (3) in the first embodiment. The booster unit (152) is provided with a booster circuit (100). In the refrigeration apparatus (150), by connecting these circuits (20, 30, 100) with piping, a refrigerant circuit (160) that performs a vapor compression refrigeration cycle is configured, as in the first embodiment.

  The refrigerator internal circuit (30) and the booster circuit (100) are connected in series in the order of the refrigerator internal circuit (30) and the booster circuit (100) with respect to the liquid side connection pipe (21) of the outdoor circuit (20). It is connected to the.

  Specifically, a liquid side closing valve (53) and a gas side closing valve (54) are provided at the end of the outdoor circuit (20), and a closing valve (140) is provided at the end of the booster circuit (100). The liquid side closing valve (53) is connected to one end of a liquid side communication pipe (21) connected to the refrigerator internal circuit (30) at the other end. On the other hand, one end of a gas-side connecting pipe (22) connected to the shut-off valve (140) at the other end is connected to the gas-side shut-off valve (54).

  Note that one end of a liquid injection main pipe (119) of the booster circuit (100) is connected to the liquid side connecting pipe (21).

<Booster unit>
Since the outdoor unit (2) and the refrigerated showcase (151) have the same configuration as the outdoor unit (2) and the refrigerated unit (3) in the first embodiment, detailed description thereof will be omitted, and the booster unit (152) will be described below. The booster circuit (100) will be described in detail.

  The booster circuit (100) of the booster unit (152) is connected to the gas side end of the refrigerator internal circuit (30) via a booster communication pipe (141). In this booster circuit (100), a fixed capacity fourth compressor (101a) and a fifth compressor (101b) and a variable capacity sixth compressor (101c) are provided in parallel with each other.

  The compressors (101a, 101b, 101c) are all hermetic and high-pressure dome type scroll compressors, and constitute a low-stage compressor of the refrigerant circuit (160). Electric power is supplied to the sixth compressor (101c) via an inverter. The capacity of the sixth compressor (101c) can be changed by changing the rotation speed of the compressor motor by changing the output frequency of the inverter. On the other hand, in the fourth and fifth compressors (101a, 101b), the compressor motor is always operated at a constant rotational speed, and its capacity cannot be changed. During the operation of the refrigeration apparatus (150), among the three compressors (101a, 101b, 101c), the variable capacity sixth compressor (101c) is preferentially operated, and the refrigeration apparatus (150) The fourth compressor (101a) and the fifth compressor (101c) are operated in this order according to the situation on the use side.

  The suction side of the compressor (101a, 101b, 101c) is connected to the booster connection pipe (141) via a low-stage suction pipe (110) to which the suction pipes (111, 112, 113) are connected. Specifically, one end is connected to the other end of the third suction pipe (113) whose one end is connected to the suction side of the sixth compressor (101c), and one end is connected to the suction side of the fourth compressor (101a). The other end of the first suction pipe (111) is connected to the lower suction pipe (110), and the lower suction pipe (110) is connected to the booster connection pipe (141) at one end thereof. Has been. The third suction pipe (113) is connected to the other end of the second suction pipe (112) having one end connected to the suction side of the fifth compressor (101b).

  The discharge side of the compressor (101a, 101b, 101c) is connected to the shut-off valve (140) via the discharge pipe (114, 115, 116), the low-stage side discharge pipe (117) and the discharge communication pipe (130). Yes. Specifically, one end of the first discharge pipe (114) is disposed on the discharge side of the fourth compressor (101a), and one end of the second discharge pipe (115) is disposed on the discharge side of the fifth compressor (101b). However, one end of a third discharge pipe (116) is connected to the discharge side of the sixth compressor (101c), and the other end of these discharge pipes (114, 115, 116) is connected to the low-stage side discharge pipe ( 117). The discharge pipes (114, 115, 116) have check valves (CV-8, CV-9) that allow only the refrigerant to flow from the compressors (101a, 101b, 101c) to the shutoff valves (140). , CV-10).

  The booster circuit (100) is provided with two oil leveling pipes (118a, 118b), a liquid injection circuit (180), and two oil recovery pipes (124a, 124b).

  The two oil leveling pipes (118a, 118b) are composed of a first oil leveling pipe (118a) and a second oil leveling pipe (118b), and constitute oil leveling means of the compressors (101a, 101b, 101c). . The first oil equalizing pipe (118a) has one end connected to a predetermined height position of the dome of the fifth compressor (101b), and the other end connected to the second suction pipe (113). It is connected to the compressor (101c) side of the connection with the suction pipe (112), and an electromagnetic valve (SV-5) is provided on the pipe line.

  The second oil equalizing pipe (118b) has one end connected to a predetermined height position of the dome of the fourth compressor (101a), and the other end connected to the second suction pipe (113). An electromagnetic valve (SV-6) is provided connected to the connection portion side of the lower suction pipe (110) than the connection portion of the suction pipe (112).

  The liquid injection circuit (180) includes a liquid injection main pipe (119) and first to third liquid injection branch pipes (119a, 119b, 119c). The liquid injection main pipe (119) has one end connected to the liquid side connecting pipe (21) and the other end connected to one end of each liquid injection branch pipe (119a, 119b, 119c). The liquid injection main pipe (119) is provided with a fourth expansion valve (120). The fourth expansion valve (120) is an electronic expansion valve whose opening degree is adjustable. Further, in the liquid injection main pipe (119), a communication pipe (fifth expansion valve (121) provided on the connection side of the liquid side communication pipe (21) with respect to the fourth expansion valve (120) ( 122) is connected at one end. The other end of the communication pipe (122) is connected to the discharge communication pipe (130).

  Each of the first to third liquid injection branch pipes (119a, 119b, 119c) is provided with a capillary tube (123a, 123b, 123c), and each of the liquid injection branch pipes (119a, 119b, 119c, The other end of 119c) is connected to the suction pipes (111, 112, 113) of the compressors (101a, 101b, 101c). As a result, the liquid refrigerant flowing through the liquid side connecting pipe (21) flows through the liquid injection branch pipes (119a, 119b, 119c) via the liquid injection main pipe (119), and the compressors (101a, 101b). , 101c) is supplied to the suction pipes (111, 112, 113), so that the discharge gas temperature of each compressor (101a, 101b, 101c) can be reduced.

  In the present embodiment, as in the first embodiment, when the refrigerant on the suction side of each compressor (101a, 101b, 101c) is dry, the superheat on the suction side and the discharge pipe temperature Td are used. While the opening degree of the fourth expansion valve (120) is controlled by the obtained outlet gas temperatures Tp1, Tp2, while the refrigerant on the suction side of the compressors (101a, 101b, 101c) is moist, The opening degree of the fourth expansion valve (120) is controlled based on the time variation of the discharge pipe temperature Td. Here, since the superheat on the suction side is obtained by the controller (190) based on the output of the second refrigerant temperature sensor (18a) of the refrigeration unit (3), the second refrigerant temperature sensor (18a) and the controller ( 190) corresponds to the superheat degree detection means of the present invention.

  The two oil recovery pipes (124a, 124b) are composed of a first oil recovery pipe (124a) and a second oil recovery pipe (124b). One end of the first oil recovery pipe (124a) is connected to a connection portion of the first oil equalizing pipe (118a) in the third suction pipe (113) of the sixth compressor (101c) and the second suction pipe (112). It is connected between the connections. On the other hand, the other end of the first oil recovery pipe (124a) is connected to the first suction pipe (111) of the four compressor (101a).

  In addition, one end of the second oil recovery pipe (124b) is connected to the connecting portion of the second liquid injection branch pipe (119b) in the second suction pipe (112) of the fifth compressor (101b) and the fifth compressor. (101b) connected to the suction side. On the other hand, the other end of the second oil recovery pipe (124b) is connected to the first oil recovery pipe (124a).

  The booster circuit (100) is provided with an oil discharge pipe (125), a first bypass pipe (126), a second bypass pipe (127) as a bypass passage, and a low-stage oil separator (128). ing.

  The oil discharge pipe (125) has one end connected to an oil discharge port (not shown) of the sixth compressor (101c) and the other end connected to the discharge communication pipe (130). The oil discharge pipe (125) is provided with a solenoid valve (SV-7). The solenoid valve (SV-7) is opened when the refrigeration oil in the sixth compressor (101c) becomes excessive. As a result, the refrigeration oil flows into the outdoor circuit (20) through the oil discharge pipe (125), and is sucked into the high-stage compressors (11a, 11b, 11c). In the oil discharge pipe (125), the sixth compressor (101c) is directed to the discharge communication pipe (130) closer to the connection portion of the discharge communication pipe (130) than the solenoid valve (SV-7). A check valve (CV-11) that allows only the flow of the refrigerant is provided.

  The low-stage oil separator (128) is provided at the other end of the low-stage discharge pipe (117) so as to separate the refrigerating machine oil from the refrigerant discharged from each compressor (101a, 101b, 101c). It is configured. An oil return pipe (129), the low-stage discharge pipe (117), and the discharge communication pipe (130) are connected to the low-stage oil separator (128).

  One end of the oil return pipe (129) is connected to the bottom of the oil recovery container of the low stage side oil separator (128), while the other end is connected to the low stage side suction pipe (110). ing. The oil return pipe (129) is provided with an openable / closable solenoid valve (SV-8). When the solenoid valve (SV-8) is opened, the low-stage oil separator (128) The refrigerating machine oil separated in (1) is configured to return into the low-stage suction pipe (110).

  The low-stage discharge pipe (117) is connected to the peripheral wall of the oil recovery container of the low-stage oil separator (128). The discharge communication pipe (130) is connected to the top of the oil recovery container of the low-stage oil separator (128).

  The first bypass pipe (126) has one end connected to the low-stage suction pipe (110) and the other end connected to the oil return pipe (129) of the low-stage oil separator (128). . The first bypass pipe (126) is provided with a solenoid valve (SV-9).

  The second bypass pipe (127) has one end connected to the low-stage suction pipe (110) and the other end connected to the discharge communication pipe (130). That is, the second bypass pipe (127) is provided so as to bypass the low-stage compressor (101a, 101b, 101c) and the low-stage oil separator (128). The second bypass pipe (127) is provided with a check valve (CV-12) that allows only the refrigerant to flow from the low-stage suction pipe (110) to the discharge communication pipe (130). Yes.

  The booster circuit (100) is also provided with various sensors and pressure switches. Specifically, the low pressure side suction pipe (110) is provided with a suction pressure sensor (131). The first discharge pipe (114), the second discharge pipe (115) and the third discharge pipe (116) are respectively provided with a pressure switch (95e, 95f, 95g) and a discharge temperature sensor (discharge pipe temperature detecting means). 19d, 19e, 19f) are provided. The low pressure side discharge pipe (117) is provided with a discharge pressure sensor (133). A temperature sensor (132) is provided in the vicinity of the closing valve (140) of the discharge communication pipe (130).

-Driving action-
Below, the operation | movement operation | movement of the freezing apparatus (10) of Embodiment 2 is demonstrated by the example of a two-stage compression operation | movement. The operation of the refrigeration apparatus (10) includes a single-stage compression operation and a defrost operation in addition to this, but in the case of a single-stage compression operation, a high-stage compressor (11a, 11b, 11c ) Only operate, and the outlet gas temperature control of the compressors (11a, 11b, 11c) is the same as that in the first embodiment, so only the two-stage compression operation will be described.

<Cooling operation>
In the cooling operation of the refrigeration apparatus (10), the interior of the refrigerator showcase (151) is cooled.

  As shown in FIG. 6, in the outdoor circuit (20) during the cooling operation, the four-way selector valve (12) is set to the first state. Moreover, while the 1st expansion valve (45) will be in a fully closed state, the opening degree of a 2nd expansion valve (46) is adjusted suitably. Furthermore, the solenoid valve (SV-1) is set to a closed state.

  In the refrigerator internal circuit (30), the opening degree of the refrigeration expansion valve (15a) is appropriately adjusted. In the booster circuit (100), the solenoid valves (SV-7, SV-8, SV-9) are set in a closed state.

  In the cooling operation, each compressor (11a, 11b, 11c) in the outdoor circuit (20) and each compressor (101a, 101b, 101c) in the booster circuit (100) are operated. As a result, in the refrigerant circuit (160), the outdoor heat exchanger (13) serves as a condenser, and the refrigerated heat exchanger (16) serves as an evaporator to perform a two-stage compression refrigeration cycle.

  The refrigerant discharged from each compressor (11a, 11b, 11c) in the outdoor circuit (20) passes through the four-way switching valve (12) from the discharge main pipe (64) and flows through the outdoor heat exchanger (13). . In this outdoor heat exchanger (13), the heat of outdoor air is imparted to the refrigerant, and the refrigerant condenses.

  The refrigerant condensed in the outdoor heat exchanger (13) passes through the first liquid pipe (81), the receiver (14), the second liquid pipe (82), and the first flow path (50a) of the refrigerant heat exchanger (50). ) And flows into the third liquid pipe (83). Part of the refrigerant flowing through the third liquid pipe (83) is distributed to the fourth liquid pipe (84), and the rest flows into the liquid side connecting pipe (21).

  The refrigerant flowing through the fourth liquid pipe (84) passes through the second expansion valve (46) and is depressurized, and then flows through the second flow path (50b) of the refrigerant heat exchanger (50). In the refrigerant heat exchanger (50), the high-pressure refrigerant flowing through the first flow path (50a) and the low-pressure refrigerant flowing through the second flow path (50b) exchange heat. As a result, the heat of the refrigerant flowing through the first flow path (50a) is taken as the evaporation heat of the refrigerant flowing through the second flow path (50b). That is, in the refrigerant heat exchanger (50), the refrigerant flowing through the first flow path (50a) is supercooled. The refrigerant evaporated in the second flow path (50b) of the refrigerant heat exchanger (50) flows into the suction main pipe (55) through the gas injection pipe (85).

  On the other hand, the refrigerant branched from the fourth liquid pipe (84) and flowing through the liquid injection main pipe (86) passes through the third expansion valve (47) and is depressurized, and then the liquid injection branch pipe (86a, 86b, 86c, 86d) branch through the capillary tubes (87a, 87b, 87c, 87d) and are supplied to the suction side of each compressor (11a, 11b, 11c).

  The refrigerant flowing into the liquid side communication pipe (21) is distributed to the refrigerator internal circuit (30) and the liquid injection main pipe (119) of the booster unit (152). Note that the refrigerant distributed to the liquid injection main pipe (119) passes through the fourth expansion valve (120) and is depressurized, and then passes through the capillary tubes (123a, 123b, 123c) to enter the compressors (101a, 101b, 101c) is supplied to the suction side.

  Since the control of the third expansion valve (47) and the fourth expansion valve (120) is the same as the control of the third expansion valve (47) in the first embodiment, a detailed description thereof will be omitted. By controlling the third expansion valve (47) and the fourth expansion valve (120) in the same manner as the third expansion valve (47) in the first embodiment, the compressors (11a, 11b, 11c, 101a, 101b, 101c) are controlled. ) Can be reliably reduced, which enables the use of a high-pressure refrigerant such as R410A even in a refrigeration system. Note that the controller (190) for controlling the third expansion valve (47) and the fourth expansion valve (120) and the refrigerant on the suction side of the compressor (11a, 11b, 11c, 101a, 101b, 101c) The liquid injection circuit (80, 180) for performing liquid injection on the outlet constitutes the outlet gas temperature control means of the present invention.

  In the refrigerator internal circuit (30), the liquid refrigerant flows through the drain pan heater (26) to prevent the drain pan from frosting and to reliably melt the frost that has fallen from the refrigeration heat exchanger (16) to the drain pan. The liquid refrigerant flowing out of the drain pan heater (26) is decompressed and expanded when passing through the refrigeration expansion valve (15a), and is introduced into the refrigeration heat exchanger (16). In the refrigeration heat exchanger (16), the refrigerant absorbs heat from the air in the cooling chamber and evaporates. Thus, in the refrigerated showcase (151), the air cooled by the refrigerated heat exchanger (16) is supplied into the cooling chamber.

  The gas refrigerant evaporated in the refrigeration heat exchanger (16) flows to the booster unit (152) through the booster connecting pipe (141).

  Specifically, the gas refrigerant flowing through the booster connecting pipe (141) flows through the low-stage compressor (101a, 101b, 101c) via the low-stage suction pipe (110) and the first to third suction pipes (111, 112, 113). ). At this time, the closing valves (SV-5, SV-6) of the first and second oil equalizing pipes (118a, 118b) are appropriately controlled to open and close.

  The refrigerant compressed and discharged by the low-stage compressors (101a, 101b, 101c) flows into the low-stage discharge pipe (117) via the first to third discharge pipes (114, 115, 116), The refrigerant is separated into gas refrigerant and refrigerating machine oil in the stage side oil separator (128). Then, the gas refrigerant flows through the discharge communication pipe (130) and returns to the outdoor unit (2) through the gas side communication pipe (22). Thereafter, the air is sucked into the high-stage compressors (11a, 11b, 11c) via the four-way switching valve (12) and the suction main pipe (55).

  Here, after the refrigerating machine oil separated in the low-stage oil separator (128) is stored in the recovery container, the solenoid valve (SV-8) on the oil return pipe (129) at a predetermined timing Is opened to flow through the oil return pipe (129) and return to the low-stage suction pipe (110). As a result, the refrigerant in the low-stage side suction pipe (110) and the refrigerating machine oil flow in a mixed state, and the refrigerating machine oil is returned to the low-stage compressors (101a, 101b, 101c). In addition, adjustment of the amount of refrigeration oil in each compressor (101a, 101b, 101c) adjusts the oil leveling pipes (118a, 118b) as the oil leveling means, the first oil drain pipe (125), and the first oil drain pipe (125 ) Is performed by a solenoid valve (SV-7).

-Effect of Embodiment 2-
As described above, according to the second embodiment, the liquid injection circuit (80, 180) is provided on the suction side of the compressor (11a, 11b, 11c, 101a, 101b, 101c), and the liquid injection main pipe ( 86, 119) is controlled in accordance with the humidity state on the suction side of the compressor (11a, 11b, 11c, 101a, 101b, 101c). Even when R410A, which is a high-pressure refrigerant (11a, 11b, 11c, 101a, 101b, 101c) where the outlet gas temperature tends to be high, is used in the refrigeration two-stage system, the outlet gas temperature can be reliably reduced.

<< Embodiment 3 >>
As shown in FIG. 7, the refrigeration apparatus (201) of Embodiment 3 injects refrigerant into a compression chamber having an intermediate pressure of a single-stage compressor (11a, 11b, 11c). It constitutes an economizer system. Since only the configuration of the outdoor unit is different from that of the first embodiment, the same portions are denoted by the same reference numerals and only different portions will be described below.

-Configuration of refrigeration equipment-
FIG. 7 is a refrigerant circuit diagram of the refrigeration apparatus (201) according to this embodiment. This refrigeration apparatus (201) includes one outdoor unit (210) having an outdoor circuit (211) and a refrigeration unit (3) having two refrigerator internal circuits (30, 30) having the same configuration as that of the first embodiment. And.

  In this refrigeration system (201), each refrigerator internal circuit (30) is connected in parallel to the outdoor circuit (211) by a liquid side communication pipe (21) and a gas side communication pipe (23), thereby being a vapor compression type. A refrigerant circuit (204) for performing the refrigeration cycle is configured.

<Outdoor unit>
The outdoor circuit (211) of the outdoor unit (210) includes three compressors (11a, 11b, 11c), an outdoor heat exchanger (13), and a receiver as in the outdoor circuit (20) of the first embodiment. (14), refrigerant heat exchanger (50), first expansion valve (45), second expansion valve (46), four-way switching valve (12), oil separator (70) and liquid injection circuit (280) Is provided.

  The three compressors (11a, 11b, 11c) are composed of two fixed capacity compressors (11a, 11b) and one variable capacity compressor (11c), as in the first embodiment. Is a fully sealed high-pressure dome type, for example, a scroll compressor having a compression mechanism composed of a scroll fluid machine.

  The suction main pipe (55) is connected to the suction side of each compressor (11a, 11b, 11c) via the suction branch pipe (61a, 61b, 61c), while the discharge side The discharge main pipe (64) is connected via the branch pipes (64a, 64b, 64c).

  Specifically, one end of the suction main pipe (55) is connected to the four-way switching valve (12), and the other end is connected to the suction branch pipes (61a, 61b, 61c). One end of the discharge main pipe (64) is connected to the four-way switching valve (12), while the other end is connected to the first discharge branch pipe (64a), the second discharge branch pipe (64b), and the third. Branches to the discharge branch pipe (64c). Each discharge branch pipe (64a, 64b, 64c) has a check valve (CV-) that allows only the flow of refrigerant from each compressor (11a, 11b, 11c) to the four-way selector valve (12). 1, CV-2, CV-3) are provided respectively.

  The discharge main pipe (64) is provided with an oil separator (70) for separating the refrigeration oil from the refrigerant discharged from each compressor (11a, 11b, 11c). One end of an oil return pipe (271) that is an oil return passage is connected to the oil separator (70). The other end of the oil return pipe (271) branches into a first oil return pipe (271a), a second oil return pipe (271b), and a third oil return pipe (271c).

  Each oil return pipe (271a, 271b, 271c) is connected to a compression chamber of intermediate pressure in the compression mechanism of each compressor (11a, 11b, 11c). The oil return pipes (271a, 271b, 271c) are provided with solenoid valves (SV-10, SV-11, SV-12), respectively. In this embodiment, the refrigerating machine oil from the oil separator (70) is returned not to the suction side but to the intermediate pressure compression chamber, so that the viscosity is not increased by being cooled by the low-pressure refrigerant.

  The inflow end of the high-pressure channel (50a) of the refrigerant heat exchanger (50) is connected to the bottom of the receiver (14) via the second liquid pipe (82), while the outflow end is connected to the third end. It is connected to the liquid side closing valve (53) via the liquid pipe (283). The third liquid pipe (283) is provided with a check valve (CV-5) that allows only the flow of refrigerant toward the liquid side communication pipe (21).

  On the other hand, the fourth liquid branched from the third liquid pipe (283) on the upstream side of the check valve (CV-5) is provided at the inflow end of the low-pressure channel (50b) of the refrigerant heat exchanger (50). Tube (284) is connected. The fourth liquid pipe (284) is provided with a second expansion valve (46). This 2nd expansion valve (46) is comprised by the electronic expansion valve which can adjust an opening degree. In addition, at the outflow end of the low-pressure channel (50b), one end of a liquid injection pipe (230), which is a liquid injection passage for injecting liquid refrigerant into the compression mechanism of each compressor (11a, 11b, 11c) Is connected.

  The liquid injection circuit (280) includes the liquid injection pipe (230), a first liquid injection pipe (230a) branched from the other end of the liquid injection pipe (230), a second liquid injection pipe (230b), and a second liquid injection pipe (230b). And a three-liquid injection tube (230c). Each liquid injection pipe (230a, 230b, 230c) is connected to the solenoid valve (SV-10, SV-11, SV-12) and compressor (11a, 11b, 11c) in each oil return pipe (271a, 271b, 271c). ) Is connected between. Each of the liquid injection pipes (230a, 230b, 230c) is provided with a solenoid valve (SV-13, SV-14, SV-15).

  One end of a gas vent pipe (227) is connected to the top of the receiver (14). The gas vent pipe (227) is provided with a check valve (CV-13), and the other end is connected to the third discharge pipe (64c). The check valve (CV-13) is provided so as to allow only the refrigerant flow from the receiver (14) to the third discharge pipe (64c).

  A liquid pipe (289) that bypasses the receiver (14) and the refrigerant heat exchanger (50) is connected between the first liquid pipe (81) and the third liquid pipe (283). The liquid pipe (289) is connected between the outdoor heat exchanger (13) and the check valve (CV-4) in the first liquid pipe (81), and the refrigerant in the third liquid pipe (283). It connects between the connection part of a heat exchanger (50) and a 4th liquid pipe (284). The liquid pipe (289) is provided with a first expansion valve (45). The first expansion valve (45) is an electronic expansion valve whose opening degree can be adjusted, and constitutes a heat source side expansion valve.

  A bypass pipe (231) that bypasses the refrigerant heat exchanger (50) is connected between the fourth liquid pipe (284) and the liquid injection pipe (230). The bypass pipe (231) is connected to the downstream side of the second expansion valve (46) in the fourth liquid pipe (284), and the compressors (11a, 11b, 11c) in the liquid injection pipe (230). ) Is connected upstream of the branch point to. The bypass pipe (231) is provided with a solenoid valve (SV-16).

  Note that the refrigeration apparatus (201) in the present embodiment is also controlled by the controller (290) as in the first and second embodiments. That is, various valves (SV-10 to SV-16, 45, 46, 15a, 15b) provided in the refrigerant circuit (204) are switched and the opening degree is adjusted, and the compressors (11a, 11b, 11c) ) And the fans (13f, 16f, 17f) are driven to control the operation of the refrigeration apparatus (201).

  Specifically, the operation of the refrigeration apparatus (201) as described later is performed, and the outlet gas temperature is controlled by performing wetness control on the suction side of the compressor (11a, 11b, 11c). Yes.

-Driving action-
Below, the operation | movement operation | movement of the freezing apparatus (201) of this embodiment is demonstrated.

<Cooling operation>
During the cooling operation, the four-way selector valve (12) is set to the first state shown in FIG. Further, the opening degree of the second expansion valve (46) is adjusted as appropriate, while the first expansion valve (45) is fully closed. In the refrigerator internal circuit (30), the opening degree of the refrigeration expansion valves (15a, 15b) is appropriately adjusted. Each solenoid valve (SV-10 to SV-16) is opened and closed according to the operating state. When the compressors (11a, 11b, 11c) are operated in this state, in the refrigerant circuit (204), the outdoor heat exchanger (13) becomes a condenser and each refrigerated heat exchanger (16, 17) becomes an evaporator. A vapor compression refrigeration cycle is performed. In the refrigerant circuit (204), the refrigerant flows as shown by a thick line in FIG.

  Specifically, when the compressor (11a, 11b, 11c) is operated, the compressor (11a, 11b, 11c) sucks low-pressure gas refrigerant, compresses it to a predetermined pressure, and discharges it. . The high-pressure gas refrigerant discharged from the compressor (11a, 11b, 11c) flows into the oil separator (70) of the discharge main pipe (64) through the discharge branch pipes (64a, 64b, 64c). In the oil separator (70), the refrigeration oil is separated from the refrigerant flowing in, and returned to the compression chamber of the intermediate pressure of the compression mechanism of the compressor (11a, 11b, 11c) via the oil return pipe (271).

  The refrigerant flowing out of the oil separator (70) flows into the outdoor heat exchanger (13) through the four-way switching valve (12), and is condensed by exchanging heat with outdoor air. Then, the condensed refrigerant flows into the receiver (14) through the first liquid pipe (81).

  The refrigerant flowing out from the receiver (14) passes through the second liquid pipe (82) and the first flow path (50a) of the refrigerant heat exchanger (50) and flows into the third liquid pipe (283). In the third liquid pipe (283), a part of the refrigerant flows into the fourth liquid pipe (284) and is depressurized by the second expansion valve (46). The remaining refrigerant flows into the liquid side connecting pipe (21).

  The refrigerant decompressed by the second expansion valve (46) is used for gas injection or liquid injection into the compressors (11a, 11b, 11c). When the solenoid valve (SV-16) of the bypass pipe (231) is closed, the refrigerant flows through the second flow path (50b) of the refrigerant heat exchanger (50) to supercool the liquid refrigerant, and then the compressor ( 11a, 11b, 11c), and when in the open state, liquid injection is performed to lower the temperature of the refrigerant discharged from the compressor (11a, 11b, 11c) by bypassing the refrigerant heat exchanger (50). Done.

  Specifically, when the solenoid valve (SV-16) of the bypass pipe (231) is closed, the refrigerant depressurized by the second expansion valve (46) is the second flow path of the refrigerant heat exchanger (50). (50b) is distributed. At that time, in the refrigerant heat exchanger (50), heat exchange is performed between the high-pressure refrigerant flowing through the first flow path (50a) and the low-pressure refrigerant flowing through the second flow path (50b). As a result, the refrigerant flowing through the first flow path (50a) is supercooled, while the refrigerant flowing through the second flow path (50b) evaporates. The gas refrigerant evaporated in the second flow path (50b) passes through the liquid injection pipes (230a, 230b, 230c) from the liquid injection pipe (230) as shown by the arrow b in FIG. 11a, 11b, 11c) flows into the compression chamber of intermediate pressure in the compression mechanism.

  On the other hand, when the solenoid valve (SV-16) is in the open state, the liquid refrigerant decompressed by the second expansion valve (46) (strictly, gas-liquid two-phase refrigerant) is supplied from the second flow path (50b). A large amount flows into the bypass pipe (231) with little pressure loss. Then, as shown by the arrow a in FIG. 8, the intermediate pressure in the compression mechanism of the compressor (11a, 11b, 11c) passes from the liquid injection pipe (230) through each liquid injection pipe (230a, 230b, 230c). Flows into the compression chamber. The amount of gas refrigerant or liquid refrigerant that flows through the liquid injection pipe (230) and is sent to the compressor (11), that is, the injection amount is adjusted by the opening of the second expansion valve (46). Control of the amount of liquid refrigerant sent to the compressor (11) will be described later.

  The refrigerant flowing into the liquid side communication pipe (21) is distributed to each refrigerator circuit (30). The refrigerant flowing into the refrigerator internal circuit (30) flows through the drain pan heaters (26, 27). The ice flowing through the drain pan heaters (26, 27) melts the ice blocks produced by freezing frost and condensed water that have fallen from the surface of the refrigeration heat exchanger (16, 17).

  The refrigerant that has flowed out of the drain pan heater (26, 27) passes through the refrigeration expansion valve (15a, 15b) and is decompressed, and then flows into the refrigeration heat exchanger (16, 17). In this refrigeration heat exchanger (16, 17), the refrigerant that has flowed in exchanges heat with the internal air and evaporates. As a result, the air in the refrigerator warehouse is cooled.

  The refrigerant evaporated in each refrigeration heat exchanger (16, 17) flows into the gas side communication pipe (22) and then flows into the outdoor circuit (20). The refrigerant flowing into the outdoor circuit (20) flows into the suction main pipe (55) through the four-way switching valve (12), and is sucked into the compressors (11a, 11b, 11c).

<Outlet gas temperature control>
Next, the outlet side gas temperature control of each compressor (11a, 11b, 11c), which is a characteristic part of the present invention, will be described.

  In this embodiment, as described above, a liquid injection circuit (280) for liquid-injecting refrigerant is provided in the intermediate pressure compression chamber of each compressor (11a, 11b, 11c), and each compressor (11a, The outlet gas temperature of 11b and 11c) is reduced.

  That is, in this embodiment, unlike the first embodiment, the liquid injection is performed in the compression chamber of the intermediate pressure of the compressor (11a, 11b, 11c), and the liquid injection is performed on the suction side. Therefore, the determination of the superheat on the suction side is not performed as shown in FIG.

  Further, as described above, since liquid injection is performed in the compression chamber of the intermediate pressure of the compressor (11a, 11b, 11c), when the liquid injection is performed, the outlet gas temperature is determined from the suction superheat and the discharge pressure. Can't guess Tp1. Therefore, in this embodiment, when the liquid injection is performed in the compression chamber of the intermediate pressure of the compressor (11a, 11b, 11c) and the control based on the time variation of the discharge pipe temperature is not performed, the discharge is performed. Control is performed using the outlet gas temperature Tp2 estimated from the tube temperature Td.

  Hereinafter, the flow of the outlet gas temperature control shown in FIG. 9 will be described.

  First, when the flow shown in FIG. 9 starts, the superheat on the suction side of the compressor (11a, 11b, 11c) obtained from the output of the suction temperature sensor (24) in step S1 ′, as in the first embodiment. Based on the output of the discharge pressure sensor (23), the predicted value Tp1 of the outlet gas temperature is obtained.

  Also in the subsequent step S2 ′, as in the first embodiment, the discharge pipe temperature detected by the discharge temperature sensor (19a, 19b, 19c) and the predicted temperature of the discharge pipe temperature and the outlet gas temperature obtained from a function, a table, etc. The difference is added to obtain the predicted value Tp2 of the outlet gas temperature. Here, since the predicted temperature difference is a function of the flow rate through the compressor, it can be obtained based on the output value of the suction pressure sensor (25) and the rotational speed of the compressor.

  In step S3 ', as in the first embodiment, it is determined whether or not the discharge pipe temperature Td detected by the discharge temperature sensor (19a, 19b, 19c) is smaller than a predetermined value. However, in this embodiment, the predetermined value is a threshold value for determining whether the temperature is so high that the liquid injection amount is not controlled by the time change amount of the discharge pipe temperature Td, as in the first embodiment. It is not a threshold value for determining whether superheat is performed on the inhalation side. That is, when it is estimated that the discharge pipe temperature Td is sufficiently low and the outlet gas temperature is low, it is not necessary to perform liquid injection with very high precision, while when the discharge pipe temperature Td is high, the outlet gas Since the temperature is high and it is necessary to perform liquid injection with high accuracy, the control contents can be switched according to the discharge pipe temperature Td. The predetermined value is defined in the same manner as in the first embodiment.

  If it is determined in step S3 ′ that the discharge pipe temperature Td is smaller than the predetermined value (in the case of YES), the process proceeds to the subsequent step S4 ′ to control the second expansion valve for controlling the liquid injection amount. Determine whether (46) is closed. For example, when the outside air temperature is low, the second expansion valve (46) is closed. In this case, liquid injection into the compression chamber of the intermediate pressure of the compressor (11a, 11b, 11c) is performed. This is because the outlet gas temperature can be estimated from the superheat on the suction side, and control can be performed using Tp1 obtained in step S1 ′.

  When it is determined in step S4 ′ that the second expansion valve (46) is closed, that is, liquid injection into the compression chamber of the intermediate pressure of the compressor (11a, 11b, 11c) is not performed. In the case of (YES), control is performed using the predicted value Tp1 in step S5 ′, while when it is determined that the second expansion valve (46) is not closed (in the case of NO), step S6 is performed. Proceeding to ', the outlet gas temperature is controlled using the predicted value Tp2 obtained in step S2'.

  The control in steps S5 ′ and S6 ′ is to adjust the opening degree of the second expansion valve (46), and the control content includes the control of the third expansion valve (47) in the first embodiment. Since it is the same, detailed explanation is omitted.

  On the other hand, when it is determined in step S3 ′ that the discharge pipe temperature Td is equal to or higher than the predetermined value (in the case of NO), the process proceeds to step S7 ′, and the discharge pipe temperature Td is set as in the first embodiment. The outlet gas temperature is controlled according to the amount of time change. The control in this step S7 'is performed according to the flow shown in FIG. 4 and is the same as that in the first embodiment, so that the description thereof is omitted.

  And after controlling the said 2nd expansion valve (46) by said step S5 ', S6', S7 ', this flow is complete | finished, it returns to a start, and this flow is started again (return).

  The controller (290) and the liquid injection circuit (280) that perform the control as described above constitute the outlet gas temperature control means of the present invention.

-Effect of Embodiment 3-
As described above, according to this embodiment, in the circuit that performs liquid injection into the intermediate pressure compression chamber of the compressor (11a, 11b, 11c), the temperature of the discharge pipe of the compressor (11a, 11b, 11c) is predetermined. If the value is higher than the value, the liquid injection amount is adjusted based on the time variation of the discharge pipe temperature, so that the outlet gas temperature of the compressor (11a, 11b, 11c) is more accurately controlled. And the outlet gas temperature can be reliably set to a predetermined temperature or lower.

  That is, if the discharge pipe temperature of the compressor (11a, 11b, 11c) is equal to or higher than a predetermined value, the control is performed accurately based on the amount of time change of the discharge pipe temperature, while the discharge pipe temperature is smaller than the predetermined value. For example, by using a conventional prediction method, the outlet gas temperature of the compressor (11a, 11b, 11c) can be controlled easily and easily.

<< Other Embodiments >>
About the said embodiment, it is good also as the following structures.

  In each of the above embodiments, the high-pressure refrigerant R410A is used as the refrigerant. However, the present invention is not limited to this, and CO2 may be used as the refrigerant.

  As described above, the present invention is particularly useful for a refrigeration apparatus that needs to reliably reduce the outlet gas temperature of a compressor, such as a refrigeration apparatus for freezing / refrigeration using a high-pressure refrigerant.

FIG. 2 is a piping system diagram illustrating a refrigerant circuit of the refrigeration apparatus according to Embodiment 1. FIG. 2 is a piping system diagram showing a refrigerant circulation direction during a cooling operation in the refrigerant circuit of FIG. 1. It is a flow of outlet gas temperature control. It is a flow of outlet gas temperature control based on the time conversion amount of discharge pipe temperature. FIG. 3 is a view corresponding to FIG. 1 of a refrigeration apparatus according to Embodiment 2. FIG. 6 is a piping diagram showing a refrigerant circulation direction during a cooling operation (two-stage compression operation) in the refrigerant circuit of FIG. 5. FIG. 3 is a view corresponding to FIG. FIG. 8 is a piping system diagram showing a refrigerant circulation direction during a cooling operation in the refrigerant circuit of FIG. 7. FIG. 6 is a view corresponding to FIG. 3 according to the third embodiment.

Explanation of symbols

1,150,201 Refrigeration equipment
10,160,204 Refrigerant circuit
11a, 11b, 11c, 101a, 101b, 101c Compressor
13 Outdoor heat exchanger (heat source side heat exchanger)
16,17 Refrigerated heat exchanger (use side heat exchanger)
18a Second refrigerant temperature sensor (superheat detection means)
19a, 19b, 19c, 19d, 19e, 19f Discharge temperature sensor (discharge pipe temperature detection means)
23,133 Discharge pressure sensor
24 Suction temperature sensor (superheat detection means)
47 3rd expansion valve
80,180,280 Liquid injection circuit (outlet gas temperature control means)
86,119 Liquid injection
86a, 86b, 86c, 86d, 119a, 119b, 119c Liquid injection branch pipe
87a, 87b, 87c, 87d, 123a, 123b, 123c Capillary tube
90,190,290 Controller (outlet gas temperature control means, superheat detection means)
120 4th expansion valve
230 Liquid injection tube
231 Bypass pipe

Claims (10)

Refrigerant circuit (10,160,204) connected to high pressure dome type compressor (11a, 11b, 11c, 101a, 101b, 101c), heat source side heat exchanger (13), and use side heat exchanger (16,17) ) A refrigeration apparatus comprising:
Discharge pipe temperature detection means (19a, 19b, 19c, 19d, 19e, 19f) for detecting the temperature (Td) of the discharge pipe of the compressor (11a, 11b, 11c, 101a, 101b, 101c);
The discharge pipe temperature detecting means (19a, 19b, 19c, 19d, 19e, 19f) so that the outlet gas temperature (Tp) of the compressor (11a, 11b, 11c, 101a, 101b, 101c) is lower than a predetermined temperature. And outlet gas temperature control means (80, 90, 180, 190, 280, 290) for controlling the outlet gas temperature (Tp) based on the time variation of the discharge pipe temperature (Td) detected by Refrigeration equipment. In claim 1,
The outlet gas temperature control means (80, 90, 180, 190) includes a liquid injection circuit (80, 180) for injecting liquid refrigerant on the suction side of the compressor (11a, 11b, 11c, 101a, 101b, 101c), and the discharge A refrigeration apparatus configured to adjust an injection amount of the liquid injection circuit (80, 180) based on a temporal change amount of a tube temperature (Td). In claim 2,
Further comprising superheat degree detection means (24,18a, 90,190) for detecting the superheat degree of the refrigerant sucked into the compressor (11a, 11b, 11c, 101a, 101b, 101c),
The outlet gas temperature control means (80, 90, 180, 190) is configured to change the discharge pipe temperature (Td) over time when the degree of superheat detected by the superheat degree detection means (24, 18a, 90, 190) is smaller than a predetermined value. A refrigeration apparatus configured to adjust the injection amount based on the above. In claim 1,
The outlet gas temperature control means (280, 290) includes a liquid injection circuit (280) for injecting liquid refrigerant into a compression chamber of intermediate pressure of the compressor (11a, 11b, 11c), and the discharge pipe temperature (Td ) Is configured to adjust the injection amount of the liquid injection circuit (280) based on the time variation of the discharge pipe temperature (Td) when the value is equal to or greater than a predetermined value. In any one of Claims 2 to 4,
The outlet gas temperature control means (80, 90, 180, 190, 280, 290) is configured to supply liquid to the compressor (11a, 11b, 11c, 101a, 101b, 101c) when the time variation of the discharge pipe temperature (Td) is zero or more. While the injection amount is increased, when the time variation is negative, the liquid injection amount to the compressor (11a, 11b, 11c, 101a, 101b, 101c) is decreased. Refrigeration equipment. In claim 5,
The outlet gas temperature control means (80, 90, 180, 190, 280, 290), when the discharge pipe temperature (Td) rises and the time change amount of the discharge pipe temperature (Td) is larger than a first predetermined amount, A refrigeration apparatus configured to increase an increase rate per unit time of the liquid injection amount as compared with a case where a time change amount is equal to or less than a first predetermined amount. In claim 5,
The outlet gas temperature control means (80, 90, 180, 190, 280, 290), when the discharge pipe temperature (Td) is lowered and the time variation of the discharge pipe temperature (Td) is smaller than a second predetermined amount, A refrigeration apparatus configured to increase a decrease rate per unit time of the liquid injection amount as compared with a case where the amount of time change is equal to or greater than a second predetermined amount. In any one of Claims 1-7,
The use side heat exchanger (16, 17) is a cooling heat exchanger for cooling the interior of the refrigerator. In any one of Claims 1-8,
The compressor (11a, 11b, 11c, 101a, 101b, 101c) is composed of a low stage compressor (101a, 101b, 101c) and a high stage compressor (11a, 11b, 11c),
The outlet gas temperature control means (80, 90, 180, 190) includes a discharge pipe temperature (Td) of at least one of the low-stage compressor (101a, 101b, 101c) and the high-stage compressor (11a, 11b, 11c). A refrigeration apparatus configured to control an outlet gas temperature (Tp) of the one compressor based on a time change amount. In any one of Claims 1-9,
A refrigeration apparatus using one of R410A and CO2 as a refrigerant.

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