JP2012515890A - Refrigeration cycle equipment - Google Patents

Abstract

The refrigeration cycle apparatus includes an expander-integrated compressor (1) having a first electric motor (12), a second compressor (2) having a second electric motor (22), and control means (7). The control means (7) determines the target rotational speed F1 of the first electric motor (12) for start-up operation and the target rotational speed F2 of the second electric motor 22 based on the outside air temperature and the like, and at the time of start-up operation, the injection valve ( 61) It is determined whether the opening degree X should be fully open or fully closed. Then, the control means (7) determines the rotational speeds f1 and f2 of the first electric motor (12) and the second electric motor (22) while keeping the opening X of the injection valve (61) in the fully open state or the fully closed state. The start-up operation is performed by controlling the target rotational speeds F1 and F2.

Description

  The present invention relates to a refrigeration cycle apparatus including an expansion mechanism and a plurality of compression mechanisms that are used in a water heater, an air conditioner, and the like.

  In recent years, a power recovery type refrigeration cycle apparatus has been proposed as a refrigeration cycle apparatus for realizing more efficient performance. In this type of refrigeration cycle apparatus, the pressure energy is recovered as mechanical energy in the process of expansion of the refrigerant, and instead of the expansion valve, the power required for driving the compression mechanism is reduced by the amount of recovered power. An expansion mechanism is used. Such a refrigeration cycle apparatus includes an expander-integrated compressor in which an electric motor, a compression mechanism, and an expansion mechanism are connected to each other by a shaft.

  Since the expander-integrated compressor includes a compression mechanism and an expansion mechanism that are connected to each other by a shaft, the ratio of the density of the refrigerant sucked into the compression mechanism and the density of the refrigerant sucked into the expansion mechanism is determined by the suction of the suction mechanism. There is a so-called “constant density ratio constraint” that is fixed at a constant ratio determined by the volume. For this reason, under certain operating conditions, the displacement of the compression mechanism or the displacement of the expansion mechanism may be insufficient. In order to maintain the recovery power and keep the coefficient of performance (COP) of the refrigeration cycle device high even under operating conditions that may cause the displacement of the compression mechanism to be insufficient, a second compressor is added to the expander-integrated compressor. A refrigeration cycle apparatus including the same has been proposed (see, for example, Patent Document 1).

  FIG. 8 is a diagram showing the configuration of the refrigeration cycle apparatus described in Patent Document 1. As shown in FIG. This refrigeration cycle apparatus includes a refrigerant circuit 140, in which a first compression mechanism 101 of an expander-integrated compressor 100 as a first compressor and a second compression mechanism 111 of a second compressor 110 are arranged in parallel. Has been. Specifically, the first compression mechanism 101 and the second compression mechanism 111 are connected to the radiator 120 through the first pipe 141 and are connected to the evaporator 130 through the fourth pipe 144. The expansion mechanism 103 of the expander-integrated compressor 100 is connected to the radiator 120 through a second pipe 142 and is connected to the evaporator 130 through a third pipe 143. In the refrigeration cycle apparatus of Patent Document 1, in order to prevent an excessive or insufficient amount of refrigerant flowing into the expansion mechanism 103, the rotation speed of the first motor 102 of the expander-integrated compressor 100 and the second speed of the second compressor 110 are set. The rotation speed of the electric motor 112 can be determined according to the outside air temperature or the like.

  Furthermore, the refrigeration cycle apparatus described in Patent Document 1 is provided with a bypass passage 160 for bypassing the expansion mechanism 103 and an injection passage 150 for further supplying refrigerant to the expansion mechanism 103 during the expansion process of the refrigerant. It has been. The bypass passage 160 and the injection passage 150 are provided with a bypass valve 161 and an injection valve 151, respectively, for adjusting the flow rate of the refrigerant. In the refrigeration cycle apparatus of Patent Document 1, the bypass valve 161 is closed and the injection valve 151 is opened in winter. The opening degree of the injection valve 151 is determined based on the outside air temperature or the like. With this configuration, the refrigeration cycle apparatus can cope with an insufficient amount of displacement of the expansion mechanism 103.

JP 2007-132622 A

  In the refrigeration cycle apparatus in which the compression mechanisms are arranged in parallel, it is conceivable to rotate the first electric motor of the expander-integrated compressor and the second electric motor of the second compressor at the same rotational speed.

  In general, in the refrigeration cycle apparatus, for example, as shown in FIG. 9, the low-pressure side pressure in winter is lower than the low-pressure side pressure in intermediate periods such as spring and autumn. The low pressure of the refrigeration cycle decreases as the outside air temperature decreases. For example, when the refrigeration cycle apparatus is used in a water heater as a heat pump unit for heating water to generate hot water, the temperature of water to be heated (for example, 20 ° C.) and the temperature of hot water to be generated (for example, 90 ° (° C.) does not change so much, the state of the refrigerant sucked into the expansion mechanism becomes substantially constant. As a result, as the outside air temperature decreases, the rotational speeds of the first electric motor of the expander-integrated compressor and the second electric motor of the second compressor increase, and at the same time, the apparent suction volume necessary for the expansion mechanism. Also decreases. Therefore, the opening degree of the injection valve is made smaller as the outside air temperature becomes lower.

  For example, FIG. 10 shows the first motor and the second motor when the outside air temperature is 2 ° C., 7 ° C., 12 ° C., and 16 ° C., assuming that the first motor and the second motor rotate at the same rotational speed. The number of rotations and the opening of the injection valve are shown. The data shown in FIG. 10 can be stored in advance in the form of a table in the control means of the refrigeration cycle apparatus. The control means refers to this table to determine how to set the rotation speeds of the first motor and the second motor and the opening of the injection valve for the start-up operation. When the actual outside air temperature is between two temperatures in the table, the rotation speed and the opening degree are each determined by a proportional distribution rule using two values corresponding to the two temperatures. That is, when the table of FIG. 10 is used, the opening degree of the injection valve is determined so as to continuously change according to the outside air temperature.

  On the other hand, in the refrigeration cycle apparatus provided with the injection path, the refrigerant flowing through the injection path is expanded to some extent in the injection valve unless the injection valve is fully opened. Therefore, a part of the expansion energy cannot be recovered.

  FIG. 11 is a graph showing experimental measurement results of energy loss (hereinafter referred to as “injection loss”) caused by pressure drop when refrigerant passes through an injection valve in a refrigeration cycle apparatus having an injection path. In FIG. 11, the horizontal axis represents the injection flow rate (that is, the flow rate of the refrigerant flowing through the injection path), and the vertical axis represents the injection loss. As shown in FIG. 11, the injection loss decreases as the injection flow rate decreases, that is, as the opening degree of the injection valve decreases, or as the injection flow rate increases, that is, as the opening degree of the injection valve increases.

  These results indicate that the injection loss varies greatly depending on the injection flow rate, that is, the opening degree of the injection valve. For this reason, it is preferable that the opening degree of the injection valve is in a fully closed state or a fully open state. Even during the start-up operation, it is preferable that the opening of the injection valve is in a fully closed state or a fully open state.

  However, when the table shown in FIG. 10 is used, the opening degree of the injection valve is determined so as to change continuously according to the outside air temperature, and the injection valve is controlled to have the determined opening degree during start-up operation. Is done. For this reason, an injection loss occurs during the start-up operation.

  The present invention has been made in view of the above problems, and an object of the present invention is to reduce injection loss during start-up operation in a refrigeration cycle apparatus including an expansion mechanism and a plurality of compression mechanisms and including an injection path. It is to suppress.

In order to solve the above problems, the present invention provides:
A first compression mechanism for compressing the refrigerant; an expansion mechanism for recovering power from the expanding refrigerant; a first electric motor coupled to the first compression mechanism and the expansion mechanism by a shaft; and the first compression A first compressor including a mechanism, the expansion mechanism, and a first hermetic container for housing the first electric motor;
A second compression mechanism for compressing the refrigerant, wherein the second compression mechanism is connected in parallel with the first compression mechanism in the refrigerant circuit; and a second electric motor connected to the second compression mechanism by a shaft; A second compressor including the second compression mechanism and a second sealed container for housing the second electric motor;
A radiator for dissipating heat from the refrigerant discharged from the first compression mechanism and the second compression mechanism;
An evaporator for evaporating the refrigerant discharged from the expansion mechanism;
A first pipe for guiding a refrigerant from the first compression mechanism and the second compression mechanism to the radiator;
A second pipe for guiding the refrigerant from the radiator to the expansion mechanism;
A third pipe for guiding the refrigerant from the expansion mechanism to the evaporator;
A fourth pipe for guiding the refrigerant from the evaporator to the first compression mechanism and the second compression mechanism;
An injection path branched from the second pipe for supplying a refrigerant to the expansion mechanism in the expansion process;
An injection valve provided in the injection path and having an adjustable opening;
An outside temperature sensor for detecting the outside temperature;
Based on the outside air temperature detected by the outside air temperature sensor, the target rotational speed of the first electric motor and the target rotational speed of the second electric motor for start-up operation are determined, and the opening degree of the injection valve is determined during the start-up operation. A target for determining whether to be in a fully open state or a fully closed state, and determining the rotation speeds of the first motor and the second motor while maintaining the opening degree of the injection valve in a fully open state or a fully closed state Control means for performing start-up operation by controlling the number of revolutions;
A refrigeration cycle apparatus comprising:

  Here, the fully closed state means a state where the flow of the refrigerant is substantially blocked by the injection valve, for example, a state where the opening degree is 5% or less. The fully open state refers to a state in which the refrigerant flow is not substantially inhibited by the injection valve, for example, a state where the opening degree is 95% or more.

  With the configuration as described above, the refrigeration cycle apparatus of the present invention can suppress injection loss at the time of start-up operation.

FIG. 1 is a schematic view of a refrigeration cycle apparatus according to an embodiment of the present invention. FIG. 2 shows a plurality of tables used in the embodiment of the present invention having the target rotational speeds of the first motor and the second motor and the opening degree of the injection valve in relation to the set discharge temperature, the water temperature and the outside air temperature. It is a figure for demonstrating. FIG. 3 shows a table when the set discharge temperature is 110 ° C. and the water temperature is 20 ° C. in the table of FIG. FIG. 4 shows a steady operation table when the set discharge temperature is 110 ° C. and the water temperature is 20 ° C. FIG. 5 shows a graph obtained by plotting the values in the table of FIG. 6A to 6C are diagrams for explaining how the rotation speeds of the first motor and the second motor are changed during the start-up operation. FIG. 7 is a flowchart of the starting operation performed by the control means. FIG. 8 is a schematic view of a conventional refrigeration cycle apparatus. FIG. 9 is a Mollier diagram representing the intermediate period and the winter period. FIG. 10 shows the conventional motor having the rotation speed of the first motor and the second motor and the opening degree of the injection valve in relation to the outside air temperature when it is assumed that the first motor and the second motor rotate at the same rotation speed. It is a figure which shows the table of a refrigerating-cycle apparatus. FIG. 11 is a diagram showing the relationship between the injection flow rate and the injection loss.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

  FIG. 1 shows a refrigeration cycle apparatus according to an embodiment of the present invention. This refrigeration cycle apparatus includes a refrigerant circuit 30. The refrigerant circuit 30 includes an expander-integrated compressor 1 as a first compressor, a second compressor 2, a radiator 4, an evaporator 5, and first to fourth pipes (refrigerants) for connecting these devices. Piping) 3a-3d are included.

  The expander-integrated compressor 1 includes a first sealed container 10 for housing a first compression mechanism 11, a first electric motor 12, and an expansion mechanism 13 that are connected to each other by a first shaft 15. The second compressor 2 has a second hermetic container 20 for housing a second compression mechanism 21 and a second electric motor 22 connected to each other by a second shaft 25. The first compression mechanism 11 and the second compression mechanism 21 are connected to the radiator 4 via a first pipe 3a having two branch pipes and a main pipe connected thereto. The radiator 4 is connected to the expansion mechanism 13 via the second pipe 3b. The expansion mechanism 13 is connected to the evaporator 5 via the third pipe 3c. The evaporator 5 is connected to the first compression mechanism 11 and the second compression mechanism 21 via a fourth pipe 3d having a main pipe and two branch pipes connected to the main pipe. In the refrigerant circuit 30, the first compression mechanism 11 and the second compression mechanism 21 are arranged in parallel. In other words, in the refrigerant circuit 30, the first compression mechanism 11 and the second compression mechanism 21 are connected in parallel to each other.

  The refrigerant compressed by the first compression mechanism 11 and the refrigerant compressed by the second compression mechanism 21 are respectively discharged from the first compression mechanism 11 and the second compression mechanism 21 to the first pipe 3a, and then the first pipe 3a. Join in. The merged refrigerant is guided to the radiator 4. The refrigerant compressed by the compression mechanisms 11 and 21 may be once discharged separately into the sealed containers 10 and 20 and then discharged from the sealed containers 10 and 20 to the first pipe 3a. The refrigerant guided to the radiator 4 radiates heat here, and then is guided to the expansion mechanism 13 through the second pipe 3b. The refrigerant guided to the expansion mechanism 13 expands here. At this time, the expansion mechanism 13 recovers power from the expanding refrigerant. The expanded refrigerant is guided to the evaporator 5 through the third pipe 3c. The refrigerant led to the evaporator 5 absorbs heat here, and then is divided into two flows led to the first compression mechanism 11 and the second compression mechanism 21 in the fourth pipe 3d.

  The displacement volume of the first compression mechanism 11 is preferably the same as the displacement volume of the second compression mechanism 21. In this case, the 1st compression mechanism 11 and the 2nd compression mechanism 21 can be comprised with a common member, and, thereby, cost reduces.

  Further, the refrigeration cycle apparatus includes an injection path 6 that is branched from the second pipe 3b and for supplying the refrigerant to the expansion mechanism 13 in the expansion process of the refrigerant. In the middle of the injection path 6, an injection valve 61 capable of adjusting the opening is provided for adjusting the flow rate.

  The refrigeration cycle apparatus of this embodiment is used as a heat pump unit for heating water to generate hot water in a hot water supply device for supplying hot water stored in the hot water storage tank 200 to the hot water tap 201. Specifically, the radiator 4 functions as a heat exchanger for exchanging heat between water and the refrigerant to heat the water. The refrigerant path 41 through which the refrigerant flows and the water path through which water (fluid) flows ( Fluid path) 42. The water flowing through the water path 42 receives heat from the refrigerant flowing through the refrigerant path 41. The refrigeration cycle apparatus further includes a supply pipe 91 for supplying water from the hot water storage tank 200 to the water path 42 and a return pipe 92 for returning water (hot water) from the water path 42 to the hot water storage tank 200.

  The refrigeration cycle apparatus mainly includes control means 7 for controlling the rotation speeds of the first motor 12 and the second motor 22 and the opening degree of the injection valve 61. In this embodiment, the control means 7 is connected to the radiator 4 through the outside air temperature sensor 82 for detecting the outside air temperature, the fluid temperature sensor 93 for detecting the temperature of the water flowing through the supply pipe 91, and the first pipe 3a. It is connected to a refrigerant temperature sensor 81 for detecting the temperature of the introduced refrigerant (more specifically, the temperature of the merged refrigerant).

The refrigerant circuit 30 is filled with a refrigerant that is in a supercritical state on the high-pressure side (specifically, a path from the first compression mechanism 11 and the second compression mechanism 21 to the expansion mechanism 13 through the radiator 4). In the present embodiment, carbon dioxide (CO ₂ ) is filled in the refrigerant circuit 30 as such a refrigerant. However, the type of refrigerant is not particularly limited. The refrigerant may be a refrigerant that does not enter a supercritical state during operation (for example, a fluorocarbon refrigerant).

  Next, the control performed by the control means 7 will be described. As shown in FIG. 6A, the control means 7 first performs a start-up operation and then performs a steady operation. Specifically, the control means 7 starts up the first electric motor 12 and the second electric motor 22 so as to smoothly shift to the steady operation. This is the start-up operation. As described with reference to FIG. 11 in the problem column, in order to suppress the injection loss small, the opening degree of the injection valve 61 is in a fully closed state or a fully open state not only during steady operation but also during start-up operation. Is preferred. For this reason, the control means 7 performs the following control. FIG. 7 is a flowchart of the control.

  Immediately before the start-up operation, the control means 7 detects the predetermined set discharge temperature of the refrigerant guided to the radiator 4 through the first pipe 3 a, the outside temperature detected by the outside temperature sensor 82, and the fluid temperature sensor 93. The obtained water temperature is acquired (step S1). Then, the control means 7 determines the target rotational speed F1 of the first electric motor 12 and the target rotational speed F2 of the second electric motor 22 for start-up operation based on the acquired set discharge temperature, outside air temperature, and water temperature. It is determined whether the opening X of the injection valve 61 should be in a fully closed state or a fully open state during start-up operation (steps S2 to S4).

  Specifically, as shown in FIG. 2, the control means 7 includes each set discharge temperature (for example, in increments of 5 ° C. from 80 ° C. to 140 ° C.) and each water temperature (for example, in increments of 2 ° C. from 10 ° C. to 30 ° C.). ) Are stored in advance. FIG. 3 shows a table when the set discharge temperature is 110 ° C. and the water temperature is 20 ° C. as a representative example of the table. In each table, the target rotational speed F1 of the first electric motor 12, the second electric motor with respect to each predetermined outside air temperature (in this embodiment, 0 ° C., 2 ° C., 7 ° C., 9 ° C., 12 ° C., 16 ° C.). The target rotational speed F2 of 22 and the opening X of the injection valve (0% or 100% in this embodiment) are determined. In each table of this embodiment, the continuity of values is interrupted at an outside air temperature of 9 ° C., that is, 9 ° C. is the threshold temperature. More specifically, as shown in FIG. 5, at a temperature of 9 ° C., the opening X of the injection valve is switched from the fully closed state to the fully opened state or vice versa, and the target rotational speed F1 of the first motor 12 and the 2 The relationship of the target rotational speed F2 of the electric motor 22 is reversed. The table has two columns for an outside air temperature of 9 ° C. When the outside air temperature is 9 ° C., the value in the left column is used. When the outside air temperature is in the range from over 9 ° C. to 12 ° C., the values in the right column are used to determine the target rotational speeds F1 and F2 of the first electric motor 12 and the second electric motor 22.

  The set discharge temperature is related to the target temperature of water to be heated by the radiator 4 (temperature of hot water to be generated). A desired value of the set discharge temperature is selected in advance according to the application or environment, and the selected value is stored in the memory of the control means 7. For example, when producing 90 ° C. hot water, a set discharge temperature of 110 ° C. is selected. The control means 7 reads the set discharge temperature from the memory and acquires the temperature. It is also possible to determine the set discharge temperature to be acquired each time based on the target temperature of the water to be heated by the radiator 4 and the outside air temperature.

  The control means 7 specifies a table group corresponding to the set discharge temperature acquired from the table immediately before starting the startup operation. Further, the control means 7 selects a water temperature table closest to the water temperature detected by the fluid temperature sensor 93 from the identified table group (step S2). Next, the control means 7 uses the selected table and based on the outside air temperature detected by the outside air temperature sensor 82, the target rotation speed F1 of the first motor 12 for start-up operation and the target rotation of the second motor 22 are set. The number F2 is determined (step S3). When the detected outside air temperature matches the outside air temperature listed in the selected table, the target rotation speeds F1 and F2 are determined to values specified in this table. When the detected outside air temperature is between the two outside air temperatures listed in the table, the target rotation speeds F1 and F2 are respectively calculated by the proportional distribution side using two values corresponding to the two temperatures. Determined value. When the detected outside air temperature is outside the range of the outside air temperature listed in the table, the target rotation speeds F1 and F2 are determined to values defined in the table relating to the nearest outside air temperature. When the detected outside air temperature is between the two outside air temperatures listed in the table, the value corresponding to the one of the two temperatures closer to the detected temperature is adopted for determining the target rotational speeds F1 and F2. May be.

  The control means 7 determines the target rotational speed F1 of the first motor 12 for start-up operation and the target rotational speed F2 of the second motor 22, and at the same time uses the selected table to detect the target rotational speed F1. Based on the outside air temperature, it is determined whether the opening X of the injection valve 61 should be in a fully closed state or a fully open state during start-up operation (step S4). In the present embodiment, if the detected outside air temperature is 9 ° C. or less, the control means 7 determines that the opening X of the injection valve 61 should be fully closed (0%), and the detected outside air temperature is If it is greater than 9 ° C., the control means 7 determines that the opening X of the injection valve 61 should be fully open (100%). As described above, when the detected outside air temperature matches the threshold temperature, it is determined that the opening X of the injection valve 61 should be fully closed in order to prevent pressure loss in the injection passage 6. preferable.

  The threshold temperature that defines the switching point between the fully closed state and the fully open state for the opening degree X of the injection valve 61 is not necessarily 9 ° C. The threshold temperature can be determined as appropriate. For example, the threshold temperature may be determined by the following method. As shown in FIG. 5, as the outside air temperature rises from 0 ° C., the target rotational speed F1 of the first electric motor 12 increases, but the target rotational speed F2 of the second electric motor 22 decreases. Therefore, the threshold temperature may be determined as the outside air temperature at the point where the ratio F1 / F2 of the target rotational speed F1 of the first electric motor 12 to the target rotational speed F2 of the second electric motor 22 exceeds the value A. This is a method aimed at keeping the balance between the lubricating oil in the sealed container 10 and the lubricating oil in the sealed container 20 by suppressing the rotation speed ratio F1 / F2 to some extent. Alternatively, the threshold temperature may be determined to be the outside air temperature immediately before the target rotational speed F1 of the first electric motor 12 exceeds the upper limit value of the rotational speed determined from the viewpoint of reliability assurance.

  Hereinafter, the values defined in the plurality of tables will be described in detail.

  In the present embodiment, each target rotational speed F2 of the second electric motor 22 in the table corresponds to the rotation of the corresponding second electric motor 22 in the steady operation table for ideal steady operation that is derived from the set discharge temperature, outside air temperature, and water temperature. It is larger than the number F2 ′. Here, the ideal steady state operation is the opening degree X of the injection valve 61 optimized on the assumption that the rotation speed of the first motor 12 is the same as the rotation speed of the second motor 22 (see FIG. 10). The state when the rotational speed of one of the first motor 12 and the second motor 22 is increased and the other rotational speed is decreased until the opening X becomes 0% or 100%. Whether to increase or decrease the rotation speed of the first motor 12 or the rotation speed of the second motor 22 is determined based on the opening degree X of the optimized injection valve 61. For example, when the opening degree X of the optimized injection valve 61 is less than 50%, the rotation speed of the first motor 12 is increased and the rotation speed of the second motor 22 is decreased so that the opening degree X approaches 0%. . When the opening degree X of the optimized injection valve 61 is 50% or more, the rotation speed of the first electric motor 12 is decreased and the rotation speed of the second electric motor 22 is increased so that the opening degree X approaches 100%. If the opening degree X of the optimized injection valve 61 is 0% or 100%, the ideal steady state operation is a state where the rotation speed of the first motor is the same as the rotation speed of the second motor.

  FIG. 4 shows a steady operation table when the set discharge temperature is 110 ° C. and the water temperature is 20 ° C. Below, the table memorize | stored in the control means 7 is called "starting-up operation table", in order to distinguish from a steady operation table.

  As shown in FIGS. 3 and 4, in the start-up operation table of the present embodiment, only the rotation speed of the second motor 22 is larger than that in the steady operation table. A steady operation table is stored in the control means 7, and the target rotational speeds F1 and F2 of the first motor 12 and the second motor 22 for the start-up operation can be determined by using the steady operation table in which the control means 7 is stored. It may be. Even in the steady operation table, the opening X of the injection valve is set to 0% or 100%. Therefore, even if the steady operation table is used, the injection loss can be suppressed during the start-up operation. However, by using the start-up operation table having a large rotation speed of the second electric motor 22 as in this embodiment, the pressure difference between the high pressure side and the low pressure side of the refrigeration cycle can be quickly established. As a result, the constituent member on the high pressure side of the refrigeration cycle apparatus can be warmed up early.

  In order to quickly establish the pressure difference between the high pressure side and the low pressure side of the refrigeration cycle, a startup operation table in which the rotation speed of the first motor 12 is larger than that in the steady operation table may be used. The ratio F1 / F2 of the target rotational speed F1 of the first electric motor 12 in the start-up operation table to the target rotational speed F2 of the second electric motor 22 that is paired with the target rotational speed F1 is the rotational speed of the second electric motor 22 in the corresponding steady operation table. It is preferably smaller than the ratio F1 ′ / F2 ′ of the rotational speed F1 ′ of the first electric motor 12 with respect to F2 ′. According to this configuration, the rotational speed of the expander-integrated compressor 1 can be reduced as compared with the rotational speed of the second compressor 2. Therefore, the apparent specific volume of the pressure expansion mechanism 13 is reduced with respect to the specific volume of the contraction mechanisms 11 and 21, and as a result, a pressure difference between the high pressure side and the low pressure side of the refrigeration cycle can be quickly established.

  Alternatively, the target motor speed F2 of the second motor 22 in the startup operation table is maintained to be equal to the corresponding rotation speed F2 ′ of the first motor 22 in the steady operation table, and then the first motor in the startup operation table. Each of the 12 target rotational speeds F1 may be set smaller than the rotational speed F1 ′ of the corresponding first electric motor 12 in the steady operation table. Using a startup operation table in which at least the rotation speed of the second electric motor 22 is set larger than that in the steady operation table can circulate a sufficient amount of refrigerant to the refrigerant circuit 30 during the startup operation. It is preferable because the constituent members of the refrigeration cycle apparatus can be warmed early.

  The difference between each target rotational speed F1 of the first electric motor 12 and the target rotational speed F2 of the second electric motor 22 that is paired with the target rotational speed F1 in the start-up operation table is under any condition (that is, any set discharge temperature, Any water temperature and any outside air temperature) is preferably smaller than the upper limit of the allowable operating range (for example, 40 Hz). Further, the ratio F1 / F2 of the target rotation speed F1 of the first motor 12 in the startup operation table to the target rotation speed F2 of the second motor 22 that is paired with the target rotation speed F1 is a lower limit value (for example, 0.5). ) And an upper limit (for example, 2). Here, the operation allowable range is the allowable minimum number of rotations and the maximum allowable number of rotations of the compression mechanisms 11, 21, or the difference in the number of rotations of the first motor 12 and the number of rotations of the second motor 22. A range that is arbitrarily determined based on factors that should be considered from the viewpoint of design, such as the degree of imbalance between the lubricating oil level and the lubricating oil level in the sealed container 20.

  The control means 7 determines the target rotational speed F1 of the first motor 12 and the target rotational speed F2 of the second electric motor 22 for the start-up operation by using the start-up operation table stored in the control means 7 in advance. At the same time, it is determined whether the opening X of the injection valve 61 should be fully closed or fully open during the start-up operation. Subsequently, the control means 7 drives the 1st electric motor 12 and the 2nd electric motor 22, and starts a starting operation (step S5). Then, the control means 7 controls the rotation speeds f1 and f2 of the first electric motor 12 and the second electric motor 22 to the determined target rotation speeds F1 and F2, respectively, until a predetermined time for starting operation elapses. The starting operation is performed by (Step S6). In the present embodiment, as shown in FIG. 6A, the control means 7 continuously increases the rotation speeds f1 and f2 of the first electric motor 12 and the second electric motor 22 to the determined target rotation speeds F1 and F2, respectively. During the start-up operation, the control means 7 increases the rotation speeds f1 and f2 of the first motor 12 and the second motor 22 to the determined target rotation speeds F1 and F2, and then maintains the target rotation speeds F1 and F2 for a certain time. May be.

  In addition, when it is determined that the opening degree of the injection valve 61 should be in a fully closed state, the control means 7 performs the starting operation while keeping the opening degree X of the injection valve 61 in a fully closed state. However, when it is determined that the opening degree of the injection valve 61 should be fully open, the control means 7 performs the starting operation while keeping the opening degree X of the injection valve 61 fully open. When the control means 7 determines that the opening degree of the injection valve 61 should be in a fully open state, the control means 7 controls the opening degree of the injection valve to be in a fully closed state for a certain period from the start of the starting operation, and then switches to the fully open state. Also good. According to this configuration, the pressure difference between the high-pressure side and the low-pressure side of the refrigeration cycle can be quickly established, and the time required for shifting from the startup operation to the steady operation can be shortened.

  After the start-up operation is completed, the control means 7 performs a steady operation. Specifically, the control means 7 changes the rotation speeds f1 and f2 of the first motor 12 and the second motor 22 to the rotation speeds F1 ′ and F2 ′ determined based on the steady operation table shown in FIG. (In the present embodiment, the rotational speed of the first electric motor 12 is maintained as it is). Thereafter, the control means 7 controls the injection valve 61 so that the high pressure of the refrigeration cycle can be maintained at the optimum high pressure by feedback control, in other words, the refrigerant temperature detected by the refrigerant temperature sensor 81 is equal to the set discharge temperature. And the rotation speeds f1 and f2 of the first motor 12 and the second motor 22 are adjusted.

  As described above, in the refrigeration cycle apparatus of the present embodiment, the start-up operation is performed with the opening X of the injection valve 61 kept in the fully closed state or the fully open state under any conditions. For this reason, the injection loss can be kept small during the start-up operation. In particular, if the opening X of the injection valve 61 is kept at 0% or 100% as in the present embodiment, it is possible to prevent injection loss.

(Modification 1)
In the embodiment, the control means 7 continuously increases the rotation speeds f1 and f2 of the first motor 12 and the second motor 22 as shown in FIG. 6A. However, the control means 7 may increase the rotation speeds f1 and f2 of the first electric motor 12 and the second electric motor 22 stepwise as shown in FIG. 6B.

  Specifically, the control means 7 divides the startup operation period into a plurality of control sections (for example, every 180 seconds) according to time. And the control means 7 increases both the rotation speed f1 of the 1st electric motor 12, and the rotation speed f2 of the 2nd electric motor 22, and the rotation speed f1, of the 1st electric motor 12 and the 2nd electric motor 22 is switched as a control area switches. The total of f2 is gradually approached to the total of the target rotational speeds F1 and F2 of the first electric motor 12 and the second electric motor 22 determined. The sudden increase in the rotation speeds f1 and f2 of the first motor 12 and the second motor 22 may cause a so-called overshoot in which the actual refrigerant discharge temperature exceeds the set discharge temperature. On the other hand, if the rotation speeds f1 and f2 of the first electric motor 12 and the second electric motor 22 are gradually increased as described above, such overshoot can be prevented.

  The control means 7 calculates the difference between the set discharge temperature and the refrigerant temperature detected by the refrigerant temperature sensor 81 every time the control section is switched. If the difference is a relatively large value, the first electric motor 12 It is preferable to relatively increase the sum of the rotational speed f1 of the second motor 22 and the rotational speed f2 of the second electric motor 22 relatively large. According to this configuration, the high pressure of the refrigeration cycle can be brought close to the target value at an early stage, and the startup operation time can be shortened.

(Modification 2)
In the example shown in FIG. 6B, the control means 7 determines the ratio f1 / f2 of the rotation speed f1 of the first motor 12 to the rotation speed f2 of the second motor 22 with respect to the determined target rotation speed F2 of the second motor 22. The rotational speeds f1 and f2 of the first electric motor 12 and the second electric motor 22 are increased as the control interval is switched while keeping the determination ratio F1 / F2 equal to the ratio of the target rotational speed F1 of the first electric motor 12. However, as shown in FIG. 6C, the control means 7 sets the rotational speed ratio f1 / f2 to be smaller than the determination ratio F1 / F2 in the first control section, and the control section is in the control section following the first control section. You may make it gradually approach the determination ratio F1 / F2 as it switches. According to this configuration, the rotational speed of the expander-integrated compressor 1 can be reduced as compared with the rotational speed of the second compressor 2. Therefore, the apparent specific volume of the expansion mechanism 13 is reduced with respect to the specific volume of the compression mechanisms 11 and 21, and as a result, a pressure difference between the high pressure side and the low pressure side of the refrigeration cycle can be quickly established.

  In this case, the control means 7 calculates the difference between the set discharge temperature and the refrigerant temperature detected by the refrigerant temperature sensor 81 every time the control section is switched. If this difference is a relatively large value, the control means 7 It is preferable to increase the number ratio f1 / f2 at a moderate rate. According to this configuration, a sufficient amount of refrigerant can be circulated through the refrigerant circuit 30 during start-up operation, and a pressure difference between the high pressure side and the low pressure side can be quickly established. Therefore, the constituent members of the refrigeration cycle apparatus can be warmed early, whereby the actual refrigerant discharge temperature can be quickly raised to the set discharge temperature.

(Other variations)
In the embodiment, the start-up operation is terminated when a predetermined time has elapsed by the control means 7. However, the control means 7 may end the start-up operation when the actual refrigerant discharge temperature exceeds the set discharge temperature. Furthermore, the control means 7 may perform the starting operation repeatedly. In this case, a start-up operation table may be prepared for each start-up operation, and after the first start-up operation is completed, step S2 to step S6 in FIG. 7 may be repeated.

  In the embodiment, the control means 7 uses the set discharge temperature in order to determine the target rotational speeds F1 and F2 of the first electric motor 12 and the second electric motor 22 for starting operation and the opening X of the injection valve 61. . However, the control means 7 may use the target temperature of water to be heated by the radiator 4 (temperature of hot water to be generated) instead of the set discharge temperature.

  Furthermore, in the embodiment, the refrigeration cycle apparatus includes the fluid temperature sensor 93. However, the water temperature may be input to the control means 7 in advance as a value that varies depending on the season. The water temperature may be a fixed value.

  In the embodiment, the radiator 4 functions as a heat exchanger for exchanging heat between the refrigerant and water. However, the heat radiator 4 may be a heat exchanger for exchanging heat between a fluid other than water (for example, air) and a refrigerant.

  The refrigeration cycle apparatus may be used for an air conditioner. In this case, the radiator 4 does not have the water path 42 and releases heat from the refrigerant to the atmosphere.

  The refrigerant circuit included in the refrigeration cycle apparatus of the present invention is not limited to the refrigerant circuit 30 for allowing the refrigerant to flow only in one direction, but includes a refrigerant circuit that can change the flow direction of the refrigerant, for example, a four-way valve. A refrigerant circuit capable of switching between heating operation and cooling operation may be used.

  The refrigeration cycle apparatus of the present invention is useful as a power recovery system for recovering expansion energy of refrigerant in the refrigeration cycle as mechanical energy.

Claims (15)

A first compression mechanism for compressing the refrigerant; an expansion mechanism for recovering power from the expanding refrigerant; a first electric motor coupled to the first compression mechanism and the expansion mechanism by a shaft; and the first compression A first compressor including a mechanism, the expansion mechanism, and a first hermetic container for housing the first electric motor;
A second compression mechanism for compressing the refrigerant, wherein the second compression mechanism is connected in parallel with the first compression mechanism in the refrigerant circuit; and a second electric motor connected to the second compression mechanism by a shaft; A second compressor including the second compression mechanism and a second sealed container for housing the second electric motor;
A radiator for dissipating heat from the refrigerant discharged from the first compression mechanism and the second compression mechanism;
An evaporator for evaporating the refrigerant discharged from the expansion mechanism;
A first pipe for guiding a refrigerant from the first compression mechanism and the second compression mechanism to the radiator;
A second pipe for guiding the refrigerant from the radiator to the expansion mechanism;
A third pipe for guiding the refrigerant from the expansion mechanism to the evaporator;
A fourth pipe for guiding the refrigerant from the evaporator to the first compression mechanism and the second compression mechanism;
An injection path branched from the second pipe for supplying a refrigerant to the expansion mechanism in the expansion process;
An injection valve provided in the injection path and having an adjustable opening;
An outside temperature sensor for detecting the outside temperature;
Based on the outside air temperature detected by the outside air temperature sensor, the target rotational speed of the first electric motor and the target rotational speed of the second electric motor for start-up operation are determined, and the opening degree of the injection valve is determined during the start-up operation. A target for determining whether to be in a fully open state or a fully closed state, and determining the rotation speeds of the first motor and the second motor while maintaining the opening degree of the injection valve in a fully open state or a fully closed state Control means for performing start-up operation by controlling the number of revolutions;
A refrigeration cycle apparatus comprising: The radiator is a heat exchanger for heating a fluid with a refrigerant, and has a refrigerant path through which the refrigerant flows and a fluid path through which the fluid flows.
The control means determines a target rotational speed of the first motor and the second motor for start-up operation based on a target temperature of the fluid to be heated by the radiator and an outside air temperature detected by the outside temperature sensor. And determining whether the opening of the injection valve should be in a fully open state or a fully closed state during start-up operation, and maintaining the opening of the injection valve in a fully open state or a fully closed state. 2. The refrigeration cycle apparatus according to claim 1, wherein the start-up operation is performed by controlling the rotation speed of the second electric motor to the determined target rotation speed. The radiator is a heat exchanger for heating a fluid with a refrigerant, and has a refrigerant path through which the refrigerant flows and a fluid path through which the fluid flows.
The control means includes the first motor and the second motor for start-up operation based on a set discharge temperature of the refrigerant guided to the radiator through the first pipe and an outside air temperature detected by the outside air temperature sensor. And determining whether the opening of the injection valve should be fully open or fully closed during start-up operation, and maintaining the opening of the injection valve in a fully open state or a fully closed state. 2. The refrigeration cycle apparatus according to claim 1, wherein the start-up operation is performed by controlling the rotation speeds of the first electric motor and the second electric motor to a determined target rotation speed without any change. A supply pipe for supplying fluid to the fluid path; and a fluid temperature sensor for detecting a temperature of fluid flowing through the supply pipe;
The control means, based on the set discharge temperature, the outside air temperature detected by the outside air temperature sensor, and the fluid temperature detected by the fluid temperature sensor, the target rotational speed of the first motor for start-up operation and the first 2 Determine the target rotational speed of the motor, determine whether the opening of the injection valve should be fully open or fully closed during start-up operation, and set the opening of the injection valve to be fully open or fully closed 4. The refrigeration cycle apparatus according to claim 3, wherein the start-up operation is performed by controlling the rotation speeds of the first motor and the second motor to the determined target rotation speed while being maintained at a predetermined value. The control means stores a plurality of tables having target rotational speeds of the first electric motor and the second electric motor and opening degrees of the injection valves in relation to a set discharge temperature, an outside air temperature, and a fluid temperature.
The control means uses the table based on the set discharge temperature, the outside air temperature detected by the outside air temperature sensor and the fluid temperature detected by the fluid temperature sensor, so that the first for start-up operation is used. 5. The refrigeration cycle apparatus according to claim 4, wherein a target rotational speed of the electric motor and the second electric motor is determined, and whether the opening of the injection valve should be fully open or fully closed during start-up operation. .   Each target rotation speed of the 2nd motor in the said table is larger than the rotation speed of the corresponding 2nd motor in the steady operation table for ideal steady operation derived from setting discharge temperature, outside air temperature, and fluid temperature. 5. The refrigeration cycle apparatus according to 5.   The ratio of each target rotational speed of the first motor in the table to the target rotational speed of the second motor that is paired with the target rotational speed of the first motor is the corresponding rotational speed of the first motor to the rotational speed of the second motor in the steady operation table. The refrigeration cycle apparatus according to claim 6, which is smaller than the ratio.   6. The refrigeration cycle apparatus according to claim 5, wherein a difference between each target rotational speed of the first motor in the table and a target rotational speed of the second motor paired therewith is smaller than an upper limit value of an allowable operation range.   6. The ratio of each target rotational speed of the first motor in the table to the target rotational speed of the second motor that is paired with the target rotational speed is within a range between a lower limit value and an upper limit value of the allowable operation range. Refrigeration cycle equipment.   The control means divides the start-up operation period into a plurality of control sections according to time, and at the start-up operation, the total number of rotations of the first motor and the second motor is changed as the control section is switched. The refrigeration cycle apparatus according to any one of claims 3 to 9, which gradually approaches the determined total target rotational speed of the first electric motor and the second electric motor. A refrigerant temperature sensor for detecting a temperature of the refrigerant guided to the radiator through the first pipe;
The control means calculates the difference between the set discharge temperature and the refrigerant temperature detected by the refrigerant temperature sensor every time the control section is switched, and if the difference is a relatively large value, The refrigeration cycle apparatus according to claim 10, wherein the total number of rotations of the first electric motor and the second electric motor is relatively increased.   The control means divides the start-up operation period into a plurality of control sections according to time, and at the start-up operation, the ratio of the rotation speed of the first motor to the rotation speed of the second motor is set to In the first control section, a determination ratio that is a ratio of the determined target rotational speed of the first motor to the determined target rotational speed of the second electric motor is set to be smaller, and in the control section that follows the first control section, the control section has no control section. The refrigeration cycle apparatus according to any one of claims 3 to 9, which gradually approaches the determination ratio as it is switched. A refrigerant temperature sensor for detecting a temperature of the refrigerant guided to the radiator through the first pipe;
The control means calculates the difference between the set discharge temperature and the refrigerant temperature detected by the refrigerant temperature sensor every time the control section is switched, and if the difference is a relatively large value, The refrigeration cycle apparatus according to claim 12, wherein the ratio of the rotation speed of the first motor to the rotation speed of the two motors is increased at a moderate rate.   The refrigeration cycle apparatus according to any one of claims 10 to 13, wherein the control unit increases both the number of rotations of the first motor and the second motor as the control section is switched.   If the control means determines that the opening of the injection valve should be in a fully open state, the control means controls the opening of the injection valve to a fully closed state for a certain period from the start of startup operation, and then switches to the fully open state. The refrigeration cycle apparatus according to any one of claims 1 to 14.

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