JP5506620B2 - Air conditioner operation control method - Google Patents

Description

  The present invention relates to an air conditioner capable of switching between a compression cycle and a refrigerant pump cycle, and more particularly, to an operation control technique for avoiding cavitation of a refrigerant pump.

A refrigerant circulation circuit (hereinafter referred to as a combined refrigeration cycle) that can be operated by appropriately switching between a compression cycle that circulates refrigerant using a compressor and a refrigerant pump cycle that circulates refrigerant using a refrigerant pump. Air conditioners are known. Such an air conditioner can be operated by a compression cycle when the outside air temperature is high in summer or the like, and can be operated by a refrigerant pump cycle (hereinafter referred to as a pump cycle) when the outside air temperature is low in winter or the like. Compared to cycle-only operation, power consumption can be reduced, and an air conditioner with excellent energy savings can be realized.
The applicant of the present application controls operation based on a temperature difference between the outside air temperature and room temperature, a cooling capacity in the compression cycle, a compressor frequency, and the like regarding the switching condition of the compression cycle / pump cycle in the combined refrigeration cycle. The technology is disclosed (Patent Document 1).
Furthermore, the applicant of the present application obtains the refrigerant subcooling degree at the refrigerant pump inlet in order to prevent instability due to cavitation generation during pump cycle operation, damage to the refrigerant pump due to vibration and erosion, and the like. The technique which controls any one of an indoor side air blower, an outdoor side air blower, and an expansion valve opening degree is disclosed (patent document 2).

JP 2002-61918 A JP 2004-169941 A

The degree of refrigerant supercooling during the pump cycle operation is not limited to the outside air temperature and operating conditions, but also the air conditioner installation conditions such as the height difference and separation distance between the outdoor unit (condenser) and the refrigerant pump, and between the outdoor unit and the refrigerant pump. It is also influenced by the refrigerant temperature rise, cooling load, etc.
For this reason, when installing this type of air conditioner, the installation conditions for the height difference and separation between the outdoor unit (condenser) and the refrigerant pump are limited, and the cycle switching condition is set to the safe side. For this reason, there is a current situation that the separation between the outdoor unit and the refrigerant pump is strictly limited, and the degree of freedom in design is narrowed. Furthermore, even if the distance between the outdoor unit and the refrigerant pump is actually short and the pump cycle operation is possible, the compression cycle operation is performed in accordance with the setting switching condition, and as a result, there are cases in which the energy saving performance is contrary.
The present application proposes an air conditioner equipped with a switching control technology corresponding to each of the above problems.

The present invention is an air conditioner equipped with a combined refrigeration cycle, and is intended to solve the above-described problems and has the following contents. That is, the combined refrigeration cycle air conditioner according to the present invention is
(1) It is comprised by the circuit containing the compressor, the indoor unit provided with the evaporator and the indoor side blower, and the outdoor unit provided with the outdoor side condenser and the outdoor side blower, and circulates a refrigerant | coolant between these elements. A circuit including a compression cycle, a refrigerant pump, the indoor unit, and the outdoor unit, and a refrigerant pump cycle for circulating the refrigerant between these elements. An air conditioner that can be operated by switching two cycles (hereinafter referred to as a combined refrigeration cycle air conditioner), and the cycle switching condition based on the refrigerant supercooling degree (ΔTc) of the refrigerant pump inlet during the refrigerant pump cycle operation It is further characterized by further comprising means for enabling updating.

  In the present invention, the “compression cycle” is constituted by a compressor, an evaporator, a condenser, an expansion valve, and a refrigerant pipe connecting them, and forms a heat pump cycle by the following refrigerant circulation. That is, the high-temperature and high-pressure gas refrigerant compressed by the compressor is led to the flow condenser in the refrigerant pipe, where it is cooled and condensed by exchanging heat with the outside air. The condensed liquid refrigerant undergoes adiabatic expansion when passing through the expansion valve, enters a coexisting state of low-pressure liquid gas, and is led to the evaporator. Here, it takes heat from the indoor air to be cooled, evaporates itself, returns to the compressor via the refrigerant pipe as a low-pressure refrigerant gas.

The “refrigerant pump cycle” is constituted by a refrigerant pump, an evaporator, a condenser and a refrigerant pipe connecting them, and forms a heat pump cycle by the following refrigerant circulation. In other words, the refrigerant is cooled by exchanging heat with the outside air in the condenser, led to the refrigerant pump in a liquid state, boosted here, and led to the evaporator. Here, heat is taken from the indoor air to be cooled and evaporated to return to the condenser as refrigerant gas.
The “combined refrigeration cycle” is realized by configuring these two cycles with the same refrigerant pipe and bypass pipe, and allowing the refrigerant circulation path to be changed by a three-way valve or a switching valve.

  Switching between the two cycles is determined, for example, according to the switching conditions (2) to (4). In the present invention, the threshold value is updated based on the refrigerant subcooling degree (ΔTc) at the refrigerant pump inlet during operation. It is possible. That is, when determining based on the outdoor unit suction temperature (To), when ΔTc is sufficiently large, the setting of the pump cycle operation allowable temperature is increased to change the refrigerant pump operation ratio, which contributes to the improvement of energy saving. On the other hand, when ΔTc is small, there is a risk of cavitation if the pump cycle operation is continued at the threshold value. In order to avoid this, the pump cycle operation allowable temperature is changed to a low setting to increase the compression cycle operation ratio.

(2) The cycle switching condition is the outdoor unit suction temperature (To) threshold (Tx), or the temperature difference between the indoor unit suction temperature (Tr) and the outdoor unit suction temperature (To) (ΔT = Tr−To). It is based on one of the threshold values (ΔTx).
Since the outdoor unit suction temperature is considered to be the outside air temperature, it is appropriate to set the threshold based on this temperature that has a large effect on the degree of refrigerant supercooling.
Furthermore, since the cooling load also affects the refrigerant supercooling degree, it is desirable to consider the indoor unit suction temperature (Tr) that is closely related to the cooling load.

(3) The outdoor unit suction temperature threshold (Tx ′) determined according to the load factor of the air conditioner or the temperature difference between the indoor unit suction temperature (Tr) and the outdoor unit suction temperature (To). It is based on the threshold value (ΔTx ′).

The present invention performs threshold setting in consideration of the air conditioner load factor for switching from the refrigerant pump cycle to the compression cycle and from the compression cycle to the refrigerant pump cycle.
Referring to FIG. 6, when switching from the compression cycle to the refrigerant pump cycle is taken as an example, a threshold function Tx ′ = G (fc) of the outdoor unit suction temperature with respect to the compressor frequency (∝ air conditioner load factor). With this as a boundary, it is divided into a compression cycle region and a pump cycle region according to (frequency, suction temperature) during operation. For example, the compression cycle operation is continued when the condition P1 (fc (1), To (1)), and the pump cycle operation is switched when the condition P2 (fc (2), To (2)). The switching from the refrigerant pump cycle to the compression cycle can be handled by setting the same threshold function Tx ′ = H (fp).
In calculating the “air conditioner load factor”, in addition to the above-mentioned compressor frequency, a method based on the relationship between the compressor frequency and the pressure and temperature on the suction side and discharge side (so-called compressor curve method) Examples include a method based on the relationship between the temperature, the blown air temperature, and the indoor total air volume.
In addition, about the update of the threshold value based on the refrigerant | coolant supercooling degree at the time of a pump cycle driving | operation, it carries out similarly to the following invention.

(4) When cavitation occurs in the refrigerant pump during refrigerant pump cycle operation, the threshold value to be applied (either Tx or ΔTx, or Tx ′ or ΔTx ′) can be changed. Features.
(5) During the refrigerant pump cycle operation, at the time of transition from the thermo-off state to the thermo-on state, the rotational speed increase rate at the start of the outdoor fan (corresponding to the refrigerant supercooling degree (ΔTc) of the refrigerant pump inlet) ( (dR / dt) is further provided with a means for controlling.

The cavitation generation mechanism in the refrigerant pump and the avoidance method according to the present invention will be described with reference to FIGS.
In the thermo-off state, when the refrigerant temperature gradually rises and the degree of supercooling at the refrigerant pump suction port becomes small, if a large capacity operation amount such as starting up the outdoor unit side blower at the rated rotation speed is given, the refrigerant pump suction Since the pressure response at the mouth is faster than the temperature response, the degree of supercooling is temporarily reduced, and cavitation is likely to occur. The lower part (b) of FIG. 10 shows an example of instantaneously driving at the rated rotational speed Rf at time τ0. Responses of the refrigerant temperature Tc and the saturation temperature Ts (the refrigerant temperature corresponding to the saturation condensation pressure) at the pump suction port at this time are shown.
Until time τ1, Tc> Ts and the degree of supercooling ΔTc is a negative value. In this case, since the refrigerant is in a gas-liquid two-phase state, it becomes a region where cavitation is likely to occur in the pump.
On the other hand, referring to FIG. 11, according to the present invention, in order to control the fan speed increase rate (dR / dt) corresponding to the refrigerant supercooling degree (ΔTc) (lower part (b) in FIG. 11), saturation is achieved. The temperature Ts gradually decreases, and the refrigerant temperature Tc is always lower than the saturation temperature Ts, that is, the supercooled state is maintained, thereby eliminating the possibility of cavitation.

(6) Each of the above inventions is characterized by comprising means for changing the switching condition in accordance with the air conditioner installation condition.
(7) The air conditioner installation condition is any one of a pipe extension from the condenser to the refrigerant pump, an effective head of the condenser and the refrigerant pump, or a pipe extension from the refrigerant pump to the evaporator. It is characterized by being.
According to the inventions of the above (6) and (7), for example, in a case where the distance between the outdoor unit and the refrigerant pump is short, the ratio of the pump cycle operation time can be increased, so that energy saving can be improved.

  According to each of the above inventions, the cycle switching condition is not a fixed value, but is updated in accordance with the degree of supercooling during the pump cycle operation. There is an effect that can be.

It is a figure which shows the structure of the air conditioner 1 which concerns on 1st embodiment. It is a figure which shows the aspect of the refrigerant | coolant circulation at the time of the compression cycle driving | operation of the air conditioner 1 (a) and the pump cycle driving | operation (b). It is a figure which shows the cycle switching condition update flow of 1st embodiment. It is a figure which shows the table which the switching condition threshold value Tx sets variably by the refrigerant | coolant piping extension L. FIG. It is a figure which shows the cycle switching condition update flow of 2nd embodiment. It is a figure which shows the table which the switching condition threshold value Tx set as a function of the compressor frequency fc. It is a figure which shows the cycle switching condition update flow of 3rd embodiment. It is a figure which shows the relationship between a refrigerant | coolant supercooling degree ((DELTA) Tc) and the rotation speed increase rate (dR / dt) at the time of starting. It is a figure which shows the cycle switching control flow of 4th embodiment. It is a figure which shows the time transition of a refrigerant | coolant supercooling degree when an outdoor air blower is started by rated rotation speed. It is a figure which shows a change same as the above, when a rotation speed increase rate is set corresponding to a refrigerant | coolant supercooling degree.

Hereinafter, each embodiment of the air-conditioning system according to the present invention will be described in more detail with reference to FIGS. In order to avoid redundant description, the same components are denoted by the same reference numerals in the respective drawings. Needless to say, the scope of the present invention is described in the claims and is not limited to the following embodiments.
(First embodiment)
The present embodiment relates to a switching condition update mode when switching from compression cycle operation to pump cycle operation and switching from pump cycle operation to compression cycle operation are performed under the same switching condition.
With reference to FIG. 1, in the air conditioner 1 according to the present embodiment, the compression cycle circuit includes a compressor 7, an evaporator 5, a condenser 6, an expansion valve 8, and a refrigerant pipe 10. The pump cycle circuit includes a refrigerant pump 9, an expansion valve 8 functioning as a pressure reducing valve, a refrigerant pipe 10, bypass pipes 11a and 11b partially branched, and branching three-way valves 12a and 12b. The refrigerant pipe (including bypass pipe) is filled with a refrigerant, and the refrigerant is configured to circulate in a gas or liquid state according to the refrigeration cycle. The evaporator 5 has an indoor blower 15 for sucking indoor return air and exchanging heat with the evaporator 5, and the condenser 6 has an outdoor fan 16 for sucking outside air and exchanging heat with the condenser 6. , Respectively.

Next, with reference to FIG. 2, the aspect of the refrigerant circulation during the compression cycle operation and the pump cycle operation of the air conditioner 1 will be described.
During the compression cycle operation, the refrigerant circulates through the thick line path in FIG. The high-temperature and high-pressure gas refrigerant compressed by the compressor 7 flows through the refrigerant pipe 10 and is led to the condenser 6, where it is cooled and condensed by exchanging heat with the outside air. The condensed liquid refrigerant undergoes adiabatic expansion when passing through the expansion valve 8, enters a coexisting state of low-pressure liquid gas, and is guided to the evaporator 5. Here, it takes heat from the indoor air that is the object of cooling and evaporates itself to return to the compressor 7 via the refrigerant pipe 10 as a low-pressure refrigerant gas.

Further, during the pump cycle operation, the refrigerant circulates in the refrigerant pipe 10 and the bypass pipes 11a and 11b along the thick line path in FIG. That is, in the condenser 6, the refrigerant is cooled by heat exchange with the outside air, and is led to the refrigerant pump 9 via the bypass pipe 11a in a liquid state. Here, the pressure is increased and led to the evaporator 5 via the expansion valve 8 functioning as a pressure reducing valve. Here, heat is taken from the indoor air to be cooled and evaporated to become refrigerant gas and return to the condenser 6 via the refrigerant pipe 10 and the bypass pipe 11b.
Note that the switching of the cycle is performed by a flow path switching operation of the three-way valves 12a and 12b according to a command from the control unit 14.

  The evaporator 5, the compressor 7, the expansion valve 8, and the indoor fan 15 are stored in the indoor unit 3 as a unit. Similarly, the condenser 6 and the outdoor blower 16 of both systems are stored in the outdoor unit 4 as a unit. A temperature sensor S2 is disposed in the vicinity of the indoor return air suction portion of the indoor unit 3, and a temperature sensor S1 is disposed in the vicinity of the outdoor air suction portion of the outdoor unit 4. Furthermore, a refrigerant temperature Tc, a temperature sensor S3 for measuring the refrigerant pressure Pc, and a pressure sensor S4 are disposed near the refrigerant pump 9 suction portion of the refrigerant pipe 10. The measured values of these sensors are taken into the control unit 14 and are configured to control cycle switching between both systems, as will be described later.

  The cycle switching control of the air conditioner 1 is performed based on a command from the control unit 14. The control unit 14 is configured to instruct each operation control execution to be described later based on the intake air temperature and the refrigerant pressure information sent from the sensors S1 to S4. Further, the control unit 14 is provided with a data database (hereinafter referred to as DB) 4a including a table including a refrigerant vapor pressure table and a switching condition set value table, and evaporating pressure / temperature, condensing pressure / temperature, Based on the calculation such as the degree of superheat, the switching condition update described later is enabled. Main components such as the control unit 14 and the sensors S1-S4, the indoor fan 15, the outdoor fan 16, and the three-way valves 12a and 12b are connected via a signal line 14b, and information necessary for the following control Exchange and operation commands are possible.

The air conditioner 1 is configured as described above. Next, a cycle switching control flow performed in the present embodiment will be described with reference to FIG. The following control is performed at predetermined time intervals in response to a command from the control unit 14.
In the initial state, the cycle switching condition is set as to whether or not the outdoor unit suction temperature (To) is equal to or higher than the threshold temperature Tx (S101). Here, it is assumed that the pump is currently operating in a pump cycle (S102). First, the outdoor unit suction temperature (To) is measured by the temperature sensor S1 at predetermined time intervals (S102). Further, the temperature sensor S3 and the pressure sensor S4 measure the refrigerant temperature Tc and refrigerant pressure Pc measurement at the outlet of the condenser 6 (S104).
Next, the refrigerant supercooling degree (ΔTc) is calculated from the vapor pressure table of the DB 4a (S105).

Further, it is determined whether or not ΔTc is within the range between the upper threshold (δ2) and the lower threshold (δ1) (S106). If it is within both threshold values (Y in S106), it is determined that the degree of supercooling is appropriate, and then it is determined whether or not the outdoor suction temperature (To) is equal to or higher than the cycle switching condition Tx (S109). . If To ≧ Tx (Y in S109), it is determined that the outside air temperature has risen, and the operation is switched to the compression cycle operation (S111). Hereinafter, although explanation is omitted, when the suction temperature decreases while the compression cycle operation continues, the pump cycle is switched again.
If ΔTc> δ2 in S106, it is determined that the degree of superheat is excessive, and the cycle switching condition set value is relaxed. That is, the set value stored in the DB 4a is updated from To ≧ Tx to To ≧ Tx + α (α: for example, 0.5 ° C.) (S107). Thereafter, the pump cycle operation is continued based on the updated set value (S110).

  If ΔTc <δ1 in S106, it is determined that the degree of superheat is insufficient, and the cycle switching condition threshold is changed to the low temperature side. That is, the setting threshold value stored in the DB 4a is changed from To ≧ Tx to To ≧ Tx−α (S108). Furthermore, in order to avoid the occurrence of cavitation, the operation is switched to the compression cycle operation (S111). The subsequent switching to the pump cycle operation is determined based on the updated threshold value, To ≧ Tx−α.

In the present embodiment, an example is shown in which the same temperature value (Tx) is used as the switching condition threshold regardless of the air conditioner installation conditions. However, for example, the setting threshold is set according to the refrigerant pipe extension (L) from the outdoor unit to the refrigerant pump. It can also be set as the aspect which can be changed.
FIG. 4 shows such an embodiment. The threshold value Tx is set as a function Tx = F (L) of the pipe extension L, and the standard initial value Tx (L0) is set at the standard extension L0 (for example, 10 m). give. A table containing the same figure is stored in the DB 4a, and an initial value can be selected according to the installation conditions at the site. For example, in the case of the pipe extension L ′ (L ′> L0), the initial value Tx ′ (Tx ′ <Tx), and in the case of L “(L“ <L0), the initial value Tx ”.
It is possible to set (Tx ″> Tx).
Furthermore, in the present embodiment, an example is shown in which the set threshold value can be changed by extending the refrigerant piping from the outdoor unit (condenser) to the refrigerant pump. However, the effective head of the condenser and the refrigerant pump, or the refrigerant pump to the indoor unit It can also be set as the aspect based on the pipe extension to (evaporator).
In addition, the aspect which makes a threshold value variable according to apparatus installation conditions in this way is applicable similarly to each following embodiment.
In the present embodiment, the switching determination is based on whether the outdoor unit suction temperature (To) is equal to or higher than the threshold temperature Tx. However, the switching between the outdoor unit suction temperature (To) and the indoor unit suction temperature (Tr) is shown. It is also possible to adopt a mode in which whether or not the temperature difference, ΔT = Tr−To, is greater than or equal to a predetermined threshold is used as a determination criterion.

(Second embodiment)
Next, another embodiment of the present invention will be described with reference to FIGS. The present embodiment relates to a control mode in which switching conditions are different between switching from compression cycle operation to pump cycle operation and switching from pump cycle operation to compression cycle operation.
The difference of the configuration of the present embodiment from the above-described embodiment is that the cycle switching condition is based not on the outside air temperature alone but on the outside air temperature and the air conditioning load.
Specifically, as shown in FIG. 6, the threshold Tx is set as a function Tx = G (fc) of the compressor frequency fc corresponding to the air conditioner load factor, and a data table containing this is stored in the DB 4a. Stored. Although not shown, in the case of pump cycle operation → compression cycle operation, the threshold value Tx is set as a function Tx = H (fp) of the pump frequency fp corresponding to the air conditioning load factor. A data table to be stored is stored in the DB 4a.
Since the other configuration is the same as that of the air conditioning system 1, a duplicate description is omitted.

Next, the cycle switching control flow in the present embodiment will be described with reference to FIG. In the initial state, the switching from the pump cycle to the compression cycle (switching condition (1)) is set to a threshold Tx = H (fp) that varies with the pump frequency. Further, the switching from the compression cycle to the pump cycle (switching condition (2)) is set to a threshold Tx = G (fc) that varies with the compressor frequency shown in FIG. 6 (S201).
The flow from S202 to S205 is the same as the flow from S101 to S105 of the first embodiment, except that pump frequency measurement is added in S203. Next, it is determined whether or not ΔTc is within the range between the upper threshold (δ2) and the lower threshold (δ1) (S206). In S206, if Y is within the threshold values, it is determined that the degree of supercooling is appropriate, and it is determined whether or not the outside air condition has changed to the cycle switching condition (1) (S207). If To ≧ H (fp) (Y in S207), it is determined that the outside air temperature has increased, and the operation is switched to the compression cycle operation (S208). In S207, if N, that is, To <H (fp), the pump cycle operation is continued (S209).

In S206, if ΔTc> δ2, it is determined that the degree of superheat is excessive, and a change is made to relax the cycle switching condition set value. That is, the switching condition (1) set value stored in the DB 4a is changed from To ≧ H (fp) to To ≧ H (fp) + α, and the switching condition (2) is set from To ≦ G (fc) to To ≦ G They are changed to (fc) + α (S210). Then, the pump cycle operation is continued according to the changed switching condition setting value (S211).
If ΔTc <δ1 in S206, it is determined that the degree of superheat is insufficient, and the cycle set value is changed to the low temperature side. That is, the switching condition (1) setting value stored in the DB 4a is changed from To ≧ H (fp) to To ≧ H (fp) −α, and the switching condition (2) setting value is changed from To ≦ G (fc). Each is changed to To ≦ G (fc) −α (S212). Furthermore, in order to avoid the occurrence of cavitation, the operation is switched to the compression cycle operation according to the changed switching condition setting value (S208).

Further, after the transition to the compression cycle operation (S208), the outdoor unit suction temperature (To) and the compressor frequency fc during operation are measured at predetermined time intervals (S213).
Further, it is determined whether or not the switching condition (2) is satisfied (S214). If applicable (Y in S210), it is determined that the outside air temperature has increased, and the operation is switched to the pump cycle operation (S215). If not applicable (N in S214), the compression cycle operation is continued (S216).

(Third embodiment)
Further embodiments of the present invention will be described with reference to FIGS. The present embodiment relates to a rotational speed control mode of the outdoor fan when shifting from the thermo-off state to the thermo-on state during the pump cycle operation.
The configuration of this embodiment is different from the above-described embodiment in that a data table having the following contents is stored in the DB 4a. That is, as shown in FIG. 8, the rate of increase in the rotational speed (dR / dt) at the time of startup of the outdoor fan is a function that changes depending on the magnitude of the refrigerant supercooling degree (ΔTc), dR / dt = J (ΔTc) Is set. Since the other configuration is the same as that of the air conditioning system 1, a duplicate description is omitted.

Next, with reference to FIG. 7, a description will be given of the rotational speed control flow during startup of the outdoor blower in the present embodiment. In the pump cycle operation thermo-off state (S301), a thermo-on determination is performed every predetermined time (S302). Specifically, it is determined whether the indoor fan suction temperature (Tr) is equal to or higher than a threshold value Tm. When Tr ≧ Tm, the outdoor blower 16 is activated at the minimum rotational speed (S303). When Tr <Tm, the thermo-off state is maintained.
Next, the temperature sensor S3 and the pressure sensor S4 measure the refrigerant temperature Tc and refrigerant pressure Pc in the refrigerant pump 9 suction section (S304), and further calculate the refrigerant subcooling degree (ΔTc) (S305).
Based on the data table stored in the DB 4a, a rotation speed increase rate corresponding to the refrigerant supercooling degree is set, and the outdoor fan 16 is operated at the rotation speed (S306).

  In the present embodiment, an example of control for avoiding cavitation by controlling the rotational speed increase rate of the outdoor blower has been shown, but instead of or in combination with this, the refrigerant pump rotational speed increase rate It can also be set as the form which controls.

  Moreover, although the example at the time of shifting from the thermo-off state at the time of a pump cycle operation to thermo-on was shown in this embodiment, the same control can be performed also when switching from a compression cycle to a pump cycle.

(Fourth embodiment)
Furthermore, another embodiment of the present invention will be described. The present embodiment relates to a control mode for determining an operation cycle change based on the degree of refrigerant supercooling when the thermo-on condition is met in a thermo-off state during pump cycle operation. Since the configuration of the present embodiment is the same as that of the air conditioning system 1, a duplicate description is omitted.

With reference to FIG. 9, the cycle selection control flow of the outdoor fan in this embodiment is demonstrated. In the pump cycle operation thermo-off state (S401), a thermo-on determination is performed every predetermined time, specifically, whether or not the indoor fan intake temperature (Tr) is equal to or higher than a threshold value Tm (S402). If Tr <Tm, the determination in S402 is repeated.
When Tr ≧ Tm (Y in S402), the outdoor blower 16 is activated as a first step (S403). When Tr <Tm, the thermo-off state is maintained.
Next, the temperature sensor S3 and the pressure sensor S4 measure the refrigerant temperature Tc and the refrigerant pressure Pc in the refrigerant pump 9 suction section (S404), and further calculate the refrigerant subcooling degree (ΔTc) (S405).
Until a certain period of time has elapsed since the start of the outdoor blower (N in S406), it is continuously determined whether or not ΔTc is secured above a threshold value (δth) (S407). If it is equal to or greater than the threshold value (Y in S407), the refrigerant pump is activated (S408) and the pump cycle operation is maintained.
On the other hand, if N in S407, that is, if ΔTc <δth, it is determined that the degree of superheat is insufficient, and the determination in S407 based on the degree of refrigerant supercooling is repeated. Further, if ΔTc does not become equal to or greater than the threshold value even after a predetermined time has elapsed (Y in S406), the operation is changed to the compression cycle operation (S409).

  The present invention is widely applicable to air conditioners equipped with a combined refrigeration cycle regardless of the type of heat source, refrigerant, air conditioning system, building structure, and the like.

1 ... Air conditioner 3 ... Indoor unit 4 ... Outdoor unit 5 ... Evaporator 6 ... Condenser 7 ... Compressor 8 ... Expansion valve ( Pressure reducing valve)
9 .... Refrigerant pump 10 ... Refrigerant pipes 11a, 11b ... Bypass pipes 12a, 12b ... Three-way valve 15 for branching ... Indoor fan 16 ... Outdoor fan 19 ... control Part S1, S2, S3 ... Temperature sensor S4 ... Pressure sensor

Claims (7)

A compression cycle that includes a compressor, an indoor unit that includes an evaporator and an indoor fan, and an outdoor unit that includes an outdoor condenser and an outdoor fan, and circulates a refrigerant between these elements. ,
A refrigerant pump cycle that includes a refrigerant pump, a circuit including the indoor unit, and the outdoor unit, and circulates the refrigerant between these elements.
An air conditioner (hereinafter referred to as a combined refrigeration cycle air conditioner) that can be operated by switching two cycles according to a predetermined cycle switching condition,
A combined refrigeration cycle air conditioner further comprising means for updating the cycle switching condition based on a refrigerant supercooling degree (ΔTc) of a refrigerant pump suction port during refrigerant pump cycle operation.   The cycle switching condition is the threshold value (Tx) of the outdoor unit suction temperature (To) or the threshold value (ΔT = Tr−To) of the temperature difference between the indoor unit suction temperature (Tr) and the outdoor unit suction temperature (To) ( The combined refrigeration cycle air conditioner according to claim 1, wherein the combined refrigeration cycle air conditioner is based on any one of ΔTx). The cycle switching condition is
Either the outdoor unit suction temperature threshold (Tx ′) determined according to the air conditioner load factor, or the temperature difference threshold (ΔTx ′) between the indoor unit suction temperature (Tr) and the outdoor unit suction temperature (To) The combined refrigeration cycle air conditioner according to claim 1, wherein the combined refrigeration cycle air conditioner is based on the above. When cavitation occurs in the refrigerant pump during the refrigerant pump cycle operation,
The combined refrigeration cycle air conditioner according to claim 2 or 3, wherein the threshold value to be applied (either Tx or ΔTx, or Tx 'or ΔTx') can be changed. During refrigerant pump cycle operation and when transitioning from the thermo-off state to the thermo-on state,
2. The apparatus according to claim 1, further comprising means for controlling a rate of increase in rotational speed (dR / dt) at the time of starting the outdoor fan in accordance with the degree of refrigerant supercooling (ΔTc) at the refrigerant pump inlet. The combined refrigeration cycle air conditioner according to any one of claims 1 to 4.   6. A combined cycle air conditioner comprising: means for changing the switching condition according to claim 1 in accordance with an air conditioner installation condition.   The air conditioner installation condition is any one of a pipe extension from the condenser to the refrigerant pump, an effective head of the condenser and the refrigerant pump, or a pipe extension from the refrigerant pump to the evaporator. The combined cycle air conditioner according to claim 6, characterized in that it is a combined cycle air conditioner.

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