JP5634389B2 - Air conditioner - Google Patents

Description

  The present invention relates to an air conditioner, and more particularly to an air conditioner that reduces power consumption while protecting a compressor.

In order to protect the compressor by preventing the liquid back phenomenon of the compressor, the conventional air conditioner keeps the difference between the discharge temperature of the compressor and the condensation temperature of the condenser above a certain value. I was in control.
Specifically, in a conventional air conditioner, the difference between the discharge temperature of the compressor and the condensation temperature of the condenser is set to a certain value or higher by controlling the operation frequency of the compressor and the opening of the expansion valve. It was controlled to keep.
More specifically, when a conventional air conditioner detects, for example, a state where the difference between the discharge temperature and the condensation temperature is 10 (° C.) or less, the operating frequency of the compressor is increased or the expansion valve The opening was reduced. Thereby, the conventional air conditioner has adjusted so that the difference of discharge temperature and condensation temperature may be maintained at 10 (degreeC) or more (for example, refer patent document 1).

  Further, the conventional air conditioner estimates the compressor shaft torque value based on the current flowing through the compressor and the voltage applied to the compressor, and controls to prevent the liquid back phenomenon of the compressor based on the estimation result. (For example, refer to Patent Document 2).

JP-A-7-19641 (FIG. 1) JP 2004-60457 A (paragraph [0092])

However, the conventional air conditioner (Patent Document 1) does not include a condition related to a physical characteristic value of a drive system inside the compressor as a control parameter, such as an operating condition such as an outside air temperature condition or an operating frequency. When the discharge superheat, which is the difference between the discharge temperature and the condensation temperature, falls below a certain value, correction control is applied uniformly.
In other words, the conventional air conditioner protects the compressor by controlling to increase the operating frequency of the compressor uniformly without considering the physical characteristic value of the drive system inside the compressor.

Therefore, the conventional air conditioner performs correction control to increase the operating frequency of the compressor even if the load on the compressor is such that no problem actually occurs.
Thus, the conventional air conditioner is supposed to increase the power consumption when protecting the compressor by preventing the liquid back phenomenon of the compressor.

  As a result, in recent years, there has been a problem that air-conditioning operation with low power consumption cannot be performed even though energy saving is required for the operation of the air conditioner.

  Further, the conventional air conditioner (Patent Document 2) performs control in consideration of the compressor shaft torque, which is one of the physical characteristic values of the drive system inside the compressor, thereby preventing the liquid back phenomenon of the compressor. Although the compressor was protected by the control, there was a problem that it was not considered in reducing the power consumption.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide an air conditioner that can reduce power consumption while protecting a compressor.

The air conditioner of the present invention includes a refrigerant circuit in which at least a compressor, a heat source side heat exchanger, expansion means, and a use side heat exchanger are connected by a refrigerant pipe to circulate the refrigerant, and a control for controlling the compressor. Means , a discharge temperature detecting means for detecting a discharge temperature of the compressor, a compressor current detecting means for detecting a current flowing through the compressor, and a compressor voltage detecting means for detecting a voltage applied to the compressor. And the control means sets an operating frequency of the compressor based on a discharge superheat degree of the compressor and an axial torque of the compressor, and controls the compressor based on the set operating frequency. The discharge superheat degree is obtained based on the discharge temperature detected by the discharge temperature detection means, and when the discharge superheat degree is less than a set superheat degree, and the compressor current detection means detects Results and above The axial torque of the compressor which is calculated on the basis of the detection result of the compressor voltage detecting means, when exceeding the set torque of the shaft torque of the compressor, and increases the operation frequency of the compressor.

  The present invention has an effect that power consumption can be reduced while protecting the compressor by controlling the discharge superheat degree of the compressor based on the discharge superheat degree of the compressor and the compressor shaft torque.

It is a refrigerant circuit figure which shows the conventional air conditioner 1 roughly. It is a flowchart explaining the conventional compressor protection operation | movement process. It is a refrigerant circuit diagram which shows roughly the air conditioner 2 in Embodiment 1 of this invention. It is a flowchart explaining the compressor protection operation | movement process in Embodiment 1 of this invention. It is a diagram which shows the correlation with the discharge superheat degree of the compressor 44 in Embodiment 1 of this invention, and the compressor shaft torque of the compressor 44. FIG. It is a diagram which shows the correlation between the discharge superheat degree of the compressor 44 and the compressor shaft torque of the compressor 44 explaining the conditions when raising the operating frequency in Embodiment 1 of this invention. It is a diagram which shows the correlation with the condensation temperature of the indoor heat exchanger 31 or the outdoor heat exchanger 47 in Embodiment 1 of this invention, and the compressor shaft torque of the compressor 44. FIG.

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

Embodiment 1 FIG.
First, prior to the description of the first embodiment, compressor protection operation processing in a conventional air conditioner will be described with reference to FIGS. 1 and 2, and the problems will be clarified. The compressor protection operation process in the first embodiment will be described with reference to FIGS.
A process for estimating the condensation temperature from the compressor shaft torque and the evaporation temperature will be described with reference to FIG.

FIG. 1 is a refrigerant circuit diagram schematically showing a conventional air conditioner 1.
As shown in FIG. 1, a conventional air conditioner 1 is a device used for indoor air conditioning (not shown) by performing a vapor compression refrigeration cycle operation, and includes an indoor unit 11 and an outdoor unit 12. Prepare.

First, the indoor unit 11 will be described.
The indoor unit 11 is installed by being embedded in an indoor ceiling or suspended. The indoor unit 11 is also installed by being hung on an indoor wall surface.
The indoor unit 11 is connected to the outdoor unit 12 via the gas connection pipe 21 and the liquid connection pipe 22 to constitute a part of the refrigerant circuit.
The indoor unit 11 includes an indoor heat exchanger 31 that functions as a use-side heat exchanger and an indoor blower (not shown).

  The indoor heat exchanger 31 cools indoor air by functioning as a refrigerant evaporator during cooling operation, and heats indoor air by functioning as a refrigerant condenser during heating operation. It is composed of a cross fin type fin-and-tube heat exchanger formed of heat transfer tubes and a large number of fins.

  The indoor blower has a function of sucking indoor air into the indoor unit 11 and supplying the air heat exchanged between the sucked indoor air and the refrigerant into the room as supply air by the indoor heat exchanger 31. . The indoor blower is attached to the indoor heat exchanger 31 and can change the flow rate of air supplied to the indoor heat exchanger 31, such as a centrifugal fan driven by a DC fan motor (not shown). It consists of a multi-blade fan.

In the indoor unit 11, an indoor heat exchanger temperature sensor 32 is installed in the vicinity of the indoor heat exchanger 31 as a sensor for detecting the temperature of the refrigerant in the gas-liquid two-phase state. The indoor heat exchanger temperature sensor 32 is composed of, for example, a thermistor.
The indoor heat exchanger temperature sensor 32 detects the evaporation temperature of the refrigerant flowing through the indoor heat exchanger 31 during the cooling operation, and detects the condensation temperature of the refrigerant flowing through the indoor heat exchanger 31 during the heating operation.

In addition, although an example of the sensor installed in the indoor unit 11 has been described here, the present invention is not limited to this. For example, a liquid side temperature sensor that detects the temperature of the refrigerant in the liquid state or the gas-liquid two-phase state may be provided on the liquid side of the indoor heat exchanger 31.
An indoor temperature sensor that detects the temperature of the indoor air flowing into the indoor unit 11 may be provided on the indoor air intake side of the indoor unit 11.
An indoor temperature sensor that detects the temperature of the indoor air discharged from the indoor unit 11 may be provided on the indoor air outlet side of the indoor unit 11.

  The indoor blower is controlled by a control unit (not shown) according to the detection value of the sensor described above.

Next, the outdoor unit 12 will be described.
The outdoor unit 12 is installed outdoors, and is connected to the indoor unit 11 via the gas connection pipe 21 and the liquid connection pipe 22 to constitute a part of the refrigerant circuit.
The outdoor unit 12 includes a first expansion valve 41, a receiver 42, a second expansion valve 43, a compressor 44, a four-way valve 46, and an outdoor heat exchanger 47 that functions as a heat source side heat exchanger. Connected through refrigerant piping.

The first expansion valve 41 is for depressurizing a high-pressure refrigerant to an intermediate pressure state, and includes, for example, an electronic expansion valve whose opening degree can be variably controlled.
The receiver 42 stores a refrigerant liquid, and has a refrigerant heat exchanger 51 (details will be described later) inside. The receiver 42 and the first expansion valve 41 are connected by a refrigerant pipe, and the receiver 42 and the second expansion valve 43 are connected by a refrigerant pipe. These refrigerant pipes are formed to a certain length inside the receiver 42, and liquid refrigerant is dropped into the receiver 42.
The second expansion valve 43 is for depressurizing the medium-pressure refrigerant to make it into a low-pressure state, and is composed of, for example, an electronic expansion valve whose opening degree can be variably controlled.

The compressor 44 has a variable operating capacity, and is composed of a positive displacement compressor driven by a DC brushless motor (not shown) whose operating frequency is controlled by an inverter, for example. Yes.
The compressor 44 is controlled by a control unit (not shown), and is controlled in accordance with, for example, a deviation between the indoor heat exchanger 31 and a set temperature (target value) of a remote controller (not shown).
Further, the compressor 44 is provided with a compressor discharge temperature sensor 45 as a sensor for detecting the discharge temperature on the discharge side. The compressor discharge temperature sensor 45 is composed of, for example, a thermistor.
The compressor discharge temperature sensor 45 corresponds to “discharge temperature detection means” in the present invention.

  Although an example of the sensor installed in the compressor 44 has been described here, the present invention is not limited to this. For example, a compressor suction temperature sensor may be provided as a sensor for detecting the suction temperature on the suction side.

  The four-way valve 46 has a function of switching the refrigerant flow path, and is configured by a valve that switches the direction of the flow of the refrigerant according to the cooling operation or the heating operation.

During the cooling operation, the four-way valve 46 connects the discharge side of the compressor 44 and the gas side of the outdoor heat exchanger 47 as shown by a broken line inside the four-way valve 46 in FIG. And the gas connection pipe 21 side are connected.
As a result, the four-way valve 46 causes the outdoor heat exchanger 47 to function as a refrigerant condenser compressed in the compressor 44 and the indoor heat exchanger 31 to function as a refrigerant evaporator condensed in the outdoor heat exchanger 47. ing.

Further, during heating operation, the four-way valve 46 connects the discharge side of the compressor 44 and the gas connection pipe 21 side as shown by the solid line inside the four-way valve 46 in FIG. The gas side of the outdoor heat exchanger 47 is connected.
Accordingly, the four-way valve 46 causes the indoor heat exchanger 31 to function as a refrigerant condenser compressed in the compressor 44 and the outdoor heat exchanger 47 to function as a refrigerant evaporator condensed in the indoor heat exchanger 31. ing.

The outdoor heat exchanger 47 functions as a refrigerant condenser during refrigerant operation, and functions as a refrigerant evaporator during heating operation. For example, a cross-fin fin formed by a heat transfer tube and a large number of fins is used.・ It consists of an and tube type heat exchanger.
In the outdoor heat exchanger 47, the gas side of the outdoor heat exchanger 47 is connected to the four-way valve 46 via the refrigerant pipe, and the liquid side of the outdoor heat exchanger 47 is connected to the second expansion valve 43 via the refrigerant pipe. ing.

  In addition, an outdoor blower (not shown) is attached in the vicinity of the outdoor heat exchanger 47. The outdoor blower has a function of sucking outdoor air into the outdoor unit 12 and discharging the air heat-exchanged between the outdoor air and the refrigerant by the outdoor heat exchanger 47 to the outside. 47. The fan is configured to be a fan capable of varying the flow rate of air supplied to 47, such as a propeller fan driven by a DC fan motor (not shown).

In the outdoor unit 12, an outdoor heat exchanger temperature sensor 48 is installed in the vicinity of the outdoor heat exchanger 47 as a sensor for detecting the temperature of the refrigerant in the gas-liquid two-phase state. The outdoor heat exchanger temperature sensor 48 is composed of, for example, a thermistor.
The outdoor heat exchanger temperature sensor 48 detects the condensation temperature of the refrigerant flowing through the outdoor heat exchanger 47 during the cooling operation, and detects the evaporation temperature of the refrigerant flowing through the outdoor heat exchanger 47 during the heating operation.

In addition, although an example of the sensor installed in the outdoor unit 12 has been described here, the present invention is not limited to this. For example, a liquid side temperature sensor that detects the temperature of the refrigerant in the liquid state or the gas-liquid two-phase state may be provided on the liquid side of the outdoor heat exchanger 47.
An outdoor temperature sensor that detects the temperature of the outdoor air that flows into the outdoor unit 12 may be provided on the outdoor air inlet side of the outdoor unit 12.

  The refrigerant heat exchanger 51 is, for example, a U-shaped suction pipe that connects the four-way valve 46 and the suction side of the compressor 44 and is provided in the receiver 42 as described above. The refrigerant heat exchanger 51 exchanges heat between the refrigerant liquid stored in the receiver 42 and the refrigerant sucked into the compressor 44.

  The compressor 44, the four-way valve 46, the outdoor blower, the first expansion valve 41, and the second expansion valve 43 are controlled by a control unit (not shown) in accordance with the detection value of the sensor described above.

  FIG. 2 is a flowchart for explaining a conventional compressor protection operation process.

(Step S11)
The control unit sets each parameter.
Specifically, the control unit includes the current operation frequency F, the compressor operation frequency correction limit value Fx based on the discharge superheat degree, the discharge superheat degree SHd which is the difference between the discharge temperature detection value and the condensation temperature detection value, and the discharge A correction start value SHdx1 for the degree of superheat is set.

More specifically, the current operating frequency F means the current operating frequency of the compressor 44 being driven.
Further, the compressor operating frequency correction limit value Fx means the lower limit value of the operating frequency in a state in which the phenomenon of liquid back does not occur. That is, the compressor operating frequency correction limit value Fx is the lowest operating frequency as the lower limit value of the operating frequency of the compressor among the operating frequencies of the compressor when the refrigerant flowing into the compressor is in the state of the gas phase refrigerant. Is defined. The operating frequency correction limit value Fx of the compressor may be obtained in advance by, for example, simulation or experiment.

Further, the discharge superheat degree SHd is obtained from the difference between the discharge temperature detected from the compressor discharge temperature sensor 45 and the condensation temperature detected from the indoor heat exchanger temperature sensor 32 or the outdoor heat exchanger temperature sensor 48. .
For example, the discharge superheat degree SHd is obtained from the difference between the discharge temperature detected from the compressor discharge temperature sensor 45 and the condensation temperature detected from the outdoor heat exchanger temperature sensor 48 during the cooling operation, and during the heating operation, the compressor This is obtained from the difference between the discharge temperature detected from the discharge temperature sensor 45 and the condensation temperature detected from the indoor heat exchanger temperature sensor 32.

The discharge superheat degree correction start value SHdx1 is a preset discharge superheat degree value, and when the value is below this value, control is performed to increase the operating frequency of the compressor. The discharge superheat degree correction start value SHdx1 is obtained, for example, by simulation or experiment. When the refrigerant is sucked into the compressor 44 in a state below this value, the sucked refrigerant becomes liquid refrigerant. It is said that many will be included. Therefore, in order to work on the safe side, the discharge superheat degree correction start value SHdx1 is set higher than the actual critical value.
However, as will be described later, even when the discharge superheat degree SHd is below the correction start value SHdx1 of the discharge superheat degree, actually, if the physical characteristic value of the drive system inside the compressor 44 is taken into account, the compression is performed. There is a state where the machine 44 is not so heavily loaded.

(Step S12)
The control unit determines whether or not the current operating frequency F is less than the operating frequency correction limit value Fx of the compressor. When the current operating frequency F is less than the compressor operating frequency correction limit value Fx, the control unit proceeds to step S13, and when the current operating frequency F is equal to or higher than the compressor operating frequency correction limit value Fx, step Proceed to S15.

(Step S13)
The control unit determines whether or not the discharge superheat degree SHd is less than the discharge superheat degree correction start value SHdx1. The control unit proceeds to step S14 when the discharge superheat degree SHd is less than the discharge superheat degree correction start value SHdx1, and proceeds to step S15 when the discharge superheat degree SHd is equal to or greater than the discharge superheat degree correction start value SHdx1.

(Step S14)
The control unit increases the operating frequency of the compressor 44 by a predetermined value, and ends the process.

(Step S15)
The control unit adjusts the opening of the expansion valve while maintaining the current frequency F, and the process ends. For example, when the control is performed to reduce the opening degree of the expansion valve and increase the discharge superheat degree, and the discharge superheat degree reaches a predetermined value, the process ends.

As described above, in the conventional control, when the difference between the discharge temperature detection value and the condensation temperature detection value is less than the correction start value of the discharge superheat degree, the operation frequency of the compressor 44 is increased by a predetermined value. By doing this, the discharge superheat degree was kept above a predetermined value. Therefore, conventionally, the liquid back phenomenon has been prevented without considering the physical characteristic values of the drive system inside the compressor 44.
As a result, the operation frequency is corrected even when it is unnecessary to correct the load applied to the compressor 44. For this reason, operation with low power consumption could not be performed.
Therefore, in the first embodiment, as will be described later, one compressor shaft torque of the physical characteristic value of the drive system inside the compressor 44 is also added to the correction condition.
Thereby, when it is not necessary to correct the operating frequency, the power consumption can be kept small.

FIG. 3 is a refrigerant circuit diagram schematically showing the air conditioner 2 according to Embodiment 1 of the present invention.
In Embodiment 1, items that are not particularly described are the same as those of the conventional air conditioner 1, and the same functions and configurations are described using the same reference numerals.
The description of the same function and configuration is omitted.

As shown in FIG. 3, the air conditioner 2 is provided with a control means 61 for detecting the current and voltage of the compressor 44 and controlling the operating frequency of the compressor based on the detection result. is there.
The control unit 61 includes a current detection unit 71, a voltage detection unit 72, a calculation unit 73, a storage unit 74, and the like. The calculation means 73 and the storage means 74 are constituted by a microprocessor unit or the like.

The current detection means 71 detects a current flowing through the compressor, for example, an instantaneous current. The current detection means 71 is for appropriately correcting a value detected by a current detection relay or the like and supplying it to the calculation means 73, for example.
The current detection means 71 corresponds to the “compressor current detection means” in the present invention.

The voltage detection means 72 detects a voltage applied to the compressor, for example, an instantaneous voltage. For example, the voltage detection unit 72 appropriately corrects a value detected by a voltage detection relay or the like and supplies the corrected value to the calculation unit 73.
The voltage detection means 72 corresponds to the “compressor voltage detection means” in the present invention.

  The computing means 73 computes the compressor shaft torque based on the detection results supplied from the current detecting means 71 and the voltage detecting means 72. The computing unit 73 performs various computations based on various data stored in the storage unit 74. For example, when each of the arithmetic expressions (1) to (8) described later is a program described by an algorithm that can be interpreted and executed by an electronic computer, the arithmetic means 73 executes the programs in order.

  The storage unit 74 stores the detection results of the current detection unit 71 and the voltage detection unit 72 as appropriate. Thereby, since the memory | storage means 74 can store these data, for example in time series, the control means 61 uses the stored data, and the deterioration state of the compressor 44 is used. The determination may be made automatically, and the correlation between the discharge superheat degree and the compressor shaft torque may be corrected according to the determination result. Thereby, since the operating frequency of the compressor can be controlled based on the current state of the compressor, the compressor can be protected more accurately.

In addition, the storage unit 74 stores a program describing the equations (1) to (8) as described above.
In addition, the storage unit 74 may store equations (1) to (8) described later as, for example, a data table so as to increase the calculation speed. Specifically, the correlation between various parameters of the equations (1) to (8) is created as discrete matrix data, and when a certain parameter is given, interpolation of the matrix data is performed. By processing, the compressor shaft torque may be finally calculated.
Further, the storage means 74 stores the correlation between the discharge superheat degree of the compressor 44 described later with reference to FIG. 5 and the compressor shaft torque of the compressor 44, and the indoor heat exchanger 31 or the outdoor heat exchanger 47 described later with reference to FIG. 6. The data on the correlation between the condensation temperature and the compressor shaft torque of the compressor 44 is stored.

  Next, calculation of the compressor shaft torque by the calculation means 73 will be described using equations (1) to (8).

The calculation of the compressor shaft torque as the motor driving torque in a motor that drives the compressor 44, for example, a brushless DC motor, uses a calculation formula consisting of inductance and current value, and a calculation formula consisting of magnetic flux and current value. There are cases where it is used.
An arithmetic expression composed of the inductance and the current value is expressed as Expression (5) using Expressions (1) to (4).
Specifically, the instantaneous voltage V is expressed by the formula (1). For this reason, if the instantaneous current I is detected, it is also possible to obtain the instantaneous voltage V based on the equation (1). If the instantaneous voltage V is also detected, the calculation of equation (1) is not necessary.

  The magnetic flux φ is expressed by equation (2). For this reason, the magnetic flux φ is calculated from the instantaneous voltage V and the instantaneous current I.

  The direction of the magnetic flux vector is expressed by equations (3) and (4). Here, α and β are fixed coordinate systems, and three phases u, v, and w are converted into two phases.

Then, the position of the brushless DC motor, that is, the position of the rotor can be estimated by the equations (1) to (4). That is, the position of the rotor can be estimated from the instantaneous current I and the instantaneous voltage V.
Further, by using constants and detection values such as the expressions (1) to (4), the instantaneous current I, and the instantaneous voltage V, the current values obtained by coordinate conversion of the input currents iu, iv, iw of the compressor 44 By obtaining id and iq, the motor driving torque, that is, the compressor shaft torque Tm is obtained as shown in the following equation (5).
In other words, the compressor shaft torque Tm according to the equation (5) is obtained from the instantaneous current I and the instantaneous voltage V.

Further, Expression (6), which is an arithmetic expression composed of the magnetic flux and the current value, obtains the torque acting on the stator of the brushless DC motor by the outer product of the primary magnetic flux and the current.
Here, the rotor torque of the brushless DC motor is a reaction force of the stator torque. Therefore, the compressor shaft torque Tm as the motor driving torque is expressed as the following equation (6).

Here, also in the formula (6), α and β are fixed coordinate systems, and three phases u, v, and w are converted into two phases. Further, λα is calculated by the following equation (7), and λβ is calculated by the following equation (8). In short, the magnetic flux can be obtained from the instantaneous voltage V.
Therefore, the compressor shaft torque Tm according to the equation (6) is also obtained from the instantaneous current I and the instantaneous voltage V.

  FIG. 4 is a flowchart illustrating the compressor protection operation process according to Embodiment 1 of the present invention.

(Step S31)
The control means 61 sets each parameter.
Specifically, the control unit includes the current operation frequency F, the compressor operation frequency correction limit value Fx based on the discharge superheat degree, the discharge superheat degree SHd that is the difference between the discharge temperature detection value and the condensation temperature detection value, and the discharge superheat. The correction start value SHdx1 of the degree, the correction start value SHdx2 by the operation frequency control of the discharge superheat degree, the compressor shaft torque Tm, and the torque value Tx (hereinafter referred to as Tx) that needs to be protected are set.

More specifically, the current operating frequency F means the current operating frequency of the compressor 44 being driven.
Further, the compressor operating frequency correction limit value Fx means the lower limit value of the operating frequency in a state in which the phenomenon of liquid back does not occur. That is, the compressor operating frequency correction limit value Fx is the lowest operating frequency as the lower limit value of the operating frequency of the compressor among the operating frequencies of the compressor when the refrigerant flowing into the compressor is in the state of the gas phase refrigerant. Is defined. The operating frequency correction limit value Fx of the compressor may be obtained in advance by, for example, simulation or experiment.
Further, the discharge superheat degree SHd is obtained from the difference between the discharge temperature detected from the compressor discharge temperature sensor 45 and the condensation temperature detected from the indoor heat exchanger temperature sensor 32 or the outdoor heat exchanger temperature sensor 48. .
For example, the discharge superheat degree SHd is obtained from the difference between the discharge temperature detected from the compressor discharge temperature sensor 45 and the condensation temperature detected from the outdoor heat exchanger temperature sensor 48 during the cooling operation, and during the heating operation, the compressor This is obtained from the difference between the discharge temperature detected from the discharge temperature sensor 45 and the condensation temperature detected from the indoor heat exchanger temperature sensor 32.

The discharge superheat degree correction start value SHdx1 (hereinafter referred to as SHdx1) is a preset value of the discharge superheat degree. , Referred to as SHdx2).
That is, even when the discharge superheat degree SHd is lower than the discharge superheat degree SHdx1, in reality, the load is not so much applied to the compressor 44 in consideration of the physical characteristic values of the drive system inside the compressor 44. Therefore, whether or not this state is present is determined based on the value of SHdx2 and Tx.
As described above, SHdx2 is a value for determining the discharge superheat degree Shd again after the determination in SHdx1.
The compressor shaft torque Tm is the current compressor shaft torque obtained based on the equations (1) to (8) described above.
Tx is a value determined based on the specification of the compressor 44, and means a torque value that is in a state that requires protection of the compressor 44, although it is not a limit torque value Tz leading to a failure described later. It is.

Here, the correlation between SHdx1, SHdx2, and the compressor shaft torque Tm will be described with reference to FIG.
FIG. 5 is a diagram showing a correlation between the discharge superheat degree of the compressor 44 and the compressor shaft torque of the compressor 44 in the first embodiment of the present invention. As shown in FIG. 5, the horizontal axis is the discharge superheat degree SHd (° C.) of the compressor 44, and the vertical axis is the compressor shaft torque Tm (Nm). At this time, the curve indicating the load condition of the compressor 44 shows a characteristic that the compressor shaft torque Tm decreases as the discharge superheat degree SHd increases. In other words, the compressor shaft torque Tm increases as the discharge superheat degree SHd decreases.

The curves indicating the load conditions of the compressor 44 are mainly classified into three cases as shown in FIG.
The first is a curve under an overload condition, the second is a curve under a standard condition, and the third is a curve under a light load condition.
In the case of SHdx1, the compressor shaft torque Tm is not the limit torque value Tz (hereinafter referred to as Tz) leading to a failure under all three conditions. However, the torque value Tx (hereinafter referred to as Tx) that needs to be protected under the standard conditions.
Further, in the case of SHdx2, it is Tz under an overload condition.

In other words, if SHd is equal to or greater than SHdx1, the compressor 44 does not cause a problem even if it continues to be driven at the operation frequency as it is.
On the other hand, if SHd is less than SHdx1 and greater than or equal to SHdx2, the compressor 44 may be Tx, but it does not result in a failure, so there is no need to increase the operating frequency of the compressor 44. . At this time, the discharge superheat degree SHd is not controlled by increasing the operating frequency of the compressor 44, but the discharge superheat degree SHd is adjusted by adjusting the opening degree of the first expansion valve 41 or the second expansion valve 43. Control.

Further, if SHd is less than SHdx1 and less than SHdx2, the compressor 44 may be at Tz. Therefore, since there is a possibility of failure, it is necessary to increase the operating frequency of the compressor 44. Therefore, at this time, the discharge superheat degree SHd may be controlled by increasing the operation frequency. However, the compressor shaft torque Tm is obtained based on the above formulas (1) to (8), and the operating frequency is increased when the value is larger than Tx.
In this way, it is possible to increase the operating frequency only when it is necessary to increase the operating frequency.
That is, the discharge superheat degree SHd is controlled based on the discharge superheat degree SHd and the compressor shaft torque Tm. As a result, the operating frequency can be increased only when necessary, so that power consumption can be reduced.

Thus, only SHdx1 increases the operating frequency of the compressor 44 when it is not necessary to increase it.
On the other hand, by using SHdx1, SHdx2 and compressor shaft torque Tm as control parameters, the operating frequency of the compressor 44 can be increased only when necessary. Thereby, power consumption can be reduced.

  As shown in FIG. 5, if SHd is SHdx1 or more, the discharge superheat degree is sufficiently high, and if SHd is less than SHdx1, the discharge superheat degree is insufficient. That is, SHdx1 is a value that determines whether to start correction control of the discharge superheat degree SHd of the compressor 44 out of the discharge superheat degree SHd of the compressor 44. The correction control of the discharge superheat degree SHd includes a case where the operating frequency is increased and a case where the opening degree of the expansion valves such as the first expansion valve 41 and the second expansion valve 43 is adjusted, for example, the opening degree is reduced. However, if SHd is not less than SHdx2, there is no need to increase the operating frequency.

  Further, as shown in FIG. 5, if SHd is SHdx2 or more, the degree of discharge superheat is insufficient, but it is not necessary to increase the operating frequency. Further, when SHd is less than SHdx2 and the discharge superheat degree Tm is greater than Tx, the discharge superheat degree is insufficient and the operating frequency needs to be increased.

  That is, when SHd is greater than or equal to SHdx2 and less than SHdx1, it is not necessary to increase the operating frequency, but it may be Tx. In this case, instead of increasing the operating frequency, the current operating frequency is not increased. What is necessary is just to adjust the opening degree of the 1st expansion valve 41 or the 2nd expansion valve 43, maintaining.

  Note that SHdx2 corresponds to the “set superheat degree” in the present invention.

  Here, returning to FIG. 4, the description of the compressor protection operation process in Embodiment 1 of the present invention is resumed.

(Step S32)
The control means 61 determines whether or not the current operating frequency F is less than the operating frequency correction limit value Fx of the compressor. When the current operating frequency F is less than the compressor operating frequency correction limit value Fx, the control means 61 proceeds to step S33, and when the current operating frequency F is equal to or higher than the compressor operating frequency correction limit value Fx, Proceed to step S36.

(Step S33)
The control means 61 determines whether SHd is less than SHdx1. The control means 61 proceeds to step S34 when SHd is less than SHdx1, and proceeds to step S36 when SHd is equal to or greater than SHdx1.

(Step S34)
The control means 61 determines whether or not SHd is less than SHdx2 and the compressor shaft torque Tm is greater than Tx. The control means 61 proceeds to step S35 when SHd is less than SHdx2 and the compressor shaft torque Tm is greater than Tx, and proceeds to step S36 when SHd is greater than or equal to SHdx2 and the compressor shaft torque Tm is less than or equal to Tx. .
The conditions at this time will be described with reference to FIG. FIG. 6 is a diagram showing a correlation between the discharge superheat degree of the compressor 44 and the compressor shaft torque of the compressor 44, which explains the conditions for increasing the operating frequency in the first embodiment of the present invention. As shown in FIG. 6, in the hatched area, the process of step S35 described below is executed.
Tx corresponds to “set torque” in the present invention.

(Step S35)
The control means 61 increases the operating frequency of the compressor 44 by a predetermined value and ends the process.

(Step S36)
The control means 61 adjusts the opening degree of the expansion valve while maintaining the current frequency F, and the process ends. For example, when the control is performed to reduce the opening degree of the expansion valve and increase the discharge superheat degree, and the discharge superheat degree reaches a predetermined value, the process ends.

As described above, in the control according to the first embodiment, one compressor shaft torque as a physical characteristic value of the drive system in the compressor 44 is also added to the correction condition.
Thereby, when it is not necessary to correct the operating frequency, the power consumption can be kept small.
Further, when it is necessary to correct the operating frequency, the operating frequency is increased, so that the compressor 44 can be protected.
Thereby, power consumption can be reduced while protecting the compressor.

  In addition, although the example which added the compressor shaft torque which is one to the physical characteristic value of the drive system of the compressor 44 to the control parameter was demonstrated above, it is not limited to this.

In the above description, an example of control of the discharge superheat degree has been described, but the present invention is not limited to this. For example, it may be control on the degree of superheat of suction. In this case, a correlation between the suction superheat degree and the compressor shaft torque may be obtained in advance.
By doing in this way, the state just before a refrigerant | coolant flows in into a compressor can be detected, and the operating frequency of a compressor can be controlled based on it.

  Next, FIG. 7 shows a process for estimating the condensation temperature of the indoor heat exchanger 31 and the outdoor heat exchanger 47 based on the evaporation temperature of the indoor heat exchanger 31 and the outdoor heat exchanger 47 and the compressor shaft torque. It explains using.

FIG. 7 is a diagram showing a correlation between the condensation temperature of the indoor heat exchanger 31 or the outdoor heat exchanger 47 and the compressor shaft torque of the compressor 44 according to Embodiment 1 of the present invention. FIG. 7 shows a characteristic curve of the evaporation temperature Te (° C.) when the horizontal axis is the condensation temperature Tc (° C.) and the vertical axis is the compressor shaft torque Tm (Nm). FIG. 7 shows characteristic curves corresponding to a plurality of evaporation temperatures Te (° C.). The correlation data as shown in FIG. 7 is stored in the storage means 74, for example.
Specifically, a correlation information group is formed as data from the compressor shaft torque, the evaporation temperature, and the condensation temperature, and is correlated so that the condensation temperature is determined from the compressor shaft torque and the evaporation temperature.
For example, as shown in FIG. 7, if the evaporation temperature Te is 0 (° C.) and the compressor shaft torque Tm is 10 (Nm), the condensation temperature Tc can be estimated to be 70 (° C.).
Therefore, if the compressor shaft torque and the evaporation temperature are determined, the condensation temperature can be estimated. And when calculating | requiring discharge superheat degree SHd, you may use the estimated condensation temperature.

  As described above, in the first embodiment, at least the compressor 44, the outdoor unit 47, the first expansion valve 41, the second expansion valve 43, and the indoor unit 31 are connected by the refrigerant pipe to circulate the refrigerant. A refrigerant circuit and a control means 61 for controlling the compressor 44. The control means 61 sets the operating frequency of the compressor 44 based on the discharge superheat degree of the compressor 44 and the axial torque of the compressor 44, By controlling the compressor 44 based on the set operating frequency, power consumption can be reduced while protecting the compressor.

  In the first embodiment, the compressor discharge temperature sensor 45 for detecting the discharge temperature of the compressor 44, the current detection means 71 for detecting the current flowing through the compressor 44, and the voltage applied to the compressor 44 are used. Voltage detecting means 72 for detecting, and the control means 61 obtains the discharge superheat degree based on the discharge temperature detected by the discharge temperature detection means, and when the discharge superheat degree is less than SHdx2, and the current detection When the axial torque of the compressor 44 calculated based on the detection result of the means 71 and the detection result of the voltage detection means 72 exceeds Tx, the compressor 44 is protected by increasing the operating frequency of the compressor 44. However, power consumption can be reduced.

  1, 2 Air conditioner, 11 Indoor unit, 12 Outdoor unit, 21 Gas connection pipe, 22 Liquid connection pipe, 31 Indoor heat exchanger, 32 Indoor heat exchanger temperature sensor, 41 First expansion valve, 42 Receiver, 43 2 expansion valve, 44 compressor, 45 compressor discharge temperature sensor, 46 four-way valve, 47 outdoor heat exchanger, 48 outdoor heat exchanger temperature sensor, 51 refrigerant heat exchanger, 61 control means, 71 current detection means, 72 voltage Detection means, 73 calculation means, 74 storage means.

Claims (1)

At least a compressor, a heat source side heat exchanger, expansion means, and a use side heat exchanger are connected by a refrigerant pipe, and a refrigerant circuit for circulating the refrigerant,
Control means for controlling the compressor;
A discharge temperature detecting means for detecting a discharge temperature of the compressor;
Compressor current detecting means for detecting current flowing in the compressor;
Compressor voltage detection means for detecting the voltage applied to the compressor,
The control means includes
Based on the discharge superheat degree of the compressor and the shaft torque of the compressor, the operation frequency of the compressor is set, and the compressor is controlled based on the set operation frequency,
Obtaining the discharge superheat degree based on the discharge temperature detected by the discharge temperature detection means, when the discharge superheat degree is less than a set superheat degree, and
When the compressor torque calculated based on the detection result of the compressor current detection means and the detection result of the compressor voltage detection means exceeds a set torque of the compressor torque, the compressor air conditioner shall be the feature to increase the operating frequency of.

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