JP4972532B2 - Air conditioner - Google Patents

Description

The present invention relates to an air conditioner using a vapor compression refrigeration cycle, which is equipped with a plurality of compressors driven by a self-starting synchronous motor, and to ensure comfort and reliability and to reduce power consumption. Suitable for the machine.

  In a conventional air conditioner, the compressor mounted is generally one that uses a DC brushless synchronous motor driven by an inverter that excels in energy savings, or one that uses an induction motor that self-starts with a commercial power supply. However, it has the characteristics of the synchronous motor and the induction motor. It starts with the induction motor at the time of start-up, and after the start-up, it is driven as a synchronous motor at the commercial power supply frequency. A compressor and a refrigeration air conditioner equipped with a self-starting synchronous motor that does not generate harmonics have been proposed (see Patent Documents 1 and 2).

  In addition, for the purpose of reducing power consumption, a sequencer is provided between the demand controller and a plurality of air conditioners that are load-controlled by the controller, a relay is attached to the plurality of air conditioners, and the relay and the sequencer are connected. The sequencer can control the compressor of each air conditioner, and the sequencer stops the predetermined number of relays in order for a predetermined time and activates the rest. When a load control command for stopping the air conditioner is output, there is a method for controlling the number of air conditioners in which the air conditioners are stopped in a predetermined order based on the load command control (see Patent Document 3 and FIG. 1). .

JP 2005-180748 A JP 2003-134773 A Japanese Patent Laid-Open No. 10-89744

In the above-described prior art, a compressor driven by a self-starting synchronous motor generates an excessive starting current compared with a normal current at the time of start-up, so that the reverse of the permanent magnet provided in the rotor in the motor. An exciting magnetic field is generated, and there is a risk of a decrease in magnetic force called demagnetization. When the magnetic force of the permanent magnet is reduced, the operating current is excessively increased due to the reduction of the motor efficiency. In the worst case, the synchronous operation may not be continued and the function as a compressor is not provided.

  The conditions under which demagnetization can occur are determined by the current that generates the magnetic field and the magnet temperature, and change depending on the magnet type and magnet arrangement method. The same motor is represented by the relationship shown in FIG. As can be seen from this relationship, the allowable current value decreases as the magnet temperature increases. For this reason, the compressor having the self-starting synchronous motor cannot be started when the magnet portion is at a high temperature.

  In an air conditioner having compressor air conditioners driven by a plurality of self-starting synchronous motors, it is necessary to control the number of operating compressors according to the increase or decrease in operating load. In the case of a stopped compressor, it is necessary to be below the allowable magnet temperature for the expected operating current in order to start the next time, so it can be started until the compressor magnet temperature after the stop reaches an allowable value. As a result, comfort may be greatly impaired.

  From the viewpoint of averaging the compressor operating life, in an air conditioner having a plurality of compressors, it is desirable that the compressors to be started be started in ascending order of operating time. When the magnet is stopped, it cannot be started until the magnet temperature becomes equal to or lower than the permissible temperature. During this time, comfort may be impaired due to insufficient capacity.

  In addition, for the purpose of reducing power consumption, it is necessary to control the number of compressors operated so that the power consumption of the air conditioner is less than or equal to the predetermined power consumption according to the demand signal from the outside. Even when it is determined only by the compressor operating time, the same phenomenon as the above problem is expected from the consideration of the magnet temperature.

  An object of the present invention is to achieve both the leveling of the compressor operation time and the suppression of the magnet temperature rise, to ensure the maximum air conditioning capacity according to the load, and to ensure the reliability of the motor without impairing the comfort. Is to provide an air conditioner and a control method thereof.

  In order to solve the above-described problems, the present invention provides an air conditioner including a plurality of compressors driven by an electric motor and a control unit that calculates an air conditioning load and controls and operates the number of compressors according to the load. The control unit includes an operation time detection unit that detects an operation time of the compressor, and a temperature detection unit that detects a temperature of the electric motor. The operation is started with priority on the lower compressor, and the compressor having a higher temperature is prioritized and stopped by the command to reduce the number of operating compressors.

  In addition, the control unit preferentially starts a compressor that has an allowable temperature or less and a short operation time in accordance with an instruction to increase the number of operating compressors.

  Further, the control unit preferentially shuts down the compressor having a long operating time that is equal to or lower than the allowable temperature in the command to reduce the number of operating compressors.

  Further, the control unit determines the number of compressors from a demand setting of power consumption from the outside, and controls the number of compressors within the power consumption of the demand setting.

  In addition, the control unit issues a start command to an external air conditioner connected to the outside if there is no compressor having an allowable temperature or lower among the stopped compressors when the command to increase the number of operating compressors is given. .

  In addition, an operating state of the plurality of compressors is displayed, and an indicator for displaying that the reason for the stop is due to the temperature detection condition of the motor is provided.

  The motor for driving the compressor is a self-starting synchronous motor.

  Furthermore, the present invention is a method for controlling an air conditioner comprising a plurality of compressors driven by an electric motor, and a controller that calculates an air conditioning load and controls the number of the compressors according to the load. In the command to increase the number of operating compressors, the compressor with the lower temperature of the motor is given priority to start operation, and in the command to decrease the number of operating compressors, the compressor with the higher motor temperature is given priority. It is characterized by stopping.

  In addition, according to the command to increase the number of operating compressors, the compressor starts with priority given to the compressor that is not more than the allowable temperature of the motor and has a short operating time.

  Further, according to the command to reduce the number of compressors to be operated, a compressor having a long operating time and a temperature lower than the allowable temperature is preferentially stopped.

  In addition, when there is no compressor having a temperature equal to or lower than the allowable temperature among the stopped compressors when the command to increase the number of operating compressors is issued, a start command is issued from the control unit to the external air conditioner.

  The motor for driving the compressor is a self-starting synchronous motor.

  According to the present invention, in an air conditioner having a plurality of compressors driven by a self-starting synchronous motor having a built-in permanent magnet, it is possible to prevent deterioration of the compressor function due to increase in the magnet temperature in the motor, and the operating compressor capacity and the number of compressors. No loss of comfort due to lack. In addition, it is possible to obtain an air conditioner that secures the air conditioning capability to the maximum with respect to the demands of the user and achieves both reduction of power consumption and ensuring of reliability.

Embodiments of the present invention will be described below with reference to FIGS. FIG. 2 is a configuration diagram of the refrigeration cycle. 1 is a variable displacement compressor (first compressor) driven by a variable speed motor, 2 is two compressors (second compressor) driven by a self-starting synchronous motor, and 3 is a four-way valve 4 is a heat source side heat exchanger, 5 is an outdoor expansion device, 6 is an electric valve, 7 is a refrigerant amount adjusting rod, 8 is an outdoor blower, and 64 is an outdoor unit control unit that controls the operation of each of the above-described parts and an indoor unit described later. And constitutes the outdoor unit 13.

  Further, 9 is an electric expansion valve, 10 is a use side heat exchanger, 11 is an indoor blower, 73 and 74 are thermistors that measure the temperature of the intake air and the blown air, and constitute the indoor unit 12. Reference numeral 72 denotes an indoor unit control unit, which is a remote controller for setting the operation start, stop, air volume, set temperature, set humidity and the like of each indoor unit 12. Furthermore, the indoor unit 12 is connected to the outdoor unit 13 by a liquid connection pipe 14 and a gas connection pipe 15, and air conditioning is performed by operating the compressor 1, the two compressors 2, the outdoor unit blower 7, and the indoor blower 11. This is done by exchanging heat with air.

  The compressor 2 is driven by a self-starting synchronous motor with low circuit loss, high efficiency, and no generation of harmonics to the power source. The thermistor 16 for measuring the magnet temperature in the motor (details will be described later). Is provided on the surface of the motor portion of the compressor. An external control unit 75 is a terminal for performing centralized control by starting / stopping the entire operation, a demand signal (cutting of electric energy), and the like.

  Here, since the electric expansion valve 9 is arranged in the indoor unit 12, regardless of whether the capacity of the compressors 1 and 2 is variable or fixed speed, whether the indoor unit 12 is single or plural, Without changing the configuration of the indoor unit 12, it can be used in common for each product group.

The operation of this embodiment will be described. In the cooling operation, the refrigerant flows in the direction of the solid arrow in the figure, and the gas refrigerant discharged from the compressors 1 and 2 passes through the four-way valve 3 and condenses in the heat source side machine heat exchanger 4 configured by a plurality of refrigerant passages. To do. The condensed refrigerant enters the refrigerant amount adjustment rod 7, and the liquid refrigerant derived from the refrigerant amount adjustment rod 7 is vaporized in the liquid connection pipe 14 connecting the outdoor unit 13 and the indoor unit 12 due to pressure loss according to the pipe length. It enters the electric expansion valve 9 as a liquid two-layer flow. The electric expansion valve 9 is an expansion device in which an arbitrary throttle amount can be set. The refrigerant decompressed by the electric expansion valve 9 is sent to the use-side heat exchanger 10 serving as an evaporator, and the refrigerant evaporates, and the indoor air Is cooled. The evaporated refrigerant passes through the gas connection pipe 15 and returns to the suction side of the compressors 1 and 2.
Next, the case of heating operation will be described. In the heating operation, the refrigerant flows in the direction of the dotted arrow by switching the four-way valve 3. The refrigerant discharged from the compressors 1 and 2 passes through the four-way valve 3 and the gas connection pipe 15, dissipates heat in the use side heat exchanger 10, condenses, and performs heating. The condensate is squeezed and expanded by the electric expansion valve 9, transported in the liquid connection pipe 14 in two phases, and sent to the outdoor unit 13. Then, the refrigerant having a greater degree of clearance due to the pressure loss of the liquid connection pipe 14 is sent to the heat source side heat exchanger 4. The two-phase refrigerant that has entered the heat source side heat exchanger 4 serving as an evaporator evaporates into a state with a high degree of draft, passes through the four-way valve 3 and returns to the compressors 1 and 2.
The efficiency of the compressors 1 and 2 is poor due to wet compression by controlling the electric expansion valve 9 during cooling and the electric expansion valve 5 during heating so that the degree of superheat on the suction side of the compressors 1 and 2 is slightly increased. Therefore, the air conditioner can be operated with better efficiency.

  FIG. 3 is an internal configuration diagram of the outdoor unit 13, in which the same parts as those in FIG.

  Reference numeral 66 denotes an air conditioning load calculation unit which receives the set temperature of the indoor unit control unit 72 and the temperatures of the intake air and the blown air measured by the thermistors 73 and 74, calculates the air conditioning load on the use side, and determines the appropriate refrigerant. Determine the amount of circulation and issue a command signal. A compressor number control unit 67 receives the command signal and controls the number of compressors operated (on number). Here, the first compressor 1 and the second compressor 2 are controlled. Reference numeral 68 denotes a variable capacity compressor capacity control unit which receives the command signal, controls the frequency of an inverter (not shown), and sends a control signal to the first compressor 1. The control units 66 to 68 constitute an operation control unit 65.

  Reference numeral 69 denotes a communication unit that exchanges signals with the compressors 1 and 2 in the outdoor unit, the indoor unit control unit 72, the external control unit 75, and the external air conditioner 100. Reference numeral 70 denotes an operation time detection unit that detects the operation time of each compressor, and reference numeral 71 denotes a temperature detection unit that detects the temperature of each motor for driving the compressor from the measurement result of the thermistor 16 of each compressor.

The units 66 to 68, 70, and 71 in the outdoor unit control unit 64 exchange signals with other parts via the communication unit 69.
FIG. 4 shows a flowchart of the operation of controlling the number of compressors by the outdoor unit controller 64 when the load changes during operation of the air conditioner of the present embodiment. In step (S) 17, load information from the indoor unit 12 is transmitted to the air conditioning load calculation control unit 66 provided in the outdoor unit 13 via the indoor unit control unit 72, and an appropriate refrigerant circulation amount is calculated. The number N1 of compressors to be determined is determined. In next S19, the current number of operating compressors is set to N2, and if N2> N1, the process proceeds to Y. In this case, it is necessary to reduce the number of operating compressors. In S20, the motor (magnet) temperatures of a plurality of compressors currently operating are measured by the thermistor 16, and the maximum temperature Tonmax is detected by the temperature detecting unit 71. To do.

  Next, in S21, the allowable upper limit magnet temperature T1 and Tonmax at the time of starting the compressor are compared. As a result, if T1 ≦ Tonmax, the process proceeds to Y, and the corresponding compressor is preferentially stopped in the next S22. If T1> Tonmax, the process proceeds to N, and in the next S23, the compressor having the longest operating time among the operating compressors is preferentially stopped. The operation time is always detected and stored by the operation time detector 70 for each compressor.

  As a result, among the operating compressors, the compressor whose magnet temperature exceeds the allowable upper limit temperature T1 at the time of starting is preferentially stopped, so that the heat can be dissipated by taking as long as possible for the stopped time. Thus, it is possible to avoid the phenomenon that the allowable upper limit magnet temperature T1 is exceeded at the next startup and the startup cannot be performed.

If it is determined N in S19 and the number of operating compressors N2 <N1 in S24, it is necessary to start the compressors that have been stopped, and the process proceeds to S25. In S25, the magnet temperature Toff (n) of the plurality of compressors that are currently stopped is detected by the temperature detection unit 71 by measurement from the thermistor 16, and in S26, one of the compressors corresponding to Toff (n) <T1 is detected. Start the compressor with a short running time. Thereby, at the time of start-up, demagnetization that occurs when the magnet temperature exceeds the allowable upper limit temperature can be prevented, and the compressor operation time can be leveled.
By performing the compressor increase / decrease control until the required number of compressors is reached, it is possible to supply an appropriate refrigerant circulation amount according to the load fluctuation, and it is possible to perform an operation that satisfies both comfort and reliability.
FIG. 5 shows a control flow during compressor operation. The current flowing through the motor in the compressor is smaller during synchronous operation after startup than when starting up. Therefore, from the relationship shown in FIG. 1, the allowable magnet temperature upper limit value T2 during operation satisfies the relationship of T2> T1 with respect to the allowable magnet temperature T1 at the time of start-up.
Even if the magnet temperature is lower than T1 at the time of start-up during the compressor operation in S28, the compressor magnet temperature in S29 due to a change in the compressor operation state due to a load increase such as an increase in suction superheat during the subsequent operation. There may be a case where Ton (n) satisfies Ton (n)> T2. In this case, the process proceeds to S30, and all the compressors are immediately stopped to avoid the deterioration of the compressor function due to the demagnetization of the permanent magnet, thereby ensuring the reliability.
Regarding T1 and T2, it is desirable to set a value having a sufficient margin in consideration of variation specific to the magnet type, thermistor error, and temperature response delay.
FIG. 6 shows a control flow in the case of starting from the stopped state of all the compressors. In accordance with the operation command and load information from the indoor unit 12, the required number N1 of compressors is determined in S32, and the compressors are started in order. Specifically, the number of operating units is increased while comparing N1 and N2 in S34 until the number of compressors N2 that are in operation due to sequential activation becomes N2 = N1.

  During the increase (N1> N2), as in the case of increasing the number of compressors in FIG. 4, the magnet temperature Toff (n) of the compressor stopped in S35 is compared with the allowable upper limit magnet temperature T1 at startup. When Toff (n)> T1, in S36, the compressors having the shortest operating time among the stopped compressors not corresponding to Toff (n)> T1 are sequentially started. Thereby, it is possible to avoid the demagnetization that occurs when the magnet temperature of the compressor to be started exceeds the allowable upper limit magnet temperature T1 at the time of starting, and to ensure reliability. In addition, when all the compressors stopped in S36 satisfy Toff (n)> T1, the compressor is not started. If N1 = N2 in S34, the operation of S31 in which the compressor is being activated is terminated in S38, and the control shifts to the normal control of FIG.

FIG. 7 shows an external view of the self-starting synchronous compressor, and FIG. 8 shows the internal structure and the attachment position of the thermistor for estimating the magnet temperature. As shown in FIG. 8, in the compressor, the compressor section for compressing the refrigerant and the motor section are separated from each other, and a commonly used compressor discharge gas temperature measurement thermistor is disposed near the discharge pipe or the compressor section. Often installed. In this embodiment, a thermistor is provided for measuring the magnet temperature. Although it is desirable to install the thermistor in or near the electric motor, it is difficult to realize the transmission of information by attaching the thermistor to the magnet in the electric motor in terms of reliability and cost. In this embodiment, as shown in FIG. 8, by providing the thermistor 16 on the outer peripheral surface of the compressor closest to the motor portion, it is possible to minimize the error when measuring the magnet temperature in the motor.
FIG. 9 shows a flowchart for controlling the number of compressors when receiving a demand signal from the external control unit 75.

When the power consumption is limited by the demand signal, the compressor capacity and the number are controlled so as not to exceed the preset power consumption. As a method for reducing the refrigerant circulation amount, there are a method for reducing the refrigerant circulation amount using a variable capacity compressor and a method for reducing the number of fixed capacity compressors. In general, since it is expensive to use variable capacity compressors for all the compressors, in this embodiment, the capacity control of the refrigerant circulation amount is performed by combining a variable capacity compressor and a fixed capacity compressor.
All compressors have a device (not shown) that can measure the current value, such as a current transformer, or are variable if the pressure sensor or the high-pressure pressure and low-pressure pressure based on the refrigerant condensing temperature and the refrigerant evaporating temperature are variable. It has a function of estimating the operating current by a function or table value depending on the capacity and the number of operating compressors, and the total current of the operating air conditioner is always transmitted as control information to, for example, the outdoor unit controller 14 that performs control. . When the power consumption restriction control is enabled by an external input signal or a preset time in S37, the necessary number of compressors to be operated is calculated in S38, and S38 to 47 in the subsequent operation flow are S19 in FIG. The number of compressors is increased / decreased similarly to the float of S27. By performing the above control, it is possible to realize the maximum air conditioning capacity required within the limited power consumption.
FIG. 10 shows a flowchart when the externally connected external air conditioner 100 is used for controlling the number of compressors. S48 to S56 in this flowchart are the same as S17 to S25 in FIG.
If the current number of operating compressors N2 <the required number of compressors N1 in S55 of FIG. 10, the stopped compressors are started, but in S57, all the stopped compressors in the outdoor unit are Toff (n) If> Toffmax, since the compressor in the outdoor unit cannot be started, a start command is issued to the external air conditioner 100 connected externally in S59. Specifically, by starting the compressor with the shortest operating time among the stopped compressors satisfying Toff (n) ≦ Toffmax in the outdoor unit mounted on the external air conditioner 100 connected to the outside. Therefore, it is possible to avoid deterioration of comfort due to a shortage of the necessary circulation amount of the refrigerant.
FIG. 11 shows an example of a display that displays the reason for stopping the compressor. In FIG. 11, the outdoor unit 13 is provided with a display 62, and the display 62 indicates the operation state of the compressor by a lamp such as an LED. Reference numeral 62a denotes a lamp for indicating that the operation is in progress, and reference numeral 62b denotes a lamp for indicating the operation prohibited state depending on the temperature condition. Here, the operation prohibited state indicates a state in which the temperature of the motor of the stopped compressor is equal to or higher than the allowable upper limit magnet temperature T1 at the time of startup. If the temperature drops due to the elapse of the stop time, this lamp goes off.

  In the display shown in FIG. 11, the first compressor is in operation, the second compressor is in operation but can be started, and the third compressor is in operation, but the start is prohibited due to temperature conditions. Indicates the state. According to this display, it is easy to confirm the operation status of the outdoor unit at the time of service, and it is suitable for improving the maintainability. Further, this information is transmitted together with the detected temperature to an external information terminal or the like by wired or wireless transmission, so that it is possible to check the outdoor unit operation status without going directly to the installation site.

Explanatory drawing of the demagnetization effect | action by operating current and temperature. The block diagram of the refrigerating cycle of the air conditioner of an Example of this invention. The internal structure of the outdoor unit of an Example of this invention. The flowchart of compressor number control by the load fluctuation | variation in driving | operation of this invention Example. The control flow during the compressor driving | operation of this invention Example. The flowchart of the compressor number control at the time of starting of this invention Example. 1 is an external view of a compressor using a self-starting synchronous motor according to an embodiment of the present invention. The compressor internal structure and thermistor attachment part enlarged view. The flowchart of compressor number control at the time of the demand signal reception of an Example of this invention. The flowchart of compressor number control by the externally connected air conditioner of an Example of this invention. Explanatory drawing of the indicator which displays the compressor stop reason.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Compressor (capacity variable type), 2 ... Compressor (capacity fixed type), 3 ... Four-way valve, 4 ... Heat source side heat exchanger, 5 ... Outdoor expansion device, 6 ... Electric valve, 7 ... Refrigerant amount regulator , 8 ... outdoor blower, 9 ... electric expansion valve, 10 ... use side heat exchanger, 11 ... indoor blower, 12 ... indoor blower, 13 ... outdoor unit, 14 ... liquid connection pipe, 15 ... gas connection pipe, 16 ... thermistor (For magnet temperature measurement), 62 ... indicator (compressor operation state display part), 64 ... control part (outdoor unit control part), 67 ... compressor number control part, 69 ... communication part, 70 ... operating time detection part , 71 ... temperature detector, 100 ... external air conditioner, T1, T2 ... allowable temperature.

Claims (12)

An air conditioner including a plurality of compressors driven by an electric motor, and a control unit that calculates an air conditioning load and controls and operates the number of the compressors according to the load,
The control unit includes an operation time detection unit that detects an operation time of the compressor, and a temperature detection unit that detects a temperature of the electric motor, and prioritizes a compressor having a lower temperature in an instruction to increase the number of operating compressors. The air conditioner is characterized in that the operation is started and the compressor having a higher temperature is preferentially stopped according to the command to reduce the number of operating compressors.   2. The air conditioner according to claim 1, wherein the control unit preferentially starts a compressor that has a temperature lower than an allowable temperature and has a short operation time according to an instruction to increase the number of operating compressors.   3. The air conditioner according to claim 1, wherein the control unit preferentially shuts down a compressor having a long operating time that is equal to or lower than an allowable temperature in a command to reduce the number of operating compressors.   The said control part determines the number of compressors from the demand setting of the power consumption from the outside, and carries out operation control of the number of compressors within the power consumption of a demand setting. The air conditioner described.   The control unit issues a start command to an external air conditioner connected to the outside if there is no compressor having an allowable temperature or lower among the stopped compressors when the command to increase the number of operating compressors is given. The air conditioner according to any one of claims 1 to 4, wherein   The air conditioner according to any one of claims 1 to 5, further comprising an indicator for displaying an operating state of the plurality of compressors and displaying that the reason for the stop is due to a temperature detection condition of the electric motor. Machine.   The air conditioner according to any one of claims 1 to 6, wherein the motor that drives the compressor is a self-starting synchronous motor. A control method of an air conditioner comprising a plurality of compressors driven by an electric motor, and a control unit that calculates an air conditioning load and controls the number of the compressors according to the load,
In the command to increase the number of operating compressors, the compressor with lower temperature of the motor is given priority to start operation, and in the command to decrease the number of operating compressors, the compressor with higher motor temperature is given priority to stop. A control method for an air conditioner.   9. The method of controlling an air conditioner according to claim 8, wherein, in accordance with an instruction to increase the number of operating compressors, the compressor is started with priority given to a compressor having a temperature lower than an allowable temperature of the motor and having a short operating time.   The method of controlling an air conditioner according to claim 8 or 9, wherein in the command to reduce the number of operating compressors, the compressor having a long operating time is preferentially stopped with a temperature lower than an allowable temperature.   The start-up command is issued from the control unit to the external air conditioner when there is no compressor having an allowable temperature or lower among the stopped compressors when the command to increase the number of operating compressors is given. The control method of the air conditioner in any one of 8-10.   The method of controlling an air conditioner according to any one of claims 8 to 11, wherein the electric motor that drives the compressor is a self-starting synchronous motor.

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