JP5501987B2 - Air conditioner - Google Patents

Description

  The present invention relates to an air conditioner.

  As an example of a conventional air conditioner, there is an air conditioner that includes the fan motor control device described in Patent Document 1 and that drives the fan motor. In this air conditioner, the fan motor control device detects the load applied to the outdoor fan motor, and controls to reduce the rotational speed of the fan motor if it is above a predetermined load, and to increase the rotational speed if it is below a predetermined load, It enhances controllability against external loads and protects them.

JP 2001-286179 A (page 1, pages 9-13, FIG. 8)

  However, the conventional air conditioner is not considered due to the load changing speed. For example, when the control is made to follow the load at the time of frost formation in the outdoor heat exchanger that changes slowly, the air conditioner can change during a gust of sudden change. There was a problem that the overcurrent protection stop of the fan occurred due to failure to follow the load fluctuation.

  The present invention has been made in view of the above, and an object of the present invention is to obtain an air conditioner that operates following a rapid load fluctuation due to a gust of wind or a gradual load fluctuation due to frosting at a low temperature of heating. To do.

  In order to solve the above-described problems and achieve the object, the present invention is based on a motor to which an outdoor fan that blows air to an outdoor heat exchanger is connected, an inverter that drives the motor, and a direct current of the inverter. An inverter control unit that controls the frequency of the voltage output by the inverter, and the inverter control unit includes a current peak value change amount deriving unit that calculates a change amount of the peak value in a predetermined period of the DC unit current; The necessity of adjustment for lowering the frequency of the motor is determined based on the direct current current, and if it is determined that adjustment is necessary, it is determined according to the calculated change amount and the assumed operating environment. Compared with a plurality of threshold values, and selects one of the three or more types of change widths determined in advance according to the comparison result. Characterized in that it comprises a frequency changing unit that performs control to reduce the frequency of the PWM driving signal for controlling the inverter.

  According to the present invention, the amount of change in the current peak value is monitored, and according to the amount of change (such as a rapid change or a gradual change), the motor rotation speed change speed is changed with a different change width. When frost is formed at low temperatures, the capacity can be improved by rotating the outdoor fan at the maximum speed that can be operated for efficient heat exchange, and when there is a sudden change in load due to a gust of wind. In addition, it is possible to perform motor control that follows load fluctuations, and it is possible to obtain a strong controllability capable of continuing operation by preventing the protective function from working.

FIG. 1 is a diagram illustrating a configuration example of Embodiment 1 of an air conditioner according to the present invention. FIG. 2 is a diagram illustrating a configuration example of the inverter control unit. FIG. 3 is a flowchart illustrating an example of the control operation of the inverter. FIG. 4 is a diagram illustrating an example of the control operation of the inverter.

  Embodiments of an air conditioner according to the present invention will be described below in detail with reference to the drawings. Note that the present invention is not limited to the embodiments.

Embodiment.
FIG. 1 is a diagram illustrating a configuration example of Embodiment 1 of an air conditioner according to the present invention. As shown, the air conditioner includes an outdoor fan 2, a motor 4, an inverter 5, a DC power supply 6, a current detection unit 7, a peak hold circuit 8, and an inverter control unit 9.

  The outdoor fan 2 is connected to the motor 4 and blows air to the outdoor heat exchanger 1 to perform heat exchange. The motor 4 includes a hall sensor 3 that detects the rotation operation (rotor position) of the outdoor fan 2. An inverter 5 that supplies a voltage to the motor 4 to drive it operates by obtaining power from a DC power source 6, and a control input terminal of the inverter 5 is connected to an inverter control unit 9. The current detection unit 7 is provided between the inverter 5 and the DC power source 6 and detects a DC unit current flowing through the inverter 5. The current detection unit 7 is connected to the inverter control unit 9 via a peak hold circuit 8 that holds a peak value. The peak hold circuit 8 holds the peak value of the current detection value by the current detection unit 7 and outputs the held value to the inverter control unit 9. It is reset at a predetermined timing (reset at regular intervals). The inverter control unit 9 controls the inverter 5 based on the peak value held by the peak hold circuit 8 and the output of the hall sensor 3. Although not shown, the air conditioner is provided with a circuit (protection circuit) for preventing an overcurrent from flowing into the inverter 5 for some reason, and operates when an overcurrent is detected. Stop operation.

  FIG. 2 is a diagram illustrating a configuration example of the inverter control unit 9. The inverter control unit 9 includes a current peak value storage unit 10, a current peak value change amount derivation unit 11, and a frequency change unit 12. The current peak value storage unit 10 stores the peak value detected by the peak hold circuit 8 (the peak value of the current detection value by the current detection unit 7). The current peak value change amount deriving unit 11 calculates the change amount of the peak value detected by the peak hold circuit 8. The frequency changing unit 12 changes the frequency of the voltage that the inverter 5 outputs to the motor 4 based on the change amount calculated by the current peak value change amount deriving unit 11 and the output value from the Hall sensor 3. PWM (Pulse Width Modulation) drive signal is generated and output to the inverter 5.

  Next, the operation of the air conditioner will be described.

  In the air conditioner shown in FIG. 1, the detection peak value of the current detector 7 is held in the peak hold circuit 8, and control is performed based on the current peak value. FIG. 3 is a flowchart showing an example of this control operation.

  In the inverter control operation in the air conditioner according to the present invention, the inverter control unit 9 first determines the output value from the peak hold circuit 8 (the peak value of the current detected by the current detection unit 7) as the current peak value storage unit 10. Is stored (step S1), and then the current peak value change amount deriving unit 11 determines whether or not the stored current peak value has reached the frequency decrease determination value (step S2). The frequency decrease determination value is a threshold value for determining whether or not the inverter 5 needs to be controlled so as to detect the fluctuation of the load applied to the outdoor fan motor and decrease the rotation speed of the motor 4. The current peak value change amount deriving unit 11 holds the current peak value in advance by simulation or the like. As a result of the determination, if the current peak value has not reached the frequency decrease determination value, nothing is performed, that is, the control for decreasing the rotation speed of the motor 4 is not performed on the inverter 5 (step S2: No). . In this case, step S1 and subsequent processing are repeatedly executed. For example, step S1 and subsequent processing are executed again after a predetermined time has elapsed. On the other hand, when the current peak value has reached the frequency decrease determination value (step S2: Yes), the control width when the rotation speed of the motor 4 is decreased by executing the processing of steps S3 to S8 described later is determined. . Hereinafter, the process after step S3 is demonstrated in detail.

  When the current peak value has reached the frequency decrease determination value (step S2: Yes), the current peak value change amount deriving unit 11 determines the previous current peak value (the current peak value storage unit 10 in step S1 in the previous control operation). Current peak value) and the current current peak value are obtained (step S3). Further, the obtained change amount is output to the frequency changing unit 12. The current peak value storage unit 10 stores a plurality of current peak values output from the peak hold circuit 8 (stores at least two, that is, current and previous output current peak values). The current peak value change amount deriving unit 11 may receive the previous current peak value and the current current peak value from the current peak value storage unit 10 and calculate the change amount, or from the current peak value storage unit 10. The current peak value may be received, and the amount of change may be calculated from this and the output value (current current peak value) of the peak hold circuit 8.

  Next, the frequency changing unit 12 compares the amount of change received from the current peak value change amount deriving unit 11 (the amount of change obtained in step S3) with the amount of change during frost formation and the amount of change during gust (step S4). S5) Based on the comparison result, the control width at the time of controlling the inverter 5 so as to decrease the rotation speed of the motor 4 is determined as any one of three reduction amounts (decrease amounts). .

  Specifically, the frequency changing unit 12 first determines whether or not the received change amount is equal to or less than the change amount during frost formation (step S4), and if it is equal to or less than the change amount during frost formation (step S4: Yes), The frequency reduction amount of the voltage output to the inverter 5 is determined as the first reduction amount (Lo) (step S6). After the determination, the PWM drive signal output to the inverter 5 is adjusted according to the determination result. The adjustment is continued until it is determined that it is no longer necessary to reduce the rotational speed of the motor 4 (adjustment is performed with the determined frequency reduction amount). This determination is made from the current peak value. For example, using the frequency increase determination value lower than the above-described frequency decrease determination value, the adjustment operation for decreasing the frequency is continued until the current peak value becomes equal to or less than the frequency increase determination value. Further, the adjustment operation may be continued until the current peak value becomes equal to or lower than the frequency increase determination value using the frequency decrease determination value described above. On the other hand, as a result of comparing the amount of change received from the current peak value change amount deriving unit 11 with the amount of change during frost formation, if the amount of change is not less than or equal to the amount of change during frost formation (step S4: No), the change amount is further increased. Is less than or equal to the amount of change during gust (step S5), and if it is less than or equal to the amount of change during gust (step S5: Yes), the frequency decrease amount of the voltage output to the inverter 5 is set to the second decrease amount (Mi). (Step S7). On the other hand, if it is not less than or equal to the amount of change due to gust (step S5: No), the frequency reduction amount of the voltage output to the inverter 5 is determined as the third reduction amount (Hi) (step S8). When steps S7 and S8 are executed, the PWM drive signal output to the inverter 5 is adjusted (the need to reduce the rotational speed of the motor 4 is no longer required), as in the case where the frequency reduction amount is determined in step S6. The adjustment operation is continued until it is judged).

  Here, the amount of change during frost and the amount of change during gust are threshold values for determining the amount of decrease in frequency, and the relationship between these amounts of change is as follows: It is assumed that “amount”. In addition, the values (threshold values) of these two changes are determined in advance by simulation or the like according to the assumed driving environment. The amount of change during frost formation is determined based on the amount of change in current when a load change occurs with the occurrence of frost formation. The amount of change during frost formation is due to moderate load fluctuations due to frost formation (or other equivalent factors) or other factors (including gusts). It is used to determine whether it is in s units or more than ms units. That is, if the amount of change in the current peak value is equal to or less than the amount of change during frost formation, it is determined that the load change accompanying the frost formation (gradual load change). On the other hand, the amount of change during gust is determined based on the amount of change in current when a load change occurs with the occurrence of gust. The amount of change in the gust is due to whether the load fluctuates at a medium speed due to factors other than frost formation and gusts, or whether there is a sudden load fluctuation due to gusts (in ms units) It is used to determine whether it is ns unit or more. That is, if the amount of change in the current peak value exceeds the amount of change during a gust, it is determined that the load change (abrupt load change) associated with the gust. The relationship between the three stages of reduction amounts is “first reduction amount (Lo) <second reduction amount (Mi) <third reduction amount (Hi)”.

  When the control operation as described above is applied, the frequency is gradually decreased when the current peak value change amount is during frost formation. That is, as shown in FIG. 4A, the motor rotation speed (motor rotation speed indicated by a solid line) decreases following the load during frost formation, and conventional control (motor rotation speed indicated by a broken line) is performed. As compared with, the motor rotation speed during frost formation can be kept high. On the other hand, in the case of a gust of wind (when the load fluctuates rapidly), as shown in FIG. 4 (b), the motor rotation speed (solid line) follows the load during the gust of wind and goes down. Compared with (dashed line), the motor rotation speed can be decreased more steeply, that is, the motor rotation speed can be decreased to the lower limit value in a shorter time than conventional. As a result, it is possible to prevent the operation of the protection function due to overcurrent from occurring more than necessary.

  In the above description, the control for lowering the motor rotation speed is shown. However, the control for increasing the motor rotation speed is the same as the conventional control. That is, the inverter control unit 9 controls the inverter 5 so as to increase the motor rotational speed when detecting that the current peak value is equal to or lower than the frequency increase determination value (see FIG. 4). Whether the current peak value is equal to or lower than the frequency increase determination value may be determined by the current peak value change amount deriving unit 11 of the inverter control unit 9 or may be performed by other components not shown. It may be. The frequency increase determination value is obtained in advance by simulation or the like, similar to the above-described frequency decrease determination value.

  As described above, the air conditioner of the present embodiment monitors the change amount of the current peak value, and changes the motor rotation speed change speed with a different change amount according to the change amount (abrupt change or gradual change). I decided to change it. Thereby, at the time of frosting of heating low temperature, the outdoor fan 2 can be rotated with the maximum rotation speed which can be drive | operated, an efficient heat exchange can be performed, and a capability improvement can be aimed at. In addition, even when a load fluctuation occurs due to a gust of wind or dust adhering to the outdoor heat exchanger 1, the motor can be controlled following the fluctuation, and a protection function (for example, an overcurrent protection stop function) works. Thus, it is possible to obtain a robust controllability that can prevent operation and continue operation.

  The peak hold circuit 8 may be deleted from the configuration shown in FIG. 1 and the current detection result by the current detection unit 7 may be directly input to the inverter control unit 9.

  In the above description, an example of operation in which there are two threshold values (such as the amount of change during frosting) for determining the amount of change in the current peak value has been described, but three or more threshold values are used. And it is good also considering the value of a frequency fall amount as 4 or more types.

  As described above, the air conditioner according to the present invention is useful as an air conditioner configured to control an inverter based on a detected value of a current flowing through an inverter that drives a motor.

DESCRIPTION OF SYMBOLS 1 Outdoor heat exchanger 2 Outdoor fan 3 Hall sensor 4 Motor 5 Inverter 6 DC power supply 7 Current detection part 8 Peak hold circuit 9 Inverter control part 10 Current peak value memory | storage part 11 Current peak value change derivation part 12 Frequency change part

Claims (5)

A motor connected to an outdoor fan that blows air to the outdoor heat exchanger; an inverter that drives the motor; and an inverter control unit that controls a frequency of a voltage output by the inverter based on a direct current of the inverter. ,
The inverter control unit
A current peak value change amount derivation unit that calculates a change amount of a peak value in a predetermined period of the DC part current;
The necessity of adjustment for lowering the frequency of the motor is determined based on the direct current current, and if it is determined that adjustment is necessary, it is determined according to the calculated change amount and the assumed operating environment. A plurality of threshold values, and according to the comparison result, select any one of three or more predetermined change widths, and select the inverter with the selected change width. A frequency changing unit that performs control to reduce the frequency of the PWM drive signal for controlling
An air conditioner comprising: The current peak value change amount derivation unit includes:
The peak value is confirmed at a predetermined timing, and when the DC section current reaches a threshold value for determining the necessity of adjustment for lowering the frequency of the motor, the peak at the time when the threshold value is reached. The air conditioner according to claim 1, wherein a change amount of the peak value immediately before reaching the threshold value is calculated. A peak hold circuit that continues to output the latest peak value by detecting the peak value of the DC section current;
The air conditioner according to claim 1 or 2, wherein the current peak value change amount derivation unit calculates a change amount of a peak value output from the peak hold circuit. The frequency changing unit is
As the plurality of threshold values, a first threshold value and a second threshold value larger than the first threshold value are used,
When the amount of change is less than or equal to a first threshold, the frequency is decreased by a first change width, and when the amount of change is greater than the first threshold and less than or equal to the second threshold Decreases the frequency by a second change width, and when the amount of change is larger than a second threshold value, decreases the frequency by a third change width,
The first change width, the second change width, and the third change width have a relationship of “first change width <second change width <third change width”. The air conditioner according to 1, 2 or 3. The first threshold value is a threshold value for determining the presence or absence of load fluctuations caused by frost formation, and the second threshold value is a threshold for determining the presence or absence of load fluctuations caused by gusts. It is set as a value. The air conditioner of Claim 4 characterized by the above-mentioned.

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