Motor drive controller and fan unit

Abstract

To control the volume of air from a fan to be constant without providing an air volume sensor.SOLUTION: In a motor drive controller 1, a control circuit 3 calculates a voltage estimated value V0 on the basis of first correspondence information 150 representing the relationship between a rotation speed and a voltage command value when the static pressure of a fan 6 is a reference value. The control circuit 3, on the basis of second correspondence information 160 representing the relationship between a rotation speed and an air volume when the static pressure of the fan 6 is the reference value, calculates an air volume estimated value Q0 corresponding to an actual rotation speed Nr when the static pressure of the fan 6 is the reference value, and calculates a ratio between the voltage estimated value V0 and the voltage command value V1. The control circuit 3 calculates an air volume estimated value Q1 on the basis of the air volume estimated value Q0 and the ratio, generates the voltage command value V1 so that the air volume estimated value Q1 matches an air volume command value Qref, and generates a drive control signal Sd.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a motor drive control device and a fan unit.

Background Art

[0002] In a ventilation fan or the like, it is known that the air volume (air flow rate) changes due to changes in pressure loss (static pressure) caused by the duct length and the internal and external states of the duct. Therefore, a motor drive control device that drives a motor of a fan such as a ventilation fan is required to have a function of controlling the motor so that the air flow of the fan remains constant even when the static pressure or the like changes.

[0003] As a conventional technique for controlling the air volume of a fan to be constant, a method is known in which a command value of the torque of the fan (motor) is calculated, and the air volume of the fan is kept constant based on the relationship between the torque and the air volume (see Patent Documents 1 and 2 below).

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, in a characteristic (P-Q characteristic) that represents the relationship between the air volume and the static pressure, such as an axial flow fan, when there is a region (surge stall region) where the air flow becomes unstable, the relationship between the air volume and the torque becomes non-uniform due to surge stall. Therefore, with the techniques represented by the above patent documents, it is difficult to control the air volume to be constant.

[0006] On the other hand, it is also possible to measure the air volume of the fan by an air volume sensor and perform air volume constant control so that the measured air volume matches the target air volume. However, in this method, it is necessary to newly provide an air volume sensor, which causes an increase in manufacturing cost due to securing the mounting position of the air volume sensor and complication of construction due to the mounting of the air volume sensor.

[0007] The present invention is for solving the above-described problems, and an object thereof is to control the air volume of a fan to be constant without providing an air volume sensor.

Means for Solving the Problems

[0008] A motor drive control device according to a typical embodiment of the present invention includes a control circuit that outputs a drive control signal for controlling the drive of a motor of a fan, and a motor drive circuit that drives the motor based on the drive control signal output from the control circuit. The control circuit includes an air volume control unit that calculates a voltage command value, which is a command value of the drive voltage of the motor, so that the air volume of the fan becomes constant, a drive control signal generation unit that generates the drive control signal based on the voltage command value, a rotation speed acquisition unit that acquires an actual rotation speed, which is the rotation speed of the rotor of the motor, and a voltage estimation unit that calculates a voltage estimated value, which is the voltage command value corresponding to the actual rotation speed when the static pressure of the fan is the reference value, based on first correspondence relation information representing the relationship between the rotation speed and the voltage command value when the static pressure of the fan is the reference value. The control circuit further includes an air volume estimation unit that calculates a first air volume estimated value, which is the air volume corresponding to the actual rotation speed when the static pressure of the fan is the reference value, based on second correspondence relation information representing the relationship between the rotation speed and the air volume when the static pressure of the fan is the reference value, calculates a ratio between the voltage command value calculated by the air volume control unit and the voltage estimated value, and calculates a second air volume estimated value, which is the air volume corresponding to the voltage command value calculated by the air volume control unit, based on the first air volume estimated value and the ratio. The air volume control unit is characterized by calculating the voltage command value so that the second air volume estimated value matches an air volume command value, which is a target value of the air volume.

Effects of the Invention

[0009] According to one aspect of the present invention, it is possible to control the air volume of the fan to be constant without providing an air volume sensor.

Brief Description of the Drawings

[0010]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Modes for Carrying Out the Invention

[0011] 1. Outline of the Embodiment First, an outline of a typical embodiment of the invention disclosed in the present application will be described. In the following description, as an example, reference numerals on the drawings corresponding to the components of the invention are described with parentheses.

[0012] 〔1〕A motor drive control device (1) according to a typical embodiment of the present invention includes a control circuit (3) that outputs a drive control signal (Sd) for controlling the drive of a motor (4) of a fan (6), and a motor drive circuit (2) that drives the motor based on the drive control signal output from the control circuit. The control circuit includes an air volume control unit (20) that calculates a voltage command value (V1), which is a command value of the drive voltage of the motor, so that the air volume of the fan becomes constant, a drive control signal generation unit (21) that generates the drive control signal based on the voltage command value, a rotation speed acquisition unit (14) that acquires an actual rotation speed (Nr), which is the rotation speed of the rotor of the motor, and a voltage estimation unit (15) that calculates a voltage estimation value (V0), which is the voltage command value corresponding to the actual rotation speed when the static pressure of the fan is the reference value, based on first correspondence relationship information (150) representing the relationship between the rotation speed and the voltage command value when the static pressure of the fan is the reference value. The control circuit further includes an air volume estimation unit (16) that calculates a first air volume estimation value (Q0), which is the air volume corresponding to the actual rotation speed when the static pressure of the fan is the reference value, based on second correspondence relationship information (160) representing the relationship between the rotation speed and the air volume when the static pressure of the fan is the reference value, calculates a ratio (V1 / V0) between the voltage command value calculated by the air volume control unit and the voltage estimation value, and calculates a second air volume estimation value (Q1), which is the air volume corresponding to the voltage command value calculated by the air volume control unit, based on the first air volume estimation value and the ratio. The air volume control unit is characterized by calculating the voltage command value so that the second air volume estimation value matches an air volume command value (Qref), which is a target value of the air volume.

[0013] 〔2〕In the motor drive control device described in the above 〔1〕, the reference value may be zero.

[0014] 〔3〕In the motor drive control device according to the above 〔1〕 or 〔2〕, the air volume estimation unit has the second correspondence relationship information, and a first air volume calculation unit (17) that calculates the first air volume estimation value based on the second correspondence relationship information and the actual rotation speed, a voltage ratio calculation unit (18) that calculates a voltage ratio (V1 / V0) which is a ratio of the voltage command value (V1) calculated by the air volume control unit to the voltage estimation value (V0), and a second air volume calculation unit (19) that multiplies a value obtained by squaring the voltage ratio by the first air volume estimation value to calculate the second air volume estimation value (Q1). It is characterized by including these components.

[0015] 〔4〕A fan unit (10) according to a typical embodiment of the present invention includes the motor drive control device (1) according to any one of the above 〔1〕 to 〔3〕, the motor (4) driven by the motor drive control device, and an impeller (5) configured to be rotatable by the rotational force of the motor. It is characterized by including these components.

[0016] 〔5〕The motor drive control method according to a representative embodiment of the present invention includes a first step (S12, S18) of calculating a voltage command value which is a command value of the drive voltage of the fan motor, a second step (S12) of generating a drive control signal for controlling the drive of the motor based on the voltage command value, a third step (S13) of obtaining an actual rotation speed which is the rotation speed of the rotor of the motor, a fourth step (S14) of calculating a voltage estimated value which is the voltage command value corresponding to the actual rotation speed when the static pressure of the fan is the reference value based on first correspondence relation information representing the relation between the rotation speed and the voltage command value when the static pressure of the fan is the reference value, a fifth step (S15) of calculating a first air volume estimated value which is the air volume corresponding to the actual rotation speed when the static pressure of the fan is the reference value based on second correspondence relation information representing the relation between the rotation speed and the air volume when the static pressure of the fan is the reference value, a sixth step (S16) of calculating a ratio between the voltage command value calculated in the first step and the voltage estimated value calculated in the fourth step, and a seventh step (S17) of calculating a second air volume estimated value which is the air volume corresponding to the voltage command value calculated in step S1 based on the first air volume estimated value calculated in the fifth step and the ratio calculated in the sixth step, wherein the first step includes a step (S18) of calculating the voltage command value such that the second air volume estimated value calculated in the seventh step matches an air volume command value which is a target value of the air volume.

[0017] 2. Specific Example of Embodiment Hereinafter, a specific example of an embodiment of the present invention will be described with reference to the drawings. In the following description, the same reference numerals are given to the common components in each embodiment, and the repeated description will be omitted. Also, it should be noted that the drawings are schematic, and the dimensional relationships and ratios of the respective elements may be different from the actual ones. There may also be parts where the dimensional relationships and ratios are different between the drawings.

[0018] ≪Embodiment≫

[0019] FIG. 1 is a diagram showing the configuration of a fan unit including a motor drive control device 1 according to an embodiment.

[0020] The fan unit 10 shown in FIG. 1 is a device that generates wind by rotating an impeller (fan). The fan unit 10 can be applied to, for example, a ventilation facility (ventilation fan) that discharges indoor air to the outside.

[0021] As shown in FIG. 1, the fan unit 10 includes a motor 4, an impeller 5, rotation position detectors 7u, 7v, 7w for detecting the rotation position (rotation angle) of the motor 4, a current detector 8 for detecting the current flowing through the motor 4, and a motor drive control device 1 for driving the motor 4.

[0022] The motor 4 is, for example, a brushless motor. In the present embodiment, the motor 4 is a brushless motor having three-phase coils. The motor drive control device 1 is a device for controlling the rotation of the motor 4. The motor drive control device 1 outputs a sine wave drive signal to the motor 4, for example, and periodically supplies a sine wave drive current to the three-phase coils Lu, Lv, Lw of the motor 4 to rotate the motor 4.

[0023] The impeller (fan) 5 is a component that generates wind and is configured to be rotatable by the rotational force of the motor 4. For example, the rotation axis of the impeller 5 may be coaxially connected to the output axis of the motor 4, or may be connected to the output axis of the motor 4 via a speed reducer. In the present embodiment, for example, it is assumed that the impeller 5 and the motor 4 constitute one fan 6.

[0024] The motor drive control device 1 has a motor drive circuit 2 and a control circuit 3. Note that the components of the motor drive control device 1 shown in FIG. 1 are a part of the whole, and the motor drive control device 1 may have other components in addition to those shown in FIG. 1.

[0025] The motor drive circuit 2 drives the motor 4 based on the drive control signal Sd output from the control circuit 3 described later. The motor drive circuit 2 includes an inverter circuit 2a and a pre-drive circuit 2b.

[0026] The inverter circuit 2a outputs a drive signal to the motor 4 based on the output signal from the pre-drive circuit 2b, and supplies power to the coils Lu, Lv, Lw provided in the motor 4. The inverter circuit 2a is configured, for example, such that pairs of series circuits of two switch elements provided across both ends of a DC power supply Vcc are respectively arranged for each phase (U phase, V phase, W phase) of the coils Lu, Lv, Lw. In each pair of two switch elements, the terminals of each phase of the motor 4 are connected to the connection point between the switch elements. Note that the reference symbol "Vcc" represents not only the DC power supply but also the voltage (power supply voltage) supplied from the DC power supply.

[0027] The pre-drive circuit 2b generates an output signal for driving the inverter circuit 2a based on the drive control signal Sd from the control circuit 3, and outputs it to the inverter circuit 2a.

[0028] The drive control signal Sd is a signal for controlling the drive of the motor 4, and is, for example, a PWM (Pulse Width Modulation) signal. Specifically, the drive control signal Sd includes six types of PWM signals corresponding to the respective switch elements of the inverter circuit 2a. Specifically, the drive control signal Sd is a signal for switching the energization pattern of the coils Lu, Lv, Lw of the motor 4 determined by the on / off states of the respective switch elements constituting the inverter circuit 2a.

[0029] The pre-drive circuit 2b corresponds to, for example, six types of PWM signals as drive control signals Sd, and generates and outputs six types of drive signals Vuu, Vul, Vvu, Vvl, Vwu, Vwl having sufficient power to drive each switch element of the inverter circuit 2a. When these drive signals are input to the inverter circuit 2a, the switch elements corresponding to the respective drive signals that make up the inverter circuit 2a perform on and off operations. As a result, power is supplied to the coils Lu, Lv, Lw of each phase of the motor 4.

[0030] The rotational position detectors 7u, 7v, 7w generate signals Hu, Hv, Hw corresponding to the rotation of the rotor of the motor 4. The rotational position detectors 7u, 7v, 7w are, for example, Hall elements. Hereinafter, the rotational position detectors 7u, 7v, 7w will also be referred to as "Hall elements 7u, 7v, 7w".

[0031] The three Hall elements 7u, 7v, 7w are provided corresponding to each phase (U phase, V phase, W phase) of the motor 4. The Hall elements 7u, 7v, 7w are arranged, for example, around the rotor of the motor 4 at substantially equal intervals from each other (for example, at an interval of 120 degrees between adjacent ones).

[0032] The Hall elements 7u, 7v, 7w each detect the magnetic poles of the rotor and output signals Hu, Hv, Hw whose voltages change according to the rotation of the rotor. The signals Hu, Hv, Hw are input to the control circuit 3. Hereinafter, the signals Hu, Hv, Hw may be collectively referred to as "rotational position detection signal Se".

[0033] Note that instead of the signals Hu, Hv, Hw from the Hall elements, other signals corresponding to the rotational position of the rotor of the motor 4 may be input as the rotational position detection signal Se. For example, an encoder, a resolver, etc. may be provided, and their detection signals may be input to the control circuit 3 as the rotational position detection signal Se. Also, when the motor drive control device 1 can calculate the rotational angle and rotational speed of the motor 4 by an operation according to a known sensorless method, the Hall elements may not be provided.

[0034] The current detector 8 generates a current detection signal Si corresponding to the current value of the current flowing through the DC side of the inverter circuit 2a that constitutes the motor drive circuit 2. The current detector 8 is, for example, a current detection element arranged on the negative side (ground side) of the inverter circuit and is a resistor (shunt resistor). The current detection element as the current detector 8 generates a voltage corresponding to the current flowing through itself and outputs it as the current detection signal Si.

[0035] Based on the air volume command signal Sf, the rotational position detection signal Se, and the current detection signal Si, the control circuit 3 generates a drive control signal Sd for driving the motor 4 (fan 6) and supplies it to the motor drive circuit 2. Specifically, the control circuit 3 monitors the rotational state of the motor 4 by obtaining information such as the rotational position and rotational speed of the rotor of the motor 4 based on the rotational position detection signal Se, and generates the drive control signal Sd to control the drive of the motor 4 so that the air volume specified by the air volume command signal Sf is supplied from the fan 6.

[0036] In the present embodiment, the control circuit 3 includes, for example, a program processing device (such as a microcontroller) having a configuration in which a processor such as a CPU, various storage devices such as RAM and ROM, and peripheral circuits such as a counter (timer), an A / D conversion circuit, a D / A conversion circuit, a clock generation circuit, and an input / output I / F circuit are connected to each other via a bus or a dedicated line.

[0037] Note that the motor drive control device 1 may have a configuration in which at least a part of the control circuit 3 and at least a part of the motor drive circuit 2 are packaged as one integrated circuit device (IC), or a configuration in which the control circuit 3 and the motor drive circuit 2 are each packaged as individual integrated circuit devices.

[0038] When the control circuit 3 controls the air volume of the fan 6 based on the air volume command signal Sf, it estimates the air volume of the fan 6 without using an air volume sensor, and performs air volume constant control to generate the drive control signal Sd so that the air volume of the fan 6 becomes constant using the estimated air volume value.

[0039] FIG. 2 is a diagram showing a functional block configuration of the control circuit 3 according to the embodiment.

[0040] As shown in FIG. 2, the control circuit 3 includes, as functional blocks for realizing constant air volume control, for example, an air volume command value acquisition unit 11, a drive current value acquisition unit 12, a rotation angle acquisition unit 13, a rotation speed acquisition unit 14, a voltage estimation unit 15, an air volume estimation unit 16, an air volume control unit 20, and a drive control signal generation unit 21. These functional blocks are realized, for example, in a program processing device as the control circuit 3 when a processor executes various arithmetic processes according to a program stored in a memory and controls peripheral circuits such as a counter and an A / D conversion circuit. Note that some or all of the above functional blocks may be realized by a dedicated hardware logic circuit.

[0041] The air volume command value acquisition unit 11 is a functional unit that acquires a command value of the air volume from the air volume command signal Sf. For example, when a user operates the operation input unit of the ventilation fan to specify a desired air volume, the operation input unit generates an air volume command signal Sf indicating the specified air volume and inputs it to the control circuit 3.

[0042] Note that the air volume command signal Sf may be input to the control circuit 3 from an information processing device such as a server or a tablet terminal via a communication network such as the Internet or short-range wireless communication.

[0043] For example, when the air volume of the fan 6 is switchable in n (n is an integer of 2 or more) steps, the air volume command signal Sf includes a value specifying any one of the n air volumes. For example, in a ventilation fan to which the fan 6 is applied, consider a case where three-step air volumes of "weak", "medium", and "strong" are settable and the air volume command signal Sf is a 2-bit digital signal. In this case, the air volume command value acquisition unit 11 determines whether the command value of the air volume is "weak", "medium", "strong", or "operation stop" based on the 2-bit logical value of the air volume command signal Sf. For example, when the air volume command signal Sf is "00", the air volume command value acquisition unit 11 determines that it is an instruction to stop the fan 6. When the air volume command signal Sf is "01", it determines that the command value of the air volume is "weak". When the air volume command signal Sf is "10", it determines that the command value of the air volume is "medium". When the air volume command signal Sf is "11", it determines that the command value of the air volume is "strong". The air volume command value acquisition unit 11 outputs the command value of the air volume determined based on the air volume command signal Sf as the air volume command value Qref.

[0044] The drive current value acquisition unit 12 is a functional unit that acquires the drive current values of the coils of each phase of the motor 4. The drive current value acquisition unit 12 calculates, for example, the measured value of the current flowing through the U-phase coil (drive current value Iu), the measured value of the current flowing through the V-phase coil (drive current value Iv), and the measured value of the current flowing through the W-phase coil (drive current value Iw) based on the current detection signal Si output from the current detector 8.

[0045] The rotation angle acquisition unit 13 is a functional unit that acquires the measured value of the rotation angle of the rotor (not shown) of the motor 4. The rotation angle acquisition unit 13 calculates the rotation angle (rotation position) θ of the rotor of the motor 4 based on, for example, the rotation position detection signal Se (signals Hu, Hv, Hw) output from the rotation position detectors 7u, 7v, 7w.

[0046] The rotation speed acquisition unit 14 is a functional unit that acquires the measured value of the rotation speed of the rotor of the motor 4. The rotation speed acquisition unit 14 calculates the actual rotation speed Nr, which is the rotation speed of the rotor of the motor 4, based on, for example, the rotation position detection signal Se (signals Hu, Hv, Hw) output from the rotation position detectors 7u, 7v, 7w.

[0047] The air volume control unit 20 is a functional unit that calculates the voltage command value V so that the air volume of the fan 6 becomes constant. Here, the voltage command value V is the command value of the drive voltage of the motor 4. The voltage command value V indicates, for example, a voltage value in the range from 0V to the power supply voltage Vcc supplied to the motor drive circuit 2. For example, the fan 6 (motor 4) operates so that the air volume increases as the voltage command value V increases.

[0048] In the following description, the voltage command value V calculated by the air volume control unit 20 may be denoted as "voltage command value V1". The details of the air volume control unit 20 will be described later.

[0049] The drive control signal generation unit 21 is a functional unit that generates the drive control signal Sd. The drive control signal generation unit 21 generates, for example, the drive control signal Sd so that the current flowing through the coils of each phase of the motor 4 becomes sinusoidal.

[0050] For example, the drive control signal generation unit 21 is based on the voltage command value V1 calculated by the air volume control unit 20, the drive current values Iu, Iv, Iw flowing through the coils of each phase of the motor 4, and the rotation angle θ of the rotor, and generates a drive control signal Sd for generating the voltage applied to the coils of each phase so that the current flowing through the coils of each phase of the motor 4 becomes sinusoidal.

[0051] Specifically, the drive control signal generation unit 21 includes a conduction phase control unit 22 and an output unit 23. The conduction phase control unit 22 generates the target values Vu, Vv, Vw of the drive voltage of the coils of each phase by a known calculation method based on the voltage command value V1, the drive current values Iu, Iv, Iw flowing through the coils of each phase of the motor 4, and the rotation angle θ of the rotor. For example, the target values Vu, Vv, Vw of the drive voltage of the coils of each phase are represented by the following formula (1).

[0052]

Equation

[0053] The output unit 23 generates a drive control signal Sd so that the target values Vu, Vv, and Vw of the drive voltages of the coils of each phase generated by the energization phase control unit 22 are applied to the coils of each phase. That is, the output unit 23 generates six types of PWM signals corresponding to the respective switch elements of the inverter circuit 2a based on the target values Vu, Vv, and Vw of the drive voltages by a known calculation method, and outputs them as the drive control signal Sd. As described above, the six types of PWM signals as the drive control signal Sd are converted into six types of drive signals Vuu, Vul, Vvu, Vvl, Vwu, and Vwl by the pre-drive circuit 2b and supplied to the inverter circuit 2a.

[0054] Note that the generation of the drive control signal Sd is not limited to the above-described energization phase control (sinusoidal drive), and may be realized by a calculation method based on a known motor drive control technique such as 120-degree conduction control or vector control, and the generation method of the drive control signal Sd is not particularly limited.

[0055] The voltage estimation unit 15 is a functional unit that calculates a voltage estimation value V0, which is a voltage command value when the static pressure of the fan 6 is a reference value. Similar to the voltage command value V1, the voltage estimation value V0 indicates a voltage value in the range from 0V to the power supply voltage Vcc supplied to the motor drive circuit 2, for example.

[0056] Here, the reference value is, for example, zero. That is, the voltage estimation unit 15 estimates the voltage command value V0 when the static pressure of the fan 6 is zero. The voltage estimation unit 15 includes correspondence relation information 150 representing the relationship between the rotation speed N and the voltage command value V when the static pressure of the fan is the reference value (zero), and based on the correspondence relation information 150, calculates the voltage estimation value V0, which is the voltage command value corresponding to the actual rotation speed Nr when the static pressure of the fan 6 is zero.

[0057] FIG. 3 is a diagram showing the relationship between the voltage command value V and the rotation speed N of the fan.

[0058] In the graph shown in FIG. 3, the horizontal axis represents the voltage command value V, and the vertical axis represents the rotation speed N of the motor.

[0059] As shown in FIG. 3, in the motor, as the voltage command value V increases, the rotational speed N tends to increase. Therefore, in advance, the change in the rotational speed N of the motor 4 when the voltage command value V of the fan 6 is changed in a situation where the static pressure can be regarded as zero is measured, and regression analysis or the like is performed based on the measurement result, so that the voltage command value V and the rotational speed N when the static pressure is zero are obtained. A function (V = f(N)) representing the relationship is obtained. Then, the information of the function (V = f(N)) is stored in advance in a storage device (not shown) in the control circuit 3 as the correspondence relationship information 150. For example, when the function representing the relationship between the voltage command value V and the rotational speed N is approximated by a quadratic curve, "V = A·N 2 +B·N + C", a function with the rotational speed N as the explanatory variable and the voltage command value V as the objective variable is stored in the storage device in the control circuit 3 as the correspondence relationship information 150. Note that the correspondence relationship information 150 is not limited to the above-described function, and may be a table representing the relationship between the voltage command value V and the rotational speed N.

[0060] The voltage estimation unit 15 substitutes the actual rotational speed Nr output from the rotational speed acquisition unit 14 into the function (V = f(N)) representing the relationship between the voltage command value V and the rotational speed N when the static pressure is zero, which is the above-described correspondence relationship information 150, to obtain the voltage estimation value V0 (= f(Nr)), which is the voltage command value corresponding to the actual rotational speed Nr when the static pressure of the fan 6 is zero.

[0061] The air volume estimation unit 16 is a functional unit that estimates the air volume of the fan 6. The air volume estimation unit 16 estimates the air volume of the fan 6 under one of the two conditions based on the correlation between the voltage ratio, which is the ratio of the voltage command values under two conditions where the rotational speed N of the motor 4 (fan 6) is constant and the static pressure is different, and the air volume ratio, which is the ratio of the air volumes under the two conditions.

[0062] Specifically, the air volume estimation unit 16 calculates an air volume estimation value Q1, which is the air volume corresponding to the voltage command value V1 calculated by the air volume control unit 20 under the condition that the static pressure is greater than zero, based on the correlation relationship (voltage ratio - air volume ratio) between the voltage ratio, which is the ratio of the estimated voltage value V0 corresponding to the actual rotation speed Nr under the condition that the static pressure is zero and the voltage command value V1 corresponding to the actual rotation speed Nr under the condition that the static pressure is greater than zero, and the air volume ratio, which is the ratio of the air volume of the fan 6 corresponding to the actual rotation speed Nr under the condition that the static pressure is zero and the air volume of the fan 6 corresponding to the actual rotation speed Nr under the condition that the static pressure is greater than zero.

[0063] More specifically, the air volume estimation unit 16 includes correspondence relationship information 160 representing the relationship between the rotation speed N and the air volume Q when the static pressure of the fan 6 is the reference value (zero). The air volume estimation unit 16 calculates an air volume estimation value Q0, which is the air volume corresponding to the actual rotation speed Nr when the static pressure of the fan 6 is the reference value (zero), based on the correspondence relationship information 160. The air volume estimation unit 16 calculates an air volume estimation value Q1, which is the air volume corresponding to the voltage command value V1 calculated by the air volume control unit 20 under the condition that the static pressure is greater than zero, based on the ratio of the voltage command value V1 calculated by the air volume control unit 20 to the estimated voltage value V0 and the air volume estimation value Q0.

[0064] Hereinafter, the principle of air volume estimation by the air volume estimation unit 16 will be described.

[0065] FIG. 4 is a diagram showing the relationship between the rotation speed N of the motor in the fan and the air volume Q.

[0066] In the graph shown in FIG. 4, the horizontal axis represents the rotation speed N, and the vertical axis represents the air volume Q of the fan.

[0067] As shown in FIG. 4, it is known from the similarity law of fluids that the air volume Q of the fan and the rotation speed N of the fan (motor) are in a proportional relationship (see Equation (2)). That is, the larger the rotation speed N, the greater the air volume Q of the fan.

[0068]

Equation

[0069] Also, it is known that the axial power L of the fan and the rotational speed N (the power of N) are in a proportional relationship (see Equation (3)).

[0070]

Number

[0071] From Equations (2) and (3), the relationship between the axial power L, the rotational speed N, and the air volume Q is expressed by Equation (4).

[0072]

Number

[0073] Also, since the axial output Pm of the motor (fan) is expressed as the product of the torque T and the rotational speed N, and the torque is expressed as the product of the torque constant Kt and the current I of the motor, the following Equation (5) holds.

[0074]

Number

[0075] Here, when considering that there is no axial misalignment in the motor, the axial power L and the axial output Pm are equal (L = Pm). Therefore, the relationship between the axial power L, the rotational speed N, and the air volume Q is expressed by the following Equation (6). When the following Equation (6) is rearranged, an equation (7) representing the relationship between the current I, the rotational speed N, and the air volume Q in the fan (motor) is obtained.

[0076]

Number

[0077]

Number

[0078] Here, consider the current I of the motor. Generally, in a motor, the current I can be expressed by the following formula (8). Here, V represents the voltage command value, N represents the rotational speed, R represents the resistance of the motor, and Ke represents the induced voltage constant.

[0079]

Equation

[0080] Here, assuming that the voltage command value V is constant, the current I can be expressed by the linear function shown in the following formula (9).

[0081]

Equation

[0082] Figure 5 is a diagram showing the relationship between the rotational speed N and the current I when the voltage command value V is constant. Figure 6 is a diagram schematically showing the relationship between the rotational speed N, the current I, and the voltage command value V when the voltage command value V is constant.

[0083] In Figure 5, the horizontal axis represents the rotational speed N, and the vertical axis represents the current I. The graph shown in Figure 5 represents the linear function expressed by the above formula (9).

[0084] As shown in Figure 5, for example, consider a fan (motor) in which the current I is "I0" and the rotational speed N is "N0" when the static pressure (pressure loss) is zero. In this fan, when the static pressure (pressure loss) increases (the static pressure becomes greater than zero), assume that the current I becomes "I1" and the rotational speed N becomes "N1". Here, when the voltage command value V is constant, as shown in Figures 5 and 6, the rotational speed N increases by the same proportion as the current I decreases. That is, the relationship between the current I and the rotational speed N of the motor is expressed by the following formula (10).

[0085]

Equation

[0086] Incidentally, the current I, the rotational speed N, and the air volume Q satisfy the relationship of the above formula (7). Therefore, the relationship among the current I0, the rotational speed N0, and the air volume Q0 under the condition (state) where the static pressure is zero is expressed by formula (11), and the relationship among the current I1, the rotational speed N1, and the air volume Q1 under the condition (state) where the static pressure is greater than zero is expressed by formula (12).

[0087]

Number

[0088]

Number

[0089] From the above formulas (11) and (12), the ratio of the current I0 under the condition where the static pressure is zero to the current I1 under the condition where the static pressure is greater than zero is expressed by the following formula (13). And formula (13) can be transformed into formula (14).

[0090]

Number

[0091]

Number

[0092] From the above formula (10), when formula (14) is transformed, the following formula (15) is obtained.

[0093]

Number

[0094] As understood from formula (15), the air volume Q1 under the condition where the static pressure is greater than 0 can be obtained by multiplying the air volume Q0 under the condition where the static pressure is zero by the value obtained by squaring the current ratio (I1 / I0).

[0095] Here, consider the relationship between the current I of the motor and the voltage command value V when the rotational speed of the motor is constant.

[0096] FIG. 7 is a diagram showing the relationship between the voltage command value V and the current I when the rotational speed of the motor is constant. FIG. 8 is a diagram schematically showing the relationship between the rotational speed N, the current I, and the voltage command value V when the rotational speed of the motor is constant.

[0097] In FIG. 7, the horizontal axis represents the voltage command value V, and the vertical axis represents the current I.

[0098] As shown in FIG. 7, in the motor, when the rotational speed is constant, the voltage command value V and the current I are in a proportional relationship. That is, the current I can be represented by a linear function shown in the following formula (16).

[0099]

Equation

[0100] For example, consider a fan (motor) in which when the static pressure (pressure loss) is zero, the current I is "I0" and the voltage command value V is "V0". In this fan, when the static pressure (pressure loss) increases (the static pressure becomes greater than zero), assume that the current I becomes "I1" and the voltage command value V becomes "V1". Here, when the rotational speed N is constant, as shown in FIGS. 7 and 8, since the voltage command value V decreases by the same proportion as the current I decreases, as described above, the voltage command value V and the current I are in a proportional relationship. Therefore, by replacing the current I in formula (15) with the voltage V, the following formula (17) can be obtained.

[0101]

Equation

[0102] As understood from the above formula (17), when the rotational speed N is constant, by multiplying the value obtained by squaring the ratio (V1 / V0) of the voltage command value V1 under the condition that the static pressure is greater than zero to the voltage command value V0 under the condition that the static pressure is zero by the air volume Q0 of the fan under the condition that the static pressure is zero, the air volume Q1 of the fan under the condition that the static pressure is greater than zero can be calculated.

[0103] Therefore, the air volume estimation unit 16 in the control circuit 3 according to the present embodiment calculates the air volume Q1 of the fan 6 under the condition that the rotational speed N is constant (=Nr) based on the above formula (17). Specifically, as shown in FIG. 2, the air volume estimation unit 16 includes a first air volume calculation unit 17, a voltage ratio calculation unit 18, and a second air volume calculation unit 19.

[0104] The first air volume calculation unit 17 is a functional unit that calculates an air volume estimation value Q0 based on the correspondence relationship information 160 and the actual rotational speed Nr.

[0105] As shown in FIG. 4, in the fan, the air volume Q and the rotational speed N are in a proportional relationship. Therefore, in advance, the change in the air volume Q when the rotational speed N of the fan 6 is changed in a situation where the static pressure can be regarded as zero is measured, and a regression analysis or the like is performed based on the measurement result to obtain a function (Q = f(N)) representing the relationship between the rotational speed N and the air volume Q when the static pressure is zero. Then, the information of the function (Q = f(N)) is stored in advance in a storage device (not shown) in the control circuit 3 as the correspondence relationship information 160. For example, when the relationship between the rotational speed N and the air volume Q is approximated by a quadratic curve, a function with the rotational speed N as the explanatory variable and the air volume Q as the objective variable such as "Q = D·N 2 +E·N+F" is used as the correspondence relationship information 160. Note that the correspondence relationship information 160 may be a table representing the relationship between the rotational speed N and the air volume Q.

[0106] The first air volume calculation unit 17 substitutes the actual rotation speed Nr output from the rotation speed acquisition unit 14 into the function (Q = f(N)) representing the relationship between the rotation speed N and the air volume Q when the static pressure is zero, which is the above-described correspondence information 160, to calculate an estimated air volume Q0 (= f(Nr)) that is the air volume corresponding to the actual rotation speed Nr when the static pressure of the fan 6 is zero.

[0107] The voltage ratio calculation unit 18 calculates the ratio between the estimated voltage value V0, which is the voltage command value corresponding to the actual rotation speed Nr under the condition that the static pressure is zero, and the voltage command value V1, which is the voltage command value corresponding to the actual rotation speed Nr under the condition that the static pressure is greater than zero.

[0108] Specifically, the estimated voltage value V0 calculated by the voltage estimation unit 15 and the voltage command value V1 calculated by the air volume control unit 20 are input to the voltage ratio calculation unit 18. The voltage ratio calculation unit 18 calculates a voltage ratio (V1 / V0), which is the ratio of the voltage command value V1 to the estimated voltage value V0, based on the input estimated voltage value V0 and voltage command value V1.

[0109] The second air volume calculation unit 19 is a functional unit that calculates the air volume under the condition that the static pressure is greater than zero and corresponds to the voltage command value V1. For example, correspondence information 170 indicating the relationship between the estimated air volume Q0, the voltage ratio (V1 / V0), and the estimated air volume Q1 is stored in advance in a storage device (not shown) in the control circuit 3. The correspondence information 170 is, for example, the function represented by the above-described formula (17) (Q1 = (V1 / V0) 2 × Q0). The second air volume calculation unit 19 uses the correspondence information 170 to calculate an estimated air volume Q1, which is the estimated air volume corresponding to the voltage command value V1 under the condition that the static pressure is greater than zero.

[0110] Specifically, the estimated air volume Q0 calculated by the first air volume calculation unit 17 and the voltage ratio (V1 / V0) calculated by the voltage ratio calculation unit 18 are input to the second air volume calculation unit 19. The second air volume calculation unit 19 substitutes the input estimated air volume Q0 and voltage ratio (V1 / V0) into the function as the correspondence information 170, respectively, to obtain the estimated air volume Q1 (= (V1 / V0)2 Calculate (V1 / V0)×Q0. As a result, an estimated air volume Q1, which is the air volume corresponding to the voltage command value V1 under the condition that the static pressure is greater than zero, that is, the estimated air volume of the air volume of the fan 6 at that time, is obtained.

[0111] Note that the correspondence information 170 is not limited to the above-mentioned function (Q1=(V1 / V0) 2 ×Q0), and may be a table in which the estimated air volume Q1 is associated with each combination of the estimated air volume Q0 and the voltage ratio (V1 / V0).

[0112] The air volume control unit 20 calculates the voltage command value V1 so that the estimated air volume Q1 as the air volume of the fan 6 at that time matches the air volume command value Qref, which is the target value of the air volume. For example, the air volume control unit 20 calculates the voltage command value V1 by PI control calculation so that the error between the estimated air volume Q1 calculated by the second air volume calculation unit 19 and the air volume command value Qref output from the air volume command value acquisition unit 11 becomes zero. For example, the air volume control unit 20 calculates the voltage command value V1 so that the voltage command value V1 increases as the error increases.

[0113] Note that the air volume control unit 20 may determine the voltage command value V1 based on the comparison result between the air volume command value Qref and the estimated air volume Q1. For example, the air volume control unit 20 increases the voltage command value V1 by a unit amount when the air volume command value Qref is greater than the estimated air volume Q1, and decreases the voltage command value V1 by a unit amount when the air volume command value Qref is smaller than the estimated air volume Q1, and sequentially updates the voltage command value V1 by executing this for each unit processing time.

[0114] The voltage command value V1 calculated by the air volume control unit 20 is input to the drive control signal generation unit 21. The drive control signal generation unit 21 generates a drive control signal Sd based on the voltage command value V1 by the above-mentioned method. As a result, the rotation of the motor 4 is controlled so that the air volume of the fan 6 matches the air volume command value Qref.

[0115] Next, the process flow of the air volume constant control by the motor drive control device 1 according to the embodiment will be described.

[0116] FIG. 9 is a flowchart showing the process flow of the air volume constant control by the motor drive control device 1 according to the embodiment.

[0117] For example, consider a case where the user operates the operation input unit of the ventilation fan to instruct the ventilation fan to operate at a predetermined air volume in a state where the operation of the ventilation fan is stopped. In this case, the operation input unit of the ventilation fan generates an air volume command signal Sf including the specified value of the air volume input according to the user's operation, and inputs it to the motor drive control device 1. Thereby, the motor drive control device 1 (control circuit 3) starts the drive of the motor (fan), that is, the process of the air volume constant control.

[0118] First, in the motor drive control device 1, the air volume command value acquisition unit 11 acquires and outputs an air volume command value Qref based on the air volume command signal Sf by the method described above (step S11). Next, in the motor drive control device 1, the air volume control unit 20 calculates a voltage command value V1 so that the air volume estimated value Q1 calculated by the air volume estimation unit 16 matches the air volume command value Qref, and the drive control signal generation unit 21 generates a drive control signal Sd, whereby the motor 4 is driven and the fan 6 rotates (step S12).

[0119] Next, in the motor drive control device 1, the control circuit 3 determines whether or not the actual rotation speed Nr of the motor 4 has been detected (step S13). Specifically, the rotation speed acquisition unit 14 determines whether or not the actual rotation speed Nr of the motor 4 has been acquired by the method described above based on the rotation position detection signal Se. If the actual rotation speed Nr has not been acquired (step S13: NO), the control circuit 3 repeatedly executes the process of acquiring the actual rotation speed Nr while continuing the drive of the motor 4.

[0120] When the actual rotational speed Nr is obtained (step S13: YES), in the motor drive control device 1, the voltage estimation unit 15 calculates a voltage estimation value V0, which is a voltage command value corresponding to the actual rotational speed Nr under the condition that the static pressure is the reference value (zero), based on the actual rotational speed Nr by the method described above (step S14).

[0121] Next, in the motor drive control device 1, the air volume estimation unit 16 calculates an air volume estimation value Q0, which is an air volume estimation value corresponding to the actual rotational speed Nr under the condition that the static pressure is the reference value (zero), based on the actual rotational speed Nr detected in step S13 by the method described above (step S15).

[0122] Also, in the motor drive control device 1, the air volume estimation unit 16 calculates a voltage ratio (V1 / V0) based on the voltage estimation value V0 calculated in step S14 and the voltage command value V1 calculated by the air volume control unit 20 in step S12 by the method described above (step S16).

[0123] Next, in the motor drive control device 1, the air volume estimation unit 16 calculates an air volume estimation value Q1 based on the air volume estimation value Q0 calculated in step S15 and the voltage ratio (V1 / V0) calculated in step S16 by the method described above (step S17). Thereby, an air volume estimation value Q1, which is an air volume corresponding to the voltage command value V1 under the condition that the static pressure is greater than zero, that is, an air volume estimation value as an estimation of the air volume of the fan 6 at that time, is obtained.

[0124] Next, in the motor drive control device 1, the air volume control unit 20 updates the voltage command value V1 so that the error between the air volume estimation value Q1 calculated in step S17 and the air volume command value Qref obtained in step S11 becomes zero by the method described above (step S18).

[0125] Thereafter, the control circuit 3 repeatedly executes the processes of steps S11 to S18 described above until an air volume command signal Sf indicating a stop instruction for the fan 6 is input. Thereby, the motor 4 is controlled so that the air volume of the fan 6 becomes constant.

[0126] FIG. 10 is a diagram showing a simulation result when the fan 6 is driven by the motor drive control device 1 according to the embodiment.

[0127] In FIG. 10, respective graphs showing the temporal changes in the air volume of the fan 6, the rotational speed of the motor 4, and the utilization rate are shown.

[0128] Here, the utilization rate is an index for simulating the change in static pressure. The utilization rate is set such that the available air volume decreases when the static pressure increases. For example, when the air volume when the static pressure is zero is taken as 100%, the case where the air volume becomes 80% due to the increase in static pressure is defined as the utilization rate = 80%.

[0129] As understood from FIG. 10, by performing the above-described constant air volume control process by the motor drive control device 1 according to the embodiment, the rotational speed of the motor 4 is adjusted according to the change in the utilization rate (change in static pressure), and the air volume of the fan 6 is controlled to be constant.

[0130] FIG. 11 is a diagram showing the measured result when the fan 6 is driven by the motor drive control device 1 according to the embodiment.

[0131] In FIG. 11, the horizontal axis represents the air volume of the fan 6, and the vertical axis represents the static pressure. In FIG. 11, reference numeral 701 represents a graph based on the measured result of the change in the air volume with respect to the change in the static pressure when the fan 6 is driven by the motor drive control device 1 according to the embodiment, and reference numeral 702 represents a graph based on the measured result of the change in the air volume with respect to the change in the static pressure when the fan 6 is driven so that the rotational speed is constant by a conventional motor drive control device as a comparative example of the present embodiment.

[0132] As understood from FIG. 11, according to the motor drive control device 1 according to the embodiment, it is possible to control the air volume of the fan to be more constant with respect to the change in the static pressure than in the conventional motor drive control device.

[0133] As described above, the motor drive control device 1 according to the embodiment calculates an estimated air volume value Q1 corresponding to the voltage command value V1 under the condition that the static pressure is greater than zero, that is, an estimated value of the air volume of the fan 6 at that time, based on the estimated air volume value Q0 of the fan 6 under the condition that the static pressure is the reference value (for example, zero), and the ratio (V1 / V0) between the voltage command value V1 corresponding to the actual rotational speed Nr under the condition that the static pressure is greater than the reference value and the voltage estimated value V0. The motor drive control device 1 calculates the voltage command value V1 so that the calculated estimated air volume value Q1 matches the air volume command value Qref which is the target value of the air volume, and drives the motor 4 by generating the drive control signal Sd based on the voltage command value V1.

[0134] According to this, since feedback control of the air volume is performed using the estimated air volume value, it is possible to achieve constant air volume control even in an axial flow fan or the like where the relationship between the air volume and the torque becomes non-uniform due to rotational stall. Further, according to the motor drive control device 1 according to the embodiment, it is not necessary to provide an air volume sensor for measuring the air volume of the fan to be controlled. Therefore, it is possible to realize a more inexpensive fan unit capable of constant air volume control.

[0135] Further, the motor drive control device 1 calculates the air volume (estimated air volume value Q1) under the condition that the static pressure is greater than zero using the air volume (estimated air volume value Q0) and the voltage command value (voltage estimated value V0) under the condition that the static pressure is zero. In other words, the motor drive control device 1 calculates the air volume when the static pressure increases with respect to the state where the static pressure at which the fan 6 can operate most stably is zero as a reference. According to this, it is possible to realize more accurate air volume estimation.

[0136] Further, since the motor drive control device 1 estimates the air volume of the fan 6 using the correspondence information 150, 160, 170, it is possible to suppress the calculation load for estimating the air volume. As a result, an inexpensive microcontroller with limited functions can be adopted as the control circuit 3, so that the manufacturing cost of the fan unit 10 can be further suppressed.

[0137] <<Expansion of Embodiment>> As described above, the invention made by the present inventor has been specifically described based on the embodiments. However, it goes without saying that the present invention is not limited thereto, and various modifications can be made without departing from the gist thereof.

[0138] For example, in the above embodiment, the case where the operation of estimating the air volume described above is performed based on the condition that the static pressure is zero has been exemplified, but it is not limited thereto. For example, the operation of estimating the air volume described above may be performed based on the condition that the static pressure is a fixed value other than zero. That is, the reference static pressure may be a value other than zero.

[0139] The number of phases of the motor driven by the motor drive control device of the above-described embodiment is not limited to three phases. Also, the number of Hall elements is not limited to three.

[0140] Also, the control circuit 3 is not limited to the circuit configuration as shown above. The control circuit 3 can apply various circuit configurations configured to meet the object of the present invention.

[0141] The above flowchart is a specific example and is not limited to this flowchart. For example, other processes may be inserted between each step, or the processes may be parallelized.

Explanation of Reference Numerals

[0142] 1... Motor drive control device, 2... Motor drive circuit, 2a... Inverter circuit, 2b... Predrive circuit, 3... Control circuit, 4... Motor, 5... Impeller (fan), 6... Fan, 7u, 7v, 7w... Rotation position detector (Hall element), 8... Current detector, 10... Fan unit, 11... Air volume command value acquisition unit, 12... Drive current value acquisition unit, 13... Rotation angle acquisition unit, 14... Rotation speed acquisition unit, 15... Voltage estimation unit, 16... Air volume estimation unit, 17... First air volume calculation unit, 18... Voltage ratio calculation unit, 19... Second air volume calculation unit, 20... Air volume control unit, 21... Drive control signal generation unit, 22... Energization phase control unit, 23... Output unit, 150, 160, 170... Corresponding relationship information, Nr... Actual rotation speed, Q0, Q1... Air volume estimation values, Qref... Air volume command value, Sd... Drive control signal, Se... Rotation position detection signal, Sf... Air volume command signal, Si... Current detection signal, θ... Rotation angle, V... Voltage command value, V0... Voltage estimation value, V1... Voltage command value calculated by the air volume control unit 20, V1 / V0... Voltage ratio.

Claims

1. A control circuit that outputs a drive control signal for controlling the drive of a motor of a fan, and A motor drive circuit that drives the motor based on the drive control signal output from the control circuit, and The control circuit includes An air volume control unit that calculates a voltage command value, which is a command value of the drive voltage of the motor, so that the air volume of the fan becomes constant, A drive control signal generation unit that generates the drive control signal based on the voltage command value, A rotation speed acquisition unit that acquires an actual rotation speed, which is the rotation speed of the rotor of the motor, Based on first correspondence relationship information representing the relationship between the rotation speed and the voltage command value when the static pressure of the fan is a reference value, a voltage estimation unit that calculates a voltage estimation value, which is the voltage command value corresponding to the actual rotation speed when the static pressure of the fan is the reference value, Based on second correspondence relationship information representing the relationship between the rotation speed and the air volume when the static pressure of the fan is the reference value, a first air volume estimation value, which is the air volume corresponding to the actual rotation speed when the static pressure of the fan is the reference value, is calculated, and a ratio between the voltage command value calculated by the air volume control unit and the voltage estimation value is calculated. An air volume estimation unit that calculates a second air volume estimation value, which is the air volume corresponding to the voltage command value calculated by the air volume control unit, based on the first air volume estimation value and the ratio, and The air volume control unit calculates the voltage command value so that the second air volume estimation value matches an air volume command value, which is a target value of the air volume Motor drive control device.

2. In the motor drive control device according to Claim 1, The reference value is zero Motor drive control device.

3. In the motor drive control device according to Claim 2, The air volume estimation unit includes A first air volume calculation unit that has the second correspondence relationship information and calculates the first air volume estimation value based on the second correspondence relationship information and the actual rotation speed, A voltage ratio calculation unit that calculates a ratio of the voltage command value calculated by the air volume control unit to the voltage estimation value, A second air volume calculation unit that multiplies a value obtained by squaring the ratio by the first air volume estimation value to calculate the second air volume estimation value Motor drive control device.

4. The motor drive control device according to any one of Claims 1 to 3, The motor driven by the motor drive control device, and An impeller configured to be rotatable by the rotational force of the motor, and Fan unit.

5. A first step of calculating a voltage command value, which is a command value of a drive voltage of the motor of the fan, so that the air volume of the fan becomes constant; A second step of generating a drive control signal for controlling the drive of the motor based on the voltage command value; A third step of obtaining an actual rotation speed, which is the rotation speed of the rotor of the motor; A fourth step of calculating a voltage estimated value, which is the voltage command value corresponding to the actual rotation speed when the static pressure of the fan is the reference value, based on first correspondence relationship information representing the relationship between the rotation speed and the voltage command value when the static pressure of the fan is the reference value; A fifth step of calculating a first air volume estimated value, which is the air volume corresponding to the actual rotation speed when the static pressure of the fan is the reference value, based on second correspondence relationship information representing the relationship between the rotation speed and the air volume when the static pressure of the fan is the reference value; A sixth step of calculating a ratio between the voltage command value calculated in the first step and the voltage estimated value calculated in the fourth step; A seventh step of calculating a second air volume estimated value, which is the air volume corresponding to the voltage command value calculated in the first step, based on the first air volume estimated value calculated in the fifth step and the ratio calculated in the sixth step, including; The first step includes a step of calculating the voltage command value so that the second air volume estimated value calculated in the seventh step matches an air volume command value that is a target value of the air volume. Motor drive control method.

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