JP2010242767A - Wind rate control method for blower - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a wind rate control method for a blower capable of maintaining at a set wind rate by making motor load torque constant through control of supply voltage on the basis of changes of supply current and rotation speed of a DC motor. <P>SOLUTION: In the blower 3 for rotating a Sirocco fan 3 by the DC motor 2, the wind rate control method drives the DC motor 2 at fixed voltage, and detects changes of load torque of the DC motor 2 on the basis of a command load drive current value for attaining driving current, motor rotational speed, and the set wind rate actually supplied to the DC motor 2, and maintains motor generated torque at a value corresponding to the command load driving current value by controlling the drive voltage in response to changes of the load torque. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an air volume control method for maintaining an air volume of a blower used in a ventilator for ventilating indoors by discharging indoor air outdoors.

Conventionally, when a fan that rotates a fan with a motor is used to exhaust indoor air through a duct and ventilate the interior, the load of the fan is determined by installation conditions such as the duct length and the duct diameter. Since it varies depending on ventilation resistance, indoor air density, etc., an air volume sensor is provided in the exhaust path of the blower, and the rotation of the motor (fan) is adjusted so that the air volume detected by the air volume sensor becomes the set air volume. Thus, the set air volume can be discharged outdoors even if the load of the blower is different.
However, since the air volume control method as described above requires an air volume sensor, there are various problems, and the air volume discharged outdoors can be maintained at the set air volume without using the air volume sensor even if the load amount of the blower is different. Various air volume control methods have been proposed.

For example, an air volume control method disclosed in Patent Document 1 has been proposed.
This air volume control method uses a blower that rotates a fan with a DC motor, sets (stores) the relationship between the energization current to the DC motor and the rotational speed in advance corresponding to different load amounts, and sets the DC motor at a constant current. The number of rotations (operation number of rotations) at the time of operation is detected, and the load amount is determined from the above setting.
Apart from this, the set rotational speed corresponding to the load amount and the air volume at that time (exhaust air volume) are stored in advance as a data table, and the set air volume corresponding to the load amount determined above based on this data table, The set rotational speed that is the set air volume is obtained.
The set rotational speed is compared with the operating rotational speed, and the output voltage is controlled so that they match.
For example, when the operating rotational speed is larger than the set rotational speed, the output voltage is decreased to reduce the air volume, and when the operating rotational speed is smaller than the set rotational speed, the output voltage is increased to increase the air volume.
Thus, the operation rotational speed of the DC motor is controlled to be the set rotational speed, and the air volume of the blower (that is, the air volume discharged outdoors) is maintained at the set air volume even when the load amount is different.

JP-A-8-152165

  According to the conventional air volume control method described above, the set air volume can be maintained without using an air volume sensor. However, the relationship between the current applied to the DC motor, the rotation speed, and the load volume, and the set rotation speed and air volume corresponding to the load volume. It is necessary to set the relationship in advance, and the relationship must be obtained by actual measurement through experiments or the like, which is troublesome and takes time.

  The present invention has been made in view of the above-described problems, and an object of the present invention is to provide a blower capable of maintaining the air volume of the blower at the set air volume even when the load torque is different without actually measuring and setting any relationship. It is to provide a method for controlling the air volume.

The present inventors have studied the air volume at the outlet side of the duct when the sirocco fan is rotated by a brushless DC motor or a DC motor with brush (hereinafter referred to as DC motor) and blown into the duct, that is, the air volume of the fan. As a result of the experiment, it was as follows.
When the voltage supplied to the DC motor was kept constant and the duct resistance of the duct was increased, the current value supplied to the DC motor decreased, the motor torque decreased, the sirocco fan speed increased, and the air flow decreased.
When the voltage supplied to the DC motor was kept constant and the duct resistance of the duct was reduced, the current value supplied to the DC motor increased, the motor torque increased, the sirocco fan speed decreased, and the air flow increased.
From this, it has been found that the value of the current supplied to the DC motor increases and decreases depending on the duct resistance of the duct and the motor torque changes, thereby increasing and decreasing the air volume.
In the above description, the motor torque can be paraphrased as the motor generated torque and the duct resistance of the duct as the load amount of the DC motor, that is, the load torque. Therefore, the current value increases or decreases depending on the magnitude of the load torque. Since the motor generated torque changes, the air volume of the blower increases or decreases.
From the above, the present inventors, in a blower that rotates a sirocco fan with a DC motor, control the motor generated torque when the load torque of the DC motor changes, and keep the load torque constant, thereby reducing the air volume. Has been found to be constant, and the present invention has been reached.

The present invention is a method for controlling the air volume of a blower 3 that rotates a sirocco fan 3 with a DC motor 2,
The DC motor 2 is driven based on the drive voltage and drive current actually supplied to the DC motor 2, the rotational speed of the DC motor 2, and the command load drive current value for obtaining the set air volume. A fan that detects a change in the load torque of the motor and controls the drive voltage supplied to the DC motor 2 in accordance with the change in the load torque to maintain the motor-generated torque at a value commensurate with the command load drive current value. This is an air volume control method.

  In the present invention, by setting the above-described command load drive current value to an arbitrary value, the set motor generation torque can be changed, and the set air volume can be set to an arbitrary value.

According to the first aspect of the present invention, when the load torque of the DC motor 2 fluctuates, the change of the load torque is obtained by the change of the drive voltage, drive current, and rotational speed supplied to the DC motor 2, By controlling the drive voltage supplied to the DC motor 2, the motor generated torque is corrected and the load torque is maintained at the set value.
Therefore, the air volume of the blower can be maintained at the set air volume even if the load torque is different based on the change in the supply current and the rotational speed of the DC motor 2 without actually measuring and setting any relationship.

It is explanatory drawing which shows embodiment of the control apparatus of this invention. It is an equivalent circuit diagram of a DC motor.

An outline of a blower air volume control device will be described with reference to FIG.
The blower 1 rotates a sirocco fan 3 with a DC motor 2, for example, a three-phase brushless DC servo motor.
The DC motor 2 is supplied with predetermined drive power (voltage, current) from a motor drive circuit 4.
The motor drive circuit 4 is supplied with predetermined power (voltage, current) from a power source (not shown).
A drive power control command is input to the motor drive circuit 4 from a control 5 such as a microcomputer.
The controller 5 is supplied with an electric power command corresponding to an arbitrary set air volume, for example, a command load driving current value for obtaining a motor-generated torque corresponding to the set air volume, from the air volume setting unit 6.
Then, the controller 5 outputs a drive power control command to the motor drive circuit 4 based on the input power command, for example, a command load drive current value, and supplies power commanded to the DC motor 2, for example, command drive current and drive voltage. Thus, the motor generation torque of the DC motor 2 is set so that the set air volume can be obtained.

  The rotational speed of the DC motor 2 is detected by the motor rotational speed detecting means 10 and input to the controller 5. For example, the pulse signal (12p / r) output from the Hall sensor 11 attached to the motor is converted into a voltage by the F / V converter 12, and the voltage is sent to an AD converter (not shown) of the controller 5. In order to make it within the input range, it is converted with the conversion coefficient TG to 0-5V.

  The power supply voltage supplied to the motor drive circuit 4 is detected by the voltage detection means 20 and input to the controller 5. For example, the power supply voltage is detected by the voltage sensor 21, and the power supply voltage is converted by the voltage converter 22 so as to be in the input voltage range (0 to 5 V) of the AD converter of the controller 5. The conversion coefficient is β.

  The drive current supplied to the DC motor 2 is detected by the current detection means 30 and input to the controller 5. For example, the drive current is detected by the current sensor 31, and the drive current is converted by the voltage converter 32 so as to be in the input voltage range (0 to 5 V) of the AD converter of the controller 5. The conversion coefficient is α.

The rotation speed of the DC motor 2 detected by the motor rotation speed detection means 10, the power supply voltage detected by the voltage detection means 20, and the drive current detected by the current detection means 30 are input to the controller 5, respectively.
The controller 5 detects a change in load torque acting on the DC motor 2 based on the input rotation speed, power supply voltage, drive current, and power command value corresponding to the set air volume, and the load torque of the DC motor 2 is detected. In response to the change, a drive power correction command is output to the motor drive circuit 4, the motor generated torque of the DC motor 2 is changed, and the load torque is maintained at a set value.

Next, an example of air volume control will be described.
When the above-described blower 1 is used as a ventilation device provided with a duct, when the voltage supplied to the DC motor 2 is constant and the drive current supplied to the DC motor 2 is different from the command drive current value, the set air volume It will not be.
For example, when the load drive current is smaller than the command load drive current value, the load torque of the DC motor 2 is small when the blower 1 is used as a ventilator having a duct with a large pipe resistance, and the sirocco The rotation speed of the fan 2 increases and the air volume is less than the set air volume.
On the contrary, when the load drive current is larger than the command load drive current value, the duct resistance of the duct is small, the load torque of the DC motor 2 is large, and the rotational speed of the sirocco fan 2 decreases. The air volume is higher than the set air volume.

  As described above, the controller 5 detects that the load resistance applied to the DC motor 2 has changed because the load drive current supplied to the DC motor 2 is different from the command load drive current value. .

As described above, when the load torque acting on the DC motor 2 changes, the controller 5 outputs a correction command to the motor drive circuit 4 to control the drive voltage supplied to the DC motor 2 and to change the load drive current. Correct to command load drive current value.
For example, the power supplied to the DC motor 2 is drive voltage × drive current, and the actual power before correction as described above is power supply voltage × command load drive current value (drive current), and the motor generated torque is It is a command value.
As described above, when the load torque acting on the DC motor 2 changes and the drive current is different from the command current value and the motor generated torque is different from the command value, the DC motor 2 actually depends on the motor rotation speed or the like. The drive current is set to a command load drive current value by making the drive voltage supplied to the power supply voltage different from the power supply voltage.

  Thereby, the motor generated torque becomes a set value (that is, the motor generated torque based on the command load drive current value), and the air volume of the blower 1 is maintained at the set air volume.

The above-described operation will be described in detail with reference to FIG. 1. The command load drive current value at which the motor-generated torque corresponding to the set air volume is obtained from the air volume setting unit 6 is input to the controller 5 as a value converted into a voltage of 0 to 5V. Is done.
A voltage is supplied to the DC motor 2.
The load drive current supplied from the motor drive circuit 4 to the DC motor 2 varies as the load torque acting on the DC motor 2 changes.
This drive current is converted into a voltage range of 0 to 5 V and is input to the controller 5, and the magnitude of the command load drive current value is determined.

  When the input load drive current is different from the command load drive current value, the controller 5 outputs a command for controlling the drive voltage supplied to the DC motor 2 to the motor drive circuit 4 and actually supplies the DC motor 2 with the command. The supplied drive voltage is made different from the power supply voltage so as to match the command load drive current value using the drive current actually supplied to the DC motor 2 (current value input to the controller 5 by the current detection means 30). To.

  Thereby, since the motor generated torque of the DC motor 2 can be controlled regardless of the load torque, the load torque can be kept constant, so that the air volume can be kept constant at the command air volume.

  Further, even when the load torque acting on the DC motor 2 fluctuates due to aging of the duct or changes in the external air pressure, the air volume can be kept constant by controlling the drive voltage in the same manner as described above.

The control theory of the air volume control method of the present invention will be described with reference to FIG.
The motor-generated torque of the brushless DC motor that rotates the sirocco fan is considered to be used as in the following equation (1).

dω
_{T = K T i a = J} --- + Dω + TL ... (1)
dt

Here, T is the motor torque, the K _T torque constant of the motor, i _a is equivalent armature current, J is the moment of inertia, D is a viscous damping coefficient, T _L is the load torque, omega is the rotational speed.
In the equation (1), the first term on the right side is acceleration / deceleration torque, the second term is viscous braking torque, and the third term is load torque.
This load torque corresponds to the load torque acting on the air volume, and the acceleration / deceleration torque and the viscous braking torque may be constant when the speed does not change.

A simple equivalent circuit of the brushless DC motor 2 including the motor drive circuit 4 is shown in FIG. In the equivalent circuit, R _a is an equivalent armature resistance, L _a is an equivalent armature inductance, R _D is an equivalent viscous resistance, C _J is an equivalent inertia capacity, and K _E ω is a counter electromotive force. _KE is the back electromotive force constant. In the SI unit system, the numerical values of the respective parameters are equal to K _E = K _T = K. V _a is an armature voltage. In i _a is equivalent armature _{current, i a = i J + i D} + i L.
The armature voltage V _a is equivalent to the drive voltage of the above, the equivalent armature current i _a is equivalent to the driving current mentioned above.

  Motor generated torque T is

_{T = K T i a = K} T i J + K T i D + K T i L ... (2)

  The generated torque T is used for the following purposes.

dω
_{T = K T i a = K} T i J + K T i D + K T i L = J --- + Dω + T L ... (3)
dt

The actual motor rotation speed omega, the equivalent winding resistance When R _a

di _a
V _a = L _{a ——} + R _a i _a + K _E ω (4)
dt

Equivalent winding inductance L _a is, V _a is when sufficiently small relative to current variation

V _a = R _a i _a + K _E ω (5)

i _a = i _J + i _D + i _L (6)

The input power P _in to the motor drive circuit 4 including the loss of the motor drive circuit 4 is obtained by the following equation, where V _s is the supply voltage to the drive circuit and i _s is the supply current.

P _in = V _S i _S (7)

On the other hand, the electric power P _m supplied to the DC motor 2 is

_{P m = (K E ω +} R a i a) × i a ... (8)

Since the power _{P m} supplied to the input power _{P in} and the DC motor 2 to the motor driving circuit 4 is equal as _P in = _{P m,} it becomes the following equation when determining the equivalent armature current _{i a} of the DC motor.

_{-K E ω ± √ (K E} ω) 2 + 4R a V S i S
i _a = -------------------- ... (9)
2R _a

Since the equivalent armature current i _a is positive, if i _a ≧ 0,

_{-K E ω + √ (K E} ω) 2 + 4R a V S i S
i _a = ――――――――――――――――――――… (10)
2R _a

If the equivalent armature current command (corresponding to the aforementioned command load drive current value) to be supplied to the DC motor 2 is _iacmd , the motor generated torque is

dω
_{K T i acmd = K T i} J + K T i D + K T i L = J --- + Dω + T L ... (11)
dt

Here, when the air volume is made constant, the load torque _TL may be controlled to be constant. In order to make the load torque _TL constant, it can be achieved by making i _L constant. In this case _{i ACMD} is expressed by the following equation.

i _acmd = i _L + i _D + i _J (12)

Here, i _D and i _J are related to the rotational speed of the motor, and are obtained by the following equations.

Dω
i _D = ―― (13)
K

J dω
_{i C = - - ... (14} )
K _T dt

(10) the estimated calculated equivalent armature current _{i a} with _equation, the driving voltage (10) to the DC motor 2 so as to be equal to _{i ACMD} controls the expression of _{V s.}

In the above description, when rotating at a constant speed and the viscosity control coefficient is negligible, i _acmd = i _a = i _L without considering i _J and i _D , the above equations (13) and (14) are set. Without using it, the drive voltage supplied to the DC motor 2 using only the equation (10), that is, the value of V _{s in} the equation (10) is set to a value at which the actual i _a becomes the commanded i _acmd .

The above-described drive voltage control uses a PID control method.
When the calculation interval is dt and the difference between the equivalent armature current command i _acmd (t) and the equivalent armature current i _a (t) is i _e (t)

_{i e (t) = i acmd} (t) -i a (t) ... (15)

If the PID control parameters are K _P , K _I , and K _D , the manipulated variable e can be obtained by the following equation.

di _e (t)
_{e = K P i e (t} ) + K I ∫i e (t) dt + K D ------ ... (16)
dt

  The e obtained here is converted into an appropriate numerical value, converted into an analog voltage of 0 to 5 V using a DA converter, and supplied to the motor drive circuit 4.

  The control voltage of the motor drive circuit 4 of the brushless DC motor 2 described above is 0.2V to 5V. When the resolution of the DA converter is 10 bits and the output voltage of the DA is 0 to 5V, the output data to the DA converter is

  DAdata = e × gain + offset (17)

  Here, offset = 40, gain is an appropriate conversion coefficient, DAdata is limited to a minimum value of 0, and a maximum value is set to 1023 (a limit is applied).

  DESCRIPTION OF SYMBOLS 1 ... Blower, 2 ... DC motor, 3 ... Sirocco fan, 4 ... Motor drive circuit, 5 ... Controller, 6 ... Air volume setting part.

Claims (2)

A method for controlling the air volume of a blower 3 that rotates a sirocco fan 3 with a DC motor 2,
The DC motor 2 is driven based on the drive voltage and drive current actually supplied to the DC motor 2, the rotational speed of the DC motor 2, and the command load drive current value for obtaining the set air volume. A fan that detects a change in the load torque of the motor and controls the drive voltage supplied to the DC motor 2 in accordance with the change in the load torque to maintain the motor-generated torque at a value commensurate with the command load drive current value. Air volume control method.   The method according to claim 1, wherein the command load drive current value can be set to an arbitrary value.

Images