JPH09215367A - Motor controller - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make it possible to realize the suitable control of a motor by accurately detecting without influence of changes oven aging of a photocoupler by identifying the current flowing to the motor from frequency information output via isolating means. SOLUTION: The photodiode 54 of a photocoupler 53 emits a light at the period of a pulse signal according to the high or low pulse signal output by V-F converting means 52 to turn ON, OFF a phototransistor 56. The connector side of a phototransistor 55 is connected to current identifying means 56, a pulse signal of a certain period is output to the means 56, and the current amount is determined by the period. The identified current information is output to route resistance identifying means 23. Thus, the air flow route resistance of a fan can suitably discriminator. Accordingly, suitable number of revolutions of a motor can be maintained in response to the air flow route resistance of an air supply route.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a motor control device for controlling rotation of a motor, and more particularly to a motor control device suitable for controlling a fan by rotating a fan.

[0002]

2. Description of the Related Art Conventionally, as a motor control device for controlling the rotation of a motor, there has been known a motor control device that detects a current flowing through the motor and performs feedback control based on the current value from the relationship between the current and the rotation speed.

Further, as a conventional motor control device used for controlling a fan or the like, as disclosed in, for example, Japanese Patent Laid-Open No. 4-36508, a wind speed sensor or the like is installed in an air flow passage, and the wind speed sensor or the like is used. In some cases, the number of rotations of the fan motor is controlled according to the detection signal.

Further, in a conventional motor control device for controlling such a fan motor, a variable voltage switching power supply is often used.

[0005]

Although there is such a motor control device in the past, the conventional one has the following problems. Conventionally, the same power supply was used for the power supply system used to drive the motor and for controlling and controlling the motor current. Therefore, current detection and control will fluctuate due to fluctuations in the power supply, and precision control is required. Had a problem that it could not be controlled sufficiently accurately.

In such a case, the power supply system for driving the motor and the power supply system for the control unit are set as different power supply systems, and the power supply system is separated, and a photocoupler is used to electrically connect the motor drive system and the control system. Although a method of transmitting a signal while shutting it off may be considered, the photocoupler has a problem that it is difficult to use it for a device used for a long period of time because the transmission rate usually greatly changes due to aging.

Further, as a motor control device used for controlling a fan, a sensor detects the amount of air blown and controls the amount of electric current of the motor. However, in the case where a wind speed sensor is installed in the air flow passage, the wind speed sensor itself is used. There was a problem that hindered the ventilation.

Therefore, the invention of the present application has been proposed in view of the above-mentioned point, and even when the current of the motor is detected by isolating it from the driving side of the motor, the influence of secular change of the isolating photocoupler or the like is considered. It is an object of the present invention to provide a motor control device that realizes appropriate motor control by accurately detecting without receiving.

Further, the present invention provides a motor control device which realizes an appropriate motor rotation control according to the flow resistance of the air flow passage without installing an air flow rate detecting means such as a wind speed sensor in the air flow passage. Is its purpose.

[0010]

In order to achieve the above object, the invention according to claim 1 is a motor control device for detecting a current flowing through a motor and controlling the motor based on the detected current. IV conversion means for outputting a voltage corresponding to the flowing current, VF conversion means for outputting a signal of a frequency corresponding to the output voltage output by the IV conversion means, and VF conversion means. Of the output signal is input and turned on / off according to the signal frequency and transmitted, and the current flowing through the motor is determined based on the frequency information output through the isolation means. To do.

Therefore, according to the first aspect of the invention, the current flowing through the motor is once converted into a voltage by the IV converting means, and further converted into a signal having a frequency corresponding to the voltage by the VF converting means. . The frequency signal is input to an isolating means such as a photocoupler and is turned on / off at the frequency to be transmitted. Then, the current flowing through the motor is determined based on the information on the frequency.

According to a second aspect of the present invention, in a motor control device for controlling the rotation of a blower fan arranged in a blower flow passage, a voltage I corresponding to a current flowing through the motor is output.
-V converting means, VF converting means for outputting a signal having a frequency corresponding to the output voltage output by the IV converting means, and the output signal of the VF converting means are inputted to the signal frequency. According to the output of the isolation means for turning on / off according to the transmission, the frequency information output through the isolation means, and the output of the rotation speed detection means for detecting the rotation speed of the motor, the flow blown by the fan motor. The present invention is characterized in that a flow path resistance determining means for determining a flow path resistance of a path and a motor rotation control are performed in accordance with the flow path resistance and the required air flow rate determined by the flow path resistance determining means.

Therefore, according to the second aspect of the invention, the current flowing through the motor is once converted into a voltage by the IV converting means, and further converted into a signal having a frequency corresponding to the voltage by the VF converting means. . The frequency signal is input to an isolating means such as a photocoupler and is turned on / off at the frequency to be transmitted. Then, the current flowing through the motor is determined based on the information on the frequency. Further, the rotation speed detection means detects the rotation speed of the fan motor,
The flow path resistance determining means determines the flow path resistance of the air blowing path blown by the fan motor based on the information on the motor current and the rotation speed. Then, the motor controls the rotation of the motor based on the information on the determined flow path resistance and the required optimum air flow rate.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be specifically described below with reference to the drawings.

FIG. 1 is a schematic configuration diagram of a hot water supply apparatus provided with a motor control device of the present invention, in which a burner 2 and a heat exchanger 3 are arranged inside a casing 1 of the hot water supply apparatus. A sirocco fan 6 driven by a fan motor 5 is provided inside a fan case 4 which is continuous with a lower side of the casing 1, and an exhaust port 7 is formed at an upper portion of the casing 1.

A fuel supply pipe 8 for supplying a fuel such as gas or oil is connected to the burner 2, and a water supply pipe 10 for supplying water is connected to the heat exchanger 3. . The fuel supply pipe 8 and the water supply pipe 10 have a valve 1
The valves 11 and 12 are controlled by a hot water supply controller 13.

The motor control device includes a rectifying / smoothing means 16 for rectifying and smoothing AC power from a commercial power supply 15 of 100 VAC, and outputting DC power, and a DC power from the rectifying / smoothing means 16 based on a control pulse. A power control means 17 for switching the fan motor 5 to supply it to the fan motor 5 as driving power, a rotation speed detection means 18 for detecting the rotation speed of the fan motor 5, and a current detection means 19 for detecting the output current of the rectifying / smoothing means 16. , The duty ratio of the control pulse is controlled so that the rotation speed of the fan motor 5 becomes the command rotation speed based on the rotation speed command signal, the rotation speed detected by the rotation speed detecting means 18, and the current flowing through the fan motor 5. Duty ratio control means 20 and current detection means 19
Output current and duty ratio control means 2 detected by
A current calculation means 21 for calculating the current flowing through the fan motor 5 based on the information about the duty ratio controlled by 0, and an optimum air flow rate determination means 22 for determining the optimum air flow rate based on the combustion charge of the burner 2. , Current calculation means 2
Flow path resistance determination means 23 for determining the flow path resistance of the air flow path formed by the fan case 4 and the casing 1 based on the current calculated by 1 and the rotation speed detected by the rotation speed detection means 18, The optimum rotation speed of the fan motor 5 is determined based on the optimum air flow rate determined by the optimum air flow rate determination means 22 and the flow path resistance determined by the flow path resistance determination means 23, and the rotation speed of the fan motor 5 is optimized. An abnormality that determines an abnormality in combustion based on the optimum flow speed determination means 24 that supplies a rotation speed command signal to the duty ratio control means 20 so that the rotation speed is reached, and the flow path resistance determined by the flow path resistance determination means 23. The determination means 25 and the abnormality processing means 26 that outputs a stop signal to the hot water supply control unit 13 to stop the combustion of the burner 2 when the abnormality determination means 25 determines that the combustion is abnormal. There.

It should be noted that the duty ratio control means 20, the current calculation means 21, the optimum air flow rate determination means 22, the flow path resistance determination means 23, the optimum rotation speed determination means 24, the abnormality determination means 25, and the abnormality processing. The means 26 is realized by the microcomputer 27. The microcomputer 27 controls the entire combustion device.

FIG. 2 is a circuit block diagram of the drive unit of the fan motor 5, which is mainly a motor drive IC 3
1. This motor drive IC 31
Terminals 31a to 31e are provided, and power control means 17 and rotation speed detecting means 18 are mounted.

The power control means 17 includes a motor driver 32 for supplying drive power to each coil of the fan motor 5,
A PWM variable speed circuit 33 for switching the drive power supplied to the fan motor 5 by the motor driver 32; The rotation speed detecting means 18 is the fan motor 5
A rotation logic 35 for calculating the number of rotations of the fan motor 5 based on a detection signal from a Hall IC 34 including a plurality of Hall elements built in the motor, and a rotation number pulse corresponding to the number of rotations calculated by the rotation logic 35 are generated. And a rotation speed pulse generation circuit 36 that performs the rotation.

The drive power from the rectifying / smoothing means 16 is input to the terminal 31a, and the drive power is supplied to the power control means 17.
Is supplied to the motor driver 32. DC power from the auxiliary power supply 37 is input to the terminal 31b, and this DC power is supplied to each part of the motor drive IC 31 as power. A control voltage is input to the terminal 31c from the duty ratio control means 20, and the control voltage is
Is supplied to the PWM variable speed circuit 33. From the terminal 31b, a rotation speed pulse is output from the rotation speed pulse generation circuit 36 of the rotation speed detection means 18, and this rotation speed pulse is supplied to the duty ratio control means 20. The terminal 31e is
This is a ground terminal.

The rectifying / smoothing means 16 is realized by a full-wave rectifier composed of, for example, a diode bridge and a smoothing circuit composed of a capacitor, and rectifies and smoothes AC power obtained from a commercial power supply 15 of 100 V, for example. Output power. The power control means 17 performs rectification / smoothing means 1 based on a control pulse whose duty ratio is controlled in accordance with a control voltage from the duty ratio control means 20.
The DC power from 6 is switched to the fan motor 5
As driving power.

That is, the DC drive power supplied to the fan motor 5 is PWM-controlled by the power control means 17. The rotation speed detecting means 18 detects the rotation of the fan motor 5 based on a detection signal from a rotation detection sensor including a Hall IC 34 including a plurality of Hall elements built in the fan motor 5.
The rotation number of the fan motor 5 is supplied to the duty ratio control means 20 and a rotation signal corresponding to the rotation of the rotation element of the fan motor 5 is supplied to the power control means 1.
7

The current detecting means 19 is equipped with, for example, a current transformer and detects the output current of the rectifying / smoothing means 16. The duty ratio control unit 20 adjusts the control voltage so that the rotation speed of the fan motor 5 becomes the command rotation speed, and supplies the control voltage to the power control unit 17.

The fan motor 5 is a three-phase brushless motor, more specifically a permanent magnet type synchronous motor,
In this embodiment, it is used to drive the sirocco fan 6 of the combustion device.

FIG. 3 is a circuit block diagram of the power control means 17, which includes a triangular wave oscillation circuit 41, a comparator 42, a three-phase distribution circuit 43, and transistors TR1 to TR6. ing. Components not directly related to the present invention, such as diodes for protecting the transistors TR1 to TR6 and circuits for detecting and protecting overcurrents flowing through the coils 5a to 5c of the fan motor 5, are illustrated and described. Is omitted.

The triangular wave oscillation circuit 41 is, for example, 20 KHz.
Outputs a triangular wave with a period of. The comparator 42 is composed of an operational amplifier, and outputs the voltage of the triangular wave from the triangular wave oscillation circuit 41 and the control voltage Vs from the duty ratio control means 20.
Is turned on when the control voltage Vs is equal to or higher than the voltage of the triangular wave, and turned off when the control voltage Vs is smaller than the voltage of the triangular wave, and outputs a control pulse having a period of 20 KHz.

That is, the duty ratio of the control pulse changes according to the control voltage Vs from the duty ratio control means 20. The three-phase distribution circuit 43 responds to the rotation signal from the rotation speed detecting means 18 by using the upper transistor T
R1 to TR3 and the lower transistor T
One of R4 to TR6 is selectively turned on.
For example, when the transistors TR1 and TR5 are on,
A drive current flows from the coil 5a of the fan motor 5 to the coil 5b.

That is, the rotation of the fan motor 5 is continued by sequentially switching the coils 5a to 5c for flowing the current and the direction of the current according to the rotational position of the rotor of the fan motor 5. Further, the three-phase distribution circuit 43 turns on / off a transistor to be turned on among the transistors TR <b> 4 to TR <b> 6 on the lower stage according to a control pulse from the comparator 42. That is, the three-phase distribution circuit 43 performs PWM control of the driving power supplied to the fan motor 5 according to the control voltage Vs from the duty ratio control unit 20.

The operation of the power control means 17 will be briefly described. The AC power from the commercial power supply 15 is rectified and smoothed by the rectifying and smoothing means 16 and supplied to the fan motor 5 via the power control means 17 as drive power. At this time, the PWM control is performed by the power control unit 17, and the drive voltage to the fan motor 5 is controlled so that the rotation speed of the fan motor 5 becomes the command rotation speed.

Now, as shown in FIG. 4, the maximum voltage of the triangular wave from the triangular wave oscillator circuit 41 is Vh, the minimum voltage is V1, and the control voltage from the duty ratio control means 20 is Vs.
Then, as shown in FIG. 5, the control pulse output from the comparator 42 turns on when the control voltage Vs is equal to or higher than the voltage of the triangular wave, and turns off when the control voltage Vs is smaller than the voltage of the triangular wave. The pulse train has the same cycle as.

Since the three-phase distribution circuit 43 applies the control pulse from the comparator 42 to the base of the transistor to be turned on among the transistors TR4 to TR6 on the lower side, the drive power of the fan motor 5 is controlled by the control pulse. Is switched by and the drive power corresponding to the duty ratio of the control pulse is supplied to the fan motor 5.

Next, the current detection will be described. FIG. 6 shows a specific circuit of a portion related to current detection. A current transformer is provided in the line for detecting the current, or a current detecting element 50 such as a resistor is provided in the line for detecting the current, and I
The -V conversion means 51 converts the current amount into a voltage amount and outputs it.

The VF converting means 52 is a means for changing the frequency of the output signal based on the input voltage. For example, the output signal is a high / low pulse signal, and the repetition cycle thereof is changed. Therefore, the output voltage of the IV conversion means 51 is input, and the signal of the period according to the voltage value is output.

The isolation means 53 is a means for transmitting a signal in a state where the power supply system is separated. For example, the photocoupler 53 is used and one power supply is Vc1. It is Vc2 and is separated. Then, signal transmission is performed by on / off control of light. The connection state of the photo coupler 53 is V-
The output of the F conversion means 52 is connected to the cathode side of the photodiode 54 of the photocoupler 53, and the anode side of the photodiode 54 is connected to the power supply voltage Vc1 via a resistor. Phototransistor 55 of photocoupler 53
Has its emitter side connected to the ground and its collector side connected to the power supply voltage Vc2 via a resistor.

Therefore, the high-low pulse signal output from the V-F converter 52 causes the photocoupler 53 to operate.
Of the photodiode 54 emits light in the cycle of the pulse signal and transmits the light to the side of the phototransistor 56.
On and off. The collector side of the phototransistor 56 is connected to the current discriminating means 56, outputs a pulse signal of a certain period to the current discriminating means 56, and discriminates the amount of current according to the period. Then, the determined current information is output to the flow path resistance determining means 23.

In FIG. 6, the output of the rotation speed detection element 34, which is, for example, a Hall element, is the rotation speed detection means 18
The rotation speed is detected from the pulse signal input to the rotation speed detection element 34 and is output to the flow path resistance determination means 23.

Therefore, in the above case, the current flowing in the motor can be detected in a form in which the line to be detected and the power supply are separated, so that the power supply on the output side can be detected without being affected by the fluctuation of the motor current. Further, in the case of a photocoupler, the current transfer characteristic changes due to aging and deterioration, but in the circuit of FIG. 6, it is once converted into a voltage by the IV conversion means 51 and further converted into a voltage by the VF conversion means 52. Since the signal of the corresponding frequency is changed, and the current information is transmitted by the photocoupler 53 as an ON / OFF signal, it is possible to detect accurately over the long term without being affected by the aging of the photocoupler as a whole. You can

Next, the operation of the above hot water supply apparatus using the above circuit will be described with reference to the flowchart shown in FIG. When an operation command is input to the controller from a remote controller (not shown), the hot water supply control unit 13
Controls the valves 11 and 12, an igniter (not shown), and the like, through the ignition operation, and at the same time, the optimum air flow rate determination means 2
2 outputs a signal corresponding to the combustion amount of the burner 2, that is, the valve opening amount of the valve 11. As a result, the optimum air flow rate determination means 2
2 is a burner 2 based on a signal from the hot water supply control unit 13.
The optimum air flow rate is calculated according to the combustion amount of the
1).

At this point in time, the fan motor 5 is not rotating and the determination result by the flow path resistance determining means 23 is not supplied to the optimum air flow rate determining means 22, so the optimum rotation speed determining means 24 is set in advance, for example. A rotation speed command signal corresponding to an initial rotation speed of about 3000 rpm is output to the duty ratio control means 20 (step S2). As a result, the duty ratio control means 20 supplies a control voltage Vs to the power control means 17 such that the fan motor 5 rotates at the initial rotation speed. As a result, the power control means 17
The driving power is controlled by the method, and the fan motor 5 is driven to rotate at the initial rotation speed.

Next, the abnormality determining means 25 activates the built-in timer (step S3).

Next, the current detecting means 19 including the current detecting element 50, the IV converting means 51, the VF converting means 52, the photocoupler 53, and the current determining means 56 detects the current flowing through the fan motor (step). Simultaneously with S4), the rotation speed detection means 18 detects the rotation speed of the fan motor 5 based on the detection signal from the Hall IC 34 of the fan motor 5 (step S5).

Next, the current calculating means 21 detects the output current of the rectifying / smoothing means 16 detected by the current detecting means 19, and
Using the control voltage Vs from the duty ratio control means 20, the current flowing through the fan motor 5 is calculated according to the above mathematical expression 1 (step S6).

That is, if there is no voltage fluctuation of the commercial power supply 15 and the output voltage of the rectifying / smoothing means 16 is always constant,
There is little need to correct the output current of the rectifying and smoothing means 16 detected by the current detecting means 19, but in reality, for example, in the case of a commercial power supply 15 of AC 100 volts, the current actually fluctuates to 75 to 120 volts. In order to correct the difference between the change in the output current of the rectifying / smoothing means 16 and the current flowing through the fan motor 5 due to the fluctuation, the current calculating means 21 calculates the fan motor 5 from the output current of the rectifying / smoothing means 16.
It is necessary to calculate the current flowing through the rectifier and correct the actually detected output current of the rectifying / smoothing means 16. Here, in order to make the description easier to understand, first, a description will be given of the flow path resistance determining operation when it is not necessary to correct the output current of the rectifying / smoothing means 16.

The flow path resistance determining means 23 is the current detecting means 1
The fan motor 4 based on the detected current from the motor 9 (that is, the current before being corrected by the current calculator 21 in this description) and the rotation speed pulse from the rotation speed detector 18.
Then, the flow path resistance Φ of the air flow path in the casing 1 is determined (step S7).

That is, regarding the relationship between the rotation speed N of the fan motor 5 and the current I flowing through the fan motor 5, as shown in FIG. 8, data on the relationship with the flow path resistance should be held in advance in a memory or the like. Thus, the flow path resistance Φ can be determined from the rotation speed N and the current I. For example, if the current I becomes I0 when the rotation speed N is N1, or if the current I becomes I1 when the rotation speed N is N2, it can be determined that the flow path resistance Φ is Φ1, and the rotation speed N becomes If the current I becomes I0 at the time of N0, it can be determined that the flow path resistance Φ is Φ0.

Φ0 is smaller than Φ1. Further, this flow path resistance Φ can be obtained experimentally by the following mathematical formula 5, for example, where N is the number of rotations of the fan motor 5 and I is the current flowing through the fan motor 5. However, g (N), f
(N) is a function of the rotation speed N. Alternatively, as another empirical formula, it is obtained by the following formula 6.

[0047]

(Equation 5)

[0048]

(Equation 6)

Next, the operation of the current calculation means 21 for correcting the current detected by the current detection means 19 will be described. As long as a constant voltage is always supplied from the commercial power supply 15, the flow path resistance can be determined by the above method. However, since the voltage of the commercial power supply 15 fluctuates in practice, it can be determined only by the above method. However, correction by the current calculation means 21 is required.

Generally, in the PAM system, the fan motor 5
When power is supplied to the fan motor 5, the fan motor 5 can be driven by a stable DC power supply.
The WM method has an advantage that the power supply unit can be simplified because the AC power is driven by DC which is only rectified and smoothed.
However, on the other hand, when the voltage of the commercial power supply 15 changes, as shown in FIG.
Since the output voltage of No. 6 fluctuates and the control works so as to absorb this fluctuation by the change of the PWM duty ratio, the output current IO of the rectifying / smoothing unit 16 also fluctuates with respect to the same rotation speed.

Therefore, in the case of the PWM system, the current value of the fan motor at the same number of revolutions fluctuates due to two factors, that is, the fluctuation of the flow path resistance of the intake / exhaust path and the fluctuation of the voltage of the commercial power supply 15.

Therefore, the current calculation means 21 performs the step S
In 6, the current I flowing through the fan motor 5 is calculated using the output current I0 detected by the current detecting means 19. This has the same meaning as correcting the current that would be detected when the voltage of the commercial power supply 15 is 100 volts. Specifically, the calculation is performed using Expression 7.

[0053]

(Equation 7)

The above formula can be obtained as follows. That is, to simplify the explanation, the PWM method shown in FIG. 10 can be expressed as shown in FIG. 11 in the PAM method. Rectifying smoothing means 16 in PWM system
Is V0, the output current is I0, the output voltage of the variable voltage power supply 51 in the PAM system is V, and the output current is I, the work of the fan motor 5 in both systems is equal,
Further, when the electric / mechanical work conversion efficiencies in the respective systems are considered equal and 100%, the following formula 8 is established.

[0055]

(8) I0 × V0 = I × V

Here, the voltage applied to the fan motor 5 in the PWM method is pulse-shaped as shown in FIG. 5, and the shaded area corresponds to the applied voltage V in the PAM method. Therefore, the area of the shaded area is shown in FIG. Control voltages Vs, Vh,
When expressed by Vl, the following Expression 9 is obtained.

[0057]

[Equation 9]

Since this corresponds to the applied voltage V in the PAM system, the following formula 10 is established.

[0059]

(Equation 10)

By substituting Equation 10 into Equation 8 and rearranging it, Equation 11 below is established.

[0061]

[Equation 11]

Transforming Equation 11 above, Equation 12 below
become that way.

[0063]

(Equation 12)

Here, the voltage width Vh- of the triangular wave shown in FIG.
When Vl is a constant k, the above equation 12 becomes the same as the above equation 7. Further, when the constant k is, for example, 3.5 V, the following formula 13 is established.

[0065]

(Equation 13)

The above formulas 11, 12, and 13 are output currents I0 detected by the current detecting means 19 in the PWM system.
Is converted into a detection current I in the PAM method.

Thus, in step S6, the current I flowing through the fan motor 5 is calculated by the current calculating means 21 to correct the output current I0 detected by the current detecting means 19, and in step S7. Since the flow path resistance is calculated by the flow path resistance determining means 23 using the current I, the flow path resistance can be accurately obtained regardless of the voltage fluctuation of the commercial power supply 15.

Next, the abnormality determination means 25 determines whether or not the flow path resistance Φ determined by the flow path resistance determination means 23 falls between a predetermined lower limit value ΦL and a predetermined upper limit value ΦH. (Step S8). In other words, when the flow path resistance Φ is out of the range between the lower limit value ΦL and the upper limit value ΦH, it is not possible to secure an appropriate air flow even if the rotation speed of the fan motor 5 is controlled. Need to
If the flow path resistance Φ is between the lower limit value ΦL and the upper limit value ΦH, an appropriate amount of air can be secured by controlling the number of revolutions of the fan motor 5, so that it can be determined that the condition is normal. The first quadrant in FIG. 8 shows the relationship between the current I flowing through the fan motor 5, the number of revolutions N, and the flow path resistance Φ.
The fourth quadrant represents the relationship among the number of revolutions N of the fan motor 5, the air flow rate Q, and the flow path resistance Φ.

If the flow path resistance Φ is between the lower limit ΦL and the upper limit ΦH, the abnormality determining means 25 determines that the flow is normal and clears the built-in timer (step S).
9). As soon as this timer is cleared, it restarts and resumes timing operation.

Next, the optimum rotation speed determination means 24 determines the optimum rotation speed based on the flow path resistance Φ determined by the flow path resistance determination means 23 and the optimum air flow rate determined by the optimum air flow determination means 22. It calculates (sweep S10) and outputs a rotation speed command signal to the duty ratio control means 20. That is, as shown in FIG. 8, the relationship between the rotation speed N of the fan motor 5 and the air flow rate Q changes with the flow path resistance Φ.
The optimum rotation speed is determined according to the flow path resistance Φ so that the optimum air volume can be obtained. The optimum rotation speed Ns is obtained by, for example, an empirical formula 14 below, where Q0 is the optimum air flow rate and Ng is the reference rotation speed determined based on the reference flow path resistance Φ0 and the combustion amount. Or,
As another empirical formula, it is also calculated by the following formula 15.

[0071]

[Equation 14]

[0072]

(Equation 15)

Thus, the duty ratio control means 20
The fan motor 5 is set to the optimum rotation speed based on the rotation speed command signal corresponding to the optimum rotation speed calculated by the optimum rotation speed determination unit 24 and the actual rotation speed from the rotation speed detection unit 18. The control voltage Vs is output to the power control means 17 (step S11).

Thus, the power control means 17 switches the DC power supplied to the fan motor 5 based on the control voltage from the duty ratio control means 20, and drives the fan motor 5 so that the fan motor 5 has the optimum rotation speed. .

Next, the optimum air blowing amount determining means 22 determines whether or not the combustion amount has been changed based on the signal from the hot water supply control unit 13 (step S12). It is determined whether or not an instruction to end the operation has been input from the remote controller (step S13), and if not, the process returns to step S5. If so, the routine ends.

If it is determined in step S12 that the optimum amount of air has been changed, the flow returns to step S1.

In step S8, the abnormality determining means 25
However, if it is determined that the flow path resistance Φ is not between the predetermined lower limit ΦL and upper limit ΦH, the abnormality determining means 25 further determines whether or not the built-in timer has timed out ( If the time is not up in step S14), the process proceeds to step S10. If the time is up,
It outputs to the abnormality processing means 26 that there is an abnormality. That is, since the flow path resistance Φ may constantly change due to the influence of wind or the like, the flow path resistance Φ is determined to be in an abnormal state only when the flow path resistance Φ reaches an abnormal value for a predetermined period of time.

Next, the abnormality processing means 26 outputs a stop signal to the hot water supply control unit 13 to stop the combustion of the burner 2 by inputting a signal indicating the abnormality from the abnormality determination means 25, for example. (Step S1)
5) End the routine.

As described above, the rectifying / smoothing means 16 for rectifying and smoothing the AC power to output the DC power, and the DC power from the rectifying / smoothing means 16 are switched based on the control pulse to drive the fan motor 5 as the driving power. Power supply control means 17, rotation speed detection means 18 for detecting the rotation speed of the fan motor 5, current detection means 19 for detecting the output current of the rectifying and smoothing means 16, rotation speed command signal and rotation speed detection means 18. The duty ratio control means 20 that controls the duty ratio of the control pulse so that the rotation speed of the fan motor 5 becomes the required rotation speed based on the rotation speed detected by the output current detected by the current detection means 19. And a current flowing through the fan motor 5 is calculated based on the duty ratio information controlled by the duty ratio control means 20. Since there is provided a current calculation unit 21,
The current flowing through the fan motor 5 can be accurately known regardless of the voltage fluctuation of the commercial power supply 15, and therefore the flow path resistance can be appropriately determined.

Further, the flow passage resistance determining means 23 for determining the flow passage resistance of the air flow passage on the basis of the current calculated by the current calculating means 21 and the rotation speed detected by the rotation speed detecting means 18 is provided. Therefore, the flow path resistance of the air flow path can be properly determined. Therefore, it becomes possible to maintain an appropriate motor rotation speed according to the flow path resistance of the air flow path.

Furthermore, the optimum rotation speed of the fan motor 5 is determined based on the optimum air flow rate determined by the optimum air flow rate determination means 22 and the flow path resistance determined by the flow path resistance determination means 23, and the fan motor 5 is determined. Since the optimum rotation speed discriminating means 24 for supplying the rotation speed command signal to the duty ratio control means 20 is provided so that the rotation speed of No. 1 becomes the optimum rotation speed, an appropriate motor rotation speed corresponding to the flow passage resistance of the air flow passage is provided. Can always be maintained. Therefore, even if the flow path resistance changes, it is possible to always maintain the optimum air flow rate.

Further, the abnormality processing for stopping the combustion of the burner 2 when the abnormality determination means 25 for determining the combustion abnormality based on the flow passage resistance determined by the flow passage resistance determination means 23 determines the combustion abnormality. Since the means 26 is provided, it is possible to accurately judge the abnormality of combustion from the flow path resistance at a stage before the flame of the burner 2 disappears, and it is possible to improve safety.

In the above embodiment, the detection position of the motor current is shown as an example, and the present invention is not limited to this. For example, as shown in FIG. Any position that can be detected may be used. Further, in FIG. 6, the current calculation means 21 is omitted in order to make the current detection of the motor easier to understand, but the current calculation means 21 is provided between the current determination means 56 and the flow path resistance determination means 23. It may be provided. Further, the current calculation means 21 may be omitted as shown in FIG. 6 when the fluctuation of the voltage power supply is small or when the accuracy is allowed to some extent.

[0084]

As described above, according to the isolation circuit of the present invention, it is possible to prevent the transmission rate of the optical transmission means such as the photocoupler from being affected by the secular change. The proper isolation can be realized without

Further, according to the motor control device of the present invention, since the above-mentioned isolation circuit is used for detecting the current of the motor used for the rotation control, the motor current can be detected regardless of the secular change. Therefore, the flow path resistance of the fan can be appropriately determined.

As a result, the optimum rotation speed of the fan motor is determined on the basis of the required optimum air flow rate and the flow path resistance of the air flow path, and the motor control means drives the fan motor to achieve the optimum rotation speed. Therefore, it is possible to maintain an appropriate motor rotation speed according to the flow passage resistance of the air flow passage. Therefore,
For example, when used as a fan motor of a combustion device, optimum combustion can be maintained even if the flow path resistance changes.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of a hot water supply device including a motor control device of the present invention.

FIG. 2 is a circuit block diagram of a motor drive unit provided with the motor control device of the present invention.

FIG. 3 is a circuit diagram of power control means provided with the motor control device of the present invention.

FIG. 4 is a waveform diagram of a triangular wave obtained by a triangular wave oscillation circuit provided with the motor control device of the present invention.

FIG. 5 is a waveform diagram of a drive voltage supplied to a fan motor provided with the motor control device of the present invention.

FIG. 6 is a circuit diagram of a current detection isolation circuit of the present invention.

FIG. 7 is a flowchart illustrating the operation of the motor control device that controls the fan motor of the present invention.

FIG. 8 is an explanatory diagram of a relationship between a current flowing through a fan motor controlled by a motor control device of the present invention, a rotation speed, and an air flow rate.

FIG. 9 is an explanatory diagram of the relationship between the detected current by the current detection means provided in the motor control device of the present invention and the rotation speed of the fan motor.

FIG. 10 is a schematic configuration diagram of a PWM type motor control device.

FIG. 11 is a schematic configuration diagram of a PWA type motor control device.

FIG. 12 is an explanatory diagram showing a modified example of the present invention.

[Explanation of symbols]

 5 Fan Motor 6 Sirocco Fan 16 Rectifying / Smoothing Means 17 Power Control Means 18 Rotation Speed Detection Means 19 Current Detection Means 20 Duty Ratio Control Means 21 Current Calculating Means 22 Optimal Air Flow Rate Means 23 Means of Flow Resistance Means 24 Optimum Speed Means Means 25 Abnormality Discriminating Means 26 Abnormality Processing Means 50 Current Detecting Elements 51 IV Converting Means 52 VF Converting Means 53 Isolating Means (Photocouplers) 56 Current Discriminating Means

Claims (2)

[Claims] 1. A motor control device for detecting a current flowing through a motor and controlling the motor based on the detected current, comprising: an IV conversion means for outputting a voltage corresponding to the current flowing through the motor; and the IV. V-F converting means for outputting a signal having a frequency corresponding to the output voltage output by the converting means, and an isolator for inputting and outputting the output signal of the VF converting means by turning it on and off according to the signal frequency. A motor control device characterized in that the current flowing through the motor is discriminated based on the frequency information output through the rate means and the isolation means. 2. A motor control device for controlling the rotation of a fan for ventilation arranged in an air flow passage, comprising: an IV conversion means for outputting a voltage corresponding to a current flowing through the motor; and the IV conversion means. V-F conversion means for outputting a signal having a frequency corresponding to the output voltage to be output, and isolation means for inputting the output signal of the V-F conversion means and turning it on and off according to the signal frequency to transmit the signal. A flow path resistance determination means for determining the flow path resistance of the flow path blown by the fan motor based on the frequency information output via the isolation means and the output of the rotation speed detection means for detecting the rotation speed of the motor. And a motor control device that controls the rotation of the motor in accordance with the flow path resistance and the required air flow rate determined by the flow path resistance determination means.