JP3514021B2 - Motor control device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an isolation circuit which electrically separates an input side and an output side and transmits a signal, and a motor control device using the same, and particularly to a motor control used for controlling a fan or the like. Regarding the device.

[0002]

2. Description of the Related Art As a conventional isolation circuit, a signal is input to the photodiode side of the photocoupler using a photocoupler and the signal is output from the phototransistor side, and the signal is transmitted while being electrically cut off by the photocoupler. It is known to do so.

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 a conventional isolation circuit as described above, the optical transmission means such as a photocoupler generally has a problem that the current cannot be accurately detected because the conductivity of light varies with age. Was there. Even with the same current value, the conductivity of light fluctuated due to aging, and the detected value also fluctuated.

Therefore, there is a problem that it is difficult to use an isolation circuit in a control device that detects the amount of electric current of the motor and controls the rotation of the motor based on the detected value.

When the variable voltage switching power supply is used, the variable voltage switching power supply is expensive, large in size and heavy in weight, which hinders cost reduction and weight reduction of the entire apparatus.

In order to solve this problem, a so-called PWM type motor drive IC is used which rotates the motor by switching the DC power obtained by rectifying and smoothing the AC power and supplying it as drive power to the motor. It is possible.

However, in this case, since the DC power obtained by rectifying and smoothing the AC power is supplied to the motor drive IC, the voltage fluctuation of the commercial power source generally used as the AC power is large and therefore flows into the motor drive IC. Even if the current is detected, the current flowing through the motor cannot be accurately known, and as a result, when the motor is used as a fan motor, the air flow passage resistance in which the fan is installed cannot be accurately calculated.

That is, since the rotation speed of the motor, the current flowing through the motor, and the flow resistance of the air flow passage have a constant relationship with each other, if the rotation speed of the motor and the current flowing through the motor are detected, It is possible to calculate the flow path resistance, but PWM
In the method, even if the rotation speed of the motor and the flow path resistance do not change, the current flowing into the motor drive IC changes due to the fluctuation of the AC voltage, and even if the current flowing into the motor drive IC is detected, The flow path resistance cannot be calculated.

The present invention has been proposed in view of the above points, and can reduce the cost and the weight of the power supply,
Moreover, it is an object of the present invention to provide a motor control device capable of accurately grasping a current flowing through a motor and thus accurately determining a flow path resistance.

Further, the present invention provides a motor control device which can always maintain an appropriate motor rotation speed according to the flow passage resistance of the air flow passage without installing an air flow rate detecting means or the like in the air flow passage. Is its purpose.

A further object of the present invention is to provide an isolated circuit which can be used in such a motor control device and which realizes detection and transmission of the motor current while reducing the variation with age as much as possible.

[0014]

In order to achieve the above object, the invention according to claim 1 detects a current flowing through a motor.
And control the motor based on the detected current.
In the control device, convert the current flowing in the motor into voltage
The first photocoupler and the first photocoupler having the same characteristics as the voltage converting means.
And the outputs of the second photocoupler and the voltage conversion means are inverted.
Input to the input terminal and output the light of the first photocoupler.
Side and the light emitting side of the second photocoupler are connected in series.
And the light received by the first photocoupler.
Side connecting the non-inverting input terminal side of the operational amplifier
Means and an output from the light receiving side of the second photocoupler.
And an output circuit for outputting.

[0015]

[0016]

According to the first aspect of the present invention, the output signal is isolated from the current of the motor and is output and detected. Then, it outputs in a state in which the influence of the secular change is reduced.

According to a second aspect of the present invention, in a motor control device for rotating a fan motor by supplying power to a fan motor for rotating a fan for ventilation arranged in an air flow passage, the AC power is rectified and smoothed. Rectifying / smoothing means for outputting DC power by means of electric power, a power control means for switching the DC power from the rectifying / smoothing means based on a control pulse to supply it to the fan motor as drive power, and detecting the rotational speed of the fan motor. Rotating speed detecting means, voltage converting means for converting the output current of the rectifying and smoothing means into voltage, first photocoupler and second photocoupler having common characteristics, and an inverting input terminal for the output of the voltage converting means. And an output for connecting the photodiode of the first photocoupler and the photodiode of the second photocoupler in series. A pump, and a feedback means for the phototransistor of the first photocoupler connected to the non-inverting input terminal of the operational amplifier, and a current detecting means for taking out the output from the phototransistor side of the second photo coupler,
Based on the rotation speed command signal and the rotation speed detected by the rotation speed detection means, a duty ratio control means for controlling the duty ratio of the control pulse so that the rotation speed of the fan motor becomes a command rotation speed, Based on the output current detected by the current detection means and the information about the duty ratio controlled by the duty ratio control means, a current calculation means for calculating the current flowing through the fan motor, and the current calculation means. And a flow path resistance determination means for determining the flow path resistance of the blower flow path based on the current and the rotation speed detected by the rotation speed detection means.

According to the second aspect of the present invention, the fan motor current is isolated and detected and output, and the fan flow path resistance is determined based on the output. Further, at that time, the flow path resistance is accurately determined in consideration of the fluctuation of the voltage applied to the motor.

[0020]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, preferred embodiments of the present invention will be specifically described 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 installed inside a fan case 4 continuous to the lower side of the casing 1, and an exhaust port 7 is formed in the upper part 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. . A valve 1 is provided on the fuel supply pipe 8 and the water supply pipe 10.
1 and 12 are interposed, and these valves 11 and 12 are controlled by a hot water supply control unit 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.

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 section of the fan motor 5, and this drive section is mainly the motor drive IC 3
It is composed of 1. This motor drive IC31 is
It is equipped with terminals 31a to 31e, and is equipped with a power control means 17 and a rotation speed detection means 18.

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

The drive power from the rectifying / smoothing means 16 is input to the terminal 31a, and this drive power is supplied to the power control means 17.
Is supplied to the motor driver 32. The 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 a power supply. A control voltage is input from the duty ratio control means 20 to the terminal 31c, and this control voltage is supplied to the power control means 17
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
It is a ground terminal.

The rectifying / smoothing means 16 is realized by, for example, a full-wave rectifier composed of 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 is based on the control pulse whose duty ratio is controlled according to the control voltage from the duty ratio control means 20, and based on the control pulse, the rectification smoothing means 1
The DC power from 6 is switched to the fan motor 5
To drive power to.

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

The fan motor 5 is a three-phase brushless motor, more specifically, a permanent magnet type synchronous motor,
In the present 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. It should be noted that components not directly related to the present invention, such as a diode for protecting the transistors TR1 to TR6 and a circuit for detecting and protecting overcurrent flowing in 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 has a triangular wave voltage from the triangular wave oscillation circuit 41 and a control voltage Vs from the duty ratio control means 20.
When the control voltage Vs is equal to or higher than the triangular wave voltage, the control voltage Vs is turned on, and when the control voltage Vs is lower than the triangular wave voltage, the control voltage Vs is turned off and a control pulse having a cycle of 20 KHz is output.

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 is responsive to the rotation signal from the rotation speed detection means 18 to form the upper transistor T.
One of 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 the transistor to be turned on among the transistors TR4 to TR6 on the lower stage side according to the control pulse from the comparator 42. That is, the three-phase distribution circuit 43 performs PWM control of the drive power supplied to the fan motor 5 according to the control voltage Vs from the duty ratio control means 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 / smoothing means 16 and supplied to the fan motor 5 as driving power via the power control means 17. At this time, the power control means 17 performs PWM control, and controls the drive voltage to the fan motor 5 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 oscillation 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 triangular wave voltage, and turns off when the control voltage Vs is lower than the triangular wave voltage. 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 for performing current detection. A current transformer is provided in the line for detecting the current, or a resistor is provided in the line for detecting, and both ends thereof are taken out as an input voltage Vin as shown in FIG. The input terminal 50 is input to the inverting input terminal of the operational amplifier 51.

The power supply voltage Vcc is equal to the resistance 58 and the first
The photocoupler 52 is connected to the ground via the phototransistor 53, and the non-inverting input terminal of the operational amplifier 51 is connected between the resistor 58 and the phototransistor 53.

The output of the operational amplifier 51 is connected to the ground through the resistor 59 through the photodiode 56 of the second photocoupler 55 and the photodiode 54 of the first photocoupler 52. Further, as a result, the photodiode 54 of the first photocoupler 52 and the phototransistor 53 constitute a feedback circuit of the operational amplifier 51.

On the output side, the power supply voltage V is connected to the ground via the resistor 60 and the phototransistor 57 of the second photocoupler 55, and is output by the second photocoupler 55 according to the output current of the operational amplifier 51. The output voltage V0 at the end 61 is output. And
This circuit is characterized by the first photocoupler 52 and the second photocoupler 52.
The same type as the photo coupler 55 is used, and the one having uniform current transfer characteristics is used.

Next, the operation of this detection circuit will be described.
Let IF be the output current of the operational amplifier 51, and let the current flowing through the phototransistor 53 of the first photocoupler 52 be Ic1,
Assuming that the current flowing through the phototransistor 57 of the second photocoupler 55 is Ic2, the following equations (1) and (2) are established.

## EQU1 ## Vi = Vcc-R58 × Ic1

## EQU00002 ## V0 = V-R60.times.Ic2

Further, since the characteristics of the first photo coupler 52 and the second photo coupler 55 are the same and the current IF flowing through the photodiodes of both is common, the following equation (3) is given.
Is established.

## EQU00003 ## Ic1 = Ic2 From the above formulas (1), (2) and (3), the output V0 is as shown in formula (4).

[Equation 4]

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. The output voltage is (R60 / R5) regardless of the characteristics of the operational amplifier or photocoupler.
8) Vi can be detected with a linear characteristic. Further, in this circuit, it is possible to contribute to the improvement of responsiveness as compared with the case where only the photo coupler is used. Further, in the case of a photocoupler, the current transfer characteristic changes due to aging and deterioration, but in the circuit of FIG. 6, since the characteristics common to the first photocoupler and the characteristics of the second photocoupler are used, Similar changes usually occur in changes. Therefore, as a whole, linear characteristics can be detected without being affected by the secular change of the photocoupler.

Next, the operation of the hot water supply apparatus using the above-described isolation 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 and an igniter (not shown) to perform an ignition operation and to the optimum air flow rate determination unit 22. A signal corresponding to the combustion amount of the burner 2, that is, the valve opening amount of the valve 11 is output. As a result, the optimum air flow rate determination means 22 calculates the optimum air flow rate according to the combustion amount of the burner 2 based on the signal from the hot water supply control unit 13 (step S1).

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. Therefore, 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 the electric power control means 17 with the control voltage Vs with which the fan motor 5 rotates at the initial rotation speed. As a result, the power control means 17 causes the PWM
The drive power is controlled by the method to drive the fan motor 5 so as to rotate at the initial rotation speed.

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

Next, the current detection means 19 detects the current flowing through the fan motor (step S4), and the rotation speed detection means 18 detects the current of the fan motor 5 based on the detection signal from the Hall IC 34 of the fan motor 5. The number of rotations is detected (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 fluctuation of the commercial power supply 15 and the output voltage of the rectifying / smoothing means 16 is always constant,
Although it is not necessary to correct the output current of the rectifying / smoothing means 16 detected by the current detecting means 19, in reality, for example, in the case of the commercial power supply 15 of 100 VAC, it varies from 75 to 120 volt. In order to correct the deviation of the change between the output current of the rectifying / smoothing means 16 and the current flowing through the fan motor 5 due to the change, the current calculating means 21 calculates the output current of the rectifying / smoothing means 16 from the output current of the rectifying / smoothing means 16.
It is necessary to calculate the current flowing through the output current and correct the actually detected output current of the rectifying / smoothing means 16. Here, in order to make the description easier to understand, first, the flow path resistance determination operation when it is not necessary to correct the output current of the rectifying / smoothing means 16 will be described.

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.
And 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, the data of 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 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 is If the current I becomes I0 at 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.

[0055]

[Equation 5]

[0056]

[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, but in reality, the voltage of the commercial power supply 15 fluctuates, so it can be determined only by the above method. Instead, correction by the current calculation means 21 becomes necessary.

Generally, in the PAM system, the fan motor 5
When the power is supplied to the fan motor, 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 AC power is driven by DC that is 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 rotation speed fluctuates due to two factors, that is, the fluctuation of the flow path resistance of the intake and exhaust paths and the fluctuation of the voltage of the commercial power supply 15.

Therefore, the current calculation means 21 performs 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 correction to the current that would be detected when the voltage of the commercial power supply 15 was 100 volts. Specifically, the calculation is performed using Expression 7.

[0061]

[Equation 7]

The above mathematical expression can be obtained as follows. That is, to simplify the explanation, FIG.
In the PAM method, the PWM method shown in can be represented as shown in FIG. In the PWM system, the output voltage of the rectifying / smoothing means 16 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.
When the work of the fan motor 5 is the same in both formulas, and the electric / mechanical work conversion efficiencies in the respective formulas are the same and 100%, the following formula 8 is established.

[0063]

(8) I0 × V0 = I × V

Here, the voltage applied to the fan motor 5 in the PWM system 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.

[0065]

[Equation 9]

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

[0067]

[Equation 10]

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

[0069]

[Equation 11]

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

[0071]

[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.

[0073]

[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 determining means 25 determines whether or not the flow path resistance Φ determined by the flow path resistance determining means 23 is between a predetermined lower limit value ΦL and upper limit value ΦH. Yes (step S8). That is, when the flow path resistance Φ is outside the range between the lower limit value ΦL and the upper limit value ΦH, it is not possible to secure an appropriate air flow rate even if the rotation speed of the fan motor 5 is controlled. Must be
If the flow path resistance Φ is between the lower limit value ΦL and the upper limit value ΦH, it is possible to determine a normal state because it is possible to secure an appropriate air flow rate by controlling the rotation speed of the fan motor 5. The first quadrant of FIG. 8 represents the relationship among the current I flowing through the fan motor 5, the rotation speed N, and the flow path resistance Φ.
The fourth quadrant represents the relationship among the rotation speed 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 value ΦL and the upper limit value ΦH, the abnormality determining means 25 determines that it is normal and clears the built-in timer (step S).
9). As soon as this timer is cleared, it restarts and restarts the timing operation.

Next, the optimum rotation speed judging means 24 determines the optimum rotation speed based on the flow path resistance Φ judged by the flow path resistance judging means 23 and the optimum air flow rate judged by the optimum air flow judging 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, since the relationship between the rotation speed N of the fan motor 5 and the air flow rate Q changes depending on the flow path resistance Φ,
The optimum rotation speed is determined according to the flow path resistance Φ so that the optimum air flow rate 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. Alternatively,
As another empirical formula, it is also calculated by the following formula 15.

[0079]

[Equation 14]

[0080]

[Equation 15]

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

As a result, the electric power control means 17 switches the DC electric 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 to reach the optimum rotation speed. .

Next, the optimum air flow rate determination means 22 determines whether or not the combustion amount has been changed based on the signal from the hot water supply controller 13 (step S12). If there is no change, the microcomputer 27 It is determined whether or not an operation end instruction has been input from the remote controller (step S13), and if not input, the processing returns to step S5. If entered, the routine ends.

In step S12, if the optimum air flow rate determination means 22 determines that the combustion amount has changed, the process 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 is up ( If the time is not up in step S14), the process proceeds to step S10. If the time is up, the abnormality processing means 26 is output to the effect 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 becomes an abnormal value for a predetermined time or longer .

Next, when the abnormality processing means 26 receives the signal indicating the abnormality from the abnormality determining means 25, it outputs a stop signal to the hot water supply control section 13 to stop the combustion of the burner 2 or the like. Error processing (step S1
5), the routine ends.

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, the position on the ground side of the motor may be used as long as it can detect the current. .

[0092]

As described above, the motor of the present invention
According to the control device, the current of the motor used for rotation control is detected.
I decided to use the above isolation circuit
Detects the motor current linearly regardless of changes over time
It is possible to properly determine the flow resistance of the fan.
can do.

[0093]

Thus, the optimum rotation speed determination means determines the optimum rotation speed of the fan motor based on the optimum air flow rate according to the combustion amount and the flow path resistance of the air flow path, and the motor control means determines the optimum rotation speed. Since the fan motor is driven so that the number becomes equal to the number, it is possible to maintain an appropriate motor rotation speed according to the flow passage resistance of the air flow passage. Therefore, even if the flow path resistance changes, optimum combustion can be maintained.

[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 the 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 an 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.

[Explanation of symbols]

5 fan motor 6 Sirocco fan 16 Rectification smoothing means 17 Power control means 18 Rotation speed detection means 19 Current detection means 20 Duty ratio control means 21 Current calculation means 22 Optimal air flow rate determination means 23 Flow path resistance determination means 24 Optimal rotation speed discrimination means 25 Abnormality discrimination means 26 Abnormality processing means 50 input end 51 operational amplifier 52 First Photocoupler 55 Second Photocoupler 61 Output end

─────────────────────────────────────────────────── ─── Continuation of front page (56) Reference JP 49-18479 (JP, A) JP 7-298677 (JP, A) JP 4-68613 (JP, A) JP 63- 258113 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) H03K 17/78 H02P 7/63 302

Claims (2)

(57) [Claims] 1. In a motor control device for detecting a current flowing through a motor and controlling the motor based on the detected current, a first characteristic having common characteristics with a voltage conversion means for converting the current flowing through the motor into a voltage. The output of the voltage converting means and the photocoupler and the second photocoupler are input to the inverting input terminal, and the output is supplied to the light emitting side of the first photocoupler and the second photocoupler.
From the light receiving side of the second photocoupler, an operational amplifier in which the light emitting side of the photocoupler is connected in series, feedback means for connecting the light receiving side of the first photocoupler to the non-inverting input terminal side of the operational amplifier, A motor control device, comprising: an output circuit that extracts an output. 2. A motor control device that supplies power to a fan motor that rotates a fan for blowing air disposed in a blower flow path to rotate the fan motor, rectifies and smoothes AC power, and outputs DC power. Rectifying / smoothing means, power control means for switching the DC power from the rectifying / smoothing means based on a control pulse to supply the fan motor as drive power, and rotation speed detection means for detecting the rotation speed of the fan motor. , A voltage converting means for converting the output current of the rectifying / smoothing means into a voltage, a first photocoupler and a second photocoupler having a common characteristic, and the output of the voltage converting means is input to an inverting input terminal to output the output. An operational amplifier in which the photodiode of the first photocoupler and the photodiode of the second photocoupler are connected in series; and the first photodiode. Feedback means for connecting the phototransistor of the coupler to the non-inverting input terminal side of the operational amplifier,
The rotation speed of the fan motor becomes the command rotation speed based on the current detection means taken out as an output from the phototransistor side of the second photocoupler, and the rotation speed command signal and the rotation speed detected by the rotation speed detection means. Based on the duty ratio control means for controlling the duty ratio of the control pulse, the output current detected by the current detection means, and the information about the duty ratio controlled by the duty ratio control means. And a flow path resistance for determining the flow path resistance of the blower flow path based on the current calculated by the current calculation means and the rotation speed detected by the rotation speed detection means. A motor control device for use in a fan motor, comprising: a determination unit.