JP2017150776A - Control unit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To detect fan motor driving current precisely even if temperature changes by correcting detection error of fan motor driving current detection level caused by temperature, and to control the drive of the fan motor precisely.SOLUTION: Pulse signal of duty ratio following driving current is generated by comparing voltage following driving current of a fan motor M with triangular wave voltage, and the pulse signal is input to a microcomputer 11. The microcomputer 11 calculates a driving current detection level based on the duty ratio of the pulse signal, and calculates ambient temperature of a triangular wave generation circuit 15 based on pulse period of signal, and corrects driving current detection level based on the ambient temperature.SELECTED DRAWING: Figure 1

Description

  The present invention detects the drive current of a fan motor mounted on a combustion device and the like, and controls the rotation speed of the fan motor based on the detected drive current and the combustion operation stop control by closing the supply / exhaust passage of the combustion device. The present invention relates to a control device that performs appropriate operation control.

  A forced water supply / exhaust water heater is provided with a fan for forcibly supplying and exhausting air. The fan is rotationally driven by a fan motor, and the rotational speed of the fan motor is controlled by a control unit.

  The water heater increases / decreases the combustion area of the combustion section composed of a plurality of burners according to the required hot water supply number, and the amount of fuel gas supplied to the combustion section is adjusted by a proportional valve. The rotation speed of the fan motor is controlled so as to be the amount of air blown according to the amount of fuel gas supplied. However, since the optimum rotation speed varies depending on the degree of blockage of the supply / exhaust passage, The number and drive current are detected, the degree of blockage of the supply / exhaust passage is estimated based on the detected rotation speed and drive current value, and the optimum target rotation speed is calculated (for example, refer to Patent Document 1). . Moreover, control which stops combustion operation | movement is performed according to the obstruction | occlusion degree of an air supply / exhaust passage (for example, refer patent document 2).

  If there is an error in the fan motor drive current detection value, the various combustion operation controls described above cannot be performed normally, combustion efficiency deteriorates due to insufficient or excessive air flow, detection delay in blockage determination, or actually normal. Although it is within the range, it may cause a misjudgment that the exhaust is blocked.

  In order to stabilize the accuracy of capturing fan motor drive current, the applicant of the present application has proposed a fan motor drive current detection device shown in Patent Document 3. This current detection device detects a drive current of a fan motor based on a voltage across a resistor connected in series with the fan motor. The current detection device includes an amplifier circuit that amplifies the voltage across the resistor, and a triangular wave voltage. A triangular wave generating circuit to be generated, a comparator circuit for comparing the output voltage of the amplifier circuit and the output voltage of the triangular wave generating circuit and outputting a pulse signal, and a drive current of the fan motor based on the pulse signal output from the comparator circuit And a microcomputer for calculating

JP 2008-261579 A JP2013-29255A JP 2001-281273 A

  In the conventional drive current detection device, the resistor, the amplifier circuit, and the triangular wave generation circuit are mainly configured by an analog circuit, and the drive circuit of the fan motor is also mainly configured by an analog circuit, so that stable combustion control is achieved. It is necessary to calibrate the drive current value in order to perform the operation, and conventionally, at the time of shipment, the microcomputer reading value of the fan motor drive current when driving the fan motor at a constant rotation speed is constant. A calibration value (coefficient) for the drive current detection value detected by the drive current detection device is stored in the EEPROM.

  However, the detection error of the drive current detection value due to the temperature fluctuation during actual use is not taken into account, and even if the exhaust is in the same exhaust blockage state, the drive current detection value varies depending on the air temperature. There were premature cuts to the closed side, and conversely, a delay in detection of exhaust blockage occurred.

  Accordingly, an object of the present invention is to accurately detect a driving current of a fan motor even when the temperature fluctuates, and to perform various controls based on the fan motor driving current accurately.

  In order to achieve the above object, the present invention takes the following technical means.

  That is, according to the present invention, in a control device including a drive current detection unit that detects a drive current of a fan motor, a temperature detection that detects a temperature of a predetermined circuit part constituting the drive current detection unit or an ambient temperature of the circuit part. And a detection error correction unit for correcting a detection error of the drive current detection value of the drive current detection unit based on the temperature detected by the temperature detection unit ( Claim 1).

  According to the control device of the present invention, even if a detection error occurs in the drive current detection value due to the fluctuation of the air temperature, the drive current is accurately corrected by correcting the detection error based on the temperature detected by the temperature detection means. It can be detected well, and various controls based on the detected drive current value can be performed accurately.

  The control device of the present invention can be suitably implemented as a fan motor control device that controls the rotational speed of the fan motor, but is not limited to this, and the supply / exhaust passage is blocked based on the drive current of the fan motor. It can also be implemented as a hot water supply control device that performs determination and performs predetermined control such as stopping of the hot water supply operation based on the determination result, and can also be implemented as a control device that performs appropriate control based on the driving current of the fan motor. . In addition, the circuit portion where the temperature is detected by the temperature detecting means may be a specific circuit component when the temperature characteristic of the specific circuit component greatly affects the detection error of the drive current detection value. When the temperature characteristic of the entire predetermined circuit such as the generation circuit affects the detection error of the drive current detection value, the entire predetermined circuit may be the circuit portion.

  In the control device of the present invention, the drive current detection means includes a current-voltage conversion circuit that converts the drive current of the fan motor into a voltage and outputs the voltage, and a periodic triangular wave voltage (in the present invention, the “sawtooth wave voltage”). And the output voltage of the current-voltage conversion circuit is compared with the output voltage of the current-voltage conversion circuit, and the duty ratio according to the output voltage of the current-voltage conversion circuit is compared. A comparator that outputs a pulse signal, and a calculation means that calculates the drive current detection value by a calculation based on the duty ratio of the pulse signal output from the comparator can be provided. The triangular wave generation circuit includes a capacitor whose capacitance changes according to temperature as a circuit component, and is configured so that the period of the triangular wave voltage changes according to the capacitance of the capacitor. Good. Further, the temperature detecting means can be configured to detect an ambient temperature of the capacitor based on a period of the pulse signal. According to the above configuration, the detection value of the drive current can be stabilized with high accuracy by keeping the accuracy of capturing the pulse signal irrespective of the magnitude of the drive current of the fan motor as disclosed in Patent Document 3 above. . Even if the capacitance of the capacitor fluctuates due to the temperature and the period of the triangular wave voltage changes, the drive current is detected based on the duty ratio of the pulse signal, so the accuracy and stability of the drive current detection value are not hindered. . On the other hand, the ambient temperature can be detected based on the period of the pulse signal for detecting the drive current, and the circuit configuration can be simplified and the number of parts can be reduced. The detection accuracy of the ambient temperature may not be as high as the detection accuracy of the drive current.

  Furthermore, since the use environment temperature range of appliances such as a water heater is assumed to be, for example, -20 ° C. or more and 60 ° C. or less, the capacitor is linear with respect to changes in ambient temperature within the assumed use environment temperature range. It is preferable that the capacitance changes. According to this, the calculation of the drive current detection value based on the period of the pulse signal can be easily performed by a predetermined mathematical expression (typically a primary expression). The term “linearly” is sufficient if the ambient temperature and the capacitance are substantially proportional, and some curvature or distortion may exist in the ambient temperature-capacitance characteristic graph. In addition, the present invention is not necessarily limited to one in which the capacitance of the capacitor changes linearly with respect to the ambient temperature for the entire range of the assumed usage environment temperature range. The capacitance of the capacitor changes linearly in a range, for example, 0 ° C. to 40 ° C., but the change rate of the capacitance becomes steep or the capacitance hardly changes in other temperature ranges. May be. The assumed use environment temperature range may be set as the use temperature range of the appliance guaranteed by the manufacturer of the appliance such as a water heater.

  The temperature detecting means may detect the ambient temperature of the predetermined portion based on the output voltage of the thermistor provided at the predetermined portion of the drive current detecting means, for example, by inputting the output voltage of the thermistor, It can be constituted by a microprocessor or the like that calculates the ambient temperature based on the voltage. According to this, the ambient temperature of the predetermined part can be detected by disposing the thermistor at an appropriate position of the drive current detecting means. In this configuration, when the detection error of the drive current detection value by the drive current detection means is greatly influenced by the temperature characteristics of the active element such as a transistor or an IC chip, the thermistor is disposed in the vicinity of the active element. The drive current detection value can be corrected based on the detected temperature value. Of course, it is also possible to provide a thermistor in the vicinity of a passive element such as a capacitor or a resistor, and to detect the ambient temperature of the passive element based on the output voltage of the thermistor. It is also possible to provide a plurality of thermistors and detect the ambient temperature of the portion where the plurality of thermistors are provided based on the average value of their output voltages.

  The present invention also provides a mixed gas of the control device, a fan motor controlled by the control device, a fan attached to a rotating shaft of the fan motor, and air and fuel gas supplied by the fan. A forced supply / exhaust water heater comprising a burner that generates combustion gas by combustion and a heat exchanger that heats water by heat exchange with the combustion gas, wherein the detection error correction means of the control device includes: The detection error of the drive current detection value of the drive current detection means when the burner is burning can be corrected (Claim 5). According to this, the detection accuracy of the drive current detection value when the combustion operation is performed in the forced supply / exhaust water heater is improved, and the rotation speed of the fan motor is optimally controlled according to the degree of blockage of the supply / exhaust passage It is possible to prevent the combustion efficiency of the forced supply / exhaust water heater from being lowered even if the temperature fluctuates. Furthermore, the corrected drive current detection value is further calibrated based on the ambient temperature according to the load characteristics of the fan motor due to temperature fluctuations, so that the fan motor can be kept at a constant air flow rate even if the air temperature varies. Can be controlled.

  As described above, according to the present invention, it is possible to accurately detect the drive current of the fan motor even if the temperature fluctuates, and perform various controls based on the fan motor drive current accurately.

It is an operation | movement principle figure of the forced air supply / exhaustion type water heater which concerns on one Embodiment of this invention. It is a schematic circuit diagram of the fan motor control device of the water heater.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 shows a forced supply / exhaust type latent heat recovery type high-efficiency water heater according to an embodiment of the present invention. The water heater includes a control device 1 (control unit) for performing various controls, and a combustion can body. 2 and a hot water supply circuit 3. Inside the can body 2, a combustion section 4 that generates combustion gas, a primary heat exchanger 5 disposed above the combustion section 4, and a secondary heat disposed further above the primary heat exchanger 5. An exchanger 6 (condensation heat exchanger) is provided. Further, a fan 7 that supplies combustion air to the combustion unit 4 is disposed below the combustion unit 4. The fan 7 is rotationally driven by a fan motor M, and the rotational speed of the fan motor M is controlled to an optimum value by the control device 1.

  The combustion part 4 is divided into four combustion regions in the illustrated example, and each combustion region is formed by a plurality of burners. A gas supply pipe 41 that supplies fuel gas as a combustion fuel from the fuel gas supply source side is connected to each combustion region. The gas supply pipe 41 is provided with an original gas electromagnetic valve 42 as a main plug and a gas proportional valve 43 for adjusting the gas supply amount in order from the fuel gas supply source side. A gas supply pipe 41 is branched for each combustion region on the downstream side of the gas proportional valve 43. The first to fourth capacity switching valves SV1 to SV4 are individually provided corresponding to each combustion area, and the supply of fuel gas to each combustion area is individually performed by opening and closing each capacity switching valve SV1 to SV4. Can be controlled. The fuel gas supplied to each combustion region is supplied to each burner through a gas passage provided for each burner, and the fuel gas and combustion air are mixed in the burner, and the mixed gas burns. As a result, combustion gas is generated.

  The primary heat exchanger 5 recovers the sensible heat of the combustion gas generated in the combustion unit 4, and the secondary heat exchanger 6 is the thermal energy of the combustion gas that cannot be recovered in the primary heat exchanger 5, that is, This is for recovering the latent heat and preheating the feed water before heating in the primary heat exchanger 5. The combustion exhaust gas after the heat energy is recovered by these heat exchangers is forcibly exhausted from the exhaust port 2 a provided in the upper part of the can body 2.

  The hot water supply circuit 3 includes a water inlet 31 for allowing tap water received from the water supply connection port to enter the secondary heat exchanger 6, and hot water heat-exchanged and heated by the secondary heat exchanger 6 and the primary heat exchanger 5. And a bypass passage 33 that branches from the water inlet 31 and supplies cold water to the hot water outlet 32. A bypass flow rate control valve 34 is provided in the bypass passage 33, and the temperature of discharged hot water can be controlled by adjusting the bypass flow rate via the bypass passage 33. A can body flow sensor 35 is provided in the water inlet 31. A can body flow rate control valve 38 is provided in the hot water outlet 32 on the upstream side of the junction with the bypass 33.

  An ignition plug 8 and a frame rod (extinguishing safety device) 9 are provided on the combustion can body 2 above the combustion unit 4. A drain collection tray 61 that collects condensed water as drain is provided below the secondary heat exchanger 6, and the collected drain is neutralized by the neutralization device 62 and then drained. In addition, sensors or measurement circuits for measuring various parameters necessary for hot water supply operation control, such as incoming water temperature, outgoing hot water temperature, can body exhaust temperature, and rotation speed of the fan motor M, are provided at appropriate positions.

  Control devices such as the fan motor M, the capacity switching valves SV1 to SV4, the original gas solenoid valve 42, the gas proportional valve 43, the bypass flow rate control valve 34, and the can body flow rate control valve 38 are controlled by the control device 1. During the hot water supply operation, the control device 1 acquires the respective detection values from the respective sensors, determines the required combustion heat amount based on these detection values and the required hot water supply capacity, and performs combustion so that the required combustion heat amount is obtained. While controlling the number of capacity stages of the unit 4 and the opening degree of the proportional valve 10, the opening degree of the can body flow rate control valve 38 and the bypass flow rate control valve 34 is controlled so that the required hot water temperature is obtained. Further, the control device 1 obtains a target rotational speed of the fan motor M by calculation so as to obtain an optimum air flow amount corresponding to the required combustion heat quantity, and rotationally drives the fan motor M at the target rotational speed.

  As shown in FIG. 2, the control device 1 includes a microprocessor 11 as a control center and a rewritable nonvolatile memory 12 (storage means) such as an EEPROM. Further, in the illustrated example, the fan motor M is a DC motor, a drive circuit 13 for applying a drive voltage corresponding to a drive voltage command signal from the microprocessor 11 to the fan motor M, and converting the drive current of the fan motor M into a voltage. Current-voltage conversion circuit 14 for output, triangular wave generation circuit 15 for generating and outputting a periodic triangular wave voltage for comparison with the output voltage of circuit 14, and output voltage and triangular wave generation for current-voltage conversion circuit 14 A comparator 16 that compares the triangular wave voltage output from the circuit 15 and outputs a pulse signal having a duty ratio corresponding to the output voltage of the current-voltage conversion circuit (that is, a duty ratio corresponding to the drive current of the fan motor M); It has.

  Although the current-voltage conversion circuit 14 may have an appropriate circuit configuration, in the illustrated example, the current-voltage conversion circuit 14 includes a resistor 14a connected in series to the fan motor M and an amplifier 14b that amplifies the voltage across the resistor 14a. Has been.

  The triangular wave generation circuit 15 is mainly composed of a first operational amplifier 15a constituting a Schmitt circuit (hysteresis circuit) and a second operational amplifier 15b constituting an integrating circuit, and a non-inverting input terminal of the first operational amplifier 15a. Is supplied with a voltage obtained by dividing the voltage difference between the output voltage of the first operational amplifier 15a and the output voltage of the second operational amplifier 15b by the voltage dividing resistors R2 and R3, and the integrating circuit includes the second operational amplifier 15b. A capacitor C provided between the inverting input terminal and the output terminal, and a resistor R1 provided at the inverting input terminal. A predetermined voltage is input to the inverting input terminal of the first operational amplifier 15a and the non-inverting input terminal of the second operational amplifier 15b.

  The oscillation frequency f of the triangular wave generation circuit 15 is expressed by the following equation (1), and the period is (1 / f) seconds.

  f = (R2 / R3) / (4 · C · R1) (1)

  In the present embodiment, as the capacitor C, a multilayer ceramic capacitor whose capacitance changes linearly with respect to a change in ambient temperature within an assumed use environment temperature range (for example, a range of −20 ° C. or more and less than 60 ° C.). For example, if the capacitance at a temperature of 20 ° C. is 100%, the capacitance is 110% at a temperature of −20 ° C., and the capacitance is 90% at a temperature of 60 ° C. Can do. In this case, the period of the triangular wave when the temperature is 60 ° C. is reduced by about 20% with respect to the temperature −20 ° C., for example, when the temperature is −20 ° C., the period is about 240 milliseconds, and when the temperature is 60 ° C. The circuit can be configured to have a period of about 200 milliseconds.

  It is also possible to employ a capacitor having a larger capacitance change rate with respect to temperature change. In addition, it is possible to use a capacitor whose capacitance changes in a quadratic curve with respect to a change in temperature, but within an assumed use environment temperature range of the environment where the water heater 1 is installed, for example, -20 ° C to 60 ° C. Among them, a capacitor whose capacitance gradually decreases or gradually increases as the temperature rises is used, and a capacitor whose capacitance is the same at two different temperatures is not used.

  The microprocessor 11 functions as various control means by executing a predetermined program. In this embodiment, in particular, the driving current detection value of the fan motor M is calculated by calculation based on the duty ratio of the pulse signal output from the comparator 16. The calculation means 11a, the current-voltage conversion circuit 14, the triangular wave generation circuit 15 and the comparator 16 constitute a drive current detection means for detecting the drive current of the fan motor M. This drive current detection means can detect the drive current detection value of the fan motor M by a method similar to the drive current detection method disclosed in Patent Document 3.

  Further, the microprocessor 11 detects the ambient temperature of the capacitor C constituting the integration circuit of the triangular wave generation circuit 15 by the temperature detection means 11b and the temperature detection means 11b that detect by the calculation based on the period of the pulse signal output from the comparator 16. Detection error correction means 11c for correcting the detection error of the drive current detection value by the drive current detection means based on the detected temperature, and a drive voltage command signal to the drive circuit so that the fan motor M reaches the target rotational speed Functions as the rotation speed control means 11d.

  The rotation speed control means 11d can have a conventionally known appropriate configuration. For example, the target rotation speed of the fan motor M for supplying the optimum amount of combustion air according to the required hot water supply number and the set hot water supply temperature. Is calculated, and the drive voltage is feedback-controlled so as to reach the target rotational speed based on the rotational speed detection signal output from the rotational speed detection means provided in the drive circuit 13 or the fan motor M. Further, the degree of blockage of the air supply / exhaust passage is estimated based on the drive current value corrected by the detection error correction unit 11c as appropriate, and the target rotation number of the fan motor M is corrected so that the rotation number corresponds to the degree of blockage. In consideration of the load characteristic that the drive current value of the fan motor M fluctuates due to the fluctuation of the ambient temperature even at the same load (at the same air flow rate), the drive current value corrected by the detection error correction means 11c is further increased. It is possible to cause the rotation speed control means 11d to perform appropriate calculations such as calibration.

  It should be noted that the programs and arithmetic expressions constituting each of the means 11a, 11b, 11c, and 11d may be implemented separately as program codes or arithmetic expressions, or may be implemented as an integral program or arithmetic expression. Also good.

  Note that the period of the triangular wave voltage output from the triangular wave generating circuit 15 has an error for each product even at the same temperature, so that the triangular wave at a predetermined ambient temperature (for example, 20 ° C.) at the time of shipment of the instrument. The temperature detection means 11b is configured to read the voltage period and store it in the rewritable nonvolatile memory 12 as a reference period and detect the temperature based on the ratio of the period of the pulse signal to the reference period in actual use. it can. When the predetermined ambient temperature environment cannot be prepared, the triangular wave voltage cycle is read under the shipping work environment temperature at the time of shipment of the instrument, and the predetermined conversion formula is converted into the cycle at the reference temperature (for example, 20 ° C.). It is also possible to convert it by using it and store it as a reference period.

  The detection error correction unit 11c corrects the drive current detection value output from the calculation unit 11a based on the temperature detection value detected by the temperature detection unit, so that the current-voltage conversion circuit 14 and the comparator 16 due to temperature fluctuations. The actual driving current value of the fan motor M is calculated by correcting the detection error due to the fluctuation of the output characteristics of the circuit constituting the driving current detecting means. The calculation method by the detection error correction unit 11c may be any appropriate one. For example, in a real machine, the relationship between the temperature (ambient temperature) and the fan motor drive current value is measured, and the measured value can be rewritten as a data table. The drive current detection value can be corrected based on the temperature detection value by storing the data in the nonvolatile memory 12 or the ROM and referring to the data table. In addition, the drive current detection value can be corrected based on the temperature detection value based on the approximate curve equation passing through the vicinity of the plurality of actual measurement values.

  The data table may store, for example, a correction rate α (T) with respect to a reference temperature at each temperature T at a predetermined temperature (for example, every 1 ° C.) in a temperature range of −20 ° C. to 60 ° C. . Then, as shown in the following equation (2), the correction rate α (T) corresponding to the temperature detection value T detected by the temperature detection means is multiplied by the drive current detection value (read value) output from the calculation means 11a. By doing so, a correct drive current value can be calculated.

  Drive current value after correction = α (T) × drive current detection value (2)

  By calibrating the fan motor rotational speed based on the corrected drive current value, more accurate fan motor rotational speed control can be performed, and the combustion efficiency can be further improved. Further, since the detection error of the drive current detection value of the drive current detection means when the combustion unit 4 is combusting is corrected, the supply / exhaust passage is based on the corrected drive current value and the fan motor rotation speed detection value. By making the control device 1 perform the blockage determination, more accurate blockage determination can be performed, and combustion stop control based on the blockage determination result can be performed at a more accurate timing.

  The present invention is not limited to the above-described embodiment, and the design can be changed as appropriate. For example, although the example of the control device for the hot water heater has been described in the above embodiment, the present invention can be implemented as a control device for various devices including a fan motor other than the hot water heater. If the fan motor is an AC motor or a PWM drive motor, the current value obtained by smoothing the drive current waveform supplied to the fan motor may be detected, or the maximum value of the drive current waveform may be detected. May be detected.

DESCRIPTION OF SYMBOLS 1 Control apparatus 4 Combustion part 5 Primary heat exchanger 6 Secondary heat exchanger 7 Fan 11a Arithmetic means 11b Temperature detection means 11c Detection error correction means 14 Current-voltage conversion circuit 15 Triangular wave generation circuit 16 Comparator M Fan motor

Claims (5)

  In a control device including drive current detection means for detecting a drive current of a fan motor, temperature detection means for detecting a temperature of a predetermined circuit part constituting the drive current detection means or an ambient temperature of the circuit part, and the temperature detection And a detection error correction unit that corrects a detection error of the drive current detection value of the drive current detection unit based on the temperature detected by the unit. The control device according to claim 1,
The drive current detection means includes a current-voltage conversion circuit that converts a drive current of the fan motor into a voltage and outputs the voltage, a triangular wave generation circuit that outputs a periodic triangular wave voltage, and an output voltage of the current-voltage conversion circuit. A comparator that compares the output voltage of the triangular wave generation circuit and outputs a pulse signal having a duty ratio corresponding to the output voltage of the current-voltage conversion circuit, and an operation based on the duty ratio of the pulse signal output by the comparator And calculating means for calculating the drive current detection value by
The triangular wave generation circuit includes a capacitor whose capacitance changes according to temperature as a circuit component, and is configured so that the period of the triangular wave voltage changes according to the capacitance of the capacitor.
The temperature detecting means detects an ambient temperature of the capacitor based on a cycle of the pulse signal.   The control device according to claim 2, wherein the capacitance of the capacitor changes linearly with respect to a change in ambient temperature within an assumed use environment temperature range.   2. The control device according to claim 1, wherein the temperature detection unit detects an ambient temperature of the predetermined part based on an output voltage of a thermistor provided at the predetermined part of the drive current detection unit. apparatus.   The control device according to any one of claims 1 to 4, a fan motor controlled by the control device, a fan attached to a rotation shaft of the fan motor, air and fuel supplied by the fan A forced supply / exhaust water heater comprising a combustion section that generates a combustion gas by burning a mixed gas with a gas, and a heat exchanger that heats water by heat exchange with the combustion gas, The forced detection / exhaust water heater is characterized in that the detection error correction means corrects a detection error of a drive current detection value of the drive current detection means when the combustion section is burning.

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