JPS6115018A - Method of detecting abnormality of fan motor for combustion control system - Google Patents

Abstract

PURPOSE:To detect improper number of rotation of fan motor with regard to the combustion rate, by setting signals of numbers of rotation which represent the allowable upper and lower limits of fluctuations, based on the signal of a set number of rotation of a fan motor corresponding to the combustion rate being fed into a fan motor driving circuit. CONSTITUTION:The output from NAND gate 15 is on a logic ''L'' and a transistor 16 maintains an OFF condition, when actual voltage signal Vrpm of a number of rotation of fan motor is correctly adjusted at a value between the upper limit value Vupr and the lower limit value Vlwr, which are determined based on a voltage signal Vso of set number of rotation at that time, so that a fan motor abnormality decision signal Sa as the potentials on both sides of a capacitor is on a logic ''H'', representing a normal condition. However, the output from the NAND gate 15 will be inverted to ''H'', when the number of rotation Vrpm of a fan motor 5 at that time is not within the upper limit value and the lower limit value.

Description

[Detailed Description of the Invention] [1. Field of Industrial Application] The present invention relates to a combustion control device for a water heater, etc., which supplies an amount of air to a combustion section according to the amount of combustion required from time to time. The present invention relates to a fan/motor abnormality detection method that is optimal for combustion equipment having a fan/motor rotation control system.

[Ir, Prior Art] In recent combustion devices for water heaters, the temperature and amount of water supplied, and the temperature of the hot water being tapped are detected, and the user can determine the hot water temperature based on these data. Many devices now have a main control system that controls the temperature as close to the set temperature as possible.

Therefore, in such devices, the amount of air supplied to the combustion section must be optimally controlled according to the required combustion amount determined from time to time as described above. Otherwise, not only will the combustion efficiency be reduced, but also This is because there is a risk of incomplete combustion.

In other words, this means that a feedback type control system is required that can also control the rotation of the fan motor with high precision. The optimum rotation speed of the fan motor is determined.

A circuit device that monitors the rotation speed of the fan motor within the permissible range of % or rp■, and can detect this as an abnormal rotation of the fan motor when the rotation speed of the fan motor falls outside of this permissible range. There is.

However, conventionally, no method or device has been provided for detecting an abnormality in a fan motor in consideration of the rotation speed set at the time.

The existing method is to simply set two fixed points: the upper limit of allowable maximum fan/motor rotation speed at maximum combustion amount and the lower limit of allowable minimum rotation speed of fan/motor corresponding to minimum combustion amount. - Only when the motor rotational speed exceeded either of these two points above or below was there something that was judged to be "abnormal."

[■1 Problems to be Solved by the Invention] However, in reality, even if the conventional method described above is within a range that would not be considered "abnormal," it is undesirable in terms of the amount of combustion at that time. It is quite possible that the rotation speed is abnormal.

This becomes clear when we give a concrete numerical example.

For example, assume that the fan motor rotates in a range from 240 rpm as the minimum rotation speed corresponding to the minimum combustion amount to 240 rpm as the maximum rotation speed corresponding to the maximum combustion amount.

In such a case, in the above conventional method, the lower limit tolerance is fixedly set to 1000 rpm, which is about 1100 rpm lower than the minimum rotation speed, and the upper limit tolerance is fixedly set to 2500 rpm, which is about 100 rpm higher than the maximum rotation speed. Regardless of the situation, if the rotational speed of the fan motor at any given time is within this range, it is not considered "abnormal" but is determined to be "normal."

However, the permissible rotational speed variation range that can reduce combustion efficiency and avoid the risk of incomplete combustion is actually ±1100 rpm compared to the optimal set rotational speed calculated theoretically according to the amount of combustion at that time. It is often about a certain degree.

As a result, it can be seen that the conventional method described above cannot detect such an abnormal situation.

In other words, if the optimal set rotation speed determined according to the combustion amount at that time is, for example, 18QOrp, then ±11
If 00rp is the allowable range, this is also 2200r for example.
The pm is supposed to be an "abnormal rotational speed" that is completely out of the allowable range, but as mentioned above, it has changed from 1100 Orp to 250 Orp.
In the conventional method, which uniquely defines up to m as the "normal range", this naturally falls within the "normal" range and cannot be detected as 'abnormal'.

First of all, the combustion amount fluctuates depending on the usage conditions at the time, and accordingly, the optimal set rotation speed of the fan motor, which is calculated theoretically, will take a different value depending on the time. In reality, a required rotation speed variation tolerance range is set for the optimum rotation speed determined from time to time, and the actual fan speed is determined for each tolerance range.
Check whether the motor rotation speed is within this range each time.
It is understood that it must be possible to discriminate between 0. For example, if the set rotation speed is 150 orpm, the minimum
From GOrpm to maximum 1800rpm, 1800rpm
In the case of m, the minimum and maximum critical values are changed depending on the set rotation speed, such as from tsoorp to 2000 rpm, and the actual value is determined based on the allowable range set at that time. The fan motor rotation speed is monitored. However, the above ±1100r
p is an example, and may be a percentage specification whose width varies depending on the absolute value of the set rotation speed.

However, if this is done, the response characteristics of the feedback control system related to the fan motor must also be considered.

When the fan/motor rotation speed falls outside of the allowable range, the feedback control system described above starts to respond and works to bring the fan/motor rotation speed to the optimal setting at that time. It takes some time to complete the process due to factors such as the inertia of the fan motor. Therefore, if a relatively narrow tolerance range is set individually depending on the amount of combustion at any given time, and if it is immediately judged as abnormal just because it falls outside the tolerance range, the function of the feedback system will be impaired. .

The present invention has been made to solve these problems, and the permissible range for determining the normal rotation speed of the fan motor simply corresponds to the maximum allowable rotation speed corresponding to one large combustion amount and the minimum combustion amount. Instead of defining the minimum allowable rotation speed uniquely and fixedly only at the two critical points, the allowable rotation speed range is defined with a predetermined width above and below the optimal set rotation speed depending on the combustion amount at that time. In addition, compared to the conventional fixed two-point judgment method, the allowable rotation speed range is narrower, and even if the fan motor rotation speed falls outside this allowable range, it is immediately considered abnormal. A fan that determines that there is an abnormality in the fan/motor rotation only when the rotation speed does not fall within the permissible rotational speed range at that time after the scheduled time determined based on the response time of the feedback control system has elapsed.・Provides a motor abnormality detection method.

[17. Means for Solving Problems] ° In order to achieve the above object, the present invention provides a set rotation speed signal that is sent from the main control device to the fan motor drive circuit in accordance with the combustion amount at the time. Based on this, upper limit and lower limit critical value signals are generated that define a permissible range of rotational speed variation appropriate to the set rotational speed at any given time.

Then, by reusing the actual rotation speed signal at that time from the fan motor used in the feedback control system, this fan motor rotation speed signal is the rotation at that time specified by the upper limit and lower limit critical value signals. Determine whether the number is within the allowable range.

This can be done, for example, by individually comparing the fan motor rotational speed signal with each of the upper and lower threshold values.

As a result, the fan motor rotation speed signal is at the upper limit,
If the rotation speed is outside the permissible rotation speed variation range for the current set rotation speed, which is defined by each lower limit threshold value signal, the timer circuit is activated.

After startup, this timer circuit will run for a predetermined scheduled time T! If the time exceeds this, it is determined that the fan motor is rotating abnormally, and the time is increased.

The feedback control system completes feedback control before the fan
When the motor rotational speed falls within the rotational speed fluctuation tolerance range at that time, the timer circuit is reset. Of course, when the timer circuit is reset, it is considered normal.

[Written by V] In the present invention, the above configuration is ignored.

The permissible rotational speed variation range of the fan motor can be different for each set rotational speed of the fan motor depending on the amount of combustion at that time. In other words, based on the set rotation speed signal sent from the main control circuit to the fan motor drive circuit at that time, an allowable range of rotation speed fluctuation is created that is appropriate for the set rotation speed at that time, so this allowable range is relatively It can also be made narrower. In other words, it is possible to relatively strictly define the air amount range in which the combustion efficiency can be optimized for the combustion amount at that time and the risk of incomplete combustion can be reliably avoided.

In this way, even if the rotation speed of the fan motor is monitored within a narrower allowable range than in the past, the response time of the feedback control system can be sufficiently considered.

In other words, if the tolerance range is narrowed, the actual rotation speed of the fan motor will easily deviate from this tolerance range, even temporarily, if the set rotation speed information from the main control circuit is changed. However, the main control system detects the difference between the set rotation speed and the actual rotation speed, responds to correct it, and sends the set rotation speed signal to the fan motor drive circuit in the corrected form. In response to this, the electromechanical component fan
The time it takes for the motor to correct its rotational speed can be used as a margin time with the help of a timer circuit so that it will not be detected as an abnormality, so the original function of the control system will not be impaired in any way.
If the actual fan/motor rotational speed does not fall within the permissible rotational speed fluctuation range after the normally considered response time has elapsed, this can be quickly detected as a fan/motor rotational abnormality.

Of course, it is possible to detect stoppage of rotation due to burnout or failure of the fan motor, or conversely, runaway accidents due to circuit failure, etc., and abnormal phenomena associated with gradual power supply voltage fluctuations over a long period of time, which are normally difficult to detect. can also be detected.

[In, Examples] A variety of circuit systems for carrying out the method of the present invention can be assembled using existing electronic circuit technology. FIG. 1 shows an example of a desirable configuration selected from among these, but before explaining this circuit system 1O, we will first explain the feedback control system of the fan motor and the combustion section involved in determining the amount of combustion. Referring to FIG. 3, reference will be made to FIG. 3 in order to also explain other control modes and an outline of the device in the existing water heater of this type, such as control.

When the main control circuit 1 receives a water quantity signal S6 from a water quantity sensor 6 provided in the water supply channel, it generates a set temperature signal Ss for commanding the hot water temperature desired by the user, and a water supply temperature signal provided in the water supply channel. The feed water temperature signal S7 from the sensor 7 and the outlet hot water temperature signal S8 from the outlet hot water temperature sensor 8 provided in the outlet path for detecting the actual outlet temperature are respectively taken in, and from these signals, the gas burner, etc. The amount of combustion to be given to the combustion section 3 is calculated.

Then, according to the result, a gas proportional valve control signal S4 is sent to the gas proportional valve 4 to control the fuel gas supply amount, and
A fan motor rotation control signal Sc is sent to the fan motor 5 based on the air supply amount or fan motor set rotation speed data corresponding to the combustion amount.

A fan motor rotation speed signal Frp indicating the actual rotation speed is output from the fan motor 5 by attaching an appropriate sensor to the fan motor 5.
The rotational speed is fed back to the main control circuit, and feedback control is performed according to the deviation between the actual rotational speed data contained in this signal and the previously set rotational speed data.

In addition, if the combustion amount calculated above exceeds the capacity of the gas burner, the main control circuit 1 outputs a water flow valve control signal S9, and in response to this, the water flow valve 9 throttles the outlet path. Regulate the amount of hot water.

Next, to explain the feedback control system part of the fan/motor that can be used with the existing configuration in Figure 1, the main control circuit 1 sends air according to the combustion amount calculated and determined at each time as described above. Fan motor set rotation speed data corresponding to the feed amount is sent as a voltage signal Vso. The signal is converted into a good set rotation speed frequency signal or set rotation speed power signal Sc, and is sent to the fan motor 5 to control it.

On the other hand, an actual rotational speed signal is sent from the fan motor 5 via an appropriate rotational speed detection sensor attached thereto, but in general, as already described with reference to FIG.
This rotational speed signal often takes the form of a rotational speed to frequency conversion signal Frp layer.

Therefore, since each signal is generally handled as a voltage-dimensional signal, the frequency-converted rotational speed signal Frpm is further converted into a corresponding voltage signal V by an appropriate F/V converter 12.
Converted to rp■.

In the fan motor feedback control system using the main control circuit 1, this actual fan motor rotation speed signal Vrpm is compared with the above-mentioned set rotation speed signal Vso, appropriate correction is made, and the fan motor is restarted. Control.

If the fan/motor abnormality detection method of the present invention is incorporated into such a circuit system that can be used with an existing configuration, it is possible to adopt the configuration shown by the abnormality determination circuit IO in FIG. 1.

First, based on the current fan/motor set rotation speed voltage signal Vgo sent from the main control circuit 1, upper and lower critical values indicating the upper and lower limits of the permissible range of rotation speed variation appropriate for the current set rotation speed are determined. This can be easily done, for example, by employing a forming potentiometer PI for forming the upper limit critical voltage value Vupr and a second potentiometer P2 for forming the lower limit critical voltage value V1wr. Therefore, of course,
If the upper and lower allowable widths are equal, the upper limit critical voltage value Vupr
and the lower limit critical voltage value V1wr, the intermediate voltage value Vctr-
(vupr+VIwr)/2 corresponds to the voltage value at the set rotation speed.

The upper limit critical voltage value created in this way (hereinafter simply referred to as the upper limit value)
Vupr is applied to the positive phase input of the upper limit value comparator CMPI, and the lower limit value V1wr is applied to the negative phase input of the lower limit value comparator CMP2.

On the other hand, both comparators CMPI, CMP217) and other inputs,
The fan/motor rotational speed voltage signal Vrp layer from the F/V converter 12 is input, and the corresponding rotational speed when the fan/motor is correctly rotating at the set rotational speed corresponding to the set rotational speed signal Vso. Adjustment is made so that the value of the voltage signal Vrpm becomes the above-mentioned allowable range intermediate value VctT.

This adjustment is made using the first and second potentiometers and meters P.
I, P2C, or, if necessary, by attaching a potentiometer to the actual fan motor rotational speed voltage signal Vrp, although not shown.

Of course, by adjusting these potentiometers and meters, it is also possible to specify different permissible fluctuation ranges for upper and lower positions even within the permissible range.

The outputs of both comparators CNPI and CMP2 are both connected to each input of a NAND gate 15, and the output of the NAND gate 15 is connected to a resistor R via a switching element 1B.
The timer circuit 17, which is simply configured with a capacitor C and a capacitor C, is selectively activated. Furthermore, in this case, the switching element 16 is also constituted by an npn type transistor, and therefore turns on when the NAND logic is adopted in the NAND gate 15, and discharges the accumulated charge in the capacitor C according to the time constant RC. However, when the transistor 1B is off or in the off state, the capacitor C is at the power supply potential Vc.
c is in a charged state or will be charged quickly.

As shown in the above configuration, the outputs of the upper limit comparator CMPI and the lower limit comparator CMP2 are determined depending on whether the actual fan motor rotation speed voltage signal Vrpm at that time is within the allowable range. The relationship with the output of the NAND gate 15 is shown in Table 1 below.

Therefore, the actual fan motor rotation speed voltage signal Vrp is located correctly between the upper limit value Vupr and the lower limit value V1wr determined for the set rotation speed voltage signal Vgo at that time. If so, the output of the NAND game) 15 is at logic "L" as shown in the 'within tolerance' area in FIG.
Since the transistor 16 maintains the off state, the fan/motor abnormality determination signal Sa, which is the potential across the capacitor, is also logic "H", indicating a normal state.

However, the set rotational speed signal Vs from the main control circuit l.

changes, and due to a feedback control response transition period in which the actual rotation of the fan motor 5 has not yet caught up with this change, or some other disturbance, the actual rotation speed Vrpm of the fan motor 5 at that time may change. The upper limit of the allowable range Vup
When the voltage exceeds r or falls below the lower limit Vlvr, the output of the NAND get 15 is inverted to logic "H" as shown in Table 1 above.

Then, the timer circuit 17 starts, and specifically in this case,
Discharging of the capacitor C starts, and the potential of the abnormality determination signal Sa as the potential across the capacitor C becomes the maximum charging potential E■a! associated with the power supply potential Vcc up to that point! The voltage begins to decrease with a predetermined time constant RC toward the ground potential.

Judgment or detection of an abnormality is made at the point when this decreasing judgment signal potential crosses the scheduled threshold value Ethe, but conversely speaking, the time required to reach that point is the margin time T until abnormality judgment.
1.

Therefore, if the fan motor rotation speed Vrpm deviates from the allowable range due to a delay in the response of the regular feedback control system or a transient fluctuation in the power supply voltage, etc., as shown in FIG.

As shown in the "tolerable range deviation ■" region, deviation from the allowable range at time to is expressed as the output of the NAND game) 15, and accordingly, the transistor 1B turns on,
Even if the potential of the abnormality determination signal Sa decreases after discharging the capacitor C, the fan motor rotation speed will continue to decrease after the response time of the feedback control system has elapsed.

When the voltage falls within the allowable range again, the output of the NAND gate 15 is inverted to "L" again, and the transistor 1B is quickly turned off, which means that the timer circuit 17 has been reset, and the abnormality determination signal is Sa is also charged again toward the maximum potential Emax without reaching the threshold Etho.

That is, in such a case, even if a situation temporarily outside the allowable range occurs, the timer circuit 17 will be reset before the time is up, and therefore the fan motor will not operate as shown in FIG. It can be determined that the rotation state is "normal".

On the other hand, if the fan motor rotation speed Vrp deviates from the allowable range due to disturbance, failure, or some other factor, the allowable range is temporarily changed as shown in the "Tolerable range deviation ■" area in Figure 2. It is difficult to imagine that the fan motor rotation speed that has deviated will come back within the allowable range after that.

Therefore, the abnormality determination signal Sa, which starts to decrease from time tl in the "permissible range deviation ■" region, will eventually fall below the predetermined threshold value Etho. That is, timer circuit 1? Considering this, the time is up after the set time Tx has elapsed, and at this point it can be identified as ``abnormal rotation of the 0 fan motor''.

Of course, as with the above mechanism, the margin time or set time 1 can be arbitrarily determined, and even if it falls outside the tolerance range, it will not be considered an abnormality. Judgment of the time can be made very easily using known and existing electronic circuit technology. Furthermore, the illustrated circuit system is merely an example, and other circuit configurations for realizing the method of the present invention may be constructed as desired.

Furthermore, the abnormality determination circuit 1 (l is a microcomputer's built-in registers, timers, and counters, which are generally used as the main control circuit 1), and is made suitable for the method of the present invention by creating an appropriate program. This can be realized even if the engine is operated at a constant speed.In such a case, the range of permissible rotational speed variation suitable for each set rotational speed is generally set as a constant width for each allowable range. Often.

Incidentally, when an abnormality in the fan motor is detected according to the present invention, the most common safety measure is to stop combustion in the main control circuit.

[■1 Effects of the Invention] According to the present invention, not only is the fan motor burnt out or broken down, or the rotation stopped or runs out of control which is clearly recognized as being abnormal due to circuit failure, but even if the fan motor seems to be rotating correctly, the amount of combustion at that time may be reduced. In this way, it is possible to detect the presence of an inappropriate rotation speed for each combustion amount in a corresponding manner, improve combustion efficiency, and almost completely avoid the risk of incomplete combustion.

However, the degree of freedom in design is extremely high since the allowable range of rotational speed variation corresponding to each combustion amount and the margin time z by the timer circuit can be set arbitrarily.

Further, even if the allowable range is made narrower than it should be strictly, there will be no adverse effect on the existing fan/motor period control system, depending on how the timer circuit is designed to provide a margin time.

[Brief explanation of the drawing]

FIG. 1 is a circuit configuration diagram of an example of a circuit for implementing the method of the present invention, FIG. 2 is a diagram of essential signal waveforms in FIG. 1, and FIG. 3 is an explanation of the outline of a combustion device to which the present invention can be applied. Figure. In the figure, l is the main control circuit, 2 is a heat converter, 3 is a combustion part such as a gas burner, 4 is a gas proportional valve, 5 is a fan motor,
6 is a water flow rate sensor, 7 is a water supply temperature sensor, 8 is an outlet hot water temperature sensor, IO is an overall abnormality determination circuit in the circuit in which the method of the present invention is implemented, 11 is a fan motor drive circuit, 12
is an F/V converter, 15 is a NAND gate, 17 is a timer circuit, and Pl. Pl is a potentiometer, CMPI and CMP2 are comparators.

Claims (1)

[Claims] In a combustion device having a fan motor for supplying an air amount corresponding to the combustion amount calculated by a main control device to a combustion section, and a fan motor control system for controlling the rotation speed of the fan motor. , a method for detecting abnormal rotation of a fan motor for a combustion control device, which detects abnormal rotation of the fan motor according to the combustion amount sent from the main control device to the fan motor drive circuit at any given time. Based on the set rotation speed signal, create upper and lower limit critical value signals that define the permissible range of rotation speed variation appropriate to the set rotation speed at that time; the actual rotation speed signal from the fan motor at that time is It is determined whether or not the current rotation speed fluctuation tolerance range is specified by the upper limit and lower limit critical value signals; as a result, the fan motor rotation speed signal falls within the above upper limit,
If the current rotational speed variation is outside the permissible range specified by each lower limit value signal, the timer circuit is activated; If the time is up, it is determined that the rotation of the fan motor is abnormal; on the other hand, if the fan motor rotation speed signal falls within the permissible rotation speed fluctuation range at that time before the time is up, the timer circuit is reset; A method for detecting abnormality in a fan/motor for a combustion control device, characterized in that: