JP2825212B2 - Combustion equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ventilation means for supplying combustion air to a combustion section having a burner, a heating type sensor for detecting the amount of air supplied to the combustion section by the ventilation means, and a method for starting combustion. The heating of the heating type sensor is started in response to the command, and the ventilation means is controlled such that the detection value of the heating type sensor is maintained at a target value determined according to the fuel supply amount supplied to the burner. And a control unit that performs the control.

[0002]

2. Description of the Related Art As such a heating type sensor, for example, there are a hot wire type wind speed sensor and a ceramic oxygen sensor. The former indirectly detects the air supply amount to the combustion section by detecting the pressure difference between the supplied combustion air and the exhaust gas after combustion from the flow velocity of the air flowing through the bypass passage. The latter indirectly detects the amount of air supplied to the combustion section by detecting the oxygen concentration in the combustion exhaust. As a conventional example of performing combustion control using this type of ceramic oxygen sensor, there is one disclosed in Japanese Utility Model Laid-Open No. 160353/1985.

The control means controls the ventilation means so that the detection value of the heating type sensor is maintained at a target value determined in accordance with the fuel supply amount supplied to the burner. Maintain volume properly. In general, the heating of the heating type sensor is started as the start of combustion is commanded, and is stopped as the stop of combustion is commanded. It is conceivable that the heating is always performed irrespective of whether or not the fuel is burning, but in this case, there is a problem in the durability of the heating sensor.

However, it takes time for the heating type sensor to be heated to an appropriate state, that is, to reach a stable operation region. Therefore, until the heating type sensor is heated to an appropriate state, the above-mentioned control of the ventilation means cannot be appropriately performed. Therefore, conventionally, when the start of combustion is instructed, the heating of the heating sensor is first started, and the heating sensor is heated to an appropriate state for a predetermined time (for example, about 1 hour).
Minutes), the burner is ignited to control the ventilation means.

[0005] In addition, since such a heating type sensor may cause high temperature deterioration due to heating, it is necessary to check by some method whether or not the detected value is normal before performing control based on the detected value. Need to be kept. Conventionally, for example, in the case of a ceramic oxygen sensor for detecting oxygen concentration in exhaust gas, whether or not a detected value in the atmosphere (oxygen concentration 21%) is normal in a state where no exhaust gas is generated, that is, before the burner is ignited. I was trying to check.

[0006]

As described above, when the heating type sensor is checked after a lapse of a predetermined time since the start of combustion is instructed, and the burner is ignited for the first time, the following problem occurs. That is, since the ignition timing is later than the combustion start command, for example, in the case of a water heater combustion device, it contributes to the deterioration of the initial hot water discharge characteristics.

In order to improve this, it is necessary to start the heating of the heating type sensor when the start of combustion is instructed and to ignite the burner at the same time, and to control the ventilation means in an open loop until the predetermined time has elapsed. Conceivable. That is, without using the closed loop control based on the detection value of the heating sensor, for example,
The operation amount of the ventilation means is maintained at a predetermined constant value. Alternatively, the ventilation means may be controlled so that the operation amount is determined according to the fuel supply amount.

However, when the burner is ignited immediately after the start of combustion is commanded as described above, it is not possible to check whether the detection value of the heating type sensor is normal or not. That is, before the burner is ignited, the above-described check cannot be performed because the heating type sensor has not yet been heated to an appropriate state, and after a predetermined time has elapsed, the atmosphere of the heating type sensor has already changed due to combustion. Cannot perform the above check.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a combustion apparatus that controls a supply amount of combustion air by using a heating type sensor. An object of the present invention is to make it possible to appropriately check whether or not the detection value of the heating type sensor is normal while preventing the occurrence of the detection.

[0010]

According to the present invention, there is provided a combustion apparatus comprising: a ventilation means for supplying combustion air to a combustion section having a burner; and a heating type sensor for detecting the amount of air supplied to the combustion section by the ventilation means. With the start of combustion, the heating of the heating sensor is started in response to a command, and the detection value of the heating sensor is maintained at a target value determined according to the fuel supply amount supplied to the burner. Control means for controlling the ventilation means, wherein the first characteristic configuration is such that the control means continues to operate the ventilation means until a predetermined time elapses after stopping the combustion, and the heating type sensor Is configured to check whether the detected value is normal.

In a second characteristic configuration, a temperature sensor for detecting an ambient temperature of the heating type sensor is provided, and the control means keeps operating the ventilation means even after the combustion is stopped, and detects a temperature detected by the temperature sensor. The operation of the ventilation means is stopped as the temperature becomes equal to or lower than a predetermined temperature, and whether or not the detection value of the heating type sensor is normal is checked.

[0012]

According to the above feature, the exhaust is driven out by continuing the operation of the ventilation means even after the combustion is stopped,
Further, the combustion chamber and the exhaust passage are cooled. As a result, the atmosphere of the heating type sensor eventually becomes a normal temperature atmospheric state. Therefore,
When it is possible to check whether the detection value of the heating sensor is normal, the control unit checks whether the detection value of the heating sensor is normal.

That is, for example, when the heating type sensor is an oxygen sensor for detecting oxygen concentration, since the oxygen concentration in the atmosphere is constant (21%), it is necessary to check whether the detected value is normal. it can. In the case of a hot-wire type wind speed sensor, it can be checked whether or not the detected value in a normal-temperature no-wind state is within a predetermined range to determine whether it is normal. That is, after the combustion is stopped, a check is made as to whether or not the detected value of the heating sensor is normal, in preparation for the start of the next combustion. In this point, it is significantly different from the conventional case where the above check is performed before the start of combustion.

The first feature configuration and the second feature configuration differ only in the following points. That is, in the first characteristic configuration, the time until the above-mentioned state in which the heating type sensor can be checked, that is, a predetermined time for continuing the operation of the ventilation means is determined in advance by an experiment, and the predetermined time is controlled. Means is governed by its internal timer. On the other hand, in the second characteristic configuration, the control unit determines whether or not the heating sensor can be checked based on the temperature detected by the temperature sensor that detects the ambient temperature of the heating sensor.

If the heating of the heating type sensor is continued even after the combustion is stopped, the heating type sensor can be checked immediately after the ventilation means is stopped, but deterioration of the heating type sensor at high temperatures is prevented as much as possible. If priority is given to this, the heating of the heating type sensor may be temporarily stopped when the combustion is stopped, and a predetermined heating may be performed when checking.

[0016]

Therefore, according to the combustion apparatus of the present invention, it is possible to appropriately check whether or not the detected value of the heating type sensor is normal while preventing the ignition timing of the burner from being delayed. Became.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the present invention is applied to a water heater will be described below with reference to the drawings. The water heater of the present embodiment is configured as shown in FIG. A fin tube type heat exchanger 4 for heating water by a high-temperature exhaust gas from a combustion section 3 having a burner 2 is provided in a cylindrical case 1. The lower end of the cylindrical case 1 is connected to the discharge side of a fan 5 as ventilation means for supplying combustion air to the combustion section 3, and the upper end of the cylindrical case 1 is connected to an exhaust passage 6.

The fuel supply path 7 to the burner 2 is provided with an electromagnetic proportional valve 8 for adjusting the fuel supply amount. The combustion controller 9 as a control means controls the opening degree by changing the exciting current of the electromagnetic proportional valve 8, thereby adjusting the fuel supply amount. The combustion controller 9 determines the hot water temperature set by the setting means R and the hot water detecting means S
The fuel supply amount is adjusted as described above on the basis of the deviation from the hot water temperature detected as described above to control the hot water temperature.

In order to control the hot water temperature, it is necessary to appropriately control not only the amount of fuel supplied to the burner 2 but also the amount of combustion air supplied to the combustion section 3. Therefore, the combustion controller 9 also controls the blowing state of the fan 5, that is, the rotation speed.
A ceramic oxygen sensor 10 for detecting the oxygen concentration in the exhaust gas is provided in the exhaust passage 6 as a sensor for detecting the amount of air supplied to the combustion section 3.

The ceramic oxygen sensor (hereinafter simply referred to as oxygen sensor) 10 indirectly detects the amount of air supplied to the combustion section by detecting the oxygen concentration in the exhaust gas after combustion. That is, if the amount of air supplied to the combustion unit is excessive, the oxygen concentration (remaining amount) in the exhaust gas is large, and if the air supply amount is slightly insufficient, the oxygen concentration (remaining amount) in the exhaust gas is large. Become smaller. Note that the oxygen sensor 10
It is a heating type sensor as described below.

As shown in FIG. 2, the oxygen sensor 10 includes a sensor element 11, terminals 12, a terminal block 13, and a mesh cover 14. As shown in FIG. 3, the sensor element 11 is formed by forming platinum electrodes 11b on both sides of a disk-shaped stabilized zirconia 11a and joining a cap 11d provided with a small hole 11c on one side thereof.
When a voltage is applied between the two electrodes 11b, a current using oxygen ions as carriers flows by a pumping action.

The flow of air into the cap 11d is limited to the small hole 1
Since the current is limited by 1c, the current becomes substantially constant (limit current) in a predetermined voltage range. Since this limit current changes in proportion to the oxygen concentration in the air, a constant voltage is applied between both electrodes 11b, and the oxygen concentration can be detected from the current value at that time. Further, since the pumping action occurs at a high temperature (about 500 ° C.), a heater 11e is integrally formed above the cap 11d, and the sensor element 11 is energized by energizing the heater 11e.
Is configured to be heated.

The energization of the heater 11e is controlled by a heater control circuit 9a in the combustion controller 9.
The detection value (current value) of the oxygen sensor 10 is input to the combustion controller 9, and the combustion controller 9 maintains the detection value at a target value determined according to the amount of fuel supplied to the burner 2. The number of rotations of the fan 5 is controlled, and the amount of air supplied to the combustion unit 3 is adjusted. The target value of the oxygen concentration is an appropriate value obtained by an experiment, and changes according to the fuel supply amount as shown in FIG.

Next, the control by the combustion controller 9 after the start of combustion is commanded will be described with reference to the flowchart of FIG. As the start of combustion is commanded, that is, the hot water tap (not shown) is opened and the water flow switch 15 is turned on, energization of the heater 11e of the oxygen sensor 10 and operation of the fan 5 are started. (Processing (a)). Gas valves such as the main solenoid valve and the solenoid proportional valve 8 are opened and the burner 2 is ignited. However, actually, the opening of the gas valve and the ignition of the burner 2 are performed about one second later than the operation of the fan 5.

It takes about one minute for the heater 11e to heat the oxygen sensor 10 (sensor element 11) to an appropriate state, ie, to reach a stable temperature (for example, 500 ° C.). Therefore, during this time, the rotation speed of the fan 5 is controlled to be the target rotation speed determined according to the fuel supply amount to the burner 2 (process (b)). That is, it is a temporary control until the detection value of the oxygen sensor 10 becomes effective. An appropriate relationship between the fuel supply amount and the target rotation speed is determined by experiments, and is in a proportional relationship as shown in FIG. The fan 5 is provided with a Hall element (not shown) for detecting the actual number of revolutions, and the detection signal is input to the combustion controller 9.

The combustion controller 9 has an internal timer 9
The time for performing the temporary control is managed by b. The internal timer 9b is reset at the start of combustion and starts counting. Then, the internal timer 9b sets a predetermined time (T
When 1) is reached, the control of the fan 5 is shifted from the temporary control to the above-described control based on the detection value of the oxygen sensor 10.
Further, as described above, the fuel supply amount is controlled by adjusting the opening of the electromagnetic proportional valve 8 (process (c)). Here, the predetermined time (T1) is a time (for example, one minute) determined beforehand by an experiment until the oxygen sensor 10 is heated to an appropriate state.

When the hot water tap is closed and the water flow switch 15 is turned off, the gas valve is closed and the combustion is stopped (process (d)). The fan 5 continues to operate, and performs a post-purge, that is, an exhaust operation after the combustion is stopped. Further, the combustion section 3 and the exhaust path 6 are cooled. The post-purge is continued until a condition described later is satisfied. During this time, when the hot-water tap is opened again and the water flow switch 15 is turned on, the combustion is restarted. That is, after the gas valve is opened and the burner 2 is ignited (process (e)), the process proceeds to the aforementioned process (c).

The post-purge is performed until the ambient temperature of the oxygen sensor 10 becomes lower than a predetermined temperature (for example, 60 ° C.). That is, as shown in FIG. 1, a temperature sensor 16 for detecting an ambient temperature of the oxygen sensor 10 is provided, and a detection signal is input to the combustion controller 9. When the temperature detected by the temperature sensor 16 falls below a predetermined temperature (for example, 60 ° C.), the combustion controller 9 stops the fan 5 and checks the oxygen sensor 10 (process (F)). At this point, the atmosphere of the oxygen sensor 10 is almost atmospheric, and if the temperature is equal to or lower than a predetermined temperature, the check of the oxygen sensor 10 is hardly affected.

The check of the oxygen sensor 10 is for checking whether or not the detected value in the atmosphere is within a predetermined range. That is, since the oxygen concentration in the atmosphere is constant (21%), if the detected value (current value) of the oxygen sensor 10 at this time is within a predetermined range, it is determined to be normal, and the power supply to the heater 11e is stopped to perform a series of control. Finish. If the temperature is outside the predetermined range, it is considered that the detection value of the oxygen sensor 10 is no longer correct due to high temperature deterioration or the like. Therefore, after the power supply to the heater 11e is stopped, the abnormal lamp (combustion lamp) (Also used as a lamp) 17 blinks. Then, the combustion control is interlocked (process (g)).

That is, since the abnormality flag is set, the gas valve is not opened and the burner is not ignited even if the water flow switch 15 is turned on next time. After performing predetermined processing such as replacement of the oxygen sensor 10, if a reset switch (not shown) is pressed, the abnormality flag is reset and the interlock is released.

Another embodiment will be described below. In the above embodiment, the post-combustion oxygen sensor 10
Although the post-purge is performed until the ambient temperature becomes equal to or lower than the predetermined temperature, the temperature sensor 16 may be omitted and the following configuration may be adopted. That is, a predetermined time (T
2) Post-purge is performed until the time has elapsed. After stopping the fan 5, the oxygen sensor 10 is checked in the same manner as in the above embodiment. The predetermined time (T2) is managed by an internal timer 9b of the combustion controller 9.

Further, both the detection value of the temperature sensor 16 and the internal timer 9 b may be used. For example, the MIN time (for example, 3 minutes) or the MAX time (for example,
Minute) by the internal timer 9b while the temperature sensor 1
The post-purge may be terminated and the oxygen sensor 10 may be checked when the detected temperature in Step 6 falls below the predetermined temperature.

In the above embodiment, the heater 11e of the oxygen sensor 10 is kept energized even after the combustion is stopped, and the oxygen sensor 10 can be checked immediately after the end of the post-purge. The heating sensor may be configured to temporarily stop heating. In this case, after the end of the post-purge, the heater 11e is energized again to check the oxygen sensor 10, and the oxygen sensor 10 is checked after a predetermined time (for example, one minute) has elapsed. It is effective to prevent the high temperature deterioration of the oxygen sensor 10 as much as possible.

The sensor for detecting the amount of air supplied to the combustion section is not limited to the ceramic oxygen sensor. For example, a hot-wire type wind speed sensor for detecting the pressure difference between the air supply side and the exhaust side from the flow velocity of the air flowing through the bypass path is used. It is also conceivable to use it. In short, the present invention can be applied to any combustion device using a heating-type sensor that needs to be checked in a non-combustion state in which normal detection can be performed only when heated to an appropriate state, and whether high-temperature deterioration is checked. can do.

The ventilation means is not limited to the blower fan, but may be, for example, a suction fan provided on the exhaust side. In the claims, reference numerals are provided for convenience of comparison with the drawings, but the present invention is not limited to the configuration shown in the attached drawings.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a water heater according to an embodiment of the present invention.

FIG. 2 is a sectional view of a ceramic oxygen sensor (heating type sensor).

FIG. 3 is a sectional view of a sensor unit.

FIG. 4 is a graph showing a relationship between a fuel supply amount and an oxygen concentration target value.

FIG. 5 is a graph showing a relationship between a fuel supply amount and a fan target rotation speed.

FIG. 6 is a flowchart showing processing of a control means (combustion controller).

[Explanation of symbols]

 2 Burner 3 Combustion unit 5 Ventilation means 9 Control means 10 Heating sensor 16 Temperature sensor

Claims (2)

(57) [Claims] A ventilation means (5) for supplying combustion air to a combustion part (3) having a burner (2), and an amount of air supplied to the combustion part (3) by the ventilation means (5) is detected. The heating type sensor (10) and the heating value of the heating type sensor (10) are started when the start of combustion is commanded, and the detection value of the heating type sensor (10) is supplied to the burner (2). Control means (9) for controlling said ventilation means (5) so as to be maintained at a target value determined in accordance with the fuel supply amount to be supplied. The operation of the ventilation means (5) is continued until a predetermined time elapses, and the heating type sensor (10)
A combustion device configured to check whether a detected value of the normal is normal. 2. A ventilation means (5) for supplying combustion air to a combustion section (3) having a burner (2), and an amount of air supplied to the combustion section (3) by the ventilation means (5) is detected. The heating type sensor (10) and the heating value of the heating type sensor (10) are started when the start of combustion is commanded, and the detection value of the heating type sensor (10) is supplied to the burner (2). Control means (9) for controlling said ventilation means (5) so as to be maintained at a target value determined according to the fuel supply amount to be supplied. Temperature sensor to detect (16)
The control means (9) continues the operation of the ventilation means (5) even after the combustion is stopped, and the temperature sensor (1)
A combustion device configured to check whether the detection value of the heating type sensor (10) is normal as the detected temperature of (6) becomes equal to or lower than a predetermined temperature.