JP3364506B2 - 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 unit for supplying combustion air to a combustion unit equipped with a burner, a heating type sensor for detecting the amount of air supplied to the combustion unit by the ventilation unit, and the heating type. And a control unit that controls the ventilation unit so that the detection value of the sensor is maintained at a target value determined according to the amount of fuel supplied to the burner.

[0002]

2. Description of the Related Art As a heating type sensor used in such a combustion apparatus, there is, for example, a ceramic oxygen sensor. This oxygen sensor indirectly detects the amount of air supplied to the combustion section by detecting the oxygen concentration in the combustion exhaust gas. Generally, in the above-mentioned heating type sensor, a sensor element has a predetermined temperature (500 to 80) called an activation temperature in view of its operating principle.
It is used after being heated to about 0 ° C.), and a heater therefor is usually provided in a state of being heated by a constant power.

The control means is constructed so as to control the ventilation means by using the detected value of the heating type sensor as it is.

[0004]

However, since the above-mentioned heating type sensor changes its output value when the sensor element temperature changes, it depends on the usage condition of the subject, such as a household gas water heater. When the exhaust gas temperature changes, the temperature change causes a temperature change in the sensor element of the heating sensor. As a result, as shown by 61 and 62 in FIG. 8, even if the oxygen concentration in the exhaust gas is the same, the detection value of the heating type sensor changes in accordance with the temperature change of the sensor element, and it is appropriate. There is a problem that the air-fuel ratio control cannot be performed. In addition, FIG.
The change in the detection value of the heating sensor when the ambient temperature changes from T1 to T1 ′ (T1> T1 ′) is shown. That is, when the oxygen concentration is 15% and the ambient temperature changes from T1 to T1 ', the detection value of the heating sensor changes from Ia to Ia'. In the figure, Vk is a monitoring voltage of the heating type sensor. The present invention has been made in view of the above circumstances, and an object thereof is to perform appropriate air-fuel ratio control in a combustion device in which exhaust gas temperature changes.

[0005]

A combustion apparatus according to the present invention comprises a ventilation means for supplying combustion air to a combustion section equipped with a burner, and a heating type sensor for detecting the amount of air supplied to the combustion section by the ventilation means. And a control means for controlling the ventilation means so that the detection value of the heating sensor is maintained at a target value determined according to the fuel supply amount supplied to the burner, the first of which is provided. Characteristic configuration, the control means, based on the ambient temperature of the heating sensor,
It is configured to correct the detection value of the heating sensor. In a second characteristic configuration, the control means estimates the ambient temperature of the heating sensor based on the fuel supply amount supplied to the burner, and the heating sensor of the heating sensor is estimated based on the estimated ambient temperature. It is configured to correct the detection value. A third characteristic configuration is that the heating type sensor is a limiting current type oxygen sensor.
In a fourth characteristic configuration, the control unit increases the monitoring voltage of the heating type sensor including the limiting current type oxygen sensor as the ambient temperature of the heating type sensor including the limiting current type oxygen sensor decreases. It is configured to be changed and set.

[0006]

According to the first characteristic configuration, the value of the air supply amount detected by the heating type sensor is corrected based on the ambient temperature of the heating type sensor so as to be closer to the actual air supply amount, and the corrected air is corrected. The ventilation means is controlled so that the supply amount becomes a target value determined according to the fuel supply amount supplied to the burner. According to the second characteristic configuration, the ambient temperature (exhaust gas temperature) of the heating type sensor corresponds to the change in the fuel supply amount supplied to the burner (that is, the change in the gas proportional valve opening degree) as shown in FIG. 7. Therefore, the ambient temperature of the heating sensor is estimated based on the amount of fuel supplied to the burner,
The value of the air supply amount detected by the heating sensor is corrected based on the estimated ambient temperature. Then, the ventilation means is controlled so that the corrected air supply amount becomes a target value determined according to the fuel supply amount supplied to the burner. According to the third characteristic configuration, it is possible to indirectly detect the air supply amount to the combustion section by detecting the oxygen concentration in the combustion exhaust gas with the limiting current type oxygen sensor. That is, if the amount of air supplied to the combustion section is excessive, the oxygen concentration in the exhaust (remaining amount) is large, and conversely, if the amount of air supplied is insufficient, the oxygen concentration in the exhaust (remaining amount) is Get smaller. According to the fourth characteristic configuration, the monitoring voltage of the heating type sensor is changed and set to be higher as the ambient temperature of the heating type sensor configured using the limiting current type oxygen sensor becomes lower. That is, as shown in FIG. 8, the ambient temperature changes from T1 to T1 ′.
When (T1> T1 ') is changed, the monitoring voltage of the heating type sensor is changed from Vk to Vk', and the ambient temperature is changed from T1 'to Tk.
When it changes to 1, the monitoring voltage of the heating sensor is changed from Vk 'to V
Change to k.

[0007]

According to the first characteristic configuration, the value of the air supply amount detected by the heating type sensor can be brought close to the actual air supply amount based on the ambient temperature of the heating type sensor. Even if the temperature changes, it is possible to detect a value that is close to the actual air supply amount, so that it is possible to perform more appropriate air-fuel ratio control than in the conventional case.
According to the second characteristic configuration, the atmosphere temperature of the heating sensor can be estimated without installing a temperature sensor or the like and measuring the atmosphere temperature of the heating sensor. Therefore, while simplifying the equipment, Even now, it has become possible to perform proper air-fuel ratio control. According to the third characteristic configuration, since the oxygen concentration in the exhaust gas is detected by the limiting current type oxygen sensor to detect the air supply flow to the combustion section, it is possible to accurately determine whether the air-fuel ratio is appropriate. Easy to judge. According to the fourth characteristic configuration,
Since the monitoring voltage of the heating type sensor composed of the limiting current type sensor is changed according to the change of the ambient temperature, the detection temperature range can be expanded. That is, the voltage Vk applied to the heating sensor as the monitoring voltage of the heating sensor is set in a stable region where the detection value I of the heating sensor does not change, as shown in FIG. Even if it becomes V
If it is fixed at k, the voltage Vk will be out of the stable region at an oxygen concentration of 15%. Therefore, the detection temperature range can be further expanded by further changing the monitoring voltage of the heating sensor. Further, since the monitoring voltage of the heating type sensor is changed according to the change of the ambient temperature, the life of the heating type sensor can be extended. In other words, as the deterioration of the heating type sensor progresses, as shown in FIG.
The current value changes as shown in. In the figure, 61 is the characteristic of the heating sensor when the ambient temperature is T1 (before deterioration progresses).
62 indicates the characteristics of the heating type sensor when the ambient temperature is T1 ′ (before deterioration progresses). Also, 6
3 and 64 show the characteristics of the heating type sensor when the deterioration progresses at the atmospheric temperatures T1 and T1 ′, respectively. Therefore, in the characteristics of the heating sensor after the deterioration progresses when the ambient temperature is T1 ', if the monitoring voltage is fixed at Vk as it is, the voltage Vk deviates from the above stable region at the oxygen concentration of 15%. This shortens the life of the heating sensor. Therefore, the life of the heating sensor can be extended by changing the monitoring voltage of the heating sensor from Vk to Vk '.

[0008]

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. As shown in FIG. 1, the water heater according to the present embodiment includes, in a cylindrical case 1, a combustion section 3 having a burner 2 and a fin tube type heat exchanger 4 for heating water by its high temperature exhaust. A discharge side of a fan 5 as a ventilation means for supplying combustion air to the combustion section 3 is connected to the lower end of the cylindrical case 1, and an exhaust passage 6 is connected to the upper end of the cylindrical case 1.

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 is a proportional valve drive circuit 9
By changing the exciting current of the solenoid proportional valve 8 at a, the opening of the solenoid proportional valve 8 is controlled, and the fuel supply amount is adjusted accordingly. Further, the combustion controller 9 adjusts the fuel supply amount as described above based on the deviation between the set hot water temperature set by the setting means R and the hot water temperature detected by the hot water temperature detecting means S, and the hot water temperature is adjusted. To control.

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

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

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

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

The energization of the heater 11e is controlled by the heater control circuit 9c in the combustion controller 9.
Further, the ambient temperature of the oxygen sensor 10 is detected by the temperature sensor 16, and the detected value is input to the combustion controller 9. Furthermore, the detection value of the oxygen sensor 10 is input to the combustion controller 9. Therefore, in the air-fuel ratio calculation circuit 9d in the combustion controller 9, the detection value of the oxygen sensor 10 is corrected based on the detection value of the temperature sensor 16 to calculate the actual oxygen concentration. That is, as shown in FIG. 8, if the atmospheric temperature is T1 and the oxygen sensor is Ia, the oxygen concentration is 1
5%, the ambient temperature is T1 ', and the oxygen sensor is I
If it is a ', the oxygen concentration is 15%.
An oxygen concentration value corresponding to the ambient temperature and the oxygen sensor output is calculated. The rotation speed of the fan 5 is controlled so that the calculated oxygen concentration is maintained at a target value determined according to the fuel supply amount to the burner 2, and the air supply amount to the combustion unit 3 is adjusted. . The target value of the oxygen concentration is a proper 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 instructed will be described based on the flowchart of FIG. As the start of combustion is commanded, that is, when the hot water tap (not shown) is opened and the water flow switch 15 is turned on, the oxygen sensor 10 is energized (the heater 11e is energized and the monitoring voltage is applied). ) And the operation of the fan 5 are started (process (a)). The main solenoid valve, the solenoid proportional valve 8 and other gas valves are opened, and the burner 2 is ignited. However, in actuality, the opening of the gas valve and the ignition of the burner 2 are performed about 1 second later than the operation of the fan 5.

It takes about 1 minute until the heater 11e heats the oxygen sensor 10 (sensor element 11) to an appropriate state, that is, until it reaches a stable temperature (for example, 500 ° C.). Therefore, during this period, the rotation speed of the fan 5 is controlled so as to reach the target rotation speed that is determined according to the fuel supply amount to the burner 2 (process (B)). That is, it is, so to speak, 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 an experiment, and has a proportional relationship as shown in FIG. The fan 5 is provided with a hall element (not shown) for detecting the actual rotation number, and the detection signal is input to the combustion controller 9.

The combustion controller 9 has its internal timer 9
The time during which the temporary control is performed is managed by e. The internal timer 9e is reset and starts counting when combustion starts. Then, the internal timer 9e causes the predetermined time (t
_When it reaches ₁ ), the control of the fan 5 is transferred from the above-mentioned temporary control to the above-mentioned control based on the detected value of the oxygen sensor 10 and the detected value of the temperature sensor 16. Further, as described above, the fuel supply amount is controlled by adjusting the opening of the solenoid proportional valve 8 (process (c)). Here, the predetermined time (t ₁ ) is a time (for example, one minute) until the oxygen sensor 10 is heated to a proper state, which is determined in advance by an experiment.

When the hot water tap is closed and the water flow switch 15 is turned off, the gas valve is closed and combustion is stopped (process (d)). The fan 5 continues to operate, and performs the post-purge, that is, the 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 the internal timer 9e reaches the predetermined time (t ₂ ). During this time, when the hot water tap is opened again and the water flow switch 15 is turned on, combustion is restarted. That is, after the gas valve is opened and the burner 2 is ignited (process (e)), the process moves to the above-mentioned process (c). When a predetermined time (t ₂ ) has elapsed, the fan 5 is stopped (processing (f)), the energization of the oxygen sensor 10 is stopped,
Stop the operation.

Other examples will be listed below. 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 above embodiment, the detection value of the oxygen sensor 10 is corrected based on the detection value of the temperature sensor 16, but the oxygen sensor 10 is corrected based on the fuel supply amount supplied to the burner 2.
It is also possible to estimate the ambient temperature and to correct the detection value of the oxygen sensor 10 based on the estimated ambient temperature. That is, the relationship between the opening of the solenoid proportional valve 8 indicating the amount of fuel supplied to the burner 2 and the ambient temperature of the heating sensor 10 changes as shown in FIG.
Based on the above, the ambient temperature of the oxygen sensor 10 can be estimated from the opening of the solenoid proportional valve 8. As described above, the ambient temperature may be estimated as follows. Detection means for detecting the amount of water supplied to the heat exchanger 4 and the water temperature is provided, and the amount of water supplied to the heat exchanger 4 is added based on the detected amount of water, the water temperature, and the hot water temperature detected by the hot water temperature detecting means S. The calorific value may be calculated, and the ambient temperature of the oxygen sensor 10 may be estimated from the calculated calorific value. In the above embodiment, the monitoring voltage of the oxygen sensor 10 is VK.
However, the monitoring voltage of the oxygen sensor 10 may be set to be higher as the ambient temperature of the oxygen sensor 10 is lower. That is, as shown in FIG. 8, when the atmospheric temperature changes from T1 to T1 ′ (T1> T1 ′), the monitoring voltage of the oxygen sensor 10 is changed from Vk to Vk ′, and the atmospheric temperature changes from T1 ′ to T1. Then, the monitoring voltage of the oxygen sensor 10 is changed from Vk 'to Vk. Thereby, the detection temperature range of the oxygen sensor 10 can be expanded, or the life of the oxygen sensor 10 can be extended. In the figure, 61 indicates the characteristics of the oxygen sensor 10 when the ambient temperature is T1 (before deterioration progresses), and 62
Shows the characteristics of the oxygen sensor 10 when the ambient temperature is T1 ′ (before the deterioration progresses). Reference numerals 63 and 64 show the characteristics of the oxygen sensor 10 when the deterioration progresses at the atmospheric temperatures T1 and T1 ′, respectively. As the heating type sensor, various types such as a hot wire wind velocity sensor can be applied in addition to the oxygen sensor 10 described in the above embodiment.

It should be noted that reference numerals are added to the claims for convenience of comparison with the drawings, but the present invention is not limited to the configurations of the accompanying drawings by the entry.

[Brief description of 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 the processing of the control means (combustion controller).

FIG. 7 is a graph showing the relationship between the gas proportional valve opening and the exhaust gas temperature according to another embodiment.

FIG. 8 is a characteristic diagram of a ceramic oxygen sensor according to another embodiment.

[Explanation of symbols] 2 burners 3 Combustion section 5 ventilation means 9 Control means 10 Heating type sensor

─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Kazuyuki Morimoto 1-52, Minami-shi Oka, Minato-ku, Osaka, Osaka 1-52 Harman Co., Ltd. (72) Inventor Hiroshi Kamiya 1-1-52 Oka, Minami-shi, Minato-ku, Osaka, Osaka Issue Harman Co., Ltd. (56) Reference JP-A-5-256442 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) F23N 1/02 103 F23N 5/24 113 G01N 27 / 26 361 G01N 27/41

Claims (4)

(57) [Claims] 1. A ventilation means (5) for supplying combustion air to a combustion part (3) provided with a burner (2), and an air supply amount to the combustion part (3) by the ventilation means (5) is detected. Heating sensor (10), and the heating sensor (10)
And a control means (9) for controlling the ventilation means (5) so that the detected value of (1) is maintained at a target value determined according to the amount of fuel supplied to the burner (2). The combustion device configured to correct the detection value of the heating sensor (10) based on the ambient temperature of the heating sensor (10). 2. The control means (9), based on the amount of fuel supplied to the burner (2),
The combustion apparatus according to claim 1, which is configured to estimate an ambient temperature of the heating sensor (10) and correct a detection value of the heating sensor (10) based on the estimated ambient temperature. . 3. The combustion apparatus according to claim 1, wherein the heating type sensor (10) is a limiting current type oxygen sensor. 4. The control means (9) is configured to change and set the monitoring voltage of the heating type sensor (10) to be higher as the ambient temperature of the heating type sensor (10) becomes lower. Combustion device as described.