JP2954005B2 - Ignition heater - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ignition heater, and more particularly to an ignition heater in which a resistor is formed on a support made of a ceramic material, and a gas or the like is ignited by energizing the resistor.

[0002]

2. Description of the Related Art There is known a gas heater which ignites a gas by energizing a resistor. As this ignition means, there is known a ceramic ignition heater which forms a resistor on a support made of a ceramic material and ignites a gas by energizing the resistor. If the flame goes out for some reason after the gas is ignited by such a ceramic ignition heater,
For safety reasons, it is required to quickly detect and stop the supply of gas and the like. Conventionally, for example, a frame sensor has been used as means for detecting the extinguishment of such a flame.

[0003] However, in the above-mentioned conventional gas heater, since the ignition means and the means for detecting the extinguishing are provided respectively, there is a disadvantage that the number of members arranged in the flame increases. In order to solve this drawback, the applicant has proposed in Japanese Patent Application No. 2-415791 a gas heater using a ceramic ignition heater, in which a gas is ignited by the ceramic ignition heater and a change in the resistance value of the ceramic ignition heater. A technology for detecting the extinguishment of a flame based on the above is disclosed.

[0004]

However, in the above disclosed technique, when the resistance value of the ceramic ignition heater is detected to detect the ignition or the extinguishing of the flame,
The resistance value is constantly measured, and when the measured resistance value falls below a predetermined value, it is determined that the flame has extinguished. Because of the variation, it was not possible to determine the extinguishing of the flame from a fixed resistance value, and there was a problem that a complicated mechanism was required for correcting the resistance value.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a ceramic ignition heater which does not require complicated adjustment of the resistance value due to variation in the resistance value of the ignition heater and can appropriately judge the extinguishing of the flame.

[0006]

According to the ignition heater of the present invention, the ceramic ignition heater, the interval setting means for setting a predetermined time interval, and the time of the flame being fired at the predetermined time interval set by the interval setting means. Resistance value detecting means for detecting the resistance value of the placed ceramic ignition heater, storage means for storing the resistance value of the ceramic ignition heater detected by the resistance value detecting means, and ceramic ignition heater detected by the resistance value detecting means And a resistance difference calculating means for calculating a difference between the resistance value of the ceramic ignition heater and the resistance value of the ceramic ignition heater detected at a predetermined time interval. Comparing means for comparing with a threshold value; and extinguishing detecting means for detecting extinguishing of the flame based on the result obtained from the comparing means. .

[0007]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing an embodiment of an ignition heater according to the present invention.

FIG. 1 is a block diagram showing an embodiment of an ignition heater according to the present invention. Ceramic ignition heater 40
Is as shown in FIGS. 2 to 4 and silicon nitride (Si
3N 4) A resistor 44 is formed by printing on a ceramic substrate 42 molded of ceramic, and fired together with another ceramic substrate 46 as shown in FIG. Further, as shown in FIG. 5, a power supply line 50 is connected to a resistor 44 via a metal fitting 48.

As shown in FIG. 1, a ceramic ignition heater
40 and a timer circuit 62 are connected, and the timer circuit 62 ignites the gas. A resistance value detection circuit 54 is connected to the ceramic ignition heater 40. As described later, the ceramic ignition heater 40 is heated, gas is supplied after a predetermined time, and after the ceramic ignition heater 40 is turned off after a predetermined time, the ceramic ignition heater 40 is turned off. The resistance value of the heater 40 is detected. An interval setting circuit 70 is connected to the resistance value detection circuit 54, and a predetermined time interval is set. The predetermined time interval is set, for example, to 30 seconds. The resistance value detection circuit 54 detects the resistance value at predetermined time intervals set by the interval setting circuit 70. The resistance value detected by the resistance value detection circuit 54 is stored in the resistance value memory 72. The resistance value difference calculation circuit 74 calculates the difference between the resistance value detected by the resistance value detection circuit 54 and the resistance value detected a predetermined time before.

A comparison circuit 78 is connected to the resistance value difference calculation circuit 74. The comparison circuit 78 compares the resistance value difference calculated by the resistance value difference calculation circuit 74 with the reference value of the resistance value difference stored in the reference value memory 76. The reference value memory 76 stores a reference value of a resistance value difference determined to be extinguished by the flame. This reference value may be, for example, 10 ohms. The extinguishing detection circuit 52 is connected to the comparing circuit 78, and the extinguishing detecting circuit 52 determines the extinguishing of the flame based on the comparison result sent from the comparing circuit 78. Although not shown, it is preferable to provide input means for inputting setting of a predetermined time interval, setting of a reference resistance value difference, and the like.

The control circuit 60 is a circuit section for controlling the entire operation, and includes an extinguishing detection circuit 52, a timer circuit 62, a switch
Connected to 68.

In each circuit section having the above connection relationship, the ceramic ignition heater 40 has excellent heat resistance, is used as an ignition device, and is also used as a sensor for detecting the extinguishing of a flame. The ceramic ignition heater 40 is
It is energized by the timer circuit 62 to reach a high temperature, is heated to a high temperature after a predetermined time has elapsed, and the gas supplied thereafter is ignited. The resistance value of the ceramic ignition heater 40 changes according to a change in temperature.

The resistance detection circuit 54 is a circuit for detecting the resistance of the ceramic ignition heater 40. Resistance value detection circuit
Since the resistance value of the ceramic ignition heater 40 detected by 54 changes depending on the temperature, the extinguishing of the flame is detected based on whether or not the difference between the resistance values at predetermined time intervals exceeds a predetermined threshold value. Instead of determining whether the difference between the resistance values exceeds a predetermined threshold value, it is determined whether the rate of decrease in the resistance value has exceeded a predetermined threshold value, for example, 5%. You may.

The extinguishing detection circuit 52 detects the extinguishing of the flame based on the result from the comparing circuit 78. Normally, when a flame is generated, the resistance value of the ceramic ignition heater 40 at 300 to 500 ° C. is detected. However, when the flame is extinguished, the temperature decreases and the detected resistance value decreases. For example, the extinguishing of the flame is detected when the temperature drops to about 100 ° C., but in the present invention, for example, 10 ohms is stored in the reference value memory 76 as the difference between the reference resistance values, and for example, every 30 seconds. The extinguishing of the flame is detected when the difference between the detected resistance values exceeds 10 ohms.

The control circuit 60 is advantageously constituted by a microprocessor, and is a control circuit which receives an input from the switch 68 or an extinguishing judgment signal sent from the extinguishing detection circuit 52 and controls each unit. The timer circuit 62 is configured by a timer that measures a predetermined time, and determines the passage of time for energizing the ceramic ignition heater 40 and controlling the opening and closing of the solenoid valve 64.

The solenoid valve 64 is provided in a nozzle pipe (not shown) and controls supply of gas to a gas burner. Also,
The switch 68 is a switch for the operator to input an instruction for ignition of the ignition heater.

When the operator inputs an instruction for ignition from the switch 68, the instruction is sent to the control circuit 60, and a control signal is output from the control circuit 60 to the timer circuit 62. Timer circuit 62
Thereby, the ceramic ignition heater 40 is energized and heated. When the energization of the ceramic ignition heater 40 is started, a control signal is output from the control circuit 60 to the timer circuit 62, and the timer circuit 62 measures a predetermined time. After a lapse of a predetermined time, for example, 10 seconds, the ceramic ignition heater 40 heats and reaches the ignition temperature of the gas, for example, 1200 ° C.
Then, when the timer circuit 62 measures the passage of 10 seconds, the timer circuit 62 opens the solenoid valve 64 to supply gas to the burner. Thereby, the gas is ignited and combustion is started.

After the solenoid valve 64 is opened to start combustion,
A control signal is output from the control circuit 60 to the timer circuit 62, and the timer circuit 62 measures a predetermined time. When the timer circuit 62 measures the elapse of a predetermined time, for example, 10 seconds, the energization of the ceramic ignition heater 40 is stopped by the timer circuit 62. As described above, the power supply to the ceramic ignition heater 40 is stopped when a predetermined time has elapsed after ignition, thereby preventing the ceramic ignition heater 40 from being deteriorated.

After the ignition, when the normal combustion is being performed, the flame strikes the ceramic ignition heater 40.
The ceramic ignition heater 40 maintains a state of being heated to a high temperature by the flame. However, when the flame is extinguished due to some cause, for example, wind, etc., the flame does not hit the ceramic ignition heater 40, so that the temperature of the ceramic ignition heater 40 drops rapidly. After ignition, as described above, the resistance value of the ceramic ignition heater 40 is detected at predetermined time intervals, for example, every 30 seconds, and the difference from the resistance value 30 seconds ago is compared with a predetermined threshold value, for example, 10 ohms. I do. If the difference between the resistance values exceeds 10 ohms, it is determined that the flame has extinguished due to a sharp decrease in the resistance value.

When the extinguishment detection circuit 52 detects extinguishment of the flame, the control circuit 60 closes the solenoid valve 64 in response to the signal from the extinguishment detection circuit 52, immediately stops the gas supply, and sets a timer circuit. The control signal is output to 62. As a result, the ceramic ignition heater 40 is energized again, and the ceramic ignition heater 40 is heated. As described above, when, for example, 10 seconds have elapsed after the start of energization of the ceramic ignition heater 40, the ceramic ignition heater 40 reaches the ignition temperature, for example, 1200 ° C.
Is opened and gas is supplied again.

In the gas heater, for example, three stages of combustion are performed: high heat, medium heat, and low heat. Therefore, for example, even when switching from high heat to medium heat or low heat or switching from medium heat to low heat, the difference in resistance value at a predetermined time interval may exceed the threshold value. In particular, when switching from high heat to low heat, there is a possibility that a difference in resistance value similar to the extinguishing of the flame may be exhibited. Therefore, the extinguishing detection circuit 52 may determine the extinguishing of the flame based on the difference in the resistance value by these switching.However, in these cases, the switching of the combustion stage is performed by the operator. An instruction may be input so as not to detect the disappearance.

As described above, according to the ignition heater of this embodiment, the ceramic ignition heater 40 is used as the ignition means and also as the flame extinguishing detection means. In this configuration, the difference between the resistance values of the ceramic ignition heaters 40 at predetermined time intervals is calculated, and the flame extinguishing is determined based on the calculated value. Since the resistance value does not need to be corrected in consideration of the variation in the resistance value of the ceramic ignition heater 40 as in the case where the flame is extinguished, the extinguishing of the flame can be appropriately determined. Therefore, the extinguishing of the flame can be easily detected without adding a complicated mechanism.

Although the above description is a preferred embodiment of the present invention, the present invention is not limited to the above embodiment, and various modifications can be made. For example, it is needless to say that the predetermined time interval and the reference threshold value of the resistance value are not limited to the above values.

[0024]

According to the ignition heater of the present invention, the ceramic ignition heater is used as the ignition means and also as the flame extinguishing detection means. In this configuration, the difference between the resistance values of the ceramic ignition heater at predetermined time intervals is calculated to determine the extinguishing of the flame. Since it is not necessary to correct the resistance value in consideration of the variation in the resistance value of the heater 40, it is possible to appropriately determine the extinguishing of the flame. Therefore, the extinguishing of the flame can be easily detected without adding a complicated mechanism.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of an ignition heater according to the present invention.

FIG. 2 is a front view showing a ceramic heater.

FIG. 3 is a perspective view showing a manufacturing process of the ceramic heater of FIG. 2;

FIG. 4 is a perspective view showing a manufacturing process of the ceramic heater of FIG. 2;

FIG. 5 is a diagram showing a configuration of the ceramic heater of FIG. 2;

[Explanation of symbols]

 Reference Signs List 40 ceramic heater 42 ceramic substrate 44 resistor 50 power supply line 52 extinction detection circuit 54 resistance value detection circuit 60 control circuit 62 timer circuit 64 solenoid valve 66 power supply 68 switch 70 interval setting circuit 72 resistance value memory 74 resistance value difference calculation circuit 76 Reference value memory 78 Comparison circuit

Continuation of the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) F23Q 7/22 605 F23Q 7/22 615

Claims (1)

(57) [Claims] 1. A ceramic ignition heater, interval setting means for setting a predetermined time interval, and detecting a resistance value of the ceramic ignition heater arranged in the flame at a predetermined time interval set by the interval setting means. Resistance value detecting means, storage means for storing the resistance value of the ceramic ignition heater detected by the resistance value detecting means, resistance value of the ceramic ignition heater detected by the resistance value detecting means, and the storage means A resistance value difference calculating means for calculating a difference between the resistance value and a resistance value before a predetermined time stored in the memory, and comparing the resistance value difference of the ceramic ignition heater detected at the predetermined time interval with a predetermined threshold value Comparing means for detecting the extinguishing of the flame based on the result obtained from the comparing means. Fire heater.