JPH01272078A - Ceramic heater - Google Patents

Abstract

PURPOSE:To simplify the circuit structure when detecting the temperature of a ceramic heater for control by providing multiple resistors and using one of them as a heating resistor and the other as a temperature detecting resistor. CONSTITUTION:When the resistor 3 of a ceramic heater 1 is excited by a current controller 42 as an ignition action, the temperature of the heater 1 is detected by a resistor 4, the heater 1 is controlled at the fixed temperature based on it. When the temperature of the heater 1 is detected as 1200 deg.C, for example, solenoid valves 21 and 22 are opened, fuel is fed to a burner group 11a. When the air-fuel mixture fed to the burner group 11a is ignited and the temperature of the heater 1 rises and the detected resistance value of the resistor 4 is abruptly increased, this change is detected by a resistance value change detecting unit 44, and an ignition signal is outputted. The excitation to the resistor 3 is stopped by the ignition signal, the ignition action is completed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application in Industry] The present invention relates to a ceramic heater used for igniting various fuels or for heating various types.

[Prior Art] Ceramic heaters have a printed heating element sealed within a ceramic substrate, and have excellent chemical durability against chemicals, heat resistance, thermal shock resistance, and the like. For this reason, in order to generate high temperatures, commercial power sources are often used directly to supply large currents.

Furthermore, in order to improve the temperature increase characteristics after the start of energization, there is a rapid temperature increase type ceramic heater in which the resistance value of the heating element is set to be small with respect to the applied voltage.

[Problems to be Solved by the Invention] However, when the temperature of a ceramic heater is to be precisely controlled, or when other controls are performed using a microcomputer etc. based on the temperature, the temperature cannot be controlled based on the voltage or current applied to the heating element. Because it is necessary to detect the There's a problem.

An object of the present invention is to provide a ceramic heater whose circuit configuration can be simplified when detecting the temperature of the ceramic heater and performing some kind of control.

[Means for Solving the Problems] The ceramic heater of the present invention includes a plurality of resistors provided inside or on the surface of a ceramic sintered body, one of which is used as a heat generating resistor and the other as a temperature detecting resistor. as a technical means.

[Operation and Effects of the Invention] The ceramic heater of the present invention is provided with a plurality of resistors, and one resistor functions as a heat generating resistor and the other resistor functions as a temperature detecting resistor. and can be used. Therefore, when controlling the heat generation temperature, the circuit configuration can be simplified by using one resistor for input and the other for output, so the current flowing through the heat generation resistor can be appropriately controlled. can do.

In addition, when detecting the temperature of the ceramic heater to perform other controls, one of the resistors can be used as a temperature detection resistor and can be installed independently from the heat generation circuit. Temperature can be detected regardless of the energization state of the resistor, and other controls can be easily performed based on the temperature.

[Example] Next, a ceramic heater of the present invention will be described based on an example shown in the drawings.

FIG. 1 shows a ceramic heater 1 according to the present invention.

This ceramic heater 1 is made of silicon nitride (Si).

Resistors 3.4 are printed on both sides of a thin plate-shaped ceramic substrate 2 formed by dry pressing N4) powder.
-L, and the same ceramic substrate 5 as above on both sides.
．． Each resistor 3.4 is completely sealed by a ceramic substrate 2.5.6.

A plurality of metallized portions are formed on the side surface of the integrated ceramic substrate 2.5.6 and are electrically connected to each of the resistors 3.4, and these metallized portions are provided with terminals 7.
8.9.10 is fixed. These terminals are provided to connect the resistor 3.4 printed on the ceramic substrate 2 with an external circuit, the terminal 7.8 is connected to the resistor 3, and the terminal 9.10 is connected to the resistor 4. and conduction treatment.

The resistor 3 is provided for generating heat, and can be heated to a maximum of 1400° C. by energization. - The paper antibody 4 is provided for detecting the temperature of the ceramic heater 1, and is printed as an independent pattern that is not electrically connected to the resistor 3. Here, the resistor 3 and the resistor 4 have the same characteristics.

Next, the function of the ceramic heater 1 will be explained based on a gas water heater using the ceramic heater 1 for ignition.

Inside the water heater case 11 of the gas water heater schematically shown in FIG. 2, there is provided a two-bar burner group 11a in which a plurality of ribbon burners are arranged in two rows.
Combustion air is supplied by the nozzle 12, mixed with the fuel gas supplied from the nozzle 13 and burned, and the combustion gas is discharged from the exhaust port 12a. Near the burner group 11a,
A ceramic heater 1 for ignition and a thermocouple 15 for detecting flame temperature are provided.

This ceramic heater 1 is of a rapid temperature rise type in which the resistance value of a resistor 3 provided especially for heat generation is set to be small with respect to the applied voltage. Therefore, if the heat generation temperature due to energization exceeds about 1400°C, self-melting will occur, so the current is controlled by a control circuit 40, which will be described later, so that it does not exceed about 1200°C. Further, the temperature detection resistor 4 is used not only to detect the temperature of the ceramic heater 1 but also as a flame detection means for the burner group 11a.

The gas pipe 20 that guides the fuel gas to the nozzle 13 is provided with a main solenoid valve 21, a main solenoid valve 22, and a proportional valve 23 for adjusting the fuel supply amount from upstream, and the gas pipe 20 branches downstream of the proportional valve 23. The burner group 1 is connected to one side of the branched gas pipe 20 that guides fuel gas to each of the two burner groups 11a.
A solenoid valve 24 is provided to combust only the series 1a.

The wood pipe 30 communicates with a supply pipe 31 and a hot water supply pipe 31a connected to a water supply source and a hot water supply inlet (not shown), respectively, and a heat exchanger 3 provided in the water heater case 11.
2 and a bypass pipe 32a, and the proportion of water passing through each of the heat exchanger 32 and the bypass pipe 32a is adjusted by a bypass valve 33.

On the other hand, the supply pipe 31 includes a water spray control valve 34 and a water flow sensor 35.
A heat exchange thermistor 37 is provided downstream of the heat exchanger 32, and an outlet water temperature thermistor 38 is provided in the hot water supply pipe 31a.

The control circuit 40 is centered around a microcomputer 40a, as shown in FIG. 3, and is operated by a controller 41.

The control circuit 40 starts combustion in a predetermined sequence in response to an operation signal from the controller 41, and controls the combustion amount and hot water supply based on the temperature set by the controller 41, the amount of water input, and the temperature detected by each thermistor. control.

Furthermore, the ratio of combustion air to fuel gas is corrected based on the output voltage of the thermocouple 15 so that the air-fuel mixture is supplied to the burner group 11a at an appropriate air-fuel ratio. Furthermore, in order to perform ignition operation by controlling the current flowing to the resistor 3 of the ceramic heater 1, and to perform flame detection based on the resistance value of the resistor 4 of the ceramic heater 1, a current control unit 42, a resistance value Each functional unit includes a detection unit 43 and a resistance value change detection unit 44.

The current control unit 42 controls the current flowing to the resistor 3 based on the control of the microcomputer 40a to maintain its temperature at about 1200°C.
This is a circuit that energizes the device to maintain it.

The resistance value detection unit 43 controls the current flowing to the resistor 3 based on the temperature of the ceramic heater 1.
This is the part where the resistance value of is determined from the applied voltage and current value.

The resistance value change detection section 44 is provided to detect the flame of the burner group 11a based on the temperature of the ceramic heater 1. In the ceramic heater 1, the resistance value of the resistor 4 changes depending on its temperature. Therefore, for example, when the temperature becomes higher than that due to self-heating caused by the burner group 11a, the resistance value changes, so that ignition can be detected. At this time, in order to detect flames more quickly, instead of detecting flames based on the resistance value itself, the change in resistance value that occurs with ignition is detected by differentiating the change in resistance value over time. flame can be detected. Therefore, in this case, when the temperature of the ceramic heater 1 changes due to ignition and the resistance value of the resistor 4 changes accordingly, what value will the resistance value of the resistor 4 become due to the change in resistance value? regardless of,
Can be detected as ignition.

Furthermore, by simultaneously outputting an ignition signal to the microcomputer 40a, the operation of the gas water heater can be shifted to post-ignition control.

In the microcomputer 40a, the temperature of the ceramic heater 1 is calculated based on the resistance value of the resistor 4 detected by the resistance value detection unit 43, and the temperature of the ceramic heater 1 is calculated based on the calculated value.
energization is performed. Furthermore, the resistance value change detection section 44
When a predetermined change in resistance value is detected, an ignition signal is obtained, and at the same time, the current supply by the current control section 42 is stopped.

In the gas water heater configured as described above, when the user sets the hot water temperature using the controller 41, turns on the operation switch, and operates the hot water tap (not shown), water passes through the water pipe 30, and a predetermined temperature is set by the control circuit 40. When the sequence starts, the blower 1112 rotates to supply combustion air, and the current control unit 42 energizes the resistor 3 of the ceramic heater 1 as an ignition operation, the resistor 4 causes the temperature of the ceramic heater 1 to increase. Based on the detected temperature, the ceramic heater 1 is controlled to a constant temperature.

If the detected temperature of the ceramic heater 1 is, for example, 120
When the temperature is detected as 0°C, each electromagnetic valve 21, 22 is opened and fuel is supplied to the burner group 11a.

When the air-fuel mixture supplied to the burner group 11a is ignited, the temperature of the ceramic heater 1 rises, and the resistance value detected by the resistor 4 increases rapidly, this change is detected by the resistance value change detection unit 44. In response to the ignition signal 6, the ignition signal is outputted, the current supply to the resistor 3 is stopped, and the ignition operation is completed. At the same time, each electromagnetic valve 21, 22 is held open.

Conversely, if the ignition signal is not obtained, each electromagnetic valve 21, 22 is closed after a predetermined period of time, and the resistor 3 is closed.
Since power supply to the ceramic heater 1 is also stopped, the temperature of the ceramic heater 1 decreases.

After ignition, after a certain period of time has elapsed, combustion amount control and water amount control are performed according to the set temperature of the controller 41 and signals from each sensor.

Furthermore, if a misfire occurs for some reason, the resistance value of the resistor 4 decreases, and the misfire can be detected from the rate of change.

In this embodiment, the case where the resistor 3 and the resistor 4 have the same characteristics is shown, but only the resistance value of the resistor 3 provided for heat generation is reduced, and the resistance value of the resistor 3 provided for temperature detection is reduced. By increasing the resistance value of No. 4, the rise of heat generation can be made faster, and the sensitivity of temperature detection can also be improved.

In addition, in this case, by changing the size of each terminal provided for connection with each resistor,
It is a good idea to prevent incorrect connections.

In this example, a rapid temperature rise type ceramic heater was used, but the resistance value is sufficient for the applied voltage, and the heat generation temperature can be controlled at a constant temperature without current control. A type of ceramic heater is also effective when performing control based on the temperature of the ceramic heater.

A second embodiment and a third embodiment of the ceramic heater 1 of the present invention are shown in FIGS. 4 and 5, respectively.

In these embodiments, a heat generating resistor 3 and a temperature detecting resistor 4 are printed on the same surface of the ceramic substrate 2. In the second embodiment shown in FIG. 4, a resistor 4 is printed inside the resistor 3, and the resistors 3 and 4 are provided completely independently. In the third embodiment, a resistor 3 and a resistor 4 are connected in series, and a conductor pattern 3b electrically connected to a current-carrying terminal (not shown) is connected to the connecting portion 3a.

As described above, in the present invention, since a plurality of resistors are provided, the energizing circuit for heater heating and the temperature detection circuit can be separated, and the circuit configuration is simplified. The circuit configuration can also be simplified when performing other controls based on the temperature.

In this example, a ceramic heater is used as an ignition device for a gas water heater, but it can also be used to heat liquids such as water, diesel oil, kerosene, etc., or to heat an engine or intake air to an engine in a vehicle. Temperature detection, temperature control, etc. can be easily performed in ceramic heaters as well.

[Brief explanation of the drawing]

Fig. 1 is a partially cutaway perspective view showing the structure of the ceramic heater of the present invention, Fig. 2 is a schematic diagram showing the configuration of the gas water heater of the present embodiment, and Fig. 3 is the control of the present embodiment. A block diagram showing the circuit, and FIGS. 4 and 5 are cross-sectional views of the printed surface of a resistor showing a part of the second and third embodiments of the ceramic heater of the present invention, respectively. In the figure, 1... Ceramic heater, 3... Resistor (heat generating resistor), 4... Resistor (temperature detection resistor).

Claims (1)

[Claims] 1) A ceramic heater characterized in that a plurality of resistors are provided inside or on the surface of a ceramic sintered body, one of which is used as a heat generating resistor and the other as a temperature detecting resistor.