Heater control device and heating device

Abstract

To provide a heater control device and a heating device capable of suppressing breakage of a ceramic heater.SOLUTION: A heater control device controls a ceramic heater that is disposed in a flow path and heats a liquid up to target temperature while monitoring temperature of the liquid flowing through the flow path. The heater control device is capable of acquiring a resistance value of the ceramic heater and reduces an output of the ceramic heater based on a magnitude of the resistance value or secular change in the resistance value in a state where the ceramic heater is controlled so as to increase temperature of the liquid.SELECTED DRAWING: Figure 5

Description

Technical Field

[0001] The present disclosure relates to a heater control device and a heating device.

Background Art

[0002] Conventionally, a heat exchange unit described in Japanese Patent Application Laid-Open No. 2006-236617 (Patent Document 1 below) has been known as a heating device for heating a fluid. This heat exchange unit is applied to a warm water washing toilet seat or the like, and includes a heat exchanger that stores washing water and a ceramic heater attached to the heat exchanger. The ceramic heater has a cylindrical shape and includes a heating element formed in a meandering shape inside. When water flows through the cylindrical ceramic heater with an electric current flowing through the heating element, warm water is generated.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] Consider a case where the amount of water in contact with the ceramic heater decreases due to water leakage or the like in a heating device provided with the ceramic heater as described above. When the amount of water in the flow path of the heating device decreases, a part of the ceramic heater comes into contact with air. Due to the difference in thermal conductivity between water and air, the part of the ceramic heater in contact with air accumulates more heat and becomes overheated compared to the part of the ceramic heater in contact with water. When water is applied to the overheated part of the ceramic heater, a thermal shock occurs in the part, and the ceramic heater may be damaged.

[0005] The present disclosure has been completed based on the above circumstances, and an object thereof is to provide a heater control device and a heating device capable of suppressing breakage of a ceramic heater.

Means for Solving the Problems

[0006] The heater control device of the present disclosure is a heater control device that controls a ceramic heater disposed in the flow path to heat the liquid to a target temperature while monitoring the temperature of the liquid flowing through the flow path, and the resistance value of the ceramic heater can be obtained. In a state where the ceramic heater is controlled to raise the temperature of the liquid, the output of the ceramic heater is reduced based on the magnitude of the resistance value or the change in the resistance value over time.

[0007] Further, the heating device of the present disclosure is a heating device including a flow path through which a liquid flows, a ceramic heater disposed in the flow path, a measuring device that measures the resistance value of the ceramic heater, and the above heater control device.

Effects of the Invention

[0008] According to the present disclosure, it is possible to provide a heater control device and a heating device capable of suppressing breakage of a ceramic heater.

Brief Description of the Drawings

[0009]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

MODE FOR CARRYING OUT THE INVENTION

[0010] [Description of Embodiments of the Present Disclosure] First, the embodiments of the present disclosure will be listed and described. (1) The heater control device of the present disclosure is a heater control device that controls a ceramic heater disposed in the flow path to heat the liquid to a target temperature while monitoring the temperature of the liquid flowing through the flow path, and is capable of acquiring the resistance value of the ceramic heater. In a state where the ceramic heater is controlled to raise the temperature of the liquid, the output of the ceramic heater is decreased based on the magnitude of the resistance value or the change in the resistance value over time.

[0011] According to such a configuration, when the amount of liquid in the flow path decreases, the output of the ceramic heater can be decreased to suppress overheating of the ceramic heater.

[0012] (2) In the heater control device according to (1), when the resistance value becomes equal to a first threshold value which is the resistance value when a part of the ceramic heater is in contact with gas, in a state where the ceramic heater is controlled to raise the temperature of the liquid, when the resistance value becomes equal to or greater than the first threshold value, it is preferable to decrease the output of the ceramic heater by multiplying the output of the ceramic heater by a first coefficient less than 1 within a range where the temperature of the liquid can be raised.

[0013] According to such a configuration, when a part of the ceramic heater is in contact with gas, overheating of the ceramic heater can be suppressed while efficiently raising the temperature of the liquid.

[0014] (3)(2)'s heater control device controls the ceramic heater to raise the temperature of the liquid. When the resistance value becomes equal to a second threshold value greater than the first threshold value, and when the resistance value becomes equal to or greater than the second threshold value while the ceramic heater is being controlled to raise the temperature of the liquid, it is preferable to significantly reduce the output of the ceramic heater by multiplying the output of the ceramic heater by a second coefficient smaller than the first coefficient.

[0015] According to such a configuration, when substantially the entire ceramic heater is in contact with the gas, overheating of the ceramic heater can be suppressed.

[0016] (4) The heater control device according to any one of (1) to (3) controls the ceramic heater to raise the temperature of the liquid. When the variation within a predetermined period of a plurality of the resistance values acquired over time becomes equal to or greater than a third threshold value, it is preferable to reduce the output of the ceramic heater within the range where the liquid can be heated.

[0017] According to such a configuration, by appropriately setting the third threshold value, when a part of the ceramic heater is in contact with the gas, overheating of the ceramic heater can be suppressed while efficiently heating the liquid.

[0018] (5) The heating device of the present disclosure includes a flow path through which a liquid flows, a ceramic heater disposed in the flow path, a measuring device that measures the resistance value of the ceramic heater, and the heater control device according to any one of (1) to (4).

[0019] According to such a configuration, a heating device capable of suppressing damage to the ceramic heater can be provided.

[0020] (6) The heating device according to (5) is mounted on a vehicle.

[0021] [Details of Embodiment 1 of the Present Disclosure] Embodiment 1 of the present disclosure will be described with reference to FIGS. 1 to 6. It should be noted that the present disclosure is not limited to these examples, but is defined by the claims, and is intended to include all modifications within the meaning and scope equivalent to the claims.

[0022] <Heating device> The heating device 10 of the present disclosure is a device that heats a liquid such as water. The heating device 10 is installed in a vehicle such as an electric vehicle (EV), and is used for heating the passenger compartment and keeping the battery warm. FIG. 1 illustrates a passenger compartment heating device 1 in which the heating device 10 is used. The passenger compartment heating device 1 includes a heating device 10, a circulation circuit 2, a heat exchanger 3 provided in the circulation circuit 2, a flow meter 4, a thermometer 5, a pump (not shown), a blower 6, and the like. Water circulates in the circulation circuit 2 by a pump. The flow rate of water is measured by the flow meter 4. The thermometer 5 is disposed upstream of the heating device 10 and measures the temperature of the water before being heated by the heating device 10 (hereinafter referred to as the inlet water temperature). The blower 6 supplies air into the passenger compartment through the heat exchanger 3. The water heated by the heating device 10 passes through the circulation circuit 2 and is supplied to the heat exchanger 3. The heat exchanger 3 is used, for example, in a heat pump type air conditioner. When the temperature of the heat exchanger 3 decreases due to a decrease in the outside air temperature, the function of the heat pump decreases. Therefore, the temperature decrease of the heat exchanger 3 is suppressed by the heated water. Heat exchange occurs between the air sent by the blower 6 and the heat exchanger 3, and the warmed air is sent into the passenger compartment.

[0023] <Ceramic heater> FIG. 2 is a schematic cross-sectional view of the heating device 10. The heating device 10 includes a cylindrical ceramic heater 11, a thermometer 12, a heater control device 13 that controls the ceramic heater 11, and a housing 14. The ceramic heater 11 includes a cylindrical member and a heating resistor formed inside the cylindrical member. The cylindrical member is mainly composed of a ceramic material such as alumina. The heating resistor is composed of a metal such as tungsten and has a meandering thin wire shape. The heating resistor generates heat when a voltage is applied from a power supply device. The ceramic heater 11 can be manufactured, for example, by sandwiching a metal pattern serving as a heating resistor between ceramic green sheets, winding it around a rod-shaped profile, and firing it.

[0024] <Heater control device> The heater control device 13 of the present embodiment is constituted by, for example, a control board. In addition to a control unit such as a CPU, a power supply device, an FET, a voltage detection unit, a current detection unit, etc. are provided on the control board. The power supply device applies a voltage to a heater circuit including the ceramic heater 11. The FET interrupts the application of voltage to the ceramic heater 11. The voltage detection unit is capable of acquiring the voltage values applied to both sides of the ceramic heater 11 in the heater circuit. The current detection unit is capable of acquiring the current value flowing through the ceramic heater 11. The control unit calculates the resistance value of the ceramic heater 11 from the voltage value applied to both sides of the ceramic heater 11 and the current value flowing through the ceramic heater 11. That is, the heater control device 13 of the present embodiment is capable of acquiring the resistance value of the ceramic heater 11. Further, the control unit is capable of acquiring the inlet water temperature measured by the thermometer 5, the water temperature (outlet water temperature described later) measured by the thermometer 12, and the water flow rate measured by the flow meter 4. The control of the ceramic heater 11 by the heater control device 13 will be described later.

[0025] The heating device 10 has a flow path 15 through which water circulates. The flow path 15 includes a first space 11A provided inside the ceramic heater 11 and a second space 14A provided between the housing 14 and the ceramic heater 11. The ceramic heater 11 is arranged so as to be in contact with both the first space 11A and the second space 14A. One end of the flow path 15 is an inlet 15A through which water is introduced into the heating device 10, and the other end of the flow path 15 is an outlet 15B through which water is discharged outside the heating device 10. As shown by the arrow, the water introduced from the inlet 15A passes through the first space 11A, passes through the second space 14A, and is discharged from the outlet 15B.

[0026] The housing 14 is made of, for example, resin or metal. The housing 14 has a thermometer holding portion 14B that holds the thermometer 12 and a substrate housing portion 14C that houses the control board. The thermometer holding portion 14B is arranged in the flow path 15 on the downstream side of the ceramic heater 11. Therefore, the thermometer 12 measures the temperature of the water heated by the ceramic heater 11 (hereinafter referred to as the outlet water temperature).

[0027] FIG. 3 is a schematic diagram enlarging the one-dot chain line area of FIG. 2. In the heating device 10 of the present embodiment, a ceramic heater 11 capable of rapidly generating high-temperature water is provided. For this reason, bubbles are likely to locally generate and grow on the surface of the ceramic heater 11. When the temperature of the water rises and the generation of bubbles becomes active, a state in which bubbles adhere to a part of the ceramic heater 11 may continue. For example, in FIG. 3, in the ceramic heater 11, a region A1 where bubbles adhere to the surface is not in contact with water and cannot transfer heat to the water, so it is overheated. Then, when the bubbles grow to a certain extent, they separate from the region A1. Then, the overheated region A1 comes into contact with relatively low-temperature water, and a temperature difference instantaneously occurs in the region A1. When this temperature difference exceeds a predetermined value, the ceramic material constituting the region A1 is damaged due to the thermal expansion difference.

[0028] In this embodiment, as described above, when a part of the ceramic heater 11 is in contact with a gas, an excessive voltage is prevented from being applied to the ceramic heater 11. Thereby, overheating of the part of the ceramic heater 11 in contact with the gas can be suppressed, and breakage of the ceramic heater 11 due to a thermal expansion difference can be suppressed. Here, the "gas" with which the ceramic heater 11 comes into contact includes not only the bubbles (water vapor) generated when water is heated by the ceramic heater 11 as described above, but also, for example, air that has entered the flow path 15 from the outside for some reason.

[0029] <Regarding the resistance value of the ceramic heater> Since the resistance value of the ceramic heater 11 is approximately proportional to the temperature, the resistance value of the ceramic heater 11 increases as the temperature rises. When a predetermined amount of heat is applied by supplying power to the ceramic heater 11 for a predetermined period, the part of the ceramic heater 11 in contact with the gas becomes hotter than the part of the ceramic heater 11 in contact with the water. Therefore, when control is being performed to raise the water temperature, the resistance value of the part of the ceramic heater 11 in contact with the gas is greater than the resistance value of the part of the ceramic heater 11 in contact with the water.

[0030] When control is being performed to raise the water temperature at a predetermined input power, a predetermined water temperature, and a predetermined water flow rate, if the resistance value of the ceramic heater 11 when the ceramic heater 11 is in water is R 1 and the resistance value of the ceramic heater 11 when the ceramic heater 11 is in the air is R 2 (>R 1) is assumed. Here, the resistance value of the ceramic heater 11 can be approximated as if the minute resistances of each part of the ceramic heater 11 are connected in series. For example, as shown in FIG. 4, the heating resistor of the ceramic heater 11 is composed of five resistors 111 to 115 connected in series, and the case where the resistance values of the respective resistors 111 to 115 are equal is considered. The five resistors 111 to 115 are arranged inside a main body 110 made of a ceramic material. In FIG. 4, the hatched portion represents water, and the white circles within the hatched portion represent gas. In the ceramic heater 11, the portion where the resistor 111 is arranged is in contact with gas, and the portions where the other four resistors 112 to 115 are arranged are in contact with water. Therefore, the resistance value of the entire ceramic heater 11 shown in FIG. 4 is considered to be approximately equal to 0.8R 1 + 0.2R 2 It is considered to be approximately equal to. Thus, depending on the resistance value of the ceramic heater 11, it can be estimated that a part of the ceramic heater 11 is in a state of being in contact with gas.

[0031] Incidentally, each of the above resistance values R 1 , R 2 depends on various variables such as the magnitude of the input power, the temperature of the ceramic heater 11, the temperature of the water, and the flow rate of the water.

[0032] <First Threshold Value> In the present embodiment, the resistance value of the ceramic heater 11 when a part of the ceramic heater 11 is in contact with gas is defined as the first threshold value. Here, "a part of the ceramic heater 11" may be a part of the surface of the ceramic heater 11, for example, 20% or more and less than 80% of the surface of the portion where the heating resistor is formed on the surface of the ceramic heater 11. The first threshold value can be determined experimentally in the usage state of the heating device 10. Further, the first threshold value may be determined theoretically by using a physical quantity corresponding to the usage state of the heating device 10 or the like. In the present embodiment, when the resistance value of the ceramic heater 11 exceeds the first threshold value, the heater control device 13 executes a process of reducing the output of the ceramic heater 11 within the range where the temperature of the water can be raised (details will be described later).

[0033] <Second Threshold Value> In addition, in the present embodiment, the resistance value of the ceramic heater 11 when substantially the entire ceramic heater 11 is in contact with the gas is defined as the second threshold value. Here, "substantially the entire ceramic heater 11" means substantially the entire surface of the ceramic heater 11, and may be, for example, 80% or more of the surface of the portion where the internal heating resistor of the ceramic heater 11 is formed. The second threshold value is larger than the first threshold value, for example, the resistance value R described above 2 is. The second threshold value can be experimentally determined in the usage state of the heating device 10. Further, the second threshold value may be theoretically determined by using a physical quantity corresponding to the usage state of the heating device 10 or the like. In the present embodiment, when the resistance value of the ceramic heater 11 exceeds the second threshold value, the heater control device 13 executes control to significantly reduce the output of the ceramic heater 11 (details will be described later). Thereby, it is possible to prevent the ceramic heater 11 from being overheated in the air.

[0034] <Control Flow of Ceramic Heater> FIG. 5 is a flowchart showing the control of the ceramic heater 11 in the present embodiment. The control unit of the heater control device 13 performs the following processes shown in S10 to S22. First, the output coefficients A and B are set to 1 which are the initial values respectively (S10). Next, the control voltage Z which is the voltage value applied to the ceramic heater 11 in the PID control is calculated (S11).

[0035] The resistance value of the ceramic heater 11 is acquired a plurality of times (for example, 5 times) (S12). Specifically, in S12, the current flowing through the ceramic heater 11 is acquired by the current detection unit, and the voltage value applied to the ceramic heater 11 is acquired by the voltage detection unit. The resistance value of the ceramic heater 11 is calculated from the acquired current value and voltage value. Subsequently, the plurality of resistance values acquired in S12 are averaged, and the average value of the resistance value of the ceramic heater 11 is acquired (S13).

[0036] The control unit determines whether the average value of the resistance of the ceramic heater 11 is equal to or greater than a preset first threshold value (S14). When the average value of the resistance is equal to or greater than the first threshold value (S14: YES), the output coefficient A is replaced with A*b (the product of A and b) (S15). Here, b is a predetermined numerical value greater than 0 and less than 1, and is regarded as the first coefficient. The first coefficient b is, for example, 0.9. When the average value of the resistance is equal to or greater than the first threshold value, it is presumed that a part of the ceramic heater 11 is in contact with the gas. Therefore, by setting the numerical value obtained by multiplying the output coefficient A by the first coefficient b as the new output coefficient A, the output can be decreased, and overheating of the portion of the ceramic heater 11 in contact with the gas can be suppressed.

[0037] When the average value of the resistance is less than the first threshold value (S14: NO), the output coefficient A is replaced with A*a (the product of A and a) (S16). Here, a is a predetermined numerical value greater than 1, and is, for example, 1.1.

[0038] After S15 or S16, the control unit performs upper and lower limit correction of the output coefficient A (S17). Specifically, when the output coefficient A newly set in S15 or S16 is 0 or less, the output coefficient A is changed to 0. Also, when the output coefficient A newly set in S15 or S16 is 1 or more, the output coefficient A is changed to 1. When the output coefficient A newly set in S15 or S16 is a numerical value greater than 0 and less than 1, the output coefficient A is not changed.

[0039] Subsequently, the control unit determines whether the resistance value of the ceramic heater 11 (the plurality of resistance values obtained in S12) is equal to or greater than a preset second threshold value (S18). Specifically, in S18, it is determined whether at least one of the plurality of resistance values obtained in S12 is equal to or greater than the second threshold value. If at least one resistance value is equal to or greater than the second threshold value (S18: YES), the output coefficient B is replaced with B*c (the product of B and c) (S19). Here, c is a predetermined numerical value that is equal to or greater than 0 and less than b, and is regarded as the second coefficient. The second coefficient c may be, for example, 0.1. When at least one resistance value is equal to or greater than the second threshold value, it is presumed that substantially the entire ceramic heater 11 is in contact with the gas. Therefore, by using the value obtained by multiplying the output coefficient B by the second coefficient c as the new output coefficient B, the output can be significantly reduced, and overheating of the ceramic heater 11 can be suppressed.

[0040] In S19, the second coefficient c may be 0. In this case, the control of the ceramic heater 11 may be stopped.

[0041] If all of the plurality of resistance values are less than the second threshold value (S18: NO), the output coefficient B remains unchanged at 1.

[0042] The final control voltage Z*A*B (the product of Z, A, and B) is calculated from the output coefficients A and B set up to S19 (S20). The duty ratio for performing PWM control is calculated so that the final control voltage is applied to the ceramic heater 11 (S21). A FET control signal is output based on the obtained duty ratio (S22). That is, the final control voltage is applied to the ceramic heater 11 by PWM control.

[0043] After S22, after a predetermined time has elapsed, the processes after S11 are repeated. The time from S22 to the transition to S11 can be, for example, 10 milliseconds. When the processes after S11 are repeated, the numerical values of the output coefficients A and B are carried over.

[0044] <Effect of Embodiment 1> As described above, the heater control device 13 of Embodiment 1 is a heater control device 13 that controls the ceramic heater 11 disposed in the flow path 15 to heat the liquid to the target temperature while monitoring the temperature of the liquid flowing through the flow path 15. The resistance value of the ceramic heater 11 can be acquired, and in a state where the ceramic heater 11 is controlled to raise the temperature of the liquid, the output of the ceramic heater 11 is decreased based on the magnitude of the resistance value or the change in the resistance value over time.

[0045] According to such a configuration, when the amount of liquid in the flow path 15 decreases, the output of the ceramic heater 11 can be decreased, and overheating of the ceramic heater 11 can be suppressed.

[0046] In the heater control device 13 of Embodiment 1, when the resistance value becomes equal to the first threshold value which is the resistance value when a part of the ceramic heater 11 is in contact with gas, and in a state where the ceramic heater 11 is controlled to raise the temperature of the liquid, when the resistance value becomes equal to or greater than the first threshold value, the output of the ceramic heater 11 is multiplied by a first coefficient b which is less than 1, thereby decreasing the output of the ceramic heater 11 within the range where the temperature of the liquid can be raised.

[0047] According to such a configuration, when a part of the ceramic heater 11 is in contact with gas, the temperature of the liquid can be efficiently raised while suppressing overheating of the ceramic heater 11.

[0048] In the heater control device 13 of Embodiment 1, when the resistance value becomes equal to the second threshold value which is greater than the first threshold value, and in a state where the ceramic heater 11 is controlled to raise the temperature of the liquid, when the resistance value becomes equal to or greater than the second threshold value, the output of the ceramic heater 11 is multiplied by a second coefficient c which is less than the first coefficient b, thereby significantly decreasing the output of the ceramic heater 11.

[0049] According to such a configuration, when substantially the entire ceramic heater 11 is in contact with gas, overheating of the ceramic heater 11 can be suppressed.

[0050] The heating device 10 of Embodiment 1 includes a flow path 15 through which a liquid flows, a ceramic heater 11 disposed in the flow path 15, a measuring device (such as a current detection unit, a voltage detection unit, a control unit, etc.) that measures the resistance value of the ceramic heater 11, and a heater control device 13.

[0051] According to such a configuration, it is possible to provide a heating device 10 that can suppress damage to the ceramic heater 11.

[0052] The heating device 10 of Embodiment 1 is mounted on a vehicle.

[0053] [Details of Embodiment 2 of the Present Disclosure] Embodiment 2 of the present disclosure will be described with reference to FIG. 6. Hereinafter, the description of the same configurations, operations, and effects as those in Embodiment 1 may be omitted. In this embodiment, the heater control device 213 is configured to detect that a part of the ceramic heater 11 is in contact with a gas due to variations in the resistance value of the ceramic heater 11.

[0054] As described in Embodiment 1, the portion of the ceramic heater 11 in contact with the bubbles cannot transfer heat to the water and thus overheats. Also, when the bubbles leave the surface of the ceramic heater 11, heat is transferred from the surface of the ceramic heater 11 to the water, and the temperature of that portion of the ceramic heater 11 decreases. Thus, when the generation and detachment of bubbles on the surface of the ceramic heater 11 are repeated, the temperature of the ceramic heater 11 locally rises or falls significantly. Since the temperature of the ceramic heater 11 is approximately proportional to the resistance value, the resistance value of the ceramic heater 11 extremely rises or falls. Therefore, when a part of the ceramic heater 11 is in contact with a gas during the process of heating the water in the heating device 10, when the resistance value of the ceramic heater 11 is measured multiple times within a predetermined period, the multiple resistance values vary greatly. In this embodiment, when such variations in the resistance value of the ceramic heater 11 are detected, the output of the ceramic heater 11 is reduced within the range where the water can be heated.

[0055] As shown in FIG. 6, the control unit of the heater control device 213 performs the following processes shown in S30 to S40. First, the output coefficient C is set to 1 which is the initial value (S30). S31, S32, and S33 are the same as S11, S12, and S13 in Embodiment 1.

[0056] The control unit determines whether or not the variation in the resistance value of the ceramic heater 11 is equal to or greater than a preset third threshold value (S34). The variation in the resistance value is, for example, the difference between the maximum value and the minimum value among a plurality of resistance values acquired in S12. The third threshold value is a numerical value such that when the variation in the resistance value is equal to or greater than the third threshold value, it is presumed that a part of the ceramic heater 11 is in contact with the gas. The third threshold value can be obtained experimentally. When the variation in the resistance value is equal to or greater than the third threshold value (S34: YES), the output coefficient C is replaced with C*e (the product of C and e) (S35). Here, e is a predetermined numerical value greater than 0 and less than 1, for example, 0.9. When the variation in the resistance value is equal to or greater than the third threshold value, it is presumed that a part of the ceramic heater 11 is in contact with the gas. Therefore, by setting the numerical value obtained by multiplying the output coefficient C by e as the new output coefficient C, the output can be decreased, and it is possible to suppress the overheating of the portion of the ceramic heater 11 in contact with the gas.

[0057] S36, S37, S38, S39, and S40 are substantially the same as S16, S17, S20, S21, and S22 in Embodiment 1, respectively.

[0058] <Effect of Embodiment 2> When the variation within a predetermined period of a plurality of resistance values acquired over time becomes equal to or greater than the third threshold value while the heater control device 213 of Embodiment 2 is controlling the ceramic heater 11 to raise the temperature of the liquid, the heater control device 213 decreases the output of the ceramic heater 11 within the range where the liquid can be heated.

[0059] According to such a configuration, by appropriately setting the third threshold value, when a part of the ceramic heater 11 is in contact with the gas, it is possible to efficiently raise the temperature of the liquid while suppressing overheating of the ceramic heater 11.

[0060] <Other Embodiments> (1) In Embodiment 1, the heating device 10 was mounted on a vehicle, but the heating device of the present disclosure may be used for applications other than vehicles.

[0061] (2) In Embodiment 1, the ceramic heater 11 was cylindrical, but the shape of the ceramic heater can be appropriately changed.

Description of Reference Numerals

[0062] 1: Heating device for passenger compartment, 2: Circulation circuit, 3: Heat exchanger, 4: Flow meter, 5: Thermometer, 6: Blower 10: Heating device, 11: Ceramic heater, 11A: First space, 12: Thermometer, 13, 213: Heater control device, 14: Housing, 14A: Second space, 14B: Thermometer holding part, 14C: Substrate housing part, 15: Flow path, 15A: Inlet, 15B: Outlet, 110: Body part, 111 - 115: Resistor A1: Region where bubbles adhere to the surface of the ceramic heater R 1 : Resistance value of the ceramic heater when the ceramic heater is in water R 2 : Resistance value of the ceramic heater when the ceramic heater is in air A, B, C: Output coefficient, b: First coefficient, c: Second coefficient

Claims

1. A heater control device that controls a ceramic heater disposed in a flow path to heat a liquid to a target temperature while monitoring the temperature of the liquid flowing through the flow path, wherein a resistance value of the ceramic heater can be obtained, and the output of the ceramic heater is reduced based on the magnitude of the resistance value or the change over time of the resistance value while the ceramic heater is controlled to increase the temperature of the liquid.

2. When the resistance value becomes equal to a first threshold value that is the resistance value when a part of the ceramic heater is in contact with a gas, while the ceramic heater is controlled to increase the temperature of the liquid, when the resistance value becomes equal to or greater than the first threshold value, the output of the ceramic heater is multiplied by a first coefficient less than 1 to reduce the output of the ceramic heater within a range where the temperature of the liquid can be increased. The heater control device according to claim 1.

3. When the resistance value becomes equal to a second threshold value greater than the first threshold value, while the ceramic heater is controlled to increase the temperature of the liquid, when the resistance value becomes equal to or greater than the second threshold value, the output of the ceramic heater is multiplied by a second coefficient smaller than the first coefficient to significantly reduce the output of the ceramic heater. The heater control device according to claim 2.

4. While the ceramic heater is controlled to increase the temperature of the liquid, when the variation within a predetermined period of a plurality of the resistance values obtained over time becomes equal to or greater than a third threshold value, the output of the ceramic heater is reduced within a range where the temperature of the liquid can be increased. The heater control device according to claim 1.

5. A flow path through which a liquid flows, a ceramic heater disposed in the flow path, a measuring device that measures the resistance value of the ceramic heater, and a heater control device according to any one of claims 1 to 4. A heating device comprising:

6. The heating device according to claim 5, mounted on a vehicle.

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