Heating device

Abstract

To reduce noise generated by a heating device.SOLUTION: A heating device 10 includes a plurality of heater circuits 13A, 13B connected in parallel to a power source 12, and a control unit 11. Each of the heater circuits 13A, 13B includes a ceramic heater 14A, 14B and a switching element 15A, 15B that turns on and off the power supply from the power source 12 to the ceramic heater 14A, 14B. The control unit 11 performs time-staggered processing to turn on and off each switching element 15A, 15B at different times.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present disclosure relates to a heating device. [Background technology]

[0002] A liquid heating device described in Patent Document 1 (JP 2022-177349 A) ​​is known. This liquid heating device includes a container and a ceramic heater attached to the container. A heating element that generates heat when electricity is applied from the outside is provided inside the ceramic heater. The heating element is made of tungsten, rhenium, or the like. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2022-177349 Summary of the Invention [Problem to be solved by the invention]

[0004] Because the ceramic heaters described above exhibit electrical and thermal properties similar to those of metals, large currents may be switched when controlling the ceramic heaters, which raises concerns about increased electrical noise generated by the ceramic heaters.

[0005] The present disclosure was made in light of the above circumstances, and has an object to reduce noise generated from a heating device. [Means for solving the problem]

[0006] The heating device of the present disclosure is a heating device comprising a plurality of heater circuits connected in parallel to a power source, and a control unit, each of the heater circuits comprising a ceramic heater and a switching element that turns on and off the supply of electricity from the power source to the ceramic heater, and the control unit performs time-staggered processing that turns on and off each of the switching elements at different times. [Effects of the Invention]

[0007] According to the present disclosure, noise generated from a heating device can be reduced. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is an explanatory diagram schematically illustrating a vehicle interior heating device including a heating device according to an embodiment. [Figure 2] FIG. 2 is a diagram showing the electrical configuration of the heating device according to the embodiment. [Figure 3] FIG. 3 is an explanatory diagram illustrating the time difference processing when the duty ratio is 40%. [Figure 4] FIG. 4 is a diagram according to a comparative example, and is an explanatory diagram for explaining heater control when the duty ratio is 40%. [Figure 5] FIG. 5 is an explanatory diagram illustrating the time difference processing when the duty ratio is 50%. [Figure 6] FIG. 6 is an explanatory diagram illustrating the time difference processing when the duty ratio is 60%. DETAILED DESCRIPTION OF THE INVENTION

[0009] [Description of the embodiments of the present disclosure] First, embodiments of the present disclosure will be listed and described. (1) The heating device of the present disclosure includes a plurality of heater circuits connected in parallel to a power source, and a control unit. Each of the heater circuits includes a ceramic heater and a switching element that turns on and off the power supply from the power source to the ceramic heater. The control unit performs time-staggered processing that turns on and off each of the switching elements at different times.

[0010] With this configuration, the ceramic heater is turned on and off at different times, which reduces the amount of current flowing from the power supply, thereby reducing noise generated by energizing the ceramic heater.

[0011] [Details of the embodiments of the present disclosure] Embodiments of the present disclosure will be described with reference to Figures 1 to 6. Note 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.

[0012] <Heating device> The heating device 10 of the present disclosure is a device for heating a liquid such as water. The heating device 10 is installed in a vehicle such as an electric vehicle (EV) and is used to heat the vehicle cabin and keep the battery warm. FIG. 1 shows an example of a vehicle cabin heating device 1 that uses the heating device 10. The vehicle cabin heating device 1 includes the heating device 10, a circulation circuit 2, a heat exchanger 3 provided in the circulation circuit 2, a flow meter 4, a first thermometer 5A, a second thermometer 5B, a pump (not shown), a blower 6, etc.

[0013] Water is circulated through the circulation circuit 2 by a pump. The water flow rate is measured by a flow meter 4. A first thermometer 5A is located upstream of the heating device 10 and measures the temperature of the water before it is heated by the heating device 10 (hereinafter referred to as the inlet water temperature). A second thermometer 5B is located downstream of the heating device 10 and measures the temperature of the water after it is heated by the heating device 10 (hereinafter referred to as the outlet water temperature). A blower 6 supplies air into the vehicle cabin via a heat exchanger 3. 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 air conditioner. If the temperature of the heat exchanger 3 drops due to a drop in outside air temperature, the function of the heat pump will decrease, so the heated water suppresses the temperature drop of the heat exchanger 3. Heat exchange occurs between the air sent in by the blower 6 and the heat exchanger 3, and the heated air is sent into the vehicle cabin.

[0014] 2, the heating device 10 includes a control unit 11 and two heater circuits 13A and 13B connected in parallel to a power source 12. The power source 12 is, for example, a constant current source. The first heater circuit 13A includes a first ceramic heater 14A and a first switching element 15A that turns on and off the supply of electricity from the power source 12 to the first ceramic heater 14A. The second heater circuit 13B includes a second ceramic heater 14B and a second switching element 15B that turns on and off the supply of electricity from the power source 12 to the second ceramic heater 14B.

[0015] The ceramic heaters 14A, 14B each include a ceramic portion and a heating resistor formed inside the ceramic portion. The ceramic portion is primarily made of a ceramic material such as alumina. The heating resistor is made of a metal such as tungsten and has a serpentine thin wire shape. The heating resistor generates heat when a current supplied from the power source 12 flows through it. The ceramic heaters 14A, 14B are arranged so as to be in thermal contact with the circulation circuit 2. For example, the ceramic portion may be cylindrical, and the internal space of the ceramic portion may form part of the circulation circuit 2.

[0016] The switching elements 15A and 15B are, for example, MOSFETs or IGBTs. The switching elements 15A and 15B are switched on or off by a signal from the control unit 11. When the switching elements 15A and 15B are on, current is supplied from the power supply 12 to the ceramic heaters 14A and 14B, respectively. When the switching elements 15A and 15B are off, current is not supplied from the power supply 12 to the ceramic heaters 14A and 14B, respectively.

[0017] The control unit 11 is configured with a CPU and the like. The control unit 11 is capable of acquiring the inlet temperature from the first thermometer 5A. The control unit 11 is capable of acquiring the inlet water temperature measured by the first thermometer 5A, the outlet water temperature measured by the second thermometer 5B, and the water flow rate measured by the flow meter 4. The control unit 11 calculates the power to be applied to the water flowing through the circulation circuit 2 based on the target water temperature to be reached by heater control, the inlet water temperature, the outlet water temperature, the water flow rate, etc., and performs on / off control of the ceramic heaters 14A and 14B. Note that while it is desirable for the vehicle interior heating device 1 to include all of the first thermometer 5A, the second thermometer 5B, and the flow meter 4, it may also include only one or two of them.

[0018] The control unit 11 controls the gate voltage applied to the gate of each of the switching elements 15A and 15B by PWM control according to the required power, thereby controlling the on / off of each of the switching elements 15A and 15B.

[0019] The ceramic heaters 14A and 14B both have a resistance value of R. A constant current (current value X) is supplied to each of the ceramic heaters 14A and 14B from the power supply 12. Therefore, the maximum power consumption of each of the ceramic heaters 14A and 14B is RX 2 The control unit 11 calculates the duty ratio based on this maximum value of power consumption and the power required for each of the ceramic heaters 14A and 14B, and controls the on / off of each of the switching elements 15A and 15B.

[0020] <Time difference processing> In this embodiment, the control unit 11 performs time difference processing to turn on and off the switching elements 15A and 15B at different timings. Specifically, the timing at which the first switching element 15A is turned on is different from the timing at which the second switching element 15B is turned on. Also, the timing at which the first switching element 15A is turned off is different from the timing at which the second switching element 15B is turned off.

[0021] Fig. 3 shows the time difference processing when the duty ratio is 40%. The waveform shown in the upper part of Fig. 3 is the PWM signal that drives the first switching element 15A. The waveform shown in the middle part of Fig. 3 is the PWM signal that drives the second switching element 15B. The waveform shown in the lower part of Fig. 3 represents the current supplied from the power supply 12. In Fig. 3, the horizontal axis represents the passage of time.

[0022] At timing T1, the control unit 11 turns on the first switching element 15A, and starts supplying a current of current value X from the power supply 12. At timing T2, the first switching element 15A is turned off, and the second switching element 15B is turned on. Then, at timing T3, the second switching element 15B is turned off, and the supply of current from the power supply 12 is stopped. Here, the time from timing T1 to timing T4 is the PWM control cycle. After timing T4, one cycle of operation from timing T1 to timing T4 is repeated. The time from timing T1 to timing T2 and the time from timing T2 to timing T3 are 40% of the PWM control cycle.

[0023] Next, consider a case where the first switching element 15A and the second switching element 15B are simultaneously turned on and off, which is different from the present embodiment. As shown in Fig. 4, at timing T5, both switching elements 15A and 15B are turned on, and the supply of current from the power supply 12 at a current value of 2X begins. At timing T6, both switching elements 15A and 15B are turned off, and the supply of current from the power supply 12 is stopped. Here, the time from timing T5 to timing T7 is the PWM control cycle. The time from timing T5 to timing T6 is 40% of the PWM control cycle.

[0024] 4, the power supply 12 supplies current to both switching elements 15A and 15B simultaneously, so that a current of 2X needs to be supplied from the power supply 12. However, in this embodiment, as shown in FIG. 3, the first switching element 15A and the second switching element 15B are turned on and off at different times, so that the current value to be supplied from the power supply 12 can be reduced to X. Therefore, noise caused by energization of the ceramic heaters 14A and 14B can be reduced.

[0025] The reduction in the current value to be supplied from the power supply 12 as described above is possible when the duty ratio of each ceramic heater 14A, 14B is equal to or less than a threshold value of (100 / N)%, where N is the number of heater circuits 13A, 13B. That is, in this embodiment, N=2, and the threshold value of the duty ratio is 50%.

[0026] 5 shows the time difference processing when the duty ratio is a threshold value of 50%. At timing T8, the first switching element 15A is turned on, and the power supply 12 starts supplying a current of current value X. At timing T9, the first switching element 15A is turned off, and the second switching element 15B is turned on. Then, at timing T10, the second switching element 15B is turned off, and the first switching element 15A is turned on. Here, the time from timing T8 to timing T10 is the PWM control cycle. The time from timing T8 to timing T9 and the time from timing T9 to timing T10 are 50% of the PWM control cycle.

[0027] 5, when the duty ratio is equal to the threshold value, not only can the current value to be supplied from the power supply 12 be reduced, but also there is no need to stop the current supply from the power supply 12 after the current supply from the power supply 12 has started. Therefore, it is possible to eliminate the change over time in the current supplied from the power supply 12, and it is possible to further reduce noise caused by the energization of the ceramic heaters 14A and 14B.

[0028] 5 shows the time difference processing when the duty ratio is 60%, which is greater than the threshold value of 50%. At timing T11, the first switching element 15A is turned on, and the power supply 12 starts supplying a current of a current value X. At timing T12, the second switching element 15B is turned on, and the current supplied by the power supply 12 is changed from X to 2X. At timing T13, the first switching element 15A is turned off, and the current supplied by the power supply 12 is changed from 2X to X. At timing T14, the second switching element 15B is turned off, and the first switching element 15A is turned on. Here, the time from timing T11 to timing T14 is the PWM control cycle. The time from timing T11 to timing T13 and the time from timing T12 to timing T14 are 60% of the PWM control cycle.

[0029] As shown in FIG. 5, when the duty ratio is greater than the threshold, there is a time period during which both switching elements 15A and 15B are on, and during this time period, power supply 12 needs to supply a current value of 2X. However, in this embodiment, by turning on and off switching elements 15A and 15B at different times, a sudden change in the current value of 2X is avoided. In other words, the current value does not change from 0 to 2X or from 2X to 0 at a predetermined timing. Therefore, the change over time in the current supplied from power supply 12 can be reduced, thereby reducing noise associated with the supply of current to ceramic heaters 14A and 14B.

[0030] The time difference processing of this embodiment may not be performed when the duty ratio is greater than a threshold, but may be performed only when the duty ratio is equal to or less than the threshold. For example, when the duty ratio is greater than the threshold, the control unit 11 may not perform PWM control, but may continue to supply a constant current of a predetermined value (e.g., 2X or X) from the power source 12 to the ceramic heaters 14A, 14B until the duty ratio becomes equal to or less than the threshold.

[0031] <Effects of the embodiment> As described above, the heating device 10 of the embodiment includes a plurality of heater circuits 13A, 13B connected in parallel to the power source 12, and the control unit 11. Each heater circuit 13A, 13B includes a ceramic heater 14A, 14B and a switching element 15A, 15B that turns on and off the power supply from the power source 12 to the ceramic heater 14A, 14B. The control unit 11 performs time-staggered processing to turn on and off each switching element 15A, 15B at different timings.

[0032] With this configuration, the ceramic heaters 14A and 14B are turned on and off at different times, thereby reducing the magnitude of the current flowing from the power supply 12. Therefore, it is possible to reduce noise generated by energizing the ceramic heaters 14A and 14B.

[0033] In this embodiment, it is preferable that the number of heater circuits 13A, 13B is N, which is an integer equal to or greater than 2, and that the control unit 11 executes the time difference processing only when the duty ratio is (100 / N)% or less.

[0034] With this configuration, the time difference process is not performed when the duty ratio is greater than (100 / N)%, so that the object can be heated to the target temperature by the heating device 10 quickly.

[0035] <Other embodiments> (1) In the embodiment, the number of heater circuits 13A and 13B is two, but the number of heater circuits may be three or more. In addition, when there are three or more heater circuits, The paths may be grouped together, and the time difference processing may be performed for each group.

[0036] (2) In the embodiment, the heating device 10 is mounted on a vehicle, but the heating device of the present disclosure may be used for purposes other than vehicles. (3) In the embodiment, the heater circuits 13A and 13B are provided with the heaters 14A and 14B, respectively. However, each heater circuit may include multiple heaters. [Explanation of symbols]

[0037] 1: Vehicle heating system, 2: Circulation circuit, 3: Heat exchanger, 4: Flow meter, 5A: 1st thermometer, 5B: 2nd thermometer, 6: Blower 10: Heating device, 11: Control unit, 12: Power supply, 13A: First heater circuit, 13B: Second heater circuit, 14A: First ceramic heater, 14B: Second ceramic heater, 15A: First switching element, 15B: Second switching element

Claims

[Claim 1] a plurality of heater circuits connected in parallel to a power supply; a control unit, Each of the heater circuits includes a ceramic heater and a switching element that turns on and off the power supply to the ceramic heater, The control unit executes time difference processing to turn on and off the switching elements at different timings.

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