HEATER CONTROL DEVICE

Abstract

Heater control device (14) which controls an electric heater (12) comprising a plurality of heat-generating sections (121, 122) which generate heat when supplied with energy and which radiates the heat of the plurality of heat-generating sections (121, 122), wherein the heater control device (14) has: a current determination unit (S103, S104, S105, S202, S203, S204, S205) which determines whether a total energy supply current value (HAt), which is a current value to be supplied to the electric heater (12) when all of the plurality of heat generating sections (121, 122) are supplied with energy, exceeds a predetermined current limit value (AL1) or not; a plurality of circuits (141, 142) which are provided accordingly for each of the plurality of heat-generating sections (121, 122), for switching on and off each of the plurality of heat-generating sections (121, 122); characterized by a power supply control unit (S102, S106, S207, S208) which, when it is determined that the total energy supply current value (HAt) exceeds the current limit value (AL1), a first heater control is executed, which supplies the electric heater (12) with energy, by controlling the plurality of circuits (141, 142) to alternately switch some or all of the plurality of heat-generating sections (121, 122) to an off state in which they cannot be supplied with energy, and when it is determined that the total energy supply current value (HAt) is equal to or less than the current limit value (AL1), a second heater control is executed, which supplies energy to the electric heater (12) by controlling the plurality of circuits (141, 142) to switch on all of the plurality of heat-generating sections (121, 122), wherein the current determination unit (S103, S104, S105, S202, S203, S204, S205) estimates the total energy supply current value (HAt) by summing current values ​​recorded during an energy supply from each of the plurality of heat generating sections (121, 122), and the current determination unit (S103, S104, S105, S202, S203, S204, S205) is configured to use, for any of the plurality of heat generation sections (121, 122) that are in the OFF state at the time of determining whether the total power supply current value (HAt) exceeds the current limit (AL1) or not, the current value of that heat generation section (121, 122) prior to the OFF state as the current value for estimating the total power supply current value (HAt).

Description

Cross-reference to related applications

[0001] This application is based on Japanese patent application JP 2016 - 132 564 A, filed on July 4, 2016. Technical area

[0002] The present disclosure relates to a heater control device for controlling an electric heater. background

[0003] A heater control device of this type is described, for example, as a power supply control system for anti-dew heaters in Patent Document 1, and is well known. The power supply control system described in Patent Document 1 cooperates with a plurality of heaters to prevent dew formation in a display case within a store.

[0004] Specifically, the power supply control system of Patent Document 1 appropriately shifts the power supply timing to the anti-dew heaters. This makes it possible to normalize the amount of electricity. In addition, when a control power that regulates the maximum power of the anti-dew heaters is determined, by adjusting a control scheme that appropriately shifts the power supply timing to the anti-dew heaters, it is possible to set the control power lower while contributing to energy savings. State of the art literaturePatent literature

[0005] Patent document 1: JP 2011 - 257 064 A Summary of the invention

[0006] In a heating system with an electric heater, a current limit is often set to energize the electric heater. In the case where the current limit is set as described above, for example, when the electric heater has a plurality of heat-generating sections, in order to prevent the current value of the electric heater from exceeding the current limit, it is considered that the power supply to the plurality of heat-generating sections could be controlled as in the power supply control system of Patent Document 1.

[0007] When this is done, the power supply timings of the individual heat-generating sections are appropriately shifted or switched, so that, with respect to a heat-generating section, the power supply period during which that heat-generating section is powered is limited. As a result, the amount of heat that the electric heater can dissipate is limited. The above points are recognized as a result of detailed consideration by the present inventor.

[0008] In view of the points described above, an object of the present disclosure is to provide a heater control device capable of increasing a heat radiation amount of a plurality of heat generating portions included in an electric heater while energizing the electric heater under a condition that a magnitude of an electric current of the electric heater is limited.

[0009] To achieve the above objects, according to one aspect of the present disclosure, a heater control device is provided according to claim 1. Further features are set out in dependent claim 2.

[0010] As a result, in a situation where the total power supply current value would exceed the current limit, the current value of the electric heater is suppressed by executing the first heater control, that is, by appropriately shifting or switching the power supply timing of each heat generation section. Conversely, under the condition that the total power supply current value is equal to or less than the current limit, the second heater control is executed, and as a result, the heat radiation amount of the electric heater is increased compared to the case where the first heater control is executed.Accordingly, it is possible to energize the electric heater under the condition that the magnitude of the current of the electric heater is limited by the current limit value, while also increasing the heat radiation amount of the electric heater compared with the case where the first heater control is continuously executed. Short description of the drawings Fig. 1 is a schematic figure showing an electric heater provided in a vehicle and its surroundings in a first embodiment. Fig. 2 is a figure showing an electrical schematic configuration of an electric heater and a heater control device in a first embodiment. Fig. 3 is a figure showing a resistance-temperature characteristic of a first heat generating portion and a second heat generating portion in a first embodiment. Fig. 4 is a timing chart showing a time change in a heater temperature and a time change in a current value of each heat generating portion from the start of energization of an electric heater in the first embodiment. Fig. 5 is a functional block diagram including an electric heater, a heater controller, and a heater operation unit according to the first embodiment. Fig. 6 is a flowchart showing a control process executed by a heater control device of the first embodiment. Fig. Fig. 7 is a timing chart showing a temporal change in each of an operation state of each heat generating section, a temperature of each heat generating section, and a current value of an electric heater when the control process of Fig. 6 is executed. Fig. 8(a) is a timing chart showing a temporal change in each of an operating state of each heat generating portion, a temperature of each heat generating portion, and a current value of an electric heater in a first comparative example, and (b) is a timing chart showing a temporal change in each of an operating state of each heat generating portion, a temperature of each heat generating portion, and a current value of an electric heater in a second comparative example. Fig. 9 is a flowchart showing a control process executed by a heater control device of a second embodiment, and corresponds Fig. 6 of the first embodiment. Fig. 10 is a timing chart showing a temporal change in each of an operating state of each heat generating section, a temperature of each heat generating section, and a current value of an electric heater when a control process is executed by a heater control device in a third embodiment, and corresponds Fig. 7. Fig. 11 is a flowchart showing a control process executed by a heater control device of a third embodiment, and corresponds Fig. 9 of the second embodiment. Embodiments for carrying out the invention

[0011] Embodiments of the present disclosure will be described below with reference to the drawings. In the following embodiments, identical or equivalent elements in the figures are denoted by the same reference numerals. (First embodiment)

[0012] As in Fig. 1, in the present embodiment, a heater system 10 is mounted in a vehicle, and the heater system 10 includes an electric heater 12, a heater control device 14, and a heater operation unit 26 (see Fig. 5). Here the arrows DR1 and DR2 indicate Fig. 1 shows the directions of the vehicle in which the heater system 10 is mounted. In particular, the arrow DR in Fig. 1 represents a vehicle longitudinal direction (front-rear) DR1, and the arrow DR2 represents an up-down direction DR2 of the vehicle.

[0013] The electric heater 12 is a heater configured in the form of a thin plate and arranged in the passenger compartment. As shown in Fig. 1 and Fig. As shown in Figure 2, the electric heater 12 generates heat by being supplied with power from a power supply 16, such as a battery or a generator, mounted in the vehicle. More specifically, the electric heater 12 has a plurality of heat generating sections 121, 122 that generate heat when energized. The electric heater 12 radiates the heat from the plurality of heat generating sections 121, 122. The electric heater 12 can be used as a device for providing immediate heat to an occupant 18. In Fig. 1, the heat radiation emitted by the electric heater 12 is shown schematically as an arrow R.

[0014] Specifically, the electric heater 12 is installed at a position opposite to a lower leg 181 of the occupant 18 who assumes a normal posture, assuming that the occupant 18 is sitting on a seat 20. That is, the electric heater 12 is installed on the lower side of a steering column 24 for supporting a steering wheel 22. With this arrangement, the electric heater 12 radiates heat radiation toward the occupant 18 as indicated by the arrow R.

[0015] As in Fig. As shown in Figure 2, the plurality of heat-generating sections 121, 122 are connected in parallel to each other and connected to the power supply 16. That is, a first heat-generating section 121 of the plurality of heat-generating sections 121, 122 is included in an electrical system provided in parallel with an electrical system including a second heat-generating section 122 of the plurality of heat-generating sections 121, 122. In short, the electric heater 12 electrically includes a plurality of systems of heat-generating sections 121, 122.

[0016] Furthermore, the heater control device 14 is arranged between the power supply 16 and the heat generating sections 121, 122. The heater control device 14 includes circuits 141, 142 capable of independently controlling the heat generating sections 121, 122.

[0017] Specifically, the first circuit 141 of the circuits 141, 142 of the heater control device 14 is connected in series with the first heat-generating section 121 and turns the first heat-generating section 121 on and off. Furthermore, the second circuit 142 of the circuits 141, 142 of the heater control device 14 is connected in series with the second heat-generating section 122 and turns the second heat-generating section 122 on and off. The two circuits 141 and 142 can be, for example, electrical relays, MOS devices, semiconductor relays, or switches that open and close mechanically.

[0018] Furthermore, a power interruption circuit 161 for protecting vehicle circuits is arranged between the power supply 16 and the heater control device 14. Although the power interruption circuit 161 of the present embodiment is a fuse, a fusible link, a circuit breaker, or the like may also be used instead.

[0019] Since the electric heater 12 includes the first heat generating section 121 and the second heat generating section 122, as described above, a heater temperature TPh, which is the temperature of the electric heater 12, can be regarded as a temperature of each of the heat generating sections 121, 122. Both the first heat generating section 121 and the second heat generating section 122 have the Fig. 3. That is, the electrical resistance of the first heat-generating portion 121 increases as the heater temperature TPh increases. Similarly, the electrical resistance of the second heat-generating portion 122 increases as the heater temperature TPh increases.

[0020] For this reason, as for example in Fig. 4, when energization of the heat generating sections 121, 122 (i.e., energization of the electric heater 12) is started, the heater temperature TPh increases over time due to Joule heating by each heat generating section 121, 122. Furthermore, due to the temperature characteristics of Fig. 3, the electrical resistance value of each of the heat generating sections 121, 122 increases as the heater temperature TPh increases. As a result, the longer a power supply period, the more the current value of each of the heat generating sections 121, 122 decreases. The power supply period is measured from the start time of the power supply. Furthermore, in the timing chart of Fig. 4 the voltage of the power supply 16 is constant.

[0021] As in Fig. 1 and Fig. As shown in Figure 5, the heater controller 14 is a controller that controls the electric heater 12. The heater controller 14 includes a microcontroller including a CPU, a ROM, a RAM, and the like (not shown). Signals from sensors or the like connected to the heater controller 14 are A / D converted by an input circuit (not shown) and then input to the microcontroller of the heater controller 14.

[0022] For example, the heater control device 14 is connected to the heater operation unit 26 provided in the passenger compartment, and signals from the heater operation unit 26 are input to the heater control unit 14. The heater operation unit 26 is an operation unit operated by the occupant 18. That is, the heater operation unit 26 is configured to include a heater operation switch that the occupant 18 can operate to selectively switch between operation and non-operation of the electric heater 12.

[0023] This heater operation switch is a switch that can be switched to a heater ON position or a heater OFF position, and is provided at a position in the passenger compartment where it is easy for the occupant to operate the heater operation switch. To energize the electric heater 12 and cause the electric heater 12 to operate, the occupant 18 would move the heater operation switch to the heater ON position. Furthermore, to de-energize the electric heater 12 and stop the electric heater 12, the occupant 18 would move the heater operation switch to the heater OFF position.

[0024] Then, the heater controller 14 drives and controls the electric heater 12 based on the signal transmitted from the heater operation switch of the heater operation unit 26. For example, when a signal indicating that the heater operation switch has been switched to the heater ON position is received from the heater operation unit 26, the heater controller 14 energizes the electric heater 12. That is, the electric heater 12 is turned on.

[0025] In addition, when a signal indicating that the heater operation switch has been switched to the heater OFF position is received from the heater operation unit 26, the heater controller 14 stops power supply to the electric heater 12. That is, the electric heater 12 is turned off.

[0026] For example, when the heater operation switch is switched to the heater OFF position, regardless of whether a first heater control or a second heater control is in the control processing of Fig. 6 is executed, the heater control device 14 stops supplying power to the electric heater 12.

[0027] More specifically, the heater control device 14 executes the control process described in Fig. 6. For example, when the ignition switch of the vehicle is turned on, the heater control device 14 starts the control process of Fig. 6.

[0028] As in Fig. 6, the heater controller 14 first acquires a signal from the heater operation unit 26 in step S101. Then, it is determined whether or not to operate the electric heater 12. The heater controller 14 determines to operate the electric heater 12 based on an occupant operating the heater operation unit 26. Accordingly, when the heater operation switch is switched to the heater ON position, the heater controller 14 determines to operate the electric heater 12. On the other hand, when the heater operation switch is switched to the heater OFF position, the heater controller 14 determines to stop the electric heater.

[0029] When it is determined in step S101 that the heater controller 14 should operate the electric heater 12, that is, when it is determined that the heater operation switch of the heater operation unit 26 is switched to the heater ON position, the process proceeds to step S102.

[0030] Conversely, if it is determined that the heater control device 14 should stop the electric heater 12, that is, if it is determined that the heater operation switch is switched to the heater OFF position, the processing of step S101 is repeated. That is, in this case, the heater control device 14 switches both of the switching circuits 141, 142 in Fig. 2 to maintain the electric heater 12 in a non-energized state or in a state in which it is not supplied with energy.

[0031] In Fig. 7, at a time ta1, the determination in step S101 is switched to the determination to start the electric heater 12. As a result, a first heater control, which will be described below, is executed in step S102 in Fig. 6 started.

[0032] In step S102 of Fig. 6, the heater control device 14 controls the electric heater 12, which is subject to a duty cycle restriction. In other words, the heater control device 14 alternately switches the control signals of the heat generating sections 121, 122 for the circuits 141, 142 on and off, as shown between times ta1 and ta2 in Fig. 7. In short, the heater controller 14 executes a first heater control that alternately supplies power to the first heat-generating section 121 and the second heat-generating section 122. This first heater control continues until a second heater control is started in step S106. Furthermore, the voltages applied to the plurality of heat-generating sections 121, 122 are equal to the voltage of the power supply 16 when their drive signals are on, and are zero when their drive signals are off.

[0033] In Fig. 7, since the first heater control is started from time ta1, the temperature of the heat generating sections 121, 122, that is, the heater temperature TPh, increases with the passage of time. As the temperature of the heat generating sections 121, 122 increases, the heat radiation amount of the heat generating sections 121, 122 also increases. Furthermore, as the heater temperature TPh increases, the electrical resistances of the heat generating sections 121, 122 also increase due to the temperature characteristics of the heat generating sections 121, 122. Therefore, the current value of the electric heater 12 gradually decreases with the passage of time. In the example of Fig. 7, for example, the voltage of the power supply 16 is maintained at a constant value or is maintained within a predetermined range that can be considered a constant voltage.

[0034] Due to the execution of the first heater control, the current value of the electric heater 12 is reduced compared to the case where the first heat generation section 121 and the second heat generation section 122 are energized simultaneously. In the present embodiment, since the first heat generation section 121 and the second heat generation section 122 are identical to each other, the current value of the electric heater 12 is, for example, half that when the first heat generation section 121 and the second heat generation section 122 are energized simultaneously. As a result of reducing the current value of the electric heater 12 as described above, the current value of the electric heater 12 is equal to or less than a predetermined upper current limit ALu.

[0035] Specifically, the current value of the electric heater 12 is the current value of the current flowing through the entirety of the first heat-generating section 121 and the second heat-generating section 122. Furthermore, the current upper limit ALu is a current value above which the current interruption circuit 161 disconnects the connection between the electric heater 12 and the power supply 16. As such, when the current value of the electric heater 12 is equal to or less than the current upper limit ALu, the current supply is maintained by the current interruption circuit 161. When the current value of the electric heater 12 exceeds the current upper limit ALu, the current interruption circuit 161 enters a power-off state.

[0036] Furthermore, during the period from ta1 to ta2 in Fig. In Figure 7, the current value of the first heat-generating section 121 is indicated by a solid line LH1, and the current value of the second heat-generating section 122 is indicated by a dashed line LH2. In addition, since the first heat-generating section 121 and the second heat-generating section 122 are alternately turned on and off, the current value of the electric heater 12 is equal to the current value of any of the first and second heat-generating sections 121, 122 that is in the ON state, that is, capable of being energized. Fig. 6, the process proceeds to step S103 after step S102.

[0037] In step S103, the heater controller 14 detects the current value of each of the heat generating sections 121, 122 during energization to estimate a total energization current value HAt of the electric heater 12.

[0038] The total power supply current value HAt is the current that would be supplied to the electric heater 12 if a voltage is applied to the plurality of heat-generating sections 121, 122 in a predetermined unrestricted state. The predetermined unrestricted state is a predetermined state in which the voltage of the power supply 16 is continuously and unrestrictedly applied to each of the plurality of heat-generating sections 121, 122. Accordingly, in the present embodiment, the total power supply current value HAt is the current that would be supplied to the electric heater 12 if all of the plurality of heat-generating sections 121, 122 are capable of being energized.Furthermore, in the present embodiment, the voltage applied to each of the heat generating sections 121, 122 is equal to the voltage of the power supply 16, that is, the power supply voltage when the heat generating sections 121, 122 can be energized.

[0039] For example, a current sensor (not shown) is provided for each of the heat-generating sections 121, 122. Then, the detection signals representing the current value of each of the heat-generating sections 121, 122 detected by these current sensors are transmitted from these current sensors to the heater controller 14.

[0040] Here, during execution of the first heater control as described above, the first heat generation section 121 and the second heat generation section 122 are alternately turned on and off. As a result, the timing at which energization occurs is different between the first heat generation section 121 and the second heat generation section 122. That is, during the processing of step S103, one of the first heat generation section 121 and the second heat generation section 122 is in an OFF state in which it cannot be energized. Therefore, the heater control device 14 uses the power supply for one of the first and second heat generation sections 121, 122 that is in the non-energizable OFF state during the processing of step S103.in the state where it cannot be energized, the current value of this heat generating portion before the OFF state is used as a current value for estimating the total power supply current value HAt. Conversely, the current value of the heat generating portion in the energizable ON state is directly detected at the time of the processing of step S103.

[0041] It should be noted that step S105, described below, is executed immediately after step S103, and in step S105, it is determined whether or not the total power supply current value HAt exceeds a current limit value AL1. Therefore, the expression "during the processing of step S103" as described above can be changed to "at the time of determining whether or not the total power supply current value HAt exceeds the current limit value AL1." Fig. 6, the process proceeds to step S104 after step S103.

[0042] In step S104, the heater controller 14 adds up the current value of each electrical system in the electric heater 12. In other words, the heater controller 14 estimates the total power supply current value HAt by adding up the current values ​​detected during the power supply of the plurality of heat generating sections 121, 122, that is, the current values ​​of each heat generating section 121, 122 obtained in step S103. In brief, the heater controller 14 calculates the total power supply current value HAt as the sum of the current values ​​of each of the heat generating sections 121, 122 obtained in step S103. After step S104, the process proceeds to step S105.

[0043] In step S105, the heater controller 14 determines whether the total power supply current value HAt of the electric heater 12 exceeds the predetermined current limit value AL1. The current limit value AL1 is a value set such that the current value of the electric heater 12 does not exceed the current upper limit ALu of the current interruption circuit 161. Therefore, in the present embodiment, the current limit value AL1 is equal to the current upper limit ALu. However, alternatively, the current limit value AL1 may be set smaller than the current upper limit ALu.

[0044] If it is determined in step S105 that the total power supply current value HAt exceeds the current limit value AL1, the process proceeds to step S103. In this step S103, execution of the first heater control continues. As such, the first heater control is control executed when the total power supply current value HAt exceeds the current limit value AL1. Then, during execution of the first heater control, the first heat generating section 121 and the second heat generating section 122 are supplied with power while the voltage applied to the first heat generating section 121 and the second heat generating section 122 is restricted, compared with the unrestricted state described above.

[0045] In contrast, if it is determined that the total power supply current value HAt is equal to or less than the current limit value AL1, the process proceeds to step S106. Fig. 7, the time ta2 shows the time at which the opposite determination is made in step S105 and the second heater control, which will be described below, is executed in step S106 of Fig. 6 is started.

[0046] In step S106 of Fig. 6, the heater control device 14 releases or cancels the duty cycle restriction and continues driving the electric heater 12. In other words, the heater control device 14 sets the drive signals of the heat generating sections 121, 122 for the circuits 141, 142 so that they are continuously on, as after the time ta2 in Fig. 7. As such, the heater control means executes the second heater control, which energizes the electric heater in a state where all of the plurality of heat generating sections 121, 122 of the electric heater 12 can be energized. In other words, in the second heater control, the restriction on the voltage applied to the heat generating sections 121, 122 for the first heater control is released, and the power supply voltage is applied to each of the heat generating sections 121, 122 in the unrestricted state described above.

[0047] According to the determination contents of the above step S105, this second heater control is a control executed when the total power supply current value HAt is equal to or less than the current limit value AL1.

[0048] In Fig. 7, at a time ta2, the power supply control for supplying power or energizing the electric heater 12 is switched from the first heater control to the second heater control. Accordingly, the current value of the electric heater 12 increases gradually at time ta2. After a time ta2 in Fig. 7, the current value of the electric heater 12, which is the sum of the current values ​​of the first and second heat generating sections 121, 122, is indicated by a solid line LH3.

[0049] Furthermore, the current value of each of the first and second heat generating sections 121, 122 is indicated by a solid line LH4.

[0050] Furthermore, in Fig. 7, as the current value of the electric heater increases to the limit at time ta2, the rate at which the heater temperature TPh increases also increases. As a result, when switching from the first heater control to the second heater control, the heater temperature TPh increases to a higher temperature compared to the case where the first heater control continues.

[0051] In addition, as can be seen from the fact that the heater temperature TPh after the time ta2 is higher than before the time ta2, it can be said that the heater controller 14 can control the electric heater 12 to a higher temperature when the second heater control is executed, compared with when the first heater control is executed.

[0052] In addition, since the second heater control is executed after it is determined that the total power supply current value HAt is equal to or less than the current limit value AL1, the current value of the electric heater 12 indicated by the solid line LH3 does not exceed the current upper limit ALu.

[0053] This second heater control continues until the electric heater 12 is turned off, for example, by switching the heater operation switch or an ignition switch. Then, as soon as the electric heater 12 is turned off, the control process starts in Fig. 6 of step S101.

[0054] It should be noted that the processing in each step of Fig. 6, which is described above, forms a functional unit that implements its corresponding functions. This also applies to the flow charts of Fig. 9 and Fig. 11, which are described below. Furthermore, steps S102 and S106 in Fig. 6 of a power supply control unit and correspond to steps S103, S104 and S105 of a current determination unit.

[0055] As described above, according to the present embodiment, as shown in Fig. 6 and Fig. As shown in Fig. 7, the first heater control, in which the first heat-generating section 121 and the heat-generating section 122 are alternately energized, is performed under the condition that the total energization current value HAt of the electric heater 12 exceeds the current limit value AL1. That is, by appropriately shifting or switching the energization timing of the individual heat-generating sections 121, 122, the current value of the electric heater 12 can be limited to be equal to or less than the current limit value AL1. Conversely, under the condition that the total energization current value HAt is equal to or less than the current limit value AL1, the second heater control is performed in which the electric heater 12 is energized while allowing all of the heat-generating sections 121, 122 to be energized.As a result, the heat radiation amount of the electric heater 12 is increased compared with when the first heater control is executed.

[0056] Accordingly, it is possible to energize the electric heater 12 under the condition that the magnitude of the current of the electric heater 12 is limited by the current upper limit ALu, while also increasing the heat radiation amount of the electric heater 12 compared with the case where the first heater control is continuously executed.

[0057] This will be described in detail using a first comparative example and a second comparative example. In the first comparative example and also in the second comparative example, as in Fig. 8(a) and (b), the condition that the magnitude of the electric current of the electric heater 12 is limited by the current upper limit ALu also applies. Furthermore, Fig. 8(a) is a timing chart of the first comparative example and is Fig. 8(b) is a timing diagram of the second comparative example. In addition, the time ta1 in Fig. 8(a), (b) the same as the time ta1 of Fig. 7, that is, the time when the heater operation switch is switched from the heater OFF position to the heater ON position. In addition, in each of the first comparative example and the second comparative example, each of the heat generating sections 121, 122 has the same temperature characteristic as that of the present embodiment shown in Fig. 3 is shown.

[0058] In the first comparison example, as in Fig. As shown in Fig. 8(a), there is no duty cycle limitation on the power supply to each of the heat generating sections 121, 122. Instead, the power supply to the first heat generating section 121 and the second heat generating section 122 is continued after a time ta1. However, since the current value of the electric heater 12 is limited to the current upper limit ALu or less, each of the heat generating sections 121, 122 in the first comparative example is a heat generating section that has a lower power consumption, that is, a lower current load, than that of the present embodiment. For example, in the first comparative example, the heater surface area of ​​the electric heater 12 that radiates heat may be smaller than that of the present embodiment, so that the current load on each of the heat generating sections 121, 122 is reduced.

[0059] For this reason, in the first comparative example, the heater temperature TPh increases according to the temperature of each of the heat-generating sections 121, 122 without a duty cycle limitation. Accordingly, the heater temperature TPh of the first comparative example increases to the same level as the heater temperature TPh when the second heater control is executed in the present embodiment. That is, in the first comparative example, the heater temperature TPh increases to a predetermined temperature at which the heat-generating performance of the electric heater 12 is sufficient.

[0060] However, in the first comparative example, as described above, the heat-generating sections 121, 122 of the electric heater 12 are heat-generating sections with lower current loads. Accordingly, when the heater temperature TPh reaches a predetermined temperature, the current value of the electric heater 12 decreases to a value much lower than the current limit ALu. Therefore, in the electric heater 12 of the first comparative example, when power supply is continued, it is not possible to obtain a sufficient amount of heat radiation corresponding to the current limit ALu.

[0061] Meanwhile, in the second comparative example, heat generating sections with a small current load, like those of the first comparative example, are not used. Instead, the electric heater 12 of the second comparative example is the same as that of the present embodiment. However, as shown in Fig. As shown in Figure 8(b), a duty cycle restriction is applied to the power supply of each of the heat generating sections 121, 122. That is, in the second comparative example, similar to the first heater control of the present embodiment, the first heat generating section 121 and the second heat generating section 122 are alternately supplied with power. Then, during the operation of the electric heater 12, the alternate power supply of the first heat generating section 121 and the second heat generating section 122 continues indefinitely.

[0062] For this reason, in the second comparative example, the instantaneous electric current value of the electric heater 12 is equal to the current value of one of the first heat generating section 121 and the second heat generating section 122, similar to during the execution of the first heater control of the present embodiment, and it is possible to supply energy to a wider heater surface area. However, as indicated by the arrow TPd in Fig. As shown in Figure 8(b), there is a possibility that the heater temperature TPh does not reach a predetermined temperature at which heat generation performance of the electric heater 12 is sufficiently performed. Therefore, in the electric heater 12 of the second comparative example, even when power supply is continued, it is also not possible to obtain a sufficient amount of heat radiation corresponding to the current upper limit ALu.

[0063] In contrast, in the present embodiment, the second heater control is executed based on the determination that the total power supply current value HAt is equal to or less than the current limit value AL1. Accordingly, even if the power supply to the electric heater 12 continues, it is possible to obtain a sufficient amount of heat radiation corresponding to the current upper limit ALu.

[0064] Furthermore, according to the present embodiment, as shown in Fig. 3, the electrical resistance of the plurality of heat generating sections 121, 122 of the electric heater 12 increases as the temperature of the electric heater 12 increases. Furthermore, as shown in Fig. 6 and Fig. As shown in FIG. 7, the heater controller 14 executes the second heater control when the electric heater 12 is at a high temperature, compared to the case of executing the first heater control. Accordingly, when the electric heater 12 is energized, the second heater control is executed after the electrical resistance of the heat generating portions 121, 122 increases due to the heat generated by the plurality of heat generating portions 121, 122 themselves. Accordingly, the current of the electric heater 12 can be appropriately controlled to be equal to or less than the current upper limit ALu.

[0065] Furthermore, according to the present embodiment, as shown in Fig. As shown in Figure 6, the heater controller 14 estimates the total power supply current value HAt by summing the current values ​​detected during the power supply of the plurality of heat generating sections 121, 122. Therefore, by detecting the current value of each of the heat generating sections 121, 122, it is possible to estimate the total power supply current value HAt.

[0066] Furthermore, according to the present embodiment, for the one of the heat generating sections 121, 122 that is in the OFF state when determining whether or not the total power supply current value HAt exceeds the current limit value AL, the heater control device 14 uses the current value of that heat generating section before the OFF state as a current value for estimating the total power supply current value HAt. Therefore, during the execution of the first heater control, it is possible to estimate the total power supply current value HAt without the need to turn on the heat generating section that is in the OFF state when determining whether or not the total power supply current value HAt exceeds the current limit value AL. (Second embodiment)

[0067] A second embodiment of the present disclosure will be described next. The present embodiment will be described primarily with reference to portions different from those of the first embodiment. In addition, explanations of portions identical or equivalent to those of the above embodiment will be omitted or simplified. This also applies to the embodiments described below.

[0068] In the present embodiment, as shown in Fig. As shown in Figure 9, the heater control device 14 controls the electric heater 12 in the same manner as in the first embodiment, but the specific control process performed by the heater control device 14 is different from that of the first embodiment. That is, the heater control device 14 of the present embodiment performs the control process shown in Fig. 9, instead of the control process shown in Fig. 6 of the first embodiment.

[0069] Specifically, as in the first embodiment, the heater control device 14 of the present embodiment starts the control process of Fig. 9, for example, when the vehicle's ignition switch is turned on.

[0070] Step S101 of the present embodiment, which is shown in Fig. 9 is the same as step S101 of the first embodiment.

[0071] When the heater control device 14 in step S101 of Fig. 9 determines that the electric heater 12 should be started, the process proceeds to step S202. Conversely, if the heater controller 14 determines that the electric heater should be stopped, the processing from step S101 is repeated.

[0072] In step S202, the heater controller 14 measures an applied voltage to each heat-generating section 121, 122. In other words, this applied voltage is detected. For example, a voltage sensor (not shown) is provided in the power supply 16, and a detection signal representing a power supply voltage, which is a voltage between the terminals of the power supply 16 detected by the voltage sensor, is transmitted from the voltage sensor to the heater controller 14. Then, the heater controller 14 detects the power supply voltage as the applied voltage of each of the heat-generating sections 121, 122. After step S202, the process proceeds to step S203.

[0073] In step S203, the heater controller 14 measures the heater temperature TPh. In other words, the heater temperature TPh is detected. For example, a heater temperature sensor (not shown) is provided in the electric heater 12, and a detection signal representing the heater temperature TPh detected by the heater temperature sensor is transmitted from the heater temperature sensor to the heater controller 14. After step S203, the process proceeds to step S204.

[0074] In step S204, the heater controller 14 estimates the current value of each heat generating section 121, 122. Here, similarly to the first embodiment, each of the heat generating sections 121, 122 has the temperature characteristic shown in Fig. 3, as described above. Therefore, in order to estimate the current value of each of the heat generating sections 121, 122, the heater control device 14 stores the temperature characteristic of Fig. 3 as a resistance-temperature map, that is, a predetermined relationship between the heater temperature TPh and the electrical resistance of the heat generating sections 121, 122.

[0075] Then, the heater control device 14 obtains or determines the electrical resistance of each of the heat generating sections 121, 122 from the resistance-temperature map, and based on this electrical resistance and the applied voltage of each of the heat generating sections 121, 122 obtained in step S202, the heater control device 14 calculates the current value of each of the heat generating sections 121, 122. In Fig. 9, the process proceeds to step S205 after step S204.

[0076] In step S205, the heater controller 14 estimates the total power supply current value HAt in the same manner as in step S104 of Fig. 6. In other words, the heater control device 14 calculates the total power supply current value HAt as the sum of the current values ​​of each of the heat generating sections 121, 122 calculated in step S204 of Fig. 9 can be obtained.

[0077] Since the estimation of the total power supply current value HAt is performed through steps S202 to S204 in this way, the heater control device 14 estimates the total power supply current value HAt based on the applied voltage of each heat generating section 121, 122 and the heater temperature TPh from the resistance temperature map described above. Fig. 9, the process proceeds to step S105 after step S205.

[0078] Step S105 of Fig. 9 is the same as step S105 of the Fig. 6 shown first embodiment.

[0079] In step S105 of Fig. 9, if it is determined that the total power supply current value HAt exceeds the current limit value AL1, the process proceeds to step S207. Conversely, if it is determined that the total power supply current value HAt is equal to or less than the current limit value AL1, the process proceeds to step S208.

[0080] The timing diagram of Fig. 7 is the same in the present embodiment, and the timing at which the above-described first heater control in step S207 of Fig. 9 is started, based on the determination in step S105, is shown as the time ta1. In Fig. 7, the time ta2 shows the time at which the opposite determination is made in step S105 and the above-described second heater control in step S208 of Fig. 9 is started.

[0081] In step S207 of Fig. 9, the heater control device 14 controls the electric heater 12 with a limited duty cycle, as in step S102 of Fig. 6. That is, the heater control device 14 executes the above-described first heater control. Furthermore, if the first heater control is already being executed, execution of the first heater control is continued. This first heater control is continued until the above-described second heater control is executed in step S208 of Fig. 9 is started. In Fig. 9, after step S207, the process proceeds to step S202.

[0082] In step S208, the heater control device 14 releases the duty cycle restriction and continues driving the electric heater 12 as in step S206 of Fig. 6. That is, the heater control device 14 executes the second heater control described above. Furthermore, if the second heater control is already being executed, execution of the second heater control is continued.

[0083] Furthermore, similar to the first embodiment, in the present embodiment, this second heater control continues until the electric heater 12 is turned off, for example, by switching the heating operation switch or an ignition switch. Then, once the electric heater 12 is turned off, the control process starts in Fig. 9 of step S101.

[0084] It should be noted that steps S207 and S208 in Fig. 9 of the power supply control unit and steps S202, S203, S204, S205 and S105 in Fig. 9 correspond to the current determination unit.

[0085] Except for the aspects described above, the present embodiment is the same as the first embodiment. Furthermore, in the present embodiment, effects similar to those of the first embodiment described above can be obtained in the same manner as in the first embodiment.

[0086] Furthermore, according to the present embodiment, as shown in Fig. 9, the heater controller 14 estimates the total power supply current value HAt based on the heater temperature TPh and the applied voltage of each heat generating section 121, 122. Therefore, even if the changes in the heater temperature TPh affect the current value of each heat generating section 121, 122, and even if changes in the applied voltage of each heat generating section 121, 122 affect the current value of each heat generating section 121, 122, it is possible to appropriately estimate the total power supply current value HAt.

[0087] For example, since the total power supply current value HAt is estimated based on the applied voltage of the heat generating sections 121, 122, even if the power supply voltage fluctuates according to the charge state of the power supply 16 or the like, it is possible to appropriately estimate the total power supply current value HAt. (Third embodiment)

[0088] A third embodiment will be described next. The present embodiment will be explained mainly with reference to portions different from those of the second embodiment.

[0089] In the present embodiment, the power supply 16 in Fig. 2, a variable voltage power supply is used, in which the power supply voltage can be changed stepwise. Furthermore, the heater control device 14 continuously changes the power supply voltage, which is the output voltage of the power supply 16. Specifically, as shown in Fig. As shown in Fig. 10, the heater controller 14 changes the power supply voltage within a range of 0V to a predetermined steady voltage Vc. The steady voltage Vc is a voltage that is continuously maintained as the power supply voltage after the heater temperature TPh is saturated. The steady voltage Vc is experimentally determined in advance so that, after the heater temperature TPh is saturated, the current value of the electric heater 12 can be maintained at a value close to the current upper limit ALu while also being equal to or less than the current upper limit ALu.

[0090] Furthermore, in the present embodiment, when the heater control device 14 sets the power supply voltage to 0V, the first heat generating section 121 and the second heat generating section 122 are turned off. Accordingly, in the present embodiment, the first switching circuit 141 and the second switching circuit 142 (see Fig. 2) is not provided. Therefore, the first heat-generating section 121 and the second heat-generating section 122 are both always connected to the power supply 16, and the power source voltage is equal to the applied voltage, that is, the drive voltage of each of the heat-generating sections 121, 122.

[0091] The heater control device 14 of the present embodiment carries out the control process described in Fig. 11, instead of the control process shown in Fig. 9 of the second embodiment. Specifically, as in the second embodiment, the heater control device 14 of the present embodiment starts the control process of Fig. 11, for example, when the vehicle's ignition switch is turned on. Furthermore, steps S101, S203, S205 and S105 of Fig. 11 are the same as the steps with the same reference numerals in Fig. 9.

[0092] In step S101 of Fig. 11, if the heater controller 14 determines that the electric heater 12 should be started, the process proceeds to step S203. After execution of step S203, the process proceeds to step S304. In contrast, if the heater controller 14 determines in step S101 that the electric heater 12 should be stopped, the process from step S101 is repeated.

[0093] In step S304, the heater controller 14 performs an estimation by calculating the current value of each of the heat generating sections 121, 122 when the voltage is applied to each of the heat generating sections 121, 122 in the above-described unrestricted state. That is, the heater controller 14 performs an estimation by calculating the current value of each of the heat generating sections 121, 122 when the steady voltage Vc is applied to each of the heat generating sections 121, 122. As in the second embodiment, each of the heat generating sections 121, 122 has the Fig. 3. Accordingly, the heater control device 14 stores the temperature characteristic of Fig. 3 as a resistance-temperature overview.

[0094] Then, the heater control device 14 obtains or determines the electrical resistance of each of the heat generating sections 121, 122 from the resistance-temperature map, and based on this electrical resistance and the steady voltage Vc, the heater control device 14 calculates the current value of each of the heat generating sections 121, 122. In Fig. 11, the process proceeds to step S205 after step S304.

[0095] In step S205 of Fig. 11, the heater control device 14 estimates the total power supply current value HAt in the same manner as in Figure 11, step S205 of Fig. 9. In other words, the heater control device 14 calculates the total power supply current value HAt as the sum of the current values ​​of each of the heat generating sections 121, 122 calculated in step S304 of Fig. 11 can be obtained. In Fig. 11, the process proceeds to step S105 after step S205.

[0096] In step S105 of Fig. 11, if it is determined that the total power supply current value HAt exceeds the current limit value AL1, the process proceeds to step S307. Conversely, if it is determined that the total power supply current value HAt is equal to or less than the current limit value AL1, the process proceeds to step S308.

[0097] A timing chart when the heater control device 14 executes the control process of Fig. 11 is here in Fig. 10. In the timing diagram of Fig. 10 is the time when the power supply of each heat generating section 121, 122 is stopped in step S307 of Fig. 11 is started based on the determination in step S105 is shown as time ta1. Furthermore, in Fig. 10, the time ta2 is the time at which the opposite determination is made in step S105 and the power supply of each heat generating section 121, 122 in step S308 of Fig. 8 is started.

[0098] During step S307 of Fig. 11, the heater controller 14 performs voltage restriction control, which energizes the first heat-generating section 121 and the second heat-generating section 122 while restricting the voltage applied to the first heat-generating section 121 and the second heat-generating section 122 compared to the unrestricted state described above. Here, restricting the applied current compared to the unrestricted state simply means setting the applied voltage lower than the steady-state voltage Vc.

[0099] Furthermore, if the voltage restriction control is already being executed, execution of the voltage restriction control is continued. This voltage restriction control is continued until a voltage non-restriction control is started in step S305.

[0100] Specifically, in the voltage restriction control of step S307, unlike the first heater control of the second embodiment, the power supply to each of the heat-generating sections 121, 122 is not switched ON and OFF. Instead, each of the heat-generating sections 121, 122 is continuously energized. Then, the heater controller 14 restricts the power supply voltage so that the current value of the electric heater 12 is equal to or less than the current upper limit ALu. For example, the power supply voltage can be determined based on the electrical resistance of each of the heat-generating sections 121, 122 obtained in step S304.

[0101] Furthermore, as in Fig. As shown in Figure 10, the heater temperature TPh rises with the passage of time from time ta1 to time ta2, and the electrical resistance of each of the heat-generating sections 121, 122 increases as the heater temperature TPh increases. Therefore, in the voltage restriction control, as the heater temperature TPh increases, the applied voltage (i.e., the drive voltage) of each of the heat-generating sections 121, 122, which is equal to the power supply voltage, is increased to approach the steady-state voltage Vc. Fig. 11, the process proceeds to step S203 after step S307.

[0102] In step S308 of Fig. 11, the heater controller 14 performs voltage unrestriction control, which applies the power supply voltage to each of the heat generation sections 121, 122 in the unrestricted state. That is, in the voltage unrestriction control, the heater controller 14 releases the restriction on the voltage applied to each of the heat generation sections 121, 122 implemented in the voltage restriction control, and continuously supplies power to each of the heat generation sections 121, 122 by applying the steady voltage Vc of the power supply 16. Furthermore, if the voltage unrestriction control is already being executed, execution of the voltage unrestriction control is continued.

[0103] After the time ta2 in Fig. 10, due to the application of voltage non-constraint control, the voltage applied to each of the heat-generating sections 121, 122 is constant at the steady voltage Vc, and the temperature of each of the heat-generating sections 121, 122 is also constant. Accordingly, the current values ​​of the heat-generating sections 121, 122 are also constant.

[0104] As described above, after the power supply to the electric heater 12 is started, the voltage restriction control and the voltage non-restriction control are executed sequentially as the heater temperature TPh increases. Therefore, the current value of each of the plurality of heat generating sections 121, 122 is always maintained at slightly less than half of the upper current limit ALu, as shown by the dashed line La in FIG. Fig. 10. As a result, the current value of the electric heater 12, which is the sum of the current value of the first heat-generating section 121 and the current value of the second heat-generating section 122, is always maintained at a value equal to or less than the current upper limit ALu, and also close to the current upper limit ALu, as shown by line Lb. Due to this, a current load on the power circuit for powering the electric heater 12 is appropriately reduced.

[0105] Furthermore, similar to the second heater control of the second embodiment, in the voltage non-restriction control of the present embodiment, this voltage non-restriction control continues until the electric heater 12 is turned off, for example, by switching the heater operation switch or an ignition switch. Then, once the electric heater 12 is turned off, the control process starts in Fig. 11 of step S101.

[0106] It should be noted that step S307 and step S308 in Fig. 11 correspond to the power supply control unit and steps S203, S304, S205 and S105 correspond to the current determination unit.

[0107] Except for the aspects described above, the present embodiment is the same as the second embodiment. Furthermore, in the present embodiment, effects similar to those of the second embodiment can be obtained in the same manner as in the second embodiment. (Other embodiments) (1) In the first embodiment described above, the electric heater 12 has two heat generating sections 121, 122, and in the first heater control executed in step S102 of Fig. 6, the heater control device 14 alternately supplies power to the first heat generating section 121 and the second heat generating section 122. However, this is only an example.

[0108] For example, the electric heater 12 may include three or more heat-generating sections electrically connected in parallel. Even when the electric heater 12 includes three or more heat-generating sections as described above, the first heater control can be performed in the same manner as in the first embodiment described above. Furthermore, in the case where the electric heater 12 includes three or more heat-generating sections, one of the heat-generating sections of the electric heater 12 may be continuously in the ON state even during the execution of the first heater control.

[0109] In short, in the first heater control, it is acceptable as long as the heater controller 14 energizes the electric heater 12 while switching among a subset or all of the heat-generating portions of the electric heater 12, those to be switched are switched to an off state in which they cannot be energized. That is, as long as the current value of the electric heater 12 is suppressed to be equal to or less than the upper-limit current ALu, it is not necessary for all the heat-generating portions of the electric heater 12 to be restricted in duty. This similarly applies to the second embodiment described above.

[0110] Furthermore, in the third embodiment, the electric heater 12 may have three or more heat generating sections. Then, in step S307 of Fig. 11, as long as the current value of the electric heater 12 is suppressed to be equal to or less than the current limit ALu, it is not necessary for the applied voltage of all heat-generating sections of the electric heater 12 to be less than the steady voltage Vc. That is, it is acceptable as long as the applied voltage of each of the heat-generating sections among all heat-generating sections of the electric heater 12 is set lower than the steady voltage Vc. (2) In each of the above-described embodiments, as shown in Fig. 1, the electric heater 12 is configured as a single device. However, the electric heater may also form a portion of a larger surface heating device. In such a heating device, for example, it is conceivable that the heating device is divided into a plurality of heating regions, and a subset of the plurality of heating regions is selectively heated. That is, it is conceivable that any one of the plurality of heating regions can be selected by an occupant or the like as a heat generation region that generates heat. In this case, the electric heater 12 of each of the above-described embodiments, in other words, the electric heater 12 to which the control processing of Fig. 6 or Fig. 9 is applied to this heat generation region. Therefore, the plurality of heat generation sections 121, 122 of the electric heater 12 does not correspond to all the heat generation sections included in the heater device, but corresponds to the heat generation sections included in the heat generation region. (3) In the first embodiment, the current value of each of the heat generating sections 121, 122 is measured in step S103 of Fig. 6. In this regard, the current value of each of the heat generating sections 121, 122 may be directly detected, or may be indirectly detected based on a physical value such as a current value detected at a location other than each of the heat generating sections 121, 122. (4) In the first embodiment described above, in step S103 of Fig. 6, for the one of the first and second heat-generating sections 121, 122 that is in the non-energizable OFF state, during the processing of step S103, the current value of that heat-generating section before the OFF state is used as a current value for estimating the total power supply current value HAt. However, this is merely an example. For example, the heat-generating section in the OFF state may be temporarily switched to the ON state, and its current value during the current ON state may be used as the basis for estimating the total power supply current value HAt.In this regard, since the heat generating section in the OFF state is momentarily switched to the ON state, the current interruption circuit 161, which is a fuse, does not interrupt the connection between the power supply 16 and the electric heater 12 even if the current value of the electric heater 12 momentarily exceeds the current upper limit ALu. (5) In the second embodiment described above, the flowchart of Fig. 9 Steps S202 and S204 but steps S202 and S204 are not essential.

[0111] For example, if the voltage of the power supply 16 is maintained at a constant value or within a predetermined range that can be regarded as a constant voltage, it is possible to treat the applied voltage of each of the heat generating sections 121, 122 as a constant. In this case, it would be easy to obtain in advance an overview of the relationship between the heater temperature TPh and the total power supply current value HAt from the temperature characteristic of Fig. 3. Then, in step S205, the heater control device 14 could estimate the total power supply current value HAt from this overview based on the heater temperature TPh. In this way, steps S202 and S204 in the flowchart of Fig. 9 unnecessary.

[0112] Furthermore, in the flow chart of Fig. 9 a configuration without steps S203 and S204 may be considered.

[0113] For example, in the case where the heat generating sections 121, 122 have the temperature characteristic shown in Fig. 3, and instead the electrical resistance of each of the heat-generating sections 121, 122 is substantially constant, regardless of the heater temperature TPh, their electrical resistance can be considered as a constant. In this case, it would be easy to provide in advance a map of the relationship between the applied voltage of each heat-generating section 121, 122 and the total power supply current value HAt. Then, in step S205, the heater controller 14 could estimate the total power supply current value HAt from this map based on the applied voltage of each heat-generating section 121, 122. In this way, steps S203 and S204 in the flowchart of Fig. 9 unnecessary. (6) In the second embodiment described above, in step S202 of Fig. 9, the applied voltage of each of the heat generating sections 121, 122 is detected. In this regard, the applied voltage of each of the heat generating sections 121, 122 can be indirectly detected based on other physical values, such as voltages other than the applied voltage. That is, in the control processing of Fig. 9, for example, estimating the total power supply current value HAt based on the applied voltage includes estimating the total power supply current value HAt based on a physical value corresponding to the applied voltage. This also applies to detecting the heater temperature TPh. (7) As in Fig. As shown in FIG. 10 of the third embodiment described above, between a time ta1 and a time ta2, during voltage restriction control, as the heater temperature TPh rises, the applied voltage of each heat generating section 121, 122 (i.e., the drive voltage) also increases, but this is an example. In voltage restriction control, as long as the voltage applied to each of the heat generating sections 121, 122 is restricted so that the current value of the electric heater is equal to or less than the current upper limit ALu, the applied voltage may instead be fixed at a predetermined value (for example, half of the steady voltage Vc). (8) In each of the above embodiments, the processing of each step shown in the flowcharts of Fig. 6, Fig. 9 and Fig.11 is implemented by a computer program, but this processing can also be implemented by hard logic or hardware logic.

[0114] The embodiments described above are not intended to be exhaustive or to limit the present disclosure. The present disclosure is intended to cover various modifications and equivalent arrangements. Individual elements or features of a particular embodiment are not necessarily essential unless the above description specifically states that the element or feature is essential, or unless the element or feature is obviously essential in principle.

[0115] An amount, value, amount, range, or the like, when specified in the exemplary embodiment described above, is not necessarily limited to the specific value, amount, range, or the like, unless it is specifically stated that the value, amount, range, or the like is necessarily the specific value, amount, range, or the like, or unless it is obviously necessary in principle for the value, amount, range, or the like to be a specific value, amount, range, or the like.Furthermore, when a material, a shape, a positional relationship, or the like is specified in the exemplary embodiments described above, it is not necessarily limited to the specific material, shape, positional relationship, or the like, unless it is specifically stated that the material, shape, positional relationship, or the like is necessarily the specific material, shape, positional relationship, or the like, or unless it is obviously necessary in principle that the material, shape, positional relationship, or the like is the specific material, shape, positional relationship, or the like. (Conclusion)

[0116] According to a first aspect specified in part or all of the above embodiments, when it is determined that the total power supply current value exceeds the current limit, the power supply control unit executes the first heater control. In the first heater control, the power supply control unit supplies power to the electric heater while switching, among some or all of the heat generation sections of the electric heater, those to be switched to an off state in which they cannot be supplied with power or are not energizable (or, among some or all of the plurality of heat generation sections, those to be switched to an off state in which they cannot be supplied with power).Furthermore, when it is determined that the total power supply current value is equal to or less than the current limit, the power supply control unit executes the second heater control. In the second heater control, the power supply control unit supplies power to all of the plurality of heat generation sections to power the electric heater.

[0117] According to the second aspect, the electrical resistance of the plurality of heat-generating sections increases as the temperature of the electric heater increases. Furthermore, the power supply control unit executes the second heater control when the electric heater is at a high temperature, compared to the case of executing the first heater control. Accordingly, when the electric heater is energized, the second heater control is executed after the electrical resistance of the heat-generating sections increases due to the heat generated by the plurality of heat-generating sections themselves. Accordingly, the current of the electric heater can be appropriately controlled.

[0118] According to a third aspect, the current determination unit estimates the total power supply current value based on the temperature of the electric heater. Therefore, even if temperature changes in the electric heater affect the current values ​​of the plurality of heat generation sections, it is possible to appropriately estimate the total power supply current value.

[0119] According to a fourth aspect, the current determination unit estimates the total power supply current value based on the applied voltage to the plurality of heat-generating sections. Therefore, even if changes in the applied voltage affect the current values ​​of the plurality of heat-generating sections, it is possible to appropriately estimate the total power supply current value.

[0120] Furthermore, according to a fifth embodiment, the current determination unit estimates the total power supply current value by summing current values ​​detected during power supply to each of the plurality of heat generation sections. Therefore, by detecting the current values, it is possible to easily estimate the total power supply current value.

[0121] Furthermore, according to a sixth aspect, the current determination unit for the one of the heat generation sections that is in the OFF state at the time of determining whether the total power supply current value exceeds the current limit uses the current value of that heat generation section before the OFF state as a current value for estimating the total power supply current value. Therefore, during the execution of the first heating control, it is possible to estimate the total power supply current value without the need to turn on the heat generation section that is in the OFF state when determining whether the total power supply current value exceeds the current limit.

[0122] Furthermore, according to a seventh aspect, when it is determined that the total power supply current value exceeds the current limit, the power supply control unit limits the voltage applied to any or all of the plurality of heat generating sections compared to a predetermined state. Furthermore, when it is determined that the total power supply current value is equal to or less than the current limit, the power supply control unit releases the limitation of the applied voltage.

Claims

[1] A heater control device (14) that controls an electric heater (12) that includes a plurality of heat generating sections (121, 122) that generate heat when energized, and that radiates the heat of the plurality of heat generating sections (121, 122), the heater control device (14) comprising: a current determination unit (S103, S104, S105, S202, S203, S204, S205) that determines whether or not a total power supply current value (HAt), which is a current value to be supplied to the electric heater (12) when all of the plurality of heat generating sections (121, 122) are supplied with power, exceeds a predetermined current limit value (AL1); a plurality of switching circuits (141, 142) provided respectively for each of the plurality of heat generating sections (121, 122) for turning on and off each of the plurality of heat generating sections (121, 122); characterized by a power supply control unit (S102, S106, S207, S208) which, when it is determined that the total power supply current value (HAt) exceeds the current limit value (AL1), executes a first heater control that supplies power to the electric heater (12) by controlling the plurality of switching circuits (141, 142) to alternately switch among some or all of the plurality of heat generating sections (121, 122) those to be switched to an off state in which they cannot be supplied with power, and when it is determined that the total power supply current value (HAt) is equal to or less than the current limit value (AL1), executes a second heater control that supplies power to the electric heater (12) by controlling the plurality of switching circuits (141, 142) to turn on all of the plurality of heat generating sections (121, 122), wherein the current determination unit (S103, S104, S105, S202, S203, S204, S205) estimates the total power supply current value (HAt) by adding up current values ​​detected during power supply of each of the plurality of heat generation sections (121, 122), and the current determination unit (S103, S104, S105, S202, S203, S204, S205) is configured to use, for any of the plurality of heat generation sections (121, 122) that is in the OFF state at the time of determining whether or not the total power supply current value (HAt) exceeds the current limit value (AL1), the current value of that heat generation section (121, 122) before the OFF state as the current value for estimating the total power supply current value (HAt). [2] Heater control device (14) according to claim 1, wherein the plurality of heat generating sections (121, 122) are configured so that the electrical resistance increases as the temperature of the electric heater (12) increases, and the power supply control unit (S102, S106, S207, S208) executes the second heater control when the electric heater (12) is at a high temperature higher than a temperature when the first heater control is executed.

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