JP7667111B2 - Seat heater and vehicle seat - Google Patents

Description

This disclosure relates to a seat heater and a seat for a vehicle.

The seat heater described in Patent Document 1 has a heater that is provided between the seat cushion material and the seat skin and has a heating wire laid on a base material, a temperature detection unit that is provided near the heating wire on the base material, and a temperature control unit that controls the temperature of the heater to approach a target temperature according to the temperature detected by the temperature detection unit. The temperature control unit calculates an estimated environmental temperature based on the rate of temperature rise detected by the temperature detection unit during a predetermined period from when the heater starts heating, and corrects the target temperature to be lower as the estimated environmental temperature is lower.

WO2019/065628

Generally, seat heaters are configured to provide the desired heating performance when the ambient temperature is relatively low, such as below freezing. For example, when the ambient temperature is -20°C, a temperature control result without overshoot or hunting can be obtained, as shown in Figure 13. In contrast, when the ambient temperature is relatively high, the temperature rises faster than expected, and the control cannot keep up, resulting in overshoot in the temperature control and hunting as shown in Figure 14. Note that Figure 14 shows the temperature control result when the ambient temperature is 15°C as an example.

This disclosure has been made in consideration of the above, and aims to provide a seat heater and a seat for a vehicle that can suppress the occurrence of overshooting and hunting in temperature control when the ambient temperature is relatively high.

The seat heater according to the first aspect includes a control unit that performs a first control for setting a power supply rate of the heater provided in the seat to a predetermined value or more until a temperature detected by a temperature detection unit provided in the seat reaches a set control switching temperature, and performs a second control for controlling power supply to the heater so that the detected temperature coincides with a target temperature after the detected temperature reaches the control switching temperature; a calculation unit that calculates a slope a of the change in the detected temperature during a period in which the control unit performs the first control; and a setting unit that sets the control switching temperature when the slope a calculated by the calculation unit is greater than a threshold value to a value lower than the control switching temperature when the slope a is equal to or less than the threshold value.

In the first aspect, the slope a of the change in the detected temperature during the period when the control unit is performing the first control changes according to the environmental temperature, and as the environmental temperature increases, the slope a also increases. In the first aspect, the control switching temperature when the slope a is greater than the threshold value is set lower than the control switching temperature when the slope a is equal to or less than the threshold value. Therefore, by starting the second control early, it is possible to suppress the occurrence of overshooting or hunting in the temperature control when the environmental temperature is relatively high.

In the second aspect, in the first aspect, the control unit performs PID control as the second control.

According to the second aspect, it is possible to more effectively prevent overshooting and hunting from occurring in the seat temperature control compared to when other control such as PI control is performed as the second control.

In the third aspect, in the first or second aspect, the calculation unit calculates the slope a based on the detected temperature T1 at a time when a first predetermined time t1 has elapsed since the start of the first control, and the detected temperature T2 at a time when a second predetermined time t2 greater than the first predetermined time t1 has elapsed since the start of the first control.

Immediately after the control unit starts the first control, the heat emitted from the heater is used to heat up the components around the heater, so the correlation between the slope a and the ambient temperature is small. In contrast, in the third aspect, the detected temperature T1 at the point in time when the first predetermined time t1 has elapsed since the start of the first control is used as the detected temperature used to calculate the slope a, instead of the temperature at the start of the first control. This makes it possible to obtain a value for the slope a that more accurately reflects the ambient temperature, and to set the control switching temperature so as to more effectively prevent overshooting and hunting from occurring in the temperature control of the seat.

In the fourth aspect, in any of the first to third aspects, the setting unit provisionally sets the control switching temperature, and when the slope a is smaller than a first threshold A1, sets the control switching temperature higher than the provisionally set value, and when the slope a is equal to or greater than a second threshold A2 that is larger than the first threshold A1, sets the control switching temperature lower than the provisionally set value.

In the fourth aspect, when the slope a is within the range of the first threshold A1 to the second threshold A2, the control switching temperature is in an insensitive region where it is not changed from the provisionally set value, so that it is possible to prevent the control switching temperature from becoming too sensitive to changes in the slope a.

In the fifth aspect, in any of the first to fourth aspects, the setting unit changes the threshold value for the slope a depending on whether the detected temperature T at the time when a predetermined time t has elapsed since the start of the first control is equal to or higher than a predetermined temperature threshold value.

According to the fifth aspect, even if the relationship between the environmental temperature and the slope changes depending on the environmental temperature, an appropriate temperature can be set as the control switching temperature.

The sixth aspect of the moving body seat is provided with a seat heater according to any one of the first to fifth aspects.

In the sixth aspect, a seat heater of any of the first to fifth aspects is provided, so that, like the first aspect, it is possible to prevent overshooting or hunting from occurring in temperature control when the ambient temperature is relatively high.

This disclosure has the effect of preventing overshooting and hunting from occurring in temperature control when the environmental temperature is relatively high.

1 is a side view of a vehicle seat according to an embodiment; 2 is a block diagram showing a schematic configuration of a seat heater ECU and its periphery. FIG. FIG. 2 is a functional block diagram of a seat heater ECU. 5 is a flowchart showing a heater control process executed by a control unit. 5 is a flowchart showing a control switching temperature setting process according to the first embodiment. 11 is a diagram for explaining calculation of a gradient a of change in temperature detected by a thermistor; FIG. FIG. 11 is a conceptual diagram showing an example of temperature control according to the embodiment. 10 is a diagram showing an example of a temperature control result when the environmental temperature is relatively high (15° C.) in the embodiment. 10 is a flowchart showing a control switching temperature setting process according to a second embodiment. 10 is a diagram for explaining the operation of the control switching temperature setting process shown in FIG. 9 . 13 is a flowchart showing a control switching temperature setting process according to the third embodiment. 12 is a diagram for explaining the operation of the control switching temperature setting process shown in FIG. 11 . FIG. 11 is a diagram showing an example of a result of temperature control of a seat when the environmental temperature is below freezing (−20° C.); 11 is a diagram showing an example of the result of seat temperature control when the environmental temperature is relatively high (15° C.);

An example of an embodiment of the present disclosure is described in detail below with reference to the drawings.

First Embodiment
1 includes a seat body 12. The seat body 12 is provided in a vehicle cabin of a vehicle, which is an example of a moving body, and is seated by an occupant of the vehicle. Note that the vehicle seat 10 is an example of a moving body seat according to the present disclosure, and the seat body 12 is an example of a seat according to the present disclosure.

The seat body 12 includes a seat cushion portion 14, a seat back portion 16, and a headrest portion 18. The headrest portion 18 is attached to the upper end portion of the seat back portion 16 in the vertical direction of the vehicle so as to be slidable along the length of the seat back portion 16. The lower end portion of the seat back portion 16 in the vertical direction of the vehicle is attached to the rear end portion of the seat cushion portion 14 in the longitudinal direction of the vehicle via a rotation mechanism (not shown), and is rotatable relative to the seat cushion portion 14 around an axis along the width direction of the vehicle.

The seat body 12 is also provided with a heater 20. The heater 20 includes a first heater mat 22 laid near the surface of the seat cushion portion 14, and a second heater mat 24 laid near the surface of the seat back portion 16. A thermistor 26 is also provided near the rear end of the seat cushion portion 14 in the vehicle front-rear direction. The thermistor 26 is disposed near the hot wire of the heater 20, and detects the temperature of the hot wire of the heater 20. The thermistor 26 is an example of a temperature detection portion in this disclosure.

The vehicle seat 10 also includes a seat heater ECU (Electronic Control Unit) 32, which is housed in the seat cushion portion 14. As shown in FIG. 2, the seat heater ECU 32 includes a CPU (Central Processing Unit) 34 and a memory 36 such as a ROM (Read Only Memory) or a RAM (Random Access Memory). The seat heater ECU 32 also includes a non-volatile storage unit 38 such as a HDD (Hard Disk Drive) or an SSD (Solid State Drive), and an I/F (Interface) unit 40. The CPU 34, the memory 36, the storage unit 38, and the I/F unit 40 are connected to each other so as to be able to communicate with each other via an internal bus 42.

The heater 20 is connected to the I/F unit 40 via a heater drive unit 28, and the thermistor 26 and seat heater switch 30 are also connected to the I/F unit 40. The heater drive unit 28 energizes the heater 20 in response to an instruction from a seat heater ECU 32 (a control unit 44 described later). The seat heater switch 30 is turned on and off by an occupant seated in the seat body 12.

The memory unit 38 of the seat heater ECU 32 also stores a seat heater control program 41. The seat heater control program 41 is read from the memory unit 38 and loaded into the memory 36, and the seat heater control program 41 loaded into the memory 36 is executed by the CPU 34, so that the seat heater ECU 32 functions as the control unit 44, the calculation unit 46, and the setting unit 48 shown in FIG. 3.

When the seat heater switch 30 is turned on, the control unit 44 performs a heater control process (described below). In this heater control process, the control unit 44 performs on/off control to keep the power supply rate of the heater 20 at a predetermined value or higher (for example, 90 to 100%) until the temperature T detected by the thermistor 26 reaches the set control switching temperature CT1. After the temperature T detected by the thermistor 26 reaches the control switching temperature CT1, the control unit 44 performs PID control to control the power supply to the heater 20 so that the detected temperature T matches the target temperature CT2. Note that the above on/off control is an example of the first control in this disclosure, and the above PID control is an example of the second control in this disclosure.

The calculation unit 46 calculates the slope a of the change in the detected temperature T during the period when the control unit 44 is performing on/off control. Furthermore, the setting unit 48 sets the control switching temperature CT1 when the slope a of the change in the detected temperature T calculated by the calculation unit 46 is greater than a threshold value to be lower than the control switching temperature CT1 when the slope a of the change in the detected temperature T is equal to or smaller than the threshold value.

Next, as an operation of the first embodiment, first, referring to FIG. 4, the heater control process executed by the control unit 44 when the seat heater switch 30 is turned on will be described.

In step 60 of the heater control process, the control unit 44 acquires the control switching temperature CT1 set by the setting unit 48 from the setting unit 48. In step 62, the control unit 44 acquires the temperature T detected by the thermistor 26 from the thermistor 26. In step 64, the control unit 44 determines whether the temperature T acquired in step 62 is equal to or higher than the control switching temperature CT1 acquired in step 60.

If the determination in step 64 is positive, the process proceeds to step 66. In step 66, the control unit 44 executes on/off control to energize the heater 20 via the heater drive unit 28 at a power supply rate equal to or higher than a predetermined value. In the next step 70, the control unit 44 determines whether the seat heater switch 30 has been turned off. If the determination in step 70 is negative, the process returns to step 60. Therefore, the heater 20 is controlled to be on/off until the temperature T detected by the thermistor 26 reaches the set control switching temperature CT1.

When the temperature T detected by the thermistor 26 reaches the set control switching temperature CT1, the determination in step 64 is negative and the process proceeds to step 68. In step 68, the control unit 44 executes PID control via the heater drive unit 28 to control the energization of the heater 20 so that the detected temperature T coincides with the target temperature CT2. This PID control continues while the seat heater switch 30 is in the ON state. Then, when the seat heater switch 30 is turned OFF, the determination in step 70 is positive and the heater control process ends.

Next, referring to FIG. 5, the control switching temperature setting process performed by the calculation unit 46 and the setting unit 48 when the control unit 44 starts executing the heater control process and turns on the heater 20 (power is started to be supplied to the heater 20) will be described.

In step 80 of the control switching temperature setting process, the setting unit 48 provisionally sets the control switching temperature CT1. The provisionally set control switching temperature CT1 may be, for example, a fixed value determined in advance, or the temperature T detected by the thermistor 26 may be obtained prior to the provisional setting of the control switching temperature CT1, and the value may be changed according to the obtained detected temperature T. In addition, the temperature T detected by the thermistor 26 may be obtained at any timing after the provisional setting of the control switching temperature CT1 (for example, the timing when a first predetermined time t1 has elapsed since the heater 20 was turned on, as described below), and the provisional setting value of the control switching temperature CT1 may be reset according to the obtained thermistor temperature T.

In step 82, the calculation unit 46 determines whether or not a first predetermined time t1 has elapsed since the heater 20 was turned on. If the determination in step 82 is negative, step 82 is repeated until the determination is positive. If the first predetermined time t1 has elapsed since the heater 20 was turned on, the determination in step 82 is positive and the process proceeds to step 84. In step 84, the calculation unit 46 obtains the detected temperature T1 from the thermistor 26 and stores the obtained detected temperature T1 in the memory 36 or the like.

In addition, in step 86, the calculation unit 46 determines whether or not a second predetermined time t2 has elapsed since the heater 20 was turned on. Note that the second predetermined time t2 is greater than the first predetermined time t1. If the determination in step 86 is negative, step 86 is repeated until the determination is positive. If the second predetermined time t2 has elapsed since the heater 20 was turned on, the determination in step 86 is positive and the process proceeds to step 88. In step 88, the calculation unit 46 obtains the detected temperature T2 from the thermistor 26 and stores the obtained detected temperature T2 in the memory 36 or the like.

In step 90, the calculation unit 46 substitutes the detected temperatures T1 and T2 stored in the memory 36 or the like into the following equation (1) to calculate the slope a (see also FIG. 6 ) of the change in the detected temperature T by the thermistor 26 during the period when the control unit 44 is performing on/off control.
a=(T2-T1)/(t2-t1)...(1)

In step 92, the setting unit 48 determines whether the slope a calculated by the calculation unit 46 is less than the slope threshold A. If the slope a is equal to or greater than the slope threshold A, the determination in step 92 is negative and the process proceeds to step 94, where the setting unit 48 lowers the control switching temperature CT1 provisionally set in the previous step 80. If the slope a is less than the slope threshold A, the determination in step 92 is positive and the process proceeds to step 96, where the setting unit 48 raises the control switching temperature CT1 provisionally set in the previous step 80.

The change range of the control switching temperature CT1 in steps 94 and 96 may be a fixed value determined in advance, or may be changed according to the detected temperature T obtained from the thermistor 26 at any timing (for example, the detected temperature T1 obtained when the first predetermined time t1 has elapsed since the heater 20 was turned on).

When the gradient a of the change in temperature T detected by the thermistor 26 is large, i.e., when the ambient temperature is estimated to be high, the control switching temperature CT1 is lowered as shown in FIG. 7, and PID control of the heater 20 is started early by the above-mentioned control switching temperature setting process. This makes it possible to prevent overshooting and hunting from occurring in temperature control when the ambient temperature is relatively high (FIG. 8 shows an example of 15° C.).

In addition, when the gradient a of the change in temperature T detected by the thermistor 26 is small, i.e., when the environmental temperature is estimated to be low, the control switching temperature CT1 is raised as shown in FIG. 7, thereby lengthening the period during which on/off control is performed on the heater 20. This makes it possible to shorten the time until the temperature T detected by the thermistor 26 reaches the target temperature CT2.

In this way, in the first embodiment, the control unit 44 performs a first control to set the power supply rate of the heater 20 provided in the seat body 12 to a predetermined value or more until the detected temperature T by the thermistor 26 provided in the seat body 12 reaches the set control switching temperature CT1. After the detected temperature T reaches the control switching temperature CT1, the control unit 44 performs a second control to control the power supply to the heater 20 so that the detected temperature T matches the target temperature CT2. The calculation unit 46 calculates the gradient a of the change in the detected temperature T during the period in which the control unit 44 performs the first control. Then, the setting unit 48 sets the control switching temperature CT1 when the gradient a of the change in the detected temperature T calculated by the calculation unit 46 is greater than a threshold value to be lower than the control switching temperature CT1 when the gradient a of the change in the detected temperature T is equal to or less than the threshold value. As a result, when the environmental temperature is relatively high, the second control is started early, and it is possible to suppress the occurrence of overshooting and hunting in the temperature control.

In addition, in the first embodiment, the control unit 44 performs PID control as the second control. This makes it possible to more effectively prevent overshooting and hunting from occurring in the temperature control compared to when other control such as PI control is performed as the second control.

In addition, in the first embodiment, the calculation unit 46 calculates the slope a of the change in the detected temperature T based on the detected temperature T1 at the time when a first predetermined time t1 has elapsed since the start of the first control, and the detected temperature T2 at the time when a second predetermined time t2 greater than the first predetermined time t1 has elapsed since the start of the first control. This makes it possible to obtain a value that more accurately reflects the environmental temperature as the slope a of the change in the detected temperature T, and to set the control switching temperature CT1 so as to more effectively suppress the occurrence of overshooting or hunting in the temperature control.

Second Embodiment
Next, a second embodiment of the present disclosure will be described. Since the second embodiment has the same configuration as the first embodiment, the same reference numerals are used for each part and the description of the configuration will be omitted. Then, with reference to FIG. 9, the control switching temperature setting process according to the second embodiment will be described only in terms of the parts that are different from the control switching temperature setting process (FIG. 5) described in the first embodiment.

In the control switching temperature setting process according to the second embodiment, in step 90, the calculation unit 46 calculates the slope a of the change in the detected temperature T, and then the process proceeds to step 100. In step 100, the setting unit 48 determines whether the slope a of the change in the detected temperature T calculated by the calculation unit 46 in step 90 is smaller than a preset slope threshold A1.

If the determination in step 100 is positive, the process proceeds to step 102, where the setting unit 48 increases the control switching temperature CT1 that was provisionally set in the previous step 80, and the process proceeds to step 104. If the determination in step 100 is negative, the process skips step 102 and proceeds to step 104.

In step 104, the setting unit 48 determines whether the slope a of the change in the detected temperature T calculated by the calculation unit 46 in step 90 is greater than a preset slope threshold A2. Note that the slope threshold A2 is greater than the slope threshold A1. If the determination in step 104 is positive, the process proceeds to step 106, where the setting unit 48 lowers the control switching temperature CT1 provisionally set in the previous step 80, and ends the control switching temperature setting process. If the determination in step 104 is negative, step 106 is skipped and the control switching temperature setting process ends.

The change range of the control switching temperature CT1 in steps 102 and 106 may be a fixed value determined in advance, or may be changed according to the detected temperature T obtained from the thermistor 26 at any timing (for example, the detected temperature T1 obtained when the first predetermined time t1 has elapsed since the heater 20 was turned on).

When the control switching temperature setting process described above is performed, if the slope threshold A1 < slope a < slope threshold A2 (as shown in FIG. 10(A)), the judgments of steps 100 and 104 are both negative, and the control switching temperature CT1 is not changed. When the slope a > slope threshold A2 (as shown in FIG. 10(B)), the judgment of step 100 is negative while the judgment of step 104 is positive, and the setting unit 48 lowers the control switching temperature CT1. When the slope a < slope threshold A1 (as shown in FIG. 10(C)), the judgment of step 100 is positive while the judgment of step 104 is negative, and the setting unit 48 raises the control switching temperature CT1.

In this way, in the second embodiment, the setting unit 48 provisionally sets the control switching temperature CT1, and when the slope a of the change in the detected temperature T is smaller than the slope threshold A1 (this slope threshold A1 is an example of the first threshold A1), the setting unit 48 sets the control switching temperature CT1 higher than the provisionally set value. Also, when the slope a of the change in the detected temperature T is larger than the second threshold A2 (this slope threshold A2 is slope threshold A2 > slope threshold A1, which is an example of the second threshold A2), the setting unit 48 sets the control switching temperature CT1 lower than the provisionally set value. As a result, when the slope a is within the range from the slope threshold A1 to the slope threshold A2, it becomes an insensitive region in which the control switching temperature CT1 is not changed from the provisionally set value, and it is possible to suppress the change in the control switching temperature CT1 from being too sensitive to the change in the slope a.

Third Embodiment
Next, a third embodiment of the present disclosure will be described. Since the third embodiment has the same configuration as the first embodiment, the same reference numerals are used for each part and the description of the configuration will be omitted. Then, with reference to FIG. 11, the control switching temperature setting process according to the third embodiment will be described only in terms of the parts that are different from the control switching temperature setting process (FIG. 9) described in the second embodiment.

In the control switching temperature setting process according to the third embodiment, in step 90, the calculation unit 46 calculates the gradient a of the change in the detected temperature T, and then the process proceeds to step 98. In step 98, the setting unit 48 determines whether the detected temperature T1 stored in the memory 36 or the like is less than a preset temperature threshold n. As an example of the temperature threshold n, 0°C may be applied, but other temperatures may also be applied. In addition, the detected temperature T compared with the temperature threshold n in step 98 is not limited to the detected temperature T1 obtained when the first predetermined time t1 has elapsed since the heater 20 was turned on, and the detected temperature T obtained from the thermistor 26 at any timing may be used.

If the detected temperature T1 is less than the temperature threshold n, the judgment in step 98 is affirmative and the process proceeds to step 100, and the process described in the second embodiment is performed in steps 100 to 106. On the other hand, if the detected temperature T1 is equal to or greater than the temperature threshold n, the process proceeds from step 98 to step 108.

In step 108, the setting unit 48 determines whether the gradient a of the change in the detected temperature T calculated by the calculation unit 46 in step 90 is smaller than a preset gradient threshold A1'. In this embodiment, the gradient threshold A1' ≠ gradient threshold A1. If the determination in step 108 is positive, the process proceeds to step 110, where the setting unit 48 increases the control switching temperature CT1 provisionally set in the previous step 80, and proceeds to step 112. The change amount of the control switching temperature CT1 in step 110 may be the same as or different from the change amount of the control switching temperature CT1 in step 102. If the determination in step 108 is negative, the process skips step 110 and proceeds to step 112.

In step 112, the setting unit 48 determines whether the gradient a of the change in the detected temperature T calculated by the calculation unit 46 in step 90 is greater than the preset gradient threshold A2'. In this embodiment, the gradient threshold A2' ≠ gradient threshold A2. If the determination in step 112 is positive, the process proceeds to step 114, where the setting unit 48 lowers the control switching temperature CT1 provisionally set in the previous step 80, and ends the control switching temperature setting process. The change amount of the control switching temperature CT1 in step 114 may be the same as or different from the change amount of the control switching temperature CT1 in step 106. If the determination in step 112 is negative, step 114 is skipped and the control switching temperature setting process ends.

When the detection temperature T1 ≧ 0°C and the slope threshold A1' < slope a < slope threshold A2' (as shown in FIG. 12(A)), the judgments of steps 108 and 112 are both negative, and the control switching temperature CT1 is not changed. When the detection temperature T1 ≧ 0°C and the slope a > the slope threshold A2' (as shown in FIG. 12(B)), the judgment of step 108 is negative while the judgment of step 112 is positive, and the setting unit 48 lowers the control switching temperature CT1. When the detection temperature T1 ≧ 0°C and the slope a < the slope threshold A1' (as shown in FIG. 12(C)), the judgment of step 108 is positive while the judgment of step 112 is negative, and the setting unit 48 raises the control switching temperature CT1.

In this way, in the third embodiment, the setting unit 48 switches the threshold for the slope a of the change in the detected temperature T to the slope thresholds A1, A2 or A1', A2' depending on whether the detected temperature T1 is equal to or greater than the temperature threshold n when the first predetermined time t1 has elapsed since the start of on/off control. This makes it possible to set an appropriate temperature as the control switching temperature CT1 even when the relationship between the environmental temperature and the slope a of the change in the detected temperature T changes depending on the environmental temperature.

In the third embodiment, a single temperature threshold n (e.g., 0°C) is set for the detected temperature T1, and the threshold for the slope a of the change in the detected temperature T is switched to the slope thresholds A1, A2 or A1', A2' depending on whether the detected temperature T1 is equal to or greater than the temperature threshold n. However, the present disclosure is not limited to this, and multiple temperature thresholds, such as "-10°C<T1<0°C", may be set for the detected temperature T1, and the slope threshold may be switched depending on the magnitude relationship between the detected temperature T1 and the multiple temperature thresholds.

In addition, in the above embodiment, the present disclosure is described as being applied to a vehicle seat, but the moving body to which the present disclosure pertains is not limited to a vehicle, and the present disclosure may be applied to the seats of moving bodies such as trains, airplanes, and ships.

In addition, although the above describes a case in which the seat heater control program 41 is pre-stored (installed) in the storage unit 38, the seat heater control program 41 can also be provided in a form in which it is recorded on a non-temporary recording medium such as an HDD, SSD, or DVD.

10 Vehicle seat 12 Seat body 20 Heater 26 Thermistor 32 Seat heater ECU
44 Control unit 46 Calculation unit 48 Setting unit

Claims (6)

a control unit that performs a first control for setting a power supply rate of a heater provided in the seat to a predetermined value or more until a temperature detected by a temperature detection unit provided in the seat reaches a set control switching temperature, and performs a second control for controlling power supply to the heater so that the detected temperature coincides with a target temperature after the detected temperature reaches the control switching temperature;
a calculation unit that calculates a gradient a of a change in the detected temperature during a period in which the control unit is performing the first control;
a setting unit that sets the control switching temperature when the slope a calculated by the calculation unit is greater than a threshold value to a value lower than the control switching temperature when the slope a is equal to or smaller than the threshold value;
Includes seat heaters. The seat heater according to claim 1, wherein the control unit performs PID control as the second control. The seat heater according to claim 1 or 2, wherein the calculation unit calculates the slope a based on the detected temperature T1 at a time when a first predetermined time t1 has elapsed since the start of the first control, and the detected temperature T2 at a time when a second predetermined time t2 greater than the first predetermined time t1 has elapsed since the start of the first control. The seat heater according to any one of claims 1 to 3, wherein the setting unit provisionally sets the control switching temperature, and when the slope a is smaller than a first threshold A1, sets the control switching temperature higher than the provisionally set value, and when the slope a is equal to or greater than a second threshold A2 that is larger than the first threshold A1, sets the control switching temperature lower than the provisionally set value. The seat heater according to any one of claims 1 to 4, wherein the setting unit changes the threshold value for the slope a depending on whether the detected temperature T at the time when a predetermined time t has elapsed since the start of the first control is equal to or higher than a predetermined temperature threshold value. A seat for a vehicle equipped with a seat heater according to any one of claims 1 to 5.