JP7620265B2 - Control device, control method, and program - Google Patents

Description

This disclosure relates to a control device, a control method, and a program, and in particular to a technology suitable for controlling a heater that melts snow.

Vehicles may be equipped with millimeter wave radars that detect the relative position and speed of targets in relation to the vehicle by irradiating targets around the vehicle with millimeter wave radio waves and receiving the reflected waves. Such millimeter wave radars are placed behind radio wave transparent members (hereafter referred to as front members) that form the front of the vehicle, such as the front bumper, front grille, emblem, etc.

When wet snow containing moisture adheres to the front member, which transmits millimeter wave radar radio waves, it affects the radio wave transmittance and causes a decrease in the performance of the millimeter wave radar. For this reason, for example, Patent Document 1 discloses a device that provides a heater on the front member and uses the heater to heat the front member to melt snow on the front member.

JP 2019-166888 A

When powering the heater to melt snow, in order to prevent thermal degradation of the heater, it is desirable to switch the heater from a powered state (ON state) to a non-powered state (OFF state) when the heater temperature reaches a specified threshold temperature. To perform such switching control, it is necessary to acquire the heater temperature. The heater temperature can be acquired directly, for example, by a temperature sensor such as a thermistor, but it can also be calculated based on the temperature dependency of the heater's resistance value.

Specifically, when the heater is ON, the heater resistance value is calculated based on the heater current and voltage values detected by the voltage and current detection circuit, and the heater temperature can be calculated based on the relationship between the calculated resistance value and temperature. Calculating the heater temperature from the resistance value eliminates the need for a temperature sensor, making it possible to reduce costs and simplify the device.

However, there are manufacturing variations in the resistance value and resistance temperature coefficient of the heater's heating wire, and there are also manufacturing variations in the resistance value and resistance temperature coefficient of the circuit elements of the voltage/current detection circuit. For this reason, depending on the combination of variations in these resistance values and resistance temperature coefficients, the heater temperature may be erroneously calculated to be higher than the actual temperature. If the heater temperature is erroneously calculated to be higher, the calculated heater temperature will reach the threshold temperature even in situations where the actual heater temperature is kept lower than the threshold temperature by the wind from the vehicle, such as when the vehicle is traveling at high speed. As a result, the heater will be frequently switched from the ON state to the OFF state, posing the problem that the heater will not be able to fully demonstrate its snow melting performance.

This disclosure has been made to solve the above problems. That is, one of the objectives of this disclosure is to effectively utilize the snow melting performance of the heater.

The device of the present disclosure comprises:
A control device (40) for a heater (30) that is provided on at least a portion of a member (FP) forming a part of an outer surface of a vehicle (10) that transmits radio waves from a radar (20) mounted on the vehicle (10), and that melts snow on the member (FP) by generating heat when electricity is applied thereto,
a temperature calculation unit (42) that calculates a resistance value of the heater (30) based on a voltage value and a current value of the heater (30) detected when the heater (30) is energized, and calculates a temperature (Th) of the heater (30) based on the calculated resistance value;
a heater control unit (43) that executes heating control for energizing the heater (30) and, when the temperature (Th) calculated by the temperature calculation unit (42) during the execution of the heating control reaches a predetermined threshold temperature (Tv), executes overheating prevention control for stopping energization of the heater (30) for a predetermined period of time;
The present invention is characterized in that it is provided with a threshold correction unit (44) that performs threshold correction to correct the threshold temperature (Tv) to a higher temperature when the overheating prevention control is executed while the vehicle (10) is traveling at high speeds at or above a predetermined speed (Vh).

The method of the present disclosure comprises:
A method for controlling a heater (30) that is provided on at least a portion of a member (FP) that forms a part of an outer surface of a vehicle (10) that transmits radio waves from a radar (20) mounted on the vehicle (10) and melts snow on the member (FP) by generating heat when electricity is applied thereto, comprising:
calculating a resistance value of the heater (30) based on a voltage value and a current value of the heater (30) detected when the heater (30) is energized, and calculating a temperature (Th) of the heater (30) based on the calculated resistance value;
A heating control is executed to energize the heater (30), and when the temperature (Th) calculated during the execution of the heating control reaches a predetermined threshold temperature (Tv), an overheating prevention control is executed to stop energizing the heater (30) for a predetermined period of time;
When the overheating prevention control is executed while the vehicle (10) is traveling at high speeds at or above a predetermined speed (Vh), a threshold correction is executed to correct the threshold temperature (Tv) to a higher temperature.

The program of the present disclosure is
A heater (30) is provided on at least a portion of a member (FP) forming a part of the outer surface of a vehicle (10) that transmits radio waves from a radar (20) mounted on the vehicle (10), and melts snow on the member (FP) by generating heat when electricity is applied to the member (FP).
calculating a resistance value of the heater (30) based on a voltage value and a current value of the heater (30) detected when the heater (30) is energized, and calculating a temperature (Th) of the heater (30) based on the calculated resistance value;
A heating control is executed to energize the heater (30), and when the temperature (Th) calculated during the execution of the heating control reaches a predetermined threshold temperature (Tv), an overheating prevention control is executed to stop energizing the heater (30) for a predetermined period of time;
When the overheating prevention control is executed while the vehicle (10) is traveling at high speeds at or above a predetermined speed (Vh), a process is executed to execute a threshold correction for correcting the threshold temperature (Tv) to a higher temperature.

According to the above configuration, when overheating prevention control is executed in a situation where the temperature rise of the heater (30) is suppressed due to high-speed driving of the vehicle (10), a threshold correction is executed to correct the threshold temperature (Tv) used to determine whether or not to execute the overheating prevention control to a higher temperature. This prevents unnecessary execution of overheating prevention control, and makes it possible to effectively demonstrate the snow melting performance of the heater (30).

In another aspect of the present disclosure,
The threshold correction unit (44) executes the threshold correction when the overheating prevention control is executed a predetermined number of times or more within a predetermined time while the vehicle (10) is traveling at high speed at or above a predetermined speed (Vh).

According to this aspect, by performing threshold correction when overheat prevention control has been performed a predetermined number of times or more, it is possible to effectively prevent unnecessary threshold correction from being performed, for example, when the estimated heater temperature (Th) accidentally reaches the threshold temperature (Tv) due to some factor.

In another aspect of the present disclosure,
The threshold correction unit (44) executes the threshold correction so that the corrected threshold temperature (Tvc) does not exceed the heat resistant temperature (Tm) of the heater (30).

According to this aspect, after performing threshold correction, the heating control can prevent the heater (30) from being heated beyond the heat resistance temperature (Tm), and thermal deterioration of the heater (30) can be effectively suppressed.

In another aspect of the present disclosure,
The heater control unit (43)
The heating control is executed when the outside air temperature (T) around the vehicle (10) is within a predetermined temperature range where wet snow containing moisture falls and when a wiper device (12) for wiping the windshield (11) of the vehicle (10) is operating.

According to this embodiment, by performing heating control in environmental conditions in which snow is likely to adhere to the vehicle (10), it is possible to reliably prevent the performance of the radar (20) from deteriorating.

In the above explanation, to aid in understanding the invention, the symbols used in the embodiments are enclosed in parentheses with respect to the constituent elements of the invention corresponding to the embodiments, but each constituent element of the invention is not limited to the embodiment defined by the symbols.

1 is a schematic diagram of a vehicle according to an embodiment of the present invention, viewed from the front. FIG. 2 is a schematic functional block diagram of a control device according to the present embodiment. 1 is a graph illustrating the relationship between a resistance value and a heater temperature. 5 is a timing chart illustrating a specific flow of heating control, overheating prevention control, and threshold correction according to the present embodiment. 4 is a flowchart illustrating a routine for heating control and overheating prevention control according to the present embodiment. 5 is a flowchart illustrating a threshold correction routine according to the embodiment.

The control device, control method, and program according to this embodiment will be described below with reference to the drawings. Identical components are given the same reference numerals, and their names and functions are also the same. Therefore, detailed descriptions thereof will not be repeated.

[General Configuration]
1 is a schematic diagram of a vehicle 10 according to this embodiment, as viewed from the front. The vehicle 10 includes a windshield 11. The windshield 11 is provided with a wiper device 12 for wiping the outer surface of the windshield 11.

A front bumper 13 extending in the vehicle width direction is attached to the front of the vehicle 10. Left and right headlights 16L, 16R are provided above the front bumper 13 at the front of the vehicle 10. A front grille 14 for taking in air while the vehicle is running is provided between the left and right headlights 13L, 13R at the front of the vehicle 10. An emblem 15 is provided as a decorative part at approximately the center of the front grille 14 in the vehicle width direction.

The vehicle 10 is equipped with a millimeter wave radar 20 that detects targets in the area ahead of the vehicle 10. The millimeter wave radar 20 radiates radio waves in the millimeter wave band and receives the reflected waves reflected by targets within the irradiation range. The millimeter wave radar 20 acquires the relative position (direction, distance) and relative speed between the vehicle 10 and the target based on the phase difference between the radiated millimeter wave and the received reflected wave, the attenuation level of the reflected wave, and the time from transmitting the millimeter wave to receiving the reflected wave. The relative position and relative speed of the target acquired by the millimeter wave radar 20 are used, for example, for driving assistance control of the vehicle 10. Examples of driving assistance control include adaptive cruise control (ACC), lane keeping control (LTA), and lane change assist (LCA).

In the illustrated example, the millimeter wave radar 20 is disposed behind the emblem 15. The millimeter wave radar 20 can be disposed behind the resin members (hereinafter simply referred to as the front member FP) that constitute the front surface of the vehicle 10, such as the front bumper 13, the front grille 14, the emblem 15, etc. In this embodiment, the front member FP is formed of a radio wave transparent member that allows the millimeter waves irradiated from the millimeter wave radar 20 to pass through.

The millimeter waves emitted from the millimeter wave radar 20 penetrate the front member FP to reach the target, and the reflected waves reflected by the target penetrate the front member FP to be received by the millimeter wave radar 20. Therefore, if wet snow containing moisture adheres to or accumulates on the front member FP, it affects the transparency of the radio waves, which causes a decrease in the performance of the millimeter wave radar 20. In this embodiment, the front member FP is provided with a heater 30 that melts snow on the front member FP by heating the front member FP.

The heater 30 is, for example, an electric heating wire, and when power is supplied, the electric heating wire generates heat to heat the front member FP. The heater 30 may be embedded in the front member FP, or may be attached to the back surface (rear surface) of the front member FP. When snow has accumulated on the front member FP, the heat generated by the heater 30 heats the front member FP, making it possible to melt and remove the snow, and when no snow has accumulated on the front member FP, making it possible to prevent snow from adhering to the front member FP.

As shown in FIG. 2, the millimeter wave radar 20 includes a heater drive circuit 21 and a voltage/current detection circuit 22. The vehicle 10 also includes an ECU 40, a drive unit 51, a steering unit 52, a braking unit 53, a power supply unit 54, etc.

The ECU 40 has a microcomputer as its main component. ECU is an abbreviation for Electronic Control Unit. The microcomputer includes a CPU, ROM, RAM, and an interface, and the CPU executes instructions (programs, routines) stored in the ROM to realize various functions. The ECU 40 is a central control device that performs various controls on the vehicle 10. To this end, the ECU 40 is communicatively connected to a drive unit 51, a steering unit 52, a braking unit 53, a vehicle speed sensor 60, an outside air temperature sensor 61, a wiper unit 12, a wiper switch 62, a millimeter wave radar 20, a heater drive circuit 21, a voltage/current detection circuit 22, and the like.

The drive device 51 generates a drive force to be transmitted to the drive wheels of the vehicle 10. Examples of the drive device 51 include an engine and an electric motor. In this embodiment, the vehicle 10 may be any of a hybrid vehicle (HEV), a plug-in hybrid vehicle (PHEV), a fuel cell vehicle (FCEV), an electric vehicle (BEV), and an engine vehicle. The steering device 52 is, for example, an electric power steering device, and applies a steering force to the wheels of the vehicle 10. The braking device 53 is, for example, a disc-type brake device, and applies a braking force to the wheels of the vehicle 10. The power supply device 54 is, for example, a battery or an alternator, and supplies power to electrical equipment, auxiliary devices, etc. mounted on the vehicle 10.

The vehicle speed sensor 60 detects the traveling speed (vehicle speed V) of the vehicle 10 and transmits the detected vehicle speed V to the ECU 40. The vehicle speed sensor 60 may be a wheel speed sensor. The outside air temperature sensor 61 detects the outside air temperature T around the vehicle 10 and transmits the detected outside air temperature T to the ECU 40.

The wiper switch 62 is a switch for operating the wiper device 12, and is disposed, for example, on a steering column (not shown) of the vehicle 10. The wiper switch 62 is configured to be selectively operable to a number of operating positions, such as an "OFF position" for deactivating the wiper device 12, an "AUTO position" for activating the wiper device 12 when a rain sensor (not shown) detects raindrops, wet snow, etc., a "LOW position" for operating the wiper device 12 at a low speed, and a "HIGH position" for operating the wiper device 12 at a high speed.

The wiper switch 62 transmits a signal to the ECU 40 according to its operating position. The ECU 40 controls the operation of the wiper device 12 according to the received signal. In the following, the signal transmitted to the ECU 40 when the wiper switch 62 is operated to the "OFF position" is referred to as the "wiper OFF signal." Also, the signal transmitted to the ECU 40 when the wiper switch 62 is operated to any of the "AUTO position," "LOW position," and "HIGH position" is collectively referred to simply as the "wiper ON signal."

The heater drive circuit 21 has a relay (not shown). The relay of the heater drive circuit 21 selectively switches between a conducting state and a cut-off state in response to an instruction signal from the ECU 40. In the following, the case where the relay is in a conducting state is referred to as the "ON state" of the heater drive circuit 21, and the case where the relay is in a cut-off state is referred to as the "OFF state" of the heater drive circuit 21. When the heater drive circuit 21 is in the ON state, power is supplied from the power supply device 54 to the heater 30, and the heater 30 generates heat. On the other hand, when the heater drive circuit 21 is in the OFF state, the connection between the power supply device 54 and the heater 30 is cut off, and no power is supplied to the heater 30.

The voltage/current detection circuit 22 detects the voltage value V and current value I of the heater 30 when the heater drive circuit 21 is ON, i.e., when the heater 30 is energized. The voltage value V and current value I of the heater 30 detected by the voltage/current detection circuit 22 are transmitted to the ECU 40.

[Heating control and overheating prevention control]
Next, the heating control and the overheating prevention control will be described. Focusing on its functions, the ECU 40 has a snow melting request determination unit 41, a heater temperature calculation unit 42, a heater drive control unit 43, and a threshold correction unit 44 as some of its functional elements. These functional elements will be described as being included in the ECU 40, which is an integrated piece of hardware, but some of these may be provided in an ECU separate from the ECU 40. Also, some of the functional elements of the ECU 40 may be provided in an external information processing device or the like that can communicate with the vehicle 10.

The snow melting requirement determination unit 41 determines whether the environmental conditions around the vehicle 10 are such that wet snow is likely to adhere to or accumulate on the front member FP, i.e., whether the snow melting requirement is high. In general, wet snow that falls when the outside air temperature is, for example, between -5°C and +5°C tends to adhere easily to the outer surfaces of the vehicle 10, such as the front member FP. On the other hand, dry snow with low humidity (water content) that falls when the outside air temperature is lower than, for example, -5°C tends not to adhere easily to the outer surfaces of the vehicle 10. It is also thought that the driver will operate the wiper device 12 when wet snow containing moisture is falling, and will not operate the wiper device 12 when dry snow is falling, as snow is less likely to adhere to the windshield 11.

The snow melting request determination unit 41 determines that the snow melting request is high when a first condition is met in which the outside air temperature T detected by the outside air temperature sensor 61 is within a predetermined temperature range (e.g., -5°C to +5°C) where wet snow containing moisture is likely to fall, and a second condition is met in which the ECU 40 receives a wiper ON signal from the wiper switch 62. On the other hand, the snow melting request determination unit 41 determines that the snow melting request is low (not high) when at least one of the first and second conditions is not met. Note that when the first condition is met, the snow melting request determination unit 41 may also determine that the snow melting request is high if the reception strength of the reflected waves of the millimeter wave radar 20 is below a predetermined lower limit, even if the second condition is not met.

The heater temperature calculation unit 42 calculates the temperature of the heater 30 (hereinafter referred to as the estimated heater temperature Th) based on the temperature dependency of the resistance value of the heater 30. Specifically, when the heater drive circuit 21 is in the ON state, the heater temperature calculation unit 42 calculates the resistance value R of the heater 30 based on the voltage value V and current value I of the heater 30 detected by the voltage/current detection circuit 22. The resistance value R may be calculated, for example, by dividing the voltage value V by the current value I. The heater temperature calculation unit 42 also calculates the estimated heater temperature Th based on the calculated resistance value R of the heater 30. The estimated heater temperature Th is calculated as a higher temperature as the resistance value R increases. The calculation method of the estimated heater temperature Th is not particularly limited, and may be calculated by referring to a map (data table) that specifies the relationship between the resistance value R and the estimated heater temperature Th, which is obtained in advance by experiment, or may be calculated based on a relational expression between the resistance value R and the estimated heater temperature Th.

When the snow melting request determination unit 41 determines that the snow melting request is high, the heater drive control unit 43 executes heating control to make the heater 30 generate heat by turning the heater drive circuit 21 ON and energizing the heater 30. In addition, after turning the heater drive circuit 21 ON, when the heater estimated temperature Th calculated by the heater temperature calculation unit 42 reaches a predetermined threshold temperature Tv, the heater drive control unit 43 executes overheating prevention control to turn the heater drive circuit 21 OFF for a predetermined period (e.g., several seconds). The threshold temperature Tv is a threshold temperature for preventing overheating of the heater 30, and is set at a temperature that is a predetermined temperature lower than the heat resistance temperature of the heating wire of the heater 30. In this way, when the heater temperature Th reaches the threshold temperature Tm, the heater drive circuit 21 is turned OFF for a predetermined period, and overheating prevention control is executed to interrupt the energization of the heater 30, thereby effectively preventing thermal deterioration of the heater 30.

However, there is manufacturing variation in the resistance value and resistance temperature coefficient of the heating wire of the heater 30, and there is also manufacturing variation in the resistance value and resistance temperature coefficient of the circuit elements of the voltage/current detection circuit 22. For this reason, depending on the combination of variations (deviation from the average variation) in these resistance values and resistance temperature coefficients, the heater temperature calculation unit 42 may erroneously calculate the estimated heater temperature Th to be higher than the actual heater temperature.

A more detailed explanation will be given with reference to FIG. 3. In the graph shown in FIG. 3, the horizontal axis is the heater temperature Ta, and the vertical axis is the resistance value R, which is the sum of the resistance value of the heater 30 and the resistance value of the voltage/current detection circuit 22. Furthermore, Tv is the threshold temperature, Tm is the heat resistance temperature of the heater 30, and Rs is the resistance value corresponding to the threshold temperature Tv.

Line L _Md shown by a solid line in Fig. 3 is a line showing the correlation between the resistance value R and the heater temperature Ta when there is almost no resistance value variation in the heater 30 and the voltage/current detection circuit 22 (when the resistance value is approximately in the middle of the variation average). Note that line L _Md also includes a case where the resistance value variation in the heater 30 is on the side that causes the heater estimated temperature Th to be calculated higher (hereinafter referred to as the positive side) and the resistance value variation in the voltage/current detection circuit 22 is on the side that causes the heater estimated temperature Th to be calculated lower (hereinafter referred to as the negative side), and these variations are in a relationship that approximately cancels each other out. Furthermore, line L _Md also includes a case where the resistance value variation in the heater 30 is on the negative side and the resistance value variation in the voltage/current detection circuit 22 is on the positive side, and these variations are in a relationship that approximately cancels each other out.

During high-speed driving where the vehicle 10 is traveling at a predetermined high speed (for example, 50 to 60 km/h or more), the front member FP is exposed to the wind and the heater 30 is constantly cooled by the wind, so it is considered that the heater temperature Ta saturates in a temperature range lower than the threshold temperature Tv. In addition, in the case of line L _Md , the heater estimated temperature Th calculated by the heater temperature calculation unit 42 is approximately equal to the actual heater temperature Ta. Therefore, in the case of line L _Md , the possibility that the heater estimated temperature Th reaches the threshold temperature Tv while the vehicle 10 is traveling at high speed is extremely low. In other words, in the case of line L _Md , the heater drive circuit 21 is continuously maintained in the ON state while the vehicle 10 is traveling at high speed, and the heating control is continuously executed, so that the heater 30 can fully demonstrate its snow melting performance.

Line L _L1 shown by a dashed dotted line in Fig. 3 is a line showing the correlation between the resistance value R and the heater temperature Ta when the resistance value variation of the heater 30 is on the negative side and the resistance value variation of the voltage/current detection circuit 22 is also on the negative side. Line L _L2 shown by a dashed dotted line in Fig. 3 is a line showing the correlation between the resistance value R and the heater temperature Ta when the resistance value variation of either the heater 30 or the voltage/current detection circuit 22 is on the negative side and there is almost no resistance value variation in the other.

In the cases of lines L _-L1 and L- _L2 , the estimated heater temperature Th calculated by the heater temperature calculation unit 42 is lower than the actual heater temperature Ta. Therefore, in the cases of lines L- _L1 and L- _L2 , as in the case of line L- _Md , the possibility that the estimated heater temperature Th will reach the threshold temperature Tv while the vehicle 10 is traveling at high speed is extremely low, and the heater drive circuit 21 is continuously maintained in the ON state, so that the heater 30 can fully exert its snow melting performance.

A dashed line _LH1 in Fig. 3 indicates the correlation between the resistance value R and the heater temperature Ta when the resistance value variation of the heater 30 is on the positive side and the resistance value variation of the voltage/current detection circuit 22 is also on the positive side. A dashed line _LH2 in Fig. 3 indicates the correlation between the resistance value R and the heater temperature Ta when the resistance value variation of either the heater 30 or the voltage/current detection circuit 22 is on the positive side and there is almost no resistance value variation in the other.

In the cases of lines L _-L1 and L- _L2 , the heater estimated temperature Th calculated by the heater temperature calculation unit 42 is higher than the actual heater temperature Ta. Therefore, particularly in the case of line L- _L1 , where the resistance value variations are both on the plus side, even if the actual heater temperature Ta is kept lower than the threshold temperature Tv due to the cooling effect of the running wind while the vehicle 10 is running at high speed, the heater estimated temperature Th calculated by the heater temperature calculation unit 42 easily reaches the threshold temperature Tv. As a result, the heater drive circuit 21 frequently repeats the ON state and the OFF state, which causes a problem that the heater 30 cannot fully exhibit its snow melting performance.

In order to solve this problem, the ECU 40 of this embodiment is equipped with a threshold correction unit 44 that performs threshold correction to correct the threshold temperature Tv to a higher temperature when the heater drive circuit 21 repeatedly switches between the ON state and the OFF state while the vehicle 10 is traveling at high speed. Details of the threshold correction are described below.

[Threshold correction]
When the snowmelt request determination unit 41 determines that the snowmelt request is high and the heater drive control unit 43 turns on the heater drive circuit 21, the threshold correction unit 44 determines whether the vehicle 10 is traveling at a high speed of a predetermined high speed Vh or more based on the detection result of the vehicle speed sensor 60. Here, the predetermined high speed Vh is not particularly limited, but may be set by experimentally determining in advance a speed at which the temperature rise of the heater 30, which generates heat when electricity is applied, is suppressed to a threshold temperature Tv or less by the cooling effect of the traveling wind. The predetermined high speed Vh is, for example, 50 to 60 km/h. It is also possible to determine whether the vehicle 10 is traveling at a high speed based on, for example, the current position of the vehicle 10 obtained from a GPS signal and map data from a navigation system, when it is acquired that the vehicle 10 is traveling on a road where the vehicle 10 can travel at a speed of the high speed Vh or more.

When the heater drive control unit 43 has turned the heater drive circuit 21 ON and the vehicle 10 is traveling at a predetermined high speed Vh or higher, the threshold correction unit 44 determines whether the heater estimated temperature Th calculated by the heater temperature calculation unit 42 has reached a predetermined threshold temperature Tv, i.e., whether the heater drive circuit 21 has been switched from the ON state to the OFF state. When the heater drive circuit 21 is switched to the OFF state, the threshold correction unit 44 sequentially counts the number of times N that the heater drive circuit 21 is switched from the ON state to the OFF state before a predetermined time (e.g., about 4 minutes) has elapsed. Then, when the number of times N counted before the predetermined time has elapsed reaches a predetermined threshold number Nm (e.g., 20 times), the threshold correction unit 44 executes threshold correction to correct the threshold temperature Tv to the higher temperature side.

The threshold correction may be performed by adding a fixed correction amount to the threshold temperature Tv for each correction, or may be performed by adding a larger correction amount to the threshold temperature Tv the shorter the time it takes for the number of switching times N to reach the threshold number of switching times Nm. In either case, the correction amount to be added to the threshold temperature Tv is set to the upper limit value of the heat resistance temperature Tm of the heater 30, and is set based on a correction amount that does not cause the corrected threshold temperature (hereinafter, the corrected threshold temperature Tvc) to exceed the heat resistance temperature Tm.

In this way, when the heater drive circuit 21 repeatedly switches between ON and OFF states in a situation where the temperature rise of the heater 30 is suppressed due to high-speed driving of the vehicle 10, a threshold correction is performed to correct the threshold temperature Tv to the higher temperature side. This prevents the heater estimated temperature Th from being calculated to the higher temperature side and exceeding the threshold temperature Tv due to variations in the resistance values of the heater 30 and the voltage/current detection circuit 22, and as a result, the heater estimated temperature Th calculated by the heater temperature calculation unit 42 does not reach the threshold temperature Tv. In other words, the heater drive circuit 21 is maintained in the ON state. This makes it possible to effectively demonstrate the snow melting performance of the heater 30.

Next, the specific flow of the heating control, overheating prevention control, and threshold correction of this embodiment will be described based on the timing chart shown in Figure 4. Note that the timing chart shown in Figure 4 is an example of a case where the resistance value deviation of both the heater 30 and the voltage/current detection circuit 22 is on the positive side, or a case where the resistance value deviation of either the heater 30 or the voltage/current detection circuit 22 is on the positive side and the other has almost no resistance value deviation.

When the ignition switch or power switch of the vehicle 10 is turned on at time t0, the snow melting request determination unit 41 determines whether a first condition is met, that is, the outside air temperature T detected by the outside air temperature sensor 61 is within a predetermined temperature range (e.g., -5°C to +5°C). If the first condition is met, the snow melting request determination unit 41 determines whether a second condition is met, that is, the ECU 40 receives a wiper ON signal from the wiper switch 62.

When the second condition is met at time t1, the snow melting request determination unit 41 determines that the snow melting request is high. When the snow melting request determination unit 41 determines that the snow melting request is high, the heater drive control unit 43 switches the heater drive circuit 21 from OFF to ON. In other words, it starts heating control to energize the heater 30. Note that the timing of operating the wiper device 12 varies depending on the driver and also depends on the snowfall conditions. For this reason, the timing of the second condition being met may be either before or after the vehicle 10 starts to move, but in the illustrated example, it is assumed that the second condition is met before the vehicle 10 starts to move.

At time t2, the vehicle 10 starts traveling, at time t3 the vehicle speed V of the vehicle 10 reaches or exceeds a predetermined high speed Vh, and at time t4 the heater estimated temperature Th calculated by the heater temperature calculation unit 42 reaches a predetermined threshold temperature Tv. In this case, the heater drive control unit 43 starts overheating prevention control to switch the heater drive circuit 21 from the ON state to the OFF state. When the heater drive circuit 21 switches from the ON state to the OFF state, the threshold correction unit 44 sets the count value of the number of switching times N to 1.

The overheating prevention control that started at time t4 ends when the heater drive circuit 21 is turned OFF for a predetermined period (e.g., several seconds). During execution of the overheating prevention control, the heater estimated temperature Th gradually decreases. If the snow melting request determination unit 41 still determines that the snow melting request is high at time t5 when the overheating prevention control ends, that is, if both the first and second conditions are satisfied, the heater drive control unit 43 resumes the heating control from time t5 by switching the heater drive circuit 21 from the OFF state to the ON state. Thereafter, if the heater estimated temperature Th reaches the threshold temperature Tv, the overheating prevention control is started, and if it is determined that the snow melting request is high at the end of the overheating prevention control, the process of resuming the heating control is repeatedly executed.

When the vehicle speed V reaches or exceeds a predetermined high speed Vh at time t3, or when the number of switching times N reaches a predetermined threshold number Nm (e.g., 20 times) at time t6 before a predetermined time has elapsed since the number of switching times N was counted as 1 at time t4, the threshold correction unit 44 executes threshold correction to correct the threshold temperature Tv to the higher temperature side. After executing threshold correction, the heater drive control unit 43 executes heating control and overheating prevention control based on the corrected threshold temperature Tvc corrected to the higher temperature side. In other words, after time t7, the heater drive circuit 21 is maintained in the ON state, or the frequency of switching to the OFF state is reduced, making it possible to effectively demonstrate the snow melting performance of the heater 30.

Next, the heating control and overheating prevention control routines executed by the CPU of the ECU 40 will be described with reference to the flowchart shown in FIG. 5. This routine is started when the ignition switch or power switch of the vehicle 10 is turned ON.

In step S100, the ECU 40 determines whether a first condition is met, that is, the outside air temperature T detected by the outside air temperature sensor 61 is within a predetermined temperature range in which wet snow containing moisture is likely to fall. If the first condition is met (Yes), the ECU 40 advances the process to step S110. On the other hand, if the first condition is not met (No), the ECU 40 temporarily ends (returns) this routine.

In step S110, the ECU 40 determines whether the second condition of receiving a wiper ON signal from the wiper switch 62 is satisfied. If the second condition is satisfied (Yes), the ECU 40 advances the process to step S120. On the other hand, if the second condition is not satisfied (No), the ECU 40 temporarily ends (returns) this routine.

In step S120, the ECU 40 determines that the snow melting requirement is high. Next, in step S125, the ECU 40 starts heating control to energize the heater 30 by switching the heater drive circuit 21 from the OFF state to the ON state.

In step S130, the ECU 40 acquires the voltage value V and current value I of the heater 30 based on the detection results of the voltage/current detection circuit 22. Next, in step S140, the ECU 40 calculates the resistance value R of the heater 30 based on the voltage value V and current value I acquired in step S130.

In step S150, the ECU 40 calculates the estimated heater temperature Th based on the resistance value R calculated in step S130. Next, in step S160, the ECU 40 determines whether the estimated heater temperature Th has reached a predetermined threshold temperature Tv. If the estimated heater temperature Th has reached the threshold temperature Tv (Yes), the ECU 40 advances the process to step S180. On the other hand, if the estimated heater temperature Th has not reached the threshold temperature Tv (No), the ECU 40 advances the process to step S170.

In step S170, the ECU 40 determines whether both the first condition and the second condition are met, i.e., whether the snow melting demand is still high. If the ECU 40 determines that the snow melting demand is high (Yes), the ECU 40 returns the process to step S125 and keeps the heater drive circuit 21 in the ON state, i.e., continues the heating control. On the other hand, if the ECU 40 determines that the snow melting demand is low (No), the ECU 40 advances the process to step S174, switches the heater drive circuit 21 from the ON state to the OFF state to end the heating control, and then ends (returns) this routine.

In step S180, the ECU 40 executes overheating prevention control by switching the heater drive circuit 21 from the ON state to the OFF state. In step S182, the ECU 40 determines whether or not a predetermined period of time has elapsed. If the predetermined period of time has not elapsed (No), the ECU 40 returns the process to step S180 and maintains the heater drive circuit 21 in the OFF state, i.e., continues the overheating prevention control. On the other hand, if the predetermined period of time has elapsed (Yes), the ECU 40 advances the process to step S184.

In step S184, the ECU 40 determines whether the first and second conditions are both met, i.e., whether the snow melting demand is still high. If the ECU 40 determines that the snow melting demand is high (Yes), the ECU 40 returns the process to step S125 and resumes heating control. On the other hand, if the ECU 40 determines that the snow melting demand is low (No), the ECU 40 ends (returns) this routine.

Next, a threshold correction routine executed by the CPU of the ECU 40 will be described based on the flowchart shown in FIG. 6. This routine is executed in parallel with the heating control and overheating prevention control routines shown in FIG. 5. Specifically, when the heater drive circuit 21 is switched to the ON state in step S125 shown in FIG. 5, the ECU 40 starts the threshold correction routine shown in FIG. 6.

In step S200, the ECU 40 determines whether the vehicle 10 is traveling at a high speed equal to or higher than a predetermined high speed Vh based on the detection result of the vehicle speed sensor 60. If the vehicle 10 is traveling at a high speed equal to or higher than the high speed Vh (Yes), the ECU 40 advances the process to step S205. On the other hand, if the vehicle 10 is not traveling at a high speed (No), that is, if the vehicle 10 is traveling or stopped at a speed slower than the predetermined high speed Vh, the ECU 40 temporarily ends (returns) this routine.

In step S205, the ECU 40 measures the elapsed time using a timer built into the ECU. In step S210, the ECU 40 counts the number of times N that the heater drive circuit 21 is switched from the OFF state to the ON state. The number of times N corresponds to the number of times the overheat prevention control is repeated, and can be obtained by counting the number of times the process of step S180 in FIG. 5 is executed. The process of starting the time measurement in step S205 may start when the number of times N is counted to 1 in step S210.

In step S220, the ECU 40 determines whether the number of switching times N reaches a predetermined threshold number of times Nm before the elapsed time measured by the timer reaches a predetermined time. If it is determined that the number of switching times N has reached the threshold number of times Nm (No), the ECU 40 advances the process to step S230. On the other hand, if it is determined that the number of switching times N has not reached the threshold number of times Nm (No), the ECU 40 advances the process to step S240.

If it is determined in step S220 that the number of switching times N has reached the threshold number of switching times Nm (Yes), it is assumed that the resistance value variation of the heater 30 and the voltage/current detection circuit 22 is on the positive side. In this case, the ECU 40 proceeds to step S230 and executes a threshold correction to correct the threshold temperature Tv to the higher temperature side. Next, in step S260, the elapsed time and the number of switching times N are reset (set to zero), and then this routine is temporarily terminated (returned).

In step S240, it is determined whether the elapsed time has reached a predetermined time. If the elapsed time has not reached the predetermined time (No), the ECU 40 returns the process to step S200. That is, while the vehicle 10 is traveling at high speed, the ECU 40 continues to measure the elapsed time and count the number of switching times N until the predetermined time has elapsed. On the other hand, if the elapsed time has reached the predetermined time (Yes), it is presumed that there is no resistance value variation in the heater 30 or the voltage/current detection circuit 22, or that the resistance value variation is on the negative side. In this case, the ECU 40 advances the process to step S260 without performing threshold correction, resets the elapsed time and the number of switching times N, and then ends (returns) this routine. Thereafter, while the heating control and overheating prevention control routines shown in FIG. 5 are being executed, the ECU 40 repeatedly executes the processes of steps S200 to S260 described above.

According to the present embodiment described above in detail, during the execution of heating control to energize the heater 30, the resistance value R of the heater 30 is calculated based on the voltage value V and current value I of the heater 30, and the estimated heater temperature Th is calculated based on the calculated resistance value R. When the estimated heater temperature Th reaches a predetermined threshold temperature Tv during the execution of heating control, overheating prevention control is executed to stop energization of the heater 30 for a predetermined period of time. Then, during high-speed driving in which the vehicle 10 is driving at a predetermined high speed Vh or higher, if the overheating prevention control is executed a predetermined number of times or more within a predetermined time, a threshold correction is executed to correct the threshold temperature Tv to the higher temperature side. After the threshold correction is executed, the overheating prevention control is performed based on the corrected threshold temperature Tvc that has been corrected to the higher temperature side.

In other words, when the vehicle 10 is traveling at high speeds, the temperature rise of the heater 30 is suppressed, and the actual temperature of the heater 30 is lower than the threshold temperature Tv, unnecessary execution of overheating prevention control can be effectively prevented. This allows the heating control to be executed continuously, and the snow melting performance of the heater 30 can be effectively demonstrated.

The above describes the control device, control method, and program according to this embodiment, but this disclosure is not limited to the above embodiment, and various modifications are possible without departing from the purpose of the present invention.

For example, in the above embodiment, the threshold correction is described as being executed when the overheating prevention control is executed a predetermined number of times or more within a predetermined time, but it may be configured to be executed when the overheating prevention control is executed once. Also, the radar sensor is described as being a millimeter wave radar 20 as an example, but it can be widely applied to other radar sensors such as lidars. Also, the heater 30 is provided on the front member FP, but it can be provided on a member other than the front member FP depending on the position where the millimeter wave radar 20 is mounted.

10...vehicle, 11...windshield, 12...wiper device, 13...front bumper, 14...front grille, 15...emblem, 20...millimeter wave radar, 21...heater drive circuit, 22...voltage/current detection circuit, 30...heater, 31...camera, 32...radar sensor, 40...ECU, 41...snow melting request determination unit, 42...heater temperature calculation unit, 43...heater drive control unit, 44...threshold correction unit, 60...vehicle speed sensor, 61...outside air temperature sensor, 62...wiper switch

Claims (6)

A control device for a heater that is provided on at least a portion of a member forming a part of an exterior surface of a vehicle, the portion being transparent to radio waves from a radar mounted on the vehicle, and that melts snow on the member by generating heat when electricity is applied thereto,
a temperature calculation unit that calculates a resistance value of the heater based on a voltage value and a current value of the heater detected when the heater is energized, and calculates a temperature of the heater based on the calculated resistance value;
a heater control unit that executes a heating control for energizing the heater, and executes an overheating prevention control for stopping energization of the heater for a predetermined period when the temperature calculated by the temperature calculation unit during the execution of the heating control reaches a predetermined threshold temperature;
a threshold correction unit that performs threshold correction to correct the threshold temperature to a higher temperature when the overheating prevention control is executed while the vehicle is traveling at high speeds at or above a predetermined speed. The control device according to claim 1 ,
The threshold correction unit executes the threshold correction when the overheating prevention control is executed a predetermined number of times or more within a predetermined time while the vehicle is traveling at a high speed equal to or faster than a predetermined speed. The control device according to claim 1 or 2,
The threshold correction unit executes the threshold correction so that the corrected threshold temperature does not exceed a heat-resistant temperature of the heater. The control device according to any one of claims 1 to 3,
The heater control unit is
The control device executes the heating control when the outside air temperature around the vehicle is within a predetermined temperature range in which wet snow containing moisture falls and when a wiper device for wiping a windshield of the vehicle is operating. A method for controlling a heater that is provided on at least a portion of a member forming a part of an exterior surface of a vehicle, the portion being transparent to radio waves from a radar mounted on the vehicle, and that melts snow on the member by generating heat when electricity is applied thereto, comprising the steps of:
calculating a resistance value of the heater based on a voltage value and a current value of the heater detected when the heater is energized, and calculating a temperature of the heater based on the calculated resistance value;
executing a heating control for energizing the heater, and executing an overheating prevention control for stopping energization of the heater for a predetermined period when the temperature calculated during the execution of the heating control reaches a predetermined threshold temperature;
a threshold correction is performed to correct the threshold temperature to a higher temperature when the overheating prevention control is executed while the vehicle is traveling at a high speed above a predetermined speed. A computer of a heater control device is provided on at least a portion of a member forming a part of an exterior surface of a vehicle that transmits radio waves from a radar mounted on the vehicle, and melts snow on the member by generating heat when electricity is applied,
calculating a resistance value of the heater based on a voltage value and a current value of the heater detected when the heater is energized, and calculating a temperature of the heater based on the calculated resistance value;
executing a heating control for energizing the heater, and executing an overheating prevention control for stopping energization of the heater for a predetermined period when the temperature calculated during the execution of the heating control reaches a predetermined threshold temperature;
a program for executing a process of performing a threshold correction for correcting the threshold temperature to a higher temperature when the overheating prevention control is executed while the vehicle is traveling at a high speed above a predetermined speed.

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