Defogger control unit

Abstract

To reduce the power consumption caused during operation of a defogger.SOLUTION: A controller for a defogger including a heating wire disposed on a window glass of a vehicle turns on the defogger. The controller repeatedly acquires a value of current flowing through the heating wire while the defogger is on. The controller turns off the defogger based on a value of a current having converged to a constant value (S310, S314).SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present disclosure relates to a controller for a defogger.

Background Art

[0002] A defogger has a heating wire provided on a window glass of a vehicle. By energizing the heating wire, it is possible to warm the window glass. Thereby, it is possible to remove fogging or the like that occurs on the window glass.

[0003] A known defogger is turned on when a user presses a switch. The defogger turns off when a certain period of time has elapsed since it was turned on. Patent Document 1 discloses a cutoff device that cuts off a current supplied to a load via an electric wire based on a predetermined condition. The cutoff device periodically calculates the temperature of the electric wire based on the value of the current flowing through the electric wire. The cutoff device cuts off the current flowing through the electric wire when the calculated temperature of the electric wire is equal to or higher than a threshold temperature. The threshold temperature is preset so as to be able to prevent smoke or fire from the electric wire.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] The power consumption that occurs during the operation of the defogger is large. In order to suppress the power consumption, it is desired to shorten the operation time of the defogger as much as possible.

Means for Solving the Problems

[0006] The following describes the means and effects of solving the above problems. According to one aspect of the present disclosure, a control device for a defogger having a heating element provided in the window glass of a vehicle is provided, comprising a processing circuit, the processing circuit configured to turn on the defogger, repeatedly acquire the value of the current flowing through the heating element while the defogger is on, and turn off the defogger based on the current value converging to a constant value. [Effects of the Invention]

[0007] The above configuration makes it easier to avoid situations where the defogger is unnecessarily activated even though it is highly likely that any condensation or fog on the window glass has been sufficiently removed. [Brief explanation of the drawing]

[0008] [Figure 1] Figure 1 shows a control device for a defogger according to one embodiment. [Figure 2] Figure 2 is a schematic diagram showing the change in current value while the defogger is operating. [Figure 3] Figure 3 is a flowchart showing the process performed by the control device shown in Figure 1. [Figure 4] Figure 4 is a flowchart showing the process performed by the control device in Figure 1. [Figure 5] Figure 5 is a sequence diagram showing the signal exchange between the control device and the air conditioning ECU shown in Figure 1. [Figure 6] Figure 6 is a flowchart showing the process related to the example of the change. [Modes for carrying out the invention]

[0009] A control device for a defogger according to one embodiment will be described below with reference to the drawings. <Outline configuration> Referring to Figure 1, the control device 10 for the defogger 20 will be described. The defogger 20 has heating elements installed in the vehicle's window glass. The defogger 20 is, for example, a rear defogger with heating elements installed in the rear window glass. The control device 10 keeps the defogger 20 on while it is repeatedly receiving an ON signal from the air conditioning ECU 30 that controls the air conditioning system. The air conditioning ECU 30 starts transmitting an ON signal based on the user pressing a button 32 connected to the air conditioning ECU 30. The control device 10 controls the on / off state of the defogger 20 by turning on and off a circuit switch 26 provided on the wire 24 connecting the power supply 22 and the defogger 20. The circuit switch 26 is a FET (Field Effect Transistor). The circuit switch 26 and the current detection unit 18, which will be described later, constitute a relay. As will be described later, if the control device 10 makes a positive determination in both step S310 and step S312 in Figure 3, it requests the air conditioning ECU 30 to stop the ON signal. That is, the control device 10 turns off the defogger 20.

[0010] The control device 10 comprises a control unit 12, a storage device 14, a drive circuit 16, and a current detection unit 18. The control unit 12 includes a CPU and RAM. The storage device 14 is, for example, ROM. The ROM stores control programs and data. The CPU executes the programs stored in the ROM. RAM is the working area for the CPU when executing programs. The control unit 12 controls the drive circuit 16. The drive circuit 16 turns the circuit switch 26 on and off by adjusting the voltage applied to the gate of the circuit switch 26. The drive circuit 16 is connected to the current detection unit 18. The current detection unit 18 is connected to the control unit 12. The current detection unit 18 detects the current flowing through the electric wire 24. Then, the current detection unit 18 outputs current information indicating the value of the detected current to the drive circuit 16 and the control unit 12. In this way, the control device 10 repeatedly acquires the value of the current flowing through the heating element while the defogger 20 is on.

[0011] <Changes in current value while defogger 20 is operating> Referring to Figure 2, the change in current value during the operation of the defogger 20 will be explained. At time T0, the defogger 20 is turned on. From time T0 to time T1, the current flowing through the heating element increases. At time T1, the current reaches its maximum value. The time interval from time T0 to time T1 is only a few seconds.

[0012] Generally, the resistance of a conductor increases as its temperature rises. Therefore, the current value gradually decreases after time T1. When the heating element is sufficiently heated, its temperature settles to a nearly constant value. This means that the resistance of the heating element settles to a nearly constant value. Therefore, the value of the current flowing through the heating element also settles to a nearly constant value. From time T2 onward, the value of the current also settles to a nearly constant value. In particular, at times T2 and T3, the value of the current is nearly identical. The period from time T0 to time T2 is only a few minutes.

[0013] When the current value settles at approximately a constant value, it is highly likely that the heating element has heated up sufficiently and any condensation on the window glass has been adequately removed. The inventor designed the control device 10 with this point in mind. The processes performed by the control device 10 will be described below.

[0014] <Processing executed by the control device 10> The processes performed by the control device 10 will be described with reference to Figures 3 and 4. When the user presses button 32, the control device 10 starts the process shown in Figure 3. As will be described later, immediately after the process shown in Figure 3 is completed, the control device 10 starts the process shown in Figure 4. In the process shown in Figure 4, the control device 10 monitors whether the user has pressed button 32 again. As described above, the air conditioning ECU 30 starts transmitting an ON signal based on the user pressing button 32 connected to the air conditioning ECU 30. The control device 10 keeps the defogger 20 ON while it is repeatedly receiving the ON signal.

[0015] In step S302, the control device 10 acquires the temperature and humidity outside the vehicle when the defogger 20 is turned on. The control device 10 may acquire the temperature and humidity outside the vehicle from the air-conditioning ECU 30.

[0016] In step S304, the control device 10 calculates a decrease amount, which is the amount by which the acquired current value has decreased from the current value acquired a predetermined period before. The decrease amount is a positive value. While the current value is increasing, the decrease amount is not calculated because the current value is not decreasing. The predetermined period is appropriately set to be shorter than, for example, the period from time T0 to T2.

[0017] In step S306, the control device 10 calculates a change rate, which is the value obtained by dividing the decrease amount by the current value acquired before the elapse of the predetermined period. When the decrease amount has not been calculated, the control device 10 sets the change rate to a default value larger than a determination threshold value described later.

[0018] In step S308, the control device 10 calculates the total power consumption, which is the total power consumed by the defogger 20 from the time when the defogger 20 is turned on. In step S310, the control device 10 determines whether the change rate is less than the determination threshold value. The determination threshold value is appropriately set to a positive value close to 0 so that it can be determined that the current value converges to a constant value. Therefore, when the change rate is less than the determination threshold value, the control device 10 determines that the current value converges to a constant value. When the control device 10 makes a negative determination in step S310 (S310: NO), it returns to step S304. When the control device 10 makes an affirmative determination in step S310 (S310: YES), it proceeds to step S312.

[0019] In step S312, the control device 10 determines whether the total power consumption is equal to or greater than the power threshold. The power threshold is set to avoid a situation where the defogger 20 is turned off even though the total power consumption is too low. Here, if the total power consumption is too low, it is highly likely that the condensation on the window glass has not been sufficiently removed. If the control device 10 determines in step S312 that the total power consumption is too low (S312: NO), it returns to step S304. If the control device 10 determines in step S312 that the total power consumption is too low (S312: YES), it proceeds to step S314.

[0020] In step S314, the control device 10 requests the air conditioning ECU 30 to stop transmitting the ON signal. That is, the control device 10 turns off the defogger 20. According to steps S310 to S314, the control device 10 turns off the defogger 20 if the total power consumption is greater than or equal to the power threshold and the current value has converged to a constant value.

[0021] Immediately after turning off the defogger 20 in step S314, the control device 10 starts the process shown in Figure 4. In step S402, the control device 10 determines whether the user has pressed button 32 again. For example, the control device 10 determines that the user has pressed button 32 again based on receiving an ON signal from the air conditioning ECU 30. If the control device 10 determines in step S402 that this is not the case (S402: NO), it proceeds to step S404. In step S404, the control device 10 determines whether a predetermined period has elapsed since the defogger 20 was turned off, based on the fact that the current value has converged to a constant value. For example, if the user presses button 32 again immediately after the defogger 20 is turned off, it is highly likely that the removal of condensation on the window glass was insufficient. This means, for example, that the power threshold value may have been smaller than the appropriate value. The predetermined period is set so that the validity of the process shown in Figure 3 can be determined. For example, the predetermined period is set to a length of less than one minute. If the control device 10 determines in step S404 that it is negative (S404: NO), it returns to step S402. According to steps S402 and S404, the control device 10 determines whether the defogger 20 was turned on again within a predetermined period from the time the defogger 20 was turned off based on the fact that the current value has converged to a constant value.

[0022] If the control device 10 determines that step S404 is positive (S404: YES), it proceeds to step S406. In step S406, the control device 10 stores the power threshold and the temperature and humidity acquired in step S302 as success data in the storage device 14.

[0023] If the control device 10 makes a positive determination in step S402 (S402: YES), it proceeds to step S408. The control device 10's positive determination in step S402 means that the control device 10 received the ON signal before the predetermined period described above had elapsed. Next, in step S408, the control device 10 stores the power threshold and the temperature and humidity acquired in step S302 as failure data in the storage device 14. According to steps S402, S404, and S408, if the defogger 20 is turned ON again within the predetermined period, the control device 10 stores the temperature and humidity and the power threshold as failure data in the storage device 14.

[0024] After executing the process in step S408, the control device 10 proceeds to step S410. In step S410, the control device 10 waits for a specified period. The specified period is a sufficient value to remove any remaining cloudiness, etc., that could not be removed through the process described with reference to Figure 3. For example, the specified period is several minutes. After waiting for the specified period in step S410, the control device 10 proceeds to step S412. In step S412, the control device 10 requests the air conditioning ECU 30 to stop transmitting the ON signal. That is, the control device 10 turns off the defogger 20.

[0025] <Signal exchange between control device 10 and air conditioning ECU 30> Referring to Figure 5, the relationship between the signal exchange between the control device 10 and the air conditioning ECU 30, and the processes shown in Figure 3 and Figure 4 will be explained. The two rectangles in Figure 5 represent the processes shown in Figure 3 and Figure 4, respectively.

[0026] When the user presses button 32, the air conditioning ECU 30 starts sending an ON signal to the control device 10. This causes the control device 10 to start the process shown in Figure 3. The air conditioning ECU 30 continues to repeatedly send the ON signal until the control device 10 requests that it stop sending the ON signal. While the control device 10 is repeatedly receiving the ON signal, it continues the process shown in Figure 3 to keep the defogger 20 powered on. In step S314 of Figure 3, the control device 10 requests the air conditioning ECU 30 to stop sending the ON signal. This stops the transmission of the ON signal from the air conditioning ECU 30, and the control device 10 turns off the defogger 20. Next, the control device 10 starts the process shown in Figure 4.

[0027] Figure 5 illustrates the case where the defogger 20 is turned on again by the user pressing button 32 within the predetermined period described above. When the user presses button 32, the air conditioning ECU 30 starts sending an ON signal to the control device 10. Based on receiving the ON signal from the air conditioning ECU 30 within the predetermined period, the control device 10 turns on the defogger 20. In step S408 of Figure 4, the control device 10 stores the temperature, humidity, and power threshold as failure data in the storage device 14. In step S410 of Figure 4, the control device 10 waits for a specified period. Then, in step S412, the control device 10 requests the air conditioning ECU 30 to stop sending the ON signal. As a result, the transmission of the ON signal from the air conditioning ECU 30 stops, and the control device 10 turns off the defogger 20.

[0028] If the control device 10 does not receive an ON signal from the air conditioning ECU 30 within a predetermined period, in step S406, the control device 10 stores the power threshold, temperature, and humidity as success data in the storage device 14. In this case, since an ON signal has not been received from the air conditioning ECU 30, the control device 10 does not turn on the defogger 20.

[0029] <Effects of this embodiment> (1) The control device 10 for a defogger 20 having an electric heating element installed in the window glass of a vehicle is configured to turn on the defogger 20, repeatedly acquire the value of the current flowing through the electric heating element while the defogger 20 is on, and turn off the defogger 20 based on the fact that the value of the current has converged to a constant value.

[0030] When the heating element of the defogger 20 is energized, its temperature rises. Generally, the resistance of a conductor increases as its temperature rises. Therefore, when the defogger 20 is turned on, the current flowing through the heating element increases to a maximum value and then gradually decreases. When the heating element is sufficiently warm, its temperature settles to a nearly constant value. This means that the resistance of the heating element has settled to a nearly constant value. Therefore, the value of the current flowing through the heating element also settles to a nearly constant value. Consequently, when the value of the current has also settled to a nearly constant value, it is highly likely that the heating element is sufficiently warm and that any condensation on the window glass has been sufficiently removed. The control device 10 turns off the defogger 20 when the value of the current has converged to a constant value. Therefore, it is easy to avoid a situation where the defogger 20 is unnecessarily activated even though it is highly likely that any condensation on the window glass has been sufficiently removed.

[0031] (2) The control device 10 is configured to calculate the decrease amount, which is the amount by which the acquired current value has decreased from the current value acquired before a predetermined period, to calculate the change rate, which is the value obtained by dividing the decrease amount by the current value acquired before the predetermined period had elapsed, and to determine that the current value has converged to a constant value if the change rate is less than a determination threshold.

[0032] A change rate below a judgment threshold indicates that the decrease in current is converging. Therefore, according to the control device 10 described above, it is possible to determine that the value of the current under energization is converging to a constant value based on the change rate being below a judgment threshold.

[0033] (3) The control device 10 is configured to repeatedly calculate the total power consumption, which is the sum of the power consumed by the defogger 20 from the time the defogger 20 was turned on, while the defogger 20 is on, and to turn off the defogger 20 if the total power consumption is equal to or greater than a power threshold and the current value has converged to a constant value.

[0034] As the total power consumption increases, the amount of fogging on the window glass decreases. The control device 10 determines whether or not to turn off the defogger 20 based on both the total power consumption and the rate of change. In other words, it is possible to avoid a situation where the defogger 20 is turned off even though the total power consumption is too low. Here, if the total power consumption is too low, it is highly likely that the fogging on the window glass has not been sufficiently removed. Therefore, the accuracy of the determination can be improved.

[0035] (4) The control device 10 further includes a storage device 14. The control device 10 is configured to acquire the temperature and humidity outside the vehicle at the time the defogger 20 is turned on, to determine whether the defogger 20 was turned on again within a predetermined period from the time the defogger 20 was turned off based on the fact that the current value has converged to a constant value, and, if the defogger 20 was turned on again within the predetermined period, to store the temperature and humidity and the power threshold as failure data in the storage device 14.

[0036] If the defogger 20 is turned on again within a predetermined period, it means that the defogger 20 was turned off before the condensation on the window glass was sufficiently removed. The control device 10 can store data acquired in such situations. This stored data can be used when designing the control device 10 to adjust the operating period of the defogger 20 based on the temperature and humidity outside the vehicle.

[0037] <Example of changes> This embodiment can be implemented with the following modifications. This embodiment and the following modifications can be combined with each other to the extent that they do not contradict each other technically.

[0038] In the above embodiment, the circuit switch 26 and the current detection unit 18 constitute a relay. The relay may be a mechanical relay or a semiconductor relay. Mechanical relays do not have a current value detection function, while semiconductor relays inherently have a current value detection function. By using a semiconductor relay, the need to provide a separate circuit for detecting the current value is eliminated. This is advantageous in terms of cost.

[0039] In the above embodiment, the control device 10 calculates the rate of change, which is the value obtained by dividing the decrease by the value of the current acquired before the predetermined period had elapsed. However, this is merely an example. For example, the rate of change may be the value obtained by dividing the decrease by the predetermined period.

[0040] The control device 10 for the defogger 20 in the modified example will be explained with reference to Figure 6. The storage device 14 of the control device stores a map that defines the relationship between a power threshold and the temperature and humidity outside the vehicle at the time the defogger 20 is turned on. In step S302, the control device 10 acquires the temperature and humidity outside the vehicle at the time the defogger 20 is turned on. In step S303, the control device 10 acquires the power threshold corresponding to the acquired temperature and humidity from the map. According to the configuration in Figure 6, the power threshold is variably set based on the temperature and humidity outside the vehicle. Therefore, the accuracy of the determination of whether or not to turn off the defogger 20 can be improved. The stored data explained with reference to Figure 4 is useful for redesigning the above map. For example, if the defogger 20 is turned on again after being turned off based on a current threshold, the current threshold in the above map can be updated to a larger value.

[0041] The defogger 20 may be configured to turn off after a certain period of time has elapsed since it was turned on. In this case, even if the control to turn off the defogger 20 based on current fails, the defogger 20 will turn off after a certain period of time has elapsed since it was turned on. Therefore, even if the control to turn off the defogger 20 based on current fails, the defogger 20 will not remain on for a long period of time. Thus, it is easier to avoid unnecessarily operating the defogger 20.

[0042] • If the total power consumption becomes excessively high, the defogger 20 may be turned off regardless of whether the current value has converged or not. Step S302 and the process shown in Figure 4 may be omitted.

[0043] Step S312 may be omitted. That is, the control device 10 may turn off the defogger 20 based on the fact that the current value has converged to a constant value, regardless of the total power consumption.

[0044] In the above embodiment, the control device 10 includes a control unit 12 and a storage device 14. The control device 10 executes software processing. However, this is merely an example. For example, the control device 10 may include a dedicated hardware circuit (e.g., an ASIC) that processes at least a part of the software processing executed in the above embodiment. That is, the control device 10 may have any of the following configurations (a) to (c): (a) The control device 10 includes a processing unit that executes all processing according to a program and a program storage device such as a ROM that stores the program. That is, the control device 10 includes a software execution unit. (b) The control device 10 includes a processing unit that executes part of the processing according to a program and a program storage device. Furthermore, the control device 10 includes a dedicated hardware circuit that executes the remaining processing. (c) The control device 10 includes a dedicated hardware circuit that executes all processing. Here, there may be multiple software execution units and / or dedicated hardware circuits. That is, the above processing can be executed by a processing circuitry that includes at least one of a software execution unit and a dedicated hardware circuitry. There may be multiple software execution units and dedicated hardware circuits included in the processing circuitry. A program storage device, or computer-readable medium, includes any available medium that can be accessed by a general-purpose or dedicated computer. [Explanation of Symbols]

[0045] 10...Control device, 14...Storage device, 20...Defogger

Claims

1. A control device for a defogger having an electric heating element installed in the window glass of a vehicle, It includes a processing circuit, and the processing circuit is Turning on the aforementioned defogger, While the defogger is on, the value of the current flowing through the heating element is repeatedly acquired. While the defogger is on, the total power consumption, which is the sum of the power consumed by the defogger from the moment it was turned on, is repeatedly calculated. The system is configured to turn off the defogger based on the fact that the total power consumption is equal to or greater than a power threshold and the current value converges to a constant value. Defogger control device.

2. The aforementioned processing circuit is The amount of decrease is calculated as the amount by which the acquired current value has decreased from the current value acquired before a predetermined period. The change rate is calculated by dividing the aforementioned decrease by the value of the current acquired before the predetermined period elapsed. The system is configured to determine that the value of the current has converged to the constant value if the rate of change is less than the determination threshold. A control device for a defogger according to claim 1.

3. The control device further comprises a storage device, The aforementioned processing circuit is The process involves obtaining the external temperature and humidity of the vehicle at the time the defogger is turned on, Based on the fact that the value of the current has converged to the constant value, it is determined whether the defogger was turned on again within a predetermined period from the time the defogger was turned off, If the defogger is turned on again within the predetermined period, the system is configured to store the temperature, humidity, and power threshold as failure data in the storage device. A control device for a defogger according to claim 1.

4. The control device further includes a storage device that stores a map defining the relationship between the power threshold and the external temperature and humidity of the vehicle at the time the defogger is turned on. The aforementioned processing circuit is The process involves obtaining the external temperature and humidity of the vehicle at the time the defogger is turned on, The system is configured to obtain the power threshold corresponding to the acquired temperature and humidity from the map, A control device for a defogger according to claim 1.

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