Raindrop detecting device and method of selecting wiping mode for vehicle

This application is based on Japanese Patent Application No. 2006-355965 filed on Dec. 28, 2006, the disclosure of which is incorporated herein by reference in its entirety.

1. Field of the Invention

The present invention relates to a raindrop detecting device and a method of selecting wiping mode for a vehicle.

2. Description of Related Art

A wiper wipes raindrop on a windshield, e.g., front windshield, of a vehicle, and a wiper automatic control apparatus automatically controls the wiper. The wiper automatic control apparatus includes a raindrop detecting device having a light-emitting element and a light-receiving element. The light-emitting element emits light, and the windshield reflects the emitted light. The reflected light is introduced into the light-receiving element, and the light-receiving element detects an amount of light received by the light-receiving element. Thus, raindrop amount can be detected, because the amount of the received light is changed in accordance with the raindrop amount. Further, a wiping mode of the wiper can be selected based on the detected raindrop amount.

EP 1 623 896 A1 (corresponding to JP-A-2004-338526) discloses a wiper automatic control apparatus having a raindrop detecting device. The wiper automatic control apparatus is required to smoothly correspond to a rapid change of a rainfall condition caused when a vehicle passes through a tunnel, for example.

The wiper automatic control apparatus determines that the vehicle enters a rainfall-blocked area, i.e., the tunnel. In response to the determination, the wiper automatic control apparatus sets the wiping mode low, relative to a rainfall having a level lower than a predetermined level. In contrast, the wiper automatic control apparatus sets the wiping mode high, relative to a rainfall having a level equal to or higher than the predetermined level.

While a subject vehicle travels through the tunnel, a front vehicle traveling in front of the subject vehicle rolls up minute water drops toward a front windshield of the subject vehicle. The rolled-up minute water drops adhere onto the front windshield of the subject vehicle, and affect a vision of a driver driving the subject vehicle. Therefore, the adhering water drops have to be detected and wiped by a wiper of the subject vehicle.

However, the rolled-up water drop has a relatively small diameter, and an amount of the rolled-up water drops is relatively small. Therefore, the wiping mode is not required to be high for a certain time before the vision of the driver is affected. If the wiping mode is set high relative to the rolled-up water drops, movement of the wiper may be troublesome for the driver before the vision of the driver is affected. That is, in the tunnel, the wiper has to wipe the adhering water drops, but the wiping mode of the wiper has to be set lower.

In contrast, when the subject vehicle travels out of the tunnel, the subject vehicle is exposed to an approximately the same amount of rainfall before the subject vehicle enters the tunnel. Therefore, the wiping mode has to be set similar to that before the subject vehicle enters the tunnel. However, the driver may feel the rainfall to become heavier when the subject vehicle travels out of the tunnel, because the vision of the driver is better in the tunnel due to its rainfall-blocked condition. Therefore, the wiping mode may have to be set higher when the subject vehicle travels out of the tunnel.

However, if the rainfall amount is small when the subject vehicle travels out of the tunnel, the wiping mode may not have to be set higher, because it takes a relatively long time before the vision of the driver is affected. That is, the wiper automatic control apparatus is required to smoothly correspond to the rapid change of the rainfall condition caused when the vehicle passes through the rainfall-blocked area.

Here, when a size of the raindrop detecting device is relatively small, it may be difficult for the small-sized raindrop detecting device to detect raindrop on the whole windshield. Further, in a case where a sensitivity controller provides a sensitivity data of a user of the vehicle to the raindrop detecting device, when the sensitivity controller is set to have a high sensitivity, the wiping mode is easily set high even if the rainfall amount is relatively small, for example. For a variety of users having different sensitivities, the sensitivity controller adjusts a relationship between the detected raindrop amount and the wiping mode.

When the sensitivity controller is set to have the high sensitivity, the wiper is moved at a higher speed, so that a time allowed to detect the raindrop amount becomes shorter. Thereby, it may be more difficult for the raindrop detecting device to accurately detect the raindrop amount. In this case, the wiping mode may be unnecessarily lowered, and movement of the wiper may become unstable.

In order to prevent this disadvantage, the wiping mode is set to be lowered when any raindrop is not detected while the wiper performs a predetermined number of wiping operations. That is, the wiping mode is lowered when the detected raindrop amount is kept to be smaller than a predetermined threshold. Alternatively, an average of the detected raindrop amounts may be calculated after the wiper performs the predetermined number of wiping operations, and the wiping mode may be lowered by comparing the calculated average with a predetermined threshold.

In these cases, although the wiping operation can be stable, responsivity for lowering the wiping mode may be delayed. Further, the responsivity depends on a sense of the user, e.g., driver, of the vehicle so that the responsivity is difficult to be determined to be fast or slow.

In contrast, when the vehicle enters the rainfall-blocked area, the responsivity for lowering the wiping mode is required to be fast, because the rainfall is blocked in the tunnel, for example.

In view of the foregoing and other problems, it is an object of the present invention to provide a raindrop detecting device and a method of selecting wiping mode for a vehicle.

According to a first example of the present invention, a raindrop detecting device for detecting a raindrop amount on a windshield of a vehicle and selecting a wiping mode of a wiper based on the detected raindrop amount includes a controller for lowering the wiping mode when the detected raindrop amount is kept to be smaller than a mode-keep threshold while the wiper performs a predetermined number of wiping operations. The controller changes the predetermined number of wiping operations based on at least one of a sensitivity data of a user of the vehicle and a rainfall block data relative to the vehicle.

According to a second example of the present invention, a raindrop detecting device for detecting a raindrop amount on a windshield of a vehicle and selecting a wiping mode of a wiper based on the detected raindrop amount includes a controller for calculating an average of a predetermined number of the detected raindrop amounts, and lowering the wiping mode when the average is smaller than a mode-keep threshold. The controller changes the predetermined number of the detected raindrop amounts based on a sensitivity data of a user of the vehicle and a rainfall block data relative to the vehicle.

According to a third example of the present invention, a method of selecting a wiping mode of a wiper for a vehicle includes a detecting, a lowering and a changing. In the detecting, a raindrop amount on a windshield of the vehicle is detected. In the lowering, the wiping mode is lowered when the detected raindrop amount is kept to be smaller than a mode-keep threshold while the wiper performs a predetermined number of wiping operations. In the changing, the predetermined number of wiping operations is changed based on at least one of a sensitivity data of a user of the vehicle and a rainfall block data relative to the vehicle.

Accordingly, movement of the wiper can be stable, and the wiping mode of the wiper can be suitable for the user of the vehicle.

The above and other objects, features and advantages of the present invention will become more apparent from the following detailed description made with reference to the accompanying drawings. In the drawings:

FIG. 1 is a schematic diagram showing a raindrop detecting device according to an embodiment of the present invention;

FIG. 2 is a schematic diagram showing a construction of the raindrop detecting device;

FIG. 3A is a schematic diagram showing a position relationship between the raindrop detecting device and a wiper, and FIG. 3B is a graph showing a relationship between a detection enabling time period and a detection disabling time period;

FIG. 4 is a flow chart showing a main routine of a wiper driving process;

FIG. 5 is a flow chart showing a subroutine of an input process in FIG. 4 ;

FIG. 6 is a flow chart showing a subroutine of a wiping mode selection in FIG. 4 ;

FIG. 7 is a flow chart showing a subroutine of a mode-down map selection in FIG. 6 ;

FIG. 8 is a diagram showing a mode-down map;

FIG. 9 is a flow chart showing a subroutine of a mode-down map selection according to a first modification of the embodiment;

FIG. 10 is a diagram showing a mode-down map of the first modification;

FIG. 11 is a flow chart showing a subroutine of a mode-down map selection according to a second modification of the embodiment; and

FIG. 12 is a flow chart showing a subroutine of a wiping mode selection according to a third modification of the embodiment.

As shown in FIG. 1 , a wiper automatic control apparatus includes a rain sensor 1 , i.e., raindrop detecting device, and a wiper controller 14 . The wiper automatic control apparatus activates a wiper 12 for wiping raindrop adhering onto a front windshield 11 of a vehicle 10 . The rain sensor 1 detects a raindrop amount on the front windshield 11 , and selects a wiping mode of the wiper 12 based on the detected raindrop amount. The rain sensor 1 inputs data into a wiper motor 13 through the wiper controller 14 , in order to automatically control the wiper 12 . That is, the rain sensor 1 outputs a driving signal for driving the wiper 12 into the wiper controller 14 , and the wiper controller 14 activates the wiper motor 13 to drive the wiper 12 in response to the driving signal output from the rain sensor 1 .

The data needed for automatically controlling the wiper 12 is constructed by an auto/manual switch data output from a mode switch 151 , a sensitivity volume data output from a sensitivity volume switch 152 , i.e., sensitivity adjuster, a vehicle speed data output from a speed sensor 16 , a rainfall block data, e.g., tunnel data, output from a navigation electronic control unit (ECU) 17 and the like. These data may be input into the rain sensor 1 without passing through the wiper controller 14 .

A wiper switch 15 includes the mode switch 151 and the sensitivity volume switch 152 . When the mode switch 151 is operated in an arrow direction R 1 , the wiper 12 is switched among a stop mode, an auto mode and a manual mode. The switch data indicative of a selected mode is input into the rain sensor 1 from the mode switch 151 through the wiper controller 14 .

When the auto mode is selected through the mode switch 151 , the sensitivity volume switch 152 is used for adjusting a relationship between a raindrop amount detected by the rain sensor 1 and a wiping mode. That is, a wiping frequency, i.e., wiping number per unit time, of the wiper 12 is changed relative to the same raindrop amount based on the sensitivity volume data. The wiping mode of the wiper 12 has an intermittent (INT) level, a continuous low (LO) level and a continuous high (HI) level, and the wiping frequency of the wiper 12 becomes larger in this order. When the sensitivity volume switch 152 is operated in an arrow direction R 2 , a wiping sensitivity is switched among a maximum level (MAX), a middle level (MID) and a minimum level (MIN). The sensitivity volume data indicative of a selected level is input into the rain sensor 1 from the sensitivity volume switch 152 through the wiper controller 14 .

As shown in FIG. 2 , the rain sensor 1 includes a light-emitting diode 2 (LED), a photo diode 3 , a prism 4 and a controller 5 . The controller 5 is constructed by a CPU and the like, and drives the LED 2 by activating a LED driving circuit 21 . Thereby, the LED 2 emits light toward a glass face 11 a of the front windshield 11 through the prism 4 . The glass face 11 a of the front windshield 11 reflects the emitted light, and the photo diode 3 receives the reflected light through the prism 4 . The photo diode 3 outputs a signal corresponding to an amount of the received light into an amplification circuit 31 . The amplification circuit 31 amplifies the signal, and the amplified signal is input into the controller 5 as a raindrop amount detected by the rain sensor 1 .

Here, when any raindrop does not adhere onto the glass face 11 a corresponding to a light path P 1 , almost all of light having the light path P 1 is reflected by the glass face 11 a , and the reflected light is received by the photo diode 3 . In contrast, when a raindrop 11 b adheres onto the glass face 11 a corresponding to a light path P 2 , light having the light path P 2 passes through the glass face 11 a and the raindrop 11 b , so that the emitted light is not received by the photo diode 3 . Therefore, when an amount of the adhering raindrop is increased in a detection area of the rain sensor 1 , the amount of light received by the photo diode 3 is decreased. Thereby, the signal output from the photo diode 3 is lowered. When the signal output from the photo diode 3 is lowered, the raindrop amount detected by the rain sensor 1 is increased.

The controller 5 is supplied with data of the raindrop amount output from the photo diode 3 , the sensitivity volume data output from the sensitivity volume switch 152 , the vehicle speed data output from the speed sensor 16 , the rainfall block data output from the navigation ECU 17 and the like. Then, the controller 5 selects the wiping mode, and outputs a driving signal for driving the wiper 12 into the wiper controller 14 .

The LED 2 , the LED driving circuit 21 , the photo diode 3 , the amplification circuit 31 and the controller 5 are mounted to a circuit board 6 . The circuit board 6 and the prism 4 are disposed in a protection case (not shown) to construct the rain sensor 1 .

As shown in FIG. 3A , the wiper 12 wipes a wiping area 11 c , 11 d of the front windshield 11 . While the wiper 12 wipes the wiping area 11 d , the rain sensor 1 cannot detect the raindrop amount. As shown in FIG. 3B , the wiper 12 wipes the wiping area 11 c , 11 d for a time period t 1 , and stops the wiping for a time period t 2 . The time period t 1 and the time period t 2 are alternately repeated to perform wiping operations of the wiper 12 .

The rain sensor 1 is allowed to detect the raindrop amount for a detection enabling time period TS, and is not allowed to detect the raindrop amount for a detection disabling time period TX. The enabling time period TS is constructed by the time period t 2 and a part of the time period t 1 for which the wiper 12 wipes the wiping area 11 c . The disabling time period TX is constructed by a part of the time period t 1 for which the wiper 12 wipes the wiping area 11 d . That is, the rain sensor 1 detects the raindrop amount in the enabling time period TS every wiping operation. The enabling time period TS becomes longer in an order of the HI level, the LO level and the INT level of the wiping mode.

Even if the enabling time period TS is relatively short, the small-sized rain sensor 1 secures to detect raindrop on the whole front windshield 11 . Therefore, the controller 5 lowers the wiping mode, when the detected raindrop amount is kept to be smaller than a first mode-keep threshold while the wiper 12 performs a predetermined number N of the wiping operations.

Further, the controller 5 is supplied with the sensitivity volume data adjusted by a user of the vehicle 10 through the sensitivity volume switch 152 , and changes the predetermined number N of the wiping operations based on the sensitivity volume data. Here, the sensitivity volume data represents a sense of the user. Because responsivity for lowering the wiping mode can be changed by the predetermined number N of the wiping operations, the responsivity for lowering the wiping mode can be changed in accordance with the sense of the user.

Next, when the auto mode is selected, a wiper driving process to be performed by the controller 5 of the rain sensor 1 will be described with reference to FIGS. 4 , 5 , 6 , 7 and 8 . As shown in FIG. 4 , a RAM of the controller 5 is initialized at step S 100 , and an input process is performed at step S 110 .

The input process of S 110 is constructed by step S 200 , S 210 and S 220 , which are shown in FIG. 5 . The speed sensor 16 inputs the vehicle speed data at S 200 . Then, the sensitivity volume switch 152 inputs the sensitivity volume data at S 210 . The navigation ECU 17 inputs the rainfall block data at S 220 . Thus, the input process of S 110 is finished.

At step S 120 in FIG. 4 , a rainfall determination threshold to be used at step S 300 in FIG. 6 is set. Due to the rainfall determination threshold, the wiping mode can be selected in accordance with the detected raindrop amount, for example. Further, a first mode-keep threshold K 1 to be used at step S 320 in FIG. 6 , and a first mode-up threshold U 1 to be used at step S 380 in FIG. 6 are also set, at S 120 . Here, the rainfall determination threshold, the first mode-keep threshold K 1 and the first mode-up threshold U 1 are changed by the data input in the input process of S 110 .

Then, at step S 130 , the raindrop amount on the front windshield 11 is detected. After S 130 , a wiping mode selection is performed at step S 140 . The wiping mode selection of S 140 is constructed by step S 300 -S 420 in FIG. 6 .

At step S 300 , the wiper 12 is determined to be stopped or not, based on a wiper motor operation signal output from the wiper controller 14 , for example. Further, the controller 5 determines that it is raining or not by comparing the detected raindrop amount with the rainfall determination threshold, for example, at S 300 .

When the wiper 12 is determined to be operating, or when the controller 5 determines that it is not raining while the wiper 12 is determined to be stopped (NO at S 300 ), a mode-down map selection is performed at step S 310 . The mode-down map selection of S 310 is constructed with step S 500 , S 510 , S 520 and S 530 , which are shown in FIG. 7 .

At step S 500 , the sensitivity volume data output from the sensitivity volume switch 152 into the controller 5 is determined to be the MAX level, the MID level or the MIN level. When the MAX level is selected, MAP 1 is selected as a mode-down map at step S 510 . When the MID level is selected, MAP 3 is selected as the mode-down map at step S 520 . When the MIN level is selected, MAP 5 is selected as the mode-down map at step S 530 .

As shown of MAP 5 in FIG. 8 , in order to stop the wiper 12 from the HI level, the predetermined number N of the wiping operations at the HI level is set to four to change the wiper 12 to the LO level, and the predetermined number N of the wiping operations at the LO level is set to one to stop the wiper 12 . In order to stop the wiper 12 from the LO level, the predetermined number N of the wiping operations at the LO level is set to three to change the wiper 12 to an INT-A level, and the predetermined number N of the wiping operations at the INT-A level is set to one to stop the wiper 12 . In order to stop the wiper 12 from the INT level, the predetermined number N of the wiping operations at an INT-B level is set to two to change the wiper 12 to an INT-C level, and the predetermined number N of the wiping operations at the INT-C level is set to one to stop the wiper 12 . Here, the INT level has the INT-A level, the INT-B level and the INT-C level, and the wiping frequency becomes smaller in this order.

Thus, the predetermined number N of the wiping operations set for lowering the wiping mode from the LO level is made smaller than that from the HI level. Further, the predetermined number N of the wiping operations set for lowering the wiping mode from the INT level is made smaller than that from the LO level. Because the enabling time period TS becomes longer in the order of the HI level, the LO level and the INT level, raindrop on the whole front windshield 11 secures to be detected even if the predetermined number N of the wiping operations is set smaller in the above-described order.

In MAP 5 of FIG. 8 , the predetermined number N of the wiping operations at the HI level is set to four to change the wiper 12 to the LO level. In contrast, according to MAP 3 shown in FIG. 8 , the predetermined number N of the wiping operations at the HI level is set to four plus an integer A (4+A) to change the wiper 12 to the LO level. Further, according to MAP 1 shown in FIG. 8 , the predetermined number N of the wiping operations at the HI level is set to four plus an integer B (4+B) to change the wiper 12 to the LO level. Here, the integer A and the integer B are set to have a relationship of B>A>0, for example. Thus, the controller 5 is constructed such that the predetermined number N of the wiping operations set for lowering the wiping mode from the HI level is increased as the sensitivity volume is switched from the MIN level to the MID level, or from the MID level to the MAX level.

Because the sensitivity volume data adjusted by the user represents the sense of the user as described above, the predetermined number N of the wiping operations can be changed in accordance with the sense of the user, due to the mode-down map selection of S 310 in FIG. 6 .

After the mode-down map selection of S 310 is finished, the raindrop amount is determined to be equal to or larger than a predetermined amount for keeping the wiping mode or not, at step S 320 . Specifically, the detected raindrop amount is determined to be equal to or larger than the first mode-keep threshold K 1 or not, at step S 320 .

When the detected raindrop amount is determined to be smaller than the first mode-keep threshold K 1 (NO at S 320 ), a mode-down counter increases its counter value, at step S 330 . The increasing of the counter value corresponds to a single wiping operation of the wiper 12 .

At step S 340 , the counter value of the mode-down counter is determined to be equal to or larger than the predetermined number N of the wiping operations or not, which has been selected at step S 310 . When the counter value of the mode-down counter is determined to be equal to or larger than the predetermined number N (YES at S 340 ), the wiping mode is lowered at step S 350 .

For example, in a case where the wiper 12 operates at the HI level, when MAP 1 is selected at S 310 , the predetermined number N is set as 4 +B at S 340 . Then, at S 350 , the wiping mode is lowered from the HI level to the LO level. After S 350 , the mode-down counter is cleared at step S 360 . Specifically, the counter value is set to zero. After S 360 , a driving signal for driving the wiper 12 at the LO level is output into the wiper controller 14 , at step S 150 in FIG.4 .

After S 150 , the controller 5 returns to S 110 . In this case, because the mode-down counter is cleared at S 360 , the counter value of the mode-down counter is to be increased from zero to one at the next-coming step S 330 .

In contrast, when the counter value of the mode-down counter is determined to be smaller than the predetermined number N (NO at S 340 ), the wiping mode is kept the same at step S 390 . For example, when the wiper 12 operates at the HI level, the wiping mode is kept to be the HI level, and the controller 5 outputs the driving signal at the HI level into the wiper controller 14 , at S 150 . After S 150 , the controller 5 returns to S 110 . Therefore, a process for keeping the wiping mode (S 390 ) is repeated until when the counter value of the mode-down counter is determined to be equal to or larger than the predetermined number N (YES at S 340 ).

That is, when the detected raindrop amount is continuously kept to be smaller than the first mode-keep threshold K 1 while the wiper 12 performs the predetermined number N of the wiping operations, the controller 5 lowers the wiping mode. Thereby, the wiping operation of the wiper 12 can be stable. Further, the responsivity for lowering the wiping mode can be changed by the predetermined number N of the wiping operations. Further, the predetermined number N can be changed in accordance with the sense of the user, due to the mode-down map selection at S 310 .

For example, when the user sets the sensitivity volume to be the MAX level, the wiping operation can be stable, because the predetermined number N is set larger. In contrast, when the user sets the sensitivity volume to be the MIN level, the responsivity for lowering the wiping mode can be fast, because the predetermined number N is set smaller. That is, the responsivity for lowering the wiping mode can be changed in accordance with the sense of the user.

Here, when the user sets the sensitivity volume to be the MIN level, the predetermined number N is set smaller. In this case, because the wiping mode is set low relative to the same detected raindrop amount, the time period t 1 (see FIG. 3B ) for which the wiper 12 operates becomes short. Thus, the enabling time period TS secures to be increased. Therefore, the wiping operation can be kept stable relative to the same detected raindrop amount.

In addition, when the wiper 12 is determined to be stopped and when it is determined not to be raining (NO at S 300 ), the wiper 12 is kept to be stopped at S 350 and S 390 , and the above-described operation is similarly to be performed at this time. Thus, the wiping operation can be stable, and the reponsivitity for lowering the wiping mode can be changed in accordance with the sense of the user.

Next, when the detected raindrop amount is determined to be equal to or larger than the first mode-keep threshold K 1 (YES at S 320 ), the mode-down counter is cleared at step S 370 . After S 370 , the detected raindrop amount is determined to be equal to or larger than the first mode-up threshold U 1 or not, at step S 380 . The first mode-up threshold U 1 is larger than the first mode-keep threshold K 1 . When the detected raindrop amount is determined to be smaller than the first mode-up threshold U 1 (NO at S 380 ), step S 390 is performed.

When the detected raindrop amount is determined to be equal to or larger than the first mode-up threshold U 1 (YES at S 380 ), the wiping mode is raised at step S 400 . After S 400 , the driving signal for driving the wiper 12 at the raised wiping mode is output into the wiper controller 14 , at S 150 . After S 150 , the controller 5 returns to S 110 .

When the wiper 12 is determined to be stopped and when the detected raindrop amount is determined to be equal to or larger than the rainfall determination threshold (YES at S 300 ), the mode-down counter is cleared at step S 410 . After S 410 , an initial wiping mode is set at step S 420 . After S 420 , the driving signal for driving the wiper 12 at the set initial wiping mode is output into the wiper controller 14 at S 150 . After S 150 , the controller 5 returns to S 110 .

In addition, the mode-down map, e.g., MAP 1 , MAP 2 or MAP 3 , shown in FIG. 8 may be changed without departing from the scope of the present disclosure. For example, the integer A may be set to zero. Further, in MAP 5 , the predetermined number N set for lowering the wiping mode from the HI level to the LO level may be set to three, or the predetermined number N set for lowering the wiping mode from the LO level to the INT-A level may be set to two.

(First Modification)

As shown in FIG. 9 , step S 610 , S 640 and S 670 are added relative to the flow chart shown in FIG. 7 . Step S 610 , S 640 and S 670 are performed based on the rainfall block data input at S 220 in FIG. 5 . Thereby, MAP 2 at step S 630 , MAP 4 at step S 660 and MAP 6 at step S 690 are added. For example, when the sensitivity volume is determined to be the MIN level at step S 600 , a rainfall block object for blocking rainfall relative to the vehicle 10 , e.g., tunnel, is determined to exist or not at step S 670 . When the vehicle 10 is determined not to enter the rainfall block object (NO at S 670 ), MAP 5 is selected at step S 680 , and the above-described advantage can be similarly provided.

In contrast, when the vehicle 10 is determined to enter the rainfall block object (YES at S 670 ), a first determination data representing that the vehicle 10 enters the rainfall block object is input into the controller 5 , and MAP 6 is selected at S 690 .

As shown of MAP 6 in FIG. 10 , in order to stop the wiper 12 from the HI level, the predetermined number N of the wiping operations at the HI level is set to four minus an integer F (4−F) to change the wiper mode to the LO level. In order to stop the wiper 12 from the LO level, the predetermined number N of the wiping operations at the LO level is set to three minus the integer F (3−F) to change the wiper mode to the INT-A level. In order to stop the wiper 12 from the INT level, the predetermined number N of the wiping operations at the INT-B level is set to two minus the integer F (2−F) to change the wiping mode to the INT-C level. That is, the predetermined number N in MAP 6 is set by subtracting the integer F from the predetermined number N in MAP 5 . Similarly, the predetermined number N in MAP 4 is set by subtracting an integer E from the predetermined number N in MAP 3 , and the predetermined number N in MAP 2 is set by subtracting an integer D from the predetermined number N in MAP 1 .

Because the predetermined number N is decreased based on the above-described first determination data, the responsivity for lowering the wiping mode can be made faster when the vehicle 10 enters the rainfall block object. For example, the wiper 12 can be stopped faster (earlier) at a tunnel entrance.

Here, the integer D, the integer E and the integer F are set to have a relationship D>E=F>0, for example. That is, the decreasing number of the predetermined number N based on the first determination data is changed based on the sensitivity data. Thereby, the responsivity for lowering the wiping mode can be made faster in accordance with the sense of the user when the vehicle 10 enters the rainfall block object.

In the first modification, the predetermined number N is set based on both of the sensitivity volume data and the rainfall block data. However, the predetermined number N may be set based on only the rainfall block data.

(Second Modification)

As shown in FIG. 11 , step S 730 , S 770 and S 810 are added relative to the flow chart shown in FIG. 9 . For example, when the sensitivity volume is determined to be the MIN level at step S 700 , and when the rainfall block object is determined to exist at step S 790 , a length (distance) of the rainfall block object is determined to be equal to or larger than a predetermined length L 1 , e.g., 30 m, or not, at step S 810 . When the length of the rainfall block object is determined to be smaller than the predetermined length L 1 (NO at S 810 ), a second determination data representing that the length of the rainfall block object is smaller than the predetermined length L 1 is input into the controller 5 , and MAP 5 is selected at step S 800 . Thus, the advantage described with reference to FIG. 7 can be similarly provided.

In contrast, when the length of the rainfall block object is determined to be equal to or larger than the predetermined length L 1 (YES at S 810 ), MAP 6 is selected at step S 820 , and the advantage described with reference to FIG. 9 can be similarly provided.

That is, when the length of the rainfall block object is determined to be smaller than the predetermined length L 1 , the predetermined number N is not decreased when the vehicle 10 enters the rainfall block object. For example, when the vehicle 10 travels under a bridge with a structural frame, and when a length of the bridge is smaller than 30 m, the rainfall-blocked condition may be short for the vehicle 10 . In this case, the predetermined number N is not needed to be decreased. In addition, the predetermined length L 1 may be any length without departing from the scope of the present disclosure.

(Third Modification)

A predetermined number M of the raindrop amounts may be successively detected, and an average of the detected raindrop amounts may be calculated. The controller 5 lowers the wiping mode when the average is smaller than a second mode-keep threshold K 2 , which may be different from the first mode-keep threshold K 1 . In the third modification, the predetermined number M is used in an average-using map, in place of the predetermined number N in the mode-down map of FIGS. 6 , 8 and 10 . The predetermined number M is set based on at least one of the sensitivity volume data and the rainfall block data.

Specifically, the wiping mode selection at S 140 in FIG. 4 is constructed by step S 900 -S 970 shown in FIG. 12 . At step S 900 , the wiper 12 is determined to be stopped or not, and it is determined to be raining or not. When the wiper 12 is determined to be operating or when it is determined not to be raining while the wiper 12 is determined to be stopped (NO at S 900 ), the average-using map is selected at step S 910 .

A process of selecting the average-using map (S 910 ) is constructed with step S 500 , S 510 , S 520 and S 530 shown in FIG. 7 . The predetermined number M is used in place of the predetermined number N in FIG. 8 . After S 910 , the raindrop amount is determined to be equal to or larger than a predetermined amount for keeping the wiping mode, at step S 920 . Specifically, the predetermined number M of the raindrop amounts is successively detected, and an average of the detected raindrop amounts is calculated. Then, the average is determined to be equal to or larger than the second mode-keep threshold K 2 or not, at step S 920 .

When the average is determined to be smaller than the second mode-keep threshold K 2 (NO at S 920 ), the wiping mode is lowered at step S 930 . Then, the driving signal for driving the wiper 12 is output into the wiper controller 14 at step S 150 in FIG. 4 . After S 150 , the controller 5 returns to step S 110 .

Thus, the wiping operation of the wiper 12 can be stable. Further, the responsivity for lowering the wiping mode can be changed by the predetermined number M of the detected raindrop amounts. Furthermore, the predetermined number M can be changed in accordance with the sense of the user, due to the average-using map selection at S 910 .

When the average is determined to be equal to or larger than the second mode-keep threshold K 2 (YES at S 920 ), the average is determined to be equal to or larger than a second mode-up threshold U 2 or not at step S 940 . The second mode-up threshold U 2 is larger than the second mode-keep threshold K 2 . When the average is determined to be smaller than the second mode-up threshold U 2 (NO at S 940 ), step S 950 is performed.

When the average is determined to be equal to or larger than the second mode-up threshold U 2 (YES at S 940 ), the wiping mode is raised at step S 960 . After S 950 or S 960 , the driving signal for driving the wiper 12 is output at S 150 in FIG. 4 , and the controller 5 returns to S 110 . In addition, the second mode-keep threshold K 2 and the second mode-up threshold U 2 are set at S 120 in FIG. 4 .

When the wiper 12 is determined to be stopped and when the detected raindrop amount is determined to be equal to or larger than the rainfall determination threshold (YES at S 900 ), an initial wiping mode is set at step S 970 . After S 970 , the controller 5 outputs the driving signal for driving the wiper 12 at the set initial wiping mode into the wiper control 14 at S 150 in FIG. 4 , and the controller 5 returns to S 110 .

In addition, when the average-using map shown in FIG. 9 is selected at S 910 , the predetermined number M may be set based on the rainfall block data. Further, when the average-using map shown in FIG. 11 is selected at S 910 , the predetermined number M is restricted from decreasing, because the vehicle is predicted to return a rainfall condition after a relatively short time. Thus, according to the modifications, the above-described advantage can be similarly provided.

Further, the rainfall block data may be provided by a light sensor (light-receiving sensor) in place of the navigation ECU 17 . When the vehicle 10 includes the light sensor for detecting two directions, i.e., traveling direction and upward direction, the length of the rainfall block object can be determined by the light sensor.

Further, the rain sensor 1 is not limited to the above-described optical rain sensor. Alternatively, a capacitive rain sensor may be used as the rain sensor 1 , in which a capacitance is varied in accordance with the raindrop amount.

Thus, the rain sensor 1 , i.e., raindrop detecting device, detects the raindrop amount on the front windshield 11 of the vehicle 10 . The rain sensor 1 selects the wiping mode of the wiper 12 based on the detected raindrop amount. The rain sensor 1 includes the controller 5 for lowering the wiping mode when the detected raindrop amount is kept to be smaller than the first mode-keep threshold K 1 while the wiper performs the predetermined number N of the wiping operations. The controller 5 changes the predetermined number N based on the sensitivity volume data output from the sensitivity volume switch 152 for adjusting the relationship between the detected raindrop amount and the wiping mode.

Thereby, the wiping operation of the wiper 12 can be stable, and the responsivity for lowering the wiping mode can be changed in accordance with the sense of the user.

Such changes and modifications are to be understood as being within the scope of the present invention as defined by the appended claims.