Abstract:
The wiper control apparatus comprises a precipitation detector, a surrounding state detector and a wiper controller. The precipitation detector detects a precipitation condition at a position where the vehicle is. The surrounding state detector detects an exit of the vehicle out of a roofed space. The wiper controller controls the wiper to be in an automatic operation mode according to the precipitation condition detected by the precipitation detector, and controlling the precipitation detector to detect the precipitation condition following the exit detected by the surrounding state detector in a response time shorter than the normal response time for the precipitation detector to detect the precipitation not following the exit.

Description:
CROSS REFERENCE TO RELATED APPLICATION  
       [0001]     This application is based upon and claims the benefit of priority of Japanese Patent Application No. 2004-031246 filed on Feb. 6, 2004, the content of which is incorporated herein by reference.  
       FIELD OF THE INVENTION  
       [0002]     The present invention relates to a wiper control apparatus for operating a wiper of a vehicle and a wiper control method for operating a wiper of a vehicle.  
       BACKGROUND OF THE INVENTION  
       [0003]     Conventional automatic wiper controller controls a vehicular wiper according to a detected amount of adhesion water caused by raindrops on a windshield. The automatic wiper controller has a control circuit, an infrared ray sensor, and so on. The infrared ray sensor irradiates an infrared ray toward the windshield and detects the infrared ray reflected on a surface of the windshield. The control circuit detects the amount of the adhesion water by the magnitude of the reflected infrared ray. The control circuit operates using a threshold value for preventing the wiper from operating erroneously by disturbances such as noises, and automatically activates the wiper when the detected amount of the adhesion water exceeds the threshold value.  
         [0004]     When the vehicle travels out of a roofed space such as a tunnel and foot of bridge, the driver needs some time to adapt the difference of brightness inside of the roofed space and that outside of the roofed space. If it rains outside the roofed space, the driver&#39;s sight outside of the roofed space becomes worse and time required to adapt the difference extends. Thus, it is desirable to activate the wiper as soon as possible when the vehicle travels out of the roofed space into outside space where it rains.  
         [0005]     However, the conventional automatic wiper controller activates the wiper after some response time, because the amount of the adhesion water is little immediately after running out of the roofed space and the control circuit determines a precipitation only when the detected amount of the adhesion water exceeds the threshold value.  
       SUMMARY OF THE INVENTION  
       [0006]     An object of the present invention is to provide a wiper control apparatus and a wiper control method for operating a wiper of a vehicle, whose response time is shorter even when the vehicle travels out of a roofed space into an outside space where it rains.  
         [0007]     To achieve the above object, a wiper control apparatus according to the present invention comprises a precipitation detector, a surrounding state detector and a wiper controller.  
         [0008]     The precipitation detector detects a precipitation condition at a position where the vehicle is. The surrounding state detector detects an exit of the vehicle out of a roofed space. The wiper controller automatically controls the wiper to start a wiping operation according to the precipitation condition detected by the precipitation detector, and controlling the precipitation detector to detect the precipitation condition following the exit detected by the surrounding state detector in a response time shorter than another response time for the precipitation detector to detect the precipitation not following the exit.  
         [0009]     It is desirable that the wiper controller increases a sensitivity of the precipitation detector when the surrounding state detector detects the exit.  
         [0010]     It is also desirable that the wiper controller activates the wiper when the precipitation detector detects a precipitation amount (the precipitation condition) more than a predetermined threshold value, and decreases the predetermined value when the surrounding state detector detects the exit. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0011]     Other features and advantages of the present invention will be appreciated, as well as methods of operation and the function of the related parts, from a study of the following detailed description, the appended claims, and the drawings, all of which form a part of this application. In the drawings:  
         [0012]      FIG. 1  is a block diagram of a wiper control apparatus for operating a wiper of a vehicle according to an embodiment of the present invention;  
         [0013]      FIG. 2  is a schematic view showing an installation of the wiper control apparatus on a rear face of the windshield according to the embodiment;  
         [0014]      FIG. 3  is a schematic view showing the detection state by a first illuminometer and a second illuminometer according to the embodiment;  
         [0015]      FIG. 4  is a schematic view showing the detection state by a rain sensor according to the embodiment; and  
         [0016]      FIG. 5  is a flowchart of an operation process of a wiper control method for operating a wiper of a vehicle according to the embodiment. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0017]     As shown in  FIG. 1 , a wiper control apparatus  100  according to the embodiment has a wiper switch  10 , a control circuit  20 , a first illuminometer  30 , a second illuminometer  40 , a rain sensor  50 , a wiper motor  60 , a wiper  70 , a RAM  80  and a ROM  90 .  
         [0018]     The wiper switch  10  generates operation signals and outputs the operation signals to the control circuit  20  thereby to direct the wiper motor  60  to operate in respective operation modes according to switching operations. The operation modes are a stop mode, an automatic mode, an intermittent mode, a low speed mode, a high speed mode or the like.  
         [0019]     The control circuit  20  is implemented by a conventional microcomputer and controls the wiper motor  60  by the operational signals to operate in one of the above modes instructed by the wiper switch  10 .  
         [0020]     When the wiper switch  10  generates the operation signal to operate the wiper motor  60  in the automatic mode, the control circuit  20  determines a driving signal for controlling the wiper motor  60  in respective operation modes based on detection signals generated by the first illuminometer  30 , the second illuminometer  40 , the rain sensor  50 , and so on. The detection signal generated by the rain sensor  50  indicates the precipitation amount. When the detection signal indicates a small amount of precipitation, the driving signal operates the wiper motor  60  in the low speed mode. When the detection signal indicates a large amount of precipitation, the driving signal operates the wiper motor  60  in the high speed mode.  
         [0021]     The control circuit  20  also determines a current value flowing through an emission portion  50   a  of the rain sensor  50 , based on the detection signals generated by the first illuminometer  30 , the second illuminometer  40  and so on.  
         [0022]     When the wiper switch  10  generates the operation signal operating the wiper motor  60  in the manual modes including the stop mode, the intermittent mode, the slow mode and the fast mode, the control circuit  20  determines a driving signals for controlling the wiper motor  60  in respective operation modes based on the operation signals generated by the wiper switch  10 .  
         [0023]     The first illuminometer  30  and the second illuminometer  40  are for detecting whether the vehicle is traveling into a space under roof (hereinafter referred to as roofed space) such as a tunnel, a foot space under a bridge, whether the vehicle is traveling out of the roofed space, and whether it is daytime or nighttime.  
         [0024]     The first illuminometer  30 , the second illuminometer  40  and the rain sensor  50  are located in a casing of a sensor portion and installed on an inner surface of the windshield F as shown in  FIG. 2 . Regardless of the above description, the first illuminometer  30  and the second illuminometer  40  may be separated from the rain sensor  50  and installed on a dash panel.  
         [0025]     As shown in  FIG. 3 , the first illuminometer  30  includes a photodiode for detecting an illuminance on a plane facing an upper space of the vehicle and outputs a first detection signal indicating the illuminance to the control circuit  20 . The second illuminometer  40  includes a photodiode for detecting an illuminance on another plane facing a front space of the vehicle and outputs a second detection signal indicating the illuminance to the control circuit  20 .  
         [0026]     As shown in  FIG. 4 , the rain sensor  50 , which detects the precipitation amount, has a ray emitter  50   a  for emitting an infrared ray toward the windshield F and a ray receptor  50   b  receiving the infrared ray reflected by the surface of the windshield F. The ray emitter  50   a  emits the infrared rays in respective intensities according to the current value determined by the control circuit  20 .  
         [0027]     In a case that a raindrop adheres to the windshield F within a detection range by the rain sensor  50 , the intensity of the infrared rays received by the ray receptor  50   b  is lower than a case that no raindrop adheres to the windshield F. The rain sensor  50  thus detects the rainfall amount based on an amount of change in the intensity of the infrared rays received by the ray receptor  50   b  and outputs a detection signal indicating the precipitation amount to the control circuit  20 .  
         [0028]     The control circuit  20  compares the detection signal of the rain sensor  50  indicating the precipitation amount and a threshold value for determining whether to automatically activate the wiper motor  60 . When the detection signal indicating the precipitation amount exceeds the threshold value, the control circuit  20  determines the driving signal according to the precipitation amount and outputs the driving signal to the wiper motor  60 .  
         [0029]     The control circuit  20  determines the current value to be high when it is nighttime and to be low when it is daytime. The night level is set larger than the daytime level. While, the control circuit  20  determines whether to activate the wiper motor  60  based on the threshold values of a tunnel level when the vehicle is traveling out of the roofed space, and based on the threshold value of a normal level except when the vehicle is traveling out of the roofed space. The tunnel level is set smaller than the normal level.  
         [0030]     The wiper motor  60  actuates the wiper  70  according to the driving signals determined by the control circuit  20 . Thus, the wipers  70  of the driver side and of the passenger side wipe the respective ranges of the windshield F.  
         [0031]     The RAM  80  is a memory field used for a process of the control circuit  20 , such as a temporal memory of the operation mode of the wiper  70  before the vehicle&#39;s entry into the roofed space. The ROM  90  memorizes programs to be executed by the control circuit  20 , and so on.  
         [0032]     The wiper control apparatus  100  according to this embodiment operates as shown in  FIG. 5 , which depicts an operation flow of the wiper control apparatus  100 . This operation flow of the wiper control apparatus  100  starts by turning on the ignition switch (not shown), that is, when the wiper control apparatus  100  is supplied electricity from the battery (not shown) of the vehicle.  
         [0033]     In step S 1 , the control circuit  20  detects the operation signal sent from the wiper switch  10  indicating whether the wiper control apparatus  100  is in the automatic mode or manual mode.  
         [0034]     In step S 2 , the control circuit  20  determines whether the wiper control apparatus  100  is in the automatic mode or in the manual mode based on the operation signal detected in step S 10 . When the control circuit  20  determines that the apparatus  100  is in the automatic mode, the process goes to step S 3  to operate the wiper  70  in the automatic mode. When the control circuit determines that the apparatus  100  is in the manual mode by the operation signal indicating any one of the stop mode, the intermittent mode, the slow mode and the fast mode, the process goes to step S 12  to operate the wiper  70  in the manual mode.  
         [0035]     In step S 12 , the control circuit  20  determines the driving signal according to the operation signal and outputs the driving signal to the wiper motor  60  to actuate the wiper  70  according to the operation mode selected by the wiper switch  10 .  
         [0036]     In step S 3 , the control circuit  20  detects illuminance indicated by the detection signals detected by the first illuminometer  30  and the second illuminometer  40 .  
         [0037]     In step S 4 , the control circuit  20  determines whether the illuminance on the plane facing the upward space of the vehicle is large or small based on the detection signal generated by the first illuminometer  30  and detected in the step S 3 . When the illuminance detected by the first illuminometer  30  is small, the process goes to step S 5  to determine whether the vehicle is outside of the roofed space in night time or the vehicle is traveling out of the roofed space in daytime. When the illuminance detected by the first illuminometer  30  is large, it is assumed that the vehicle is outside of the roofed space in daytime and the process goes to step S 8 .  
         [0038]     In step S 8 , that is, when it is assumed that the vehicle is not in the roofed space and it is daytime, the driver&#39;s sense of sight is not impaired. Therefore, the control circuit  20  determines the current value through the ray emitter  50   a  to a daytime level (low sensitivity), and the threshold value for determining whether to activate the wiper motor  60  to the large level.  
         [0039]     In step S 5 , the control circuit  20  determines whether the illuminance on the place facing a front space of the vehicle is large or small based on the detection signal generated by the second illuminometer  40 . When the illuminance detected by the second illuminometer  40  is small, that is, when it is assumed to be nighttime, the process goes to step S 6 . When the illuminance detected by the second illuminometer  40  is large, that is, when it is assumed that the vehicle is traveling out of the roofed space in daytime, the process goes to step S 7 .  
         [0040]     In step S 6 , that is, in nighttime, the driver&#39;s sense of sight is impaired. If it rains, the driver&#39;s sense of sight is further impaired. Therefore, it is required to activate the wiper  70  in a short response time when the vehicle is traveling in nighttime out of the roofed space into outside where it is raining, to secure a required level of the driver&#39;s sense of sight. Thus, the control circuit  20  determines the current value through the ray emitter  50   a  to the nighttime level (high sensitivity), and the threshold value for determining whether to activate the wiper motor  60  to the large level.  
         [0041]     By setting the current value flowing through the ray emitter  50   a  to the nighttime level, which is larger than the daylight level, the intensity of the infrared rays emitted by the ray emitter  50   a  becomes larger than that when the current value is set to the daytime level. Thus, a detection range on the windshield F when it is nighttime is larger than the detection range in daytime. Accordingly, the precipitation amount detected by the rain sensor  50  in nighttime is larger than that in daytime, so that the rain sensor  50  can generate in nighttime the detection signal in a shorter response time than that in daytime.  
         [0042]     In step S 7 , that is, when the vehicle is traveling out of the roofed space in daytime, the driver&#39;s sense of sight is temporarily impaired during adaptation to light. If it rains, the driver&#39;s sense of sight is further impaired, so that it is required to activate the wiper  70  in a short response time when the vehicle is traveling in daytime out of the roofed space into outside where it is raining, to secure a required level of the driver&#39;s sense of sight. Thus, the control circuit  20  determines the current value through the ray emitter  50   a  to the nighttime level, and the threshold value for determining whether to activate the wiper motor  60  to the tunnel level.  
         [0043]     As described above, by setting the current value flowing through the ray emitter  50   a  to the nighttime level, which is larger than the daylight level, the intensity of the infrared rays emitted by the ray emitter  50   a  becomes larger than that when the current value is set to the daytime level. Thus, a detection range on the windshield F when the vehicle is traveling out of the roofed space is larger than the detection range in daytime. While, the threshold value for determining whether to activate the wiper motor  60  is set to the tunnel level smaller than the threshold value of the normal level, so that the rain sensor  50  can generate the detection signal when the vehicle is traveling out of the roofed space by detecting the precipitation amount smaller than that required for the rain sensor  50  to generate the detection signal when the vehicle is not traveling out of the roofed space in daytime or in nighttime.  
         [0044]     Thus, when the vehicle is traveling out of the roofed space, the wiper control apparatus  100  can activate the wiper  70  in an early timing by the increased detection sensitivity of the rain sensor  50  and the decreased threshold value relative to a unit precipitation amount. Only decreasing the threshold value serves to start the wiper  70  in a short response time, so that the detection sensitivity of the rain sensor  50  may not always be increased together with decreasing the threshold value.  
         [0045]     In step S 9 , the control circuit  20  directs the rain sensors  50  to detect the precipitation amount by making a current value determined in any one of steps S 6  to S 8  flow through the ray emitter  50   a , to determine whether to activate the wiper motor  60  or not.  
         [0046]     In step S 10 , the control circuit  20  determines whether the precipitation amount detected in step S 9  is smaller than the threshold value determined in any one of steps S 6  to S 8 . When the precipitation amount is larger than the threshold value, that is, it is assumed that it is raining and that the wiper  70  should be activated, the process goes to step S 11 . When the precipitation amount is smaller than the threshold value, that is, it is assumed that it is not raining and that the wiper  70  should not be activated, the process returns to step S 1 .  
         [0047]     In step S 11 , the control circuit  20  outputs the driving signal according to the detection signal indicating the precipitation amount detected by the rain sensor  50  to the wiper motor  60 , so that the wiper  70  wipes a wiping range of the windshield F.  
         [0048]     As a modification of the above embodiment, in a case that the illuminance on the plane facing the front space of the vehicle is large in step S 5  and also in step  10 , the detection signal is larger than the threshold value determined in step S 7 , the control circuit  20  may store the operation mode when the vehicle is traveling into the roofed space a in the RAM  80  and output a driving signal to the wiper motor  60  to operate in the operation mode stored in the RAM  80  when the vehicle is traveling out of the roofed space.  
         [0049]     As another modification of the above embodiment, the wiper control apparatus  100  may include a recording media such as a hard disk storing a table data associating the detection signals indicating the precipitation amount during the manual mode with the driving signals of the wiper motor  60 . Thus, in a case that the illuminance in front of the vehicle is large in step S 5 , and in step  10 , the detection signal is larger than the threshold value determined in step S 7 , the control circuit  20  compares the detection signal detected by the rain sensor  50  with the table data memorizing the precipitation amount. Thus, the control circuit  20  can extract the driving signal according to the detection signal indicating the precipitation amount and output the driving signal to the wiper motor  60 . Accordingly, the wiper control apparatus  100  can operate the wiper  70  in the operation mode according to the driver&#39;s preference.  
         [0050]     As a third modification of the above embodiment, the wiper  70  may be activated on a condition that the rain sensor  50  continues to detect precipitation whose amount is over a threshold value for a predetermined time. In this case, the response time of the wiper  70  just after the vehicle travels out of the roofed space may be shortened so as to activate the wiper  70  in an earlier timing. It is a matter of course that the reduction of the threshold value and the shortening the response time may be adopted together.  
         [0051]     The wiper control apparatus  100  may cooperate with the position detection apparatus such as GPS receivers and mapping apparatus storing the mapping data including the positions of roofed spaces such as tunnels and bridges. In this case, the wiper control apparatus  100  can determine whether the vehicle is traveling into the roofed space and whether the vehicle is traveling out of the roofed space, based on the vehicular position detected by the position detection apparatus and the mapping data stored in the mapping apparatus.  
         [0052]     The wiper control apparatus  100  also may include an image sensor implemented by cameras such as CCD and CMOS. In this case, the wiper control apparatus  100  can determine whether the vehicle is traveling into the roofed space and whether the vehicle is traveling out of the roofed space using the image sensor.