Abstract:
A vehicle headlight apparatus includes a headlight and an actuator. The actuator horizontally changes a lighting direction of the headlight. The vehicle headlight apparatus drives the actuator such that the actuator horizontally changes the lighting direction of the headlight based on a target swivel angle that is determined based on a travel condition, upon the occurrence of one of the following conditions: (a) the vehicle headlight apparatus detects a dark road section located on a downstream side of a current position of a vehicle, or (b) the headlight is switched on.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
   This application is based on and incorporates herein by reference Japanese Patent Application No. 2005-169834 filed on Jun. 9, 2005. 
   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to a vehicle headlight apparatus, which performs a swivel operation that changes an optical axis of a headlight in a horizontal direction correspondingly to a steering operation. 
   2. Description of Related Art 
   Conventionally, there has been proposed an adaptive front-lighting system (AFS) that radiates light in a direction, which a driver of a vehicle desires. The AFS is realized by changing a direction of radiation (i.e., an optical axis) of a headlight of the vehicle. The AFS includes a leveling mechanism and a swivel mechanism for changing a direction of the optical axis of the headlight. Here, the leveling mechanism vertically changes the direction of the optical axis, and the swivel mechanism horizontally changes the direction of the optical axis. 
   In the swivel mechanism of the above functions, a target swivel angle is computed based on inputted data, such as a headlight switch signal, a vehicle speed and a steering angle. Then, there is preformed an operation for driving an actuator that changes the optical axis of the headlight such that the optical axis corresponds to the target swivel angel. For example, in a case of a right turn, the optical axis of the headlight is changed to a right direction. Also, in a case of a left turn, the optical axis is changed to a left direction. Therefore, this improves the viewability in a vehicle drive direction at night travel (see Japanese Unexamined Patent Publication No. 2003-72460 corresponding to U.S. Pat. No. 6,778,892). 
   However, the conventional swivel mechanism has a disadvantage. The conventional swivel mechanism starts driving the actuator based on the headlight switch signal so that the optical axis of the headlight is changed to set at the target swivel angle at one stroke when the headlight is turned on during the vehicle travels on a curve. For example, here is supposed a vehicle, which has an automatic lighting apparatus for automatically lighting the headlight when a travel environment indicates a predetermined darkness. When this vehicle travels into a tunnel, which curves to the right, the headlight is automatically turned on, and simultaneously the optical axis of the headlight is widely moved to the right. 
   SUMMARY OF THE INVENTION 
   The present invention is made in view of the above disadvantages. Thus, it is an objective of the present invention to provide a vehicle headlight apparatus, which obviates or mitigates at least one of the above disadvantages. 
   To achieve the objective of the present invention, there is provided a vehicle headlight apparatus, which includes a headlight, an actuator, a swivel controlling means, a dark road section detecting means and a headlight determining means. The headlight lights a downstream side of a current position of a vehicle in a traveling direction of the vehicle. The actuator horizontally changes a lighting direction of the headlight. The swivel controlling means drives the actuator. The dark road section detecting means detects a dark road section, which is located on the downstream side of the current position, wherein the dark road section is a segment of a road with a predetermined darkness; the segment of the road extending for a predetermined distance. The headlight determining means determines whether the headlight lights. The swivel controlling means drives the actuator such that the actuator horizontally changes the lighting direction of the headlight based on a target swivel angle, which is determined based on a travel condition, when one of the following conditions is satisfied. A first condition is that the dark road section detecting means detects the dark road section, which is located on the downstream side of the current position of the vehicle. A second condition is that the headlight determining means determines that the headlight lights. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention, together with additional objectives, features and advantages thereof, will be best understood from the following description, the appended claims and the accompanying drawings in which: 
       FIG. 1  is a block diagram showing a system structure of a vehicle headlight apparatus of a first embodiment of the present invention; 
       FIG. 2  is a flowchart showing a control processing of the vehicle headlight apparatus; 
       FIG. 3  is a schematic diagram showing an example of a change of an optical axis of a headlight driven by an actuator; 
       FIG. 4  is a schematic diagram showing operating conditions of the headlight and the actuator when the vehicle passes through a tunnel; and 
       FIG. 5  is a block diagram showing a system structure of a vehicle headlight apparatus of a second embodiment of the present invention. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
   First Embodiment 
   The first embodiment will be described with reference to accompanying drawings. 
   In  FIG. 1 , a left headlamp  10 L and a right headlamp  10 R are provided on a front side of a vehicle to serve as a headlight. An illumination sensor  11  is provided in an interior of the vehicle to detect an illumination of a travel environment of the vehicle. When the illumination sensor  11  detects that the travel environment indicates darker than a predetermined darkness (i.e., a degree of brightness in the travel environment is less than a predetermined value), the headlamps  10 L,  10 R are automatically turned on by a headlamp light switch  17 . Also, when the illumination sensor  11  detects that the travel environment indicates brighter than the predetermined darkness (i.e., the degree of brightness in the travel environment is larger than the predetermined value), the headlamps  10 L,  10 R are automatically turned off by the headlamp light switch  17 . Here, a headlight of the present invention includes the headlamps  10 L,  10 R, and an automatic light controlling means of the present invention includes the headlamp light switch  17 . 
   An electronic control unit (ECU)  20  includes a CPU  21 , a ROM  22 , a RAM  23  and an input/output circuit  25  to operates a drive control of each of the actuators  12 L,  12 R for the corresponding headlamp  10 L,  10 R. Here, the CPU  21  serves as a central processing unit for performing well-known various processes. The ROM  22  stores a control program. The RAM  23  stores various data. 
   A navigation device  30  includes a storage device (not shown) and a touch-sensitive display  30   a . The storage device stores road information. The touch-sensitive display  30   a  is so located in an interior of the vehicle that the touch-sensitive display  30   a  is easily seen by an occupant (driver) seated on a driving seat. The navigation device  30  utilizes a global positioning system (GPS) to estimate a traveling position (i.e., a computed current position) of the vehicle. The navigation device  30  displays a map and the estimated traveling position in the touch-sensitive display  30   a . The road information stored by the navigation device  30  includes a location of a dark road section (e.g., a road in a tunnel, an underpass of a bridge, an underpass of an overhead crossing) such that the navigation device  30  can detect the dark road section, which is located ahead of the estimated traveling position of the vehicle (i.e., which is located on a downstream side of the current position of the vehicle in a traveling direction). Here, the dark road section is defined as a segment of a road with a predetermined darkness (i.e., the degree of brightness of the segment of the road is less than a predetermined value). Also, the segment of the road extends to a predetermined distance. The navigation device  30  serves as a dark road section detecting means of the present embodiment. 
   The ECU  20  receives an outputs signal supplied by a speed sensor  14 , which senses a vehicle speed, an outputs signal supplied by a steering angle sensor  16 , which senses a steering angle of a steering wheel  15 , an output signal supplied by the headlamp light switch  17 , which turns on the headlamps  10 L,  10 R, information supplied by the navigation device  30  and other various sensor signals. Here, the information supplied by the navigation device  30  includes the location of the dark road section and the length thereof. Then, the ECU  20  computes a target swivel angel based on the output signal supplied by the speed sensor  14  and the output signal supplied by the steering angle sensor  16 . Here, the target swivel angle θ indicates an angle between an adjusted optical axis of the headlamp  10 L,  10 R and a longitudinal axis (fore-and-aft axis) of the vehicle when adjustment of the direction of the headlamp  10 L,  10 R is completed by the actuator  12 L,  12 R. Each of the actuators  12 L,  12 R is driven upon receiving an output signal based on the target swivel angle such that a direction of each optical axis of the headlamps  10 L,  10 R is adjusted to a direction of a visual axis of the occupant. Here, the visual axis of the occupant relates to a steering operation of the vehicle. In the present specification, explanation of the computing method of the target swivel angle based on the vehicle speed and the steering angle is omitted, because the computing method thereof is similar to the conventional well-known method. 
   Next, the control process of the vehicle headlight apparatus  1  performed by the CPU  21  of the ECU  20  will be described with reference to  FIGS. 2 and 3 . A dashed line in  FIG. 3  indicates the longitudinal direction (fore-and-aft direction) of the vehicle. A control program described as a flowchart in  FIG. 2  is stored in the ROM  22 . The CPU  21  reads the control program from the ROM  22  to execute the program. 
   In the flowchart shown in  FIG. 2 , at step  1 , the target swivel angle θ is computed based on the vehicle speed supplied by the speed sensor  14  and the steering angle supplied by the steering angle sensor  16  (hereinafter, step  1  is abbreviated as S 1 , and other steps will be similarly abbreviated). 
   Next, at S 2 , it is determined whether the headlamps  10 L,  10 R have been turned on based on the output signal supplied by the headlamp light switch  17 . When it is determined at S 2  that the headlamps  10 L,  10 R have been turned on (Yes at S 2 ), the actuators  12 L,  12 R are driven based on the target swivel angle θ at S 3  as shown in  FIG. 3  (i.e., the actuators  12 L,  12 R are driven such that the angle between the optical axis of the headlamp and the longitudinal axis of the vehicle is set at the target swivel angle θ). 
   When it is determined at S 2  that the headlamps  10 L,  10 R have not been turned on (NO at S 2 ), at S 4 , it is determined whether the navigation device  30  has detected the dark road section, which is located ahead of the estimated traveling position of the vehicle. When it is determined at S 4  that the dark road section located ahead of the estimated traveling position of the vehicle has not been detected (NO at S 4 ), the actuators  12 L,  12 R are driven at S 6  such that the headlamps  10 L,  10 R faces an ahead of the vehicle at S 6  (i.e., the optical axes of the headlamps  10 L,  10 R extend in the longitudinal direction of the vehicle). 
   When it is determined at S 4  that the dark road section located ahead of the estimated traveling position of the vehicle has been detected (YES at S 4 ), it is determined at S 5  whether an elapsed time, which is a period of time since time of that the dark road section is detected, is equal to or larger than a certain period of time. When the elapsed time is less than the certain period of time (NO at S 5 ), the actuators  12 L,  12 R are driven at S 3  such that the angle between the optical axis of the headlamp and the longitudinal axis of the vehicle corresponds to the target swivel angle θ (see  FIG. 3 ). The certain period of time may be, for example, set at about several seconds. 
   When the elapsed time since the time of detecting the dark road section ahead of the vehicle is equal to or larger than the certain period of time (YES at S 5 ), the actuators  12 L,  12 R are driven at S 6  such that the headlamps  10 L,  10 R face the ahead of the vehicle (i.e., the optical axes of the headlamps  10 L,  10 R extend in the longitudinal direction of the vehicle). 
   Here, steps S 1  through S 6  serve as a swivel controlling means of the present invention. 
   Next, with reference to a schematic diagram of  FIG. 4 , there will be explained a change of a condition of the headlamps in the case of that the vehicle passes through a tunnel T in a daytime. Here, numerals S 1  to S 6  in the explanation correspond to steps  1  to  6  in  FIG. 2 . 
   Firstly, at (1), where the vehicle is on the way to the tunnel T, the headlamps  10 L,  10 R of the vehicle has been turned off, because the degree of brightness in the travel environment is substantially high. Also, because the navigation device  30  has not detected the dark road section located ahead of the estimated traveling position of the vehicle, the actuators  12 L,  12 R are driven such that the headlamps  10 L,  10 R faces the ahead of the vehicle. 
   At (2), where the vehicle has reached a predetermined distance (e.g., 150 m) frontward from the tunnel T (i.e., the vehicle is located on an upstream side of the tunnel by the predetermined distance in the traveling direction of the vehicle), the navigation device  30  detects the dark road section located ahead of the estimated traveling position of the vehicle at S 2 . Then, the actuators  12 L,  12 R are driven such that the angle between the optical axis of the headlamp and the longitudinal axis of the vehicle corresponds to the target swivel angle θ at S 3  (see  FIG. 3 ). 
   At (3), where the vehicle travels into the tunnel T, the illumination sensor  11  detects that the degree of brightness becomes a predetermined value so that the headlamps  10 L,  10 R are automatically turned on by the headlamp light switch  17 . At this time, because the actuator  12 L,  12 R has been already driven such that the angle between the optical axis of the headlamp and the longitudinal axis of the vehicle corresponds to the target swivel angle θ, a sudden change (movement) of the direction of the optical axis at the time of lighting the headlamps  10 L,  10 R is limited. Therefore, the occupant is limited from feeling wrongness due to the sudden change. 
   At (4), where the vehicle travels out of the tunnel T, the illumination sensor  11  detects that the degree of brightness becomes more than the predetermined value so that the headlamps  10 L,  10 R are automatically turned off by the headlamp light switch  17 . Also, because the navigation device  30  has not detected the dark road section located ahead of the estimated traveling position of the vehicle, the actuators  12 L,  12 R at S 6  are driven such that the headlamps  10 L,  10 R faces the ahead of the vehicle. 
   As it is clearly seen in the above description, in the present embodiment, when the headlamps  10 L,  10 R are turned on during a night travel or the travel on the dark road section, such as the tunnel, the actuators  12 L,  12 R are driven based on the target swivel angle θ, which is determined based on the travel condition (e.g., the vehicle speed, the steering angle). Thus, the optical axes of the headlamps  10 L,  10 R are adjusted in the direction of the visual axis of the occupant. In contrast, even at the time of that the headlamps  10 L,  10 R have been turned off, the actuators  12 L,  12 R are driven based on the target swivel angle θ when the navigation device  30  detects the dark road section located ahead of the vehicle. Here, the dark road section is the segment of the road with a predetermined darkness, and the segment of the road extends the predetermined distance. When the vehicle travels into the dark road section, such as the tunnel, the headlamps  10 L,  10 R are automatically turned on. At this time, the actuators  12 L,  12 R have been already driven based on the target swivel angle θ so that the sudden change (movement) of the direction the optical axes of the headlamps  10 L,  10 R at the time of lighting the headlamps  10 L,  10 R is limited. Therefore, the occupant is limited from feeling the wrongness. 
   Also, in a case of that the headlamps  10 L,  10 R have been turned off and that the certain period of time has elapsed since the navigation device  30  detected the dark road section located ahead of the vehicle, the actuators  12 L,  12 R are driven such that the headlamps  10 L,  10 R are set at normal positions (i.e., the headlamps face the ahead of the vehicle). The above case corresponds to, for example, a case, where the vehicle has stopped at a position frontward from the dark road section located ahead of the vehicle. 
   Also, because the navigation device  30  serves to detect the dark road section located ahead of the vehicle, the dark road section, such as the tunnel, the underpass of the overhead crossing, the underpass of the bridge, can be detected with a high degree of accuracy based on the prestored road information, which is prestored in the navigation device  30 . 
   Second Embodiment 
   Next, a vehicle headlight apparatus  101  of the second embodiment of the present invention will be described with reference to  FIG. 5 . Similar components of the vehicle headlight apparatus of the second embodiment, which are similar to the components of the vehicle headlight apparatus of the first embodiment, will be indicated by the same numerals. Explanation of the similar components will be omitted. 
   In the above first embodiment, the navigation device  30  serves as the dark road section detecting means, which detects the dark road section located ahead of the vehicle. However, the vehicle headlight apparatus  101  of the present embodiment utilizes image recognition to detect the dark road section located ahead of the vehicle. 
   As shown in  FIG. 5 , the vehicle headlight apparatus  101  includes a charge coupled device (CCD) camera  31  and an image recognition device  32  alternatively to the navigation device  30  of the first embodiment. The CCD camera  31  serves as an imaging device of the present invention. 
   The CCD camera  31  is arranged between the headlamps  10 L,  10 R that are provided on a front portion of the vehicle, and captures an image ahead of the vehicle (i.e., image of the downstream side of the current position of the vehicle in the traveling direction) to output the captured image. 
   The image recognition device  32  is electrically connected with the CCD camera  31 . The image recognition device  32  includes a CPU, a ROM, a RAM and an input/output circuit, all of which are not shown. When the image recognition device  32  receives the captured image data ahead of the vehicle from the CCD camera  31 , the captured image data is transmitted to the RAM. A dark road section recognition program for recognizing images, the program being stored in the ROM, is executed such that the dark road section (e.g., a tunnel) is detected based on the image processing of the captured image. 
   The detection result by the image recognition device  32  is inputted to the ECU  20 , and then the flowchart shown in  FIG. 2  is executed. Therefore, also in the present embodiment, at the time of that the vehicle travels into the dark road section, such as the tunnel, and that the headlamps  10 L,  10 R have been turned on, the actuators  12 L,  12 R will have been already driven based on the target swivel angle θ, which is determined based on the travel condition of the vehicle. Thus, the sudden change of the direction of the optical axes of the headlamps  10 L,  10 R at the time of turning on the headlamps  10 L,  10 R is limited. Thus, the occupant is limited from feeing the wrongness. 
   In the present embodiment, even in a case of that the vehicle travels on a hidden dark road section, which is not indicated by the road information stored in the navigation device  30 , the hidden dark road section, such as the tunnel, located ahead of the vehicle can be reliably detected. Here, the hidden dark road section, which is not indicated by the road information, includes a newly opened tunnel. 
   Here, additional advantages and modifications will readily occur to those skilled in the art. The invention in its broader terms is therefore not limited to the specific details, representative apparatus, and illustrative examples shown and described. 
   For example, in the above embodiments, the headlamps  10 L,  10 R are automatically turned on or off in response to the degree of brightness sensed through the illumination sensor  11 . However, the headlamp light switch  17  may be manually turned on or off such that the headlamps  10 L,  10 R are turned on or off. 
   The present invention can be applied to a vehicle headlight apparatus, which can perform a swivel operation that changes an optical axis of a headlight in a horizontal direction correspondingly to a steering operation.