Abstract:
In an automatic beam-axis adjustment system, a beam-axis of a headlight is gradually swivel to a position determined based on a steering angle of a steering wheel. The beam-axis returns to the initial position and a swivel control is inhibited when a vehicle is at a stop or slowly moving in an intersection, regardless of the steering angle. The swivel control is restarted after the vehicle starts running straight ahead. In other words, the swivel control is not restarted until the vehicle stats running straight ahead even when the speed of the vehicle exceeds a predetermined value. Therefore, the movement of the headlights does not disturb a driver.

Description:
CROSS REFERENCE TO RELATED APPLICATION  
       [0001]    This application is based on and incorporates herein by reference Japanese Patent Application No. 2003-116055 filed on Apr. 21, 2003. 
     
    
     
       FIELD OF THE INVENTION  
         [0002]    The present invention relates to an automatic beam-axis adjustment system for vehicular headlights.  
         BACKGROUND OF THE INVENTION  
         [0003]    In a known automatic beam-axis adjustment system, a beam-axis of a vehicular headlight is horizontally swiveled according to a steering angle of a steering wheel. When a vehicle is at a stop or slowly moving in an intersection to turn, the beam-axis returns to an initial position, which is a straight-ahead position, regardless of the steering angle. The beam-axis is instantaneously swiveled to a position that is determined based on the steering angle. Such a movement of the headlight may disturb a driver.  
         SUMMARY OF THE INVENTION  
         [0004]    The present invention therefore has an objective to provide an automatic beam-axis adjustment system that for adjusting a beam-axis of a headlight without disturbing a driver. In the beam-axis adjustment system of the present invention, the beam-axis of the headlight is adjusted using a swivel control procedure based on a vehicle speed and a steering angle of a steering wheel. Prior to the adjustment, it is determined whether an indication of a turn is provided based on signals from various sensors. If the indication is provided, the system uses the other swivel control procedure for gradually adjusting the beam-axis. As a result, the driver will not be disturbed by the movement of the headlight.  
           [0005]    Furthermore, a higher-order smoothing is used when the vehicle speed is higher than a predetermined value and the headlight is swiveled to a position determined based on the steering angle. With the higher-order smoothing, the headlight is gradually swiveled. Therefore, the movement of the headlight does not disturb the drive. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0006]    The above and other objectives, 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:  
         [0007]    [0007]FIG. 1 is a block diagram of an automatic headlight beam-axis adjustment system for vehicular headlights according to embodiments of the present invention;  
         [0008]    [0008]FIG. 2 is an explanatory diagram showing light distribution areas of the headlights and swivel control ranges;  
         [0009]    [0009]FIG. 3 is a flowchart showing a swivel control procedure performed by a CPU included in the adjustment system according to the first embodiment of the present invention;  
         [0010]    [0010]FIG. 4 is a flowchart showing a swivel control procedure according to the second embodiment;  
         [0011]    [0011]FIG. 5 is a flowchart showing a swivel control procedure according to the third embodiment;  
         [0012]    [0012]FIG. 6 is a flowchart showing a swivel control procedure according to the fourth embodiment;  
         [0013]    [0013]FIG. 7 is a flowchart showing a swivel control procedure according to the fifth embodiment;  
         [0014]    [0014]FIG. 8 is a flowchart showing a subroutine program of the swivel control procedure for executing a turning determination procedure according to the first to the fifth embodiments;  
         [0015]    [0015]FIG. 9 is a flowchart showing a flowchart showing a modified subroutine program of the swivel control procedure shown in FIG. 8; and  
         [0016]    [0016]FIG. 10A is waveforms showing vehicle speeds, steering angles, and movements of the headlights responding to changes in the steering angles;  
         [0017]    [0017]FIG. 10B is a waveform of a steering angle flag signal;  
         [0018]    [0018]FIG. 10C is a waveform of an indicator signal;  
         [0019]    [0019]FIG. 10D is a waveform of a turning determination signal;  
         [0020]    [0020]FIG. 10E is a waveform of a swivel control flag signal. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0021]    The preferred embodiments of the present invention will be explained with reference to the accompanying drawings. In the drawings, the same numerals are used for the same components and devices.  
         [0022]    [First Embodiment] 
         [0023]    Referring to FIG. 1, headlights  10 L,  10 R are installed on the front of a vehicle. Actuators  11 L,  11 R are connected to the headlights  10 L,  10 R for horizontally adjusting beam-axes of the headlights  10 L,  10 R. An electronic control unit (ECU) includes a CPU  21 , a ROM  22 , a RAM  23 , a backup (U/B) RAM  24 , an input/output (I/O) circuit  25 , and a bus line  26 . The CPU  21  performs various operating processes, the ROM  22  and the RAM  23  store control programs and data, respectively.  
         [0024]    The ECU  20  receives signals from a left wheel speed sensor  16 L, a right wheel speed sensor  16 R, a steering angle sensor  18 , and other sensors (not shown). The left wheel speed sensor  16 L detects a left wheel speed VL, and the right wheel speed sensor  16 R detects a right wheel speed VR. The steering angle sensor  18  detects a steering angle STA of the steering wheel  17 . The ECU  20  outputs signals to the actuators  11 L,  11 R to adjust the beam-axes of the headlights  10 L,  10 R.  
         [0025]    Referring to FIG. 2, the headlights  10 L,  10 R are horizontally swiveled in the swivel control ranges based on the movement of the steering wheel  17 . Light distribution areas (low beam) of the headlights  10 L,  10 R are adjusted by this swivel operation. The swivel control ranges are determined so that clear view to the front and sides is ensured when the vehicle turns. When the steering wheel  17  is turned clockwise, the swivel control range of the headlight  10 R is larger than that of the headlight  10 L. When the steering wheel  17  is turned counterclockwise, the swivel control range of the headlight  10 L is larger than that of the headlight  10 R.  
         [0026]    A swivel control procedure performed by the CPU  21  will be explained referring to FIGS. 3 and 10. In FIG. 10, a vehicle speed SPD (km/h) and a steering angle STA (°) are indicated by fine solid lines and thick solid lines, respectively. The beam-axes of the headlights  10 L,  10 R that change directions in response to the steering angles STA are indicated by thick dashed lines. The swivel control process is repeated every predetermined period.  
         [0027]    The CPU  21  receives various sensor signals (S 101 ). The signals indicate the vehicle speed SPD, the steering angle STA, and an ON/OFF condition of an indicator signal. The vehicle speed SPD is calculated based on the left and the right wheel speeds VL, VR determined by the left and the right wheel speed sensors  16 L,  16 R, respectively. The steering angle STA is determined by the steering angle sensor  18 . The ON/OFF condition of the indicator signal indicates an operating condition of an indicator (not shown).  
         [0028]    In the next step, the first subroutine is called to execute a turning determination process (S 102 ). After the first subroutine is completed, the second subroutine is called to calculate swivel angles of the headlights  10 L,  10 R (S 103 ). Then, it is determined whether an indication of a turn is provided (S 104 ). If the indication is provided, a swivel control  1  is performed, which is a regular control procedure (S 105 ), and the procedure is completed. The results of the swivel control  1  are shown in FIG. 10A between time t09 and time t10.  
         [0029]    If the indication is not provided, a swivel control  2  is performed (S 106 ), and the procedure is completed. The results of the swivel control  2  are shown in FIG. 10A between time t04 and time t05. In other words, the CPU  21  performs the swivel control  2  rather than the swivel control  1  when the indication of a turn is provided. Therefore, the headlights  10 L,  10 R are smoothly swiveled and the movement of the headlights  10 L,  10 R does not disturb a driver.  
         [0030]    [Second Embodiment] 
         [0031]    Referring to FIG. 4, steps S 201  to S 204  are performed in the same manner as steps S 101  to S 104  in FIG. 3. When an indication of a turn is provided (S 204 ), a swivel control that uses a lower-order smoothing is performed (S 205 ) and the procedure is completed. If the indication of a turn is not provided (S 204 ), the other swivel control that uses a higher-order smoothing is performed (S 206 ) and the procedure is completed.  
         [0032]    A new swivel angle is calculated by the following (S 203 ):  
         [0033]    Swivel angle=a×f(SPD, STA)+(1−a)×(old swivel angle),  
         [0034]    where  
         [0035]    a=0.30 for the lower-order smoothing  
         [0036]    a=0.02 for the higher-order smoothing.  
         [0037]    The swivel control is performed by a swivel control circuit that includes the actuators  11 L,  11 R, and the ECU  20 . The circuit switches the filter from the lower-order smoothing to the higher-order smoothing when the indication of a turn is provided. When the vehicle speed is higher than the predetermined value SPDth, the headlights  10 L,  10 R are gradually swiveled to the position determined based on the steering angle STA. Therefore, the movement of the headlights  10 L,  10 R does not disturb the driver. This swivel control procedure is repeated by the CPU  21  every predetermined period.  
         [0038]    [Third Embodiment] 
         [0039]    Referring to FIG. 5, signals from the sensors are read in the first step (S 301 ). Then, the first subroutine is called to execute a turning determination process in the next step (S 302 ). When the first subroutine is completed, it is determined whether an indication of a turn is provided (S 303 ). If the indication is provided, a turn indication flag is set (S 304 ). This is a condition shown in FIG. 10D between time t05 to time t08. If the indication is not provided, the flag is not set.  
         [0040]    In the next step (S 305 ), it is determined whether an absolute value of the steering angle STA is smaller than the predetermined value STAth. If so, the indication flag is cleared (S 306 ). This is a condition shown in FIG. 10D before time t05 or after time t08. If the absolute value is larger than the predetermined value STAth (t04 to t08, t09 to t10 in FIG. 10B), the flag is not cleared. Then, it is determined whether the indication flag is set (S 307 ). If not, a swivel control process using a lower-order smoothing is performed (S 308 ) and the procedure is completed. If the indication flag is set, a swivel control process using a higher-order smoothing is performed (S 309 ) and the procedure is completed.  
         [0041]    The swivel control is performed by a swivel control circuit that includes the actuators  11 L,  11 R, and the ECU  20 . The circuit switches the filter from the higher-order smoothing to the lower-order smoothing when the steering angle STA is smaller than the predetermined value STAth. In other words, the regular filter is used when the steering wheel  17  is turned close to the initial position. The filter is switched back to the lower-order smoothing after the turn of the vehicle is nearly completed. Therefore, the movement of the headlights  10 L,  10 R does not disturb the driver. This swivel control procedure is repeated by the CPU  21  every predetermined period.  
         [0042]    [Fourth Embodiment] 
         [0043]    Referring to FIG. 6, steps S 401  to S 404  are performed in the same manner as the steps S 101  to S 104  in FIG. 3. If an indication of a turn is not provided, a regular swivel control is performed (S 405 ) and the procedure is completed. The results of this swivel control are shown in FIG. 10A between time t09 and time t10. If the indication of a turn is provided, the swivel control is inhibited (S 406 ) and the procedure is completed.  
         [0044]    Referring to FIG. 10E, a swivel control flag for activating a swivel control is set between time t04 and time t08 during normal operations as indicated with horizontal dashed lines. However, the flag is cleared between time t05 and time t08 because the indication of a turn is provided.  
         [0045]    The swivel control is performed by a swivel control circuit that includes the actuators  11 L,  11 R, and the ECU  20 . The circuit inhibits the swivel control when the indication of a turn is provided. The swivel control is inhibited even when the vehicle speed is higher than the predetermined value SPDth and an instruction to adjust the headlights  10 L,  10 R based on the steering angle STA is issued. Therefore, the movement of the headlights  10 L,  10 R does not disturb the driver. This swivel control procedure is repeated by the CPU  21  every predetermined period.  
         [0046]    [Fifth Embodiment] 
         [0047]    Referring to FIG. 7, steps S 501  to S 507  are performed in the same manner as the steps S 301  to S 207  in FIG. 5. If an indication of a turn is provided, the regular swivel control is performed (S 508 ) and the procedure is completed. If the indication of a turn is not provided, the regular swivel control is inhibited (S 509 ) and the procedure is completed.  
         [0048]    Referring to FIG. 10E, a swivel control flag for activating a swivel control is set between time t04 and time t08 during normal operations as indicated with horizontal dashed lines. However, the flag is cleared between time t05 and time t08 because the indication of a turn is provided.  
         [0049]    The swivel control is performed by a swivel control circuit that includes the actuators  11 L,  11 R, and the ECU  20 . The circuit restarts the swivel control when the steering angle STA is smaller than the predetermined value STAth. The regular swivel control is restarted for adjusting the headlights  10 L,  10 R from the initial position to a position determined by the steering angle STA. Therefore, the movement of the headlights  10 L,  10 R does not disturb the driver. This swivel control procedure is repeated by the CPU  21  every predetermined period.  
         [0050]    The subroutine for turning determination will be explained in detail referring to FIG. 8. This subroutine is repeated every predetermined period by the CPU  21 . Signals from the sensors are read (S 601 ) and it is determined whether the vehicle speed SPD is lower than the predetermined value SPDth based on the signals (S 602 ).  
         [0051]    If the speed is lower than the predetermined value SPDth, it is determined whether the indicator is turned on (S 603 ). If the indicator is turned on (t03 to t07 in FIG. 10C), the turn indication flag is set (S 604 ) and this subroutine is completed. This condition is shown in FIG. 10D between time t05 and time t08. If the speed is higher than the predetermined value SPDth or the indicator is turned off (before t03 and after t07 in FIG. 10C), the flag is not set and the subroutine is completed.  
         [0052]    The other swivel control is used when the vehicle speed SPD is lower than the predetermined value SPDth, the indicator is turned on, and the indication of a turn is provided. The other swivel control is set so that the headlights  10 L,  10 R swivels according to the steering angle. Therefore, the movement of the headlights  10 L,  10 R does not disturb the driver.  
         [0053]    Another subroutine for turning determination will be explained in detail referring to FIG. 9. Signals from the sensors are read (S 701 ) and it is determined whether the vehicle speed SPD is lower than the predetermined value SPDth based on the signals (S 702 ). If the speed is lower than the predetermined value SPDth, it is determined whether the absolute value of the steering angle is larger than the predetermined value STAth (S 703 ). If the steering angle is larger than the value STAth (between t04 and t08, between t09 and t10 in FIG. 10B), the turn indication flag is set (S 704 ) and this subroutine is completed. The condition that the turn indication flag is set is shown in FIG. 10D between t05 and t08.  
         [0054]    If the speed is higher than the predetermined value SPDth or the absolute value of the steering angle STA is smaller than the value STAth, the flag is not set and this subroutine is completed.  
         [0055]    The other swivel control is used when the vehicle speed SPD is lower than the value SPDth and the absolute value of the steering angle STA is larger than the value STAth. The other swivel control is set so that the headlights  10 L,  10 R swivels according to the steering angle. Therefore, the movement of the headlights  10 L,  10 R does not disturb the driver.  
         [0056]    The present invention should not be limited to the embodiment previously discussed and shown in the figures, but may be implemented in various ways without departing from the spirit of the invention. For example, the swivel control may be restarted after the vehicle travels straight ahead for a while. More specifically, the swivel control may be restarted when the steering angle STA becomes substantially zero degree, that is, less than ±5 (°) including play of the steering wheel  17 . The swivel control is inhibited when the speed SPD is lower than the value SPDth. Then, the swivel control is restarted when the speed SPD is higher than the value SPDth and the steering angle remains less than the value STAth for the predetermined period.  
         [0057]    When the indication of a turn is provided and the steering angle STA is larger than the value STAth, the headlights  10 L,  10 R may be temporarily in a non-swivel control range. The non-swivel control range is a range that the swivel control is not performed even when the steering angle STA is larger than the value STAth if the speed SPD is lower than the value SPDth. The swivel control range is a range that the swivel control is performed when the speed SPD is higher the value STAth and the steering angle STA is larger than the value STAth, as shown in FIG. 2. The headlights  10 L,  10 R are back into a swivel control range when the speed SPD is higher than the value SPDth and the angle STA remains substantially zero degree for the predetermined period. Therefore, the movement of the headlights  10 L,  10 R does not disturb the driver.  
         [0058]    The indication of a turn can be provided by an onboard car navigation system, which provides information on intersections. In such a case, the swivel control procedure can be switched based on a distance between the current position of the vehicle and the intersection.  
         [0059]    The present invention is not limited to headlights of a vehicle. The adjustment system may be applied to other lights. Furthermore, the beam-axes may be diagonally adjusted from side to side. The beam-axes may be gradually adjusted to a position determined based on the absolute value of the steering angle STA if the beam-axes is returned to the initial position. Then, the swivel control is restarted.