(12) United States Patent
`Toda et al.
`
`US006305823B1
`US 6,305,823 B1
`Oct. 23, 2001
`
`(10) Patent N0.:
`(45) Date of Patent:
`
`(54) AUTOMATIC LEVELING DEVICE FOR
`AUTOMOTIVE VEHICLE HEADLAMPS
`
`(75) Inventors: Atsushi Toda; Hideaki Takeuchi, both
`of ShiZuoka (JP)
`
`(73) Assignee: Koito Manufacturing Co., Ltd., Tokyo
`(JP)
`
`( * ) Notice:
`
`Subject to any disclaimer, the term of this
`patent is extended or adjusted under 35
`USC 154(b) by 0 days.
`
`(21) Appl. No.: 09/417,782
`(22) Filed:
`Oct. 14, 1999
`(30)
`Foreign Application Priority Data
`
`Oct. 14, 1998
`
`(JP) ............................................ .. P.10-291891
`
`(51) Int. Cl.7 ................................................... .. B60Q 10/76
`(52) US. Cl. ........................ .. 362/276; 362/464; 362/465;
`362/467
`(58) Field of Search ................................... .. 362/276, 464,
`362/465, 467, 272, 286, 271
`
`(56)
`
`References Cited
`
`U.S. PATENT DOCUMENTS
`
`4/1965 Trowbridge ........................ .. 362/467
`3,177,355
`5/1968 Lemberger
`362/467
`3,385,961
`2/1980 Tallon et a1. .... ..
`362/549
`4,188,655
`7/1989 Watanabe et a1.
`362/515
`4,845,598
`5,195,816 * 3/1993 Moss, Jr. et al.
`.. 362/460
`5,787,370 * 7/1998 Kutscher et al. .
`701/49
`5,877,680 * 3/1999 Okuchi et al.
`340/468
`6,109,759 * 8/2000 Tanabe et al. ....................... .. 362/42
`
`OTHER PUBLICATIONS
`
`“HID System With Adaptive Vertical Aim Control”, Society
`of Automotive Engineers, Inc. (1998) pp. (13—18).
`
`* cited by examiner
`
`Primary Examiner—Thomas M. Sember
`Assistant Examiner—Ronald E. DelGiZZi
`(74) Attorney, Agent, or Firm—Fish & Richardson PC.
`
`(57)
`
`ABSTRACT
`
`An automatic leveling device for automotive vehicle head
`lamps is described. The device automatically stops driving
`an actuator if the actuator is determined to be failing, While
`the other normally operating actuator is used to perform a
`leveling of the optical axis of the headlamp as close to a
`proper leveling as possible. In an implementation, a pair of
`left and right headlamps 1L, 1R have optical axes L that are
`tilted individually by driving left and right actuators 10L,
`10R, respectively. A single control unit 16 simultaneously
`controls the driving of the left and right actuators 10L, 10R.
`Avehicle speed detection means 12, a pitch angle detection
`means 14, and failure detection means 20L, 20R are
`included. The control unit 16 controls the driving of the
`actuators 10L, 10R based on a detected pitch angle such that
`the optical axes of the headlamps stay in a certain inclined
`state With respect to the surface of a road, and When an
`actuator is determined to be failing, the CPU unit 16 stops
`driving the failing actuator, While driving the normally
`operating actuator, thereby performing a leveling of the
`optical axis of the headlamp as close to a proper leveling as
`possible.
`
`9 Claims, 5 Drawing Sheets
`
`12
`)
`VEHICLE SPEED SENSOR
`
`VEHICLE HEIGHT SENSOR |—
`5
`14
`
`TIMER
`
`MOTOR DRIVER
`
`so (30R) 5
`
`SL Corp. Exhibit 1005
`
`

`
`U.S. Patent
`U.S. Patent
`
`0a. 23, 2001
`Oct. 23, 2001
`
`Sheet 1 0f5
`Sheet 1 0f5
`
`US 6,305,823 B1
`US 6,305,823 B1
`
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`
`U.S. Patent
`
`Oct. 23, 2001
`
`Sheet 2 of5
`
`US 6,305,823 B1
`
`( START )
`
`7
`
`100
`
`NO
`
`SWITCH
`ON HEAD LAMP
`
`YES
`
`102
`
`STOP
`THE VEHICLE
`
`YES
`
`104
`
`A
`CERTAIN TINIE HAS
`ELASPED
`YES
`
`NO
`
`OPERATE A PITCH
`106 ~ ANGLE WHEN THE
`vEHICLE IS AT HALT
`
`NO
`
`120
`
`IS A FLAG SET?
`
`NO
`
`122
`
`VEHICLE
`SPEED > REFERENCE
`SPEED
`YES
`
`124
`ACCELERATION
`< REFERENCE
`SPEED
`
`YES
`
`126
`
`YES
`
`NO
`
`NO
`
`A
`CERTAIN TIME HAS
`ELASPED
`
`NO
`
`YES
`
`128 N OPERATE A PITCH ANGLE WHEN
`THE vEHICLE IS RUNNING
`
`130
`
`_
`
`DOES ACT FAIL?
`
`YES
`
`I
`
`N0
`
`131
`
`PROCESS FAILURE OF ACT
`
`_
`
`l
`
`108
`
`OPERATE ACT
`
`V
`
`

`
`U.S. Patent
`
`Oct. 23, 2001
`
`Sheet 3 0f 5
`
`US 6,305,823 B1
`
`FIG. 3
`
`132
`
`DOES
`ACT ON R SIDE
`FAIL?
`N
`0
`
`136
`
`DOES
`ACT ON L SIDE
`FAIL?
`NO
`
`YES
`
`GENERATE AN R SIDE N
`ACT, STOP SIGNAL
`134
`
`YES
`
`GENERATE AN L SIDE N
`ACT, STOP SIGNAL
`138
`
`130,131 <
`
`108 N DPERATE ACT
`
`I
`
`

`
`U.S. Patent
`
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`US 6,305,823 B1
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`
`U.S. Patent
`
`0a. 23, 2001
`
`Sheet 5 0f5
`
`US 6,305,823 B1
`
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`

`
`US 6,305,823 B1
`
`1
`AUTOMATIC LEVELING DEVICE FOR
`AUTOMOTIVE VEHICLE HEADLAMPS
`
`BACKGROUND OF THE INVENTION
`The present invention relates to an automatic leveling
`device for automotive vehicle headlamps for controlling the
`driving of optical axis tilt adjusting actuators based on an
`inclination in a longitudinal direction of a vehicle
`(hereinafter, referred to as a pitch angle). A pitch angle
`detection means detects and automatically tilt adjusts the
`optical axes of the headlamps (hereinafter, referred to as
`automatic leveling) in a direction to offset an angle corre
`sponding to the detected pitch angle. In addition, the auto
`matic leveling device includes a fail safe function that
`automatically stops driving the optical axis tilt adjusting
`actuators should they happen to fail.
`KnoWn automatically adjustable headlamps include a
`re?ector having a light source securely inserted therein and
`supported in such a manner as to be tilted around a hori
`Zontal tilt shaft relative to a lamp body. The optical axis of
`the re?ector (headlamp) is tiltable around the horiZontal tilt
`shaft by means of an actuator. A conventional automatic
`leveling device includes a pitch angle detection means, a
`vehicle speed sensor, a controlling section for controlling the
`driving of an actuator based on signals from the detection
`means and sensor, and the like, all of Which are mounted on
`a vehicle. The optical axes of the headlamps (re?ectors) are
`adjusted so as to stay in a certain state With respect to the
`surface of the road at all times.
`In the conventional automatic leveling device, hoWever,
`no countermeasures are provided against a failure of the
`actuators. Thus, if the actuators fail and become inoperable,
`the optical axes of the headlamp are ?xed in the position
`Where they Were directed When the actuators failed. If the
`optical axes are ?xed as being directed more upWardly than
`a desirable level, although the driver of the subject vehicle
`can get good visibility, a driver of an oncoming vehicle Will
`be daZZled by the light from the headlamps. Conversely, if
`the optical axes are ?xed as being directed too loW, although
`there is no problem for oncoming vehicles, the visible
`distance is shorter and may cause the driver to detect an
`object on the road too late, thus putting the driver into a
`dangerous situation.
`SUMMARY OF THE INVENTION
`The present invention provides an automatic leveling
`device for automotive vehicle headlamps, Wherein if one of
`the actuators for automatically leveling the optical axes fails,
`the failing actuator is automatically stopped from being
`driven, While the actuator that is operating normally is used
`to restore as close to a proper leveling state as possible.
`An automatic leveling device for automotive vehicle
`headlamps includes a pair of left and right headlamps Whose
`optical axes are tilted individually vertically relative to a
`vehicle body through driving of left and right actuators,
`respectively. A single control unit simultaneously controls
`the driving of the left and right actuators. A vehicle speed
`detection means detects the speed of the vehicle, and a pitch
`angle detection means detects the pitch angle of the vehicle.
`The control unit controls the driving of the actuators based
`on a detected pitch angle such that the optical axes of the
`headlamps stay in a certain inclined state With respect to the
`surface of a road. A failure detection means is provided for
`each of the actuators that detect a failure thereof, Whereby
`When a failure is detected in either of the actuators by the
`failure detection means, driving of only that failed actuator
`is stopped.
`
`2
`The optical axis of the headlamp having the failing
`actuator is ?xed to a predetermined position, Which is
`different from a desirably proper position because the driv
`ing control of the actuator is stopped. But since leveling of
`the other headlamp is properly performed, the degree of
`reduction in the visible distance for the driver is reduced,
`and glaring light directed at an oncoming vehicle is reduced.
`The invention may include one or more of the folloWing
`features. The automatic leveling device may include a
`control unit that determines, based on a signal from said
`failure detection means, Whether or not the actuators fail,
`respectively, and Wherein When determining that either of
`the actuators fails, the control unit outputs a driving stop
`signal to the failed actuator to stop driving the actuator.
`Since the control unit determines Whether or not the actua
`tors fail and stops driving the actuators, the number of
`constituent components of the automatic leveling device is
`reduced, and the construction thereof is simpli?ed. The
`actuator may include a motor as an actuator main body,
`position detection means for detecting the driving magnitude
`of the motor, and a motor driver for feedback controlling the
`driving of the motor based on a signal from the position
`detection means. Since the motor driver built in the actuator
`feedback controls the motor, the quantity of information
`processed by the control unit is reduced. Therefore, the load
`on the control unit is reduced as Well, Whereby the number
`of functions demanded from the control unit is reduced.
`The actuator may include a driving stop circuit for stop
`ping driving of the motor, Whereby When the failure detec
`tion means detects a failure in said actuator, the driving stop
`circuit is put into operation. When the motor is detected as
`failing by the failure detection means, the driving stop
`circuit is started to operate so as to stop the motor. In other
`Words, the actuators themselves are provided With a fail safe
`function, and the number of functions required of the control
`unit is reduced accordingly.
`Further, the automatic leveling device may include indi
`cator means for informing the driver that either of the
`actuators is failing When the failure detection means so
`detects. The indicator means informs the driver that auto
`matic leveling is not functioning properly.
`A mode of operation of the invention Will be described
`With reference to embodiments.
`
`BRIEF DESCRIPTION OF THE DRAWING
`
`FIG. 1 illustrates an overall construction of an automatic
`leveling device for automotive vehicle headlamps according
`to a ?rst embodiment of the present invention.
`FIG. 2 illustrates a ?oW chart of a control unit of the
`automatic leveling device according to the invention.
`FIG. 3 is a detailed ?oWchart of an actuator failure
`detection control routine and an actuator failure processing
`routine of FIG. 2.
`FIG. 4 is a ?oWchart of control unit (CPU) processing as
`a main part of an automatic leveling device for automotive
`vehicle headlamps according to a second embodiment of the
`present invention.
`FIG. 5 illustrates an alternate embodiment of an automatic
`leveling device for automotive vehicle headlamps according
`to the invention.
`
`10
`
`15
`
`25
`
`35
`
`45
`
`55
`
`65
`
`DETAILED DESCRIPTION
`In FIG. 1, reference number 1 (1L, 1R) denotes a pair of
`left and right headlamps for an automotive vehicle, the
`headlights having the same construction. A front lens 4 is
`
`

`
`US 6,305,823 B1
`
`3
`mounted in the front opening of a lamp body, so that a lamp
`space S is provided. In the lamp space S, a parabolic
`re?ector 5 having a bulb 6 as a light source securely inserted
`therein is supported in such a manner as to be tilted around
`a horiZontal tilt shaft 7 (in FIG. 1, a shaft normal relative to
`the surface of paper) and the parabolic re?ectors 5 are then
`constructed so as to be tilt adjusted by actuators 17 (17L,
`17R), respectively. The actuators 17 (17L, 17R) each com
`prise a stepping motor 10 (10L, 10R) Which includes an
`actuator main body and a motor driver 18 (18L, 18R).
`The headlamp automatic leveling device includes the
`actuators 17 (17L, 17R) for tilt adjusting respective optical
`aXes L of the headlamps 1 (1L, 1R) vertically, actuator
`failure detection sensors 20 (20L, 20R), a headlamp sWitch
`on sWitch 11, vehicle speed sensors 12 as a vehicle speed
`detection means for detecting the speed of a vehicle, vehicle
`height sensors 14 constituting a part of a vehicle pitch angle
`detection means, a CPU 16 as a control unit. The CPU 16
`calculates vehicle speed depending on data from sensors 12
`and calculates vehicle height depending on data from sen
`sors 14, judges Whether the headlamps are sWitched on or
`off, and output to motor drivers 18 (18L, 18R) a control
`signal for driving the motors 10 (10L, 10R) a magnitude
`corresponding to operating pitch angle data. A timer 13 is
`also connected to the CPU 16. Here, the CPU 16 includes a
`RAM Which is a storage section for storing the operated
`vehicle pitch angle data or the like.
`In addition, the CPU 16 determines Whether or not the
`motors 10 (10L, 10R) are failing based on signals from the
`actuator failure detection sensors 20 (20L, 20R). When they
`are judged as failing, the CPU 16 then outputs a driving stop
`signal to the motor drivers 18 (18L, 18R) to stop driving the
`motors 10 (10L, 10R). The CPU 16 also functions to sWitch
`on Warning lamps 30 (30L, 30R), Which is an indicator
`means for optically indicating that the actuators fail.
`When a signal is inputted into it from the vehicle speed
`sensor 12, the CPU 16 calculates a vehicle speed and an
`acceleration based on this inputted signal to thereby deter
`mine Whether the vehicle is stopped or running. If it deter
`mines that the vehicle is running, the CPU 16 then deter
`mines Whether or not the vehicle is run stably based on
`conditions inputted thereinto in advance.
`When a signal is inputted into it from the vehicle height
`sensors 14, the CPU 16 calculates a vehicle inclination angle
`(pitch angle) in a longitudinal direction of the vehicle from
`the signal corresponding to a displacement distance of
`suspensions. When a tWo-sensor system is used in Which
`vehicle height sensors are provided on both the front and
`rear Wheels, the vehicle pitch angle is obtained from dis
`placement distances of the vehicle height at the front and
`rear of the vehicle and a Wheel base of the vehicle, or a
`distance betWeen front and rear aXles of the vehicle.
`Alternately, When a single sensor system is used in Which
`sensors are provided on either the front Wheels or the rear
`Wheels, the pitch angle can be estimated from a displace
`ment distance of the vehicle height. Then, the CPU 16
`outputs a signal to the motor drivers 18 (18L, 18R) so as to
`tilt the optical aXes L of the left and right headlamps 1 (1L,
`1R) a predetermined distance in a direction to correct for the
`obtained or estimated pitch angle.
`When the vehicle is stationary, since the proper pitch
`angle of the vehicle can be detected in principle, the driving
`of the motors 10 (10L, 10R) is ?rst controlled based on the
`vehicle pitch angle obtained When the vehicle is at halt. In
`addition, When the CPU detects a signal from the vehicle
`height sensors 14, since there is no disturbance, the CPU 16
`
`15
`
`25
`
`35
`
`45
`
`55
`
`65
`
`4
`operates at a relatively fast sampling speed. But While the
`vehicle is running, in order to eliminate disturbance, the
`CPU 16 is constructed so as to calculate a pitch angle of the
`vehicle only on condition that the vehicle speed is equal to
`or higher than a reference value, the acceleration is equal to
`or loWer than a reference value, and this state (in Which the
`vehicle speed is equal to or higher than the reference value
`and the acceleration is equal to loWer than the reference
`value) continues for a predetermined period of time or
`longer. For eXample, When a vehicle is running on a rough
`road in Which disturbance is caused by irregularities on the
`road surface or the like, the vehicle cannot run at a speed of
`30 km/h or higher, and in order to eliminate an abrupt
`acceleration causing the vehicle posture to be changed, it is
`proper to limit the acceleration to 0.5 m/s2 or loWer.
`Therefore, an abrupt detection of an abnormal value and any
`in?uence from the detection of an abnormal value are
`impeded by permitting calculation of a pitch angle of the
`vehicle to occur only on condition that the state in Which the
`vehicle speed is equal to or higher than 30 km/h and the
`acceleration is equal to or loWer than 0.5 m/s2 continues for
`three seconds or longer. In addition, the CPU 16 determines
`Whether the lighting sWitch is sWitched on or off, and it
`outputs a signal to the motor drivers 18 (18L, 18R) to drive
`the motors 10 (10L, 10R) only When the lighting sWitch is
`sWitched on.
`The CPU 16 compares a signal from the actuator failure
`detection sensors 20 (20L, 20R) With conditions inputted in
`advance and determines Whether or not the actuators are
`failing. When it determines that one of the actuators failed,
`the CPU 16 outputs a motor stop signal to the motor driver
`18 so as not to drive the motor for the failed actuator, While
`it continues to control the driving of the actuator that is not
`detected as failing.
`The actuator failure detection sensor 20 includes a motor
`lock detection means for detecting Whether or not the motor
`is in a locked state because the driven portion of the re?ector
`is froZen or because the driving of the motor is locked due
`to damage from an accident that caused a lock current to
`?oW, Whereby the motor is burned out. In addition, the
`actuator failure detection sensor 20 includes a poWer supply
`loW voltage detection circuit for detecting the poWer supply
`voltage of the motor because a reduction in the poWer supply
`voltage of the motor may loWer the torque of the motor,
`Whereby a lock current is caused to ?oW. Furthermore, also
`included is a poWer supply high voltage detection circuit
`because a rise in the poWer supply voltage increases the coil
`current of the motor, Which could cause the motor to burn
`out. Moreover, also included is a control unit-actuator in
`betWeen the short-circuit detection means because if a short
`circuit occurs betWeen the CPU 16 and the motor drivers an
`undesirable upWard tilt of the optical aXes of the headlamps
`may occur.
`The ?oW charts of FIGS. 2 and 3 illustrate the control of
`the motors 10 by the CPU 16 as a control unit. In step 100
`of FIG. 2, it is determined from a signal from the headlamp
`lighting sWitch 11 Whether the headlamps are sWitched on or
`off. If NO (sWitched off), return to step 100; if YES, move
`to step 102. In step 102, it is determined from signals from
`the vehicle speed sensors 12 Whether the vehicle is at halt or
`moving; if YES, in step 104, it is determined Whether or not
`a predetermined time period, for instance 10 seconds has
`elapsed. If no, (if 10 seconds has not elapsed), the vehicle is
`regarded as being stopped, and move to step 106, Where a
`pitch angle 01 When the vehicle is at halt is calculated, and
`the calculated pitch angle is then stored in the RAM, Which
`is a storage section. Then, move to step 108 via an actuator
`failure judgment control step 130 (actuator failure process
`ing step 131).
`
`

`
`US 6,305,823 B1
`
`5
`In the actuator failure judgment control step 130, as Will
`be described later, the control unit 16 determines based on
`signals from the actuator failure detection sensors 20 (20L,
`20R) Whether or not there is a failure of driving of the motors
`10 (10L, 10R). If no failure is detected, move to step 108
`Where the control unit 16 outputs signals to the motor drivers
`18 (18L, 18R) so as to drive the motors 10 (10L, 10R) a
`magnitude corresponding to the pitch angle 01 When the
`vehicle is at halt, and then return to step 100. This simul
`taneously levels the left and right headlamps 1 (1L, 1R).
`HoWever, in step 130, if a failure is determined as
`occurring, move to the actuator failure processing step,
`Where the control unit 16 outputs a signal to the motor driver
`18 to stop driving the motor 10 judged as failing (the motor
`10 is prevented from being driven) and sWitches on the
`Warning lamp 30, thereafter moving to step 108. Due to this
`processing, the motor driver 18 cannot drive the failing
`motor 10, and hence the headlamp Whose motor is failing
`cannot be leveled. In addition, the driver can con?rm from
`the Warning lamp 30 that the automatic leveling device is out
`of order.
`In step 102, if No (the vehicle is running), move to step
`120, Where it is determined Whether or not a ?ag is set. In
`other Words, in step 108, if a leveling has already been
`performed based on the pitch angle at the time of stable
`running, a ?ag has been set, but in step 120, if No (it is
`determined that the ?ag is not set, that is the motors have not
`yet been driven based on the pitch angle at the time of stable
`running), move to step 122, and it is determined Whether or
`not the vehicle speed exceeds the reference value (30 Km/h).
`If YES (the vehicle speed exceeds 30 km/h), in step 124, it
`is determined Whether or not the acceleration is loWer than
`the reference value When the vehicle is at halt. In step 124,
`if YES (loWer than 0.5 m/s2), then in step 126 it is deter
`mined Whether or not a state continues for a predetermined
`time period (three seconds) or longer in Which the vehicle
`speed exceeds 30 km/h and the acceleration is loWer than 0.5
`m/s2. In step 126, if YES (if such a state is determined as
`continuing three seconds or longer) move to step 128, Where
`a pitch angle 02 at the time of stable running is calculated,
`and an operated pitch angle 02 is stored in the RAM Which
`is a storage section. Next, move to step 108 via the actuator
`failure judgment control step 130 (actuator failure process
`ing step 131).
`As previously described about the actuator failure judg
`ment control step 130, the control unit 16 determines
`Whether or not there exists a failure of driving of the motors
`10 (10L, 10R) based on the signals from the actuator failure
`detection sensors 18 (18L, 18R). If no failure is determined
`as existing, then move to step 108, and the control unit 16
`outputs signals to the motor drivers 18 (18L, 18R) so as to
`drive the motors a magnitude corresponding to the pitch
`angle 02 at the time of stable running and sets a ?ag, then
`returning to step 100. This simultaneously levels the left and
`right headlamps.
`The vehicle posture at the time of stable running is
`substantially identical to that When the vehicle is at a halt,
`and it is easily detected. Moreover, since the pitch angle 02
`of the former is substantially identical to that 01 of the latter,
`even if the driving of the actuators (motors 10) are controlled
`based on the pitch angle 02 at the time of stable running, no
`problem Will be caused. In particular, as to the pitch angle of
`01 When the vehicle is at a halt, an erroneous pitch angle
`Would be detected When the vehicle rides on the curb, but the
`pitch angle 01 When the vehicle is stationary is corrected by
`the pitch angle 02 at the time of stable running (the driving
`of the actuators is controlled based on the pitch angle 02 at
`
`10
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`20
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`30
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`
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`6
`the time of stable running) While running, Whereby a level
`ing of the optical axes based on the erroneous pitch angle
`When the vehicle is at a halt is avoided.
`In step 130, if a failure is determined to exist, then move
`to the actuator failure processing step 131, Where the control
`unit 16 outputs a stop signal to the motor driver 18 so as to
`make it stop driving the failing motor 10 (the motor 10 is
`prevented from being driven) and sWitches On the Warning
`lamp 30, thereafter moving to step 108. Due to this
`processing, the motor driver 18 is not permitted to drive the
`failing motor, and hence the optical axis of the headlamp
`having the failing motor is not leveled.
`In addition, in step 120, if YES (if a ?ag is set, in step 108,
`as in the case Where a leveling is performed based on the
`pitch angle 02 at the time of running, if the pitch angle is
`corrected While running), and for the cases in steps 122, 124,
`and 126, are NO, respectively, (in cases, respectively, Where
`the vehicle speed is equal to or loWer than the reference
`value of 30 km/h, the acceleration is equal to or higher than
`the reference value of 0.5 m/s2, and such a state does not
`continue for three seconds or longer), in any case, then
`return to step 100 Without controlling the driving of the
`motor 10.
`Referring to FIG. 3, a detailed ?oWchart of the actuator
`failure determination control step 130 and the actuator
`failure processing step 131 Will be described. In the case
`Where the stepping motor 10 (10L, 10R), Which is the
`actuator main body, fails, the driving of the actuator is
`stopped.
`First, in step 132, a signal from the actuator failure
`detection sensor 20R is compared With an alloWable value
`set in advance, and from this it is determined Whether or not
`the leveling motor 10R of the right-hand side headlamp 1R
`fails. If NO (no failure), move to step 136, Where a signal
`from the actuator failure detection sensor 18L is compared
`With an alloWable value set in advance, and from this it is
`determined Whether or not the leveling motor 10L of the
`left-hand side headlamp 10L fails. If NO (no failure) then
`move to step 108, Where the control circuit 16 outputs
`signals to the motor drivers 18R, 18L so as to control the
`motors 10R, 10L based on the pitch angle 01 When the
`vehicle is at a halt calculated in step 106 and stored in the
`RAM (or the pitch angle 02 at the time of stable running
`operated in step 128 and stored in the RAM), then returning
`to step 100. Thus, in a case Where neither of the leveling
`motors 10L, 10R of the left and right headlamps is failing,
`the left and right headlamps are simultaneously leveled. In
`addition, in a case Where the driving of the motors 10L, 10R
`is controlled based on the pitch angle 02 at the time of stable
`running, as is previously described, a ?ag is set.
`Conversely, in step 132, if YES (the right leveling motor
`is determined to be failing), in step 134, a stop signal is
`outputted to the motor driver 18R of the right-hand side
`headlamp, and the Warning lamp 30R is sWitched on. Next,
`in step 136, if YES (the left leveling motor is determined to
`be failing), then in step 138, a stop signal is outputted to the
`motor driver 18L of the left-hand side headlamp, and the
`Warning lamp 30L is sWitched on. Then, in step 108, since
`motor driving stop signals from the control circuit 16
`outputs are output to the motor drivers 18L, 18R, the motors
`10L, 10R are not driven and hence neither of the left and
`right headlamps are leveled, and the optical axes of the
`respective headlamps are left in a ?xed state.
`In addition, if YES (the right leveling motor is determined
`to be failing) in step 132, While NO (no failure is
`determined) in step 136, the CPU 16 outputs a stop signal to
`
`

`
`US 6,305,823 B1
`
`7
`the motor driver 18R of the right-hand side headlamp and
`switches on the Warning lamp 30R. Therefore, in step 108,
`the optical axis of the left-hand side headlamp 1L is properly
`leveled, but no leveling is performed With respect to the
`right-hand side headlamp 1R, and hence the optical axis
`thereof is ?xed.
`HoWever, if NO (no failure is determined) in step 132,
`While YES (the left leveling motor is determined to be
`failing) in step 136, then in step 138 the CPU 16 outputs a
`stop signal to the motor driver 18L of the left-hand side
`headlamp 1L and sWitches on the Warning lamp 30L.
`Therefore, in step 108 the right-hand side headlamp 1R is
`properly leveled, but no leveling is carried out With respect
`to the left-hand side headlamp 1L, and the optical axis
`thereof is ?xed.
`In addition, if the failure is eliminated after the leveling of
`the affected headlamp is stopped, then move to step 108 via
`steps 132, 136, Where both the headlamps are properly
`leveled, and therefore no safety problem is caused.
`Thus, in this embodiment, if the stepping motor 10 (10L,
`10R), Which is the actuator main body, fails, only the failing
`motor is stopped. The properly operating motor continues to
`be driven and controlled. Due to this, the headlamp having
`the failing motor is not leveled and the optical axis thereof
`is ?xed at a predetermined position. But since the headlamp
`having the properly operating motor is properly leveled, the
`driver does not have to experience a too-short visible
`distance and no excessive glaring light is directed at an
`oncoming vehicle, thus the running safety of both of the
`vehicles is secured.
`The process How (shoWn in FIG. 3) from the actuator
`failure determination control step 130 (actuator failure pro
`cessing step 131) to the actuator driving step 108 may be
`constituted by a process How chart 140 shoWn in FIG. 4. In
`particular, in this implementation, instep 142, it is deter
`mined based on a signal from the actuator failure detection
`sensor 20R Whether or not the leveling motor 10R of the
`right-hand side headlamp 1R fails. If NO (no failure is
`determined), move to step 144 Where it is determined based
`on a signal from the actuator failure detection sensor 20L
`Whether or not the leveling motor 10L of the left-hand side
`headlamp 1L fails. If NO (no failure is determined) then in
`steps 146, 148, signals are outputted to the motor drivers
`18R, 18L so as to control the motors 10R, 10L based on the
`pitch angle 01 (or pitch angle 02), then returning to step 100.
`Conversely, if YES (the leveling motor 10L for the
`left-hand side headlamp fails) in step 144, then in step 150,
`a stop signal is outputted to the motor driver 18L of the
`left-hand side headlamp and the Warning lamp 30L is
`sWitched on. Then in step 152 a signal is outputted to the
`motor driver 18R so as to control the motor 10R of the
`right-hand side headlamp 1R based on the pitch angle 01 (or
`pitch angle 02), then moving back to step 100. HoWever, if
`YES (the leveling motor 10R of the right-hand side head
`lamp 1R is failing) in step 142, then in step 154 it is
`determined from a signal from the actuator failure detection
`sensor 18L Whether or not the leveling motor 10L of the
`left-hand side headlamp 1L fails. If NO (no failure is
`determined), move to step 156, and a stop signal is outputted
`to the leveling motor 10R of the right-hand side headlamp
`1R, and the Warning lamp 30R for the right-hand side
`headlamp is sWitched on. Next, instep 158 a signal is
`outputted to the motor driver 18L so as to control the motor
`10L based on the pitch angle 01, (or pitch angle 02), then
`moving back to step 100. If YES (the leveling motor 10L of
`the left-hand side head lamp 1L fails) in step 154, then in
`
`10
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`15
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`25
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`35
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`45
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`55
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`65
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`8
`steps 160, 162, stop signals are outputted to the motor
`drivers 18L, 18R of the left and right headlamps,
`respectively, and the Warning lamps 30L, 30R for the left
`and right headlamps are sWitched on, the returning to step
`100. The remaining portions of this embodiment are the
`same as those of the ?rst embodiment, and hence a repeated
`description is omitted.
`FIG. 5 is a draWing shoWing an overall construction of a
`third embodiment of the present invention. In the third
`embodiment, actuators 117 (117L, 117R) comprise DC
`motors 110 (110L, 110R) and motor drivers 118 (118L,
`118R) for controlling the driving of the motors 110 (110L,
`110R). The motor drivers 118 (118L, 118R) are constructed
`so as to feedback control the DC motors 110 (110L, 110R)
`such that positional data from the potentiometers 112 (112L,
`112R), Which are position detection means, approximates
`pitch angle data input from the CPU 16 based on the
`positional data from the potentiometers 112 (112L, 112R). In
`addition, actuator failure detection circuits 120 (120L,
`120R) provided for the actuators 117 (117L, 117R) deter
`mine Whether or not the DC motors 110 (110L, 1