(12) United States Patent
`Izawa
`
`(10) Patent N0.:
`(45) Date of Patent:
`
`US 6,229,263 B1
`May 8, 2001
`
`US006229263B1
`
`(54) LIGHTING-DIRECTION CONTROL UNIT
`FOR VEHICLE LAMP
`
`5,907,196 * 5/1999 Hayamietal. ................... .. 307/108
`6,049,171 * 4/2000 Stam et al. ........................... .. 315/82
`
`(75) Inventor: Makoto IzaWa, ShiZuoka (JP)
`
`* cited by examiner
`
`(73) Assignee: Koito Manufacturing Co., Ltd., Tokyo
`(JP)
`
`( * ) Notice:
`
`Subject to any disclaimer, the term of this
`patent is extended or adjusted under 35
`U.S.C. 154(b) by 0 days.
`
`(21) Appl. N0.: 09/488,349
`(22) Filed:
`Jan. 20, 2000
`(30)
`Foreign Application Priority Data
`
`Jan. 22, 1999
`
`(JP) ............................................... .. 11-014167
`
`(51) Int. Cl.7 ..................................................... .. B60Q 1/26
`(52) U.S. Cl. ................ ..
`315/80; 701/49
`(58) Field of Search ................................ .. 315/80, 77, 78,
`315/79, 82; 307/108, 10.1; 701/49, 36,
`37, 48; 250/2081, 214 AL
`
`(56)
`
`References Cited
`
`U.S. PATENT DOCUMENTS
`
`Primary Examiner—Don Wong
`Assistant Examiner—Chuc D Tran
`(74) Attorney, Agent, or Firm—Fish & Richardson PC.
`(57)
`ABSTRACT
`
`A lighting-direction control unit 1 for a lamp of a vehicle
`incorporates a vehicle-height detecting means 2 for detect
`ing change in the height of an aXle of front Wheels or that of
`rear Wheel of the vehicle. In response to a signal represent
`ing the detected height of the vehicle, the pitch angle of the
`vehicle is obtained to change the lighting direction of a lamp
`6 to correspond to the change in the attitude of the vehicle.
`A means 3 for detecting the change rate of acceleration for
`obtaining the change rate of acceleration With respect to time
`in the direction in Which the vehicle runs is provided. When
`the change rate With respect to time is high, a lighting control
`means 4 transmits a control signal to an operating means 5
`in such a manner that the response of the control of the
`lighting direction of the lamp 6 is quickened. Therefore,
`delay in the control is prevented When the change in the
`acceleration is great.
`
`5,787,370 * 7/1998 Kutscher et al. .................... .. 701/49
`
`11 Claims, 8 Drawing Sheets
`
`1
`r/
`
`5
`/
`: OPERATING
`MEANS
`
`6
`
`2
`/
`VEHICLE-HEIGHT
`DETECTING MEANS
`3
`/
`ACCELERATION
`CHANGE RATE
`DETECTING MEANS
`
`4
`/
`
`LIGHTING
`CONTROL
`MEANS
`
`‘
`
`Page 1 of 15
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`BMW 1008
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`

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`U.S. Patent
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`May 8,2001
`
`Sheet 1 of s
`
`US 6,229,263 B1
`
`2
`/
`VEHICLE-HEIGHT
`DETECTING MEANS
`
`3
`/
`ACCELERATION
`CHANGE RATE
`DETECTING MEANS
`
`4
`/
`
`MEANS
`
`>
`
`=
`
`5
`/
`
`_ OPERATING
`'
`MEANS
`
`Page 2 of 15
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`

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`U.S. Patent
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`May 8,2001
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`Sheet 2 of s
`
`m GI
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`Page 3 of 15
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`

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`U.S. Patent
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`May 8,2001
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`Sheet 3 of 8
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`US 6,229,263 B1
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`
`
`@523 Q<mI
`
`.3
`
`$9.02
`
`m>EQ
`
`H5050
`
`30m
`
`A
`
`A
`
`M
`
`A
`
`2:.
`
`MI’
`
`Page 4 of 15
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`

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`U.S. Patent
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`May 8,2001
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`Sheet 4 of s
`
`US 6,229,263 B1
`
`f
`
`A
`
`\
`
`( sTART )
`
`FRCNI STEP S6
`
`s1 ~ PERFoRM INITIALIzATICN
`
`57 ~ INPUT vEHICLE-vELoCITY PULSE
`
`N SET REFERENCE
`32
`POSITION FOR CONTROL
`
`N
`S8
`CALCULATE VEHICLE VELOCITY
`
`83 ~ PERMIT INTERRUPTICN
`
`99 ~ CALCULATE ACCELERATION
`
`FRCNI sTEP s22
`_____
`SHOWN IN FIG- 6
`YES
`
`TURNING?
`
`84
`
`T
`PROCEED TO STEP s10
`SHOWN IN FIG. 5
`
`85 N DETECT
`VEHICLE HEIGHT
`
`PROCEED TO STEP S17
`SHOW IN FIG. 5
`
`86 N CALCULATE PITCH
`ANGLE OF VEHICLE
`
`T
`
`TO STEP S7
`
`Page 5 of 15
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`

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`U.S. Patent
`
`May 8,2001
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`Sheet 5 of 8
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`US 6,229,263 B1
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`FIG. 5
`
`/\
`
`FROM STEP S9 SHOWN IN FIG. 4
`
`YES
`
`$10
`
`CHANGE
`RATE OF ACCELERATION
`HIGH?
`NO
`
`$11
`
`I A I > 5A1?
`No
`
`FROM STEP S4
`SHOWN IN FIG. 4
`I
`PERFORM DATA
`517 ~ PROCEss WHEN
`VEHICLE TuRNs
`I
`PROCEED TO STEP s20
`SHOWN IN FIG. 6
`
`$14
`
`No
`
`IA | > 8A2?
`
`YES
`
`PERFORM
`LINEAR ~ s12
`CONTROL
`
`PERFORM CONTROL BY
`815 \’ AVERAGING PITCH ANGLES
`(AVERAGE IN T1 SECOND)
`
`PERFORM CONTROL BY
`AVERAGING PITCH ANGLES N 816
`(AVERAGE IN T2 SECOND)
`
`II
`TO STEP S18 SHOWN IN FIG. 6
`
`Page 6 of 15
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`

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`U.S. Patent
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`May 8,2001
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`Sheet 6 6f 8
`
`US 6,229,263 B1
`
`FIG. 6
`
`FROM STEPS S12, S15 AND S16 SHOWN IN FIG. 5
`
`S18
`
`YES
`
`CONTROL
`MODE SHIFTED
`?
`NO
`
`PERFORM LINEAR
`CONTROL FOR T3 ~ 819
`SECOND
`
`FROM STEP S17
`SHOWN IN FIG. 5
`
`CALCULATE DATA FOR OPERATION
`
`~ 820
`
`S21
`
`HEAD
`LAMP SWITCH ON
`?
`
`YES
`
`S22 M CONTROL OPERATION OF ACTUATOR
`
`II
`RETURN TO STEP S4 SHOWN IN FIG. 4
`
`Page 7 of 15
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`U.S. Patent
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`May 8,2001
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`Sheet 7 of 8
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`US 6,229,263 B1
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`A [m/s2]
`4*
`
`L
`
`RD
`
`_
`
`....................................................................................................................... ..
`
`RB
`
`RB
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`...................................................................................................................... ..
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`RA
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`RC
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`[km/h]
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`_SA2_
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`RA
`5
`
`RB
`
`RB
`
`_SA1_
`
`....................................................................................................................... ..
`RD
`
`2
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`Page 8 of 15
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`U.S. Patent
`
`May 8,2001
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`Sheet 8 of 8
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`US 6,229,263 B1
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`FIG. 8
`
`
`
`RELATIVE ANGLE
`
`V
`
`Page 9 of 15
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`

`
`US 6,229,263 B1
`
`1
`LIGHTING-DIRECTION CONTROL UNIT
`FOR VEHICLE LAMP
`
`2
`(glare) Which arises When the response of the control is
`determined can be prevented.
`
`BACKGROUND OF THE INVENTION
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`The present invention relates to an apparatus Which
`detects changes in the height of an axle of a front Wheel
`and/or an axle of a rear Wheel of a vehicle so as to control
`the lighting direction of a vehicle lamp in accordance With
`change in the attitude of the vehicle.
`An apparatus (a so-called “automatic leveling apparatus”)
`is knoWn Which performs automatic correction in such a
`manner that a predetermined lighting direction of lamps
`(headlights) provided for a vehicle is alWays maintained if
`the attitude of running of the vehicle is changed.
`An automatic leveling apparatus has a structure that, for
`example, a vehicle-height sensor is provided for each of
`front Wheels and rear Wheels of a vehicle or either of the
`front Wheels or the rear Wheels the vehicle. The foregoing
`automatic leveling apparatus is arranged to cause the
`vehicle-height sensor to measure change in the pitch angle
`(or the pitching angle) of the vehicle to move re?ecting
`mirrors in the headlights to cancel the foregoing change so
`as to control the lighting direction of the lamp or the height
`of the cut line of a light distribution pattern of the loW beam.
`Thus, glare (light) caused from change in the attitude of the
`vehicle can be prevented.
`The conventional apparatus is arranged to change the
`response of the control to correspond to the degree of
`acceleration of the vehicle. Thus, control is quickly per
`formed When the acceleration is large and the control is
`sloWly performed When the acceleration is small.
`The velocity of change of the pitch angle of the vehicle is
`not changed to correspond to the degree of the acceleration.
`The foregoing velocity is changed in proportion to the
`change rate of the acceleration With respect to time.
`Therefore, if quick change in the acceleration occurs in a
`state in Which the acceleration is sloW, delay in the control
`takes place. If light Which is more upWard than a horiZontal
`plane is unnecessary emitted as daZZling light, there is
`apprehension that glare occurs.
`
`SUMMARY OF THE INVENTION
`
`Accordingly, an object of the present invention is to
`reduce frequency of occurrence of daZZling light caused
`from determination of the response of control of the lighting
`direction of a lamp for a vehicle With the degree of the
`acceleration so as to appropriately control the lighting
`direction of the lamp if the pitch angle of the vehicle is
`changed.
`To solve the above-mentioned problems, according to the
`present invention, there is provided a lighting-direction
`control unit for a lamp for a vehicle structured to detect
`change in the height of an axle of a front Wheel and/or an
`axle of a rear Wheel of a vehicle to change a lighting
`direction of a lamp in accordance With change in the attitude
`of the vehicle, the lighting-direction control unit for a lamp
`for a vehicle comprising: lighting control means for obtain
`ing a change rate of acceleration in a direction in Which the
`vehicle runs With respect to time to change a control
`response of the lighting direction of the lamp in accordance
`With the degree of the change rate.
`Therefore, according to the present invention, the control
`response of the lighting direction is changed in accordance
`With the change rate of the acceleration in the direction in
`Which the vehicle runs With respect to time. Thus, a problem
`
`10
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`15
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`25
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`35
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`55
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`65
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`FIG. 1 is a block diagram shoWing the basic structure of
`the present invention;
`FIGS. 2 and 3 to 8 shoW an example of the embodiment
`of the present invention and FIG. 3 is a diagram shoWing an
`example of the layout of an automatic leveling apparatus for
`an automobile;
`FIG. 3 is a block diagram shoWing an example of the
`structure of the apparatus;
`FIGS. 4 to 6 are How charts of an example of the control
`procedure and FIG. 4 shoWs a ?rst portion of the How chart;
`FIG. 5 shoWs an intermediate portion of the process;
`FIG. 6 shoWs a ?nal portion of the process;
`FIG. 7 is a graph shoWing an example of modes of the
`control; and
`FIG. 8 is a schematic graph shoWing a state of control.
`
`DETAILED DESCRIPTION OF THE
`PREFERRED EMBODIMENTS
`
`FIG. 1 shoWs the basic structure of an apparatus according
`to the present invention. The apparatus is structured to detect
`change in the height of the axle of front Wheel and/or axle
`of rear Wheel of a vehicle so as to change the lighting
`direction of a lamp in accordance With change in the attitude
`of the vehicle.
`A lighting-direction control unit 1 incorporates a vehicle
`height detecting means 2; a means 3 for detecting the change
`rate of acceleration for detecting the change rate of the
`acceleration of the running vehicle With respect to time;
`lighting control means 4; and an operating means 5. In
`response to a signal representing the detected vehicle height
`and supplied from the vehicle-height detecting means 2, the
`lighting-direction control unit 1 obtains a pitch angle (or a
`pitching angle) of the vehicle so as to change the lighting
`direction of a lamp 6 in accordance With change in the
`attitude in the longitudinal direction of the vehicle. The lamp
`6, the lighting direction of Which is controlled by the lighting
`control means 4 through the operating means 5, is exempli
`?ed by a head lamp, a fog lamp and a cornering lamp in a
`case of a lamp for a vehicle.
`The vehicle-height detecting means 2 is provided for the
`axle of the front Wheel and/or the axle of the rear Wheel of
`the vehicle to detect change in the height of the vehicle. A
`signal representing the detected vehicle height is basic
`information from Which the attitude of the stopped vehicle
`and the attitude of the running vehicle are obtained. A
`method of detecting the vehicle height may be a method With
`Which the distance betWeen the vehicle-height detecting
`means 2 and the surface of the road is measured by using a
`detecting Wave, such as an ultrasonic Wave or a laser beam.
`Another method may be employed With Which a vehicle
`height sensor serving as the vehicle-height detecting means
`2 is provided Which detects vertical change of the axle of the
`front Wheels or rear Wheels to detect an amount of
`expansion/contraction of the suspension. Any method Which
`is capable of detecting change in the attitude of the vehicle
`in the direction in Which the vehicle runs may be employed.
`The means 3 for detecting the change rate of acceleration
`is required to obtain the change rate of the acceleration in the
`direction in Which the vehicle runs With respect to time.
`Information about the change rate With respect to time is
`
`Page 10 of 15
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`

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`US 6,229,263 B1
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`3
`transmitted to the following lighting control means 4 so as
`to be used as basic information for determining the response
`of the control of the lighting direction of the lamp 6.
`A method of calculating the change rate of acceleration
`With respect to time is exempli?ed by the folloWing method.
`(1) A method With Which the foregoing change rate is
`directly obtained from information (the velocity or the
`acceleration) indicating a state of running of the vehicle.
`(2) A method Which uses indirect information obtained as
`change in the attitude of the vehicle.
`The method (1) include a method With Which an accel
`eration sensor for detecting the acceleration of the vehicle in
`the direction in Which the vehicle runs is provided for the
`vehicle to obtain time differentiation (?rst order
`differentiation) value of a detection signal (a signal indicat
`ing the value of acceleration) of the sensor. Another method
`may be employed Which obtains a second order differentia
`tion value of a vehicle velocity signal obtained by a velocity
`sensor in terms of time. The latter method has an advantage
`in that the conventional velocity sensor can be used.
`The method (2) is exempli?ed by a method With Which an
`acceleration sensor joined to the axle is operated to calculate
`the change rate of the attitude of the vehicle With respect to
`time in the direction in Which the vehicle runs. Another
`method may be employed With Which an angular velocity
`sensor (for example, a gyro sensor) for detecting change in
`the pitch angle of the vehicle is provided for the vehicle to
`obtain the rate of change in the pitch angle in accordance
`With information obtained from the foregoing sensor.
`Moreover, a method may be employed Which uses any
`one of a variety of detecting means for analyZing the attitude
`of running of the vehicle or a means for detecting informa
`tion (for example, force applied to an accelerator pedal or a
`brake pedal) about the driving operation of a driver. That is,
`any one of a variety of methods adaptable to the employed
`detected means may be employed. From a vieWpoint of
`simplifying the structure and prevention of excessive
`enlargement of the cost, it is preferable that the foregoing
`method is employed. That is, it is preferable that the method
`is employed With Which the detecting means for detecting
`change in the acceleration of the vehicle in the direction in
`Which the vehicle runs or change in the attitude of the
`running vehicle is provided to calculate the change rate of
`the acceleration With respect to time or change rate of the
`attitude of the running vehicle With respect to time so as to
`change the response of the control of the lighting direction
`of the lamp.
`The lighting control means 4 is supplied With the detec
`tion signals from the vehicle-height detecting means 2 and
`the means 3 for detecting the change rate of acceleration to
`perform the folloWing control.
`(A) Correction of the lighting direction in accordance
`With change in the pitch angle of the vehicle.
`(B) Determination of the response of control of the
`lighting direction in accordance With the change rate of
`acceleration With respect to time.
`The control (A) is performed by obtaining change in the
`pitch angle corresponding to change in the attitude of the
`vehicle to correct the lighting direction of the lamp to cancel
`the foregoing change. That is, if the front portion of the
`vehicle is changed to someWhat face upWards (or
`doWnWards), the lighting direction of the lamps provided for
`the front portion of the vehicle is undesirably made to face
`someWhat upWards (or doWnWards) as compared With a
`horiZontal plane. Therefore, modi?cation to cause the light
`
`10
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`4
`ing direction to be doWnWards (or upWards) is performed to
`make the foregoing direction to alWays face a predetermined
`direction.
`The control (B) is control Which is an essential portion of
`the present invention. That is, When the change rate of
`acceleration With respect to time is high, the response of the
`control is quickened. When the change rate of acceleration
`With respect to time is loW, the response of the control is
`sloWed (for example, the proportional relationship is deter
`mined betWeen the tWo factors).
`The response may be determined by, for example, a
`method With Which time (sampling time) required to obtain
`data Which is necessary to calculate the change rate of
`acceleration With respect to time, detection time (time to
`determine a period of time for Which average values are
`calculated) Which is the subject of an averaging operation or
`the like is changed. Another method may be employed With
`Which the duty cycle or the like of the control signal Which
`is transmitted to the operating means 5 is changed. The
`present invention is not limited to the determining methods.
`Therefore, any one of knoWn methods may be employed.
`The control of the response may be performed by a
`method With Which the response is continuously changed or
`a method With Which a threshold value is determined to
`perform change in a stepped manner. In the former case,
`relational equations and/or a data table for determining the
`response of the control of the change rate of acceleration
`With respect to time is previously prepared. In accordance
`With the equations or the data table, control is performed in
`such a manner that the response of the control is quickened
`as the change rate of acceleration With respect to time is
`raised. In the latter case, the change rate of acceleration With
`respect to time or an amount of change corresponding to the
`foregoing change rate is compared With a predetermined
`threshold value. In accordance With a result of the
`comparison, the response is determined.
`The method (1) may be performed such that the quantity
`of the second order differentiation of the change rate of
`acceleration obtained from the acceleration sensor With
`respect to time or the velocity obtained by the velocity
`sensor in terms of time is obtained. When the obtained value
`is larger than a threshold value (a reference value for the
`determination), the response is obtained to quickly change
`the lighting direction of the lamp. The method (2) may be
`performed such that the change rate of the attitude of the
`vehicle With respect to time or the velocity of change in the
`pitch angle of the vehicle is obtained. When the obtained
`value is larger than a threshold value (a reference value for
`the determination), the response is obtained to quickly
`change the lighting direction of the lamp.
`When driving information of the driver is used, the
`folloWing method may be employed: in accordance With
`information about the operation of the accelerator or the
`brake pedal, Whether or not shift from an acceleration state
`of the vehicle to the deceleration state or inverse shift from
`the deceleration state to the acceleration state is completed
`in a short time is used as a reference for the determination.
`Time required to complete the shift is compared With a
`threshold value. If required time is short, control is sWitched
`to quicken the response so as to quickly change the lighting
`direction of the lamp.
`In response to the control signal transmitted from the
`lighting control means 4 to the operating means 5, control of
`the lighting direction of the lamp 6 is performed. The control
`is performed by a method With Which the overall portion of
`irradiation light is caused to direct a predetermined direction
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`Page 11 of 15
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`US 6,229,263 B1
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`5
`or a method With Which a portion of irradiation light is
`directed to a predetermined direction. The former method is
`exempli?ed by a method With Which the overall body of the
`lamp is rotated around its rotational shaft to change the
`direction of the irradiation axis of the lamp. Another method
`may be employed With Which the attitude of the element of
`the lamp, for example, the re?ecting mirror, the lens, the
`light source, the light shielding member or the like is
`controlled to change the direction of the optical axis of the
`optical system. The latter method is exempli?ed by a method
`With Which the irradiation axis of a speci?c lamp of an
`apparatus incorporating a plurality of lamps is changed to
`partially change the irradiation direction (for example, the
`irradiation axis of only one or tWo lamps of three lamps,
`Which are a head lamp a fog lamp and a cornering lamp,
`provided for an automobile, is changed). Another method
`may be employed With Which the attitude of one or a
`plurality of elements of the lamp is controlled (for example,
`the re?ecting mirror is composed of a ?xed re?ecting mirror
`and a movable re?ecting mirror and the optical axis of the
`movable re?ecting mirror is directed to a required direction).
`Thus, according to the present invention, if rapid accel
`eration or deceleration of the running vehicle is performed,
`the response of the control of the lighting direction of the
`lamp can appropriately be changed in accordance With the
`change rate of acceleration With respect to time in the
`direction of running. Thus, the effect of control to prevent
`daZZling light Which causes glare can signi?cantly be
`improved.
`FIGS. 2 to 8 are diagrams shoWing an embodiment in
`Which the present invention is applied to a lighting-direction
`control unit for a lamp for a vehicle (an automatic leveling
`apparatus).
`FIG. 2 schematically shoWs an example of the layout of
`the lighting-direction control unit 7 in the vehicle. An ECU
`(an electronic control unit) 8 Which is a controller for the
`lighting-direction control unit 7 is disposed in the rear
`portion of the vehicle. A detection signal from each of a
`vehicle-height sensor 9, a vehicle-velocity sensor 10 and a
`steering sensor 11 is supplied to the ECU 8.
`The vehicle-height sensor 9 corresponding to the forego
`ing vehicle-height detecting means 2 is provided for the left
`rear Wheels of an automobile, the vehicle-height sensor 9
`being a sensor provided for an electronic control air sus
`pension for the rear Wheel. The vehicle-velocity sensor (the
`vehicle velocity detecting means) 10 is a sensor for an ABS
`(Anti-skid Brake System) provided for the rear Wheel. The
`steering sensor 11 is provided for detecting the steering
`angle of the steering Wheel.
`A signal for controlling the ECU 8 is transmitted to an
`actuator portion 12 so that the lighting direction of a head
`lamp 13 is performed (note that FIG. 2 shoWs only the
`left-hand actuator and head lamp).
`In this embodiment, only one vehicle-height sensor 9 is
`provided for the rear Wheel. In accordance With data about
`the detected vehicle height, the attitude of the vehicle is
`detected (in response to a detection signal supplied from the
`vehicle height sensor, the stopping attitude of the vehicle is
`calculated and the relationship betWeen the attitude of the
`running vehicle and the detection signal from the vehicle
`height sensor is previously determined so that the attitude of
`running of the vehicle is obtained). As a matter of course,
`also the vehicle height sensor may be provided for the axle
`of the front Wheels to detect the attitude of the vehicle in
`accordance With data of a plurality of detected heights.
`FIG. 3 shoWs the structure of the lighting-direction con
`trol unit 7. The ECU 8 including a microcomputer is
`
`5
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`supplied With an instruction signal to turn on/off the head
`lamp from a head-lamp sWitch 14 and detection signals from
`the foregoing vehicle-height sensor 9, the vehicle-velocity
`sensor 10 and the steering sensor 11.
`The actuator portion 12 (12‘) corresponding to the oper
`ating means 5 incorporates a motor drive circuit 16 for
`controlling the rotation of a stepping motor 15 (15‘) in
`response to a control supplied from the ECU 8. The actuator
`portion 12‘ is provided to correspond to a head lamp 13‘
`disposed in the right-hand portion of the vehicle, the actuator
`portion 12‘ having a stepping motor 15‘ and a motor drive
`circuit 16‘.
`The actuator portion 12 (12‘) is individually controlled in
`such a manner that the lighting of the corresponding head
`lamp faces a required direction by inclining the re?ecting
`mirror in the head lamp 13 (13‘) With respect to a vertical
`plane including its optical axis. Thus, the height of the cut
`line (or the cut-off) for determining the boundary of the loW
`beam distribution betWeen a bright portion and a dark
`portion can be changed.
`FIGS. 4 to 6 are ?oW charts shoWing a main process
`Which is performed by the ECU 8. In step S1 shoWn in FIG.
`4, an I/O (input/output) port and a memory are initialiZed.
`Then, a control reference position is determined in step S2,
`that is, the initial positions of the actuator portions 12 and 12‘
`are determined.
`Then, the operation proceeds to step S3 so that interrup
`tion of timer of the CPU (Central Processing Unit) in the
`ECU 8 is permitted. In step S4 Whether or not the Wheels are
`being rotated is determined in response to a detection signal
`supplied from the steering sensor 11. If the Wheels are
`rotated, the operation proceeds to step S17 shoWn in FIG. 5.
`If a negative determination is made, the operation proceeds
`to next step S5.
`In step S5 the height of the vehicle is detected. That is, a
`vehicle-height detection signal obtained from the vehicle
`height sensor 9 is received by the ECU 8.
`In step S6 the pitch angle of the vehicle is calculated in
`response to the vehicle-height detection signal. Then, the
`detection signal (a pulse signal) supplied from the vehicle
`velocity sensor 10 is, in step S7, supplied to the ECU 8. Note
`that the foregoing process is an interruption process.
`In step S8 the vehicle velocity (Which is expressed as “V”)
`is obtained by a calculation for obtaining the same. In step
`S9 the acceleration (Which is expressed as “A”) is calculated
`by performing differentiation operation. Then, the operation
`process to step S10 shoWn in FIG. 5. The acceleration can
`easily be obtained by dividing the amount of change in the
`velocity With time required to complete the change.
`In step S10 Whether or not the change rate of the accel
`eration of the vehicle With respect to time is high is deter
`mined by making a comparison With its threshold value. If
`the change rate of acceleration With respect to time is high,
`the operation proceeds to step S12 so that linear control
`(obtained vehicle-height detection data is directly used to
`correct the lighting direction of the head lamp Without
`performing a ?ltering process of the obtained vehicle-height
`detection data) is performed. If the change rate of accelera
`tion With respect to time is loW, the operation proceeds to
`step S11.
`In step S11, Whether or not the magnitude |A| of the
`acceleration A obtained in step S9 is larger than its threshold
`value SA1 (for example, SA1=3 m/s2 to 5 m/s2) is deter
`mined. If an affirmative determination is made, the operation
`proceeds to step S12. If |A|§SA1, the operation proceeds to
`step S13.
`
`Page 12 of 15
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`US 6,229,263 B1
`
`7
`In step S13 Whether or not the vehicle velocity V obtained
`in step S18 is loWer than its threshold value SV (for
`example, SV=1 km/h to 3 km/h) (that is, the vehicle is being
`substantially stopped) is determined. If an affirmative deter
`mination is made, the operation proceeds to step S15. It
`|V|§SV, the operation proceeds to step S14.
`In step S14 Whether or not the magnitude |A| of the
`acceleration A is larger than its threshold value SA2
`(SA2<SA1, for example, SA2=1 m/s2 to 2 m/s2) is deter
`mined. If an affirmative determination is made, the operation
`proceeds to step S15. If A§SA2, the operation proceeds to
`step S16.
`In step S15 a predetermined time average, for example, an
`average value of the pitch angle in, for example, T1=1
`second is calculated. Then, control data corresponding to the
`average value is obtained.
`In step S16 a predetermined time average, for example, an
`average value of the pitch angle in, for example, T2=5
`seconds (that is, a time average in time T2>T1 Which is
`longer than the time employed in step S15) is calculated.
`Then, control data corresponding to the average value is
`obtained.
`When a state of turning of the vehicle has been detected
`in step S4 shoWn in FIG. 4, the operation proceeds to step
`S17 shoWn in FIG. 5 so that a data process Which must be
`performed When a vehicle is being turned is performed. The
`reason for this Will noW be described. If the pitch angle of
`the vehicle obtained from the detection signal supplied from
`the vehicle-height sensor 9 When the vehicle is being turned
`is employed as it is to control the lighting direction of the
`lamp, there sometimes arises a problem. If the height of the
`vehicle in the rear left Wheel portion is enlarged When the
`vehicle is being turned to the left in a state in Which the
`vehicle-height sensor is joined to only the rear left Wheel of
`the vehicle, the lighting direction of the lamp is undesirably
`controlled to an upWard direction from a horiZontal plane.
`To prevent the above-mentioned problem, correction must
`be performed in such a manner that the foregoing change is
`canceled and the upWard change in the lighting direction can
`be prevented. When the vehicle is being turned to the right,
`the height of the vehicle in the rear left Wheel portion is
`reduced. Therefore, the lighting of the lamp is undesirably
`controlled to a doWnWard direction from the height plane. To
`prevent this, correction must be performed in such a manner
`that the foregoing change is canceled and the doWnWard
`change in the lighting direction can be prevented. After step
`S17 has been completed, the operation proceeds to step S20
`shoWn in FIG. 6.
`In this embodiment, the control has various modes as
`steps S12, S15 and S16 to correspond to the degree of the
`velocity V and the acceleration A.
`FIG. 7 has axis of abscissa Which stands for the velocity
`V of the vehicle and axis of ordinate Which stands for the
`acceleration A of the vehicle to illustrate an example of a
`mode map. Referring to FIG. 7, the control described in step
`S15 is performed in a region (OéVéSV and |A|§SA1)
`indicated With symbols RA and a region (SVéV and
`SA2§|A|§SA1) indicated With symbols RB such that the
`average process for time T1 is performed. Referring to FIG.
`7, the control described in step S16 is performed in a region
`(SV<V and |A| §SA2) indicated With symbols RC such that
`the average process for time T2 is performed. The control
`described in step S12 is performed in a region (|A|>SA1)
`indicated With symbols RD such that the real time process
`(as a substitute for an average value of data about the pitch
`angle of the vehicle, a process to Which sampling data which
`
`10
`
`15
`
`25
`
`35
`
`45
`
`55
`
`65
`
`8
`is obtained in a real time manner is directly re?ected) Which
`is the linear control described in step S12 is performed.
`The conventional method is structured such that the
`response of the control is determined in accordance With
`only the magnitude of the acceleration. In this case, When the
`state of driving of the vehicle Which is a deceleration state
`(refer to operating point P1 (v1, a1)) has been changed to an
`acceleration state (refer to operating point P2 (v2, a2)),
`relatively great change (=a2-a1 Where a1<0) in the accel
`eration is shoWn. Since the degrees |a1| and |a2| of the
`acceleration is included in the region RC, the control of the
`lighting direction by performing the average process for
`time T2 is undesirably carried out. In this case, there is
`apprehension that the response of the control deteriorates
`(control is delayed).
`On the other hand, this embodiment is structured to detect
`the change rate of the acceleration in step S10 so that a
`determination is made When occurrence of the change in the
`state of driving of the vehicle from point P1 to point P2
`means a fact that the change rate (a2—a1) of acceleration
`With respect to time is great. Thus, the operation proceeds to
`step S12. Therefore, the control of the lighting direction is
`performed by carrying out the real time process. Therefore,
`if points P1 and P2 are included in the region RC, the
`response of the control is quickened With respect to the
`change in the acceleration. Therefore, any delay in the
`control can be prevented.
`In step S18 shoWn in FIG. 6 Whether or not transition
`betWeen the control modes has occurred (refer to, for
`example, arroWs L, M and N shoWn in FIG. 7