U.S. patent application number 09/745710 was filed with the patent office on 2001-10-04 for automatic leveling system for automotive headlamps.
Invention is credited to Takeuchi, Hideaki, Tode, Atsushi.
Application Number | 20010027365 09/745710 |
Document ID | / |
Family ID | 18493094 |
Filed Date | 2001-10-04 |
United States Patent
Application |
20010027365 |
Kind Code |
A1 |
Tode, Atsushi ; et
al. |
October 4, 2001 |
Automatic leveling system for automotive headlamps
Abstract
An automatic leveling system has a headlamps optical axes L
adapted to tilt vertically relative to a body of a vehicle by
driving actuators 10, a control part 16 for controlling the driving
of the actuators 10, a vehicle speed sensor 12, a vehicle height
sensor 14 and a storage part 20 for storing pitch angle data
detected by the vehicle height sensor 14. The control part 16
controls the actuators 10 based on a detected pitch angle such that
the optical axes L of the headlamps are inclined to a predetermined
angle relative to the road surface.
Inventors: |
Tode, Atsushi; (Shizuoka,
JP) ; Takeuchi, Hideaki; (Shizuoka, JP) |
Correspondence
Address: |
CHRIST T. MIZUMOTO
Fish & Richardson P.C.
45 Rockefeller Plaza, Suite 2800
New York
NY
10111
US
|
Family ID: |
18493094 |
Appl. No.: |
09/745710 |
Filed: |
December 21, 2000 |
Current U.S.
Class: |
701/49 ;
307/10.8 |
Current CPC
Class: |
B60Q 2300/116 20130101;
B60Q 1/115 20130101; B60Q 2300/114 20130101; B60Q 2300/112
20130101; B60Q 2300/132 20130101 |
Class at
Publication: |
701/49 ;
307/10.8 |
International
Class: |
G06F 017/00 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 27, 1999 |
JP |
P. HEI.11-368918 |
Claims
What is claimed is:
1. An automatic leveling system for automotive headlamps
comprising: headlamps optical axes adapted to tilt vertically
relative to a body of a vehicle; control means for controlling
actuators to correct the tilt of the optical axes; vehicle speed
detecting means for detecting speeds of the vehicle; pitch angle
detecting means for detecting pitch angles of the vehicle; and a
storage part for storing pitch angle data of the vehicle detected
by said pitch angle detecting means; wherein said control means is
configured to control said actuators based on pitch angle not
influenced by a change in posture of the vehicle resulting when the
vehicle starts.
2. The automatic leveling system for automotive headlamps as set
forth in claim 1, wherein if the start of the vehicle is detected
by said vehicle speed detecting means within a predetermined set
time after a control of said actuators is carried out, said control
means determines that said control and the start of the vehicle
substantially coincide with each other.
3. The automatic leveling system for automotive headlamps as set
forth in claim 2, wherein said predetermined set time is equal to
or longer than an interval of time between the depression of an
accelerator pedal and the detection of the start of said
vehicle.
4. The automatic leveling system for automotive headlamps as set
forth in claim 1, wherein if the actuators have been controlled
more than once before they are controlled at the time of the start
of the vehicle, pitch angle data detected before the start of the
vehicle are used for controlling the actuators.
5. The automatic leveling system for automotive headlamps as set
forth in claim 1, if the actuators are controlled for the first
time, pitch angle data which is detected just previous to the
depression of the accelerator pedal while the vehicle is at a stop
is used for controlling the actuators.
6. The automatic leveling system for automotive headlamps as set
forth in claim 1, if the actuators are controlled for the first
time and no pitch angle is detected previous to the depression of
the accelerator pedal, said actuators are prevented from being
driven.
7. The automatic leveling system for automotive headlamps as set
forth in claim 1, wherein said storage part is configured such that
older pitch angle data are replaced with newer pitch angle data in
the order stored when latest pitch angle data are entered to update
the pitch angle data.
8. The automatic leveling system for automotive headlamps as set
forth in claims 1, wherein controlling the driving of said
actuators is carried out on condition that said headlamps are
illuminated.
9. The automatic leveling system for automotive headlamps as set
forth in claim 1, wherein an interval at which said actuators are
driven is configured such that said interval becomes longer than a
maximum driving time of said actuators needed to perform a single
leveling.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to an automatic leveling
system for adjusting optical axes of atutomotive headlamps based on
a pitch angle of a vehicle, and more particularly to an automatic
leveling system for vertically adjusting optical axes of headlamps
based on a pitch angle of a stationary vehicle.
BACKGROUND OF THE INVENTION
[0002] A headlamp of the type used in an automatic leveling system
is constructed such that a reflector with a light source securely
inserted therein is supported to tilt about a horizontal tilting
axis relative to a lamp body. An actuator is used to tilt the
optical axis of the reflector (a headlamp) about the horizontal
tilting axis.
[0003] A conventional automatic leveling system is constituted by a
pitch angle detecting means, a vehicle speed sensor, and a control
part for controlling the driving of actuators based on detection
signals from the detecting means and the sensor, which are provided
on a vehicle. The optical axes of headlamps (reflectors) are
adjusted to remain in a certain position relative to the surface of
a road at all times.
[0004] The conventional automatic leveling system automatically
levels the headlamps in real-time, such as when a vehicle posture
changes because of acceleration or deceleration or when the load is
loaded or unloaded, or the passengers get in or out of the vehicle.
This increases the operations of the actuators, leading to greater
power consumption. Moreover, a high durability is required for
driving mechanism components such as motors and gears, which leads
to greater production costs.
[0005] To provide an automatic leveling system that can reduce the
frequency of use of actuators and that is inexpensive and durable,
an automatic leveling system was proposed (Japanese Patent
Application No. 10-274859) in which actuators are driven at
predetermined intervals (ten second intervals) while a vehicle is
at a stop.
[0006] However, while the actuators of the above automatic leveling
system are controlled based on a pitch angle detected during a
predetermined interval time, if an interval control coincides with
the start of the vehicle, automatic leveling cannot be properly
performed. The problem is described with reference to FIG. 6.
[0007] FIG. 6 is a chart showing changes in vehicle speed and
vehicle posture from the start of the vehicle until it reaches a
constant running speed. As shown in the chart, it takes a
predetermined length of time (T) before the vehicle actually starts
running after an accelerator pedal is depressed. In other words,
the vehicle speed starts increasing after the predetermined length
of time (T) has elapsed. Because of this, the vehicle sensor
detects the start of the vehicle at a predetermined start detection
delay time T after the accelerator pedal is depressed.
[0008] As to the vehicle posture, when the accelerator pedal is
depressed, a rear part of the vehicle first lowers and the vehicle
continues to remain in that state. That is, when the vehicle sensor
detects the start of the vehicle (when a control part detects the
start of the vehicle based on an output from the vehicle sensor),
the rear part of the vehicle is in a lowered position or,
alternatively, the front part of the vehicle is in a raised
position.
[0009] Because of this, as shown in FIG. 6, there may be a case
where the timing of an interval control falls within (T), a time
period between the lowering of the rear part of the vehicle by the
depression of the accelerator pedal and the detection of the start
of the vehicle by the vehicle speed sensor. A vehicle pitch angle
for use for interval control in this case is improper because the
pitch angle is calculated based on the vehicle's lowered position.
The control part is forced to control the actuators based on the
improper pitch angle data.
[0010] An object of the present invention is to provide an
automatic leveling system for automotive headlamps that is
inexpensive and that can provide a longer service life by reducing
the frequency of use of actuators by controlling the actuators at
predetermined intervals. Another object of the invention is to
provide an automatic leveling system adapted to operate properly
even if the timing of interval control coincides with the start of
the vehicle.
SUMMARY OF THE INVENTION
[0011] According to a first embodiment of the invention, an
automatic leveling system for automotive headlamps comprises
headlamps optical axes adapted to tilt vertically relative to a
body of a vehicle by driving actuators, a control means for
controlling the driving of the actuators, a vehicle speed detecting
means for detecting speeds of the vehicle, a pitch angle detecting
means for detecting pitch angles of the vehicle and a storage part
for storing pitch angle data of the vehicle detected by the pitch
angle detecting means. The control means controls the actuators
based on the pitch angle data detected by the pitch angle detecting
means such that the optical axes of the headlamps are tilted in a
certain tilted angle relative to a road surface.
[0012] The storage part is configured to store a plurality of data
detected at predetermined time intervals.
[0013] The control means is configured to control the actuators
based on pitch angle data not affected by a change in posture of
the vehicle when the vehicle is started and the interval control is
carried out substantially at the same time. The control means
controls the actuators at predetermined intervals based on the
latest pitch angle data.
[0014] Additionally, according to a second embodiment of the
invention, an automatic leveling system for automotive headlamps is
provided such that the start of the vehicle is detected by the
vehicle speed detecting means within a predetermined set time after
an interval control of the actuators is carried out. The control
means determines that the interval control and the start of the
vehicle substantially coincide with each other.
[0015] Furthermore, according to a third embodiment of the
invention, an automatic leveling system for automotive headlamps is
provided such that the predetermined set time, which is used to
determine whether the interval control and the start of the vehicle
coincide with each other, isequal to or longer than a vehicle start
detection delay time, which is a time from an accelerator pedal is
depressed until the vehicle speed detecting means detects the start
of the vehicle.
[0016] Pitch angle data generated while the vehicle is at a stop
are more accurate than pitch angle data generated while the vehicle
is running because there are less disturbing factors when the
vehicle is stationary. Since the actuators is controlled based on
the more accurate pitch angle data, a more accurate automatic
leveling can be provided with the former pitch angle data.
[0017] In addition, since the control of the actuators is limited
to a certain time interval, the frequency at which the actuators
are driven is reduced to that extent. Thus, power consumption is
reduced and the wear on the driving mechanism is reduced.
[0018] Moreover, the start of the vehicle may be detected by the
vehicle speed sensor. If an interval control coincides with the
start of the vehicle the actuators may be driven based on an
improper pitch angle. A proper automatic leveling can be effected
by controlling the actuators based on a proper pitch angle obtained
before the depression of the accelerator pedal.
[0019] Referring to FIG. 6, a proper automatic leveling process is
described in detail. If an interval control of the actuators
happens substantially at the same time that the vehicle starts,
that is, if an interval control falls within a vehicle start
detection delay time T (from the time the accelerator pedal is
depressed until the vehicle speed sensor detects the start of the
vehicle), a pitch angle used for this specific interval control is
that detected by the pitch angle detection means when the interval
control occurs. Hence, there may be a risk that the pitch angle
data so detected include data generated when the vehicle is lowered
when it is about to start. Therefore, the pitch angle data may not
be necessarily proper for use. That is, the actuators (automatic
leveling) may be driven based on improper pitch angle data.
[0020] To address this, instead of a pitch angle detected when the
vehicle changes posture, a pitch angle detected prior to the
vehicle start detection delay time T (pitch angle data designated
by reference character A in FIG. 6 which are detected before the
accelerator pedal is depressed) may be used.
[0021] Although it varies depending on the type of vehicle, in
general, a time of 1 to 3 seconds elapse before the vehicle
actually starts. Because of this, it is desirable to set the
vehicle start detection delay time to range from 1 to 3 seconds.
Whether or not the interval control is carried out substantially at
the same time that the vehicle starts can easily be determined if
the predetermined set time described in the second embodiment of
the invention is set to fall within the range of the vehicle start
detection delay time (1 to 3 seconds).
[0022] In addition, according to a fourth embodiment of the
invention, an automatic leveling system for automotive headlamps is
provided such that one or more interval controls have been carried
out before an interval control that coincides with the start of the
vehicle. Pitch angle data used for an interval control preceding
the interval control coinciding with the start of the vehicle, can
be used for correcting the headlamp leveling. If an interval
control is carried out for the first time, pitch angle data
detected just previous to the depression of the accelerator pedal
while the vehicle is at a stop, can be used to correct the headlamp
leveling. If an interval control is carried out for the first time
and if there is no stored pitch angle data detected previously to
the depression of the accelerator pedal, the actuators are
prevented from being driven.
[0023] If a number of interval controls have been carried out, a
control based on the latest pitch angle data while the vehicle is
at a stop is made possible by using the pitch angle data used for
the preceding interval control (the pitch angle data detected while
the vehicle is at a stop).
[0024] In addition, if the interval control is carried out for the
first time, because there is no pitch angle data that are used for
the preceding interval control, a control based on the proper pitch
angle data is made possible by using pitch angle data detected just
prior to the depression of the accelerator pedal (pitch angle data
detected before the vehicle speed detection means detects the start
of the vehicle, for example, before a predetermined start detection
delay time).
[0025] Moreover, the actuator is prevented from being driven if the
interval control is carried out for the first time and that a time
during which the vehicle is stopped is shorter than the
predetermined start detection delay time (assuming that there is no
pitch angle data preceding the depression of the accelerator
pedal).
[0026] According to a fifth embodiment of the invention, an
automatic leveling system for automotive headlamps has a storage
part configured such that older pitch angle data are replaced with
newer pitch angle data in the order stored, when latest pitch angle
data are received so that data can be updated.
[0027] Pitch angle data of the predetermined time can be taken out
at any time, and the capacity of the storage part does not have to
be expanded.
[0028] According to a sixth emobidment of the invention, an
automatic leveling system for automotive headlamps controls the
actuators, provided that the headlamps are illuminated.
[0029] The actuators are not driven as long as the headlamps are
not illuminated, and thus the number of times the actuators are
operated is reduced by that extent. Therefore, power consumption
can be reduced and the wear on the constituent members of the
driving mechanism can be reduced.
[0030] According to a seventh embodiment of the invention, an
automatic leveling system for automotive headlamps configures an
interval at which the actuators are driven such that the interval
becomes longer than a maximum driving time of the actuators, which
is needed to perform a single leveling operation.
[0031] If an interval between the previous control and the next
control is shorter than the maximum driving time of the actuators,
the actuators start the next operation before a target value is
reached. In this situation, the actuators will be driven more often
and may have their service life reduced. However, according to the
construction as set forth in the seventh embodiment of the
invention, the actuators are driven in the next control after the
actuators have reached their target value in the previous control.
Thus, the number of times the actuators are driven is reduced by
that extent, and the service life of the actuators is not
reduced.
[0032] In addition, a change in the pitch angle within the time
interval from the previous control until the next control can be
omitted without triggering the driving of the actuators by
extending the interval at which the actuators are driven.
Alternatively, all the operations within the interval can be
converged on the driving of the actuators in the next control, and
therefore the number of times the actuators is driven is reduced by
such an extent.
[0033] Additionally, pitch angle data of the vehicle, detected by
the pitch angle detection means, are taken into the control part at
all times for arithmetic operation as control data, even during
intervals between driving operations of the actuators. By using all
the pitch angle data that are taken into the control part as
control data, many pitch angles can be used as control data. Thus,
a proper leveling of the headlamps is attained in association with
the detection of the accurate posture (pitch angle) of the
vehicle.
[0034] Moreover, an automatic leveling system for automotive
headlamps, is provided such that while the vehicle is running, when
the vehicle runs in a stable running condition over a predetermined
length of time where the vehicle speed is equal to or faster than a
predetermined value, and the acceleration is equal to or less than
a predetermined value, the driving of the actuators is controlled
based on pitch angle data resulting during the stable running
period. In this case, leveling (optical axes correction) based on
the pitch angle data resulting during the stable running condition
can function to correct the leveling (optical axes correction)based
on pitch angle data resulting while the vehicle is improperly
stopped such as along a slope or on a curb.
BRIEF DESCRIPTION OF THE DRAWINGS
[0035] FIG. 1 is a diagram showing a construction of an automatic
leveling system for automotive headlamps according to a first
embodiment of the invention.
[0036] FIG. 2 is a diagram showing a configuration of a storage
part of the automatic leveling system.
[0037] FIG. 3 is a diagram showing a flowchart of a CPU which is a
control part of the automatic leveling system.
[0038] FIG. 4 is a diagram showing a configuration of a main part
of a storage part of an automatic leveling system for automotive
headlamps according to a second embodiment of the invention.
[0039] FIG. 5 is a diagram showing a flowchart of a CPU which is a
control part of the automatic leveling system.
[0040] FIG. 6 is a chart showing transitions of the vehicle speed,
the output from the vehicle height sensor (vehicle posture) and an
actuator driving control signal from the vehicle starts after the
accelerator pedal is depressed until the vehicle reaches a constant
running speed.
DETAILED DESCRIPTION OF THE INVENTION
[0041] The invention will be described based on following
embodiments.
[0042] FIGS. 1 to 3 show one embodiment of the invention. FIG. 1 is
a diagram showing a construction of an automatic leveling system
for automotive headlamps according to a first embodiment of the
invention. FIG. 2 is a diagram showing configurations of a storage
part of the automatic leveling system. FIG. 3 is a diagram showing
a flowchart of a CPU which is a control part of the automatic
leveling system.
[0043] In FIG. 1, an automotive headlamp 1 is shown. A front lens 4
is assembled to a front opening in a lamp body 2 to define a lamp
chamber S. A parabolic reflector 5 having a bulb 6 which is a light
source securely inserted therein is supported in the lamp chamber S
in such a manner as to tilt around a horizontal tilting axis (an
axis normal to the surface of the paper on which FIG. 1 is shown)
7, and the reflector 5 is constructed so as to be tilted for
adjustment by means of a motor 10 which is an actuator.
[0044] An automatic leveling system for the headlamp 1 comprises
the motor 10 which is an actuator for adjusting an optical axis L
of the headlamp 1 in vertical directions, a lighting switch 11 for
the headlamp 1, a vehicle speed sensor 12 which is a vehicle speed
detection means for detecting speeds of a vehicle, a vehicle height
sensor 14 constituting a part of a pitch angle detecting means for
detecting pitch angles of the vehicle, a CPU 16 for determining
whether the headlamp 1 is switched on or off, a storage part 20 for
storing pitch angle data of the vehicle detected by the vehicle
height sensor 14 and calculated by the CPU 16, an interval timer 22
for setting a timing of driving the motor 10, a stop time detecting
timer 24 for detecting a time over which the vehicle is stopped, a
timer 26 for detecting a time between a completed interval control
and the start of the vehicle, and a stable running time detection
timer 28 for detecting a stable running time of the vehicle.
[0045] The CPU 16 is configured to determine whether the vehicle is
running or at a stop based on a signal from the vehicle speed
sensor 12, to calculate pitch angles and accelerations of the
vehicle based on signals from the vehicle height sensors 14 and, to
send control signals for driving the motor 10 to a motor driver 18
based on the pitch angle data calculated.
[0046] When a signal enters the CPU 16 from the vehicle sensor 12,
the CPU 16 controls the motor 10 such that the motor 10 is driven
at certain intervals when the vehicle is determined to be at a
stop. When the vehicle is determined to be running, the CPU 16
controls the motor 10 when the stable running conditions are
satisfied.
[0047] Additionally, when a signal enters the CPU 16 from the
vehicle height sensor 14, the CPU 16 calculates a longitudinal
inclination (a pitch angle) of the vehicle from the signal
corresponding to a displacement of a suspension. A single sensor
system is adopted in which the vehicle height sensor 14 is provided
on a suspension for a rear right-hand side wheel, and pitch angles
of the vehicle can be estimated from changes in height detected by
the vehicle height sensor 14. Then, the CPU 16 sends a control
signal to the motor driver 18 for tilting the optical axis L over a
predetermined distance in a direction that cancels a pitch angle so
detected.
[0048] The storage part 20 stores pitch angle data detected by the
vehicle height sensor 14 and calculated by the CPU 16. As shown in
FIG. 2A, ten data D1 to D10 are stored in a storing portion 20A of
the storage part 20 which are sampled for one second at intervals
of 100 ms. In addition, thirty data Dl to D30 are stored in a
storing portion 20B of the storage part 20 which are sampled for
three seconds at intervals of 100 ms. The storage part 20 is
configured such that new data are captured in the storing portions
20A, 20B every 100 ms, respectively, while the oldest data are
discarded (older data are sequentially rewritten with newer
data).
[0049] Moreover, as shown in FIG. 2C, the storage part 20 comprises
a storing portion 20C for storing current pitch angle data, a
storing portion 20D for storing pitch angle data one second before,
a storing portion 20E for storing pitch angle data two seconds
before and a storing portion 20F for storing pitch angle data three
seconds before. A newly detected one second average pitch angle is
written in the current pitch angle storing portion 20C every time
one second elapses. The current pitch angle stored in the storing
portion 20C is shifted to the storing portion 20D, the
one-second-before pitch angle stored in the storing portion 20D is
shifted to the storing portion 20E, the two-second-before pitch
angle stored in the storing portion 20E is shifted to the storing
portion 20F, and the three-second-before pitch angle stored in the
storing portion 20F is deleted.
[0050] Furthermore, the CPU 16 determines whether the lighting
switch 11 is switched on or off and sends a control signal to the
motor driver 18 for driving the motor 10 when the lighting switch
11 is switched on.
[0051] In addition, the CPU 16 sends a control signal to the motor
driver 18 for driving the motor 10 when a predetermined interval
time has elapsed, which is set in the interval timer 22 while the
vehicle is at a stop.
[0052] The range over which the optical axis of the headlamp 1 can
be tilted is determined, and therefore, a maximum driving time of
the motor 10 required for a single leveling is also determined. If
an interval (time) at which the motor is driven is shorter than the
maximum driving time of the motor 10 required for a single
leveling, the motor 10 may be driven so frequently to follow
sequentially changes in vehicle posture (pitch angle) associated
with passengers getting into and out of the vehicle, that the motor
10 repeats clockwise and counterclockwise rotation, stopping with
the optical axis L (the motor 10) never reaching a target position.
Thus, this may lead to a reduced service life of the motor.
[0053] To address this, the interval at which the motor is driven
is set to a time (for example, ten seconds) longer than the maximum
driving time of the motor 10 required for a single leveling so that
the target position of the optical axis is prevented from changing
while a leveling operation is carried out (while the motor is
operated).
[0054] While the vehicle is stopped, the CPU 16 controls the
driving of the motor 10 based on latest one second average pitch
angle data (an average taken from the data D1 to D10) stored in the
storage part 20 (the storing portion 20A). If the timing of
interval control substantially coincides with the start of the
vehicle, the motor 10 is controlled based on accurate pitch angle
data obtained prior to the start of the vehicle while it is at a
stop (pitch angle data when the vehicle is stopped, which is stored
in the storage part 20) rather than on improper pitch angle data
based on a change in posture during the start of the vehicle.
[0055] As shown in FIG. 6, pitch angle data detected within a time
(a start detection delay time) T, which is between the accelerator
pedal is depressed and the vehicle speed sensor detects the start
of the vehicle, are not necessarily acccurate because of the fact
that the vehicle is lowered when it starts. If an interval control
is carried out within the start detection delay time T (three
seconds), it is assumed that the motor 10 is controlled based on
improper pitch angle data detected while the rear part of the
vehicle is lowered. In addition, the time T required before the
vehicle sensor 12 detects the start of the vehicle (a start
detection delay time) ranges in general from 1 to 3 seconds,
depending on the type of vehicle. However, the time T should not
exceed 3 seconds. In the embodiment, the start detection delay time
T is set to be 3 seconds. It is determined that an interval control
based on improper pitch angle data is performed if the vehicle
speed sensor 12 detects the start of the vehicle within 3 seconds
after the interval control is carried out. The motor 10 is
controlled using proper pitch angle data (three-second-before pitch
angle data) detected prior to the start of the vehicle (refer to
reference character A in FIG. 6) while the vehicle is at a stop and
stored in the storing portion 20F of the storage part 20.
[0056] The timer A28 detects the time between the execution of the
interval control and the detection of the start of the vehicle by
the vehicle speed sensor 12.
[0057] The CPU 16 controls the motor 10 based on latest one-second
average pitch angle data detected by the vehicle height sensor 14
while the vehicle is at a stop. However, leveling (correcting the
optical axis) may be carried out based on pitch angle data detected
while the vehicle is stopped improperly such as stopped along a
slope or stopped on a curb. This erroneous leveling can be
corrected by controlling the motor 10 once while the vehicle is
running stably based on pitch angle data detected during that time.
If the pitch angle data detected while the vehicle is at a stop are
proper (for example, not stopped along a slope or on a curb), the
pitch angle data detected during the stable running condition is
substantially equal to that detected while the vehicle is at a
stop. Therefore, the position of the optical axis leveled based on
the pitch angle data during the vehicle is running stably should be
substantially identical to the position of the optical axis leveled
while the vehicle is at a stop.
[0058] The CPU 16 continuously detects signals from the vehicle
height sensor 14, performs sampling quickly (100 ms) and calculates
one-second average pitch angle data and three-second average pitch
angle data. While the vehicle is stopped, the motor 10 is
controlled at intervals of ten seconds. While the vehicle is
running, the motor 10 is designed to be driven when the vehicle
speed is equal to or faster than a reference value, and the
acceleration is equal to or less than a reference value and when
the above two conditions continues for a certain length of time or
longer.
[0059] On an irregular road surface, a vehicle normally could not
run at a speed equal to or faster than 30 km/h. Also, to avoid a
drastic acceleration, which changes the vehicle posture, it is
appropriate not to exceed the acceleration of 0.78 m/s.sup.2.
Therefore, a vehicle is defined to be running stably if the vehicle
speed is equal to or faster than 30 km/h and the acceleration is
equal to or less than 0.78 m/s.sup.2 over three seconds or longer.
The operation of pitch angles of the vehicle is designed to be
performed when the above condition is satisfied. Thus, detection of
an improper value or its influence is reduced by adapting the above
definition for the control of the actuators. Whether the stable
running condition continues over three seconds or longer is
determined by the CPU 16 which starts the stable running time
detection timer 28 when the vehicle speed is 30 km/h or faster and
the acceleration is 0.78 m/s.sup.2 or less is confirmed.
[0060] Next, the control of the motor 10 by the CPU 16 will be
described using a flowchart shown in FIG. 3.
[0061] In Steps 102, 104, vehicle speed and acceleration are
calculated from outputs from the vehicle sensor 12, respectively.
In Steps 106, 108, one-second average pitch angle data and
three-second average pitch angle data are calculated from outputs
from the vehicle height sensor 14, respectively. In the following
step 110, whether or not the headlamp is illuminated is determined
from an output from the lighting switch 11. If the headlamp is
being illuminated, the flow advances to Step 112, while if the
headlamp is being switched off, the flow returns to Step 102 after
a running correction flag is reset in Step 111.
[0062] In Step 112, whether or not the vehicle has shifted from a
stopped state to a starting state is determined from an output from
the vehicle speed sensor 12.
[0063] In Step 112, if the vehicle has not shifted, whether or not
the vehicle is running is determined in Step 104. In Step 114, if
the vehicle is at a stop, a running correction flag is reset in
Step 115. If the control of the motor (the correction of the
optical axis) is already completed based on the pitch angle data
detected while the vehicle is running, the running correction flag
is reset in Step 115. A running correction flag designed to be set
in Step 137 is described later.
[0064] The flow advances to Step 116, where whether or not a second
has elapsed after the vehicle has stopped is determined by the stop
time detection timer 24. If one second has elapsed, in Step 161, a
two-second-before pitch angle stored in the storing portion 20E of
the storage part 20 is shifted to the storing portion 20F, and
three-second-before pitch angle stored in the storing portion 20F
is deleted. In Step 162, one-second-before pitch angle stored in
the storing portion 20D is then shifted to the storing portion 20E.
In Step 163, a current pitch angle stored in the storing portion
20C is shifted to the storing portion 20D. In Step 164, one-second
average pitch angle detected is written in the storing portion 20C,
and the flow moves to Step 117.
[0065] On the other hand, in Step 116, if one second has not
elapsed since the vehicle is brought to a stop, the flow advances
directly to Step 117 without passing through Steps 161 to 164. In
Step 117, whether or not the interval time (ten seconds) has
elapsed is determined by the interval timer 22. In Step 117, if ten
seconds has elapsed, the timer A 26 is reset, that is, the timer A
26 for detecting a time between the interval control has been
completed and the start of the vehicle is detected, is cleared in
Step 118A. In Step 119, the one-second average pitch angle stored
in the storing portion 20C of the storage part 20 is selected.
Then, the flow moves to Step 120, at which a control signal based
on the selected one-second average pitch angle is sent to the motor
driver 18 for driving the motor 10. Then, the flow returns to Step
102.
[0066] On the other hand, in Step 117, if ten seconds has not yet
elapsed, after counting up the timer A 26 in Step 118, the flow
returns to Step 102 without driving the motor 10.
[0067] In addition, in Step 114, if the vehicle is running, the
timer A 26 is reset in Step 128. Then, the flow advances to Step
130. In Step 130, whether or not the running correction flag is
set, that is, whether or not the optical axis is corrected or
whether or not a leveling is carried out, is determined. Then, if
the running correction flag is not set, that is, if no correction
of the optical axis or no leveling is carried out while the vehicle
is running, whether or not the vehicle speed is equal to or faster
than the reference value (30 km/h) is determined in Step 131. If
the vehicle speed is equal to or faster than 30 km/h, whether or
not the acceleration is equal to or less than the reference value
(0.78 m/s.sup.2) is determined in Step 132. In Step 132, if the
acceleration is equal to or less than 0.78 m/s.sup.2, the stable
running time detection timer 28 is counted up in Step 133. In Step
134, whether the vehicle speed is equal to or faster than 30 km/h
and the acceleration is equal to or less than 0.78 m/s.sup.2at
least for a predetermined length of time (three seconds)is
determined.
[0068] In Step 134, if the vehicle speed is equal to or faster than
30 km/h and the acceleration is equal to or less than 0.78
m/s.sup.2 for over three seconds or longer, the flow advances to
Step 135, where the stable running time detection timer 28 is
reset. Then, the flow advances to Step 137.
[0069] In Step 137, the running correction flag is reset, and the
flow moves to Step 138, where a three-second average pitch angle is
selected. Then, in Step 120, a control signal based on the
three-second average pitch angle data is sent to the motor driver
18 for driving the motor 10, and the flow returns to Step 102.
[0070] In addition, if the running correction flag is reset in Step
130, (the correction of the optical axis, i.e., the leveling is
carried out while the vehicle is running) or if the vehicle speed
is slower than the reference value of 30 km/h, and the acceleration
exceeds the reference value of 0.78 m/S.sup.2 in Steps 131, 132,
the count of the stable running time detection timer 28 is reset in
Step 139. The flow then returns to Step 102.
[0071] Additionally, if the vehicle speed is equal to or faster
than the reference value of 30 km/h, and the acceleration is equal
to or less than the reference value of 0.78 m/S.sup.2, but the
above conditions do not continue over three seconds or longer in
Step 134, the flow returns to Step 102 without driving the motor
10.
[0072] On the other hand, in Step 112, if the vehicle is shifted
from a stop to a run, i.e., the vehicle starts, whether or not the
stop is equal to or shorter than 3 seconds (which is equal to the
start detection delay time of the vehicle speed sensor 12) is
determined by the stop time detection timer 24 in Step 121. Then,
in Step 121, if it takes 3 seconds or shorter before the vehicle is
shifted from a stop to a run, the time from a stop to a run does
not exceeds the start detection delay time of the vehicle speed
sensor 12 (3 seconds), and there is no vehicle pitch angle data
that are not affected by the lowering of the vehicle prior to the
depression of the accelerator pedal. The flow returns to Step 102
without driving the actuator.
[0073] Furthermore, in Step 121, if it takes 3 seconds or longer
from a stop to a start, the time required until the vehicle starts
from a stop exceeds the start detection delay time (3 seconds) of
the vehicle sensor, and vehicle pitch angle data which are not
affected by the lowering of the vehicle prior to the depression of
the accelerator pedal exist. Then, the flow moves to Step 122,
where whether or not the stop time is equal to or longer than the
interval time (ten seconds) is determined by the stop time
detection timer 24. If the stop time is less than ten seconds in
Step 122, then the flow moves to Step 124. In Step 124,
three-second-before pitch angle data stored in the storing portion
20F of the storage part 20 are selected, and in Step 120, a control
signal based on the three-second-before pitch angle data is sent to
the motor driver 18 for driving the motor 10. The flow then returns
to Step 102.
[0074] Additionally, in Step 122, if the stop time is ten seconds
or longer, the flow advances to Step 126, where whether or not the
timer A 26 is equal to or shorter than 3 seconds, or whether or not
a time between the timing of driving the actuator and the timing of
the detection of the start by the vehicle speed sensor 12 is equal
to or shorter than the start detection delay time of the vehicle
speed sensor 12 (3 seconds) is determined. Then, in Step 126, if an
improper pitch angle based on the lowering of the vehicle is
assumed to be detected by the vehicle height sensor and stored in
the storage part, the flow advances to Step 127, where the
three-second-before pitch angle stored in the storing portion 20F
of the storage part 20 are selected. Then, in Step 120, a control
signal based on the selected three-second-before pitch angle data
is sent to the motor driver 18 for driving the motor 10. The flow
then returns to Step 102. On the other hand, in Step 126, if no
improper pitch angle is assumed to be detected, the flow returns to
Step 102 without driving the actuator.
[0075] FIGS. 4, 5 show a second embodiment of the invention. FIG. 4
is a diagram showing the construction of a part of an automatic
leveling system for automotive headlamps FIG. 5 is a diagram
showing a flowchart of a CPU which is a control part of the
automatic leveling system.
[0076] In this second embodiment, a counter C (not shown) is
provided for counting the number of times of performing the
interval control while the vehicle is at a stop.
[0077] In addition, as shown in FIG. 4, the storage part 20
comprises a storing portion 20G for storing current pitch angle
data and a storing portion 20H for storing pitch angle data used
for the previous interval control. Newly selected pitch angle data
are stored in the storing portion 20G every time the interval time
(ten seconds) has elapsed, and then the current pitch angle data
stored in the storing portion 20G are shifted to the storing
portion 20H, the previous pitch angle data stored in the storing
portion 20H are then deleted.
[0078] If an interval control is carried out for the first time or
a first interval control is carried out, the actuator is controlled
based on the three-second-before pitch angle data. If the interval
control is carried out for the second time or more, because there
was an interval control based on proper pitch angle data before,
the actuator is controlled by using the one-second average pitch
angle data used for the previous interval control. Thus, a proper
automatic leveling can be attained.
[0079] The process flow of the CPU 16 according to the second
embodiment is different from the process flow of the CPU 16
according to the first embodiment in steps between Step 117 and
Step 120, as well as between Step 126 and Step 127, which
correspond to the aforesaid different configuration. Because the
remaining portions of the process flow of the second embodiment are
identical to the process flow of the first embodiment, the
different process flow steps will be described and like reference
numerals are given to like portions. The description of the
remaining flow portions will be omitted.
[0080] In Step 117, if ten seconds has elapsed, the timer A 26 is
reset in Step 118A. Then in Step 118C, the counter C for counting
up the number of times of carrying out the interval control is
counted up, and thereafter, in Step 119, the one-second average
pitch angle data are selected. Then, in Step 119A, pitch angle data
stored in the storing portion 20G are shifted to the storing
portion 20H. In Step 119B, newly detected one-second average pitch
angle data are stored in the storing portion 20G. Thus, the driving
of the actuator is controlled based on the one-second average pitch
angle data so stored.
[0081] In Step 126, if the time required for the vehicle sensor to
detect the start of the vehicle after the depression of the
accelerator pedal is equal to or shorter than the start detection
delay time (3 seconds) of the vehicle speed sensor and if the
actuator is assumed to be controlled based on the improper pitch
angle data because of the lowering of the vehicle, the flow moves
to Step 126A, and whether or not the counter C is equal to or
greater than 2 is determined. If the interval control is carried
out for the first time, the flow advances to Step 127, and
three-second-before pitch angle data stored in the storage part 20
are selected. On the other hand, in Step 126A, if the interval
control has been carried out twice or more times, the actuator is
controlled using the one-second average pitch angle data used for
the previous interval control.
[0082] In Step 128, while the vehicle is running, the timer A 26 is
reset, and after the counter C is reset in Step 129, the flow is
designed to advance to Step 130.
[0083] In the two embodiments described above, while the interval
(time) at which the actuator (motor) is driven is described as
being ten seconds, the interval time is not limited to ten seconds
but may be set optionally relative to the maximum driving time of
the actuator (motor).
[0084] Additionally, in the above embodiments, while the stable
running condition is described as such that the vehicle speed is 30
km/h or faster and the acceleration is 0.78 m/s.sup.2 or less, and
that these continue for over 3 seconds, but the stable running
condition is not limited to the specific conditions described
above.
[0085] In addition, in the above embodiments, while the automatic
leveling of the reflector moving type headlamp in which the
reflector 5 is tiltably supported relative to the lamp body 2 fixed
to the vehicle body, the invention can be equally applied to the
automatic leveling of a unit moving type headlamp in which the lamp
body and the reflector unit are tiltably provided relative to the
lamp housing fixed to the vehicle body.
[0086] According to the automatic leveling system of the first
embodiment of the invention, because the driving of the actuator
through the automatic leveling is designed to occur at every
certain interval time while the vehicle is stopped, the number of
times of activating the actuator, power consumption, and the wear
on members of the driving mechanism are all reduced. Thus, an
automatic leveling system that is inexpensive and than can operate
accurately can be provided.
[0087] In addition, if the timing of carrying out the interval
control coincides with the start of the vehicle, because the
actuator is controlled based on the proper pitch angle data
detected while the vehicle is stopped, the proper automatic
leveling can be provided while the vehicle is stopped, or when the
vehicle starts.
[0088] Furthermore, according to the second and third embodiments
of the invention, because the improper interval control can easily
be specified, the control of the automatic leveling can be carried
out smoothly.
[0089] Moreover, according to the fourth embodiment of the
invention, because the control based on optimum data can be carried
out whether or not an interval control is carried out, or whether
or not there exists data detected prior to the depression of the
accelerator pedal, an optimal automatic leveling can be
realized.
[0090] In addition, according to the fifth embodiment of the
invention, because pitch angle data detected a certain time can be
fetched and moreover since the capacity of the storage part does
not have to be expanded, the automatic leveling system is simple in
construction and low in cost.
[0091] Additionally, according to the sixth embodiment of the
invention, because the actuator is designed not to be driven as
long as the headlamp is not illuminated, the number of times the
actuator is operated is reduced. Thus, power is conserved, and the
wear of the members of the driving mechanism is reduced Therefore,
an automatic leveling system that is economical and that can
operate more accurately can be provided.
[0092] Moreover, according to the seventh embodiment of the
invention, because the number of times the actuator is driven is
reduced, an automatic leveling system that can operate accurately
over a long period of time can be provided.
[0093] The present invention claims priority from Japanese patent
application serial no. H11-368918, which is incorporated herein by
this reference in its entirety.
[0094] Several embodiments of the invention have been described
herein, but it should be understood that various additions and
modifications could be made which fall within the scope of the
following claims.
* * * * *