GB2325757A

GB2325757A - Determining initial position of lamp direction controlling apparatus

Info

Publication number: GB2325757A
Application number: GB9810896A
Authority: GB
Inventors: Makoto Izawa; Masaaki Ishikawa
Original assignee: Koito Manufacturing Co Ltd
Current assignee: Koito Manufacturing Co Ltd
Priority date: 1997-05-26
Filing date: 1998-05-20
Publication date: 1998-12-02
Anticipated expiration: 2018-05-20
Also published as: GB9810896D0; JPH10326505A; JP3128618B2; DE19823487C2; DE19823487A1; GB2325757B

Abstract

In an irradiation direction control apparatus 1, drive means 4 for directing the irradiation direction of a lamp 5 to a desired direction includes a stepping motor 6 and a drive mechanism 7. The rotational angular range of the stepping motor 6 is restricted by the movable range of the drive mechanism 7. After the apparatus is activated, instruction means 2 sends control means 3 an instruction signal to determine an initial position of the drive means 4, the control means 3 sends the stepping motor 6 a control signal including an angle instruction indicating a rotational angle exceeding the rotational angular range equivalent to the movable range of the drive mechanism 7 and a speed instruction for causing the stepping motor 6 to rotate at a first rotational speed (or rotational speed profile) N1 at that time. When a time indicating the end of the movable range is reached, the lamp may bounce. To stop the bounce as soon as possible, the control means 3 sends the stepping motor 6 a control signal for rotating the stepping motor 6 by a predetermined number of steps at a second rotational speed (or rotational speed profile) N2 (lower than the first rotational speed N1), thereby reaching the limit position of its movable range without bouncing. The rotation speed profiles may be linear or curved, and the system may move a reflector, lens or a light/dark boundary.

Description

m 2325757 IRRADIATION DIRECTION CONTROL APPARATUS FOR LAMP The present

invention relates to an irradiation direction control apparatus for a lamp, which uses a stepping motor as a drive source to direct the irradiation direction of the lamp to a desired direction.

There are known apparatus capable of manually or automatically changing the irradiation direction of a lamp installed in a vehicle. The former type is a so-called leveling apparatus which adjusts the irradiation direction of a lamp using an operation switch provided inside a vehicle in accordance with the load condition or riding condition. The latter type is a so-called auto-leveling apparatus which always corrects the irradiation direction of lamp installed in a vehicle in such a way as to cancel out change in the running state of the vehicle in order to prevent the direction of the irradiated light from the lamp from being changed by the change in the state of the vehicle.

Those types of apparatuses have some sort of drive means for altering the irradiation direction of a lamp within a-given angular range, for example, one designed to control the inclination angle of a reflector by means of an actuator using a stepping motor. From the viewpoint of cost reduction or due to a reason that a positional deviation occurs when a large shock is applied to the apparatus (because the rotor is easily movable if no power is supplied to the motor), such an apparatus is not equipped with position detecting means on purpose.

Because the position of the rotor of the stepping motor is unstable at the time the operation starts, the aforementioned apparatus executes just once an initializing operation for positioning the motor (determining the initial position) at the position at which the motor, after being turned in a predetermined direction. to detect the original position, stops rotating, i.e., at the upper limit position or lower limit position in the movable range of the actuator.

At that time, if the stepping motor is rotated at a speed substantially equal to the rotational speed, involved in controlling the irradiation direction of the lamp, at a phase angle equivalent to the full stroke of the actuator (or the distance between the upper limit position and the lower limit position), it is difficult to make accurate positioning at the limit position (the upper limit position - period of time.

or the lower limit position) in a short In a case of, for example, FIG. 11 which conceptually shows how the initializing operation is carried out with the horizontal scale representing time t with the operational start point of the apparatus taken as the origin and the vertical scale representing a position x (the rotational angle of the stepping motor or the moved distance of the actuator), when the movable portion of the actuator causes the stepping motor to rotate at a speed indicated by an arrow L from the state at a position of t = 0 and x = xO, the motor cannot rotate beyond the origin 0 of the coordinate position (e.g., the lower limit of the movable range of the actuator), so that vibration occurs as illustrated, causing rebounding. With "Ax" denoting the width of the vibration, it is ideally desirable that Ax - 0 when the stepping motor stops rotating. As the value of Ax is large in the above method, it is dif f icult to detect the accurate position of the origin.

Accordingly, it is an objective of the present invention to provide an irradiation. direction control apparatus for a lamp using a stepping motor, which apparatus can accurately and quickly determine the initial position of the motor.

To achieve this object, an irradiation direction control apparatus for a lamp is designed in such a manner that after the apparatus is activated, instruction means sends control means an instruction signal for determining an initial position of the drive means, the control means sends the stepping motor a control signal including an angle instruction for indicating a rotational angle exceeding a rotational angular range equivalent to the movable range of the drive mechanism and a speed instruction for causing the stepping motor to rotate at a first rotational speed at that time, and then sends the stepping motor a control signal for rotating the stepping motor by a predetermined number of steps at a second rotational speed lower than the first rotational speed.

According to this invention, therefore, in determining the initial position of the drive means, the stepping motor is rotated at the first rotational speed first, and after no further rotation of the stepping motor becomes possible, the stepping 'motor is rotated at the second rotational speed lower than the first one. This can suppress the width of a vibration-originating rebound.

4 - Other aspects and advantages of the -invention will become apparent from the following description, taken in conjunction with the accompanying drawings, illustrating by way of example the principles of the invention.

The invention, together with objects and advantages thereof, may best be understood by reference to the following description of the presently preferred embodiments together with the accompanying drawings in which-

Figure 1 is a block diagram illustrating the basic constitution of an irradiation direction control apparatus according to this invention; Figure 2 is a graph exemplifying initialization control; Figure 3 is a graph exemplifying initialization control different from the one in Figure 2; Figure 4 is a block diagram illustrating the constitution of an irradiation direction control apparatus according to one embodiment of this invention, together with Figures 5 through 10; Figure 5 is a diagram depicting the constitutions of the essential portions of the apparatus; Figure 6 is a flowchart illustrating the flow of initialization; Figure 7 is an explanatory diagram showing, together with Figure 8, a case where initialization is executed with the moving shaft of an actuator located near an upper limit position and showing a time- dependent change in the speed of the moving shaft of the actuator; Figure 8 is an explanatory diagram showing a time- dependent change in the position of the moving shaf t;.

Figure 9 is an explanatory diagram showing, together with Figure 10, a case where initialization is executed with the moving shaft of an actuator located about in a middle of its movable range and showing a time-dependent change in the -or; speed of the moving shaft of the actuat Figure 10 is an explanatory diagram showing a timedependent change in the position of. the moving shaft; and Figure 11 is an explanatory diagram for explaining the conventional drawback.

Figure 1 shows the basic constitution of an irradiation direction control apparatus according to this invention.

An irradiation direction control apparatus 'L comprises instruction means 2, control rneans 3 and drive means 4. A lamp 5 whose irradiation direction is controlled via the drive means 4 by the control means 3 is a headlamp (including a fog lamp and cornering lamp besides a headlamp in a narrower sense) in the case of a vehicular lamp, for example.

m Lhe drive means 4, which is provided to direct the irradiation direction of the lamp 5 to a desired direction, includes a stepping motor 6 and a drive mechanism 7 to be driven by the stepping motor 6. The drive means 4 is constructed in such a way that the rotational angular range of the stepping motor 6 is restricted by the movable range of the drive mechanism 7.

The instruction means 2 sends the control means 3 an -ial position of instruction signal for determining the init the drive means 4 after the apparatus 1 is activated. When receiving the instruction signal, the control means 3 first sends the stepping motor 6 a control signal including an angle instruction for indicating a rotational angle exceeding a rotati-onal angular range equivalent to the movable range of the drive mechanisrn 7 and a speed instruction for causing the stepping motor 6 to rotate at a first rotational speed N1 at that time. Note that in addition to the instruction signal, the instruction means 2 sends the control means 3 a signall necessary to control the irradiation direction of the lamp 5 (e.g., a manipulation signal when the irradiation direction of the lamp is controlled manually or a detection signal based on which the irradiation direction of the lamp is controlled automatically (a detection signal of the vehicle's state in an auto-leveling apparatus).

:The control means 3 then sends the stepping motor 6 a control signal for rotating the stepping motor 6 by a predetermined number of steps at a second rotational speed N2 lower than the first rotational speed N1.

Figures 2 and 3 conceptually illustrate a rotational speed instruction which is sent to the stepping motor 6 from the control means 3 in the initializing operation, and show a change in the speed instruction with time t taken on the hcrizontal scale and the rotational speed N taken on the vertical scale.

A graph line 91 indicated by the solid 'Line in Figure 2 shows a case where the rotational speeds N1 and N2 are constant; the rotational speed N1 of the stepping motor 6 is fIxed to Na during a period of 0 s t s tc and the rotational speed N2 oil the stepping motor 6 is changed to a value Nb 1 (<< Na) sufficiently lower than Na during a period of tc < t:g te. While the control of the rotational speed may be so executed as to reduce the rotational speed in multiple steps as indicated by a graph line g2 indicated by a one-dot chain in the diagram, besides the one indicated by the graph line gir it is preferable to change the rotational speed in a few steps as indicated by the graph line gl in order to carry out initialization in a short period of time.

Figure 3 shows an example of reducing the rotational speed continuously. Control indicated by a graph line g3 in the diagram reduces the first rotational speed N1 linearly as indicated by a line g3a inclined lowerrightward, then gradually reduces the second rotational speed N2 in the period tc < t s te as indicated by a line g3b less inclined than the line 93a. Besides such linear deceleration control, non-linear deceleration control can be taken as indicated by a graph line g4 of a two-dot chain line in Figure 3.

In the deceleration control on the stepping motor 6 at the time of initialization, as apparent from the above, NI or N2 is constant or NI or N2 is reduced in a stepwise manner or continuously with the passage of time. While the point te can be defined as a time instruction specified by the control means 3, the precision of positioning to the origin can be improved if the point te is defined as a predetermined number of steps (i. e., the point te depends on the rotational speed). Specifically, as the maximum width of a rebound of the drive mechanism 7 which occurs in the initial stage in the period of tc < t s te is substantially determined by the first rotational speed N1, the rebound width can be made narrower by rotating the stepping motor 6 in the maximum width at the second rotational speed N2 (at which no rebound occurs).

8 - Methods of changing the irradiation direction of the lamp 5 by the drive means 4 incl ude a scheme of allowing the drive means 4 to tilt the whole lamp to thereby change the irradiation direction and a scheme of controlling the driving of a part of the components of the lamp. For instance, the drive means 4 may tilt a reflector within the vertical plane to alter the direction of the reflected light, or the drive means 4 may tilt the lens to alter the direction of the irradiated light that has passed the lens.

Various other schemes may be realized by various combinations of the optical components of the lamp. For example, instead of tilting the whole reflector or the whole lens, the position of part of the reflector or lens may be controlled to change the essential portion of the irradiated light to the desired direction, or the shade may be shifted in the desired direction by the drive means 4 to change the dark-bright boundary in the light distribution pattern of the _11.amp. Alternatively, the drive means 4 may move a combination of the reflector and the light source, a combination of the lens and the reflector, or a combination of the lens and the shade to thereby change the direction of the irradiated lighlE in the up and down direction.

Figures 4 through 10 illustrate one embodiment of the invention as adapted to an irradiation direction control apparatus for a vehicular lamp.

An apparatus 8 is an auto-leveling apparatus which automatically responds to a change in the vehicle's state to correct the irradiation direction of the lamp. As shown in Figure 4, the auto-leveling apparatus 8 has an EW (Electronic Control Unit) 9 which incorporating a computer that accomplishes the function of the control means 3. Input signals to the ECU 9 are detection signals from vehicle body height sensors 10 and 11, respectively provided at the front and rear axle shaft portions of the vehicle, a lighting instruction signal SW issued by a headlamp switch 12. an ignition signal Iq which ignites the engine and a detection signal from a vehicle speed sensor 13.

The vehicle body height sensors 10 and ll are vehicle state detecting means and serve to detect the vehicle's state (including the up or down inclination in the running direction of the vehicle) while the vehicle is still and/or is moving. Available detection schemes include a scheme of detecting the amount of expansion or contraction of the suspension of an axle, a scheme of measuring the distance between the vehicle height sensor and the road surface using detection waves, such as ultrasonics, a laser beam, and a scheme of detecting the vehicle's state by using a gyrosensor (which is used in a two wheeler or the like).

A compensation signal output from the EM 9 is sent to drive sections 14 and 14' which respectively control the irradiation directions of left and right lamps provided at the front portion of the vehicle. The drive sections 14 and 141 are respectively provided with stepping motors 14a and 141a as drive sources and motor drivers 14b and 1Cb for the respective motors. As the stepping motor 14a or 141a rotates, the slide shaft of an actuator 14c or 141c provided in the lamp 15 or 151, for example, moves back and forth in the direction of the axle shaft. This tilts the associated reflector in the vertical plane to alter the direction of the optical axis of the reflector in the lamp 15 or 151, thereby controlling the irradiation direction of the lamp 15 or 151.

Figure 5 exemplifies the constitutions of the essential portions. The signals SW and IG are input via an OR gate 19, which is comprised of diodes 18 and 181, to a power supply circuit 17 which supplies power to a computer 16, the control center. The OR signal from the OR gate 19 is equivalent to the signal from the instruction means 2. Specifically, the signal SW becomes an H (High) level signal at the time of instructing the light-ON event and becomes an L (Low) level signal at the time of instructing the lightOFF event, while the signal Ig becomes an H-level signal at the time of starting the engine and becomes an L-level signal otherwise.

The power supply circuit 17 is designed to supply power to the computer 16 when the signal SW or the signal Ig has an H level.

The OR signal, obtained by ORing the signals SW and Ig through diodes 20 and 201', is sent as a supply voltage to coils 21 of the stepping motor 14a. The motor driver 14b, has semiconductor switch elements, dumpers or the like to directly drive the col.1s 21 of the individual phases of the stepping motor 14a.

When the signal SW or the signal Ig has an H level, the power supply circuit 17 supplies power to the computer 16 and the stepping motor 14a.. At that time, the execution of the initialization program by the computer 16 causes the motor driver 14b to drive the stepping motcr 14a so that the full-stroke driving of the actuator 14c is performed only once at the beginning for positioning to the origin.

Figure 6 is a flowchart illustrating one example c:E control procedures for the initializing operation. When the aforementioned OR signal instructs the operation of the apparatus, the stepping motor 14a is rotated in a predetermined direction (which directs the optical axis of ll - the lamp or the reflector downward with respect to the horizontal plane) by a rotational angle (phase angle) equivalent to the full stroke of the actuator 14c at the rotational speed N1 in step S1.

in step S2, it is determined if the rotation instruction in the step S1 has been completed, i.e., if full-stroke driving of the actuator. 14c has been completed.

If the rotation instruction has been completed, the flow proceeds to the next step S3, and if not, the flow returns to step SI.

When the actuator 14c reaches the limit position of the movable range, a rebound occurs. In this respect, the stepping motor 14a Is rotated at the rotational speed N2 set low enough not to cause a rebound (the pulse rate is defined to a low frequency), and the number of steps of the rotation, TS, is defined in step 53. If the maximum value of a rebound is a distance of ten steps when the pulse rate equivalent to the rotational speed N1 is about 150 to 200 PPS (Pulse Per Second), for example, severa 1 steps are added to the ten steps to define the value of TS in such a way that the resultant number of steps becomes an integer multiple of the minimum number of driven steps of the stepping motor 14a.

In step S4, it is determined if driving with the step number TS has been completed. The flow proceeds to the next step S5 when the driving has ended, but returns to step S3 if not.

In step S5, to set the reference position of autoleveling (or the reference position of the irradiation direction control on the lamp), the stepping motor 14a is rotated at the rotational speed NI in the reverse direction to drive the actuator 14c. In the subsequent step S6, it is determined if driving the actuator 14c has been completed. When the driving has been completed, the initializing operation is terminated, but the flow returns to step S5 otherwise.

Figures 7 through 10 schematically show time-dependent changes in the speed V of the moving shaft of the actuator 14c and the position x of the moving shaft (t representing the time axis). Figures 7 and 8 show a case where the aforementioned initializing operation is executed with the moving shaft of the actuator 14c located near the upper limit position, and Figures 9 and 10 show a case where the initializing operation is executed with the moving shaft of the actuator 14c located about in a middle of its movable range. in the diagram, "xn" indicates the value of x corresponding to the reference position of auto-leveling.

The speed V is set to 'W1" in a period of 0 % t x ta, "V22" in a period of ta < t % tb and "-V1" in a period of tb < t:s tn, which indicates the period for movement to the reference position of auto-leveling.

As shown in Figure 8, although a deviation h (distance from the lower limit position) occurs when the moving shaft cf the actuator 14c comes to the lower limit position and rebounds at time t = ta, the deviation h gradually becomes smaller thereafter and becomes nearly zero at time t tb.

In Figure 9, as the moving shaft of the actuator 14c reaches the lower limit position before t = ta, the moving shaft rebounds during a period Tr.

As shown in Figure 10, therefore, although the moving shaft of the actuator 14c repeatedly comes to the lower limit position andrebounds at time t = tal (13 ta), during which period the deviation h (about ten steps at a maximum) occurs almost periodically as apparent from, the enlarged circle, the deviation h falls within a few steps near time t = tb so that a positioning error is reduced.

If time tn needed for the moving shaft to reach x = = is set shorten than a time needed for the lamp to become on from the point of time at which the signal SW is set to an H signal immediately after setting the signal Ig to an H signal, initialization can be completed before the lamp gets on. That is, delayed initialization results in a change in the irradiation direction of the lamp, which may perplex the driver of the vehicle.

According to this embodiment of this invention, as apparent from the foregoing description, in determining the initial position of the drive means, the stepping motor is rotated at the first rotational speed first, and after no further rotation of the stepping motor becomes possible, the stepping motor is rotated at the second rotational speed lower than the first one. This can suppress the width of a vibration-originating rebound, thereby improving the precision of positioning to the origin and reducing the time required foz the positioning.

According to a modification of this invention, the first rotational speed or the second rotational speed is set constant, thus simplifying the control and the structure of the apparatus and quickening initialization.

According to another modification of this invention, the first rotational speed or the second rotational speed is reduced in a stepwise fashion or contLnuously as time goes by, making it possible to reduce the width of vibration that occurs when and after the drive mechanism reaches the limit posit-Lon ofthe movable range.

- 15.L

Claims

1. An -irradiation direction control apparatus for a lamp comprising: drive means for directing an irradiation direction of a lamp to a desired direction, said drive means including a stepping motor and a drive mechanism to be driven by said stepping motor, a rotational angular range of said stepping motor being restricted by a movable range of said drive mechanism; instruction means for outputting an instruction signal for determining an initial position of said drive means after said apparatus is activated; and control means for, when receiving said instruction signal from said instruction means, sending said stepping motor a control signal including an angle instruction for indicating a rotational angle exceeding a rotational angular range equivalent to said movable range of said drive mechanism and a speed instruction for causing said stepping motor to rotate at a first rotational speed at that time, and sending said stepping motor a control signal for rotating said -stepping motor by a predetermined number of steps at a second rotational speed lower than said first rotational speed after said angle instruction.

2. The irradiation direction control apparatus according to claim 1, wherein said first rotational speed or said second rotational speed is constant.

3. The irradiation direction control apparatus according to claim 1, wherein said first rotational speed or said second rotational speed is reduced in a stepwise fashion or continuously with the passage of time.

4. The irradiation direction control apparatus according to claim 3, wherein said first rotational speed or said second rotational speed is reduced linearly..

5. The irradiation direction control apparatus according to claim 3, wherein said first rotational speed or said second.rotational speed is reduced along a curved control line.

6. The irradiation direction control apparatus according to any one of claims 1 to 5, wherein said drive means tilts the entire lamp to change said irradiation direction of said lamp.

7. The irradiation direction control apparatus according to any one of claims 1 to 5, wherein said drive means controls driving of a part of components of said lamp to change said irradiation direction of said lamp.

8. The irradiation direction control apparatus according to claim 7, wherein said drive means tilts a reflector in a vertical plane to change a direction of reflected light.

9. The irradiation direction control apparatus according to claim 7, wherein said drive means tilts a lens to change a direction of irradiated light having passed said lens.

10. The irradiation direction control apparatus according to claim 7, wherein said drive means moves a shade in a predetermined direction to change a dark-bright boundary of a light distribution pattern of said lamp in an up and down direction.

11. The irradiation direction control apparatus according to any one of claims 1 to 5, wherein said drive means controls driving of a combination of components of said lamp to change said irradiation direction of said lamp.

12. The irradiation direction control apparatus according to claim 8, wherein said drive means controls a position of part of said reflector to direct an essential part of irradiated light to a desired direction.

13. The irradiation direction control apparatus according to claim 9, wherein said drive means controls a position of part of said lens to direct an essential part of irradiated light to a desired direction.