HEADLIGHT UNIT

Abstract: This invention provides a headlight unit having a light source (5) and reflector mirror (4) for reflecting the light from the light source (5) into a beam. The mirror can be pivoted about an axis P by means of an actuator (15). The actuator (15) is controlled by a circuit (16) which includes pre-settable re­ sistances which determine the range of movement of the re­ flector mirror (4).

Description: This invention relates to a headlight unit, and particularly to a headlight unit for motor vehicles, such as cars, in which the high beam and the low beam are obtained by rotating a reflecting mirror. In the case of car headlights, there is a requirement for switching between a high beam and a low beam, and two principal systems are used for this purpose. One of these uses a sealed beam type lamp in which two light sources are provided in conjunction with a reflecting mirror. When one of these light sources is operated, the low beam is generated, and when the other light source is operated or both light sources are operated at the same time, the high beam is generated. In this type lamp the beams are switched by switching the light sources. In the other system, one light source is used with a reflecting mirror. The beam is switched by rotating or tilting the reflecting mirror or the light source, itself, upward and downward. This invention relates to the latter system, the problems of which are discussed below. In headlights which switch between low beam and high beam, the downward attitude of the reflecting mirror when the low beam is lit must be controlled with great accuracy to avoid blinding oncoming traffic. Previously, a vertical aiming bolt and a surrounding coil spring have been used to control the attitude of the reflecting mirror in the vertical direction. This bolt acts as a stopper which controls the downward attitude position of the reflecting mirror. In addition, the spring is designed to permit the rotation of the reflecting mirror to allow upward rotation. Moreover, an actuator is used to make the reflecting mirror rotate upward and downward. Hitherto, solenoid systems, compressed gas systems, or motor drive systems have been used as actuators. A headlight system which uses this kind of actuator with a vertical direction aiming bolt controls the downward attitude position of the reflecting mirror through the vertical aiming bolt and determines the high beam direction by rotation of the reflecting mirror upward in response to the working stroke of the actuator. This type of headlight is susceptible to errors, such as errors in manufacture of the reflecting mirror, manufacturing errors and installation errors of the light source, and installation errors in the attitude of the reflecting mirror in the vehicle, and adjustments to correct such errors can be carried out after installing the headlight on the vehicle body. It is known from GB-A-2075653 for a vehicle headlamp to comprise a scanning reflector which generates a desired light beam from a fixed light source and for the reflector to be scanned about two different predetermined positions in order to provide a high beam and a low beam. According to the present invention, a headlight unit comprises a light source; a movable reflector pivotable between a first position and a second position for reflecting light from the source into a high beam and a low beam, respectively; an electric actuator coupled to the reflector and responsive to manually operable selecting means through an electric circuit for positioning the reflector at the selected first or second position; characterised in the provision of a first variable resistor in the electrical circuit to the actuator to provide a first adjustment to the actuator so that, when the first position is manually selected, the actuator moves the reflector to the first position; and a second variable resistor connected additionally in the electrical circuit to the actuator when the selecting means selects the second position to provide a second adjustment to the actuator to pivot the reflector through a predetermined angle from the first position to the second position. The headlight unit may have a motor with an adjustable angle of rotation of the actuator, for example, a servo-motor or a stepping motor, and a controller to control this motor. In order that the invention may be more readily understood, it will now be described, by way of example only, with reference to the accompanying drawings, in which:- Figure 1 is a vertical transverse cross-sectional view of a headlight unit according to an embodiment of the invention; Figure 2 is a transverse cross-sectional view of a headlight unit according to the embodiment of the invention; and Figure 3 is a schematic diagram of a control circuit for the headlight unit of Figures 1 and 2. In the drawings, a housing 1 is secured to a car body (not shown). A transparent cover 2 transmits the beam projected from a headlight 3 in the forward direction and plays the role of the front lens. Headlight 3 is housed in the space enclosed by housing 1 and transparent cover 2. Headlight 3 is constructed by housing a light source, for instance a small metal vapour discharge lamp 5, in a reflecting mirror 4. Reflecting mirror 4 is formed of a metal with high reflectivity, such as bright aluminium. Reflecting mirror 4 is supported on housing 1 by center pivot 6 and left/right directional aiming bolt 7. In addition, brackets 8 and 9 are connected to the back of reflecting mirror 4. A rod 10 which supports center pivot 6 is secured to housing 1. Left/right directional aiming bolt 7 is inserted through housing 1. On one side, bracket 8 is connected to rod 10 of center pivot 6 through ball joint 11, which is free to rotate. On the other side, left/right directional aiming bolt 7 is inserted through bracket 9. A nut 12, a spring washer 13 and a spring 14 are fitted to this left/right directional aiming bolt 7. The position of this bracket 9 can be altered by adjusting the position of nut 12. By this position change, it becomes possible for reflecting mirror 4 to rotate to the left or right (in the directions of arrow A in Figure 2) about ball joint 11. Therefore, the left/right direction of reflecting mirror 4 (in the directions of arrow A in Figure 2) can be adjusted by left/right directional aiming bolt 7. Moreover, reflecting mirror 4 is supported in such a way that its front opening is capable of rotating upward and downward about the line P - P (shown by point P in Figure 1) drawn between ball joint 11 of center pivot 6 and nut 12 of left/right directional aiming bolt 7. This type of reflecting mirror 4 is rotated upward and downward by actuator 15, which is fitted in the bottom of housing 1. Actuator 15 is, for example, composed of a direct current type servo-motor. The angle of rotation of this motor is controlled by controller 16 shown in Figure 3. Controller 16 is constructed as follows. Numeral 17 designates an encoder, numeral 18 designates an adder and numeral 19 designates a high beam/low beam changeover switch. The numeral 20 designates an adjuster to adjust the amount of vertical rotation ϑ of the headlight, and is composed of variable resistors, etc. The numeral 21 designates an adjuster for adjusting the vertical aiming and is also composed of variable resistors, etc. The numeral 22 designates an auxiliary resistor. Controller 16 constructed in this way is connected to the headlight main switch 23. Headlight main switch 23 is connected to a small metal-vapour discharge lamp 5, which is the light source, and to the lighting circuit 24. A rubber cover 25 covers the open section at the back of housing 1 and insulates the supply terminals of small metal-vapour discharge lamp 5. Rubber cover 25 permits the movement of small metal-vapour discharge lamp 5 when reflecting mirror 4 is rotated upward or downward. Moreover, a water drain hole 26 is formed in this rubber cover 25. Water drain hole 26 allows water to drain out when it has penetrated the upper part of reflecting mirror 4. The operation of a headlight of this construction is explained below. When small metal-vapour discharge lamp 5, which is the light source, is lit by closing headlight main switch 23, the light emitted from this light source is reflected by reflecting mirror 4 and is projected forward as a beam. This beam passes through transparent cover 2 and illuminates the road surface ahead. In this case, when servo-motor 15, which is the actuator, is operated, headlight 3 rotates about center-line of rotation P - P and the axis of the beam can be rotated upward or downward between the lines 0₁ - 0₁ and 0₂ - 0₂, as shown in Figure 1. When the beam coincides with the line 0₁ - 0₁, the high beam is obtained, and when it coincides with the line 0₂ - 0₂, the low beam is obtained. However, upward beam 0₁ - 0₁ and downward beam 0₂ - 0₂ must each be set with great accuracy. The directions of these beams are determined by the amount of rotation ϑ of headlight 3 and the vertical aiming position. In this embodiment the amount of rotation ϑ of headlight 3 and the vertical aiming position can be adjusted by servo-motor 15, which acts as the actuator. As shown in Figure 3, when the resistance of vertical aiming adjuster 21 is adjusted in the state where the main switch 23 for the headlight is closed and changeover switch 19 is connected to the high beam side, the amount of rotation of servo-motor 15 is determined according to the value of this resistance (according to the voltage level). This amount of rotation of servo-motor 15 determines the direction of upward beam 0₁ - 0₁ by rotating headlight 3. Thus, it determines the vertical aiming position. After this aiming is set, when changeover switch 19 is connected to the low beam side and the resistance value of rotation adjuster 20 is adjusted, the amount of rotation of servo-motor 15 is determined according to the value of this resistance (according to the voltage level). This amount of rotation of servo-motor 15 determines the direction of downward beam 0₂ - 0₂ by rotating headlight 3. Thus, it determines the amount of rotation ϑ of headlight 3. As a result, when headlight main switch 23 is closed and changeover switch 19 is connected to the high beam side, encoder 17 and adder 18 control the angle of rotation of servo-motor 15 in response to the voltage level amount reduced by the resistance of vertical aiming adjuster 21. Headlight 3 is rotated upward by this angle of rotation of servo-motor 15, so that upward beam 0₁ - 0₁ is projected. Also, when headlight main switch 23 is closed and changeover switch 19 is connected to the low beam side, encoder 17 and adder 18 control the angle of rotation of servo-motor 15 in response to the voltage level amount, reduced by the sum of the resistance of vertical aiming adjuster 21 and the resistance of rotation amount adjuster 20. Headlight 3 is rotated downward by this angle of rotation of servo-motor 15, so that downward beam 0₂ - 0₂ is projected. Moreover, when it is necessary to adjust the vertical aiming position, only the resistance value of vertical aiming adjuster 21 need be changed. In this case, even when vertical aiming adjuster 21 is adjusted, since there is no need to alter the amount of vertical rotation ϑ of the headlight, there is no need to readjust rotation amount adjuster 20. Also, when it is necessary to adjust the upward and downward rotation ϑ , only the resistance value of rotation adjuster 20 need be changed. In this case, even when rotation adjuster 20 is adjusted, there is no need to readjust vertical aiming adjuster 21 since there is no need to alter the vertical aiming position of the headlight. Since there is no longer a requirement for the vertical aiming bolt and spring if this invention is used, the number of parts is reduced, and the assembly work in conjunction with these is also eliminated. Furthermore, since the vertical aiming adjustment and the rotation amount ϑ can be carried out independently from each other, there is no complicated work such as readjusting the one after the other is adjusted. Although in the embodiment, a servo-motor is used to control the angle of rotation, it is also possible to use a step motor. Also, a magnetic system or a compressed gas system with an adjustable angle of rotation could be used as the actuator. Moreover, the position of installation of the actuator is not confined to the lower part of the headlight. It also could be installed in the upper part or rear part of the headlight. Furthermore, this invention is not restricted to the use of small metal-vapour discharge lamps as light sources. Incandescent bulbs, such as halogen bulbs, also could be used. This invention is capable of use with, for example, sealed beam lamps, etc, when lamps housing single light sources and their envelopes are operated together by actuators. According to this embodiment described above, since, as well as adjusting the vertical aiming position of the headlight, the amount of vertical rotation of the headlight is also adjusted by using a motor which can control the angle of rotation as the actuator and controlling this motor by a controller, the conventional vertical aiming bolt and spring can be eliminated. Moreover, adjustment of the vertical position determination and adjustment of the amount of rotation of the reflecting mirror can be carried out independently from each other or in succession using a single motor. Also, the work of adjustment is simple, since even if one is adjusted there is no need to readjust the other.

Claims: A headlight unit comprising a light source (5); a movable reflector (4) pivotable between a first position and a second position for reflecting light from the source into a high beam (01) and a low beam (02), respectively; an electric actuator (15) coupled to the reflector and responsive to manually operable selecting means (19) through an electric circuit (16) for positioning the reflector at the selected first or second position; characterised in the provision of a first variable resistor (21) in the electrical circuit (16) to provide a first adjustment to the actuator (15) so that, when the first position is manually selected, the actuator moves the reflector to the first position; and a second variable resistor (20) connected additionally in the electrical circuit (16) when the selecting means (19) selects the second position to provide a second adjustment to the actuator (15) to pivot the reflector through a predetermined angle (ϑ) from the first position to the second position. A headlight unit as claimed in claim 1, characterised in that the electric actuator (15) comprises a motor having an adjustable angle of rotation. A headlight unit as claimed in claim 2, characterised in the provision of an adder (18) the output of which supplies said motor, said adder receiving the output signal from the selecting means (19) and from an encoder (17) representing the angular position of the motor.

Inventors: BABA, MASAHARU C/O PATENT DIVISION, HAYASHI, NOBUHIKO PATENT DIVISION
Applicants: KABUSHIKI KAISHA TOSHIBA
Application year: 1986
Main classification: F21M3
IPC codes: F21S8, F21V17, F21V14, F21V5