GB2346956A

GB2346956A - Vehicle headlamp defaults to low beam if power to a beam switching device is cut off

Info

Publication number: GB2346956A
Application number: GB0010990A
Authority: GB
Inventors: Toshihisa Hayami; Mitsuyuki Mochizuki; Hirohiko Oshio; Michio Tsukamoto; Michihiko Hayakawa
Original assignee: Koito Manufacturing Co Ltd
Current assignee: Koito Manufacturing Co Ltd
Priority date: 1997-12-24
Filing date: 1998-12-04
Publication date: 2000-08-23
Anticipated expiration: 2018-12-04
Also published as: GB0010991D0; GB2346957A; GB2346956B; GB2346957B; GB0010990D0

Abstract

Vehicle headlamp comprising a bulb supporting member which is pivotable about a horizontal axis and a beam switching device which switches between high and low beams by displacing the bulb supporting member and is arranged to default to a low beam if the power to the switching device is cut off. The switching device may include a spring member urging a moving iron core of a solenoid to a non-energized position.

Description

VEHICLE HEADLAMP The present invention relates to a vehicle headlamp which is arranged to be switched between a high beam condition and a low beam condition while using a single light source.

A vehicle headlamp is typically designed to form a light distribution pattern of a high beam or a low beam by causing a reflective optical system to emit light from a light source forwards. Although different light sources are generally used for emitting the high and low beams respectively, vehicle headlamps using a single light source are also well known.

A vehicle headlamp using a single light source is so arranged as to switch between the high (driving) and low (dipped) beams by displacing an optical member forming part of the aforesaid reflective optical system and equipped with a beam switching device.

There are conventionally known beam switching devices using a motor.

In the vehicle headlamp equipped with the aforesaid conventional beam switching device, switching of beams becomes unlikely when supply of power to the beam switching device is cut off because of e. g., trouble resulting from a disconnection fault, and the reflective optical system remains providing the beam emitting condition at the time the trouble developed. Therefore, the vehicle concerned has no choice but to travel with the high beam even though there is a vehicle coming the other way when the aforesaid trouble occurs in the high beam condition. The problem is that an oncoming vehicle driver in subjected to glare.

An object of the present invention in these circumstances is to provide a vehicle headlamp which is adapted to selectively switch between a high beam and a low beam while using a single light source and capable of preventing an oncoming vehicle driver from being subjected to glare when a power supply to a beam switching device ie cut off because of trouble resulting from a disconnection fault.

According to the present invention, a vehicle headlamp comprises a reflective optical system for emitting forwardly a desired beam of light from a light source and a power-operated beam switching device for selectively switching the beam between a high beam and a low beam by displacing an optical member forming part of the reflective optical system, characterized in that the beam switching device is arranged to default the beam to the low beam condition when supply of power to the beam switching device ia cut off.

The aforesaid"light source^ is not limited to a specific kind of light source but may be, for examplo, filaments of incandescent bulbs, or light-emitting portions of discharge bulbs.

The aforesaid"optical member^ is not limited to a specific optical member as long as it forms part of the reflective optical system; for example, light source bulbs equipped with light sources, reflectors, or shades.

As shown in the aforesaid arrangement, the vehicle headlamp according to the present invention is such that the beam switching device is adapted to selectively switch the beam emitted by the reflective optical system between high and low beams, and that the beam is only the low beam when supply of power to the beam switching device is cut off. Hence, it is possible to prevent a vehicle form being compelled to travel with the high beam because of trouble such as a disconnection fault.

Accordingly, even the vehicle headlamp so designed as to switch between the high and low beams using a single light source according to the present invention is capable of preventing an oncoming vehicle driver from being subjected to glare even when the beam switching device is made nonconductive by trouble such as a disconnection fault.

The specific construction of the beam switching device may comprise an electromagnet ; a moving part which is movable between an attracted high beam position in which the moving part is attracted to the electromagnet and a non-attracted low beam positionwherethemovingpartisseparatedformtheelectromagnet ; a spring for urging the moving part towards the non-attracted position; and a motor unit for moving the moving part to the attracted position against the urging force of the spring, characterized in that the switching of the low beam to the high beam is carried out by energizing the electromagnet and driving the motor unit, and in that the switching of the high beam to the low beam is carried out by de-energizing the electromagnet.

With this construction, the load of the motor unit becomes reducible because the motor unit is driven only when the low beam is switched to the high beam.

The motor unit may comprise, a motor, a moving-part engaging member which is rotated by the driving of the motor so as to swing the moving part towards the attracted position, and a motor drive control circuit for allowing the motor to be supplied with power while the moving part is in the non-attracted position and for cutting off the supply of power to the motor when the moving-part engaging member has been rotated through a predetermined angle and the moving part has reached its attracted position.

The specific construction of the beam switching device may alternatively comprise a solenoid and a spring member for urging a moving iron core of the solenoid to a non-energized position, characterized in that the switching of the low beam to the high beam is carried out by energizing the solenoid and that the switching of the high beam to the low beam is carried out by deenergizing the solenoid. With this arrangement, the beam switching device is extremely simplified, though the stroke of the moving iron core is restricted to a range dependent on the available magnetic attraction.

In the accompanying drawings: Figure l (a) is a sectional side view of a first embodiment of a vehicle headlamp a low beam condition according to the present invention, and Figure 1 (b) is the vehicle headlamp a high beam condition; Figure 2 (a) is a diagram illustrating a beam switching device in a low beam condition of the first embodiment in more detail, Figure 2 (b) shows the beam switching device in a condition where the low beam is switched to a high beam, and Figure 2 (c) shows the device in the high beam condition; Figure 3 is a circuit diagram of the beam switching device in the first embodiment; Figure 4 (a) are sectional side views of a second embodiment of a vehicle headlamp in a low beam condition in accordance with the invention illustrating, and Figure 4 (b) shows the vehicle headlamp in a high beam condition; and Figure 5 (a) is a sectional side view of the principal part of the reflector unit of a vehicle headlamp in a high beam state according to a third embodiment of the invention, and Figure 5 (b) is a sectional side view of the reflector unit in a low beam state.

As shown in Fig. 1, a vehicle headlamp 10 embodying the present invention is provided with a reflector unit 16 installed in a space formed by a lens 12 and a lamp body 14, the reflector unit 16 being vertically and horizontally tiltable. The reflector unit 16 comprises a discharge bulb (metal halide bulb) 18, a bulb supporting member 20, a reflector 22 and a beam switching device 24.

The lens 12 is a transparent lens and a light distribution function is given to the reflector unit 16. In other words, the reflector 22 has a reflective surface 22a for forwardly reflecting light from a light-emitting portion 18a of the discharge bulb 18 and is so arranged as to forwardly emit a beam for forming a predetermined light distribution pattern by the use of the diffusive or deflective reflection function of the reflective surface 22a.

The discharge bulb 18 is fitted and fixed in the bulb supporting member 20. Furthermore, at its upper-end pin joint 26, the bulb supporting member 20 is mounted pivotally around an axis extending laterally. As shown in Fig. 1 (a), the optical axis Axl of the discharge bulb 18 corresponds to the optical axis Ax of the reflector 22 and its light-emitting portion 18a is positioned on the optical axis Ax when the bulb supporting member 20 is kept in contact with the edge 22b of a rear opening of the reflector 22 and the reflector unit 16 is caused to provide a low beam. As shown in Fig. l (b), on the other hand, the optical axis Axl of the discharge bulb 18 is directed downward while the bulb supporting member 20 is separated from the edge 22b through a predetermined angle and the light-emitting portion 18a is displaced downward with respect to the optical axis Ax of the reflector 22. The reflector unit 16 is then caused to provide a high beam.

The beam switching device 24 is provided at the rear of the lower end portion of the reflector 22 and has a body of 30 fixed via a bracket 28 to the reflector 22, a pivotal output shaft 32 extending laterally, and a cam 34 fixed to the shaft 32.

A driven pin 36 projects backwards from the lower end portion of the bulb supporting member 20 and the end of the driven pin 36 is in contact with the cam face of the cam 34. The bulb supporting member 20 is urged backward by a spring (not shown), whereby the bulb supporting member 20 is held at an angle of inclination determined by the angular position of the cam 34. The cam 34 is pivoted together with the pivotal output shaft 32 and stopped in either of the angular positions shown in Figs. 1 (a) andl (b). The beam switching device 24 is thereby adapted to switch the beam between the high and low beams.

As shown in Fig. 2, the body 30 essentially consists of an electromagnet 40, a moving arm 42, a spring 44 and a motor unit 46, these being contained in a casing 38.

The electromagnet 40 is fixed to the casing 38 and the moving arm 42 is fixed to the pivotal output shaft 32. This moving arm 42 is a substantially U-shaped plastics member with metal plates 42a, 42b fitted into both its respective side portions.

Furthermore, the moving arm 42 is arranged so that it is capable of taking an attracted position (as shown in Figs. 2 (b), (c)) where it has been attracted to the electromagnet 40 and a non-attracted position (as shown in Fig. 2 (a)) where it has been separated therefrom. The metal plate 42a is attracted to the electromagnet 40 in the attracted position, whereas in the non-attracted position, the metal plate 42b is brought into contact with a pair of contacts 48 provided on the inner surface of the casing 38 so as to connect both contacts 48.

When the moving arm 42 is in the attracted position, the cam 34 is brought to the angular position of Fig. l (b) and accordingly the reflector unit 16 is in the high beam condition. when the moving arm 42 is in the non-attracted position, on the other hand, the cam 34 is brought to the angular position of Fig. l (a) and accordingly the reflector unit 16 is in the low beam condition.

The spring 44 is mounted on the pivotal output shaft 32 and always urges the moving arm 42 towards the non-attracted position.

The aforesaid motor unit 46 is used for swinging the moving arm 42 down to the attracted position against the urging force of the spring 44 and comprises a motor 50, a worm 52, a worm wheel 54 pivotally supported with the casing 38 in such a way as to mesh with the worm 52, a substantially arcuate protrusion 56 formed in the outer peripheral edge portion of one face of the worm wheel 54 and a motor drive control circuit 58 as will be described hereinafter. The protrusion 56 is brought into contact with the moving arm 42 in order to swing down the moving arm 42 toward the attracting position by making the motor drive control circuit 58 drive the motor 50 of the motor unit 46 to rotate the worm wheel 54 in the direction of an arrow in Fig. 2.

The other edge face of the worm wheel 54 is disposed close and opposite to the inner wall surface of the casing 38.

A double arcuate conducting pattern 60 is formed on the inner wall surface of the casing 38, a brush 62 is formed on the other edge face of the worm wheel 54 in such a manner as to bridge over the double arcuate conducting pattern 60. The brush 62 is formed in such as angular position that the protrusion 56 is positioned on the upstream side in the rotational direction of the worm wheel 54, with respect to the moving arm 42 when the brush 62 is situated in the discontinuous angular position of the conducting pattern 60.

As shown in Fig. 3, the motor unit 46 and the electromagnet 40 are connected in parallel to a battery 64 and a beam change-over switch 66 in the beam switching device 24.

Moreover, the motor 50 and the motor drive control circuit 58 are connected in series in the motor unit 46. In the motor drive control circuit 58, a first switch SW1 comprising the brush 62 and the conducting pattern 60 is connected in parallel to a second SW2 switch comprising the metal plate 42b of the moving arm 42 and the pair of contacts 48.

In the beam switching device 24, furthermore, the low beam is switched to the high beam by turning on the beam change-over switch 66 to put the electromagnet 40 in the energized condition and driving the motor 50, whereas the high beam is switched to the low beam by turning off the beam change-over switch 66 to set the electromagnet 40 in the non-energized condition.

As shown in Fig. 2 (a), the motor 50 is driven to rotate the worm wheel 54 in the direction of the arrow when the beam change-over switch 66 is turned on since the second switch SW2 is held"on"by the spring 44 while the moving arm 42 is in the non-attracted position (i. e., in the low beam condition). Then the protrusion 56 together with the worm wheel 54 is rotated until it is brought into contact with the moving arm 42 and forces the moving arm 42 to pivot in the direction of the arrow against the urging force of the spring 44. Although the second switch SW2 is turned off because the moving arm 42 is separated from the non-attracted position at this time, the rotation of the worm wheel 54 has by that time brought the brush 62 into contact with the conducting pattern and the fist switch SW1 is held"on", whereby the worm wheel 54 rotates in this condition, thus keeping the protrusion 56 moving the moving arm 42 down.

The moving arm 42 is rotated down to the angular position shown in Fig. 2 (b) and close to the electromagnet 40 which has been energized when the beam change-over switch 66 is turned on and attracts and holds the moving arm 42 in the attracted position.

Thus the beam is switched to the high beam.

Although the worm wheel 54 is kept rotating even after the moving arm 42 is thus attracted to the electromagnet 40, the rotation of the worm wheel 54 is stopped when the first switch SW1 is turned off after the brush 62 has ridden off the conducting pattern 60.

When the electromagnet 40 is set in the non-energized condition after the beam change-over switch 66 is turned off, the force of attracting the moving arm 42 is canceled and the moving arm 42 is pivoted reversely by the urging force of the spring 44 up to the non-attracted position shown in Fig. 2 (a) with the effect of switching the beam to the low beam. Thereafter, the beam is again switched to the high beam when the beam change-over switch 66 is turned on.

When supply of power to the beam switching device 24 is cut off because of trouble resulting from a disconnection fault, even while the beam change-over switch 66 remains in the"on"state, however, the electromagnet 40 becomes non-energized and loses the attracting force holding the moving arm 42. Consequently, the urging force of the spring 44 makes the moving arm 42 swing back up to the non-attracted position, so that the beam is switched to the low beam. In this case, as power is never supplied to the electromagnet 40 and the motor unit 46, even though the beam change-over switch 66 is operated then, and the beam is thus fixed to the low beam.

Although the beam switching device 24 of the vehicle headlamp 10 according to this embodiment of the invention is adapted to switch the beam emitted forward by the reflector unit 16 selectively between the high and low beams as afoxesaid in detail, the beam switching device 24 is capable of preventing a vehicle from being compelled to travel with the high beam because of trouble such as a disconnection fault since the beam switching device 24 is designed to make the beam provide only the low beam when supply of power to the beam switching device 24 is cut off.

In the vehicle headlamp adapted to switch between the high and low beams using the single light source according to this embodiment of the invention, it i possible to prevent an oncoming vehicle driver from being subjected to glare even in the case where the beam switching device is inactive because of trouble such as a disconnection fault.

The beam switching device 24 according to this embodiment of the invention comprises the electromagnet 40, the moving arm 42 capable of pivoting between the attracted position where it is attracted to the electromagnet 40 and the non-attracted position where it is separated from the electromagnet 40, the spring 44 for urging the moving arm 42 toward the non-attracted position and the motor unit 46 for moving the moving arm 42 to the attracted position against the urging force of the spring 44.

Furthermore, the switching of the low beam to the high beam is carried out by energizing the electromagnet 40 and also driving the motor unit 46, whereas the switching of the high beam to the low beam is carried out by making the electromagnet 40 nonenergized to ensure that the light distribution pattern is fixed to the low beam when supply of power to the beam switching device 24 is cut off. Moreover, the load of the motor unit 45 is low since the motor unit 46 is driven only at the time the low beam is switched to the high beam.

Furthermore, the motor unit 46 comprises the motor 50, the protrusion 56 which is rotated by the driving of the motor 50 so as to swing down the moving arm 42 towards the attracting position and the motor drive control circuit 58 for allowing the motor 50 to be supplied with power while the moving arm 42 is in the non-attracted position and for cutting off the supply of power to the motor 50 when the protrusion 56 is turned from the rotation angle position where the moving arm 42 is attracted to the attracted position by the predetermined angle, whereby the relatively simple motor unit 46 can be formed.

Fig. 4 shows sectional side views of a vehicle headlamp according to a second embodiment of the invention.

As shown in Fig. 4, a vehicle headlamp 10'according to this embodiment of the invention is similar in basic constitution to the vehicle headlamp 10 according to the first embodiment thereof ; however, a beam switching device 68 is different from the beam switching device 24 according te the aforesaid embodiment thereof.

More specifically, the beam switching device 68 according to this embodiment of the invention comprises a solenoid 72 fixed via a bracket 70 to the reflector 22 and a spring 76 for urging the moving iron core of the solenoid 72 toward a nonenergized position.

The moving iron core 74 i a shaft member projecting forward and has a spherical leading end portion. The spherical leading end portion 74a is coupled by a ball-joint coupling to a spherical nut 76 fixed to the lower end portion of the bulb supporting member 20. The ball-joint coupling 1s a structure capable of relative movement in the vertical direction.

The switching of beams is carried out by the beam switching device 68 as followse A beam change-over switch (not shown) is turned on to energize the solenoid and move the iron core 74, rearwardly to and against the urging force ot the spring 76, whereby the low beam is switched to the high beam. On the other hand, when the beam change-over switch is turned off to deenergize the solenoid so that the iron core 74 is then moved up to the forward nonenergized position because of the urging force of the spring 76, whereby the high beam is switched to the low beam.

Even when the beam change-over switch is kept in the "on"state, the moving iron core 74 is moved by the spring to tho non-energized position, when supply of power to the solenoid 72 in cut off because of trouble such as a disconnection fault, and the beam is switched to the low beam. In this case, the beam remains f ixed as the low beam because power is not supplied to the solenoid 72 even though the beam change-over switch is operated.

It is therefore possible to prevent an oncoming vehicle driver from being subjected to glare even in the case in which the beam switching device is non-active because of trouble such as a disconnection fault in the vehicle headlamp.

In the case where the beam switching device 68 using the solenoid 72 is employed, as in this embodiment of the invention, the constitution of the beam switching device 68 is extremely simplified, though the stroke of the moving iron core is restricted to a range determined by the magnetic field produced by the solenoid.

A third embodiment of the invention will be described as follows.

Figs. 5 (a) and 5 (b) show sectional side views of the principal part of the reflector unit 16 of a vehicle headlamp in a low beam condition and a high beam condition, respectively, embodying the present invention.

As shown in Figs. 5 (a) and 5 (b), the vehicle headlamp according to the third embodiment of the invention is equipped with a solenoid-type beam switching device 80 as similar to the second embodiment described above, but different from the latter in that the discharge bulb 18 is fixedly supported by the reflector 22; a shade 82 is installed; and the shade 82 is used as an optical member to be displaced at the time of switching the beam.

The beam switching device 80 comprises a solenoid 86 fixed via a bracket 84 to the reflector 22, a spring 90 (elastic member) for urging the moving iron core 88 of the solenoid 86 toward the non-energized position and a shade-supporting bracket 92 fixed to the bracket 84. A washer 94 for stopping the urging force of the spring 90 by contacting the leading end portion of the spring 90 is mounted on the mid-portion of the moving iron core 88. Furthermore, the leading end portion 88a of the moving iron core 88 is laterally forked and the inner diameter of the spring 90 is set substantially equal to the outer diameter of the moving iron core 88.

The shade 82 has a cylindrical body 82a a rear edge of which is formed into a complicated uneven shape and a stay 82b extending downward from the lower end portion of the shade body 82a to the slightly rear side.

The shade 82 is supported pivotally in the longitudinal direction by the beam switching device 80. When the beam switching device 80 is actuated, the shade 82 pivotally moves between the low beam position shown in Fig. 5 (a) and the high beam position shown in Fig. 5 (b). In the low beam position, moreover, the shade 82 causes light necessary for only low beam irradiation to be incident on the reflective surface 22a by restricting the quantity of light directed onto the reflective surface 22a of the reflector 22 from the discharge light-emitting portion 18a of the discharge bulb 18, whereas the shade 82 causes the quantity of light necessary for high beam irradiation to be secured by substantially releasing the restriction imposed by the shade body 82a on light incident onto the reflective surface 22a in the high beam position.

The shade 82 is pivotally supported by the leading end portion of the shade-supporting bracket 92 via a bolt 96 and pivots around the axis of the bolt 96 in the mid-portion of its stay 82b. Furthermore, the shade 82 is coupled to the leading end portion 88a of the moving iron core 88 via a pin 98 in the leading end (lower end) portion of the stay 82b; the shade 82 is thus coupled thereto by passing the pin 98 in the lateral direction in such a condition where the leading end portion of the stay 82b is clamped in the forked leading end portion 88a of the moving iron core 88. The pin 98 at this time is firmly secured to the leading end portion of the moving iron core 88.

On the other hand, a slot 82c vertically extending so as to let the pin 98 pass therethrough is formed in the leading end portion of the stay 82b whereby to absorb the variation of the distance between the bolt 96 and the pin 98 caused by the pivoting of the shade 82.

In the beam switching device 80 according to the third embodiment of the invention, the beam is switched as follows ! A beam change-over switch (not shown) fs turned on to energize the solenoid and move the iron core 88 to the rear energized position against the urging force of the spring 90, whereby the low beam is switched to the high beam. On the other hand, the beam change-over switch is turned off to deenergize the solenoid so that the moving iron core 88 is then moved linearly up to the forward non-energized position because of the urging force of the spring 90, whereby the high beam is changed to the low beam.

Even when the beam change-over switch is kept in the "state, the moving iron core 88 is in the non-energized condition when supply of power to the solenoid 86 is cut off due to trouble such as a disconnection fault. In this condition, the moving iron core 88 is moved by the urging force of the spring 90 to the non-energized position and the beam is switched to the low beam. in this case, the beam remains fixed to the low beam because power is not supplied to the solenoid 86 even though the beam change-over switch is operated to be turn-on state.

It is therefore possible to prevent an oncoming vehicle driver from being subjected to glare even in the case where the beam switching device is non-active because of trouble such as a disconnection fault in the vehicle headlamp thus adapted to switch between the high and low beams using a single light source according to this embodiment of the invention.

Since the spring 90 and the moving iron core 88 are substantially equal in diameter and built coaxially, both of them are unobstructive to any other member and make feasible the effective utilization of the space.-Moreover, by making them substantially equal in diameter and coaxial allows the urging force of the spring 90 to be efficiently transmitted to the moving iron core 88 according to the third embodiment of the invention.

Moreover, setting the spring constant of the spring 90 at a certain high value ensures that the shade 82 is prevented from being not only deflected (minutely vibrated) due to the vibration of the vehicle but also backlashed and consequently it is not feared that the irradiation beam is badly affected according to this embodiment of the invention.

Although the beam switching device 80 is used to pivot the shade 82 according to the third embodiment of the invention, the same effect as what is achievable according to this embodiment of the invention is also made obtainable by employing a predetermined beam switching device for reciprocating the shade 82 along the optical axis Ax in the longitudinal direction.

Claims

CLAIMS 1. A vehicle headlamp comprising: a reflective optical system for emitting forwardly a desired beam of light from a light source bulb mounted on a bulb supporting member which is able to pivot about a substantially horizontal axis, and a power-operated beam switching device for selectively switching the beam between a high beam and a low beam, wherein the beam switching device switches the beam between the low beam and the high beam by displacing the position of the bulb supporting member, and wherein the beam switching device is arranged to default the beam to the low beam when supply of power to the beam switching device is cut off.
2. A vehicle headlamp as claimed in claim 1, wherein the beam switching device comprises a solenoid and a spring member for urging a moving iron core of the solenoid to a non-energized position, wherein the switching of the low beam to the high beam is carried out by energizing the solenoid and that the switching of the high beam to the low beam is carried out by deenergizing the solenoid.
3. A vehicle headlamp as claimed in claim 1 and substantially as herein described with reference to the accompanying drawings.