GB2332741A

GB2332741A - Headlight which is kept on as long as passing switch is held on

Info

Publication number: GB2332741A
Application number: GB9825945A
Authority: GB
Inventors: Hirohiko Oshio; Toshihisa Hayami
Original assignee: Koito Manufacturing Co Ltd
Current assignee: Koito Manufacturing Co Ltd
Priority date: 1997-12-24
Filing date: 1998-11-26
Publication date: 1999-06-30
Anticipated expiration: 2018-11-26
Also published as: GB2332741B; GB2332741A9; DE19857341B4; DE19857341A1; GB9825945D0; JPH11185506A

Abstract

When a passing operation is performed during the off state of a vehicle headlamp, a light source bulb 18 is normally turned on while a passing switch is held "on." When the passing switch is turned off, the light source bulb is turned off after it has been kept "on" for a predetermined time. The light source bulb 18 is held "on" without being turned off on condition that the interval between the time the passing switch turned off and the time it is turned on again is within the predetermined time of. Consequently, the light source bulb 18 is held "on" without interruption when the continuous passing operations are performed with the effect of preventing the life of the light source bulb from being shortened. The headlamp beam may be selectively switched from high beam to low beam by displacement of an optical member, e.g. shade 22.

Description

VEHICLE HEADLAMP The present invention relates to a vehicle headlamp which is adapted to switch between a high beam and a low beam by the use of a single light source.

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

A vehicle headlamp using a single light source like this is so arranged as to switch between the driving and low beams by displacing an optical member forming part of the aforesaid reflective optical system and equipped with a beam switching device. Then turning on/off the lamp and selecting one of the beams are carried out by a driver operating a lamp switch.

A vehicle headlamp is sometimes arranged to be temporarily turned on in a high beam mode by turning on a passing switch when it is needed to call the attention of a drier of an oncoming or preceding vehicle to the intention to overtake, when the headlamp is in a low beam mode at night or without turning on the headlamp during the daytime.

However, there develop the following problems when the vehicle headlamp equipped with the aforesaid beam switching device is turned on in the aforesaid passing mode while the lamp is held "off." As shown by P in Fig: 3(a), the optical member, such as a shade, is displaced by the beam switching device form a low beam position, such as a retraced position for the shade, to a high beam position and the light source is turned on when the passing switch is turned on, whereas the optical member is displaced by the beam switching device from the high beam position to the low beam position and the light source is turned off when the passing switch is turned off.

Since the operation above is performed whenever the passing switch is turned on or off, the light source is turned on and off frequently and repeatedly when the on-off operations of the passing switch are successively performed as shown by P1, P2, P3 in Fig. 3(a). The problem is that the life of the light source bulb is shortened. This is particularly so when the light source bulb is a discharge bulb.

An object of the present invention is to provide a vehicle headlamp which is arranged to switch between a high beam and a low beam using a single light source and capable of effectively preventing the life of a light source bulb from being shortened even when on-off operations of a passing switch are continuously performed.

In order to accomplish the object above, a predetermined light-off delay circuit is provided.

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 beam switching device for selectively switching the beam to a high beam or a low beam by displacing an optical member forming part of the reflective optical system; wherein, when a passing switch is turned on while a lamp switch for turning on and off the light source is held "off," the optical member is set to a high beam position and the light source is turned on, and when the passing switch is turned off, the optical member is set to a low beam position and the light source is turned off; characterized by providing a light-off delay circuit for turning off the light source after keeping the light source "on for a predetermined time when the passing switch is switched from an on state to an off state while the lamp switch is held "off." The aforesaid "light source" is not limited to a specific kind of light source but may be, for example, filaments of incandescent bulbs or discharge light-emitting portions of discharge bulbs.

The aforesaid "optical member" is not limited to a specific optical member as long as it is what forms part of the reflective optical system; for example, light source bulbs, reflectors, shades or the like are.adoptable for the purpose.

Although it is generally so arranged that such a light source as aforesaid is held "on" while the passing switch is held "on" when the passing operation is performed while the lamp switch is held "off" (i.e., while the lamp is held "off"), the vehicle headlamp according to the present invention is such that when the passing switch is switched from "on" to "off" while the lamp switch is held "off," the light source is turned off after it is held "on" for a predetermined time by the light-off delay circuit, whereby the light source is held "on" without being turned off on condition that the interval between the time the passing switch is turned off and the time it is turned on again is within the predetermined time. Consequently, the light source is held "on" without interruption when the on-off operations of the passing switch are performed with great frequency.

When the passing switch is turned off and the light source is thus held "on", the optical member is displaced by the beam switching device from the high beam position to the low beam position and it is displaced thereby from the low beam position to the high beam position when the passing switch is turned on again, whereby the passing function is fulfilled by increasing and decreasing the beam intensity in response to the on-off operations even though the on-off operations of the passing switch are frequently performed.

Even when the on-off operations of the passing switch are continuously performed in the vehicle headlamp adapted to switch between a high beam and a low bream using a single light source, it is possible effectively to restrain the life of a light source bulb from being shortened.

Since the life of the discharge bulb is extremely shortened when the on-off operations are repeated at short intervals in the case of employing a discharge bulb as the aforesaid "light source", the adoption of the arrangement according to the present invention is especially effective.

The length of the aforesaid "predetermined time" is not particularly limited on condition that it is longer than the time interval between "off" and "on" when the on-off operations of the passing switch are continuously performed.

The aforesaid predetermined time td (seconds) is preferably set at 0.5 < td < 3.

The reason for the lower limit to be set at 0.5 second is that when a driver performs the passing operation continuously, the time required until the passing switch is turned on again after it is turned off is normally 0.5 second or less and the reason for the upper limit to be set at 3 seconds is that while the lamp switch is held "off," drivers of the vehicle concerned and another would be given a feeling of incorrectness if the light source is left "on" for some time after the passing operations.

Furthermore, the predetermined time td (seconds) may be set at 1 < td < 2. The reason for the lower limit to be set at 1 second is that it has been taken into consideration that even when the passing operations are performed continuously by the driver, the operations may be performed relatively slowly and the reason for the upper limit to be set at 2 seconds is to ensure that a feeling of incorrectness if obviated because of leaving the light source "on" after the passing operations.

In the accompanying drawings: Figure 1 is a perspective view of a vehicle headlamp embodying the present invention; Figure 2 shows a vehicle headlamp circuit diagram together with a lamp switch and a passing switch; and, Figures 3(a) to (c) show time charts of the operations of a light source bulb when the switching operation of the passing switch is performed while the lamp switch is held "off" in comparison with an example of the prior art.

Figures 4(a) and 4(b) show positions of the moving member and the shade in advanced and retracted positions, respectively.

As shown in Fig. 1, a reflector unit 16 which is tiltable in the vertical and horizontal directions is provided in a space formed with a lens 12 and a lamp body 14 in a vehicle headlamp 10 embodying the present invention.

The reflector unit 16 comprises a discharge bulb (metal halide bulb) 18, a reflector 20 for mounting and supporting the discharge bulb 18, a shade 22 for partially surrounding the discharge bulb 18 and a beam switching device 24.

The lens 12 is a plain-glass lens and the reflector unit 16 is equipped with a light-distribution control function. In other words, the reflector 20 is fitted with a reflective surface 20a for reflecting light from the discharge light emitting portion 18a of the discharge bulb 18 forward and with the diffusion or deflective reflection function of the reflective surface 20a, used for emitting forwardly a beam for forming a predetermined light-distribution pattern.

The beam switching device 24 comprises a device body 26 fixed to the reflector 20 and a moving member 28 fixed to a shade 22 and extending upward from the device body 26, thus selectively switching the beam to a high beam or a low beam.

More specifically, the moving member 28 is capable of not only moving back and forth in the longitudinal direction (as shown by a double-headed arrow) with respect to the device body 26 but taking an advanced and a retracted position when the device body 26 is driven. As shown in Fig.

4(a), when the moving member 28 stays in the advanced position, the solid angle of the shade 22 with respect to the light emanated from the discharge light emitting portion 18a becomes small, so that the beam emitted from the reflector unit 16 forms a high beam. On the other hand, as shown in Fig. 4(b), when the moving member 28 stays in the retraced position, the solid angle of the shade 22 with respect to the light emanated form the discharge light emitting portion 18a becomes large, so that the beam emitted from the reflector unit 16 forms a low beam.

While the device body 26 is conducting, the beam switching device 24 sets the shade 22 to the advanced position but to the retracted position while it is not conducting.

More specifically, not illustrated in the figures, the moving member 28 secured to the shade 22 engages with a resilient member such as a spring or the like and also with an actuating device such as a motor, solenoid or the like. The moving member 28 and the shade 22 are in the original position, that is, the retraced position by the elastic force of the resilient member when the device body 26 is not conducting where the beam emitting from the reflector unit 16 forms a low beam. When the device body 26 is conducting, the actuating device is actuated to move the moving member 28 to the advanced position against the elastic force of the resilient member, so that the beam emitting from the reflector unit 16 forms a high beam. When the device body 26 is turned off, the actuating device is deactivated and, accordingly, the moving member 28 and the shade 22 are retracted to the original position by the elastic force of the resilient member.

Fig. 2 is a vehicle headlamp circuit diagram together with a lamp switch 102 and a passing switch 104.

As shown in Fig. 2, the discharge bulb 18 of the vehicle headlamp 10 is connected to a light-on circuit 36 and a light-off delay circuit 38 in series, the light-on circuit 36 comprising a starting circuit 32 and a stabilizing circuit 34. The lamp switch 102 and the passing switch 104 are connected in parallel to the light-off delay circuit 38.

Moreover, these lamp switch 102 and the passing switch 104 are also connected in parallel to the beam switching device 24 of the vehicle headlamp 10.

The lamp switch 102 is allowed to selectively take a high beam mode (MAIN), a low beam mode (SUM) or a light-off mode (OFF) and the passing switch 104 is allowed to take an on- and an off-position. The lamp and passing switches 102, 104 are provided inside the vehicle and the mde-s"tduiig of the lamp switch 102 and the on-off switching of the passing switch 104 are carried out by a driver. The lamp switch 102 of the beam switching device 24 is connected to its high beam mode terminal.

When the high beam mode is selected by the lamp switch 102, the shade 22 is set to the advanced position and the discharge bulb 18 is turned on so as make emission in the high beam mode, whereas when the low beam mode is selected by the lamp switch 102, the shade 22 is set to the retraced position and the discharge bulb 18 is turned on so as to make emission in the low beam mode. when the light-off mode is selected by the lamp switch 102, the shade 22 is set to the retracted position and the discharge bulb 18 is turned off.

The passing switch 104 is allowed to be turned on only when the lamp switch 102 is in the low beam mode (SUB) or light-off mode (OFF) by another device not shown in the figures.

When the passing switch 104 is turned on while the lamp switch 102 in the low beam mode, the shade 22 is displaced to the advanced position and the beam is switched to the high beam. When the passing switch 104 is turned off, the shade 22 is displaced to the retracted position and the beam is returned to the low beam.

When the passing switch 104 is turned on while the lamp switch 102 is in the light-off mode as shown by P in Figs. 3, the shade 22 is displaced to the advanced position and the discharge bulb 18 is turned on so as to make emission in the high beam mode. When the passing switch 104 is turned off, the shade 22 is displaced to the retracted position and the discharge bulb 18 is turned off.

However, it has also been arranged that the discharge bulb 18 is not turned off simultaneously when the passing switch 104 turned off but turned off after the discharae bulb 18 is held "on" for a predetermined time of td (which in one a'bodinnt is 1.5 seconds) after the passing switch 104 is turned off.

This light-off delay operation is performed by the light-off delay circuit 38.

Hence, the discharge bulb 18 is held "on" without being turned off on condition that the interval between the time the passing switch 104 is turned off the time it is turned on again is within a predetermined time of td.

Consequently, as shown in Fig. 3(c), the discharge bulb 18 is held "on" without interruption when the on-off operations of the passing switch 104 are performed with great frequency.

When the passing switch 104 is turned off even though the discharge bulb 18 is thus held "on," on the other hand, the shade 22 is displaced by the beam switching device 24 from the advanced position to the retracted position and it is displaced thereby from the retracted position to the advanced position when the passing switch 104 is turned on again, whereby the passing function is secured by increasing and decreasing the beam intensity in response to the on-off operations even though the on-off operations of the passing switch 104 are continuously performed.

Although the life of the discharge bulb 18 is extremely shortened when the on-off operations of the discharge bulb 18 are repeated at short intervals, the life thereof can effectively be improved since the on-off operations of the discharge bulb 18 are never repeated at short intervals even when the on-off operations of the passing switch 104 are continuously performed according to this embodiment of the invention.

As the light-off delay time, that is, the predetermined time td is set at 1.5 seconds according to this embodiment of the invention, the discharge bulb 18 can be held "on" even when the continuous passing operations are slowly performed. Moreover, it is also prevented to give a feeling of incorrectness to drivers of the vehicle concerned and another when the discharge bulb 18 is left "on" after the passing operations.

Although the light-off delay circuit 38 is arranged separately from the light-on circuit 36 according to this embodiment of the invention, the former may be incorporated in the latter.

Claims

1. A vehicle headlamp comprising a reflective optical system for emitting forwardly a desired beam of light from a light source and a beam switching device for selectively switching the beam to a high beam or a low beam by displacing an optical member forming part of the reflective optical system, wherein when a passing switch is turned on while a lamp switch for turning on and off the light source is held "off," the optical member is set to a high beam position and the light source is turned on, and when the passing switch is turned off, the optical member is set to a low beam position and the light source is turned off, characterized by providing a light-off delay circuit for turning off the light source after keeping the light source "on" for a predetermined time when the passing switch is switched from an on state to an off state when the lamp switch is held "off."

2. A vehicle headlamp as claimed in claim 1, wherein the light source is the discharge light emitting portion of a discharge bulb.

3. A vehicle headlamp as claimed in either claim 1 or claim 2, wherein the predetermined time td (sec.) is set at 0.5 < td < 3.

4. A vehicle headlamp as claimed in claim 3, wherein the predetermined time td (sec.) is set at 1 < td < 2.

5. A vehicle headlamp as claimed in claim 1, wherein the optical member forming comprises a shade.

6. A vehicle headlamp, substantially as described with reference to Figures 1, 2 and 3(c) of the accompanying drawings.

Amendments to the claims have been filed as follows

5. A vehicle headlamp as claimed in claim 1, wherein the optical member comprises a shade.