The present invention relates to a vehicle headlamp capable of varying light distribution of a lamp fixture by moving a movable shade.
A vehicle headlamp reflects light from a light source forward by a reflector to emit a beam as a low beam or high beam. Since a required light distribution pattern is different between the low beam and the high beam, switching between low beam and high beam is commonly conducted by switching the ON/OFF state of two light sources included in a light source bulb or the ON/OFF state of two light source bulbs.
A vehicle headlamp for conducting beam switching by using a single light source is also known in the art. In particular, a two-lamp-type headlamp using a discharge bulb as a light source bulb often has such a structure.
A method for conducting beam switching by moving a movable shade, as disclosed for example in Japanese Patent Application No. 2000-207918, is conventionally known as one of the beam switching methods using a single light source.
In the beam switching method described above, a solenoid is used to move the movable shade between two prescribed positions having different light-shielding amounts for the light incident on a reflector from the light source.
In this case, a plunger of the solenoid is connected to a leg of the movable shade in order to transmit the driving force of the solenoid to the movable shade. One example of such a connection structure is the engagement structure as shown in FIG. 13, which is an improvement of the connection structure described above.
More specifically, in this engagement structure, a slit (slot) 2a extending in the axial direction of a longitudinally extending plunger 2 is formed in the front end face of the plunger 2, and a through hole 2b extending perpendicularly to the slit 2a is formed in the plunger 2 at a position near the tip thereof. A spring pin 4 is press-fitted in the through hole 2b. A long groove 6a is formed at the tip of a shade leg 6. The tip of the shade leg 6 is inserted into the slit 2a of the plunger 2 so that the spring pin 4 is engaged with the long groove 6a. 
This engagement structure uses the spring pin 4 to engage the plunger 2 with the shade leg 6. This requires the costs for the spring pin, costs for mounting the same, and processing costs for forming the slit 2a and the through hole 2b in the plunger 2, thereby increasing the overall cost for the lamp fixture.
Such a problem generally occurs not only when switching between low beam and high beam is conducted by moving the movable shade, but also when light distribution of the lamp fixture is varied by moving the movable shade.
The present invention is made in view of the above problems. The present invention provides a vehicle headlamp that varies light distribution of a lamp fixture by moving a movable shade, and enables reduction in costs for the structure for engagement between a plunger and a shade leg.
The present invention improves the structure for engagement between the plunger and the shade leg.
More specifically, a vehicle headlamp according to the present invention includes a light source, a reflector for reflecting light forward from the light source, a movable shade capable of shielding part of light incident on the reflector from the light source or part of light reflected from the reflector, and a shade driver for moving the movable shade between two prescribed positions having different light-shielding amounts for the incident light or the reflected light. The movable shade includes a shade body and a shade leg extending from the shade body, the shade driver including a solenoid having a plunger extending in a longitudinal direction, the plunger having a prescribed notch formed in its peripheral surface at a position near a tip thereof, and the shade leg having an engaging portion for engaging with the notch. As the engaging portion abuts on a front end face and a rear end face of the notch, reciprocating movement of the plunger is converted into movement of the movable shade.
The type of the xe2x80x9clight sourcexe2x80x9d is not limited. For example, a discharge light-emitting portion of a discharge bulb or a filament of an incandescent bulb such as halogen bulb may be used.
The specific structure of the xe2x80x9cmovable shadexe2x80x9d is not limited as long as it is capable of shielding part of light incident on the reflector from the light source bulb or part of light reflected from the reflector. The shade body may be integral with the shade leg, or the shade body and the shade leg may be separate elements.
The xe2x80x9ctwo prescribed positions having different light-shielding amounts for the incident light or the reflected lightxe2x80x9d may be such positions that the movable shade forms a low-beam light distribution pattern or a high-beam light distribution pattern, or may be such positions that the movable shade forms another light distribution pattern.
The specific structure of the xe2x80x9cshade driverxe2x80x9d is not limited as long as it includes a solenoid having a longitudinally extending plunger and moves the movable shade between the above two positions. Moreover, the manner in which the movable shade is xe2x80x9cmovedxe2x80x9d by the shade driver is not limited. For example, pivoting or linear reciprocation may be employed.
The specific structure of the xe2x80x9cnotch,xe2x80x9d such as its shape and position, is not limited. The notch may be formed either as a recess or a through hole.
The specific structure of the xe2x80x9cengaging portionxe2x80x9d such as its shape and position is not limited as long as it engages with the notch such that it can abut on the front end face and the rear end face of the notch. The xe2x80x9cengaging portionxe2x80x9d need not simultaneously abut on both the front and rear end faces of the notch, but need only abut on one of the front and rear end faces.
As described above, in the vehicle headlamp of the present invention, a movable shade including a shade body and a shade leg is moved between prescribed positions by using a solenoid having a longitudinally extending plunger. The plunger has a prescribed notch formed in its peripheral surface at a position near the tip thereof, and the shade leg has an engaging portion for engaging with the notch. As the engaging portion abuts on a front end face and a rear end face of the notch, reciprocating movement of the plunger is converted into movement of the movable shade. As a result, unlike conventional headlamp structures, engagement between the plunger and the shade leg can be obtained without using a spring pin.
This eliminates the costs for the spring pin and costs for mounting the same. Moreover, the notch need only be formed in the plunger instead of forming a slit and a through hole as in the conventional example. This enables reduction in processing costs.
The present invention thus enables reduction in costs for the structure for engagement between the plunger and the shade leg in a vehicle headlamp that varies light distribution of a lamp fixture by moving the movable shade.
In the above structure, the movement of the movable shade may be realized as pivoting movement in the longitudinal direction. In this case, forming a front end face and a rear end face of the engaging portion with an approximately circular-arc shape enables reciprocating movement of the plunger to be smoothly converted into movement of the movable shade.
The shape of the xe2x80x9cnotchxe2x80x9d is not limited, as described above. The notch may be a U-shaped recess having a U-shape in cross section including an axis of the plunger. This enables the engaging portion to reliably abut on the front end face and the rear end face of the notch. In this case, the engaging portion can be inserted into the notch either along the U-shaped recess or laterally into the U-shaped recess. This enables the lamp fixture to be mounted with improved flexibility.
The xe2x80x9cnotchxe2x80x9d may alternatively be an annular recess formed in a whole peripheral surface of the plunger and having a U-shaped cross section. This enables the engaging portion to reliably abut on the front end face and the rear end face of the notch regardless of the angular position of the plunger with respect to its axis. As a result, mounting operation can be conducted with improved efficiency. Moreover, the engaging portion can be inserted into the notch from any direction, whereby the lamp fixture can be mounted with further improved flexibility. Furthermore, forming the notch as such an annular recess enables the notch to be easily formed by a turning process, thereby achieving further reduction in processing costs for the plunger.
Alternatively, the xe2x80x9cnotchxe2x80x9d may be a rectangular slot extending through the plunger and having a rectangular cross section. This enables the engagement between the plunger and the shade leg to be reliably maintained even when the plunger and the movable leg become excessively loose, or the like.
In an alternate structure, the shade leg may have a pair of engaging portions formed with a prescribed gap therebetween. The pair of engaging portions may engage with the notch by holding therebetween the plunger at a position near the tip thereof. This configuration enables the engagement between the plunger and the shade leg to be reliably maintained regardless of the shape of the notch.
Hereinafter, embodiments of the present invention will be described in conjunction with the accompanying drawings.