EP2228593A2

EP2228593A2 - Vehicle headlamp

Info

Publication number: EP2228593A2
Application number: EP10156398A
Authority: EP
Inventors: Ippei Yamamoto
Original assignee: Koito Manufacturing Co Ltd
Current assignee: Koito Manufacturing Co Ltd
Priority date: 2009-03-12
Filing date: 2010-03-12
Publication date: 2010-09-15
Anticipated expiration: 2030-03-12
Also published as: JP5618312B2; JP2010218689A; EP2228593A3; EP2228593B1

Abstract

A vehicle headlamp (10) is provided with a movable shade (20). The movable shade (20) includes a large thickness portion (20A). When the movable shade (20) positions at a light shading position, the large thickness portion (20A) positions in a vicinity of the optical axis (Ax), an upper end face (20Aa) of the large thickness portion (20A) has a concave-curved section shape in a vertical plane parallel to the optical axis (Ax), a rear focal point (F) of a projection lens (18) positions between a front end edge (20Aa1) and a rear end edge (20Aa2) of the upper end face (20Aa), and the front end edge (20Aa1) passes through the optical axis (Ax).

Description

BACKGROUND OF THE INVENTION

The present invention relates to a so called projector type of headlamp for use in a vehicle. Specifically, the invention relates to a vehicle headlamp including a movable shade.

Generally, a vehicle headlamp of a projector type is structured in the following manner. That is, a projection lens is disposed on an optical axis which extends in a front-and-rear direction of a vehicle, a light source is disposed in a rear side of a rear focal point of the projection lens, and a light emitted from the light source is reflected onto a position in a vicinity of the optical axis by a reflector. When a light distribution pattern for a low beam is formed by the vehicle headlamp of the projector type, a shade is used. The shade is disposed in a vicinity of the rear focal point of the projection lens, and an upper end edge of the shade positions in a vicinity of the optical axis. Specifically, a portion of the reflected light from the reflector is shaded by the shade to form a given cutoff line in a upper end of the low beam light distribution pattern.
In Patent Reference 1 and Patent Reference 2, as a shade for use in a vehicle headlamp of the projector type, there is disclosed a plate-shaped movable shade which is structured such that it can be moved between a light shading position and a light shading reducing position. The light shading position is a position where an upper end edge of the shade is situated near to the optical axis in the vicinity of the rear focal point of the projection lens, and the light shading reducing position is a position where the shade reduces the light shading amount of the reflected light from the reflector when compared with the light shading amount at the light shielding position.
In Patent Reference 3, there is disclosed a plate-shaped shade disposed such that its upper end edge passes through the rear focal point of a projection lens, while the shade includes a flat portion which extends forwardly from such upper end edge. According to the vehicle headlamp disclosed in Patent Reference 3, a portion of the reflected light from a reflector is reflected upwardly by the flat portion of the shade to emit it as an upwardly going light from the projection lens, thereby forming a light distribution pattern which is used to radiate the light onto overhead signs existing ahead of a vehicle.

Patent Reference 1: JP-A-62-195802
Patent Reference 2: JP-A-2003-257218
Patent Reference 3: JP-U-5-066806

In order to enhance the remote visibility of the vehicle headlamp while a vehicle is running with a high beam, preferably, the intensity of the center light in the high beam light distribution pattern may be set as high as possible.
However, in a conventional vehicle headlamp of a projector type, problems are found as follows.
That is, as disclosed in Patent Reference 1 and Patent Reference 2, in a case where the low and high beams are switched over to each other by moving the movable shade, the high beam light distribution pattern is formed by superimposing a portion of the reflected light shaded by the movable shade in the low beam light distribution on the low beam light distribution pattern. Therefore, if the center light intensity of the high beam light distribution pattern should be increased, the center light intensity of the low beam light distribution pattern should also be increased accordingly. That is, this raises a problem that, without increasing the center light intensity of the low beam light distribution pattern more than necessary, the center light intensity of the high beam light distribution pattern cannot be increased.
On the other hand, when such a shade as disclosed in Patent Reference 3 is used as a movable shade, in a state where the movable shade is present at the light shading reducing position, since a portion of the reflected light from the reflector is reflected upwardly in the flat portion extending forwardly from the upper end edge of the movable shade, the center light intensity of the low beam light distribution pattern can be reduced by an amount equivalent to such upward reflection of the reflected light.
However, this structure is not sufficient yet in order to reduce the center light intensity of the low beam light distribution pattern effectively. Also, in this structure, since the direction of the reflected light from the reflector is simply reversed up and down in the flat portion of the shade, a light distribution pattern to be formed by the upward emitted light from the projection lens is a pattern which spreads upwardly from the cutoff line of the low beam light distribution pattern. Therefore, there is a fear that such distribution pattern for radiating the overhead signs can give the glare to the driver of an oncoming vehicle and the like.

SUMMARY OF THE INVENTION

One or more embodiments of the invention provide a projector type vehicle headlamp including a movable shade which can increase a center light intensity of a high beam light distribution pattern, without increasing a center light intensity of a low beam light distribution pattern more than necessary nor without giving a glare to a driver of an oncoming vehicle.
According to the invention, by improving a structure of a movable shade, the above problem is resolved.
In accordance with one or more embodiments of the invention, a vehicle headlamp is provided with: a projection lens disposed on an optical axis extending in a front-and-rear direction of a vehicle; a light source disposed on a rear side of a rear focal point of the projection lens; a reflector configured to reflect a light from the light source forwardly near to the optical axis; a movable shade configured to shade a portion of the reflected light from the reflector; and an actuator configured to move the movable shade between a light shading position where an upper end edge of the movable shade passes in a vicinity of the rear focal point of the projection lens and a light shading reducing position where an amount of shading of the reflected light is reduced with respect to a light shading amount at the light shading position. The movable shade is configured so that, in a state where the movable shade positions at the light shading position, the movable shade includes a large thickness portion in a vicinity of the optical axis, an upper end face of the large thickness portion has a concave-curved section shape in a vertical plane parallel to the optical axis, the rear focal point positions between a front end edge and a rear end edge of the upper end face, and the front end edge passes through the optical axis.
The kind of the above-mentioned "light source" is not limited to a specific kind but, for example, there can be employed a light emitting portion of a discharge bulb or a filament of a halogen bulb.
The above-mentioned "concave-curved section shape" may include a section shape formed only of a concave-curved line or may include a section shape having an uneven shape in part, provided that it is a downwardly recessed section shape as a whole.
The above-mentioned "large thickness portion" means that at least a portion of the movable shade located in the vicinity of the optical axis has a large thickness. That is, a remaining portion of the movable shade than the large thickness portion may or may not have a large thickness.
Referring to the above-mentioned expression "a front end edge (20Aa1) of the upper end face (20Aa)", a shape thereof is not limited to any specific shape, provided that it is formed to pass through the optical axis. That is, it can be set properly according to the cutoff line shape of the low beam light distribution pattern.
In the above vehicle headlamp, since the movable shade is structured such that a portion thereof in the vicinity of the optical axis is formed as a large thickness portion, and the rear focal point of the projection lens is situated between the front and rear end edges of the upper end face of the large thickness portion, when it is compared with a conventional movable shade which is formed as a plate-like shade, it can shade a large amount of the reflected light that is reflected from the reflector and goes toward the vicinity of the rear focal point of the projection lens. In this case, since the front end edge of the upper end face of the large thickness portion is situated forwardly of the rear focal point of the projection lens and the rear end edge thereof is situated rearwardly of the rear focal point of the projection lens, it is possible to shade the light that goes toward the vicinity of the rear focal point of the projection lens, including not only the reflected light from such area of the reflecting surface of the reflector as existing upwardly of the optical axis but also the reflected light from such area thereof as existing downwardly of the optical axis.
Since the reflected light reflected from the reflector and going toward the vicinity of the rear focal point of the projection lens provides the light that contributes toward the center light intensity of the low beam light distribution, by shading a large amount of such light, the center light intensity of the low beam light distribution pattern can be controlled by an amount equivalent to such shaded light. Therefore, even in a case where the reflecting surface of the reflector is formed such that it increases the center light intensity of the high beam light distribution pattern, it is possible to prevent the center light intensity of the low beam light distribution pattern from increasing more than necessary.
In this case, since the upper end face of the large thickness portion of the movable shade has a concave-curved section shape in a vertical plane parallel to the optical axis, there can be obtained the following operation effects.
That is, assuming that the upper end face of the large thickness portion of the movable shade is formed as a plane, the light reflected in such area of the upper end face as existing rearwardly of the rear focal point of the projection lens is emitted as the downwardly going light from the projection lens, whereas the light reflected in such area of the upper end face as existing forwardly of the rear focal point is emitted as the upwardly going light from the projection lens and provides the light that spreads upwardly from the cutoff line of the low beam light distribution pattern, thereby giving the glare to the driver of an oncoming vehicle and the like.
On the other hand, according to the vehicle headlamp of the embodiments of the invention, since the upper end face of the large thickness portion has a concave-curved section shape in a vertical plane parallel to the optical axis, the front area of the upper end face provides a rearwardly inclined curved surface. Due to this, most of the light reflected in such front area can be prevented from entering the projection lens. This makes it possible to effectively control the generation of the glare that spreads upwardly from the cutoff line of the low beam light distribution pattern.
Moreover, since a rear area of the upper end face of the large thickness portion provides a forwardly inclined curved surface, by forming this inclined curved surface in a proper shape, the light reflected in this rear area can be radiated into the projection lens as a controlled light and also can be emitted from the projection lens as an upwardly going controlled light. This makes it easy to form, upwardly of the cutoff line of the low beam light distribution pattern, a light distribution pattern which is suitable to radiate overhead signs on the road ahead of the vehicle.
In addition, according to the embodiments of the invention, since the front end edge portion of the upper end face of the large thickness portion is formed such that it passes through the optical axis, there can be obtained the following operation effects.
That is, according to the above-mentioned conventional movable shade, the upper end edge of the movable shade is disposed to pass through the rear focal point of the projection lens, whereby the cutoff line of the low beam light distribution pattern can be formed cleanly or highly visibly. On the other hand, according to the embodiments of the invention, the upper end face of the large thickness portion of the movable shade is disposed not to pass through the rear focal point of the projection lens. However, according to the embodiments of the invention, since the front end edge of the upper end face of the large thickness portion is formed to pass through the optical axis, when the light reflected from such reflecting area of the reflecting surface of the reflector as existing substantially flush with the optical axis is used as the light for forming the cutoff line, the cleanliness, that is, the visibility of the cutoff line can be secured sufficiently.
As described above, according to the embodiments of the invention, there is provided a projector type of vehicle headlamp including a movable shade which can enhance the center light intensity of the high beam light distribution pattern without enhancing the center light intensity of the low beam light distribution pattern more than necessary nor without giving the glare to the driver of a vehicle and the like. Owing to this, the remote visibility of the high beam can be enhanced.
In the above structure, if a configuration that the rear end edge of the upper end face of the large thickness portion is formed substantially flush with the front end edge of the upper end face of the large thickness portion is adopted, the rear end edge is also allowed to contribute toward forming the cutoff line, thereby being able to enhance the cleanliness of the cutoff line further.
Moreover, if a configuration that the deepest portion of the upper end face of the large thickness portion is situated forwardly of the rear focal point of the projection lens is adopted, since the inclination angle of such front area of the upper end face as existing forwardly of the deepest portion provides a large angle, it is further easier to prevent the light reflected by such front area from entering the projection lens. Also, since such rear area of the upper end face of the large thickness portion as existing rearwardly of the deepest portion can secure large area, the light reflected from such rear area can be controlled closely. This makes it further easier to form a light distribution pattern which is suitable to radiate overhead signs.
Other aspects and advantages of the invention will be apparent from the following description, the drawings and the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1 is a side section view of a vehicle headlamp according to an exemplary embodiment of the invention.
Fig. 2 is a detailed view of main portions of Fig. 1.
Fig. 3 is a perspective view of the main portions of the above vehicle headlamp.
Fig. 4 is a detailed view of a portion shown by a reference line IV in Fig. 2.
Figs. 5A and 5B are perspective views of light distribution patterns to be formed by the light radiated forwardly from the vehicle headlamp on a virtual vertical screen disposed at a position situated 25m forwardly of the headlamp, in which Fig. 5A shows a light distribution pattern for a low beam PL, and Fig. 5B shows a light distribution pattern for a high beam PH.

DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENTS

An exemplary embodiment of the invention is described in reference to the appended drawings.
Fig. 1 is a side section view of a vehicle headlamp according to an exemplary embodiment of the invention.
As shown in Fig. 1, a vehicle headlamp 10 according to the present embodiment is structured as a lamp unit of a projector type and can be used in a state where it is incorporated into a lamp body (not shown) or the like.
The vehicle headlamp 10 includes a light source bulb 12, a reflector 14, a holder 16, a projection lens 18, a movable shade 20 and an actuator 22, and also has an optical axis Ax which extends in the front-and-rear direction of a vehicle. Here, according to the vehicle headlamp 10, in the stage where its aiming adjustment is completed, the optical axis Ax extends in a direction which is inclined downwardly about 0.5 - 0.6° with respect to the vehicle front-and-rear direction.
The projection lens 18 is made of a plano-convex aspherical lens structured such that its front surface is a convex surface and its rear surface is a plane surface; and, the projection lens 18 is disposed on the optical axis Ax. According to the projection lens 18, a light source image, which is formed on its rear focal plane (that is, a focal plane containing the rear focal point of the projecting lens 18), is projected on a vertical virtual screen disposed forwardly of the headlamp.
The light source bulb 12 is a discharge bulb such as a metal halide bulb with its discharge light emitting portion as a light source 12a and is inserted into and fixed to an opening 14b, which is formed in the rear top portion of the reflector 14, from behind. The light source 12a of the light source bulb 12 is structured as a line light source which extends substantially coaxially with the optical axis Ax and is disposed backwardly of the rear focal point F of the projection lens 18.
The reflector 14 includes a reflecting surface 14a which reflects the light emitted from the light source 12a forwardly near to the optical axis Ax. The section shape of the reflecting surface 14a along a plane containing the optical axis Ax is formed substantially as an elliptical shape, while the eccentricity of the reflecting surface 14a is set such that it increases gradually from its vertical section toward its horizontal section. Owing to this, the light emitted from the light source 12a and reflected by the reflecting surface 14a is converged substantially near to the rear focal point F in the vertical section and, in the horizontal section, the converging position is shifted forwardly of the rear focal point F.
In this case, the boundary portions of the reflecting surface 14a between the upper reflecting area 14a1 and lower reflecting area 14a2 of the reflecting surface 14a respectively situated upwardly and downwardly of the optical axis Ax (that is, the two right and left reflecting areas of the opening 14b respectively situated substantially flush with the optical axis Ax) are formed such that the convergence of the reflected light in these boundary portions to the rear focal point F can be enhanced with respect to the vertical direction. Also, the lower reflecting area 14a2 is formed such that the convergence of the reflected light in such area 14a2 to the rear focal point F can be enhanced with respect to the vertical and horizontal directions.
The holder 16 is formed such that it extends substantially in a cylindrical manner forwardly from the front end opening of the reflector 14; and, the rear end portion of the holder 16 fixes and supports the reflector 14, while the front end portion thereof fixes and supports the projection lens 18. The lower portion of the holder 16 is cut away.
The movable shade 20 is disposed such that it is situated substantially in the lower half portion of the internal space of the holder 16, while the lower end portion of the movable shade 20a is rotatably supported on the holder 16 through a rotary pin 24 extending in the right and left direction. And, the movable shade 20 is structured such that it can take a light shading position shown by a solid line in Fig. 1 and a light shading reducing position to which the movable shade 20 is rotated by a given angle backwardly from the light shading position and also which is shown by a two-dot chained line.
Fig. 2 is a detailed view of the main portions of Fig. 1. Also, Fig. 3 is a perspective view of the main portions of the vehicle headlamp 10.
As shown in these figures as well, such portion of the movable shade 20 as exists near the optical axis Ax when the movable shade 20 takes the light shading position is formed as a large thickness portion 20A. In this case, the thickness of the large thickness portion 20A is set about 6 ∼ 10 mm (for example, about 8 mm). On the other hand, the general portion 20B of the movable shade 20 (that is, the other portion of the movable shade 20 than the large thickness portion 20A) is formed to have a thickness of about 1 ∼ 5 mm (for example, 3 mm). And, the two right and left end portions of the large thickness portion 20A are formed such that their thicknesses reduce gradually toward the general portion 20B.
The movable shade 20 is disposed such that, in a state where it takes the light shading position, the rear focal point F of the projection lens 18 is situated between the front end edge 20Aa1 and rear end edge 20Aa2 of the upper end face 20Aa of the large thickness portion 20A of the movable shade 20. According to the present embodiment, the rear focal point F of the projection lens 18 is situated substantially in the center between the front end edge 20Aa1 and rear end edge 20Aa2.
The large thickness portion 20A is structured such that its upper end face 20Aa has a concave-curved section in a vertical plane parallel to the optical axis Ax. And, a mirror surface treatment such as aluminum deposition has been enforced on the upper end face 20Aa.
The front end edge 20Aa1 of the upper end face 20Aa of the large thickness portion 20A is formed such that it passes through the optical axis Ax and has an uneven shape in the right and left portions thereof. That is, the area of the front end edge 20Aa1 on its own vehicle side (that is, the area existing leftward of the optical axis Ax) extends horizontally from the optical axis Ax, whereas the area of the front end edge 20Aa1 on the oncoming vehicle side extends obliquely downwardly from the optical axis Ax and, after then, extends horizontally.
The rear end edge 20Aa2 of the upper end face 20Aa of the large thickness portion 20A is formed substantially flush with the front end edge 20Aa1 and is uneven in the right and left portions thereof.
Here, the upper end face 20Ba of the general portion 20B of the movable shade 20 is formed to have a plane shape.
Fig. 4 is a detailed view taken along the IV line portion shown in Fig. 2.
As shown in Fig. 4, the deepest portion 20Aa3 of the upper end face 20Aa of the large thickness portion 20A of the movable shade 20 is situated forwardly of the rear focal point F of the projection lens 18.
Such front area 20AaF of the upper end face 20Aa as exists forwardly of the deepest portion 20Aa3 is formed as a concave-curved surface having a substantially circular arc-shaped section from the front end edge 20Aa1 to the deepest portion 20Aa3. On the other hand, the rear area 20AaR of the upper end face 20Aa existing rearwardly of the deepest portion 20Aa3 is formed as a curved surface. Specifically, this curved surface includes a concave-curved surface having a substantially circular arc-shaped section, a convex-curved surface having a substantially circular arc-shaped section and a concave-curved surface having a substantially circular arc-shaped section respectively connected together smoothly in this order from the rear end edge 20Aa2 to the deepest portion 20Aa3.
Here, the two right and left end portions of the upper end face 20Aa of the large thickness portion 20A are formed such that their respective surfaces are shifted gradually from a concave-curved surface to a plane toward the upper end face 20Ba of the general portion 20B formed to have a plane shape.
As shown in Fig. 1, the movable shade 20 is disposed such that, when the movable shade 20 exists at the light shading position, the upper end face 20Aa thereof passes through the lower vicinity of the rear focal point F of the projection lens 18, whereby the movable shade 20 can shade a portion of the reflected light from the reflecting surface 14a of the reflector 14 to remove the major part of the upwardly going light that is emitted forwardly from the projection lens 18. On the other hand, when the movable shade 20 is moved from the light shading position to the light shading reducing position, the upper end face 20Aa thereof is shifted rearwardly and obliquely downwardly to thereby reduce the shading amount of the reflected light from the reflecting surface 14a. According to the present embodiment, at the light shading reducing position, the shading amount of the reflected light from the reflecting surface 14a is set substantially zero.
The actuator 22 is made of a solenoid having a plunger 22a extending in the front-and-rear direction and is fixed to a mounting portion 14c formed in the lower end portion of the reflector 14. The plunger 22a of the actuator 22 is structured such that its leading end portion is engaged with a stay 20Bb provided in the movable shade 20 so as to project downwardly from the movable shade 20, whereby the reciprocating motion of the plunger 22a in the front-and-rear direction can be transmitted as the rotating motion of the movable shade 20. And, the actuator 22, when a beam change-over switch (not shown) is operated, is driven to move the plunger 22a in the front-and-rear direction, whereby the movable shade 20 can be moved between the light shading position and light shading reducing position.
In Fig. 2, there is illustrated a case where the optical paths of the lights respectively radiated from the above two positions are reflected on such point of the reflecting surface 14a of the reflector 14 as exists backwardly obliquely upwardly of the light source 12a.
Such reflected lights, as shown by oblique lines in Fig. 2, go forward obliquely downwardly while they are spreading according to the longitudinal length of the light source 12a; and, a substantially half portion of the reflected lights as it is arrives at the projection lens 18, while the remaining portion thereof arrives at the movable shade 20. Of the light that has arrived at the movable shade 20, the light having arrived at the upper end face 20Aa of the movable shade 20 is reflected upwardly on the upper end face 20Aa.
In this case, the front area 20AaF of the upper end face 20Aa is formed as a concave-curved surface having a substantially circular arc-shaped section from the front end edge 20Aa1 to the deepest portion 20Aa3, that is, it provides a curved surface which is inclined backwardly. Therefore, the light, which has arrived at the front area 20AaF, is reflected on the front area 20AaF to thereby provide the light that goes upwardly with a large angle. As a result of this, the light reflected on the front area 20AaF does not enter the projection lens 18,
On the other hand, the rear area 20AaR of the upper end face 20Aa is formed as a curved surface including a concave-curved surface having a substantially circular arc-shaped section, a convex-curved surface having a substantially circular arc-shaped section and a concave-curved surface having a substantially circular arc-shaped section respectively connected together smoothly in this order from the rear end edge 20Aa2 to the deepest portion 20Aa3. Therefore, a portion of the light having arrived at the rear area 20AaR is reflected on the rear area 20AaR to provide an upwardly going light with a small angle and is allowed to pass through the downward vicinity of the rear focal point F and enter the projection lens 18, whereas the remaining portion of the light provides the light that goes in a direction where it does not enter the projection lens 18.
Figs. 5A and 5B are perspective views of light distribution patterns to be formed by the light radiated forwardly from the vehicle headlamp 10 on a virtual vertical screen disposed at a position situated 25m forwardly of the headlamp 10. Specifically, Fig. 5A shows a light distribution pattern for a low beam PL, while Fig. 5B shows a light distribution pattern for a high beam PH.
The low beam light distribution pattern PL is a light distribution pattern which is formed when the movable shade 20 is situated at the light shading position, while the high beam light distribution pattern PH is a light distribution pattern to be formed when the movable shade 20 is situated at the light shading reducing position. And, when the movable shade 20 is situated at the light shading position, there is formed an additional light distribution pattern PA together with the low beam light distribution pattern PL.
The low beam light distribution pattern PL shown in Fig. 5A is the low beam light distribution pattern of a leftward distributed light and includes, in its upper end edge, cutoff lines CL1 and CL2 which are different in level from each other in the right and left directions. These cutoff lines CL1 and CL2 respectively extend in the horizontal direction in such a manner that they are different in level from each other in the right and left directions with respect to the V-V line passing in the vertical direction through the point H-V, that is, the vanishing point existing in the front direction of the headlamp. Here, the oncoming vehicle side portion existing rightward of the V-V line is formed as a low stage horizontal cutoff line CL1, while the own vehicle side portion existing leftward of the V-V line is formed as an upper stage horizontal cutoff line CL2 which is stage-raised through an inclined portion from the low stage horizontal cutoff line CL1.
In the low beam light distribution pattern PL, an elbow point E, which is an intersection point where the low stage horizontal cutoff line CL1 and V-V line intersects each other, is situated downwardly of the point H-V by about 0.5 ∼ 0.6°. This is because the optical axis Ax of the headlamp unit 20 extends in a direction going about 0.5 ∼ 0.6° downwardly with respect to the vehicle front-and-rear direction. And, in the low beam light distribution pattern PL, there is formed a hot zone HZL, that is, a high light intensity area, in such a manner that it surrounds the elbow point E.
The low beam light distribution pattern PL can be formed in such a manner that the image of the light source 12a formed on the rear focal plane of the projection lens 18 by the light, which is emitted from the light source 12a and reflected by the reflecting surface 14a of the reflector 14, is projected as an inverted projection image on the virtual vertical screen by the projection lens 18. The cutoff lines CL1 and CL2 of the low beam light distribution pattern PL, are formed as the inverted projection images of the upper end edges of the movable shade 20 (according to the present embodiment, the upper end face 20Aa of the large thickness portion 20A and the upper end face 20Ba of the general portion 20B).
In this case, the main portions of the cutoff lines CL1 and CL2 are formed by the front end edge 20Aa1 of the upper end face 20Aa of the large thickness portion 20A. Although the front end edge 20Aa1 is situated forwardly of the rear focal plane, since the reflected light from the reflecting area of the reflecting surface 14a situated substantially flush with the optical axis Ax is formed such that it can enhance its convergence to the rear focal point F with respect to the vertical direction, the visibility of the cutoff lines CL1 and CL2 can be maintained sufficiently.
Also, since the rear end edge 20Aa2 of the upper end face 20Aa of the large thickness portion 20A is formed substantially flush with the front end edge 20Aa1, the rear end edge 20Aa2 can also contribute toward forming the cutoff lines CL1 and CL2.
In this case, since the front end edge 20Aa1 forms the cutoff lines CL1 and CL2 using the reflected light from the upper reflecting area 14a1, when only the front end edge 20Aa1 is used, the cutoff lines CL1 and CL2 become bluish due to chromatic aberrations. On the other hand, since the rear end edge 20Aa2 forms the cutoff lines CL1 and CL2 using the reflected light from the lower reflecting area 14a2, when only the rear end edge 20Aa2 is used, the cutoff lines CL1 and CL2 become reddish due to chromatic aberrations. Therefore, when not only the front end edge 20Aa1 but also the rear end edge 20Aa2 is allowed to contribute toward forming the cutoff lines CL1 and CL2 to thereby cancel the influences of the chromatic aberrations, the cutoff lines CL1 and CL2 can be prevented from looking bluish.
The additional light distribution pattern PA shown in Fig. 5A is formed as an oblong light distribution pattern at a position distant upwardly from the cutoff lines CL1 and CL2 in the low beam light distribution pattern PL.
This additional light distribution pattern PA is a light distribution pattern which is used to radiate the overhead signs OHS existing ahead of the vehicle running road and also which is formed by the obliquely upward going light reflected by the rear area 20AaR of the upper end face 20Aa of the large thickness portion 20A of the movable shade 20 and is emitted forwardly from the projection lens 28.
On the other hand, the high beam light distribution pattern PH shown in Fig. 5B is formed in such a manner that it spreads upwardly to a certain degree from the cutoff lines CL1 and CL2 with respect to the low beam light distribution pattern PL; and, the high beam light distribution pattern PH includes a hot zone HZH in the vicinity of the H-V point.
In this case, since the lower reflecting area 14a2 of the reflecting surface 14a of the reflector 14 is formed such that it can enhance the convergence of the reflected light to the rear focal point F, the center light intensity of the hot zone HZH can be made fairly high.
As has been described heretofore in detail, the vehicle headlamp 10 according to the present embodiment is structured as a projector type of vehicle headlamp including the movable shade 20, such portion of the movable shade 20 as exists in the vicinity of the optical axis Ax when the movable shade 20 is situated at the light shading position is formed as the large thickness portion 20A, and, between the front end edge 20Aa1 and rear end edge 20Aa2 of the upper end face 20Aa of the large thickness portion 20A, there is interposed the rear focal point F of the projection lens 18. Therefore, when compared with a structure where the movable shade 20 is formed as a plate-shaped movable shade 20 like the above-mentioned conventional movable shade 20, the present structure can shade a large amount of reflected light from the reflector 14 going toward the vicinity of the rear focal point F of the projection lens 18. In this case, since the front end edge 20Aa1 of the upper end face 20Aa of the large thickness portion 20A is situated forwardly of the rear focal point F of the projection lens 18 and also the rear end edge 20Aa2 thereof is situated rearwardly of the rear focal point F of the projection lens 18, the movable shade 20 can shade the light going toward the vicinity of the rear focal point F of the projection lens 18 including the reflected light from the upper reflecting area 14a1 of the reflecting surface 14a of the reflector 14 and the reflected light from the lower reflecting area 14a2 thereof.
The light from the reflector 14, which goes toward the vicinity of the rear focal point F of the projection lens 18, provides the light that contributes toward the center light intensity of the low beam light distribution pattern PL. Therefore, when a large amount of such reflected light is shaded, the center light intensity of the low beam light distribution pattern PL can be reduced accordingly. Thanks to this, although the lower reflecting area 14a2 of the reflecting surface 14a of the reflector 14 is formed such that it enhances the center light intensity of the high beam light distribution pattern PH, the center light intensity of the low beam light distribution pattern PL can be prevented from increasing more than necessary.
In this case, since the upper end face 20Aa of the large thickness portion 20A of the movable shade 20 has a concave-curved-shaped section shape in a vertical plane parallel to the optical axis Ax, there can be obtained the following operation effects.
That is, assuming that the upper end face 20Aa of the large thickness portion 20A of the movable shade 20 is formed as a plane, the light reflected by such area of the upper end face 20Aa as exists rearwardly of the rear focal point F of the projection lens 18 is emitted from the projection lens 18 as a downwardly going light; and, on the other hand, the light reflected by such area as exists forwardly of the rear focal point F is emitted as an upwardly going light and provides a light which spreads upwardly from the cutoff lines CL1 and CL2 of the low beam light distribution pattern PL, whereby the light gives the glare to the driver of an oncoming vehicle and the like.
In this respect, according to the present embodiment, since the upper end face 20Aa of the large thickness portion 20A has a concave-curved-shaped section shape in a vertical plane parallel to the optical axis Ax, the front area 20AaF of the upper end face 20Aa provides a curved surface which is inclined rearwardly. Thus, most of the light reflected by the front area 20AaF can be prevented from entering the projection lens 18. This can effectively restrict the generation of the glare light which spreads upwardly from the cutoff lines CL1 and CL2 of the low beam light distribution pattern PL.
On the other hand, since the rear area 20AaR of the upper end face 20Aa of the large thickness portion 20A provides a curved surface which is inclined forwardly, when this inclined curved surface is set in a proper shape, the light reflected by this rear area 20AaR can be radiated onto the projection lens 18 as a controlled light and can be emitted from the projection lens 18 as a controlled upward light. Owing to this, it is easy to form, upwardly of the cutoff lines CL1 and CL2 of the low beam light distribution pattern PL, the additional light distribution pattern PA which is suitable to radiate the overhead signs OHS provided on the road ahead of the vehicle.
Also, according to the present embodiment, since the front end edge 20Aa1 of the upper end face 20Aa of the large thickness portion 20A is formed such that it passes through the optical axis Ax, there can be obtained the following operation effects.
That is, in the present embodiment, the upper end face 20Aa of the large thickness portion 20A of the movable shade 20 is disposed such that it passes through the downward vicinity of the rear focal point F of the projection lens 18 but is not disposed such that it passes through the rear focal point F. However, in the present embodiment, the front end edge 20Aa1 of the upper end face 20Aa of the large thickness portion 20A is formed such that it passes through the optical axis Ax, and also the light from the reflecting area situated substantially flush with the optical axis Ax is used as the light for forming the cutoff lines CL1 and CL2. Therefore, the visibility of the cutoff lines CL1 and CL2 can be secured sufficiently.
According to the present embodiment structured in the above manner, in the projector type of vehicle headlamp 10 including the movable shade 20, the center light intensity of the high beam light distribution pattern PH can be enhanced without enhancing the center light intensity of the low beam light distribution pattern more than necessary nor without giving the glare to the driver of an oncoming vehicle and the like. This can enhance the remote visibility of the high beam.
Also, in the present embodiment, since the rear end edge 20Aa2 of the upper end face 20Aa of the large thickness portion 20A is formed such that it is substantially flush with the front end edge 20Aa1, the rear end edge 20Aa2 can also be made to contribute toward forming the cutoff lines CL1 and CL2, thereby being able to enhance the visibility of the cutoff lines CL1 and CL2 further.
Especially, since the light source 12a of the vehicle headlamp 10 according to the present embodiment provides the discharge light emitting portion of a discharge bulb, the employment of the above structure can prevent the cutoff lines CL1 and CL2 from looking bluish.
That is, since the front end edge 20Aa1 of the upper end face 20Aa of the large thickness portion 20A forms the cutoff lines CL1 and CL2 using the reflected light from the upper reflecting area 14a1, when only the front end edge 20Aa1 is used, the cutoff lines CL1 and CL2 become bluish due to chromatic aberrations. On the other hand, since the rear end edge 20Aa2 forms the cutoff lines CL1 and CL2 using the reflected light from the lower reflecting area 14a2, when only the rear end edge 20Aa2 is used, the cutoff lines CL1 and CL2 become reddish due to chromatic aberrations. Therefore, when the front end edge 20Aa1 and the rear end edge 20Aa2 are both allowed to contribute toward forming the cutoff lines CL1 and CL2 to cancel the influences of the chromatic aberrations, the cutoff lines CL1 and CL2 can be prevented from looking bluish.
Also, according to the present embodiment, since the deepest portion 20Aa3 of the upper end face 20As of the large thickness portion 20 is situated forwardly of the rear focal point F of the projection lens 18, there can be obtained the following operation effects.
That is, since the inclination angle of the front area 20AaF of the upper end face 20Aa situated forwardly of the deepest portion 20Aa3 is large, it is further easier to prevent the light reflected by the front area 20AaF from entering the projection lens 18. Also, since the rear area 20AaR of the upper end face 20Aa of the large thickness portion 20A situated rearwardly of the deepest portion 20Aa3 can secure large area, the reflected light from the rear area 20AaR can be controlled closely, which makes it further easier to form a light distribution pattern suitable to radiate the overhead signs.
Specifically, according to the present embodiment, the rear area 20AaR of the upper end face 20Aa is formed as a curved surface which, from the rear end edge 20Aa2 to the deepest portion 20Aa3, includes a concave-curved surface having a substantially circular arc-shaped section, a convex-curved surface having a substantially circular arc-shaped section and a concave-curved surface having a substantially circular arc-shaped section respectively connected together smoothly in this order. Therefore, a portion of the light having arrived at this rear area 20AaR can be reflected by the rear area 20AaR as an upwardly going light having a small angle and can be made to enter the projection lens 18 through the downward vicinity of the rear focal point F; whereas, the remaining portion of the light can be formed as a light which goes in a direction where it is prevented from entering the projection lens 18.
Here, numeral values shown as specifications in the above embodiment are just an example and thus, of course, they can also be set for other proper values.
Also, in the above embodiment, description has been given of a case where there is formed the low beam light distribution pattern PL for the leftward distributed light. However, also in a case where there is formed a low beam light distribution pattern PL for the rightward distributed light, when a similar structure to the above embodiment is used, there can be obtained similar operation effects to the above embodiment.

[Description of Reference Numerals and Signs]

10:: Vehicle headlamp
12:: Light source bulb
12a:: Light source
14:: Reflector
14a:: Reflecting surface
14a1:: Upper reflecting area
14a2:: Lower reflecting area
14b:: Opening
14c:: Mounting portion
16:: Holder
18:: Projection lens
20:: Movable shade
20A:: Large thickness portion
20Aa:: Upper end face
20Aa1:: Front end edge
20Aa2:: Rear end edge
20Aa3:: Deepest portion
20AaF:: Front area
20AaR:: Rear area
20B:: General portion
20Ba:: Upper end face
20Bb:: Stay
22:: Actuator
22a:: Plunger
24:: Rotary pin
Ax:: Optical axis
CL1:: Low stage horizontal cutoff line
CL2:: Upper stage horizontal cutoff line
E:: Elbow point
F:: Rear focal point
HZH,: HZL: Hot zone
PA:: Additional light distribution pattern
PH:: High beam light distribution pattern
PL:: Low beam light distribution pattern

Claims

A vehicle headlamp (10) comprising:
a projection lens (18) disposed on an optical axis (Ax) extending in a front-and-rear direction of a vehicle;

a light source (12a) disposed on a rear side of a rear focal point (F) of the projection lens (18);

a reflector (14) configured to reflect a light from the light source (12a) forwardly near to the optical axis (Ax);

a movable shade (20) configured to shade a portion of the reflected light from the reflector (14); and

an actuator (22) configured to move the movable shade (20) between a light shading position where an upper end edge of the movable shade (20) passes in a vicinity of the rear focal point (F) of the projection lens (18) and a light shading reducing position where an amount of shading of the reflected light is reduced with respect to a light shading amount at the light shading position,

characterized in that the movable shade (20) is configured so that, in a state where the movable shade (20) positions at the light shading position, the movable shade (20) includes a large thickness portion (20A) in a vicinity of the optical axis (Ax), an upper end face (20Aa) of the large thickness portion (20A) has a concave-curved section shape in a vertical plane parallel to the optical axis (Ax), the rear focal point (F) positions between a front end edge (20Aa1) and a rear end edge (20Aa2) of the upper end face (20Aa), and the front end edge (20Aa1) passes through the optical axis (Ax).
The vehicle headlamp (10) according to Claim 1, wherein the rear end edge (20Aa2) is formed substantially flush with the front end edge (20Aa1), in the state where the movable shade (20) positions at the light shading position.
The vehicle headlamp (10) according to Claim 1 or 2, wherein a deepest portion (20Aa3) of the upper end face (20Aa) is positioned in a front side of the rear focal point (F), in the state where the movable shade (20) positions at the light shading position.