Patent Grant
9803821
The present invention relates to a vehicle-mounted headlamp that uses an LED as a light source and includes a projector lens that projects light emitted by the LED to the front of a vehicle.
In the present circumstances, where efforts are being undertaken to reduce amounts of discharged carbon dioxide which promotes global warming, and bright LEDs exhibiting high luminous efficiency have come into practical use, LEDs (light emitting diodes, semiconductor light sources) with low power consumption are starting to become more popular in place of conventional tungsten filament light bulbs as light sources of vehicle light fixtures. The LED has a long life and can be controlled simply by supplying a constant current thereto so as to emit a stable brightness, and therefore the LED can be used favorably as a light source of a vehicle light fixture. Moreover, the output (the luminous intensity) of LEDs has increased in recent years, and as a result, LEDs are starting to become more popular as light sources for vehicle-mounted headlamps.
Note that, a vehicle-mounted headlamp, and in particular a low-beam lamp, differs from an usual illumination lamp, a light distribution unique to vehicle-mounted use is required with which drivers of oncoming vehicles are not dazzled, or in other words, with which light is not emitted into the eyes of drivers of oncoming vehicles (i.e. a light distribution with which the positions corresponding to the eyes of drivers of oncoming vehicles become dark).
A conventional example of this type of vehicle-mounted headlamp, in which a low-beam lamp light distribution is formed by providing a light distribution member between an LED and a projector lens and the light emitted by the LED is used effectively, will be described below.
In a vehicle-mounted headlamp according to Patent Document 1, as shown in FIGS. 4 and 9 of Patent Document 1, a low-beam lamp light distribution is formed by a first reflecting surface provided on an optical axis, while light emitted upward by an LED is guided frontward by a second reflecting surface provided above the optical axis, and thereby used effectively.
In this configuration, light emitted downward from the LED is reflected by the first reflecting surface, but the reflected light travels toward the second reflecting surface and is then reflected repeatedly between the two reflecting surfaces so that the light attenuates. Therefore, room for improvement remains with respect to effective use of the light emitted by the LED.
Further, in a configuration shown in FIG. 11 of Patent Document 1, light emitted frontward by the LED enters through an incident surface of an optical member having a function of a convex lens, while the light emitted upward by the LED is guided frontward through being reflected by a convex surface-shaped reflecting surface that forms an inner surface of the incident surface.
In this configuration, the light emitted downward from the LED leaks out, so that room for improvement remains with respect to effective use of the light emitted by the LED.
An optical unit for a vehicle according to Patent Document 2 does not relate to a headlamp, but includes a light incident portion and a reflecting surface for guiding light emitted around from an LED to an exit surface without allowing the light to escape. When this configuration is employed as it is, however, it is impossible to form a light distribution for a headlamp in which a particular light distribution is required.
Patent Document 1: Japanese Patent Application Laid-open No. 2010-49886
Patent Document 2: Japanese Patent Application Laid-open No. 2012-119277
In Patent Documents 1 and 2, because configurations as described above are adopted, there is a problem that the light emitted by the LED cannot be used effectively while forming a light distribution for a low-beam lamp.
The present invention has been designed to solve the problem described above, and an object thereof is to provide a vehicle-mounted headlamp in which light emitted by an LED is used effectively while forming a light distribution for a low-beam lamp.
A vehicle-mounted headlamp according to the present invention includes an LED having a light emitting surface that is directed to the front of a vehicle, a projector lens that projects light emitted by the LED frontward, and a light distribution member disposed between the LED and the projector lens in order to form a light distribution for a low-beam lamp, wherein the light emitting surface of the LED is disposed on an upper side of an optical axis of the projector lens such that a gap is provided between the light emitting surface and the optical axis, and the light distribution member includes a first incident surface disposed opposing to the LED such that light emitted frontward by the LED enters through the first incident surface, a first reflecting surface disposed on the optical axis such that a projector lens side end edge thereof overlaps an LED side focus position of the projector lens, a second incident surface and a second reflecting surface disposed on the upper side of the optical axis such that light emitted upward by the LED enters through the second incident surface and the light entering through the second incident surface is reflected frontward by the second reflecting surface, and a third incident surface and a third reflecting surface disposed on the upper side of the optical axis such that light emitted downward by the LED enters through the third incident surface and the light entering through the third incident surface is reflected frontward by the third reflecting surface.
According to the present invention, the light distribution member that forms a light distribution for a low-beam lamp includes the second incident surface and the second reflecting surface disposed on the upper side of the optical axis such that the light emitted upward by the LED enters through the second incident surface and the light entering through the second incident surface is reflected frontward by the second reflecting surface, and the third incident surface and the third reflecting surface disposed on the upper side of the optical axis such that the light emitted downward by the LED enters through the third incident surface and the light entering through the third incident surface is reflected frontward by the third reflecting surface. As a result, a vehicle-mounted headlamp that uses the light emitted over a wide range by the LED effectively while forming a light distribution for a low-beam lamp can be provided.
The present invention will be described in further detail below by explaining embodiments thereof on the basis of the attached drawings.
As shown in
The light distribution member 3 is formed of transparent resin, glass, or the like, and is configured such that a first incident surface 3a through which light emitted frontward from a light emitting surface 1a of the LED 1 enters, a second incident surface 3b through which light emitted upward from the light emitting surface 1a of the LED 1 enters, and a third incident surface 3c through which light emitted downward from the light emitting surface 1a of the LED 1 enters are disposed on an upper side of an optical axis. Further, the following surfaces are formed: a first reflecting surface 3d disposed on the optical axis such that a projector lens 2 side end edge thereof overlaps an LED 1 side focus position F of the projector lens 2; a second reflecting surface 3e that reflects incident light from the second incident surface 3b frontward; and a third reflecting surface 3f that reflects incident light from the third incident surface 3c frontward.
The light that enters the light distribution member 3 and is reflected by the inner surfaces thereof exits through an exit surface 3g so as to be inverted vertically and horizontally by the projector lens 2 and projected to the front of the vehicle.
In a light distribution for a low-beam lamp, a dark portion must be provided on an upper side of the emitted light to ensure that the driver of an oncoming vehicle is not illuminated, and therefore the upper side must be made dark while the lower side (a road surface side) is made bright. The boundary line between the upper side dark portion and the lower side bright portion of the emitted light is the cutoff line.
In Embodiment 1, light that is emitted downward from the LED 1 and then passes through the projector lens 2 so as to travel above the cutoff line is reflected by the first reflecting surface 3d of the light distribution member 3 so as to be guided downward below the cutoff line (light L1 in
Furthermore, by providing the second reflecting surface 3e above the second incident surface 3b and providing the third reflecting surface 3f below the third incident surface 3c, light that may leak out in the vertical direction is guided frontward (light L2, L3 in
At this time, for providing the third reflecting surface 3f below the third incident surface 3c, the light emitting surface of the LED 1 is displaced upward from the optical axis (as represented by the arrow A in
Incidentally, to ensure that the low-beam lamp emitted light is formed in a similar light distribution from a point immediately in front of the vehicle to a far distance, the projector lens 2 side end edge of the light distribution member 3 is disposed to overlap the focus position F of the projector lens 2. However, the end edge does not have to overlap the focus position F precisely, and may be “in the vicinity” thereof.
Here, referring to
When “in the vicinity” is used to indicate the positional relationship between the focus position F of the projector lens 2 and the projector lens 2 side end edge of the light distribution member 3, the projector lens 2 side end edge of the light distribution member 3 is disposed within 1/10 of the distance D1 (i.e. such that D2≦D1/10) on either the projector lens 2 side or the LED 1 side of the focus position F of the projector lens 2.
More preferably, the projector lens 2 side end edge of the light distribution member 3 is disposed within 1/20 of the distance D1 (i.e. such that D2≦D1/20) on either the projector lens 2 side or the LED 1 side of the focus position F of the projector lens 2.
Even more preferably, the projector lens 2 side end edge of the light distribution member 3 is disposed within 1/50 of the distance D1 (i.e. such that D2≦D1/50) on either the projector lens 2 side or the LED 1 side of the focus position F of the projector lens 2.
However, note that
The distance of the projector lens 2 side end edge of the light distribution member 3 from the focus position F of the projector lens 2 may be determined in accordance with requirements for the light distribution of the emitted light. Incidentally, when the projector lens 2 side end edge of the light distribution member 3, which forms the cutoff line of the low-beam lamp, is disposed closer to the focus position F of the projector lens 2, the cutoff line of the emitted light becomes sharply defined far in front of the vehicle and blurred in locations close to the vehicle. When the projector lens 2 side end edge of the light distribution member 3 is disposed on the LED 1 side at a far position from the focus position F of the projector lens 2, the cutoff line of the emitted light becomes sharply defined in locations close to the vehicle and blurred far in front of the vehicle.
According to Embodiment 1, as described above, the projector type vehicle-mounted headlamp is configured such that the light emitting surface of the LED 1 is disposed on the upper side of the optical axis of the projector lens 2 with a gap from the optical axis (the arrow A in
In Embodiment 2, respective LED side tip end portions of the second incident surface 3b and the third incident surface 3c of the light distribution member 3-1 form an incident surface 3h shaped to surround the light emitting surface 1a of the LED 1, not shown in the drawing. As a result, the light emitted from the LED 1 in the horizontal direction can enter the light distribution member 3-1 in addition to the light emitted from the LED 1 in the vertical direction. Accordingly, leakage of the light emitted by the LED 1 over a wide range in the vertical and horizontal directions can be reduced so that the light emitted by the LED 1 can be used efficiently, and as a result, a vehicle-mounted headlamp that emits light of sufficient brightness can be realized even in a small size.
Note that as well as forming the incident surface 3h by adding horizontal direction incident surfaces to the vertical direction second and third incident surfaces 3b, 3c of the LED 1, the inner surfaces of the light distribution member 3-1 may be formed as a reflecting surface 3i by adding horizontal direction reflecting surfaces to the vertical direction second and third reflecting surfaces 3e, 3f such that the light emitted in the horizontal direction is also reflected frontward.
In Embodiment 3, an upper portion of the first incident surface 3a of the light distribution member 3-2 is located closer to the projector lens 2 than a lower portion of the first incident surface 3a, or in other words, is inclined frontward (such that a portion far from the optical axis is positioned further frontward) (the arrow B in
Note that in
By increasing the brightness in the location just below the cutoff line, or in other words the location that extends into far distance as in the light distribution shown in
Note that when the gap between the light emitting surface of the LED 1 and the optical axis is wide, the lower end edge of the apparent light emitting surface of the LED 1 may be brought closer to the optical axis by either increasing the incline of the first incident surface 3a of the light distribution member 3-2 or increasing the optical axis direction thickness of the light distribution member 3-2 (i.e. increasing the distance over which light passes) such that the light emitted by the LED 1 is refracted to the optical axis side.
Further, the exit surface 3g of the light distribution member 3-2 is not limited to the frontward inclined shape such as shown in
According to the third embodiment, as described above, the light distribution member 3-2 is configured such that the upper portion of the first incident surface 3a is closer to the projector lens 2 than the lower portion of the first incident surface 3a, or in other words such that the first incident surface 3a inclines frontward (such that the portion far from the optical axis is positioned further frontward), and therefore the light emitted by the LED 1 can be refracted to the optical axis side such that the lower end edge of the apparent light emitting surface of the LED approaches the optical axis. Accordingly, a favorable light distribution with which bright light can be emitted into far distance is not impaired even when a gap is provided between the light emitting surface of the LED 1 and the optical axis for providing the third incident surface 3c below the LED 1.
In the examples shown in
Note that by forming the first incident surface 3a to be the shape of the convex lens 7 in an upper side of the optical axis of the convex lens 7, a similar effect to that obtained by inclining the first incident surface 3a frontward (so that the upper portion is closer to the projector lens 2 than the lower portion) is obtained.
Further, in the example shown in
By forming the reflecting surfaces as concave surfaces as shown in
In the example shown in
As shown in
As a matter of course, in a left-hand drive headlamp, the shapes of the projector lens 2 side end edges of the light distribution member 3-5 are left-right reversed so that the horizontal portion 3j and the inclined portion 3k are formed respectively on the right side (the sidewalk side) and the left side (the opposing lane side) in the frontward direction of the vehicle.
Note that as long as a planar surface that serves as the first reflecting surface 3d can be formed on the optical axis side, the light distribution member 3-5 may take a shape other than that shown in
A light distribution member 3-6 shown in
A light distribution member 3-7 shown in
A light distribution member 3-8 shown in
A light distribution member 3-9 shown in
Note that
According to Embodiment 5, as described above, the projector lens 2 side end edges of the first reflecting surface 3d of the light distribution member 3-5 are configured such that the horizontal portion 3j is formed on the sidewalk side and the inclined portion 3k that inclines downward is formed on the opposing lane side. Accordingly, the cutoff line on the opposing lane side can be made horizontal so as not to illuminate drivers of oncoming vehicles, while the cutoff line on the sidewalk side can be raised so that pedestrians on the sidewalk can be illuminated. As a result, a vehicle-mounted headlamp having a favorable light distribution can be realized.
In Embodiment 6, several examples of the projector lens used in the vehicle-mounted headlamp will be described.
In Embodiment 6, a projector lens set 2-1 is formed from an emission side convex lens 2a and an LED side convex lens 2b, which are disposed so as to overlap in the optical axis direction. By combining a plurality of projector lenses, the projector lens 2-1 can be configured to have a short focal length using the convex lenses 2a, 2b, which have realistic thicknesses. By adopting a projector lens having a short focal length, a favorably shaped vehicle-mounted headlamp having a small aperture and a short depth can be realized.
Further, by controlling the respective lens shapes and refraction amounts of the convex lenses 2a, 2b, an even more favorable vehicle-mounted headlamp can be realized. The lens shape and the refraction amount will be described below with reference to
As shown in
Here,
As a matter of course, the parts on the lower side of the optical axis that do not receive light may also be omitted from the projector lenses 2 according to Embodiments 1 to 5 so that the lower side of the optical axis is reduced in size in comparison with the upper side of the optical axis.
In the projector lens, contrast is generated on the upper and lower sides of the cutoff line by vertical direction refraction, and a light distribution in which the light emitted from the headlamp spreads out in the horizontal direction is generated by horizontal refraction.
By forming the projector lens using elliptical convex lenses 2a, 2b, which have different refraction amounts (lens surface curvatures) between the vertical and horizontal directions, as shown in
Note that, in
By employing the elliptical convex lenses 2a, 2b, or in other words convex lenses in which the vertical direction curvature of the lens surface is larger than the horizontal direction curvature, light can be emitted over a wide range in the horizontal direction while maintaining the frontward brightness and the shape of the cutoff line. As a result, a favorable headlamp light distribution enabling illumination of pedestrians on a far edge of a sidewalk, a shoulder of the oncoming lane, and so on can be formed.
According to Embodiment 6, as described above, the projector lens 2-1 is constituted by the plurality of convex lenses 2a, 2b disposed so as to overlap in the optical axis direction, and therefore the focal length of the projector lens is shortened such that a favorably shaped vehicle-mounted headlamp having a small aperture and a short depth can be realized. Further, by controlling the shapes and refraction amounts of the respective lenses, even more favorable vehicle-mounted headlamp can be realized.
Furthermore, according to Embodiment 6, by adopting the convex lenses 2a, 2b respectively having different sizes on the upper side and lower side of the optical axis as the projector lens 2-1, a small vehicle-mounted headlamp can be realized.
Moreover, according to Embodiment 6, by employing the convex lenses 2a, 2b configured such that the vertical direction curvature of the lens surface differs from the horizontal direction curvature as the projector lens 2-1, a vehicle-mounted headlamp having an even more favorable light distribution can be realized.
Note that in Embodiments 1 to 6, examples in which an LED (a light emitting diode, a semiconductor light source) that emits visible light is used as the light source of the vehicle-mounted headlamp were described, but a light source formed from a combination of an LED that emits a specific type of light such as laser light and a wavelength conversion element (a fluorescent material) may be used instead.
Other than the configurations described above, the embodiments may be combined freely within the scope of the present invention. Further, any of the constituent elements of the respective embodiments may be modified, and any of the constituent elements may be omitted from the respective embodiments.
As described above, the vehicle-mounted headlamp according to the present invention is configured using a light distribution member so that light emitted by an LED is emitted efficiently to the front of a vehicle. Accordingly, the vehicle-mounted headlamp according to the present invention is suitable for use as a low-beam headlamp or the like.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/JP2014/050810 | 1/17/2014 | WO | 00 |
| Publishing Document | Publishing Date | Country | Kind |
|---|---|---|---|
| WO2015/107678 | 7/23/2015 | WO | A |
| Number | Name | Date | Kind |
|---|---|---|---|
| 8201981 | Brendle | Jun 2012 | B2 |
| 20030147252 | Fioravanti | Aug 2003 | A1 |
| 20100046243 | Yatsuda | Feb 2010 | A1 |
| 20100053987 | Nakabayashi | Mar 2010 | A1 |
| 20100103694 | Saxena et al. | Apr 2010 | A1 |
| 20100226142 | Brendle et al. | Sep 2010 | A1 |
| Number | Date | Country |
|---|---|---|
| 10 2008 056 403 | May 2010 | DE |
| 10 2009 008 631 | Aug 2010 | DE |
| 2 187 114 | May 2010 | EP |
| 2003-260975 | Sep 2003 | JP |
| 2010-49886 | Mar 2010 | JP |
| 2010-61902 | Mar 2010 | JP |
| 2010-73439 | Apr 2010 | JP |
| 2012-119277 | Jun 2012 | JP |
| 2013-242996 | Dec 2013 | JP |
| Number | Date | Country | |
|---|---|---|---|
| 20160341386 A1 | Nov 2016 | US |
