Headlight for in-vehicle use

In a headlight for in-vehicle use, an LED serving as an optical source is provided in which one edge side of its light-emitting face is formed into a linear portion and placed at a side of an optical axis so that the center of the light-emitting face is displaced from the optical axis. A projection lens is constituted by a radiation-side convex lens and an LED-side convex lens that are arranged in a direction of the optical axis. Between the LED and the projection lens, a light distribution member is placed that is formed using a transparent material and has, on its inner surface, a reflection face for reflecting light emitted by the LED.

TECHNICAL FIELD

The present invention relates to a headlight for in-vehicle use in which an LED is used as an optical source and a projection lens is provided that projects light emitted by the LED ahead of a vehicle.

BACKGROUND ART

Under tendency to reduce the amount of emission of carbon dioxide that promotes global warming, and in recent/current situation in which bright LEDs with high luminous efficiency are realized, low-power LEDs (light emitting diodes, semiconductor optical sources) are beginning to be popular also as optical sources of lamp devices for in-vehicle use, in place of conventional tungsten filament-based light bulbs. These LEDs are long-life and can produce stable brightness under easy control that makes constant a current supplied thereto, and are thus, well-suited as optical sources of lamp devices for in-vehicle use. Thus, also with the help of recent increase in output power (luminance intensity), they are beginning to be popular also as optical sources of the headlights for in-vehicle use.

Meanwhile, the optical systems of the headlights for in-vehicle use are classified to: a parabolic type in which a concave mirror reflector is used and the light emitted by an optical source is reflected by the mirror reflector so as to go out ahead of the vehicle; and a projector type in which a convex projection lens is used and the light emitted by an optical source is refracted by the projection lens so as to go out ahead of the vehicle.

In the followings, supplemental description will be made about configurations of the projector-type headlights for in-vehicle use that are related to the invention of this application.

In a conventional configuration that uses a tungsten filament as an optical source, lead wires are connected to both ends of the filament with a length of about 4 mm that radiates light all around, and in addition, a glass bulb exists outward of the filament. Thus, it is unable to arbitrarily modify the shape of a light emitting portion or the light radiation direction.

For that reason, a spheroidal mirror reflector is used and a filament serving as an optical source is placed at one focal point of the spheroidal mirror reflector, so that the light emitted by the filament is converged at the other focal point to thereby form a real image of the filament. Since no structural object exists near the real image of the filament, an arbitrary optical member can be used there, so that a light distribution for passing light for in-vehicle use that illuminates the front of a vehicle is formed by projecting ahead of the vehicle a necessary portion in the light that passes through the real image of the filament. That is to say, a light shielding plate is placed near the real image of the filament, so that unwanted light is blocked by the light shielding plate to thereby form a dark portion that is essential for passing light so as not to illuminate the driver of an oncoming vehicle. Namely, when an optical source is the filament in a state covered by the glass bulb without change, it is unable to be used as an optical source that radiates a light distribution for passing light. Thus, such a configuration is applied in which the real image of the filament around which no structural object exists is forcibly formed using the spheroidal mirror reflector, and the real image of the filament is subjected to shape modification, and then guided into the projection lens.

However, with respect to a projector-type headlight for in-vehicle use in which the above-described LED is used as an optical source, a light emitting portion, that is, a light emitting face of the LED can be formed into an arbitrary shape, and no glass bulb exists outward. Thus, it is also allowable to place a member for adjusting the light distribution near the LED. Namely, with respect to the projector-type headlight for in-vehicle use in which the LED is used as an optical source, it is unnecessary to follow the conventional optical system and light distribution technology in which a tungsten filament is used.

In the followings, examples will be described about the headlight for in-vehicle use that does not use a conventional spheroidal mirror reflector even though it is a projector type, and that is configured so that the light-emitting face of the LED is directed ahead of the vehicle and the light emitted by the LED is made directly incident on the projection lens.

A direct-projection type lamp device for illumination according to Patent Document 1 is configured so that, in the light emitted by the LED, widely-spread light that is non-incident on a projection lens is recovered using an auxiliary lens placed around the LED. Because of the use of the auxiliary lens, the light-beam utilization rate can be enhanced.

However, since it is configured so that the light that is non-incident on the projection lens is guided ahead of the vehicle while bypassing the projection lens, the auxiliary lens that is larger than the aperture of the projection lens is used. As the result, the opening portion of the lamp device is larger, so that the device is not suited as a compact headlight or optical member.

A lamp unit for vehicle according to Patent Document 2 is configured with a light-scattering optical face provided at the rear focal point of a projection lens in order to mitigate unevenness (illuminance unevenness) of light emitted by an LED optical source composed of a plurality of LEDs, wherein light emitted by each of the LEDs is caused to pass through the optical face to be combined together, and is then guided into the projection lens. The illumination light having been projected through scattering by that lens face, becomes optically uniform.

For example in FIG. 1, etc. of Patent Document 2, there is illustrated a configuration in which a projection lens (20) is composed of a plurality of lenses (21, 22); a face (S1) of the lens (21) closest to an optical source unit (30) is formed into a shape for scattering light; and this lens face (S1) is placed to be matched to the rear focal point of the projection lens (20).

Further, for example in FIG. 5, FIG. 6, etc. of Patent Document 2, there is illustrated a configuration in which a cylindrical light guide member (32) whose inside serves as a reflection face (31a) is provided between the projection lens (20) and the optical source unit (30); the face (S1) of the lens (21) closest to the optical source unit (30) is formed into a shape for scattering light; and an outlet port (31c) of the light guide member (32), the lens face (S1) for scattering light, and the rear focal point of the projection lens (20) are matched to the same position.

In the foregoing, the numerals in the parentheses are cited from those in Patent Document 2.

Because the surface of the projection lens is formed into a light-scattering shape as described above, it is possible to make uniform brightness produced by the respective LEDs; however, when the configuration in Patent Document 2 is used for passing light for in-vehicle use, a boundary between the upper dark portion and the lower light portion for passing light will be blurred due to the presence of the scattering face. Thus, this configuration is not suited for passing light that requires clear lightness and darkness in the upper and lower sides.

A headlight for vehicle according to Patent Document 3 is configured with a first reflection face being a planer face and a second reflection face being a curved face that are placed in the upper side and the lower side, respectively, so that an optical axis of an LED is sandwiched between them, wherein a short side of the first reflection face is matched to the focal point group of a projection lens.

For example in FIG. 8, etc. of Patent Document 3, there is illustrated an optical member (16B) in which a portion surrounded by the first reflection face (22) and the second reflection face (26) is filled with a resin (36). The light emitted by an LED optical source (12) is guided into a projection lens (14) while being reflected on the first and second reflection faces (22, 26), so that the utilization rate of the LED optical source (12) can be enhanced and a thin lamp device with a short depth can be configured (the numerals in the parentheses are cited from those in Patent Document 3).

However, the first and second reflection faces have to be subjected to surface treatment for reflection. Namely, each reflection face to be used is required to be mirror face, and in order to form such a reflection mirror, a plurality of processes, for example, a vapor deposition of a metal for reflection, an antioxidant treatment of the vapor deposited face, and the like become necessary. Accordingly, its unit price as a component rises. Further, because of the use of a plurality of components, the configuration becomes complex, so that there may also be a possibility that the assembly man-hours increase.

CITATION LIST

Patent Document

SUMMARY OF THE INVENTION

Problems to be Solved by the Invention

As described above, the configurations of above Patent Documents 1 to 3 have both merits and demerits, so that further improvements are just desired therefor.

This invention has been made from such a viewpoint, and an object thereof is to achieve a headlight for in-vehicle use that is small-sized but can produce a sufficient brightness, and further that is simple and inexpensive.

Means for Solving the Problems

A headlight for in-vehicle use of the invention comprises: an LED that constitutes an optical source and has a light-emitting face whose one edge side is linearly formed and placed at a side of an optical axis so that the center of the light-emitting face is displaced from the optical axis; two convex lenses that are arranged in a direction of the optical axis to constitute a projection lens; and a light distribution member that is placed between the LED and the projection lens, that is formed using a transparent material and that has, on its inner surface, a reflection face for reflecting the light emitted by the LED, so as to form a cut-off line at a projection-lens-side edge of the reflection face.

Effect of the Invention

According to the invention, because the projection lens is constituted by the two convex lenses, the light emitted by the LED can be used effectively even if the respective lenses are made small in diameter, so that it is possible to achieve a headlight for in-vehicle use that is small-sized but can produce a sufficient brightness. Further, because the light distribution member is formed using a transparent material and its inner surface is used as the reflection face, it is unnecessary to apply a mirror finishing thereto, so that an inexpensive headlight for in-vehicle use can be achieved with a simple configuration.

MODES FOR CARRYING OUT THE INVENTION

Hereinafter, for illustrating the invention in more detail, embodiments for carrying out the invention will be described according to the accompanying drawings.

As shown inFIG. 1, a headlight for in-vehicle use according to Embodiment 1 is an example of a projector-type headlight for passing light, and includes: an LED1for passing light having a light-emitting face1awhose one edge side is linear and given as a linear portion1b, said linear portion being placed at a side of an optical axis so that the center of the light-emitting face1ais displaced from the optical axis; a projection lens2constituted by a radiation-side convex lens2aand an LED-side convex lens2bthat are arranged in the direction of the optical axis; a light distribution member3that is placed between the LED1and the projection lens2, that is formed using a transparent material and that has, on its inner surface, a reflection face3afor reflecting the light emitted by the LED1, wherein a projection-lens-side edge3bof the reflection face3ais placed on the optical axis; a heat-dissipation and fixing member4that serves as a heatsink for the LED1and also as a member for fixing the LED1, the projection lens2and the light distribution member3; a casing5that accommodates them; and a front lens6.

The projection lens2as a set mainly serves such that the LED-side convex lens2bconverges the light emitted by the LED1and that the radiation-side convex lens2aprojects the light ahead of a vehicle. For example, if there is a lack of the LED-side convex lens2b, light L1agoing toward an upper side from the LED1is leaked out obliquely upward of the radiation-side convex lens2aand not utilized as illumination light of the headlight. In contrast, when the LED-side convex lens2bis provided, light L1going toward an upper side from the LED1is refracted in the LED-side lens2bto be incident on the radiation-side convex lens2a, and is thus radiated ahead of the vehicle. Hence, the light emitted by the LED1is utilized effectively.

Because the projection lens, that has heretofore been a single lens, is constituted by two lenses of the radiation-side convex lens2aand the LED-side convex lens2bas shown inFIG. 1, its focal point becomes shorter. Thus, it is possible to make a face of the LED-side convex lens2b, that is facing toward the LED1, closer to a focal point F in the side of the LED1of the projection lens2as a set, so that the LED-side convex lens2bcan be placed in the vicinity of the LED1and the light distribution member3.

Accordingly, even if small-aperture lenses are used as the projection lens2, it is possible to reduce a leakage of the light of the LED1emitted over a wide range, and thus to cause the light to be effectively incident on the projection lens2.

FIG. 2shows a condition of illumination light for passing light that is radiated from the headlight for in-vehicle use ahead of a vehicle, in which a bright portion of the illumination light is deeply depicted and a dark portion thereof is lightly depicted.

For the light distribution for passing light, it is essentially required to provide a dark portion at the upper side in the illumination light in order not to illuminate the driver of an oncoming vehicle, and thus it is required to darken the upper side and to lighten the lower side (road-surface side). The boundary between the upper dark portion and the lower light portion in the illumination light is a cut-off line.

Further, it is also required to brighten just below the cut-off line, namely, a portion that illuminates a place distant from the vehicle.

In order to fulfill the above requirements, the light distribution member3is interposed between the LED1and the projection lens2. Light that is emitted toward a lower side from the LED1and going toward an upper side of the cut-off line through the projection lens2, is reflected by the reflection face3aof the light distribution member3, so that the light is guided, in reverse, to just below the cut-off line (for example, L2inFIG. 1). This darkens the upper side in the illumination light, and at the same time, brightens a portion in the lower side just below the cut-off line, to thereby form a light distribution for passing light.

Note that, in order to form the cut-off line for passing light more clearly, it is desirable that the edge side of the light-emitting face1aof the LED1, that corresponds to the linear cut-off line and is placed in the side of the optical axis, be linearly formed into the linear portion1b.

In order that the edge side of the light-emitting face1aof the LED1is linear, an LED whose light-emitting face1ais rectangle may be used, or a plurality of LEDs may be used that are arranged so that their respective one sides become linear. Furthermore, as the LED1, a semiconductor optical source, such as a laser LED, an organic LED, etc. may be used.

Here, inFIG. 3, a positional relationship among the LED1, the projection lens2and the light distribution member3, and an example of the shape of the light distribution member3are shown. In the LED1, the light-emitting face1ais made perpendicular to the optical axis, and the linear portion1bof the light-emitting face1ais placed at the side of the optical axis so that the center of the light-emitting face1ais displaced from the optical axis.

The light distribution member3is formed of a transparent resin, a glass or the like, in which the reflection face3ain a planar form is formed on the optical-axis side in the light distribution member3, and the projection-lens-side edge3bof the reflection face3ais placed on the optical axis. An incident face3con which the light emitted by the LED1is incident and an outgoing face3dthrough which the incident light goes out to the LED-side convex lens2bare perpendicular to the optical axis. In such a configuration, in the light emitted from the LED1toward its lower side, light L3that is incident at a shallow angle on the reflection face3ainside the light distribution member3is totally reflected. Namely, it is possible to constitute a preferred reflection face3awithout applying a mirror finishing to the light distribution member3.

Further, with respect to the example of the shape of the light distribution member3shown inFIG. 3, in the projection-lens-side edge3bof the reflection face3a, a portion in the left side as viewed ahead of the vehicle (walking path-side) is made horizontal to provide a horizontal face3b-1and a portion in the right side as viewed likewise (oncoming lane-side) is made inclined downward to provide an inclined portion3b-2. Due to such a shape of the projection-lens-side edge3b, as shown inFIG. 2, it is possible to form a light distribution for passing light that can illuminate up to a higher position in the left side (walking path-side) while keeping the light-dark boundary in the right side (oncoming lane-side) horizontal.

As a matter of course, in a headlight for right-hand traffic, the shape of the projection-lens-side edge3bof the light distribution member3is right-to-left reversed, so that a portion in the right side as viewed ahead of the vehicle (walking path-side) provides a horizontal face3b-1and a portion in the left side as viewed likewise (oncoming lane-side) provides an inclined portion3b-2.

As described above, radiation is made while projecting the shape of the projection-lens-side edge3bof the reflection face3aahead of the vehicle using the projection lens2, so that a light distribution for passing light is formed.

Furthermore, in order to radiate the illumination light for passing light to an area from just front of the vehicle up to a distant place with a uniform light distribution, the projection-lens-side edge3bof the light distribution member3is placed in the vicinity of (within a predetermined distance from) the focal point F of the projection lens2as a set.

Here, referring toFIG. 4, an arrangement example of the focal point F of the projection lens2as a set will be described. A distance from an LED1-side face of the LED-side convex lens2bto the focal point F of the projection lens2as a set is defined as A, and a distance from the focal point F of the projection lens2as a set to the projection-lens-side edge3bof the light distribution member3is defined as B.

The phrase “in the vicinity of (within a predetermined distance from)”, that represents the positional relationship between the focal point F of the projection lens2and the projection-lens-side edge3bof the light distribution member3, means that the projection-lens-side edge3bis placed nearer to the projection lens2or to the LED1within one-fifth of the distance A relative to the focal point F of the projection lens2(namely, B≦A/5).

Preferably, it means that the projection-lens-side edge3bis placed nearer to the projection lens2or to the LED1within one-tenth of the distance A relative to the focal point F of the projection lens2(namely, B≦A/10).

More preferably, it means that the projection-lens-side edge3bis placed nearer to the projection lens2or to the LED1within one-fiftieth of the distance A relative to the focal point F of the projection lens2(namely, B≦A/50).

However, inFIG. 4, only the distance B in the case of placing the projection-lens-side edge3bnearer to the LED1relative to the focal point F of the projection lens2is shown, so that the distance in the case of placing the projection-lens-side edge3bnearer to the projection lens2is not shown.

It suffices to determine the distance for placing the projection-lens-side edge3brelative to the focal point F according to a demand for a light distribution of the illumination light. In this connection, when the projection-lens-side edge3bof the light distribution member3, that forms a cut-off line for passing light, is placed close to the focal point F of the projection lens2as a set, the cut-off line of the illumination light at a distant place ahead of the vehicle becomes clear, whereas the cut-off line of the illumination light at a nearby place of the vehicle is blurred. When the projection-lens-side edge3bof the light distribution member3is placed apart toward the LED1from the focal point F of the projection lens2as a set, the cut-off line of the illumination light at a nearby place ahead of the vehicle becomes clear, whereas the cut-off line of the illumination light at a distant place ahead of the vehicle is blurred.

Note that, the shape of the light distribution member3may be other than that shown inFIG. 3so long as it is a shape that can provide a planar face serving as the reflection face3ain the side toward the optical axis. As modified examples of the light distribution member3,FIG. 5(a)toFIG. 5(f)are shown.

A light distribution member3-1atFIG. 5(a)has a rectangular parallelepiped shape, in which a lower rectangular planar face is provided as the reflection face3a. A cut-off line for passing light is formed by the projection-lens-side edge3bof the lower reflection face3a. The cut-off line formed by the projection-lens-side edge3bof the light distribution member3-1is given to be linear so that its heights at the walking path-side and the oncoming road-side are the same.

A light distribution member3-2atFIG. 5 (b)has a shape obtained by inclining the incident face3cand the outgoing face3dof the light distribution member3-1shown atFIG. 5 (a), with respect to a plane perpendicular to the optical axis. The incident face3cand the outgoing face3dare inclined to be more toward the unshown projection lens2as a distance thereof increases from the optical axis. Because the light distribution member3-2is inclined so that its upper portion apart from the optical axis is more toward the projection lens2in such a manner, the light emitted by the LED1can be refracted at the incident face3cand the outgoing face3dto be guided toward the optical axis, so that it becomes unnecessary to place the linear portion1bof the light-emitting face1aof the LED1to abut on the optical axis.

In other words, the linear portion1bof the light-emitting face1aof the LED1can be placed apart from the optical axis.

A light distribution member3-3atFIG. 5(c)is that obtained by inclining downward a right-side (oncoming lane-side) edge in the reflection face3aof the light distribution member3-2shown atFIG. 5(b), as similar to the light distribution member3shown inFIG. 3, to form the inclined portion3b-2.

A light distribution member3-4atFIG. 5(d)is that obtained by forming the outgoing face3dof the light distribution member3-1shown atFIG. 5(a)into a curved shape so that the projection-lens-side edge3bis formed into a circular arc shape. When, due to aberration of the projection lens2, a focal point-equivalent line (focal point group) where the light passing through the projection lens2becomes parallel light, is not given as a straight line perpendicular to the optical axis but is given with a circular arc shape, the light distribution member3-4is used in which the projection-lens-side edge3bof the same circular arc shape is formed. Due to the shape of the projection-lens-side edge3b, it is possible to form light-dark portions in the upper and lower sides while making clear the cut-off line over a wide range from the center of the vehicle toward the right and left sides.

A light distribution member3-5atFIG. 5(e)has a shape obtained by inclining the incident face3cand the outgoing face3dof the light distribution member3-4shown atFIG. 5(d)with respect to a plane perpendicular to the optical axis, as similar to inFIG. 5(b).

A light distribution member3-6atFIG. 5(f)is that obtained by inclining downward a right-side (oncoming lane-side) edge of the reflection face3aof the light distribution member3-5shown atFIG. 5(e), as similar to the light distribution member3shown inFIG. 3, to form the inclined portion3b-2.

Not that, inFIG. 5(b),FIG. 5(c),FIG. 5(e)andFIG. 5(f), although both of the incident face3cand the outgoing face3dare inclined toward the projection lens2, only either one of them may be inclined instead.

Here, a configuration example of an optical system that uses the light distribution member3-3atFIG. 5(c)is shown inFIG. 6. Since the light distribution member3-3refracts to guide the light emitted by the LED1toward the optical axis, the linear portion1bof the light-emitting face1aof the LED1can be placed apart from the optical axis.

When it is necessary to take a large separation interval d between the linear portion1bof the LED1and the optical axis, an inclined angle θ of the light distribution member3-3is made larger or a thickness t of the light-emitting face3-3is made thicker so that the light emitted by the LED1is refracted largely toward the optical axis, to thereby make the apparent liner portion1bof the LED1as if it were closer to the optical axis.

Meanwhile, in the configuration example inFIG. 6, a heat-dissipation fin4afor dissipating heat generated by the LED1is mounted on the heat-dissipation and fixing member4. The heat-dissipation fin4amay be exposed to the outside of the casing5to thereby achieve enhancement in heat-dissipation ability.

In addition, in the configuration example inFIG. 6, the radiation-side convex lens2a, the LED-side convex lens2band the light distribution member3-3are formed of the same material (for example, an acrylic resin), and the LED-side convex lens2band the light distribution member3-3are molded integrally.

When the LED-side convex lens2band the light distribution member3-3are molded integrally, both of them are mutually fixed. Further, the LED-side convex lens2band the light distribution member3-3can be fabricated using the same material by a common process, so that a component member therefrom can be achieved that is highly accurate in their mutual positions and is low in cost. Furthermore, the configuration in which the incident face3cand the outgoing face3dof the light distribution member3-3are inclined, is favorable for a mold used for molding the LED-side convex lens2band the light distribution member3-3integrally, to ensure its draft angle.

InFIG. 6, in the projection lens2and under the optical axis, there are portions C1, C2where the light emitted by the LED1does not reach due to interruption by the reflection face3aof the light distribution member3-3. The portions C1, C2of the convex lenses where the light does not reach are useless and are optically non-problematic even if they are eliminated. Accordingly, the portions C1, C2where the light does not reach may be eliminated.

Here, inFIG. 7, examples of a convex lens that is usable as the radiation-side convex lens2aor the LED-side convex lens2bare shown. The convex lens shown as three-sided views atFIG. 7(a)is a standard convex lens whose one side is a convex face and the other side is a planar face. By using this convex lens as the radiation-side convex lens2aor the LED-side convex lens2b, lightness and darkness in the upper and lower sides of the cut-off line are produced due to refraction in up-down direction of the convex lens; the illumination light of the headlight is spread right and left due to refraction in right-left direction of the convex lens; and an inclined cut-off line is provided as being formed due to the inclined portion3b-2.

Note that the standard convex lens ofFIG. 7(a)serves to converge the light emitted by the LED1to the center (toward the optical axis) and thus, it is suited, in particular, to be used as the LED-side convex lens2b.

The convex lens ofFIG. 7(b)has a shape that is obtained by eliminating from the standard convex lens shown atFIG. 7(a), the portion C1or C2(namely, a part in the side lower than the optical axis) where the light does not reach as described usingFIG. 6, to thereby make a lower side D2from the optical axis smaller than an upper side D1therefrom. As shown inFIG. 8, this convex lens can be used as a radiation-side convex lens2a-1or an LED-side convex lens2b-1. This makes it possible to downsize the headlight for in-vehicle use in up-down direction.

In the headlight for in-vehicle use, with respect to the convex lens used as the radiation-side convex lens2aor the LED-side convex lens2b, it is not necessarily required to make equivalent its vertical refraction amount to its horizontal refraction amount as inFIG. 7(a), and thus, the lens may be a convex lens with an elliptical shape as shown atFIG. 7(c)or a convex lens in a semicircular-column shape as shown atFIG. 7(d).

When a curvature of the lens face is large, the passing light is largely refracted at the lens face, so that a convex lens with a short focal distance is formed. In contrast, when a curvature of the lens face is small, the refraction amount of the passing light is small, so that a convex lens with a long focal distance is formed.

By using, as a radiation-side convex lens2a-2, a convex lens with an elliptical shape in which the curvature in up-down direction is larger than the curvature in right-left direction as shown inFIG. 7(c), it is possible to radiate light horizontally over a wide range while making clear lightness and darkness in the upper and lower sides. Thus, it is possible to illuminate, for example, a pedestrian in a deep side of the walking path and a shoulder of the oncoming lane, so that a more preferable light distribution for the headlight can be formed.

When a convex lens in a semicircular-column shape as shown atFIG. 7(d)that has a convex-lens effect only in up-down direction is used as a radiation-side convex lens2a-3, although it is unable in up-down direction to form a light distribution with inclination for illuminating up to a higher position in the walking path-side like the case ofFIG. 7(c), it is possible in right-left direction to form a light distribution for the headlight that illuminates over a range wider than that in the case ofFIG. 7(c).

Note that, although a convex lens with an elliptical shape is shown atFIG. 7(c), this elliptical shape is shown for just illustrating that a curvature in up-down direction and a curvature in right-left direction are different to each other, and it is not problematic if an unwanted portion thereof is eliminated as shown inFIG. 7(b). Thus, so long as the convex lens has a lens face in which the curvature in up-down direction and the curvature in right-left direction are different to each other, it is unnecessary to pay a lot of attention to its outer shape.

Likewise, with respect also to the standard convex lens atFIG. 7(a), it is not problematic if its outer shape is quadrangular, for example, and thus, the outer shape is unnecessary to be a circular shape.

Further, the convex lens with an elliptical shape shown atFIG. 7(c)and the convex lens in a semicircular-column shape shown atFIG. 7(d)are shaped to be circularly curved in their shorter directions; however, they may be shaped to be circularly curved in their longer directions. Furthermore, it is allowable to form a fine unevenness on the surface to thereby blur the illumination light.

Further, while, as convex lenses, there are those of a type in which the convex face is spherical and a type in which it is non-spherical, the convex lens of either one of these types is usable as the radiation-side convex lens2aor the LED-side convex lens2b. Furthermore, while, as convex lenses, there are those of types in which both of front and back faces are convex faces, in which one of the faces is a convex face and the other is a flat face (for example,FIG. 7(a)), and in which one of the faces is a convex face and the other is a concave face or the like, the convex lens of any one of these types is usable as the radiation-side convex lens2aor the LED-side convex lens2b.

Moreover, as the radiation-side convex lens2aor the LED-side convex lens2b, a Fresnel lens is also usable.

InFIG. 9, a configuration example of an optical system in which a Fresnel lens is used as an LED-side convex lens2b-4is shown. Because of providing the Fresnel lens as the LED-side convex lens2b-4, a thick-walled portion at the center of the convex lens can be made thinner, to thereby save its weight and reduce its component unit price.

When a Fresnel lens is used as the radiation-side convex lens2a, there may be a case that is inappropriate in design because concentric rings of the Fresnel lens can be seen through the front lens6at the time the headlight for in-vehicle use is viewed from the front; however, when it is used as the LED-side convex lens2b-4, the rings cannot be seen through the front lens6, so that there is no case of affecting the design in appearance of the vehicle.

Consequently, according to Embodiment 1, the headlight for in-vehicle use is configured to include: the LED1that has the light-emitting face1awhose one edge side is formed as the linear portion1band placed at the side of the optical axis so that the center of the light-emitting face1ais displaced from the optical axis; the radiation-side convex lens2aand the LED-side convex lens2bthat are arranged in the direction of the optical axis to constitute the projection lens2; and the light distribution member3that is placed between the LED1and the projection lens2, that is formed using a transparent material and that has, on its inner surface, the reflection face3afor reflecting the light emitted by the LED1, so as to form a cut-off line at the projection-lens-side edge3bof the reflection face3a.

Because the projection lens2is thus constituted by the radiation-side convex lens2aand the LED-side convex lens2b, the focal distance becomes shorter and thus, the projection lens2and the LED1can be placed close to each other, so that, even if small-aperture lenses are used as the projection lens2, it is possible to cause the light emitted by the LED1to effectively incident on the projection lens2. Accordingly, it is possible to achieve a headlight for in-vehicle use that is small-sized but can produce a sufficient brightness. Furthermore, because a low-power LED1can be used and thus the power consumption can be lower, it is allowable to make smaller the heat dissipation member of the heat-dissipation and fixing member4. This results in downsizing of the headlight for in-vehicle use.

Further, because the light distribution member3is formed using a transparent material and its inner surface is used as the reflection face3a, a previously-described mirror finishing as in Patent Document 3 becomes unnecessary, so that an inexpensive headlight for in-vehicle use can be achieved with a simple configuration.

Further, according to Embodiment 1, the focal point F of the projection lens2as a set being formed by the radiation-side convex lens2aand the LED-side convex lens2b, is placed within a predetermined distance from the projection-lens-side edge3bof the light distribution member3, so that a headlight for in-vehicle use with an appropriate light distribution can be achieved.

Further, according to Embodiment 1, as shown inFIG. 5, the light distribution members3-2,3-3,3-5,3-6are each configured to include: the incident face3cwhich is facing toward the LED1and on which the light emitted by the LED1is incident; and the outgoing face3dwhich is facing toward the projection lens2and through which the incident light goes out, wherein either one of the incident face3cand the outgoing face3d, or each of these faces, is inclined with respect to a plane perpendicular to the optical axis. In more detail, it is so configured that at least the incident face3dis inclined to be more toward the projection lens2as a distance increases from the optical axis.

Thus, the light emitted by the LED1that is placed at a position apart from the optical axis, can be refracted at either one of the incident face3cand the outgoing face3d, or each of these faces, to be guided toward the optical axis. Thus, a light-emitting direction in which light is brightly emitted by the LED1can be directed to near a portion just below the cut-off line, so that a headlight for in-vehicle use can be achieved that radiates illumination light for passing light which is bright at just below the cut-off line.

Further, according to Embodiment 1, as shown inFIG. 6, it is so configured that the light distribution member3-3is fixed to the LED-side convex lens2b. In addition, the light distribution member3-3and the LED-side convex lens2bare formed using a same type of resin. Thus, the LED-side convex lens2band the light distribution member3-3can be fabricated using the same material by a common process, so that a component member therefrom can be achieved that is highly accurate in their mutual positions and is low in cost.

Note that, with respect not only to the light distribution member3-3but also to a light distribution member in another shape, it may be fixed likewise to the LED-side convex lens2b.

Further, according to Embodiment 1, as shown inFIG. 8, it is so configured that, in either one or both of the radiation-side convex lens2a-1and the LED-side convex lens2b-1, the portions C1, C2(FIG. 6) where the light emitted by the LED1does not reach are eliminated, so that the lens differs in size between its upper side and its lower side from the optical axis. Thus, a small-sized headlight for in-vehicle use can be achieved.

Further, according to Embodiment 1, as shown inFIG. 7, it is so configured that either one or each of the lens faces of the radiation-side convex lens2a-2,2a-3and the LED-side convex lens2b-2,2b-3, has a curvature in up-down direction and a curvature in right-left direction that are different to each other. By thus making a difference between the curvatures of the lens face to thereby make a difference between the refraction amounts of the projection lens2in up-down direction and right-left direction, a headlight for in-vehicle use with a more preferred light distribution can be achieved.

Further, according to Embodiment 1, as either one or each of the radiation-side convex lens2aand the LED-side convex lens2b, a non-spherical lens may be used. When a lens with an arbitrary optical property is used in this manner, a headlight for in-vehicle use with an appropriate light distribution can be achieved.

Further, according to Embodiment 1, as either one or each of the radiation-side convex lens2aand the LED-side convex lens2b, a Fresnel lens may be used. This allows the convex lens to become thinner and lighter, and to reduce its component unit price.

Further, according to Embodiment 1, as shown inFIG. 3andFIG. 5, the light distribution members3,3-3,3-6are each configured into a shape in which, in the projection-lens-side edge3bof the reflection face3a, a portion in the oncoming lane-side is inclined downward. Thus, it is possible to achieve a headlight for passing light with a light distribution in which illumination light radiated ahead of a vehicle illuminates up to a higher position in the walking path-side but does not dazzle the driver driving an oncoming vehicle (does not illuminate an eye location of the driver).

FIG. 10is a diagram showing a configuration example of an optical system of a headlight for in-vehicle use according to Embodiment 2. In Embodiment 2, the LED1for passing light is placed in the upper side of the optical axis, and further, a second LED11for upper-side illumination is placed in the lower side of the optical axis. In more detail, the linear portion1bin the lower side of the light-emitting face1aof the LED1for passing light is placed apart by a separation interval d from the optical axis, and a linear portion11bin the upper side of a light-emitting face11aof the LED11for upper-side illumination is placed to be matched to the optical axis.

These LEDs1,11, radiation-side convex lens2a, LED-side convex lens2band light distribution member3-3are fixed to the heat-dissipation and fixing member4shown inFIG. 1, and are accommodated in the casing5and the front lens6, to provide the headlight for in-vehicle use.

Note that inFIG. 10, the same reference numerals are given to the same or equivalent parts inFIG. 1toFIG. 9, so that their description is omitted here.

FIG. 11shows a condition of illumination light for driving light that is radiated ahead of a vehicle when the LED1for passing light and the LED for upper-side illumination are lighted at the same time, in which a bright portion of the illumination light is deeply depicted and a dark portion thereof is lightly depicted.

The lower side of a cut-off line is illuminated by the LED1for passing light placed in the upper side of the optical axis, and the upper side of the cut-off line is illuminated by the LED11for upper-side illumination placed in the lower side of the optical axis, so that a light distribution for driving light can be formed. By turning off the LED11for upper-side illumination while lighting the LED1only, it is possible to switch to the passing light shown inFIG. 2.

Note that the separation interval d is an interval that is reluctantly formed because, when the LED11for upper-side illumination is to be provided additionally to the LED1for passing light, the light-emitting face1aof the LED1cannot be joined to the light-emitting face11aof the LED11due to the electrodes for connection, etc. being placed on the edges of these LEDs1,11. Even with the separation interval d, as described in Embodiment 1, the light emitted by the LED1can be refracted to be guided toward the optical axis using the light distribution member3-1,3-3,3-5or3-6inFIG. 5. This is equivalent to placing the linear portion1bon the optical axis by optically cancelling the separation interval d. Accordingly, in the illumination light for driving light, no dark portion corresponding to the separation interval d between the LEDs1, emerges, so that it is possible to obtain preferred illumination light.

Although the light distribution member3-3is placed in the upper side of the optical axis inFIG. 10, it may inversely be placed in the lower side of the optical axis.

Here, such a modified example of the optical system is shown inFIG. 12. InFIG. 12, the linear portion1bin the lower side of the light-emitting face1aof the LED1for passing light is placed to be matched to the optical axis, and the linear portion11bin the upper side of the light-emitting face11aof the LED11for upper-side illumination is placed apart by the separation interval d from the optical axis. Further, in the lower side of the optical axis, a light distribution member3-7having a shape inclined to become more toward the projection lens2as a distance from the optical axis increases is placed, so that the separation interval d is optically cancelled to thereby equivalently place the linear portion11bof the LED11for upper-side illumination on the optical axis. This makes it possible to obtain preferred illumination light when the LED1for passing light and the LED11for upper-side illumination are lighted at the same time, without emergence of a dark portion corresponding to the separation interval d in the illumination light for driving light. Note that, the inner side of the reflection face3aof the light distribution member3-7reflects the light emitted by the LED11for upper-side illumination, whereas the outer side of the reflection face3areflects the light emitted by the LED1for passing light.

As shown inFIG. 10, when the light emitted by the LED1for passing light passes through the light distribution member3-3, because of the refraction index of the light distribution member3-3, the distance between the LED1and the projection lens2becomes as if it were apparently shorter, so that the light emitted by the LED1is efficiently guided to the LED-side convex lens2band thus, bright light is radiated ahead of the vehicle. In contrast, as shown inFIG. 12, when the light emitted by the LED1does not pass through the light distribution member3-7, the LED1and the projection-lens-side edge3bof the reflection face3ado not become closer to each other, so that an influence by unevenness of the light emitted by the LED1is mitigated, and thus a clear cut-off line is radiated. Accordingly, it suffices to select either the configuration ofFIG. 10orFIG. 12, according to a demand for a light distribution of the illumination light.

Consequently, according to Embodiment 2, the headlight for in-vehicle use is so configured that the second LED11for upper-side illumination different to the LED1for passing light, is placed on the opposite side by which the optical axis is sandwiched, to thereby illuminate the upper side of the cut-off line. Thus, it is possible to achieve a headlight for in-vehicle use that is capable of radiating a light distribution for passing light by lighting only the LED1, and radiating a light distribution for driving light by lighting both of the upper and lower LEDs1,11at the same time, and thus that can light up the passing light or the driving light in a switched manner (that can work both for the passing light and for the driving light).

It should be noted that unlimited combination of the respective embodiments, modification of any configuration element in the embodiments and omission of any configuration element in the embodiments may be made in the present invention without departing from the scope of the invention.

INDUSTRIAL APPLICABILITY

As described above, the headlight for in-vehicle use according to the invention is configured to efficiently project the light emitted by an LED ahead of a vehicle using two convex lenses and a transparent light distribution member for forming a cut-off line, so that it is suited to be used as a headlight for passing light or the like.

DESCRIPTION OF REFERENCE NUMERALS AND SIGNS