Headlamp with beam distribution switch mechanism

A headlamp 1 has a beam distribution switch mechanism that comprises a hood 3 and a reflecting mirror 4. The hood 3 includes a fixed member 31 having a cut portion 31a on the upper side and a moving member 32 for opening and closing the cut portion. The reflecting mirror 4 includes a first reflecting surface 41 for reflecting the light beam from the light source 2 when the cut portion 31a is closed and the second reflecting surface 42 for reflecting the light beam from the light source 2 when the cut portion 31a is opened.

BACKGROUND OF THE INVENTION
 1. Field of the Invention
 The present invention relates to a headlamp for a car or other vehicles.
 More specifically, the present invention relates to a headlamp using a
 metal halide discharge lamp such as an iodine lamp for a light source, in
 which is difficult to include two light sources for the high beam and the
 low beam.
 2. Background Art
 An example of a headlamp in the prior art that uses a discharge lamp as a
 light source and has a switch mechanism for selecting the high beam
 distribution or the low beam distribution is disclosed in Japanese
 Unexamined Patent Publication No. Hei 8-111101. As shown in FIG. 10, the
 principal part of the headlamp 90 includes a discharge lamp 91, a
 reflecting mirror 93 and a lever 92 that is placed vertically with a
 rocking pin 92a disposed above the discharge lamp 91. The discharge lamp
 91 is attached to the lever 92, and the light source 91a that is a burner
 of the discharge lamp 91 is positioned substantially on the optical axis Z
 when the discharge lamp 91 is in the low beam position. When switching to
 the high beam position, the lever 92 is rotated in the backward direction
 for a predetermined angle .alpha. around the rocking pin 92a by the
 actuator 94 such as a motor or a solenoid. Then, the position of the
 discharge lamp 91 is moved backward and downward from the low beam
 position with respect to the reflecting mirror 93, so that the discharge
 lamp 91 moves into the high beam position.
 However, in the above-mentioned switching mechanism for selecting the high
 beam distribution or the low beam distribution in the prior art, it is
 essential to maintain very high accuracy of the relative position of the
 light source 91a to the reflecting mirror 93 in order to obtain a
 predetermined characteristic of the light distribution. Therefore, the
 light source 91a should be moved between the low beam position and the
 high beam position with high accuracy. However, the accuracy can be
 deteriorated by vibration, an impact, an abrasion due to a repeated
 movement of the light source or other factors when the car is moving. In
 order to solve this problem, the known mechanism is complicated and large,
 resulting in a high cost.
 SUMMARY OF THE INVENTION
 An object of the present invention is to provide a headlamp that does not
 need to move a moving member with high accuracy when switching the low
 beam distribution to the high beam distribution or vice versa by moving
 the member.
 Another object of the present invention is to provide a headlamp that has a
 simple mechanism for switching the low beam distribution and the high beam
 distribution with an ensured accuracy and without being subject to a
 variation due to vibration, an impact, an abrasion due to a repeated
 movement or other factors when the car is moving.
 Another object of the present invention is to provide a headlamp that
 satisfies the above mentioned characteristics and can be compact in size.
 According to an aspect of the present invention, in a headlamp having a
 beam distribution switch mechanism for selecting the low beam distribution
 or the high beam distribution, the beam distribution switch mechanism
 comprises a hood including a fixed member having a cut portion on the
 upper or the lower side and a moving member for opening and closing the
 cut portion of the fixed member, a reflecting mirror including a first
 reflecting surface for reflecting the light beam from the light source
 when the cut portion of the hood is closed so as to generate the low beam,
 and a second reflecting surface for reflecting the light beam passing
 through the cut portion from the light source when the cut portion is
 opened so as to generate an auxiliary beam distribution that is added to
 the low beam distribution to generate the high beam distribution.
 According to another aspect of the present invention, the fixed member of
 the above-mentioned headlamp is formed in a box shape having an opening on
 the rear side, the moving member is a platy member disposed in parallel to
 and pivoted to the side that has the cut portion by a pivot shaft, and the
 cut portion is opened or closed by rotating the moving member.
 Furthermore, according to another aspect of the present invention, the
 fixed member of the above-mentioned headlamp is formed in a box shape
 having an opening on the rear side, the moving member is a saddle-like
 member disposed inside the fixed member and is pivoted to each side face
 of the fixed member that is perpendicular to the side that has the cut
 portion by a pair of pivot shafts, and the cut portion is opened or closed
 by swinging the moving member.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
 The present invention is described in detail hereinafter with reference to
 embodiments shown in the accompanying drawings.
 As shown in FIG. 1, headlamp 1 according to the present invention comprises
 a light source 2, a hood 3, a reflecting mirror 4 and a lens 5. This
 headlamp 1 of the present invention also comprises a beam distribution
 switch mechanism for selecting the low beam distribution or the high beam
 distribution which is composed of the hood 3 and the reflecting mirror 4.
 FIG. 2 shows a structure of the hood 3 that is a part of the beam
 distribution switch mechanism. The hood 3 is formed substantially in a box
 shape that has an opening 3a at one side. The hood 3 comprises a fixed
 member 31 having a cut portion 31a on one side adjacent to the opening 3a,
 and a platy moving member 32 that is disposed parallel to the side 31b
 with the cut portion 31a of the fixed member 31 and is pivoted to a side
 31b by a pivot shaft 32a. The moving member 32 has a lever member 32b,
 which is actuated by appropriate means such as a solenoid or a motor (not
 shown), so that the cut portion 31a can be closed or opened selectively.
 As shown in FIG. 1, the hood 3 covers the light source 2 so that the light
 beam can reach the reflecting mirror 4 within a proper range, as explained
 in detail later. In addition, the hood 3 is provided with a proper stay
 (not shown) for connecting the hood 3 to the reflecting mirror 4 to make a
 unit, and the relative position between the hood 3 and the reflecting
 mirror 4 is hardly altered. Furthermore, the light source 2 is also fixed
 to the reflecting mirror 4 by a socket for example, and the relative
 position between the light source 2 and the reflecting mirror 4 is hardly
 altered.
 FIGS. 3 and 4 show the reflecting mirror 4 that is a part of the beam
 distribution switch mechanism, the light source 2 and the hood 3, and
 particularly illustrates the relationship between the action of the hood 3
 and the light source 2. First, in the state that the cut portion 31a of
 the hood 3 is closed by the moving member 32 as shown in FIG. 3, in an
 area that the light beam from the light source 2 reaches a first
 reflecting surface 41 is formed on the reflecting mirror 4. The first
 reflecting surface 41 is formed in the shape such as to generate the low
 beam distribution S as shown in FIG. 5.
 One example of the method for generating the low beam distribution is as
 follows. The first reflecting surface 41 is formed in a paraboloid shape,
 and the light source 2 is disposed properly in front of the focal point of
 the paraboloid. In addition, a part of the light beam from the light
 source 2 that can reach the lower potion of the first reflecting surface
 41 is cut by the hood 3. Then, the reflected light beam that is generated
 by the first reflecting surface 41 does not contain the upward light beam.
 Then, the reflected light beam is diffused horizontally by the lens cut 5a
 (see FIG. 1) provided to the lens 5, so that the substantial low beam
 distribution can be obtained.
 FIG. 4 shows the state wherein the moving member 34 is moved so as to open
 the cut portion 31a of the hood 3. In this state, the light beam from the
 light source 2 passes through the cut portion 31a to be added to the light
 beam that reaches the first reflecting surface 41. Furthermore in the
 present invention, a second reflecting surface 42 is formed on the
 reflecting mirror 4 in the area that the light beam passing through the
 cut portion 31a reaches.
 In this structure, the second reflecting surface 42 generates a reflected
 light beam shown as an auxiliary beam distribution A in FIG. 6, which
 contains a slightly upward beam and is emitted horizontally to reach to a
 distance in front of the vehicle. This auxiliary beam distribution A is
 added to the low beam distribution S generated by the first reflecting
 surface 41 so as to generate the composed beam that can be used as a high
 beam distribution M as shown in FIG. 7.
 Next, actions and effects of the headlamp 1 having the above-mentioned
 structure according to the present invention will be explained. In the
 structure of the present invention, only the moving member 32 provided to
 the hood 3 moves when switching from the low beam distribution M to the
 high beam distribution S or switching vice versa. The moving member 32
 moves only for opening or closing the cut portion 31a. Therefore, not so
 high accuracy is required, but stoppers or the like provided to both ends
 of the rotation range, for example, will provide a sufficient accuracy.
 Furthermore, in the present invention, the relative positions among the
 light source 2, the hood 3 and the reflecting mirror 4, for example, which
 requires high accuracy for generating a proper light beam distribution,
 are securely fixed. Therefore, there is little possibility to cause
 variation by a vibration, an impact, an abrasion due to a repeated
 movement or other factors when the car is moving, and the switching
 accuracy can be ensured with the above-mentioned simple structure.
 FIG. 8 shows a second embodiment of the present invention. On the contrary
 to the first embodiment in which the upper side of the fixed member 31 of
 the hood 3 is provided with the cut portion 31a and the moving member 34,
 this embodiment has a cut portion 33a and a moving member 34 on the lower
 side of the fixed member 33 of the hood 3. The upper side of the fixed
 member 33 in this embodiment is made in the shape such that the cut potion
 31a in the first embodiment is closed.
 The reflecting mirror 4 is provided with a first reflecting surface 41 for
 generating the low beam in the area that the light beam from the light
 source 2 reaches when the cut portion 33a is closed. Since the upper side
 of the fixed member 33 is made in the shape such that the cut potion 31a
 in the first embodiment is closed, the first reflecting surface 41 should
 be made basically in the same area and shape as in the first embodiment.
 Furthermore, the reflecting mirror 4 is also provided with a second
 reflecting surface 43 in the area that the light beam from the light
 source 2 reaches when the cut portion 33a is opened. The second reflecting
 surface 43 is formed in a paraboloid shape whose focal point is the light
 source 2, for example. Then, the reflected light beam from the second
 reflecting surface 43 contains a slightly upward beam and is emitted
 horizontally to reach to a distance in front of the vehicle. Therefore,
 the high beam distribution can be obtained by adding this reflected light
 beam to the low beam distribution.
 In this embodiment, the first reflecting surface 41 and the second
 reflecting surface 43 are formed in the upper area and the lower area with
 respect to the light source, while the first embodiment have to employ the
 second reflecting surface 42 formed in the above area of the first
 reflecting surface 41. Thus, the present embodiment can facilitate a
 compact size of the headlamp 1.
 FIG. 9 shows a principal part of the headlamp 1 according to the third
 embodiment of the present invention. In this embodiment too, the hood 6 is
 formed substantially in a box shape having the opening 6a in the rear
 side. This hood 6 comprises a fixed member 61 having a cut portion 61a
 adjacent to the opening 6a, and a moving member 62 for opening or closing
 the cut portion 61a of the fixed member 61.
 In this embodiment, the moving member 62 has a substantially rectangular
 shape. More specifically, the moving member 62 is formed in a saddle-like
 shape having a back portion 62a for closing the cut portion 61a and a pair
 of leg portions 62b hanging from each end of the back portion 62a
 perpendicularly. The moving member 62 is pivoted to each side face 61b of
 the fixed member 61 at each leg portion 62b by a pair of pivot shafts 62c.
 The side face 61b of the fixed member 61 is perpendicular to the upper
 side provided with the cut portion 61a.
 The moving member 62 is disposed inside the fixed member 61 and attached to
 the inside of the fixed member 61. One of the leg portions 62b is extended
 to make a lever portion 62d, which is manipulated so that the back portion
 62a of the moving member 62 swings backward and forward. Thus, the cut
 portion 61a is opened or closed, so that the same effect can be obtained
 as the preceding embodiments.
 As mentioned above, according to the present invention, the low beam
 distribution and the high beam distribution can easily switched by the
 simple action, i.e., opening or closing the cut portion without changing
 the relative positions among the light source, the reflecting mirror and
 the hood that require a high accuracy. Thus, excellent effects can be
 obtained for cost reduction and improvement of reliability, that is little
 possibility of causing variation by a vibration, an impact, an abrasion
 due to a repeated movement or other factors when the car is moving.
 While the presently preferred embodiments of the present invention have
 been shown and described, it will be understood that the present invention
 is not limited thereto, and that various changes and modifications may be
 made by those skilled in the art without departing from the scope of the
 invention as set forth in the appended claims.