Headlamp with beam distribution switch mechanism

Abstract: 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.

Description: 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, which is difficult to include two light sources for the high beam and the low beam. 2. Background Art An example of the 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 a 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 becomes 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 a 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 mechanism will be complicated and large, resulting in a high cost. The French published patent application FR-A-1376728 discloses a projector lamp with a cylindrical hood having two windows. The lower one of the windows can be closed by means of a moving member. By closing the lower window of the hood the itensity of the light emitted can be changed, but a switching operation from a low beam distribution to a high beam distribution is not possible. EP-A 0 380 396 discloses a projector lamp having a beam switch mechanism for selecting a low beam distribution and a high beam distribution by moving a member. This is done in order to provide the head light in which the photometric characteristics of the beam, and in particular the definition and the position of the cut off a dipped beam or of a fog light beam, are independent of any possible play or inaccuracy that may exist in the position of a masking screen used for forming the beam in question. US-A-1834542 discloses a head light for automobiles, which comprises a reflector and a light source in combination with an extendible and contractible shade consisting of a plurality of shade sections hinged to each other and being rotabte on a common axis around the light source. SUMMARY OF THE INVENTION An object of the present invention is to provide a headlamp that does not need to move a moving member in a 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 distrbution with an ensured accuracy and without a variation by a 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 of light emitted from a light source, 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 with being 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. BRIEF DESCRIPTION OF THE DRAWINGS These and other objects and advantages of the present invention will become clear from the description with reference to the accompanying drawings, wherein: Fig. 1 is a cross section of the headlamp in accordance with a first embodiment of the present invention; Fig. 2 is a perspective view of a hood that is the principal part of the headlamp shown in Fig. 1; Fig. 3 is a schematic illustration showing the headlamp shown in Fig. 1 generating the low beam distribution; Fig. 4 is a schematic illustration showing the headlamp shown in Fig. 1 generating the high beam distribution; Fig. 5 illustrates the low beam distribution generated by the headlamp shown in Fig. 1; Fig. 6 illustrates an auxiliary beam distribution generated by the headlamp shown in Fig. 1; Fig. 7 illustrates the high beam distribution generated by the headlamp shown in Fig. 1; Fig. 8 is a cross section of the headlamp in accordance with a second embodiment of the present invention; Fig. 9 is a perspective view of the principal part of the headlamp in accordance with a third embodiment of the present invention; and Fig. 10 is a cross section of the headlamp in the prior art. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention is described in detail hereinafter with reference to an embodiment 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 proper 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 that 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 position 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, is securely fixed to each other. Therefore, there is little possibility to cause a 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 a 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.

Claims: A headlamp having a beam distribution switch mechanism for selecting a low beam distribution or a high beam distribution of light emitted from a light source (2), characterized in that the beam distribution switch mechanism comprises a hood (3) including a fixed member (31; 61) having a cut portion (31a; 33a; 61a) on the upper or the lower side thereof and a moving member (32; 43; 62) for opening and dosing the cut portion (31a; 33a; 61a) of the fixed member (31), a reflecting mirror (4) including a first reflecting surface (41) for reflecting the light beam from the light source (2) when the cut portion (31 a; 33a) of the hood (3) is closed so as to generate the low beam distribution, and a second reflecting surface (42; 43) for reflecting the light beam passing through the cut portion (31a) from the light source (2) when the cut portion (31a; 33a; 61a) is opened so as to generate an auxiliary beam distribution that is added to the low beam distribution to generate the high beam distribution. The headlamp according to claim 1, characterized in that the fixed member (31) is formed in a box shape having an opening (3a) on the rear side, the moving member (32; 43) is a platy member disposed in parallel to and pivoted to the side (31b) that has the cut portion (31a; 33a) by a pivot shaft (32a), and the cut portion (31a; 33a) is opened or closed by rotating the moving member (32; 34). The headlamp according to claim 1, characterized in that the fixed member is formed in a box shape having an opening (6a) on the rear side, the moving member (62) is a saddle-like member disposed inside the fixed member (61) with being pivoted to each side face (61b) of the fixed member (61) that is perpendicular to the side that has the cut portion (61 a) by a pair of pivot shafts (62c), and the cut portion (61 a) is opened or closed by swinging the moving member (62).

Inventors: IWASAKI HIROSHI, SATO TAKASHI, TANIUCHI HITOSHI, IWASAKI, HIROSHI, SATO, TAKASHI, TANIUCHI, HITOSHI
Applicants: STANLEY ELECTRIC CO LTD, STANLEY ELECTRIC CO., LTD.
Application year: 1998
Main classification: F21V14
IPC codes: F21V14, F21V7