JPS6293851A - Headlight for vehicle - Google Patents

Abstract

PURPOSE:To improve the heating efficiency of a light emission tube by arranging a preheater below the light emission tube while to protect a vehicle on the opposite lane from glare by positioning the center of light emission at the same position or in front of the focus position of a reflection mirror. CONSTITUTION:Since it is lighted while bringing an outer tube 1 into horizontal and a preheater 3 is arranged below a light emission tube 2, the light emission tube 2 is subjected to the radiation heat and the convection heat from the preheater 3 thus to improve the heating efficiency. If the center of light emission LO of the light emission tube 2 is in front of the focus point F, the downward light C will increase to reduce the upward light A, B considerably thus to never cause glare for a vehicle on the opposite lane. Consequently, when positioning the center of light emission LO at same position or in front of the focus position F, it will never cause glare for a vehicle on the opposite lane even if the preheater 3 is arranged at the underside of the light emission tube 2.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a vehicle headlamp that uses a small high-pressure metal vapor discharge lamp such as a metal halide lamp or a high-pressure sodium lamp as a light source.

[Conventional technology]

For example, incandescent bulbs have traditionally been used as the light source for vehicle headlights, but incandescent bulbs have drawbacks such as low luminous efficiency and short lifespan, requiring frequent replacement of lamps. There are problems such as.

On the other hand, discharge lamps are known as light sources with high luminous efficiency and long life. For example, fluorescent lamps, which are low-pressure discharge lamps, are used as interior lights in buses and trains. However, even if it is attempted to use a fluorescent lamp as a headlamp light source, it is too large to be applied.

For this reason, high-pressure metal vapor discharge lamps, which have much higher luminous efficiency than fluorescent lamps and can be easily miniaturized,
For example, research is underway to use metal halide lamps and high-pressure sodium lamps as light sources for headlights.

When such a high-pressure metal vapor discharge lamp is used as a light source for headlights, its power source is the battery installed in the vehicle, that is, 12V (Pol 1-) or 24V DC. High pressure metal vapor discharge lamp is 10
It is constructed in a small size of 0W (watt) or less, and uses a battery as a power source for direct current lighting.

Incidentally, vehicle headlights are required to turn on instantaneously and to produce instantaneous luminous flux. However, metal vapor discharge lamps generally have problems in that they are difficult to start and require several minutes to several tens of minutes for the luminous flux to rise.

When metal vapor discharge lamps with such properties are used as a light source for vehicle headlights, applying high-voltage pulses has become more likely to achieve instant lighting.
Immediate improvements are now required regarding the rise of the luminous flux.

Conventionally, a method has been considered in which the arc tube is heated with a heater. For example, Japanese Patent Application Laid-Open No. 51-4881 discloses a technique in which a heat-retaining heater is placed near the coldest part of an arc tube. However, the purpose of the invention disclosed in the above publication is to adjust the color temperature of the lamp by changing the heating water of the heater depending on the current flowing through the heater, and by arbitrarily changing the temperature of the coldest part of the arc tube from the outside. However, it is also thought to be related to the improvement of the luminous flux rise of the lamp, which is the problem mentioned above.

Therefore, if a heater is installed near the arc tube and the arc tube is heated by this heater in advance before starting, the metal sealed inside the arc tube will have been evaporated, and the specified luminous flux can be obtained almost immediately after starting. It is.

However, in the past, it was thought that the arc tube would be heated only by the radiant heat of the preheater, so the temperature rise rate of the arc tube was low and the rise time of the luminous flux could not be shortened enough for practical use. was there.

On the other hand, the preheating heater must not cause discharge within the outer tube due to the high voltage pulse applied when starting the arc tube. For this reason, it is possible to cover the heating element with an insulator, and the use of a ceramic heater is optimal. Such a ceramic heater is placed near the arc tube in order to efficiently heat the arc tube.

[Problem that the invention seeks to solve]

However, when the above ceramic heater is placed near the arc tube, this ceramic heater blocks the light emitted from the arc tube, and changes the light distribution characteristics of the beam light irradiated by the reflector from the vehicle headlight. There are cases where the characteristics differ from those required for the lamp. Therefore, the present invention improves the heating efficiency of the arc tube by the preheating heater, and utilizes the light shielding effect of the preheating heater in an efficient manner for the light distribution characteristics required by the vehicle headlight, thereby improving the light distribution characteristics of the vehicle. The purpose of this project is to provide a headlamp for use in vehicles.

[Means for solving problems]

The present invention is based on the fact that the headlights of recent vehicles tend to be made thinner due to car design. Therefore, the metal vapor discharge lamp used as a light source is not only made smaller as described above, but also has an anode and a cathode arranged in the front and rear direction. In order to accommodate the fact that the lamp is installed inside the reflector in a so-called horizontal lighting position, we installed a preheater with a light-shielding function below the arc tube, and also installed such a small high-pressure metal vapor discharge lamp in the reflector. , the light emitting center of the arc tube is located at the same position as the focal position of the reflecting mirror or in front of the focal position.

[Effect]

According to this configuration, since the preheater is installed below the arc tube, the arc tube is heated by convection heat in addition to the radiant heat from the preheater, improving the heating efficiency of the arc tube. Small high pressure metal vapor discharge lamps such as
Since the light emitting center of the arc tube is located at the same position as the focal position of the reflector or ahead of the focal position, the light shielding effect of the preheater restricts the upward light in the beam, causing glare to oncoming vehicles. will no longer be given.

[Embodiments of the invention]

The present invention will be described below based on an embodiment shown in the drawings.

FIG. 1 is a diagram showing a schematic configuration of a 35 W metal halide lamp that is lit by a DC power source, and 1 is an outer bulb. Inside the outer tube 1, an arc tube 2 and a preheater 3 are housed.

The arc tube 2 has an anode 4a and a cathode 4b disposed opposite to each other at both ends of a bulb made of quartz glass. It is connected to arc tube lead wires 7a, 7b via foils 6a, 6b. Arc tube lead wire 7a
, 7b pass through the sealing portion 1a of the outer tube 1 in an airtight manner.

The arc tube 2 is filled with a starting rare gas, mercury, and scandium iodide and sodium iodide as metal halides.

Such an arc tube 2 has the above-mentioned Iiii pole 4a and the negative pole 1i4.
b is accommodated in the outer tube 1 along the tube axis direction of the outer tube.

The preheating heater 3 is a ceramic heater formed by coating a heating element made of tungsten or the like (not shown) with ceramic, and is formed to have a V-shaped cross section and a power of 40 W, for example. Such a preheater 3 is installed on one side of the arc tube 2 at a distance of 0.1 m to 1.2 m from the arc tube 2, and is curved so that the negative side faces the arc tube 2.

The preheating heater 3 includes an anode 4a to a cathode 4b1 and a cathode 4.
The large area facing the sealing part 5b on the b side, that is, the anode 4a
It is formed in a size excluding the side sealing part 5a.

Preheating heater 3 has preheating heater lead $j; +8a, 8
b, and these preheating heater lead wires 8a.

8b passes through the sealing portion 1a of the outer tube 1 in an airtight manner.

Note that at least one of the arc tube lead wires 7a and 7b is covered with an insulator such as a glass tube 9 to prevent discharge inside the outer tube, and the preheating heater lead wires 8a and 8b are also covered with an insulator such as a glass tube 9 to prevent discharge inside the outer tube. Therefore, it is covered with an insulator such as a glass tube 10.

Note that 11 indicates a getter.

A metal halide lamp having such a configuration is housed in a reflecting mirror body 12 shown in FIG. The anti-04 mirror body 12 is made of high-brightness aluminum or the like, and has a reflecting surface consisting of a paraboloid of revolution 12a and flat surfaces 12b and 12b continuous thereto.

The metal halide lamp is attached to the top of the paraboloid of revolution 12a of the reflecting body 12 via four arms (not shown). In this case, the 1ift pole 4a and the cathode 4b in the arc tube 2 are connected to the optical axis O-
The anode 4a and the cathode 4b are horizontally opposed to each other. That is, metal halide lamps are lit horizontally. In this case, the sealing parts 5a and 5b of the arc tube 2 are installed so that the crushed surfaces with a wide area face in the vertical direction, and the preheater 3 is placed below the arc tube 2. , are arranged so that their upper surfaces face each other from the anode 4a of the arc tube 2 to the cathode 4b and the sealing portion 5b on the side of the cathode 4b.

Note that the anode 3a is located on the opening side of the reflecting mirror body 6.

In the arc tube 2, the emission center 1o occurs between the anode 4a and the cathode 4b, that is, at the midpoint 11/2 of the inter-electrode distance 11 shown in FIG. As shown in FIG. 2, the emission center 1o is at the same position as the focal point F of the reflector 12, or the emission center 1° is farther from the focal point m of the reflector 12 (in the irradiation direction) than IfF. It is located on the side.

The operation of the embodiment with such a configuration will be explained.

When the preheating heater 3 is energized in advance to generate heat, the preheating heater 3 heats the arc tube 2 and evaporates the mercury, scandium iodide, and sodium iodide sealed in the arc tube 2.

In this state, by applying a high voltage pulse from the DC power source 1i to the arc tube lead wires 7a and 7b,
DC discharge begins between the anode 4a and the cathode 41, and in this case, the arc tube 2 has already been heated by the preheater 3, so the container pressure of mercury, scandium iodide, and sodium iodide in the arc tube 2 is sufficiently high. Therefore, a predetermined luminous flux can be obtained almost at the same time as starting.

In the present invention, since the outer tube 1 is turned on horizontally and the preheater 3 is placed below the arc tube 2, the arc tube 2 receives convection heat as well as the radiant heat from the preheater 3, and is thus heated. Increased efficiency.

In this embodiment, the sealing portions 5a and 5b of the arc tube 2 are installed so that the crushed surfaces having a large area face the preheater 3, so that the heat receiving area becomes large and the temperature of the arc tube increases. The rise becomes ♀.

Note that when the discharge of the arc tube 2 becomes stable, the power supply to the preheater 3 is stopped to stop the preheater 3 from heating the arc tube 2.

However, even during agitation when the discharge of the arc tube 2 is stable, if the preheater 3 continues to be energized, the following effects occur.

That is, in the case of horizontal lighting and direct current lighting as described above, the coldest part occurs at the base of the electrode in the shadow $44b,
Since metal ions are attracted to the coldest part, a difference occurs in the vapor pressure distribution within the arc tube, resulting in a so-called cataphoresis phenomenon. As a result, color separation occurs within the arc tube, and the anode 4a (Il
There is a problem that there is a difference in the emitted light color between II and the negative ti4b side.

On the other hand, when the preheating heater 3 continues heating, the preheating heater 3 of this embodiment starts from the anode 4a to the anode i4. lb and the size facing the sealing part 5b on the cathode 4b side, that is, l! i
, since it is formed to a size excluding the sealing part 5a on the 1iida side, it is possible to increase the temperature on the shade (Φ4b side).
The temperature difference between the anode 4a side and the cathode 4b side can be reduced. This prevents the occurrence of cataphoresis and reduces the difference in emitted light color within the arc tube.

The light emitted from the arc tube 2 is reflected by the reflective surface of the anti-reflective mirror body 12, and is irradiated forward as a beam of light from the front opening of the reflective mirror body 12.

By the way, in general, on a reflecting surface that is a paraboloid of revolution, as shown in Fig. 2, the light emitted from the focal image ff1F is reflected as a parallel ray as shown by the solid arrow A. Light emitted from a short position is spread out and reflected as shown by the broken line arrow B. Light emitted from a position longer than the focal length is focused and reflected as shown by the two-dot chain arrow C, but as these rays reach far away, they may intersect on the optical axis O-O. In this case, the reflected light spreads out more than the reflected light indicated by the broken line arrow B above. Therefore, the light distribution of these 3 fm reflected lights is as shown in FIG. In other words, in Fig. 3, the same lines as the rays in Fig. 2 show the light distribution, and the parallel rays indicated by the solid arrow A are in the center, and the reflected light spreading out as indicated by the broken arrow B is in the surrounding area, and the two-dot chain line The reflected light indicated by arrow C is the outermost portion.

According to the configuration of the above embodiment, since the preheater 3 is disposed below the arc tube 2 in order to improve the heating efficiency of the arc tube 2, the light emitted downward from the arc tube 2 is This preheater 3 cuts off a part of the air.

Observing this light-blocking state, you will see the following.

In other words, in FIG. 4, the emission center LO of the arc tube 2 is the focal image '
This is the case when the vehicle is located behind aF, and the light distribution characteristics in this case are as shown in FIG. 5, where the upward light becomes large and dazzles oncoming vehicles.

FIG. 6 shows a case where the light emission center LO of the arc tube 2 is located at the same position as the focal point F, and the light distribution characteristics in this case are approximately equal in the vertical direction as shown in FIG. 7.

Fig. 8 shows a case where the light emitting center LO of the arc tube 2 is located in front of the focal point F, and the light distribution characteristics in this case are as shown in Fig. 9, where the downward light becomes larger and the upward light becomes larger. There is very little light, so there is no need to worry about dazzling oncoming vehicles.

Therefore, if the light emission center LO is placed at the same position as the focal image ffF or in front of it, even if the preheater 3 is placed below the arc tube 2, it will not dazzle oncoming vehicles.

Incidentally, in the configuration shown in FIG. 2, since the light emission center LO is located in front of the focal point F of the reflecting mirror body 12, the characteristics shown in FIGS. 8 and 9 are reduced by (!7).

In the above embodiment, a metal halide lamp was used as the light source, but the present invention also uses a high-pressure lamp.
It may also be a helium lamp.

〔Effect of the invention〕

As explained above, according to the present invention, since the preheater is installed below the arc tube, the arc tube is heated by convection heat in addition to the radiant heat from the preheater, improving the heating efficiency of the arc tube. However, in this case, the light emitting center of the small high-pressure metal vapor discharge lamp was positioned at the same position as the focal position of the reflector or in front of the focal position of the reflector, so the beam was blocked by the light shielding effect of the preheating heater. The upward light in the light is dimmed and no longer dazzles oncoming vehicles. Therefore, the light shielding effect, which is originally considered to be a problem when using a preheating heater, is actively utilized to improve the light distribution characteristics required for vehicle headlamps.

[Brief explanation of drawings]

The drawings show an embodiment of the present invention; Fig. 1 is a cross-sectional view showing the structure of a metal halide lamp, Fig. 2 is a view of the lamp attached to a reflector, and Fig. 3 is a general light distribution pattern. FIG. 4 is an explanatory diagram showing the case where the luminous center of the arc tube is behind the focal point position, FIG. 5 is a diagram of the light distribution pattern in that case, and FIG. Fig. 7 is a diagram of the light distribution pattern in that case, Fig. 8 is an explanatory diagram of the case where the light emitting center of the arc tube is in front of the focal position, and Fig. 9 is a diagram of the light distribution pattern in that case. It is a light distribution pattern diagram in case. 1... Outer tube, 2... Arc tube, 3... Preheating heater,
4 (1...Anode, 4b...Cathode, 12...Reflector, L,,a...Emission center, F...Focus position. Applicant's agent Patent attorney Takehiko Suzue Figure 2 Figure 3

Claims (1)

[Claims] The light source is a small high-pressure metal vapor discharge lamp consisting of an arc tube and a preheater that heats the arc tube inside the outer bulb. In a vehicle headlamp installed in the lighting position, the preheating heater has a light shielding function, and the preheating heater is installed below the arc tube, and such a small high pressure metal vapor discharge lamp is installed as above. A vehicle headlamp characterized in that the light emitting center of the arc tube is installed on the reflector so that the light emitting center is located at the same position as the focal position of the reflector or in front of the focal position of the reflector.