JPH08148285A - Discharge lamp lighting apparatus - Google Patents

Abstract

PURPOSE: To provide two or more light distribution patterns only by a single lamp by making at least one of output frequency and output waveforms of current, voltage, and electric power variable in a lighting circuit and making the discharge arc shape variable. CONSTITUTION: Input a.c. is transformed into d.c. by a rectifying and filtering circuit 14 and transformed into a.c. again by an inverter circuit 19. The output frequency of the circuit 19 is changed to be frequency at the time when transistors 16, 17 are reciprocally turned ON and OFF by a driving circuit 20. When a discharge lamp 11 is started by high voltage pulses, the output from the circuit 19 is applied to a series circuit of the lamp and the lighting is retained and at that time the shape of the discharge arc becomes different due to the alteration of the frequency and light distribution pattern alters based on the position relation with a light controlling means. Also, in the case lighting is retained by the supplied electric power from a power amplifying circuit after starting of the lamp 11, the arc shape is changed by making the output current waveforms be triangular waveforms or rectangular waveforms. Moreover, the current waveforms may be changed by voltage alteration.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a discharge lamp lighting device, and more particularly to a discharge lamp lighting device when the discharge lamp is used as a vehicle headlight.

[0002]

2. Description of the Related Art In recent years, a discharge lamp having characteristics such as higher luminous efficiency, better color rendering, and longer life than a halogen lamp has attracted attention and is being used as a vehicle headlight. For the conventional discharge lamp lighting device, the 1987 Illuminating Society Tokyo Branch Conference Proceedings No. There is one described in 10.

FIG. 17 is a basic configuration diagram of the above-described conventional discharge lamp lighting device. In FIG. 17, 91 is a metal halide lamp which is a discharge lamp, and 92 is a lighting circuit for starting and lighting the metal halide lamp 91. The lighting circuit 92 includes a DC power source 93 and an inverter circuit 9.
4 and a high voltage pulse generation circuit 95. The DC power supply 93 is a rectifying / smoothing circuit 97 for rectifying and smoothing the output of the commercial AC power supply 96 and converting it to DC, and a transistor for controlling the power supplied to the discharge lamp 91 by inputting the output of the rectifying / smoothing circuit 97 to a predetermined value. 98, diode 99, choke coil 100, capacitor 101, resistors 102, 10
3 and 104 and a step-down chopper circuit 106 including a control circuit 105. The step-down chopper circuit 106 detects the output voltage by the resistors 102 and 103, and detects the output current by the resistor 104. One detection signal is calculated by the control circuit 105, and the transistor 98 is ON / OFF controlled by the output signal of the control circuit 105 so that the output power of the step-down chopper circuit 106 becomes a predetermined value.

The inverter circuit 94 includes a transistor 10
7, 108, 109, 110 and the driving circuit 111, and the period in which the transistors 107, 110 are turned on by the output signal of the driving circuit 111 and the transistor 108,
The inverter circuit 94 converts the output of the DC power supply 93 into AC and outputs it by alternately generating the periods in which 109 is ON. The high voltage pulse generation circuit 95 generates a high voltage pulse for starting the metal halide lamp 91.

The operation of the discharge lamp lighting device configured as described above will be described below. The metal halide lamp 91 is started by the high voltage pulse generated from the high voltage pulse generation circuit 95. After the start, a signal proportional to the lamp voltage of the metal halide lamp 91 detected by the resistors 102 and 103 and a signal proportional to the lamp current of the metal halide lamp 91 detected by the resistor 104 are calculated by the control circuit 105 and supplied to the metal halide lamp 91. Turn on / off the transistor 98 so that the power reaches a predetermined lamp power.
FF control is performed, and the instantaneous electric power converted into alternating current by the inverter circuit 94 does not change temporally and a rectangular alternating current waveform having a constant waveform is supplied to the metal halide lamp 91 and the metal halide lamp 91 maintains lighting. The frequency of the alternating current converted by the inverter circuit 94 is H
Fluctuation, extinction, or metal halide lamp 91 of the discharge arc caused by the acoustic resonance phenomenon peculiar to the ID lamp
It is usually set to several hundreds of Hz in order to avoid problems such as bursting. When the discharge lamp is used as a vehicle headlight, the AC power supply 96 is a DC battery and the DC power supply 93 is a boost chopper circuit, but the basic configuration is almost the same.

A halogen lamp is used as a conventional vehicle headlamp, and in the case of a two-lamp type, it has a structure as shown in FIG. In FIG. 18, 121 is a filament for passing beams, 122 is a filament for traveling beams,
Reference numeral 123 is a light shielding plate installed below the low beam filament 121, 124 is a parabolic reflector for irradiating the light from the low beam filament 121 and the traveling beam filament 122 forward, and 125 is a parabolic reflector. It is an outer lens that projects the light reflected by 124 forward.

In the conventional vehicle headlamp having the above-described structure, when forming a low beam, the low beam filament 121 is caused to emit light. At this time, since the passing beam filament 121 is positioned in front of the focal point of the parabolic reflecting mirror 124, the light traveling downward from the passing beam filament 121 is reflected by the parabolic reflecting mirror 124, and then the light passing upward. Since the light becomes heading light and becomes glare light, the light is blocked by the light blocking plate 123. In addition, as shown in FIG. 18, the passing beam filament 121
The light traveling upward from is reflected by the parabolic reflector 124,
A predetermined passing beam is formed by projecting with the outer lens 125.

On the other hand, when forming a traveling beam, the traveling beam filament 122 is caused to emit light. This time,
The traveling beam filament 122 is a parabolic reflector 12.
Since it is located behind the focal point of 4, the light emitted from the traveling beam filament is reflected by the parabolic reflecting mirror 124, then becomes light having a vertical spread, and is projected forward by the outer lens 125. A predetermined traveling beam is formed. That is, two light emitting portions are formed by using two filaments, and the passing beam and the traveling beam are switched by selectively using each of them.

[0009]

However, the above conventional discharge lamp lighting device has a problem that only one light distribution pattern can be formed because the discharge lamp has only one light emitting portion. Furthermore, when the discharge lamp is used for a vehicle headlight, two light-emitting parts cannot be selectively used as in a conventional vehicle headlight that uses a halogen lamp. Only a passing beam or a traveling beam can be configured, and 4 lights type (2 on one side)
There is also a problem that it is not possible to switch between the passing beam and the traveling beam unless it is a vehicle headlight.

SUMMARY OF THE INVENTION The present invention is intended to solve such a conventional problem, and to provide a discharge lamp lighting device capable of forming at least two light distribution patterns with one discharge lamp having one arc. It is an object of the present invention to provide a discharge lamp lighting device capable of switching between a passing beam and a traveling beam even with a two-lamp system when the discharge lamp is used as a light source of a vehicle headlight.

[0011]

First, the present invention provides a lighting circuit, a discharge lamp connected to an output end of the lighting circuit, and a light control for irradiating light emitted from the discharge lamp in a predetermined direction. The lighting circuit has at least one of an output frequency and an output waveform of voltage, current, or power.
It is possible to change the shape of the discharge arc of the discharge lamp by lighting the discharge lamp with the lighting circuit.

Secondly, in order to selectively form discharge arcs having different shapes, the lighting circuit varies at least one of the output frequency and the output waveform of voltage, current or power, and at least two distributions are provided. The configuration is such that a light pattern can be formed.

Thirdly, in order to form two light distribution patterns, the lighting circuit varies at least one of an output frequency and an output waveform of voltage, current or power, and
The above-mentioned light distribution pattern is used as a passing beam, and the second light distribution pattern is used as a traveling beam to provide a vehicle headlight.

Fourthly, a linear arc and a curved arc are formed, and the linear arc is used for a beam which is frequently used.

[0015]

According to the present invention, according to the above-described structure, the lighting circuit outputs a plurality of types of signals in which at least one of the output frequency and the output waveform is changed, and applies the signals to the discharge lamp. In the discharge lamp, the shape of the discharge arc, that is, the bending of the discharge arc changes depending on the type of the applied signal. When the shape of the discharge arc changes, the positional relationship with the optical system changes, and the light distribution pattern also changes. That is, by changing at least one of the output frequency and the output current waveform of the lighting circuit, the shape of the discharge arc can be changed and a plurality of light distribution patterns can be formed.

If the output signal of the lighting circuit is configured so as to correspond to two light distribution patterns and is used as a vehicle headlight, the first light distribution pattern causes a passing beam,
A traveling beam can be formed with the second light distribution pattern, and the passing beam and the traveling beam can be switched, so that the passing beam and the traveling beam can be realized by one discharge lamp, and for a vehicle using a two-lamp discharge lamp. A headlight can be configured.

[0017]

Embodiments of the present invention will be described below with reference to the drawings. First, the results of the first experiment will be described. This shows the relationship between the output current waveform of the lighting circuit, the output frequency, and the magnitude of bending of the discharge arc. FIG.
FIG. 3 is a diagram showing a shape of a metal halide lamp which is a discharge lamp used for the examination. In the metal halide lamp of FIG. 19, 131 is quartz glass forming a discharge space, 1
Reference numerals 32 and 133 are electrodes. In this figure, assuming that the length L of the discharge space that intersects the discharge arc is the inner diameter of the central portion of the discharge space that is the maximum inner diameter of the discharge space, the length L of the discharge space that intersects the discharge arc is 2.7 mm.

FIG. 2 is a diagram showing the relationship between the output frequency of the lighting circuit and the size of the bending of the discharge arc of the discharge lamp when the discharge lamp shown in FIG. 19 is lit. The bending size of the discharge arc indicates the distance between the line connecting the centers of the electrodes and the center of the discharge arc. The solid line A shows the characteristics of the output frequency of the lighting circuit and the magnitude of the bending of the discharge arc when the output current waveform of the lighting circuit is a triangular wave, and the solid line B shows the lighting circuit when the output current waveform of the lighting circuit is a sine wave. Shows the characteristics of the output frequency and the bending magnitude of the discharge arc, and the solid line C shows the characteristics of the output frequency of the lighting circuit and the bending magnitude of the discharge arc when the output current waveform of the lighting circuit is a rectangular wave.

It can be seen from FIG. 2 that even if the output current waveform of the lighting circuit is the same, the magnitude of the bending of the discharge arc is different if the output frequency is different. Further, it is found that even if the output frequency of the lighting circuit is the same, the magnitude of the bending of the discharge arc is different if the output current waveform is different. That is, by changing at least one of the output frequency and the output current waveform of the lighting circuit, the bending size of the discharge arc, that is, the shape of the discharge arc can be changed. At this time, the shape of the discharge arc can be changed even if the voltage is changed to change the output current waveform. That is, if the lighting circuit is configured to be able to change at least one of the output frequency and the output current waveform, a plurality of discharge arcs having different shapes can be selectively formed, so that the light distribution pattern. It is possible to realize a discharge lamp lighting device that can be switched over and can form a plurality of light distribution patterns. Normally, when a discharge lamp is lit at a high frequency, fluctuations in the discharge arc due to an acoustic resonance phenomenon, a frequency range in which extinguishing occurs, and a frequency range in which there is stable lighting exist intermittently, but here,
For each output current waveform, the discharge lamp steadily lit 5
The bending magnitude of the discharge arc is shown only in the range of -10 kHz.

Next, specific examples based on the results of this experiment will be described. FIG. 1 shows a block diagram of a discharge lamp lighting device according to a first embodiment of the present invention. In FIG. 1, 11 is a discharge lamp and 12 is a discharge lamp 11.
Is a lighting circuit for starting and lighting. Lighting circuit 1
Reference numeral 2 denotes a DC power supply 1 including a commercial AC power supply 13 and a rectifying / smoothing circuit 14 that converts the output of the AC power supply 13 into DC.
5, transistors 16 and 17 which are switching elements,
An inverter circuit 19 which has a capacitor 18 and which receives a DC output of a DC power supply 15 and converts it into an AC; a transistor 16 which has a drive frequency changeover switch (not shown);
A drive circuit 20 for alternately controlling ON / OFF of 17, a choke coil 21 which is a reactance element for limiting the lamp current of the discharge lamp 11, and a high voltage pulse generation circuit 22 for generating a high voltage pulse for starting the discharge lamp 11. Composed. The high-voltage pulse generation circuit 22 stops the generation of high-voltage pulses when the discharge lamp 11 is turned on.

The operation of the discharge lamp lighting device of this embodiment constructed as above will be described below. The rectifying / smoothing circuit 14 converts the alternating current input from the alternating-current power supply 13 into the direct current, and the inverter circuit 19 converts it into the alternating current again. At this time, the output frequency from the inverter circuit 19 is such that the drive circuit 20 turns on the transistors 16 and 17 alternately.
It changes depending on the frequency when N / OFF, and here,
The combination of different arc shapes is, for example, 5 kHz and 10 kHz indicated by circles in FIG. Discharge lamp 1
A high-voltage pulse is applied from the high-voltage pulse generation circuit 22 to the discharge lamp 11 until 1 is started. When the discharge lamp 11 is started, the AC output from the inverter circuit 19 is applied to the series circuit of the choke coil 21 and the discharge lamp 11,
The current is limited by the choke coil 21 and the lighting of the discharge lamp 11 is maintained. The lamp current waveform at this time becomes a waveform close to a triangular waveform by the choke coil 21, as shown in FIG. Further, the shapes of the discharge arc when the output frequencies of the inverter circuit 19 are 5 kHz and 10 kHz are as shown in FIGS. 4A and 4B, and the shapes of the discharge arc are different depending on the respective frequencies. This difference in the shape of the discharge arc causes a change in the positional relationship between the discharge arc, which is the light emitting section, and the light control means when the light control means is considered, resulting in a change in the light distribution pattern.

As described above, according to the first embodiment,
By switching the drive frequency of the drive circuit 20 and changing the output frequency of the inverter circuit 19, two discharge arcs of different shapes can be selected, so that two light distribution patterns can be realized.

The second embodiment of the present invention will be described below with reference to the drawings. FIG. 5 is a block diagram of a discharge lamp lighting device according to the second embodiment of the present invention. In FIG. 5, reference numeral 31 is a discharge lamp, 32 is a high-voltage pulse generation circuit for starting the discharge lamp 31, 33 is a power amplification circuit that amplifies power with a waveform according to the input and supplies power to the discharge lamp 31, and 34 is a power amplification circuit. A selector switch for switching the input to 33, a triangular wave generating circuit 35 for generating a triangular wave, and a rectangular wave generating circuit 36 for generating a rectangular wave.

The operation of the discharge lamp lighting device of this embodiment constructed as described above will be described below. The high-voltage pulse generated from the high-voltage pulse generation circuit 32 starts the discharge lamp 31. Power amplifier circuit 33 after starting
Supplies power to the discharge lamp 31 and keeps lighting. The output current waveform of the power amplifier circuit 33 depends on the input waveform, and in this embodiment, the triangular wave generating circuit 35 and the rectangular wave generating circuit 36.
Since the output from the power amplifier circuit is input to the power amplifier circuit 33 via the switch 34, the output current waveform from the power amplifier circuit 33 becomes a triangular wave or a rectangular wave. Here, the output frequencies of the triangular wave generation circuit 35 and the rectangular wave generation circuit 36 are shown by the triangular marks in FIG.
And The shape of the discharge arc when lit with a triangular wave is
As shown in FIG. 4 (b), the shape of the discharge arc when illuminated with a rectangular wave is as shown in FIG. 4 (a). By changing the output current waveform from the lighting circuit 37 in this way, the shape of the discharge arc can be changed. This difference in the shape of the discharge arc causes a change in the positional relationship between the discharge arc, which is the light emitting unit, and the light control means when considering the light control means, resulting in a change in the light distribution pattern.

As described above, according to the second embodiment, by changing the output current waveform from the lighting circuit 37,
The shape of the discharge arc can be changed, and two different shape discharge arcs can be selected by switching the changeover switch 34, so that two light distribution patterns can be realized.

The third embodiment of the present invention will be described below with reference to the drawings. FIG. 6 is a block diagram of a discharge lamp lighting device according to the third embodiment of the present invention. In FIG. 6, 41 is a metal halide lamp which is a discharge lamp, and 42 is a lighting circuit for starting and lighting the metal halide lamp 41. The lighting circuit 42 includes a DC power supply 43, an inverter circuit 44, a high-voltage pulse generation circuit 45, and a choke coil 46 that is a reactance element that limits the lamp current of the discharge lamp 41.

The DC power supply 43 rectifies and smoothes the output of the commercial AC power supply 47 and converts it to DC, and the power supplied to the discharge lamp 41 by inputting the output of the rectification and smoothing circuit 48 to a predetermined value. It includes a transistor 49 for controlling, a diode 50, a choke coil 51, a capacitor 52, resistors 53, 54 and 55, and a step-down chopper circuit 57 including a control circuit 56. The step-down chopper circuit 57 has a resistor 53, The output voltage is detected at 54 and the resistance 5
5, the output current is detected, two detection signals are calculated by the control circuit 56, and the transistor 49 is ON / OFF controlled by the output signal of the control circuit 56 so that the output power of the step-down chopper circuit 57 becomes a predetermined value. .

The inverter circuit 44 includes the transistor 5
8, 59, 60, 61 and a drive circuit 62 having a drive frequency changeover switch (not shown), and a period in which the transistors 58, 61 are turned on at a predetermined frequency according to the drive frequency changeover switch and the transistor. 5
The inverter circuit 44 converts the output of the direct-current power supply 43 into alternating current and outputs it by alternately generating the periods in which 9 and 60 are turned on. The high-voltage pulse generation circuit 45 generates a high-voltage pulse for starting the metal halide lamp 41.

The operation of the discharge lamp lighting device of this embodiment having the above structure will be described below. The metal halide lamp 41 is started by the high voltage pulse generated from the high voltage pulse generation circuit 45. Resistance 5 after starting
The control circuit 5 outputs a signal proportional to the lamp voltage of the metal halide lamp 41 detected by 3, 54 and a signal proportional to the lamp current of the metal halide lamp 41 detected by the resistor 55.
The transistor 49 is turned on so that the power calculated in 6 and supplied to the metal halide lamp 41 becomes a predetermined lamp power.
N / OFF control.

The inverter circuit 44 supplies the metal halide lamp 41 with an AC waveform having a predetermined frequency according to the drive frequency changeover switch of the drive circuit 62, and the metal halide lamp 41 keeps lighting. Here, the output frequency of the inverter circuit 44 is such that the discharge arc is stable and the shape of the discharge arc is different, for example, 400.
The drive circuit 62 is configured so that it can be switched to Hz and 10 kHz. When the output frequency of the inverter circuit 44 is 400 Hz, since 400 Hz is a relatively low frequency, it is not affected by the choke coil 46, which is a current limiting element, and the current is limited by the DC power supply 43 to flow into the metal halide lamp 41. Has a rectangular wave shape as shown in FIG. When the output frequency of the inverter circuit 44 is 10 kHz, the current flowing through the metal halide lamp 41 by the choke coil 46, which is a current limiting element, has a triangular waveform as shown in FIG. At this time, as shown in FIG. 4, the shape of the discharge arc when lighting at each output frequency is different, and the difference in the shape of the discharge arc is the discharge of the light emitting portion when considering the light control means. A change in the positional relationship between the arc and the light control means results in a change in the light distribution pattern.

As described above, according to the third embodiment,
By switching the drive frequency of the drive circuit 62 and changing the output frequency of the inverter circuit 44, the lighting circuit 4
Since two output frequencies and output current waveforms can be changed and two discharge arcs having different shapes can be selected, two light distribution patterns can be realized.

Next, the second experimental result will be described. FIG. 8 shows the relationship between the enclosed material of the metal halide lamp shown in FIG. 19, the amount thereof, and the average sound velocity in the discharge space and the average temperature in the discharge space obtained from the inner volume of the discharge space. When the temperature at the center of the discharge arc is about 5000 ° C and the temperature near the tube wall is about 1000 ° C, the average temperature in the discharge space is 300
It can be estimated that the temperature is 0 ° C., and the sound velocity in the discharge space at that time is 414 m / s from FIG. The results obtained by substituting the above conditions into the general formula (Equation 1) and obtaining the frequency f are shown in (Table 1).

[0033]

[Equation 1]

[0034]

[Table 1]

Table 2 shows the sine wave waveform, the triangular wave waveform and the 400 Hz rectangular wave waveform of the frequency shown in (Table 1) when the metal halide lamp A shown in FIG. The results of a comparative study of the shape of the discharge arc and the size of the bend of the discharge arc (the distance between the line connecting the electrodes and the center of the discharge arc), the luminous efficiency, the temperature above the discharge space, and the temperature below the discharge space are shown.

[0036]

[Table 2]

From the above results, the shape of the discharge arc when lit by the rectangular wave lighting method of the prior art is obviously curved, whereas the triangular wave waveform of frequency f obtained from the general formula (Equation 1) is used. It can be seen that the discharge arc has a linear shape when is supplied to the lamp. The reason for this can be explained by the compression wave generated from the discharge arc. When the compressional wave generated from the discharge arc travels toward the tube wall and is reflected in the discharge arc direction by the tube wall, the compressional wave generated from the discharge arc in the entire circumferential direction surrounding the discharge arc is reflected and reflected by the tube wall. All compression waves have the same amplitude at the center of the vertical section of the discharge space. Further, the amplitude of the compressional wave generated from the discharge arc is considered to change almost in synchronism with the change of the instantaneous value of the lamp voltage, the lamp current or the lamp power, but the instantaneous voltage or the frequency f shown by the general formula (Equation 1) or When a waveform in which the instantaneous current or the instantaneous power changes with time is supplied to the metal halide lamp shown in FIG. 19, the amplitude of the compressional wave generated from the discharge arc at the center of the vertical cross section of the discharge space and the reflection on the tube wall, and the discharge arc The amplitudes of all compressional waves that have returned to are at the same level.

On the other hand, at frequencies other than the general formula (Equation 1),
The compression wave generated from the discharge arc and the compression wave reflected from the tube wall do not have the same level of amplitude, and the phase of the compression wave generated from the discharge arc causes the compression wave generated from the discharge arc to have the same amplitude as the compression wave. Since the magnitude relation of the amplitude of the compressional wave reflected by the wall changes, as a result, the discharge arc moves to the lower amplitude level, and the discharge arc is not stable. That is, at the frequency f represented by the general formula (Equation 1), the amplitude of the compressional wave generated from the discharge arc and the amplitudes of all compressional waves reflected by the tube wall are generated from the discharge arc at the center of the vertical cross section of the discharge space. The discharge arc becomes stable at the center of the vertical cross section because the level is always the same regardless of the phase of the compressional wave.

From the results of the comparative study shown in (Table 2), when the discharge arc is curved, the temperature of the upper part of the discharge space becomes 1000 ° C. or more, but when the shape of the discharge arc becomes straight, the temperature of the upper part of the discharge space becomes 1000 ° C. or less. I understand. FIG.
The quartz glass forming the metal halide lamp shown in
If the temperature exceeds 1000 ° C., the quartz glass deteriorates rapidly, and devitrification or deformation (swelling) of the quartz glass occurs. These cause a decrease in luminous flux and a change in light emission characteristics. However, by turning on the light at the frequency f determined by the general formula (Equation 1), the temperature of the upper part of the discharge space, which is the highest temperature of the quartz glass, becomes 1000 ° C. or less. Since the deterioration of the quartz glass can be suppressed, the life of the lamp can be extended. That is, the life can be extended by lighting the discharge lamp at the frequency f represented by the general formula (Equation 1) with a waveform in which the instantaneous voltage, the instantaneous current, or the instantaneous power changes with time.

Although the average temperature during rated lighting is set to 3000 ° C. here, it can be seen from FIG. 8 that the average sound velocity in the discharge space changes if the average temperature in the discharge space changes. That is, when the lamp current is varied and dimmed, when the ambient temperature changes, the period until the average temperature in the discharge space reaches a predetermined value immediately after the lamp is lit, the average temperature at rated lighting is 3000 ° C. Are different temperatures, the average sound velocity value is different for 414 m / s. Further, FIG. 8 is obtained from the filled substance of the metal halide lamp shown in FIG. 19, the filled amount thereof, and the inner volume of the discharge space. If the filled substance, the filled amount, and the inner volume of the discharge space are changed, the inside of the discharge space is changed. It is obvious that the average sound velocity of the lamp changes, and the average sound velocity in the discharge space has a unique value for each lamp.

The fourth embodiment of the present invention will be described below with reference to the drawings. FIG. 9 is a block diagram of a discharge lamp lighting device according to a fourth embodiment of the present invention, in which the discharge lamp lighting device of the present invention is used as a vehicle headlight.

In FIG. 9, 72 is a discharge lamp, 71 is a lighting circuit for starting and lighting the discharge lamp 72, 7
Reference numeral 3 is a parabolic reflector for irradiating the light emitted from the discharge lamp 72 to the front, and reference numeral 74 is an outer lens for controlling light distribution.
As shown in FIG. 10, the lighting circuit 71 has a DC power supply 77 including a battery 75 that is a power supply and a booster circuit 76 that boosts the voltage of the battery to a predetermined voltage, and transistors 78 and 79 that are switching elements. DC power supply 7
Inverter circuit 8 that receives the DC output of 7 and converts it to AC
1. A driving frequency changeover switch (not shown) is used, and the transistors 78 and 79 have a frequency determined by the general formula (Equation 1) of 76.7 kHz and a frequency at which the discharge arc is stable at other frequencies, for example, from FIG. ON / O at 10 kHz
The drive circuit 82 for FF control, the choke coil 8 which is a reactance element for limiting the lamp current of the discharge lamp 72.
3. A high voltage pulse generating circuit 84 for generating a high voltage pulse for starting the discharge lamp 72. In addition,
The high-voltage pulse generation circuit 84 stops the generation of high-voltage pulses when the discharge lamp 72 is turned on. The shapes of the discharge arcs when the output frequencies of the lighting circuit 71 are 76.7 kHz and 10 kHz are as shown in FIGS. 11 (a) and 11 (b), respectively.

The operation of the discharge lamp lighting device of this embodiment constructed as described above will be described below. The lighting circuit 71 includes a DC power source 77 as compared with the first embodiment.
The configuration includes a step-up circuit instead of a rectifying and smoothing circuit for direct current because the input is a battery, and the transistor 7
The drive frequency of the 8,79 drive circuit is 76.7 kHz, 1
The configuration is almost the same except that the frequency is 0 kHz, and the basic operation is almost the same as that of the first embodiment, so the description thereof is omitted. First, the case where the beam that is frequently used is the traveling beam will be described.

12 and 13 are views showing the position where the discharge lamp 72 is arranged and the direction in which light is emitted. In this case, the output frequency of the lighting circuit 71 is 7
When the shape of the arc is 6.7 kHz, that is, the shape shown in FIG. 11A, the parabolic reflector 73 is arranged so that the focal point thereof is substantially at the center of the discharge arc. Lighting circuit 7
The output frequency of 1 is set to 76.7 kHz, and the discharge lamp 72
When is turned on, the shape of the discharge arc becomes straight as shown in FIG. 11A, so that the position of the discharge arc, which is the light emitting portion, and the focal point 85 of the parabolic reflector 73 substantially coincide with each other. As shown in FIG. 16, the light reflected by the reflecting mirror becomes light substantially parallel to the optical axis, the light is projected in a predetermined direction by the outer lens 74, and the traveling beam distribution as shown in FIG. Form a light pattern.

The output frequency of the lighting circuit 71 is set to 10 kHz.
When the discharge lamp 72 is turned on with z, the shape of the discharge arc becomes a curved shape as compared with FIG. 11A as shown in FIG. 11B, and the position of the discharge arc which is the light emitting portion is a parabolic surface. Since it is located above the focal point 85 of the reflecting mirror 73,
As shown in FIG. 3, the light reflected by the reflecting mirror becomes light directed downward with respect to the optical axis. Then, the outer lens 74 projects the light in a predetermined direction to form a light distribution pattern of the low beam as shown in FIG.

Next, the case where the frequently used beam is the passing beam will be described. 14 and 15
FIG. 3 is a diagram showing a position where a discharge lamp 72 is arranged and a light irradiation direction. In this case, when the output frequency of the lighting circuit 71 is 10 kHz, that is, the shape of the arc is the shape shown in FIG.
It is arranged so that the focal point of 3 is almost at the center of the discharge arc.

The output frequency of the lighting circuit 71 is 76.7 kHz.
When the discharge lamp 72 is turned on with z, the shape of the discharge arc becomes straight as shown in FIG. 11 (a), so that the position of the discharge arc which is the light emitting portion is located at the parabolic reflector 7.
Since it is located below the focal point 85 of No. 3, the light reflected by the reflecting mirror becomes light directed upward with respect to the optical axis as shown in FIG. 15, and is inverted and projected by the outer lens 74, as shown in FIG.
A light distribution pattern of the low beam is formed as shown in FIG.

The output frequency of the lighting circuit 71 is set to 10 kHz.
When the discharge lamp 72 is turned on with z, the shape of the discharge arc becomes a curved shape as compared with FIG. 11A as shown in FIG. 11B, and the position of the discharge arc which is the light emitting portion is a parabolic surface. The light substantially coincident with the focal point 85 of the reflecting mirror 73 and reflected by the reflecting mirror as shown in FIG. 14 becomes light parallel to the optical axis. Then, the outer lens 74 provides an inverted projection view,
A traveling beam light distribution pattern as shown in FIG. 16B is formed.

As described above, according to the fourth embodiment,
By changing the lighting frequency when the passing beam is selected and when the traveling beam is selected, two light distribution patterns can be formed by a headlight using one discharge lamp having one arc,
Since the passing beam and the traveling beam can be switched,
It is possible to realize a vehicle headlight that uses a discharge lamp with a two-lamp system. Also, by setting the discharge arc to be a linear discharge arc when the beam is used frequently, it is possible to suppress devitrification and deformation (bulging) of the discharge lamp, which causes luminous flux deterioration and emission characteristics. , Longer life.

In the first embodiment, the lighting circuit 1
The output frequencies of 2 are set to 5 kHz and 10 kHz, for example, but other combinations of frequencies may be used as long as the discharge arc is stable and the shapes are different. Although the output current waveform is a triangular wave, it may be another waveform (for example, a sine wave). Further, although two light distribution patterns are realized, the output frequency of the lighting circuit 12 may be three or more, and three or more light distribution patterns may be realized.

Further, in the second embodiment, the lighting circuit 3
The output current waveform of 7 is, for example, a triangular wave and a rectangular wave,
If the shape of the discharge arc is different, a combination of other waveforms may be used. Further, although two light distribution patterns are realized, the output current waveform of the lighting circuit 37 may be three or more, and three or more light distribution patterns can be realized.

In addition, in the third embodiment, the lighting circuit 4
2 output frequency and output current waveform, for example, 400Hz,
Although the rectangular wave and the triangular wave of 10 kHz are used, other combinations may be used as long as the discharge arc is stable and the shapes are different. Further, although the two light distribution patterns are realized, the number may be three or more.

Further, although the parabolic reflector and the outer lens are used as the light control means in the fourth embodiment, other light control means may be used. Further, the output frequency of the lighting circuit 71 is set to 76.7 kHz and 10 kHz, for example,
Other combinations of frequencies may be used as long as the discharge arc is stable and the shape of the discharge arc is different.

[0054]

As described above, according to the present invention,
A plurality of light distribution patterns can be realized by configuring the lighting circuit so as to apply a plurality of types of output signals.
Further, by using the discharge lamp lighting device of the present invention for a vehicle headlamp, it is possible to switch between a passing beam and a traveling beam in a vehicle headlamp using one discharge lamp having one arc. Its practical effect is great.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a discharge lamp lighting device according to a first embodiment of the present invention.

FIG. 2 is a diagram showing a relationship between a lamp current waveform, a lighting frequency, and a bending magnitude of a discharge arc.

FIG. 3 is a waveform diagram of the output current of the lighting circuit of the embodiment.

4 (a) and 4 (b) are diagrams showing different shapes of discharge arcs.

FIG. 5 is a configuration diagram of a discharge lamp lighting device according to a second embodiment of the present invention.

FIG. 6 is a configuration diagram of a discharge lamp lighting device according to a third embodiment of the present invention.

FIG. 7 is a waveform diagram of the output current of the lighting circuit of the same embodiment.

FIG. 8 is a diagram showing the relationship between the average temperature in the discharge space and the average sound velocity in the discharge space.

FIG. 9 is a configuration diagram of a vehicle headlamp according to a fourth embodiment of the present invention.

FIG. 10 is a configuration diagram of a lighting circuit of the same embodiment.

11 (a) and (b) are views showing the difference in shape of the discharge arc of the same embodiment.

FIG. 12 is a diagram showing a light distribution direction at the time of forming a traveling beam in the embodiment.

FIG. 13 is a diagram showing a light distribution direction when forming a low beam in the same embodiment.

FIG. 14 is a diagram showing a light distribution direction when forming a traveling beam in the embodiment.

FIG. 15 is a diagram showing a light distribution direction when forming a low beam in the same embodiment.

16 (a) and 16 (b) are diagrams showing light distribution patterns of a low beam and a traveling beam.

FIG. 17 is a configuration diagram of a conventional discharge lamp lighting device.

FIG. 18 is a configuration diagram of a conventional vehicle headlamp.

FIG. 19 is a diagram showing the shape of the lamp used in the experiment.

[Explanation of symbols]

 11, 31, 41, 72 Discharge lamp 12, 37, 42, 71 Lighting circuit 15, 43, 77 DC power supply 19, 44, 81 Inverter circuit 20, 62, 82 Drive circuit 22, 32, 45, 84 High voltage pulse generation circuit 43 Step-down chopper circuit 73 Parabolic reflector 74 Outer lens 131 Quartz glass 132, 133 Electrode

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shigeru Horii 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd.

Claims (5)

[Claims] 1. A lighting circuit, a discharge lamp connected to an output end of the lighting circuit, and light control means for irradiating light emitted from the discharge lamp in a predetermined direction, wherein the lighting circuit has an output frequency. And a characteristic that at least one of the output current waveforms can be changed, the discharge lamp is turned on by the lighting circuit, and the shape of the discharge arc of the discharge lamp is changed. 2. The lighting circuit varies at least one of an output frequency and an output waveform of voltage, current, or power to selectively form discharge arcs having different shapes to form at least two light distribution patterns. The discharge lamp lighting device according to claim 1, which is capable of being. 3. A lighting circuit varies at least one of an output frequency and an output waveform of voltage, current, or power to form two light distribution patterns, and the first light distribution pattern is changed to a passing beam. 3. The discharge lamp lighting device according to claim 2, wherein the second light distribution pattern is used as a traveling beam to provide a vehicle headlamp. 4. The discharge lamp lighting device according to claim 3, wherein the shape of the discharge arc of the discharge lamp is substantially linear when the beam is used frequently. 5. An output waveform of an instantaneous voltage, an instantaneous current or an instantaneous power of a lighting circuit when a beam is used frequently is a waveform which changes with time, V is a sound velocity in a discharge space medium of a discharge lamp, L Is the length of the discharge space that intersects the discharge arc of the discharge lamp, the output frequency f is (nV) /
The discharge lamp lighting device according to claim 4, wherein the discharge lamp lighting device is represented by (2L) (n is a natural number).