JPS62162774A - Laser ignition device for internal combustion engine - Google Patents

Abstract

PURPOSE:To enable the laser ignition device in the caption to be on board and its cooling system to be simplified by connecting a laser oscillator to an excitation light source part by means of flexible optical fiber. CONSTITUTION:A laser oscillator 3 is taken on board the engine 1 side and an excitation light source part 5 on the body side, and both are connected to each other by flexible optical fiber 4. The excitation light source part 5 consists of a fluorescent mirror 51, a flash lamp 52 and an interference filter 53. Light emitted from the flash lamp 52 is focused on the end face of the flexible optical fiber 4 by the fluorescent mirror 51. Since the interference filter 53 is inserted in the optical path, only the light with the necessary wavelength is allowed to enter the flexible optical fiber 4 and transmitted to the laser oscillator 3 in order to generate laser light for ignition. In the excitation light source part 5, since the major part of light energy is changed into heat through a process of electricity light conversion loss, a cooling process is achieved through a cooling system composed of a heat exchanger 8 and a cooling fan 9. Also, since the laser oscillator 3 generates hardly any unnecessary energy, air cooling is enabled and miniaturization can be achieved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an ignition device for an internal combustion engine, and more particularly to a laser ignition device for igniting an air-fuel mixture using a laser beam.

[Conventional technology]

The laser light used for ignition of an internal combustion engine requires a very strong light density (l O"W/cnl), but the laser light after passing through an optical fiber cannot be focused to the above density, so it is difficult to ignite it. To do this, the laser oscillator itself must be mounted on the engine, which requires a small, high-output laser oscillator.

Conventionally, compact, high-output laser oscillators have used solid-state lasers, and a large number of LEDs as shown in Japanese Patent Laid-Open No. 56-24989. A type has been devised in which a light emitting diode (light emitting diode) or an LD (laser diode) is used as an excitation light source by condensing light through an optical fiber.

[Problem that the invention seeks to solve]

However, type (1) includes a Fransch lamp in the oscillator, which requires water cooling, resulting in a large-sized laser oscillator for laser ignition.
The type requires no cooling and the oscillator is small, but it requires a very large number of LEDs or LDs (for example, 104 to 10b) to obtain the above light density, and both are unsuitable for laser ignition. .

Therefore, the present invention provides a small laser oscillator that does not require water cooling, and
The purpose of this invention is to realize a high-output excitation light source and provide a laser ignition device for an internal combustion engine that can be mounted on a vehicle.

[Means for solving problems]

In order to achieve the above object, the present invention, for example, mounts a laser oscillator on the engine side and an excitation light source section on the vehicle body side, and connects the laser oscillator and the excitation light source section with a flexible optical fiber. The excitation light source includes a condenser mirror, a flash lamp,
It consists of an interference filter.

[Effect]

In the above configuration, the light emitted from the flash lamp is focused on the end face of the optical fiber by the focusing mirror. An interference filter having the characteristics shown in FIG. 2, for example, is inserted into this optical path, so that only the necessary wavelength of light enters the optical fiber and is transmitted to the laser oscillator to generate ignition laser light. In the excitation light source section, there is an electric-to-optical conversion loss and most of the light energy (required wavelength is a few percent) is converted into heat, so it is cooled by an adjacent cooling system, for example, and this excitation light source section is mounted on the vehicle body. Easy to connect. Furthermore, since the laser oscillator generates almost no unnecessary energy, it can be cooled by air, making it possible to achieve miniaturization.

〔Example〕

The present invention will be described below with reference to embodiments shown in the drawings.

FIG. 1 shows its overall configuration, in which a condenser lens 2 is fixed at a position that focuses near the center of the combustion chamber of an engine 1. Furthermore, a laser oscillator 3 (details will be described later) is inserted from the outside of the engine and fixed.

Both the condenser lens 2 and the laser oscillator 3 are equipped with an engine. Further, the laser oscillator 3 is connected to an excitation light source section 5 via a flexible optical fiber 4. This excitation light source section 5 is composed of a condenser mirror 51, a Franche lamp 52, an interference filter 53, and an end face of the optical fiber 4, and the positional relationship is such that a flash lamp 52 is placed at one focal point of the ellipsoidal condenser mirror 51. , and the end face of the optical fiber 4 is placed at another focal point. An interference filter 53 having the characteristics shown in FIG. 2 (for example, 730-820 nm bandpass in the case of a Nd YAG laser) is placed between these two focal points.

Note that the light emission timing and the like in the excitation light source section 5 are controlled by a power supply/controller section 6 to which a rotation signal and the like are input. Further, the excitation light source section 5 is cooled with pure water by a cooling system including a pump 7, a heat exchanger 8, and a cooling fan 9. The excitation light source section 5, the power supply/controller section 6,
The pump 7, heat exchanger 8, and cooling fan 9 are mounted on the body.

In addition, the laser oscillator 3 includes a dye-based passive Q switch 32 and a laser rod 34 arranged in an optical resonator composed of a semi-transparent mirror 31 and a total reflection mirror 35 that are arranged facing each other, as shown in FIG. and configure. Also, laser rod 3
4 is placed at one focal point of the ellipsoidal condenser 33,
An optical fiber scattering section 41 is arranged at the other focal point.

Next, the operation of the apparatus configured as described above will be explained. A voltage is applied from the power supply/controller unit 6 to the flash lamp 52 to emit light according to an ignition signal calculated from an engine rotation signal or the like. The light emitted from the Franche lamp is reflected by an ellipsoidal condenser mirror 51, passes through an interference filter 53, and is focused onto the end of the optical fiber 4 at another focal point of the ellipsoid. At this time, light outside the absorption band of the laser is reflected by the interference filter 53 having filter characteristics shown in FIG. 2 and converted into heat. The transmitted and focused light passes through an optical fiber 4 and enters a laser oscillator 3 shown in FIG.

The light spread by the optical fiber scattering section 41 in the laser oscillator 3 is reflected by the ellipsoidal condenser 33, and is reflected by the laser rod 34.
The light is uniformly focused on and excites this laser rod. As a result, fluorescent light is emitted from the laser rod 34, and when this fluorescent light exceeds a certain output level, the passive Q switch 32 is opened, a laser resonance state is created between the semi-transparent mirror 31 and the total reflection mirror 35, and the laser rod The energy stored in the 34 is emitted as a laser beam 36, which is focused by the condenser lens 2 at the center of the combustion chamber of the engine.The laser beam 36 has a peak output of several MW. Because it becomes a giant pulse, it causes breakdown at the focal point and ignites the air-fuel mixture in the combustion chamber.

On the other hand, heat generated in the excitation light source section 5 and the TA/controller section 6 is released to the outside of the engine by the pure water pump 7, heat exchanger 8, and cooling fan 9.

In addition, in the above embodiment, the laser oscillator 3, the optical fiber 4
, a condensing mirror 51, etc. are provided for each cylinder, but as shown in FIG. 10 may be used to distribute the light to each cylinder. Here, the controller 6' controls the optical distributor 10, t[[6#.

In the above embodiment, a passive Q switch was used as the laser Q switch, but it is also possible to use an active Q switch using a Pockels cell or the like for external control.

Further, the coupling between the optical fiber scattering section 41 in the laser oscillator 3 and the laser rod 34 may be such that the light emitted from the scattering section 41 is uniformly focused on the laser rod 34. As shown in Figure 5, a light scatterer (metal piece) 411
Alternatively, a method using a condensing mirror 33' having a shape as shown in FIG. 6 may be used.

〔Effect of the invention〕

As described above, the laser ignition device of the present invention connects the laser oscillator and the excitation light source section with a flexible optical fiber, and connects the excitation light source section with a condensing mirror, a Franch lamp, a
Since it is constructed using an interference filter, the laser oscillator is small and can be air cooled, the excitation light source can be made to have a high output, and the heat generating part can be mounted, for example, on the vehicle body, which has the excellent effect of simplifying the cooling system. be.

[Brief explanation of drawings]

FIG. 1 is an overall configuration diagram showing one embodiment of the present invention, FIG. 2 is a characteristic diagram of the interference filter in FIG. 1, FIG. 3 is a configuration diagram showing an example of the laser oscillator in FIG. 1, and FIG. FIG. 4 is an overall block diagram showing another embodiment of the present invention, and FIGS. 5 and 6 are block diagrams showing other examples of the laser oscillator. DESCRIPTION OF SYMBOLS 1... Engine, 3... Laser oscillator, 4... Optical fiber, 5... Excitation light source part, 10... Optical distributor,
51... Concentrating mirror, 52... Flash lamp, 53
... Interference filter, 101 ... Polarizing prism, 10
2... Pockelsel. Representative Patent Attorney Takashi Okabe 4: tfufuiha 5° yuan f1g, advance agent 4to 51: JL Katsuyo 52: flasher 8; 1 (41: Full 4Ic elephant destination (Fig. 3)

Claims (3)

[Claims] (1) In a laser ignition device that ignites the air-fuel mixture of an internal combustion engine with a laser beam, a laser oscillator that generates the laser beam and its excitation light source section are arranged separately, and the light from the excitation light source section is converted into flexible light. The excitation light source unit includes a flash lamp that generates light, a condenser mirror that condenses the light of the flash lamp, and light from the flash lamp and condenser mirror. A laser ignition device for an internal combustion engine, comprising: an interference filter that passes only light in a wavelength range necessary for the laser oscillator. (2) The laser oscillator and the excitation light source section are provided with one each,
2. The laser ignition device for an internal combustion engine according to claim 1, wherein the laser beam is distributed to each cylinder by a light distributor. (3) According to claim 1 or 2, the laser oscillator is installed in an internal combustion engine, and the excitation light source part is installed in a body part of a vehicle that is remote from the internal combustion engine. A laser ignition device for an internal combustion engine as described above.