JP2010101266A - Laser spark plug, laser igniter and engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a laser spark plug, a laser igniter and an engine exhibiting stable ignition performance by low electric power consumption. <P>SOLUTION: This laser igniter includes a laser device 1, an optical fiber 2 being a transmission passage, and the laser spark plug G. This laser spark plug G includes a lens device 3 and a target T. The laser device 1 output a laser beam to be made incident on the transmission passage 2. The lens device 3 is connected to the transmission passage 2, and emits the laser beam so as to be condensed to the target T. A characteristic of this invention is in a point that the target T includes an oxidation catalyst 41. This oxidation catalyst 41 can produce large explosive force for promoting oxidation combustion of combustion gas by this heat when generating heat by condensing the laser beam to the target. The oxidation catalyst 41 is generally hardly consumed, and has a property of being semipermanently usable, and is substantially unrelated to the secular deterioration. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a laser spark plug, a laser ignition device, and an engine using the same.

In recent years, an engine using a laser ignition device has been developed as an alternative to a conventional spark plug. According to this method, since the condensing position of the laser beam can be controlled, unlike the spark plug that can be ignited only at the fixed position, the combustion efficiency of the combustion gas is improved by instantaneously igniting at a plurality of locations. be able to. For this reason, there is great expectation as a technique for reducing CO ₂ emission from the viewpoint of energy saving.

  Further, the laser ignition device does not generate a large noise unlike an ignition plug, and thus has a feature that an adverse effect on an electric circuit around the engine can be reduced. For this reason, the laser ignition device can save equipment such as a shield for noise and a noise filter, and is advantageous in that the number of wirings can be reduced by superimposing a control signal on a power supply line, for example. It is.

  In using the laser ignition device, in addition to the problem of power consumption that is common in laser devices, the unique problem of stabilizing the ignition performance must be overcome. For example, Patent Document 1 discloses a technique for always condensing laser light at a predetermined position by providing a lens driving device that controls the lens position in accordance with the rotational speed of the engine. Further, in Patent Document 2, the plurality of wedge substrates installed on the optical path of the laser light are rotated at different rotational speeds, and the laser light is swung over a wide range, thereby reducing the wear of the target that is the focal position of the laser light. Techniques for reducing are disclosed.

However, these disclosed technologies all have complicated mechanisms, so that high-precision control is required. After all, in order to focus the laser beam on the piston itself, target wear occurs. The problem is not fundamentally solved. In addition, as disclosed in Patent Document 3, it is possible to stabilize the ignition performance by improving the degree of freedom of target selection using a prism, but since high accuracy is required for the prism, After all it is hard to say that it is practical.
JP-A-7-217521 Japanese Patent Laid-Open No. 9-42138 JP 2006-132492 A

  An object of the present invention is to provide a laser ignition plug, a laser ignition device, and an engine that exhibit stable ignition performance with low power consumption.

  In order to solve the above-described problems, a laser spark plug according to the present invention includes a lens device and a target. The lens device focuses incident laser light on the target.

  The laser spark plug according to the present invention is characterized in that the target includes an oxidation catalyst. Since this oxidation catalyst promotes the oxidative combustion of the combustion gas by the heat when the laser beam is focused on the target in the combustion gas atmosphere to generate heat, it can generate a large explosive force. In addition, the oxidation catalyst is generally hardly consumed and has a property that it can be used semipermanently, so it is substantially free from deterioration over time.

  For this reason, the laser spark plug according to the present invention can exhibit stable ignition performance, suppress the power required for the laser light, and reduce power consumption.

  The laser ignition device according to the present invention includes a laser device, a transmission path, and a laser spark plug. The laser device outputs laser light and makes it incident on the transmission path. The laser spark plug is the above-described laser spark plug, and the lens device is connected to the transmission path.

  Since the laser ignition device according to the present invention includes the above-described laser ignition plug in its configuration, it is obvious that the same effect can be obtained.

  Furthermore, the engine according to the present invention includes a laser ignition device and a cylinder head. The laser ignition device is the laser ignition device described above, the lens device is provided in the cylinder head, and the target is disposed in a combustion chamber of the cylinder head. The laser device outputs the laser light in synchronization with engine rotation.

  According to the engine of the present invention, since the target is provided in the combustion chamber, ignition in synchronization with the rotation of the engine can be performed in the combustion chamber. Since the engine according to the present invention includes the above-described laser ignition device, it is obvious that the same effect can be obtained.

  As described above, according to the present invention, there is provided a laser ignition plug, a laser ignition device, and an engine that exhibit stable ignition performance with low power consumption.

  FIG. 1 shows a laser ignition plug and a laser ignition device according to the present invention. The laser ignition device includes a laser device 1, an optical fiber 2 serving as a transmission path, and a laser spark plug G. The laser spark plug G includes a lens device 3 and a target T.

  The laser device 1 is a general semiconductor laser device driven by a pulse signal, and outputs a laser beam to enter the optical fiber 2. As the laser light, for example, an infrared (IR) laser having a large thermal energy can be adopted in order to facilitate ignition. In addition, although an optical fiber is cited as the transmission line of the present embodiment, the transmission line may be configured using other optical components such as a mirror and a prism as long as laser light can be transmitted with low loss. Is possible.

  The lens device 3 is connected to the optical fiber 2 and focuses the incident laser light on the target T. The lens device 3 includes an objective lens 31, a Selfoc lens 32, a front end cover 33, a body cover 34, a stopper 35, and a rear end cover 36.

  The Selfoc lens 32 is connected to the optical fiber 2 with the optical axis of the laser light aligned. In connection, since the end surface of the SELFOC lens 32 is a flat surface, the optical axis alignment with the optical fiber 2 becomes very easy. Further, since the SELFOC lens 32 has an advantage that it is excellent in mass productivity, a merit in cost can be obtained. Since the SELFOC lens 32 has a characteristic that its imaging characteristic changes depending on the lens length because of its characteristic refractive index distribution, the SELFOC lens 32 needs to have an optimum length from an optical viewpoint. The laser light incident on the SELFOC lens 32 from the optical fiber 2 further enters the objective lens 31.

  The objective lens 31 is optically connected to the SELFOC lens 32 and converges the light beam of the laser beam along the optical path L to the focal point P on the target T. As the objective lens 31, any type of general condensing lens such as a convex lens can be used, but considering the application to the engine as described later, a material having high heat resistance such as quartz and sapphire. What was formed in is desirable.

  In addition, since the objective lens 31 is directly exposed to combustion by laser light, it is considered that products such as carbon generated by the combustion adhere to the surface. However, this deposit is not a problem because it is scattered and removed by irradiation with laser light. The removal of the adhering matter may be performed by irradiation with laser light at the time of ignition, or may be performed separately by irradiation with periodic laser light for the purpose of cleaning.

  The objective lens 31 is supported by the tip cover 33 and is exposed toward the target T. The tip cover 33 has a substantially conical shape with an apex opened, and the objective lens 31 is exposed from the opening. The objective lens 31 can be freely tilted and rotated in the tip cover 33 so that the focal point P can be set in accordance with the position of the target T. The focal point P along the optical axis direction can be adjusted by adjusting the length of the Selfoc lens 32.

  The Selfoc lens 32 is housed and supported over the front end cover 33 and the body cover 34. The body cover 34 is a cylindrical case, and a fixing screw groove C is formed on the side surface thereof, that is, on the outer peripheral surface of the lens device 3. By forming the screw groove C so as to coincide with the screw groove of the conventional spark plug, the spark plug attached to the engine can be easily replaced with the laser spark plug G according to the present invention. Is obtained.

  A plate-like connecting member 37 extends from one end of the body cover 34 on the front end cover 33 side, and the connecting member 37 is integrally connected to the holding plate 42 of the target T. It is held so as to face the device 3. The holding position at this time follows the focal length determined by adjusting the SELFOC lens 32 and the objective lens 31.

  Further, both ends of the body cover 34 are connected to a tip cover 33 and a stopper 35, respectively.

  The stopper 35 is a ring-shaped member having a larger diameter than the body cover 34, and is provided to fix the fixing position when the lens device 3 is screwed in the screw groove C. The rear end side of the stopper 35 is connected to the rear end cover 36.

  The rear end cover 36 has a substantially conical shape with an apex opened, and the optical fiber 2 is introduced into the inside through the opening. As for the materials of the front end cover 33, the body cover 34, the stopper 35, and the rear end cover 36, it is desirable to use a metal material having high heat resistance such as iridium in view of application to the engine. The same applies to the connecting member 37 and the holding plate 42.

  The configurations of the laser device 1, the transmission path 2, the lens device 3, and the target T described so far can be found in the prior art. The feature of the laser spark plug and the laser ignition device according to the present invention is that the target T is an oxidation catalyst 41. It is in the point including. The oxidation catalyst 41 is fixed on the holding plate 42, and when the laser light is collected on the target in the combustion gas atmosphere to generate heat, the oxidation catalyst 41 promotes oxidative combustion of the combustion gas by this heat. Can produce a large explosive power. In addition, the oxidation catalyst 41 is generally hardly consumed and has a property that it can be used semi-permanently, so it is substantially free from aging.

  As the oxidation catalyst 41, vanadium pentoxide or platinum is preferable on the assumption of application to an engine. In particular, vanadium pentoxide has a feature that, even if it is consumed and changed to vanadium, it returns to vanadium pentoxide again by oxidation.

  For this reason, the laser ignition device according to the present invention can exhibit stable ignition performance, suppress the power required for the laser light, and reduce power consumption.

  Next, an engine to which the laser ignition device according to another embodiment of the present invention is applied will be described. FIG. 2 shows an engine to which the laser ignition device according to the present invention is applied.

  The engine includes the above-described laser ignition device, the fuel injection control unit 10, and the cylinder C. The cylinder C includes the cylinder head 5, the piston 71, the piston rod 72, the intake valve 61, the exhaust gas, and the exhaust gas. And a valve 62.

  As known in the art, the air-fuel mixture is guided to the combustion chamber R by the intake valve 61 and the piston 71 and the piston rod 72 are driven by the explosive force obtained by igniting the air-fuel mixture. The gas is discharged by the exhaust valve 62. Here, reference signs D1 to D3 indicate driving directions of the intake valve 61, the exhaust valve 62, and the piston 71, respectively.

  The laser spark plug and the laser ignition device according to the present invention are applied as an alternative to the conventional spark plug in such an engine.

  The lens device 3 is provided on the cylinder head 5. Specifically, the lens device 3 is screwed in a position where a conventional spark plug is provided, that is, in the plug hole 53 in the upper part of the cylinder head 5. As described above, the screw can be fixed by the screw groove C formed in the body cover 34. The laser light emitted from the lens device 3 is focused on the target T along the optical path L. The target T is disposed in the combustion chamber R of the cylinder head 5.

  The laser device 1 receives a synchronization signal S of a pulse wave from the engine control device, and based on this, outputs a laser beam in synchronization with the rotation of the engine. As described above, since the target T is provided in the combustion chamber R, in the combustion chamber R, ignition can be performed in synchronization with the rotation of the engine, and the air-fuel mixture can be oxidized and burned.

  As described above, since the engine according to the present invention includes the above-described laser ignition device, it is obvious that the same effect can be obtained. However, the present embodiment is not limited to this. The laser ignition device according to the present embodiment includes a beam splitter 8 and a temperature detection device 9 in addition to the above-described configuration. The temperature detection device 9 further includes an optical filter 91 and a light receiving element 92. This is because there is a characteristic effect that the combustion temperature in the combustion chamber R can be detected. This will be described below.

  The beam splitter 8 is connected to the optical fiber 2, splits the combustion light of the target T obtained through the lens device 3, and makes it incident on the light receiving element 92. In the case of the prism type, the beam splitter 8 is an optical component in which the surfaces of two bonded right-angle prisms are coated, and has a characteristic of reflecting a part of incident light and transmitting the other part.

  In the present embodiment, the beam splitter 8 is disposed between the optical fiber 2 and the laser device 1 and reflects part of the combustion light generated by ignition in the combustion chamber R in the direction Rx, while the laser device 1 The laser beam output from is transmitted in the direction Tx and is incident on the optical fiber 2. The combustion light reflected by the beam splitter 8 first passes through the filter 91. This filter 91 blocks the laser light component emitted from the laser device 1 and transmits only the visible light component of the combustion light in preparation for analysis by the temperature detector 93.

  Next, the combustion light transmitted through the filter 91 is received by the light receiving element 92, and the light receiving element 92 converts the combustion light into an electric signal E. As the light receiving element 92, for example, a photodetector used for an imaging element or the like can be employed.

  The temperature detector 93 detects the combustion temperature K of the target T based on the electric signal E. The temperature detector 93 includes color temperature measuring means such as a luminance meter and a color meter, and detects the combustion temperature K by measuring the color temperature when the target T is ignited and its change with time. In detection, the temperature detection unit 93 is timing-controlled based on the input synchronization signal S.

  As described above, according to the laser ignition device according to the present embodiment, it is possible to monitor whether the combustion is properly performed in the combustion chamber R by detecting the combustion temperature K with the temperature detection unit 93. . Furthermore, as described below, feedback control can also be performed using the detected combustion temperature K.

  The fuel injection control unit 10 normally controls the fuel injection amount by adjusting the mixing ratio of the fuel and air fed into the combustion chamber R or the opening degree of the intake valve 61. Therefore, in order to reflect the combustion temperature K in the fuel injection amount, the fuel injection control unit 10 controls the fuel injection amount into the fuel chamber R according to the combustion temperature K detected by the temperature detection unit 93. For example, follow-up control is possible in which a predetermined combustion temperature pattern is set and an appropriate fuel injection amount is calculated from the difference between this pattern and the combustion temperature K.

  Thus, according to the engine according to the present embodiment, the oxidative combustion in the combustion chamber R can be suitably controlled using the detected combustion temperature K. For this reason, it is possible to improve the combustion efficiency, reduce the power consumption of the laser, and exhibit a stable ignition performance. Furthermore, as another application, it is also possible to provide an engine performance test by measuring a signal related to engine control, for example, simultaneously with detection of the combustion temperature K.

  By the way, in the engine described so far, since the target T is provided integrally with the lens device 3, the ignition position in the combustion chamber R is fixed, and there may be a case where it is not appropriate depending on the engine. However, by providing the target T separately from the lens device 3, the ignition position can be set freely.

  An engine according to such an embodiment is shown in FIG. Here, the upper surface of the piston 71 is the target T, and the oxidation catalyst 41 is embedded in the piston 71. For this reason, an ignition position is set on the upper surface of the piston 71.

  Thus, by providing the target T independently from the lens device 3, the degree of freedom of the ignition position is improved, but the merit is not limited to this. By setting a plurality of targets T in the combustion chamber R, oxidation combustion can be generated at a plurality of positions. Thereby, the merit of the improvement of the combustion efficiency demonstrated by the item of background art is acquired. Of course, in this case, the lens device 3 is provided with a lens driving mechanism, and position control of the focal point P is required.

  Although the contents of the present invention have been specifically described above with reference to the preferred embodiments, it is obvious that those skilled in the art can take various modifications based on the basic technical idea and teachings of the present invention. It is.

1 shows a laser spark plug and a laser ignition device according to the present invention. 1 shows an engine to which a laser ignition device according to the present invention is applied. The engine which concerns on other embodiment is shown.

Explanation of symbols

1 Laser device 2 Optical fiber (transmission path)
DESCRIPTION OF SYMBOLS 3 Lens apparatus 32 Selfoc lens 4 Oxidation catalyst 5 Cylinder head 8 Beam splitter 92 Light receiving element 93 Temperature detection part 10 Fuel injection control part G Laser ignition plug T Target C Screw groove R Combustion chamber

Claims (6)

A laser spark plug including a lens device and a target,
The lens device focuses incident laser light on the target,
The target includes an oxidation catalyst;
Laser spark plug. A laser spark plug according to claim 1, comprising:
The oxidation catalyst is vanadium pentoxide or platinum;
Laser spark plug. A laser spark plug according to claim 1 or 2,
The target is held so as to face the lens device.
Laser spark plug. A laser ignition device including a laser device, a transmission path, and a laser spark plug,
The laser device outputs laser light and enters the transmission path,
The laser spark plug is a laser spark plug according to any one of claims 1 to 3,
The lens device is connected to the transmission path,
Laser ignition device. The laser ignition device according to claim 4,
Including a beam splitter, a light receiving element, and a temperature detector,
The beam splitter is connected to the transmission path, divides the combustion light of the target obtained through the lens device, and enters the light receiving element,
The light receiving element converts the combustion light into an electrical signal,
The temperature detection unit detects a combustion temperature of the target based on the electrical signal;
Laser ignition device. An engine including a laser ignition device and a cylinder head,
The laser ignition device is a laser ignition device according to claim 4 or 5,
The lens device is provided in the cylinder head,
The target is disposed in a combustion chamber of the cylinder head;
The laser device outputs the laser beam in synchronization with engine rotation.
engine.

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