JP2006194174A - Device for utilizing waste heat of laser ignitor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a waste heat-utilizing device capable of stabilizing the operation of a laser ignitor by inhibiting temperature elevation and also of utilizing waste heat generated at the ignitor. <P>SOLUTION: The device for utilizing waste heat of the laser ignitor is provided with the laser ignitor 50 for irradiating a mixed gas in the combustion chamber 17 of an internal combustion engine with a laser to ignite, and a vapor-liquid heat exchanger 39 which is arranged at the periphery of the laser ignitor, warms up a liquid with waste heat of the ignitor while cooling the ignitor. By the vapor-liquid heat exchange in the above heat exchanger 39, the laser ignitor is cooled and the liquid is warmed up. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a gas-liquid heat exchanger or a waste heat utilization device that performs thermoelectric conversion using waste heat of a laser ignition device.

  As an ignition device for igniting (igniting) an air-fuel mixture in a combustion chamber in an internal combustion engine, an ignition device including an ignition coil and an ignition plug is generally used. The power supply voltage is boosted to a high voltage by an ignition coil, a spark is generated by an ignition plug, and an air-fuel mixture is ignited (spark ignition). However, spark ignition may not be appropriate depending on the characteristics of the fuel (for example, flame-retardant fuel). The spark plug is fixed at a predetermined position on the cylinder head in a predetermined direction. For efficient ignition, the position of the ignition part is changed according to the direction and concentration of the spray injected from the fuel injection valve. It is desirable to be able to do it.

In consideration of such circumstances, in recent years, a laser ignition device that ignites an air-fuel mixture with laser light emitted from a laser oscillator has been developed (see Patent Document 1). According to the laser ignition device, even a flame-retardant fuel can be ignited by a laser beam having a high energy density, and the ignition position can be easily changed by adjusting a lens.
JP-A-9-303244

  However, the conventional laser ignition device has room for improvement in the following points. For example, the solid-state laser oscillator shown in FIG. 5 includes a pump power supply 100, a pumping lamp lamp light source 102, a laser rod 104, a reflection mirror 106, an output mirror 108, and the like. Laser light is oscillated by the pump power source 100 and the lamp light source 102, and the oscillated laser light is amplified by the laser rod 104 and the reflection mirror 106.

  In this solid-state laser oscillator, there is a risk of adverse effects due to temperature rise and performance deterioration. More specifically, only a few percent of the light from the lamp light source 102 is used to excite the light-emitting atoms, and the remaining 90 percent is used to increase the temperature of the laser rod 104. As a result, the temperature of the laser rod 104 rises and is damaged. In addition, the energy distribution of the light-emitting atoms is affected, and the gain decreases and the laser efficiency decreases. Furthermore, due to the thermal expansion of the laser rod 104, a portion having a different refractive index is formed in the material, the refractive index is changed, the light is bent and cannot be reciprocated between the reflecting mirror 106 and the output mirror 108, and the laser oscillation efficiency is lowered. To do.

On the other hand, in the semiconductor laser oscillator shown in FIG. 6, a pn junction layer 116 is formed between the p-type semiconductor 112 and the n-type semiconductor 114. When a voltage is applied between the p-type semiconductor 112 and the n-type semiconductor 114 by the power source 118, the p-type semiconductor 112 receives the electrons stored in the n-type semiconductor 114, and laser light is generated when the electrons move. Here, the laser output depends on the magnitude of the current flowing between the p-type semiconductor 112 and the n-type semiconductor 114. The current value is dependent upon the temperature of the p-type semiconductor 112 and the n-type semiconductor 114, the laser individual characteristic temperature and T _0, the current value I is represented by _{I = I 0 exp (T /} T 0) . Therefore, when the temperature rises above a certain value, the output rises too much and becomes unstable.

  When a fixed laser oscillator or a semiconductor laser oscillator is used as an ignition device, it is necessary to be able to oscillate laser light in a very short time (warm air → warm air state) in response to the start of the engine. Increasing the value increases the calorific value. If a cooling means is provided in order to suppress the temperature increase due to heat generation, the temperature increase can be suppressed, but the cost of the ignition device increases accordingly. In addition, it is useless in terms of energy to cool the heat generated by the laser ignition device by the cooling means.

  The present invention has been made in view of the above circumstances, and it is possible to stabilize the operation of the laser ignition device by suppressing the temperature rise of the laser ignition device, and simultaneously use the waste heat generated by the laser ignition device. It aims at providing a utilization apparatus.

  The inventor of the present invention conceived that the waste heat generated in the laser ignition device is subjected to gas-liquid heat exchange or thermoelectric conversion to cool the laser ignition device and recover it as energy in different states. .

  (A) A waste heat utilization device for a laser ignition device according to a first aspect of the present invention comprises: a laser ignition device that irradiates a mixture in a combustion chamber of an internal combustion engine with a laser beam to ignite; A gas-liquid heat exchanger disposed around the apparatus for warming the liquid by the waste heat of the laser ignition apparatus and cooling the laser ignition apparatus. According to a second aspect of the present invention, there is provided a waste heat utilization device for a laser ignition device, wherein a laser ignition device that irradiates a mixture in a combustion chamber of an internal combustion engine with a laser beam and ignites the laser ignition device. And a thermoelectric converter that generates power by waste heat of the laser ignition device and cools the laser ignition device.

  (B) Hereinafter, various aspects of the components of the first invention and the second invention will be described. The internal combustion engine is typically a vehicle engine, but is not limited to a vehicle. The internal combustion engine includes a cylinder, a piston, a fuel injection valve that injects fuel into the combustion chamber, and a laser ignition device that irradiates the mixture with laser light. The fuel injection valve may be a type that injects fuel into the intake holes (manifold type) or a type that injects fuel into the combustion chamber (direct injection type). Spray and air are mixed in the combustion chamber to form an air-fuel mixture. The laser ignition device may be any one using a solid laser, one using a semiconductor laser, or a combination of both. The top position of the cylinder head is typical for the mounting position of the laser ignition device, but it may be located at other locations. The laser ignition device and the gas-liquid heat exchanger or thermoelectric converter constitute a waste heat utilization device.

  The gas-liquid heat exchanger uses the waste heat of the laser ignition device to warm the liquid and raise the liquid temperature, and also cools the laser ignition device. The liquid is typically a fuel (for example, gasoline), but is not limited thereto. The gas-liquid heat exchanger preferably includes a part of a fuel pipe extending from the fuel tank to the fuel injection valve, and this part is preferably spirally wound around the oscillation part of the laser ignition device. Further, the fuel pipe is formed with a detour connecting the upstream side and the downstream side of the laser ignition device, and a switching valve can be provided at the upstream branch point.

  The thermoelectric converter generates power using the waste heat of the laser ignition device (Seebeck effect) and cools the laser ignition device. The magnitude of the thermoelectromotive force obtained by the Seebeck effect is determined by the type of metal (conductor, semiconductor) to be combined and the temperature difference at the junction. For example, a p-type semiconductor and an n-type semiconductor made of bismuth telluride (BiTe), which is one of semiconductors, can be used. Since BiTe has a large thermoelectromotive force and low thermal conductivity, it is suitable as a thermoelectric conversion element if a pn junction is made by melting Sb or Se. Specifically, one ends of the plurality of p-type semiconductors and the plurality of n-type semiconductors are in close contact with the surface of the oscillating portion (pn junction portion). In order to promote heat dissipation, it is desirable to attach a cooling fin to the other end of the p-type semiconductor and the n-type semiconductor.

  (1) According to the waste heat utilization device of the laser ignition device according to the first aspect of the present invention, since the oscillation part of the laser oscillator is cooled by the liquid of the gas-liquid heat exchanger, warm-up can be performed in a short time when the vehicle engine is started. Can be in a state. Further, since the liquid in the liquid circulation unit is warmed by the oscillation unit of the laser oscillator, the thermal energy of the gas is recovered as the thermal energy of the liquid.

  According to the waste heat utilization device of the laser ignition device of the second and third aspects, since the spiral portion of the fuel pipe is wound around the oscillation portion, the heat exchange efficiency is further improved. As a result, the oscillator of the laser ignition device is effectively cooled, the liquid temperature of the fuel at the start of the engine rises, and the hydrocarbon (HC) in the exhaust gas decreases. According to the waste heat utilization device of the laser ignition device of the fourth aspect, since the switching valve and the bypass circuit are provided in the middle of the fuel pipe, particularly when the engine is started which requires cooling of the oscillator and heating of the fuel, Can be reliably circulated around the laser ignition device.

  (2) According to the waste heat utilization device of the laser ignition device according to the second aspect of the present invention, since the oscillating portion of the laser oscillator is cooled by the liquid of the gas-liquid heat exchanger, warm-up can be performed in a short time when the vehicle engine is started. Can be in a state. In addition, the electric energy converted from the heat energy can be used for various purposes. For example, the battery can be charged to drive a starter motor, or used as a power source for in-car electrical products such as an electronic control device. According to the waste heat utilization apparatus of the laser ignition device of the sixth aspect, since both the p-type semiconductor and the n-type semiconductor are made of BiTe, heat exchange is efficiently performed. According to the waste heat utilization apparatus of the laser ignition device of the seventh aspect, since the cooling fin is provided in the oscillation part, the heat dissipation of the oscillation part is further improved.

  The best mode of the present invention will be described below with reference to the accompanying drawings.

<First best mode>
(Constitution)
FIG. 1 shows a first best mode. The internal combustion engine (engine) includes a cylinder block 10, a piston 14, a cylinder head 16, a fuel injection valve 35, a laser ignition device 45, and the like. Among these, a water jacket 11 through which cooling water circulates is formed in the cylinder block 10, and a piston 14 is slidably engaged with the cylinder bore 12. The upper end opening of the cylinder block 10 is covered with a cylinder head 16 to define a combustion chamber 17.

  An intake hole 21 for introducing air to one side of the cylinder head 10 is connected to an exhaust hole 25 for discharging combustion gas to the other side. An intake valve 22 is disposed at the inlet of the intake hole 21 and is opened and closed by an opening / closing mechanism 23 at a predetermined time. An exhaust valve 26 is disposed at the outlet of the exhaust hole 25 and is opened and closed by an opening / closing mechanism 27 at a predetermined time. A fuel injection valve 35 is arranged on one side of the cylinder head 10 (the same side as the intake valve 22), and is connected to a fuel tank 38 via a laser ignition device 45 by a fuel pipe 36. The fuel in the fuel tank 38 is pumped to the fuel injection valve 35 through the fuel pipe 36 by the fuel pump 39.

  As shown in FIGS. 1 and 2, an oscillating portion 46 of a laser ignition device 45 is disposed in the middle of the fuel pipe 36, and a switching valve 50 is disposed on the upstream side (fuel pump 39 side). A bypass circuit 52 extends around the oscillating unit 46 from the switching valve 50 to the downstream side of the oscillating unit 46. When the switching valve 50 is switched to the first switching position by a control mechanism (not shown), the fuel flows through the oscillating portion 46, and when switched to the second switching position, the fuel flows through the bypass 52.

  As shown in FIG. 2, a spiral portion 37 formed around a portion of the fuel pipe 36 is wound around the oscillation portion 46. An irradiation part 48 of the laser oscillator 45 extends from the center part of the cylinder head 16 into the combustion chamber 17. The operation of the laser ignition device 45 is controlled by an ECU 55 that is linked to the control mechanism that switches the switching valve 50. The oscillator 46 and the spiral portion 37 constitute a gas / liquid heat exchanger 39.

(Function)
Next, the operation of this best mode will be described. However, the suction, compression, explosion and discharge processes by the reciprocating motion of the piston 14, opening and closing of the intake valve 22 and the discharge valve 26 at that time, fuel injection by the fuel injection valve 35, and ignition of the air-fuel mixture by the laser ignition device 45 Etc. are all known and are not directly related to the present invention. Therefore, these explanations are omitted.

  When the engine is started, the switching valve 50 is switched to the first switching position. Then, the fuel pumped from the fuel tank 38 through the fuel pipe 36 passes through the oscillating portion 46 of the laser ignition device 45 and then reaches the fuel injection valve 35, and spray is injected into the combustion chamber 17. When passing through the oscillating unit 46, gas-liquid heat exchange is performed between the high heat of the oscillating unit 46 and the low-temperature fuel in the spiral unit 37. As a result, the oscillation unit 46 is cooled by the low temperature fuel, and the temperature rise is suppressed. On the other hand, the low temperature fuel is warmed by the high heat of the oscillating unit 46, and the liquid temperature rises. On the other hand, after the engine is started, the switching valve 50 is switched to the second switching position. Then, the fuel does not pass through the oscillating portion 46, flows through the bypass 52, reaches the fuel injection valve 35, and spray is injected into the combustion chamber 17.

(effect)
According to this best mode, the following effects can be obtained. First, the temperature rise of the oscillating unit 46 of the laser ignition device 45 is suppressed to about 18 to 28 ° C. by the fuel flowing in the helical part 37 of the fuel pipe 36. As a result, the operation of the laser ignition device 45 is stabilized even if the oscillation unit 46 generates a large amount of heat. Secondly, the liquid temperature of the fuel is raised from about 18 to 28 ° C. by the oscillation unit 46 of the laser ignition device 45. In particular, the increase in the liquid temperature of the fuel at the time of starting the engine (particularly the time until the rotation speed reaches 400 rpm) can reduce the hydrocarbon content in the exhaust gas after the air-fuel mixture is ignited and the fuel is burned. The time for the engine speed to reach 400 rpm depends on the temperature of the engine and the fuel, and is about 1 second around 0 ° C., for example.

  Thirdly, in connection with the first and second effects, the spiral portion 37 of the fuel pipe 36 is wound around the oscillating portion 46 so that the contact area between the gas and the liquid in the gas-liquid heat exchanger 39 is increased. The heat exchange efficiency is good. Further, since the switching valve 50 and the bypass circuit 52 are provided in the middle of the fuel pipe 36, the gas-liquid heat exchange can be performed positively at the start of the engine in which the cooling of the oscillation part 46 and the heating of the fuel are particularly required. it can.

<Second best mode>
3 and 4 show the second best mode. This second best mode is different from the first best mode in the arrangement of the laser igniter 60 and the use of waste heat, and the other points are the same as the first best mode. In the following, different configurations will be mainly described.

  Nothing is arranged on the fuel pipe 36 extending from the fuel tank 38 to the fuel injection valve 35, and the oscillating unit 61 of the laser ignition device 60 is attached to the top of the cylinder head 16, and the irradiation unit 63 is disposed in the combustion chamber 17. It extends to.

  As shown in FIG. 4, a thermoelectric conversion element 65 is arranged around the oscillating unit 61, and a thermoelectric converter 70 is configured by both. More specifically, a plurality of p-type semiconductors 66 and a plurality of n-type semiconductors 67 are alternately arranged on one surface 62a of the oscillation unit 61 of the laser ignition device 60, and form a pair of p-type semiconductor (BiTe) 66 and n-type semiconductor. Copper cooling fins 69 are arranged over (BiTe) 67. Both the p-type semiconductor 66 and the n-type semiconductor 67 are Bi2Te3 compounds, which are divided into p-type and n-type depending on the type of additive. There is Pb-added or Bi-added Bi2Te3 as the p-type, and CuI-added Bi2Te3 as the n-type. Similarly, a plurality of p-type semiconductors 66 and a plurality of n-type semiconductors 67 are alternately arranged on the other surface 62 b of the oscillating portion 61, and cooling fins 69 are arranged across the paired p-type semiconductor 66 and n-type semiconductor 67. Has been.

  According to the second best mode, first, the heat energy is converted into electric energy by the heat transfer converter 70, so that the temperature rise of the oscillation unit 61 of the laser ignition device 60 is suppressed. As a result, the operation of the laser ignition device 60 is stabilized even if the oscillation unit 61 generates a large amount of heat. The obtained electric energy can be used, for example, by charging a battery to drive a starter motor or as a power source for in-car electrical products such as an electronic control device. Furthermore, since the cooling fins 69 are provided over the other ends of the p-type semiconductor 66 and the n-type semiconductor 67, the cooling (heat radiation) efficiency is further improved.

1 is an overall explanatory view of a waste heat utilization device of a laser ignition device according to a first best mode of the present invention. It is detail drawing of the gas-liquid heat exchanger of FIG. It is a whole explanatory drawing of the waste heat utilization apparatus of the laser ignition device by the 2nd best form of the present invention. FIG. 4 is a detailed view of the thermoelectric converter of FIG. 3. It is explanatory drawing which shows the conventional solid state laser oscillator. It is explanatory drawing which shows the conventional semiconductor laser oscillator.

Explanation of symbols

11: Cylinder 14: Piston 17: Combustion chamber 21: Intake hole 25: Exhaust hole 35: Combustion injection valve 37: Spiral part 39: Gas-liquid heat exchanger 45: Laser ignition device 46: Oscillation part 48: Irradiation part 50: Switching Valve 52: Detour

Claims (7)

A laser ignition device (45) for igniting a gas mixture in a combustion chamber (17) of an internal combustion engine by irradiating it with a laser beam;
A gas-liquid heat exchanger (39) disposed around the laser ignition device, for warming the liquid by waste heat of the laser ignition device and cooling the laser ignition device;
An apparatus for utilizing waste heat of a laser ignition device.   The laser ignition according to claim 1, wherein the liquid is fuel and the gas-liquid heat exchanger includes a part (37) of a fuel pipe (36) extending from a fuel tank (38) to a fuel injection valve (35). Waste heat utilization equipment of equipment.   The waste heat utilization device for a laser ignition device according to claim 2, wherein a part of the fuel pipe is a spiral wound around the laser ignition device.   The waste heat of the laser ignition device according to claim 3, wherein a bypass (52) connecting the upstream side and the downstream side of the laser ignition device is formed, and a switching valve (50) is disposed at the upstream branch point. Use device. A laser ignition device (60) that irradiates and ignites an air-fuel mixture in a combustion chamber of an internal combustion engine;
A thermoelectric converter (70) disposed around the laser ignition device and generating power by waste heat of the laser ignition device and cooling the laser ignition device;
An apparatus for utilizing waste heat of a laser ignition device.   The waste heat utilization device for a laser ignition device according to claim 5, wherein the thermoelectric converter includes a thermoelectric conversion element (66, 67) made of a semiconductor, the p-type semiconductor is BiTe, and the n-type semiconductor is BiTe.   The waste heat utilization apparatus of a laser ignition device according to claim 6, wherein cooling fins (69) are provided on surfaces of the p-type semiconductor and the n-type semiconductor.

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