JP6752042B2 - Fuel gas concentration measuring device for internal combustion engine - Google Patents

Description

The present invention relates to a fuel gas concentration measuring device for an internal combustion engine.

Conventionally, as a device for detecting the air-fuel ratio of the gas in the cylinder of an internal combustion engine, a gas sensor using a non-dispersed infrared absorption method (that is, NDIR method) is integrally provided with a spark plug attached to the internal combustion engine. There is something. For example, Patent Document 1 discloses a device in which a gas sensor is integrated with a conventional general mass-produced spark plug configuration. Specifically, first, the mass-produced spark plug includes a rod-shaped center electrode extending in the plug axis direction, a tubular insulating insulator that holds the center electrode inside, and a housing that holds the insulating insulator inside. And a ground electrode formed at the tip of the housing and provided so as to face the tip of the center electrode. Then, in the mass-produced spark plug, an optical element made of sapphire is provided inside the center electrode along the center electrode, and a reflection portion is provided at a position facing the tip of the optical element in the ground electrode. A ground electrode is provided on the side of the tip of the center electrode. The optical element is optically connected to the light source and the light receiving intensity detecting unit. In the apparatus of Patent Document 1 having such a configuration, light is emitted from the tip of the optical element, the synchrotron radiation is reflected by the reflecting portion to the tip of the optical element, and the reflected light is detected to detect the tip. The air-fuel ratio of the air-fuel mixture is measured by detecting the gas concentration between the part and the reflective part.

Japanese Unexamined Patent Publication No. 2004-93282

However, in the configuration disclosed in Patent Document 1, a new ground electrode is provided on the side of the tip of the center electrode in addition to the ground electrode in the mass-produced spark plug. Therefore, the formation of the air flow in the discharge portion formed between the center electrode and the new ground electrode is hindered by the reflection portion provided in a member separate from the new ground electrode. As a result, in this configuration, the airflow in the discharge portion of the mass-produced spark plug is not reproduced, and the air-fuel ratio in the mass-produced spark plug cannot be accurately derived. In particular, in a direct injection type internal combustion engine, the air-fuel mixture is stratified and the air-fuel mixture concentration has a spatial distribution. Therefore, the air-fuel mixture concentration may differ significantly due to a slight difference in spatial position. It is becoming more difficult to accurately derive the air-fuel ratio.

Further, in the configuration of Patent Document 1, the center electrode is held inside the tubular insulator, and a new ground electrode is provided on the side of the tip end portion of the center electrode. Therefore, the discharge portion between the center electrode and the ground electrode is formed at a position close to the insulating insulator. Therefore, the initial spark formed in the discharge portion is easily cooled by the insulating insulator. As a result, since the ignitability is inferior to that of the mass-produced spark plug, the internal combustion engine that burns lean may not be able to ignite the air-fuel mixture, and the air-fuel ratio cannot be calculated accurately.

The present invention has been made in view of this background, and an object of the present invention is to provide a fuel gas concentration measuring device for an internal combustion engine capable of accurately measuring the in-cylinder gas concentration of an internal combustion engine in order to calculate the air-fuel ratio. It is a thing.

One aspect of the present invention is a light source (10) that emits light having a predetermined wavelength that is absorbed by fuel vapor and whose intensity is attenuated.
The light receiving intensity detection unit (20) that detects the light intensity,
It has a center electrode (31) , a cylindrical insulating porcelain (37) that holds the center electrode inside, and a ground electrode (35), and is provided with a tip portion (32) of the center electrode and the ground electrode. A spark plug (30) in which a discharge portion (G) is formed between the ground electrode tip (36) and the ground electrode tip (36).
It is provided inside the center electrode so as to be along the center line (30a) of the spark plug, and is optically connected to the light source and the light receiving intensity detection unit, and the light of the light source is directed to the tip in the plug axial direction (Y). An optical element (40) that emits light from the optical element end (41), which is the end of the side (Y1), and transmits light incident from the optical element end to the light receiving intensity detection unit.
A reflecting portion (50) formed at a position facing the end of the optical element on the ground electrode and reflecting light emitted from the end of the optical element toward the end of the optical element.
A space to be measured (60), which is a space between the end of the optical element and the reflection portion, through which light emitted from the end of the optical element and reflected by the reflection portion is transmitted.
It is configured to measure the fuel gas concentration based on the attenuation of the intensity of the light incident from the end of the optical element that has passed through the measured portion.
The tip end portion (371) of the insulating insulator is located on the proximal end side (Y2) in the plug axial direction with respect to the tip end portion of the center electrode.
The end of the optical element is located closer to the base end in the plug axial direction than the tip of the center electrode, and is located closer to the tip of the insulating insulator in the plug axial direction than the tip of the insulator. ,
The ground electrode chip is located outside the projection region (S1) formed by projecting the end of the optical element in the plug axis direction in the ground electrode, and at least a part of the ground electrode chip is the above. The ground electrode is located in the fuel gas concentration measuring device (1) for an internal combustion engine , which is located inside a projection region (S2) formed by projecting the tip of the center electrode in the plug axis direction .

In the fuel gas concentration measuring device for an internal combustion engine, both the reflecting portion and the grounding electrode tip are formed on the grounding electrode and are integrally configured. As a result, since it is not necessary to provide a ground electrode of a member separate from the reflecting portion, the airflow formation of the discharge portion is less likely to be hindered, and the same airflow formation as in the case of the mass-produced spark plug can be reproduced. Therefore, the in-cylinder gas concentration of the internal combustion engine can be accurately measured, and the air-fuel ratio can be accurately derived. As a result, the gas concentration can be accurately measured even in the air-fuel mixture stratified in the direct injection type internal combustion engine, and the air-fuel ratio can be easily derived.

Further, the ground electrode chip is located on the ground electrode outside the projection region formed by projecting the end of the optical element in the plug axis direction. This prevents the ground electrode chip from preventing the light emitted from the end of the optical element from traveling through the unit to be measured. As a result, the gas concentration in the unit to be measured can be measured more accurately, and the air-fuel ratio can be derived more accurately.

Further, since the discharge portion is formed at a position substantially the same as that of the mass-produced spark plug, the initial spark is not easily cooled by the insulating insulator as compared with the case of the mass-produced spark plug. As a result, ignitability equivalent to that of a mass-produced spark plug can be obtained, and the air-fuel ratio of the mass-produced spark plug can be reproduced.

As described above, according to the present invention, in order to accurately derive the air-fuel ratio, it is possible to provide a fuel gas concentration measuring device for an internal combustion engine that can accurately measure the in-cylinder gas concentration of the internal combustion engine.

The reference numerals in parentheses described in the scope of claims and the means for solving the problem indicate the correspondence with the specific means described in the embodiments described later, and limit the technical scope of the present invention. It's not a thing.

The schematic diagram which shows the structure of the fuel gas concentration measuring apparatus for an internal combustion engine in Embodiment 1. FIG. FIG. 6 is a schematic cross-sectional view of the spark plug according to the first embodiment. FIG. 2 is a partially enlarged view of the discharge section and its surroundings. FIG. 3 is a perspective view of the discharge portion and its surroundings. FIG. 3 is an enlarged view of a part of a cross section of the discharged portion and its surroundings in the modified form 1 of the first embodiment. FIG. 2 is an enlarged view of a part of a cross section of the discharged portion and its surroundings in the modified form 2 of the first embodiment. FIG. 2 is an enlarged view of a part of a cross section of the discharged portion and its surroundings in the second embodiment.

(Embodiment 1)
An embodiment of the fuel gas concentration measuring device for an internal combustion engine will be described with reference to FIGS. 1 to 4.
As shown in FIG. 1, the fuel gas concentration measuring device 1 for an internal combustion engine (hereinafter, also referred to as a gas concentration measuring device 1) of the present embodiment includes a light source 10, a light receiving intensity detecting unit 20, a spark plug 30, and an optical element 40. It includes a reflection unit 50 and a measurement unit 60.
The light source 10 emits light having a predetermined wavelength that is absorbed by the vapor of the fuel and whose intensity is attenuated.
The light receiving intensity detecting unit 20 detects the intensity of light.
As shown in FIG. 2, the spark plug 30 has a center electrode 31 and a ground electrode 35, and a discharge portion G is provided between the tip portion 32 of the center electrode 31 and the ground electrode tip 36 provided on the ground electrode 35. Is formed.

As shown in FIGS. 1 and 2, the optical element 40 is provided inside the center electrode 31 along the center line 30a of the spark plug 30, and is optically connected to the light source 10 and the light receiving intensity detecting unit 20. The light of the light source 10 is emitted from the optical element end 41, which is the end of the tip side Y1 in the plug axial direction Y, and the light incident from the optical element end 41 is transmitted to the light receiving intensity detection unit 20.
As shown in FIGS. 2 and 3, the reflection portion 50 is formed at a position of the ground electrode 35 facing the optical element end portion 41, and directs the light emitted from the optical element end portion 41 toward the optical element end portion 41. Reflects.

As shown in FIG. 3, the measured portion 60 is a space between the optical element end portion 41 and the reflecting portion 50, and the light emitted from the optical element end portion 41 and reflected by the reflecting portion 50 is transmitted. To do.
The gas concentration measuring device 1 is configured to measure the fuel gas concentration based on the attenuation of the intensity of the light transmitted from the measured unit 60 and incident from the optical element end 41.
The ground electrode tip 36 is located on the ground electrode 35 outside the projection region S1 formed by projecting the end portion 41 of the optical element in the plug axial direction Y.

As shown in FIG. 1, in the gas concentration measuring device 1, the side inserted into the combustion chamber 101 is the tip side Y1, and the opposite side is the base end side Y2. Further, in the present specification, the plug axial direction Y means a direction parallel to the center line 30a of the spark plug 30, as shown in FIG.

Hereinafter, the gas concentration measuring device 1 of the present embodiment will be described in detail.
As shown in FIG. 1, in the present embodiment, the gas concentration measuring device 1 is attached to the combustion chamber 101 of the direct injection type internal combustion engine 100.
The gas concentration measuring device 1 includes a spark plug 30 for igniting the air-fuel mixture in the combustion chamber 101. As shown in FIG. 2, the spark plug 30 includes a substantially rod-shaped center electrode 31, a tubular insulating insulator 37 that holds the center electrode 31 inside, and a tubular housing 38 that holds the insulating insulator 37 inside. Be prepared. A ground electrode 35 is formed so as to project from the end 381 of the tip side Y1 in the plug axial direction Y of the housing 38. The material for forming the housing 38 and the ground electrode 35 can be, for example, Inconel or SUS316.

As shown in FIGS. 2 and 3, the tip portion 371 of the tip side Y1 of the insulating insulator 37 in the plug axial direction Y is located closer to the tip side Y1 than the end portion 381 of the tip side Y1 of the housing 38. Further, the tip portion 32 of the center electrode 31 is located on the tip side Y1 of the tip portion 371 of the insulating insulator 37. The material for forming the center electrode 31 is preferably a metal material having a coefficient of thermal expansion close to that of the material for forming the optical element 40 described later. This is because it becomes easy to metallize and join the two. In this embodiment, the center electrode 31 is made of Kovar.

In the present embodiment, the arrangement of the center electrode 31, the ground electrode 35, the insulating insulator 37, and the housing 38 in the spark plug 30 is the same as that in the case of the conventional mass-produced spark plug.

Further, as shown in FIGS. 2 and 3, the spark plug 30 of the present embodiment is provided with an optical element 40. The optical element 40 is located inside the center electrode 31 along the center line 30a of the spark plug 30. The optical element 40 is preferably made of a material having a low absorption rate of light having a wavelength in the infrared region, and in the present embodiment, is made of sapphire. In this example, the optical element end 41, which is the end of the optical element 40 on the tip side Y1, is located at the same position as the tip 32 of the center electrode 31 in the plug axial direction Y. That is, the end portion 41 of the optical element and the tip portion 32 are flush with each other.

As shown in FIG. 1, the optical fiber 11 is connected to the base end portion 42, which is the end portion of the base end side Y2 in the plug axial direction Y of the optical element 40. One end 11a of the optical fiber 11 is connected to the base end 42 of the optical element 40, the other end 11b of the optical fiber 11 is bifurcated, the first end 111 is connected to the light source 10, and the second end 112 receives light. It is connected to the intensity detection unit 20. As a result, the light radiated from the light source 10 enters the optical fiber 11 from the first end 111 of the optical fiber 11 and propagates through the optical fiber 11, and from one end 11a to the base end 42 of the optical element 40. Incident. The light incident from the base end portion 42 of the optical element 40 is emitted from the optical element end portion 41 of the optical element 40 as shown by reference numeral F1 in FIG.

The light source 10 is configured to emit light having a specific wavelength that is absorbed by the vapor of the fuel and whose intensity is attenuated. For example, as the light source 10, a light source capable of emitting infrared laser light having a wavelength of 1.3 to 1.4 μm, 3.39 μm, 4.3 μm or the like can be adopted. In this example, as the light source 10, a light source in which the wavelength of the emitted light is variable is adopted, and the wavelength of the emitted light is changed and used according to the component of the fuel gas to be measured.

As shown in FIGS. 2 and 3, the ground electrode 35 provided in the spark plug 30 has a bent portion 351 bent so as to face the tip portion 32 of the tip side Y1 of the center electrode 31 at a predetermined interval. doing. Then, as shown in FIGS. 3 and 4, in the bent portion 351, the light radiated from the optical element end portion 41 is reflected toward the optical element end portion 41 in the region S0 facing the optical element end portion 41. The reflective portion 50 is formed.

In the bent portion 351, the reflecting portion 50 preferably includes the projection region S1 and is formed in a region wider than the projection region S1. In this example, as shown in FIG. 3, the reflection portion 50 is formed in the bending portion 351 in a region S0 including a projection region S1 and a projection region S2 facing the tip end portion 32 of the center electrode 31. The reflecting portion 50 can be formed, for example, by subjecting the region S0 to a mirror surface treatment or forming a metal film having a high reflectance in the region S0. Then, the measured portion 60 is formed between the optical element end portion 41 and the reflecting portion 50. As will be described later, the fuel gas concentration in the air-fuel mixture existing in the unit to be measured 60 will be measured.

As shown in FIGS. 3 and 4, the ground electrode 35 is formed with a ground electrode tip 36 at the bent portion 351. The ground electrode tip 36 forms a discharge portion G with the tip portion 32 of the center electrode 31. That is, the spark plug 30 is configured to generate a spark discharge between the tip 32 of the center electrode 31 and the ground electrode tip 36 to ignite the surrounding fuel gas. The ground electrode tip 36 is made of, for example, an alloy such as iridium or platinum. The ground electrode tip 36 is located on the ground electrode 35 outside the projection region S1 formed by projecting the end 41 of the optical element in the plug axial direction Y. Further, in this example, as shown in FIG. 3, at least a part of the ground electrode tip 36 is located in the projection region S2 formed by projecting the tip portion 32 of the center electrode 31 toward the plug axis Y in the ground electrode 35. doing.

As shown in FIG. 3, the light F1 radiated from the optical element end 41 passes through the measured unit 60, reaches the reflective unit 50, and is reflected by the reflective unit 50 toward the optical element end 41. To. The reflected light F2 passes through the unit to be measured 60 and is incident on the optical element 40 from the end portion 41 of the optical element. A part of the light F1 and the reflected light F2 radiated from the end portion 41 of the optical element is absorbed by the fuel gas existing in the measured unit 60 when passing through the measured unit 60. Then, the light incident from the end portion 41 of the optical element is propagated from the base end portion 42 of the optical element 40 to the light receiving intensity detection unit 20 connected to the second end portion 112 via the optical fiber 11, and the intensity is detected. Will be done. Then, as shown in FIG. 1, the gas concentration calculating means 21 connected to the light receiving intensity detecting unit 20 calculates the gas concentration based on the intensity of the light.

Next, the action and effect of the gas concentration measuring device 1 of the present embodiment will be described in detail.
According to the gas concentration measuring device 1 of this example, both the reflecting portion 50 and the ground electrode tip 36 are formed on the ground electrode 35 and are integrally formed. As a result, since it is not necessary to provide a ground electrode that is a separate member from the reflecting portion 50, the airflow formation of the discharge portion G is less likely to be hindered, and the same airflow formation as in the case of the conventional mass-produced spark plug can be reproduced. Therefore, the gas concentration in the combustion chamber 101 of the internal combustion engine 100 can be accurately measured, and the air-fuel ratio can be accurately derived. As a result, the gas concentration can be accurately measured and the air-fuel ratio can be accurately derived even in the air-fuel mixture stratified in the direct injection type internal combustion engine 100 as in the present embodiment.

Further, the ground electrode chip 36 is located on the ground electrode 35 outside the projection region S1 formed by projecting the optical element end 41 in the plug axial direction Y. As a result, the ground electrode chip 36 prevents the light F1 emitted from the end portion 41 of the optical element from being prevented from traveling through the unit to be measured 60. As a result, the gas concentration in the unit to be measured 60 can be measured more accurately, and the air-fuel ratio can be derived more accurately.

Further, since the discharge portion G is formed at a position substantially the same as that of the mass-produced spark plug, the initial spark is not easily cooled by the insulating insulator 37 as compared with the case of the mass-produced spark plug. As a result, ignitability equivalent to that of a mass-produced spark plug can be obtained, and the air-fuel ratio of the mass-produced spark plug can be reproduced.

Further, in the present embodiment, at least a part of the ground electrode tip 36 is located inside the projection region S2 formed by projecting the tip portion 32 of the center electrode 31 in the plug axial direction Y on the ground electrode 35. As a result, the ground electrode tip 36 is arranged close to the tip portion 32 of the center electrode 31, so that the generation of spark discharge in the discharge portion G can be promoted.

In the present embodiment, the ground electrode tip 36 is attached to the tip of the bent portion 351 of the ground electrode 35, but instead of this, the tip of the bent portion 351 is attached as in the modified form 1 shown in FIG. It may be bent to the base end side Y2 in the plug axial direction Y, and the tip bent portion may be used as the ground electrode tip 360. Even in this case, the same effect as that of the present embodiment is obtained.

In the present embodiment, one ground electrode chip 36 is provided, but the present invention is not limited to this, and a plurality of ground electrode chips 36 may be provided. For example, as in the modified form 2 shown in FIG. 6, two ground electrode chips 36 may be provided. In this modified form, the ground electrode tip 36 is provided so as to sandwich the projection region S1 formed by projecting the end portion 41 of the optical element. The ground electrode tips 36 are arranged so that the distances from the tip 32 of the center electrode 31 are the same. Although occurring between the ground electrode tip 36 of the discharge Yes Zureka in the discharge section G, both the ground electrode tip 36 is the distance between the tip 32 of the center electrode 31 is the same, discharge is less likely to bias in one .. As a result, it is possible to disperse the damage caused by the electric discharge in the portion of the optical element end portion 41 close to the discharge portion G, and to prevent the damage to the optical element end portion 41 from becoming locally large. This contributes to extending the life of the gas concentration measuring device 1.

As described above, according to the present embodiment, in order to accurately derive the air-fuel ratio, it is possible to provide the gas concentration measuring device 1 capable of accurately measuring the in-cylinder gas concentration of the internal combustion engine.

(Embodiment 2)
In the gas concentration measuring device 1 of the first embodiment, as shown in FIG. 3, it is assumed that the end portion 41 of the optical element and the tip portion 32 of the center electrode 31 are flush with each other. In the gas concentration measuring device 1 of the embodiment, as shown in FIG. 7, the optical element end portion 41 is located on the proximal end side Y2 of the tip end portion 32 of the center electrode 31. In the present embodiment, the distance between the tip portion 32 of the center electrode 31 and the end portion 41 of the optical element in the plug axial direction Y, that is, the dent amount P can be set to 1.0 mm, for example.
In the present embodiment, the same reference numerals are given to the configurations equivalent to those in the first embodiment, and the description thereof will be omitted.

In the gas concentration measuring device 1 of the present embodiment, the optical element end portion 41 is located on the proximal end side Y2 of the central electrode 31 from the distal end portion 32, so that the optical element end portion 41 is separated from the discharge portion G. It will be. As a result, it is possible to prevent the end portion 41 of the optical element from being damaged by the spark discharge generated in the discharge unit G, and to accurately detect the intensity of the light that has passed through the unit to be measured.

Further, in the gas concentration measuring device 1 of the present embodiment, as shown in FIG. 7, the spark plug 30 includes a cylindrical insulating insulator 37 that holds the center electrode 31 inside, and the tip portion of the insulating insulator 37. The 371 is located on the base end side Y2 of the center electrode 31 with respect to the tip end portion 32, and the optical element end portion 41 is located on the tip end side Y1 of the insulating insulator 37 with respect to the tip end portion 371. As a result, the end portion 41 of the optical element is separated from the discharge portion G within a predetermined range, so that the spark discharge generated in the discharge portion G suppresses the damage of the end portion 41 of the optical element and the optical element. Since the element end portion 41 is not too far from the discharge portion G, the gas concentration of the airflow in the discharge portion G can be measured more accurately. In addition, also in this embodiment, the effect of the first embodiment is exhibited.

The present invention is not limited to each of the above embodiments and variants, and can be applied to various embodiments without departing from the gist thereof. For example, the configuration of the ground electrode tip 36, 360 in the modified form 1 or the modified form 2 may be combined with the configuration of the optical element end portion 41 in the second embodiment.

1 Fuel gas concentration measuring device for internal combustion engine 10 Light source 20 Light receiving intensity detector 30 Spark plug 31 Center electrode 32 Tip 35 Ground electrode 36 Ground electrode tip 40 Optical element 41 Optical element end 50 Reflecting part 60 Measured part S1, S2 Projection area

Claims (2)

A light source (10) that emits light of a predetermined wavelength that is absorbed by fuel vapor and whose intensity is attenuated.
The light receiving intensity detection unit (20) that detects the light intensity,
It has a center electrode (31) , a cylindrical insulating porcelain (37) that holds the center electrode inside, and a ground electrode (35), and is provided with a tip portion (32) of the center electrode and the ground electrode. A spark plug (30) in which a discharge portion (G) is formed between the ground electrode tip (36) and the ground electrode tip (36).
It is provided inside the center electrode so as to be along the center line (30a) of the spark plug, and is optically connected to the light source and the light receiving intensity detection unit, and the light of the light source is directed to the tip in the plug axial direction (Y). An optical element (40) that emits light from the optical element end (41), which is the end of the side (Y1), and transmits light incident from the optical element end to the light receiving intensity detection unit.
A reflecting portion (50) formed at a position facing the end of the optical element on the ground electrode and reflecting light emitted from the end of the optical element toward the end of the optical element.
A space to be measured (60), which is a space between the end of the optical element and the reflection portion, through which light emitted from the end of the optical element and reflected by the reflection portion is transmitted.
It is configured to measure the fuel gas concentration based on the attenuation of the intensity of the light incident from the end of the optical element that has passed through the measured portion.
The tip end portion (371) of the insulating insulator is located on the proximal end side (Y2) in the plug axial direction with respect to the tip end portion of the center electrode.
The end of the optical element is located closer to the base end in the plug axial direction than the tip of the center electrode, and is located closer to the tip of the insulating insulator in the plug axial direction than the tip of the insulator. ,
The ground electrode tip is located outside the projection region (S1) formed by projecting the end of the optical element in the plug axis direction in the ground electrode, and at least a part of the ground electrode tip is the above. A fuel gas concentration measuring device (1) for an internal combustion engine, which is located inside a projection region (S2) formed by projecting the tip end portion of the center electrode in the ground electrode in the plug axis direction . The ground electrode tip has a plurality equipped, for an internal combustion engine fuel gas concentration measuring apparatus according to claim 1.

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