JP2882736B2 - Air introduction device in exhaust pipe of internal combustion engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a device for introducing air into an exhaust pipe of an internal combustion engine, which heats air introduced into the exhaust pipe of the internal combustion engine to promote the activation of a catalyst and improve the efficiency of purifying exhaust gas. It is.

[0002]

2. Description of the Related Art Conventionally, as this type of air introduction device in an exhaust pipe, for example, those disclosed in JP-A-51-62220 and JP-A-52-132020 are known. In the conventional exhaust pipe air introduction device, in order to improve the purification efficiency by the catalyst was warmed as much as possible quickly immediately after the start of the internal combustion engine, the air introduced into the catalytic, engine
Preheated by the heat of
Is heated. That is, immediately after the start of the internal combustion engine, since the catalyst temperature is low and the exhaust gas purification efficiency is low, heated air is introduced into the exhaust pipe from the air introduction pipe connected upstream of the catalyst to promote activation of the catalyst. doing.

When air is introduced into the exhaust pipe, HC (hydrocarbon), CO (carbon monoxide) and the like in the exhaust gas are oxidized and purified, but when the introduced air is heated as described above,
In response to the heat of the introduced air and the heat generated by the reaction, the temperature of the catalyst quickly rises, and the activation of the catalyst is promoted. As a result, the above reaction is promoted by the activated catalyst, and the purification efficiency of the exhaust gas is improved.

FIG. 8 is a configuration diagram showing an example of a conventional air introduction device in an exhaust pipe of an internal combustion engine. In FIG. 1, an internal combustion engine 1 is connected to an intake pipe 2 for introducing air and an exhaust pipe 3 for discharging harmful exhaust gas generated by combustion to the atmosphere. An air cleaner 4 for removing dust in the atmosphere is provided at an upstream portion of the intake pipe 2.
Downstream of the air cleaner 4, an airflow sensor 5 for measuring the amount of air taken into the internal combustion engine 1 is provided. Further, a throttle valve 6 for changing the passage area of the intake pipe 2 to adjust the amount of air taken into the internal combustion engine 1 is provided downstream of the air flow sensor 5.

In the middle of the exhaust pipe 3, there is provided a catalytic converter 7 having a catalyst for purifying exhaust gas by a chemical reaction. Downstream of the air cleaner 4 of the intake pipe 2 and the exhaust pipe 3
An air introduction pipe 8 is connected between the upstream side of the catalytic converter 7 and the upstream side. In the middle of this air introduction pipe 8, the exhaust pipe 3
An air pump 9 is provided for forcibly sending air into the air pump. As the air pump 9, a mechanical pump driven by the internal combustion engine 1 is used.

Downstream of the air pump 9 of the air introduction pipe 8,
An air regulating valve 10 for adjusting the amount of introduced air, a heater 11 as heating means for heating the introduced air, and a check valve 12 for preventing exhaust gas from flowing back to the air introducing pipe 8 are provided. . A controller 13 for controlling the air regulating valve 10 and the heater 11 is connected thereto.

[0007] The internal combustion engine 1 is provided with a crank angle sensor 14 that outputs rectangular waves having different periods in accordance with the rotation thereof. The exhaust pipe 3 is provided with an exhaust gas sensor 15 that outputs a voltage corresponding to the concentration of oxygen contained in the exhaust gas. The crank angle sensor 14, the exhaust gas sensor 15, the above-described air flow sensor 5, and the throttle valve 6 are connected to a controller 13, which controls the air regulating valve 10 and the The heater 11 is controlled. Note that here, the internal combustion engine 1
The illustration of the injector for supplying fuel to the fuel cell and its control system is omitted.

Next, the operation will be described. The clean air that has passed through the air cleaner 4 is sent from the intake pipe 2 to the internal combustion engine 1 in an amount corresponding to the opening of the throttle valve 6. Fuel injected from an injector is also supplied to the internal combustion engine 1, and a mixture of the air and the fuel is burned in the internal combustion engine 1. The harmful exhaust gas generated by the combustion is discharged to the exhaust pipe 3.

On the other hand, when the air pump 9 rotates with the rotation of the internal combustion engine 1, a part of the air passing through the air cleaner 4 is forcibly taken into the air introduction pipe 8 and sent to the air regulating valve 10. In the air adjustment valve 10, the air amount is adjusted so as to be the optimum introduced air amount determined by the controller 13. The air that has passed through the air regulating valve 10 is supplied to the heater 1
After being heated at 1, it is introduced into the exhaust pipe 3 upstream of the catalytic converter 7 via the check valve 12.

The air thus introduced into the exhaust pipe 3 is mixed with the exhaust gas discharged from the internal combustion engine 1 and is introduced into the catalytic converter 7. In the catalytic converter 7, air reacts with HC and CO, which are harmful components in the exhaust gas, that is, HC and CO are oxidized by oxygen in the introduced air to be converted into H ₂ O, CO _{2, and the} like. The gas is purified. Immediately after the start of the internal combustion engine 1, the catalyst is not activated, and the above reaction does not occur sufficiently. Therefore, heating the introduced air with the heater 11 accelerates the temperature rise of the catalyst. Promotes activation.

[0011]

In the conventional air introduction device in the exhaust pipe of an internal combustion engine configured as described above,
When the internal combustion engine 1 is mounted on a vehicle, the air introduction pipe 8
Since the running air of the vehicle hits the heater 11 and the heater 11, the air introduction pipe 8 and the heater 11 are cooled by air, and the temperature of the introduced air is lowered. For this reason, there has been a problem that the temperature of the mixed gas of the exhaust gas and the air sent to the catalytic converter 7 also becomes low, the temperature rise of the catalyst is hindered, and the purification efficiency of the exhaust gas decreases.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and it is possible to prevent the temperature of air introduced into an exhaust pipe from decreasing, thereby reducing exhaust gas. It is an object of the present invention to obtain an air introduction device in an exhaust pipe of an internal combustion engine that can improve the purification efficiency of the exhaust gas.

[0013]

According to a first aspect of the present invention, there is provided an air introduction device in an exhaust pipe of an internal combustion engine, wherein a portion of the air introduction tube downstream of the heating means and at least a part of an outer peripheral portion of the heating means are provided. And a bypass passage forming member for forming an exhaust gas bypass passage.

According to a second aspect of the present invention, there is provided an exhaust pipe air introduction device for an internal combustion engine, wherein a gas passage switching means for switching an exhaust gas passage for introducing exhaust gas into a bypass passage is provided.

[0015]

In the present invention, an exhaust gas bypass passage is formed in at least a part of the outer periphery of the air introduction pipe and the heating means, and high-temperature exhaust gas is passed through the bypass passage to be heated by the heating means. This prevents the introduced air from being cooled by the traveling wind of the vehicle.

[0016]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. Embodiment 1 FIG. FIG. 1 is a configuration diagram illustrating an air introduction device in an exhaust pipe of an internal combustion engine according to a first embodiment of the present invention. FIG. 2 is a configuration diagram illustrating an enlarged main part of FIG. 1. The same reference numerals are given and the description is omitted.

In the figure, an outer cylinder 21 as a bypass passage forming member is provided at a portion of the air introduction pipe 8 downstream of the heater 11 so as to cover the outer periphery thereof. Outer cylinder 21
An exhaust gas inflow pipe 22 communicates between the vicinity of the heater 11 side end and the exhaust pipe 3. Further, between the vicinity of the end on the opposite side of the outer cylinder 21 and the exhaust pipe 3, an exhaust gas outflow pipe 2 is provided.
3 communicates. Therefore, part of the exhaust gas flowing in the exhaust pipe 3 flows between the air inlet pipe 8 and the outer cylinder 21 by bypass. That is, an exhaust gas bypass passage is formed inside the outer cylinder 21.

The air pump 9 may be of a mechanical type similar to the conventional type driven by the internal combustion engine 1, but in the first embodiment, an air pump of an electric motor type driven by a DC power supply is used. 13 controls the driving. Further, as the air adjusting valve 10, a mechanical type in which a diaphragm is operated by a negative pressure to change an opening degree, an electromagnetic solenoid valve, a stepping motor valve, or the like is used.

Next, the operation will be described. The air pump 9 receives a control signal from the controller 13 and
It rotates according to the rotation of. Thereby, the air cleaner 4
A part of the clean air that has passed through is taken into the air introduction pipe 8 and sent to the air regulating valve 10. In the air adjustment valve 10, the air amount is adjusted so as to be the optimum introduced air amount determined by the controller 13. After the air adjusted to the optimum amount is heated by the heater 11, the air is exhausted into the exhaust pipe 3 through the check valve 12.
Is introduced upstream of the catalytic converter 7.

At this time, in the apparatus of the first embodiment, the portion of the air inlet pipe 8 downstream of the heater 11 and the check valve 12
Is covered with an outer cylinder 21 to form a double structure.
High temperature exhaust gas flows inside. That is, the exhaust gas flowing into the outer cylinder 21 from the exhaust gas inflow pipe 22
As shown in the figure, the air flows in the outer cylinder 21 along the air introduction pipe 8 and the check valve 12 and returns from the exhaust gas outflow pipe 23 to the exhaust pipe 3.

Therefore, the air introduction pipe 8 is generated by the wind of the vehicle.
Is not directly cooled, and the cooled air introduction pipe 8 is cooled.
Therefore, the introduced air is not cooled. Therefore, the introduced air heated by the heater 11 can be kept at a high temperature and introduced into the exhaust pipe 3. Further, the exhaust gas in the outer cylinder 21 is heated by the introduced air, and the heated exhaust gas is returned from the exhaust gas outflow pipe 23 into the exhaust pipe 3, so that the exhaust gas flowing through the exhaust pipe 3 has a higher temperature. .

The air thus kept warm and introduced into the exhaust pipe 3 is mixed with the high-temperature exhaust gas discharged from the internal combustion engine 1 and introduced into the catalytic converter 7. In the catalytic converter 7, air reacts with HC and CO, which are harmful components in the exhaust gas, to purify the exhaust gas. That is, HC and CO are oxidized and converted into H ₂ O, CO _{2 and the} like.

FIG. 3 is a relationship diagram showing the relationship between the catalyst inlet gas temperature and the conversion rate as an example of such purification efficiency in the catalytic converter 7. As shown in the figure, the catalyst temperature is 400 ° C.
, The CO in the exhaust gas is converted to a 100% detoxifying component. Therefore, as in the first embodiment, by preventing cooling of the introduced air due to the traveling wind, the catalyst temperature can be made higher, and the purification efficiency of the exhaust gas can be improved.

Embodiment 2 FIG. Next, FIG. 4 is a configuration diagram showing a main part of an air introduction device in an exhaust pipe of an internal combustion engine according to a second embodiment of the present invention. In the first embodiment, the outer cylinder 21 is provided at a portion downstream of the heater 11 of the air introduction pipe 8, but in the second embodiment, in addition to the outer cylinder 21 of the first embodiment, a bypass passage forming member is used. A certain outer cylinder 24 is also provided on the outer periphery of the heater 11 to form a bypass passage for the exhaust gas flowing in the order of the exhaust gas inflow pipe 22, the outer cylinder 24, the connection pipe 25, the outer cylinder 21, and the exhaust gas outflow pipe 23. I have.

FIG. 5 is a diagram showing the relationship between the energizing time and the temperature of the heated air indicating the temperature rise characteristics of the heater 11, wherein the broken line indicates the case where cooling by the traveling wind is present, and the solid line indicates the case where there is no traveling wind. . In the apparatus according to the second embodiment, since the high-temperature exhaust gas flows not only around the air introduction pipe 8 but also around the heater 11, cooling of the heater 11 by traveling wind is prevented. Therefore, the heating efficiency of the heater is improved from the broken line to the solid line in FIG. That is, the temperature of the introduced air can be raised to a higher temperature in a short time.

Embodiment 3 FIG. Next, FIG. 6 is a configuration diagram showing a main part of an air introduction device in an exhaust pipe of an internal combustion engine according to Embodiment 3 of the present invention. In the figure, a heater 11 of an air introduction pipe 8 is shown.
A heat retaining tube 26, which is a bypass passage forming member, is spirally wound around the outer peripheral portion on the downstream side. An exhaust gas inflow pipe 22 and an exhaust gas outflow pipe 23 are connected to both ends of the heat retaining pipe 26, and these form an exhaust gas bypass passage.

In an apparatus using such a heat retaining tube 26,
Since the high-temperature exhaust gas flows into the heat retaining pipe 26, the air introduction pipe 8 is prevented from being cooled by the traveling wind, and the heater 1
The air heated in 1 is kept at a high temperature and introduced into the exhaust pipe 3. Further, the exhaust gas flowing through the heat retaining pipe 26 can be warmed, and the heated exhaust gas is returned into the exhaust pipe 3 so that the temperature of the exhaust gas flowing through the exhaust pipe 3 becomes even higher, and the purification of the exhaust gas is promoted. Is done.

Embodiment 4 FIG. Next, FIG. 7 is a configuration diagram showing a main part of an air introduction device in an exhaust pipe of an internal combustion engine according to Embodiment 7 of the present invention. In the figure, a passage opening / closing valve 31 as a gas passage switching means is provided downstream of a connection portion of the exhaust pipe 3 with the exhaust gas inflow pipe 22. The passage opening / closing valve 31 forcibly causes exhaust gas to flow into the exhaust gas inflow pipe 22 by reducing the passage area of the exhaust pipe 3. Also,
The opening degree of the passage opening / closing valve 31 is adjusted according to the operation state and the elapsed time of the internal combustion engine 1 by a control signal from the controller 13. Other configurations are the same as those in the first embodiment.

Next, the operation will be described. Internal combustion engine 1
The exhaust gas exhausted from the exhaust gas is sent to the catalytic converter 7 through the exhaust pipe 3, where the air pump 9 and the air regulating valve 10
When the heater 11 and the like are operating according to the control signal from the controller 13, the opening of the passage opening / closing valve 31 is reduced as much as possible so that the operating state of the internal combustion engine 1 does not deteriorate,
The amount of exhaust gas sent to the exhaust gas inflow pipe 22 is increased. When the air introduction control in the exhaust pipe is not performed, the opening of the passage opening / closing valve 31 is fully opened, and the pressure loss in the exhaust pipe 3 is reduced.

Therefore, when it is necessary to keep the temperature of the introduced air, the exhaust gas can be forcibly sent to the bypass passage in the outer cylinder 21, and a sufficient heat retaining effect can be obtained. When air is not introduced into the exhaust pipe 3, the passage area of the exhaust pipe 3 is increased so that the exhaust gas hardly flows into the exhaust gas inflow pipe 22, and the exhaust pressure loss during high load traveling is reduced. Can be reduced.

Although the check valve 12 is provided downstream of the heater 11 in each of the above embodiments, if the exhaust gas flowing through the exhaust pipe 3 can be prevented from flowing backward, another check valve can be provided. It may be provided in a part.

Further, in the fourth embodiment, the exhaust gas is caused to flow into the exhaust gas inflow pipe 22 by using the passage opening / closing valve 31 whose opening degree changes according to the control signal from the controller 13. As long as it can be forcibly sent to the gas inflow pipe 22 side, for example, a three-way valve for completely switching the passage or a vacuum cut valve may be used.

Further, in each of the above embodiments, the controller 13 controls the air pump 9, the air regulating valve 10, the heater 11 and the like in response to signals from various sensors for detecting the operating state of the internal combustion engine 1. However, a control signal corrected based on various temperatures, battery voltage, atmospheric pressure, and the like of the internal combustion engine 1 may be output. Further, the controller 13 may be integrated with an engine controller (not shown) for performing fuel control and the like of the internal combustion engine 1.

Further, the outer circumferences of the outer cylinders 21, 24, the exhaust gas inflow pipe 22, the exhaust gas outflow pipe 23, the connection pipe 25, the heat insulation pipe 26 and the like may be covered with a heat insulating material or a material having a heat insulation effect. Cooling of the introduced air can be more reliably prevented. Needless to say, it is preferable to make the exhaust gas inflow pipe 22 as short as possible.

When an electric motor type air pump 9 capable of adjusting the amount of air to be discharged is used, the air adjusting valve 10 may be omitted.

[0036]

As described above, according to the first aspect of the present invention, the apparatus for introducing air into an exhaust pipe of an internal combustion engine has a portion downstream of the heating means of the air introduction pipe and an outer peripheral portion of at least a part of the heating means. Is provided with a bypass passage forming member for forming an exhaust gas bypass passage, and a high-temperature exhaust gas is introduced into the bypass passage, so that the temperature of the air introduced into the exhaust pipe is reduced by the traveling wind of the vehicle. Can be prevented and the exhaust gas can be warmed,
As a result, it is possible to suppress a decrease in the heating efficiency of the heating means and to improve the exhaust gas purification efficiency.

Further, the exhaust pipe air introduction device for an internal combustion engine according to the second aspect of the present invention is provided with the gas passage switching means for switching the exhaust gas passage for introducing the exhaust gas into the bypass passage. In addition to the same effects as those of the invention, when it is necessary to keep the introduced air warm, the exhaust gas can be forcibly flown into the bypass passage to keep the temperature sufficiently, and when the air is not introduced into the exhaust pipe, the exhaust gas can be exhausted. This has the effect of increasing the pipe passage area and reducing the exhaust pressure loss during high-load running.

[Brief description of the drawings]

FIG. 1 is a configuration diagram illustrating an air introduction device in an exhaust pipe of an internal combustion engine according to a first embodiment of the present invention.

FIG. 2 is a configuration diagram showing an enlarged main part of FIG. 1;

FIG. 3 is a relationship diagram showing an example of a relationship between a catalyst inlet gas temperature and a conversion rate of the apparatus of FIG.

FIG. 4 is a configuration diagram illustrating a main part of an air introduction device in an exhaust pipe of an internal combustion engine according to a second embodiment of the present invention;

FIG. 5 is a diagram showing the relationship between the energizing time and the temperature of the heated air, showing the difference in the temperature rise characteristics of the heater between when there is cooling by running wind and when there is no cooling.

FIG. 6 is a configuration diagram illustrating a main part of an air introduction device in an exhaust pipe of an internal combustion engine according to a third embodiment of the present invention;

FIG. 7 is a configuration diagram illustrating a main part of an air introduction device in an exhaust pipe of an internal combustion engine according to Embodiment 4 of the present invention;

FIG. 8 is a configuration diagram showing an example of a conventional air introduction device in an exhaust pipe of an internal combustion engine.

[Explanation of symbols]

 Reference Signs List 1 internal combustion engine 3 exhaust pipe 7 catalytic converter 8 air introduction pipe 11 heater (heating means) 21 outer cylinder (bypass passage forming member) 24 outer cylinder (bypass passage forming member) 26 heat retaining pipe (bypass passage forming member) 31 passage opening and closing Valve (gas passage switching means)

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) F01N 3/30 F01N 3/32

Claims (2)

(57) [Claims] 1. An air introduction pipe for introducing air upstream of a catalyst in an exhaust pipe of an internal combustion engine, heating means provided in the air introduction pipe for heating the introduced air, and heating of the air introduction pipe. An internal combustion engine provided with a bypass passage forming member provided on at least a part of an outer peripheral portion of a portion downstream of the unit and the heating unit and forming a bypass passage for exhaust gas on the outer peripheral unit. Air introduction device in the exhaust pipe of the engine. 2. An air introduction pipe for introducing air upstream of a catalyst in an exhaust pipe of an internal combustion engine, heating means provided on the air introduction pipe for heating the introduced air, and heating of the air introduction pipe. A bypass passage forming member that is provided so as to cover at least a part of the heating unit and a portion downstream of the unit and that forms an exhaust gas bypass passage in the outer peripheral portion; and that the exhaust gas is introduced into the bypass passage. And a gas passage switching means for switching the passage of the exhaust gas to perform the exhaust gas in the exhaust pipe of the internal combustion engine.