JPH08291772A - Egr gas taking-out structure for engine - Google Patents

Abstract

PURPOSE: To provide an EGR device having a compact structure which can remove carbon particles in EGR gas. CONSTITUTION: In a pre-silencer 6 inserted in a common exhaust passageway 4, an expansion room 30 is formed between a casing 26 and a cylindrical member 27 with many fine holes 28 and the expansion room 30 is filled with sound absorbing material 29. An EGR taking-out port 17a of a first EGR passageway 17 is opened to the expansion room 30. Exhaust gas in the cylindrical member 27 flows into the expansion room 30 via the fine holes 28, passes through the layer of the sound absorbing material 29 to the EGR taking-out port 17a and then the first EGR passageway 17 and is supplied to an intake system as EGR gas. When the EGR gas passes through the sound absorbing material 29, carbon particles in the EGR gas are removed by the sound absorbing material 29. For this reason it is not necessary to place a carbon filter and thus the EGR device is made compact.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an EGR gas extraction structure for an engine.

[0002]

2. Description of the Related Art Generally, in an automobile engine,
Inevitably NOx (nitrogen oxides) accompanying combustion of fuel
However, when such exhaust gas containing NOx is discharged into the atmosphere, it causes air pollution. Therefore, it is necessary to reduce the NOx generation amount as much as possible. Where NOx
The generated amount increases as the combustion temperature of the fuel in the combustion chamber, that is, the exhaust temperature increases. Therefore, if the combustion temperature is lowered by some method, the NOx generation amount can be reduced.

Therefore, an engine usually has an inactive component.
An EG that lowers the combustion temperature and reduces the amount of NOx produced by extracting a part of the exhaust gas rich in (N ₂ , CO _2, etc.) from the exhaust passage and supplying it as EGR gas to the intake passage.
An R device is provided. Then, in such a conventional EGR device, E for guiding EGR gas from the exhaust system to the intake system is provided.
A GR passage and an EGR control valve that opens and closes the EGR passage according to the operating state of the engine are provided, and the EGR control valve is closed to stop the supply of EGR gas to the intake system in an operating region where EGR gas is unnecessary. It is supposed to be done.

By the way, in general, exhaust gas of an engine contains solid particles such as carbon particles (hereinafter, simply referred to as carbon particles). Therefore, when EGR gas is supplied to the intake system, the carbon particles enter the intake system. Will be brought in. Then, the carbon particles brought into the intake system may adhere to various devices constituting the intake system and hinder their operation.

Particularly, in an engine with a mechanical supercharger, the downstream end of the EGR passage is opened to the intake passage upstream of the mechanical supercharger so that EGR gas can be supplied to the intake system even during supercharging. However, in this case, if the carbon particles in the EGR gas are caught in the sliding parts of the mechanical supercharger, for example, between the rotating members that are in sliding contact with each other, or between the rotating member and the casing, the mechanical excessive The feeder may be damaged.

Therefore, generally, a carbon filter or a carbon trap for removing carbon particles in the EGR gas is provided in the EGR passage (see, for example, Japanese Patent Laid-Open No. Hei 5-
187327).

[0007]

However, the EGR
In order to effectively remove carbon particles in the gas, the capacity of the carbon filter or carbon trap must be increased considerably, so the EGR device becomes large and the layout of various devices in the engine room deteriorates. Occurs.

Further, if the temperature of the EGR gas is too high, the charging efficiency and the engine output will decrease, or the temperature of the air taken into the combustion chamber will increase and knocking will easily occur. Occurs. Therefore, in the conventional EGR device, an EGR cooler is usually provided in the EGR passage to cool the EGR gas (cold EGR). However, when the EGR cooler is provided as described above, the EGR device becomes larger and larger, and the above problem becomes more serious. A second EGR device (hot EGR) that supplies a small amount of high-temperature EGR gas to the intake system in the low-speed low-load region where the combustibility of the air-fuel mixture is reduced is provided to raise the temperature of the intake air and to improve the combustibility of the air-fuel mixture. Or, an engine is proposed which is designed to improve the ignitability and reduce the pumping loss.

The present invention has been made to solve the above-mentioned conventional problems, and can effectively remove carbon particles in EGR gas, and more preferably EG
It is an object of the present invention to obtain an EGR device having a compact structure capable of effectively cooling R gas.

[0010]

The first aspect of the present invention, which has been made to achieve the above object, is an EGR gas recirculation in which a part of exhaust gas in an exhaust system is taken out as EGR gas and recirculated to an intake system. In the EGR gas extraction structure of the engine provided with the means, one opening communicates with an upstream side portion of the exhaust passage, and the other opening downstream of the exhaust passage forms a part of an exhaust system. A hollow cylindrical member formed between an outer peripheral portion of the tubular member and an inner peripheral portion of the casing, and filled with a sound absorbing material. A silencer is provided, and the EGR gas outlet of the EGR gas recirculation means is open to the hollow portion inside the silencer.

A second aspect of the present invention is the EGR of an engine provided with an EGR passage for extracting a part of the exhaust gas in the exhaust system as EGR gas and returning it to the intake system.
In the gas extraction structure, a catalytic converter is provided in an exhaust passage forming a part of an exhaust system, and an expandable silencer having an expansion chamber is provided in the exhaust passage at a downstream side of the catalytic converter. The silencer and the silencer are arranged in close proximity to each other so that their axes are substantially aligned in the front-rear direction of the vehicle body.
A concave tunnel portion is formed below which has a half-open space portion that opens downward and accommodates the catalytic converter and the silencer in the half-open space portion, and the EGR gas outlet of the EGR passage opens into the expansion chamber of the silencer, The EGR passage extending from the EGR gas outlet to the intake system side is arranged in the half-open space of the tunnel portion.

According to a third aspect of the present invention, in the engine EGR gas extraction structure according to the second aspect of the present invention, the silencer has one opening communicating with the upstream side portion of the exhaust passage. Is provided with a porous tubular member communicating with the downstream side portion of the exhaust passage and a casing surrounding the tubular member, and an expansion chamber is formed between the tubular member outer peripheral portion and the casing inner peripheral portion. The expansion chamber is filled with a sound absorbing material.

[0013]

In the first aspect of the present invention, a part of the exhaust gas in the porous tubular member flows into the hollow portion through the pores of the tubular member, and further passes through the sound absorbing material layer. After reaching the EGR outlet, EGR is passed to the intake system through the EGR passage.
Supplied as gas. Here, when the EGR gas passes through the sound absorbing material layer, carbon particles in the EGR gas are caught by the sound absorbing material layer and are supplied to the intake system.
R gas does not contain carbon particles. The carbon particles are also removed to some extent when the EGR gas passes through the pores. Further, when the EGR gas passes through the sound absorbing material layer, fine particles of condensed water in the EGR gas are removed, and adhesion of the condensed water to the inner wall of the EGR passage is reduced. Further, the exhaust gas in the tubular member expands when flowing into the hollow portion through the pores, and the temperature thereof decreases. Further, since the silencer is generally arranged relatively downstream of the exhaust passage, the temperature of the exhaust gas in the tubular member is originally low. Therefore, the temperature of the EGR gas supplied to the intake system becomes low. Since the silencer and hence the EGR gas outlet are provided relatively downstream of the exhaust passage, the exhaust pulsation is reduced by the EGR.
Transmission to the intake system via the passage is suppressed.

In the second aspect of the present invention, the portion of the EGR passage extending from the EGR gas outlet to the intake system side is
The EGR passage can be easily laid out because it is arranged in the half-open space of the tunnel that houses the catalytic converter and the silencer. Further, the exhaust gas in the silencer expands when flowing into the expansion chamber and its temperature decreases. Further, since the silencer is arranged on the downstream side of the catalytic converter, that is, on the relatively downstream side of the exhaust passage, the temperature of the exhaust gas in the silencer is originally low. Therefore, the temperature of the EGR gas supplied to the intake system becomes low. Since the silencer and thus the EGR gas outlet is provided relatively downstream of the exhaust passage,
The exhaust pulsation is suppressed from being transmitted to the intake system via the EGR passage.

In the third aspect of the present invention, basically the same operation as the EGR gas extraction structure of the engine according to the second aspect of the present invention occurs. Further, a part of the exhaust gas in the porous tubular member flows into the expansion chamber through the pores of the tubular member, further passes through the sound absorbing material layer to reach the EGR outlet, and then passes through the EGR passage. It is supplied to the intake system as EGR gas. Here, when the EGR gas passes through the sound absorbing material layer, the carbon particles in the EGR gas are captured by the sound absorbing material layer, so the EGR gas supplied to the intake system does not contain carbon particles. Therefore, it is possible to prevent carbon particles from being brought into the intake system without providing a carbon filter or a carbon trap. The carbon particles are also removed to some extent when the EGR gas passes through the pores. Further, since the fine particles of the condensed water in the EGR gas are removed when the EGR gas passes through the sound absorbing material layer, the adhesion of the condensed water to the inner wall of the EGR passage is reduced.

[0016]

EXAMPLES Examples of the present invention will be specifically described below.
As shown in FIG. 6, the four-cylinder engine 1 burns the air-fuel mixture (mixture of air and fuel) supplied from the independent intake passages 2 (four) in each combustion chamber (not shown) to generate combustion gas. (Exhaust gas)
Is discharged to the common exhaust passage 4 via the independent exhaust passages 3 (four). Here, in the common exhaust passage 4,
A catalytic converter 5 using a three-way catalyst that removes (purifies) harmful components such as NOx and HC in the exhaust gas in order from the upstream side in the exhaust gas flow direction, and a pre-silencer 6 which will be described in detail later are provided. Has been done.

Then, air for fuel combustion is applied to the engine 1.
A common intake passage 7 for supplying (hereinafter, referred to as intake air) is provided. In this common intake passage 7, an air cleaner 8 for removing floating dust in the intake air and a throttle valve 9 that is opened and closed in conjunction with an accelerator pedal (not shown) are sequentially installed from the upstream side in the flow direction of the intake air. There are provided a Rishorum type mechanical supercharger 10 driven by an engine output shaft 13, and an intercooler 11 for cooling air pressurized by the supercharger 10 and having a high temperature. The downstream end of the common intake passage 7 is connected to a surge tank 12 that stabilizes the flow of intake air, and the surge tank 12 is connected to the upstream end of each of the independent intake passages 2.

A bypass intake passage 14 is provided which connects a portion of the common intake passage 7 upstream of the supercharger 10 and a portion downstream of the intercooler 11 to the bypass intake passage 14. A relief valve 15 is provided. The relief valve 15 is the actuator 1
It is designed to be opened / closed by 6. here,
When the supercharging pressure is high during supercharging, the relief valve 15 is opened at an opening degree corresponding to the supercharging pressure. At this time, a part of the pressurized intake air downstream of the supercharger is partially bypassed.
Is relieved to the upstream side of the supercharger, and the supercharging pressure is maintained below a predetermined upper limit value. The relief valve 15 is fully opened during non-supercharging, and intake air is supplied to the combustion chamber through the bypass intake passage 14.

Further, the engine 1 has a common exhaust passage 4
An EGR device E for extracting a part of the exhaust gas therein and supplying it to the intake system as EGR gas is provided. The EGR device E is composed of a first EGR device E ₁ and a second EGR device E ₂ . Here, the first EGR device E ₁ has a relatively low temperature E in the intake system in a predetermined high speed region or high load region.
The GR gas is supplied to lower the combustion temperature to reduce the NOx generation amount, and at the same time, to prevent the heat damage in the exhaust system due to the high temperature of the exhaust gas (cold EGR). On the other hand, the second EGR device E ₂ supplies a relatively high temperature EGR gas to the intake system in a predetermined low speed and low load region to raise the temperature of the intake air to enhance the combustibility or ignitability of the air-fuel mixture, and to pump It is designed to reduce loss (hot EGR).

The first EGR device E ₁ has one end (EG
The upstream end (as viewed in the R gas flow direction) opens to the expansion chamber 30 (see FIG. 3) of the pre-silencer 6 described later, and the other end
The first EG (downstream end when viewed in the EGR gas flow direction) is connected to the common intake passage 7 upstream of the connection part of the bypass intake passage 14 with the common intake passage 7 when viewed in the intake air flow direction.
An R passage 17 is provided. And this first EGR
A first EGR control valve 18 for opening and closing the passage 17 is provided in the passage 17.

Here, in a predetermined high speed region or high load region, the first EGR control valve 18 is opened and the first EGR passage 1
EGR gas is supplied to the intake system through 7. On the other hand, in the predetermined low speed and low load region, the first EG
The R control valve 18 is closed, and the supply of EGR gas to the intake system through the first EGR passage 17 is stopped.

On the other hand, one end (upstream end in the EGR gas flow direction) of the second EGR device E ₂ is connected to the common exhaust passage 4 upstream of the catalytic converter 5 in the exhaust gas flow direction, A second EGR passage 19 whose other end (downstream end when viewed in the EGR gas flow direction) is connected to the surge tank 12 is provided. A second EGR control valve 20 that opens and closes the second EGR passage 19 is provided in the second EGR passage 19.

Here, in the predetermined low speed and low load region, the second EGR control valve 20 is opened, and the EGR gas is supplied to the intake system through the second EGR passage 19. On the other hand, in the predetermined high speed region or high load region,
The second EGR control valve 20 is closed and the second EGR passage 19
The supply of EGR gas to the intake system through the is stopped.

Hereinafter, the exhaust system or the first EGR device E
A specific structure or function such as ₁ will be described. In the following, for convenience, the front side (left side in FIGS. 1 and 2) and the rear side (right side in FIGS. 1 and 2) of the vehicle equipped with the engine 1 are simply referred to as “front” and “rear”, respectively. The right side and the left side of the front of the vehicle are simply referred to as “right” and “left”, respectively. As shown in FIGS. 1 and 2, the independent exhaust passage 3
The (exhaust manifold) extends slightly forward from the front end surface of the engine 1 and then bends substantially 90 ° and extends downward, and is connected to the common exhaust passage 4 near the lower end of the engine 1. The common exhaust passage 4 extends rearward through the lower side of the engine 1 and is arranged below the vehicle body floor 21 behind the engine room 31.

In the vicinity below the rear end of the engine 1,
A flexible tube 24 is provided in the common exhaust passage 4. The flexible tube 24 is a tubular member that is expandable and contractible and bendable, and is a common exhaust passage 4.
It is provided to relieve external force or stress applied to.

At a portion sandwiched between a driver's seat (not shown) and a passenger's seat (not shown), a vehicle body floor 21 bulges upward to form a tunnel portion 21a, and a shift lever 22 is formed at the tunnel portion 21a. And a hand brake 23 are attached. As a result of the tunnel portion 21a bulging upward as described above, the inside of the tunnel portion 21a (under the floor wall)
A half-open space portion 32 that opens downward is formed in the. Then, in the half open space 32, the catalytic converter 5 and the pre-silencer 6 are arranged (stored) at positions close to each other so that their axes are substantially straight in the front-rear direction. The area of the cross section of the pre-silencer 6 (the section cut along the plane orthogonal to the axis) is set smaller than the area of the cross section of the catalytic converter 5 (FIGS. 4 and 5).
reference).

As shown in FIG. 3, the pre-silencer 6 is
Basically, it is composed of a substantially cylindrical casing 26, and a porous (made of a perforated plate) substantially cylindrical tubular member 27 that is arranged in the casing 26 substantially coaxially therewith.
(That is, the tubular member 27 is surrounded by the casing 26). The cylindrical member 27 is formed with a large number of pores 28 penetrating the peripheral wall thereof in the radial direction. The tubular member 27 has a diameter smaller than that of the casing 26, and a space portion having a substantially annular cross section formed between an outer peripheral portion of the tubular member and an inner peripheral portion of the casing serves as an expansion chamber 30. Here, the sound absorbing material 29 (for example, glass wool) is provided in the expansion chamber 30.
Is filled.

The pre-silencer 6 is an expansion type silencer which mainly removes high frequency sound radiated in the radial direction of the exhaust passage, and in the pre-silencer 6, the cylindrical member 2 is used.
Sound waves in 7 (especially high-frequency sound) are attenuated as they propagate through the pores 28 to the expansion chamber 30, and
It is also attenuated when passing through the sound absorbing material 29 inside in the radial direction. Thus, exhaust noise (especially high frequency noise) is reduced.
Although not shown, an expanded resonance type main silencer mainly for reducing low-frequency noise is provided downstream of the common exhaust passage 4.

The EGR gas outlet 17a of the first EGR passage 17 opens from the upper side to the inner peripheral surface of the casing 26 of the pre-silencer 6 (the outer peripheral edge of the expansion chamber 30). The first EGR passage 17 is an opening to the pre-silencer 6.
After extending slightly upward from (EGR gas outlet 17a),
It curves approximately 90 ° and extends forward. Where the first
The EGR passage 17 is located in the half-open space portion 3 of the tunnel portion 21a.
It is located at 2. That is, as shown in FIGS. 4 and 5, the first EGR passage 17 effectively utilizes an idle space portion generated between the lower surface of the top of the tunnel portion 21a and the upper surface of the top of the pre-silencer 6 or the catalytic converter 5. Are arranged. Therefore, the layout of the first EGR passage 17 is extremely easy.

Thus, in the first EGR device E ₁ , a part of the exhaust gas in the tubular member 27 flows into the expansion chamber 30 through the pores 28, further passes through the layer of the sound absorbing material 29, and the EGR gas is discharged. After reaching the outlet 17a, it is supplied to the intake system (common intake passage 7) as EGR gas through the EGR passage 17. Here, when the EGR gas passes through the sound absorbing material 29, the carbon particles in the EGR gas are captured by the sound absorbing material 29, so the EGR gas supplied to the intake system does not contain the carbon particles. For this reason,
Even if a carbon filter or a carbon trap is not provided, it is possible to prevent carbon particles from being brought into the intake system, and prevent carbon from being attached to or caught in various parts of the intake system (for example, sliding parts of the supercharger 10). It In addition,
Carbon particles are also removed to some extent when the EGR gas passes through the pores 28.

In general, when the water vapor in the EGR gas is condensed to generate condensed water, the condensed water absorbs various components in the EGR gas and becomes corrosive.
Since the fine particles of condensed water in the EGR gas are removed when the R gas passes through the sound absorbing material 29, the amount of condensed water adhering to the inner wall of the EGR passage 17 is reduced, and the occurrence of rust or corrosion on the inner wall. As a result, the durability of the first EGR passage 17 is enhanced.

Further, the exhaust gas in the tubular member 27 expands when flowing into the expansion chamber 30 through the pores 28, and the temperature thereof decreases. Further, since the pre-silencer 6 is arranged at a relatively downstream portion of the common exhaust passage 4, the tubular member 27 is provided.
The temperature of the exhaust gas inside is originally low. For this reason, the temperature of the EGR gas supplied to the intake system becomes low, and it becomes unnecessary to provide an EGR cooler, or the capacity of the EGR cooler can be reduced. Therefore, EGR
The device E is further downsized and simplified. Since the pre-silencer 6 and thus the EGR gas outlet 17a are provided relatively downstream of the common exhaust passage 4, the exhaust pulsation is suppressed from being transmitted to the intake system via the first EGR passage 17, The flow of intake air in the intake system is stabilized.

[0033]

According to the first aspect of the present invention, when the EGR gas passes through the sound absorbing material layer, the carbon particles in the EGR gas are caught by the sound absorbing material layer and are supplied to the intake system. Since no carbon particles are contained in the EGR device, it is not necessary to provide a carbon filter or a carbon trap, and the EGR device is simplified and downsized,
The layout in the engine room is improved. Also, E
Since the amount of condensed water attached to the inner wall of the GR passage is reduced and the occurrence of rust or corrosion on the inner wall is suppressed, the durability of the EGR passage or the EGR device is enhanced. further,
The temperature of the EGR gas supplied to the intake system becomes low, and E
Eliminating the need for GR cooler or EGR
Since the capacity of the cooler can be reduced, the EGR device can be further simplified and downsized. And the exhaust pulsation is EG
Since the transmission to the intake system via the R passage is suppressed, the flow of intake air in the intake system is stabilized.

According to the second aspect of the present invention, since the EGR passage is arranged by utilizing the idle space portion, the layout of the EGR passage is easy, and the layout of the vehicle equipped with the EGR device is easy. Will get better. Further, since the temperature of the EGR gas supplied to the intake system becomes low and it is not necessary to provide an EGR cooler, or the capacity of the EGR cooler can be reduced, the EGR device can be simplified, downsized, and simplified. , The layout in the engine room is improved. Note that the exhaust pulsation is suppressed from being transmitted to the intake system via the EGR passage, and the flow of intake air in the intake system is stabilized.

According to the third aspect of the present invention, basically, the same effect as the EGR gas extraction structure of the engine according to the second aspect of the present invention can be obtained. Further, when the EGR gas passes through the sound absorbing material layer, carbon particles in the EGR gas are captured by the sound absorbing material layer, and the EGR gas supplied to the intake system does not contain carbon particles, so that the carbon filter or the carbon It is not necessary to provide a trap, and the EGR device is further simplified and downsized. In addition, the adhesion of condensed water to the inner wall of the EGR passage is reduced, and the occurrence of rust or corrosion on the inner wall is suppressed.
The durability of the R passage or the EGR device is enhanced.

[Brief description of drawings]

FIG. 1 is a side view of an exhaust system of an engine having an EGR gas extraction structure according to the present invention.

2 is a plan view of the exhaust system shown in FIG. 1. FIG.

FIG. 3 is a partial cross-sectional side view diagram of the pre-silencer.

FIG. 4 is an elevation cross-sectional explanatory view of an exhaust system near an EGR gas outlet of a first EGR passage.

FIG. 5 is an elevation cross-sectional explanatory view of an exhaust system near the catalytic converter.

FIG. 6 is a system configuration diagram of an engine having an EGR gas extraction structure according to the present invention.

[Explanation of symbols]

E ... EGR device E ₁ ... first 1EGR device E ₂ ... first 2EGR apparatus 1 ... engine 2 ... independent intake passage 3 ... independent exhaust passages 4 common exhaust passages 5 catalytic converter 6 ... pre silencer 7 ... common intake passage 10 ... excessive Feeder 17 ... First EGR passage 17a ... EGR gas outlet 18 ... First EGR control valve 19 ... Second EGR passage 20 ... Second EGR control valve 21 ... Vehicle body floor 26 ... Casing 27 ... Cylindrical member 28 ... Pores 29 ... Sound absorbing material 30 ... Expansion room 31 ... Engine room 32 ... Half open space

Claims (3)

[Claims] 1. An EGR gas extraction structure for an engine, comprising an EGR gas recirculation means for extracting a part of exhaust gas in an exhaust system as EGR gas and returning the EGR gas to an intake system. A porous tubular member having one opening communicating with an upstream side portion of the exhaust passage and the other opening communicating with a downstream side portion of the exhaust passage, and a casing surrounding the tubular member. A silencer having a sound absorbing material is provided in a hollow portion formed between the outer peripheral portion of the tubular member and the inner peripheral portion of the casing, and the EGR gas outlet of the EGR gas recirculation means is provided in the silencer. An EGR gas extraction structure for an engine, wherein the EGR gas extraction structure has an opening in the hollow portion. 2. An EGR gas extraction structure for an engine, wherein an EGR passage for extracting a part of exhaust gas in an exhaust system as EGR gas and returning the exhaust gas to an intake system is provided in an exhaust passage forming a part of an exhaust system. Along with the catalytic converter, an expandable silencer with an expansion chamber is installed in the exhaust passage downstream of the catalytic converter, and the axes of the catalytic converter and the silencer are substantially straight in the longitudinal direction of the vehicle body. Are arranged in close proximity to each other, and a half-open space portion that opens downward is formed in the vehicle body floor portion, and a concave tunnel portion is formed below the half-open space portion that houses the catalytic converter and the silencer. The EGR gas outlet of the EGR passage opens to the expansion chamber of the silencer, and the EGR passage extending from the EGR gas outlet to the intake system side is a tunnel. EGR gas takeout structure for an engine, characterized in that disposed in the half-open space portion of the. 3. The EGR of the engine according to claim 2.
In the gas extraction structure, a silencer surrounds the porous tubular member, one opening of which communicates with an upstream portion of the exhaust passage and the other opening of which communicates with a downstream portion of the exhaust passage. An EGR gas extraction structure for an engine, comprising: a casing, wherein an expansion chamber is formed between an outer peripheral portion of the tubular member and an inner peripheral portion of the casing, and the expansion chamber is filled with a sound absorbing material.