JP2012246866A - Egr device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To achieve stable combustion by enhancing mixing properties of air and EGR gas, even when a distance from a discharge opening of an EGR flow path to a cylinder is short.SOLUTION: This EGR device 1 includes: an EGR flow path 6 in which a discharge opening 6a is provided at an intake port 4; an EGR valve 7 adjusting an opening of the EGR flow path 6; an intake bypass path 11 leading some of the intake into the chamber 13 of the EGR flow path 6; and a second throttle valve 12 adjusting an opening of the intake bypass path 11. Since the EGR gas supplied from the discharge opening 6a into the intake port 4 is mixed with air, nearly homogeneous EGR gas distribution is formed in a cylinder, and stable combustion is thereby achieved. Accordingly, the amount of EGR gas can be increased, and fuel economy is improved by reducing pumping loss.

Description

  The present invention relates to an EGR device (exhaust gas recirculation device) that guides a part of exhaust gas discharged from an engine (an internal combustion engine that generates power by combustion of fuel) to an intake passage as EGR gas, and reduces pumping loss by EGR gas. The present invention relates to a technique suitable for use in a technique for improving fuel economy.

・ Suppresses the generation of NOx (nitrogen oxide) in exhaust gas,
・ Suppress the occurrence of knocking,
An EGR device that returns EGR gas (inert gas) to an intake passage for the purpose of suppressing pumping loss is known.
In particular, the technology for suppressing the pumping loss requires that a large amount of EGR gas be led to the intake passage in order to improve fuel consumption.

On the other hand, it is assumed that the diffusion rate of EGR gas sucked into the cylinder together with air is low.
A specific example will be described with reference to FIG. In addition, the same code | symbol is attached | subjected to the same function thing as [the form for inventing] mentioned later and [Example].
As shown in FIG. 6A, in order to prevent EGR gas from remaining in the intake passage and to improve engine responsiveness, the exhaust port 6a of the EGR flow path 6 provided in the intake port 4 is EGR. Since the distance from the discharge port 6a of the flow path 6 to the cylinder is short, the EGR gas hardly mixes with air (see, for example, Patent Document 1).

  For this reason, for example, even if vortex flow (tumble flow, swirl flow, etc.) is generated in the cylinder using the vortex flow control valve 17 (tumble flow control valve, swirl flow control valve, etc.), the diffusivity of EGR gas is low, As shown by the solid line α in FIG. 3, the fluctuation rate of the EGR gas in the cylinder greatly changes.

The EGR gas sucked into the cylinder together with the air is somewhat diffused and mixed with the air in the compression stroke. However, sometimes the concentrated EGR gas remains, and the concentrated EGR gas sometimes collects in the spark discharge portion of the spark plug 16 as shown in FIG. In this case, even if the spark plug 16 performs an ignition operation, the combustion is not promoted, resulting in unstable combustion such as misfire.
In FIG. 6B, a region A in the combustion chamber indicates a region of high-concentration EGR gas, and a region B in the combustion chamber indicates a region of low-concentration EGR gas.

JP 2010-281273 A

  The present invention has been made in view of the above-described problems, and an object thereof is to provide an EGR device that can improve the mixing of air and EGR gas and realize stable combustion.

[Means of Claim 1]
In the EGR apparatus according to the first aspect, air is supplied into the EGR flow path by the air supply means, so that EGR gas mixed with air is introduced into the intake passage from the outlet of the EGR flow path.
Thereby, since the mixability of air and EGR gas becomes high, the density | concentration difference of EGR gas in a cylinder can be suppressed, and stable combustion can be implement | achieved.

[Means of claim 2]
The EGR device according to claim 2 is provided with an exhaust port for EGR gas at the intake port of the engine.
As a result, the distance from the discharge port of the EGR flow path to the cylinder is shortened, but since the EGR gas mixed with air is discharged from the discharge port as described above, the mixing property of the air and the EGR gas in the intake port. Increases, the difference in the concentration of EGR gas in the cylinder can be suppressed, and stable combustion can be realized.

[Means of claim 3]
According to a third aspect of the present invention, there is provided an air supply means for leading a part of the intake air upstream of the throttle valve into the EGR flow path downstream of the EGR valve and adjusting the opening of the intake bypass path. And a second throttle valve.

[Means of claim 4]
According to a fourth aspect of the present invention, a chamber (volume part) for mixing EGR gas and air is provided at the connection part between the EGR flow path and the intake bypass path.
Since air and EGR gas are mixed inside the chamber, the stability of the mixing of air and EGR gas discharged to the intake passage can be increased, and as a result, the rate of fluctuation of EGR gas in the cylinder can be reduced. Can be suppressed.

[Means of claim 5]
According to a fifth aspect of the present invention, when the accelerator is operated to the closing side (opening side), the control device includes cleanup means for controlling the EGR valve to the closing side and controlling the second throttle valve to the opening side.
By operating the accelerator to the closing side, the intake negative pressure on the intake downstream side of the throttle valve increases. At this time, even when the EGR gas in the intake passage increases, the EGR gas in the intake passage is diluted by the air that passes through the intake bypass passage and is supplied to the intake passage, thereby preventing combustion deterioration such as misfire. Can do.
Further, when the accelerator is closed (when fully closed), the EGR gas can be scavenged by opening the second throttle valve greatly. For this reason, the responsiveness of the engine when the accelerator is opened can be improved.

[Means of claim 6]
The air supply means of claim 6 is an air pump for supplying air into the exhaust passage through which the exhaust passes.
The EGR channel introduces part of the air discharged from the air pump together with part of the exhaust gas from the exhaust passage.
Thus, since the exhaust gas mixed with air is introduced into the EGR flow path, the mixing ability of the air discharged into the intake passage and the EGR gas can be used without using the chamber shown in the means of claim 4. Can increase the degree of stability.
Since the chamber is not used, the passage volume between the EGR valve and the outlet of the EGR flow path can be reduced, and the response of “increase / decrease in EGR gas amount in the cylinder” to “EGR valve opening control” is improved Thus, the EGR control at the time of transition can be improved.

[Means of Claim 7]
The air pump according to claim 7 is an air pump of a secondary air supply system that supplies air into the exhaust passage on the exhaust upstream side of the catalyst that purifies the exhaust gas.
Since the air pump of the secondary air supply system is used, the implementation cost of the present invention can be suppressed.

It is a schematic block diagram of an EGR apparatus (Example 1). (Example 1) which is explanatory drawing at the time of an intake stroke and the time of ignition. 6 is a time chart showing changes in the concentration of EGR gas in a cylinder (Example 1). It is a schematic block diagram of an EGR apparatus (Example 2). It is a schematic block diagram of an EGR apparatus (Example 3). It is explanatory drawing at the time of a suction stroke and ignition (conventional example).

[Description of Embodiments] [Mode for carrying out the invention] will be described with reference to the drawings.
The EGR device 1
An EGR passage 6 for guiding EGR gas to an intake port 4 (an intake passage 5 closest to the engine combustion chamber) formed in the cylinder head 3 of the engine 2;
An EGR valve 7 for adjusting the opening degree of the EGR flow path 6;
Air supply means 8 for supplying air into the EGR flow path 6;
It comprises.

The air supply means 8
An intake bypass passage 11 for leading a part of the intake air in the intake passage 5 upstream of the throttle valve 9 into the EGR flow path 6 downstream of the EGR gas from the EGR valve 7;
A second throttle valve 12 for adjusting the opening of the intake bypass passage 11;
Is provided.
A chamber 13 for mixing EGR gas and air is provided at a connection portion between the EGR flow path 6 and the intake bypass path 11.

Hereinafter, a specific example (example) of the present invention will be described with reference to the drawings. The following examples disclose specific examples, and it goes without saying that the present invention is not limited to the examples.
In the following embodiments, the same reference numerals as those in the above-mentioned [Mode for Carrying Out the Invention] denote the same functional objects.

[Example 1]
Embodiment 1 will be described with reference to FIGS.
The engine 2 of this embodiment is
A spark ignition internal combustion engine (gasoline engine, etc.) for driving a vehicle,
(A) an intake passage 5 for introducing intake air (air in the atmosphere) into each cylinder of the engine 2;
(B) an exhaust passage 14 for exhausting exhaust gas generated in each cylinder to the atmosphere;
(C) an injector 15 for injecting and supplying fuel;
(D) a spark plug 16 for igniting the air-fuel mixture compressed in each cylinder;
(E) an EGR device 1 for leading a part of the exhaust gas discharged from the engine 2 to the intake passage 5 as EGR gas;
(F) a vortex control valve 17 for generating a vortex suitable for the operating state of the engine 2 in each cylinder;
Is provided.

The intake passage 5 includes an intake pipe 21, an intake manifold 22, and an intake port 4. An air cleaner that filters intake air is measured in the middle of the intake passage 5, and the amount of air that passes through the intake passage 5 is measured. Are provided, an air flow meter 23 for adjusting the air flow, a throttle valve 9 for adjusting the amount of air sucked into the cylinder, a surge tank 24 for preventing intake pulsation and intake air interference, and the like.
The exhaust passage 14 includes an exhaust port 25, an exhaust manifold, and an exhaust pipe, and a catalyst for purifying exhaust, a muffler for noise reduction, and the like are provided in the middle of the exhaust passage 14.

The injector 15 is a well-known one that injects spray fuel by being energized and controlled by an ECU (abbreviation of engine control unit: corresponding to a control device).
In the drawings, an example in which the injector 15 injects fuel into the intake port 4 is shown, but the present invention is not limited to this, and the injector 15 may be a direct injection type in which fuel is directly injected into the cylinder.
The ECU is equipped with a known computer, and performs injection control of the injector 15 in accordance with the driving state of the vehicle (engine parameters: occupant driving state, vehicle speed, engine operating state, etc.).

  An ignition device that ignites an air-fuel mixture compressed in a cylinder has a predetermined ignition timing in addition to a spark plug 16 that performs spark discharge at a spark discharge portion that is exposed in the cylinder when a high voltage is applied. A high voltage generator that applies a high voltage to the spark plug 16 (for example, immediately before top dead center during the compression stroke) is provided.

  The EGR device 1 includes an interior of the exhaust passage 14 in a range where high exhaust pressure is generated (the exhaust upstream side of the catalyst) and an interior of the intake passage 5 in a range where the negative intake pressure is generated (downstream of the throttle valve 9). Is an exhaust gas recirculation device that can return a large amount of EGR gas to the engine 2 and is intended to improve fuel efficiency by suppressing pumping loss as well as NOx suppression control in the exhaust gas. .

  The EGR device 1 includes an EGR passage 6 that guides a part of the exhaust gas to the intake passage 5 as EGR gas, and an EGR valve 7 that controls the opening degree of the EGR passage 6. The EGR valve 7 is an ECU. Is controlled by the opening.

  In this embodiment, the exhaust port 6a of the EGR flow path 6 is provided in the intake port 4 to shorten the distance from the exhaust port 6a to the inside of the cylinder. As a result, when the EGR valve 7 is closed when the accelerator is OFF, the amount of EGR gas remaining in the intake passage 5 can be suppressed, and as a result, an air-fuel mixture with a small amount of EGR gas is supplied into the cylinder when the accelerator is ON. The responsiveness of the engine 2 can be improved.

The ECU includes NOx suppression means (control program) for controlling the opening degree of the EGR valve 7 for suppressing NOx, and pumping loss suppression means (control program) for controlling the opening degree of the EGR valve 7 for suppressing pumping loss. Is installed.
This pumping loss suppression means opens the EGR valve 7 when the vehicle driving state (engine parameter) is in a predetermined driving state (in a driving state suitable for suppressing fuel loss and improving fuel consumption), A large amount of EGR gas is introduced into the cylinder.

The vortex flow control valve 17 is a drift flow generation valve that causes a bias in the intake air flow sucked into the cylinder and positively generates a vortex flow in the cylinder, and its opening degree is controlled by the ECU.
The drawing shows an example in which the vortex control valve 17 is disposed in the intake port 4, but is not limited, and may be disposed on the intake downstream side of the intake manifold 22. It may be disposed in a passage member disposed between the manifold 22 and the intake port 4.

(Feature Technology 1 of Example 1)
The ECU controls the eddy current control valve 17 to close when the pumping loss suppression means is in operation (when a large amount of EGR gas is introduced into the cylinder), thereby promoting the mixing of EGR gas and air. A drift generation means (control program) is installed.

  However, when the above-described pumping loss suppression means is operated, the amount of EGR gas guided into the cylinder is large and the distance from the discharge port 6a of the EGR flow path 6 to the cylinder is short, so that the vortex control valve 17 is closed. Even if controlled, the EGR gas is not easily mixed with the air, and the concentrated EGR gas may collect in the spark discharge portion of the spark plug 16 (see FIG. 6B), resulting in unstable combustion such as misfire. There are concerns.

Therefore, the EGR device 1 of this embodiment employs air supply means 8 for supplying air into the EGR flow path 6.
Specifically, the air supply means 8 of this embodiment is
(A) A part of the intake air in the intake passage 5 further upstream of the air flow meter 23 provided upstream of the intake of the throttle valve 9 is moved downstream of the EGR valve 7 to the EGR gas downstream side (from the EGR valve 7 to the intake passage 5). An intake bypass passage 11 that leads in the middle of the EGR passage 6 on the near side),
(B) a second throttle valve 12 for adjusting the opening degree of the intake bypass passage 11;
(C) a second air flow meter 26 for measuring the amount of air passing through the intake bypass passage 11;
(D) a chamber 13 provided at a connection portion between the EGR flow path 6 and the intake bypass path 11 for mixing EGR gas and air;
Is provided.

  Similar to the EGR valve 7, the opening degree of the second throttle valve 12 is controlled by the ECU. The ECU controls the amount of air flowing through the intake bypass passage 11 by controlling the opening of the second throttle valve 12 based on the detected value of the second air flow meter 26.

A typical operation example of this embodiment will be described using the engine partial load operation.
When the operation state of the engine 2 is a partial load operation state, the second throttle valve 12 is opened by an instruction from the ECU, and air is caused to flow into the chamber 13. At this time, the EGR valve 7 is also opened according to an instruction from the ECU, and EGR gas flows into the chamber 13.
The air and EGR gas that flowed into the chamber 13 are mixed in the chamber 13 and flow into the intake port 4 from the discharge port 6 a of the EGR flow path 6.

  Thus, since the EGR gas supplied into the intake port 4 from the discharge port 6a of the EGR flow path 6 is mixed with air, the EGR gas is supplied to the vortex control valve 17 as shown in the intake stroke of FIG. Even when riding on the airflow formed in this way, it is possible to form a nearly homogeneous distribution of EGR gas in the cylinder, as shown at the time of ignition in FIG.

A specific example of this will be described with reference to FIG.
In the conventional technique (a technique in which air is not supplied to the inside of the EGR flow path 6), even if the vortex flow is generated in the cylinder using the vortex flow control valve 17, the diffusivity of the EGR gas is low and is shown by a solid line α in FIG. As described above, the fluctuation rate of the EGR gas in the cylinder greatly changes.
On the other hand, in this embodiment, the EGR gas supplied into the intake port 4 from the discharge port 6a of the EGR flow path 6 is already mixed with air in the EGR flow path 6, so that the EGR gas in the cylinder As shown by the broken line β in FIG. 3, the fluctuation rate of the EGR gas in the cylinder is kept small.
FIG. 3 is a time chart in which the EGR rate (EGR gas ratio) in the spark discharge portion of the spark plug 16 is measured.

As described above, since the EGR gas supplied into the intake port 4 from the exhaust port 6a is mixed with air, even if it rides on the airflow formed by the vortex control valve 17, it is homogeneous in the cylinder. A close EGR gas distribution can be formed.
That is, as shown in FIG. 2B, the difference in EGR gas concentration between the spark discharge portion of the spark plug 16 and its surroundings can always be reduced, and stable combustion can be realized reliably.

  In this embodiment, since the distribution of the EGR gas close to homogeneity can be formed in the cylinder, stable combustion can be realized even if the amount of EGR gas is increased as compared with the prior art. For this reason, by further increasing the amount of EGR gas as compared with the prior art, it becomes possible to further reduce the pumping loss as compared with the prior art, and the fuel consumption can be further improved.

(Feature Technology 2 of Example 1)
The ECU of this embodiment controls the EGR valve 7 to the closing side when the accelerator is operated to the closing side (when the accelerator pedal is depressed) and the second throttle valve 12 is controlled. Clean-up means (control program) for controlling the side that opens the door is installed.

When the accelerator is operated to close the engine 2 during operation, the intake negative pressure on the intake downstream side of the throttle valve 9 increases. At this time, even when the EGR gas in the intake passage 5 increases, the EGR gas in the intake passage 5 is diluted by the air that passes through the intake bypass passage 11 and is supplied to the intake passage 5, and burns such as misfire. Deterioration can be prevented.
Further, when the accelerator is closed (when fully closed), the EGR gas in the intake passage 5 and in the cylinder can be quickly scavenged by controlling the second throttle valve 12 to be fully open. For this reason, the responsiveness of the engine 2 when the accelerator is opened can be enhanced, and the acceleration responsiveness can be enhanced.

[Example 2]
Embodiment 2 will be described with reference to FIG. In the following embodiments, the same reference numerals as those in the first embodiment denote the same functions.
The intake bypass passage 11 of the first embodiment guides a part of the intake air in the intake passage 5 upstream of the air flow meter 23 to the middle of the EGR flow path 6 (specifically, in the chamber 13). It was.
On the other hand, in the intake bypass passage 11 of the second embodiment, a part of the intake air in the intake passage 5 on the intake downstream side of the air flow meter 23 and on the intake upstream side of the throttle valve 9 is partway in the EGR flow path 6 ( Specifically, it is led into the chamber 13).
By providing in this way, a part of the intake air measured by the air flow meter 23 is guided to the intake air bypass passage 11, so that the second air flow meter 26 used in the first embodiment can be eliminated.

[Example 3]
Embodiment 3 will be described with reference to FIG.
The air supply means 8 of the first and second embodiments guides part of the intake air flowing through the intake passage 5 to the middle of the EGR flow path 6 using the intake bypass path 11.
On the other hand, the air supply means 8 of the third embodiment is an air pump 27 of a secondary air supply system that supplies air into the exhaust passage 14 on the exhaust upstream side of the catalyst, and the EGR passage 6 is connected to the exhaust passage 14. Together with the exhaust gas, the air discharged from the air pump 27 is introduced together.

  Specifically, the inlet 6b of the EGR channel 6 (the connection port of the EGR channel 6 to the exhaust passage 14) opens to the exhaust passage 14 where air is supplied from the air pump 27, and the exhaust gas in the exhaust passage 14 is exhausted. A part of the gas and a part of the air discharged from the air pump 27 are provided so as to be guided into the EGR flow path 6 from the inflow port 6b.

A typical operation example of this embodiment will be described using the engine partial load operation.
When the operation state of the engine 2 is a partial load operation state, the air pump 27 discharges air into the exhaust passage 14 according to an instruction from the ECU. At this time, the EGR valve 7 is also opened by an instruction from the ECU. As a result, EGR gas mixed with air is introduced into the EGR flow path 6, passes through the EGR flow path 6, and flows into the intake port 4 from the exhaust port 6 a.

  As in the first embodiment, the EGR gas supplied from the discharge port 6a of the EGR flow path 6 into the intake port 4 is mixed with air, so even if it rides on the airflow formed by the vortex control valve 17 In the cylinder, a distribution of EGR gas that is always nearly homogeneous can be formed. For this reason, as shown in the first embodiment, it is possible to increase the amount of EGR gas as compared with the prior art, and it is possible to improve the fuel consumption by reducing the pumping loss.

Further, in this embodiment, since the chamber 13 shown in the first and second embodiments is not used, the passage volume between the EGR valve 7 and the discharge port 6a of the EGR flow path 6 can be reduced. For this reason, the responsiveness of “increase / decrease change in EGR gas amount in the cylinder” with respect to “opening control of EGR valve 7” can be improved, and EGR control at the time of transition can be improved.
Furthermore, in this embodiment, since the air is supplied into the EGR flow path 6 using the air pump 27 of the secondary air supply system, the implementation cost of the present invention can be suppressed.

  In the first and second embodiments, the example in which the chamber 13 is provided at the joint portion between the intake bypass passage 11 and the EGR flow path 6 has been described. However, the chamber 13 may be eliminated. Even if the chamber 13 is abolished in this way, EGR gas and air are mixed to some extent in the EGR flow path 6 from the junction between the intake bypass path 11 and the EGR flow path 6 to the outlet 6a of the EGR flow path 6. It is what is done.

  In the above embodiment, an example in which the present invention is combined with the eddy current control valve 17 has been described, but the eddy current control valve 17 may not be mounted. However, since the vortex control valve 17 is mounted, the mixing ability of a large amount of EGR gas can be improved, so that the effect of improving the fuel consumption by increasing the EGR gas amount and reducing the pumping loss can be enhanced.

  In the above embodiment, the present invention is applied to a spark ignition internal combustion engine. However, the present invention may be applied to a compression ignition internal combustion engine (diesel engine or the like).

DESCRIPTION OF SYMBOLS 1 EGR apparatus 2 Engine 3 Cylinder head 4 Intake port 5 Intake passage 6 EGR passage 6a Exhaust port 6b Inlet 7 EGR valve 8 Air supply means 9 Throttle valve 11 Intake bypass passage 12 Second throttle valve 13 Chamber 14 Exhaust passage 27 Air pump

Claims (7)

An EGR flow path (6) for guiding a part of the exhaust gas as EGR gas to an intake passage (5) through which intake air passes;
An EGR valve (7) for adjusting the opening of the EGR flow path (6);
Air supply means (8) for supplying air into the EGR flow path (6);
EGR device comprising: In the EGR device (1) according to claim 1,
The EGR flow path (6) is provided with an EGR gas discharge port (6a) in an intake port (4) formed in a cylinder head (3) of an engine (2). In the EGR device (1) according to claim 1 or claim 2,
The air supply means (8)
A part of the intake air in the intake passage (5) on the intake upstream side of the throttle valve (9) for adjusting the opening of the intake passage (5), and the EGR on the EGR gas downstream side of the EGR valve (7). An intake bypass path (11) leading into the flow path (6);
A second throttle valve (12) for adjusting the opening of the intake bypass passage (11);
An EGR device comprising: In the EGR device (1) according to claim 3,
An EGR apparatus characterized in that a chamber (13) for mixing EGR gas and air is provided at a connection portion between the EGR flow path (6) and the intake bypass path (11). In the EGR device (1) according to claim 3 or claim 4,
The EGR device (1) includes a control device that controls opening and closing of the EGR valve (7) and the second throttle valve (12),
This control device controls the EGR valve (7) to the closing side and the second throttle valve (12) to the opening side when the accelerator operated by the passenger is operated to the closing side. An EGR device comprising an up means. In the EGR device (1) according to claim 1 or claim 2,
The air supply means (8) is an air pump (27) for supplying air into an exhaust passage (14) through which exhaust passes.
An EGR gas inlet (6b) that guides a part of the exhaust gas into the EGR flow path (6) is provided in the exhaust passage (14) at a portion that receives supply of air from the air pump (27). EGR device characterized by this. In the EGR device (1) according to claim 6,
The EGR device, wherein the air pump (27) is an air pump of a secondary air supply system that supplies air into the exhaust passage (14) on the exhaust upstream side of a catalyst that purifies exhaust gas.

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