JP2002349356A - EGR device for internal combustion engine - Google Patents

Abstract

(57) Abstract: Provided is an EGR device for an internal combustion engine capable of controlling residual internal EGR gas in a combustion chamber while preventing deterioration of fuel efficiency. SOLUTION: The apparatus includes a combustion chamber pressure changing means capable of changing the amount of residual internal EGR gas by changing a combustion chamber pressure by an exhaust throttle, and an intake throttle means changing an intake air amount by an intake throttle, When the combustion chamber pressure is changed by the combustion chamber pressure changing means (S10, S12), the intake air amount is changed by the intake throttle means so as to compensate the exhaust throttle loss fluctuating with the change of the combustion chamber pressure by the intake throttle loss. (S1
Four).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an EGR for an internal combustion engine.
More specifically, the present invention relates to a technique for controlling residual internal EGR gas in a combustion chamber while preventing deterioration of fuel efficiency.

[0002]

2. Related Art A technique (EGR) for reducing NOx generated by combustion by recirculating exhaust gas to an intake side is generally known. As EGR,
External EGR providing an external passage communicating between the exhaust side and the intake side
And an internal EGR without an external passage. The internal EGR further includes a blown-back internal EGR that is blown back toward the intake pipe when the intake valve and the exhaust valve are simultaneously opened, and the internal EGR remains in the combustion chamber. Remaining internal EG
There is R.

[0003] By the way, the external EGR and the internal EG
R is supplied by the negative pressure of the intake pipe, and the negative pressure of the intake pipe is generated by the intake throttle loss of the intake system. Such intake throttle loss is generally called pumping loss. This is a factor in worsening fuel economy. Further, since the EGR gas generated by the external EGR and the blown back EGR is basically supplied by movement, the gas temperature decreases due to heat transfer to the external passage and the intake valve during the movement, and the gas temperature decreases. This leads to worse combustion, which is also a factor in worse fuel economy.

On the other hand, the residual internal EGR is basically different from the external EGR and the blow-back internal EGR, so that the gas temperature does not decrease, so that it is difficult to deteriorate the combustion. Rather, the high temperature EGR gas accelerates the fuel vaporization. And has the characteristic that combustion is improved. Therefore, in order to improve the combustion, it has been considered to control the residual internal EGR. For example, the exhaust gas is throttled and the exhaust pressure is controlled to increase the gas density in the combustion chamber, thereby reducing the EG.
It has been considered to increase the amount of R gas.

[0005]

However, performing the exhaust throttling as described above involves an exhaust throttling loss, and as well as the intake throttling loss, causes a deterioration in fuel efficiency. For example, in the case of a general gasoline engine, the output control is performed by controlling the amount of intake air by intake throttle means such as a throttle valve. If the exhaust throttle is performed to increase the EGR, the exhaust throttle loss is added to the intake throttle loss, and there is a possibility that the fuel efficiency is greatly deteriorated by the two throttle losses of the intake throttle loss and the exhaust throttle loss. It is not preferable.

SUMMARY OF THE INVENTION The present invention has been made to solve such a problem, and an object of the present invention is to provide an EGR of an internal combustion engine capable of controlling residual internal EGR gas in a combustion chamber while preventing deterioration of fuel efficiency. It is to provide a device.

[0007]

According to one aspect of the present invention, there is provided an EGR device for an internal combustion engine that utilizes residual gas in a combustion chamber as residual internal EGR gas. Combustion chamber pressure changing means capable of increasing or decreasing the amount of the residual internal EGR gas by changing the combustion chamber pressure, intake throttle means changing the intake air amount by an intake throttle, and combustion chamber pressure changing by the combustion chamber pressure changing means. And control means for changing the intake air amount by the intake throttle means so as to compensate for the exhaust throttle loss fluctuating with the change of the combustion chamber pressure by the intake throttle loss.

Accordingly, the exhaust gas is throttled by the combustion chamber pressure changing means, so that the pressure in the combustion chamber changes to increase or decrease the gas density in the combustion chamber, thereby controlling the residual internal EGR gas. The control means changes the intake air amount by the intake throttle means so that all or a part of the exhaust throttle loss caused by the exhaust throttle is compensated by the intake throttle loss, thereby reducing the increase in the throttle loss as a whole. The control of the residual internal EGR gas is appropriately realized without reducing or minimizing the fuel consumption, and
NOx is reduced.

In the invention of claim 2, the means for changing the pressure in the combustion chamber changes the sectional area of the exhaust passage. Therefore, the exhaust throttle is easily performed by a simple method of changing the cross-sectional area of the exhaust passage, the pressure in the combustion chamber is changed, and the control of the residual internal EGR gas is appropriately realized.

Further, the invention according to claim 3 is characterized in that the control means reduces the intake throttle loss when the exhaust throttle loss is large, and increases the intake throttle loss when the exhaust throttle loss is small. Therefore, the control means controls the intake throttle loss to be small when the exhaust throttle loss is large, while controlling the intake throttle loss to be large when the exhaust throttle loss is small, and thus the overall throttle loss. Increase is suitably prevented,
Residual internal EG without deteriorating or minimizing fuel consumption
An increase in the amount of R gas is properly realized, and NOx is reduced.

Further, the invention of claim 4 is characterized in that the output control of the internal combustion engine is not based on the intake air amount control but on the supplied fuel amount control. Therefore,
Exhaust throttling is performed by the combustion chamber pressure changing means so that all or part of the exhaust throttling loss is compensated by the intake throttling loss,
When the intake air amount is changed by the intake throttle means, in a general gasoline engine, the output control is performed by the intake air amount control by the intake throttle means such as a throttle valve as described above. When the amount is changed, there is a possibility that the output of the internal combustion engine may change at all. However, the output of the internal combustion engine is controlled by controlling the amount of supplied fuel (for example, a direct injection type spark ignition type). In the case of an internal combustion engine, even if the intake air amount is changed by the intake throttle means, the output of the internal combustion engine does not change carelessly and the residual internal EGR gas The increase is appropriately realized, and the NOx is reduced.

[0012]

Embodiments of the present invention will be described below with reference to the accompanying drawings. Referring to FIG. 1, there is shown a schematic configuration diagram of an EGR device for an internal combustion engine according to the present invention,
Hereinafter, the configuration of the EGR device of the internal combustion engine will be described. As shown in the figure, an engine body (hereinafter, referred to as an internal combustion engine)
In-cylinder injection-type spark ignition, in which the fuel injection mode is switched to perform fuel injection in the intake stroke (intake stroke injection mode) and fuel injection in the compression stroke (compression stroke injection mode) as the engine 1. A gasoline engine is adopted. And this in-cylinder injection type engine 1
For example, in the intake stroke injection mode, for example, in addition to the operation at the stoichiometric air-fuel ratio (stoichiometric) or the operation at the rich air-fuel ratio (rich air-fuel ratio operation), the operation at the lean air-fuel ratio (lean air-fuel ratio operation) In the compression stroke injection mode, operation at a lean air-fuel ratio (lean air-fuel ratio operation) or operation at a super-lean air-fuel ratio (super-lean air-fuel ratio operation) is possible. The in-cylinder injection type engine 1
Is already known.

As shown in FIG. 1, an electromagnetic fuel injection valve 6 is mounted on a cylinder head 2 of an engine 1 together with a spark plug 4 for each cylinder, whereby fuel is directly injected into a combustion chamber. It is possible. An ignition coil 8 that outputs a high voltage is connected to the ignition plug 4. Further, a fuel supply device (not shown) having a fuel tank is connected to the fuel injection valve 6 via a fuel pipe 7. More specifically, the fuel supply device is provided with a low-pressure fuel pump and a high-pressure fuel pump, whereby the fuel in the fuel tank is supplied to the fuel injection valve 6 at a low fuel pressure or a high fuel pressure. Can be injected from the fuel injection valve 6 into the combustion chamber at a desired fuel pressure.

An intake port 9 is formed in the cylinder head 2 in a substantially upright direction for each cylinder.
On the combustion chamber 5 side, there are provided intake valves 11 which open and close in accordance with the cam of a camshaft 12 which rotates in accordance with the rotation of the engine to open and close the communication between each intake port 9 and the combustion chamber 5. ing. One end of an intake manifold 10 is connected to each intake port 9, and the intake manifold 10 is provided with an electromagnetic throttle valve (intake throttle means) 17 for adjusting the amount of intake air.

An exhaust port 13 is formed in the cylinder head 2 in a substantially horizontal direction for each cylinder, and a camshaft 16 that rotates in accordance with the engine rotation is provided on the combustion chamber 5 side of each exhaust port 13. Exhaust valves 15 are provided respectively, which open and close in accordance with the cams described above, and perform communication and cutoff between each exhaust port 13 and the combustion chamber 5. One end of an exhaust manifold 14 is connected to each exhaust port 13. Here, as the exhaust manifold 14, for example, a dual-type exhaust manifold system is adopted.

As shown in FIG.
An exhaust pipe 20 is connected to the other end of the exhaust pipe 20. A three-way catalyst 30 is interposed in the exhaust pipe 20 as an exhaust purification catalyst device. The three-way catalyst 30 is provided on a carrier as active noble metals such as copper (Cu), cobalt (Co), silver (Ag), and platinum (P).
t), rhodium (Rh), or palladium (Pd).

As shown in FIG. 1, the exhaust pipe 20 is provided with an exhaust pressure sensor 22 for detecting an exhaust pressure and an O ₂ sensor 24. Further, an exhaust throttle device (combustion chamber pressure changing means) 40 is provided in a portion of the exhaust pipe 20 downstream of the three-way catalyst 30. Exhaust throttle device 4
Numeral 0 is for increasing the exhaust pressure in the exhaust system (including the exhaust manifold 14 and the exhaust pipe 20 from the combustion chamber 5 (including the exhaust valve section)). It is possible to increase the internal pressure and increase the gas density in the combustion chamber 5 to increase the residual internal EGR gas.

More specifically, the exhaust throttle device 40 is connected to the exhaust pipe 2.
2 is a closed on-off valve 42 capable of adjusting the cross-sectional area of the exhaust passage. As the closed-on on-off valve 42, for example, FIG. 2A shows a closed state, and FIG. As described above, a butterfly valve having a simple configuration in which the cross-sectional area of the exhaust passage of the exhaust pipe 20 can be adjusted by rotating the valve body 44 about the shaft 43 penetrating the exhaust pipe 20 is employed. The butterfly valve is provided with an actuator 45 (see FIG. 1), and the butterfly valve rotates the valve body 44 about the shaft 43 by the actuator 45 to open and close.

The ECU 60 includes an input / output device, a storage device (R
OM, RAM, nonvolatile RAM, etc.), central processing unit (C
PU), a timer counter, and the like.
With 0, comprehensive control of the EGR device including the engine 1 is performed. The input side of the ECU 60, other exhaust pressure sensor 22, O ₂ sensor 24 described above, various sensors such as a crank angle sensor 62 are connected, the detection information from these sensors are input.

On the other hand, various output devices such as the above-described fuel injection valve 6, ignition coil 8, throttle valve 17, and actuator 45 are connected to the output side of the ECU 60.
These various output devices output a fuel injection amount, a fuel injection timing, an ignition timing, an exhaust pressure control amount, and the like calculated based on detection information from various sensors. Fuel is injected at an appropriate timing, spark ignition is performed at an appropriate timing by the spark plug 4, and the closed-type on-off valve 42 is opened and closed at an appropriate timing to obtain a desired exhaust pressure.

More specifically, in the case of a direct injection type spark ignition gasoline engine, at least when the residual internal EGR gas is used, in the compression stroke injection mode, the target average effective pressure Pe and the volume obtained from the accelerator opening θacc and the engine speed Ne are obtained. The target fuel injection amount is determined based on the efficiency Ev and the engine speed Ne or the intake pressure or the throttle opening.

That is, in the case of the in-cylinder injection type engine 1,
In the compression stroke injection mode, the fuel injection amount is determined regardless of the intake air amount Qa, and the output control is performed not by the intake air amount control but by the supplied fuel amount control. Hereinafter, the operation of the EGR device for an internal combustion engine according to the present invention configured as described above will be described.

Referring to FIG. 3, a control routine of the residual internal EGR gas control is shown by a flowchart (control means), and the residual internal EGR according to the present invention will be described with reference to FIG.
The gas control will be described. First, in step S10, it is determined whether the operation mode is the residual internal EGR gas use mode, that is, in a situation where NOx is to be reduced,
It is determined whether or not it is a situation where gas is desired to be used. Here, for example, whether the combustion temperature is high and NOx is likely to be generated is determined based on the target average effective pressure Pe and the engine rotation speed Ne.
Is within a predetermined range.

If the result of the determination in step S10 is false (No), the process proceeds to step S20, in which the engine 1 is controlled normally. On the other hand, if the determination result is true (Yes) and the residual internal EG
If it is determined that the user wants to use the R gas, the process proceeds to step S12. In step S12, the residual internal E
In response to the situation in which it is desired to use the GR gas, the exhaust pressure is controlled to the target exhaust pressure. Specifically, the required EGR
The relationship between the gas amount and the target exhaust pressure is set in advance through experiments or the like and is mapped, and the target exhaust pressure is read from the map. The required EGR gas amount is set according to, for example, the accelerator opening θacc (engine load), the engine rotation speed Ne, the cooling water temperature of the engine 1, and the like, so that the accelerator opening θacc and the engine rotation speed N
e, The relationship between the cooling water temperature and the like and the target exhaust pressure may be mapped, and the target exhaust pressure may be read from the map.

Then, in order to reach the target exhaust pressure,
The operation of the closed type on-off valve 42 is controlled. That is, an exhaust pressure control amount signal corresponding to the target exhaust pressure is supplied from the ECU 60 to the actuator 45, and the butterfly valve, which is the closed-type on-off valve 42, is closed to perform exhaust throttle. As described above, when the exhaust gas is throttled by the closed type on-off valve 42, the exhaust pressure of the entire exhaust system including the combustion chamber 5 increases, and the combustion chamber 5
As a result, the residual internal EGR gas increases to the required EGR gas amount.

By the way, when the exhaust throttle is performed in this manner, as described above, the exhaust throttle loss increases, which leads to deterioration of fuel efficiency and is not a preferable thing.
Therefore, in the next step S14, the opening degree (throttle opening degree) of the throttle valve (intake throttle means) 17 is controlled in order to compensate for the exhaust throttle loss with the intake throttle loss. That is, the exhaust throttle loss is compensated by the intake throttle loss so as to eliminate or minimize the fluctuation (increase or decrease) of the entire throttle loss. For example, when the exhaust pressure is large and the exhaust throttle loss is large, the opening of the throttle valve 17 is increased to suppress the intake resistance to reduce the intake throttle loss,
When the exhaust pressure is small and the exhaust throttle loss is small, the opening degree of the throttle valve 17 is kept small to increase the intake throttle loss. More specifically, the relationship between the closed-type on-off valve 42 and the opening of the throttle valve 17 is mapped in advance by experiments or the like so that the exhaust throttle loss can be compensated for by the intake throttle loss. Control for degree.

When the exhaust pressure is small and the exhaust throttle loss is small, it is not always necessary to increase the intake throttle loss, and the opening of the throttle valve 17 may be changed only when the exhaust pressure is large. Further, the opening of the throttle valve 17 may be controlled in accordance with the intake pressure and the exhaust pressure. As a result, even if the exhaust throttle loss changes, the fluctuation (increase or decrease) of the entire throttle loss is reduced, and deterioration of fuel efficiency due to the throttle loss is suitably prevented.

In step S16, the compression stroke injection mode is selected as the fuel injection mode. As described above, the reason why the compression stroke injection mode is selected is that, in the compression stroke injection mode, the super lean air-fuel ratio operation is possible and the fuel injection amount can be determined regardless of the intake air amount Qa. , Throttle valve 1 to change intake throttle loss
This is because the output of the engine 1 is hardly affected even if the intake air amount Qa is changed by adjusting the opening degree of the engine 7.

From the above, in practice, the above step S
In 14, when the exhaust pressure is high and the exhaust throttle loss is large, the opening of the throttle valve 17 may be fully opened, and this does not affect the output of the engine 1 at all. Then, in step S18, as described above, the target fuel injection is performed based on the target average effective pressure Pe, the volume efficiency Ev, the engine rotation speed Ne, the intake pressure and the throttle opening determined from the accelerator opening θacc and the engine rotation speed Ne. The amount is determined so that fuel is injected in the compression stroke. At this time, the fuel injection amount may be corrected based on the cooling water temperature, the oil temperature, the intake air temperature, and the like of the engine 1.

As described above, the description of the embodiment is completed. As described above, in the residual internal EGR gas control according to the present invention, in order to control the residual internal EGR gas, the exhaust pressure is adjusted by the closed-type on-off valve 42, and The throttle valve 17 is adjusted so that the throttle loss does not fluctuate, and the exhaust throttle loss is compensated for by the intake throttle loss. Therefore, the EG according to the present invention
If the R device is used, the control of the residual internal EGR gas can be appropriately realized without deterioration of the fuel efficiency, whereby the NOx can be satisfactorily reduced.

In the above embodiment, the case where only the residual internal EGR is performed as the EGR has been described as an example. However, an external passage may be provided and the external EGR may be performed together. You may make it implement. Further, in the above-described embodiment, in the in-cylinder injection type spark ignition gasoline engine, the case where the compression stroke injection mode is selected and the output control is performed by the fuel supply amount control is described as an example. The control of the fuel supply amount and the control of the intake air amount may be used together, and the effect of the present invention can be sufficiently obtained.

In view of the fact that the output control of the diesel engine is performed by controlling the fuel supply amount, the present invention can be applied to a diesel engine as long as the diesel engine has intake throttle means.

[0033]

As described above in detail, according to the EGR device for an internal combustion engine of the first aspect of the present invention, the exhaust gas is throttled by the combustion chamber pressure changing means, so that the pressure in the combustion chamber is changed and the combustion is performed. When the gas density in the room increases or decreases,
At this time, the GR gas is controlled. At this time, the intake throttle means changes the intake air amount so that all or part of the exhaust throttle loss caused by the exhaust throttle is compensated by the intake throttle loss. Thus, the throttle loss as a whole can be reduced, and the control of the residual internal EGR gas can be properly realized without deteriorating or minimizing the fuel consumption, and the NOx can be satisfactorily reduced.

According to the EGR system for an internal combustion engine of the present invention, the exhaust gas can be easily throttled by a simple method of changing the cross-sectional area of the exhaust passage, and the pressure in the combustion chamber can be changed. Control can be properly realized. According to the EGR device for an internal combustion engine of the third aspect, control is performed such that the intake throttle loss is reduced when the exhaust throttle loss is large, and is controlled such that the intake throttle loss is increased when the exhaust throttle loss is small. As a result, the increase in the throttle loss as a whole can be reduced, the increase in the residual internal EGR gas can be appropriately realized without deteriorating or minimizing the fuel consumption, and the NOx can be reduced favorably. Can be.

Further, according to the EGR system for an internal combustion engine of the present invention, the exhaust throttle is performed by the combustion chamber pressure changing means so that all or part of the exhaust throttle loss is compensated by the intake throttle loss, and the exhaust throttle is performed by the intake throttle means. In the case of changing the intake air amount, in a general gasoline engine, the output control is performed by the intake air amount control by the intake throttle means such as a throttle valve as described above. If this is done, there is a possibility that the output of the internal combustion engine will change at all. However, in the case of controlling the output of the internal combustion engine by controlling the supplied fuel amount (for example, a direct injection type spark ignition type internal combustion engine) If there is, even if the intake air amount is changed by the intake throttle means, while keeping the output of the internal combustion engine from changing carelessly,
The amount of residual internal EGR gas can be appropriately increased stably without deterioration of fuel efficiency, and NOx can be reduced satisfactorily.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of an EGR device for an internal combustion engine according to the present invention.

FIG. 2 is a view showing a butterfly valve as an exhaust throttle device.

FIG. 3 is a flowchart illustrating a control routine of residual internal EGR gas control.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Engine main body 5 Combustion chamber 6 Fuel injection valve 13 Exhaust port 14 Exhaust manifold 17 Throttle valve (intake throttle means) 20 Exhaust pipe 30 Three-way catalyst 40 Exhaust throttle device (combustion chamber pressure changing means) 42 Sealed on-off valve 60 ECU (ECU) Electronic control unit)

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) F02D 9/04 F02D 9/04 DE 21/08 301 21/08 301A 301C 41/02 310 41/02 310E 325 325E 43/00 301 43/00 301G 301K 301N (72) Inventor Naoto Yamada 5-33-8 Shiba, Minato-ku, Tokyo Inside Mitsubishi Motors Corporation (72) Inventor Koujiro Okada Shibago, Minato-ku, Tokyo No. 33-8, Mitsubishi Motors Corporation (72) Inventor Tomohiro Ohashi 5-33-8, Shiba, Minato-ku, Tokyo Mitsubishi Motors Corporation F-term (reference) 3G062 AA03 AA07 AA10 BA04 BA06 DA01 DA02 FA02 FA05 FA06 FA23 GA02 GA04 GA06 GA08 GA12 GA17 GA22 3G065 AA04 AA09 AA10 CA12 DA04 DA15 EA07 FA07 FA12 GA01 GA06 GA09 GA10 GA16 GA27 GA41 GA46 HA06 HA21 HA22 JA04 JA09 JA11 KA02 3G084 AA03 AA04 BA05 BA09 BA13 BA19 BA20 CA03 CA04 DA02 DA10 EA05 EA11 EB09 EB12 EC01 EC03 FA00 FA02 FA10 FA11 FA20 FA21 FA29 FA33 FA38 3G092 AA01 AA06 AA09 AA03 EA01 EA01 EA01 EA01 EA01 DCA EA11 EB05 EC01 EC10 FA17 FA21 FA24 GA03 HA05Z HC01Z HD05X HD05Z HD06X HD06Z HD08X HD08Z HE01Z HE03Z HE08Z HF08Z 3G301 HA01 HA04 HA06 HA13 HA16 JA02 JA25 KA06 LA03 LB04 LC03 MA01 MA11 MA19 NA08 NE11 NE10 PA11 NE11 PA11 PC02Z PD02A PD02Z PD14A PD14Z PE01Z PE03Z PE08Z PF03Z

Claims (4)

[Claims] 1. An EGR device for an internal combustion engine that utilizes residual gas in a combustion chamber as residual internal EGR gas, wherein the amount of the residual internal EGR gas can be increased or decreased by changing the pressure in the combustion chamber by an exhaust throttle. Indoor pressure change means, intake throttle means for changing the amount of intake air by an intake throttle, and when the pressure in the combustion chamber is changed by the combustion chamber pressure change means, exhaust throttle loss that fluctuates with the change in the combustion chamber pressure is taken in. Control means for changing the amount of intake air by the intake throttle means so as to compensate for the throttle loss. 2. The EGR device for an internal combustion engine according to claim 1, wherein said combustion chamber pressure changing means changes an exhaust passage sectional area. 3. The internal combustion engine according to claim 1, wherein the control means reduces the intake throttle loss when the exhaust throttle loss is large, and increases the intake throttle loss when the exhaust throttle loss is small. EGR device. 4. The EGR device for an internal combustion engine according to claim 1, wherein the output control of the internal combustion engine is not based on the intake air amount control but on the supplied fuel amount control.