JP2001355520A - Exhaust gas recirculation system for in-cylinder injection engine - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To an exhaust gas recirculation device for a direct injection engine,
Without disassembling the intake system, without impairing the diffusion characteristics of fuel spray and reducing the design flexibility,
It is possible to reliably prevent deposits from being deposited on the inner wall of the intake port. SOLUTION: Detergent supply means 54 having an exhaust gas recirculation passage 52 for guiding a part of the exhaust gas of the direct injection engine 1 to an intake system 13, and supplying the exhaust gas recirculation passage 52 with a cleaning agent 54e for cleaning the intake system. It is configured to have

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust gas recirculation system for an in-cylinder injection engine that directs exhaust gas to an intake system in an in-cylinder injection engine that directly injects fuel into a combustion chamber.

[0002]

2. Description of the Related Art EGR (exhaust gas recirculation) and blow-by gas are introduced to purify exhaust gas from an engine (internal combustion engine). In the case of introducing EGR, exhaust gas in the exhaust passage is guided into the intake passage through the EGR passage, thereby suppressing the combustion temperature and reducing the generation of NOx.
In the case of introducing a blow-by gas, that is, an evaporated component of oil or hydrocarbon (HC), an unburned fuel or the like is burned by guiding a blow-by gas into an intake passage, thereby suppressing the emission of HC.

However, when the exhaust gas or blow-by gas is introduced into the intake passage as described above, as shown in FIG. 3, a part of the exhaust gas component and the evaporation component of oil and hydrocarbons (HC) are deposited on the exhaust port. As it is gradually deposited. If such deposits increase in the exhaust port, there is a possibility that problems such as a decrease in output due to an insufficient suction amount and a decrease in in-cylinder pressure due to the engagement of an intake valve may occur. Particularly, in a diesel engine or a lean burn gasoline engine that performs lean combustion, a large amount of EGR or blow-by gas may be introduced, so that the deposit is likely to increase and such a problem is likely to occur.

[0004] It is known that a cleaning agent for cleaning intake system dirt is effective for removing the deposit. For example, a gasoline to which a cleaning agent is added or a gasoline to which a cleaning agent is added in advance is used. Thus, a detergent is supplied into the exhaust port together with the fuel injection to remove the deposit. However, in the case of an engine that injects fuel into the exhaust port, the deposit in the exhaust port can be removed by adding a detergent to gasoline, but the fuel is directly injected into the combustion chamber 101 as shown in FIG. In the case of a direct injection engine that injects gas, even if a detergent is added to gasoline and injected from the injector 102, the detergent hardly reaches the exhaust port 103, so that the deposit 104 in the exhaust port 103 cannot be removed. Can not.

[0005] For this reason, in the case of a direct injection engine, it is conceivable to disassemble the intake system and wash the inside of the exhaust port to remove deposits. However, disassembling the intake system requires many man-hours. It takes a lot of time to work, and the work cost becomes large. Therefore, Japanese Patent Application Laid-Open No.
As disclosed in Japanese Patent Application Laid-Open Publication No. H10-207, in a direct injection engine, a technique for preventing a deposit from accumulating by causing a part of a fuel containing a detergent injected from an injector to collide with an umbrella portion of an intake valve being opened. Has been proposed.

[0006]

However, the technology described in the above publication has the following problems. Since the fuel is caused to collide with the head of the intake valve, there is a problem that the diffusion characteristics of the fuel spray are impaired. Since the fuel containing the detergent hardly reaches the inner wall of the intake port on the upstream side of the umbrella portion of the intake valve, no effect can be expected as a measure for preventing the accumulation of deposits on the inner wall of the intake port.

[0007] Further, since the mounting position and the direction of the injector are restricted, there is a problem that the degree of freedom in design is reduced. The present invention has been made in view of the above problems,
Without disassembling the intake system, without impairing the diffusion characteristics of fuel spray and reducing the design flexibility,
It is an object of the present invention to provide an exhaust gas recirculation device for a direct injection engine, which is capable of reliably preventing deposits from being deposited on an inner wall of an intake port.

[0008]

Therefore, an exhaust gas recirculation system for an in-cylinder injection engine according to the present invention is provided with an exhaust gas recirculation passage for guiding a part of exhaust gas from the in-cylinder injection engine to an intake system. Since a detergent supply means for supplying a detergent is provided, accumulation (deposit) of dirt on the intake system is suppressed by the supplied detergent.

Further, when the detergent supply means is configured to supply the detergent under a condition that the exhaust gas recirculation valve provided in the exhaust gas recirculation passage is open, the detergent can be efficiently supplied. In addition, the accumulation (deposit) of dirt on the intake system can be efficiently suppressed. Note that it is preferable that the detergent supplied into the exhaust gas recirculation passage be injected under pressure. Thereby, atomization and vaporization of the detergent are promoted, and the detergent can be used more efficiently.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIGS. 1 and 2 show an exhaust gas recirculation system for a direct injection engine according to an embodiment of the present invention. 1 is an enlarged view of a main part thereof, and FIG. 2 is a schematic sectional view of an engine equipped with the present device.

In-cylinder injection engine according to this embodiment (hereinafter also referred to as a direct injection gasoline engine or simply an engine)
Is mounted on an automobile and is configured as shown in FIG. 2. Each cylinder 3 is mounted on a cylinder head 2 of the engine 1.
Each time, an ignition plug 4 and a fuel injection valve 6 that opens directly into the combustion chamber 5 are provided. The ignition plug 4 is driven by an ignition coil 4A, and the fuel injection valve 6 is driven by a driver 6A. A piston 8 connected to a crankshaft 7 is provided in the cylinder 3, and a hemispherically concave cavity 9 is formed on a top surface of the piston 8.

The cylinder head 2 has an intake port 11 that can communicate with the combustion chamber 5 via an intake valve 10 and an exhaust port 13 that can communicate with the combustion chamber 5 via an exhaust valve 12. The intake port 11 is disposed substantially vertically above the combustion chamber 5, and cooperates with the cavity 9 on the top surface of the piston 8 to form a reverse tumble flow by intake air in the combustion chamber 5. A water temperature sensor 16 for detecting a cooling water temperature is provided on a water jacket 15 on the outer periphery of the cylinder 3, and a crank angle sensor 17 for outputting a signal at a predetermined crank angle position is provided on the crankshaft 7. Each of the camshafts 18 and 19 for driving the cylinder 12 is provided with a cylinder identification sensor (cam angle sensor) 20 for outputting a cylinder identification signal according to the position of the camshaft. Since the engine rotation speed can be calculated based on the crank angle signal, the crank angle sensor 17 also functions as engine rotation speed detection means.

The intake system includes an air cleaner 21,
Intake pipe 22, throttle body 23, surge tank 2
4, the intake manifold 25 is arranged in this order, and the intake port 11 is provided at the downstream end of the intake manifold 25. The throttle body 23 is provided with an electronically controlled throttle valve (ETV) 30 as air amount adjusting means for adjusting the amount of air flowing into the combustion chamber 5.
The opening degree control of 0 can perform not only control according to the accelerator opening degree, but also idle speed control and control for introducing a large amount of intake air during lean operation, which will be described later.

Further, an air flow sensor 37 for detecting the intake air flow rate is provided immediately downstream of the air cleaner 21.
The throttle body 23 has a throttle position sensor 38 for detecting the throttle opening of the ETV 30 and an ETV 3
And an idle switch 39 for detecting the fully closed state of 0 and outputting an idle signal. The exhaust system includes an exhaust manifold 2 having an exhaust port 13 from the upstream side.
6, an exhaust pipe 27, and a three-way catalyst 29 for purifying exhaust gas is interposed in the exhaust pipe 27.
6 is provided with an O ₂ sensor 40.

Although the fuel supply system is not shown, the pressure is a predetermined high pressure [several tens of atmospheres (for example, 2 to 7MPa).
a) is adjusted to the fuel injection valve 6,
High-pressure fuel is injected from the fuel injection valve 6. Also, the accelerator pedal depression amount (accelerator opening) θ
An accelerator opening sensor 42 for detecting ap is provided.

In this engine, an exhaust gas recirculation passage (EGR passage) 52 and an EGR passage 52 extend from an exhaust system (here, an exhaust port 13) to an intake system (here, a portion immediately upstream of the surge tank 24). An exhaust gas recirculation device (EG) including an interposed exhaust gas recirculation valve (EGR valve) 53
R device) 51 is provided. And the EGR passage 5
2, a detergent supply mechanism (detergent supply means) 54 for supplying a detergent for cleaning the intake system to the intake system is provided. The detergent supply mechanism 54 of the present embodiment operates in conjunction with the movement of the EGR valve 53, and is configured to supply the detergent to the intake system when the EGR valve 53 is opened.

That is, as shown in FIG.
The valve 53 includes a valve body 53a in which an exhaust gas recirculation passage 53c is formed, and a passage 5 in the valve body 53a.
Valve body (needle) 53 equipped to open and close 3c
b, the valve 53b is driven by an electromagnetic coil 53d between a closed state in which the passage 53c is closed and an open state in which the passage 53c is opened.

The valve body 53a and the valve body 53b
Are provided with detergent supply passages 54a and 54b, and the detergent supply passage 54a is connected to a detergent tank 54d through a detergent supply pipe 54c. In the detergent tank 54d, a detergent 54e for cleaning intake system dirt is stored, and the detergent 54e is pressurized to an appropriate pressure state (for example, 2 atm). At one end of the detergent supply passage 54b, an injection port 54f opened from the valve body 53b to the downstream side of the EGR passage 52 is formed.
Detergent supply passage 54a of valve body 53a and valve body 53b
The cleaning agent supply passage 54b is formed when the EGR valve 53 is opened, that is, when the valve body 53b is opened to a predetermined opening degree or more.
Only when the EGR valve 53 is closed.

Further, this engine has cylinders 3 and
A blow-by gas recirculation passage (PCV) 55 is provided for guiding blow-by gas from between the pistons 8 to the intake system (in this case, the surge tank 24) from the cylinder head. A switching valve (PCV valve) 56 whose opening is adjusted in accordance with the intake negative pressure is interposed in the blow-by gas recirculation passage 55.

Then, the ignition plug 4, the fuel injection valve 6, E
In order to control the operation of each engine control element such as the TV 30 and the EGR valve 53, an electronic control unit (ECU) 60 having a function as control means of the internal combustion engine is provided. The ECU 60 includes an input / output device, a storage device for storing a control program, a control map, and the like, a central processing unit, a timer and a counter, and the like.
The ECU 60 controls each of the above-described engine control elements based on detection information from the various sensors described above, key switch position information, and the like.

In particular, the present engine is a direct injection engine, which can perform fuel injection at an arbitrary timing, performs uniform mixing and uniform combustion by fuel injection mainly in the intake stroke, and also mainly performs compression in the compression stroke. By the fuel injection, stratified combustion can be performed using the above-mentioned reverse tumble flow. The operation modes of the present engine include a stoichiometric operation mode in which the air-fuel ratio is kept close to the stoichiometric air-fuel ratio by feedback control based on information detected by the O ₂ sensor 40, and an enrich operation mode in which the air-fuel ratio is made richer than the stoichiometric air-fuel ratio. And a lean operation mode in which the air-fuel ratio is made leaner than the stoichiometric air-fuel ratio to perform lean combustion.

The ECU 60 selects one of the operation modes based on a map (not shown) according to an engine speed (hereinafter referred to as engine speed) Ne and a target value (target Pe) of the average effective pressure Pe indicating the engine load state. In the state where the engine speed Ne is small and the target Pe is small, the super lean operation mode (compression lean operation mode) by the stratified combustion is selected, and the engine speed Ne and the target Pe increase. Accordingly, the operation mode is selected in the order of lean operation mode (intake lean operation mode) by uniform combustion, stoichiometry, and enrichment.

The engine speed Ne is calculated from the output signal of the crank angle sensor 17, and the target Pe is calculated from the engine speed Ne and the accelerator opening detected by the accelerator opening sensor 42. In the ECU 60, the opening and closing of the EGR valve 53 is controlled through an electromagnetic coil 53d.
It is opened in an operation mode such as a compression lean operation mode or a stoichiometric operation mode in which Ox is easily generated, and the opening is set according to the engine speed Ne and the target Pe.

The exhaust gas recirculation system for a direct injection engine according to one embodiment of the present invention is configured as described above. Therefore, when the EGR valve 53 is closed, FIG.
As shown in (b), the communication between the detergent supply passage 54a of the valve body 53a and the detergent supply passage 54b of the valve body 53b is cut off, and the detergent 54e for cleaning the intake system is not injected.

Then, depending on the operating state of the engine, E
When the GR valve 53 is opened, as shown in FIG. 1A, the detergent supply passage 54a of the valve body 53a and the valve body 5
The cleaning agent supply passage 54b of FIG. 3b communicates with the cleaning agent 54e for cleaning the pressurized intake system in the cleaning agent tank 54d.
The fuel is injected from the injection port 54f to the downstream side of the EGR passage 52 through the ports a and 54b.

The injected detergent 54e is supplied to the intake system (directly upstream of the surge tank 24) together with the EGR gas and the blow-by gas, so that the detergent 54e is provided on the inner wall of the intake port 11 and the back of the umbrella of the intake valve 10. 54e is reliably supplied,
Intake port 1 with EGR gas and blow-by gas components
Deposit 104 on the inner wall 1 and on the back side of the umbrella of the intake valve 10
Is reliably prevented (see FIG. 3). Therefore,
It is possible to surely avoid the possibility of causing a problem such as a decrease in output due to a shortage of intake air caused by accumulation of deposits on the intake port 11 or the intake valve 10 and a decrease in in-cylinder pressure due to intake valve jamming. it can.

In particular, since the detergent 54e is mixed with the EGR gas and supplied to the inner wall of the intake port 11 and the back side of the umbrella of the intake valve 10, it does not affect the fuel injection system at all, and Accumulation can be prevented, and the mounting position and direction of the injector are not limited. Of course, there is no need to disassemble the intake system to remove the deposit. Further, the supply of the detergent 54e is performed in conjunction with the opening of the EGR valve 53, so that the detergent 54e is supplied efficiently. In other words, the supplied detergent 54e decomposes the unburned HC in the EGR gas, which makes it difficult for nuclei of the deposit to be generated and is guided into the combustion chamber together with the intake air. That is, the generation of the deposit itself is suppressed.

Further, since the cleaning agent 54e is mixed with the high-temperature EGR gas and supplied, the cleaning agent 54e is sufficiently mixed with the EGR gas, so that the cleaning agent 54e is formed on the inner wall of the intake port 11 and the back of the umbrella of the intake valve 10. It can be supplied evenly. Further, the detergent 54e is provided in the detergent tank 54.
d, and is injected at a high pressure into the EGR gas, so that when the detergent 54e is mixed into the EGR gas, the atomization is promoted, and the inner wall of the intake port 11 and the intake valve 10
The cleaning agent 54e can more easily reach the back side of the umbrella part. Further, the detergent 54e injected at a high pressure into the EGR gas deprives the EGR gas of heat of vaporization during vaporization.
There is also an effect of cooling the high-temperature EGR gas, the effect of suppressing the combustion temperature by the EGR gas is further enhanced, and the amount of required EGR can be reduced in order to enhance the NOx reduction effect. There is also an advantage that can contribute to combustion stabilization.

The exhaust gas recirculation system for a direct injection engine according to the present invention is not limited to the above-described embodiment, but can be implemented in various modifications without departing from the spirit of the present invention. For example, in the above embodiment, EG
Although the R valve 53 is of an electromagnetic type, it may be of a type utilizing intake negative pressure, and the driving method of the EGR valve 53 is not limited to this.

In the above embodiment, the cleaning agent 54e is supplied in conjunction with the opening of the EGR valve 53 (for example, when the EGR valve 53 is opened at a predetermined opening degree or more).
The detergent supply mechanism (detergent supply means) 54 is not limited to this. For example, the detergent supply mechanism is provided in another part of the EGR passage independently of the EGR valve 53, and the EGR valve is provided. The supply of the detergent may be controlled separately from 53.

In this case as well, a certain valve or the like (for example, an electromagnetic type or an intake negative pressure type) is used for the detergent supply control, but under a more specific condition while the EGR valve 53 is opened, the detergent supply is controlled. It is preferable that the supply is performed so that atomization of the detergent and cooling of the EGR gas can be promoted.

[0032]

As described above in detail, according to the exhaust gas recirculation system for a direct injection engine according to the first aspect of the present invention, the cleaning agent for cleaning the intake system dirt is exhaust gas for recirculation (EGR gas).
The cleaning agent can be reliably supplied to the intake port inner wall and the intake valve, deposits that are likely to occur in this part are reliably prevented, and output is reduced due to insufficient intake air volume. It is possible to reliably avoid the possibility of causing a problem such as a decrease in the in-cylinder pressure due to the engagement of the intake valve. Further, since the fuel injection system is not affected at all, the accumulation of deposits can be prevented, and the mounting position and direction of the injector are not limited. Of course, there is no need to disassemble the intake system.

Further, when the detergent is supplied into the EGR gas, the atomization of the detergent when mixed into the EGR gas is promoted, so that the detergent can easily reach the required part of the intake system evenly. There is also an advantage, and the cleaning agent injected into the EGR gas deprives the EGR gas of heat of vaporization at the time of vaporization, and thus has an effect of cooling the high-temperature EGR gas.

According to the exhaust gas recirculation system for a direct injection engine according to the present invention, the detergent is supplied under the condition that the exhaust gas recirculation valve is open. Not only decomposition of the deposit attached to the system, but also generation of the deposit itself is suppressed, and deposition of the deposit can be efficiently prevented.

[Brief description of the drawings]

FIG. 1 is an enlarged sectional view of a main part (an enlarged view of a main part of FIG. 2) showing an exhaust gas recirculation device of a direct injection engine as one embodiment of the present invention, wherein (a) is an open state of an exhaust gas recirculation valve; (B) is a diagram showing a closed state of the exhaust gas recirculation valve.

FIG. 2 is a schematic cross-sectional view of an engine provided with an exhaust gas recirculation device for a direct injection engine as one embodiment of the present invention.

FIG. 3 is a cross-sectional view of a main part of the direct injection engine illustrating the problem of the present invention.

[Explanation of symbols]

 51 Exhaust gas recirculation device (EGR device) 52 Exhaust gas recirculation passage (EGR passage) 53 Exhaust gas recirculation valve (EGR valve) 54 Detergent supply mechanism (detergent supply means) 54e Detergent for cleaning intake system dirt

Claims (2)

[Claims] An exhaust gas recirculation passage for guiding a part of the exhaust gas of a direct injection engine to an intake system is provided.
An exhaust gas recirculation device for a direct injection engine, comprising a detergent supply means for supplying a detergent for cleaning intake system dirt. 2. The cleaning agent supply means is configured to supply the cleaning agent on condition that an exhaust gas recirculation valve provided in the exhaust gas recirculation passage is open. Item 2. An exhaust gas recirculation device for a direct injection engine according to Item 1.