JPH06323201A - Exhaust gas recirculation system of engine - Google Patents

Abstract

PURPOSE:To satisfy the required EGR ratio corresponding to an engine load and to effectively reduce HC and NOx by providing first and second EGR systems and an EGR control means. CONSTITUTION:A spark ignition type engine is controlled under air fuel ratio so that the air ratio becomes larger in a low load region than in a high load region. A first EGR system for recirculating high humidity exhaust gas to a combustion chamber 1 and a second EGR system for recirculating a low temperature exhaust gas are provided. The first EGR system is provided with a short EGR port 4 communicating between an exhaust port 3 and the combustion chamber 1, a timing valve 4A and a first control valve 15. The second EGR system is provided with an external EGR route 17 and a second control valve 13. The high temperature exhaust gas and the low temperature exhaust gas are both recirculated in the low load region. The total recirculation ratio of exhaust gas to the combustion chamber 1 is set smaller in the low load region than in the high load region.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an engine exhaust gas recirculation system.

[0002]

2. Description of the Related Art In an engine, particularly a spark ignition type automobile engine represented by a gasoline engine, EGR is often performed to recirculate exhaust gas to a combustion chamber. In Japanese Unexamined Patent Publication No. 63-183260, in addition to an intake port and an exhaust port, a short EGR port connected to the exhaust passage is opened in the combustion chamber, and this EGR port is opened.
It is disclosed that the hot exhaust gas is recirculated from the engine to the combustion chamber. Further, in Japanese Patent Laid-Open No. 2-245460,
It is disclosed that only the high temperature exhaust gas is recirculated in the low load region to the combustion chamber and the low temperature exhaust gas is recirculated in the high load region.

[0003]

By recirculating the hot exhaust gas to the combustion chamber, the combustibility is improved and the H
While it is preferable for reducing C, it tends to be too hot in the combustion chamber, which is disadvantageous for reducing NOx. On the other hand, it is preferable to recirculate the low-temperature exhaust gas into the combustion chamber in order to reduce NOx, but it is disadvantageous in reducing HC because the combustibility deteriorates. Then, the required EGR for the engine load
The rate is required to decrease in accordance with an increase in engine load. However, if only the high temperature exhaust gas or only the low temperature exhaust gas is recirculated to the combustion chamber, the required EGR rate can be satisfied. , HC and NOx cannot be effectively reduced.

Particularly, in recent spark ignition engines for automobiles, from the viewpoint of improving fuel efficiency, air-fuel ratio control is performed so that the excess air ratio becomes larger in the low load region than in the high load region, that is, low load. The region is required to have a relatively lean air-fuel ratio compared to the high load region,
In an engine in which such air-fuel ratio control is performed, the HC
The problem is how to effectively carry out reduction and NOx reduction.

Therefore, an object of the present invention is to satisfy HC and NO while satisfying the required EGR rate according to the engine load.
An object of the present invention is to provide an exhaust gas recirculation system for an engine that can reduce x more effectively.

[0006]

To achieve the above object, the present invention basically has the following configuration. That is, in an engine that is of a spark ignition type and that controls the air-fuel ratio so that the excess air ratio becomes smaller in the high load region than in the low load region, in order to recirculate the hot exhaust gas to the combustion chamber. The first EGR system of
A second EGR system for recirculating exhaust gas having a temperature lower than that of the exhaust gas recirculated from the first EGR passage into the combustion chamber; and controlling at least one of the first EGR system and the second EGR system according to an engine load. EGR that recirculates both the high-temperature exhaust gas and the low-temperature exhaust gas into the combustion chamber at least in the low load region and reduces the total recirculation rate of the exhaust gas into the combustion chamber in the high load region as compared with the low load region. And a control means.

A preferred embodiment of the present invention based on the above configuration is as described in claims 2 and below in the claims.

[0008]

According to the present invention, it is possible to reduce HC and NOX by basically satisfying the required EGR rate according to the engine load. Further, in the low load region where the excess air ratio becomes large and the combustibility deteriorates, the exhaust gas recirculation using both the high temperature exhaust gas and the low temperature exhaust gas and the high temperature of the high temperature exhaust gas are used to generate NOx.
It is possible to significantly reduce the amount of HC and the amount of HC by improving the combustibility. Of course, in a high load region where the excess air ratio is small, the recirculation ratio of exhaust gas to the combustion chamber is small, so that NOx reduction can be achieved while preventing an extremely high temperature of the combustion chamber due to exhaust gas. Become.

According to the second aspect of the invention, the required EGR rate according to the engine load can be more optimally satisfied.

With the structure as described in claim 3, HC and NOx in a low load region and a medium load region are provided.
It is possible to more satisfy the reduction and the NOx reduction in the high load region.

With the configuration as described in claim 4, it is possible to obtain the same effect as the effect obtained in claim 3, while simplifying the control for the second EGR system as much as possible.

With the structure as described in claim 5, exhaust gas having a sufficiently high temperature can be recirculated to the combustion chamber. In this case, by adopting the structure described in claim 6, it is possible to open and close the EGR port easily and surely at a predetermined time.

The structure as described in claim 7 is preferable for preventing a situation in which the recirculation rate of the high-temperature exhaust gas to the combustion chamber becomes abnormally large.

With the structure as described in claim 8, the combustibility is improved by stopping the recirculation of the exhaust gas to the combustion chamber when the engine is warm, and the high temperature is obtained when the engine is cold. Since the combustion chamber is heated to a high temperature by the exhaust gas, the combustibility is improved and the acceleration performance can be improved.

With the structure as described in claim 9, it is preferable in order to improve the combustibility by appropriately raising the temperature of the cold combustion chamber by utilizing the heat of the exhaust gas. In this case, with the structure as described in claim 10, the high temperature exhaust gas can be utilized to more effectively raise the temperature of the combustion chamber to an appropriate level.

According to the eleventh aspect of the present invention, the exhaust gas recirculation amount in each of the EGR systems is controlled while controlling the exhaust gas recirculation amount in both EGR systems while obtaining the structure of the recirculation passage for the high temperature exhaust gas and the low temperature exhaust gas to the combustion chamber. It becomes possible to adjust independently by using.

With the structure as described in claim 12, the recirculation rates of the high temperature exhaust gas and the low temperature exhaust gas to the combustion chamber are finely adjusted in a continuously variable manner, and the effect of claim 1 is enhanced. It is preferable for obtaining the dimension. In this case, with the structure as set forth in claim 13, the high temperature exhaust gas is utilized to effectively obtain an appropriate temperature increase in the combustion chamber when the engine is cold, thereby improving the combustibility. Is preferable.

With the structure as set forth in claim 14, the adjustment of the low-temperature exhaust gas amount is made relatively simple to reduce the load on the control system, and the high-temperature exhaust gas amount is finely controlled to achieve the engine. Required EGR according to load
The rate can be fully satisfied. In this case, claim 1
With the configuration as described in 5, it is possible to effectively obtain an appropriate temperature rise of the combustion chamber using the high-temperature exhaust gas and improve the combustibility when the engine is cold.

According to the sixteenth aspect of the present invention, the adjustment of the high temperature exhaust gas amount is made relatively simple to reduce the load on the control system, and at the same time, the low temperature exhaust gas amount is finely controlled to achieve the engine. Required EGR according to load
The rate can be fully satisfied. In this case, claim 1
By adopting the configuration as described in 7, it is possible to obtain a moderately high temperature of the combustion chamber using the exhaust gas, and effectively increase the moderately high temperature of the combustion chamber using the high temperature exhaust gas particularly in a high load region. As a result, the combustibility when the engine is cold can be improved.

With the structure as set forth in claim 18, the load on the control system for adjusting the low temperature exhaust gas amount is eliminated, and the required EGR according to the engine load is controlled by finely controlling the high temperature exhaust gas amount. The rate can be fully satisfied. In this case, by using the configuration as described in claim 19, by utilizing the high temperature exhaust gas,
It is possible to effectively obtain an appropriate temperature rise in the cold combustion chamber and improve the combustibility when the engine is cold.

With the structure as described in claim 20, the load on the control system for adjusting the high temperature exhaust gas is eliminated, and the required EGR according to the engine load is controlled by finely controlling the low temperature exhaust gas amount. The rate can be fully satisfied. In this case, with the configuration described in claim 21, it is possible to utilize the exhaust gas to appropriately raise the temperature of the cold combustion chamber and improve the combustibility when the engine is cold.

The configuration as described in claim 22 is preferable in reducing the load on the control system required for the low temperature exhaust gas adjustment and the high temperature exhaust gas adjustment. In this case, with the structure as set forth in claim 23, it is possible to effectively and effectively raise the temperature of the cold combustion chamber by utilizing the high temperature exhaust gas and improve the combustibility when the engine is cold. it can.

The configuration as described in claim 24 is preferable in reducing the load on the control system as compared with the case of claim 22. In this case, by adopting the structure as set forth in claim 25, it is possible to appropriately and effectively raise the temperature of the cold combustion chamber by using the high temperature exhaust gas and improve the combustibility when the engine is cold. it can.

The configuration as described in claim 26 is preferable in reducing the load on the control system as compared with the case of claim 22. In this case, with the structure as set forth in claim 27, it is preferable in utilizing the exhaust gas to appropriately raise the temperature of the cold combustion chamber and improve the combustibility when the engine is cold. .

[0025]

Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 shows a structure in the vicinity of a combustion chamber of a spark ignition type engine of a 4-cycle reciprocating type. In FIG. 1, reference numeral 1 is a combustion chamber, and an EGR port 4 is opened in the combustion chamber 1 in addition to an intake port 2 and an exhaust port 3. The intake port 2 is opened and closed by the intake valve 2A, and the exhaust port 3 is opened and closed by the exhaust valve 3A. The intake valve 2A and the exhaust valve 3A are respectively driven by a camshaft which is rotationally driven by the engine output shaft. , Is opened and closed at a known timing in synchronization with engine rotation. Also, EGR
The port 4 is opened and closed by an EGR valve 4A as a timing, and this EGR valve 4A also has an intake valve 2A and an exhaust valve 3
Similar to A, a cam shaft (not shown) rotationally driven by the engine output shaft opens and closes at a predetermined timing described later in synchronization with engine rotation. And
The combustion chamber 1 is provided with a spark plug 5 and a fuel injection valve 6 for directly injecting fuel into the combustion chamber 1.

The orientation of the fuel injection valve 6 is set so that a rich air-fuel mixture is formed near (the ignition gap of) the spark plug 5. That is, in the embodiment,
The lean air-fuel ratio is used in the low load range and the medium load range, the rich air-fuel ratio is used in the high load range, and the air excess ratio is increased in the low load range compared to the high load range so that the air excess ratio becomes large. The fuel ratio is set. In order to improve the ignitability especially in the low load region, at least in the low load region, a rich air-fuel mixture is present near (the ignition gap of) the spark plug 5,
The directivity direction of the fuel injection valve 6 is set toward the ignition plug 5.

In the embodiment, the throttle valve for adjusting the intake air amount is not provided, and the engine load is adjusted by adjusting the fuel injection amount according to the accelerator opening. Therefore, the EGR rate in this embodiment has substantially the same meaning as the EGR amount. Of course, the present invention can be applied to an engine in which the intake air amount is adjusted by the throttle valve. In this case, for example, in the low and medium load range, the air-fuel ratio is leaner than the stoichiometric air-fuel ratio.
And, in the high load region, it can be the theoretical air-fuel ratio).

The EGR port 4 is formed in the cylinder head and serves to recirculate the hot exhaust gas from the exhaust port 3 to the combustion chamber 1. That is, E
The passage length of the GR port 4 is made as short as possible, and the first control valve 15 is arranged in the middle thereof, that is, on the upstream side of the EGR valve 4A. The first control valve 15 adjusts the opening degree of the EGR port 4 in a continuously variable manner, and its drive, that is, the continuously variable opening degree adjustment of the first control valve 15, is performed by an electromagnetic actuator. This is done by controlling the duty of 16 for example.

The EGR valve 4A is of an umbrella valve type and substantially constitutes the inner surface of the combustion chamber when the valve is closed, like the intake valve 2A and the exhaust valve 3A. The opening timing is, for example, the intake stroke. The timing is such that the fresh air from the intake port 2 and the high temperature exhaust gas can be mixed in the combustion chamber 1 before the ignition timing, such as during the middle of the compression stroke and before the ignition timing. Of course, the opening timing of the EGR valve 4A is selected so that the backflow from the combustion chamber 1 to the EGR port 4 does not occur (the exhaust port 3 or EGR port 4 pressure is The opening timing of the EGR valve 4A is selected at a timing higher than the pressure of the combustion chamber 1). Thus, the EGR port 4, the EGR valve 4A, and the first control valve 15
And constitute a first EGR system for returning the high-temperature exhaust gas to the combustion chamber 1.

The maximum effective opening area of the EGR port 4 including the EGR valve 4A is smaller than the maximum effective opening area of the exhaust port 3 including the exhaust valve 3A. That is,
The maximum effective opening area of the port is determined by the maximum effective opening area of the port itself or the maximum lift amount of the valve that opens and closes the port. In the embodiment, the maximum effective opening area of the EGR port 4 itself is determined. The opening area is smaller than the maximum effective opening area of the exhaust port 3 itself, and the maximum lift amount of the EGR valve 4A is also smaller than the maximum lift amount of the exhaust valve 3A. The maximum effective opening area of the EGR port 4 including the EGR valve 4A is such that the maximum recirculation rate of the high temperature exhaust gas to the combustion chamber 1 is maintained even when the EGR valve 4 remains open due to some abnormality. It is set so as not to become abnormally large, especially in an engine rotation range higher than a predetermined engine speed.

The exhaust port 3 and the intake port 2 are connected through a long external pipe 17 arranged outside the cylinder head. An electromagnetic second control valve 18 capable of continuously variable opening adjustment is connected to the external pipe 17. With this external pipe 17 and the second control valve 18, E
A second EGR system is configured to recirculate exhaust gas having a temperature sufficiently lower than that of the high temperature exhaust gas from the GR port 4 to the combustion chamber 1.

The control valve 15 (driving actuator 1
6) and 18 are controlled by a control unit U configured by using a microcomputer. The signals from the sensors S1 to S3 are input to the control unit U. The sensor S1 detects an engine load such as an intake air amount, and the sensor S2 detects an engine cooling water temperature. The sensor S3 is for detecting the acceleration of the engine and detects, for example, the accelerator opening.

The EGR control by the control unit U will be described with reference to FIG. 5 by taking the engine warm time (for example, when the cooling water temperature is 60 ° C. or higher) as an example. In the following description and drawings, the recirculation of the high temperature exhaust gas from the EGR port 4 to the combustion chamber 1 will be referred to as internal EGR, and the recirculation of the low temperature exhaust gas from the external pipe 17 to the combustion chamber 1 will be referred to as the external EGR. Sometimes expressed as. In FIG. 5, when the engine load is F1 or less, the low load range is set, when F2 or more, the high load range is set, and the range between F1 and F2 is set as the middle load range.

First, the α line in the figure indicates the high temperature exhaust gas (internal E
The total exhaust gas recirculation rate to the combustion chamber 1 which is the sum of GR) and the low temperature exhaust gas (external EGR) is shown. This α ray is set so as to gradually decrease with increasing engine load from the low load region to the high load region, and is set so as to sufficiently satisfy the required EGR rate according to the engine load. ing. Then, in the figure, the hatched area indicates the EGR rate of the low-temperature exhaust gas, and the unhatched area indicates the EGR rate of the high-temperature exhaust gas. That is, when the engine load is the smallest, the EGR rate of the high temperature exhaust gas is shown by G1, the EGR rate of the total exhaust gas is shown by G2, and the EGR rate of the low temperature exhaust gas is "G2-G."
1 ”.

In the low load region where the engine load is F1 or less, the internal EGR rate due to the high temperature exhaust gas remains constant at G1, while the external EGR rate due to the low temperature exhaust gas is maintained.
The rate is gradually reduced with increasing engine load, and the total recirculation rate of exhaust gas to the combustion chamber 1 is gradually reduced with increasing engine load. In the low load region, the temperature of the combustion chamber 1 due to combustion does not rise so much, so that both the high temperature exhaust gas and the low temperature exhaust gas are sufficiently circulated to the combustion chamber 1 to improve the combustibility and reduce HC. While NO
A sufficient reduction of x is achieved. Then, as the engine load increases, the EGR rate of the low-temperature exhaust gas is reduced to satisfy the required EGR rate, and a sufficient amount of high-temperature exhaust gas is used to reduce HC in particular. .

When the engine load becomes F1, the recirculation rate of the low temperature exhaust gas to the combustion chamber 1 becomes zero. Medium load range, F
In the range between 1 and F2, the combustion temperature resulting from combustion is also higher than in the low load range, so the EGR of the high temperature exhaust gas is increased.
The rate is gradually decreased as the engine load increases as indicated by the β line, but at this time, the reduction rate of the high-temperature exhaust gas is larger than the degree of reduction of the EGR rate of the total exhaust gas indicated by the α line. To be done. That is, in the medium load region, the high temperature exhaust gas is gradually replaced by the low temperature exhaust gas, and while preventing the combustion chamber 1 from abnormally high temperature, the HC and N
Ox is reduced in a balanced manner.

When the engine load becomes F2, the recirculation rate of the high temperature exhaust gas to the combustion chamber 1 becomes zero, and in the high load region thereafter, only the low temperature exhaust gas is gradually reduced as the engine load increases. Go. As a result, NOx is sufficiently reduced while preventing abnormally high temperature in the combustion chamber 1 (in the high load range, the combustibility is good, and the generation of HC is small).

Although FIG. 5 shows the engine warm, the exhaust gas recirculation mode is changed when the engine is cold, as shown in the right column (cold column) of FIG. 2 (1). Note that FIG.
What is shown in the warm column corresponding to the left column of (1) of FIG. In this cold state, the high-temperature exhaust gas recirculation region is expanded to the high load region (in the high load region above a predetermined level, only the high-temperature exhaust gas recirculates), and overall the total exhaust gas recirculation ratio Is increased. As a result, the temperature of the combustion chamber 1 is increased as much as possible in the cold state, the combustibility is improved, and the HC is effectively reduced.

The control unit U changes the exhaust gas recirculation mode as described above depending on whether the engine is cold or warm, but it also depends on whether the engine is accelerating or not. The exhaust gas recirculation mode is changed. That is,
Originally, in a warm state where the combustibility is good, all the exhaust gas recirculation is forcibly stopped when acceleration is detected, and the combustion suppressing effect by the exhaust gas is not performed, so that the acceleration performance is improved. . Further, in the cold state where the combustibility is not so good, when the acceleration is detected, only the high temperature exhaust gas is forcibly recirculated to improve the combustibility, thereby improving the acceleration performance.

The control contents of the above-mentioned control unit U will be described with reference to the flowchart shown in FIG. 4, and in the following description, Q indicates a step. First, after the signals from the sensors S1 to S3 are read in Q1, it is determined in Q2 whether the engine cooling water temperature is warm, for example, 60 degrees C or higher. When the determination in Q2 is YES, in Q3, the exhaust gas recirculation mode for warm time (recirculation mode of FIG. 5) shown in the left column of (1) of FIG. 2 is selected in Q3. After that, in Q4, it is judged whether or not the vehicle is accelerating by observing changes in the accelerator opening and the like. If YES in the determination in Q4, all the exhaust gas recirculation is stopped in Q5, and N is determined in the determination in Q4.
When it is O, the process directly returns to Q1 without passing through Q5.

If NO in the determination in Q2, it means that the engine is cold, so in this case, in Q6, as shown in FIG.
The exhaust gas is recirculated in the above-described cold mode shown in the right column of (1). After Q6, it is determined in Q7 whether or not the vehicle is accelerating (corresponding to Q4). When the determination in this Q7 is YES, all the recirculated exhaust gas is replaced with the high-temperature exhaust gas in Q8. Aspect. If NO in Q7, the process returns to Q1 without going through Q8.

Here, the first control valve 15 and the second control valve 18
Is not limited to a continuously variable opening adjustment type, but can be fully closed or fully open (O
N / OFF), a two-alternative method for selectively selecting
Alternatively, it can be replaced with a fixed opening type that remains fixed at a predetermined opening. 2 (2) to (4) of FIG. 2 and (1) to (4) of FIG. 3 show exhaust gas recirculation modes in the combination of the continuously variable type, the alternative type, and the fixed type. . However, if both the high-temperature exhaust gas and the low-temperature exhaust gas are fixed types, the exhaust gas recirculation rate cannot be adjusted, so it cannot be adopted.

First, (2) of FIG. 2 shows the case where the high temperature exhaust gas amount adjustment is a continuously variable type and the low temperature exhaust gas amount adjustment is a two-way type. In this case, in the warm state, the EGR rate of the low-temperature exhaust gas is equivalent to fully open in the low load range and the high load range, and fully closed in the medium load range. Then, by controlling the EGR rate of the high temperature exhaust gas continuously variable,
The total exhaust gas recirculation rate is gradually reduced from the low load region to the high load region as the engine load increases.

During cold, the EGR rate of the low-temperature exhaust gas is set to be fully closed in the high load region, and the high-temperature exhaust gas has a low recirculation rate so that the total recirculation rate of the exhaust gas is increased. Correction is increased from the load range to the high load range. With this, the temperature of the cold combustion chamber 1 is appropriately raised,
Combustibility is improved (HC reduction).

FIG. 2 (3) shows an example in which the high temperature exhaust gas amount adjustment is a two-choice type and the low temperature exhaust gas amount adjustment is a continuously variable type. In this case, at warm time,
The EGR rate of the high temperature exhaust gas is set to be fully open in the low load range to the medium load range and fully closed in the high load range. Then, by controlling the EGR rate of the low-temperature exhaust gas in a continuously variable manner, the total recirculation rate of the exhaust gas is gradually reduced as the engine load increases. Even when the engine is cold, the EGR rate of the high temperature exhaust gas is set to fully open even in the high load range, and the EGR rate of the low temperature exhaust gas is also increased, so that the total exhaust gas recirculation from the low load range to the high load range is achieved. The rate is increased.

In (4) of FIG. 2, the high temperature exhaust gas amount adjustment is a continuously variable type, and the low temperature exhaust gas amount adjustment is a fixed type with a predetermined opening. In this case, the EGR rate of the high-temperature exhaust gas is gradually reduced as the engine load increases in the warm state. Further, when cold, the EGR rate of the high-temperature exhaust gas is increased and corrected overall from the low load region to the high load region.

In (1) of FIG. 3, the adjustment of the high temperature exhaust gas amount is a fixed type corresponding to a predetermined opening degree, and the low temperature exhaust gas amount adjustment is a continuously variable type. In this case, the EGR rate of the low-temperature exhaust gas is gradually reduced as the engine load increases during the warm period. When cold, EG of low temperature exhaust gas
The R rate is corrected to be increased, and the total recirculation rate of the exhaust gas is increased from the low load range to the high load range.

In (2) of FIG. 3, the adjustment of the high temperature exhaust gas amount and the adjustment of the low temperature exhaust gas amount are two alternatives. In this case, the EGR rate of the low-temperature exhaust gas is set to be fully open over the entire low load range and the high load range during the warm period. On the other hand, the EGR rate of the high temperature exhaust gas is fully opened in the low load region and the medium load region, and is fully closed in the high load region. When cold, in the high load region, high temperature exhaust gas is returned to the combustion chamber 1 instead of low temperature exhaust gas.

In (3) of FIG. 3, the hot exhaust gas amount adjustment is a two-choice type, and the low temperature exhaust gas amount adjustment is a fixed type with a predetermined opening. In this case, the EGR rate of the high-temperature exhaust gas is fully open in the low load region and the medium load region, but is fully open in the high load region during the warm period. When cold, the high-temperature exhaust gas recirculation region is expanded and corrected so that the high-temperature exhaust gas recirculation region is fully opened up to a higher load region than when it is warm, but there is a load region where the high-temperature exhaust gas does not recirculate in the high load region. It is left as it is.

In FIG. 3 (4), the high temperature exhaust gas amount adjustment is a fixed type with a predetermined opening, and the low temperature exhaust gas amount adjustment is a two-way type. In this case, in the warm state, the EGR rate of the low-temperature exhaust gas is set to be fully open in the low load range to the medium load range, and is fully closed in the high load range. When cold, the recirculation region of the low-temperature exhaust gas is expanded and corrected so that it is fully opened up to a higher load region than when it is warm, but there was a load region where the low-temperature exhaust gas did not recirculate in the high load region. To be left alone.

Although the embodiment has been described above, when the high temperature exhaust gas is recirculated, the EGR valve 4A can be used as it is without providing a separate first control valve. That is, in order to selectively adjust the amount of high-temperature exhaust gas, a valve stop mechanism is provided in the drive mechanism of the EGR valve 4A to stop the EGR valve 4A (hold the valve closed state). Can be done. In the case of the continuously variable type, it can be performed by providing a variable valve timing mechanism or a variable valve lift amount mechanism. Of course, in the case of a fixed type fixed at a predetermined opening degree, it can be performed by providing a fixed orifice in the passage for both low temperature exhaust gas and high temperature exhaust gas. In the case of high temperature exhaust gas, the first control valve Eliminate 15 and E
This can be done by fixing the lift amount and opening / closing timing of the GR valve 4A.

[Brief description of drawings]

FIG. 1 is a schematic system diagram of a main part showing an embodiment in the vicinity of a combustion chamber according to an embodiment of the present invention.

FIG. 2 is a diagram showing an example of EGR rate adjustment according to a method of adjusting a high-temperature exhaust gas amount and a low-temperature exhaust gas amount.

FIG. 3 is a diagram showing an example of EGR rate adjustment according to a method of adjusting a high-temperature exhaust gas amount and a low-temperature exhaust gas amount.

FIG. 4 is a flowchart showing an example of control by a control unit.
To.

FIG. 5 is a diagram showing an example of EGR rate adjustment in the case where the adjustment of the high-temperature exhaust gas amount and the adjustment of the low-temperature exhaust gas amount are each made a continuously variable opening adjustment method.

[Explanation of symbols]

 1: Combustion chamber 2: Intake port 3: Exhaust port 4: EGR port (for high temperature exhaust gas) 4A: EGR valve (timing valve) 5: Spark plug 6: Fuel injection valve 15: First control Valve (for adjusting high temperature exhaust gas amount) 16: Actuator (for driving first control valve) 17: External passage (for low temperature exhaust gas) 18: Second control valve: (for adjusting low temperature exhaust gas amount) U: Control Unit S1: Sensor (engine load) S2: Sensor (cooling water temperature) S3: Sensor (acceleration detection)

Front Page Continuation (72) Inventor Kyo Iwanaga 3-1, Shinchi, Fuchu-cho, Aki-gun, Hiroshima Mazda Motor Corporation

Claims (27)

[Claims] Claim: What is claimed is: 1. An engine, which is of a spark ignition type and in which an air-fuel ratio is controlled so that an excess air ratio becomes smaller in a high load region than in a low load region, a high temperature exhaust gas is introduced into a combustion chamber. A first EGR system for recirculation, a second EGR system for recirculating exhaust gas having a temperature lower than that of the exhaust gas recirculated from the first EGR passage into the combustion chamber, the first EGR system and the second EGR system depending on engine load.
At least one of the GR system is controlled to recirculate both the high temperature exhaust gas and the low temperature exhaust gas to the combustion chamber at least in the low load range, and the exhaust gas is burned in the high load range as compared with the low load range. E to reduce the total return rate to the chamber
An exhaust gas recirculation system for an engine, comprising: a GR control means. 2. The total recirculation rate of exhaust gas to a combustion chamber according to claim 1, wherein the total recirculation rate of exhaust gas from a low load region to a high load region is gradually reduced with an increase in engine load. 3. The recirculation rate of the high-temperature exhaust gas to the combustion chamber according to claim 2, which is constant in a low and medium load range and is gradually reduced in a high load range as the engine load increases. The recirculation rate of the low-temperature exhaust gas to the combustion chamber is gradually reduced from a low load range as the engine load increases. 4. The method according to claim 1, wherein the second EGR system adjusts the recirculation amount of the low temperature exhaust gas to the combustion chamber by a fully closed or fully open alternative opening adjustment method. It is fully opened in the low load region and the high load region, and is fully closed in the medium load region, and the adjustment method of the recirculation amount of the high temperature exhaust gas to the combustion chamber in the first EGR system is a continuously variable opening adjustment. The expression is controlled so that the recirculation rate of the high temperature exhaust gas to the combustion chamber gradually decreases as the engine load increases. 5. The short EGR port according to claim 1, wherein the first EGR system communicates the exhaust port with the combustion chamber, and the pressure in the exhaust port is higher than the pressure in the combustion chamber. A timing valve that is opened at a certain time to open the EGR port. 6. The valve according to claim 5, wherein the timing valve is opened and closed by an engine output shaft in synchronization with engine rotation. 7. The maximum effective opening area of the EGR port including the timing valve is set to be smaller than the maximum effective opening area of the exhaust port so as to be equal to or larger than a predetermined value of the engine. It is set so that the high-temperature exhaust gas recirculation rate does not exceed a predetermined value in a high rotation range. 8. The engine according to claim 1, wherein both the high temperature exhaust gas and the low temperature exhaust gas are stopped from being recirculated to the combustion chamber during acceleration while the engine is warm, and the low temperature exhaust gas combustion chamber is accelerated during acceleration when the engine is cold. And the high temperature exhaust gas is recirculated to the combustion chamber. 9. The engine according to claim 1, wherein the amount of exhaust gas recirculated to the combustion chamber is increased when the engine is cold, or the operating range where the exhaust gas is recirculated to the combustion chamber is expanded, as compared with when the engine is warm. What is done. 10. The engine according to claim 9, wherein when the engine is cold, at least the recirculation rate of the high-temperature exhaust gas to the combustion chamber is increased, or when the high-temperature exhaust gas is recirculated to the combustion chamber. One that expands the operating range. 11. The EGR port according to claim 1, wherein the first EGR system is a short EGR port that communicates an exhaust port with a combustion chamber and is opened and closed in synchronization with engine rotation. A timing valve that opens and closes the valve at a predetermined timing, and is disposed in the EGR port on the exhaust port side of the timing valve.
A second control system for adjusting the opening degree of the GR port, wherein the second EGR system includes an external passage arranged outside the engine body to exhaust gas through the intake port to the combustion chamber. An external EGR passage that recirculates to the external EGR passage and a second control valve that adjusts the opening degree of the external EGR passage. 12. The method according to claim 2, wherein the adjustment of the recirculation amount of the high temperature exhaust gas to the combustion chamber in the first system and the adjustment of the recirculation amount of the low temperature exhaust gas to the combustion chamber in the second EGR system are continuously variable. It is set as an opening adjustment formula of the formula, so that the recirculation rate of the high-temperature exhaust gas to the combustion chamber becomes constant in the low load region, and gradually decreases in the medium load region as the engine load increases. The exhaust gas is recirculated to the combustion chamber from the low load region to the high load region, and the total recirculation rate of the exhaust gas to the combustion chamber is equal to the engine load. It is controlled so that it gradually decreases as it increases. 13. The engine according to claim 12, wherein, when the engine is cold, the low-temperature exhaust gas is stopped from being recirculated to the combustion chamber at least in a high load range, and the exhaust gas is spread from a low load range to a high load range. The total amount of reflux to the combustion chamber is increased. 14. The low-temperature exhaust gas in the second EGR system according to claim 1, wherein the adjustment of the recirculation amount of the high-temperature exhaust gas to the combustion chamber in the first EGR system is set as a continuously variable opening degree adjustment formula. The amount of recirculation to the combustion chamber is set as an alternative opening adjustment formula, either fully closed or fully opened, and fully opened in the low load region and the high load region and fully closed in the medium load region. The first EGR system is controlled so that the total recirculation rate of the exhaust gas to the combustion chamber gradually decreases as the engine load increases from the low load range to the high load range. 15. The engine according to claim 14, wherein, when the engine is cold, the second EGR system is fully closed in a high load range, and exhaust gas from the low load range to the high load range is transferred to the combustion chamber. The total reflux rate is increased. 16. The low flow rate control system according to claim 1, wherein the recirculation amount of the high temperature exhaust gas to the combustion chamber in the first EGR system is set as a selectively closed or fully opened opening adjustment formula. It is fully opened in the load range and medium load range and fully closed in the high load range, and the adjustment of the recirculation amount of the low temperature exhaust gas to the combustion chamber in the second EGR system is set as a continuously variable opening adjustment method. Then, the total recirculation rate of exhaust gas to the combustion chamber is controlled to gradually decrease as the engine load increases from the low load region to the high load region. 17. The engine according to claim 16, wherein, when the engine is cold, the first EGR system is fully opened from a low load range to a high load range, and a total recirculation rate of exhaust gas to the combustion chamber is a low load range. From the above, the second EGR system is controlled so as to be increased and corrected over a high load range. 18. The low temperature exhaust gas in the second EGR system according to claim 1, wherein the recirculation amount adjustment of the high temperature exhaust gas to the combustion chamber in the first EGR system is set as a continuously variable opening adjustment formula. Of the exhaust gas to the combustion chamber is set as a fixed opening type, and the total recirculation rate of the exhaust gas to the combustion chamber is set from the low load region to the high load region. The first EGR system is controlled so that the first EGR system is gradually decreased with the increase of. 19. The engine according to claim 18, wherein the recirculation rate of the high temperature exhaust gas to the combustion chamber is increased and corrected from a low load range to a high load range when the engine is cold. 20. The first EGR system according to claim 1, wherein an adjustment of an amount of the high-temperature exhaust gas recirculated to the combustion chamber is set as a fixed opening degree fixed at a predetermined opening degree. The low-temperature exhaust gas recirculation amount adjustment to the combustion chamber in is set as a continuously variable opening adjustment formula, the low-temperature exhaust gas recirculation rate to the combustion chamber engine from a low load region to a high load region. The second EGR system is controlled such that the second EGR system gradually decreases as the load increases. 21. The engine according to claim 20, wherein the recirculation rate of the low temperature exhaust gas to the combustion chamber is increased and corrected from a low load range to a high load range when the engine is cold. 22. The first EGR system and the second EGR system according to claim 1, wherein each of the first EGR system and the second EGR system is set as an alternative opening adjustment formula of fully closed and fully opened, and the second EGR system is set from a low load range. It is fully opened in a high load range, and the first EGR system is fully opened in a low load range and a medium load range and fully closed in a high load range. 23. The first EGR system according to claim 22, wherein the first EGR system is fully opened in a high load range when the engine is cold. 24. The first EGR system according to claim 1, wherein the first EGR system is set as an opening degree adjustment formula which is alternatively selected from fully closed and fully opened, and the second EGR system is fixed at a predetermined opening degree. In addition, the first EGR system is fully opened in a low load range and a medium load range and is fully closed in a high load range. 25. The engine load range in which the first EGR system is fully opened is expanded and corrected to a higher load range when the engine is cold, 26. The first EGR system according to claim 1, wherein the first EGR system is set as a fixed opening type fixed at a predetermined opening degree, and the second EGR system is selectively closed or fully open. The second EGR system is fully opened in the low load range and the medium load range, and is fully closed in the low load range. 27. The engine load range in which the second EGR system is fully opened is expanded and corrected to a higher load range when the engine is cold.