JPH0882235A - Engine intake system - Google Patents

Abstract

(57) [Abstract] [Purpose] NO in exhaust gas while avoiding engine misfire
It significantly reduces x and secures good fuel economy. A fuel is injected into a mixture gas supply port 57 by a first injector 60 to form a mixture gas inside the port,
The swirl is generated in the combustion chamber 14 while being supplied into the combustion chamber 14 to stratify the air-fuel mixture to enhance the combustibility. Further, a second injector 62 that injects fuel also to the first intake port 16 is provided. The EGR rate is controlled according to the operating state of the engine, and in the region where the EGR ratio is high, the fuel injection by the first injector 60 is performed to stratify the air-fuel mixture, and in the region where the EGR rate is low, the on-off valve 61 is used. The mixture supply port 57 is closed and only the fuel injection by the second injector 62 is performed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an engine provided with an air-fuel mixture supply port for forming an air-fuel mixture by mixing pressurized air and fuel and supplying the mixture into a combustion chamber, in addition to an ordinary intake port. The present invention relates to an intake device.

[0002]

2. Description of the Related Art Conventionally, as means for promoting the vaporization and atomization of fuel to stratify the air-fuel mixture, for example, JP-A-5-3972 is known.
The device shown in Japanese Patent No. 0 is known. This device
While the swirl is generated in the combustion chamber by the intake air from the intake port, an air-fuel mixture supply port is opened in the combustion chamber separately from the intake port, and this air-fuel mixture supply port is communicated with a closed space having a predetermined volume and An injector is provided in the space, and the air-fuel mixture supply port is opened by a timing valve in the first half of the exhaust stroke and the second half of the intake stroke. According to this device, the exhaust gas (pressurized gas) taken into the air-fuel mixture supply port in the latter half of the exhaust stroke and the fuel from the injector are mixed in the closed space to form the air-fuel mixture. Combustibility is enhanced by being supplied to the central part of the swirl and stratified.

In the above publication, the improvement of combustibility due to the stratification of the air-fuel mixture is utilized to realize favorable lean combustion and improve fuel efficiency.

[0004]

In recent years, the regulation of the amount of NOx contained in exhaust gas has been strict, and reduction of NOx has become an important issue. As a means for reducing NOx, exhaust gas recirculation (hereinafter referred to as EGR) is used. Although effective, as in the above publication, in a device in which the air-fuel ratio is set to a large lean side in order to improve fuel economy, the increase in EGR rate is significantly limited due to the decrease in combustion stability, and particularly NOx generation occurs. It is not possible to sufficiently reduce NOx in a remarkable operating region (for example, a high load operating region).

In view of such circumstances, the present invention provides an intake system for an engine capable of reducing NOx in exhaust gas by enabling a large amount of EGR while maintaining good combustion stability while reducing fuel consumption. The purpose is to do.

[0006]

As a means for solving the above problems, the present invention provides a mixing for forming a mixture by mixing pressurized air and fuel separately from an intake port and supplying the mixture into a combustion chamber. An engine provided with an air supply port, a first fuel supply means for supplying fuel to the air-fuel mixture supply port, and an air-fuel mixture supply valve for opening the opening of the air-fuel mixture supply port from the latter half of the intake stroke to the compression stroke. In the intake device, the air-fuel mixture supply port is a closed space, and the air-fuel mixture in the air-fuel mixture supply port is drawn into the combustion chamber at the initial opening of the air-fuel mixture supply port and thereafter the air-fuel mixture supply port is closed until the air-fuel mixture is closed. Gas is forced into the mixture supply port, and the intake port is arranged so that swirl is generated in the combustion chamber by intake air from the intake port. EGR means for opening the supply port in the direction of the center line of the cylinder with respect to the center of the bore near the spark plug, recirculating exhaust gas to the intake port, and second fuel supply means for supplying fuel to the intake port, EGR rate control means for changing the EGR rate by the EGR means according to the operating state of the engine, opening / closing means for opening / closing the opening of the mixture supply port or a portion in the vicinity thereof, and opening / closing means for the region where the EGR rate is equal to or higher than a certain level. And a fuel injection control means for causing the fuel to be supplied from at least the first fuel supply means, and for closing the opening / closing means in a region where the EGR rate is less than a constant to supply the fuel only from the second fuel supply means. (Claim 1).

The opening / closing means may include an opening / closing valve for opening / closing the mixture supply port at a position upstream of the mixture supply valve (claim 2). The air-fuel mixture supply valve may also be used. In the latter case, a valve stop means for forcibly closing the air-fuel mixture supply valve is provided, and the air-fuel mixture supply valve is forcibly closed by the valve stop means only in a region where the EGR rate is less than a certain value. The fuel injection control means may be configured (claim 3).

In addition to the intake port, the present invention provides a mixture gas supply port for forming a mixture gas by mixing pressurized air and fuel and supplying the mixture gas into the combustion chamber, and pressurizing the mixture gas supply port. An air pressurizing means for supplying air, a first fuel supply means for supplying fuel to this mixture supply port, and a mixture supply valve for opening the opening of the mixture supply port from the latter half of the intake stroke to the compression stroke. In an intake system for an engine provided with, the intake port is arranged so that swirl is generated in the combustion chamber by intake air from the intake port, and the mixture supply port is disposed substantially with respect to the center of the bore near the ignition plug. EGR means for opening exhaust gas in the cylinder center line direction and for recirculating exhaust gas to the intake port, second fuel supply means for supplying fuel to the intake port, and operation of the engine The EGR rate control means for changing the EGR rate by the EGR means according to the condition, and the air pressurizing means is operated to supply fuel from at least the first fuel supply means in a region where the EGR rate is equal to or higher than a certain level. In a region where is less than a certain value, the fuel injection control means for stopping the air pressurizing means and supplying the fuel only from the second fuel supply means is provided (claim 4).

As a specific control, in a region where the EGR rate is less than a certain value, fuel is supplied only from the first fuel supply means, and when switching the fuel supply means to be used, the fuel supply means to be used after this switching. The fuel injection control means is configured to gradually increase the fuel supply quantity by 0 from 0 and gradually decrease the fuel supply quantity by the fuel supply means stopped after the switching (claim 5). It is suitable.

In each of the above devices, the EGR rate is 30%.
The fuel injection control means is configured so that only the fuel is supplied by the first fuel supply means in the above region.
More preferable (Claim 6).

[0011]

According to the apparatus of the present invention, in the operating region where the EGR rate is high, the air-fuel mixture is formed by mixing the fuel supplied into the air-fuel mixture supply port by the first fuel supply means and the pressurized air. At the beginning of opening the air-fuel mixture supply port, the air-fuel mixture is drawn into the combustion chamber. Since this air-fuel mixture is supplied to the center of the swirl generated in the combustion chamber and is well stratified, it is possible to secure a sufficient air-fuel mixture around the spark plug while setting the EGR rate high. It is possible to suppress NOx generation in heavy EGR while avoiding engine misfire. After the air-fuel mixture is supplied, the air in the combustion chamber is conversely taken into the air-fuel mixture supply port, and when the air-fuel mixture supply valve is closed, the pressurized air is confined in the air-fuel mixture supply port.

On the other hand, in an operating region where the EGR rate is low, that is, in a region where stratification of the air-fuel mixture is low, the opening or closing means closes the opening of the air-fuel mixture supply port or a portion in the vicinity thereof, so that the first engine is operated as in a normal engine. (2) Since the fuel is supplied to the intake port only from the fuel supply means, the gas flow loss between the inside of the mixture supply port and the combustion chamber and the heat of the gas taken into the mixture supply port cause this mixture supply port. The heat loss due to heat dissipation from the outside is significantly suppressed or eliminated, and fuel consumption is improved accordingly.

Here, in the apparatus according to claim 2, a high EG
In the R rate region, the fuel is supplied from the first fuel supply means in a state where the opening / closing valve on the upstream side of the air-fuel mixture supply valve is opened, and the air-fuel mixture is supplied from the air-fuel mixture supply port into the combustion chamber, while the low EGR is performed. By closing the on-off valve in the rate region, the flow of gas between the combustion chamber and the mixture gas supply port on the upstream side of the on-off valve is blocked.

On the other hand, in the apparatus according to the third aspect of the present invention, the mixture gas supply valve is forcibly held in the closed state in the low EGR rate region, so that the combustion chamber and the mixture gas supply port are both closed. The gas flow is blocked.

According to the fourth aspect of the present invention, in the high EGR rate region, the mixture is formed by mixing the pressurized air supplied from the air pressurizing means into the mixture supply port with the fuel, and is supplied into the combustion chamber. On the other hand, in the low EGR rate region, since the operation of the air pressurizing means is stopped, the mechanical load is reduced and fuel consumption is reduced.

As a specific control, in the device according to the fifth aspect, the fuel is supplied only from the first fuel supply means in the region where the EGR rate is less than a constant value, and the fuel is supplied only in the region where the EGR rate is a certain value or more. Fuel is supplied only from the second fuel supply means. That is, the fuel supply means used is selectively switched. Moreover, when switching the used fuel supply means,
The fuel supply amount by one fuel supply means (fuel supply means switched to a non-use state) is gradually increased, and the fuel supply amount by the other fuel supply means (fuel supply means switched to a use state) is gradually reduced to zero. Since it is reduced, torque shock due to a sudden change in the air-fuel mixture distribution state hardly occurs at the time of the above switching.

In the apparatus according to claim 6, the EGR rate is 30.
By supplying the fuel only from the first fuel supply means in the region of not less than%, instability of combustion due to a large amount of EGR can be effectively prevented.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described with reference to the drawings.

In each cylinder of the engine body 10 shown in FIG. 1, a piston 12 is housed so that it can move up and down, and a combustion chamber 14 is formed above it. In the combustion chamber 14, the first intake port 16, the second intake port 18, and 2
Two exhaust ports 20 are open. As shown in FIG. 2, the first intake port 16 and the second intake port 18 are arranged on one side (left side in FIGS. 1 and 2) with the center part as a boundary, and both exhaust ports 20 are arranged on the other side (FIG. 1). , 2 on the right side), and an ignition plug 26 is provided at the approximate center of the bore. Both intake ports 16 and 18 have intake valves 22 respectively.
The exhaust port 20 is opened and closed by the operation of the exhaust valve 24.

First intake port 16 and second intake port 1
A first intake pipe 28 and a second intake pipe 30 are connected to each other, and both intake pipes 28 and 30 are common to the surge tank 3
Connected to 2. An air cleaner 34 and a throttle valve 36 are provided in the independent intake pipe upstream of the surge tank 32.
Is provided. A swirl control valve 38 is provided in the middle of the second intake port 18, and is opened and closed by an actuator 40. The first intake port 16 enters the combustion chamber 14 from a direction closer to the horizontal direction than the second intake port 18, and the first intake port 16 with the swirl control valve 38 closed.
The swirl (transverse swirl) generation in the combustion chamber 14 is promoted by the intake air from.

Each exhaust port 20 is connected to the exhaust manifold 4
1 is connected to a common exhaust pipe 42, and a NOx purification catalyst 44 such as a three-way catalyst is provided in the middle of the common exhaust pipe 42. An O ₂ sensor 46 is provided on the upstream side of the NOx purification catalyst 44. It is provided.

The common exhaust pipe 42 and the intake system (surge tank 32 in the illustrated example) are an EGR pipe 48 for exhaust gas recirculation.
An EGR valve 50 is provided in the middle of this EGR pipe 48. The EGR valve 50 is composed of a diaphragm valve, and the inside of the EGR valve 50 is connected to the second port of the first port, the second port, and the atmosphere opening port of the three-way switching valve 56 via the pressure introducing pipe 54. The first port of the three-way switching valve 56 is connected to the surge tank 32 via the pressure introducing pipe 52. The three-way switching valve 56 is switched in response to a control signal. When the first port and the second port are in communication with each other, the EGR valve 50 is opened by the negative pressure in the surge tank 32. If the air port and the second port are connected,
The EGR valve 50 is configured to be closed. The EGR rate (exhaust gas recirculation rate) is variable by adjusting the opening degree of the three-way switching valve 56.

Further, in this engine, the intake port 1
An air-fuel mixture supply port 57, which is different from those of Nos. 6 and 18, opens in the direction of the cylinder center line (upward and downward in the figure) with respect to the center of the bore near the ignition plug 26. The air-fuel mixture supply port 57 is a closed space into which fuel is injected from a first injector (first fuel supply means) 60, and the air-fuel mixture is supplied into the combustion chamber 14. The opening of the port 57 is opened and closed by the operation of the center valve (mixture supply valve) 58. Further, in the first intake port 16, a second injector (second fuel injector) that injects fuel into the first intake port 16 is used as in a normal engine.
A fuel supply means) 62 is provided. Further, in the air-fuel mixture supply port 57, an opening / closing valve 61 for opening / closing this portion is provided at a portion immediately upstream of the center valve 58.

FIG. 3 shows the intake valve 22 and the center valve 5 described above.
The valve timings of 8 are the broken line 71 and the solid line 72, respectively.
It is shown in. As shown in the drawing, the intake valve 22 is opened from before the piston top dead center to immediately after the piston bottom dead center, and the center valve 58 is opened (that is, the mixture supply port 57 is opened). It is from before the bottom dead center (that is, the latter half of the intake stroke) to before the next piston top dead center (that is, the latter half of the compression stroke).

In this engine, in addition to the O ₂ sensor 46, various sensors such as an engine speed sensor 64, an intake pressure sensor 66, a throttle sensor 68, etc. are provided, and their detection signals are obtained by ECU (EGR rate control means and It is adapted to be input to the fuel injection control means) 70. This EC
The U70 is configured to perform the following control according to the operating state grasped from the detection signal. A control signal is output to the actuator 40 in a specific operation region (for example, a region excluding the idle operation region) to close the swirl control valve 38. In the above range, the control signal is output to the three-way switching valve 56, and the EG
The R valve 50 is opened and the EGR rate is controlled according to the operating state of the engine. Specifically, a map as shown in FIG. 4 is stored, and in a low load operation region in which the actual engine load is below the boundary value determined according to the engine speed, the target EGR rate is set to a relatively large value (for example, 40%)
And the target EGR rate is a relatively small value (for example, 10
%). A pulse signal is appropriately output to each injector 60, 62 to control the fuel injection timing and the fuel injection amount. Specifically, based on the detection signal of the O ₂ sensor 46, the fuel injection amount is feedback-controlled so that the air-fuel ratio is maintained at the target air-fuel ratio corresponding to each operating region. In the switching of the used injector, fuel injection is performed only by the first injector 60 in the low load operation range, and fuel is injected only by the second injector 62 in the high load operation range. Then, the fuel injection amount of the injector to be used from now on is gradually increased from 0, and the fuel injection amount of the injector to stop using is gradually reduced to 0. The on-off valve 61 is opened in the low load operation region, and the on-off valve 61 is closed in the high load operation region.

Next, the operation of this engine will be described.

First, in the above-mentioned specific operation region, the swirl control valve 38 is closed and intake air is taken in only from the first intake port 16, and swirl is generated in the combustion chamber 14 by this intake air.

In the low load operation region, the on-off valve 61 is opened and the air injected into the air-fuel mixture supply port 57 in the previous stroke and the fuel injected from the first injector 60 are mixed and the air-fuel mixture is mixed. When the center valve 58 is opened in the latter half of the intake stroke, the air-fuel mixture is drawn out of the air-fuel mixture supply port 57 into the combustion chamber 14 by the intake negative pressure. After that, when the pressure in the combustion chamber 14 rises in the compression stroke, the air therein reversely reverses and the air-fuel mixture supply port 57
It is pushed in and is closed when the center valve 58 is closed. By repeating this, the air-fuel mixture is supplied to the combustion chamber 14 in each cycle. This supply air-fuel mixture is supplied to the center of the swirl generated in the combustion chamber 14 to be stratified, and surrounds the periphery of the spark plug 26 in the center of the bore. Therefore, in this low load operation region, even if the EGR rate is set high, good combustion is ensured by stratification of the air-fuel mixture supplied from the air-fuel mixture supply port 57, and engine misfire is prevented.

On the other hand, in the high load operation region where the required fuel injection amount is large and the EGR rate is low, the fuel injection by the first injector 60 is stopped and the on-off valve 61 is closed. Air flow between the air supply port 57 and the combustion chamber 14 is blocked. Therefore, the flow loss at the time of air circulation and the heat loss due to the heat of the air taken into the air-fuel mixture supply port 57 being radiated to the outside from the air-fuel mixture supply port 57 are significantly reduced or eliminated. As also shown in the data described below, fuel consumption is reduced compared to the case where fuel is injected from only the first injector 60.

Further, in this embodiment, when the injector to be used is switched at the time of transition between the low load operation region and the high load operation region, the fuel injection amount of the injector to be used is gradually increased from 0 and stopped. Since the fuel injection amount of the injector is gradually stopped to 0, there is also an advantage that the torque shock due to the sudden change of the air-fuel mixture distribution state can be effectively mitigated.

* Experimental data FIG. 5 shows a case where fuel is supplied only from the first injector 60 to the air-fuel mixture supply port 57 without changing various operating conditions (Mixture Injection), and from the second injector 62 to the first intake port. When fuel is supplied only to 16 (Po
rt Injection), the relationship between the EGR rate, the fuel consumption amount, the NOx generation amount, and the average effective pressure fluctuation rate (that is, the torque fluctuation degree) is shown.

As shown in the upper and middle rows of this figure,
When fuel is supplied only to the air-fuel mixture supply port 57, EG
The average effective pressure fluctuation rate remains low regardless of the R rate (that is, good combustion stability is secured),
Further, in particular, while the NOx generation amount is sufficiently suppressed in the region where the EGR rate is 30% or more, when the fuel is supplied only to the first intake port 16, the above-mentioned fluctuation rate is obtained in the region where the EGR rate is 30% or more. Is increasing rapidly and combustion is unstable. On the other hand, as shown in the lower part of the figure, in the region where the EGR rate is 30% or less, when the fuel is supplied only to the first intake port 16 than when the fuel is supplied only to the mixture supply port 57, Fuel consumption is significantly reduced.

Therefore, by performing the fuel injection by the first injector 60 in the region where the EGR rate is high, it is possible to suppress NOx generation with sufficient EGR while ensuring stable combustion, while in the region where the EGR rate is low, the air-fuel mixture is mixed. The second injector 6 is stopped by stopping the air-fuel mixture supply from the supply port 57.
By only performing fuel injection with 0, fuel consumption can be significantly reduced.

In particular, from the viewpoint of combustion stability, it is more preferable to perform fuel injection only by the first injector 60 in the region where the EGR rate is 30% or more.

Next, a second embodiment will be described with reference to FIG. In this embodiment, instead of providing the opening / closing valve 61, a valve stop mechanism 63 such as a conventionally known one is provided with the center valve 58.
And the drive mechanism thereof, the ECU 70 is configured to operate the valve stop mechanism 63 and forcibly hold the center valve 58 in the closed state in the low EGR rate region.
Also in this embodiment, in the low EGR rate region, the forced closing of the center valve 58 can prevent the air flow between the combustion chamber 14 and the air-fuel mixture supply port 57.
Fuel consumption can be reduced as in the embodiment. In particular, in this embodiment, the mechanical load for opening and closing the center valve 58 is also eliminated, so that the fuel consumption saving effect becomes more remarkable.

The present invention is not limited to the above embodiment, and the following modes can be adopted as examples.

(1) In the above embodiment, the air-fuel mixture supply port 5
Although a closed space of 7 is shown, an air pressurizing means such as an air pump 69 as shown in FIG. 7 is connected to the air-fuel mixture supply port 57 to supply pressurized air and fuel supplied from the air pump 69. A mixture may be formed by mixing the above. In this case, in the low EGR rate region, the mechanical load for driving the air pump 69 can be eliminated by stopping the first injector 60 and the air pump 69 as well. Fuel economy can be saved.

(2) In the present invention, mixed gas stratification and EG
The operating range in which R and R are simultaneously executed may be freely set.
Further, the air-fuel ratio and the required fuel injection amount may be set appropriately according to the operating state. The control of the EGR rate is not a digital switching, but, for example, as shown in FIG. 8, the EGR rate is changed in an analog manner according to the engine load (net average effective pressure). May be set as a peak) or may be controlled based on the engine speed in addition to such engine load.

(3) In the above embodiment, the fuel is injected from only the first injector 60 in the low EGR rate region, but both injectors 60 and 62 may simultaneously inject fuel in this region.

(4) In the present invention, the number of intake ports and exhaust ports is not particularly limited and may be set freely.

[0041]

As described above, according to the present invention, the following effects can be obtained.

In the apparatus according to the first aspect, the air-fuel mixture is stratified by the use of the air-fuel mixture supply port having a closed space, which is different from the intake port, and the swirl generation, and the EGR is performed according to the operating state of the engine. Rate is controlled, in the high EGR rate region, the air-fuel mixture supply port is opened to perform the stratification of the air-fuel mixture, and in the low EGR ratio region, the air-fuel mixture supply port is forcibly closed to supply fuel only to the intake port. In the operating region where the EGR rate is high, the stratification of the air-fuel mixture enables heavy EGR while maintaining good combustion stability, thereby significantly reducing the NOx generation amount. , Operating range with low EGR rate,
That is, in a region where the necessity of increasing the combustibility by stratification of the air-fuel mixture is relatively small, only the fuel is supplied to the intake port to prevent the air flow between the air-fuel mixture supply port and the combustion chamber, so that flow loss and It has the effect of significantly reducing heat loss and fuel economy. In particular, in the device according to claim 3, the air flow is blocked by forcibly closing the air-fuel mixture supply valve in the low EGR rate region. Therefore, in addition to reducing the flow loss and heat loss, A mechanical load for opening and closing the mixture supply valve can be eliminated, and fuel consumption can be significantly reduced.

Further, in the apparatus according to claim 4, high EGR
By operating the air pressurizing means and the first fuel supplying means in the rate region, the air-fuel mixture is formed and stratified in the air-fuel mixture supply port, while the air pressurizing means is stopped in the low EGR rate region. By doing so, there is an effect that the mechanical load for the driving is eliminated, and thereby fuel consumption can be reduced.

In the apparatus according to the fifth aspect, the fuel supply means to be used is selectively switched depending on the magnitude of the EGR rate, so that appropriate fuel injection control can be executed with simple control. Moreover, at the time of switching the used fuel supply means, the fuel supply amount by one fuel supply means (fuel supply means switched to the non-use state) is gradually increased from 0,
Since the fuel supply amount by the other fuel supply means (fuel supply means for switching to the use state) is gradually reduced to 0, the torque shock at the time of switching can be sufficiently mitigated.

In the apparatus according to claim 6, the EGR rate is 30.
By supplying fuel only from the first fuel supply means in the region of not less than%, there is an effect that the loss of combustion stability due to a large amount of EGR can be reliably avoided.

[Brief description of drawings]

FIG. 1 is an overall configuration diagram of an engine according to a first embodiment of the present invention.

FIG. 2 is a schematic plan view showing the arrangement of ports in the engine.

FIG. 3 is a diagram showing valve timings of an intake valve and a center valve in the engine.

FIG. 4 is an EGR rate controlled in the engine,
It is a graph which shows the relationship with an engine speed and an engine load.

FIG. 5 is a graph showing the EGR rate and the fuel when the fuel is supplied only from the first injector to the air-fuel mixture supply port and the fuel is supplied only from the second injector 62 to the first intake port in the engine. It shows the relationship between the consumption amount, the NOx generation amount, and the average effective pressure fluctuation rate.

FIG. 6 is an overall configuration diagram of an engine according to a second embodiment of the present invention.

FIG. 7 is an overall configuration diagram of an engine according to another embodiment of the present invention.

FIG. 8 is a graph showing a modified example of EGR rate control based on engine load.

[Explanation of symbols]

10 Engine Body 14 Combustion Chamber 16, 18 Intake Port 22 Intake Valve 38 Swirl Control Valve 48 EGR Pipe 50 EGR Valve 57 Mixture Supply Port 58 Center Valve 60 First Injector (First Fuel Supply Means) 61 On-off Valve 62 Second Injector (Second Fuel Supply Means) 63 Valve Stopping Mechanism 69 Air Pump (Air Pressurizing Means) 70 ECU (EGR Rate Control Means and Fuel Injection Control Means)

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Internal reference number FI Technical display location F02D 41/34 C 9247-3G F02M 25/07 570 A 69/04 R (72) Inventor Masakazu Matsumoto 3-1, Shinchi, Fuchu-cho, Aki-gun, Hiroshima Prefecture Mazda Motor Corporation

Claims (6)

[Claims] 1. An air-fuel mixture supply port for forming an air-fuel mixture by mixing pressurized air and fuel and supplying the air-fuel mixture into the combustion chamber separately from the intake port, and a fuel supply port for supplying fuel to the air-fuel mixture supply port. (1) In an intake system of an engine provided with a fuel supply means and a mixture supply valve that opens the opening of the mixture supply port from the latter half of the intake stroke to the compression stroke, the mixture supply port is a closed space, and this mixture The gas mixture in the combustion chamber is drawn into the combustion chamber at the initial opening of the gas supply port, and then the gas in the combustion chamber is pressed into the mixture gas supply port until the gas mixture supply port is closed. Then, the intake port is arranged so that swirl is generated in the combustion chamber by the intake air from the intake port, and the mixture gas supply port is substantially cylindrical with respect to the center of the bore near the spark plug. The EGR means for opening exhaust gas in the direction of the center line of the exhaust gas and recirculating exhaust gas to the intake port, the second fuel supply means for supplying fuel to the intake port, and the EGR rate by the EGR means according to the operating state of the engine. EGR rate control means for changing, opening / closing means for opening / closing the opening of the air-fuel mixture supply port or a portion in the vicinity thereof, and opening / closing means in a region where the EGR rate is equal to or higher than a certain level to supply fuel from at least the first fuel supply means. Let
An intake system for an engine, comprising: a fuel injection control unit that closes the opening / closing unit and supplies fuel only from the second fuel supply unit in a region where the EGR rate is less than a certain value. 2. The engine intake system according to claim 1, wherein the opening / closing means includes an opening / closing valve for opening / closing the mixture supply port at a position upstream of the mixture supply valve. Intake device for the engine. 3. The engine intake system according to claim 1, wherein the air-fuel mixture supply valve also serves as the opening / closing means.
A valve stop means for forcibly closing the air-fuel mixture supply valve is provided, and the fuel injection is performed so that the air-fuel mixture supply valve is forcibly closed only by the valve stop means in a region where the EGR rate is less than a certain value. An intake system for an engine, characterized by comprising a control means. 4. An air-fuel mixture supply port for forming an air-fuel mixture by mixing pressurized air and fuel and supplying the mixture into the combustion chamber, separately from the intake port, and supplying pressurized air to the air-fuel mixture supply port. And a first fuel supply means for supplying fuel to the mixture supply port, and a mixture supply valve for opening the opening of the mixture supply port from the latter half of the intake stroke to the compression stroke. In the intake system of an engine, the intake port is arranged so that swirl is generated in the combustion chamber by intake air from the intake port, and the mixture supply port is arranged approximately at the cylinder center line with respect to the center of the bore near the spark plug. EGR means for opening exhaust gas in the above direction and recirculating exhaust gas to the intake port, a second fuel supply means for supplying fuel to the intake port, and an upper portion according to the operating state of the engine. The EGR rate control means for changing the EGR rate by the EGR means, and the air pressurizing means is operated to supply fuel from at least the first fuel supply means in a region where the EGR rate is above a certain level, and the EGR rate is below a certain level. An intake system for an engine, comprising: a fuel injection control means for stopping the air pressurizing means in a region and supplying fuel only from the second fuel supply means. 5. The engine intake system according to any one of claims 1 to 4, wherein fuel is supplied only from the first fuel supply means in a region where the EGR rate is less than a fixed value, and a fuel supply to be used. When switching the means, the fuel injection amount is gradually increased from 0 by the fuel supply means used after this switching, and the fuel supply quantity by the fuel supply means stopped after the switching is gradually decreased to 0. An intake system for an engine, characterized by comprising a control means. 6. The engine intake system according to any one of claims 1 to 5, wherein the fuel injection control means is configured to perform only fuel supply by the first fuel supply means in a region where the EGR rate is 30% or more. An intake system for an engine, which is characterized in that