JPS6116257A - Engine exhaust recirulation control system - Google Patents

Abstract

PURPOSE:To enhance the flammability of mixture by providing a means to complete the supply of exhaust gas to the suction system before a prescribed period of time precedent to the completion time of suction stroke and a means to cause swirl to exhaust gas supplied into the cylinder, at least at the low load operation of engine. CONSTITUTION:The downstream part of a suction passage 7 is divided into a primary suction passage 7b and a secondary suction passage 7c by a division wall 16, and the downstream end of the primary suction passage 7b having a smaller corss-sectional area is opened to the suction passage at a slightly upstream point from a suction valve 9 in the circumferential direction to a cylinder 4 to become a means 17 to cause swirl. Further, the downstream end of an EGR passage 21 branched from an exhaust passage 8 is opened to the primary suction passage 7b, and the quantity of recirculating exhaust gas is controlled by an EGR valve 22. In addition, a rotary valve 30 in which the opening time of valve is regulated by a valve timing variable mechanism 31 is interposed in the EGR passage on the downstream side of the EGR valve 22, and this rotary valve controls the supply of exhaust gas to complete before a prescribed period of time precedent to the completion time of suction stroke at a low load operation.

Description

Detailed Description of the Invention (Industrial Field of Application) The present invention relates to an exhaust recirculation system that recirculates part of exhaust gas into a cylinder during the intake stroke of an engine, in which the timing of exhaust recirculation is controlled. This relates to eight control positions.

(Prior Art) Conventionally, as disclosed in, for example, Japanese Unexamined Patent Application Publication No. 56-148636, in an engine equipped with a fuel injection position of 1>1ti, an intake passage communicating with a combustion chamber via an intake valve is used. A fuel injection valve is provided, and in the low load range of the engine, the fuel injection valve 1. By injecting fuel from s t, the air-fuel mixture is unevenly distributed and stratified in the upper part of the combustion chamber where the spark plug is located, and a swirl is given to the intake air drawn into the combustion chamber, and this swirl is J to suppress the diffusion of stratified air-fuel mixture in the compression stroke and to cause stratified combustion in the explosion expansion stroke.
: Sea urchin technology is known.

(Problems to be Solved by the Invention) By the way, it is not limited to fuel injection engines that perform stratified combustion as described above, but also fuel injection engines and carburetor engines that inject fuel into the intake passage regardless of the stroke of the cylinder. When a part of the exhaust gas is supplied into the cylinder during the intake stroke to perform so-called exhaust recirculation to reduce NOx in the exhaust gas, as is normally done, the intake stroke, When exhaust gas is supplied into the cylinder for the entire period of A problem arises in that the spark source becomes unstable and ignitability deteriorates.

The present invention has been made in view of the above, and its purpose is to improve the timing at which exhaust gas supply ends when exhaust gas is recirculated to supply exhaust gas into the cylinder during the intake stroke of the engine, as described above. By appropriately setting , it is possible to distribute only the air-fuel mixture near the ignition plug located at the top of the cylinder, ensuring a stable source of spark from the ignition plug, thereby reducing the reduction in engine ignitability due to exhaust gas recirculation. The goal is to prevent

(Means for Solving the Problems) In order to achieve the above object, the solving means of the present invention is such that an ignition plug and an opening of an intake passage are disposed in the upper part of the cylinder, and a part of the exhaust gas is disposed inside the cylinder. In an exhaust gas recirculation control device for an engine, which is equipped with an exhaust supply means for supplying a The present invention is provided with an exhaust supply control means for terminating the supply of exhaust gas by the exhaust supply means, and a swirl generation means for generating a swirl in at least the exhaust gas supplied into the cylinder.

(Function) With the above configuration, in the present invention, at least when the load of the engine is low, the air inside the cylinder is maintained between the time when the exhaust supply means finishes supplying exhaust gas during the intake stroke and the time when the air-fuel mixture ends flowing into the cylinder. Supplying only the air-fuel mixture to the cylinder, the air-fuel mixture is unevenly distributed near the spark plug at the top of the cylinder, and the uneven distribution of the air-fuel mixture near the spark plug is maintained until the end of the compression stroke by the swirl generated by the swirl generating means. This improves the ability of the spark plug to ignite the air-fuel mixture.

(Example) Hereinafter, an example of the present invention will be described in detail based on the drawings.

1 to 3 show a device configuration according to a first embodiment of the present invention, in which 1 is an engine having a cylinder 4 formed by a cylinder block 2 and a cylinder head 3;
5 is a piston that reciprocates within the cylinder 4; 6 is a combustion chamber defined within the cylinder 4 by the piston 5; 7 is a combustion chamber defined within the cylinder 4 by the piston 5;
8 is an intake passage that supplies intake air into the combustion chamber 6, and 8 is the combustion chamber 6.
An exhaust passage for discharging exhaust gas from inside the intake passage 7.
Openings 7a and 8a of the exhaust passage 8 to the combustion chamber 6 are formed in the cylinder head 3, and an intake valve 9 for opening and closing the opening 7a of the intake passage 7 is provided at the opening 7a of the intake passage 7. Exhaust valves 1o for opening and closing the openings 8a are respectively disposed in the exhaust valves 8a.

Furthermore, an ignition plug 11 for igniting the air-fuel mixture in the combustion chamber 6 is attached to the cylinder head 3 at a side portion of the opening 7a of the intake passage 7 and the opening 8a of the exhaust passage 8. Plug 11 and opening 7a of intake passage 7
is arranged above the combustion chamber 6 within the cylinder 4.

In the intake passage 7, in order from the upstream side, there is an air flow meter 12 that detects the amount of intake air sucked into the combustion chamber 6;
Thrower valve 1 that controls the amount of intake air
3 and a leege tank 14 that absorbs the pulsation of intake air are provided, and the upstream end of the intake passage 7 is connected to an air cleaner 15.

Further, as shown in enlarged detail in FIGS. 2 and 3, the intake passage 7 downstream of the surge tank 14 is divided into a primary intake passage 7b and a secondary intake passage 7G by a partition wall 16. The passage area of the primary side intake passage 711 is set smaller than that of the secondary side intake passage 7c, and
The upstream end of b is the intake passage 7 slightly upstream of the intake valve 9.
The cylinder 4 is opened in the circumferential direction of the cylinder 4, and the intake air flowing through the primary side intake passage 7b is introduced into the cylinder 4 in the circumferential direction while increasing its flow velocity. Swirl generating means 17 configured to generate swirl K is configured.

Further, the downstream end of the secondary intake passage 7C opens in a direction substantially parallel to the center line of the cylinder 4, that is, toward the upper surface of the piston 5, and the air flows into the cylinder 4 through this secondary intake passage 7C. Swirl K is not applied to the intake air. Further, a swirl control valve 18 is disposed in the middle of the secondary intake passage 7C to control the intensity of the swirl by opening and closing the secondary intake passage 7C.
Reference numeral 8 is drivingly connected to an actuator (not shown), and the operation is controlled by the actuator according to the rotational speed and load condition of the engine 1. When the engine 1 is in a low speed and low load region, the swirl control valve 18 closes to control the intake air. flows into the cylinder 4 from the primary side intake passage 7b to strengthen the swirl, and as the engine 1 shifts to a high-speed, high-load region, the opening degree of the swirl control valve 18 increases. It is configured to increase the inflow ratio of intake air from the next intake passage 7C and weaken the swirl strength within the cylinder 4.

Further, the secondary intake passage 7 downstream of the swirl control valve 18
In C, one fuel injector directs fuel to combustion chamber 6.
DAl- is arranged so that the flame 1'! 1.1 @ A constant fuel pressure is applied to the valve 19, and one fuel injection valve changes the fuel injection amount by changing the valve opening time according to the pulse width of the input pulse signal. be.

On the other hand, a catalyst 20 for purifying exhaust gas is disposed in the middle of the exhaust passage 8, and the upstream end of the exhaust gas recirculation passage 21 is opened in the exhaust passage 8 upstream of the catalyst 20. The downstream end is opened to the primary intake passage 7b of the intake passage 7. Further, an exhaust gas recirculation valve 22 is disposed in the middle of the exhaust gas recirculation passage 21, and the exhaust gas recirculation valve 22 includes a valve body 23 that throttles and opens and closes the exhaust gas recirculation passage 21, and a diaphragm 24 that is drivingly connected to the valve body 23. and the diaphragm 2
A negative pressure chamber 25 partitioned by 4 and the negative pressure space 25
and a spring 26 that urges the diaphragm 24 in the valve closing direction of the valve body 23. It is in communication with a pressure source (not shown). Then,
An exhaust gas supply means 29 is configured such that a part of the exhaust gas flowing through the exhaust passage 8 flows into the primary side intake passage 7b of the intake passage 7 and is supplied to the combustion chamber 6 of the set cylinder 4 while controlling the flow rate by an exhaust gas recirculation valve 22. has been done. Therefore, the swirl generating means 17 generates a swirl in the exhaust gas that is supplied to the combustion chamber 6 together with the intake air by the exhaust gas supply means 29.

Further, two exhaust recirculation passages downstream of the exhaust recirculation valve 22 are provided with a low recirculation valve 30 that opens and closes the exhaust recirculation passage 21. engine 1
The drive is connected to the

A control system for controlling the operation of the fuel injection valve 19, the duty valve 27 for controlling the exhaust recirculation valve 22, and the variable 11 mechanism 31 for controlling the rotary valve 30 will be described. 32 is the valve of the throttle valve 13. A throttle sensor 33 detects the opening degree, and a crank angle sensor 33 detects the crank angle of the engine 1 from the rotation angle of the distributor 34.The outputs of the throttle sensor 32, crank angle sensor 33, and air flow meter 12 are Upon receiving the output signal, the fuel injection valve 19
, the duty valve 27 and the variable mechanism 31 are controlled.
The crank angle sensor 1 is inputted to a controller 35 having a built-in CPU for
Crank angle signal from No. 33 and air flow meter 1
Based on the airflow signal from the engine 1, the rotational speed c15 and the load condition of the engine 1 are detected, and compared with the fuel 1131 map that has been set and stored in advance, the amount of fuel injection is determined. Injection t) Ja is corrected in accordance with the throttle signal from the throttle sensor 32 to determine the execution fuel injection amount, and a signal with a pulse width corresponding to the execution fuel injection amount is used to inject fuel at a predetermined time of the intake stroke of the engine 1. It is configured to output the fuel to the valve 19 to inject the fuel necessary for combustion.

That is, the fuel injection timing by the fuel injection valve 19 is set from the time IO when the intake valve 9 opens before the top dead center TDC to the BDC after the bottom dead center in the valve opening curve of the intake valve 9 shown in FIG.
For the intake stroke up to the point IC when the subsequent intake valve 9 closes, the injection end times θE and INJ are set around the time when the piston speed reaches its maximum approximately in the middle of the intake stroke, and the injection end times θE, The injection start time θ [
3, INJ, and as the load on the engine 1 increases and the fuel injection pulse width increases, the injection angle θINJ corresponding to the pulse width increases, and the injection angle θINJ increases at approximately the middle of the intake stroke. Injection start time θB centered on
, INJ and injection end timing θE, INJ are changed.

Further, the controller 35 controls the opening degree of the exhaust recirculation valve 22 and the opening timing of the low recirculation valve 300 according to the load state of the engine 1, and when the engine 1 is in a low load region, the fuel injection is performed during the intake stroke. At the same time that fuel is injected from one valve, the low-return valve 30
The valve is opened to distribute the recirculated exhaust gas in the space where the combustible moisture mixture is distributed in the combustion chamber 6, and at the point when the flow of the mixture into the cylinder 4 is substantially completed, J, that is, the mixture is Exhaust supply control means 36 that closes the rotary valve 30 for a predetermined period of time before the end of injection of fuel from one of the constituent fuel injection valves to end the supply of exhaust gas by the exhaust supply means 29. is configured.

Next, the operation of exhaust gas recirculation when the engine 1 is in the low-medium load range in the above embodiment will be explained with reference to the flowchart shown in FIG.
In Step 1, the airflow signal from the airflow meter 12 and the crank angle signal from the crank angle sensor 33 are input to the controller 35, and in the next step S2, the rotation speed and load condition of the engine 1 are detected based on both of the input signals. The exhaust recirculation amount is determined by comparing the engine speed and load condition with a map stored in advance. After that, in step S3, the controller 3
5 CPU.

Fuel injection start timing θB from the fuel injection valve 19.

INJ and injection end timing θE, INJ are read,
The injection end timing θF read above in step S4,
By subtracting the crank angle θ corresponding to the predetermined period from 'l N J, the injection end timing θE is determined.

Exhaust recirculation end time θε earlier than INJ by a predetermined period,
ε(1, R is determined. Then, in the next step S6, exhaust gas recirculation is performed so that the amount of exhaust gas recirculated determined in step S2 is supplied to the combustion chamber 6 within the period in which the rotary valve 30 is opened. The valve 22 is operated, and in step S, the closing timing of the low-return valve 30 is set to the exhaust gas recirculation end timing θE, EGR determined in step S4, and when the cylinder 4 moves to the intake stroke, the closing timing is set as described above. The rotary valve 30 opens and closes at the appropriate timing, and the exhaust gas flows into the combustion chamber 6.
can be supplied to. With the above, one cycle of operation is completed,
Thereafter, the process returns to the first step S1 and the same operation as above is repeated.

Therefore, with the above control, when the engine 1 is in the low-medium load range, the rotary valve 30 is opened in synchronization with the fuel injected from the fuel injection valve 19 in the middle of the intake stroke, and the exhaust gas is The air-fuel mixture is sucked into the combustion chamber 6 together with the air-fuel mixture, and when the intake of the air-fuel mixture into the combustion chamber 6 ends with the end of fuel injection from the fuel injection valve 19, the low-return valve 30 closes and the air-fuel mixture flows into the combustion chamber 6. Since the inflow of exhaust gas is stopped, at the end of the intake stroke when the intake valve 9 closes,
As schematically shown in FIG. 5, an intake air layer Z1 consisting only of intake air is formed above the combustion chamber 6 near the top surface of the screw 1-5.
However, in the middle part of the combustion chamber 6 above the intake air layer Z1, there is a recirculation exhaust layer Z2 in which the recirculated exhaust gas is mixed into the mixture of fuel and intake air, and in the upper part of the combustion chamber 6 near the ignition plug 11, the mixture is mixed. The combustion chamber 6 is formed with an air-fuel mixture layer Z3 consisting of only
The inside of the combustion chamber G is stratified, and this stratification is strongly maintained due to the swirl generated within the combustion chamber G by the swirl generating means 17.

Therefore, when the ignition plug 11 is supplied with electricity at the end of the compression stroke after the intake stroke, the ignition flame generated from the ignition plug 11 becomes a stable spark due to the mixture layer Z3 unevenly distributed near the ignition plug 11. It is possible to reliably improve the ignitability of.

FIG. 7 shows a second embodiment of the present invention. The same parts as in FIG. 1 are given the same reference numerals and detailed explanations are omitted. This method was applied to a fuel injection type engine, which supplies the fuel necessary for one combustion cycle, whereas it was applied to a carburetor type engine.

That is, in this embodiment, in the configuration of the first embodiment, a carburetor 37 is disposed in the intake passage 7 between the air flow meter 12 and the throttle valve 13, and the fuel injection valve 19 and the throttle sensor 32 are Omitted.

Further, the controller 35' detects the rotation speed and load condition of the engine 1 based on the air flow signal from the air flow meter 12 and the crank angle signal from the crank angle sensor 33, and responds to the engine rotation speed and load condition. It only has the function of controlling the amount of exhaust gas recirculated by the exhaust gas recirculation valve 22 and the timing of continuous exhaust gas flow by the rotary pulp 3o.

The operation of this second embodiment will be explained with reference to the flowchart shown in FIG. 8. In step S'+ after the start and subsequent step S'2,
Similar to steps S1 and S2 in the embodiment, the air flow signal from the air flow meter 12 and the crank angle signal from the crank angle sensor 33 are input, and the exhaust gas recirculation amount is determined based on these both signals, and then step S At '3, exhaust gas recirculation end timing θ'
・E and EG'R are determined. That is, the determination of the exhaust gas recirculation end timing θ'E, EGR is determined by the carburetor 37.
Combustion chamber 6 of the mixture of intake air and fuel generated by
The end time of the mixed air flow person θE, INT,
That is, the time point at which intake air blowback begins is determined based on the engine speed, and the crank angle θ' corresponding to a predetermined period is subtracted from the mixture flow end time θE, INT. After that, step S'4 OJ: and S'
Steps S5 and S6 in the first embodiment
Similarly, after the exhaust recirculation valve 22 is activated and the rotary valve 30 closing timing is set, step S'
The control returns to + and the subsequent control is repeated.

Therefore, in this embodiment as well, since the exhaust gas recirculation ends before the inflow of the air-fuel mixture into the combustion chamber 6 substantially ends, there is air in the vicinity of the spark plug 11 in the upper part of the combustion chamber 6 that is free of exhaust residue. Only the mixture of fuel and fuel is distributed and stratified, so that the same effects as in the above embodiment can be achieved.

Although the above embodiments are applied to a fuel injection engine and a carburetor engine that inject fuel at a predetermined time in the intake stroke, the present invention is applicable to a fuel injection engine and a carburetor engine that inject fuel into the intake passage simultaneously regardless of the stroke of the cylinder. Of course, the present invention can also be applied to fuel injection type engines.

(Effects of the Invention) As described above, according to the present invention, in an engine that performs exhaust gas recirculation, the exhaust gas recirculation is performed for a predetermined period before the time when the air-fuel mixture substantially ends flowing into the cylinder during the intake stroke. The air-fuel mixture is unevenly distributed near the ignition point at the top of the cylinder, and this state is maintained by swirl until the end of the compression stroke, so a stable source of spark from the ignition plug can be ensured. Therefore, it is possible to reliably prevent a decrease in the ignitability of the engine due to exhaust gas recirculation.

[Brief explanation of drawings]

1 to 6 show a first embodiment of the present invention, in which FIG. 1 is a general schematic diagram, FIG. 2 is a vertical sectional view of the main parts of the engine, and FIG. 3 is a bottom view of the cylinder head. , FIG. 4 is a control flowchart, FIG. 5 is an explanatory diagram showing the gas composition in the cylinder at the end of the intake stroke, FIG. 6 is an explanatory diagram showing the exhaust gas recirculation timing in the intake stroke, and FIGS.
The figure shows the second embodiment, and FIG. 7 is a view corresponding to FIG.'1, and FIG.
The figure is a diagram equivalent to Figure 3. DESCRIPTION OF SYMBOLS 1... Engine, 4... Cylinder, 6... Combustion chamber, 7... Intake passage, 7a... Opening, 11... Spark plug, 12... Air flow meter, 17...・Swirl generating means, 19...Fuel injection valve, 21...Exhaust recirculation passage, 22...Exhaust recirculation valve, 29...Exhaust gas supply means, 3o...Rotary valve, 32...Throttle sensor The, 33...Crank angle sensor, 35.35'
...Controller, 36...Exhaust supply control means, 3
7... Vaporizer. Figure 5 Figure 4 Figure 8 Figure 7 Figure 1 Bow

Claims (1)

[Claims] (1) In an exhaust gas recirculation control device for an engine, in which an ignition plug and an intake passage opening are disposed in the upper part of the cylinder, and an exhaust supply means for supplying part of the exhaust gas into the cylinder is provided, Exhaust supply control means for terminating the supply of exhaust gas by the exhaust supply means at least a predetermined period before the point at which the air-fuel mixture substantially ends flowing into the cylinder during the intake stroke; 1. An exhaust gas recirculation control device for an engine, comprising: a swirl generating means for generating a swirl in the exhaust gas.