JPS63189663A - Exhaust recirculation control method for internal combustion engine - Google Patents

Abstract

PURPOSE:To spread an exhaust gas recirculation (EGR) region, by stopping the EGR, when a parameter representing a load of an engine is in a predetermined value or more, while setting this predetermined value, when a transmission is an automatic transmission, to a larger value than that when the transmission is a manual transmission. CONSTITUTION:An electronic control unit 5, setting a valve opening instruction value of an exhaust gas recirculation (EGR) valve 22 on the basis of detection values from an intake pipe internal absolute pressure sensor 7 and an engine speed sensor 10, performs a feedback control on the basis of the actual valve opening value of an EGR valve 22 detected by a valve lift sensor 28. When an engine speed as the parameter, representing a load of an engine, exceeds a predetermined value, the EGR is stopped, but this predetermined value is switched, for instance, so as to obtain 4200rpm, when a transmission is an automatic transmission, while 4000rpm when the transmission is a manual transmission.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an exhaust gas recirculation control method for an internal combustion engine, and in particular to an exhaust gas recirculation method that allows exhaust gas recirculation to be appropriately controlled depending on the type of transmission connected to the engine. This invention relates to a reflux control method.

(Prior art and its problems) Conventionally, there has been an exhaust gas recirculation control method that recirculates part of the exhaust gas of an internal combustion engine into the intake passage to reduce nitrogen oxides (NOX), which is one of the harmful gases generated from the engine. widely known. In addition, in order to prevent a drop in engine output during high-load or high-speed operation and ensure stable drivability, the operating parameter values used to detect the engine load, such as the absolute pressure in the intake pipe, are set at or above a predetermined value. The present applicant has already proposed an exhaust gas recirculation control method in which the exhaust gas recirculation is stopped when the engine rotational speed is higher than or equal to a predetermined value (Japanese Patent Application No. 60-232819).

However, the proposed control method has room for improvement in performing control corresponding to a case where a different type of transmission is connected to the applied internal combustion engine. In other words, a vehicle equipped with an automatic transmission with a fluid coupling such as a torque converter (hereinafter referred to as "rAT vehicle") is different from a vehicle equipped with a manual transmission without fluid coupling (hereinafter referred to as "rMT vehicle").
), the load on the engine is greater by the load of the fluid coupling, and for this reason, the engine load and engine speed of AT vehicles are set higher in order to achieve the same driving performance as MT vehicles. On the other hand, in the proposed control method, the predetermined value of the operating parameter value for determining whether the engine is in a high-load operating state, that is, the predetermined value of the absolute pressure value in the intake pipe or the engine speed value, etc. The same value is applied regardless of the type of transmission installed in the vehicle, ie, whether it is an AT vehicle or a MT vehicle. Therefore, when the above control method is applied to an AT vehicle using the predetermined operating parameter values set to suit a MT vehicle, the engine tends to enter the exhaust gas recirculation stop region, and as a result, nitrogen oxides are (NOx) purification frequency is lower than in MT cars, and exhaust gas characteristics equivalent to MT cars cannot be achieved.

On the other hand, when the above control method is applied to an MT car using the predetermined values of the operating parameters set to suit an AT car, the engine tends to enter the exhaust gas recirculation execution region, and as a result, the engine output decreases. This decrease leads to a decrease in drivability.

(Object of the Invention) The present invention was made to solve the above-mentioned problems, and provides an internal combustion engine that improves exhaust gas characteristics and driveability regardless of the type of transmission connected to the engine. The purpose of the present invention is to provide an exhaust gas recirculation control method.

(Means for Solving the Problems) In order to achieve the above object, the present invention adjusts the valve opening degree of an exhaust recirculation valve disposed in an exhaust gas recirculation passage connecting an exhaust passage and an intake passage of an internal combustion engine. In the method for controlling exhaust gas recirculation of an internal combustion engine according to an operating parameter value, the exhaust gas recirculation is stopped when the internal combustion engine is in an operating state in which an operating parameter value representative of the load of the internal combustion engine is equal to or higher than a predetermined value; The predetermined value is changed depending on whether the transmission connected to the internal combustion engine is an automatic transmission or a manual transmission.

(Example) Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is an overall configuration diagram showing an internal combustion engine equipped with an exhaust gas recirculation control device to which the method of the present invention is applied, and is denoted by l.
shows, for example, a four-cylinder internal combustion engine, an intake pipe 2 is connected to the engine 1, and a throttle valve 3 is provided in the middle of the intake pipe 2.

The throttle valve 3 is equipped with a throttle valve opening sensor (hereinafter referred to as θ
A TH sensor (hereinafter referred to as "rEcUJ") 4 is connected to convert the opening degree of the throttle valve 3 into an electrical signal and send it to an electronic control unit (hereinafter referred to as rEcUJ) 5.

A fuel injection valve 6 is provided in the intake pipe 2 between the engine 1 and the throttle valve 3. This fuel injection valve 6 is provided for each cylinder slightly upstream of an intake valve (not shown) in the intake pipe 2, and each injection valve 6 is connected to a fuel pump (not shown) and electrically connected to the ECU 3. Te, EC
The valve opening time of fuel injection is controlled by the signal from U3. On the other hand, an absolute pressure sensor (
Hereinafter referred to as "rPa^sensor") 7 is provided.

The intake pipe absolute pressure signal converted into an electrical signal by this PB^ sensor 7 is sent to the ECU 3.

Further, an intake air temperature sensor (hereinafter referred to as "T^ sensor") 8 is installed downstream thereof, and this T^ sensor 8 converts the intake air temperature into an electrical signal and supplies it to the ECU 3.

The main body of engine 1 is equipped with an engine cooling water temperature sensor (r
A Tw sensor (referred to as "Tw sensor") 9 is provided, and this Tw sensor 9 is made of a thermistor or the like, and is installed in the circumferential wall of the engine cylinder filled with cooling water, and supplies the detected cooling water temperature signal to the ECU 3.

Engine speed sensor (hereinafter referred to as rNe sensor) 1
0 is attached around the camshaft or crankshaft (not shown) of the engine, and is an engine rotation speed signal, that is, 18o of the engine crankshaft.

A predetermined control signal pulse (
This TDC signal pulse is sent to the ECU 3.

A three-way catalyst 12 is disposed in the exhaust pipe 11 of the engine 1 to purify HC, CO, and NOx components in the exhaust gas. An 02 sensor 13 is inserted into the exhaust pipe 11 on the upstream side of the three-way catalyst 12, and this 02 sensor 13 detects the oxygen concentration in the exhaust gas and supplies the detected value signal to the ECU 3.

Furthermore, the ECU3 has an atmospheric pressure sensor (hereinafter referred to as "P^sensor").
) 14 is connected, and the detected value signal from the P^ sensor 14 is supplied to the ECU 3.

Next, an exhaust gas recirculation mechanism 20 forming a part of the exhaust gas recirculation control device
I will explain about it.

The exhaust gas recirculation path 21 of this mechanism 20 has one end 21 a communicating with the upstream side of the three-way catalyst 12 of the exhaust pipe 11 and the other end 21 b communicating with the downstream side of the throttle valve 3 of the intake pipe 2 . In the middle of this exhaust gas recirculation path 21, there is an exhaust gas recirculation valve 2 that controls the amount of exhaust gas recirculation.
2 is interposed.

The exhaust gas recirculation valve 22 is operatively connected to a diaphragm 23a of a negative pressure response device 23.The negative pressure response device 23 has a negative pressure chamber 2 defined by the diaphragm 23a.
3b and a lower chamber 23c, and a spring 23d inserted into the negative pressure chamber 23b presses the diaphragm 23a in the direction in which the exhaust recirculation valve 22 is closed. The lower chamber 23c communicates with the atmosphere via an air passage 27, and the negative pressure chamber 23b communicates with the downstream side of the throttle valve 3 of the intake pipe 2 via a negative pressure passage 24 having a throttle. An electromagnetic three-way valve 25 is provided in the middle of this negative pressure path 24, and when the solenoid 25a of the electromagnetic three-way valve 25 is energized, the valve body 25b passes through the atmospheric air path 26 equipped with a filter and a throttle. Since the opening 25c communicating with is closed and the negative pressure path 24 is opened, negative pressure on the downstream side of the throttle valve 3 of the intake pipe 2 is introduced into the negative pressure chamber 23b of the negative pressure response device 23. As a result 1, a difference occurs in the pressures acting on both sides of the diaphragm 23a, so the diaphragm 23a is displaced against the spring 23d, causing the exhaust gas recirculation valve 22 to open. That is, when the solenoid 25a of the electromagnetic three-way valve 25 is energized, the exhaust gas recirculation valve 22 increases its opening degree to recirculate a portion of the exhaust gas to the intake pipe 2 via the exhaust gas recirculation path 21. On the other hand, the solenoid 25a of the electromagnetic three-way valve 25
When the valve body 25b is deenergized, the valve body 25b closes the opening 24a of the negative pressure path 24.
Since the opening 25c is closed and the opening 25c is opened, the atmosphere is introduced into the negative pressure chamber 23b of the negative pressure response device 23. At this time, the difference in pressure acting on both sides of the diaphragm 23a becomes approximately zero, and the diaphragm 23a is pressed and displaced by the spring 23d, thereby moving the exhaust gas recirculation valve 22 in the closing direction. That is, if the solenoid 25a of the electromagnetic three-way valve 25 continues to be deenergized, the exhaust gas recirculation valve 22 will be fully opened to cut off the recirculation of exhaust gas.

A solenoid 25a of the electromagnetic three-way valve 25 is electrically connected to the ECU 3. Reference numeral 28 is a valve lift sensor connected to the diaphragm 23a of the negative pressure response device 23, and detects the amount of deviation of the diaphragm 23a, that is, the actual valve opening of the exhaust gas recirculation valve 22. The valve lift sensor 28 is also electrically connected to the ECU 3. It is connected to the.

The ECU 3 determines the engine operating state based on the engine parameter signals from the various sensors mentioned above, and sets the valve opening command value of the exhaust recirculation valve 22 according to the intake pipe absolute pressure PB^ and the engine speed Na. In order to make the deviation between LcMD and the actual valve opening value LAcT of the exhaust recirculation valve 22 detected by the valve lift sensor 28 zero, an on-off signal is sent to the electromagnetic three-way valve 25 at a duty ratio according to the deviation. At the same time, the fuel injection time Tau of the fuel injection valve 6 given by the formula shown below is calculated.

The valve opening command value L CMD is set to gradually increase after the engine operating state shifts from a region where exhaust gas recirculation is to be performed to a region where it is not to be performed.

Touv = Ti It is set depending on whether the three-way valve 25 is in operation or not.

1 and 2 are the various sensors mentioned above, namely θTH sensor 4, Pa^ sensor 7, T^ sensor 8, 7w sensor 9,
Ne sensor 10.02 Correction coefficient and correction variable calculated according to engine parameter signals from sensor 13 and P^ sensor 14, and depending on the engine operating state, starting characteristics, exhaust gas characteristics, fuel consumption characteristics, engine acceleration Calculation is performed based on a predetermined calculation formula so that various characteristics such as characteristics are optimized.

The ECU 3 calculates the fuel injection time To obtained as described above.
A drive signal for opening the fuel injection valve 6 is supplied to the fuel injection valve 6 based on u〒.

FIG. 2 is a block circuit diagram showing the internal configuration of the ECU 3 shown in FIG.
The interrupt signal is supplied to the Me counter 502 (hereinafter referred to as rcPUJ) as an interrupt signal to start the control program described in the flowchart shown in FIG. The Me counter 502 counts the time interval from when the previous predetermined position signal was input from the Ne sensor 10 to when the current predetermined position signal was input, and the counted value Me is proportional to the reciprocal of the engine rotation speed Ne. The Me counter 502 sends this counted value Me to the CPU 50 via the data bus 510.
Supply to 3.

θ〒H sensor 4, Pa^ sensor 7.7w sensor 9゜P^
The respective output signals from various sensors such as the sensor 14 and the valve lift sensor 28 are corrected to a predetermined voltage level by a level correction circuit 504, and then sequentially outputted to A by a multiplexer 505.
/D converter 506. The A/D converter 506 sequentially converts the output signals from the aforementioned sensors into digital signals and supplies the digital signals to the CPU 503 via the data bus 510.

The CPU 503 is further connected to a read-only memory (hereinafter referred to as FROMJ) 507, a random access memory (hereinafter referred to as rRAMJ) 508, and drive circuits 509 and 511 via a data bus 510.
08 temporarily stores calculation results etc. in the CPU 503,
The ROM 507 stores a control program for exhaust gas recirculation control, which will be described later, to be executed by the CPU 503.

In accordance with this control program, as described later, the CPU 503 determines the operating state of the engine according to output signals from various engine parameter sensors, and sends an on-off control signal for the electromagnetic three-way valve 25 that controls the amount of exhaust gas recirculation to the drive circuit. 5
11, and also calculates the fuel injection time Tou〒 of the fuel injection valve 6 according to the operating state of the engine, and supplies this calculated value to the drive circuit 509 via the data bus 510. The drive circuit 509 controls the fuel injection valve 6 according to the calculated value.
A control signal for opening the valve is supplied to the injection valve 6, and a drive circuit 511 supplies an on-off drive signal for turning the electromagnetic three-way valve 25 on and off to the electromagnetic three-way valve 25.

Next, details of the operation of the exhaust gas recirculation control method of the present invention applied to the apparatus configured as described above will be explained.

FIG. 3 is a flowchart of a program when the ECU 3 of FIG. 1 performs exhaust gas recirculation control in synchronization with the TDC signal pulse.

First, in step 301, it is determined whether the engine cooling water temperature Tw is greater than a predetermined value TWE (for example, 70° C.). When this answer is negative (No), that is, when Tw≦TWE holds true, it is determined that the engine 1 is in a warm-up operation state, so the process proceeds to step 302, where the flag FE is set to 0, and then, in step 303, the exhaust gas The valve opening command value LcMp of the reflux valve 22 is set to 0, and this program ends. That is, in this case, exhaust gas recirculation is not performed, thereby preventing an engine stall or the like due to exhaust gas recirculation being performed during warm-up operation of the engine 1.

If the answer to step 301 is Yes, that is, TV>
When TWE is established, the process proceeds to step 304, where it is determined whether a predetermined time TDEGR has elapsed after the engine 1 was started. The answer to this step 304 is negative (No)
, that is, after engine 1 is started.

If the predetermined period of time has not elapsed, steps 302 and 303 are executed, and the program is terminated assuming that no exhaust gas recirculation is performed. This ensures complete explosion of the engine 1 during startup.

If the answer to step 304 is affirmative (Yes), that is, the predetermined time Toto* has elapsed after starting the engine 1, the process proceeds to step 305, where the engine rotation speed Ne is lower than the first predetermined value N e (for example, 650 rp+s). Determine whether it is small or not. The answer to this step 3Q5 is affirmative (
Yes), that is, when N e < N e 1 holds true, the process proceeds to step 306 and sets the flag FE (hR to 1), and then executes step 303 to end this program. Stability is ensured.

The answer to step 305 is negative (No), that is, Ne≧N
When the condition e is established, the process proceeds to step 307, where it is determined whether the vehicle in which the engine is mounted is a manual transmission vehicle. This determination may be made, for example, if the vehicle is an MT vehicle or an AT vehicle.
This is performed in accordance with the output of a switch for each transmission type, which is switched between ON and OFF states depending on which vehicle the vehicle is in.

If the answer to step 307 is negative (No), that is, the vehicle is an AT vehicle, the process proceeds to step 308, where the engine speed Ne is greater than the second predetermined value Na2^y for AT vehicles (for example, 4.200 rpm). Determine whether or not.

The answer to this step 308 is affirmative (Yes), that is, Ne)
When Ne,^〒 is established, steps 306 and 303 are executed and the program is ended.

If the answer to step 308 is negative (No), that is, Ne≦
When Ne, ^↑ holds true, step 310 will be described later.
Proceed to.

If the answer to step 307 is affirmative (Yes), that is, the vehicle is a manual transmission vehicle, the process proceeds to step 309, where the engine speed Ne is a manual transmission vehicle whose engine speed Ne is smaller than the second predetermined value for automatic transmission vehicles. It is determined whether or not the second predetermined value Ne is greater than M (for example, 4.000 rpm). The answer to this step 309 is affirmative (Yes), that is, Ne>Ne
, M〒 holds true, steps 306 and 303 are executed, and the program ends. The answer to step 309 is negative (No), that is, Ne≦Ne−〒
If this holds true, the process advances to step 310.

As described above, in steps 307 to 309, it is first determined whether the vehicle is a manual transmission vehicle, that is, whether the transmission to which the engine 1 is connected is a manual transmission or an automatic transmission. A second predetermined value Ne of the engine speed for determining whether the engine 1 is in a high-speed operating state in which exhaust gas recirculation should be stopped according to this determination result.
2M〒 or Ne2^〒 is applied. Further, the second predetermined value Ne2^T for AT cars is the second predetermined value 8 for MT cars.
The reason why the value is set to be larger than that of 02M is because, as mentioned above, the engine speed of an AT vehicle is set higher than that of an MT vehicle in order to obtain the same driving performance. Therefore, through the above-described control, it is appropriately determined whether or not the engine 1 is in a high-speed operating state in which exhaust gas recirculation should be stopped, depending on the type of transmission connected to the engine 1. On the other hand, nitrogen oxides (NOx
), it is possible to improve the exhaust gas characteristics by increasing the frequency of purification, and to prevent a decrease in the output of the engine 1 for manual transmission vehicles.

Next, in step 310, it is determined whether the intake pipe absolute pressure Pa^ is larger than a predetermined value PBAH (for example, 700 n*Hg). This answer is affirmative (Yes), that is, Pa^>P
When BAH is established, steps 306 and 303 are executed and the program is terminated.

The answer to step 310 is negative (No), that is, Pa^≦
When P BAH is established, the process proceeds to step 311;
The throttle valve opening degree θ〒H is set to a predetermined value θ〒HH (for example, 50
”). This answer is affirmative (Ye
s), that is, θ〒H〉θTO)I, steps 306 and 303 are executed and the program ends. If the answer to step 311 is negative (No), that is, θdH≦θ〒HH holds true, the process proceeds to step 312.

That is, in steps 310 and 311.

Whether or not the engine 1 is in a high load operating state is determined based on the intake pipe absolute pressure Pa^ and the throttle valve opening θ〒H, and when it is determined that the engine 1 is in a high load operating state,
Exhaust reflux is stopped. This prevents the output of the engine 1 from decreasing during high-load operating conditions.

In step 312, it is determined whether the engine 1 is in the process of making the air-fuel ratio leaner or in the process of cutting fuel. If the answer is affirmative (Yes), that is, if the engine 1 is in the process of lean air-fuel ratio or fuel cut, steps 306 and 303 are executed, and the program ends. This ensures appropriate control of the air-fuel ratio when the engine 1 is adjusting the air-fuel ratio or cutting fuel.

If the answer to step 312 is negative (No), that is, if the engine 1 is neither lean air-fuel ratio nor fuel cut, the process proceeds to step 313, where flag F is set.
Determine whether EGI is equal to 1 or not. If the answer is negative (No), that is, the flag FE is not equal to 1 and is o, then step 303 is executed and the program is terminated. That is, the answer to step 304 is positive (
When the loop returns ``Yes'', the answers to steps 305, 308, and 312 are all negative (
Even if it is determined that the engine 1 is in an operating state in which exhaust gas recirculation should be performed (No), since the flag FEC)R is set to 0 in step 302, exhaust gas recirculation will not be performed. This prevents a sudden change in the combustion state of the air-fuel mixture and a resulting decrease in the output of the engine 1 that would occur if exhaust gas recirculation is performed at the time when warm-up is completed.

When the answer to step 313 is affirmative (Yes), that is, the flag Fte+e is equal to 1, the process proceeds to step 314, where the valve opening command value LCMD of the exhaust gas recirculation valve 22 is determined.
Next, in step 315, the actual valve opening value LAc of the exhaust gas recirculation valve 22 detected by the valve lift sensor 28 is determined.
and the valve opening command value LcMo determined in step 314 above.
The on-off duty ratio of the electromagnetic three-way valve 25 is determined according to the deviation from the current value, and the program ends.

Note that in this embodiment, the predetermined value of the engine rotation speed Ne for determining whether or not to stop exhaust gas recirculation is set to a different value depending on the type of transmission connected to the engine 1. , alternatively or in parallel, other operating parameter values representative of the engine load, e.g.
Predetermined value P of the intake pipe absolute pressure Pa^ in step 310 in the figure
BAHL or throttle valve opening θ in step 311
The predetermined value θTHH of 〒H may be changed depending on the type of transmission to which it is applied.

In this case, it is appropriately determined depending on the type of transmission whether the engine 1 is in a high-load operating state in which exhaust gas recirculation should be stopped, and therefore the same effects as in this embodiment can be obtained.

(5@light effect) As described in detail above, the present invention can reduce the amount of exhaust gas generated when the engine is in a high-load operating state represented by, for example, the engine speed, depending on the type of transmission connected to the internal combustion engine. The implementation of recirculation can be optimally inhibited, thereby increasing the frequency of cleaning nitrogen oxides (NOx) and improving exhaust gas characteristics when the transmission is an automatic transmission, and reducing engine output when the transmission is a manual transmission. Therefore, the exhaust gas characteristics and drivability can be improved regardless of the type of transmission connected to the engine.

[Brief explanation of the drawing]

Fig. 1 is an overall configuration diagram of an internal combustion engine equipped with an exhaust gas recirculation control device to which the present invention is applied; Fig. 2 is a block circuit diagram showing the internal configuration of the electronic control unit (ECU) shown in Fig. 1; The figure is a flowchart of a program showing an exhaust gas recirculation control method according to the present invention. 1... Internal combustion engine, 2... Intake pipe, 4... Throttle valve opening (θ〒H) sensor, 5... Electronic control unit (ECU), 7... Absolute pressure (Pa^)
sensor. 10... Engine speed (Ne) sensor, 11...
Exhaust pipe, 20... Exhaust recirculation mechanism, 21... Exhaust recirculation path, 22... Exhaust recirculation valve, 28... Valve lift sensor.

Claims (2)

[Claims] 1. In an exhaust gas recirculation control method for an internal combustion engine, the valve opening degree of an exhaust recirculation valve disposed in an exhaust gas recirculation passage connecting an exhaust passage and an intake passage of the internal combustion engine is controlled according to operating parameter values of the internal combustion engine. The transmission connected to the internal combustion engine is an automatic transmission that stops the exhaust gas recirculation and changes the predetermined value when the internal combustion engine is in an operating state in which an operating parameter value representing engine load is equal to or greater than a predetermined value. 1. A method for controlling exhaust gas recirculation for an internal combustion engine, characterized in that the method is changed depending on whether the transmission is a manual transmission or a manual transmission. 2. 2. The method of controlling exhaust gas recirculation for an internal combustion engine according to claim 1, wherein the operating parameter representative of the load on the internal combustion engine is engine rotational speed.