JPH03111651A - Air-fuel ratio controller of internal combustion engine with exhaust gas recycle device - Google Patents

Abstract

PURPOSE:To prevent overlean of air-fuel ratio by decreasingly compensating fuel calculated by a fuel supply calculation means in response to circular exhaust gas under an activation condition of exhaust gas recycle device, and compensating it in response to increase in temperature of cooling water. CONSTITUTION:Operation conditions of cooling water temperature, intake pipe pressure and the like are detected by an operation condition detection means A. An exhaust gas recycle (EGR) range is judged by the temperature of cooling water and other operation conditions with an (EGR) condition judgement means B. An exhaust gas recycle activation is attained in an EGR activation means C when it is in the EGR range. Fuel supply is calculated by a fuel injection calculation means D, and fuel calculated by a fuel supply means E is supplied to an engine. The fuel supply is decreasingly compensated in response to an EGR rate at an EGR compensation calculation means F. The fuel supply is compensated to increase the decreasing compensation by the EGR in response to the increase of the cooling water temperature in a temperature compensation calculation means G.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an air-fuel ratio control device for an internal combustion engine with an exhaust gas recirculation device.

[Conventional technology]

In the exhaust gas recirculation system of an internal combustion engine, the exhaust gas recirculation operation is stopped to ensure stable combustion in the engine when the engine is cold, and exhaust gas recirculation is enabled when the engine temperature reaches a predetermined value. Ru. The ratio of the amount of recirculated exhaust gas to the total amount of intake air introduced into the engine (EGR rate) is determined by the intake pipe pressure or intake air amount per rotation speed ratio corresponding to the engine load,
The rate is set at a predetermined rate (for example, constant) depending on the engine speed.

The so-called D- in which the fuel injection amount is calculated based on the intake pipe pressure detected by an intake pipe pressure sensor installed in the intake pipe.
In a J-type fuel injection system, the intake pipe pressure is affected by the EGR rate. That is, if the fuel injection amount is determined based on the output value of the intake pipe pressure sensor as is, the amount of fuel will be excessive with respect to the amount of intake air actually introduced into the engine. Therefore,
In the DJ type fuel injection system, the fuel injection amount is determined by subtracting the EGR rate, so that the engine is supplied with the amount of fuel that matches the intake air amount, regardless of EGR control. There is. For example, JP-A-60-81449
See issue.

[Problem to be solved by the invention]

In the conventional technology, the engine is started from a cold state, and it is determined that the engine has warmed up (determined based on a predetermined value of water temperature). Supplied to the engine as gas. In this case, when the water temperature exceeds a predetermined value and the EGR starts operating, the fuel is corrected by recirculating the entire amount of exhaust gas in accordance with the recirculated exhaust gas determined by the load and rotational speed at that time.

However, the correction amount of the fuel injection amount by EGR is a correction value for obtaining the optimum fuel injection amount at the time of complete warm-up.

In other words, the factors that reduce the amount of fuel injection should be corrected, including the reduction in fresh air due to EGR during complete warm-up and the reduction in air density introduced into the combustion chamber due to the heating effect of high-temperature EGR gas. It is. However,
Immediately after the engine starts from a cold state and crosses a predetermined value at which exhaust gas recirculation begins, the air temperature increases little due to the recirculated exhaust gas and the air density does not increase significantly. On the other hand, since the fuel injection amount is corrected based on the assumption that the air density is low due to the high exhaust gas temperature, the result is an excessive correction, and the air-fuel ratio is overcorrected toward the lean side.

An object of the present invention is to prevent the air-fuel ratio from overleaning when the engine is started from a cold state and shifts to the EGR control range.

[Means to solve the problem]

The air-fuel ratio control device for an internal combustion engine equipped with an exhaust gas recirculation device according to the present invention includes: means A for detecting operating conditions including the cooling water temperature and intake pipe pressure of the internal combustion engine; and exhaust gas recirculation based on the cooling water temperature. Means B1 for determining the operating range in which exhaust gas recirculation is to be carried out; Exhaust gas recirculation operating means C1 for carrying out exhaust gas recirculation in the operating range; Fuel supply amount calculation means D for calculating the amount of fuel to be supplied to the internal combustion engine from intake pipe pressure; a fuel supply means E for supplying the amount of fuel to the internal combustion engine; Correction amount calculation means F1 A second correction amount calculation means G1 that further corrects the fuel amount calculated by the fuel supply amount calculation means under the operating conditions of exhaust gas recirculation so as to decrease in accordance with a rise in cooling water temperature. do.

[Operation]

Operating condition detection means A detects cooling water temperature, intake pipe pressure, and other operating conditions.

The EGR condition determining means B determines the EGR range based on the cooling water temperature and other operating conditions as necessary, and if it is determined to be the EGR range, the EGR operating means C achieves exhaust gas recirculation operation.

The fuel supply amount calculation means calculates the fuel supply amount, and the fuel supply means F supplies the calculated amount of fuel to the engine.

The EGR correction amount calculation means F corrects the fuel supply amount by decreasing it according to the EGR rate.

The temperature correction amount calculation means G performs EGR according to the increase in cooling water temperature.
The fuel supply amount is further corrected so that the reduction correction by .

〔Example〕

In FIG. 2, lO is the main body of the internal combustion engine, 12 is the intake pipe, 14 is the throttle valve, 16 is the fuel injector, and 18 is the intake pipe.
is an exhaust pipe, and 20 is a distributor. Intake pipe 1
An exhaust gas recirculation (EGR) passage 22 is provided connecting 2 and the exhaust pipe 18. 24 is an EGR valve device,
An EGR valve 28 provided in the R passage 22, a valve seat 30,
A diaphragm mechanism 32 connected to the EGR valve 28 is provided. An orifice 34 is disposed in the EGR passage 22 immediately upstream of the valve seat 30 in the exhaust gas flow direction, and the orifice 34
8 and the orifice 34 form a constant pressure chamber 36.

The diaphragm mechanism 32 has a diaphragm chamber 32-1, and the diaphragm chamber 32-1 is connected via a negative pressure conduit 40 to a negative pressure boat 42 (normally an EGR (referred to as a boat). As is well known, the pressure transforming valve 44 is
An operation is achieved in which the negative pressure introduced from the GR boat 42 into the diaphragm chamber 32-1 of the EGR valve device 24 is controlled so as to obtain a constant EGR rate. The variable pressure valve 44 has a diaphragm 44-1 and a spring 44-2, and an exhaust gas chamber 46 formed below the diaphragm 44 is communicated with the constant pressure chamber 36 via an exhaust gas pressure conduit 48. On the other hand, the atmospheric chamber 50 above the diaphragm 44-1 is open to the atmosphere.

This atmospheric chamber 50 controls the amount of air from the atmospheric chamber 50 to the negative pressure conduit 40 according to the exhaust gas pressure in the exhaust gas chamber 46,
As a result, the constant pressure chamber 36 is controlled to a constant pressure close to atmospheric pressure, so that the amount of recirculated exhaust gas is proportional to the pressure of the exhaust pipe 18, and the so-called EGR rate can be controlled to a constant value regardless of the load. .

To explain the mechanism of pressure control in the constant pressure chamber 36, when the exhaust gas pressure in the constant pressure chamber 36 exceeds a predetermined value, the diaphragm 44-1 closes the valve vibe 44-3 against the spring 44-2, and the conduit 40 The amount of atmospheric pressure bleed to the EGR boat 42 decreases, and the negative pressure in the diaphragm chamber 32 of the EGR valve actuator 32 connected to the EGR boat 42 becomes stronger. As a result, the diaphragm 32-2 is connected to the spring 32-2.
-3, the EGR valve 28 is lifted, and the amount of EGR gas passing through the EGR passage 22 increases. As a result, the pressure in the constant pressure chamber 36 becomes low (then,
The spring 44-2 pushes down the diaphragm 44-1, the pipe 44-3 is opened, air is bled from the atmospheric chamber 44-1, the pressure in the diaphragm chamber 32-1 approaches atmospheric pressure, and the spring 32-1 pushes down the EGR. The valve 28 is raised and the lift from the valve seat 30 is reduced (and the constant pressure chamber 3 is
6 pressure increases. By repeating such control, the pressure in the constant pressure chamber is controlled to be substantially constant.

A three-way electromagnetic switching valve 60 is provided in the negative pressure piping between the EGR valve 24 and the pressure transformation valve 44, and this electromagnetic valve 60 introduces atmospheric pressure into the EGR valve 24 when not energized. 32-3, and EGR operation is stopped. When the solenoid valve 60 is energized, it introduces the regulated negative pressure from the pressure transformation valve 44 to the EGR valve 28 , and the EGR valve 28
The valve opens and EGR operation is performed.

The control circuit 62 is configured as a microcomputer system, and forms a fuel injection signal to the combustion injector 16 as well as a drive signal for the three-way electromagnetic switching valve 60 for EGR control. Operating condition signals from various sensors are input to the control circuit 62 .

The intake pipe pressure sensor 64 generates a signal corresponding to the intake pipe pressure PM downstream of the throttle valve 14. Crank angle sensors 64 and 66 are provided in the distributor 20, and the first crank angle sensor 64 generates a pulse signal for the reference position every rotation of the distributor shaft 20-1, that is, every 720° rotation of the crankshaft. However, the second crank angle sensor 66 generates a pulse signal every 30° rotation of the crankshaft, so that the engine speed NE can be determined. The water temperature sensor 70 can detect the temperature TIIW of the cooling water contained in the cooling water jacket 72 of the engine body 10.

The operation of the control circuit 62 will be explained with reference to FIGS. 3 and 4. FIG. 3 shows an EGR control routine, which can be executed in the course of the main routine. In step 80, it is determined whether the temperature TIIW of the cooling water in the cooling water jacket 72 is greater than a predetermined value T0, and in step 82, the intake pipe pressure PM is set to a predetermined value P. In step 84, the engine speed NB is determined.
It is determined whether or not is larger than a predetermined value NEo. TIIW
>To, when the engine load is at or below a predetermined value (PM≦po), and when the engine speed is at or below a predetermined value (NE≦NEo), that is, when the cooling water temperature is at or above the predetermined value, the load is low. , the operating range in which EGR operation is performed is when the rotation speed is low.
1), in step 88, the 3-way solenoid switching valve (VSV) 6
0 is applied with a signal to turn it ON. Therefore, the switching valve 60 is switched as shown in black, and the negative pressure is changed to EGR.
The fuel is introduced into the valve 24 and EGR operation is performed.

When at least one of THW≦TO, PM >po or NE>NE holds true, that is, when the cooling water temperature is below a predetermined value, or when the cooling water temperature is above a predetermined value but the load or rotation is high. The flow goes to step 90, the flag FEGR is reset, and in step 92, the 3-way electromagnetic switching valve (VS
V) A signal is applied to 60 to turn it off. Therefore, the switching valve 60 is switched as shown in white,
Atmospheric pressure is introduced into the EGR valve 24, and EGR operation is stopped.

FIG. 4 shows a fuel injection routine, and this routine is executed every time fuel is injected into each cylinder. The fuel injection timing for each cylinder is determined, and this timing is cleared every time a 720° CA (one revolution of the engine) signal arrives from the first crank angle sensor 64, and a 30° CA signal from the second crank angle sensor 66 is cleared. This can be determined by the value of a counter that is incremented each time the double signal arrives. When it is detected from the value of the counter that the fuel injection timing for that cylinder has arrived, the routine shown in FIG. Here, the basic fuel injection time TP is the load (PM
) and the rotation speed NH, this is the valve opening time of the fuel injector 16 to obtain the stoichiometric air-fuel ratio. Map 1 is two-dimensional data of the basic fuel injection time TP for the combination of intake pipe pressure PM and rotational speed NE, and the basic fuel injection time TP for the intake pipe pressure PM and rotational speed NE detected at that time is interpolated. Calculated by In step 96, it is determined whether the flag FEGR.l is set, that is, whether the EGR operation is being executed.

While EGR operation is not being executed, FEGR is 0, and the process proceeds to step 98, where the EGR correction amount T during the basic fuel injection time is determined.
PEGR=0. That is, since EGR is not being performed, the fresh air amount remains the same as the pressure value detected by the intake pipe pressure sensor 63, and there is no need to perform correction, and the correction is stopped.

When EGR is being performed (FEGR・1), the process proceeds to step 100, and the EGR correction amount TP during the fuel injection time is determined.
EGR is calculated. During EGR operation, the value measured by the intake pipe pressure sensor 63 includes the EGR gas, and the amount of fresh air gas is reduced by that amount, so the fuel injection time is reduced by this amount. The effect of EGR is reflected in this way. The value of TPEGR is shown in map 2 as a value for intake pipe pressure PM and rotational speed NB.
is stored in In other words, the amount of EGR gas out of the total amount of gas introduced into the engine changes depending on the engine load and rotation speed, so the TPEGR value is calculated based on the amount of EGR gas at that time for the load and rotation speed. This correction is made to obtain a fuel injection time that corresponds purely to the amount of fresh air. In step 100, an EGR correction value TPEGR for the detected intake pipe pressure PM and rotational speed NB is calculated by interpolation.

In step 102, the water temperature correction coefficient KEGH is corrected using the map 3. This correction coefficient KEGR is calculated by crossing the temperature-based EGR operating point when starting a low-temperature engine (Yes at step 80 in Fig. 3 (for example, THW>60°C)), and when EGR is performed. , then the engine is completely warmed up (e.g. TOW>80°
This is a factor that prevents excessive correction of the decrease in fresh air due to EGR until reaching C). That is, the fuel injection time correction value TPEGR in step 100 is a factor for correcting the total decrease in fresh air due to EGR during complete warm-up. This correction factor actually accounts for not only the total reduction in fresh air caused by EGR, but also the total fresh air caused by the introduction of high-temperature exhaust gas into the intake pipe by BGH, which increases the intake air temperature and reduces the air density. It also compensates for the decrease. However, immediately after entering the EGR operation condition based on water temperature (ie, around 60° C. where TIIW is a threshold value), the water temperature is still considerably lower than the water temperature at the time of complete warm-up. Then, the intake air is not heated by the EGR gas until after it is completely warmed up, and the air density is high. On the other hand, the correction amount at step 100 is E
The determination is made on the assumption that the GR gas has completely warmed up and the air density has decreased. Therefore, E due to water temperature
Immediately after the GR operating condition is entered, the air temperature rise due to EGR gas is overestimated, and the fuel injection is unnecessarily shortened, assuming that the density has decreased even though it has not yet decreased. Therefore, fuel injection is not performed in an amount commensurate with the amount of fresh air, and the air-fuel ratio becomes over-lean. The KEGR in step 102 corrects this, and the EGR
The value is the EGR operation switching point depending on water temperature (T11W=TO)
It is set to have a value of 1.0 (no correction is performed) at a water temperature corresponding to complete warm-up (TIIW=T I ).

In step 104, the l1GR correction amount is finally
Calculated by R=TPEGRxKEGR.

The step final fuel injection time TAU is calculated by TAU=TPX(1-TPEGR) xk. Here, k represents various correction coefficients whose detailed explanation will be omitted because they are not related to this invention.

In step lO8, an injector activation signal is generated so that the injector 16 of the cylinder to which fuel is to be injected is opened for the valve opening time TAU calculated in step 108. This process itself is well known and is not an important part of this invention, so detailed explanation will be omitted.

〔effect〕

According to this invention, when a cold engine enters an EGR condition due to a cooling water temperature exceeding a threshold value, a reduction correction for the fuel injection amount by exhaust gas recirculation is performed so as to decrease in accordance with an increase in the cooling water temperature. ing. In other words, when the cooling water temperature is still low under IEGR conditions, the intake air temperature is lower and the air density is higher than when completely warmed up, and if the same amount of correction as when completely warmed up, the reduction correction will be excessive. , the air-fuel ratio becomes over-lean and drivability deteriorates.However, in this invention, the amount of fuel injection is corrected to be reduced by exhaust gas recirculation so that it decreases in accordance with the increase in the cooling water temperature. It is possible to optimize the fuel reduction correction during EGR operation, which is not high, so as to obtain an appropriate air-fuel ratio, prevent over-lean, and improve drivability.

[Brief explanation of drawings]

FIG. 1 is a block diaphragm diagram showing the functional configuration of the present invention. FIG. 2 is a schematic diagram showing the configuration of an embodiment of the present invention. 3 and 4 are flowcharts illustrating the operation of the control circuit of FIG. 2. DESCRIPTION OF SYMBOLS 10... Engine body, 12... Intake pipe, 14... Throttle valve, 16... Fuel injector, 18...
Exhaust pipe, 20...Distributor, 22...E
GR passage, 24... EGR device, 28... EGR valve, 30... Valve seat, 34... Constant pressure orifice, 36...
...Constant pressure chamber, 42...EGR boat, 44...Transformer valve, 60...3-way solenoid valve, 62...Control circuit, 63
...Intake pipe pressure sensor, 64.66...Crank angle sensor, 70...Cooling water temperature sensor Diagram

Claims (1)

[Claims] In an internal combustion engine equipped with an exhaust gas recirculation device, a means for detecting operating conditions including a cooling water temperature and an intake pipe pressure of the internal combustion engine, an operation in which exhaust gas recirculation is performed based on the cooling water temperature. Exhaust gas recirculation operating means for recirculating exhaust gas in the operating range; Fuel supply amount calculation means for calculating the amount of fuel to be supplied to the internal combustion engine from intake pipe pressure; A fuel supply means for supplying fuel to the internal combustion engine; a first correction amount calculation means for reducing the amount of fuel calculated by the fuel supply amount calculation means under the operating conditions of exhaust gas recirculation according to the amount of recirculated exhaust gas; Air-fuel ratio control for an internal combustion engine, comprising: second correction amount calculation means for further correcting the fuel amount calculated by the fuel supply amount calculation means under gas recirculation operating conditions so as to reduce the amount of fuel calculated by the fuel supply amount calculation means in accordance with a rise in cooling water temperature. Device.