JPS62118042A - Air-fuel ratio control device for exhaust gas recirculating type internal combustion engine - Google Patents

Abstract

PURPOSE:To maintain an air-fuel ratio at a given value, by providing a correcting means which decreases an amount of fuel supplied for correction, based on a rotational speed detected by an operating condition detecting means and a value obtained through division of an intake air pressure by an atmospheric pressure. CONSTITUTION:An exhaust gas recirculating valve 22 is located in a reflux pipe 21. The fuel system of an engine 1 is formed with a fuel feed source 16 and a fuel injection valve 17. An intake air pressure sensor 31, measuring an intake air pressure, and a rotation angle sensor 36, outputting a rotation angle signal, are provided. An electronic control device 40 is provided with a correcting means, decreasing an amount of fuel supplied for correction, based on a rotation speed and a value obtained through division of an intake air pressure by an atmospheric pressure. This constitution enables maintenance of an air-fuel ratio at a given value, and improves exhaust characteristics.

Description

[Detailed Description of the Invention] R"shi February" 1 [Industrial Application Field] The present invention relates to an air-fuel ratio control device for an exhaust recirculation internal combustion engine, and specifically relates to an exhaust recirculation internal combustion engine that performs altitude compensation. The present invention relates to an air-fuel ratio control 211 device.

[Prior Art] In recent years, various control devices have been developed for the purpose of reducing harmful components contained in the exhaust gas of internal combustion engines. Among the above harmful components, especially for the purpose of suppressing NOx generation,
One type of engine is an exhaust gas recirculation type internal combustion engine that is configured to return a portion of the exhaust gas to the intake side. This is based on the fact that when a portion of the exhaust gas is returned to the intake side, the heat capacity of the air-fuel mixture increases and the maximum hot water temperature for combustion decreases. However, increasing the amount of exhaust gas recirculation makes combustion unstable and increases misfires, resulting in poor fuel efficiency and increased HC emissions. For this reason, combustion tends to become unstable in the low rotational speed range and low load range of the internal combustion engine, so the exhaust recirculation rate is reduced.
On the other hand, in a high rotational speed region and a high load region, control is performed to reduce the exhaust gas recirculation rate in order to improve output.

An air-fuel ratio control device intended for an exhaust gas recirculation internal combustion engine as described above needs to perform air-fuel ratio control that takes into account not only the volume or pressure of intake air but also the amount of recirculated exhaust gas. Air-fuel ratio control tI of such an exhaust recirculation internal combustion engine
For example, the amount of fuel supplied to the internal combustion engine determined in relation to the wake intake pressure of the throttle valve in the intake system of the internal combustion engine is determined by the flow of exhaust gas from the exhaust system of the internal combustion engine to the intake system. ``Electronic control device for internal combustion engines'' that properly controls reflux IQ IXI
-81449) etc. have been proposed.

[Problems to be Solved by the Invention] The conventional air-fuel ratio control device for an exhaust gas recirculation internal combustion engine has the following problems. In other words, (1) The fuel injection amount when exhaust gas recirculation is not performed is determined by making a predetermined correction to the basic fuel injection amount defined by a two-dimensional map based on intake air pressure and rotational speed; In this case, the fuel injection amount is determined by correcting the basic fuel injection layer using a correction coefficient defined by a two-dimensional map based on the throttle valve opening and rotational speed.

Therefore, a throttle position sensor is required that outputs a signal that is accurately proportional to the throttle valve opening.

Therefore, unless the detection accuracy of the throttle position sensor is at a high level and its reliability and durability are insufficient, there is a problem that the fuel injection amount cannot be accurately corrected when performing exhaust gas recirculation. The throttle position sensor that outputs an accurate proportional signal as described above has a complicated structure, and its use in harsh environments has a particularly negative effect on accuracy and life.

In addition, as a countermeasure to the above-mentioned problems, the correction coefficient when performing exhaust gas recirculation without using the above-mentioned throttle position sensor is also adjusted based on the intake air pressure and rotational speed.
It was also considered to define it as a two-dimensional map based on 1 degree. However, with this configuration, as shown in Figure 8, the exhaust recirculation fl (EGR rate) also changes as the atmospheric pressure in the environment in which the vehicle runs changes. Another problem is that it becomes difficult to accurately correct the fuel injection amount, and the air-fuel ratio fluctuates, resulting in a decrease in the output and exhaust characteristics of the internal combustion engine.

SUMMARY OF THE INVENTION An object of the present invention is to provide an air-fuel ratio control device for an exhaust gas recirculation internal combustion engine that simplifies the configuration of a detector and roughly performs altitude compensation of the air-fuel ratio.

3. [Means for solving the problems] In order to solve the above problems, the present invention adopts the configuration illustrated in FIG. 1. That is, the present invention, as illustrated in FIG. The amount of fuel supplied to engine M1 is a
11 fuel control means M3; and exhaust gas recirculation means M4 for circulating a part of the exhaust gas of the internal combustion engine M1 into the intake air of the internal combustion engine M1 when the operating state is within the normal range. In the exhaust gas recirculation type internal combustion n-leap air-fuel ratio It, II II device, when the exhaust gas is circulated by the exhaust gas recirculation means M4, the rotational speed detected by the operation state detection means M2 and a correction means M5 for reducing the amount of fuel supplied based on the value obtained by dividing the intake air pressure by the atmospheric pressure. This is a summary.

The operating state detection means M2 detects the operating state of the internal combustion engine M1. For example, it can be constructed from sensors that measure various quantities such as the pressure and temperature of the intake air of the internal combustion engine M1, the rotational speed, and the temperature of the cooling water of the internal combustion engine M1.

The fuel control means M3 is for adjusting the amount of fuel supplied. For example, the basic supply amount may be calculated based on the intake air pressure and rotational speed of the internal combustion engine M1.

Exhaust i! i! The flow means M4 is for recirculating exhaust gas. For example, a recirculation pipe that recirculates exhaust gas from the exhaust system of the internal combustion engine M1 to the intake system downstream of the throttle valve, and a recirculation pipe that is installed in the recirculation pipe and adjusts the amount of recirculated exhaust gas by changing its cross-sectional area. Control valve and its control 1l
When the intake air pressure and rotational speed of the internal combustion engine M1 fall within a predetermined range, the exhaust gas can be recirculated by the action of the WW controller. Here, the opening degree of the control valve may be determined depending on, for example, the difference between intake air pressure and atmospheric pressure.

The correction means M5 is for reducing the basic supply amount of fuel based on the rotational speed of the internal combustion ira+ and the value obtained by dividing the intake air pressure by the atmospheric pressure when exhaust gas recirculation is performed. .

The fuel control means M3. The exhaust gas recirculation means M4 and the correction means M5 can be realized, for example, as independent discrete logic circuits.

For example, ROM is mainly used for the well-known CPU.

It may be configured as a logic operation circuit together with a RAM and other peripheral circuit elements, and may implement each of the above means according to a predetermined processing procedure.

[Operation] As illustrated in FIG. 1, the air-fuel ratio control device for an exhaust gas recirculation internal combustion engine according to the present invention controls the fuel control stage M3 according to the operating state detected by the operating state detection means M2. The amount of fuel supplied is adjusted, and on the other hand, when the operating state is within a predetermined range, the exhaust gas recirculation means M4 recirculates the exhaust gas.
When the exhaust gas is recirculated, the correction means M5:
Based on the rotational speed of the internal combustion engine and the value obtained by dividing the intake air pressure by atmospheric pressure, the amount of fuel supplied is corrected to decrease.

Therefore, the air-fuel ratio control device for an exhaust gas recirculation internal combustion engine of the present invention works to control the air-fuel ratio to a predetermined value even when atmospheric pressure changes. The technical problems of the present invention are solved by each component of the present invention acting as described above.

[Example] Next, a preferred example of the present invention will be described in detail based on the drawings.

FIG. 2 shows the system configuration of an engine equipped with the air-fuel ratio control device for an exhaust gas recirculation internal combustion engine of the present invention.

As shown in FIG. 2, the engine 1 has a combustion chamber 5 formed by a cylinder 2, a piston 3, and a cylinder head 4.

The intake system of the engine 1 includes an intake pipe 8 that communicates with the combustion chamber 5 via an intake valve 7, a surge tank 10 that absorbs pulsation of intake air, and a throttle valve 11 that adjusts the amount of intake air. There is.

On the other hand, the exhaust system of the engine 1 is provided with an exhaust pipe 15 that communicates with the combustion chamber 5 via an exhaust valve 12 and guides exhaust gas.

The fuel system of the engine 1 includes a fuel supply source 16 consisting of a fuel tank and a fuel pump, and a fuel injection valve 17 disposed in a fuel supply pipe and an intake pipe 8.

The ignition system of the engine 1 includes an igniter (not shown) that outputs the high voltage necessary for ignition, and a crankshaft (also not shown) that distributes the high voltage generated by the igniter to the spark plugs (not shown) of each cylinder. It has a distributor 19 for supplying.

The engine 1 also has a recirculation pipe 21 that recirculates a portion of the exhaust gas from the exhaust pipe 15 to the intake pipe 8, and the recirculation pipe 21 has an exhaust gas recirculation valve (
22 (hereinafter simply referred to as EGRV) is installed. EG
The RV 22 has a diaphragm chamber 22a, and the diaphragm chamber 22a is connected to the intake pipe 8 upstream of the throttle valve 11 via a negative pressure switching valve 24. When the negative pressure switching valve 24 is excited and becomes in communication, the upstream negative pressure of the throttle valve 11 of the intake pipe 8 is transferred to the diaphragm chamber 22.
a, the EGRV 22 opens at an opening degree corresponding to the pressure difference between the negative pressure and atmospheric pressure.

Therefore, a predetermined amount of exhaust air determined by the opening degree is released into the exhaust pipe.
5 to the intake pipe 8. On the other hand, when the excitation of the negative pressure switching valve 24 is interrupted and the valve enters the cutoff state, the negative pressure in the intake pipe 8 is no longer introduced, so the EGRV 22 is closed. Therefore, the circulation of exhaust gas is interrupted.

The engine 1 includes, as detectors, an intake pressure sensor 31 that is installed in the intake pipe 8 and measures the intake air pressure, an intake air temperature sensor 32 that is installed in the air cleaner that measures the intake air temperature, and a throttle valve 11 that is fully open. a throttle position sensor 33 that detects the state or fully open state, and a water temperature sensor 34 that is installed in the cooling system and detects the temperature of the cooling water.
is provided.

Also, inside the distributor 19, every 1/24 rotation of the camshaft of the distributor 19,
That is, a rotation angle sensor 36 is provided which also serves as a rotation speed sensor and outputs a rotation angle signal at every integer multiple of the crank angle 00 to 30'.

The signals detected by each of the above sensors are electronically controlled bag W1 (
(hereinafter simply referred to as ECU) 40, and the ECU 40
controls the engine 1 by driving the fuel injection valve 17 and negative pressure switching valve 24 described above based on each signal.

Next, the configuration of the ECU 400 will be explained based on FIG. 3. ECU3O inputs and calculates each signal detected by each sensor mentioned above according to a control program, and also performs processing for controlling each device mentioned above.
PU40a, 6ROM40b in which the above control program and initial data are stored in advance, input data to ECU4O, RAM40c in which 8 types of signals and data necessary for arithmetic control are temporarily stored, key switch for engine 1. A backup RAM 40 backed up by a battery so that it can store and retain various data necessary for controlling the engine 1 from now on even if it is turned off by the driver.
It is configured as a logic operation circuit centering around d, etc., and is connected to an input/output port 40f and an input port 40q via a common bus 40e.
, is connected to the output port 40h to perform input/output with external equipment.

The ECIJ40 has a buffer r for the output signals from the intake pressure sensor 31, water temperature sensor 34, and intake temperature sensor 32, which have already been described.
40i, 40j, and 40k, a multiplexer 40m that selectively outputs the output signals of the above-mentioned sensors to the CPU 30a, and an A/D converter 40n that converts analog signals into digital signals. Each of these signals is input to the CPU 40a via the input/output port 40f.

The ECU 4O also includes a waveform shaping circuit 40p that shapes the waveform of the output signal of the rotation angle sensor 36 described above. Signals from the throttle position sensor 33 and rotation angle sensor 36 are input to the CPU 40a via an input boat 40Q.

Further, the ECU 4O includes a drive circuit 40 (1,
40r, and the CPU 30a outputs a control signal to both drive circuits 40 (1, 4Or) through an output port 40h.The CPU 30a also outputs a control signal to the output port 40h at a predetermined time preset by the CPU 40a. A down counter that outputs an interrupt signal is provided.

Note that the ECU 4O includes a CPU 30a and a ROM 40b.

It also includes a clock circuit 40s that sends a clock signal serving as control timing to the RAM 40c and the like at predetermined intervals.

Next, the fuel injection amount control process executed by E140 in one embodiment of the present invention will be explained based on the flowchart shown in FIG. This fuel injection amount control process is repeatedly executed at predetermined time intervals as the engine 1 operates.

First, in step 100, a process of detecting the intake air pressure Pa from the intake pressure sensor 31 is performed.

In the following step 110, a process of detecting a rotation angle signal from the rotation angle sensor 36 is performed. Next step 120
Then, processing is performed to detect the cooling water temperature THW from the water temperature sensor 34 and the intake air temperature THA from the intake air temperature sensor 32. In the following step 130, the rotational speed aNe of the engine 1 is calculated by taking the reciprocal of the interval between the rotational angle signals detected in step 110.

Next, the process proceeds to step 140, in which a process is performed to calculate the basic fuel injection iiτ from the rotational speed Ne calculated in step 130 and the intake air pressure Pa detected in step 100. Here, the basic injection time τ is defined as a two-dimensional map of the rotational speed Ne and the intake air pressure Pa. The ECIJ 40 stores in advance a basic injection time map as described above in the ROM 40b, and calculates the basic injection time τ based on the map. In the subsequent step 150, the corrected basic injection time τ1 is determined using the cooling water temperature correction coefficient KW and the intake air temperature correction coefficient Ka, which are determined based on the cooling water temperature HW detected in the step 120 and the intake air temperature THA. is calculated as shown in the following equation (1).

τ1==Iτxl(wxl(a −(1
) Next, the process proceeds to step 160, where it is determined whether the cooling water temperature THW detected in step 120 exceeds the Ml temperature To. That is, it is determined whether or not the engine 1 has finished warming up. If it is determined that engine 1 is still insufficiently warmed up, step 2
Proceed to 60. Here, processing is performed in which the negative pressure switching valve 24 is not excited, and therefore the EGRV 22 is placed in a cutoff state.

This is to stabilize combustion by preventing exhaust gas from being recirculated since the engine 1 has not been sufficiently warmed up. Next, the process proceeds to step 250, where the corrected basic injection time τ1 calculated in step 150 is set in the down counter of the output boat 40h as the optimum injection time, and then the process is exited to [NEXTJ and ends this process]. .

On the other hand, in step 160, if the engine 1 has finished warming up, the cooling water temperature THW is set to the reference temperature TO.
, so the process proceeds to step 170. Step 170
Then, the rotational speed Ne calculated in step 130 above is the reference speed NOC of 3000 [r, l), m,
] ) A determination is made as to whether or not it is less than . That is, it is determined whether the rotation speed Ne of the engine 1 is in the high speed rotation range. If it is determined that the rotational speed Ne is equal to or higher than the reference speed No, step 260 described above is performed.
Then, in order to ensure the output of the engine 1, exhaust gas is not recirculated, and after passing through step 250 described above, the rNEXT
It can be handled as J and this process ends.

On the other hand, if it is determined that the rotational speed Ne is less than the reference speed N0, the process proceeds to step 180.

In step 180, it is determined whether the exhaust gas recirculation conditions are satisfied. The exhaust gas recirculation condition is the intake air pressure Pa
This is true when both the rotational speed Ne and the rotational speed Ne are included in a predetermined exhaust gas recirculation permissible region. The ECU 40 stores in advance a map of the exhaust gas recirculation permissible region in a predetermined area of the ROM 40b, and determines whether the exhaust gas recirculation condition is satisfied based on the map. If it is determined that the exhaust gas recirculation conditions are not satisfied, step 260.
After 250, the process is returned to rNEXTJ and the process ends.

On the other hand, if it is determined that the exhaust gas recirculation conditions are satisfied,
Proceed to step 190. In step 190, in order to recirculate the exhaust gas, the negative pressure switching valve 24 is energized and the EGRV
22 is opened to a predetermined opening degree. In the following step 200, it is determined whether a delay time Td has elapsed since the excitation of the negative pressure switching valve 24 was started in the step 190. Here, the delay time Td is a time determined corresponding to the operating time of the negative pressure switching valve 24 and the EGRV 22. If it is determined that the delay time Td has not yet elapsed, it is assumed that steady exhaust gas recirculation has not started, and the process proceeds to step 250 described above, where 1 is optimally calculated using the corrected basic injection time calculated in step 150. After the process of setting the injection time is performed, it can be handled as rNEXTJ and the process ends.

On the other hand, if it is determined that the delay time Td has elapsed, it is assumed that steady exhaust gas recirculation has started, and the process proceeds to step 210. In step 210, the intake pressure sensor 31
A process is performed to detect atmospheric pressure Pc from . here,
The atmospheric pressure pc is determined as the output value of the intake pressure sensor 31 when the throttle position sensor 33 detects that the throttle valve 11 is fully open. Next step 2
2o, the intake air pressure Pa detected in step 100, the atmospheric pressure Pc detected in step 210, and the predetermined and stored reference atmospheric pressure Pb (760 [m
mHO] ), a process is performed to calculate the pressure correction value Pd as shown in the following equation (2).

P d - P a x P b / P c
-(2>Next, the process proceeds to step 230, and the correction coefficient Fegr is calculated based on the rotation speed Ne calculated in step 130 and the pressure correction value Pd calculated in step 220.
Processing to calculate is performed. As shown in FIG. 5, the correction coefficient Fea is defined as a two-dimensional map based on the rotational speed Ne and the pressure correction value Pd.ECU 40
has previously stored in the ROM 40b a map as shown in FIG. 5, and based on the map, the correction coefficient Feg
Calculate r.

In the following step 240, the injection time τ0 is set to the above step 1.
Corrected basic injection time τ1 calculated in step 50 and step 2 above
Using the correction coefficient Fegr calculated in step 30, calculation processing is performed as shown in the following equation (3).

τo−r1 xFegr −(3
) Next, the process proceeds to step 250, in which the injection time τ0 calculated in step 240 is set in the down counter described above as the optimum injection time.
This process ends after being handled as XTJ. Here, the above correction coefficient 1''egr is the pressure correction value Pd, as shown in FIG.
It changes depending on.

Therefore, while exhaust gas recirculation is being carried out steadily, the optimum injection time is corrected to be shorter than the corrected basic injection time τ1 in accordance with the pressure correction value Pd. From then on,
This process is repeatedly executed at predetermined time intervals. Note that the fuel injection valve 17 is opened and fuel is supplied to the engine 1 by a fuel injection process (not shown) over the optimum injection time set in the down counter in step 250 of this process.

In this embodiment, the engine 1 corresponds to the internal combustion engine M1, and the intake pressure sensor 31, the rotation angle sensor 36, and the ECU 4
E
Processes executed by the CU 40 and the ECLJ 40 (
Step 140°150.250) is the fuel control means M3
They each function as In addition, the reflux pipe 21 and EGRV2
2, the negative pressure switching valve 24, the ECU 40, and the ECtJ40
The process executed by (steps 180, 190゜26
0) is the exhaust gas recirculation means M4, and the ECtJ40 and the E
Processing executed by CtJ40 (step 210.2
20, 230, and 240) respectively function as correction means M5.

As explained above, in this embodiment, while steady exhaust gas recirculation is being performed in the engine 1, the pressure correction value P is calculated by dividing the product of the intake air pressure Pa and the reference atmospheric pressure pb by the atmospheric pressure Pc.
The corrected basic injection time τ1 is reduced by a correction coefficient Fegr determined by d and the rotational speed Ne to calculate the optimum injection time. Therefore, by using the intake pressure sensor 31 and the rotation angle sensor 36, it is possible to calculate an appropriate fuel injection time depending on the size of the recirculated exhaust gas.

In addition, even if the atmospheric pressure pc changes depending on the driving environment,
Since the correction coefficient Fegr'4ri is calculated based on the pressure correction value Pd, altitude compensation is possible.

As a result of the above effects, the air-fuel ratio can always be controlled to a predetermined value, so that the content of harmful components in the exhaust gas can be reduced and drivability can also be maintained in good condition.

Furthermore, there is no need for a throttle position sensor that generates an output proportional to the opening of the throttle valve, and only a throttle position sensor with a simple structure that detects only the fully open and fully open states of the throttle valve can be used, making the device reliable. Improves durability and durability.

Note that in order to detect the atmospheric pressure Pc, a dedicated atmospheric pressure sensor may be used in addition to the intake pressure sensor.

Furthermore, the atmospheric pressure Pc can be detected on the upstream side of the throttle valve during fuel cut such as during deceleration.

In this embodiment, when performing exhaust gas recirculation, the corrected basic injection amount τ1 is corrected by a correction coefficient 1:egr. However, when performing exhaust gas recirculation, for example, the optimum injection time is calculated based on a two-dimensional map that defines the injection time during exhaust gas recirculation based on the pressure correction value Pd and rotational speed Ne as shown in FIG. Even if configured to do so, the effects of the present invention can still be achieved.

Although the embodiments of the present invention have been described above, the present invention is not limited to these embodiments, and it goes without saying that it can be implemented in various forms without departing from the gist of the present invention. .

11.31 As described in detail above, in the air-fuel ratio control device for an exhaust gas recirculation internal combustion engine of the present invention, the operating state detection means detects the operating state of the internal combustion engine, and the fuel control means controls the fuel according to the operating state. On the other hand, when the operating condition is within a predetermined range, the exhaust gas recirculation means recirculates the exhaust gas; however, if the exhaust gas recirculation is being performed, the correction means controls the internal combustion engine. The fuel supply amount is corrected to decrease based on the rotational speed of the engine and the value obtained by dividing the intake air pressure by the atmospheric pressure. Therefore, even if atmospheric pressure changes when exhaust gas recirculation is performed, the air-fuel ratio can be maintained at a predetermined value simply by detecting the intake air pressure and rotational speed. play.

Furthermore, along with the above effects, the exhaust characteristics are improved.

Furthermore, since the air-fuel ratio can be controlled simply by detecting the intake air pressure and rotational speed of the internal combustion engine, there is no need for a complicated detector configuration, improving the reliability of the device and reducing the number of parts, reducing costs. can be reduced.

[Brief explanation of drawings]

Fig. 1 is a basic configuration diagram illustrating the contents of the present invention, Fig. 2 is a system configuration diagram of an embodiment of the present invention, and Fig. 3 is a block diagram for explaining the configuration of the electronic control unit (ECU). 9 and 4 are flowcharts of processing executed by the ECU in one embodiment of the present invention, FIG. 5 is a graph showing a map defining the relationship between pressure correction value, rotational speed, and correction coefficient, and FIG. Graph showing the relationship between pressure correction value and correction coefficient, Figure 7 is a graph showing the relationship between pressure correction value, rotational speed and injection time, and Figure 8 is the relationship between intake air pressure, EGR rate and atmospheric pressure. This is a graph showing. Ml... Internal combustion engine M2... Operating state detection means M3... Fuel control means M4... Exhaust recirculation means M5... Correction means 1... Engine 17... Fuel injection valve 21... Reflux pipe 22...Exhaust gas recirculation valve (EGRV) 24...Negative pressure switching valve 31...Intake pressure sensor 36...Rotation angle sensor 40...Electronic control unit (ECU') Fig. 3 Figure 5 Rotational speed Ne (r, p, m,)

Claims (1)

[Scope of Claims] 1. Operating state detection means for detecting the operating state including intake air pressure and rotational speed of the internal combustion engine, and adjusting the amount of fuel supplied to the internal combustion engine according to the detected operating state. an exhaust gas recirculation type internal combustion engine, comprising: a fuel control means for recirculating a part of the exhaust gas from the internal combustion engine to the intake air of the internal combustion engine when the operating condition is within a predetermined range; In the air-fuel ratio control device, when the exhaust gas is circulated by the exhaust gas recirculation means, the rotational speed detected by the operating state detection means and the value obtained by dividing the intake air pressure by the atmospheric pressure. An air-fuel ratio control device for an exhaust gas recirculation internal combustion engine, comprising a correction means for reducing the amount of fuel supplied based on the above.