JPH0689682B2 - Air-fuel ratio controller - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an internal combustion engine system including a recirculation control device that recirculates exhaust gas of an internal combustion engine to an intake pipe thereof, at a predetermined air-fuel ratio regardless of changes in atmospheric pressure. The present invention relates to an air-fuel ratio control device capable of operating an internal combustion engine.

[Prior Art] Conventionally, in an internal combustion engine system that performs exhaust gas recirculation control, uncombusted new air (hereinafter referred to as "fresh air") and burned exhaust gas are mixed in intake air of the internal combustion engine. The speed-density control system cannot directly detect the amount of fresh air, which makes air-fuel ratio control a difficult problem.

Therefore, as in the technique disclosed in Japanese Patent Laid-Open No. 48-27130, there is known a device for correcting the air-fuel ratio using the intake pipe pressure and the rotational speed of the internal combustion engine as variables.

However, in the above device, since only the intake pipe pressure is used as a variable for pressure information, if the atmospheric pressure of the environment in which the internal combustion engine is operated changes, the back pressure changes, so even if the same intake pipe pressure value is used, the actual engine The amount of air supplied to the engine and the amount of exhaust gas recirculation change. Therefore, in the speed density method, since the intake air amount is estimated only from the intake pipe pressure, changes in the intake air amount and the recirculation amount due to back pressure cannot be corrected and the air-fuel ratio shifts. .

[Object of the Invention] The present invention has been made to solve the above-mentioned problems.
It is an object of the present invention to provide an air-fuel ratio control device capable of operating an internal combustion engine with the exhaust gas recirculation control execution region not fluctuating even when a change occurs in the atmospheric pressure at which the internal combustion engine is operated, and moreover, with the air-fuel ratio always being a predetermined value. Has an aim.

[Structure of the Invention] As shown in the basic composition of FIG. 1, the structure of the present invention for attaining the above-mentioned object includes a rotational speed detection portion II A for detecting the rotational speed of the internal combustion engine I and an intake pipe pressure. An operating state detecting means II including an intake pipe pressure detecting portion II B for detecting, and the internal combustion engine I detected by the operating state detecting means II.
Of the basic fuel amount to be supplied to the internal combustion engine I on the basis of the rotational speed of the engine and the intake pipe pressure, and a recirculation for controlling the opening / closing of a recirculation passage for recirculating the exhaust gas of the internal combustion engine I to the intake pipe. In an air-fuel ratio control device including a road opening / closing means IV, a differential pressure detecting means V for detecting a differential pressure between the intake pipe pressure of the internal combustion engine I and the atmospheric pressure, the differential pressure detecting means V and the operating state. Based on the detection result of the detection means II, the reflux control means VI for controlling the reflux path opening / closing means IV into two states of open or closed, and regardless of the opening / closing of the reflux path opening / closing means IV by the reflux control means VI, Exhaust gas recirculation amount correction for the basic fuel amount calculated by the basic fuel amount calculation unit III based on the differential pressure detected by the differential pressure detection unit V and the rotation speed detected by the rotation speed detection unit II A. A first correction means VII for performing When the recirculation passage opening / closing means IV by the recirculation control means VI opens the recirculation passage, the basic fuel amount calculation means III
The gist is an air-fuel ratio control device characterized by comprising: a second correction means VIII for performing atmospheric pressure correction on the basic fuel amount obtained by

[Operation] The differential pressure detecting means detects the difference between the intake pipe pressure of the internal combustion engine and the atmospheric pressure, and based on the detection result of the differential pressure detecting means and the operating state detecting means, the reflux control means opens and closes the return path. The means is controlled in two states: open or closed. Then, when the return passage opening / closing means opens the return passage, the first correction means calculates the basic fuel amount based on the differential pressure detected by the differential pressure detection means and the rotation speed detected by the rotation speed detection unit. The exhaust gas recirculation amount is corrected with respect to the basic fuel amount obtained by the means. At the same time, the atmospheric pressure correction for the basic fuel amount obtained by the basic fuel amount calculation means is performed by the second correction means regardless of the opening / closing of the return passage opening / closing means by the return control means.

That is, for example, when the differential pressure is large, the intake air amount increases, the recirculated exhaust gas amount (exhaust gas recirculation amount) decreases (that is, the EGR rate decreases), and the fuel tends to run short,
On the other hand, when the pressure difference is small, the intake air amount is small and the fuel tends to be excessive. However, by correcting the basic fuel amount (by the first correction means) by the pressure difference and the rotational speed, Specifically, for example, when the differential pressure is large, the basic fuel amount is increased, while when the differential pressure is small, the basic fuel amount is decreased, whereby the preferable air-fuel ratio control can be realized.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

[Embodiment] FIG. 2 is a schematic diagram of an internal combustion engine equipped with an air-fuel ratio control apparatus according to one embodiment of the present invention and peripheral equipment thereof. An intake pipe 12 and an exhaust pipe 14 are attached to the internal combustion engine 10, and the operating states of these systems are always detected by various sensors, and the internal control of the internal combustion engine 10 is performed by the electronic control unit 50 using the detection results. It is possible to work in the best possible conditions.

The intake pipe 12 supplies fresh air and recirculated exhaust gas to the internal combustion engine 10. An air filter 16 for purifying air is provided at a fresh air intake port, and a fresh air intake amount is adjusted in the passage. The throttle valve 18 is provided with a throttle opening sensor 20 for outputting the opening information to the electronic control unit 50.

Further, the exhaust gas recirculation to the intake pipe 12 is performed by the EGR pipe 24 which connects the exhaust pipe 14 and the intake pipe 12 via the exhaust gas recirculation control device 22. The exhaust gas recirculation control device 22 is a diaphragm type control valve, and the diaphragm moves up and down the control valve against the cylindrical spring in accordance with the atmospheric pressure connected to the control pipe 22A to control the amount of exhaust gas flowing in the EGR pipe 24. Control. The control tube 22A is
It is connected to an intake pipe on the air cleaner 16 side slightly from the throttle valve 18 via an electromagnetic control valve 26 that executes an opening / closing operation in response to a signal from the electronic control unit 50. Therefore, when the electromagnetic control valve 26 is operated and almost atmospheric pressure is sent to the control pipe 22A, the diaphragm is pushed up by the force of the spring and EG
If the R pipe 24 is closed by a control valve and exhaust gas recirculation is not performed, the operation of the electromagnetic control valve 26 is stopped, and if the throttle valve 18 is open above a predetermined level, a negative pressure is introduced to the control pipe 22A and the diaphragm. Lifts the control valve against the spring EG
Exhaust gas recirculation is performed through the R pipe 24. That is, the electromagnetic control valve 26 is controlled in two states of open and closed.

As described above, the conditions of the fresh air and the exhaust gas introduced into the intake pipe 12 are detected by the intake pipe pressure sensor 30 which measures the negative pressure thereof and output to the electronic control unit 50. Reference numeral 32 is a fuel injection valve for injecting fuel into the air sucked into the internal combustion engine 10, 34 is a distributor, 36 is a rotation angle sensor for detecting the number of revolutions of the internal combustion engine 10, 38 is an internal combustion engine 10 The water temperature sensor for detecting the temperature of the cooling water is shown. 40 is an oxygen sensor that detects the amount of oxygen remaining in the exhaust pipe 14, and 42 is the air cleaner 16 and throttle valve.
It represents an atmospheric pressure sensor for detecting atmospheric pressure from a pipe opened in the intake pipe between 18 and.

FIG. 3 is a block diagram showing the information transmission of the system configured as described above centering on the electronic control unit 50. The electronic control unit 50 is composed of a microcomputer 52, an A / D converter 54, and two drive circuits 56 and 58 as shown in the figure. The various sensor outputs described above are once input to an A / D converter 54 including a buffer and a waveform shaping circuit, and appropriately transmitted to the microcomputer 52. A driving circuit for executing various arithmetic processes in the microcomputer 52 according to the information and operating the internal combustion engine 10 in an optimum state.
The operation signals are sent to 56 and 58 to execute the exhaust gas recirculation control and the fuel injection control.

FIG. 4 shows a flow chart of an air-fuel ratio control routine which is one of various control routines executed by the electronic control unit 50.

The control target of this routine is to determine the valve opening time Tp of the fuel injection valve 32, which serves as a reference for the amount of fuel supplied to the internal combustion engine 10. Therefore, this routine must be executed at a high frequency according to the operating state of the internal combustion engine 10, and based on the output of the rotation angle sensor 36, every predetermined number of revolutions of the internal combustion engine 10 or built in the microcomputer 52. It is executed every predetermined time using a timer.

The processing of this routine will be described in detail below for each step.

First, when the execution of the microcomputer 52 shifts to the processing of this routine, step 100 is executed, and the throttle opening sensor 20, the intake pipe pressure sensor 30, the rotation angle sensor 36,
Various sensor outputs of the water temperature sensor 38 and the atmospheric pressure sensor 42 are taken in to detect the current operating state of the internal combustion engine 10, such as the intake pipe pressure PM, the rotational speed NE of the internal combustion engine 10, and the like.

Step 110, from the above detection data, using PM, NE to convert the basic fuel injection amount that is the optimal fuel amount to be supplied to the internal combustion engine 10 to the basic fuel injection time Tp of the fuel injection valve 32, calculated To do. Either a method of actually calculating using a relational expression containing variables PM and NE for the calculation, or a method of preliminarily storing and preparing a two-dimensional map of the two variables PM and NE and then searching for this map. May be

It should be noted that this Tp is a fuel injection time determined under the assumption that all the intake air drawn into the internal combustion engine 10 is fresh air.

In step 120, it is determined whether or not all the conditions for executing the exhaust gas recirculation control are satisfied. The exhaust gas recirculation control condition is that the rotational speed NE of the internal combustion engine 10 is lower than a predetermined value NE ₀ , the detected value TW of the water temperature sensor 38 is higher than a predetermined temperature TW ₀ , and the throttle opening sensor output indicates that the throttle is open. In this state, it is detected that the engine is not idle, and the condition that the difference between the output PM of the intake pipe pressure sensor 30 and the output PO of the atmospheric pressure sensor 42, that is, the differential pressure P is larger than a predetermined value P ₀ is satisfied. In other words, that is, if it is determined that the exhaust gas recirculation control condition is satisfied only in the steady running state after warming up, the process proceeds to the next step 130, and if any one of the above conditions is not satisfied. Go to step 160.

First, the processing after step 130 will be described.

Steps 130 to 150 are for executing the exhaust gas recirculation control and correcting the fuel injection amount associated with the control.

First, in step 130, in order to execute exhaust gas recirculation, an output signal is output to the drive circuit 58 to stop the operation of the electromagnetic control valve 26,
The negative pressure in the intake pipe 12 is introduced into the control pipe 22A, whereby the control valve of the exhaust gas recirculation control device 22 rises and the exhaust gas recirculation is executed.

In the following step 140, the correction coefficient K1 for reducing the amount of fuel corresponding to the amount of exhaust gas recirculated to the intake pipe 12 of the internal combustion engine pipe 10 by the exhaust gas recirculation control executed in step 130 is calculated. . Here, the correction coefficient K1 means that the oxygen concentration in the intake air amount of the internal combustion engine 10 is decreased only in the exhaust gas amount. This is a coefficient that shortens the basic fuel injection time Tp because the condition that there is no longer holds. Therefore, it is determined from the relationship between the pressure difference between the exhaust pipe 14 and the intake pipe 12 where the exhaust gas recirculation is executed and the rotational speed of the internal combustion engine 10. That is, the ratio (EGR rate) of the recirculated exhaust gas amount (EGR amount) in the intake air amount generally changes depending on the atmospheric pressure, but in this embodiment, the pressure difference between the exhaust pipe 14 and the intake pipe 12 The first correction coefficient is obtained from the number and the first correction coefficient is used (in addition to the atmospheric pressure correction described later).
Since the basic fuel injection time Tp is corrected, it is possible to suitably cope with changes in the EGR rate. The pressure in the intake pipe 12 is controlled by the output PM of the intake pipe pressure sensor 36, and is equal to the pressure in the exhaust pipe 14 at the atmospheric pressure PO. Therefore, in this step, the differential pressure P prepared in advance in the microcomputer 52 is calculated by a relational expression including two variables of the difference P between PM and PO (= PM-PO) and the rotational speed NE.
The correction coefficient K1 is calculated using a two-dimensional map of the rotation speed NE and the rotation speed NE.

Specifically, when the pressure difference P is large, the intake air amount increases (the exhaust gas recirculation amount decreases as the EGR rate decreases), and the fuel tends to run short, so the basic fuel injection time
The correction coefficient K1 is set so as not to reduce Tp so much. On the other hand, when the difference P is small, the intake air amount becomes small and the fuel tends to become excessive, so the correction is made to greatly reduce the basic fuel injection time Tp. A map is set in advance so that the coefficient is set to K1.

In step 150, the calculation for actually shortening the basic fuel injection time Tp is performed using the correction coefficient K1. In this example
Calculate as K1 <1 and multiply Tp by the coefficient K1 to obtain Tp
Shows an example in which

Exhaust gas recirculation control is performed in steps 130 to 150, but step 160, which is processed when it is determined in step 120 that the condition for executing this exhaust gas recirculation control is not satisfied, is this exhaust gas recirculation control. Activate the system to cease control. That is, the exhaust gas recirculation control device 22
In order to close the valve, the drive circuit 58 is operated to operate the electromagnetic control valve 26 to guide the atmospheric pressure to the control pipe 22A. As a result, all of the intake air taken into the internal combustion engine 10 becomes fresh air, and the assumption in step 110 is established, so there is no need to correct the value of the basic fuel injection time Tp.

Step 170 is executed after the processing of step 150 or step 160 regardless of whether or not the exhaust gas recirculation control as described above is executed, and so-called atmospheric pressure correction of the fuel amount is performed. When the fuel is burned in the internal combustion engine 10, the intake air and the exhaust air into the fuel chamber of the internal combustion engine 10 show a close relationship with the atmospheric pressure, and for example, if the atmospheric pressure decreases, the exchange of gas in the combustion chamber will occur. Running smoothly will tend to run out of fuel. Therefore, the output PO of the atmospheric pressure sensor 42
Based on the above, the correction coefficient K2 is searched so as to shorten the fuel injection time Tp if the atmospheric pressure is high, and conversely extend the fuel injection time Tp if the atmospheric pressure is low. For this search, the same technique as the search for the correction coefficient K1 may be used. It may be based on a relational expression including PO or may be prepared in advance.
It is calculated using a one-dimensional map of PO.

The following step 180 is the correction coefficient K2 obtained in the previous step.
The fuel injection time Tp is actually corrected using
Move on to 190.

In step 190, the optimum fuel injection time Tp for the current internal combustion engine 10 calculated by the above various calculations and various corrections is set in the output counter. As a result, at the time of fuel injection executed by another routine, the amount of fuel corresponding to the data of Tp in the output counter is injected into the internal combustion engine 10, and the purpose can be achieved.

In the air-fuel ratio control device of the present embodiment as described above, the intake pipe pressure sensor 30 corresponds to the intake pipe pressure detection unit, the rotation angle sensor 36 corresponds to the rotation speed detection unit, the operating state together with other various sensors It constitutes a detection means. Further, the exhaust gas recirculation control device 22 causes the recirculation passage opening / closing means to execute the processing of step 140 in FIG. 4 for calculating the difference between the intake pipe pressure detected by the operating state detection means and the atmospheric pressure. The detection means executes the exhaust gas recirculation control in steps 130 and 160 and stops the exhaust gas recirculation control by the recirculation control means in step 14
In step 0 and step 150, the step of correcting the fuel injection time based on the correction coefficient K1 is performed by the first correction means.
The second correction means corresponds to the correction of the fuel injection time based on the correction coefficient K2 in 170 and step 180.

Compared with a conventional air-fuel ratio control device, such an air-fuel ratio control device, when controlling the electronic control valve 26 in the open / closed two states, has a correction coefficient K1 for performing exhaust gas recirculation amount correction and a correction for performing atmospheric pressure correction. Since the amount of fuel is corrected by using the coefficient K2, the excellent performance that the internal combustion engine 10 can always be operated under a desired air-fuel ratio is exhibited despite the simple configuration.

In this embodiment, in order to calculate the differential pressure P, two pressure sensors, the intake pipe pressure sensor 30 and the atmospheric pressure sensor 42, are used and the difference is used as the differential pressure.
Only one of the 30 is installed as a sensor,
The device may be simplified by taking in information when the intake pipe pressure at the moment the key is turned on is still equal to the atmospheric pressure, and regarding the data as atmospheric pressure.

[Effects of the Invention] As described above in detail with reference to the embodiments, the air-fuel ratio control device of the present invention controls the return flow passage opening / closing means to be in the open / closed state, and the first correction means causes differential pressure and rotation. The exhaust gas recirculation amount is corrected based on the number, and the atmospheric pressure is corrected by the second correction means.

Therefore, it is possible to prevent the overcorrection of the fuel amount due to the apparent change of the intake pipe pressure due to the change of the atmospheric pressure, and to always operate the internal combustion engine under the desired air-fuel ratio. It plays.

[Brief description of drawings]

FIG. 1 is a basic configuration diagram of the present invention, FIG. 2 is a structural schematic diagram of one embodiment, FIG. 3 is a block diagram of its control system, and FIG. 4 is its control flow chart. I ... Internal combustion engine II ... Operating state detection means II A ... Rotation speed detection section II B ... Intake pipe pressure detection section III ... Basic fuel amount calculation means IV ... Reflux passage opening / closing means V ... Differential pressure detection Means VI ...... Recirculation control means VII ...... First correction means VIII ...... Second correction means 10 ...... Internal combustion engine 12 ...... Intake pipe 30 ...... Intake pipe pressure sensor 42 ...... Atmospheric pressure sensor 50 ...... Electronic control device

Claims (1)

[Claims] 1. An operating state detecting unit including a rotational speed detecting unit for detecting the rotational speed of the internal combustion engine and an intake pipe pressure detecting unit for detecting an intake pipe pressure, and the internal combustion engine detected by the operating state detecting unit. A basic fuel amount calculating means for calculating a basic fuel amount to be supplied to the internal combustion engine based on the rotational speed and the intake pipe pressure; and a return passage opening / closing means for controlling opening / closing of a return passage for returning exhaust gas of the internal combustion engine to the intake pipe. In the air-fuel ratio control device including, a differential pressure detecting means for detecting a differential pressure between the intake pipe pressure and the atmospheric pressure of the internal combustion engine, and based on the detection result of the differential pressure detecting means and the operating state detecting means. A recirculation control means for controlling the recirculation path opening / closing means into two states of opening and closing; and a reluctance control means for detecting when the recirculation path opening / closing means opens the recirculation path by the differential pressure detecting means. Differential pressure and the rotation First correction means for correcting the exhaust gas recirculation amount with respect to the basic fuel amount calculated by the basic fuel amount calculation means based on the rotation speed detected by the detection unit; and the recirculation passage opening / closing means by the recirculation control means. An air-fuel ratio control device comprising: a second correction unit that performs atmospheric pressure correction on the basic fuel amount calculated by the basic fuel amount calculation unit regardless of whether the air-fuel ratio is opened or closed.