JPH10205395A - Controller for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a controller for an internal combustion engine, able to use an exhaust gas component sensor having the low request of heat resistance, and to be accurately operated even if it is used for a diesel engine. SOLUTION: Exhaust gas to be allowed to flow in an exhaust pipe 6 of an engine 1 is partially recirculated from a recirculation gas introducing port 8 into an intake pipe 4 through an EGR pipe 1, and the amount is controlled by an EGR valve 9. An oxygen sensor 10 for detecting the oxygen concentration of gas in the EGR pipe 7 is arranged between the EGR valve 9 of the EGR pipe 7 and the intake pipe 4. An ECU calculates the correction factor for correcting the output of the oxygen sensor 10 detecting air after the specified time passes after the EGR valve 9 is closed so that the output may be the output at the time the regular article detects the air.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control device for an internal combustion engine, and more particularly to a control device for an internal combustion engine that uses an output of an exhaust gas component sensor to control a control amount of the engine.

[0002]

2. Description of the Related Art In an internal combustion engine provided with an EGR (exhaust gas recirculation device), an EGR control valve is interposed in the middle of the EGR passage, which connects the exhaust pipe and the intake pipe, on the upstream side of the EGR control valve (exhaust pipe Side), an exhaust component sensor is disposed, and the control amount of the engine is determined based on the output value of the exhaust component sensor.
Reference).

[0003]

However, when an exhaust gas component sensor is disposed upstream (exhaust pipe side) of the EGR control valve as in the device disclosed in the above publication, the exhaust gas component sensor becomes
It is exposed to exhaust gas regardless of the opening and closing of the control valve. here,
Since the temperature of the exhaust gas becomes extremely high, high heat resistance is required for the exhaust gas component sensor, and as a result, the production cost of the sensor is high due to the use of expensive heat-resistant materials or the adoption of a heat shielding structure. Problem. In addition, when disposed in the exhaust pipe of a diesel engine, soot adheres around the sensor, so that the sensor cannot accurately detect the concentration of the component gas in the exhaust gas. Cannot be correctly reflected in the control amount.

SUMMARY OF THE INVENTION In view of the above problems, it is an object of the present invention to provide a control device for an internal combustion engine which requires a low heat resistance for an exhaust gas component sensor and operates accurately even when applied to a diesel engine.

[0005]

According to the first aspect of the present invention, there is provided an EGR passage which is provided in communication between an exhaust passage and an intake passage, and recirculates exhaust gas from the exhaust passage to the intake passage.
An EGR control valve disposed in the middle of the EGR passage to control the recirculation amount of exhaust gas; and an EGR control valve disposed in the EGR passage between the EGR control valve and the intake passage to reduce a concentration of a specific component in the exhaust gas. An exhaust gas component sensor to be detected and a control device for an internal combustion engine are provided, wherein the output of the exhaust gas component sensor is used for determining a control amount of the internal combustion engine. In the control device for an internal combustion engine configured as described above, the concentration of a certain component in the exhaust gas can be accurately reflected in the determination of the control amount of the internal combustion engine.

According to a second aspect of the present invention, in addition to the control device of the first aspect, an operating state detecting means for detecting an operating state of the engine is provided, and the EG is provided when the engine is running at a high speed or a high load.
There is provided a control device for an internal combustion engine in which an R control valve adjusts a valve opening amount so as to reduce an exhaust gas recirculation amount. In the control device for an internal combustion engine configured as described above, the EGR control valve controls the exhaust gas recirculation amount to be small when the operating state detecting means detects that the engine is rotating at a high speed or under a high load.

According to a third aspect of the present invention, in the control device according to the first or second aspect, the output of the oxygen sensor is provided when the exhaust gas component sensor is an oxygen sensor and the EGR control valve is closed. A control device for an internal combustion engine is provided which corrects the output of the oxygen sensor by using the above. In the control device for an internal combustion engine configured as described above, the EGR
The output of the oxygen sensor is corrected using the output of the oxygen sensor when the control valve is closed.

[0008]

Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a diagram schematically showing the configuration of the present invention. The engine 1 is a diesel engine having an exhaust supercharger 2. The engine 1 is provided with an intake pipe 4 for guiding intake air to an intake valve 3 and an exhaust pipe 6 for guiding exhaust discharged from an exhaust valve 5 to the outside.
A part of the exhaust gas passing through the EGR pipe 7 is recirculated from the recirculation gas inlet 8 into the intake pipe 4 through the EGR pipe 7, and the amount thereof is adjusted by the EGR valve 9.

An oxygen sensor 10 for detecting the oxygen concentration of the gas in the EGR pipe 7 is provided between the EGR valve 9 and the intake pipe 4 of the EGR pipe 7. Further, a pressure sensor 11 that detects the pressure of intake air near the oxygen sensor 10 is provided near the oxygen sensor 10. Reference numeral 12 denotes a fuel injection pump. The fuel injection pump 12 pressurizes the fuel sucked up from a fuel tank (not shown) and sends it to a fuel injection valve 13 under pressure. The fuel injection valve 13 sends the fuel sent under pressure to an electronic control unit. According to a signal from an ECU (hereinafter referred to as an ECU) 20, a predetermined amount of fuel is injected into the sub chamber 14 at a predetermined timing to cause self-ignition.

Reference numeral 20 denotes an electronic control unit (hereinafter referred to as an ECU), which is an input interface 2 connected to each other.
1, a digital computer having a CPU 22, a RAM 23, a ROM 24, and an output interface 25.
The ECU 20 calculates the basic injection amount TAUB based on the signals of the rotation speed sensor 31 and the accelerator opening sensor 32, and further uses the output as a value obtained by correcting the value with the output of the oxygen sensor 10 and the output of the pressure sensor 11. Output interface 2
5 to the fuel injection valve 13. In addition, the rotation speed sensor 3
1. The supply of the negative pressure stored in the vacuum pump 16 to the diaphragm chamber of the EGR valve 9 is controlled based on the signal of the accelerator opening sensor 32 and the like to control the amount of exhaust gas to be recirculated. In addition, the ECU 20 performs various controls and includes various sensors for this purpose, but those which are not relevant to the present invention are omitted.

FIG. 2 shows the element 10 of the oxygen sensor 10.
The element 100 has a solid electrolyte 101 made of zirconia, an anode 102 made of platinum formed on both surfaces thereof, a cathode 103, and a porous diffusion-controlling layer 104 formed outside the cathode. And a heater 105 for heating the element to a constant temperature, for example, about 700 ° C. in order to keep the element in an active state. A predetermined voltage is applied between the anode 102 and the cathode 103 to try to flow oxygen ions from the anode to the cathode, but the amount of oxygen molecules limited by the diffusion-controlling layer 104 depends on the oxygen concentration in the intake pipe. Since it changes, the oxygen concentration in the EGR pipe can be detected by measuring the ion current (limit current) flowing between the two electrodes. Due to such a structure, in a diesel engine, if it is arranged in a place that is constantly exposed to exhaust gas as in the prior art, the surface of the diffusion-controlling layer is covered by soot in the exhaust gas and the exhaust gas It is not possible to accurately detect the oxygen concentration in it.

FIG. 3 shows the output oxygen concentration with respect to the actual oxygen concentration for various oxygen sensors.
The output differs depending on the individual oxygen sensor, but this is due to variations at the time of manufacture and changes with time after the start of use. In FIG. 3, the dotted line indicates ideal output characteristics of a regular product having the same actual oxygen concentration and output oxygen concentration. For example, when the gas to be detected is air having an oxygen concentration of 21%. Has an output oxygen concentration of 21%.

On the other hand, in the case of the oxygen sensor shown by the solid line A in FIG. 3, the output oxygen concentration is larger than the actual oxygen concentration. For example, when the gas to be detected is air, the output oxygen concentration Is higher than 21%, and the solid line B
In the case of the oxygen sensor indicated by, the output oxygen concentration is lower than the actual oxygen concentration. For example, when the gas to be detected is air, the output oxygen concentration is lower than 21%. Therefore, in the case of the oxygen sensor shown by the solid line A and the oxygen sensor shown by the solid line B, it is necessary to correct the output so as to match the actual oxygen concentration. Therefore, in this embodiment, when the gas to be detected is air, the output value of the oxygen sensor is corrected so that the output oxygen concentration becomes 21%.

FIG. 4 is a flowchart of a control routine in this embodiment for correcting the output of the oxygen sensor based on the above concept. This routine is EGR
The automatic start is performed when the valve 9 is closed. At the same time as the start, the necessary parameters are read in step 41, and the timer for counting the elapsed time after the EGR valve 9 is closed is started. I do.

In step 42, it is determined whether or not the elapsed time Tegr counted by the timer started in step 41 after closing the EGR valve 9 has exceeded a predetermined value Tx. In this step, even if the EGR valve 9 is closed, the portion where the oxygen sensor 10 is installed has the same oxygen concentration as that of the intake air until all the exhaust gas flowing before the valve is closed is introduced into the intake pipe 4. Rather, it is intended to prevent erroneous correction from being made if correction is performed using the oxygen concentration obtained in such a case. Therefore, experimentally, the elapsed time T at which the oxygen concentration always reaches the same as the intake air
x, the elapsed time Te after the EGR valve 9 is closed is determined.
When gr exceeds Tx, it is determined that the portion where the oxygen sensor 10 is installed has the same oxygen concentration as the intake air,
Only in that case, the following correction is performed.

In step 42, YES, that is, EGR
If a predetermined time has elapsed since the valve 9 was closed, the routine proceeds to step 43, where the oxygen concentration Oa of the air indicated by the current oxygen sensor and the oxygen concentration O
The ratio α when n is detected is obtained, and this value is stored as a correction factor in a predetermined location in the RAM 23. The process proceeds to step 44, where the timer is cleared and the process is terminated.

As described above, in this embodiment, E
Since the correction rate α of the oxygen concentration output is calculated every time the GR valve 9 is closed, it is possible to correct a variation due to a variation in the manufacture of the oxygen sensor and a change with the passage of time. In the above, in order to avoid an erroneous correction, the condition for calculating the correction rate is that the elapsed time Tegr after the closing of the EGR valve 9 exceeds a predetermined value Tx. The correction may be avoided, for example, when the elapsed time from the change in the intake pressure PA detected by the pressure sensor 11 exceeds a predetermined value.

On the other hand, the effective fuel injection amount TAUA injected by the fuel injection valve 13 is a basic fuel injection amount TAU calculated based on signals from the rotation speed sensor 31 and the accelerator opening sensor 32.
B is determined by correcting it as shown in the following equation (1). TAUA = TAUB × (a × PA) × (b × Oa) × C (1) where PA is an intake pressure detected by the pressure sensor 11,
a is a conversion coefficient for obtaining a correction coefficient based on the intake pressure based on the intake pressure PA. Oa is the concentration of the oxygen sensor, and b is a conversion coefficient for obtaining a correction coefficient based on the oxygen concentration based on the concentration Oa of the oxygen sensor. C is another correction coefficient.

Therefore, in the present embodiment, the output oxygen concentration Oa of (b × Oa) in the above equation (1) is
The effective fuel injection amount TAUA is determined by multiplying the correction rate α determined as described above, as in the following equation (2). TAUA = TAUB × (a × PA) × (b × α × Oa) × C (2) The ECU 20 calculates the effective fuel injection amount TAUA as described above, and this effective fuel injection amount TAUA is calculated at a predetermined timing. A signal for instructing the fuel injection valve 13 to open is transmitted from the injection valve 13 to the sub-chamber of each cylinder of the engine 1, and the fuel injection valve 13 opens according to the received valve opening instruction signal. And inject fuel.

[0020]

According to the present invention, since the exhaust gas component sensor that contributes to the determination of the control amount of the internal combustion engine is disposed downstream of the EGR control valve, the exhaust gas component sensor is constantly exposed to high-temperature exhaust gas. And the degree of heat resistance required for the exhaust gas component sensor is low. Therefore, the material and / or
An inexpensive exhaust component sensor can be used in terms of the heat shielding structure. In particular, according to the second aspect, the exhaust component sensor is not exposed to the exhaust gas at the time of high rotation or high load where the exhaust gas is particularly high temperature, so that the durability of the exhaust component sensor is improved. Conversely, since the requirement for heat resistance is further reduced, an inexpensive exhaust component sensor can be used in terms of the material and the heat shielding structure. Especially,
According to the third aspect, the control amount of the engine is corrected based on the output of the exhaust gas component sensor which is the oxygen concentration sensor when the EGR control valve is closed. Variations and deviations due to aging can be absorbed, and accurate control can always be performed.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of the present invention.

FIG. 2 is a diagram showing a structure of an element portion of the oxygen sensor.

FIG. 3 is a diagram showing variations in the output of an oxygen sensor.

FIG. 4 is a flowchart of a calculation routine for correcting a correction term of a fuel injection amount based on an oxygen concentration of exhaust gas.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Engine 4 ... Intake pipe 6 ... Exhaust pipe 7 ... EGR pipe 9 ... EGR valve 10 ... Oxygen sensor 11 ... Pressure sensor 20 ... ECU31 ... Accelerator opening sensor 32 ... Rotation speed sensor 100 ... Sensor element 101 ... Solid electrolyte 102 ... Anode 103 ... Cathode 104 ... Diffusion controlling layer 105 ... Heater

Claims (3)

[Claims] An exhaust passage is provided so as to communicate with an exhaust passage, and an exhaust gas is recirculated from the exhaust passage to the intake passage.
A GR passage, an EGR control valve disposed in the middle of the EGR passage for controlling the recirculation amount of exhaust gas, a GR passage disposed between the EGR control valve and the intake passage, A control device for an internal combustion engine, comprising: an exhaust component sensor for detecting a concentration of a component; and control means for using an output of the exhaust component sensor to determine a control amount of the internal combustion engine. 2. An engine operating state detecting means for detecting an operating state of the engine, wherein the EGR control valve adjusts an opening amount of the EGR control valve so that a recirculation amount of exhaust gas is reduced when the engine is at a high speed or a high load. The control device for an internal combustion engine according to claim 1, wherein: 3. The exhaust gas sensor according to claim 1, wherein the exhaust gas sensor is an oxygen sensor, and the output of the oxygen sensor is corrected using an output of the oxygen sensor when the EGR control valve is closed. The control device for an internal combustion engine according to claim 1 or 2.