JPH0318650A - Egr valve control system - Google Patents

Abstract

PURPOSE:To activate an oxygen density detecting means speedily by closing an EGR valve to stop EGR when the oxygen density detecting means provided at the exhaust gas route of an internal combustion engine is not activated. CONSTITUTION:A control circuit 1 feedback-controls the fuel injection quantity from an injector 8 on the basis of the output of an oxygen density detector 25 provided at an exhaust pipe 14 in such a way that the air fuel ratio becomes the specified value. The control circuit 1 then opens an EGR valve 38 provided at the by pass pipe 37 of the exhaust pipe 14 and an intake pipe 7 according to the specified operating state so as to perform exhaust gas recirculation control. When the inactivation of the oxygen density detecting means 25 is judged by the output of a sensor, the EGR valve 38 is placed in the closed state so as to stop the exhaust gas recirculation control. The oxygen density detecting means can be thus activated speedily, and accurate air-fuel ratio control, that is, desirable exhaust gas purification can be started in a short time.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a method for controlling an EGR valve that adjusts the amount of EGR in an exhaust gas recirculation (abbreviated as EGR) device. BACKGROUND OF THE INVENTION In order to reduce nitrogen oxides (NOx) in the exhaust gas of an internal combustion engine, an EGR device is used that mixes a portion of the exhaust gas from the internal combustion engine into the intake air of the engine. By performing such EGR, it is possible to reduce NOx as described above, but at the same time, problems such as a decrease in output and a deterioration in driving performance due to unstable combustion occur. Therefore, in order to minimize such problems, it is necessary to control the amount and timing of EGR depending on the operating state of the internal combustion engine. For this reason, typical prior art is configured to stop EGR when the temperature of the cooling water of the internal combustion engine is low, such as during warm-up. In other conventional technologies, EGR is stopped when the intake air flow rate is low or when the intake air pressure is low, such as during idling.

On the other hand, conventionally, an oxygen concentration sensor or a so-called lean mixture sensor that detects zirconia or the like has been installed in the exhaust path, and based on the oxygen concentration detected by these sensors, the air-fuel ratio is determined to reduce NOx. In this way, a structure is used that controls the amount of fuel supplied and the amount of intake air. Problems to be Solved by the Invention In order to accurately detect oxygen concentration, the temperature of the sensor portion of the oxygen concentration sensor must be, for example, 400°C or higher, and the lean mixture sensor must have a temperature of, for example, 700°C or higher. However, by mixing EGR, the exhaust gas temperature decreases, and as a result, the temperature of the oxygen concentration sensor also decreases, making it difficult to maintain the sensor in an activated state.However, the EGRi! In l11, in the method based on the cooling water temperature, when the cooling water temperature remains high and only the sensor temperature decreases, such as when restarting the internal combustion engine, EGR stop control is not performed. Moreover, in the method based on the intake air flow rate and intake air pressure, even when starting the internal combustion engine, if the intake air flow rate is large due to the accelerator pedal being depressed, or if the intake air pressure is high, The EGR stop control is not performed. Therefore, it takes a long time for the sensor to reach a state in which it can perform accurate detection operations, that is, to reach an activated state and to be able to accurately control the air-fuel ratio. An object of the present invention is to provide an EGR valve control system that can quickly make the oxygen concentration detection means viscous and perform accurate air-fuel ratio control.

Means for Solving the Problems The present invention provides an oxygen concentration detection means in the exhaust route, performs air-fuel ratio control based on the output of the oxygen concentration detection means, and also provides an open circuit that bypasses the exhaust route and the intake route. In the EGR valve Ilfll method in which an EGR valve is provided and the opening degree of the EGR valve is adjusted to increase the EGR amount by vJw, when the oxygen concentration detection means is not activated, the EGR valve is put into a leap state and the EGR is activated. This is an EGR valve control method that is characterized by stopping the EGR valve. According to the present invention, air-fuel ratio control is performed based on the output of the oxygen concentration detection means provided in the exhaust path, and the oxygen concentration detection means is not in a state in which it can perform accurate detection operations. In other words, when the EGR valve is not activated, the EGR valve provided in the side path that bypasses the exhaust path and the intake path is closed, and EGR is stopped.

Therefore, even when restarting the internal combustion engine or starting under high load conditions, the E
GR will remain stopped. Therefore, the oxygen 'a
The air-fuel ratio detection means is quickly activated, and accurate air-fuel ratio control can be started in a short time.

Embodiment II2l is a control system 1 for an internal combustion engine according to an embodiment of the present invention.
! 1 and its related elliptical precepts. Combustion air introduced from the intake port 2 is purified by an air cleaner 3, passed through an intake pipe 4, and its inflow amount is adjusted by a throttle valve 5 interposed in the intake pipe 4, and then sent to a surge tank 6. The inflowing combustion air flowing out from the surge tank 6 is mixed with fuel injected from the fuel injection valve 8 interposed in the intake pipe 7, and is then transferred to the internal combustion engine 111 via the intake valve 9.
3 1 0 is supplied to 1 liter of combustion chamber. The combustion chamber 11 is provided with an ignition plug 12 , and the exhaust gas from the combustion chamber 11 is discharged through an exhaust valve 13 and an exhaust pipe 14 .
It is then released into the atmosphere through a three-way catalyst 15. Said intake! #4 is provided with an intake air temperature detector 21 for detecting the temperature of intake air, a throttle valve opening detector 22 is provided in connection with the throttle valve 5, and an intake pressure detector 23 is provided in the surge tank 6. It will be established. In addition, the combustion i
A cooling water temperature detector 24 is provided near ll, an oxygen concentration detector 25 is provided upstream of the three-way catalyst 15 in the exhaust pipe 14, and an exhaust temperature detector is provided downstream of the three-way catalyst 15. 26 will be provided. The rotational speed of the internal combustion engine 1o, that is, the number of rotations per unit time, is detected by the crank angle detector 27.

In addition to the above-mentioned detectors 21 to 27, the control device l includes a vehicle speed detector 28, a start detector 29 that detects whether the starter motor 33 that starts the internal combustion engine 1o is activated, and the use of the air conditioner. The air conditioning detector 30 detects mI! When the vehicle in which the automatic transmission 10 is installed is equipped with an automatic transmission, a detection result from a neutral detector 31 that detects whether the gear position of the automatic transmission is in the neutral position is input. Furthermore, this control device 1 is powered by a battery 34, and the control device 1 is powered by the detection results of the respective detectors 21 to 31 and the power supply voltage of the battery 34 detected by the voltage detector 20. Based on this, the fuel injection amount, ignition timing, etc. are calculated, and the fuel injection valve 8 and spark plug 12 are
control etc. The intake pipe 4 is also formed with a side passage 35 that bypasses the upstream and downstream sides of the throttle valve 5, and this side passage 35 is provided with a flow rate control valve 36. The flow rate control valve 36 adjusts and controls the flow rate of combustion air during idling, when the throttle valve 5 is substantially fully closed, based on the output from the control device 1. Control unit Wl1 also drives fuel pump 32 when internal combustion engine 10 is operating.

Further, the space between the intake pipe 7 and the exhaust pipe 14 is bypassed by a side passage 37. This side road 37 includes the barrier road 37
An EGR valve 38 is provided for regulating and controlling the flow rate of exhaust gas recirculated through the exhaust gas. The EGR valve 38 has an oval shape using, for example, a diaphragm, and its opening degree is controlled by controlling energization/de-energization of a vacuum switching valve that introduces negative intake pressure into the diaphragm chamber. Like this E G
By controlling the opening of the R valve 38, the amount of exhaust gas mixed into the intake air is changed, and the air-fuel ratio can be changed. FIG. 2 is a block diagram showing the specific configuration of the control device 1. The detection results of the detectors 20 to 25 are sent from the input interface circuit 41 to analog/digital,
is applied to the processing circuit 43 via the tal converter 42.
Further, the detection results of the detectors 22, 27 to 31 are provided to the processing circuit 43 via an input interface circuit 44. The processing circuit 43 is provided with a memory 45 for storing various control maps, learning values, etc., and the processing circuit 43 is provided with a memory 45 for storing various control maps and learning values. Supplied via The control output from the processing circuit 43 is derived via an output interface circuit 47, and is applied to the fuel injection valve 8 to control the fuel injection amount, and is also applied to the ignition plug 12 via the igniter 48 to control the ignition. The timing is controlled, and is also applied to the flow control valve 36 to control the timing (l1) during idling.
Incoming air presentation through nI35 is controlled and E G
The EGR amount is controlled by being applied to the R valve 38.

The detection result of the exhaust gas temperature detector 26 is given to the exhaust gas temperature detection circuit 49 in the control device i, and when the detection result is abnormally high temperature, the warning light 5 is turned on via the drive circuit 50.
l is lit.

The control device 1 configured as described above controls the EGR valve 38 based on the intake air pressure, the rotation speed of the internal combustion engine rmto, etc.
Control the opening. As a result, the exhaust gas l recirculated via the side passage 37 is changed, and the ratio of the flow rate of fresh air from the throttle valve 5 to the flow rate of air flowing into the combustion chamber 11 is changed. Also control. The device 1 controls the fuel injection amount based on the output of the oxygen concentration detector 25 so that the air-fuel ratio is around the theoretical air-fuel ratio of, for example, 14.5, at which purification of exhaust gas in the three-way catalyst 15 is easy. ．． On the other hand, in order for the oxygen concentration detector 25 to perform an accurate detection operation, when the oxygen concentration detector 25 is an oxygen concentration sensor as described above, the temperature of the sensor portion must be set to a predetermined temperature, for example, 400°C. It is necessary that the above
Furthermore, when the sensor is a lean mixture sensor, it is necessary to have an even higher temperature, for example, 700°C or higher.
For this reason, the control device 1 determines whether the sensor portion of the oxygen concentration detector 25 is in an activated state where the temperature is higher than the above, and if it is not in an activated state, closes the EGR valve 38 to stop EGR, The combustion temperature of hot air in the combustion chamber 11 is controlled to increase.

The determination as to whether the oxygen concentration detector 25 is in the activated state is performed as follows. That is, for example, the oxygen concentration detector 25 is IS! If it is an elementary concentration sensor,
When a signal indicating that the air-fuel ratio is in a rich state is continuously derived for 0.2 seconds or more, it is determined that the activated state is present, whereas a signal indicating that the air-fuel ratio is in a lean state is determined. If it is derived continuously for 8 seconds or more, it is determined that the state is inactive. Further, when the oxygen concentration detector 25 is a lean mixture sensor, the relationship between its output voltage and the control air-fuel ratio is as shown in FIG. 3, and therefore the output voltage corresponds to the predetermined control air-fuel ratio. When the state in which the output voltage is equal to or greater than the value continues for a predetermined period or longer, it is determined that the activated state is present, whereas the state in which the output voltage is less than the value corresponding to the predetermined @control air-fuel ratio is predetermined. If it continues for a period of time or more, it is determined that it is in an inactivated state.

When the inactivation state is determined as described above, the EGR valve 38 is closed to raise the combustion temperature of the air-fuel mixture. This allows oxygen i! +
The temperature of the sensor portion of the temperature detector 25 quickly reaches or exceeds the predetermined temperature, and accurate air-fuel ratio control can be started in a short time. Therefore, it is possible to quickly achieve a state in which exhaust gas purification can be performed satisfactorily. In addition, in the EGR valve control method according to the present invention, the control execution conditions are not only based on the cooling water temperature and the rotation speed of the internal combustion engine 10 as described in the prior art section, but also based on the actual oxygen concentration detector 25. Based on the output of , the oxygen concentration detector 25 is activated immediately as described in step 5. be able to.
FIG. 4 is a flowchart for explaining the EGR stop operation as described above. In step n1, the control device 1 determines whether the conditions for setting the EGR valve 38 to the leap state are satisfied based on the rotational speed of the internal combustion engine 10, intake air pressure, cooling water temperature, etc. If not, proceed to step n2. In step n2,
Based on the output from the oxygen concentration detector 25, it is determined whether the oxygen concentration detector 25 is malfunctioning. The failure determination of the oxygen concentration detector 25 is performed based on, for example, whether a constant output voltage continues to be derived. When it is determined in step n2 that the oxygen concentration detector 25 is normal, the process moves to step n3, where it is determined whether the oxygen concentration detector 25 is in a state where it can perform normal detection operations, that is, in an activated state. If so, the process moves to step n4. Further, when the EGR stop condition has already been established in step n1, and when the oxygen concentration detector 25 has failed in step rl2, directly step n4
Move to.

At step r+4, the EGR valve 38 is closed, the EGR is stopped, and the engine F is ended. The direct operation is also terminated when it is determined in step n3 that the oxygen concentration detector 25 is in an inactivated state. Effects of the Invention As described above, according to the present invention, I! Since EGR is stopped when the oxygen concentration detection means is not activated, EGR is stopped until the oxygen concentration detection means is activated even when the internal combustion engine is restarted or started under a high load condition.
The valve remains stopped. Therefore, the oxygen concentration detection means is quickly activated and the accurate air-fuel ratio il is detected.
II control, that is, good exhaust gas purification can be started in a short time.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an III control device 1 of an internal combustion engine according to an embodiment of the present invention and a structure connected thereto;
3 is a block diagram showing the specific structure of the control device l, FIG. 3 is a graph showing the relationship between the controlled air-fuel ratio and the output voltage of the lean sensor, and FIG. 4 is a flow chart for explaining the EGR stop operation. be. DESCRIPTION OF SYMBOLS 1... Control device, 4.7... Intake pipe, 5... Throttle valve, 10... Internal combustion engine, 14... Exhaust pipe, 2
0 to 31...detector, 3 5 3 7...side passage, 3 8...EGR valve

Claims (1)

[Claims] An oxygen concentration detection means is provided in the exhaust route, and the air-fuel ratio is controlled based on the output of the oxygen concentration detection means.An EGR valve is provided in a side route that bypasses the exhaust route and the intake route, and the opening of the EGR valve is provided. In the EGR valve control method in which the EGR amount is controlled by adjusting the oxygen concentration, when the oxygen concentration detection means is not activated, the EGR valve is closed and EGR is stopped.
R valve control method.